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Biomedical subjects

B L Taylor

Publications and source records attributed to B L Taylor.

At least 73 records · Page 4Linked to original sources
PubMed1990

Central venous cannulation using the infraclavicular axillary vein.

A new percutaneous approach to central venous catheterization was recently described which seemed to offer advantages over others commonly used. To evaluate the technique, it was successfully used in 102 consecutive patients for monitoring, drug infusion, pulmonary arterial catheterization, and parenteral nutrition. There was a low incidence of complications, the most frequent being arterial puncture. The results confirm that this is an effective and relatively safe technique that deserves consideration in patients who require central venous catheterization.

Adult↗
PubMed1990

Cholinesterase deficiency and the Churg-Strauss syndrome.

We report two patients with the Churg-Strauss syndrome who were found to have decreased cholinesterase activity despite normal phenotypes. Suspicion of abnormal sensitivity to suxamethonium in the first case was raised after prolonged paralysis under anaesthesia. The findings in the second were incidental during the course of intensive care treatment. Both patients received immunosuppressive therapy. Differentiation between the effects of this and the disease process itself cannot be established.

Adult↗
PubMed1988

The influence of anaesthetic technique on metabolism of oral morphine.

The pharmacokinetics of oral controlled release morphine were studied in 10 patients to investigate the effect of two different anaesthetic techniques on its absorption and metabolism. Five patients received general anaesthesia with neuromuscular blockade; the remainder received lumbar epidural analgesia with general anaesthesia but without neuromuscular blocking agents. Blood samples were collected throughout the peri-operative period for estimation of plasma morphine concentration using two radio immunoassay techniques, one specific for morphine, the other less specific and crossreacting with morphine glucuronides. Plasma morphine concentrations with the specific method were similar for the two groups of patients but there was a statistically significant difference between the two groups with the less specific method at 30 and 45 minutes after induction of anaesthesia. This difference was because of the varying concentrations of morphine metabolites and may reflect the change in splanchnic blood flow produced by lumbar epidural analgesia.

Administration, Oral↗
PubMed1988

Signal transduction in chemotaxis to oxygen in Escherichia coli and Salmonella typhimurium.

Pathways previously proposed for sensory transduction in chemotaxis to oxygen (aerotaxis) involved either (i) cytochrome o, the electron transport system, and proton motive force or (ii) enzyme IIGlucose and the phosphoenolpyruvate:carbohydrate phosphotransferase system for active transport. This investigation distinguished between these possibilities. Aerotaxis was absent in a cyo cyd strain of Escherichia coli that lacked both cytochrome o and cytochrome d, which are the terminal oxidases for the branched electron transport system in E. coli. Aerotaxis, measured by either a spatial or temporal assay, was normal in E. coli strains that had a cyo+ or cyd+ gene or both. The membrane potential of all oxidase-positive strains was approximately -170 mV in aerated medium at pH 7.5. Behavioral responses to changes in oxygen concentration correlated with changes in proton motive force. Aerotaxis was normal in ptsG and ptsI strains that lack enzyme IIGlucose and enzyme I, respectively, and are deficient in the phosphotransferase system. A cya strain that is deficient in adenylate cyclase also had normal aerotaxis. We concluded that aerotaxis was mediated by the electron transport system and that either the cytochrome d or the cytochrome o branch of the pathway could mediate aerotaxis.

Chemotaxis↗
PubMed1988

Identification of a site of ATP requirement for signal processing in bacterial chemotaxis.

In Escherichia coli and Salmonella typhimurium, ATP is required for chemotaxis and for a normal probability of clockwise rotation of the flagellar motors, in addition to the requirement for S-adenosylmethionine (J. Shioi, R. J. Galloway, M. Niwano, R. E. Chinnock, and B. L. Taylor, J. Biol. Chem. 257:7969-7975, 1982). The site of the ATP requirement was investigated. The times required for S. typhimurium ST23 (hisF) to adapt to a step increase in serine, phenol, or benzoate were similar in cells depleted of ATP and in cells with normal levels of ATP. This established that ATP was not required for the chemotactic signal to cross the inner membrane or for adaptation to the transmembrane signal to occur. Depletion of ATP did not affect the probability of clockwise rotation in E. coli cheYZ scy strains that were defective in the cheY and cheZ genes and had a partially compensating mutation in the motor switch. Strain HCB326 (cheAWRBYZ tar tap tsr trg::Tn10), which was deficient in all chemotaxis components except the switch and motor, was transformed with the pCK63 plasmid (ptac-cheY+). Induction of cheY in the transformant increased the frequency of clockwise rotation, but except at the highest levels of CheY overproduction, clockwise rotation was abolished by depleting ATP. It is proposed that the CheY protein is normally in an inactive form and that ATP is required for formation of an active CheY* protein that binds to the switch on the flagellar motors and initiates clockwise rotation. Depletion of ATP partially inhibits feedback regulation of the cheB product, protein methylesterase, but this may reflect a second site of ATP action in chemotaxis.

Adenosine Triphosphate↗
PubMed1988

The management of massive haemorrhage.

Determined appropriate treatment of massive haemorrhage can reduce complications and save lives, yet failure to recognize or rectify acute blood loss undoubtedly still contributes to preventable hospital mortality. Anticipation and organization are the keys to improvement.

Blood Volume↗
PubMed1987

Oxygen as attractant and repellent in bacterial chemotaxis.

Studies of bacterial chemotaxis to oxygen (aerotaxis) over a broad range of oxygen concentrations showed that at high concentrations, oxygen was a repellent of Salmonella typhimurium, Escherichia coli, and some bacilli, whereas it is known that at lower concentrations (less than or equal to 0.25 mM dissolved oxygen), oxygen is an attractant. In a temporal assay of aerotaxis, S. typhimurium in medium equilibrated with air (0.25 mM dissolved oxygen) and then exposed to pure oxygen (1.2 mM) tumbled continuously for approximately 20 s. The oxygen concentration that elicited a half-maximal negative (repellent) response was 1.0 mM for both S. typhimurium and E. coli. The receptor for the negative chemoresponse to high concentrations of oxygen is apparently different from the receptor for the positive chemoresponse to low concentrations of oxygen, since the oxygen concentration that elicits a half-maximal positive (attractant) response in S. typhimurium and E. coli is reported to be 0.7 microM. Adaptation to high concentrations of oxygen, like adaptation to low concentrations of oxygen, was independent of methylation of a transducer protein. Only the response to low oxygen concentrations, however, was altered by interaction with the amidated Tsr transducer in cheB mutants.

Chemotaxis↗
PubMed1986

Inversion of aerotactic response in Escherichia coli deficient in cheB protein methylesterase.

Mutants of Escherichia coli and Salmonella typhimurium that were deficient in protein methylesterase activity encoded by cheB had an inverted response to oxygen; they were repelled by concentrations of oxygen that attract wild-type bacteria. Normal responses to oxygen and phosphotransferase substrates were observed in mutants that were deficient in protein methyltransferase (CheR) and the methyl-accepting transducing proteins (Tsr, Tar, Trg). However, the methylation-independent response to oxygen was modified by the loss of esterase activity. The inversion was apparently effected by the amidated Tsr protein present in cheB tsr+ mutants because aerotaxis was normal in cheB tsr strains. Chemotaxis to phosphotransferase sugars was normal in cheB mutants provided the extreme clockwise bias of the flagellar motors was modified to increase the probability of counterclockwise rotation.

Adaptation, Physiological↗
PubMed1986

Evidence against direct involvement of cyclic GMP or cyclic AMP in bacterial chemotactic signaling.

Defects in phosphotransferase chemotaxis in cya and cpd mutants previously cited as evidence of a cyclic GMP or cyclic AMP intermediate in signal transduction were not reproduced in a study of chemotaxis in Escherichia coli and Salmonella typhimurium. In cya mutants, which lack adenylate cyclase, the addition of cyclic AMP was required for synthesis of proteins that were necessary for phosphotransferase transport and chemotaxis. However, the induced cells retained normal phosphotransferase chemotaxis after cyclic AMP was removed. Phosphotransferase chemotaxis was normal in a cpd mutant of S. typhimurium that has elevated levels of cyclic GMP and cyclic AMP. S. typhimurium crr mutants are deficient in enzyme III glucose, which is a component of the glucose transport system, and a regulator of adenylate cyclase. After preincubation with cyclic AMP, the crr mutants were deficient in enzyme II glucose-mediated transport and chemotaxis, but other chemotactic responses were normal. It is concluded that cyclic GMP does not determine the frequency of tumbling and is probably not a component of the transduction pathway. The only known role of cyclic AMP is in the synthesis of some proteins that are subject to catabolite repression.

Adenylyl Cyclases↗
PubMed1984

Oxygen taxis and proton motive force in Salmonella typhimurium.

The aerotactic response of Salmonella typhimurium SL3730 has been quantitatively correlated with a change in the proton motive force (delta p) as measured by a flow-dialysis technique. At pH 7.5, the membrane potential (delta psi) in S. typhimurium changed from -162 +/- 13 to -111 +/- 15 mV when cells grown aerobically were made anaerobic, and it returned to the original value when the cells were returned to aerobiosis. The delta pH across the membrane was zero. At pH 5.5, delta psi was -70 mV in aerobiosis and -20 mV in anaerobiosis, and delta pH was -118 and -56 mV for aerobic and anaerobic cells, respectively. A decrease in delta p resulted in increased tumbling, and an increase in delta p resulted in a smooth swimming response at either pH. Inhibition of aerotaxis at pH 7.5 by various concentrations of KCN correlated with a decreased delta p, due to a decreased delta psi in aerobiosis and little change in delta psi in anaerobiosis. At concentrations up to 100 mM, 2,4-dinitrophenol decreased delta psi, but did not inhibit aerotaxis because the difference between delta psi in aerobic and anaerobic cells remained constant. Considered as a whole, the results indicate that aerotaxis in S. typhimurium is mediated by delta p.

2,4-Dinitrophenol↗