Drinking,but not feeding,is opiate-sensitive in hamsters

The long-lasting opiate antagonist, naltrexone (NTX), was examined for its effects on various types of consummatory behavior in male golden hamsters and rats. Rat, but not hamster, 24 hr food and water intakes were significantly decreased by four daily NTX (10.0 mg/kg) injections. Hamsters displayed a minimal night to day feeding ratio compared to rats. hamsters increased food intake following insulin (50 U/kg) administration, but not after 24 hr food deprivation (FD) or 2-deoxy-D-glucose (2-DG; 800 mg/kg) injections. NTX (1.0 and 10 mg/kg) had no effect on feeding, but markedly attenuated hamster drinking induced by 48 hr water deprivation or hypertonic saline injection. Dexamethasone (DEX), a glucocorticoid which depletes pituitary β-endorphin and produces anorexia in rats, had no effect on daily hamster intake. Since the normal feeding profile of the hamster is similar to that of naloxone and DEX-treated rats, hamsters appear to lack an opiate-sensitive feeding system. In contrast, stimulated drinking behavior of hamsters operates through an opiate-sensitive mechanism. Thus, there are marked species differences concerning the involvement of endogenous opioids is consummatory behavior.     

Give me a break,but not in mitosis

DNA double-strand breaks (DSBs) are extremely cytotoxic with a single unrepaired DSB being sufficient to induce cell death. A complex signalling cascade, termed the DNA damage response (DDR), is in place to deal with such DNA lesions and maintain genome stability. Recent work by us and others has found that the signalling cascade activated by DSBs in mitosis is truncated, displaying apical, but not downstream, components of the DDR. The E3 Ubiquitin ligases RNF8, RNF168 and BRCA1, along with the DDR mediator 53BP1, are not recruited to DSB sites in mitosis, and activation of downstream checkpoint kinases is also impaired. Here, we show that RNF8 and RNF168 are recruited to DNA damage foci in late mitosis, presumably to prime sites for 53BP1 recruitment in early G1. Interestingly, we show that, although RNF8, RNF168 and 53BP1 are excluded from DSB sites during most of mitosis, they associate with mitotic structures such as the kinetochore, suggesting roles for these DDR factors during mitotic cell division. We discuss these and other recent findings and suggest how these novel data collectively contribute to our understanding of mitosis and how cells deal with DNA damage during this crucial cell cycle stage.     

Children, but not chimpanzees, prefer to collaborate

Human societies are built on collaborative activities. Already from early childhood, human children are skillful and proficient collaborators. They recognize when they need help in solving a problem and actively recruit collaborators [1, 2]. The societies of other primates are also to some degree cooperative. Chimpanzees, for example, engage in a variety of cooperative activities such as border patrols, group hunting, and intra- and intergroup coalitionary behavior [3-5]. Recent studies have shown that chimpanzees possess many of the cognitive prerequisites necessary for human-like collaboration. Chimpanzees have been shown to recognize when they need help in solving a problem and to actively recruit good over bad collaborators [6, 7]. However, cognitive abilities might not be all that differs between chimpanzees and humans when it comes to cooperation. Another factor might be the motivation to engage in a cooperative activity. Here, we hypothesized that a key difference between human and chimpanzee collaboration-and so potentially a key mechanism in the evolution of human cooperation-is a simple preference for collaborating (versus acting alone) to obtain food. Our results supported this hypothesis, finding that whereas children strongly prefer to work together with another to obtain food, chimpanzees show no such preference.     

Bid, but not Bax, regulates VDAC channels

During apoptosis, cytochrome c is released from mitochondria into the cytosol, where it participates in caspase activation. Various and often conflicting mechanisms have been proposed to account for the increased permeability of the mitochondrial outer membrane that is responsible for this process. The voltage-dependent anion channel (VDAC) is the major permeability pathway for metabolites in the mitochondrial outer membrane and therefore is a very attractive candidate for cytochrome c translocation. Here, we report that properties of VDAC channels reconstituted into planar phospholipid membranes are unaffected by addition of the pro-apoptotic protein Bax under a variety of conditions. Contrary to other reports (Shimizu, S., Narita, M., and Tsujimoto, Y. (1999) Nature 399, 483-487; Shimizu, S., Ide, T., Yanagida, T., and Tsujimoto, Y. (2000) J. Biol. Chem. 275, 12321-12325; Shimizu, S., Konishi, A., Kodama, T., and Tsujimoto, Y. (2000) Proc. Natl. Acad. Sci. U. S. A. 97, 3100-3105), we found no electrophysiologically detectable interaction between VDAC channels isolated from mammalian mitochondria and either monomeric or oligomeric forms of Bax. We conclude that Bax does not induce cytochrome c release by acting on VDAC. In contrast to Bax, another pro-apoptotic protein (Bid) proteolytically cleaved with caspase-8 affected the voltage gating of VDAC by inducing channel closure. We speculate that by decreasing the probability of VDAC opening, Bid reduces metabolite exchange between mitochondria and the cytosol, leading to mitochondrial dysfunction.     

Gender differences in leucine, but not lysine, kinetics.

There is a controversy in the literature as to the effects of gender on leucine kinetics. Two research groups found that men oxidize more leucine during exercise, whereas another group showed no gender effects. The purpose of our study was to examine the effects of gender on leucine and, for comparison purposes, lysine kinetics. Our subjects (n = 14) were seven matched pairs of men and women selected for their exercise habits and age. After 1 wk of a standardized diet, they exercised at 50% of maximal O(2) uptake for 1 h. There was an effect of exercise in both genders: an increased leucine oxidation and an attenuation in nonoxidative leucine disposal compared with rest (P < 0.05). Furthermore, our study confirms that there are gender differences in leucine, but not lysine, kinetics. Men had a higher rate of leucine oxidation and a lower rate of nonoxidative leucine disposal during exercise (P < 0.05). For women, a larger proportion of their exercise energy needs came from fat; for men, a greater fraction came from carbohydrate (P < 0.05). We conclude that female exercisers rely to a greater extent on fat as an energy source, thereby using less carbohydrate, amino acid, and protein as a fuel source.