RNA cleavage without hydrolysis. Splitting the catalytic activities of binase with Asn101 and Thr101 mutations

We have developed a model of ischaemia-reperfusion injury in C57BL/6 mice involving ischaemia for 0.5 to 2.5 h with an elastic tourniquet on one hind limb and reperfusion for 24 h, analogous to a well-established model of ischaemia-reperfusion injury in the rat. Viability was assessed in tissue homogenates of the gastrocnemius muscles from the affected and contralateral control limb by a triphenyl tetrazolium chloride dye reaction, measuring the activity of the oxidative mitochondrial enzymes. After 1.5 h ischaemia and 24 h reperfusion, viability in the ischaemic-reperfused limb was 13%, with the control muscle regarded as 100% viable. Significant improvements in viability to 86% (P < 0.05) and 56% (P < 0.05) were achieved, with administration 30 min prior to tourniquet release, of the nitric oxide (NO) synthase inhibitor nitro-L-arginine methyl ester (L-NAME, 30 mg/kg) and the anti-inflammatory glucocorticoid dexamethasone (2.5 mg/kg) respectively, with similar findings in the rat tourniquet model.     

Sequence comparison of the EcoHK31I and EaeI restriction-modification systems suggests an intergenic transfer of genetic material

The genes coding for the EcoHK31I and EaeI restriction-modification (R-M) systems from Escherichia coli strain HK31 and Enterobacter aerogenes, respectively, have been cloned and sequenced. Both ENases recognize and cleave Y/GGCCR leaving 4 nucleotide 5'-protruding ends, while the MTases modify the internal cytosine. The systems were isolated on a 2.3kb AseI fragment for EcoHK31I, and a 4.6 kb HindIII fragment for EaeI. The R and M genes of both systems converge and overlap by 14 nucleotides. Previously, we found that M.EcoHK31I consisted of two subunits, (alpha and beta), with the beta subunit being translated from an alternative open reading frame within the gene encoding the alpha subunit. Sequence comparison between the EcoHK31I and EaeI systems reveals striking similarity. The eaeIM gene also encodes alpha and beta polypeptides of 309 and 176 amino acids which share 96% and 97% identity, respectively, with those of ecoHK31IM. ecoHK31IR and eaeIR encode proteins of 318 and 315 aa, respectively, which share 92% identity but are otherwise unique in the GenBank database. The EaeI and the EcoHK31I R-M systems were found to be flanked by genes coding for integrases. It is possible that these integrases have facilitated the transfer of this system among different bacterial species.     

Eucapnic hypoxia lowers human cold thermoregulatory response thresholds and accelerates core cooling

Hypoxia lowers the basic thermoregulatory responses of animals and humans. In cold-exposed animals, hypoxia increases core temperature (Tco) cooling rate and suppresses shivering thermogenesis. In humans, the experimental effects of hypoxia on thermoregulation are equivocal. Also, the effect of hypoxia has not been separated from that of hypocapnia consequent to hypoxic hyperventilation. To determine the isolated effects of hypoxia on warm and cold thermoregulatory responses and core cooling during mild cold stress, we examined the Tco thresholds for sweating, vasoconstriction, and shivering as well as the core cooling rates of eight subjects immersed in 28 degrees C water under eucapnic conditions. On 2 separate days, subjects exercised on an underwater cycle ergometer to elevate Tco above the sweating threshold. They then rested and cooled until they shivered vigorously. Subjects inspired humidified room air during the control trial. For the eucapnic hypoxia trial, they inspired 12% O2-balance N2 with CO2 added to maintain eucapnia. Eucapnic hypoxia lowered the Tco thresholds for vasoconstriction and shivering by 0.14 and 0.19 degrees C, respectively, and increased core cooling rate by 33% (1.83 vs. 1.38 degrees C/h). These results demonstrate that eucapnic hypoxia enhances the core cooling rate in humans during mild cold stress. This may be attributed in part to a delay in the onset of vasoconstriction and shivering as well as increased respiratory heat loss during hypoxic hyperventilation.     

Lambda Xis degradation in vivo by Lon and FtsH

Lambda Xis, which is required for site-specific excision of phage lambda from the bacterial chromosome, has a much shorter functional half-life than Int, which is required for both integration and excision (R. A. Weisberg and M. E. Gottesman, p. 489-500, in A. D. Hershey, ed., The Bacteriophage Lambda, 1971). We found that Xis is degraded in vivo by two ATP-dependent proteases, Lon and FtsH (HflB). Xis was stabilized two- to threefold more than in the wild type in a lon mutant and as much as sixfold more in a lon ftsH double mutant at the nonpermissive temperature for the ftsH mutation. Integration of lambda into the bacterial chromosome was delayed in the lon ftsH background, suggesting that accumulation of Xis in vivo interferes with integration. Overexpression of Xis in wild-type cells from a multicopy plasmid inhibited integration of lambda and promoted curing of established lysogens, confirming that accumulation of Xis interferes with the ability of Int to establish and maintain an integrated prophage.     

Anxiety in early adulthood

There is no doubt that the relatively recent changes in our society must have effects on the development of the early adult. These include changes in society's attitudes, permissiveness, changing roles, equal employment and wage opportunities, women's liberation, the 'single mother by desire', changing divorce laws, integrated university colleges of residence, to mention but a few factors. The effects of drugs, illegal and legal, alcohol, the motor vehicle, pollution and environmental change must also be remembered as possible sources of anxiety in early adulthood.