Search PubMed⌕ Search

Biomedical subjects

K Robinson

Publications and source records attributed to K Robinson.

At least 217 records · Page 12Linked to original sources
PubMed1988

Studies of the sodium-calcium exchanger in bull-frog atrial myocytes.

1. Experimental measurements and computer simulations have been used in attempts to identify an exchanger current (Iex) generated by an electrogenic Na+-Ca2+ exchanger in single cells from bull-frog atrium. 2. Voltage clamp measurements of an inward 'slow tail' current observed upon repolarization after depolarizing clamp pulses that elicit net inward Ca2+ currents (ICa) (see Campbell, Giles & Shibata, 1988c), show that these slow tails have a cationic dependence different from ICa. Slow tails are large and prominent in normal [Na+]o solutions containing either Ca2+ or Sr2+, but they are markedly reduced or absent in Ba2+, Ca2+-free, and Na+-free solutions. 3. Kinetic measurements on the slow tails show that they are not generated by deactivation of ICa, and suggest that they may be due to activation of Iex at negative potentials (-70 to -100 mV). 4. Computer simulations of the influx, buffering, and extrusion of Ca2+ provide further indirect evidence that the slow tails correspond to Iex. In addition, these calculations give insights into one plausible mechanism of Ca2+ homeostasis in frog atrium. When the Na+-Ca2+ exchanger formalism of Mullins (1979, 1981), as modified by DiFrancesco & Nobel (1985), is combined with equations for intracellular Ca2+ buffering by myoplasmic proteins (cf. Robertson, Johnson & Potter, 1981), slow inward tails are produced which are qualitatively similar to those recorded experimentally. 5. Comparisons of the size and time course of ICa with those of Iex suggest that Iex does not generate a physiologically significant current (or membrane potential change) during the plateau of the action potential. However, at potentials near the resting potential the inward current due to Iex may be significant. 6. Our theoretical results suggest that in the intact single atrial cell myoplasmic Ca2+-binding proteins (e.g. calmodulin and troponin) could be physiologically important modulators of the amplitude, polarity and kinetics of Iex. Hence, the specificity, capacity and kinetics of intracellular Ca2+ binding are essential components of any quantitative treatment of Iex in excitable tissue.

Action Potentials↗
PubMed1988

Cryoablation of the accessory pathway in Wolff-Parkinson-White syndrome: initial results and long term follow up.

Cryoablation of the accessory pathway was used in the management of 20 patients with pre-excitation syndromes. All patients had presented with paroxysmal atrioventricular reentrant tachycardia; in addition, six had experienced atrial fibrillation. In 16 patients pre-excitation was overt and in four the accessory pathway was concealed. Intraoperative epicardial and endocardial mapping showed 10 left free wall pathways, seven septal pathways, and four right free wall pathways. One patient had two right free wall accessory pathways. There was one postoperative death (from a ruptured cerebral haemangioma) and one patient had transient hemiparesis. There was early recurrence of arrhythmia or pre-excitation in six patients and five of these were among the first ten in the series. Four of the six underwent successful reoperation; 17 patients remain symptom free of all antiarrhythmic treatment. Two patients did not undergo reoperation--one became symptom free on drugs that had previously been ineffective and the other received an antitachycardia pacemaker. The mean period of follow up was six years. Accessory pathway function was not restored and atrioventricular nodal function was preserved in all patients, demonstrating the feasibility of this technique in the long term management of patients with the pre-excitation syndrome.

Adult↗
PubMed1988

Wolff-Parkinson-White syndrome: atrial fibrillation as the presenting arrhythmia.

Atrial fibrillation was identified as the initial arrhythmia complicating the Wolff-Parkinson-White syndrome in ten (9%) of 108 patients. Despite initially rapid ventricular responses in seven, long term survival and control of arrhythmia were excellent on medical treatment. Whereas symptom free patients with the pre-excitation syndrome who have additional underlying disease predisposing to atrial fibrillation may need detailed electrophysiological study, a more conservative approach is suitable for the typical symptom free individual.

Adolescent↗
PubMed1988

Type A Wolff-Parkinson-White syndrome obscured by left bundle branch block associated with a vascular malformation of the coronary sinus.

A case of Wolff-Parkinson-White syndrome type A with coexisting ipsilateral bundle branch block is presented. The diagnosis was suspected because of subtle electrocardiographic changes and was confirmed at electrophysiological study. Necropsy showed a vascular anomaly of the coronary sinus that contained bundles of myocardial muscle which crossed the atrioventricular ring at a site that was consistent with the predicted accessory pathway.

Aged↗
PubMed1988

Smoking and acute coronary heart disease: a comparative study.

Nine hundred and seventy eight patients with a first documented myocardial infarction were studied to detect smoking related differences in clinical profile and in-hospital outcome. The distribution of infarct sites differed significantly between smokers and non-smokers. Smokers had higher peak cardiac enzyme concentrations. In spite of this, smokers had a better prognosis than non-smokers. There are important differences between smokers and non-smokers, both in clinical profile and in-hospital outcome, which may reflect a difference in the nature of the underlying coronary disease.

Age Factors↗
PubMed1988

Relation of infarct site to 15 year prognosis in patients who survived for 28 days after a first myocardial infarction.

Six hundred and eighty four patients (629 men), all aged under 60 years, who had survived for 28 days after a first acute myocardial infarction were studied to determine the influence of the site of infarction on long term prognosis. The infarct site was not significantly related to age nor to extent of infarct at the time of the acute episode. Mechanical complications were more common in patients with anteroseptal infarctions, while atrioventricular conduction disturbances were more commonly found in those with inferior infarction. The site of infarction was not related to smoking habits or angina before the infarction or at 2 year follow up. Life table methods did not show any relation between infarction site and morbidity or mortality either two years or 15 years after the initial infarction.

Age Factors↗
PubMed1988

TOXBASE: a microcomputer database for post mortem toxicology.

A cheap microcomputer program for the storage, retrieval, and analysis of the results of toxicological investigations on samples obtained at necropsy was devised. The program was written using FoxBASE+, a dBase III clone, which is both cheaper and faster than other comparable software. The hardware requirements are an IBM PC compatible microcomputer, preferably with both hard and floppy disc drives, and a suitable printer. The system was found to be particularly useful when preparing reports for coroners and in retrieving data for administrators concerned with aspects of work in the laboratory. The system is flexible and can be readily adapted to other uses.

Autopsy↗
PubMed1988

The supraventricular tachycardias.

Most supraventricular tachycardias can be diagnosed confidently using the standard 12-lead electrocardiogram, the more so if such a tracing in sinus rhythm is also available. The underlying mechanisms may often be determined and these may have important therapeutic consequences. This chapter reviews the electrocardiographic appearances of the supraventricular arrhythmias. Extrasystoles are common but rarely require specific treatment. Automatic atrial tachycardias are common and usually amenable to simple management. Reentrant circuits related to atrial and atrioventricular tachycardias are also described, and where possible, treatment is related to underlying mechanisms.

Atrial Fibrillation↗
PubMed1988

Secular changes in mortality among survivors of unstable angina and myocardial infarction.

Seven hundred and ninety-four males under 60 years who survived a first episode of unstable angina or myocardial infarction by 28 days were admitted to St. Vincent's Hospital between 1965 and 1981 inclusive. They were followed for at least 4 years: 1-, 2- and 4-year mortality during the follow-up period did not alter significantly during the 17 years. Significant changes did take place over time in the severity of the coronary attacks and in the risk profile of the patients. A greater number of complicated infarcts occurred in the later years and there were fewer smokers and more hypertensives. There was a significant increase over time in the number of initial cigarette smokers who stopped after the coronary attack. Changing methodology made secular changes in cholesterol levels difficult to interpret.

Adult↗
PubMed1988

The effects on auditory function of damage to the pontine olivo-cochlear bundle in man.

A patient with multiple sclerosis (MS) in whom a lesion developed in the pons between successive nuclear magnetic resonance image scans (MRI) is described. The patient developed intolerance of loud sounds, with distorted perception of speech and music, and abnormalities of stapedius reflex threshold, masked speech audiometry, and masking level difference assessment in the presence of an unchanged pure tone threshold. These abnormalities partially resolved over a number of months. It is postulated that the efferent olivo-cochlear bundle was involved on one side of the pons and the abnormalities are interpreted in terms of bilateral removal of inhibition from the hair cells of the cochlea.

Adult↗
PubMed1988

Bedside data system aids pharmacy.

The challenge of managing quality in the healthcare field is becoming increasingly difficult. New technology is now available that provides computerized record keeping in the patient-care area. These bedside information systems, also known as point-of-care systems, have many applications in hospital pharmacies, especially in relation to the administration of medications.

Colorado↗
PubMed1988

Removal of anterior chamber intraocular lenses: a surgical technique.

With the increasing trend toward intraocular lens implantation we are finding more cases in which explantation is indicated. The criteria and surgical techniques for explanation should be individualized depending on the type of lens. We describe removal of anterior chamber intraocular lenses.

Anterior Chamber↗
PubMed1987

Recidivism in a cohort of young Australian drinking-drivers.

Four hundred and sixty-three men aged 18-25 years were referred to a counselling programme in 1975-1977, after their first conviction for an alcohol-related traffic offence. Records of the Victoria Police, and those of the Motor Registration Board, were searched for subsequent alcohol-related traffic offences up to February 1984. Those subjects who had left the State of Victoria or had died were identified, and a "survival" curve was constructed where survival implied freedom from reconviction for an alcohol-related traffic offence. By means of Cox's proportional hazards model, the rate ratios of a number of predictor variables of recidivism were calculated; those of significance were the number of drinks per week, social class, and a history of "family troubles with drinking". Reduction of alcohol consumption may be a more appropriate goal in programmes that are concerned with the counselling of young drinking-drivers than is attempted modification of the drinking-driving nexus.

Accidents, Traffic↗
PubMed1987

Current mortality in the Australian petroleum industry: the healthy-worker effect and the influence of life-style factors.

A surveillance system, to monitor mortality and cancer morbidity on a continuing basis, has been established in the Australian petroleum industry. A baseline survey of 11,573 employees, by personal interview, was carried out in 1981-1983. By the end of June 1986, 33,712 person-years of observation in men had accrued, with 109 deaths. Standardized mortality ratios, with the Australian national death rates as reference, indicate that in terms of mortality from all causes and in mortality from the more common diseases, the death rates in this population are substantially lower than in the national population. Standardization was also carried out in the case of employed men, with data from contributors to the Commonwealth superannuation fund as reference, in order to provide a more appropriate contrast. The risks of tobacco smoking are demonstrated, as is the probable protective effect of mild-to-moderate alcohol consumption. The advantages to the occupational physician in being able to describe current mortality patterns, and in being able to delineate "at-risk" groups are discussed, particularly in the context of health promotion and other interventions.

Alcohol Drinking↗
PubMed1987

Developmental toxicity studies of caprolactam in the rat and rabbit.

Caprolactam was evaluated for developmental toxicity potential in both rats and rabbits by the oral route. In rats dosed on days 6-15 of gestation with 100, 500 or 1000 mg/kg/day of caprolactam, the maternal survival rate was significantly lower in the high-dose group and implantation efficiencies were slightly lower in the 100 and 1000 mg/groups (but not the 500 mg/kg) than in the control. The incidence of fetal death was comparable for all groups, and the incidence of fetal viability was considerably lower in the high-dose group (but not the mid or low) than in the control group. Visceral anomalies and one visceral variant were observed in one 100 mg/kg and one 500 mg/kg pup, respectively. The anomalies included exencephaly, an incomplete left eyelid, microphthalmia (right), and a protruding tongue. No skeletal anomalies were observed. It was concluded that caprolactam at levels up to at least 500 mg/kg of body weight produced no teratogenic effects in the Fischer 344 rats. In rabbits receiving 50, 150 or 250 mg/kg caprolactam on days 6-28 of gestation, the pregnancy rate in all groups was at least 80%. The numbers of corpora lutea, live and dead fetuses, resorptions, the sex ratio and the pre- and post-implantation losses were not significantly different among the test and control groups. The incidence of major malformations and of minor skeletal anomalies was unaffected by treatment with caprolactam. Maternal weights were depressed in the group receiving 250 mg/kg. Treatment of a separate group with a positive control substance (6-aminonicotinamide) resulted in significantly (P less than 0.001) increased incidences of major malformations, minor visceral anomalies and minor skeletal anomalies. Maternal toxicity in terms of mortality was observed in pregnant rabbits treated with caprolactam at a dose of 250 mg/kg/day. Fetotoxicity was evidenced by lower fetal weights at the 150 and 250 mg/kg/day levels, and an increased incidence of thirteenth ribs was observed at the 250 mg/kg/day dose level. Neither embryotoxicity nor teratogenicity occurred at any dose level.

Animals↗