Interchange of Grooming and Agonistic Support in Chimpanzees

We investigated the temporal relationship between grooming given and agonistic support received in a group of chimpanzees at Chester Zoo, U.K. We compared grooming levels the day before a conflict-with-support to those the day before a conflict-without-support and to baseline to investigate whether individuals groom potential supporters in anticipation of the need for support. We also compared grooming and aggression levels the day after conflicts-with-support to levels the day after conflicts-without-support and to baseline levels to determine whether chimpanzees reward individuals that support them or punish those that do not. Finally, we compared grooming and aggression levels the day after conflicts-with-unsuccessful-solicitations-for-support to those the day after conflicts-with-support and to baseline to examine the behavioral consequences of not providing support when an individual had solicited but did not receive it. Future recipients of support groomed future supporters more the day before receiving support, compared to the day before conflicts-without-support, indicating that grooming increased the likelihood of support. The relationship between prior grooming and support held true only for aggressor and not victim support and is consistent with behavior expected if chimpanzees anticipated the need for agonistic support and groomed their supporter the day before to increase the likelihood of support. We found evidence of a system of reward and punishment. Individuals experienced significantly lower rates of aggression after conflicts in which they provided support than at baseline and after conflicts in which they did not provide support. The finding was true only for aggressor support. We found no evidence that chimpanzees punished individuals whom or that they unsuccessfully solicited with aggression or a reduction in grooming. However, solicitors groomed individuals that they solicited for support significantly more after unsuccessful solicitations than after individuals provided support (but with no difference from baseline), indicating that individuals may attempt to recement their relationship after an unsuccessful solicitation. The findings are consistent with a mechanism of calculated interchange in chimpanzees.     

Detection of ligand-induced CNTF receptor dimers in living cells by fluorescence cross correlation spectroscopy

Ciliary neurotrophic factor (CNTF) signals via a receptor complex consisting of the specific CNTF receptor (CNTFR) and two promiscuous signal transducers, gp130 and leukemia inhibitory factor receptor (LIFR). Whereas earlier studies suggested that the signaling complex is a hexamer, more recent analyses strongly support a tetrameric structure. However, all studies so far analyzed the stoichiometry of the CNTF receptor complex in vitro and not in the context of living cells. We generated and expressed in mammalian cells acyl carrier protein-tagged versions of both CNTF and CNTFR. After labeling CNTF and CNTFR with different dyes we analyzed their diffusion behavior at the cell surface. Fluorescence (cross) correlation spectroscopy (FCS/FCCS) measurements reveal that CNTFR diffuses with a diffusion constant of about 2 × 10^− 9 cm² s^− 1 independent of whether CNTF is bound or not. FCS and FCCS measurements detect the formation of receptor complexes containing at least two CNTFs and CNTFRs. In addition, we measured Förster-type fluorescence resonance energy transfer between two differently labeled CNTFs within a receptor complex indicating a distance of 5-7 nm between the two. These findings are not consistent with a tetrameric structure of the CNTFR complex suggesting that either hexamers and or even higher-order structures (e.g. an octamer containing two tetramers) are formed.     

Human pancreas-specific protein disulfide isomerase homolog (PDIp) is redox-regulated through formation of an inter-subunit disulfide bond

Protein disulfide isomerase (PDI) and its homologs are catalysts of the formation of disulfide bonds in secretory proteins, and they also serve as molecular chaperones. In the present study, we investigated the redox-mediated regulation of the structures and functions of human pancreas-specific PDI homolog (PDIp). We found that formation of an inter-subunit disulfide bond in the recombinant human PDIp can alter not only its structure, but also its functions. PDIp exists predominantly as monomer under reducing conditions, but the dimeric form is significantly increased following the removal of the reducing agent, due to the formation of an inter-subunit disulfide bond. The oxidized PDIp (with an inter-subunit disulfide bond) appears to expose more hydrophobic patches and is more sensitive to protease digestion compared to the reduced form. Along with these structural changes, the oxidized PDIp also exhibits an enhanced chaperone activity. The formation of the inter-subunit disulfide bond in PDIp is mainly contributed by its non-active cysteine residue (cysteine-4), which is only present in human and primate PDIp, but not in rodent PDIp. In addition, we observed that the formation of the inter-subunit disulfide bond in PDIp is redox-dependent and is favored under oxidizing conditions, and that PDIp can function as a chaperone to form stable complexes with various non-native cellular proteins, particularly under oxidizing conditions. In light of these observations, it is concluded that the structures and functions of human PDIp are redox-regulated through formation of an inter-subunit disulfide bond between two cysteine-4 residues.     

巨桉连栽对土壤微生物生物量和数量的影响

为探讨巨桉连栽对土壤微生物生物量和数量的影响,采用时空互换法,研究了马尾松(Pinus massoniana)林和不同连栽代次的巨桉(Eucalyptus grandis)人工林的微生物生物量、数量与土壤理化性质的关系。结果表明,巨桉一代林的土壤微生物生物量碳、生物量氮和土壤真菌、细菌数量与马尾松林的差异不显著,放线菌数量则显著增加。随巨桉连栽代次增加,土壤微生物生物量碳、生物量氮和土壤细菌、放线菌、真菌数量均递减。回归分析表明,土壤全磷能独立解释微生物生物量氮、细菌和真菌数量71.7%、86.1%和63.0%的变异,与总孔隙度共同解释微生物生物量碳87.9%的变异,与全氮共同解释放线菌数量89.6%的变异。可见,土壤全磷较大程度解释了微生物的变化。     

Influence of salinity on the concentration and rate of interchange of dissolved phosphate between water and sediment in Fuente Piedra lagoon (S. Spain)

Short (60 minutes) and long term (3 hours) experiments were performed to measure the final equilibrium phosphate concentration in water and the net fluxes of phosphate interchange between water and sediment at different salinities. The rate of phosphate release from the sediment increases with the salinity increment, as well as the final equilibrium phosphate concentration. In both short and long term experiments, the net rate of dissolved phosphate removal follows a saturation kinetics except for long term experiments at 70 g l^–1 salinity. In this case, the relationship between net removal and dissolved phosphate concentration is linear. The experiments show that salinity stimulates phosphate release from sediment.     

A molecular basis for retinol stimulation of vesicle budding in vivo and in vitro

Retinol stimulates the formation of transition vesicles in situ and in all free systems based on rat liver. The stimulation is on vesicle formation from transitional endoplasmic reticulum and not on vesicle fusion with donor membranes. Vesicle budding in the cell free system requires a nucleoside triphosphate and is sensitive to inhibition by thiol reagents. In this report we develop and test a model whereby a retinol-modulated NADH:protein disulfide reductase (NADH oxidase) with protein disulfide-thiol interchange activity is implicated in the vesicle budding mechanism. The protein has the ability to restore activity to scrambled, inactive RNase A and is stimulated or inhibited by retinol depending on the redox environment. Under reducing conditions and in the presence of a chemical reductant such as GSH, the partial reaction stimulated by retinol appears to be the oxidation of membrane disulfides. This is the first report of an enzymatic mechanism to explain specific retinol effects both in vivo and in vitro on membrane trafficking not given by retinoic acid.