Effect of photoperiod on the size of the Leydig cell population and the rate of recruitment of Leydig cells in adult Syrian hamsters

The number of Leydig cells was determined by stereologic procedures in adult Syrian hamsters housed in long days (14L:10D) to maintain testicular activity (active), in short days (5L:19D) for 12-13 wk to induce testicular regression (photoperiod-induced regressed), or in short days for a period of 21 wk or more to allow spontaneous gonadal recrudescence (spontaneously recrudesced). Testes were removed, sliced, fixed, embedded in Epon 812, and observed by bright-field microscopy. Testicular and seminal vesicle weights, plasma testosterone concentration, total Leydig cell volume per testis, and volume of single Leydig cell were greater (p less than 0.01) in active and recrudesced animals than in regressed animals. The density of Leydig cells was greater in the regressed testes, but the total number per testis was not influenced by photoperiod. In Experiment 2, the rate of recruitment of Leydig cells was determined in 5 adult hamsters exposed to long days (active) or 5 hamsters whose testes were regressed by exposure of animals to short days for 13 wk followed by long-day exposure to initiate testicular growth (photoperiod-induced recrudescing). Hamsters were injected for 3 days/wk for 3 wk with tritiated thymidine, 0.5 or 1 microCi/g body weight. Testes were fixed and tissues prepared, as above, and processed for autoradiography. Again, the photoperiod did not influence the number of Leydig cells per testis. Labeling of Leydig cell nuclei revealed that recruitment of new Leydig cells occurred at approximately 1.3% per day in recrudescing testes but also occurred at approximately 0.6% per day in active testes. Without change in the total number of Leydig cells, new Leydig cells were added continually to the existing population in adult hamsters with either recrudescing or active testes.     

Altered concentrations of gonadotrophin, prolactin and GnRH receptors, and endogenous steroids in the abdominal testes of adult unilaterally cryptorchid rats

Testicular descent was prevented unilaterally in newborn rats by cutting the gubernaculum testis. At 100 days of age, the number of Leydig and Sertoli cells per testis, the concentration of receptors for LH, FSH, prolactin and GnRH, and endogenous concentrations of progesterone and testosterone were determined. The weight of the abdominal testes was reduced by 80%, but in spite of this they contained as many Sertoli (32.8 +/- 1.3 X 10(6), mean +/- s.e.m., n = 6) and Leydig (28.2 +/- 1.7 X 10(6) cells as did scrotal testes (32.1 +/- 2.5 X 10(6) and 24.3 +/- 1.2 X 10(6) respectively). The numbers of receptors for LH (3.2 +/- 0.2 and 1.0 +/- 0.2 pmol/testis, mean +/- s.e.m., n = 11), FSH (358 +/- 11.0 and 96.3 +/- 12.6 fmol/testis) and prolactin (535 +/- 32.7 and 92.4 +/- 13.2 fmol/testis) were reduced (P less than 0.001) in abdominal testes, but the number of GnRH receptors was unaffected (8.9 +/- 1.4 and 12.1 +/- 1.8 fmol/testis, n = 6). Testicular testosterone concentration (30.9 +/- 4.4 vs 15.4 +/- 3.2 ng/g, n = 11, P less than 0.001), but not that of progesterone (0.87 +/- 0.10 vs 1.01 +/- 0.21 ng/g), was decreased in abdominal testes. The decreased receptor and androgen values reflect functional disturbances in the abdominal testes. The changed local milieu within abdominal testes may reduce hormone receptor concentrations which are then involved in the observed Leydig cell dysfunction.     

Influence of the photoperiod on TGF-β1 and p15 expression in hamster Leydig cells

Adult hamsters exposed to short photoperiods show a marked atrophy of their internal reproductive organs, including a reduction in size, though not number of Leydig cells. Transforming growth factor-β1 (TGF-β1) is involved in the regulation of growth and proliferation of different cell types. The aim of the present study was to examine the influence of photoperiod on the protein and gene expression of TGF-β1 and its receptors as well as gene expression of p15. The effect of TGF-β1 on the expression of p15 in purified Leydig cells from regressed and non-regressed hamster testes was also tested. Protein and gene expression of TGF-β1 was detected in both regressed and non-regressed testes. In contrast to the activin receptor-like kinase 1 (ALK-1), the TGF-β1, the activin receptor-like kinase 5 (ALK-5) and the co-receptor endoglin all showed a greater basal expression in regressed than non-regressed hamster testes. Melatonin induced the TGF-β1 mRNA expression in purified Leydig cells from non-regressed testes. The p15 mRNA level was greater in regressed than non-regressed testes. A high dose of TGF-β1 during a short incubation period increased the p15 mRNA level in Leydig cells from non-regressed testes. ALK-5 and mitogen-activated protein kinase (MAPK) p38 might have played a role in this process. In regressed hamster testes, the p15 mRNA level increased due to a low dose of TGF-β1 after short incubation periods and to a high dose after longer incubation periods; in both instances, ALK-5, ERK 1/2 and p38 were involved. Collectively, these results suggest that the alterations in p15 expression, mediated by MAPK, are involved in the shift between the active and inactive states in hamster Leydig cells.     

Timing of testicular recrudescence in siberian hamsters is unaffected by pinealectomy or long-day photoperiod after 9 weeks in short days

In this study, the authors asked whether pinealectomy or temporary exposure to a stimulatory photoperiod affects the timing of spontaneous testicular recrudescence in adult Siberian hamsters chronically exposed to short days (9:15 light:dark). In Experiment 1, hamsters were pinealectomized after 6, 9, or 12 weeks in short days. Pinealectomy after 9 or 12 weeks did not affect the timing of spontaneous gonadal growth (27.7 +/- 1.9 and 25.4 +/- 1.3 weeks, respectively) compared to sham-operated controls (28.6 +/- 0.9 weeks). Enlarged testes occurred earlier in animals that were pinealectomized after 6 weeks in short days (21.8 +/- 2.1 weeks). In Experiment 2, adult hamsters were exposed to short days for 9 weeks, transferred to long days (16:8 light:dark) for 4 weeks, and then returned to short days for 23 additional weeks. Although long-day interruption caused gonadal growth in 15 out of 19 hamsters, the temporary long-day exposure did not affect the timing of spontaneous gonadal growth following return to short days (28.2 +/- 0.9 weeks) in 10 of the 15, relative to the timing observed in control hamsters continuously maintained in short days (28.2 +/- 1.1 weeks). Four out of 19 hamsters did not show gonadal growth following long-day exposure. Spontaneous gonadal growth in these hamsters (28.0 +/- 1.4 weeks) also occurred at the same time as controls. The remaining 5 hamsters exhibited enlarged testes following long-day exposure (12.0 +/- 0.0 weeks) but were refractory to the second short-day exposure. All hamsters exhibited entrainment of wheel-running activity following the change in photoperiod. A final group of 13 animals were pinealectomized before long-day transfer. They exhibited gonadal growth (at 17.2 +/- 0.8 weeks) but failed to regress a second time when returned to short days. The timing of gonadal growth in these animals was delayed relative to the sham-operated hamsters temporarily transferred to long days (Experiment 2) but accelerated relative to the hamsters pinealectomized at 9 weeks, which remained continuously in short days (Experiment 1). The results of both experiments suggest that a pineal-independent process mediates the timing of spontaneous gonadal growth in Siberian hamsters chronically exposed to a short-day photoperiod.     

An enzymatic method for the isolation of mouse Leydig cells

Mouse Leydig cells were obtained by dispersion of testes of adult animals (aged 6-15 months) with a neutral protease from B. polymxa (dispase; EC 3.4.24.4). The crude Leydig cell suspension was purified by centrifugation on a discontinuous Percoll gradient using a special centrifugation procedure similar to elutriation. The crude cell suspension obtained from 50 testes could be processed in one run. The combination of these two methods yielded 320000 +/- 53000 Leydig cells/testis (n = 554 testes). The purity of the Leydig cell fraction was greater than or equal to 95% (nucleated cells) based on morphological and histochemical (staining for naphthyl esterase) identification. The purified Leydig cells showed an excellent ultrastructural appearance. More than 98% excluded trypan blue. In the presence of NADPH, testosterone biosynthesis was increased only 1.15 +/- 0.1-fold yielding a "quality factor" of 34.8. Maximal hCG doses induced 10(6) purified Leydig cells to produce 5 nmol testosterone/hr. (40-fold stimulation in comparison to basal values). The Leydig cells showed 43100 +/- 2500 LH/hCG receptors and an association constant of Ka = 1.95 x 10(9) M-1. Due to the reproducibility of the method, to the yield as well as to the morphological and functional state of the purified Leydig cells at least 25% of laboratory animals could be saved.     

Evidence of an annual rhythm in a small proportion of Siberian hamsters exposed to chronic short days

Siberian hamsters are photoperiodic seasonally breeding rodents. To date, there has been no evidence that Siberian hamsters exhibit an annual rhythm in reproductive, thermoregulatory, molt, or body mass changes. However, given that the termination of their winter cycle is under endogenous control, the authors thought it possible that under particular conditions, other aspects of their seasonal cycle may be endogenously mediated. Consequently, the authors monitored the reproductive condition, body mass, and molt of hamsters chronically exposed to short days (LD 9:15) for up to 2 years. All animals were taken from previous experiments and had exhibited gonadal regression, followed by refractoriness to shorts days and spontaneous gonadal growth, as well as a complete cycle of body mass and molt changes. Although some hamsters died during the study, the authors continued to monitor some animals for up to 106 weeks of short-day exposure. Of the 57 animals monitored, 4 (7.02%) exhibited a second cycle of reproductive regression and recrudescence. Furthermore, the timing of the second regression was similar in the 4 animals, occurring about 1 year after the initial short-day exposure (50.5 +/- 1.71 weeks). However, the timing of the second bout of recrudescence was more variable, occurring at about week 80 (79.5 +/- 8.01 weeks). Hamsters exhibited regressed gonads for about 7 months (29.0 +/- 8.02 weeks). Although the body mass of the 4 hamsters declined at the time of the second cycle of gonadal regression, it never recovered. No hamster exhibited a second molt cycle. These observations indicate that a small percentage of Siberian hamsters chronically exposed to short days can exhibit an annual cycle of reproduction.     

Differential activity of matrix metalloproteinases (MMPs) during photoperiod induced uterine regression and recrudescence in Siberian hamsters (Phodopus sungorus)

Siberian hamsters adapt to seasonal changes by reducing their reproductive function during short days (SD). SD exposure reduces uterine mass and reproductive capacity, but underlying cellular mechanisms remain unknown. Because matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are important in uterine development, parturition, and postpartum remodeling, their expression in uterine tissue from Siberian hamsters undergoing photoperiod-mediated reproductive regression and recrudescence was investigated. Female hamsters were exposed to long day (LD, 16L:8D, controls) or SD (8L:16D) for 3-12 weeks (regression); a second group was exposed to SD or LD for 14 weeks and then transferred to LD for 0-8 weeks (recrudescence). Hamsters were euthanized, uteri collected, and homogenates analyzed by gelatin zymography or Western blotting for MMP and TIMP protein levels. Uterine weight decreased (67-75%) at SD weeks 12-14 and increased post-LD transfer (PT) reaching LD values by PT week 2. MMP-2, but not MMP-9 activity was reduced by SD week 12 or 14 but increased to LD levels at PT week 2. MMP-3 expression increased at SD week 9 compared to other SD and LD groups. MMP-14 and -13 protein levels decreased at SD week 3 but returned to LD levels by SD week 6. During recrudescence, MMP-3 (PT weeks 0-2), MMP-13 (PT week 4), and MMP-14 (PT weeks 2, 4) protein levels were higher than LD. TIMP-1 and 2 were present at low levels. Significant and differential variations in uterine MMP activity/expression during photoperiod-induced regression and recrudescence were observed. These changes likely reflect increases in tissue remodeling during both the adaptation to SD and the restoration of reproductive function.     

Differences in aromatase activity between Leydig cells from the scrotal and abdominal testis in the naturally unilateral-cryptorchid boar

In an earlier study, estrogen production was much lower in Leydig cells from the abdominal than from the scrotal testis in naturally occurring unilateral cryptorchidism in the boar. A more direct assessment of aromatase activity was made in thirty-two mature male pigs to examine this observation further, using nonradioactive androstenedione (delta 4A 1.0 x 10(-6) M - 1.5 x 10(-5) M) and [1 beta, 2 beta-3H] delta 4A as substrates. Purified Leydig cells were prepared from normal boars and from unilaterally and bilaterally cryptorchid animals. Combined estrone sulfate (E1S) and estrone (E1) formation from delta 4A were measured by radioimmunoassay. Little or no estrogen secretion was seen with cells from the abdominal testis in unilaterally cryptorchid boars (n = 7), and E1S formation from delta 4A was 6- to 14-fold higher for scrotal cells (n = 6). Aromatase activity as reflected in percent conversion of substrate to [3H]-labeled water was clearly lower in cells from the abdominal testis (1.10 +/- 0.08 and 11.22 +/- 0.7%, respectively, p less than 0.01, n = 6). No marked reduction was noted for unilaterally cryptorchid boars with an inguinally located testis (10.18 +/- 0.27 and 13.09 +/- 0.58% for inguinal and scrotal testes, respectively, n = 3). Concentrations of E1S in testicular arterial and venous blood (n = 9) gave additional evidence of lower estrogen production by the undescended testis of the cryptorchid boar. It was concluded that lower aromatase activity is present in Leydig cells of the abdominal testis.     

Effect of photoperiod on the rate of 3H-thymidine incorporation of epididymal principal cells in adult Syrian hamsters

Photoperiod-induced cycles of gonadal regression and recrudescence in the Syrian hamster were used to determine if epididymal growth in adults involves mitotic activity of principal cells. In Experiment 1, the following groups of adult hamsters were examined: induced recrudescing (5L:19D [5 hr light and 19 hr dark] for 13 wk followed by 14L:10D for at least 3 wk), spontaneous recrudescing (5L:19D for 25 wk), and active gonadal state (14:10D). In Experiment 2, adult hamsters were divided into the following groups: induced recrudescing, active, and regressed (5L:19D for 16 wk). Hamsters received subcutaneous injections of 0.5 microCi 3H-thymidine/g body weight three times/wk for 3 wk. The epididymis was fixed in a glutaraldehyde followed by osmium, embedded in Epon 812, and sectioned at 1 micron. Slides were dipped in Kodak NTB-3 emulsion, exposed for 2 or 3 months, developed, and evaluated for isotopic labeling of principal and basal cell nuclei by scoring 500 to 1,000 nuclei. In Experiment 1, the percentages of labeled principal cell nuclei for the induced recrudescing, spontaneous recrudescing, and active groups were 26 +/- 2%, 23 +/- 5%, and 9 +/- 1%, respectively. Considering the intermittent availability of 3H-thymidine during 21 days, this represents daily recruitment of 6.3%, 5.6%, and 2.2%, respectively. In Experiment 2, the percentages of labeled principal cell nuclei for induced recrudescing, active, and regressed groups were 12 +/- 4%, 3 +/- 1%, and 4 +/- 1%, respectively. There was no effect of photoperiod on labeling pattern of basal cells (1.5 +/- 0.6%, 1.2 +/- 0.1%, 0.4 +/- 0.1% for the three photoperiod groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Twenty-four-hour profiles of serum leptin in siberian and golden hamsters: photoperiodic and diurnal variations

Serum leptin concentrations were obtained from male Siberian hamsters (Phodopus sungorus) and golden hamsters (a.k.a. Syrian, Mesocricetus auratus) housed on long [light:dark (LD) 16:8] and short (LD 6:18) photoperiods for 10-11 weeks. Blood samples were collected at 45-min intervals for 24 h from individual animals using an in-dwelling atrial catheter. In Siberian hamsters, exposure to short photoperiods as compared to long photoperiods reduced body weight (32.5 +/- 1.5 vs 47.7 +/- 1.1 g) and leptin (24-h mean: 5.3 +/- 0.4 ng/ml vs 18.6 +/- 2.1 ng/ml). Although photoperiod influenced the temporal distribution of leptin in golden hamsters, the main effect of photoperiod on leptin levels in golden hamsters did not reach significance (24-h mean: 7.1 +/- 1.0 ng/ml vs 5.1 +/- 0.8 ng/ml.). Body weights of golden hamsters did not vary significantly following exposure to short photoperiod for 11 weeks (178.3 +/- 3.6 g in LD 6:18 vs 177.8 +/- 7.3 g in LD 16:8). There was no nocturnal increase in serum leptin in either species. Marked interindividual differences were apparent in individual leptin profiles. Periodogram analysis revealed that only a few animals exhibited 24-h periodicities; the presence of a significant 24-h periodicity was more common in hamsters exposed to short days. Photoperiod-associated differences in the 24-hour profile of leptin secretion may be the result of photoperiod-associated changes in feeding behavior or metabolism. A full understanding of the regulation of leptin secretion in multiple time domains may enhance our understanding of the function of leptin.     

The effect of duration and time of food availability on the photoperiodic response in the male house sparrow, Passer domesticus

We investigated the effects of food availability on the seasonal testicular growth in the photoperiodic house sparrow (Passer domesticus). Two experiments were performed, each lasting 4 weeks. In experiment 1, sparrows were exposed to natural (NDL; group 1), short (8L:16D; group 2) and long (16L:8D; groups 3-5) day lengths with access to food ad libitum (groups 1-3) or for 10 h (zeitgeber time (zt) 0-10, group 4; zt 0 is the time of light onset) or for 8 h (zt 8-16, group 5). Testes recrudesced under long, but not short and natural, day lengths, and the recrudescence under long days was influenced by the duration of food availability. In experiment 2, the sparrows were exposed to short (8L:16D, group 1) and long (16L:8D, groups 2-5) day lengths with access to food ad libitum (for groups 1 and 2) or for 6 h (for groups 3-5) at different times during the 16 h light period (group 3- zt 0-6, group 4- zt 5-11, group 5- zt 10-16). As the expected, the testes recrudesced only under long lengths, but the photoinduction was variable among the 4 groups. The testes grew to full size in groups 2 and 3 that received food either ad libitum or for 6 h at zt 0-6, but to sub-maximal size in the groups that received 6 h food either at zt 5-11 (group 4) or at zt 10-16 (group 5). Altogether, these results support the idea that the photoperiodic regulation of reproduction in a seasonally breeding species is influenced both by the duration and the time of food availability.     

Catecholamine effects on testicular testosterone production in the gonadally active and the gonadally regressed adult golden hamster

Several lines of evidence support a role of testicular innervation and peripheral catecholamines in the control of male gonadal function, particularly before puberty. It was therefore of interest to compare the effects of catecholamines on androgen production during the periods of gonadal activity and quiescence in a seasonally breeding species. We have examined direct effects of epinephrine (EPI), norepinephrine (NE), the beta-adrenergic agonist isoproterenol (ISO), and the alpha-adrenergic agonist phenylephrine (PHE) on testicular testosterone (T) production in hamsters with gonadal regression induced by 12 wk exposure to short photoperiod (SD) and in gonadally active hamsters maintained in long photoperiod (LD). Fragments of decapsulated testes were incubated with various combinations of these catecholamines (10(-5)-10(-9) M), human chorionic gonadotropin (hCG; 3.1 mIU/ml), the beta-receptor antagonist propranolol (10(-5) M) and the alpha-l-receptor antagonist prazosin (10(-5) M), for 6 h. In the incubations of testes from LD hamsters, the accumulation of T in the medium was stimulated by hCG but not affected by either catecholamine. However, EPI, NE, and PHE at 10(-5) M, but not ISO, augmented the stimulation of T by hCG. In sharp contrast to these findings, T production by the regressed testes of SD animals was stimulated by EPI (at 10(-8)-10(-5) M), NE (at 10(-6)-10(-5) M), and PHE (at 10(-6)-10(-5) M) in a dose-related manner, but unaffected by ISO. These stimulatory effects were prevented by prazosin, but not by propranolol. Moreover, 10(-5) M of EPI, NE, and PHE augmented the stimulatory effect of hCG on T production. We conclude that the seasonal transition from gonadal activity to quiescence in the adult golden hamster is accompanied by a major increase in the responsiveness of testicular steroidogenesis to catecholamines acting via the alpha-1-adrenoreceptor and that catecholamines can modulate Leydig cell response to gonadotropins in this species. These findings could be related to up-regulation of the alpha-1-receptor in the testis of the SD animal and suggest that catecholamines may be involved in the regulation of the testis during physiological suppression of gonadotropin release and during stress.     

Morphometric studies on hamster testes in gonadally active and inactive states: light microscope findings

This study provides quantitative information on the testes of seasonally breeding golden hamsters during active and regressed states of gonadal activity. Seminiferous tubules occupied 92.5% of testis volume in adult gonadally active animals. Leydig cells constituted 1.4% of the testicular volume. The mean volume of an individual Leydig cell was 1092 microns 3, and each testis contained about 25.4 million Leydig cells. The volume of an average Sertoli cell nucleus during stage VII-VIII of the cycle was 502 microns 3. A gram of hamster testis during the active state of gonadal activity contained 44.5 million Sertoli cells, and the entire testis contained approximately 73.8 million Sertoli cells. Testes of the hamsters exposed to short photoperiods for 12-13 wk displayed a 90% reduction in testis volume that was associated with a decrease in the volume of seminiferous tubules (90.8% reduction), tubular lumena (98.8%), interstitium (72.7%), Leydig cell compartment (79.3%), individual Leydig cells (69.7%), Leydig cell nuclei (50.0%), blood vessels (85.5%), macrophages (68.9%), and Sertoli cell nuclei (34.1%). The diameter (61.1%) and the length (36.8%) of the seminiferous tubules were also decreased. Although the number of Leydig cells per testis was significantly lower (p less than 0.02) after short-photoperiod exposure, the number of Sertoli cells per testis remained unchanged. The individual Sertoli cell in gonadally active hamsters accommodated, on the average, 2.27 pre-leptotene spermatocytes, 2.46 pachytene spermatocytes, and 8.17 round spermatids; the corresponding numbers in the regressed testes were 0.96, 0.20, and 0.04, respectively. The striking differences in the testicular structure between the active and regressed states of gonadal activity follow photoperiod-induced changes in endocrine function and suggest that the golden hamster may be used as a model to study structure-function relationships in the testis.     

High androgen receptor immunoexpression in human "Sertoli cell only" testis

Our purpose was to evaluate cellular androgen receptor (AR) distribution and intensity of immunostaining in the human azoospermic testis. Thirty six biopsy specimens from azoospermic men were immunostained, using a monoclonal antibody of human AR. The localization and the intensity of AR immunostaining was evaluated in Sertoli Cell Only (SCO) testis (G1, n = 21), in spermatogenesis arrest testis (G2, n = 11) and in histologically normal testis (G3, n = 4). We found an AR immunostaining in Sertoli, peritubular myoid and Leydig cells, but not in germ cells. The intensity of the immunostaining varied substantially between biopsy specimens of different patients. Sertoli and Leydig cells AR immunostaining (score and intensity) in SCO group was higher than in the other groups. For Sertoli cells, the score means of AR immunoreactivity were 20 +/- 2.36, 10.18 +/- 1.0 and 1 +/- 1, for G1, G2 and G3 groups, respectively. For Leydig cells, the score means were 10.24 +/- 1.37, 6 +/- 0.71 and 0, for G1, G2 and G3 groups, respectively. We found significant differences between G1 and G2 (p = 0.0008), between G1 and G3 (p = 1.54 10-7) and G2 and G3 (p = 0.00032). These results suggest that in the testis AR is located exclusively in somatic cells and its expression is higher in SCO syndrome than in normal and in arrest spermatogenesis testes.     

Morphometric analysis of cell types in the ovine corpus luteum throughout the estrous cycle

The cellular composition of ovine corpora lutea obtained during the early (Day 4), mid (Days 8 and 12), and late (Day 16) stages of the estrous cycle was determined by morphometric analysis. Individual corpora lutea were collected via midventral laparotomy from a total of 19 ewes. A center slice from each corpus luteum was processed for electron microscopy and subsequent morphometric analysis of the numbers and sizes of steroidogenic and nonsteroidogenic cells. Luteal weight progressively increased throughout the estrous cycle (p less than 0.05). Corpora lutea collected on Day 16 were assigned to one of two subgroups on the basis of gross appearance and weight: nonregressed (NR, 542 +/- 25 mg) or regressed (R, 260 +/- 2 mg). There were no significant changes in the proportion of the corpus luteum occupied by small luteal cells (19 +/- 2%) or large luteal cells (36 +/- 1%) throughout the estrous cycle. The total number of steroidogenic cells per corpus luteum increased from 21.8 +/- 3.7 (X 10(6)) on Day 4 to 61.7 +/- 5.4 (X 10(6)) on Day 8 (p less than 0.05) and remained elevated thereafter. The number of small luteal cells was 10.0 +/- 2.7 (X 10(6)), 39.7 +/- 1.4 (X 10(6)), 46.1 +/- 5.8 (X 10(6)), 49.0 +/- 13.7 (X 10(6)), and 29.9 +/- 8.6 (X 10(6)) on Days 4, 8, 12, 16 (NR), and 16 (R), respectively (p less than 0.05, Day 4 vs. Days 8, 12, 16 NR). In contrast, the number of large luteal cells was 11.8 +/- 1.5 (X 10(6)) on Day 4 and did not vary significantly during the remainder of the estrous cycle. The numbers of nonsteroidogenic cell types increased (p less than 0.05) from Day 4 to Day 16 (NR) but were decreased in regressed corpora lutea (Day 16 R). Regression was characterized by a 50% decrease (p less than 0.05) in the total number of cells per corpus luteum from 243 +/- 57 ( X 10(6)) on Day 16 (NR) to 125 +/- 14 ( X 10(6)) on Day 16 (R) (p less than 0.05). Small luteal cells remained constant in volume throughout the entire estrous cycle (2520 +/- 270 microns 3), whereas large luteal cells increased in size from 5300 +/- 800 microns 3 on Day 4 to 16,900 +/- 3300 microns 3 on Day 16 (NR) (p less than 0.05). In summary, small luteal cells increased in number but not size throughout the estrous cycle, whereas large luteal cells increased in size but not number.     

Reproductive pattern in the male Angolan free-tailed bat, Tadarida (Mops) condylura (Microchiroptera: Molossidae) in the Eastern Transvaal, South Africa

The reproductive pattern in male Angolan free-tailed bats Tadarida (Mops) condylura was studied at two localities in the Eastern Transvaal during the period 1989-1991. Males displayed a nine-month breeding season extending from June to February. Following testicular recrudescence in early June, spermatogenic activity displayed two periods of peak activity in August/early September and November/early December. Although testes became involuted in March, baseline spermatogenic activity was maintained and tests never regressed to prepubertal conditions. Leydig cell morphology closely followed spermatogenic activity, with the diameter of Leydig cell nuclei displaying a concomitant seasonal pattern.     

Photoperiodic regulation of glutamatergic stimulation of secretion of luteinizing hormone in male Syrian hamsters.

It has been suggested that changes in endogenous glutamatergic stimulation of secretion of luteinizing hormone (LH) induced by photoperiod play a role in regulating seasonal cycles of reproductive activity. The aim of this study was to test the hypothesis that the glutamatergic control of the secretion of LH in the male Syrian hamster is sensitive to photoperiod, by determining whether the glutamate agonist N-methyl-D-aspartate (NMDA) could stimulate LH secretion in this species and, if so, to determine whether the response varied among animals exposed to different daylengths. In the first experiment, adult male hamsters were housed in either short day (8 h light: 16 h dark) for 6 weeks to induce testicular regression, or long days (16 h light: 8 h dark) to maintain testicular function, and the effects of systemic administration of NMDA on serum LH concentrations were determined. In the short-day hamsters, all s.c. doses of NMDA (25-75 mg kg-1 body weight) produced a robust rise in serum LH concentrations within 15 min. In the long-day hamsters, basal LH concentrations were higher than in short-day hamsters, but only the highest dose of NMDA produced a significant increase in LH concentrations, and the magnitude of this increment was less than those observed in short days. In hamsters in long days, the low doses of NMDA that did not significantly alter LH concentrations nevertheless significantly suppressed serum prolactin concentrations, demonstrating the efficacy of the drug. In hamsters in short days, serum prolactin concentrations were at the limit of detection of the assay, so no inhibitory effect of NMDA on prolactin secretion could be determined on this photoperiod. In the second experiment, the effects of a fixed dose of NMDA (50 mg kg-1 body weight) was tested at intervals in hamsters exposed to short days for a prolonged period such that their testes initially regressed, but then became scotorefractory and testicular recrudescence occurred. After 6 and 12 weeks in short days, NMDA stimulated LH secretion. However, after 24 weeks in short days when testicular recrudescence was complete, the response to NMDA was lost. A third experiment determined whether the reduced response to NMDA in hamsters on long days relative to those in short days might result from higher concentrations of circulating testosterone. Hamsters in long days were castrated to remove the influence of gonadal feedback, and the response to NMDA tested 3 weeks later when endogenous LH concentrations had risen to levels characteristic of the chronically castrated condition.(ABSTRACT TRUNCATED AT 400 WORDS)     

Differential ovarian expression of KiSS-1 and GPR-54 during the estrous cycle and photoperiod induced recrudescence in Siberian hamsters (Phodopus sungorus)

Kisspeptins, coded by the KiSS-1 gene, regulate aspects of the reproductive axis by stimulating GnRH release via the G protein coupled receptor, GPR54. Recent reports show that KiSS/GPR54 may be key mediators in photoperiod-controlled reproduction in seasonal breeders, and that KiSS-1/GPR54 are expressed in the hypothalamus, ovaries, placenta, and pancreas. This study examined the expression of KiSS-1/GPR54 mRNA and protein in ovaries of Siberian hamsters (Phodopus sungorus). Ovaries from cycling hamsters were collected during proestrus (P), estrus (E), diestrus I (DI), and diestrus II (DII). To examine KiSS-1/GPR54 during stimulated recrudescence, additional hamsters were maintained either in long day (LD 16L:8D, control) or short day (SD 8L:16D) for 14 weeks and then transferred to LD for 0-8 weeks. Staining of KiSS-1/GPR54 protein was detected by immunohistochemistry in steroidogenic cells of pre-antral and antral follicles, and corpora lutea. Immunostaining peaked in P and E, but decreased in the diestrus stages (P < 0.05). In recrudescing ovaries, KiSS-1/GPR54 immunostaining was low after 14 weeks of SD exposure (post-transfer [PT] week 0), and increased during the early weeks of recrudescence. Expression of KiSS-1/GPR54 mRNA was low with short day exposure, but increased during recrudescence and was higher at PT week 8 as compared to PT weeks 0 and 2 (P < 0.05). The elevated KiSS-1/GPR54 expression during P and E suggests a potential role in ovulation in Siberian hamsters. Transient increases in KiSS-1/GPR54 expression following LD stimulation are also suggestive of possible involvement in ovulation and/or restoration of ovarian function.     

Testicular apoptosis is down-regulated during spontaneous recrudescence in white-footed mice (Peromyscus leucopus).

Among individuals of many nontropical species, seasonal breeding is timed by tracking changes in the daily photoperiod. Transfer of rodents to short (< 12 h of light/day) day lengths for 6 to 14 weeks can induce regression of the testes mediated by apoptosis. After 16 to 20 weeks of short day exposure, reproductive function is "spontaneously" initiated, and testicular recrudescence is observed. The gonadal mechanisms that underlie testicular recrudescence are not fully understood. If the onset of testicular regrowth that occurs during spontaneous recrudescence reflects a down-regulation of apoptotic signals, then a decline in apoptosis should be noted concurrent with increased testis mass. This experiment sought to assess the role of apoptosis in the restoration of reproductive capacity to photoperiod-inhibited white-footed mice. Males were assigned to long (16:8 LD) or short (8:16 LD) photoperiods for 0, 14, 18, 22, 26, or 30 weeks. At each of these time points, testis mass and testosterone concentrations were assessed. In addition, apoptotic activity was measured using both in situ terminal deoxynucleotidyl transferase dNTP end labeling (TUNEL) and DNA laddering. Short photoperiod exposure induced maximal decreases in testicular parameters after 14 weeks (p < 0.05). After 26 weeks of short days, testis mass was no longer different between males housed in long days and those housed in short days. In contrast, the high incidence of apoptotic TUNEL labeling and DNA laddering observed at 14 weeks was reduced to long day values after 22 weeks of short day exposure. Together, our results establish that a decrease in testicular apoptosis coincides with testicular recrudescence in white-footed mice. The current study demonstrates a decline in the incidence of testicular cell death concomitant with changes in testis mass or length, elucidating a timeline of changes at the cellular level related to the onset of recrudescence.     

Circadian rhythms of self-selected lighting in golden hamsters: relation to gonadal condition

Golden hamster (20 males, 8 females) were maintained in isolation boxes for 4-7 weeks. The animals had access to wheels and selected their own lighting by pressing one bar to turn light-on and another bar to turn the light-off. All hamsters maintained circadian rhythms of wheel-running activity. Seventeen of 28 hamsters selected lighting with a circadian periodicty. For 9 hamsters, there was a significant positive correlation between wheel-running activity and self-selected darkness, while this correlation was significantly negative for 10 hamsters. Four hamsters had regressed testes at the end of the experiment. These 4 had significant positive correlations between activity and self-selected darkness, while none of the hamsters with significant negative correlations between activity and self-selected darkness had regressed testes. Light in phase with activity seems to be more important to the prevention of testicular regression than is the total daily amount of light.