Diagnostic value of blood picture analysis. The study of the morphological composition of blood is one of the most important diagnostic methods in clinical practice. The hematopoietic organs are extremely sensitive to various physiological and especially pathological influences on the body, and the blood subtly reflects the results of these influences.
A general (clinical) blood test includes determining the concentration of hemoglobin, the number of red blood cells, other indicators of red blood, leukocytes, leukogram, and determining the erythrocyte sedimentation rate.
It must be remembered that the composition and properties of peripheral blood undergo certain changes under the influence of many factors. The morphological picture of blood is influenced by the age, breed and constitution of the animal, muscle tension, season, lactation, feeding conditions, housing, etc. Thus, the composition of blood normally in animals can vary.
During the neonatal period, the content of erythrocytes, platelets and leukocytes in animals is increased; these indicators decrease significantly 2...4 weeks after birth; in the leukogram of young animals in the first days of life, the number of neutrophils is increased (in calves up to 80%) and the number of eosinophils is reduced; among the neutrophils there are young ones; an increased percentage of band forms is observed. With age, as the animal ages, the number of leukocytes and lymphocytes in the blood decreases, and the number of neutrophils increases.
Morphological differences in blood composition associated with the sex of the animal were also noted. Males have a higher red blood cell count and hemoglobin level than females.
With muscle tension in animals (especially horses), the level of hemoglobin, hematocrit, and the number of erythrocytes and leukocytes increase for a short time (for several hours) with relative and absolute neutrophilia, lymphocytopenia and eosinopenia.
In mountainous areas, where partial air pressure is reduced, the number of red blood cells and hemoglobin in animals is noticeably higher than in animals in lowland areas. Cattle have more leukocytes in their blood at the end of summer than at the end of winter.
In dairy (Angel, Dutch, East Frisian, Yaroslavl) and meat breeds of cattle (Shorthorn and Hereford), the content of erythrocytes and leukocytes is higher than in meat and dairy animals (Schwitz mixed breeds and Simmental mixed breeds). Animals of the Kostroma breed have relatively more red blood cells, hemoglobin and leukocytes than cows of other breeds. Caucasian brown cows have a very high percentage of lymphocytes and contain more than usual leukocytes. Highly productive animals have more formed elements in their blood than low-productive animals.
The morphological composition of animal blood is greatly influenced by sunlight: for example, the content of red blood cells in cattle increases in the spring and summer and decreases noticeably in winter.
The nature of the feed and the type of feeding of the animals also affects the composition of the blood. Nutritionally insufficient feeding contributes to a decrease in basic blood counts. One-sided feeding also has an unfavorable effect, including with abundant feeding of succulent or concentrated feed.
Red blood cell counting. The active period of the life cycle of erythrocytes occurs in the peripheral blood, where they
drink from red bone marrow. An erythrocyte is a highly specialized cell designed to perform its main function - transport of O2 from the lungs to tissues and CO2 from tissues to the lungs, which is provided by hemoglobin included in the cell. In addition, red blood cells take part in the regulation of acid-base balance (hemoglobin buffer), transport amino acids and lipids to tissues, adsorb toxins, participate in a number of enzymatic processes, and also maintain ionic balance in the blood and tissues.
The process of formation of red blood cells - erythropoiesis - occurs in the red bone marrow. The parent element of erythropoiesis is an erythropoietin-sensitive cell, which cannot be determined by conventional methods. This cell further differentiates into erythroblasts, the earliest recognizable erythron cells capable of synthesizing hemoglobin. Subsequently, erythroblasts mature and differentiate (with 3...4 mitotic divisions). The following stages of erythrocyte development are distinguished: basophilic, polychromatophilic and oxyphilic normoblasts, anucleate reticulocytes and, finally (already in the peripheral blood) mature erythrocytes.
Completing their life cycle after 110...130 days, red blood cells are phagocytosed by reticular cells, histiocytes, macrophages and polynuclear leukocytes in the spleen, liver, lungs, lymph nodes and other organs. Under the influence of hydrolytic enzymes in erythrophagosomes, hemolysis and intensive breakdown of hemoglobin, stroma and membrane of erythrocytes occurs until the formation of low molecular weight products.
Erythrocytes are counted under a microscope in Goryaev’s counting chamber after preliminary dilution of the blood in melangeurs (incest mixers) or in test tubes (N. M. Nikolaev’s method). Special devices are also used - erythrohemometers, photo-electrocolorimeters and conductometric particle counters (SFEK-Ts-0.4, Celloscope, Coulter, Pikoskel, etc.). The number of red blood cells in the blood of healthy animals of different species is indicated in Table 9.12.
A morphological blood test widely used in clinical practice is called general clinical trial. This analysis includes the study of the quantitative and qualitative composition of blood cells: determination of the number of red blood cells and the hemoglobin content in them, determination of the total number of leukocytes and the ratio of individual forms among them, determination of the number of platelets. In some patients, depending on the nature of the disease, additional studies are performed: reticulocyte count, platelet count, etc.
The development of hematology in recent years has led to a revision of the decades-old concept of the reticular cell as the source of all cellular elements of the blood. Currently, the hematopoietic scheme is presented as follows. The first class of pluripotent progenitor cells is represented by the so-called hematopoietic stem cell. Stem cells have the ability to self-renew, rapidly proliferate and differentiate.
The second class of partially committed pluripotent progenitor cells is represented by the precursors of lymphopoiesis and hematopoiesis; their ability to self-sustain is limited; these cells are found in the bone marrow.
The third class of unipotent progenitor cells includes cultured colony-forming cells (granulocyte and monocyte precursors), erythropoietin-sensitive cells, B-lymphocyte progenitor cells, and T-lymphocyte progenitor cells.
The fourth class includes morphologically recognizable proliferating cells, the fifth class includes maturing cells, and the last, sixth class consists of mature cells with a limited life cycle. Usually, mainly class six cells enter the peripheral blood.
The cellular composition of the blood of a healthy person is quite constant, so various changes in it can have diagnostic significance. However, small fluctuations can also be observed during the day under the influence of food intake, physical activity, etc. To eliminate the influence of these factors, blood for repeated tests should be taken under the same conditions.
Taking blood. Blood testing begins with the simultaneous receipt of blood samples for all studies performed. Blood is taken from the fourth finger of the left hand. The finger is disinfected by wiping it with a cotton swab moistened with a mixture of alcohol and ether. The puncture is made with disposable scarifier needles. The injection is made from the side into the flesh of the first phalanx to a depth of 2.5-3 mm. The blood must flow freely, since with strong pressure it is mixed with tissue fluid, which reduces the accuracy of the study. The first drop is wiped off with dry cotton wool.
Determination of hemoglobin level. There are three main groups of methods for determining hemoglobin levels: colorimetric (which have found the widest use in practical medicine), gasometric and based on the iron content in the hemoglobin molecule. Until recently, the inaccurate Saly method, proposed back in 1895, was widely used.
The cyanmethemoglobin method, adopted as standard by the International Committee for Standardization in Hematology, has received universal recognition as the most accurate and objective. The method is based on the oxidation of hemoglobin (Hb) under the action of red blood salt into methemoglobin (MetHb, according to the new nomenclature - hemoglobin Hi), which with CN ions forms a stable, red-colored complex - cyanmethemoglobin (CNMetHb) or hemiglobin cyanide (HiCN ). Its concentration can be measured using a spectrophotometer, photo-electrocolorimeter or hemoglobinometer.
Fluctuations in hemoglobin concentration in healthy women are 120-160 g/l, in men - 130-175 g/l.
Red blood cell counting. To count red blood cells in the chamber, the blood is diluted 200 times in a 3.5% sodium chloride solution, for which 0.02 ml of blood is added to a pre-measured 4 ml of dilution solution or a mixer is used. The suspension is thoroughly mixed and then filled with a counting chamber (a glass plate with one or two counting grids applied to it). The cover glass must be firmly pressed to the underlying strip, which is achieved by “rubbing it in” until “Newton’s rings”—rainbow lines, ovals or rings—appear above the side strips. A drop of diluted blood is pipetted under the ground cover glass of the chamber. The liquid is sucked through the capillaries and fills the space above the mesh.
Counting is carried out after 1 minute (when the red blood cells settle to the bottom of the chamber), using lens 40 and eyepiece 7 or lens 8 and eyepiece 15.
There are many different counting grids, but they are all built on the same principle. The grids consist of large and small squares, their area is equal to "/25 and "Aoo mm2, respectively. Most often used Goryaev's grid. It consists of 225 large squares, 25 of which are divided into
Rice. 141. Scheme for counting red blood cells.
ly, 16 squares each. Red blood cells are counted in 5 large squares, divided into small ones, adhering to a certain counting sequence (Fig. 141): moving from square to square horizontally, one row from left to right, the next from right to left, as shown in the figure with a dotted arrow. In addition to those inside the square, all red blood cells lying on two lines, for example, on the left and top, are counted, and all those lying on the right and bottom are skipped. The number of red blood cells in 5 large squares is converted to their content in 1 liter. The normal number of red blood cells in women is 3.4-5.0* 10 12, in men - 4.0-5.6- 10 12 in 1 liter of blood.
The number of red blood cells can also be determined using devices that simplify and automate this study. These include erythrohemometers and elvctrophotocolorimeter(make it possible to judge the number of red blood cells by measuring, using a photocell, the amount of light absorbed and scattered as it passes through a suspension of red blood cells) and automatic counting devices such as celoscope(Red blood cells are directly counted). The principle is that blood cells change the resistance of an electrical circuit as they pass through a narrow capillary. This change is recorded using an electromagnetic counter. Each cell is reflected on the oscilloscopic screen and recorded on the instrument scale.
Knowing the number of red blood cells in the blood and the hemoglobin content in it, we can calculate the extent to which each red blood cell is saturated with it. There are different ways to establish this value. The first is the calculation of the color index. This is a conditional value derived from the ratio of hemoglobin and the number of red blood cells. It is calculated by dividing three times the number of grams of hemoglobin by the first three digits of the number of red blood cells. Normally, this value approaches 1. A number less than 1 indicates insufficient saturation of red blood cells with hemoglobin; a number greater than 1 occurs in cases where the volume of red blood cells is greater than normal. There is no oversaturation with hemoglobin; a normal red blood cell is saturated with it to the limit.
Currently, in accordance with the desire to express constants in absolute values, instead of a color indicator, the weight content of hemoglobin in erythrocytes is calculated. Having determined the hemoglobin content in 1 liter, this value is divided by the number of red blood cells in the same volume. Normally, 1 red blood cell contains 27-33 ng of hemoglobin.
Leukocyte count. To count white blood cells, blood is diluted either in mixers or in test tubes. For this purpose, use a 3-5% solution of acetic acid (to destroy red blood cells), tinted with some aniline dye (to color the nuclei of leukocytes). The counting grid is filled in the same way as for counting red blood cells. Leukocytes are counted in 100 large squares. In Goryaev’s grid it is convenient to count them in ungraphed squares (there are 100 of them on the grid). Taking into account the blood dilution and the volume of liquid above the squares, a constant multiplier is calculated; when diluted 20 times, it is equal to 50. When working with test tubes, 0.38 ml of liquid is first poured into them and 0.02 ml of blood is released into it. For counting in automatic counting tubes, red blood cells are hemolyzed with saponin. The normal content of leukocytes is 4.3-10 9 -11.3 10 9 / l, or 4300-11 300 in 1 μl of blood.
The leukocyte formula is calculated in stained smears.
A good brushstroke meets the following requirements: it is thin, and the shaped elements lie in one layer; in this case, the smear turns out to be yellow and translucent. Its width should not reach the edges of the glass by 2-3 mm, and its length should occupy 2/3-4 of the glass. A good smear is uniform and the cells are not damaged by smearing. In order for the blood to lie evenly on the glass, it is degreased by burning it over the flame of a gas burner or kept in a mixture of alcohol and ether. The end of the glass is touched to the freshly released small drop of blood and without delay it is smeared on the glass. Before staining, the smear is fixed by immersion in methanol for 3 minutes, in ethyl alcohol or its mixture with ether for 30 minutes. There are a number of other clamps. The smear, dried after fixation, is filled with dye.
To distinguish blood cells (determine the leukocyte formula), differential staining is used. The Romanovsky-Giemsa stain is the most widely used. This dye is a mixture of slightly acidic (eosin) and slightly alkaline (azur II) dyes. Cells and their parts, depending on the reaction of the environment in them, perceive one or another component of the dye: acidic (basophilic) substances are stained blue with azure, alkaline (oxyphilic) substances are stained red with eosin; neutrals perceive both colors and become violet.
Leukocyte formula They call the percentage of individual forms of blood leukocytes. To accurately calculate it, you need to look at at least 200 leukocytes.
Counting is carried out using an immersion system. Due to the fact that the cells are located unevenly in the smear (larger ones go to the edges), it is important to adhere to an order of movement along the smear in which its edges and middle are equally visible. One of two methods of movement is used: according to one of them, the smear is moved from the top edge to the bottom, moved 2-3 fields of view along the edge, then goes in the opposite direction to the top edge, etc. With the second method, they move from the edge by 5 -6 fields to the middle of the stroke, then the same number to the side, then back to the edge, move a few fields to the side and again repeat the movement until 50 cells are counted. Look at 4 such areas at 4 corners of the smear. Each cell found when viewing a smear must be identified and recorded. It is convenient to use a special key counter when counting; in its absence, the cells are marked with a note on paper. After counting 200 cells, the number is divided in half and the number of each type of leukocyte is determined.
Leukocytes are elements of the blood that quickly respond to various external influences and changes within the body. Therefore, changes in the leukocyte formula are of great diagnostic importance. However, individual fluctuations in the composition of leukocytes are quite large, as a result of which, when comparing with the norm, one has to focus not on average values, but on the limits of normal fluctuations given in the Appendices.
When assessing the composition of leukocytes, you need to keep in mind that changes in percentages can give an incorrect idea about the changes occurring in the blood. Thus, an increase in the absolute content of one type of cell in the blood leads to a decrease in the percentage of all other cellular elements. The opposite picture is observed when the absolute content of one of the types of blood cells decreases. The correct judgment is given not by relative (percentage) but by absolute values, i.e., the content of a given type of cell in 1 μl, and according to SI - in 1 liter of blood.
Determining the total number of leukocytes can be of great diagnostic value, as it reveals the state of the hematopoietic organs or their reaction to harmful influences. An increase in the number of leukocytes - leukocytosis - is the result of activation of leukopoiesis, a decrease in their number - leukopenia - may depend on the inhibition of hematopoietic organs, their exhaustion, increased breakdown of leukocytes under the influence of anti-leukocyte antibodies, etc. Neutrophils. The most variable group of leukocytes are neutrophils, the number of which increases with many infections, intoxications and tissue breakdown. Characteristic of active neutropoiesis is not only an increase in the total number of neutrophils in the blood, but also the appearance of immature forms in it: the number of stab forms increases, young neutrophils, and sometimes even myelocytes appear. This “rejuvenation” of the composition of neutrophils is called a shift of the leukocyte formula to the left, because in this case, in the usual recording of the composition of neutrophils in the leukocyte formula on a laboratory form, the numbers on its left side increase from left to right. Distinguish regenerative and degenerative (dystrophic) “left shifts” neutrophils. With the first, the changes described above are noted, with the second, in the absence of leukocytosis, an increase in the number of only band forms with dystrophic (“degenerative”) changes in neutrophils (vacuolization of the cytoplasm, nuclear pyknosis, etc.) is observed. A regenerative shift indicates an active protective reaction of the body, a degenerative shift indicates the absence of such. The protective role of neutrophils is determined by their phagocytic function, bactericidal effect and the release of proteolytic enzymes that promote the resorption of necrotic tissue and wound healing.
Most often, a regenerative shift appears in the presence of some kind of inflammatory process or focus of necrosis. A very sharp shift to the left to promyelocytes and even myeloblasts with significant leukocytosis is called leukemoid reaction. Decrease in the number of neutrophils - absolute neutropenia- occurs when the bone marrow is depressing the effects of toxins of certain microorganisms (causative agents of typhoid fever, brucellosis, etc.) and viruses, ionizing radiation, and a number of medications.
Lymphocytes. Increase in the absolute number of lymphocytes - lymphocytosis - occurs less frequently. It is observed during the period of recovery from acute infectious diseases, with infectious mononucleosis, infectious lymphocytosis, lymphocytic leukemia, rubella, brucellosis, thyrotoxicosis. Much more often, lymphocytosis turns out to be only relative, associated with a decrease in the number of neutrophils, as well as relative leukopenia with an increase in the number of neutrophils. Absolute lymphopenia occurs with radiation sickness, systemic lesions of the lymphatic system: lymphogranulomatosis, lymphosarcoma.
Eosinophils. They are found in the blood in relatively small quantities (contained mainly in tissues), but their number increases, sometimes significantly, with allergic processes (serum sickness, bronchial asthma), helminthic infestations, and itchy dermatoses. Eosinophilia in allergic processes is associated with the role of eosinophils in eliminating the toxic products that arise during this reaction. Decrease in the number of eosinophils - eosinopenia- up to their complete disappearance is observed in sepsis, severe forms of tuberculosis, typhus, severe intoxication.
Basophils. They are carriers of important mediators of tissue metabolism (blood “equivalents” of mast tissue cells). When the body is sensitized, their number increases; when the allergen is re-introduced, it sharply decreases as a result of their decay.
Monocytes. Increase in the number of "monocytes - monocytosis - serves as an indicator of the development of immune processes. Monocytes are recognized as analogues of tissue macrophages. Monocytes are found in a number of chronic diseases (chroniosepsis, tuberculosis, malaria, visceral leishmaniasis, syphilis) and in infectious mononucleosis. Monocytopenia sometimes observed in severe septic, hypertoxic forms of typhoid fever and other infections.
Calculating the leukocyte formula requires the ability to distinguish blood cells well (Fig. 142). Oocyte granules. Distinctive features of granulocytes are segmented nuclei (purple, like all leukocytes), oxyphilic (pink) cytoplasm containing granularity. U neutrophil leukocyte(diameter 10-15 microns) grains are small, of different sizes, colored brownish-violet; the core of a rough structure with alternating intensely and lightly colored areas consists of 2-5 (usually 3-4) segments of different sizes and shapes, connected by thread-like bridges. Core rod-nuclear neutrophil approximately the same size and color, but represents a complex curved ribbon, nowhere narrowing to a thread-like bridge. Cores eosinophils consist in most cases of two approximately identical and symmetrically located segments (three-segment ones can also be found), similar in color and structure to the segments of neutrophils. Eosinophil granularity is abundant. The entire cytoplasm is “stuffed” with grains; they are large, round, all the same, painted in a bright orange-red color. The cell diameter is about 15 microns. Basophil somewhat smaller in size than other granulocytes (9-14 µm). Its core can be segmented, but more often it has an irregular lobed shape and is colored dark purple. This is due to metachromasia of the grains: the blue color makes them purple.
Agranulocytes. A distinctive feature of agranulocytes is a non-segmented nucleus and basophilic (blue) cytoplasm. Lymphocyte is the smallest white blood cell; the diameter of most cells is 7-12 µm, but some lymphocytes reach 12-15 µm. The kernel is round, oval or bean-shaped; occupies most of the cell, intensely colored. The cytoplasm of most lymphocytes surrounds the nucleus with a narrow rim, is colored light blue and becomes clearer towards the nucleus. In addition to such “small” lymphocytes, there are also “medium” ones, which have a large zone of sky-blue cytoplasm. Some lymphocytes have several large cherry-red (azurophyl) grains in their cytoplasm. A monocyte is the largest of the blood cells, with a diameter of up to 20 microns. Large kernel of irregular shape and relatively light color. The cytoplasm is grayish-blue, smoky in color, and does not clear towards the nucleus. When stained well, some cells reveal abundant fine (pulverized) azurophilic granularity.
In addition to the listed cells, plasma cells are rarely found in normal blood, and in diseases they can often be found. They are distinguished by an eccentrically located dense nucleus, often with a wheel-shaped structure, and rarely basophilic vacuolated cytoplasm. The number of these cells increases in some infectious diseases, wound sepsis, hypernephroma, myeloma, etc. Their role appears to be in the production of γ-globulins.
When calculating the leukocyte formula, attention is paid not only to quantitative changes in it, but also to qualitative changes in the formed elements. Degenerative changes in leukocytes have been previously noted. In severe intoxication, the granularity of neutrophils becomes abundant, large, intensely colored and is called toxic (or toxogenic). Sometimes blood smears show blurry spots, colored like the nuclear substance of leukocytes. These are the so-called Botkin-Gumprecht shadows - remnants of nuclear chromatin, indicating increased fragility of leukocytes, leading to their disintegration - leukocytolysis.
Morphological assessment of red blood cells. Red blood cells are also assessed in the same smears (Fig. 143). Pay attention to their size, shape, color and cellular inclusions. Normal red blood cells in a smear are round in shape, their diameter is 6-8 microns, the average diameter is 7.2 microns. With anemia of various types, the size of red blood cells often changes. Changes in size usually do not affect all red blood cells equally; the appearance of red blood cells of different sizes is called anisocytosis. The predominance of small red blood cells - microcytosis- characteristic of iron deficiency anemia; when the hematopoietic function of the liver is disordered, macrocytosis occurs; with a lack of vitamin B 12 in the body (B 12 deficiency anemia) appear in the blood megalocytes - large (more than 12 microns) oval hyperchromic erythrocytes formed during the maturation of megaloblasts. Under pathological conditions of erythrocyte maturation, along with anisocytosis, a change in their shape is noted - poikilocytosis: in addition to round ones, oval, pear-shaped, etc. red blood cells appear. If the red blood cells are insufficiently saturated with hemoglobin (color indicator<0,85) они слабо воспринимают окраску, становятся гипохромными, при дефиците витамина В, 2 они интенсивно окрашены - гиперхромны (цветовой показатель >1). A fully mature red blood cell is oxyphilic, that is, it is colored pink. An immature red blood cell is polychromatophilic. Such erythrocytes with supravital staining are revealed as reticulocytes. In normal blood, polychromatophilic erythrocytes are found in small numbers - a few per 1000 erythrocytes. Since they are less noticeable than reticulocytes, reticulocytes are counted to count young cells that have just entered the blood. The significance of this study is that the number of reticulocytes in the blood indicates the degree of bone marrow activity. Normally, this number is 2-10 per 1000 red blood cells. With blood loss and hemolysis, erythropoiesis in normal bone marrow is activated and the number of reticulocytes in it and in peripheral blood increases. The absence of such an increase indicates a decrease in bone marrow function, and, conversely, reticulocytosis in the absence of anemia is an indicator of hidden, but well-compensated blood losses.
Large reticulocytosis is also observed with effective treatment of B 12-deficiency anemia.
Reticulocyte staining is performed on unfixed smears of freshly released blood, in which the red blood cells have not yet died. Various alkaline dyes and different coloring methods are used. The best dye is diamond cresyl blue. A drop of a saturated alcohol solution of the dye is applied to a degreased glass slide and a smear is made in the same way as a blood smear in a routine clinical examination. After the dye has dried, a thin blood smear is made on top of it, which is immediately placed in a moist chamber (a Petri dish with a piece of wet filter paper inserted into it). After 5 minutes, the smear is removed, allowed to dry and examined in an immersion system. Mature red blood cells are colored greenish. In reticulocytes against this background, blue threads and grains are found, which, depending on the degree of maturity of the reticulocyte, have the appearance of a corolla, ball, mesh, individual threads or grains. Normally, the last two most mature forms predominate.
When counting reticulocytes, their number is determined per 1000 red blood cells. For ease of calculation, the field of view of the microscope is reduced by inserting a special window or a window cut out of paper into the eyepiece. The total number of red blood cells and reticulocytes in the field of view is counted. The counting continues until 1000 red blood cells are counted.
If the erythropoietic function of the bone marrow is insufficient, more immature “nuclear” (still containing nuclei) elements of the red blood are washed out into the blood - normoblasts, erythroblasts. When erythrocytes mature under pathological conditions, remnants of the nucleus may remain in the form Jolly corpuscle- round chromatin formations with a diameter of 1-2 microns, painted cherry red, and Cabot rings red, which look like rings, figure eights, etc.; they are considered remnants of the core shell. They occur mainly in B 12 deficiency anemia.
Basophilic granularity of erythrocytes - also the result of their abnormal maturation. It appears in the form of blue grains on a pink background with the usual coloring of a fixed smear. It should not be confused with the granularity of reticulocytes, which is revealed only by supravital staining. Basophilic granular erythrocytes are found in pernicious (B, 2-deficiency) anemia and some intoxications, especially lead poisoning. Platelets. The platelet diameter is 1.5-2.5 microns. Their number is normal 180,0- 320,0 10 9 /l (180,000-320,000 in 1 μl) of blood. When stained according to Romanovsky-Giemsa, a central part is distinguished - a granulomer with abundant azurophilic granularity and a surrounding non-granular hyalomer. With a significant decrease in the number of platelets - thrombocytopenia - there is a tendency to bleeding. The critical figure at which hemorrhage occurs is considered to be 30.0 # 10 9 /l (or 30,000 in 1 μl). Thrombocytopenia occurs when the bone marrow is damaged by infectious agents, ionizing radiation, taking certain medications and during an autoimmune process, thrombocytosis- after bleeding, with polycythemia, malignant neoplasms.
To determine the platelet count, it is necessary to prevent platelet agglutination. To do this, apply a drop of 14% magnesium sulfate solution to the finger prick site. Blood flowing from the wound immediately mixes with this solution. From their mixture, smears are made, which are fixed and stained according to Romanovsky-Giemsa twice as long as blood smears. Using the window (as when counting reticulocytes), 1000 red blood cells and all platelets encountered are counted across the fields of view. Then, knowing the number of red blood cells in 1 μl, the number of platelets in 1 μl and in 1 liter of blood is calculated.
In addition to indirect platelet counting, you can also perform a direct count in a counting chamber by diluting the blood in a mixer with special solvents, for example, a 1% ammonium oxalate solution. Counting is carried out using a phase contrast microscope. This method gives more accurate results than indirect counting. For some diseases of the hematopoietic organs, the “platelet formula” is calculated. There are young, mature, old platelets, differing in size, shape, color, structure; sometimes “degenerative” forms appear.
Changes in the morphological composition of the blood should be used when diagnosing the disease, not in isolation, but always in combination with other examination data of the patient.
Determination of erythrocyte sedimentation rate (ESR). Erythrocyte sedimentation was previously somewhat inaccurately called the erythrocyte sedimentation reaction (ESR), although no reaction occurs. In the blood flow, red blood cells carrying a negative charge repel each other, which prevents them from sticking together. Outside the blood vessels, in blood protected from coagulation by some anticoagulant and drawn into a vertical vessel, red blood cells begin to settle under the influence of gravity, and then they agglomerate - they join into groups, which, due to greater gravity, settle faster. Agglomeration is promoted by some protein components of plasma (globulins, fibrinogen) and mucopolysaccharides, therefore processes leading to an increase in their content in the blood are accompanied by an acceleration of erythrocyte sedimentation. It is observed in most inflammatory processes, infections, malignant tumors, collagenosis, amyloidosis, tissue breakdown and is to a certain extent proportional to the severity of the lesion. Some diseases are characterized by the absence of acceleration of erythrocyte sedimentation in the initial period of the disease (viral hepatitis, typhoid fever) or its slowdown (heart failure).
Erythrocyte sedimentation rarely serves as an independent diagnostic symptom, but allows one to judge the activity of the process. ESR is of particular importance in this sense in tuberculosis, rheumatism, and collagenosis. ESR does not always change in parallel with other activity indicators. Thus, it is delayed compared to leukocytosis and increased body temperature during appendicitis or myocardial infarction and normalizes more slowly than them. A normal ESR does not exclude a disease in which it is usually increased; Along with this, an increase in ESR does not occur in healthy people. The most widely used method in our country is the method of determining ESR according to Panchenkov. A 5% solution of sodium citrate is filled to the 50 mark in a Panchenkov capillary 1 mm wide, having 100 divisions of 1 mm each, which is then blown onto a watch glass or into a test tube. After pricking your finger, blood is drawn into the same capillary 2 times to the 100 ml mark. To do this, the capillary is placed horizontally against the flowing drop of blood, which, due to capillary forces, enters the pipette. The blood is mixed with the reagent (ratio 4:1), the mixture is drawn into the capillary to the 0 mark (100 divisions) and placed in a Panchenkov stand strictly vertically. After an hour, the number of millimeters of the settled column of plasma is noted. The norm for men is 2-10 mm/h, for women - 2-15 mm/h.
1. Morphological composition of blood
2. Chemical composition of blood and its fractions
3. Properties of blood
4. Nutritional and industrial value of blood
^ 1. Morphological composition of blood
Blood is the internal medium of the body, which connects organs and tissues and performs respiratory, nutritional, excretory, regulatory and protective functions.
Animal blood is a homogeneous, thick, red liquid, consisting of a liquid part - plasma- And shaped elements(cells): red blood cells, white blood cells and platelets.
Plasma is a straw-yellow liquid. The formed elements are a thick mass of dark red color, which is caused by the presence of hemoglobin protein in red blood cells. Red blood cells make up the bulk of the formed elements (about 99%).
The total amount of blood in cattle and small ruminants averages 7.6-8.3%, in pigs - 4.5-6.0%, in poultry - 7.6-10% of live weight. When bleeding, about 50-60% of this amount is recovered.
^ 2. Chemical composition of blood and its fractions
The chemical composition of blood depends on the species, age, fatness, and living conditions of the animals. Average data on the chemical composition of blood and its fractions are given in table. 7.
Table 7
The bulk of blood proteins consists of albumins, globulins, fibrinogen And hemoglobin. Their approximate content in the blood of animals is shown in Table. 8.
Table 8
Organic non-protein substances in blood are varied in chemical composition. Of their total amount, about 75% are lipids.
Inorganic substances in the blood are found in the form of mineral compounds and in organically bound form with proteins (iron, copper).
The blood contains a large number of physiologically active substances: enzymes, hormones, vitamins. The very diverse and complex chemical composition of blood is associated with its lifetime biological functions.
The most important and quantitatively predominant component of blood from a technological point of view are proteins. In terms of protein content, blood is practically no different from meat.
Serum albumin, serum globulin and fibrinogen are the main fractions of plasma proteins. These are complete, easily digestible proteins. Fibrinogen is the main component of the blood coagulation system. In plasma it is in a dissolved state, but under certain conditions under the influence of plasma enzymes it can turn into an insoluble filamentous protein fibrin. The remaining liquid is called serum; Compared to plasma, it contains 0.3-0.4% less protein.
Over 80% of the protein substances of erythrocytes are hemoglobin. Hemoglobin is a complex protein that gives blood its red color. In structure and properties it is close to the muscle pigment myoglobin, but more complex. The hemoglobin molecule consists of four subunits, each of which includes a polypeptide chain connected to heme. Hemoglobin does not contain isoleucine, so it is an incomplete protein. Hemoglobin is soluble in water and is digested by pepsin and trypsin.
In the blood, hemoglobin can be found in three forms:
native hemoglobin (red);
oxyhemoglobin (bright red);
methemoglobin (red-brown color).
^ 3. Properties of blood
Density blood and its fractions are different and average:
for blood - 1050-1065;
plasma - 1020-1030;
formed elements - 1080-1090 kg/m 3.
Under certain conditions, blood hemoglobin can pass from red blood cells into plasma and, dissolving in it, color it red. This phenomenon is called hemolysis. Hemolysis occurs under the influence of various factors leading to the destruction of the erythrocyte membrane. This may be a decrease in the osmotic pressure of the environment (for example, due to dilution of blood with water), mechanical effects, exposure to organic solvents, etc. In technological practice, hemolysis should be avoided when obtaining plasma or serum. When producing food dyes, on the contrary, hemolysis is carried out to release the pigment - hemoglobin from red blood cells.
At a temperature of about 60 o C, denaturation of hemoglobin begins, accompanied by a change in blood color due to the formation of brown hematins.
The withdrawn blood is a good nutrient medium for microflora and is easily exposed to microbial spoilage. Therefore, blood intended for food and medical purposes must be processed very quickly or preserved.
A few minutes after blood collection rolls up(6.5-10 minutes for cattle, 3.5-5 minutes for pigs, 4-8 minutes for small cattle, less than 1 minute for poultry). This property of blood is an important protective device of the animal body. In blood processing technology, the coagulation process is undesirable, as it complicates the transportation and processing of blood.
Blood clotting is caused by the conversion of soluble plasma protein fibrinogen into insoluble protein fibrin. This is a complex multi-stage process, the final stage of which is education. clot from a network of fibrin threads filled with formed elements and serum. The formation of a clot is preceded by a number of transformations of enzymatic and non-enzymatic nature associated with the interaction of many blood components. The reactions that occur during coagulation are closely interrelated; for each subsequent reaction to occur, all previous reactions must occur.
The process of blood clotting involves enzymes, proteins, and calcium ions called coagulation factors.
Inhibition or prevention of the blood clotting process is based on knowledge coagulation mechanism. Let's look at a simplified diagram of blood coagulation. The blood clotting process can be divided into three stages.
1. When blood vessels are damaged, protein factors in the blood plasma are activated. One of them promotes the destruction of the platelet membrane and the release of important coagulation components. When tissue is injured, tissue coagulation factor enters the plasma. Under the influence of protein factors and calcium ions, an active enzyme is formed thromboplastin.
2. With the participation of thromboplastin, calcium and other factors, an active enzyme is formed from inactive prothrombin thrombin.
3. The resulting active thrombin acts on fibrinogen, converting it into fibrin - monomer, which, under the influence of calcium and other factors, polymerizes into insoluble fibrin - polymer with the formation of a three-dimensional protein network, capturing shaped elements in its structure and forming a clot. Fibrin filaments contract under the influence of platelet ATPase, which is accompanied by thickening of the clot and separation of serum. Fibrin threads are colorless. The color of the clot is due to the presence of colored red blood cells.
To slow down or prevent the clotting process during blood processing, it is subjected to stabilization, using substances of various chemical natures, called stabilizers or anti-coagulants.
The principle of operation of stabilizers first type associated with the removal from the coagulation system of individual components necessary for the conversion of inactive enzymes into their active forms (for example, decalcification of blood due to the binding of calcium ions into insoluble or poorly soluble complexes). For this, phosphates, oxalates, citrates and other compounds are used.
Stabilizers second type inhibit the formation of active thrombin. This group of stabilizers includes table salt, physiological stabilizers (heparin), etc.
The effectiveness of the stabilizer depends on its properties and the type of blood being stabilized.
Blood clotting can be completely eliminated by defibrination- separation of the threads that form fibrin during coagulation.
After adding the stabilizer, the blood is called stabilized, and after removing fibrin - defibrinated.
^ 4. Nutritional and industrial value of blood
The blood of farm animals is a valuable raw material for the production of food, medical, feed and technical products due to its chemical composition and properties.
The nutritional value of blood is determined by its fairly high protein content (16-18%), in which it is close to meat. However, more than 60% of blood proteins are defective hemoglobin, so the biological value of blood is lower than that of meat.
Whole blood and its fractions are used for the production of meat products: blood sausages, brawn, canned food, pates, boiled sausages, etc.
The feasibility of using blood for food purposes is determined not only by the high protein content, but also by the high functional and technological properties of blood and plasma.
The basis of medicinal products produced from blood are proteins containing metals (for example, iron) in an organically bound form. Hematogen, hemostimulin and other drugs are produced from formed elements and whole blood.
The presence of highly soluble proteins in the blood makes it suitable for the production of food and technical dark and light albumins, a foaming agent. Protein feed is produced from blood and its fractions that are not used for one reason or another for food and medicinal purposes.
The blood of slaughtered animals is a valuable protein raw material. The content and properties of blood proteins make it possible to use it for the production of food, medical, feed and technical products. The nutritional value of blood is determined by its high protein content (16-18%) and iron content in organic form. In terms of nutritional and biological value, blood is inferior to meat, since the main blood protein, hemoglobin, is inferior. The use of blood for food purposes is limited by its color due to hemoglobin. The division of blood into fractions allows one to obtain plasma and formed elements. The protein content in plasma is 7-8%. All plasma proteins are complete. After removal, the blood undergoes clotting. To inhibit and prevent this phenomenon, in technological practice, blood is stabilized or defibrated.
Topic 7. Characteristics of meat as an object of technology
1. Industrial concept of meat
2. Meat quality indicators
3. Factors determining meat quality
4. The role of meat in human nutrition
^ 1. Industrial concept of meat
Under meat in the industrial sense we mean a carcass or part thereof obtained during the slaughter of farm animals and poultry and representing totality various fabrics in their natural proportions. In addition to muscle tissue, which is a necessary feature of meat, its composition may include connective, fatty, cartilage tissue, bone, and blood in varying quantities.
The quantitative ratio of tissues in the composition of meat depends on the type, age, breed, sex, conditions of fattening and fatness of the animals, and on the anatomical origin of the part of the carcass. In industrial practice, the natural ratio of tissues in meat is purposefully changed by freeing it from low-value tissues: cartilage, connective tissue, bone.
The quantitative ratio of tissues in meat determines its quality: chemical composition, nutritional value and properties of meat.
^ 2. Meat quality indicators
Meat quality characterized by nutritional and biological value, sanitary and hygienic indicators and functional and technological properties.
^ The nutritional value meat is determined by its chemical composition: the content of proteins, fats, extractives, B vitamins, macro- and microelements; energy value and organoleptic properties.
^ Biological value meat characterizes the quality of protein substances in terms of the content and balance of essential amino acids and protein digestibility, as well as the quality of fats in terms of the content of polyunsaturated fatty acids and fat digestibility.
Important indicators of meat quality that are easily perceived by the senses ( organoleptic) are color, taste, aroma, consistency. These indicators depend on the chemical composition and condition of the meat. They play an important role in shaping the quality of meat products and their absorption by the body.
Color meat is one of the main indicators of quality, assessed by the consumer, by which they judge the presentation of meat and some chemical transformations in it. The color of meat depends on the quantitative content and condition of muscle tissue pigment - myoglobin. The color of adipose tissue in meat is determined by the content of pigments in it - carotenoids.
^ Taste and aroma meat. In their formation, a decisive role is played by extractive substances, contained in small quantities and being the so-called precursors of taste and aroma. Extractive substances are formed after heat treatment of raw meat. The main source of these compounds is muscle tissue, as well as adipose tissue, since low-molecular-weight products of fat transformation determine specific species-specific characteristics of the taste and aroma of meat.
^ Meat consistency. Indicators of meat consistency include tenderness, softness, and juiciness. The consistency of meat is determined by a number of factors:
diameter of muscle fibers;
the content of connective tissue, including intermuscular;
the ratio of collagen and elastin fibers in the connective tissue;
the state of muscle proteins: the degree of their hydration, the degree of myofibril contraction, the level of hydrolytic changes;
fat content within muscle fibers, between muscles and muscle groups (marbling of meat).
For meat, which is the raw material for the manufacture of a wide range of meat products, it is important functional and technological properties (FTS). They determine the behavior of protein as the main component in complex meat systems in interaction with other components (fat, water, minerals, etc.) under the influence of various technological factors.
FTS is understood as a set of indicators: pH value, water-binding, emulsifying, fat-binding, gelling abilities; solubility in water, saline solutions and other properties of meat.
According to the Federal Customs Service, one can judge the degree of acceptability of meat for the production of meat products of a certain assortment group.
^ 3. Factors determining meat quality
It is important to note that the quality of meat obtained during slaughter and processing of animals can change significantly under the influence of various factors, which can be combined into the following groups:
natural factors: species, age, breed, sex, animal fatness, anatomical origin of the cut;
post-mortem biochemical and physico-chemical factors: - autolytic and microbiological changes, oxidative processes;
technological factors: conditions for raising and transporting, pre-slaughter housing of animals; conditions of slaughter and primary processing; parameters of refrigeration processing and storage of meat; conditions of salting, heat treatment, smoking, drying, etc.
^ Types of meat. The tissue composition of meat from different types of animals is given in Table. 9.
Table 9
Average data on the chemical composition of animal and poultry meat are presented in table. 10.
Table 10
As can be seen from table. 9 and 10, the chemical composition of the meat of different animals differs, which is associated with different quantitative ratios of tissues, determined by the activity of the animals’ intravital movements.
Species differences in meat are manifested in color, consistency, smell and taste. Of the industrially significant types of meat, beef is the most intensely colored. The myoglobin content in beef is 0.25-0.37% by weight of muscle tissue, for pork - 0.08-0.23%.
Pork has a more tender consistency. It has less connective tissue than beef, and it is less rough and easier to cook.
Pork has a high fat content, which contains more polyunsaturated fatty acids and is better digestible than beef and lamb. Due to this, the industrial value of pork is determined by the content of both muscle and fat tissue. The technological significance of beef lies in the presence of water- and salt-soluble proteins.
Different types of meat differ in the content and composition of extractive substances, which affects the specific taste and aroma of meat.
The peculiarities of the quantitative ratio of soft tissues of beef, pork, and lamb determine some differences in the amino acid composition of meat.
No significant difference in the digestibility of proteins of different types of meat has been established. The rate of digestibility of beef meat by the human body is on average 82-83%.
Poultry meat contains less connective tissue than animal meat. Its biological value is higher and it is easier to digest than animal meat. Poultry fat contains more polyunsaturated fatty acids than animal fat.
Thus, it can be noted that the species factor has a significant impact on the quality of meat.
^ The influence of age. With age, the morphological and chemical composition of meat, its physicochemical and organoleptic properties change.
As animals and poultry grow, the fat content in meat increases and the amount of moisture decreases. The stiffness of meat increases due to thickening of muscle fibers, an increase in the proportion of elastin fibers in connective tissue and strengthening of collagen fibers, which reduces the degree of hydrothermal breakdown of collagen. For this reason, the meat of young animals has a more tender consistency after heat treatment.
The meat of young animals is also lighter in color.
In pigs, maximum quality characteristics are formed mainly by 8 months, in cattle - at the age of 12 to 18 months.
To ensure relative identity in quality indicators of meat, cattle at slaughter are divided depending on age into 2 groups: animals older than 3 years (meat of adult animals) and animals aged from 3 months to 3 years (meat of young animals).
^ Influence of breed. Animals of different breeds have differences in live weight, yield and quality of meat. Meat breeds of cattle have well-developed muscle and fatty tissue; such meat is more juicy, tender, and tasty. Meat obtained from dairy and meat-and-milk breeds is characterized by an increased content of connective tissue and bone, a lower content of intramuscular fat, and worse organoleptic characteristics.
In meat breeds, muscle tissue develops mainly in the parts of the carcass that produce the most valuable meat - in the back, lower back, and hip areas.
^ Influence of gender. The sex of the animals affects the quality and quantity of meat obtained. Sex differences in the meat of young animals have almost no effect on the quality of the meat, but they are noticeably manifested in adult and old animals. The meat of females is fattier, more tender, and lighter in color. The meat of castrated animals has a marbling pattern. The meat of uncastrated males has a specific unpleasant odor. For this reason, meat from bulls and boars is not allowed for sale, but is used for industrial processing.
In sausage production, special importance is attached to bull meat, which contains more muscle tissue than meat from oxen and cows, and is distinguished by its dark red color.
^ The influence of fatness. All other things being equal, animal fatness has a decisive influence on the yield, tissue and chemical composition of meat. The fatness of animals is determined by the degree of development of muscle and fat tissues and their ratio.
With an increase in the fatness of animals and poultry, the content of the fleshy part and the most valuable muscle and fat tissues in the carcass increases. At the same time, the proportion of collagen and elastin in the total amount of meat proteins decreases and the content of complete proteins increases.
Fatness also affects the content of many other substances in meat. For example, content glycogen in the meat of cattle of average fatness it is about 460 mg%, and in the meat of lean animals - only about 190 mg%.
Depending on fatness, beef, lamb, and pork are divided into categories.
It should be noted that the fatness of animals directly depends on the conditions of their keeping and diet.
^ Influence of anatomical origin. For retail trade and industrial processing, beef, pork half-carcasses, lamb carcasses and poultry carcasses are divided into parts. Different parts of the same carcass differ in the quantitative ratio of tissues, since during the life of the animal these parts bear different loads. The higher the load, the more connective tissue in the meat, the thicker and stronger the muscle and collagen fibers, and therefore, the tougher the meat. The muscles of the neck, chest, abdominal parts of the carcass and limbs are hard-working muscles, and therefore contain more connective tissue than the muscles of the rear and upper parts of the carcass. The best types of meat are located in the dorsal part of the animal; the closer to the head and lower from the back, the worse the grade of meat.
The strength properties of certain muscles are associated with the structure and content of connective tissue in them, with the diameter of muscle fibers.
For example, in the psoas muscle the connective tissue is represented by thin collagen fibers located between the muscle bundles in the form of parallel threads. There are few elastin fibers. As a result, this muscle is highly tender.
The connective tissue of the external pectoral muscle has a rhomboid weave and forms a highly developed perimysium, collagen fibers of considerable thickness and complex weave, and many elastin fibers. All these factors together determine the increased stiffness of a given muscle.
The higher the diameter of the muscle fibers, the higher the rigidity of the meat, since the sarcolemma of thicker fibers is more developed and stronger. With an increase in fiber diameter by 10%, cutting resistance increases by 20-30%.
Differences in parts of an animal carcass in anatomical terms determine the difference in their tissue and chemical composition, and therefore in nutritional value, which dictates the advisability of the combined use of meat half-carcasses during their processing and sale.
^ 4. The role of meat in human nutrition
The importance of meat in human nutrition is determined by its nutritional value, which is primarily associated with the content of biologically complete and easily digestible proteins. In addition, meat is a good source of B vitamins and some minerals, such as iron in organically bound form. Pork is also a supplier of high-quality fats.
Due to the presence of extractive substances and their transformation during heat treatment, meat has high taste and aromatic characteristics, which increases its digestibility by the human body due to its effect on the secretion of digestive juices.
The unique composition and properties of meat together ensure normal physical and mental activity of a person when eating meat and meat products. The physiologically based norm of consumption of meat and meat products, according to the Institute of Nutrition of the Academy of Medical Sciences of the Russian Federation, should be at least 70 kg per person per year.
Topic 8. Autolytic changes in meat
1. The concept of autolysis, stages of autolysis
2. Autolytic changes in carbohydrates, their significance
3. Changes in the protein system of meat, their significance
4. Characteristics of consumer and technological properties of meat at different
Stages of autolysis
5. The influence of various factors on the rate of autolytic changes in meat
6. The concept of meat with an unconventional nature of autolysis
^ 1. The concept of autolysis, stages of autolysis
Autolytic processes are the processes of decomposition of meat tissue components under the influence of enzymes contained in them, which retain their catalytic activity for a long time. Autolysis(Greek autos - itself and lysis - dissolution) begins in the tissues of the animal immediately after slaughter due to the cessation of oxygen supply, the absence of oxidative changes and blood circulation, the cessation of synthesis and energy production, and the accumulation of metabolic products in the tissues.
During autolysis, the quality characteristics of meat change significantly: mechanical strength, organoleptic and technological properties, resistance to microbiological processes.
Changes in the properties of meat develop in a certain sequence in accordance with the main stages of autolysis: paired state - post-mortem rigor (rigor mortis) - resolution of post-mortem rigor - maturation - deep autolysis.
The main external sign of autolysis is a change in the strength properties of meat.
Fresh meat (3-4 hours after slaughter) is characterized by a delicate consistency.
During the first days after slaughter, the development of rigor mortis (at 0-4 o C) leads to an increase in the mechanical strength of meat.
At the stage of rigor resolution (after 2 days of autolysis at 0-4 o C), as well as during ripening, the consistency of the meat improves.
The change in the strength properties of meat during autolysis is associated with a change in the state of myofibrillar proteins of muscle tissue, which are part of the muscle contraction-relaxation system. But autolytic transformations of meat are based on changes in the carbohydrate system.
^ 2. Autolytic changes in carbohydrates, their significance
After slaughter, glycogen resynthesis in meat does not occur due to the lack of oxygen supply, and its anaerobic breakdown begins along the path of phosphorolysis and amylolysis (Fig. 6) with the formation of lactic acid and glucose.
After 24 hours, glycolysis stops due to the depletion of ATP reserves and the accumulation of lactic acid, which suppresses phosphorolysis.
The most important consequence of glycolysis is a shift in the pH of muscle tissue to the acidic side due to the accumulation of organic acids (Fig. 7).
By the time of maximum development of rigor mortis (about 24 hours of autolysis at 0-4 o C), the pH value reaches a minimum value (5.5-5.6). As rigor mortis develops, it slowly increases by 0.1-0.2, without reaching the pH value of fresh meat, and stabilizes at 5.6-5.8.
The shift in pH to the acidic side depends on the glycogen content in muscle tissue at the time of slaughter of the animal, therefore, in healthy and rested animals, the final pH value is always lower than in tired, exhausted animals.
Glucose
Maltose
Polysaccharides
Lactic acid
Pyruvic acid
ATP - H 3 PO 4
During
6-8 days, 10% glycogen
During
90% glycogen
Glycogen
Phosphorolysis (glycolysis)
Amylolysis
Rice. 6. Anaerobic breakdown of glycogen
Rice. 7. Changes in the properties of muscle tissue during the process of autolysis (at 0-4 o C);
The pH value of meat can be measured quite accurately and simply using pH meters, which allows you to track the stages of autolysis and identify meat with an unconventional nature of autolytic changes.
The pH value of meat is the most important indicator of its quality, since changes in the autolysis process entail significant practical consequences, namely:
the resistance of meat to the action of putrefactive microorganisms increases;
the solubility of muscle proteins, their level of hydration, and water-binding capacity decrease due to the pH of the meat approaching the isoelectric point of proteins (4.7-5.4);
swelling of connective tissue collagen occurs;
the activity of cathepsins increases (optimal pH 5.3), causing protein hydrolysis at later stages of autolysis.
^ 3. Changes in the protein system of meat, their significance
The accumulation of organic acids in meat has a significant impact on the state of muscle proteins, which in turn determines the technological properties of meat: consistency, VSS, protein solubility, their emulsifying ability, etc.
At the first stage of autolysis, the level of energy-intensive ATP in meat is important, due to the dephosphorylation (breakdown) of which the process of phosphorolysis of glycogen is carried out. At the same time, dephosphorylation energy ensures the contraction of myofibrillar proteins.
The essence of changes in the protein system of meat at the initial stages of the post-slaughter period is mainly associated with the formation of the actomyosin complex and depends on the presence of energy and calcium ions (Ca 2+) in the system. Immediately after slaughter, the amount of ATP in meat is high, Ca 2+ is bound in the sarcoplasmic reticulum of the muscle fiber, actin is in globular form and is not associated with myosin, which causes a relaxed state of the fibers, a large number of hydrophilic centers and a high BCC of proteins. Shifts the pH of meat to the acidic side starts the mechanism transformations of myofibrillar proteins:
calcium ions are released from the channels of the sarcoplasmic reticulum, their concentration increases;
calcium ions increase the ATPase activity of myosin;
globular actin (G-actin) transforms into fibrillar (F-actin), capable of interacting with myosin in the presence of ATP decay energy;
the energy of ATP breakdown initiates the interaction of myosin with fibrillar actin with the formation of the actomyosin complex and contraction of myofibrils and muscle fibers.
Thus, the decrease in SCD during postmortem rigor is due not only to a shift in the pH of the environment to the isoelectric point of muscle proteins, but also to a decrease in the number of hydrophilic centers of contractile proteins due to the formation of actomyosin. The dynamics of changes in VSS and strength properties of muscle tissue during autolysis are shown in Fig. 7 (page 45).
Post-mortem contractions of fibers begin immediately after slaughter, but unlike intravital synchronous contractions, they are extended in time and occur randomly. The first signs of rigor become noticeable 2-3 hours after slaughter. During the process of rigor rigor, the number of fibers passing into a contracted state gradually increases, reaching the greatest number at the time of maximum development of rigor (by 18-24 hours - autolysis of pork, beef at 0-4 o C), which is consistent with the greatest increase in meat hardness at this stage. autolysis stage (see Fig. 7 on page 45).
Thus, the most important consequences of muscle rigor are:
a significant increase in the mechanical strength (stiffness) of meat;
decreased solubility of muscle proteins, and therefore their emulsifying ability;
decreased degree of protein hydration and SCD;
decreased digestibility of muscle proteins by digestive enzymes;
deterioration of collagen digestibility.
The mechanism of further changes in myofibrillar proteins leading to resolution of rigor is not yet fully understood. However, it has been established that in the first stages of maturation, partial dissociation of actomyosin occurs, accompanied by muscle relaxation and growth of the VSS (see Fig. 7 on page 48).
In addition, at the stage of resolution of rigor mortis, processes of protein proteolysis may begin with the participation cathepsins, which also helps to reduce the strength of muscle fibers.
Further, in the process of ripening meat, proteolysis processes come to the fore and their intensity is determined by the amount of proteolytic enzymes in muscle tissue and their activity, which is positively influenced by acidification of the tissue during autolysis and partial destruction of lysosome membranes.
The process of meat ripening is a set of changes in its properties caused by the development of autolysis, as a result of which the meat acquires a well-defined aroma, taste, becomes soft and juicy, more accessible to the action of digestive enzymes compared to meat at the rigor stage.
It is important to note that the transformation of proteins from the moment of slaughter to the stage of rigor mortis resolution is mainly conformational character(the spatial structure of the protein changes). Meat ripening is related to the process hydrolysis proteins.
The main consequences of ripening meat are:
reducing meat toughness, improving consistency;
increasing the solubility, hydration level and WSS of proteins;
increasing the degree of protein digestibility due to the destruction of the actomyosin complex;
improvement of collagen digestion;
formation of taste and aroma of meat due to enzymatic transformations of proteins and other substances of meat.
Thus, in the process of ripening meat, there is a significant improvement in organoleptic and technological characteristics, nutritional value compared to meat at the rigor stage.
^ 4. Characteristics of consumer and technological
properties of meat at different stages of autolysis
Fresh meat is characterized by high technological properties: water-binding, emulsifying ability, maximum digestibility of collagen, therefore it is advisable to use fresh meat in the production of emulsified (boiled) sausages and boiled piece meat products. This ensures a high yield of products and reduces the likelihood of defects during heat treatment.
The use of fresh meat also provides significant advantages from an economic point of view due to the elimination of losses and energy costs for refrigeration processing.
However, it should be remembered that working with fresh meat requires efficiency (the time interval from the slaughter of the animal to the heat treatment of the products should not exceed 3 hours). Otherwise, it is necessary to use special techniques aimed at inhibiting glycolysis and the formation of the actomyosin complex, namely:
rapid freezing of boneless minced or unground fresh meat;
quick deboning and chopping of fresh meat and salting with the introduction of 2-4% salt;
injection of brine into cuts immediately after cutting fresh carcasses, etc.
^ Meat in the rigor stage is characterized by minimal consumer and technological properties (see Fig. 7 on page 48) and for these reasons is not suitable for processing and consumption, and it must be kept until rigor mortis resolves (about 48 hours at 0-4 o C - average temperature cooling and storage of chilled meat).
^ Resolving rigor accompanied by an improvement in the properties of autolyzing meat raw materials. It becomes suitable for industrial processing. However, culinary standards have not yet reached optimal values and continue to improve during the ripening process during storage and processing of meat.
Deadlines maturation meat depend on its type, part of the carcass, fatness of the animal, and storage temperature.
As a rule, in meat with normal development of autolysis, its tenderness and VSS reach optimum after 5-7 days of storage at 0-4 o C, taste and aroma - by 10-14 days. In this regard, the duration of meat ripening is chosen depending on the method of further technological use of raw materials. In this case, it is necessary to take into account the possibility of microbial spoilage of chilled meat during storage.
^ 5. Influence of various factors
on the rate of autolytic changes in meat
The rate of autolytic processes depends on the characteristics of the animal organism and environmental conditions.
^ Influence of species, age, fatness, anatomical site, condition of the animal before slaughter.
In beef, the full development of rigor mortis occurs after 18-24 hours at a temperature of 0-4 o C. In pork, rigor mortis occurs faster - after 16-18 hours of autolysis due to slow heat removal due to the presence of a layer of lard; in chicken meat - after 5 hours, turkeys - after 8 hours.
Differences in the concentration and activity of muscle enzymes explain the faster development of rigor mortis in the meat of young animals than in old ones.
Rigor mortis occurs more intensely in cuts that bear an active intravital muscle load and have more muscle enzymes (skeletal muscles of the limbs, etc.).
In the muscles of well-fed, rested animals, the maximum development of rigor occurs later than in sick, tired animals, due to the higher glycogen content in muscle tissue.
The most important external factor determining the rate of biochemical processes is the ambient temperature: in the muscles of animals at a temperature of 15-18 o C, maximum rigor mortis occurs after 10-12 hours, and at 0-4 o C - after 18-24 hours.
The development of rigor rigor is sharply inhibited when table salt is introduced into fresh meat, which inhibits the ATPase activity of myosin and the formation of the actomyosin complex.
Rapid freezing of fresh meat also slows down the rate of enzymatic autolytic processes.
These technological techniques make it possible to eliminate or minimize the consequences of rigor mortis, i.e. stabilize the properties of fresh meat.
An increase in the rate of meat autolysis can be achieved by electrical stimulation of steamed carcasses, as a result of which glycolysis reactions are accelerated and the duration of ripening of raw materials is reduced.
^ 6. The concept of meat with an unconventional nature of autolysis
When producing meat, one has to deal with raw materials in which the nature of autolytic processes (patterns of changes in the properties of meat during autolysis) differs significantly from normal development of autolysis (discussed above). In some regions, the amount of such raw materials is more than 50% of the total number of processed animals. Such meat is called meat with an unconventional autolysis character.
Based on available scientific data, it is currently believed that the main reason for the appearance of meat with deviations in properties is the industrial technology of raising animals. Its main characteristics are physical inactivity, intensive fattening, selection for early maturity and meat production. Under these conditions, an increased susceptibility of animals to stress is formed, as a result of which the biochemical processes of autolysis are disrupted.
Meat with deviations during autolysis differs from normal meat in organoleptic (color, consistency) and technological properties (pH, VSS, etc.), taking into account which two types of groups are distinguished:
P - Pale (pale) D - Dark (dark)
S - Soft (soft) F - Firm (hard)
E - Exudative (watery) D - Dry (dry)
Meat with signs of DFD has a pH value above 6.3 24 hours after slaughter, a dark color, a coarse fiber structure, has a high VSS, increased stickiness and is usually characteristic of young cattle exposed to various types of long-term stress before slaughter. Due to the intravital breakdown of glycogen, the amount of lactic acid formed after slaughter in the meat of such animals is small, myofibrillar proteins have good solubility and VSS.
High pH values reduce the microbiological stability of DFD meat and limit its refrigerated shelf life.
Exudative PSE meat is characterized by light color, soft crumbly consistency, low BCC, and sour taste.
Signs of PSE most often have pork obtained from the slaughter of animals with intensive fattening and limited mobility during maintenance. The appearance of PSE-quality meat may also be due to genetic consequences, exposure to short-term stress before slaughter of animals.
After slaughter, intense breakdown of glycogen occurs in muscle tissue, and rigor mortis occurs faster. Within an hour, the pH value of the meat drops to 5.3-5.5. The temperature of the raw materials at this time remains at a high level. As a result, denaturation of sarcoplasmic proteins occurs and their interaction with myofibrillar proteins, which leads to a decrease in the WSS of meat. PSE meat is more shelf stable than DFD meat, but suffers from higher refrigeration shrinkage.
Significant differences in the properties of meat with different types of autolysis determine the advisability of its sorting. It is convenient to sort raw materials by pH value, measured 1-2 hours after slaughter.
The use of electrical stimulation of carcasses determines three quality groups: 1) pH 1 5.3-5.5 PSE; 2) pH 1 5.6-6.2 NOR; 3) pH 1 is greater than 6.2 DFD.
Sorting raw materials according to the nature of autolysis contributes to the rational use of meat during its processing into meat products.
Cells, non-cellular structures, formless matter, which are in certain relationships with each other and adapted to perform certain functions, form the tissues of the body. The variety of tissues existing in the animal body is usually combined into main groups: epithelial (integumentary) tissue; supporting-trophic tissues (i.e. tissues of the internal environment: blood, lymph, connective, adipose, cartilage, bone tissue); muscle tissue; nerve tissue. Each group of tissues performs a large number of different vital functions. The various functions of supporting-trophic tissues include: metabolism, protective, trophic (nutritive), hematopoietic, mechanical functions. The functions of blood are diverse and are determined by the functions of its formed elements.
Lymph is a tissue fluid that performs a drainage function, circulating in a closed lymphatic system consisting of vessels of different sizes. Typically, lymph vessels follow the course of blood vessels, collecting into ducts, which in turn flow into the central venous vessels. Lymph consists of water and inorganic and organic substances dissolved in it (fats, proteins, carbohydrates).
Morphological composition of blood. In addition to water with substances dissolved in it (plasma), the blood contains cells of various shapes that perform important functions.
Erythrocytes are red blood cells. The formation of red blood cells (erythropoiesis) occurs in the bone marrow of the skull, ribs and spine, the lifespan of a dog red blood cell is 107 days, destruction (hemolysis) occurs in the liver and spleen. Typically, red blood cells have the shape of a biconcave disc. In some animals (for example, camel, frog), red blood cells are oval in shape. The contents of the red blood cell are represented mainly by the respiratory pigment hemoglobin, which causes the red color of the blood. An important role in the erythrocyte is played by the cellular (plasma) membrane, which allows gases (oxygen, carbon dioxide), ions (Na, K) and water to pass through. The shape of the biconcave disc ensures the passage of red blood cells through the narrow lumens of the capillaries. In the capillaries they move at a speed of 2 centimeters per minute, which gives them time to transfer oxygen from hemoglobin to myoglobin. Myoglobin acts as a messenger, taking oxygen from hemoglobin in the blood and passing it on to cytochromes in muscle cells. On the surface of the lipoprotein membrane of the erythrocyte there are specific antigens of a glycoprotein nature - agglutinogens - factors of blood group systems (more than 15 blood group systems have been studied at the moment: A0, Rh factor, Duffy, Kell, Kidd), causing agglutination of erythrocytes.
Functions of red blood cells: respiratory - the function is performed by red blood cells due to the pigment hemoglobin, which has the ability to attach and release oxygen and carbon dioxide. The nutritional function of red blood cells is to transport amino acids to the cells of the body from the digestive organs. Protective - determined by the function of red blood cells to bind toxins due to the presence on their surface of special substances of a protein nature - antibodies. Enzymatic - due to the fact that red blood cells are carriers of various enzymes.
Leukocytes- white blood cells - a heterogeneous group of blood cells of different appearance and functions, identified on the basis of the absence of independent coloring and the presence of a nucleus. The main sphere of action of leukocytes is protection. They play a major role in the specific and nonspecific protection of the body from external and internal pathogenic agents, as well as in the implementation of typical pathological processes. All types of leukocytes are capable of active movement and can pass through the capillary wall and penetrate into tissues, where they perform their protective functions. The content of leukocytes in the blood is not constant, but changes dynamically depending on the time of day and the functional state of the body. Thus, the number of leukocytes usually increases slightly in the evening, after eating, as well as after physical and emotional stress. White blood cells vary in origin, function and appearance. Some of the white blood cells are able to capture and digest foreign microorganisms (phagocytosis), while others can produce antibodies.
Based on morphological characteristics, leukocytes stained according to Romanovsky-Giemsa are traditionally divided into two groups: granular leukocytes, or granulocytes- cells with large segmented nuclei and revealing a specific granularity of the cytoplasm; Depending on the ability to perceive dyes, they are divided into neutrophilic, eosinophilic and basophilic. Non-granular leukocytes, or agranulocytes- cells that do not have a specific granularity and contain a simple non-segmented nucleus, these include lymphocytes and monocytes. The ratio of different types of white cells, expressed as a percentage, is called the leukocyte formula. Eosinophils are leukocytes containing a bilobed nucleus and granules that stain red with eosin. They regulate allergic reactions, their number increases with allergies, as well as in cases of infection with worms.
Thrombocytes(blood platelets) - small flat colorless bodies of irregular shape, circulating in large quantities in the blood; These are postcellular structures, which are fragments of the cytoplasm of giant bone marrow cells - megakaryocytes - surrounded by a membrane and devoid of a nucleus. Formed in red bone marrow. The life cycle of circulating platelets is about 7 days (with variations from 1 to 14 days), then they are utilized by reticuloendothelial cells of the liver and spleen. There are 5 forms of platelets: young (10%), mature (80-85%), old (5-10%), irritable forms and degenerative forms. The main function of platelets is to participate in the process of blood clotting (hemostasis) - an important protective reaction of the body that prevents large blood loss when blood vessels are injured. It is characterized by the following processes: adhesion, aggregation, secretion, retraction, spasm of small vessels and viscous metamorphosis, the formation of a white platelet thrombus in microcirculatory vessels with a diameter of up to 100 nm.
Another function of platelets is angiotrophic - nutrition of the endothelium of blood vessels.
Blood (sanguis) is a type of connective tissue. Blood consists of plasma and formed elements and is formed through the interaction of many organs and systems of the body. The formed elements of blood include red blood cells, white blood cells and platelets. The formed elements of blood make up about 45% of its volume, and 55% is the share of its liquid part - plasma.
In addition to formed elements and plasma, the blood system includes lymph, organs of hematopoiesis and immunopoiesis (red bone marrow, thymus, spleen, lymph nodes, accumulations of lymphoid tissue). All elements in the blood system are interconnected histogenetically and functionally and obey the general laws of neurohumoral regulation.
On average, the amount of blood is 6–8% of a person’s body weight; With a weight of 70 kg, the blood volume is approximately 5 liters.
Blood is the most mobile medium in the body, sensitively reacting to very minor physiological and, especially, pathological changes in the body.
By recording and assessing the dynamics of changes in blood composition, the clinician seeks to understand the processes occurring in various organs and tissues. Correct and early diagnosis of the disease, appropriate treatment, and correct prognosis of the course of the disease are often completely impossible without data from morphological and biochemical blood tests. In this case, repeated studies are extremely important, since the dynamics of hematological changes largely reflect the dynamics of the pathological process.
General information about hematopoiesis
All blood cells develop from a common pluripotent stem cell, the differentiation (transformation) of which into various types of blood cells is determined both by the microenvironment (reticular tissue of the hematopoietic organs) and by the action of special hematopoietins.
The processes of cell destruction and new formation are balanced and, therefore, the consistency of the quantity and composition of blood is maintained.
Close interaction between the organs of hematopoiesis and immunopoiesis is carried out through migration, circulation and recycling of blood cells, neurohumoral regulation of hematopoiesis and blood distribution.
Under normal conditions, bone marrow hematopoiesis not only covers the needs of the body, but also produces a fairly large supply of cells: there are 10 times more mature neutrophils in the human bone marrow than in the bloodstream. As for reticulocytes, there is a three-day supply of them in the bone marrow.
Of exceptional importance for practical medicine and physiology is the question of what should be considered the hematological norm.
In table Table 1 shows the average statistical values of hemogram indicators for residents of Kharkov, calculated by the authors of this manual for the last 3 years. These indicators were obtained in the clinical laboratory of the Clinical Diagnostic Center of the National Pharmaceutical University.
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Table 1. Average hemograms of healthy residents |
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| Indicators | Floor | X Sx ± |
| , ×10 12 | husband. | 4.39 ± 0.58 |
| wives | 4.21 ± 0.43 | |
| , g/l | husband. | 137.48 ± 15.32 |
| wives | 121.12 ± 14.78 | |
| 0.90 ± 0.04 | ||
| husband. | 0.46 ± 0.07 | |
| wives | 0.40 ± 0.06 | |
| Reticulocytes, % | 7.20 ± 0.75 | |
| Platelets, ×10 9 /l | 315.18 ± 58.40 | |
| ESR, mm/hour | husband. | 4.25 ± 2.15 |
| wives | 3.10 ± 1.86 | |
| , ×10 9 /l | 5.84 ± 1.42 | |
| P/nuclear, % | 1.58 ± 0.88 | |
| C/nuclear, % | 61.42 ± 8.74 | |
| , % | 2.35 ± 1.41 | |
| , % | 31.78 ± 6.95 | |
| , % | 4.04 ± 2.19 | |
The average values of the normal content of leukocytes, erythrocytes and hemoglobin according to various authors have not undergone significant changes over the past hundred years. Consequently, we can conclude that hematopoiesis is stable, despite changes in the human environment caused by the scientific and technological process.
Of other cellular elements, the following are important:
Plasmocytes (plasmocytus)
Plasmocyte (plasmocytus) is a cell of lymphoid tissue that produces immunoglobulins. It has a wheel-shaped nucleus and sharply basophilic vacuolated cytoplasm (Fig. 14).
In a healthy person, plasma cells are present in the bone marrow and lymphatic tissues, and less often in the peripheral blood.
Appear in the blood in small quantities (0.5–3%) during any infectious and inflammatory process:
- viral infections (rubella, scarlet fever, measles, whooping cough, viral hepatitis, adenoviral infection, infectious mononucleosis),
- tumors,
- serum sickness,
- collagenoses,
- after irradiation.
LE cell phenomenon
LE cell phenomenon includes the following formations:
- hematoxylin bodies,
- "sockets"
- LE cells.
Of the three mentioned formations, the most important is the detection of LE cells.
LE cells(lupus erythematosus cells, Hargraves cells) - mature granulocytes, the nuclei of which are pushed to the periphery by the phagocytosed nuclear substance of another cell (Fig. 15).
Appears when:
- systemic lupus erythematosus (80% of patients);
- rheumatoid arthritis;
- acute hepatitis;
- scleroderma;
- medicinal lupus-like syndromes (taking anticonvulsants, procainamide, methyldopa).
Morphological blood test
A complete morphological study of human blood is very extensive and time-consuming, and therefore is carried out only in special cases or for scientific purposes.
When examining a patient, a blood test is usually used, which is called a general clinical analysis.
This analysis includes the study of the quantitative and qualitative composition of blood cells:
- determination of hemoglobin amount;
- determination of the number of red blood cells;
- calculation of color index;
- determination of the number of leukocytes and the ratio of individual forms among them;
- determination of erythrocyte sedimentation rate (ESR).
In some patients, depending on the nature of the disease, additional studies are performed:
- reticulocyte count,
- platelets,
- determination of clotting time.
For clinical analysis, peripheral blood is taken. In this case, it is advisable to take blood from the patient in the morning, before meals, since food intake, medications, intravenous injections, muscle work, temperature reactions and other factors can cause various morphological and biochemical changes in the composition of the blood.
Blood collection technique
Blood collection should be carried out wearing rubber gloves, observing the rules of asepsis, treating the gloves with 70° alcohol before each collection;
Blood is taken from the terminal phalanx of the 4th finger of the left hand (in special cases, it can be taken from the earlobe or from the heel - in newborns and infants);
The puncture site is first wiped with a cotton swab soaked in 70° alcohol; the skin must dry, otherwise the drop of blood will spread;
To puncture the skin, use a disposable sterile needle scarifier;
The puncture should be made on the side surface of the finger, where the capillary network is thicker, to a depth of 2–3 mm; it is recommended to make the incision (puncture) across the fingerprint lines of the finger, since in this case the blood flows easily and abundantly;
The first drop of blood should be removed, as it contains a large amount of tissue fluid; after each blood draw, its residues on the finger are wiped off and the subsequent draw is made from a newly protruding drop;
After taking blood, a new sterile swab moistened with 70° alcohol is applied to the wound surface.
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