Neonatal androstenedione and adult sexual behavior in golden hamsters.

Notes that male rats castrated and given androstenedione neonatally can show high levels of both masculine and feminine copulatory behavior in adulthood. In the present study, 24 intact female and 30 intact male hamsters castrated at birth were treated for their 1st 20 days with oil, free testosterone, or androstenedione. All neonatal androgen treatments mimicked the naturally occurring developmental process of the male in that all androgenized groups were capable of high levels of male behavior (males but not females showing ejaculation patterns) as well as moderate levels of lordotic receptivity. There were no significant differences in effect among neonatal androgen treatments. Results are discussed as they relate to species differences, sex differences, hamster "bisexuality," and posthormone copulatory performance. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal androgenic stimulation and adult sexual behavior in male and female golden hamsters.

In an experiment with 48 male and 48 female golden hamsters, neonatally and adult castrated males as well as neonatally androgenized and nonandrogenized females were tested for both mounting and lordosis behaviors during treatment with either testosterone or ovarian hormones. Neonatal androgenization facilitated mounting behavior in adult Ss administered either testosterone or ovarian hormones and suppressed lordosis behavior in adult ovarian-hormone-treated Ss. Early androgen effects on the display of lordosis behavior during adult testosterone treatment were complex and varied with the exact timing of perinatal endogenous or exogenous androgenization. Species differences in hormone-behavior relationships and the possible role of perinatal androgenization in the development of rodents' ability to aromatize androgens are discussed. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anabolic-androgenic steroid exposure during adolescence and aggressive behavior in golden hamsters

Anabolic androgenic steroid (AAS) abuse by adolescents represents a significant health care risk due to the potential for long-term negative physical and psychological sequelae, including increased aggressive behavior. The current experiments examined the effects of AAS use in young male adolescent hamsters (Mesocricetus auratus) and their consequences on aggressive behavior. It was hypothesized that AAS administration during adolescence predisposes hamsters to heightened levels of aggressive behavior (i.e., offensive aggression). To test this hypothesis adolescent male hamsters were administered high doses of synthetic AAS to mimic a 'heavy use' self-administration regimen used by athletes. Immediately following the exposure to AAS hamsters were tested for aggressive behavior using a resident-intruder model. Animals treated with high doses of AAS during their adolescent development showed heightened measures of offensive aggression i.e., decreased latency to bite and increased total number of attacks and bites) during the test period, while measures of total activity (total contact time) between the animals remained unchanged. AAS-treated males did not differ in body weight from controls, suggesting that the increased aggression was not due to increased body mass. The results of this study show that exposure to AAS during adolescence facilitates aggressive response patterns, but does not alter body weight.     

Dietary self-selection in chronically insulin-treated golden hamsters.

24 adult male golden hamsters were maintained on either Purina Rat Chow (chow group) or a self-selection diet consisting of high-protein chow, pure carbohydrate, and pure fat (choice group). Ss were injected for 12 consecutive days with either long-acting insulin (20, 60, and 100 U/kg for 4 days each) or physiological saline. Insulin-injected Ss under both dietary conditions increased their total caloric consumption by up to 33% and gained significantly more weight than saline-injected controls. Choice Ss increased their fat intake in response to the 60 and 100 U/kg dose of insulin, but carbohydrate and protein consumption increased only in response to the 100 U/kg dose. Choice Ss derived approximately 65% of the excess calories ingested during insulin administration from fat but only 20% from carbohydrate and 15% from protein. Results are related to those previously observed in other species. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory sensitive periods in albino rats and golden hamsters.

Examined odor preferences of 72 infant, juvenile, and adult Sprague-Dawley rats and 119 Syrian hamsters in a 2-choice situation following 3–10 days of differential olfactory exposure. Exposure increased preferences for a simple botanical odor in infants and juveniles but not adults of both species. Preference differences between exposure groups were greatest for infants, moderate for juveniles, and insignificant for adults, suggesting that olfactory sensitive periods occur in these altricial rodent species. Age of exposure differentially influenced responses to combinations of conspecific and botanical odors. Results suggest that olfactory experience has a similar impact on responses of rats and hamsters to botanical but not conspecific odors. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shifting strategies for behavioral thermoregulation in developing golden hamsters.

Studied developmental changes in the golden hamster pup's capacity for behavioral temperature regulation. Groups of 3 pups aged 4-24 days were tested at room temperature (22°C), on a strong gradient (34-22°C), and on a mild gradient (30-22°C). The proportion of time engaged in the following behaviors was recorded: contact with the warm edge (thermotaxis), active huddling, and quiet huddling. Results show that Ss tested at 22° engaged in active huddling, and their temperature dropped rapidly. Only on Day 14 were they able to maintain their temperature constant with a combination of vigorous exploration and quiet huddling. On the strong gradient, Ss were able to regulate their temperature at all ages. Young Ss (4-5 days) depended on thermotaxis rather than huddling, separating when their temperature started to rise. With age, quiet huddling replaced thermotaxis as a dominant behavior. On the mild gradient, Ss combined active and quiet huddling with thermotaxis, so that their temperature dropped at a slow steady rate. It is concluded that hamster pups have a well-developed capacity for behavioral temperature regulation. Whether they attempt to keep their temperature constant or tolerate a slow rate of drop depends on the amount of exogenous heat available, which under natural conditions would be supplied predominantly by the mother. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flank-marking behavior and the neural distribution of vasopressin innervation in golden hamsters with suprachiasmatic lesions

In golden hamsters, microinjections of arginine-vasopressin (AVP) within the anterior hypothalamus trigger a stereotyped scent-marking behavior, flank marking. Our experiment was carried out to test the contribution of AVP neurons within the suprachiasmatic nucleus (SCN) in the control of this behavior. Our results suggest that the SCN does not contribute to flank-marking behavior. Whereas SCN lesions disrupted circadian rhythms of wheel running, the same lesions did not disrupt flank-marking. The results also suggest that neurons located outside the SCN contribute significantly to the vasopressinergic innervation of the brain and the expression of AVP-dependent behaviors, such as flank-marking behavior. Although AVP-immunoreactive fibers were severely (ca. 95%) depleted from several forebrain areas in SCN-lesioned hamsters, the effect of the lesions was much more limited within the forebrain areas involved in flank-marking behavior as well as within the midbrain and hindbrain.     

Serotonin regulation of aggressive behavior in male golden hamsters (Mesocricetus auratus).

These studies examined the neurochemistry and neuroanatomy of the serotonin (5-HT) system innervating the anterior hypothalamus (AH) and the interaction of 5-HT receptor agonists with arginine vasopressin (AVP) in the regulation of offensive aggression in golden hamsters. Because specific 5-HT1A, 5-HT1B, and AVP V1A binding sites were observed within the AH by in vitro autoradiography, the hamsters were tested for offensive aggression after microinjections of AVP in combination with either the 5-HT1A agonist 8-hydroxy-2-(di-n-propylarnino) tetraline (DPAT) or the 5-HT1B agonist CGS-12066A (CGS) directly within the AH. Though treatment with DPAT resulted in a dose-dependent inhibition of AVP-facilitated offensive aggression, CGS was ineffective. In addition, a retrograde tracer was injected within the AH to localize the distribution of 5-HT neurons projecting to the area. Retrogradely labeled 5-HT neurons were found within the dorsal, median, and caudal linear raphe nuclei and are suspected to inhibit AVP-facilitated offensive aggression by an activation of 5-HT1A receptors in the AH. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distribution of small vasopressinergic neurons in golden hamsters

In rats, small (diameter: ca. 10 micrograms) vasopressinergic neurons have been localized in the forebrain, including extrahypothalamic sites, such as the bed nucleus of the stria terminalis (BST) and the medial amygdala (MeA). In golden hamsters, no such neurons have ever been described in extrahypothalamic sites, while their presence in some hypothalamic sites, such as the paraventricular nucleus (PVN), remains controversial. The present studies were carried out to confirm the existence of small vasopressinergic neurons in the forebrain of golden hamsters, using rats as a positive control. The presence of small vasopressinergic neurons in these sites was first tested by immunocytochemistry in colchicine-treated animals. The resulting distribution was corroborated by in situ hybridization for vasopressin (AVP) mRNA. While a large number of small AVP-immunoreactive (AVP-ir) neurons was found in the BST and MeA of colchicine-treated rats, none was found in the same locations in hamsters. Interestingly, as a few large (diameter: 20-25 micrograms) AVP-ir neurons were found in the BST just medial to the small neurons in rats, the same area contained a few large and small AVP-ir neurons in hamsters. In the PVN, large and small AVP-ir neurons were found in rats and hamsters. However, three to four times more neurons were counted in rats. These data were confirmed by in situ hybridization. Indeed, in hamsters, no labelling for AVP mRNA was detected in small neurons within the BST and MeA. Furthermore, the PVN of rats contained more labelling for AVP mRNA, as compared to hamsters. These results confirm that the distribution of vasopressinergic neurons in rats cannot be generalized to other species without a detailed analysis.     

Physical and behavioral aspects of sexual maturation in male golden hamsters.

Male golden hamsters ( Mesocricetus auratus ) were examined from 3 to 9 wks of age for morphological, physiological, and behavioral indices of sexual maturation. Although each of the 8 variables (e.g., testis weight, seminal vesicle fluid, and rear mounts) selected for measurement displayed a unique developmental profile, a principal-components analysis of these variables resulted in the extraction of 2 principal components, one tentatively labeled physical and gross behavioral maturation (accounting for 66% of the total variance) and the other designated perfection of mounting orientation (accounting for an additional 12% of the variance). This result indicates that puberty in the male hamster is best viewed as 2 independent processes, rather than as a unitary process or as an arbitrary term applied to a variety of unrelated developmental phenomena. Advantages of using multivariate composite scores and selected univariate measurements are discussed, as are methods of comparing developmental changes in different variables. A 2nd experiment confirmed an unexpectedly early onset of androgen secretion and an unusual pattern of body weight gain. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste aversions to food flavors and vaginal secretion in golden hamsters.

Although rodents readily associate virtually any distinctive flavor with gastrointestinal illness when the flavor and illness have been paired, experience with a flavor can provide information that interferes with later attempts to produce aversions to the familiar taste. The vaginal secretion of female hamsters carries sexual information for males, which does not depend on previous experience; it was studied, in the present 3 experiments, whether that built-in information might interfere with associations between flavor of the excretion and illness. Surprisingly, the Ss, 32 male Syrian hamsters, showed dramatic changes in behavior toward the vaginal secretion when its presentation was followed by lithium chloride poisoning. Results suggest that mammalian responses to sex pheromones are far more easily modified by experience than has been supposed. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pancreatic neoplasms induced in Syrian golden hamsters. I. Scanning electron microscopic observations

Pancreases from Syrian golden hamsters treated with N-nitrosobis(2-hydroxy-proply)amine for 10 to 25 weeks were examined under scanning electron microscopy (SEM). Findings indicate that the neoplasms originated from the ductal epithelium and developed progressively. Adenomas were lined by epithelium of differing cells types, ranging from a flat singly ciliated form to cuboidal-columnar types, or to mixed cell populations. The epithelial lining of the ductal carcinomas exhibited tubular and papillary cystic spaces, and cell surfaces were similar to the cuboidal and columnar epithelium of adenomas and of ductal epithelial hyperplasia. However, microvilli were dense and of varied lengths. The SEM observations correlated with patterns seen in routine histologic preparations.     

Retinal degeneration induced by N-methyl-N-nitrosourea in Syrian golden hamsters

BACKGROUND: The sequential retinal changes in Syrian golden hamsters induced by N-methyl-N-nitrosourea (MNU) have not been studied. METHODS: Female hamsters received a single intraperitoneal injection of 90 mg/kg MNU at 50 days of age, and the retina was examined light and electron microscopically, immunohistochemically and by the TdT-mediated dUTP-digoxigenin nick end labeling (TUNEL) method until 20 weeks after the treatment. RESULTS: The retinal changes were as follows: (1) Photoreceptor apoptosis occurred 1 day after the treatment and resulted in photoreceptor loss at day 7. During the degeneration, Müller cell proliferation was conspicuous at day 5. (2) After the photoreceptor cell loss, migration of the pigment epithelial cells in all layers of the retina which were in contact with blood vessels occurred. Due to the Müller cell proliferation, gliosis was prominent at the later stage. CONCLUSIONS: The MNU injection caused photoreceptor apoptosis followed by pigment epithelial cell migration around the blood vessels, accompanied by gliosis. The primary event and the course of this disease closely resemble those of retinitis pigmentosa in humans.     

Effects of immobilization restraint on Syrian golden hamsters

A 2 x 2 x 4 factorial design was used to study variation of protein and fat contents in beef broths as affected by cut type (flank, shank), salt treatments (addition of salt to the medium, no salt), and initial temperatures of simmering (25, 70, 75, and 100 degrees C). Flank portions yielded slightly more protein (0.29 g/100 mL) and had three-fold less fat (0.39 g/mL) than those of shank (0.25 and 1.12 g/mL, respectively) (P < 0.05). No linear relationship of temperature and amount of extractable components was observed, but it was clear that the greatest protein extraction was accomplished when meat was immersed in cooking water at boiling point (P < 0.05). In general, salting of water reduced fat content of beef broths. However, a significant Salting x Cut type interaction showed this effect was only present in shanks (P < 0.05). Conversely, the reducing effect (P < 0.05) of salting on amount of protein extracted from flank was not observed in shanks. Based on these data, we conclude that larger amounts of protein and less fat could be transferred from meat pieces to the medium by immersing beef in salted water at the boiling point.     

Behavioral alterations in male golden hamsters exposed to chlorodibromomethane

STUDY OBJECTIVE: Carcinoembryonic antigen (CEA) is the most frequently used tumor marker in pleural fluid. Nevertheless, little is known about the causes of false-positive results. The aim of the study was to analyze the frequency, etiologies, and characteristics of the nonmalignant pleural effusions associated with elevated levels of CEA in pleural fluid. PATIENTS: Two hundred seventy-three consecutive patients with pleural effusions were evaluated, 91 (33%) associated with malignancy, and 182 (67%) due to benign diseases (51 transudates, 38 tuberculosis, 37 parapneumonic, 56 other). RESULTS: A level of CEA in pleural fluid above 10 ng/mL was found in 47% of pleural effusions associated with malignancy. Elevated levels of CEA were also found in 17 of the 182 (9%) nonmalignant pleural effusions: all five empyemas, one of the 23 typical parapneumonic (4%), two of the six borderline complicated (33%), and four of the eight complicated parapneumonic effusions (50%), one of the 38 tuberculous pleurisy (3%), one of the 11 hepatic transudates (9%), in the only patient with urinothorax, in the only patient with acute pancreatitis, and in one patient with postsurgery pleural effusion but with esophageal carcinoma and elevated CEA level in serum. CONCLUSIONS: Although an elevated level of CEA in pleural fluid is suggestive of malignancy, CEA can be elevated in 9% of pleurisy owing to benign diseases, especially in empyemas and in complicated parapneumonic effusions. Identifying the most frequent causes of false-positive results of CEA helps to correctly interpret the findings of this tumor marker.     

Selection of relevant cues in volume discrimination by golden hamsters reared in different environments.

11 gold hamsters were reared from birth to adulthood in a spatially diversified environment, and their performances were compared with those of 13 Ss housed in standard laboratory cages. The task was to discriminate between 2 cubic volumes of differing size (from inside). Ss were presented with a test situation in which 1 or more walls (or parts of walls) of the volumes had been cut out. Results show that "enriched" Ss made learning transfers to more diversified test situations, whereas "standard" Ss appeared mainly to take the nearest parts of the stimuli into account. (French abstract) (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of putative satiety peptides on feeding and drinking behavior in golden hamsters (Mesocricetus auratus).

Intraperitoneal cholecystokinin octapeptide (CCK-8 [0.1–5 μg/kg]) reduced feeding in Syrian hamsters in a dose-related fashion, except for males tested during the light phase of the illumination cycle. Proglumide (200 or 400 mg/kg), a putative CCK receptor antagonist, did not alter spontaneous food intake and did not reverse the suppression of feeding resulting from CCK-8. Bombesin (BBS [0.5–20 μg/kg]), thyrotropin releasing hormone (TRH [5–200 μg/kg]), and calcitonin (CC [2–22 μg/kg]) produced a dose-related suppression of food intake. BBS appeared to do so specifically. In contrast, TRH appeared to reduce feeding by temporarily debilitating the Ss and CC by evoking behavior (increased locomotor activity) incompatible with feeding. Intracerebroventricular (icv) injections of CCK-8, BBS, and CC produced dose-related inhibition of feeding, but only CCK-8 appeared to affect feeding behavior selectively. Reduced feeding after icv BBS was associated with excessive grooming, and icv CC, like systemic CC, increased locomotor behavior. (72 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conflicts over selfishness: One aspect of some women's wish for a baby.

The wish for a baby has traditionally been associated with femininity in Western culture. However, the connection between the two has never been fully explicated. This article focuses on one of the potential meanings of the wish for a baby: the organization of a sense of a feminine self around giving to and caring for others, exemplified by the fantasy of the mother caring unambivalently for her baby. This aspect of the wish has both intrapsychic and interpersonal (including social and cultural) impetus and meaning for each individual. Three clinical examples illustrate the significance of this often unconscious and/or unarticulated meaning of the wish for a baby. (PsycINFO Database Record (c) 2010 APA, all rights reserved)