Activation of the olfactory system in response to male odors in female prepubertal mice.

Exposure to male odors during the prepubertal period accelerates puberty, a phenomenon known as the Vandenbergh effect. This experiment identifies the parts of the olfactory pathway that respond to male odors in prepubertal female mice. Female mice were kept in a room free of adult male odors from birth until odor exposure. At post-natal day 21, 24 or 28, (ages representing time points early, intermediate, and late in the prepubertal period) mice were exposed to clean bedding, soiled bedding from castrated males, or soiled bedding from intact males. Each group was exposed to odor in separate rooms to prevent cross contamination. Ninety minutes after odor exposure, mice were sacrificed, the brains removed and prepared for c-Fos immunohistochemistry. The numbers of neurons expressing c-Fos were counted in a defined area of the following nuclei: AOB mitral layer, AOB granular layer, MOB, MEPV, MEPD, Aco, BNST, MPOA, and VMH. There was a significant effect of age on c-Fos-expression in the MEPV, MEPD, Aco, MPOA, BNST and piriform cortex. There was a significant effect of odor on c-Fos-expression in the MEPV, MEPD, Aco, MPOA, and VMH, showing that these areas are differentially sensitive to intact male odors vs. clean bedding and that these brain areas may be responsible for communicating odor information that drives puberty acceleration.

Mesenteric infusion of a volatile fatty acid prevents body weight loss and transiently restores luteinising hormone pulse frequency in ovariectomised, food-restricted ewes.

Pulsatile luteinising hormone (LH) secretion is suppressed by food restriction and rapidly restored by return to ad lib. feeding concomitant with an increase in the oxidation of free fatty acids, although there is no increase in plasma leptin concentrations or body fat content in ovariectomised ewes. The ingestion of food may stimulate LH secretion by increasing availability of oxidisable metabolic substrates. Ruminal digestion is characterised by the production of volatile fatty acids and, of these, propionate is the major gluconeogenic substrate, and both glucose and propionate are oxidisable in a variety of tissues. To examine whether increases in mesenteric propionate concentrations are sufficient for restoration of pulsatile LH secretion during a period of food restriction, adult, food-restricted, hypogonadotrophic, ovariectomised ewes received mesenteric vein infusions of 5 µmol/min/kg body weight (BW) propionate or saline, whereas normal weight, ad lib.-fed ewes received mesenteric infusions of saline for 10 days. Blood samples were taken every 10 min for 5 h before the start of the 10-day infusion period, and continued throughout the first 5 h of infusion on the afternoon of day 1, and in the morning on days 2, 7 and 10. Propionate-infused, food-restricted and ad lib.-fed, saline-infused ewes showed a significantly higher LH pulse frequency compared to that of food-restricted-saline-infused ewes on postinfusion days 1 and 2 but not on days 7 and 10, and only the saline-infused, food-restricted group lost a significant amount of body weight. These results indicate that the reproductive system can respond acutely to infusion of metabolic fuels such as propionate, although a sustained recovery of pulsatile LH secretion requires more than an increase in this single metabolic substrate.

Changes in insulin, glucose and ketone bodies, but not leptin or body fat content precede restoration of luteinising hormone secretion in ewes.

The reproductive system, including pulsatile luteinising hormone (LH) secretion, is inhibited by deficits in energy availability and restored by energy surfeits. Plasma LH, insulin, leptin, ghrelin, glucose, ketone body, and nonesterified fatty acid concentrations were measured in ovariectomised, food-restricted ewes before and after return to ad libitum feeding to determine the factors that change in time to account for the restoration of pulsatile LH secretion. At 07.00 h, blood was sampled every 10 min for 5 h from ovariectomised, hypogonadotrophic, chronically food-restricted and ad libitum-fed ewes (Fed). At 12.00 h, four of the food-restricted sheep were given ad libitum access to food (Re-Fed), while three ewes continued to be food restricted (Restricted). Sampling continued for 5 h and resumed again on the mornings of days 2, 4, and 9. A pulse of LH was seen within 1 h of re-feeding in all Re-Fed ewes, and interpulse interval (IPI) was significantly shorter in Re-Fed compared to Restricted ewes and longer than in Fed ewes during the period after re-feeding. Re-Fed LH IPI was not restored to that of Fed ewes until sometime between days 4 and 9. The first pulse occurred within minutes, whereas restoration of IPI occurred after 4-8 days. Prior to the initial LH pulses seen in Re-Fed ewes, plasma ketone bodies first fell and then rose to levels significantly above those in Restricted ewes. Significant changes in circulating insulin, ghrelin, glucose, and total ketone body concentrations, daily food intake and lean body mass preceded restoration of Re-Fed LH IPI some time between days 4 and 9, but there were no significant changes in adiposity or circulating leptin concentrations, consistent with the hypothesis that LH pulses are reinitiated by changes in the availability of oxidisable metabolic fuels and possibly insulin, but not leptin concentrations.

A re-examination of body image distortion: evidence against a sensory explanation.

OBJECTIVE: This study was designed to assess female bulimic and control subjects' sensitivity to changes in their own and a model's body. METHOD: A video distortion camera was employed. Each subject (20 bulimics, 20 controls) compared a constant image of her undistorted body with 180 separate images of her body at various distortion levels (-16%, -12%, -8%, -4%, 0%, 4%, 8%, 12%, 16%) using the method of constant stimuli. The procedure was repeated using prerecorded images of a model. RESULTS: Bulimics and controls were equally adept at detecting increases and decreases in the model's body and at detecting decreases in their own bodies. Bulimics, however, detected increases in their own bodies less well than controls. DISCUSSION: The data provide evidence against a purely sensory/perceptual explanation of body image distortion.