Oxytocin inhibits aggression in female Syrian hamsters.

Dominant subordinate relationships are formed as the result of social conflict and are maintained at least in part by communication. At this time, little is known about the neural mechanisms that are responsible for coordinating the social behaviours (e.g. aggression) that occur in association with the formation and maintenance of these relationships. The purpose of the present study was to investigate the role of oxytocin (OXT) within the medial preoptic anterior hypothalamic continuum (MPOA-AH) in the control of aggression in female hamsters. OXT injected into the MPOA-AH immediately before testing significantly reduced the duration of aggression in a dose-dependent manner. Injection of an OXT antagonist 30 min before testing significantly increased the duration of aggression. In contrast, the duration of aggression was not altered when hamsters were tested either 30 min after injection of OXT or immediately following injection of an OXT-antagonist. These data support the hypothesis that OXT release within the MPOA-AH regulates social behaviours important in the formation and maintenance of dominant subordinate relationships in female hamsters.

Social experience and social context alter the behavioral response to centrally administered oxytocin in female Syrian hamsters.

The type of social behavior displayed by an individual is profoundly influenced by its immediate social environment or context and its prior social experience. Although oxytocin is important in the expression of social behavior in several species, it is not known if social factors alter the ability of oxytocin to influence behavior. The purpose of the present study was to test the hypothesis that social experience and social context alter the ability of oxytocin to regulate flank marking (a form of scent marking) in female Syrian hamsters. Oxytocin was microinjected into the medial preoptic anterior hypothalamic continuum (MPOA-AH) of socially experienced, dominant female hamsters which were then tested with either a subordinate partner, with a novel partner, or alone. Oxytocin induced flank marking in a dose-dependent manner but only when the experienced dominant hamsters were tested with their familiar, subordinate partners. Oxytocin did not induce flank marking when injected into socially naive female hamsters that were tested with an opponent or alone. In males, by contrast, oxytocin induced flank marking in dominant hamsters when they were tested with their subordinate partner or alone. These data support the hypothesis that social experience and social context interact to regulate the ability of oxytocin to stimulate flank marking by its actions in the MPOA-AH in female hamsters.

Poromas of the head and neck.

BACKGROUND: The "eccrine" poroma is a benign neoplasm previously thought to originate from the eccrine sweat gland. Early studies suggested that these were primarily lesions of the hairless acral surfaces. OBJECTIVE: This article reports the clinical and histologic findings of 10 cases of poroma of the head and neck area. METHODS: The clinical and histologic findings of 10 cases of poroma of the head and neck area are compared with 10 poromas occurring on the extremities. RESULTS: Some poromas demonstrated evidence for apocrine origin. Unlike poromas found on the extremities, head and neck poromas were usually asymptomatic and were never correctly diagnosed clinically. Although 9 of 10 poromas on the extremities occurred in male patients, the head and neck poromas showed no gender predilection. CONCLUSION: Clinicians should be aware that poromas can occur in the head and neck area and may be of apocrine origin.

Human papillomavirus, smoking, and cancer.

BACKGROUND: The effect of smoking on human papillomavirus (HPV) activity and subsequent dysplasia and neoplasia remains controversial. OBJECTIVE: To determine any reported effects of smoking on either HPV activity or HPV-related dysplasia/cancer using retrospective analysis of the literature from 1966 through 1998 via Toxline and PubMed to search for "smoking," "papillomavirus," and "cancer." CONCLUSION: Several recent large studies demonstrated that smoking was associated with a greater incidence of cervical, vulvar, penile, anal, oral, and head and neck cancer in a dose-dependent fashion, while other studies did not show any correlation between smoking and cervical dysplasia after multivariate adjustment. Recent studies have also indicated that smoking may be more closely related to high-grade lesions of the cervix and vulva. These data provide evidence of an association between HPV, smoking, and cancer. Progression of dysplasia likewise seems to be associated with smoking. Several groups have attempted to discern whether the connection between smoking and cervical cancer is from local immunosuppression and/or from direct carcinogenic effects.

Conversion of testosterone to estradiol may not be necessary for the expression of mating behavior in male Syrian hamsters (Mesocricetus auratus).

Male sexual behavior is mediated in part by androgens, but in several species, mating is also influenced by estradiol formed locally in the brain by the aromatization of testosterone. The role of testosterone aromatization in the copulatory behavior of male Syrian hamsters is unclear because prior studies are equivocal. Therefore, the present study tested whether blocking the conversion of testosterone to estradiol would inhibit male hamster sexual behavior. Chronic systemic administration of the nonsteroidal aromatase inhibitor Fadrozole (2.0 mg/kg/day) for 5 or 8 weeks did not significantly increase mount latency or reduce mount frequency, intromission frequency, ejaculation frequency, or anogenital investigation relative to levels shown by surgical controls. However, Fadrozole effectively inhibited aromatase activity, as evidenced by the suppression of estrogen-dependent progesterone receptor immunoreactivity in the male hamster brain. The JZB39 anti-progesterone receptor antibody labeled significantly more neurons in brains of sham-treated hamsters than in brains of Fadrozole-treated hamsters. These data suggest that aromatization of testosterone to estradiol is not necessary for normal mating behavior in Syrian hamsters.

Differential expression of the HHV-8 vGCR cellular homolog gene in AIDS-associated and classic Kaposi's sarcoma: potential role of HIV-1 Tat.

Human herpesvirus 8 (HHV-8) has been causally linked to Kaposi's sarcoma (KS). There is significant homology between some HHV-8 genes and cellular genes including D-type cyclin (vCYC), G protein coupled receptor (vGCR), macrophage inflammatory proteins (vMIP-I, vMIP-II), bcl-2 (vBCL2), interferon regulatory factor-1 (vIRF1), interleukin-6 (vIL6), and complement-binding protein (vCBP). In this study, we analyzed expression of these viral homologs and HIV-1 Tat by reverse-transcriptase polymerase chain reaction (RT-PCR) coupled with Southern blot hybridization in AIDS-KS (AKS) tissue, classic KS tissue(CKS), and peripheral blood mononuclear cells, and phorbol ester (TPA)-treated and untreated HHV-8 positive lymphoma cells (BCBL1). While vCYC (AKS 6 of 6; CKS 3 of 3), vMIP-I (AKS 5 of 6, CKS 3 of 3), vBCL2 (AKS 6 of 6; CKS 3 of 3), and vIRF1 (AKS 5 of 6, CKS 3 of 3) transcripts were detected in both AKS and CKS, vGCR and HIV-1 Tat were expressed only in AKS samples (vGCR: AKS 3 of 6, CKS 0 of 3; Tat: AKS 4 of 6, CKS 0 of 3). vMIPII, vCBP, and vIL6 expression were not detected in any KS samples. Since vGCR expression is limited to AKS, it is possible that vGCR is activated by HIV-1 Tat. These results suggest that HIV-1 Tat may contribute to AKS pathogenesis through the tumorigenic and angiogenic effects of vGCR.

Stressors, including social conflict, decrease plasma prolactin in male golden hamsters.

Following exposure to a stressor, plasma prolactin (PRL) rises in most species. The purpose of the present study was to examine the effect of social conflict or of footshock stress on PRL responsiveness in male Syrian hamsters. Contrary to expectations, PRL was significantly lower in subordinate hamsters than in their dominant opponents or in controls following one, five, or nine exposures to social conflict. Similarly, PRL was reduced in hamsters subjected to a mild footshock stressor. By contrast, adrenocorticotropin, another stress-responsive hormone, was elevated following exposure to each of these stressors. We also demonstrate that PRL release is inhibited by dopamine as it is in other species by showing that there is a dose-dependent increase in PRL release following treatment with the dopamine receptor blocker, domperidone.

Ethanol-induced stimulation and depression on measures of locomotor activity: effects of basal activity levels in rats.

Male Sprague-Dawley rats selected for low (LA) and high activity (HA) were used to investigate the biphasic actions of ethanol (EtOH) (20% v/v) on spontaneous measures of activity. Following IP injections of low to moderate doses of EtOH (0.10 g/kg and 0.50 g/kg), horizontal and vertical activities were assessed at 0-10- and 30-40-min intervals. Rats preselected for LA exhibited an increase in performance on both measures. The stimulatory effect, however, was observed only during the 0-10-min session with the lowest dose of EtOH (0.10 g/kg). The 0.50-g/kg dose had no effect on either measure at the 0-10-min interval; however, both doses suppressed activity at the 30-40-min interval. In contrast, activity was suppressed in HA animals independent of the EtOH dose level or time interval. These results demonstrate that basal response profiles are important predictors of behavioral activation following low stimulant doses of EtOH. Moreover, the results demonstrate the importance of selecting animals for basal activity levels to reliably interpret the mechanisms controlling the stimulant and depressant effects of EtOH.

Hormonal responses to fighting in hamsters: separation of physical and psychological causes.

Male Syrian hamsters were paired and allowed to interact with a conspecific for 15 min a day for 4 days. On the fifth day, the animals were again paired, but they were kept physically separated by a mesh partition that allowed visual, olfactory, and auditory contact between the animals. Controls were placed with conspecifics on each of the 5 testing days, but the partition between them was never removed. Hamsters that were submissive on days 1-4 exhibited elevated plasma adrenocorticotropin-like immunoreactivity (ACTH-LI), beta-endorphin-like immunoreactivity (B-EP-LI), and cortisol on day 5 even though no fighting occurred on that day. Dominant hamsters did not differ from controls. These data support the hypothesis that there is an important psychological component to the pituitary-adrenocortical response in defeated hamsters.

Ro15-4513 attenuates the consumption of ethanol in deprived rats.

This research investigated the effects of Ro15-4513 (Ro15), a partial inverse benzodiazepine agonist, on the drinking behavior of 23-1/2 hr fluid deprived rats. Water-deprived rats were maintained on a two-bottle regimen of a saccharin-ETOH solution along with tap water available for 30 min/day for several days. Following this acclimation period, animals were pretreated with either Ro15 (1.0, 2.5, and 5.0 mg/kg) or Tween-80 vehicle injections. Pretreatment with Ro15 at all doses tested resulted in a significant reduction of the saccharin-ETOH solution; however, Ro15 did not alter the rats' consumption of water. The effects of Ro15 on general fluid consumption was investigated in Experiment 2. Following acclimation to a two-bottle regimen of a saccharin-solution and tap water 30 min/day, naive animals were pretreated with Tween-80 vehicle or Ro15 injections. Ro15 failed to alter saccharin or water consumption. The results of this study support previous reports suggesting that Ro15 attenuates the oral consumption of ETOH; however, this effect does not appear to be due to a general suppression of fluid intake.

Acute and repeated exposure to social conflict in male golden hamsters: increases in plasma POMC-peptides and cortisol and decreases in plasma testosterone.

The purpose of the present study was to characterize the hormonal response of dominant and submissive male hamsters to acute and repeated exposure to social conflict. We found that submissive, but not dominant, males exhibited elevated plasma levels of adrenocorticotropin (ACTH), cortisol, and beta-endorphin (beta-EP) following one exposure to an agonistic encounter. After five exposures to a dominant opponent, submissive males showed smaller, but still significant, elevations in these plasma hormones. After nine exposures, submissive hamsters showed significant elevations only in plasma ACTH and beta-EP. Plasma testosterone was significantly suppressed in submissive males that fought nine times. We conclude that hamsters are a useful species with which to study the neuroendocrine correlates of social behavior.

Hana kai ii: a 17-day dry saturation dive at 18.6 ATA. II. Energy balance.

Since previous saturation dives have caused loss of body weight despite apparently adequate-to-high food intake, a complete study of energy balance was undertaken during the saturation dive Hana Kai II. Over a 30-day period in the hyperbaric chamber (3 days of predive control, 1 day of compression, 16 days at 18.6 ATA, 7 days of decompression, and 3 days of postdive control), all food, urine, and feces for five men were analyzed by bomb calorimetry; 24-h energy expenditure (M) was measured from continuous VO2, VCO2, and urine N. Body weight was taken daily; body composition was assessed from density, total body water, and skinfold thickness. Food intake was high throughout the 30 days (about 3500 kcal/day) while fecal and urinary losses were a normal 6-8% of intake. Energy expenditure was increased a little by the hyperbaric condition, but averaged only 2431 kcal/day for the 30 days and yet there was an average loss of adipose tissue of 0.8 kg for each man for the entire period. Nitrogen balance was positive. There was no evidence of heat gain or loss. The energy balance, total fuel compared with energy expenditure, required an additional 919 kcal/man-day for 30 days, an unidentified term which is not measured by conventional techniques.

Oxygen consumption and conservation during apnea in the anesthetized dog.

Apnea was initiated by clamping off the tracheal tube in 6 anesthetized dogs. Bradycardia, reduction in cardiac output and peripheral vasoconstriction developed gradually throughout the entire apneic period. O2 consumption during apnea was measured by monitoring the rate of O2 removal from the lung (VLO2), from the arterial blood (Va02), and from the venous blood (VV02). Total 02 consumption (VT02) was calculated by summing (VL02--Va02), VaQ2 and VV02-VL02, estimated by the product of arteriovenous O2 content difference and cardiac output, decreased continuously during apnea. At the end of 80 sec the rate of O2 removal from the lung was one-fourth of the pre-apneic rate, 5.29 +/- 0.51 ml-min-1kg-1. Oxygen disappearance form the blood was estimated by measuring arterial and venous O2 content at 20-sec intervals and by assuming a constant blood volume throughout the apneic period of 86 ml/kg, 25% of which is in the arterial tree and 75% of which is in the venous compartment. During the last 20 sec of an 80-sec apnea, VV02 represented 69% of VT02. The result indicated that VT02 during apnea was not significantly different from that of pre-apneic values. It is concluded from the present study that an oxygen conservation mechanism if existent, was not operative during an 80-sec apnea in the anesthetized dog.