Seminiferous Tubule Cross-sections Research Articles

Repopulation of the Seminiferous Epithelium of the Rhesus Monkey after X Irradiation

Repopulation of the seminiferous epithelium became evident from Day 75 postirradiation onward after doses of 0.5, 1.0, and 2.0 Gy of X rays. Cell counts in cross sections of seminiferous tubules revealed that during this repopulation the numbers of Apale (Ap) spermatogonia, Adark (Ad) spermatogonia, and B spermatogonia increased simultaneously. After 0.5 Gy the number of spermatogonia increased from approximately 10% of the control level at Day 44 to 90% at Day 200. After 1.0 and 2.0 Gy the numbers of spermatogonia increased from less than 5% at Day 44 to 70% at Days 200 and 370. The number of Ad and B spermatogonia, which are considered to be resting and differentiating spermatogonia, respectively, already had increased when the number of proliferating Ap spermatogonia was still very low. This early inactivation and differentiation of a large part of the population of Ap spermatogonia slows down repopulation of the seminiferous epithelium of the primates. By studying repopulating colonies in whole mounts of seminiferous tubules various types of colonies were found. In colonies consisting of only A spermatogonia, 40% of the A spermatogonia were found to be of the Ad type, which indicates that even before the colony had differentiated, 40% of the A spermatogonia were inactivated into Ad. Differentiating colonies were also found in which one or two generations of germ cells were missing. In some of those colonies it was found that the Ap spermatogonia did not form any B spermatogonia during one or two cycles of the seminiferous epithelium, while in other colonies all Ap spermatogonia present had differentiated into B spermatogonia. This indicates that the differentiation of Ap into B spermatogonia is a stochastic process. When after irradiation the density of the spermatogonia in the epithelium was very low, it could be seen that the populations of Ap and Ad spermatogonia are composed of clones of single, paired, and aligned spermatogonia, which are very similar to the clones of undifferentiated spermatogonia in non-primates.

Tests for urethane induction of germ-cell mutations and germ-cell killing in the mouse

Urethane, a chemical that has given varied results in mutagenesis assays, was tested in the mouse specific-locus test, and its effect on germ-cell survival was explored. Altogether 32 828 offspring were observed from successive weekly matings of males exposed to the maximum tolerated i.p. dose of 1750 mg urethane/kg. The combined data rule out (at the 5% significance level) an induced mutation rate greater than 1.7 times the historical control rate. For spermatogonial stem cells alone, the multiple ruled out is 3.2, and for poststem-cell stages, 3.5. Litter sizes from successive conceptions made in any of the first 7 weeks give no indication of induced dominant lethality, confirming results of past dominant-lethal assays. That urethane (or an active metabolite) reaches germ cells is indicated by SCE induction in spermatogonia demonstrated by other investigators. Cytotoxic effects in spermatogonia are suggested by our finding of a slight reduction in numbers of certain types of spermatogonia in seminiferous tubule cross-sections and of a borderline decrease in the number of litters conceived during the 8th and 9th posttreatment weeks. The negative results for induction of gene mutations as well as clastogenic damage are at variance with Nomura's reports of dominant effects (F 1 cancers and malformations) produced by urethane.

Attempted protection of spermatogenesis from single doses of gamma-irradiation in the androgen pretreated rat.

Spermatogenic stem-cell survival after gamma-irradiation has been investigated in the adult Wistar rat. Single doses of 4.5 and 9 Gy gamma-rays were administered to the testes of rats who received arachis oil (0.1 ml/100 g body weight) or testosterone enanthate (240 micrograms/100 g body weight) subcutaneously three times weekly for 6 weeks prior to radiation and during the week in which the radiations were given. A mean percentage of regenerating seminiferous tubule cross-sections of 32.45% and 7.26% was found in the testes of androgen-pretreated rats at 8 weeks after 4.5 and 9 Gy, respectively. Similar values (33.4% and 6.2%) were obtained in arachis oil-pretreated controls. We therefore conclude that protection of rat spermatogenesis from single doses of gamma-rays cannot be achieved by androgen pretreatment.

Detection of alterations in testicular and epididymal function in laboratory animals.

The potential impact of an agent altering male reproductive function is greater for humans than for animals. Consequently, it is essential that sensitive criteria be used to look for effects on a multiplicity of target sites when an agent is evaluated using an animal model. No animal model has reproductive characteristics similar to those of humans, but this does not negate the validity of using animal models. Classic methodologies for reproductive toxicology are limited by the approaches used for subjective evaluation of testicular histology and use of natural mating for fertility tests. After dosing for an interval at least equal to six times the duration of one cycle of the seminiferous epithelium, sperm from ejaculated semen or the cauda epididymidis can be evaluated for normalcy of morphology or function and should be used for artificial insemination of females to critically evaluate fertility. Normal males of animal models ejaculate a great excess of sperm. A 50 or 90% reduction in the number of fertile sperm deposited during mating probably will not markedly reduce fertility. Artificial insemination of a critical number of sperm, selected to result in slightly less than maximal fertility for control animals, will maximize the probability of detecting a decrease in fertility if the same critical number of sperm is inseminated for treated animals as for control animals. Testicular function should be evaluated by objective, rather than subjective, criteria. For each male, a piece of testicular tissue should be appropriately fixed and an aliquot of parenchyma should be homogenized to allow enumeration of homogenization-resistant spermatids. Among the more sensitive criteria of testicular function are the minor diameter of essentially round seminiferous tubules, the ratio of leptotene spermatocytes to Sertoli cells, the corrected numbers of germ cells per seminiferous tubule cross section, and the number of homogenization-resistant spermatids per testis.

Age-related variation in seminiferous tubules in men. A stereologic evaluation.

Tubular boundary tissue and seminiferous epithelia were evaluated stereologically in testes from 28 men aged 20 to 48 years and 28 men aged 50 to 90 years. Testes obtained at autopsy within 15 hours of death were perfused with glutaraldehyde, embedded in Epon (Ladd Research Industries, Inc., Burlington, VT), sectioned at 0.5 micron, and stained with toluidine blue. Volume densities (percentage of the testicular parenchyma) of various parameters determined by point counting and diameter measurements were used to calculate total volumes, length of tubules, and number of cells. Electron microscopy was used to determine the volume density of myoid cells in the boundary tissue. Significant (P less than 0.01) age-related reductions occurred in paired testicular weights, paired parenchymal weights, total volume of seminiferous tubules and of seminiferous epithelium, and length of tubules. The volume density and thickness of boundary tissue increased (P less than 0.01) with age. The volume of boundary tissue per man and the volume density of myoid cells in the boundary tissue did not vary with age. Although the number of myoid cells per man tended to be lower in the older group, the number of myoid cells per cross section of seminiferous tubule was increased (P less than 0.01) in older men. The age-related thickening of the boundary tissue was not due to an increase in boundary tissue but resulted from a reduction in the length of the seminiferous tubules.

The XYY condition in a wild mammal: an XY/XYY mosaic common shrew (Sorex araneus).

XY/XYY sex-chromosome mosaicism was demonstrated in both bone marrow and germ cells of a wild adult common shrew. Secondary sexual characteristics were those of a normal male, but the testes were small, and the sperm count was only about 3% of normal. Most of the seminiferous tubule cross-sections examined revealed serious spermatogenic impairment and a reduced diameter. A range of sex-chromosome pairing configurations was observed in XYY primary spermatocytes, including configurations involving the X and both Y chromosomes in a linear or radial array. The presence of metaphase II (MII) spreads with an XY sex-chromosome complement indicated that XYY primary spermatocytes could contribute products to MII. Following Burgoyne (1979) and Burgoyne and Biddle (1980), a number of models of spermatocyte loss were tested. The data indicated that there was an association between the sex-chromosome complement of primary spermatocytes and their contribution to MII. The best fit to the observed MII frequency data was provided by a model which assumed that all XYY primary spermatocytes with a univalent Y chromosome and a high proportion of XYY primary spermatocytes with an unpaired X chromosome failed to contribute products to MII.

Daily sperm production of zebus ( [formula omitted][formula omitted]) estimated by quantitative histology of the testis

Microscopic parameters were studied quantitatively in testes from six Nelore zebus ( Bos indicus ), aged 4 to 6 years, with normal spermatogenesis, which were kept at sexual rest. Ratios of germ cell nuclei, counted in cross sections of seminiferous tubules, indicated that cellular losses in the spermatogenic process of the zebu are higher than those observed in taurines. Daily sperm production, estimated from the number of round spermatids in stage 1 of the cycle of the seminiferous epithelium and the duration of this cycle, was (mean ± SD) 12.2 ± 0.9 × 10 6 spermatids/gram of testis parenchyma/day and 2.6 ± 0.5 × 10 9 spermatids/testis/day. These values are smaller than those of taurines.

Reproductive effects of inhaled methyl chloride in the male Fischer 344 rat: II. Spermatogonial toxicity and sperm quality

Studies were performed to assess the effects of inhaled methyl chloride (MeCl) on sperm quality and testicular histopathology in the Fischer 344 rat. Adult male F-344 rats were exposed to 1000 or 3000 ppm MeCl 6 hr/day for 5 days, or received an ip injection of 0.2 mg triethylenemelamine (TEM)/kg on the afternoon of Day 5. Five males from a control group and each of the three treatment groups were killed weekly for 8 weeks, and five more from the control and 3000 ppm groups at Week 16 postexposure. Male rats from the 1000 ppm MeCl- and TEM-exposed groups exhibited no consistent difference from control males in any parameter measured. In the 3000 ppm MeCl group, over 50% of the males had uni- or bilateral sperm granulomas in the cauda epididymis. Testes weights were significantly depressed in these males by 3 weeks postexposure, and remained depressed as late as 8 weeks after treatment. Testicular spermatid head counts were significantly lower by 2 weeks postexposure, and the testes showed a characteristic cytotoxic response to MeCl exposure, including a delay in spermiation, chromatin margination in round spermatids, epithelial vacuolation, luminal exfoliation of spermatogenic cells, and multinucleated giant cells. Counts of repopulating seminiferous tubule cross sections and of testicular sperm heads at 7 weeks postexposure indicated that 60 to 70% of the spermatogonial stem cells had been killed by MeCl exposure. Sperm isolated from the vasa deferentia had significantly depressed numbers and an elevated frequency of abnormal sperm head morphology by Week 1 postexposure, and significantly depressed sperm motility and an elevated frequency of headless tails by Week 3 postexposure. All parameters measured in the testes and in vasa deferentia sperm showed varying degrees of recovery, and all were near the normal range by Week 16 postexposure except sperm count. These data suggest that the previously reported high preimplantation loss caused by methyl chloride exposure may be primarily due to cytotoxic effects on the testis and epididymal epithelium, rather than to direct genotoxic effects on the sperm.

Cycle of the seminiferous epithelium and its duration in the zebu, Bos indicus

The cycle of the seminiferous epithelium was studied in Nelore zebu bulls 4–6 years old. The stages of the cycle were determined according to the shape and position of spermatid nuclei and the presence of meiotic divisions in cross-sections of seminiferous tubules. The relative frequencies of stages 1 to 8 were, respectively: 31.3 ± 0.5, 12.2 ± 0.7, 21.2 ± 0.5, 8.8 ± 0.6, 4.2 ± 0.4, 5.7 ± 0.6, 6.3 ± 0.5 and 10.3 ± 0.5. The duration of the cycle was estimated by autoradiography using tritiated thymidine injected directly into the testes. The mean duration of one cycle was estimated to be 14.0 ± 0.4 days.

Spermatogenesis in the vasectomized monkey: quantitative analysis.

The seminiferous epithelium in mature vasectomized Macaca fascicularis was examined quantitatively to assess spermatogenesis. Monkeys were bilaterally vasectomized and controls were bilaterally sham operated. At postoperative periods of 10 and 18 months, groups of monkeys were castrated and their testes prepared for morphologic analysis. Diameters were measured in 100 cross sections of seminiferous tubules from each animal. Numbers of spermatogonia (Ad and Ap), preleptotene spermatocytes, pachytene spermatocytes, and step 7 spermatids, relative 10 Sertoli cell nucleoli, were counted in stage VII tubules. Tubule diameter and germ cell numbers per Sertoli cell nucleoli were not altered by vasectomy. Our study demonstrates quantitatively that spermatogenesis in the monkey is not inhibited up to 18 months following vasectomy.

Frequency and duration of the stages of the cycle of the seminiferous epithelium of the nine-banded armadillo (Dasypus novemcinctus).

The majority of the cross-sections of seminiferous tubules of nine-banded armadillos show only one type of cellular association as in most eutherian and metatherian mammals with scrotal testes. The spermatogenic cycle was divided into 8 stages, in relation to the shedding of the spermatozoa. The relative frequencies (%) of stages 1-8 were, respectively: 16.6, 7.5, 12.9, 9.1, 9.7, 18., 11.7 and 13.6. The duration of the cycle was 8.15 days, as determined by intratesticular injection of [3H]thymidine and removing the tissue at different times after injection.

Quantitative aspects of spermatogenesis in rats and dogs after repeated hexachlorophene treatment

Hexachlorophene was administered orally, at subneurotoxic doses, to rats (5 mg/kg/day) and dogs (3 mg/kg/day) for 9 weeks: some of the rats and dogs were observed for a further 13 weeks. The serum concentrations of pituitary gonadotrophin and testosterone were unaffected in either species. No changes were induced in the testicular dimensions or semen characteristics of dogs and no macroscopic post mortem abnormalities, organ weight differences or lesions detectable by conventional light microscopy were found in their testes, pituitaries or secondary sex organs. A transient reduction in the number of germ cells counted in cross-sections of seminiferous tubules was seen in rats after 4 weeks treatment. After 9 weeks treatment, reduced spermatogonial counts were recorded in canine seminiferous tubules; in other respects spermatogenesis was proceeding normally. No delayed effects were apparent in either species. It is concluded that repeated administration of hexachlorophene at subneurotoxic levels did not induce significant impairment of spermatogenesis in rats or dogs.

Testicular Function in Boars Exposed to Elevated Ambient Temperature1

Pituitary-testicular function was examined in yearling boars exposed to 23 ± 1#{176}C (control) or 34.5 ± 1#{176}C for 8 h and 31 ± 1#{176}C for 16 h during each 24 h period (heat stressed). Plasma testosterone and immunoreactive LI concentrations were monitored throughout treatment and testes were removed after 13 weeks to quantify spermatogenesis and assess steroidogenesis by measuring the incorporation of E1�l 4C1 acetate into selected L� 4C1 androgens by slices of testicular tissue incubated in vitro. Plasma testosterone and LI concentrations were similar when control and heat stressed boars were bled infrequently during treatment. However, heat stress significantly altered androgen biosynthesis in vitro as evidenced by decreased amounts of II Cl associated with androstenedione, testosterone and dihydrotestosterone and increases in androsterone and androstanediol. Addition of LH and FSH to testicular incubates markedly enhanced the amount of (1-’ 4CI acetate incorporated into 1l 4C1 androgens but further differences between control and heat stressed boars were not apparent. In another experiment, plasma testosterone was quantified in the serum of boars every 30 mm for 12 h on Days 0, 7 and 14 during exposure to 23 ± 1#{176}C (control) or 34.5 ± 1#{176}C (heat stressed). Serum testosterone was reduced (P(0.10) after 7 days of heat stress. Elevated ambient temperature for 90 days significantly reduced the number of young spermatids in round cross sections of seminiferous tubules at stage 1 of the cycle of the seminiferous epithelium but failed to affect the number of type A spermatogonia or preleptotene and pachytene spermatocytes. The results demonstrate that heat stress can exert a transitory decline in plasma

Inhibition of Canalization in Rat Seminiferous Cords by Medroxyprogesterone Acetate

Due to interest in progestins as male contraceptives, Provera was used to study lumen formation in seminiferous cords. Seven day old rats received daily subcutaneous Depo Provera injections (500 μg/100 g b. w.). At 23 and 28 days of age testes from treated and control animals were prepared for 1 μ plastic sections. At least 100 cross sections of seminiferous cords and tubules were studied in each animal and the per cent of tubules with lumens was calculated. Lumen formation was significantly retarded in the experimental animals. At 23 days tubules in the treated and control animals comprise 7.5 ± 4.1 and 33.3 ± 13.6 % respectively, and at 28 days 15.8 ± 8.3 and 47.5 ± 16.0%. Another series of animals received daily doses of FSH (12.5 μg/100 g b. w.) and LH (50 μg/100 g b. w.) with Depo Provera. Lumen formation in this series was similar to that in animals receiving Depo Provera alone.

Quantitative Analysis of The Seminiferous Epithelium In Human Testicular Biopsies, and The Relation of Spermatogenesis to Sperm Density

Quantitative analysis of the seminiferous epithelium was performed in bilateral testicular biopsy specimens from 14 patients with sperm counts ranging from 0 to 89 million/ml. All Sertoli cells and germ cells within each seminiferous tubule cross-section were counted in all biopsies. Results were expressed either as number of cells per unit length of seminiferous tubule circumference or as number of cells per Sertoli cell. Results were correlated with sperm count (millions per milliliter), total sperm count (millions per ejaculate), and age. A significant correlation between sperm density and germ cell counts was demonstrated. Coefficients of correlation were higher when results were expressed per unit of tubular wall length than when expressed per Sertoli cell. In men with sperm counts below 5 million/ml the number of germ cells in the biopsy was lower than in men with higher sperm counts. Spermiogenesis appeared to be most affected. In this group of patients an adverse effect of age on spermatogenesis was noted.

Influence of age on the response of rat stem spermatogonia to -radiation.

Testes of Sprague–Dawley rats aged either 2 or 12 months were administered 285 rads of 60Co γ-radiation at 45 rads/min. Irradiated animals along with controls (10 per group) were killed at postirradiation intervals varying from 5 to 120 days. Irradiation effects were assayed through testicular weights and counts of type-A spermatogonia in 50 cross sections of seminiferous tubules at stages 5 to 8 of the spermatogenic cycle. No significant difference in number of type-A spermatogonia was observed in testes of nonirradiated rats between the ages of 2 and 16 months. Irradiation reduced spermatogonial numbers to 21 to 25% of control in both age groups, but the postirradiation interval at which it occurred was different—day 5, 2 months; day 10, 12 months. By 24 days after irradiation, spermatogonial numbers had increased to 55% of control in 2-month testes, but 12-month testes were only at 40% of control. The magnitude of the difference between young and old did not change at later postirradiation stages. At 80 days after irradiation, spermatogonial numbers peaked at 90% of control in 2-month testes and 74% of control in 12-month testes. Percents of control at 120 days postirradiation were 84 and 70% for 2- and 12-month testes, respectively. These results lead to the conclusion that irradiation produces a permanent decrement in the stem spermatogonial population with the magnitude of the decrement being age dependent.

Effect of dose-rate ( -radiation) on the mitotically-active and differentiating germ cell of the prenatal male rat.

SummaryRat foetuses, aged 15, 17, or 19 days of gestation were subjected to 95 rads of 60Co γ-radiation administered at rates of 0·95, 9·5 or 45 rads/min and examined 6, 28, and 49 days after birth. Dose-rate effects were assayed at day 6 by enumerating germ cells in 150 cross sections of seminiferous tubules and measuring testicular weights. At days 28 and 49, dose-rate effects were determined by means of testicular weights and counts of fertile and sterile tubular cross-sections.Germ-cell survival was inversely related to age at irradiation. Dose-rate effects were pronounced (P < 0·05) in testes iradiated at day 15 (germ cells mitotically active), equivocal at day 17 (germ cells mitotically active and differentiating), and absent at day 19 (germ cells differentiating only). Both testicular weights and tubular counts measured at day 28 were apparently directly related to the germ-cell counts.The mitotically-active gonocyte was comparatively refractory to the necrotizing effects of ionizing radiation, and...

Localization of irradiation damage in rat seminiferous tubules.

VISIBLE irradiation damage to the germ cells in mammalian gonads has been investigated extensively (review in ref. 1), but many questions about the dynamics of cellular turnover and the nature of barriers to recovery remain unanswered. Following certain radiation treatments, cross-sections of seminiferous tubules have been observed either to be spermatogenically inactive or to possess various degrees of spermatogenic activity2. In testes of animals irradiated during foetal or early postnatal life, the lack of adjoining active and inactive tissue within a single seminiferous tubule might be a barrier to recovery. Germinal elements are unlikely to migrate through the rete testes from one tubule to another, and so an entirely atrophied tubule would be unlikely to recover, but active tissue might repopulate an adjacent inactive area. To determine whether single seminiferous tubules contain both active and inactive tissue, serial longitudinal sections of isolated fragments of seminiferous tubule were obtained and examined histologically.

Number of spermatogonia after x-irradiation of the adult rat.

SummaryThe testes of adult rats were exposed to 0–3000 r x-irradiation, and the animals were killed 6 hours to 21 days after treatment. The numbers of type-A, intermediate, and type-B spermatogonia, degenerating cells and mitotic figures were counted in fifty cross sections of seminiferous tubules in each testis.Statistical analyses showed that a curvilinear relationship exists between the number of type-A spermatogonia, and the number of intermediate and type-B spermatogonia, and (a) the dose administered and (b) the time after irradiation.The survival curves for type-A spermatogonia are indicative of a population of cells possessing a heterogeneity of radio-sensitivities. A comparison of the present results with corresponding data reported for the mouse by Oakberg reveals that for a given dose, the rate of depletion and subsequent recovery of spermatogonia is slower, and the incidence of degenerating cells lower, in the rat than in the mouse.The results suggest that the depletion of spermatogonia in the...