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S B Walker

Publications and source records attributed to S B Walker.

24 records · Page 2Linked to original sources
PubMed1983

Pyrene actin: documentation of the validity of a sensitive assay for actin polymerization.

The fluorescence of pyrene-labelled actin is much higher after polymerization. We have characterized in detail the polymerization properties of pyrene actin and report that native and pyrene actin are identical using the following criteria: (1) the time course of polymerization; (2) the elongation rate constants; (3) the intrinsic viscosity; and (4) the critical concentration. Native and pyrene actin copolymerize. Fluorescence of polymerized pyrene actin is 7-10 times higher than monomer. The fluorescent signal is proportional to polymer weight concentration and is insensitive to filament length distribution. Bleaching can be minimized by appropriate filters to allow continuous monitoring of signal. Measurements do not influence polymerization kinetics. This establishes that pyrene actin fluorescence is a valid assay for actin polymerization that is more sensitive than any other current assay.

Actins↗
PubMed1980

The mechanism of enhancement of the neurogenic oedema response by baclofen.

The effect of baclofen on the neurogenic oedema response to electrical stimulation of the saphenous nerve in rats was investigated. Baclofen 2.5 x 10(-6) mol given intravenously enhanced the neurogenic oedema response and increased blood pressure. The enhancement was not specific to the neurogenic oedema response since plasma exudation responses to substance P, histamine and 5-hydroxytryptamine were also enhanced. No local interactions between baclofen and agents inducing plasma exudation were found which would account for this effect of baclofen. Since agents which abolished the pressor response to baclofen (alpha and beta-adrenoceptor antagonists, hexamethonium, reserpine) also abolished the enhancement of neurogenic oedema, it was concluded that baclofen enhanced the response by its action on the cardiovascular system.

Animals↗
PubMed1980

The effect of baclofen on the cardiovascular system of the rat.

1 The cardiovascular responses to baclofen were investigated in anaesthetized rats. 2 Low doses of baclofen (less than 5 X 10(-8) mol), given intravenously, produced a transient fall in blood pressure and heart rate. Higher doses (greater than 5 X 10(-7) mol) produced a marked and prolonged increase in blood pressure accompanied by a rise in heart rate and cutaneous arterial dilatation. 3 The pressor and heart rate responses exhibited tachyphylaxis, and were abolished by hexamethonium, cervical cord section, reserpine-treatment and by a combination of alpha- and beta-adrenoceptor antagonists. 4 It is concluded that the increases in blood pressure and heart rate produced by high doses of baclofen are of central sympathetic origin.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Bitolterol mesylate: a beta-adrenergic agent. Chemistry, pharmacokinetics, pharmacodynamics, adverse effects and clinical efficacy in asthma.

Bitolterol, (3-4 diester colterol) is a new beta 2-adrenergic agonist. Since it in itself is biologically inactive, bitolterol is considered a pro-drug. When administered it is activated within the lung by esterase hydrolysis to the active compound colterol catecholamine N-t-butyl-arterenol). In preclinical and clinical studies to date, bitolterol has proved to be an effective bronchodilator for adult and pediatric patients with chronic stable asthma and for some with chronic obstructive pulmonary disease. Bitolterol has been compared with other beta 2 agents, including isoproterenol, metaproterenol and albuterol. There is no evidence for cardiotoxicity when bitolterol is used in combination with theophylline in human studies. It is effective for control of exercise-induced asthma.

Animals↗
PubMedDate not supplied

Prevalence of caseous lymphadenitis and usage of caseous lymphadenitis vaccines in sheep flocks.

OBJECTIVE: To estimate the prevalence of caseous lymphadenitis (CLA), determine the current usage of vaccines against CLA and to measure the effectiveness of these vaccines on sheep farms. DESIGN AND POPULATION: A survey was undertaken on 223 sheep flocks in New South Wales, Victoria and Western Australia. METHOD: The prevalence of CLA was measured by conventional inspection techniques at abattoirs in lines of sheep that could be traced back to a farm. Managers of the flocks were sent a questionnaire about their vaccine practices, management practices and knowledge of CLA. RESULTS: The average prevalence of CLA in adult sheep in these flocks was 26% and varied from 20% in Western Australia to 29% in New South Wales. About 43% of sheep producers used CLA vaccines; only 12% used them as recommended. Awareness of CLA was highest in Western Australia. More producers would use CLA vaccine if they knew the prevalence of CLA in their flock and producers obtained most information about CLA from vaccine resellers. CONCLUSIONS: Only 10 to 15% of producers are currently achieving effective CLA control through the use of recommended CLA vaccination programs. In Western Australian flocks more than 25% of effectively vaccinated ewes will be sent to abattoirs in the 2 to 3 years after this study. However, large decreases in the prevalence of CLA can be achieved by about 70% of producers by either making adjustments to their vaccination programs or buying a vaccine with a CLA component. Two or three key facts on effective CLA vaccination could be made available at the point of sale of vaccines and from abattoirs that reported the prevalence of CLA to farmers.

Animals↗