Social structure, robustness, and policing cost in a cognitively sophisticated species

Conflict management is one of the primary requirements for social complexity. Of the many forms of conflict management, one of the rarest and most interesting is third-party policing, or intervening impartially to control conflict. Third-party policing should be hard to evolve because policers personally pay a cost for intervening, while the benefits are diffused over the whole group. In this study we investigate the incidence and costs of policing in a primate society. We report quantitative evidence of non-kin policing in the nonhuman primate, the pigtailed macaque. We find that policing is effective at reducing the intensity of or terminating conflict when performed by the most powerful individuals. We define a measure, social power consensus, that predicts effective low-cost interventions by powerful individuals and ineffective, relatively costly interventions by low-power individuals. Finally, we develop a simple probabilistic model to explore whether the degree to which policing can effectively reduce the societal cost of conflict is dependent on variance in the distribution of power. Our data and simple model suggest that third-party policing effectiveness and cost are dependent on power structure and might emerge only in societies with high variance in power.     

Rat kinesin light chain 3 associates with spermatid mitochondria

We recently discovered that in rat spermatids, kinesin light chain KLC3 can associate with outer dense fibers, major sperm tail components, and accumulates in the sperm midpiece. Here, we show that mitochondria isolated from rat-elongating spermatids have bound KLC3. Immunoelectron microscopy indicates that the association of KLC3 with mitochondria coincides with the stage in spermatogenesis when mitochondria move from the plasma membrane to the developing midpiece. KLC3 is able to bind in vitro to mitochondria from spermatids as well as somatic cells employing a conserved kinesin light chain motif, the tetratrico-peptide repeats. Expression of KLC3 in fibroblasts results in formation of large KLC3 clusters close to the nucleus, which also contain mitochondria: no other organelles were present in these clusters. Mitochondria are not present in KLC3 clusters after deletion of KLC3's tetratrico-peptide repeats. Our results indicate that the rat spermatid kinesin light chain KLC3 can associate with mitochondria.     

Administration of phosphatidylcholine-cholesterol liposomes partially reconstitutes fat absorption in chronically bile-diverted rats

BACKGROUND AND AIMS: Intestinal bile deficiency in cholestatic patients leads to fat malabsorption. We addressed the potency of model bile, bile salts and phosphatidylcholine (PC)-cholesterol (CH) liposomes to reconstitute fat absorption in permanently bile-diverted (BD) rats. METHODS: The plasma appearance of 13C-labeled palmitic acid (13C-16:0) and linoleic acid (13C-18:2) was determined after their enteral administration to BD or to control rats with an intact enterohepatic circulation (EHC) (13C-16:0 and 13C-18:2 dissolved in 25% olive oil-75% medium chain triacylglycerol oil mixture). BD rats were intraduodenally infused with buffer, model bile [consisting of 60 mM taurocholate (TC), 8 mM PC and 1 mM CH], buffer with TC, buffer with PC and CH liposomes, or buffer with lyso-PC and CH. RESULTS: Plasma concentrations of 13C-16:0 and 13C-18:2 were consistently three- to eightfold higher in control rats than those in buffer-infused BD rats (P < 0.01). ID administration of either model bile or TC to BD rats restored plasma appearance of 13C-fatty acids at least to concentrations observed in control rats. Administration of PC + CH liposomes to BD rats partially reconstituted the plasma appearance of 13C-16:0, but did not affect that of 13C-18:2. Compared with control rats, the area under the curve (AUC) of plasma 13C-16:0 concentrations was 13.0 +/- 6.9% in buffer-infused rats and 40.9 +/- 3.1% in liposome-infused rats (P < 0.005). CONCLUSIONS: Enteral administration of PC + CH liposomes to BD rats partially corrects the absorption of palmitic acid. Present data suggest that administration of PC + CH liposomes could enhance fat absorption in clinical conditions of cholestasis in which bile salt supplemention is contraindicated.     

Susceptibility of human metabolic phenotypes to dietary modulation

Dietary composition has been shown to influence metabolism and to impact on the prevalence and risk for certain diseases, but hitherto, there have been no systematic studies on the effects of dietary modulation of human metabolic phenotype (metabotype). Here, we have applied 1H NMR spectroscopy in combination with multivariate statistical analysis to characterize the effects of three diets: "vegetarian", "low meat", and "high meat" on the metabotype signature of human participants. Twelve healthy male participants (age range of 25-74 years) consumed each of these diets, in a randomized order, for continuous 15-day-periods with an intervening washout period between each diet of 7 days duration. Each participant provided three consecutive 24-hour urine collections on days 13, 14, and 15 of each dietary period, and 1H NMR spectra were acquired on all samples. Pattern recognition analysis allowed differentiation of the characteristic metabolic signatures of the diets with creatine, carnitine, acetylcarnitine, and trimethylamine-N-oxide (TMAO) being elevated in the high-meat consumption period. Application of orthogonal projection to latent structure discriminant analysis (O-PLS-DA) allowed the low-meat diet and vegetarian diet signatures to be characterized, and p-hydroxyphenylacetate (a microbial mammalian cometabolite) was higher in the vegetarian than meat diet samples, signaling an alteration of the bacterial composition or metabolism in response to diet. This work shows the potential for the routine use of metabonomics in nutritional and epidemiological studies, in characterizing and predicting the metabolic effects and the influence of diet on human metabotypes.     

Coronary vasoconstrictor influence of angiotensin II is reduced in remodeled myocardium after myocardial infarction

The renin-angiotensin system plays an important role in cardiovascular homeostasis by contributing to the regulation of blood volume, blood pressure, and vascular tone. Because AT(1) receptors have been described in the coronary microcirculation, we investigated whether ANG II contributes to the regulation of coronary vascular tone and whether its contribution is altered during exercise. Since the renin-angiotensin system is activated after myocardial infarction, resulting in an increase in circulating ANG II, we also investigated whether the contribution of ANG II to the regulation of vasomotor tone is altered after infarction. Twenty-six chronically instrumented swine were studied at rest and while running on a treadmill at 1-4 km/h. In 13 swine, myocardial infarction was induced by ligation of the left circumflex coronary artery. Blockade of AT(1) receptors (irbesartan, 1 mg/kg iv) had no effect on myocardial O(2) consumption but resulted in an increase in coronary venous O(2) tension and saturation both at rest and during exercise, reflecting coronary vasodilation. Despite increased plasma levels of ANG II after infarction and maintained coronary arteriolar AT(1) receptor levels, the vasodilation evoked by irbesartan was significantly reduced both at rest and during exercise. In conclusion, despite elevated plasma levels, the vasoconstrictor influence of ANG II on the coronary circulation in vivo is reduced after myocardial infarction. This reduction in ANG II-induced coronary vasoconstriction may serve to maintain perfusion of the remodeled myocardium.     

Mechanism of graded persistent cellular activity of entorhinal cortex layer v neurons

Working memory is an emergent property of neuronal networks, but its cellular basis remains elusive. Recent data show that principal neurons of the entorhinal cortex display persistent firing at graded firing rates that can be shifted up or down in response to brief excitatory or inhibitory stimuli. Here, we present a model of a potential mechanism for graded firing. Our multicompartmental model provides stable plateau firing generated by a nonspecific calcium-sensitive cationic (CAN) current. Sustained firing is insensitive to small variations in Ca2+ concentration in a neutral zone. However, both high and low Ca2+ levels alter firing rates. Specifically, increases in persistent firing rate are triggered only during high levels of calcium, while decreases in rate occur in the presence of low levels of calcium. The model is consistent with detailed experimental observations and provides a mechanism for maintenance of memory-related activity in individual neurons.