الفهرس 
The biological activity of zincOnly 14 pages are availabe for public view
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Abstract
Twenty-five adult male albino rats were used in this study. Then were divided into two groups: A control group consisted of five rats for studying the normal histology and the ultrastructure of the testis and an experimental group consisted of twenty rats all of them were subjected to intraperitoneally propyl thiouracil (PTU) for fourteen days to induce hypothyroidism. The effect of propyl thiouracil (PTU) on the testicular function was assessed histologically after unilateral orchidectomy on the fifteenth day. The hypothyroidic rats were then divided into four groups and treated for the next 15 days (from 16-30) as follows: group I: (Hypothyroidic group): no additional treatment was given to them. group 11: (L-thyroxin replacement group) were exposed to L-thyroxin subcutanously for studying the effect of thyroxin repletion on the hypothyroidic testis. group 111: (zinc supplementation group) were exposed to zinc sulphate orally for studying the effect of zinc on hypothyroidic testis. group IV: (zinc and L-thyroxin replacement group) were exposed to zinc and L-thyroxin simultaneously for studying their effects on the structure of the hypothyroidic rat testis. Then on the thirty first day all the remaining testicles were removed and processed for both histological and ultrastructural studies. -The Hypothyroidic (group I) showed decrease of the diameter with obliteration of lumens of many seminiferous tubules.Its walls appeared irregular in outlines as compared with the control group.Spermatogenesis arrested early up to spermatocytic stage where lumens of most tubules showed no spermatozoa. Sertoli cells decreased in number. SUMMARY AND CONCLUSION An acidophilic exudate appeared in the interstitium, with atrophy of Leydig cells. -In L-thyroxin replacement (group 11) improvement of histological architecture of the testis was noticed. Seminiferous tubules showed minimal acidophilic exudate in the interstitium and the spermatogenesis was mostly in the spermatid stage. Sertoli cells increased in number and appeared frequently inbetween spermatogenic cells. Leydig cells became frequently seen in the interstitium. -In zinc supplemented (group 111), there was slight improvement of the histological picture of the testis appeared. The seminiferous tubules were still affected and appeared widely separated with irregular outlines. Many tubules showed various stages of spermatogenesis up to the spermatocytes .The primary sperrnatocytes revealed aggregated chromatin and few spermatids were noticed in few tubules. Sertoli cells were infrequently seen within the wall of tubules and the Leydig cells number was apparently decreased. -In zinc and L-thyroxin replacement (group IV) maximal improvement was achieved in testicular histology. Sections of the testis showed normal diameter of the seminiferous tubules, maximal improvement of spermatogenesis occurred where many spermatozoa were seen in the lumens of the tubules and the Sertoli and Leydig cells increased in numbers and became frequently seen. These results indicated a possible combined role of zinc and L-thyroxin on the testicular function. By electron microscope, the hypothyroidic (group I) showed marked thickening of the limiting membrane with atrophy of the myoid cells and an increase of collagen fibers in the non cellular Layer. Spermatogonia showed large nucleus with condensed clumps of chromatins and slight irregularity of the nuclear membrane, primary spermatocytes showed degenerative changes in the form of shrunken nuclei with condensed clumps of chromatin, distorted nuclear membrane and increased vacuolated mitochondria. Sertoli cells showed less folded nucleus with condensed clumps of chromatin close to the nuclear membrane and prominent nucleolus. Their cytoplasm contained more smooth endoplasmic reticulum (SER), fat droplets and phagocytosed germ cells. Leydig cell showed high irregularity of the nuclear membrane and condensed chromatin. The cytoplasm contained more rough endoplasmic reticulum (RER), few smooth endoplasmic reticulum (SER) with varying shaped mitochondria, and some fat droplets. -In zinc supplement group (group 111), the thickness of limiting membrane decreased than group I. Myoid cell appeared normal with marked decrease of collagen fibrils in the non cellular layer. The primary spermatocytes showed large nucleus with slightly condensed chromatin and irregular contour than. . Sertoli cells appeared with slightly folded nucleus with extended chromatin and prominent nucleolus and its cytoplasm contained more vesicles of smooth endoplasmic reticulum (SER), centrally vacuolated mitochondria and some fat droplets The nucleus of Leydig cells showed with mild irregularity of its nuclear membrane and condensed mass of chromatin .The cytoplasm contained more cisterns of smooth endoplasmic reticulum (SER), mitochondria of varying shape and size and few fat droplets. -In zinc and L-thyroxin replacement group (group IV), the limiting membrane with myoid cell and the collagen fibrils in non cellular layer appeared normal as control group. The primary spermatocytes appeared with large nucleus exhibiting dispersed chromatin .The lumen of seminiferous tubule contained spermatids and mature spermatozoa. The nucleus of Sertoli cell was highly folded with dispersed chromatin and prominent nucleolus .The nucleus of Leydig cell showed slightly irregular contour with thin rim of heterochromatin close to the nuclear membrane. The cytoplasm contained more cisternae of smooth endoplasmic reticulum (SER), many mitochondria and fat droplets. It could be concluded that experimental hypothyroidism caused significant changes in the histology and ultrastructure of the rat testis and the treatment of hypothyroidic mature rats with levo-thyroxin and zinc produced reversal of these changes .As a result : i. Zinc deficiency may play a role in the detrimental effect of hypothyroidism on spermatogenesis. . . 11. Treatment of hypothyroidism with levo-thyroxin alone increased spermatogenesis and zinc level, without however, reaching normal level, iii. Oral zinc treatment per se had no effect on thyroid functions as the slight improvement occurring was due to a direct effect on the testicular steroidogenesis. iv. Optimal results have been achieved with levo-thyroxin and zinc replacement therapy.