Landscape structure affects food quality of sika deer (<Emphasis Type="Italic">Cervus nippon</Emphasis>) evidenced by fecal nitrogen levels

Evaluating the quality of wildlife habitat is essential for understanding and predicting population dynamics in heterogeneous environments. We used fecal nitrogen levels as an indicator of habitat quality of sika deer (Cervus nippon) and explored important landscape elements influencing nitrogen levels, taking deer density into account. We established 92 plots differing in deer density and landscape structure on the Boso Peninsula, central Japan, and collected fecal samples along a 1-km transect at each plot. The regression models involving two independent variables, i.e., deer density and the length of forest edge within an area of 100 or 200 m from the transect, were selected based on the Akaike’s Information Criterion (AIC). Levels of fecal nitrogen were positively correlated with the length of the forest edge and negatively correlated with population density of deer. The area of 100 or 200 m from the transect most likely reflected the behavioral scale of the deer. Coverage of palatable understory vegetation increased with proximity to forest edge and decreased with deer density. Variability in the level of fecal nitrogen could thus be explained by food availability in the landscape. These results suggest that landscape alterations increase the carrying capacity of sika deer and thereby increase impacts upon the ecosystem.     

Direct comparison of the pharmacodynamics of four antifungal drugs in a mouse model of disseminated candidiasis using microbiological assays of serum drug concentrations

The aim of this study was to compare the pharmacodynamics of the azole antifungal drugs fluconazole, itraconazole and ketoconazole, and the polyene antifungal amphotericin B, in a mouse model of disseminated Candida albicans infection. In order to directly compare effective serum concentrations of these antifungals, drug concentrations were assayed microbiologically by measuring inhibition of C. albicans mycelial growth (mMIC) in a mouse serum-based assay (serum antifungal titer). Efficacy in the mouse infection model was determined using an organ-based (kidney burden) endpoint. For all four drugs, the serum antifungal titers, 8 hr after administration of single doses of drugs at a range of drug concentrations, correlated closely with C. albicans kidney fungal burden in the mouse model. The results showed that determining serum antifungal titer may be used to accurately represent kidney fungal burden in a mouse model of disseminated candidiasis and allowed direct comparison of the pharmacodynamics of differing classes of antifungal drugs.     

Homologous pairing and ring and filament structure formation activities of the human Xrcc2*Rad51D complex

The Xrcc2 and Rad51D/Rad51L3 proteins, which belong to the Rad51 paralogs, are required for homologous recombinational repair (HRR) in vertebrates. The Xrcc2 and Rad51D/Rad51L3 genes, whose products interact with each other, have essential roles in ensuring normal embryonic development. In the present study, we coexpressed the human Xrcc2 and Rad51D/Rad51L3 proteins (Xrcc2 and Rad51D, respectively) in Escherichia coli, and purified the Xrcc2*Rad51D complex to homogeneity. The Xrcc2 small middle dotRad51D complex catalyzed homologous pairing between single-stranded and double-stranded DNA, similar to the function of the Xrcc3*Rad51C complex, which is another complex of the Rad51 paralogs. An electron microscopic analysis showed that Xrcc2*Rad51D formed a multimeric ring structure in the absence of DNA. In the presence of ssDNA, Xrcc2*Rad51D formed a filamentous structure, which is commonly observed among the human homologous pairing proteins, Rad51, Rad52, and Xrcc3*Rad51C.     

Metabolic consequence of long-term exposure of pancreatic beta cells to free fatty acid with special reference to glucose insensitivity.

Long-term exposure of the pancreatic beta cells to free fatty acid (FFA) reportedly inhibits glucose-stimulated insulin secretion. We here studied the impact of FFA on glucose and lipid metabolism in pancreatic beta cells with special reference to insulin secretion. Pancreatic beta-cell line MIN6 was exposed to various concentrations of palmitate for 3 days. Glucose-stimulated insulin secretion and insulin content were decreased corresponding to the concentration of the palmitate exposed. Glycolytic flux and ATP synthesis was unchanged, but pyruvate-stimulated change in NAD(P)H concentration was decreased. Pyruvate carboxylase was decreased at the protein level, which was restored by the removal of palmitate or the inhibition of beta-oxidation. Intracellular content of triglyceride and FFA were elevated, beta-oxidation was increased, and de novo lipogenesis from glucose was decreased. NADPH content and citrate output into the medium, which reflected pyruvate malate shuttle flux, were decreased, but malic enzyme activity was unaffected. The malic enzyme inhibitor alone inhibited insulin response to glucose. In conclusion, long-term exposure of FFA to beta cells inhibits glucose-stimulated insulin secretion via the decreased NADPH contents due to the inhibition of pyruvate carboxylase and malate pyruvate shuttle flux.     

Separate Intramolecular Targets for Protein Kinase A Control N-Methyl-d-aspartate Receptor Gating and Ca2+ Permeability

Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca²⁺ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca²⁺ permeability (P_Ca/P_Na) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca²⁺ conductance, because neither Na⁺ conductance nor Ca²⁺-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca²⁺ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca²⁺ permeability.     

Calphobindins (placental annexins) inhibit protein kinase C.

Calphobindins (CPBs, placental annexins) are intracellular Ca(2+)- and phospholipid-dependent proteins like protein kinase C [EC 2.7.1.37]. We investigated the inhibitory effects of calphobindins on the protein kinase C activity in vitro. CPB I inhibited the protein kinase C activity for both histone phosphorylation and lipocortin phosphorylation, but CPB II and CPB III inhibited only the protein kinase C activity for histone phosphorylation. In the case of histone phosphorylation, all CPBs inhibited the protein kinase C activity in a concentration-dependent manner, and the IC50 (concentration required for 50% inhibition) value of CPB I was 70 nM. The inhibition of protein kinase C by CPB I was Ca(2+)-dependent, and did not disappear upon increasing the concentration of phosphatidyl-serine. Kinetic analysis by double-reciprocal plots indicated that CPB I interacted not only with phosphatidylserine but also with protein kinase C. Although CPB I partially interacts with phospholipid, it is conceivable that the inhibitory action of CPB I on protein kinase C results from direct interaction of CPB I with protein kinase C. Since CPBs are mainly present under the plasma membrane, it is presumed that CPB I is an endogenous inhibitor of protein kinase C, and according to intracellular circumstances, CPB II and CPB III may also be endogenous inhibitors.     

Separation and quantification of serum alkaline phosphatase isozymes in the rat by affinity electrophoresis

The purpose of this study was to examine the possibility of separation and quantification of serum alkaline phosphatase (ALP) isozymes in rats by wheatgerm lectin affinity electrophoresis. Cellulose acetate electrophoresis of the liver and bone ALPs without lectin results in overlapping bands, but in the presence of lectin, the mobility of the band of bone enzyme was retarded and well separated from the liver enzyme band. With this affinity electrophoretic method, we determined the serum ALP isozymes in fed and fasting rats grouped by age. As a result, the absolute activity of bone isozyme showed a downward trend with age in the fed and fasting rats. The serum ALP activity was steadily higher in fed rats than in fasting rats, and the increase was due to intestinal ALP isozyme. There was low activity bordering complete absence in liver isozyme under both nutritional conditions. The affinity electrophoretic method provided a rapid, reproducible, and relatively simple technique for further clinical characterization of ALP isozyme in the rat serum.     

Ser-130 of Natronobacterium pharaonis halorhodopsin is important for the chloride binding

Pharaonis halorhodopsin (phR) is an inward light-driven chloride ion pump from Natronobacterium pharaonis. In order to clarify the role of Ser-130(phR) residue which corresponds to Ser-115(shR) for salinarum hR on the anion-binding affinity, the wild-type and Ser-130 mutants substituted with Thr, Cys and Ala were expressed in E. coli cells and solubilized with 0.1% n-dodecyl beta-D-maltopyranoside The absorption maximum (lambda(max)) of the S130T mutant indicated a blue shift from that of the wild type in the absence and presence of chloride. For S130A, a large red shift (12 nm) in the absence of chloride was observed. The wild-type and all mutants showed the blue-shift of lambda(max) upon Cl(-) addition, from which the dissociation constants of Cl(-) were determined. The dissociation constants were 5, 89, 153 and 159 mM for the wild-type, S130A, S130T and S130C, respectively, at pH 7.0 and 25 degrees C. Circular dichroic spectra of the wild-type and the Ser-130 mutants exhibited an oligomerization. The present study revealed that the Ser-130 of N. pharaonis halorhodopsin is important for the chloride binding.