The effects of constant light and dark exposure of pubertal male rats on the pituitary-gonadal axis and thyroid activity were studied. The indices of thyroid activity were weight of the thyroid gland, estimation of serum levels of thyroxine (T 4) by radioimmunoassay (RIA) technique and histological studies of the thyroid gland. The indices of gonadal activity chosen were weight and histological study of the testes and determination of serum levels of Luteinizing hormone (LH) and Follicle Stimulating Hormon (FSH) by RIA technique. In the rats exposed to continuous light, the weight of the thyroid gland increased significantly (P<0.02) and the serum level of T 4 also increased significantly (P<0.02). The histological observations revealed thyroid follicles that were sparsely filled with colloid while the epithelial cells were more columnar, evidence of increased glandular activity. The size of the testes increased significantly (P<0.001). The serum level of FSH was increased significantly (P<0.001) while there was a slight rise in the serum level of LH. Histological observations in the testes showed that the seminiferous tubules were well spaced out and appeared to contain more spermatozoa when compared with the control. In the rats exposed to constant darkness, the weight of the thyroid gland was significantly lower (P<0.02) when compared with that of the control. The serum level of T 4 remained unchanged while histological examination of the thyroid gland showed the follicles containing less colloid and the epithelial cells appearing more columnar when compared with the control. The weight of the testes was markedly reduced (P<0.001). The serum level of LH was reduced significantly (P<0.05) while there was a slight fall in the serum level of FSH. The histological examination of the testes showed that the, seminiferous tubules clustered together and contained little or no spermatozoa. When compared with the rats that were exposed to normal lighting rhythm, continuous darkness exposure resulted in a decrease in the thyroid activity as well as a marked decrease in gonadal activity in male rats.
Male reproductive function is one of the mammalian systems that are impaired by diabetes mellitus and on the average, it will affect many more men prior to and during their reproductive years. The present study aimed to compare proliferating cell nuclear antigen (PCNA) immunostaining effects at stage VII of the spermatogenic cycle in streptozotocininduced and insulin resistant diabetic rat testis. Male adult Sprague-Dawley rats (120-140 g) were randomly divided into 3 groups. Group 1: control group; fed on normal rat pellets. Group 2: streptozotocin diabetic group; received a single dose IP injection of streptozotocin 45 mg/kg BW in Na + citrate buffer pH 4.5. Group 3: insulin resistant diabetic group; fed ad libitum on a special diet containing 25% fructose W/W. Following hyperglycaemia confirmation, animals were perfused with 4% Paraformaldehyde (PFA). Testes were isolated, and fixed in 4% PFA overnight, embedded in paraffin, 5µm thick sections were made and mounted on poly-L-lysine coated slides. Immunohistochemical staining was carried out on the positively charged slides using the PCNA as primary antibody.The results of this study showed that diabetes mellitus induced by streptozotocin injection and chronic fructose consumption through insulin resistance significantly (P<0.05) reduced PCNA index, mean seminiferous tubular diameter and testicular diameter. It could also be inferred from the results that diabetes mellitus and insulin resistance may necessarily not impair differentiation of primordial germ cells (gonocytes) into Type A and Type B spermatogonia.
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