Pulmonary responses to acute ozone exposure in fasted mice: effect of leptin administration.

Leptin is a satiety hormone that also has proinflammatory effects, including augmentation of ozone-induced pulmonary inflammation. The purpose of this study was to determine whether reductions in endogenous levels of leptin can attenuate pulmonary responses to ozone. To reduce serum leptin, we fasted mice overnight before ozone exposure. Fasting caused a marked reduction in serum leptin to approximately one-sixth the levels observed in fed mice, and continuous infusion of leptin via Alzet micro-osmotic pumps restored serum leptin to, but not above, fed levels. Ozone exposure (2 ppm for 3 h) caused a significant, approximately 40% increase in pulmonary resistance (P < 0.01) and increased airway responsiveness in fasted but not in fed mice. The increased effect of ozone on pulmonary mechanics and airway responsiveness in fasted mice was not observed when leptin was restored via continuous infusion. Ozone exposure caused pulmonary inflammation, as evident by increases in bronchoalveolar lavage cells, protein, and soluble tumor necrosis factor receptors. There was no effect of fasting status on ozone-induced changes in the bronchoalveolar lavage inflammatory profile, and leptin treatment did not alter these responses. Our results indicate that fasting augments ozone-induced changes in pulmonary mechanics and airway responsiveness in mice. These effects of fasting are the result of declines in serum leptin. The mechanistic basis for this protective effect of leptin in fasted mice remains to be determined but is not related to effects on ozone-induced inflammation.     

Glucose and fatty acids synergize to promote B-cell apoptosis through activation of glycogen synthase kinase 3β independent of JNK activation

Background

The combination of elevated glucose and free-fatty acids (FFA), prevalent in diabetes, has been suggested to be a major contributor to pancreatic β-cell death. This study examines the synergistic effects of glucose and FFA on β-cell apoptosis and the molecular mechanisms involved. Mouse insulinoma cells and primary islets were treated with palmitate at increasing glucose and effects on apoptosis, endoplasmic reticulum (ER) stress and insulin receptor substrate (IRS) signaling were examined.

Principal Findings

Increasing glucose (5–25 mM) with palmitate (400 µM) had synergistic effects on apoptosis. Jun NH2-terminal kinase (JNK) activation peaked at the lowest glucose concentration, in contrast to a progressive reduction in IRS2 protein and impairment of insulin receptor substrate signaling. A synergistic effect was observed on activation of ER stress markers, along with recruitment of SREBP1 to the nucleus. These findings were confirmed in primary islets. The above effects associated with an increase in glycogen synthase kinase 3β (Gsk3β) activity and were reversed along with apoptosis by an adenovirus expressing a kinase dead Gsk3β.

Conclusions/Significance

Glucose in the presence of FFA results in synergistic effects on ER stress, impaired insulin receptor substrate signaling and Gsk3β activation. The data support the importance of controlling both hyperglycemia and hyperlipidemia in the management of Type 2 diabetes, and identify pancreatic islet β-cell Gsk3β as a potential therapeutic target.     

Double muscling in Marchigiana beef breed is caused by a stop codon in the third exon of myostatin gene

Double muscling is a partially recessive trait present in some beef breeds. It shows a high frequency in some breeds, while in others the frequency is low, and double-muscled individuals are rare. The double muscling is caused by an allelic series of mutations that cause a loss of function of the myostatin gene ( GDF8). We describe here a new mutation in the myostatin gene in Marchigiana breed, a typical beef breed of Central Italy, in which rare double-muscling individuals have been described. A PCR product of the third exon was sequenced in subjects phenotypically showing double muscling, and a G > T transversion was discovered that introduces a premature stop codon. The variant found adds to the large series of mutations present in cattle, and particularly to the only two causative of double muscling in the third exon. A PCR-RFLP test is described for the rapid and effective identification of both heterozygous and homozygous subjects. It was applied to a larger survey carried on the same and also in two other beef breeds, Chianina and Romagnola. Further individuals carrying the new variant were found in Marchigiana, but none in the other breeds. The results may be important for a better comprehension of the role of myostatin in muscular development, for commercial use and for the inference of phylogeny of this gene.     

Acceleration of surface-dependent autocatalytic activation of blood coagulation factor XII by divalent metal ions

The effect of divalent metal ions on the rate of dextran sulfate dependent autocatalytic activation of human blood coagulation factor XII was studied at pH 7.4 and 25 degrees C. Zn2+ and Cu2+, but not Co2+, increased the rate of factor XII activation induced by dextran sulfate with optimum effects at approximately 5 and 1 microM, respectively, while Ca2+ acceleration required much higher concentrations (millimolar). Further investigation of the effect of Zn2+ on factor XII activation demonstrated a complete dependence on the presence of dextran sulfate, lack of inhibition by soybean trypsin inhibitor, the appearance of alpha-XIIa as the primary reaction product, and reaction kinetics characteristic of an autocatalytic process. These results were consistent with Zn2+ affecting only the rate of surface-mediated factor XII autoactivation. The initial turnover velocity of dextran sulfate induced factor XII autoactivation increased linearly with factor XII concentration in the absence of Zn2+ up to 0.9 microM factor XII but showed saturation behavior over this same concentration range in the presence of 5 microM Zn2+, indicating that Zn2+ increased the reaction rate primarily by lowering the apparent Km. Comparison of the kinetics of autoactivation at mu = 0.15 and 0.24 revealed that the enhancement in the apparent kcat/Km brought about by Zn2+ increased from 19-fold to 520-fold, respectively, due to a differential dependence of the Zn2+-stimulated and unstimulated reactions on ionic strength.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hawkmoth Pollinators Decrease Seed Set of a Low-Nectar Petunia axillaris Line through Reduced Probing Time

Media player

Lack of effect of oral magnesium on high blood pressure: a double blind study.

Seventeen unselected patients with mild to moderate essential hypertension and whose average supine blood pressure after two months'' observation with no treatment was 154/100 mm Hg were entered into a double blind randomised crossover study of one month''s treatment with magnesium aspartate (15 mmol magnesium/day) and treatment with placebo for a further month. This preparation of magnesium was well tolerated and did not cause diarrhoea. Despite a significant increase in plasma magnesium concentration and a significant increase in urinary excretion of magnesium while taking magnesium aspartate there was no fall in blood pressure compared with either treatment with placebo or values before treatment. The results provide no evidence for a role of dietary magnesium in the regulation of high blood pressure and are contrary to recent speculations.     

A novel asparaginase-like protein is a sperm autoantigen in rats

A novel asparaginase-like protein (ALP) of spermatozoa was cloned from rat and human testis cDNA libraries on the basis of reactivity with antibodies produced after vasectomy. Although obstruction of the male reproductive tract is known to cause an immunologic response, few of the sperm antigens responsible for the generation of autoantibodies have been characterized. We are identifying proteins of interest by coring autoantigenic protein spots from two-dimensional (2-D) gels of rat sperm extracts and microsequencing them by mass spectrometry. The peptide sequences from ALP, a 28 kDa, pI 5.7 protein, matched to a single partial length rat EST. These peptide sequences were used to clone a cDNA encoding a novel 333 amino acid open reading frame. The new protein had a similarity to portions of L-asparaginases of plants (43%) and to glycosylasparaginases in animal cells (32%). Human ALP cDNA was subsequently cloned. It showed 77% identity to the rat ALP sequence and the gene, ASRGL1 (asparaginase-like 1), mapped to chromosome locus 11q12.3. Purified recombinant rat ALP (rALP), expressed in E. coli, was used to raise polyclonal antiserum in guinea pigs. Two observations verified that the correct protein had been cloned: 1) the anti-rALP antibody reacted with both rALP and rat sperm; and 2) post-vasectomy sera bound rALP. Anti-rALP antibody stained the midpiece of rat and human sperm coincident with staining by MitoTracker Green FM, suggesting that ALP is associated with the mitochondria. Northern analysis revealed that rat ALP message was abundantly expressed in the testis but was also present in heart, brain, liver, skeletal muscle, and kidney.