Biomedical subjects

S K Hall

Publications and source records attributed to S K Hall.

44 records · Page 3Linked to original sources

PubMed1990

Hemodynamic and arrhythmogenic effects of aversive stress during myocardial ischemia.

Pavlovian conditioning was accomplished in two groups of dogs by following a 30-s tone (the CS+) with a short (less than or equal to 1 s) electric shock). An inflatable occluder was implanted around the left circumflex coronary artery in all animals. The CS+ was presented to Group I dogs (n = 6) during control (i.e., no coronary occlusion) and at 30 s and 3 min after the onset of a 4-min left circumflex coronary occlusion. The CS+ evoked a robust increase in heart rate and blood pressure in the control state. A conditional cardiovascular response was still evoked during the acute coronary occlusion despite the evolving myocardial ischemia. No increase in ventricular ectopic beats occurred during the CS+. An anterior myocardial infarction (16.8 +/- 1.7% of left ventricular mass, mean +/- SEM) was created in Group II dogs (n = 8) at the time of surgery. A CS+ was presented, as above, both alone and 1 min after the beginning of a 2-min left circumflex coronary occlusion. There were significant differences in the conditional response in heart rate, left ventricular (systolic) pressure (LVP) and d(LVP)/dt for trials given during the coronary occlusion compared with no occlusion. These dogs were then classified as 'resistant' or 'susceptible' to ventricular arrhythmias approx. 4 weeks later using an exercise and coronary occlusion test. Three of five susceptible dogs, but none of three resistant dogs, evidenced increased severity of arrhythmias during the CS+. We conclude that the nature of the cardiovascular response to behavioral stress during myocardial ischemia depends in part upon the timing of the CS+, the presence or absence of a resident myocardial infarction and the status of the autonomic reflexes controlling the heart.

Animals↗

PubMed1990

Analysis and presentation of intracellular measurements obtained with ion-selective microelectrodes.

We have considered the manner in which data obtained with ion-selective electrodes should be evaluated. The potential difference recorded by such electrodes, with respect to a stable reference, is converted to a concentration by a non-linear transformation--the Nernst or Nikolsky equation. The mean and standard deviation of such estimations of concentration are then usually presented, which assumes that the latter variable is normally distributed. If, however, the recorded potential difference (PD) is the normally distributed variable and the mean value calculated, then a different value of mean concentration will be obtained. We show here that the recorded PD is indeed the normally distributed variable using data from a variety of ion-selective electrode measurements and conclude that the mean values of quoted ion concentrations have been overestimated by 6-43%.

Animals↗

PubMed1990

Rapid anticonvulsant monitoring in an epilepsy clinic.

The relevance of providing a rapid anticonvulsant monitoring service was assessed over a five year period at a paediatric epilepsy outpatient clinic. Altogether 481 drug assays were performed on 144 patients when considered clinically indicated. Drugs most frequently assayed were carbamazepine and sodium valproate, singly or in combination; sodium valproate, single or in combination; 90% of assays performed for phenytoin were from patients who were also taking another anticonvulsant. There were only six assays for ethosuximide and 10 for phenobarbitone. Physician's choice of drug dosage was recorded on a questionnaire before and after each assay result was known. Comprehensive patient details were analysed by a paediatric clinical pharmacologist, whose decision as to total daily anticonvulsant dosage was affected by knowledge of the drug concentration significantly less often than that of the clinicians for all the more commonly assayed drugs. There were a large number of drug assays that had no discernable clinical application. A more discriminating use of assays may both improve patient management and reduce considerably the number of anticonvulsant assays required.

Adolescent↗

PubMed1990

Sweat sodium and chloride concentrations--essential criteria for the diagnosis of cystic fibrosis in adults.

Criteria for a positive sweat test in children (sweat sodium greater than 60 mmol/L and sweat chloride greater than 70 mmol/L) were investigated in a series of adults aged between 18 and 40 years using the standard Gibson and Cooke technique of pilocarpine iontophoresis. A significant number of non-cystic fibrosis adults had sweat sodium values greater than 60 mmol/L whereas a concentration of chloride greater than 70 mmol/L always discriminated adults with cystic fibrosis from normal adults and those with chest disease not due to cystic fibrosis. In all cases of adult cystic fibrosis the sweat sodium concentration was greater than 80 mmol/L. The Na:Cl ratio and sum of Na and Cl provided additional helpful criteria in distinguishing between adults with and without cystic fibrosis.

Adolescent↗

PubMed1988

Speech acts and the pragmatic deficits of autism.

In a videotaped free-play session with a parent, autistic children were compared with mental-age matched Developmental Language Delay (DLD) children and with normally developing (ND) 2-year-olds in the use of communicative acts by parent and child. Groups were matched for language level. Autistic children had more incidents of no responses, produced less affirming, turn-taking vocalization, and gesture, and were less likely to initiate communication than other children. Parent groups differed only in a greater amount of initiating and use of imperatives by parents of autistic children. Few relations between parent behaviors and child behaviors were found. Nonresponses by all children were concentrated subsequent to parent imperatives and questions, but no group differences were found in the distribution of nonresponses to various parent communicative acts. Results are interpreted to support the hypothesis that autistic children's language can serve a number of useful functions but that their pattern of language functions differs from that of nonautistic language-impaired children and much younger normal children of similar language level.

Autistic Disorder↗

PubMed1982

Effects of cigarette smoking on pulmonary function in asymptomatic asbestos workers with normal chest radiograms.

A comprehensive health screening program consisting of standardized health and occupational history questionnaire, blood chemistry profile, complete blood count, urinalysis, chest radiograph, and pulmonary function testing was organized for the Asbestos Workers Union Local Number 1 in St. Louis, Missouri. The program was available on a voluntary basis to all the workers in the Union. One hundred and thirty-five male caucasian workers or 44% of the membership volunteered to participate and all the data were used in this study. All blood chemistry profiles and urinalysis results were within normal limits. Twenty-two of the asbestos workers had radiologic pulmonary abnormalities as well as severe pulmonary function impairment. The remaining 113 workers were divided into subgroups based on the number of years of exposure to asbestos and their smoking history. Although asymptomatic, workers with more than 20 years exposure to asbestos had significantly decreased pulmonary functions compared to those with less than 20 years exposure. When smokers and nonsmokers were compared, an additive effect between smoking and asbestosis was observed. This study also discovered that significant decreases in pulmonary functions occur early in the exposure to asbestos.

Adult↗

PubMedDate not supplied

Acute renal vascular occlusion: an uncommon mimic.

Two adult patients with acute renal vascular occlusion with infarction are described. Both patients were believed to have ureteral colic. In each instance, the correct diagnosis was overlooked at the initial emergency department visit. An uncommon clinical entity that continues to go undiagnosed, acute vascular occlusion of the kidney must be considered in the differential diagnosis of acute flank pain. Absence of the nephrogram phase on an intravenous pyelogram (IVP) should alert emergency physicians to this possible diagnosis and to the need for further work-up. Subsequent diagnostic evaluation should begin with renal ultrasonography to rule out obstructive uropathy. If hydroureteronephrosis is not present, follow-up perfusion studies are necessary to confirm the absence of renal perfusion. Greater awareness of this uncommon clinical entity and its potential morbidity is essential to correct diagnosis and management.

Acute Disease↗

PubMedDate not supplied

Use of ion-sensitive microelectrodes to study intracellular free magnesium concentration and its regulation in mammalian cardiac muscle.

Ion-sensitive microelectrodes (ISEs) have been used to measure intracellular [Mg2+] ([Mg2+]i) in cardiac muscle, although most measurements have tended to overestimate the value due to the poor selectivity of the Mg2+ ionophore in the sarcoplasm and to inaccurate collation of individual ISE measurements. This paper highlights the correct method for analysis of data from multiple ISE experiments. Since [Mg2+]i is constrained at a lower concentration than would be expected by passive distribution of the ion, some of the possible mechanisms underlying Mg2+ extrusion from ferret ventricular myocardium were investigated. During elevation of the extracellular [Mg], mean [Mg2+]i rose from 1.61 to 1.91 mM. The same intervention had no significant effect on membrane potential, intracellular [Na+] or pH measured with ISEs, and there was no change in resting [Ca2+], as assessed from fura-2 fluorescence. The data are not consistent with a simple mechanism for Na(+)-Mg2+ exchange as the primary mode of Mg2+ regulation in cardiac muscle or with an Mg2+ extrusion mechanism involving steady-state ion exchange.

Animals↗