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The histologic effect of 400 mg/M*/day of hydrocortisone, given alternatively from day 7 to day 19 after birth, was studied on the spleen of the immunologically immature rat. Two days after the cessation of treatment, the penarteriolar lymphatic sheaths were found to be largely depleted of small lymphocytes. Immunoperoxidase studies confirmed a depletion of T lymphocytes. The effects of hydrocortisone on the thymus seem to be more important than its direct lymphocytolytic effect in producing this splenic lesion. In contrast, no apparent change in the number of medium-sized B lymphocytes in the marginal zone was detected. Medium-sized B lymphocytes of the spleen, reported to be responsible for IgM synthesis, appeared to be subjected to a different mechanism of hydrocortisone action, other than lysis, resulting in a decrease in antibody production. Primary folliclcs were not seen in spleens of hydrocortisone-treated rats. Twentythree days after treatment, spleens had a histologically normal appearance.Keywords. Lcwis rat; hydrocortisone sc; spleen; histology; T and B lymphocytes; immunoperoxidase INTRODUC~~ON In the previous article, we showed that immunologically immature rats treated with alternate-day hydrocortisone followed by a recovery period suffered from overall growth retardation, undergrowth followed by overgrowth of the thymus and spleen, slowly reversible Iymphocytopenia, and reduced IgM concentrations.The effect of hydrocortisone on the immature immune system may be partially due to its action on the thymus (6) as well as a possible direct effect on antibody-forming cells in tissues.To complete the picture, it is necessary to investigate the effect of such a regimen on lymphoid organs. Many studies have confirmed the destructiveeffects of corticosteroid on lymphoid tissue of steroid-sensitive species (2, 1 I , 12). Others have reported the sensitivity of small lymphocytes present in lymphoid organs to the effect of hydrocortisone (1, 14). In the present article, the effect of alternateday hydrocortisone therapy on the histology of the

ABSTKACTThe histologic effects of the alternate-day hydrocortisone therapy (400 mg/M2 from day 7 to day 19 after birth) were studied on the mesenteric lymph nodes of immunologically immature rats. In rats sacrificed 2 days following the cessation of therapy, depletion of lymphocytes of the thymus-independent area was apparent. Smaller lymphocytes were more susceptible to the effect of hydrocortisone than larger ones. The absence of primary follicles, normally present at this age, suggested a possible retardation in development of the immune system. B lymphocytes appeared to be the target of the direct lymphocytolytic effect of hydrocortisone. In rats sacrificed 23 days following the treatment, immunological maturity was achieved, indicating the reversibility of the hydrocortisone effect.

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In the present experiment 164 pregnant white Wistar rats were used to study the effect of Naja haje (Egyptian cobra) venom on the developing kidney. The rats were divided into 3 groups; a control group, a group receiving one LD₅₀ of N. haje venom and the third injected with % of LD₅₀. The injection was performed at different stages of gestation. After birth, the neonates of group I and III and embryos of group II were examined histologically, histochemically and electron-microscopically. Both lethal and sublethal doses of N. haje venom produced haemorrhages and vascular congestion of the developing kidney. The lethal dose had degenerative effects on the podocytes and endothelium. Tubular damage appeared mainly as mitochondrial degeneration and bud-like extension, protrusions of cytoplasm and vacuolization. The succinic dehydrogenase enzyme showed decreased activity. The sublethal dose had an effect on the glomerular basement membrane in the form of splitting, increased mesangial cells and matrix, mitochondrial degeneration and fusion of podocyte processes. Tubulization of the parietal epithelium, vacuolization of the proximal tubules, mitochondrial degeneration and apical budding were evident.