A family of amphiphilic dioxidovanadium(V) hydrazone complexes as potent carbonic anhydrase inhibitors along with anti-diabetic and cytotoxic activities

BioMetals - A family of dioxidovanadium(V) complexes (1–4) of the type [Na(H2O)x]+[VVO2(HL1?4)]? (x?=?4, 4.5 and 7) where HL2? represents the dianionic form of...     

Open-channel block by the cytoplasmic tail of sodium channel beta4 as a mechanism for resurgent sodium current

Voltage-gated sodium channels with "resurgent" kinetics are specialized for high-frequency firing. The alpha subunits interact with a blocking protein that binds open channels upon depolarization and unbinds upon repolarization, producing resurgent sodium current. By limiting classical inactivation, the cycle of block and unblock shortens refractory periods. To characterize the blocker in Purkinje neurons, we briefly exposed inside-out patches to substrate-specific proteases. Trypsin and chymotrypsin each removed resurgent current, consistent with established roles for positively charged and hydrophobic/aromatic groups in blocking sodium channels. In Purkinje cells, the only known sodium channel-associated subunit that has a cytoplasmic sequence with several positive charges and clustered hydrophobic/aromatic residues is beta4 (KKLITFILKKTREK; beta4(154-167)). After enzymatic removal of block, beta4(154-167) fully reconstituted resurgent current, whereas scrambled or point-mutated peptides were ineffective. In CA3 pyramidal neurons, which lack beta4 and endogenous block, beta4(154-167) generated resurgent current. Thus, beta4 may be the endogenous open-channel blocker responsible for resurgent kinetics.     

Studies on the existence of a pathway in liver and muscle for the conversion of glucose into glycogen without glucose 6-phosphate as an intermediate

Mixtures of (14)C-labelled glucose plus pyruvate were incubated either with rat diaphragm or slices of rat liver. Incorporation of glucose carbon into glycogen was compared with its incorporation into glucose 6-phosphate relative to the incorporation of pyruvate carbon into these metabolic products. There was no preferential incorporation of glucose carbon relative to pyruvate carbon into glycogen compared with glucose 6-phosphate in the liver slices, but there was in diaphragm. On the assumption that glucose 6-phosphate is a necessary intermediate in the conversion of pyruvate carbon into glycogen, this is evidence for the existence in muscle, but not in liver, of more than one pool of glucose 6-phosphate or of a pathway from glucose to glycogen without glucose 6-phosphate as an intermediate. Galactose carbon, relative to pyruvate carbon, was preferentially incorporated into liver glycogen, so that a substrate converted in liver into glycogen without glucose 6-phosphate as an intermediate could be detected by this approach.     

LeuX tRNA-dependent and -independent mechanisms of Escherichia coli pathogenesis in acute cystitis

Uropathogenic Escherichia coli (UPEC) contain multiple horizontally acquired pathogenicity-associated islands (PAI) implicated in the pathogenesis of urinary tract infection. In a murine model of cystitis, type 1 pili-mediated bladder epithelial invasion and intracellular proliferation are key events associated with UPEC virulence. In this study, we examined the mechanisms by which a conserved PAI contributes to UPEC pathogenesis in acute cystitis. In the human UPEC strain UTI89, spontaneous excision of PAI II(UTI89) disrupts the adjacent leuX tRNA locus. Loss of wild-type leuX-encoded tRNA(5)(Leu) significantly delayed, but did not eliminate, FimB recombinase-mediated phase variation of type 1 pili. FimX, an additional FimB-like, leuX-independent recombinase, was also found to mediate type 1 pili phase variation. However, whereas FimX activity is relatively slow in vitro, it is rapid in vivo as a non-piliated strain lacking the other fim recombinases rapidly expressed type 1 pili upon experimental infection. Finally, we found that disruption of leuX, but not loss of PAI II(UTI89) genes, reduced bladder epithelial invasion and intracellular proliferation, independent of type 1 piliation. These findings indicate that the predominant mechanism for preservation of PAI II(UTI89) during the establishment of acute cystitis is maintenance of wild-type leuX, and not PAI II(UTI89) gene content.     

Effects of Exogenous Selenium on Nicotine-Induced Oxidative Stress in Rats

The effect of two different doses of selenium [1 and 50 μg selenium/100 g body weight (wt)] on nicotine-induced oxidative damage in liver was investigated in experimental rats. Male albino rats were maintained for 60 days as follows: (1) control group (normal diet), (2) nicotine group (0.6 mg/kg body wt)/day, (3) high-dose selenium (50 μg/100 g body wt)/day, (4) high-dose selenium (50 μg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day, (5) low-dose selenium (1 μg/100 g body wt)/day, and (6) low-dose selenium (1 μg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day. Nicotine administration caused a decrease in the activity of antioxidant enzymes, an increase in the concentration of lipid peroxidation products and protein carbonyls and an increase in the activity of nitric oxide synthase compared to the control group. Coadministration of nicotine and selenium reduced the concentration of lipid peroxidation products and increased the activity of antioxidant enzymes compared to the nicotine group. Selenium also enhanced the metabolism of nicotine. The antioxidant effect was more significant in the group administered a low dose of selenium.     

The link between the PDL1 costimulatory pathway and Th17 in fetomaternal tolerance

Fetomaternal tolerance has been shown to depend both on regulatory T cells (Tregs) and negative signals from the PD1-PDL1 costimulatory pathway. More recently, IL-17-producing T cells (Th17) have been recognized as a barrier in inducing tolerance in transplantation. In this study, we investigate the mechanisms of PDL1-mediated regulation of fetomaternal tolerance using an alloantigen-specific CD4(+) TCR transgenic mouse model system (ABM-tg mouse). PDL1 blockade led to an increase in embryo resorption and a reduction in litter size. This was associated with a decrease in Tregs, leading to a lower Treg/effector T cell ratio. Moreover, PDL1 blockade inhibited Ag-specific alloreactive T cell apoptosis and induced apoptosis of Tregs and a shift toward higher frequency of Th17 cells, breaking fetomaternal tolerance. These Th17 cells arose predominantly from CD4(+)Foxp3(-) cells, rather than from conversion of Tregs. Locally in the placenta, similar decrease in regulatory and apoptotic markers was observed by real-time PCR. Neutralization of IL-17 abrogated the anti-PDL1 effect on fetal survival rate and restored Treg numbers. Finally, the adoptive transfer of Tregs was also able to improve fetal survival in the setting of PDL1 blockade. This is to our knowledge the first report using an alloantigen-specific model that establishes a link between PDL1, Th17 cells, and fetomaternal tolerance.     

Combined effect of ascorbic acid and selenium supplementation on alcohol-induced oxidative stress in guinea pigs

Oxidative stress is a key step in the pathogenesis of ethanol associated liver injury. Ethanol administration induces an increase in lipid peroxidation either by enhancing the production of oxygen reactive species or by decreasing the level of endogenous antioxidants. In this present study, four groups of male guinea pigs (Cavia porcellus) were maintained for 45 days as follows: Control group (1 mg ascorbic acid (AA)/100 g body wt./day); Ethanol group (1 mg AA/100 g body wt./day+900 mg ethanol/100 g body wt./day); Selenium+AA group (25 mg AA+0.05 mg sodium selenite/100 g body wt./day); Ethanol+Se+AA group (25 mg AA+0.05 mg sodium selenite/100 g body wt.+900 mg ethanol/100 g body wt./day). Malondialehyde (MDA), hydroperoxides (HP) and conjugated dienes (CD) were significantly increased, while the activities of scavenging enzymes superoxide dismutase (SOD) and catalase were reduced in the alcohol administered groups. Co-administration of Se+AA along with alcohol increased the activities of scavenging enzymes and reduced the lipid peroxidation products level in hepatic tissues of guinea pigs. Activities of glutathione peroxidase (GPX) and glutathione reductase (GR) were enhanced in co-administered group. gamma-Glutamyl transpeptidase (GGT), a marker enzyme of alcohol induced toxicity, was also reduced, as was the glutathione content. This study suggests that the combined effect of Se+AA, provides protection against alcohol-induced oxidative stress as evidenced from the decreased levels of lipid peroxidation products and enhanced activities of scavenging enzymes.