Reproductive coordination in the golden hamster: Female influences on the male

Gonadal regression in male golden hamsters was induced by short day length. Exposure to sexually receptive females living under either long- or short-day conditions failed to induce testicular recrudescence among the males with regressed testes. The combination of long day length and exposure to either sexually receptive females or cages soiled by these females significantly enhanced testicular recrudescence in comparison to males exposed only to long day length. These results indicate that photoperiodic and social stimulation can interact to enhance reproductive functioning in the male hamster and that the social stimuli involved may be chemical cues from the female.     

Predictors of dominance in the male golden hamster (Mesocricetus auratus)

The outcome of social interactions between four male hamsters was significantly related to body weight (r_s=0·66) and to the size and pigmentation of their lateral flank glands (r_s=0·82). Weight was held constant in a second experiment and variations in gland size and pigmentation remained significantly related to the outcome of social encounters (r_s=0·77). In a third experiment, castrate hamsters of uniform weight receiving either no hormone, 0·1 mg, 0·50 mg, or 1·00 mg testosterone propionate exhibited flank gland variations significantly related to social rank (r_s=0·81). These experiments demonstrate that the state of the flank gland, which is related to endogenous androgen levels, can be used as a predictor of social rank in male hamsters.     

Multinucleated erythroid cells in blood of golden hamster embryos

Blood smears of 11 and 13-day-old embryos (20) and newborns (10) of golden hamsters were analysed. The smears were stained with brilliant cresyl blue in a moist chamber for 5--7 min. About 2--6 thousand cells were counted in 200 visual fields. By means of an ocular micrometer MOB-1 the diameters of 300 cells were measured and the curves on cell distribution were plotted according to the diameters. It was found that the blood of 11-day-old golden hamster embryos contained about 8% of binuclear and sixnuclear megaloblasts, and that of 13-day-old embryos--about 2.5% of binuclear and sixnuclear erythroblasts and megablasts of the second generation. In the bloood of newborn hamster polynuclear cells are absent.     

Changes in social behavior of the male golden hamster accompanying photoperiodic changes in reproduction

Testicular regression and decreased serum testosterone levels result when male hamsters are placed in a short-day photoperiod, and these changes are reversed after reexposure to long-days. The present study was undertaken to determine whether these physiological changes lead to modifications in social behavior in the male hamster. Animals in a nonstimulatory short-day (LD 6:18) or a stimulatory long-day (LD 14:10) photoperiod were observed every 3 weeks for 21 weeks. After 9 weeks, half of the LD 6:18 males were returned to LD 14:10 and showed rapid testicular recrudescence. The other half remained in LD 6:18 and showed a slower rate of testicular recrudescence. Assessment of aggression was accomplished by placing an intruder in the home cage of a test animal and recording latency to attack, decisive encounters, number of attacks, and number of aggressive postures. Dominance was evaluated in a neutral arena with opponents of different weights, using the same parameters. Scent-marking was recorded in response to both bedding from an intact male and bedding from an ovariectomized female in a clean cage. Short-day animals undergoing testicular regression showed heightened levels of aggression and an upward shift in their dominance status. Alteration of the photoperiod did not affect the pattern or number of scent marks. As animals underwent testicular recrudescence, there was a return to lower levels of aggression and to a lower dominance status. Males undergoing rapid testicular recrudescence also showed the most rapid decline in aggressive behaviors. These results suggest that levels of agonistic behavior in the male hamster are inversely related to serum testosterone levels. Scent-marking appears to be unreleated to androgen levels in the male hamster and its role in hamster social behavior remains unclear.     

A dense-cored filamentous body in Leydig cells of the golden hamster

Summary A unique cytoplasmic structure has been observed in Leydig cells of the golden hamster. It consists of a laminar core made up of electron dense material surrounded by a filamentous matrix of lower density, and is tentatively called a dense-cored filamentous body (DCFB). DCFBs vary in overall size and in configuration of the centrally disposed dense lamina. They are typically located in the vicinity of the centrosome and the Golgi complex. The body has no limiting membrane, and may be in contact with virtually every type of organelle. The DCFB is well developed in active Leydig cells, whereas it is small in the quiescent stage of the secretory cell. It is likely that the DCFB is a constant organelle in the hamster Leydig cell and may be involved in the physiological function of the Leydig cell, which remains to be specified.This work was supported in part by a grant from the National Science Council, the Republic of China (NSC-66B-0412-02-13)     

Restorative effect of various androgens on copulatory behavior of the male golden hamster

Adult male hamsters were castrated, and four weeks later, after a single mating test, began receiving daily 100 μg injections of testosterone (T), androstenedione (AD), or testosterone propionate (TP). Mating tests were conducted at regular intervals during the eight week treatment period. Results indicated the superiority of TP in reinstating intromissions and ejaculations. The T and AD groups did not differ on any of the measures, a result which agrees with previous similar experiments using rats.     

Apoptosis in the epididymal epithelium of adult male golden hamster exposed to diethylstilbestrol.

Apoptosis in the testis and prostate exposed to disrupters of endocrine function, including diethylstilbestrol (DES), during neonatal or postnatal periods has repeatedly been demonstrated, but not in the mature epididymis. We investigated the effects of DES, a potent and synthetic estrogen, on apoptosis in the adult. Adult male golden hamsters received an SC injection of DES and were then sacrificed to collect epididymides after 1, 4, or 7 days of treatment. A significant decrease in epididymal weight and an increase in apoptotic cells were shown on the first day after DES injection. Flow cytometry showed that DES treatment (1 mg/kg) for 1, 4, or 7 days induced significant apoptosis both in the caput and the cauda epididymides. Greater numbers of apoptotic cells were detected in the caput than in the cauda at a fixed time after DES treatment. Serum levels of testosterone decreased markedly within 24 hr after DES administration, reaching undetectable levels of 0.1 ng/ml at 4 days and thereafter. These results indicate that DES administration can increase epididymal apoptosis with a decrease in serum testosterone levels. Because DES used to be injected into domestic animals, adult males also have a chance to take this substance through food. Our study indicates that exposure to DES in adults is as toxic as that in the perinatal period.     

Immunocytochemical studies on prolactin cells in the adenohypophysis of the golden hamster

Mammotrophs or prolactin (PRL) cells were identified in the adenohypophysis of adult golden hamsters by immunocytochemical techniques with a polyclonal anti-PRL, that was proved to be specific to PRL by the dot immunoblotting test. Postembedding immunostaining was performed on Araldite thin sections by immunoperoxidase and immunogold methods. PRL cells were classified into three types according to the different size of the secretory granules. The Type A cells were usually small and angular or oval in shape, and had secretory granules ranging in diameter from 100-230 nm, and showed poorly developed organelles. The Type B and C cells were larger and round or ovoid in shape, contained larger granules, 230-280 nm and 280-570 nm, respectively, and displayed well developed organelles. Immunoreactive PRL cells in the male pituitaries were far less numerous than in the nonpregnant female glands, and were mostly of the Type A and B, whereas in the female the Type C and B cells predominated. In pregnant females, Type C cells became activated and increased in number, while the other two types decreased in proportion. In lactating females, Type A and B cells significantly increased in number at the expense of the Type C cells; meanwhile, the exocytosis of secretory granules was frequently found in all types of PRL cells. The present findings suggest that Type C and B PRL cells, especially the former, are potent in producing and releasing PRL and highly responsive to various physiological stimuli, while Type A cells are probably relatively inert in synthetic activity.     

Interstitial and parenchymal cells in the pineal gland of the golden hamster

Summary A combined thin-section/freeze-fracture study was performed on the superficial pineal gland of the golden hamster, comparing the parenchymal and interstitial cells of this animal with those previously investigated in rats. In contrast to rats, no gap junctions and gap/tight junction combinations could be found between pineal parenchymal cells of the hamster. Furthermore, the interstitial cells of the hamster pineal gland were found to have large flat cytoplasmic processes, which abut over large areas equipped with tight junctions. In thin sections, profiles of interstitial cell processes were seen to surround groups of pinealocytes. Interstitial cells and their sheet-like, tight junction-sealed processes thus appear to delimit lobule-like compartments of the hamster pineal gland. Because the classification of the interstitial cells is uncertain, the expression of several markers characteristic of mature and immature astrocytes and astrocyte subpopulations has been investigated by indirect immunohistology. Many of the non-neuronal elements in the pineal gland are vimentin-positive glial cells, subpopulations of which express glial fibrillary acidic protein (GFA) and C1 antigen. The astroglial character of these cells is supported by the lack of expression of markers for neuronal, meningeal and endothelial cells. M1 antigen-positive cells have not been detected.Supported by a grant from Deutsche Forschungsgemeinschaft (Scha 185/9-2)     

Different lectin-binding patterns of the male and female harderian gland in the golden hamster.

Ten lectin-binding patterns were examined with the PAP method for the detection of sugar residues on the Harderian glands of golden hamsters of both sexes. Each lectin showed a specific binding pattern. The most characteristic pattern was exhibited by DBA which intensely stained cells with small lipid vacuoles, but not cells with large lipid vacuoles in the male gland. In the female gland, both cell types showed no reaction with the DBA. The PNA had almost the opposite binding pattern. From the lectin-binding patterns, it can be derived that, not only do the two cell types in same sex glands have different glycoconjugate distribution, but also the same type of cells in different sex glands has a different glycoconjugate distribution. Therefore, the sexual dimorphism of the golden hamster Harderian gland also occurs in its carbohydrate moieties. In this study, the duct of the Harderian glands revealed no sexual dimorphism in the lectin-binding patterns.     

Melatonin: Failure of pharmacological doses to induce testicular atrophy in the male golden hamster

Effects of graded doses of melatonin on reproductive function of the male golden hamster were studied. Daily injections of melatonin at 17:00 h brought about complete testicular regression when the hamster received 10, 25, and 100 ug melatonin; larger doses of 1,000 ug or 2,500 ug had a partial or no effect on testicular or accessory sex organ weights. The dose response relationship of testicular and accessory sex organ weights to melatonin treatment somewhat resembled an inverted bell-shaped curve. Plasma, LH and prolactin concentrations followed the pattern of the testicular and accessory sex organ weights; small doses of melatonin suppressed plasma, LH and prolactin while larger doses had no suppressive effects. These results indicate that melatonin can exert a reproductive inhibitory effect if injected with small, but not with larger doses.     

Effects of male accessory sex gland secretions on early embryonic development in the golden hamster

The ventral prostates, dorsolateral prostates, coagulating glands, seminal vesicles and/or ampullary glands were bilaterally removed from adult male hamsters. Removal of these glands did not affect the fertilization rate and cleavage of the embryos at 48 h post coitum (p.c.). Air-dried preparations of the embryos showed a delay in cleavage at 72 h p.c. and a significant number of degenerated embryos was also found in females mated with males from which all the male accessory sex glands had been removed. A significant implantation loss was also observed at 122 h p.c. The results suggest that, in the golden hamster, removal of the male accessory sex gland causes a slower cleavage rate in embryonic development and a significant embryonic loss during pregnancy.     

Immunocytochemical identification of growth hormone cells in the adenohypophysis of the golden hamster

Somatotrophs or growth hormone (GH) cells in the adenohypophysis of golden hamsters were identified by immunocytochemical staining with polyclonal rabbit anti-human GH. They were oval or columnar in shape, and had secretory granules of two size ranges, 90-150 nm and 280-320 nm, which were present in the same cells; no subtypes of GH cells were observed. Secretory granules were located in the peripheral portion of the cytoplasm or concentrated at the vascular pole of the cell. Flattened cisternae of the rough endoplasmic reticulum in parallel array and a moderately developed Golgi apparatus were often found in the cytoplasm. No sex difference was noticed in the population ratio of GH cells. Immunocytochemical staining with anti-GH or anti-prolactin (PRL) antibodies on separate adjacent sections revealed that the GH and PRL were stored in two different cell types.