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Biomedical subjects

K Robinson

Publications and source records attributed to K Robinson.

At least 199 records · Page 11Linked to original sources
PubMed1989

Comparative study of the effect of nifedipine versus diltiazem on exercise performance, serum propranolol levels, and ST-segment abnormalities in patients with chronic stable angina taking propranolol.

Twelve patients (10 men and 2 women), mean age 60.6 years (range 50 to 75), with stable angina pectoris were administered propranolol until beta blockade was evident. Treadmill exercise testing was performed, 24-hour ambulatory electrocardiograms were recorded, and serum propranolol levels were assessed at 1 and 2 hours after dosing with propranolol alone, and after 2 weeks of combined therapy with either nifedipine, 10 or 20 mg, or diltiazem, 60 or 120 mg, administered every 8 hours. Patients were assigned to treatment regimens in randomized, double-blind, crossover fashion. At the time of exercise testing, maximal exercise time, time to angina, peak exercise heart rate and systolic blood pressure and time to 1 mm of ST-segment depression were measured. The rate-pressure product was also calculated. Maximal exercise time increased from 708 +/- 140 seconds with propranolol alone to 795 +/- 156 seconds after combined propranolol-nifedipine therapy (p less than 0.05), and to 790 +/- 107 seconds (p less than 0.05) after propranolol-diltiazem therapy. Time to onset of angina increased from 472 +/- 191 seconds with propranolol alone to 564 +/- 123 seconds (p = NS) after propranolol-nifedipine treatment and to 607 +/- 197 seconds (p less than 0.05) after propranolol-diltiazem treatment. Peak exercise heart rate remained unchanged with propranolol-nifedipine therapy (103 +/- 16 beats/min vs 104 +/- 17 with propranolol alone). However, with propranolol-diltiazem therapy, peak exercise heart rate significantly decreased to 95 +/- 14 beats/min (p less than 0.05); peak systolic blood pressure and rate-pressure products were comparable on all treatment regimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Digoxin--a redundant drug in congestive cardiac failure.

Controversy continues concerning the use of digoxin as a positive inotropic agent in the treatment of heart failure in patients in sinus rhythm. Digoxin is properly used to control the heart rate in patients in atrial fibrillation. The findings from 14 uncontrolled and 6 controlled clinical trials have been examined. Digoxin does exert a small chronic positive inotropic effect. Although some individual patients, particularly those with fluid overload, appear to benefit from digoxin, controlled clinical trials in patients, most of whom have been treated with diuretics, have failed to demonstrate an increase of exercise capacity. No mortality trial has been attempted. Digoxin has the potential to be harmful in patients with ischemic heart disease. Alternative and safer therapies have been shown to be equal or superior to digoxin.

Digoxin↗
PubMed1989

The digoxin-amiodarone interaction.

To assess the cause of the digoxin-amiodarone interaction, the systemic availability and renal excretion of digoxin were examined in 10 patients. Patients were studied before and after 1 week and 6 weeks of concurrent amiodarone therapy, and four were also studied after 4-8 months. Mean (+/- SD) peak plasma digoxin concentration rose from 1.55 +/- 0.6 microgram /1 prior to amiodarone therapy to 2.85 +/- 1.3 micrograms/1 after 1 week of combined therapy (p less than 0.01). Mean AUC also rose from 7.2 +/- 2.1 micrograms/1.h to 12.1 +/- 6.4 micrograms/1.h (p less than 0.01) during this period. Mean peak plasma digoxin concentration and AUC remained elevated after 6 weeks and, in the patients studied, at 4-8 months. Mean urinary digoxin clearance remained unchanged. Plasma amiodarone and desethylamiodarone concentrations were consistent with the prescribed doses. This study confirmed previous findings of raised plasma digoxin concentrations following the addition of amiodarone. It has also shown that this interaction is sustained for at least several months. The cause has not been fully elucidated but does not appear to be due to a change in the renal clearance of digoxin.

Aged↗
PubMed1989

Correlation between behavioral and pathological changes in the evaluation of neurotoxicity.

Recently the EPA has implemented new guidelines under Section 4 of TSCA to undertake neurotoxicity testing. It is expected that other agencies, both national and international, will follow suit. The evaluation of neurotoxicity will be based primarily on behavioral and morphological observations and particularly on the correlation between them. Initially, considerable information will have to be gathered from various laboratories to form the background data on which decisions of toxic effects can be made. This paper presents our experience to date with behavioral and neuropathological procedures for the evaluation of chemical compounds or dietary regimens in rats for potential neurotoxicity. Reference is made to acrylamide, 2,5-hexanedione, 3,3'-iminodipropionitrile, amphetamine, physostigmine, ethanol, triethyltin, food and water deprivation, and carbon tetrachloride. The question of whether every change induced by xenobiotics can be considered as a sign of toxicity is discussed.

Acrylamide↗
PubMed1989

Computer analysis, using a digitizer, of ataxic mouse gait due to drugs.

A simple objective method using the irregularity of the spacing of rats' footprints to determine drug-induced locomotor ataxia has been adapted for mice and for computer analysis, by means of a digitizer-based program. Results obtained by the usual manual method of measuring and analyzing the records are compared with results of the computerized method. The computer method improves speed, and perhaps accuracy, of measurement and analysis, especially with large numbers of records, although manual scoring gives satisfactory results and remains essential for unusual records. Inter-observer agreement of the computerized method was high, and there was good agreement between measurements and subjective ratings of ataxia. The use of footprints to measure ataxia, with or without computer aid, is recommended as a routine test in laboratory evaluation of psychoactive drugs. Other uses discussed include determining changes in different characteristics of gait such as step width and step length in animal and human subjects affected not only by drugs, but also by movement disorders such as Parkinsonism.

Amobarbital↗
PubMed1989

An embryo-lethal mutant of Arabidopsis thaliana is a biotin auxotroph.

Lethal mutants have been used in a variety of animal systems to study the genetic control of morphogenesis and differentiation. Abnormal development has been shown in some cases to be caused by defects in basic cellular processes. We describe in this report an embryo-lethal mutant of Arabidopsis thaliana that can be rescued by the addition of biotin to arrested embryos cultured in vitro and to mutant plants grown in soil. Mutant plants rescued in culture produced phenotypically normal seeds when supplemented with biotin but became chlorotic and failed to produce fertile flowers in the absence of biotin. Arrested embryos were also rescued by desthiobiotin, the immediate precursor of biotin in bacteria. Langridge proposed 30 years ago (1958, Aust. J. Biol. Sci. 11, 58-68) that the scarcity of plant auxotrophs might be caused by lethality prior to germination. The bio1 mutant of Arabidopsis described in this report clearly demonstrates that some auxotrophs in higher plants are eliminated through embryonic lethality. Further analysis of this mutant should provide valuable information on the nature of plant auxotrophs, the biosynthesis and utilization of biotin in plants, and the underlying causes of developmental arrest in lethal mutants of Arabidopsis.

Biotin↗
PubMed1989

Social class as indicated by area of residence: a mortality study within an Australian industrial population.

The influence of social class on morbidity and mortality is well known and, in many epidemiological settings, its role as a potential confounding variable must be addressed. In occupational studies, particularly those based within a single industry, it is difficult to measure social class by scales based on occupational prestige. In a population study within the Australian petroleum industry, the all-cause mortality of males has been examined by social class, as indicated by area of residence, specifically, postcode. Rates of mortality were higher in the lower social classes, and the gradient was similar to that observed previously. The mortality rate of the lowest social class group relative to the highest was 1.73, and the test for trend was significant (p = 0.003). Whilst adjustment for smoking reduced the gradient somewhat, a social class effect remained.

Adult↗
PubMed1989

When does the risk of acute coronary heart disease in ex-smokers fall to that in non-smokers? A retrospective study of patients admitted to hospital with a first episode of myocardial infarction or unstable angina.

Nine hundred and seventy eight patients admitted with a first myocardial infarction or episode of unstable angina were studied to determine for how long after they gave up smoking did the risk in ex-smokers continue to resemble those of current smokers. Logistic regression was used to calculate a score, based on a combination of age, cholesterol, and hypertension, that separated current smokers from lifetime non-smokers. When this function was applied to ex-smokers, only those who had given up at least 15 years before the attack had a risk factor profile similar to that of non-smokers. Those who had given up less than five years before the ischaemic attack had a significantly higher level of other risk factors than current smokers; those who had stopped for between five and 15 years had levels similar to those of current smokers. Ex-smokers are at higher risk of acute coronary disease for at least 15 years after stopping, but some immediate reduction in risk is possible.

Angina Pectoris↗
PubMed1989

Randomised double blind controlled trial of cyclosporin in multiple sclerosis.

In a 2 year double blind controlled trial of cyclosporin against placebo in multiple sclerosis conducted at two centres there was a beneficial effect of the therapy upon the progression of the disease, relapse rate and relapse severity at one of the centres where the patients received a mean dose of 7.2 mg/kg/day. This beneficial effect was not seen in the other centre where a lower dose (mean 5 mg/kg/day) was given. Reduction in clinical progression was accompanied by decreased IgG synthesis in the central nervous system. Side effects included hypertension, renal insufficiency and anaemia and were of such severity to preclude the use of cyclosporin in a high enough dose to alter the course of the disease.

Adolescent↗
PubMed1988

Risk factors and in-hospital course of first myocardial infarction in the elderly.

We studied 980 patients with a first episode of unstable angina or myocardial infarction (MI), to examine age-related differences in risk factors and in-hospital complications and mortality. Of the total group, 52.9% were over 60 years of age and 24.3% over 70 years. The proportion of females rose with increasing age, as did the proportion of ex-smokers, while the proportion of current smokers fell. Age correlated negatively with total cholesterol levels, and positively with high-density lipoprotein cholesterol levels. The proportion of hypertensives rose with age, as did in-hospital systolic, but not diastolic, blood pressure. Older patients were more likely to have diabetes, and to have had chronic angina. There was no relation between age and either size or site of infarction. the proportion admitted with unstable angina fell with age, and, among infarctions, the proportion developing complications rose. Mortality rose from 3.1% in the under 60 subjects to 20.0% in those over 70. Cardiogenic shock tended to become more lethal with advancing age, but the outcome of ventricular fibrillation was not influenced by age. With the current aging coronary care population, management and secondary prevention methods derived from studies confined to younger subjects may be inappropriate.

Age Factors↗
PubMed1988

Teratological assessment of exposure to time-varying magnetic field.

A teratological assessment was performed using rats that were exposed to an alternating magnetic field. The magnetic field had a sawtooth waveform similar to that produced by video display terminals (VDTs). Female rats were exposed 2 weeks prior to and throughout pregnancy at a rate of 7 h/day. Three intensities of magnetic field (5.7, 23 or 66 microT) were used. All of these field intensities were much greater than those to which VDT users are exposed. A slight but statistically significant decrease in maternal lymphocyte count for the highest intensity field was found as compared with the control group. However, the lymphocyte count was within the normal range, and the observed changes in hematological parameters were considered mild. No other maternal or fetal parameters that were examined showed a significant difference for any of the three field intensities. Where minor variations in skeleton development were observed they were known to be the common "noise" that appears in every teratological evaluation.

Animals↗
PubMed1988

Risk factors and in-hospital course of first episode of myocardial infarction or acute coronary insufficiency in women.

This study examines the risk factor profile, in-hospital course and outcome of 337 women and 643 men admitted with a first episode of acute coronary insufficiency or myocardial infarction. The women were older than the men and had a risk factor profile dominated by hypertension and hypercholesterolemia rather than smoking. Women had a higher rate of unstable angina than did men after adjustment for age distribution. Women with acute infarction showed a higher rate of complications, which was associated with their greater age. They had a higher in-hospital mortality rate (12.6%) than did men (6.6%, p = 0.002). A logistic regression was used to adjust mortality and complication rates for differences in age between the sexes. When this was done, women and men had similar in-hospital prognoses. It is concluded that differences in risk factor profile may result in differences between the sexes in the expression of acute coronary heart disease, but that gender as such does not exert an independent influence on short-term prognosis in this disease.

Adult↗
PubMed1988

Aetiological and prognostic correlates of site of myocardial infarction.

This is a study of the relationship between the site of infarction and both risk factors and in-hospital outcome in 745 consecutive patients admitted with a first myocardial infarction. Patients with anterior infarctions were significantly more likely never to have smoked than patients with inferior infarctions. They had a higher prevalence of hypertension and a higher mean cholesterol level. In-hospital prognosis was worse in anterior infarctions, with significantly higher rates of death and complications. Atrioventricular blocks were more common in inferior infarctions. Non-Q-wave infarctions had a lower incidence of complications than Q-wave infarctions. There was no difference in risk factor levels between Q-wave and non-Q-wave infarctions. Anterior and inferior infarctions were of similar size. Non-Q-wave infarctions were significantly smaller. A logistic regression showed a negative relationship between in-hospital mortality and smoking, and a positive one with peak cardiac enzyme levels. Any effect of site of infarction on mortality was eliminated when corrected for these factors. Our data indicate that the adverse prognosis associated with anterior myocardial infarction is related to differences in aetiology rather than to infarction size.

Cholesterol↗