Adverse effects of tempol on hidrosaline balance in rats with acute sodium overload

We studied the effects of tempol, an oxygen radical scavenger, on hydrosaline balance in rats with acute sodium overload. Male rats with free access to water were injected with isotonic (control group) or hypertonic saline solution (0.80 mol/l NaCl) either alone (Na group) or with tempol (Na-T group). Hydrosaline balance was determined during a 90 min experimental period. Protein expressions of aquaporin 1 (AQP1), aquaporin 2 (AQP2), angiotensin II (Ang II) and endothelial nitric oxide synthase (eNOS) were measured in renal tissue. Water intake, creatinine clearance, diuresis and natriuresis increased in the Na group. Under conditions of sodium overload, tempol increased plasma sodium and protein levels and increased diuresis, natriuresis and sodium excretion. Tempol also decreased water intake without affecting creatinine clearance. AQP1 and eNOS were increased and Ang II decreased in the renal cortex of the Na group, whereas AQP2 was increased in the renal medulla. Nonglycosylated AQP1 and eNOS were increased further in the renal cortex of the Na-T group, whereas AQP2 was decreased in the renal medulla and was localized mainly in the cell membrane. Moreover, p47-phox immunostaining was increased in the hypothalamus of Na group, and this increase was prevented by tempol. Our findings suggest that tempol causes hypernatremia after acute sodium overload by inhibiting the thirst mechanism and facilitating diuresis, despite increasing renal eNOS expression and natriuresis.     

Effects of garlic and onion oils on glutathione peroxidase activity, the ratio of reduced/oxidized glutathione and ornithine decarboxylase induction in isolated mouse epidermal cells treated with tumor promoters

Garlic oil, onion oil and one of its constituents, dipropenyl sulfide, all increase, to diverse degrees, glutathione (GSH) peroxidase (GSH:H2O2 oxidoreductase, EC 1.11.1.9) activity in isolated epidermal cells incubated in the presence or absence of the potent tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA). The stimulatory effects of these oils on epidermal GSH peroxidase activity are concentration-dependent and long-lasting, and thus, abolish totally the prolonged inhibitory effect of TPA on this enzyme. Moreover, garlic oil (5 micrograms/ml) inhibits by about 50% TPA-induced ornithine decarboxylase (ODC, L-ornithine carboxy-lyase, EC 4.1.1.17) activity in the same epidermal cell system. This concentration of garlic oil also increases remarkably GSH peroxidase activity and inhibits ODC induction in the presence of various nonphorbol ester tumor promoters. Since the same oil treatments inhibit dramatically the sharp decline in the intracellular ratio of reduced (GSH)/oxidized (GSSG) glutathione caused by TPA, it is suggested that some of the inhibitory effects of garlic and onion oils on skin tumor promotion may result from their enhancement of the natural GSH-dependent antioxidant protective system of the epidermal cells.     

Lateral interactions among membrane proteins. Implications for the organization of gap junctions.

We have studied the relationship between interprotein forces and the lateral distribution of proteins in disordered mouse liver gap junctions. Data on protein positions are obtained from freeze-fracture electron micrographs. Short-ranged correlations in observed positions are characteristic of interacting particles in a fluid state. An analysis derived from statistical mechanics allows the determination of the magnitude and functional form of interprotein forces. We find that jap junction proteins are mutually repulsive, in a manner consistent with electrostatics and excluded volume. This dictates that long-ranged protein aggregation into jap junction plaques cannot arise solely from interparticle interactions. An alternative is the balance of lateral pressures between the junction and the surrounding glycocalyx. This idea is quantified into a model. Junctional pressure arises from protein-protein interactions and is computed from a pressure equation based on the force and a radial distribution function describing order. The pressure from the glycocalyx is assumed to arise from mixing, electrostatic, and elastic interactions of sugar residues, and is described with terms from Flory-Krigbaum and McMillan-Mayer theories. The results of this modeling are in reasonable agreement with available experimental data.     

PRIMAL: Fast and Accurate Pedigree-based Imputation from Sequence Data in a Founder Population

Founder populations and large pedigrees offer many well-known advantages for genetic mapping studies, including cost-efficient study designs. Here, we describe PRIMAL (PedigRee IMputation ALgorithm), a fast and accurate pedigree-based phasing and imputation algorithm for founder populations. PRIMAL incorporates both existing and original ideas, such as a novel indexing strategy of Identity-By-Descent (IBD) segments based on clique graphs. We were able to impute the genomes of 1,317 South Dakota Hutterites, who had genome-wide genotypes for ~300,000 common single nucleotide variants (SNVs), from 98 whole genome sequences. Using a combination of pedigree-based and LD-based imputation, we were able to assign 87% of genotypes with >99% accuracy over the full range of allele frequencies. Using the IBD cliques we were also able to infer the parental origin of 83% of alleles, and genotypes of deceased recent ancestors for whom no genotype information was available. This imputed data set will enable us to better study the relative contribution of rare and common variants on human phenotypes, as well as parental origin effect of disease risk alleles in >1,000 individuals at minimal cost.