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Biomedical subjects

K Walsh

Publications and source records attributed to K Walsh.

At least 271 records · Page 15Linked to original sources
PubMed1986

Effect of early treatment with nifedipine in suspected acute myocardial infarction.

In this single centre prospective, double blind study, 98 patients with suspected acute myocardial infarction (AMI) were randomized, within six hours, to nifedipine 10 mg (46 patients) or placebo (52 patients) both administered sublingually. The delay time from onset of chest pain to treatment was 3.33 +/- 0.2 hours (mean +/- SEM) and 3.28 +/- 0.18 hours for the nifedipine and placebo treated groups, respectively. Treatment was continued orally for 3 days. AMI was confirmed in 28 patients given nifedipine and 23 patients given placebo. Infarct sizing by CK-MB isoenzyme release was possible, for technical reasons, in only 23 patients on nifedipine and 17 patients on placebo. CK-MB isoenzyme release was 710 +/- 104 IU l-1 and 655 +/- 118 IU l-1 for the nifedipine and placebo treated groups respectively (P greater than 0.05). In the acute coronary insufficiency (ACI) group--18 patients given nifedipine and 29 patients given placebo--there was no significant difference in duration of admission, urgent cardiac readmission or progression to AMI within one month. Study withdrawal occurred in 15.3%--8 nifedipine and 7 placebo. Overall, one month mortality was 10.2% with 5 deaths in both the nifedipine and placebo treated groups. Early treatment with nifedipine did not reduce enzymatically determined infarct size or one month mortality in patients with AMI, or reduce one month morbidity or mortality in patients with ACI.

Acute Disease↗
PubMed1986

Optimum pacing mode for patients with angina pectoris.

A within patient double blind prospective study of symptoms and exercise tolerance was designed to determine the preferred pacing mode in 10 patients with programmable dual chamber pacemakers who also had angina pectoris. Patients were randomly allocated to one month in each of the following modes: ventricular pacing at 70 beats/min (VVI) or atrioventricular synchronous upper rate 150 beats/min (DDD 150) or 100 beats/min (DDD 100). Medications were unchanged throughout the study; none was taking beta blockers. At the end of each month patients underwent an exercise test. During each month patients recorded symptoms and their preferred pacing mode. DDD 100 was the preferred mode (seven patients). There was significantly less chest pain with this mode than with either of the other modes. There were significantly more episodes of dizziness in VVI, and two patients who developed pacemaker syndrome were unable to complete the pacing period. Three patients developed angina during exercise testing in DDD 150. Atrial synchronous ventricular pacing is better than ventricular pacing for the control of symptoms in patients with angina pectoris provided that the upper atrial tracking rate is limited.

Aged↗
PubMed1985

Branch point control by the phosphorylation state of isocitrate dehydrogenase. A quantitative examination of fluxes during a regulatory transition.

To understand how enzymatic pathways respond to changing external conditions, the fluxes through the tricarboxylic acid cycle and ancillary reactions were determined under three different growth conditions in Escherichia coli. The velocities through the major steps in each pathway were measured (a) for growth on acetate alone, (b) for growth on acetate plus glucose, and (c) during the transition caused by addition of glucose to cells growing on acetate. During the transition, the carbon flow through the Krebs cycle decreased by a factor of 5 despite an increase in the growth rate of the culture. Under these conditions, the dephosphorylation of isocitrate dehydrogenase caused a 4-fold increase in its activity. This, together with the decreased rate of substrate production and the kinetic parameters of the branch point enzymes, led to a cessation of the flux through the glyoxylate shunt. The decreased rate of acetyl-CoA turnover, not an inhibition of acetate transport, caused a slower rate of acetate uptake in the presence of glucose. The modulation of protein phosphorylation and metabolite levels is one of the regulatory mechanisms which enables the bacterium to make dramatic shifts between metabolic pathways within a fraction of a doubling time.

Acetates↗
PubMed1985

Characterization of rate-controlling steps in vivo by use of an adjustable expression vector.

Citrate synthase (EC 4.1.3.7) was varied from 10% to 5000% the level found in wild-type Escherichia coli by means of recombinant DNA techniques. When acetate was the sole carbon source, cell growth and carbon flow through the Krebs cycle were greatly affected by the under-production of citrate synthase. In contrast, when glucose was the main nutrient, the same underproduction of citrate synthase had little effect on either growth or carbon flux. When the enzyme was overproduced 50-fold, cultures would grow on glucose but cell division could be abruptly stopped by adding acetate to the medium. These results indicate that the regulatory properties of citrate synthase are highly dependent on the carbon-source composition of the medium. Furthermore, recombinant DNA technology can be used to alter rate-controlling steps in biological pathways and elucidate the regulatory properties of metabolic systems.

Citrate (si)-Synthase↗
PubMed1984

The branch point effect. Ultrasensitivity and subsensitivity to metabolic control.

The interdependence of the activities of branch point enzymes which compete for a common substrate can yield ultrasensitivity or subsensitivity to control, even if the competing enzymes follow Michaelis-Menten kinetics. The nature of this "branch point effect" for a particular system depends on the kinetic parameters of the competing enzymes, the rate of substrate production leading into the branch point and the type of regulatory mechanism involved. With physiologically reasonable parameter values, the branch point effect can give ultrasensitivity equivalent to an allosteric enzyme with a Hill coefficient of 8 or higher. An experimental example of this ultrasensitivity was provided by the branch point between isocitrate lyase (of the glyoxylate bypass) and isocitrate dehydrogenase in Escherichia coli. The glyoxylate bypass is very active during growth on acetate but its flux decreases by a factor of approximately 150 upon addition of glucose. This inhibition is brought about by two relatively modest events: a 4-fold increase in the maximum velocity of isocitrate dehydrogenase and a factor of 5.5 decrease in the rate of isocitrate production. The mechanism which underlies this sensitivity amplification is discussed.

Acetates↗
PubMed1984

Determination of flux through the branch point of two metabolic cycles. The tricarboxylic acid cycle and the glyoxylate shunt.

The branch point of the tricarboxylic acid and glyoxylate shunt has been characterized in the intact organism by a multidimensional approach. Theory and methodology have been developed to determine velocities for the net flow of carbon through the major steps in acetate metabolism in Escherichia coli. Rates were assigned based on the 13C NMR spectrum of intracellular glutamate, measured rates of substrate incorporation into end products, the constituent composition of E. coli, and a series of conservation equations which described the system at steady state. The in vivo fluxes through the branch point of the tricarboxylic acid and glyoxylate cycles were compared to rates calculated from the kinetic constants of the branch point enzymes and the intracellular concentrations of their substrates.

Acetates↗
PubMed1984

Incidence of Legionella organisms in selected Ontario (Canada) cities.

The distribution of Legionella pneumophila in water inside buildings was examined by means of culture methods. Cooling tower sumps and condenser valves harboured the organism at the highest frequency and in the highest concentrations. The bacterium was also frequently isolated from potable water systems, including hot and cold mixed taps, drinking water fountains and showers. When water quality parameters were examined, only elevated pH, total particulate nitrogen and alkalinity were correlated with the occurrence of L. pneumophila. Survival of the organism in water was increased at slightly basic pH and lower temperatures. The proliferation of the organism in water within buildings is probably due to a number of interrelated environmental factors that influence its survival and growth.

Culture Media↗
PubMed1984

Application of a computerized medical decision-making process to the problem of digoxin intoxication.

A computerized medical decision-making system was used to monitor signs and predisposing factors of digoxin intoxication in patients receiving digoxin. This process automatically reviewed the patient's data base nightly for drug interactions, laboratory data and electrocardiographic findings with known association with digoxin intoxication. These decisions were formated into a "digoxin alert report" and sent to line printers in the nursing division to be placed on the individual patients' charts. To assess the effect of these reports on patient management, a randomized double-blind study was undertaken. Patients were assigned to an alert or nonalert group. Alert reports were withheld from charts of patients in the nonalert group. A medical record review was subsequently carried out, wherein the physician's orders were searched to identify actions taken with possible relation to the digoxin alerts. The computer monitored 396 patients over a 3 month period. Of these, 211 (53%) were randomized to the alert group and 185 (47%) to the nonalert group. Seventy-two percent of patients received at least one alert. The most frequently occurring alerts included: hypoxemia, hypokalemia, concurrent use of a beta-adrenergic blocking agent, renal insufficiency and ventricular arrhythmia. Results from the record review demonstrated a 22% increase in physician actions for the alert group. Specifically, patients in the alert group were 2.7 times more likely to have a serum digoxin determination ordered and 2.8 times more likely to have digoxin withheld on the day of a digoxin alert than were patients in the nonalert group.

Aged↗
PubMed1981

Another world.

Explore the source record for details and available documents.

Adult↗
PubMed1979

Factors affecting perceptual functioning and activity in albino rats.

The effects of crowding and estrus cycling upon visual observing behavior and general activity level in the albino rat were investigated. Experimental groups were composed of non-estrus or estrus females and were subjected to one of three different crowding conditions. Measures of the frequency and duration of observing of photographic slides were taken as well as a measure of general activity. Slides were composed of either geometric patterns or color photographs depicting rats in various social postures. Contrary to previous reports, observing measures did not vary with levels of crowding or stage of estrus. There were, however, differences among the various crowded conditions on a measure of general activity. Relatively short-term crowding was shown to affect estrus based cyclical variation in activity and observing.

Animals↗
PubMed1977

Visual observing behavior in the albino rat: effects of nature and complexity of visual stimuli and stage of estrus.

The effect of varying levels of complexity within two types of visual stimuli on observing behavior of albino rats (60 females, 30 males, CD Strain, Charles River) was examined. Measures of frequency and duration of looking, as well as measures of general activity, were recorded. Differences in duration of observing as a function of group membership and type of stimuli were obtained. Activity was affected by the level of complexity. A re-examination of the concept of complexity is suggested. Further delineation of variables affecting observing behavior is also needed.

Animals↗
PubMedDate not supplied

Calculating the frequency of occurrence of a blood type for a 'random man'.

A scheme is offered for the calculation of blood group frequencies for mixed racial populations. The issue of which population to model is discussed. Consideration is also given to the racial composition of the desired survey and to the rule of mutual independence. The scheme can in many cases be applied to existing data.

Bayes Theorem↗