Enhanced performance of nano-sized SiC reinforced Al metal matrix nanocomposites synthesized through microwave sintering and hot extrusion techniques

In the present study, nano-sized SiC (0, 0.3, 0.5, 1.0 and 1.5 vol%) reinforced aluminum (Al) metal matrix composites were fabricated by microwave sintering and hot extrusion techniques. The structural (XRD, SEM), mechanical (nanoindentation, compression, tensile) and thermal properties (co-efficient of thermal expansion- CTE) of the developed Al-SiC nanocomposites were studied. The SEM/EDS mapping images show a homogeneous distribution of SiC nanoparticles into the Al matrix. A significant increase in the strength (compressive and tensile) of the Al-SiC nanocomposites with the addition of SiC content is observed. However, it is noticed that the ductility of Al-SiC nanocomposites decreases with increasing volume fraction of SiC. The thermal analysis indicates that CTE of Al-SiC nanocomposites decreases with the progressive addition of hard SiC nanoparticles. Overall, hot extruded Al 1.5 vol% SiC nanocomposites exhibited the best mechanical and thermal performance as compared to the other developed Al-SiC nanocomposites.     

Calcium sensitivity of succinate and pyruvate dehydrogenases in the denervated amphibian skeletal muscle

Zusammenfassung Es wird nachgewiesen, dass die Aktivität von Succinat Dehydrogenase und von Pyruvat Dehydrogenase in Extrakten normaler und denervierter Muskulatur durch Ca⁺⁺ im pH-Bereich von 5,8 bis 7,8 in verschiedenem Ausmass erhöht bzw. erniedrigt wird.     

The genome sequence of Bacillus anthracis Ames and comparison to closely related bacteria

Bacillus anthracis is an endospore-forming bacterium that causes inhalational anthrax. Key virulence genes are found on plasmids (extra-chromosomal, circular, double-stranded DNA molecules) pXO1 (ref. 2) and pXO2 (ref. 3). To identify additional genes that might contribute to virulence, we analysed the complete sequence of the chromosome of B. anthracis Ames (about 5.23 megabases). We found several chromosomally encoded proteins that may contribute to pathogenicity--including haemolysins, phospholipases and iron acquisition functions--and identified numerous surface proteins that might be important targets for vaccines and drugs. Almost all these putative chromosomal virulence and surface proteins have homologues in Bacillus cereus, highlighting the similarity of B. anthracis to near-neighbours that are not associated with anthrax. By performing a comparative genome hybridization of 19 B. cereus and Bacillus thuringiensis strains against a B. anthracis DNA microarray, we confirmed the general similarity of chromosomal genes among this group of close relatives. However, we found that the gene sequences of pXO1 and pXO2 were more variable between strains, suggesting plasmid mobility in the group. The complete sequence of B. anthracis is a step towards a better understanding of anthrax pathogenesis.     

Control of dynamic CFTR selectivity by glutamate and ATP in epithelial cells

Cystic fibrosis is caused by mutations in cystic fibrosis transmembrane conductance regulator (CFTR), an anion channel. Phosphorylation and ATP hydrolysis are generally believed to be indispensable for activating CFTR. Here we report phosphorylation- and ATP-independent activation of CFTR by cytoplasmic glutamate that exclusively elicits Cl-, but not HCO3-, conductance in the human sweat duct. We also report that the anion selectivity of glutamate-activated CFTR is not intrinsically fixed, but can undergo a dynamic shift to conduct HCO3- by a process involving ATP hydrolysis. Duct cells from patients with DeltaF508 mutant CFTR showed no glutamate/ATP activated Cl- or HCO3- conductance. In contrast, duct cells from heterozygous patients with R117H/DeltaF508 mutant CFTR also lost most of the Cl- conductance, yet retained significant HCO3- conductance. Hence, not only does glutamate control neuronal ion channels, as is well known, but it can also regulate anion conductance and selectivity of CFTR in native epithelial cells. The loss of this uniquely regulated HCO3- conductance is most probably responsible for the more severe forms of cystic fibrosis pathology.     

Possible significance of aminotransferases in tissues of the aestivating fresh water mussel,Lamellidens marginalis (Lamarck)

Summary Both aspartate and alanine aminotransferase levels increased in digestive gland, foot and mantle on aestivation. The free amino acids and pyruvic acid also increased in all tissues. The significance of these changes is discussed in relation to gluconeogenesis.Acknowledgment. The authors thank Professor K.S. Swami, Head, Department of Zoology, for encouragement and Mr I. Kabeer Ahamed for his help.     

Evaluation of participation of glucose in elevation of glycemia of scorpion (Heterometrus fulvipes) caused by the hyperglycemic principle of the scorpion and crab

Summary A single injection of the hyperglycemic principle obtained from scorpion cephalothoracic ganglionic mass causes an elevation of glycemia in the scorpionH. fulvipes in which little glucose is involved (10.8%). With the crustacean hyperglycemic principle, the elevation of glycemia is initially almost exclusively contributed by glucose (glucose is 92% of total carbohydrate at 2 h post injection); 6 h after treatment, non-glucose carbohydrates appear to participate in the elevation of glycemia.Acknowledgments. We wish to express our gratitude to CSIR, New Delhi for providing financial support to P.S.R., Reprint requests should be addressed to Prof. R. Ramamurthi.