The ionizing-radiation-resistant fractions of two soil bacterial communities were investigated by exposing an arid soil from the Sonoran Desert and a nonarid soil from a Louisiana forest to various doses of ionizing radiation using a 60 Co source. The numbers of surviving bacteria decreased as the dose of gamma radiation to which the soils were exposed increased. Bacterial isolates surviving doses of 30 kGy were recovered from the Sonoran Desert soil, while no isolates were recovered from the nonarid forest soil after exposure to doses greater than 13 kGy. The phylogenetic diversities of the surviving culturable bacteria were compared for the two soils using 16S rRNA gene sequence analysis. In addition to a bacterial population that was more resistant to higher doses of ionizing radiation, the diversity of the isolates was greater in the arid soil. The taxonomic diversity of the isolates recovered was found to decrease as the level of ionizing-radiation exposure increased. Bacterial isolates of the genera Deinococcus, Geodermatophilus, and Hymenobacter were still recovered from the arid soil after exposure to doses of 17 to 30 kGy. The recovery of large numbers of extremely ionizing-radiationresistant bacteria from an arid soil and not from a nonarid soil provides further ecological support for the hypothesis that the ionizing-radiation resistance phenotype is a consequence of the evolution of other DNA repair systems that protect cells against commonly encountered environmental stressors, such as desiccation. The diverse group of bacterial strains isolated from the arid soil sample included 60 Deinococcus strains, the characterization of which revealed nine novel species of this genus.Extreme ionizing-radiation resistance has been observed in several members of the domains Bacteria and Archaea. Of the genera containing ionizing-radiation-resistant organisms, Deinococcus and Rubrobacter show the highest levels of resistance, and all species of these genera have been shown to be

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The amygdala is rich in melanocortin 4 receptors. Because the reduction in dietary fat intake after enterostatin is injected in the central nucleus of the amygdala (CeA) is blocked by a melanocortin 4 receptor antagonist, we investigated the role of melanocortin activity in the CeA in regulating food intake and macronutrient choice. Sprague-Dawley rats, fitted with CeA cannulas, were fed either chow, a high-fat (HF) diet, or adapted to a two-choice HF or low-fat (LF) diet. Injections of the MC4R agonist melanotan II (MTII) in the CeA had a dose-dependent inhibitory effect on food intake that lasted for at least 24 h. This response was greater in rats fed a HF diet. The inverse agonist agouti-related protein (AgRP) and antagonist SHU-9119 increased food intake in a dose-dependent manner, with the hyperphagia lasting for 60 h. In rats adapted to a two-choice HF/LF diet, MTII decreased HF consumption but had no effect on LF consumption, resulting in a long-lasting decrease in total calorie intake (Ϫ35.5% after 24 h, P Ͻ 0.05). Total calorie intake increased in both AgRP-and SHU-9119-treated rats (32 and 109% after 24 h, respectively) as the result of increased intake of HF diet. There was no modification of LF consumption with AgRP treatment and a transient nonsignificant decrease with SHU-9119 treatment. Amygdala brain-derived neurotrophic factor expression was increased by AgRP in fed rats. These results identify the amygdala as a site of action for the melanocortin system to control food intake and dietary preferences.agouti-related protein; melanotan II; SHU-9119; brain derived neurotrophic factor, food intake FOR YEARS, HYPOTHALAMIC CENTERS have been considered as the major brain centers regulating food intake and/or macronutrient selection (45). The neural circuits involved in the regulation of feeding behavior are complex, and more recent studies implicate other parts of the brain in the regulation of ingestive behaviors. Areas such as the nucleus accumbens, the amygdala, the brain stem, and many others form together with the hypothalamic areas a complex circuitry regulating all levels of feeding behavior (6,8,55). Indeed, the paraventricular nucleus (PVN) is not essential for either neuropeptide Y (NPY)-induced feeding or the anorexic response to melanocortin activity (16) since both are evident in PVN-lesioned rats. Furthermore, the anorectic response to melanotan II (MTII) is evident in the dorsovagal complex of the brain stem (52,58).A number of neuropeptides and compounds are known to selectively affect macronutrient intake when administered centrally. For example, the orexigenic NPY (47, 48, 50) , norepinephrine (30, 50), or agouti-related protein (AgRP) (23) have been reported to induce specific selection of macronutrients. Enterostatin, a satiety factor secreted in the gastrointestinal tract and expressed also in the central nervous system, induces an immediate reduction in food intake and inhibits appetite specifically for dietary fat when injected peripherally or centrally (31,37,39).It has been hy...