Japanese Journal of Veterinary Research;Volume 10, Number 4

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HISTOLOGICAL AND HISTOCHEMICAL STUDIES ON THE POSTNATAL LYMPH NODES OF THE CAT : ABOUT STRUCTURAL VARIATIONS WITH RELATION TO DIFFERENTIATION, LOCATION AND AGE

SUGIMURA, Makoto

Permalink : http://hdl.handle.net/2115/1770
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Abstract

Detailed histological and histochemical observations on the postnatal lymph nodes of the cat were made with special reference to the relation between structural variations of the lymph node and the degree of differentiation, location or age, on the basis of the writer's detailed macroscopical study of the cat lymphatic system. A. Structural Variations as Regards the Degree of Differentiation The degree of differentiation of the lymph node was determined by the existence of trabeculae, medullary cords, secondary nodules, medullary and intermediate sinuses, and the distinction between and arrangement of the cortex and medulla. On the basis of the degree of differentiation, the lymph nodes in the adult cat were classified into five types, D.I〜D.V. On the basis of the ontogeny and phylogeny of the lymph node, it was suggested that the writer's D.I type is the most primitive structure and that the D.II type is a somewhat advanced form, though most structural elements are absent. These two types were concluded to be an embryonic node. Type D.III corresponds to the structure of JOB's type II, observed in the rat lymph nodes, and was frequently found in the infant cat. Accordingly this type was treated as an immature node, or intermediate type. The D.IV and D.V types showed the ordinary developed structure of the lymph node. Type D.V was a more advanced form than D.IV type with respect to the cortex arrangement. The two types were treated as a mature node. In the adult cat, the occurrences of each type differed among the occurrence groups, which were macroscopically classified on the basis of the ratio of occurrence and appearances of the afferent lymphatic vessels, but the occurrences of each type were not related intimately with the regional groups, which were classified as the location and regional lymphatic drainage area. More particularly, in occurrence group O.I, which occurred constantly and consisted usually of large main lymph nodes, the mature node was almost the only sort found. In group O.II, which occurred inconstantly and consisted usually of small main lymph nodes, and in group O.III, which included accessory nodes of the main lymph nodes in the lymphcenter, immature and embryonic nodes were principally found. The writer suggested that these embryonic and immature nodes are an excess-developed lymph node and become atrophic at an early period, however, that they may be able to perform a compensatory function of the main node under certain conditions. B. Structural Variations as Regards the Regional Difference Conspicuous regional difference was found as to the development of the medullary trabeculae, irregularity of the cortex arrangement, width of the medulla, occurrence of the medullary nodule and of the secondary nodule of the medulla and fatty involution. Slight regional difference was also detected as to development of the cortical trabeculae, and of the cortex layer, size of secondary nodule, width of the medullary sinus and occurrence of the reticular fiberless sinuses. The relation between these findings and regional groups are summarized, as shown in table 28. As shown in the table, the relationships fall into 7 categories. Group 1 (large intestinal, small intestinal, submandibular and retropharyngeal nodal groups) : This group is peculiar in having the wide medullary sinus and medulla, and to show usually the conspicuous occurrence of the medullary nodule and irregularity of the cortex arrangement. The development of the trabeculae is also conspicuous, but fatty involution is poor and rarely found. Group 2 (hepatogastric group) : This group has also wide medulla, wide medullary sinuses and poor fatty involution, but development of the trabeculae and disorder of the cortex arrangement are not conspicuously found. Group 3 (gastrolienal group) : In this group, structural peculiarity is poor. Group 4 (parotid and tracheobronchial groups) : This group is similar to Group 3,but conspicuous fatty involution appears. In details, the tracheobronchial group, which has numerous dust cells, can be distinguished from the parotid group. Group 5 (lumbar and iliac groups) : This group is similar to Group 4,but has somewhat wide medulla. Group 6 (cervical, axillar, inguinal and popliteal groups) : The special features of this group are very well developed medullary trabeculae and conspicuous fatty involution. Group 7 (mediastinal group) : This group is somewhat similar to Group 6,but the wide medulla and narrow cortex are peculiar in this group. On the basis of these findings, it may be considered that the old disputes as regards regional difference are owing to insufficient observation of the lymph node, obtained from only a few locations, usually only two or a few. C. Structual Variations as Regards the Age-Difference Age-differences were pointed out with respect to the development of the trabeculae and of the cortex layer, irregularity of the cortex arrangement, occurrence of the medullary nodule, occurrence and type of the secondary nodule, breadth of the subcapsular sinus, and fatty involution. These age changes were detected from birth till the age of 2 or 4 months, being continued during occurrence of uncomplete structure of the lymph node, but at about 4 months old, the mature structure was completed, after which neither chronological development nor atrophy were usually found, except for the type of the secondary nodule. Moreover, regional difference as regards the degree of maturity was found as to the cortex layer, trabeculae, medullary nodule, secondary nodule and fatty involution from birth to 4 months old, but afterwards, such regional change owing to the degree of maturity did not show a chronological tendency with advance in age. In other words, age differences of the lymph node were not found in cats over 4 months old, but regional differences became conspicuous. D. Two Divisions of the Lymphatic Parenchyma as Regards the Distribution of Several Kinds of Cells and a Pattern of the Lymph Node The writer could histochemically identify several kinds of cells, small lymphocytes, lymphoblasts, plasma cells, RUSSELL's bodies, mast cells and sudanophilic PAS-positive cells, whose substance may be regarded as glycolipin and a lipofuscin-like substance. Moreover, in the infant and juvenile cats, less than 4 months old, conspicuous ectopic myelopoiesis was sometimes found in the lymph nodes. In this report, the distribution of the above various cells has been described in detail. On the basis of his observations, the writer could classify the lymphatic parenchyma except for the secondary nodule into two types, proper and varied ; the "proper parenchyma" is composed of a sponge-like framework of reticular cells and free cells, densely filled small lymphocytes and scattered lymphoblasts, in the meshes of the stroma, but there were no other free cells in this parenchyma. The "varied parenchyma" is composed of slit-like meshes of finer reticular fibers than those of the "proper" one and of various free cells, such as lymphocytes, plasma cells, RUSSELL's bodies and sudanophilic PAS-positive cells, in the meshes. Moreover, conspicuous ectopic myelopoiesis, in the juvenile cat, and fatty involution, in the cat older than 4 months, appeared in this second type parenchyma. The "varied lymphatic parenchyma" appeared in the medullary cords, juxta-medullary zone and internodular zone of the cortical mass. On the other hand, the "proper" one occupied the cortical mass, except for the secondary nodules and above two zones, and medullary nodules except for the secondary nodules. The distinction between the two parenchymas became clear under certain conditions in which large numbers of plasma cells or conspicuous ectopic myelopoiesis appeared in the "varied" one, contrary to the old view. After referring to the above classification of the lymphatic parenchyma, a normal pattern of the cat lymph node was newly drawn, as shown in schema 1.

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