Association of the suckling-weaning transition with development of the hypothalamic arcuate nucleus neurons in rat pups.

Feeding behavior is regulated by feeding-related peptides in the hypothalamus. The neurons of the arcuate nucleus (ARC), which produces feeding-related peptides, develop and function by three weeks of age in rodents. Because rodents are weaned at three weeks, we studied whether the process of weaning is involved in the development of ARC neurons using monosodium glutamate. Rat pups injected neonatally with monosodium glutamate ingested a large amount of mother's milk at weaning. Monosodium glutamate treatment induced a decrease in the number of ARC cells and mRNA levels of neuropeptide Y and agouti-related protein in the hypothalamus. The alteration of milk consumption following monosodium glutamate treatment appears to cause failure of ARC neuron development and neuropeptide expression.

Impaired growth of small intestinal epithelium by adrenalectomy in weaning rats.

Functional maturation of the small intestine occurs during the weaning period in rats. It is known that this development is facilitated by glucocorticoid. However, the effect of glucocorticoid on morphological development of small intestine has yet to be clarified. The present study evaluated the morphological development and cell proliferation of the small intestine in adrenalectomized (ADX) rat pups. To further understand the mechanism of glucocorticoid effects on intestinal development, we examined the localization of the glucocorticoid receptor in the small intestine. Microscopic analysis showed that growth of villi and crypts is age-dependent, and is significantly attenuated in ADX rats compared with sham-operated rats. BrdU-positive cells, i.e. proliferating cells, were primarily observed in crypt compartments and rapidly increased in number during the early weaning period. The increase in BrdU-positive cells could be attenuated by adrenalectomy. The morphological development of small intestine may be associated with increased proliferation of epithelial cells. On the other hand, glucocorticoid receptors were found in epithelial cells of the mid- and lower villi and not in crypts where BrdU-positive cells were localized. These results indicate that the growth of small intestine is attenuated by adrenalectomy, and that glucocorticoid indirectly acts on proliferation of epithelial cells during the weaning period.

[Survival of Salmonella in spices and growth in cooked food].

Contamination of spices with pathogens has been reported worldwide, and Salmonella might result in foodborne infections. In this study, we investigated the survival of Salmonella in black pepper and red pepper, and the growth of the surviving Salmonella in cooked food. Salmonella Enteritidis, Salmonella Weltevreden and Salmonella Senftenberg were inoculated into spices, and their survival during storage was examined. In black pepper, S. Enteritidis was no longer viable after storage for 28 days, but S. Weltevreden and S. Senftenberg remained viable. In red pepper, S. Weltevreden and S. Senftenberg survived for 28 days although S. Enteritidis was not viable after 7 days. Salmonella Weltevreden and Salmonella Senftenberg were inoculated into cooked food, and their survival during storage was determined. In potato salad, egg salad, namul and kimchi as cooked foods, both pathogens grew at 30 degrees C, but not at 10 degrees C. Our results indicate that cooked food should be stored at low temperature after addition of spices, such as black pepper and red pepper, following the cooking.