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Abstract The present study investigated and compared the effect of noise stress exposure on the testis and the ovary of albino rats at three critical periods of life; the prenatal, prepubertal and adult stages. The aim was to reveal the most susceptible period of lifetime during which these organs are prone to injury. Seventy two albino rats (36 males and 36 females) of Wistar strain were used in the study. The experimental groups were exposed to noise at an intensity of 100 dB for a period of 6 hours daily from 8am to 2pm o’clock for all groups. Pregnant mothers were exposed to noise stress for 12 days (from day 8 – day 20 of gestation) then fetuses were extracted while pre-pubertal (aged 3weeks) and adult (aged 3 months) rats were exposed to noise stress for 4 weeks. Rats were assigned to 12 groups (each containing 6 rats); both control and experimental. At the end of the experiment, all animals; control and those exposed to noise (20 days old fetuses, 7 weeks old rats and 4 months old rats) were sacrificed using over dose of ether inhalation. The testes and ovaries of all rats were collected. The specimens were processed for paraffin block 249 embedding and stained with standard histological stains (Hx&E, PAS and Masson’s Trichrome) for light microscopic examination. Immunohistochemical staining for apoptosis was performed on paraffin sections utilizing TUNEL assay. Histomorphometric analysis was performed utilizing image analysis software and results were subjected to statistical analysis using ANOVA test. Regarding the testis, the three age control groups showed histological differences. The tunica albuginea increased in thickness in contrast to tunica vascuolsa which diminished in thickness as age advanced. Size of the seminiferous tubules increased with age. Regarding the germinal epithelium, the testes of 20 days old rat fetuses was composed only of two types of cells; the gonocytes and the supporting cells. In the 7 weeks old rats, the germinal epithelium was formed of several cell types; spermatogonia, the spermatocytes, the round immature spermatids. Few elongated mature spermatids were detected in this age group. Regarding the 4 months old group, the germinal epithelium was formed of spermatogonia, spermatocytes, round spermatids and elongated spermatids, arranged in that order from the basal compartment to the adluminal compartment. Sertoli cells were more detected in the adult group compared to the 7 250 weeks old rats. The interstitial cells of Leydig increased in number as age advanced. Examination of the testes of 20 days old albino rat fetuses whose mothers were exposed to noise revealed that the tunica albuginea was apparently thicker than the control group and the tunica vasculosa was also formed of less densely arranged loose connective tissue compared to the control group. Seminiferous follicles were gathered into clusters and their size decreased compared to the control group. The supporting cells were detached from the basement membrane and were closely packed with pyknotic nuclei. The gonocytes also showed pyknotic nuclei with vacuolated cytoplasm compared to the control group. Examination of testes of the 7 weeks old albino rats which were exposed to noise, at the age of 3 weeks for one month, showed the presence of localized thickening of tunica albuginea and increased thickness of tunica vasculosa. Size of seminiferous tubules was smaller compared to the control group. Some areas showed wide separation of the tubules from the capsule. Most of the tubules showed rupture of their basement membranes. The spermatogenic cells lining the tubules showed pyknotic nuclei with massive cytoplasmic vacuolation while others 251 were exfoliated into the lumen. Some Sertoli cells also showed pale staining of their nuclei. Interstitial cells of Leydig had dark nucleus with presence of congested blood vessels in some interstitial tissue spaces. The most characteristics observation was retardation of development of seminiferous tubules. This could be detected by the absence of mature spermatids which were detected in the control group. Examination of testes of 4 months old albino rats exposed to noise revealed relative thinning of tunica albuginea and thickening with congestion of blood vessels in tunica vascuolsa compared to control group. The seminiferous tubules were reduced in size. Various forms of affection of the spermatogenic cells lining the seminiferous tubules were seen ranging from extreme thinning out of the epithelium in some locations to patches of focal degeneration or exfoliation into the tubular lumen. Spermatogonia, spermatocytes and spermatids showed fusion of their cell membranes, cytoplasmic vacuolation, nuclear disintegration and cellular necrosis. Some Sertoli cells also showed faint stained degenerated nuclei while others were unaffected. Most of the interstitial cells of Leydig showed faint staining of their nuclei. Few of them showed small dark nuclei. 252 Regarding the ovary, the three age control groups showed histological differences. The size of the ovary increased as age advanced. The ovary was surrounded by surface epithelium which in the prenatal group was multilayered while it was single in the 7 weeks old rats and adult groups. As for the types of follicles, in the 20 days old fetuses, different types of structures were observed. Some oocytes were devoid of cell boundaries and were packed together in pockets surrounded by connective tissue collagen fibers. Other oocytes acquired cell boundaries and were arranged in groups mainly in the peripheral part of the ovary. Darker cells were seen scattered in between the oocytes. In some areas, one or two of these cells were observed attached to the cell membranes of the oocyte. In some sections, oocytes were observed surrounded by a single layer of flattened cells. In the core, some of the oocytes were seen surrounded by cuboidal cells changing them into follicle-like structures. In the 7 weeks old group there were primordial follicles, primary, secondary, tertiary, Graafian follicles with apparent predominance of the secondary follicles. Corpus luteum was occasionally detected in the examined sections. In the 4 months old group, the same types of follicles of the previous group were noticed. Corpora lutea increased in number compared 253 to the younger age. Regarding the medulla, it became more distinct with advancement of age. On examination of ovaries of the 20 days old albino rat fetuses whose mothers were exposed to noise, the ovarian surface epithelium showed focal areas of increased thickness. The ovarian tissue showed shrunken follicle-like structues. The oocytes showed dark stained cytoplasm and pyknotic nuclei. Also the surrounding pregranulosa cells had pyknotic nuclei. The observed different structures in the control group could not be deteceted in the experimental group. Examination of ovaries of the 7 weeks old albino rats which were exposed to noise, at the age of 3 weeks for one month, showed that the ovary was apparently decreased in size. There was apparent reduction in the number of follicles. Graafian follicles and corpus luteum were not detected in the examined sections. The oocytes either showed dark stained cytoplasm or vacuolated one with small pale stained or shrunken pyknotic nuclei. The surrounding granulosa cells showed marked vacuolation of the cytoplasm and completely degenerated nuclei. Neither Graafian follicle nor corpus luteum could be detected in the examined sections. 254 Examination of ovaries of 4 months old albino rats exposed to noise showed apparent shrinkage in the size of the ovary with apparent decrease in the number of follicles. The ovary showed marked predominance of the atretic follicles and corpora lutea as compared to the control group. The medulla showed deeply stained stromal cells and congested blood vessels. Different stages of the follicles showed degenerated oocytes with pyknotic nuclei and vacuolated cytoplasm. The surrounding granulosa cells also appeared loosely arranged with vacuolated cytoplasm and pyknotic nuclei. Separation between granulosa and theca cell layers was observed. Apoptosis of cells in testicular and ovarian tissues exposed to noise was much more than control sections. Positive stained immune cells in testes were scattered in the testicular tissue. On the other hand, positive stained apoptotic cells in the ovaries were primarily localized at granulosa and theca cell layers. Only minority of positive stained cells were dispersed elsewhere in the ovary. Histomorphometric assessment of testes confirmed the histological findings. The three parameters assessed in the current study were significantly decreased in noise groups of 20 days old rats and the 7 weeks old rats compared to their controls. However, adult testicular tissue 255 didn’t show significant differences. Regarding the ovary, the measurement of the length showed significant difference regarding the 20 days old rats and the 7 weeks old rats, whereas in the adult group, it didn’t show significant difference compared to the control groups. The measurement of the width showed significant difference in the prenatal group but it didn’t show significant differences in the other two groups compared to their controls. |