Role of peripheral chemoreceptors in response to smoke-induced apnea vs tracheal occlusion

Reflex autonomic changes which occur after cigarette smoke enters the upper airways are partially due to peripheral chemoreceptor stimulation. Chemoreceptor denervation attenuates but does not abolish smoke induced bradycardia. Denervation nearly abolishes bradycardia induced by tracheal occlusion. Hypertension accompanies smoke induced apnea but does not occur during tracheal occlusion.     

Role of peripheral chemoreceptors in response to smoke-induced apnea vs tracheal occlusion

Summary Reflex autonomic changes which occur after cigarette smoke enters the upper airways are partially due to peripheral chemoreceptor stimulation. Chemoreceptor denervation attenuates but does not abolish smoke induced bradycardia. Denervation nearly abolishes bradycardia induced by tracheal occlusion. Hypertension accompanies smoke induced apnea but does not occur during tracheal occlusion.Acknowledgments. This study was supported by Oral Roberts University research funds.     

Bacterial oligopeptide-binding proteins

This review focuses on bacterial oligopeptide-binding proteins, which form part of the oligopeptide transport system belonging to the ATP-binding cassette family of transporters. Depending on the bacterial species, these binding proteins (OppA) capture peptides ranging in size from 2 to 18 amino acids from the environment and pass them on to the other components of the oligopeptide transport system for internalisation. Bacteria have developed several strategies to produce these binding proteins, which are periplasmic in Gram^– bacteria and membrane-anchored in Gram⁺, with a higher stoichiometry (probably necessary for efficient transport) than the other components in the transport system. The expression of OppA-encoding genes is clearly modulated by external factors, especially nitrogen compounds, but the mechanisms of regulation are not always clear. The best-understood roles played by OppAs are internalisation of peptides for nutrition and recycling of muropeptides. It has, however, recently become clear that OppAs are also involved in sensing the external medium via specific or non-specific peptides.Received 10 February 2003; received after revision 9 April 2003; accepted 24 April 2003     

Bacterial endotoxin and impaired fetal development

Summary Small doses ofE. coli endotoxin given to pregnant mice on the 13th day of pregnancy caused only a mild maternal illness but induced resorption of approximately half the number of fetuses in each mouse. The remaining live fetuses developed normally and showed no evidence of retarded growth or malformations. The weights of their placentas and maternal spleens increased significantly. Endotoxin given on the 6th day of pregnancy caused a small reduction in fetal weights.Acknowledgments. I am indebted to Mrs.Heather Sandison for technical assistance and to Mr.M. J. R. Healy for statistical examination of the results. Dr.A. B. G. Lansdown kindly advized on the interpretation of histological findings.     

Bacterial protein toxins and cell vesicle trafficking

A group of bacterial protein toxins interfere with vesicular trafficking inside cells. Clostridial neurotoxins affect mainly the highly regulated fusion of neurotransmitter- and hormone-containing vesicles with the plasma membrane. They cleave the three SNARE proteins: VAMP, SNAP-25 and syntaxin, and this selective proteolysis results in a blockade of exocytosis. TheHelicobacter pylori cytotoxin is implicated in the pathogenesis of gastroduodenal ulcers. It causes a progressive and extensive vacuolation of cells followed by necrosis, after a cytotoxin-induced alteration of membrane trafficking by late endosomes. Vacuoles originate from this compartment in a rab7-dependent process and swell because they are acidic and accumulate membrane-permeant amines.     

Bacterial suicide through stress

Outside of the laboratory, bacterial cells are constantly exposed to stressful conditions, and an ability to resist those stresses is essential to their survival. However, the degree of stress required to bring about cell death varies with growth phase, amongst other parameters. Exponential phase cells are significantly more sensitive to stress than stationary phase ones, and a novel hypothesis has recently been advanced to explain this difference in sensitivity, the suicide response. Essentially, the suicide response predicts that rapidly growing and respiring bacterial cells will suffer growth arrest when subjected to relatively mild stresses, but their metabolism will continue: a burst of free-radical production results from this uncoupling of growth from metabolism, and it is this free-radical burst that is lethal to the cells, rather than the stress per se. The suicide response hypothesis unifies a variety of previously unrelated empirical observations, for instance induction of superoxide dismutase by heat shock, alkyl-hydroperoxide reductase by osmotic shock and catalase by ethanol shock. The suicide response also has major implications for current [food] processing methods. Received 29 March 1999; received after revision 14 May 1999; accepted 17 May 1999     

Bacterial targets and antibiotics: genome-based drug discovery

The requirement for novel classes of antibiotics to combat the emergence of resistant and multi-resistant bacteria has coincided with the completion sequencing of a number of bacterial genomes. The in silico analysis of these genomes coupled with innovative genetic manipulation has already led to the identification of conserved essential (either in vitro or in vivo, depending on the methodology) genes that are potential targets for antibacterial research. New technologies, made possible by access to the genomic sequences, are capable of simultaneously quantifying almost the entire complement of gene products synthesised by bacterial cells. These technologies are opening up the way for the analysis of expression patterns elicited in cells in response to changes in their environment. The integration of these technologies into the drug discovery process is still in its infancy and the potential wealth of information, some of it already available, has yet to be fully realised.