Naoki Arizono

Phenotypic changes in mast cells proliferating in the rat lung following infection withNippostrongylus brasiliensis

SummaryNumerous mast cells appear in rat pulmonary granulomas associated with infection by the nematodeNippostrongylus brasiliensis. The kinetics and histochemical characteristics of these mast cells were studied and compared with those of intestinal mucosal mast cells. The number of lung mast cells showed a distinct increase 2 weeks after infection and then gradually decreased. In a study using bromodeoxyuridine (BrdU), which is incorporated into cellular DNA at the S-phase, mast-cell labeling was highest 12–13 days after infection, and returned to the normal level 21 days after infection. This indicates that lung mast cells proliferate for only a short time. Intestinal mucosal mast cells showed a similar pattern. A parallel increase in globule leukocytes in the bronchus and trachea was also observed. The proliferating lung mast cells in the early period were stained with alcian blue but were negative for berberine and avidin-biotin-peroxidase complexes (ABC). In a lung extract, type II protease, which has been reported to be confined to mucosal mast cells, increased until the 14th day, and decreased thereafter. This indicates that lung mast cells, at least in the initial stage of proliferation, are similar to intestinal mucosal mast cells in terms of their cell kinetics and histochemical characteristics. However, histochemical studies of mast cells at a later stage of infection showed a different result. After 12 weeks of infection when the mast-cell density was still high, almost all the lung mast cells became positive with berberine and/or ABC, both of which are supposed to be bound to heparin within mast cell granules. The latter result shows that after a long period of infection, lung mast cells resemble connective tissue mast cells. Thus, a phenotypic change in mast cells from the mucosal to the connective tissue type may have occurred.

Kinetics and staining properties of mast cells proliferating in rat small intestine tunica muscularis and subserosa following infection with Nippostrongylus brasiliensis

Mucosal mast‐cell hyperplasia occurs in the rat small intestine mucosa after infection with Nippostrongylus brasiliensis. In the present study, the number of mast cells was found to increase in the muscularis and subserosa as well as in the mucosa of rat small intestines 2–3 weeks after infection with this nematode. Mast cells in the muscularis were stained blue by the alcian blue/safranin sequence and did not bind berberine sulfate. The staining was blocked when tissues were fixed in neutral formalin. The increase in mast cells was transient and gradually disappeared; the half‐life was 40 days. After an intravenous administration of compound 48/80, mast cells in the muscularis did not discharge granules. The results indicate that these mast cells were of the mucosal type. The mast cell phenotype in the muscularis did not change even 12 weeks after infection. Mast cells in the subserosal tissue were first of the mucosal type as were those in muscularis. After 8–12 weeks, however, many subserosal mast cells became positive for berberine sulfate and safranin. These results show that mucosal‐type mast cells do not undergo phenotypic changes during the period of observation when these cells appear in the muscularis but the phenotypic expression may change as the cells arise in subserosal tissue.

MORPHOMETRIC ANALYSIS OF HUMAN NEUROMUSCULAR JUNCTION IN DIFFERENT AGES

Application of morphometric analysis to the study of neuromuscular junction is helpful to the quantitative approach of ultrastructural changes. In this study, twelve autopsied subjects of different ages were examined on the ultra‐structure of neuromuscular junctions using morphometric analysis. The postsynaptic area and postsynaptic membrane length were significantly greater in adults than in infants. The results indicate that the number and/or depth of the secondary synaptic clefts of adults are greater than those of infants. In the aged subjects, presynaptic membrane length and postsynaptic membrane density showed a significant decrease. The latter observations were thought to be the results of regressive changes of pre‐ and postsynaptic structure with aging. The variations of each structural element were also studied. The large variations were found in the postsynaptic area, postsynaptic membrane length, and membrane length ratio of adults and aged group. On the other hand, variations in postsynaptic membrane density were small in all age groups. The importance of the knowledge of these age related changes and variations in the studies of neuromuscular junction was discussed. ACTA PATHOL. JPN. 34: 1243–1249. 1984.

Activation of human complement by rat peritoneal mast cells and its inhibition by a rat serum factor

The effects of normal sera from humans, rats, and guinea pigs on unsensitized rat peritoneal mast cells were studiedin vitro. Five to 20% fresh human sera induced mast cell death and substantial histamine release. The factor was heat labile. Neither hereditary C3-deficient sera nor experimentally Clq-depleted sera showed cytotoxicity. The CH50 activity of human serum was decreased to about one half after a 15-min incubation with 2×106 mast cells/ml at 37°C. The cytotoxic activity and CH50 reduction were completely eliminated by an addition of 10 mM Mg-EGTA to the serum. These data demonstrated that unsensitized rat mast cells served as both the initiator and target of complement activity when human serum was used as a complement source. Requirements of both Ca++ and Clq suggested the activation of the classical pathway of complement. Fresh 5–20% sera from rats and guinea pigs, on the other hand, showed neither cytotoxicity nor CH50 reduction. Furthermore, these sera strongly inhibited the human serum-induced reaction. The latter results indicated the presence of a modulating factor in rat and guinea pig sera, which inhibits mast cell associated complement activation.