Hematology(redirected from panic value)
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the study of blood and the hematopoietic system, their structure and functions, and their diseases and methods of treatment.
Modern hematology makes use of the techniques of optical, electron, phase contrast, and fluorescence microscopy, microcinematography, microscopic histochemistry, and cytochemistry. Paracentetic biopsy (obtaining the cells and tissues of the bone marrow, lymph nodes, spleen, and liver during life) is widely used for diagnostic purposes. Biochemical, enzymological, cytogenetic, chemicogenetic, spec-trocytophotometric (including the study of deoxyribonucleic and ribonucleic acids), radiological (isotopic), and immunological methods, electrophoresis and immunoelectrophoresis, tissue cultures, and cytokinesis are also used in hematological study.
Hematology as a science began with the discovery of red blood cells in man and animals by the Italian anatomist M. Malpighi (1661) and the Dutch biologist A. Leeuwenhoek (1673), and of white blood cells by the English surgeon W. Hewson. Thrombocytes were discovered in 1877-78 by the French scientist G. Hayem and in 1882 by the Italian scientist G. Bizzòzero. In 1892 the Russian scientist E. Metchnikoff substantiated the theory of phagocytosis. The theory of the reticuloendothelial system was later elaborated by the German pathologist L. Aschoff.
The initial clinical phase in the development of hematology was characterized primarily by the detailed description of the symptoms and the clinicomorphological classification of various blood diseases. Study of the causes and mechanisms of development of blood diseases became possible after the French physician L. C. Malassez introduced into laboratory practice a special chamber (1870; later perfected) for counting the cellular (formed) elements of the blood and the German scientist P. Ehrlich proposed (1878) methods for staining the blood (perfected in 1891 by the Russian scientist D. L. Romanovskii).
The systematic description of hematic diseases began in the 19th century, although many of these diseases were known long before. Leukemias were described by the German scientists R. Virchow in 1845 and E. Neumann in 1870, pernicious anemia by the English physician T. Addison in 1855 and by the German physician A. Biermer in 1872, aplastic anemia by P. Ehrlich in 1888, and hemolytic anemia by G. Hayem in 1898, by the German scientist O. Minkowski in 1900, and by the French scientist A. Chauffard in 1907.
One of the principal concerns of hematology is the study of blood formation (hematopoiesis). A leading factor in the development of the field was the monophyletic (unitarian) theory of hematopoiesis, proposed by the Russian scientists A. A. Maksimov and A. N. Kriukov and by the German hematologist A. Pappenheim early in the 20th century. According to this theory, all blood cells develop from cells of the reticular tissue through the hemohistoblast and hemocytoblast stages. Additional theories of hematopoiesis included the dualist theory of the Swiss hematologist O. Naegeli and others and the trialist (polyphyletic) theory of L. Aschoff and others. The origin and mechanism of development of various systemic shifts in the correlation of formed elements can be explained from the standpoint of the monophyletic theory.
The clinicomorphological study of blood diseases led to the creation of so-called classical hematology, which developed rapidly after the introduction of important diagnostic techniques: the sternal puncture, by the Soviet physician M. I. Arinkin (1927), and the cytological diagnosis of puncture samples from the lymph nodes, spleen, and liver, by the Soviet physician I. A. Kassirskii (1938-42). These techniques made possible the more precise diagnosis intravitam of many blood diseases.
Anemic conditions are another major concern of hematology. Research in this field is being conducted at the molecular and submolecular levels in hematological institutes both in the USSR and abroad. Hematologists are working to establish the norms of hemoglobin concentration and the standards for its measurement. The epidemiology and geomed-icine of iron deficiency anemias and the question of iron exchange have been studied in detail. Classifications of the anemias and their differentiated treatment, including the use of drugs, have been developed by the Soviet physicians M. S. Dul’tsin and G. A. Alekseev. Radiological investigations have played a major role in the study of hematopoiesis and the mechanism of development (pathogenesis) of anemias. Radioactive chromium (51Cr), tritium thymidine, and other chemicals are used in tagging plasma, erythrocytes, thrombocytes, and leukocytes. Introduction of tagged erythrocytes into the bloodstream makes it possible to determine the total volume of circulating red blood cells and their life-span as well as the amount of blood lost in hemorrhages. The absorption of iron in the gastrointestinal tract, the rate of disappearance of iron from the plasma, its appearance in the red blood cells, and its accumulation in deposits are being studied with the iron isotope 59Fe and a common radiation counter. In 1929 the American scientist W. Castle discovered the cause of pernicious anemia in a deficiency of vitamin B12 (cyanocobalamin). With tagged cobalt (60Co), the paths of B12 activity in the organism and the delicate mechanisms by which the vitamin influences the differentiation of erythroblasts were determined.
Soviet hematologists also take into consideration the social causes of anemia. According to the data of the World Health Organization, hemoglobin concentrations have decreased slightly, primarily in women, all over the world. This phenomenon is particularly widespread in countries where the population is poorly nourished and in places where the practice of certain religious ceremonies and other rituals lead to the violation of the most important nutritional standards, to protracted breast feeding (as long as three years), and to the lowered protein content of women’s diets. The pathogenesis of almost all hemolytic anemias was elucidated in the 1960’s by the English scientist J. Dacie and the Soviet scientists Iu. I. Lorie, L. I. Idel’son, and others. Research is under way on hereditary deficiency of enzymes, such as of glucose-6-phosphate dehydrogenase, the lack of which brings about an intolerance for drugs and certain foods that is manifested by acute disintegration of the blood (hemolysis).
Familial (congenital) spherocytic hemolytic jaundice is being studied at the molecular level. Removal of the spleen in those suffering from this condition results in complete recovery.
Modern hematology has made great progress in the study of blood clotting. The Russian scientist A. A. Shmidt was a pioneer in this field; in the middle of the 19th century he advanced the enzymatic theory of blood coagulation. Between the 1940’s and 1960’s the mechanism of action of a number of clotting and anticlotting factors, the equilibrium between which prevents intravascular thrombosis, was defined more precisely through data gathered by the Soviet scientists B. A. Kudriashov, M. S. Machabeli, Z. S. Bar-kagan, the American scientists M. Stefanini and W. Dame-shek, and others. Disturbances of the clotting system (hemorrhagic diatheses) constitute an entire field of hematology. Effective methods have been found for treating certain of these disturbances, such as splenectomy for thrombocytopenic purpura and introduction of adenosine triphosphate for thrombasthenia. Drugs have been developed to prevent the formation of thrombi, including heparin and fibrinolysin, or, on the other hand, to intensify the activity of the clotting system and to thicken the vascular wall, including drugs such as Є-aminocaproic acid, vicasol (a vitamin K preparation), rutin, serotonin, and protamine sulfate.
A new branch of hematology—immunohematology, or the study of the normal immunological characteristics of hematic elements and the immunological factors and mechanisms that may be at the root of a number of blood diseases—made rapid advances in the 1950’s and 1960’s. The field is also concerned with the study of blood groups and the so-called Rh factor, the bases of blood transfusion and one of the most important divisions of hematology. Immunohematology also deals with the problems of autoimmunization, or the formation of antibodies to one’s own tissues, which is pathological when the number of such antibodies becomes excessive. The formation of antibodies to foreign tissues, finally, is an important concern in transplantation.
Hematology in its various aspects (clinical, chromosomal, biochemical, genetic, and geogenetic) also studies the approximately 50 hereditary blood diseases. Isoserology, which investigates the heritable group properties of blood (according to the ABO system, the Rh factors, and so on), has made transfusions of ABO-compatible and Rh-compatible blood almost completely safe. The Philadelphia (Ph) chromosome was discovered as a result of the cytogenetic studies of chronic myeloid leukemia. The chromosome is formed by the loss of approximately half of the long arm of one of the chromosomes of the 21st-22nd pair; the ring-shaped chromosome can be observed in radiation damage.
Moreover, the phenomenon of aneuploidy, that is, the addition (hyperploidy) or loss (hypoploidy) of one or more chromosomes, has been found in particularly acute leukemias. The genetic origin of leukemias is confirmed by the fact that the disease often develops in identical twins. Hematologists have made great progress in studying the hereditary nature of conditions in which an enzyme deficiency gives rise to a severe pathology, such as hemolysis or hemorrhagic diathesis. The hereditary diseases include the hemoglobinopathies, which are very common in Africa and the Mediterranean area. Hemoglobinopathies are genetically determined impairments of hemoglobin synthesis in which one of the polypeptide chains of globin is altered; in the Mediterranean form of the disease, heme synthesis is impaired as well.
The study of leukemias is another branch of hematology. Several chemical agents have been developed for rational treatment (stabilization and support) in chronic forms of the disease.
Research in hematology in the USSR is conducted by institutes of hematology and blood transfusion, clinics of medical institutes, and scientific laboratories. In 1926 the Soviet scientist A. A. Bogdanov organized the world’s first scientific institute of blood transfusion, today called the Central Institute of Hematology and Blood Transfusion. This was followed by the creation of the Azerbaijan, Armenian, Byelorussian, Georgian, Kiev, Kirov, Leningrad, L’vov, Ukrainian, and Uzbek institutes. There is an International Society of Hematology and an International Society of Blood Transfusion. Specialized journals devoted to hematology are published in the USSR (Problemy gematologii i perelivaniia krovi; 1956—), West Germany (Blut: Zeitschrift für die gesamte Blutforschung; Munich, 1955—), France (Nouvelle Revue française d’Hématologie; Paris, 1961—), Great Britain (British Journal of Haemathology; Oxford, 1955—), the United States (Blood; New York, 1946—), Italy (Haema-tolagica; Naples, 1920—), Japan (Acta haematologica Japanica; Kyoto, 1937), Hungary (Haematologia; Budapest, 1967—), Rumania (Documenta haematologica; Bucharest, 1966—), and elsewhere.
REFERENCESDul’tsin, M. S. “Uspekhi sovetskoi gematologii za 50 let.” Problemy gematologii i perelivaniia krovi, 1967, vol. 12, no. 10.
Kassirskii, I. A., and G. A. Alekseev. Klinicheskaia gematologiia, 4th ed. Moscow, 1970. (Bibliography.)
Heilmeyer, L., and A. Hittmair. Handbuch der gesamten Hämatologie, vols. 1-5. Munich, 1957-64.
I. A. KASSIRSKII