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Biomedical subjects

H L Greene

Publications and source records attributed to H L Greene.

At least 19 recordsLinked to original sources
PubMed1992

A study of the cardiac effects of bromochlorodifluoromethane (halon 1211) exposure during exercise.

Bromochlorodifluoromethane (halon 1211, a fire extinguisher), like other fluorocarbons, has been linked with ventricular arrhythmias and myocardial depression. Ten healthy firefighters, aged 40-50, were exposed to 1,000 ppm halon while exercising, in a double-blind, placebo-controlled crossover experiment, and were monitored during and after exposure. Complex ectopy (ventricular couplets and idioventricular rhythm) occurred in two subjects with halon, but none with placebo. One subject had 49.5 ventricular premature beats (VPB)/hour during the period of halon exposure and subsequent 8 hours and only 8.7 VPB/hour during the same period of placebo. In addition, 8 of the 10 subjects had a smaller systolic blood pressure rise during exercise with halon than with placebo. None of the observed differences was statistically significant. These results are consistent with findings in other investigations, suggesting that occupational fluorocarbon exposures may be cardiotoxic in certain individuals, although the small sample sizes used in this and other studies have resulted in limited statistical power to demonstrate this effect.

Adult↗
PubMed1992

Pattern generator system as a versatile visual stimulator.

We have designed and implemented a Motorola 68000 microprocessor-based pattern generator system (PGS) that uses a color video display terminal (VDT) to provide light stimuli to the intact vertebrate retina. This communication is intended for those who are considering acquisition of a commercial retinal stimulator or those who are custom designing their own pattern generator system. The discussion surveys the features to be included as well as design factors which must be considered in such a device. The memory organization of the PGS allows as stimuli multiple, complex patterns consisting of one or more disks, annuli, bars or gratings to flash or modulate in intensity according to a pre-defined function. In addition, patterns can move smoothly in any direction at selectable, uniform speeds without the re-drawing of video memory. The presence of a 12-bit A/D converter internal to the PGS allows a dynamic change in stimulus position, speed or pattern based upon physiological feedback. A physically realistic image size (0.9 cm2) and resolution (20 mu/pixel) in the retinal plane are achieved with simple intervening optics. The video field rate of 60 Hz is above the flicker fusion frequency for most vertebrate animals and does not induce artifacts in cellular responses. The PGS operating in a PC-based environment meets the requirements of a versatile optical stimulator for investigations in retinal electrophysiology.

Ambystoma↗
PubMed1992

The Cardiac Arrhythmia Suppression Trial: first CAST ... then CAST-II.

The Cardiac Arrhythmia Suppression Trial (CAST) was a study designed to test the hypothesis that suppression of ventricular premature complexes after a myocardial infarction would improve survival. Preliminary results showed that suppression of ventricular premature complexes with encainide and flecainide worsened survival, and the CAST continued as the CAST-II with moricizine compared with its placebo. The protocol for the CAST-II was changed to attempt to enroll patients more likely to experience serious arrhythmias. The enrollment time was narrowed to 4 to 90 days after myocardial infarction; the qualifying ejection fraction was lowered to less than or equal to 0.40; a higher dose of moricizine could be used; early titration itself was double-blind with a placebo, and the definition of disqualifying ventricular tachycardia was changed to allow patients with more serious arrhythmias to be entered into the trial. The Cardiac Arrhythmia Suppression Trial-II was subsequently terminated prematurely because 1) patients treated with moricizine had an excessive cardiac mortality rate during the 1st 2 weeks of exposure to the drug, and 2) there appeared to be little chance of showing a long-term survival benefit from treatment with moricizine. This report outlines the rationale behind the Cardiac Arrhythmia Suppression Trial and the reasons for selection of the drugs used in the CAST and CAST-II.

Anti-Arrhythmia Agents↗
PubMed1992

Plasma lipids and lipoproteins during 6 d of maintenance feeding with long-chain, medium-chain, and mixed-chain triglycerides.

This study assessed fasting plasma lipids and lipoproteins and postprandial plasma lipids in healthy male subjects fed liquid-formula diets containing 40% of total energy as long-chain (LCT, primarily C18:1 and C18:2), medium-chain (MCT, C8:0-C10:0), or mixed-chain (structured lipid, STL, mostly C8:0, C10:0, and C22:0) triglycerides for 6 d. None of the diets altered plasma cholesterol concentrations. HDL cholesterol was decreased 14% by the STL diet (P < 0.044) and 15% by the MCT diet (P < 0.004) but was unchanged by the LCT diet. Plasma triglycerides were elevated 42% by the MCT diet (P < 0.006), but were unaltered by either the STL or LCT diets. Neither the STL nor the MCT diets produced changes in fasting lipoprotein lipid composition; however, during the LCT diet, VLDLs became enriched in triglyceride and LDLs became enriched in cholesterol. Postprandial triglyceridemia was significantly greater after subjects consumed the LCT diet than it was after they consumed either the STL or MCT diets, which were similar. Short-term feeding of MCT and STL diets produces significant changes in lipid metabolism. An understanding of the long-term effects of these diets awaits further study.

Adult↗
PubMed1992

Vitamin update.

Explore the source record for details and available documents.

Anorexia↗
PubMed1992

Clinical significance and management of arrhythmias in the heart failure patient.

Congestive heart failure (CHF) is a common manifestation of hypertension, coronary artery disease, and dilated cardiomyopathy. The Framingham study showed that the incidence of CHF increases twofold with each decade of age. The presence of CHF increases the age-adjusted death rate 5.5-fold for women and 8-fold for men, and it increases the sudden death rate 5.5-fold in both men and women. Ventricular arrhythmias are a common accompaniment of CHF. Ambient ventricular premature complexes occur in most of these patients, and nearly one half of all CHF patients will have nonsustained ventricular tachycardia on a 24-h ambulatory electrocardiographic (Holter) recording. In addition, low left ventricular ejection fraction (LVEF) predicts inducible sustained ventricular tachycardia on electrophysiologic study. One-year mortality increases with worsening New York Heart Association (NYHA) Functional Class and decreasing LVEF. As the overall yearly mortality increases, the proportion of patients who die of arrhythmias decreases. The precise mechanism of death is frequently difficult to assess. Nonarrhythmic causes of death include CHF, shock, electromechanical dissociation, and myocardial rupture. Arrhythmic causes are most commonly due to ventricular tachycardia/ventricular fibrillation. Bradycardic events (asystole or heart block) are usually associated with progressively worsening CHF. Noncardiac causes that may confuse classification include pulmonary embolus and cerebrovascular accident. Because many patients have ischemic heart disease as the etiology of the CHF, a recurrent ischemic event can likewise make classification difficult. Overall, approximately one half of all deaths in CHF are arrhythmic and one half are nonarrhythmic.

Adult↗
PubMed1992

Retinol (vitamin A) and riboflavin (vitamin B2) administration and metabolism in very low birth weight infants.

The combination of marginal hepatic retinol stores at delivery and the reduction of daily retinol dose due to complications with the delivery system places the VLBW infant receiving parenteral nutrition at high risk for retinol deficiency during the first month of life. This has serious health implications because retinol is essential during this period for normal growth and repair of the pulmonary tissue in VLBW infants. Enterally fed VLBW infants, on the other hand, receive relatively higher doses of retinol from vitamin-supplemented premature infant formula and fortified breast milk. Equally serious is the problem of monitoring vitamin A status in infants receiving supplemental doses of vitamin A. It seems clear that while plasma vitamin A levels are the most easily available method of monitoring vitamin A status, further studies are necessary to determine if these levels correlate with hepatic content. This is of particular concern since liver disease is common in VLBW infants and vitamin A hepatotoxicity has been described in a cohort of 41 patients receiving therapeutic doses of the vitamin. While further research of daily enteral and parenteral retinol requirements of VLBW infants should continue, formulation of a specific VLBW parenteral vitamin supplement should also be developed.

Delivery, Obstetric↗
PubMed1979

Predictability of the response to the ergonovine test. Value in the diagnosis of coronary spasm.

Thirty-five patients with atypical chest pain were given ergonovine maleate as a provocative test for coronary spasm. None of the patients had significant coronary atherosclerosis. The patients were divided into two groups based on clinical information available before ergonovine testing. Group 1 patients (n=13) had objective evidence of cardiac disease manifested by episodes of syncope, ventricular tachyarrhythmias, myocardial infarction, or transient ST segment shifts with chest pain. Group 2 patients had chest pain but no objective evidence of cardiac disease. The ergonovine test was positive in 11 of 13 patients in group 1. None of the 22 group 2 patients had a positive response to ergonovine. These data suggest that ergonovine testing does not allow for any more precise recognition of patients with atypical chest pain who have coronary artery spasm than do clinical data alone.

Adult↗
PubMed1979

Nocturnal intragastric therapy in type I glycogen storage disease: effect on hormonal and amino acid metabolism.

The acute hormonal and amino acid responses to differing food substrates were examined in type 1 glycogen storage disease. Ingestion of a glucose load or a glucose-plus-beef meal caused an acute fall in the initially elevated plasma glucagon, alanine, proline, and lactate. Ingestion of beef alone caused a sharp rise in these parameters. Long term nocturnal intragastric therapy of a high carbohydrate and moderate amino acid content resulted in a similar fall in these parameters as well as a fall in the elevated plasma glutamate, uric acid, triglycerides, and RBC-reduced glutathione. A remarkable clinical improvement and growth spurt accompanied the improvement in these biochemical values. The possible relation between the disturbed plasma hormonal and amino acid findings and growth failure and hyperuricemia is discussed.

Adolescent↗
PubMed1979

Coronary spasm with ventricular fibrillation during thyrotoxicosis: response to attaining euthyroid state.

Although myocardial ischemia may occur in thyrotoxic patients with normal coronary arteries, the mechanism remains unclear. This report describes a woman with hyperthyroidism who had ventricular fibrillation during an apisode of myocardial ischemia. The event was documented with continuous ambulatory electrocardiography. Subsequent angiography revealed normal coronary anatomy with spasm of the right coronary artery that disappeared after ingestion of one sublingual nitroglycerin tablet. The angina, electrocardiographic evidence of myocardial ischemia, ventricular arrhythmias and the patient's need for nitroglycerin were eliminated after she became euthyroid. These findings suggest that coronary spasm may be associated with myocardial ischemia and arrhythmias in a hyperthyroid patient.

Coronary Angiography↗
PubMed1979

Clinical indicators of left main coronary artery disease in unstable angina.

Two hundred consecutive catheterized patients with unstable angina pectoris were reviewed to find clinical and noninvasive indicators of left main coronary artery disease (greater than or equal to 50% lesion). Thirty-five patients (17.5% of total) had left main coronary artery disease. There were no differences between patients with and without left main coronary artery disease in age, sex, results of resting electrocardiogram, congestive heart failure, dyspnea during pain, duration of longest pain, arrhythmias, response to medical therapy, or other risk factors. Crescendo angina pectoris (worsening of pre-existing angina), transient ST-segment depression with pain, simultaneous anterior and inferior ST changes during pain, and fluoroscopic calcification of the left main coronary artery were all significantly more common in patients with left main coronary artery disease. However, low sensitivity or low predictive value, or both, limit the usefulness of these clinical predictors. Left main coronary artery disease cannot be reliably predicted in patients with unstable angina pectoris before coronary arteriography.

Angina Pectoris↗