Biomedical subjects
Publications and source records attributed to M Greenspan.
Psychology's impact as an ergogenic aid across sports and competitive levels has been well documented. In addition, exercise can play a major role in disease prevention and health enhancement while also enhancing psychological well-being. In addition to its preventive value, exercise is being recognized as a valuable therapeutic tool. Like most therapeutic modalities, however, exercise also has some potentially negative qualities.
3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase was purified to homogeneity from rat liver cytoplasm. The active enzyme is a dimer composed of identical subunits of Mr = 53,000. The amino acid composition and the NH2-terminal sequence are presented. Partial cDNA clones for the enzyme were isolated by screening of a rat liver lambda gt11 expression library with antibodies raised against the purified protein. The identity of the clones was confirmed by hybrid selection and translation. When rats were fed diets supplemented with cholesterol, cholestyramine, or cholestyramine plus mevinolin, the hepatic protein mass of cytoplasmic synthase, as determined by immunoblotting, was 25, 160, and 1100%, respectively, of the mass observed in rats fed normal chow. Comparable changes in enzyme activity were observed. Approximately 9-fold increases in both HMG-CoA synthase mRNA mass and synthase mRNA activity were observed when control diets were supplemented with cholestyramine and mevinolin. When rats were fed these two drugs and then given mevalonolactone by stomach intubation, there was a 5-fold decrease of synthase mRNA within 3 h. These results indicate that cytoplasmic synthase regulation occurs primarily at the level of mRNA. This regulation is rapid and coordinate with that observed for HMG-CoA reductase. The chromosomal localization of human HMG-CoA synthase was determined by examining a panel of human-mouse somatic cell hybrids with the rat cDNA probe. Interestingly, the synthase gene resides on human chromosome 5, which has previously been shown to contain the gene for HMG-CoA reductase. Regional mapping, performed by examination of a series of chromosome 5 deletion mutants and by in situ hybridization to human chromosomes indicates that the two genes are not tightly clustered.
A retrospective study was conducted to define the incidence of ventricular ectopic beats with exit block (concealed extrasystoles). Of 904 Holter recordings, 92 were admitted for study on the basis of sufficient ventricular ectopic beats on rhythm strips. Concealed bigeminy conforming to the equation of S = 2n - 1 (where S = the interectopic sinus beat and N = any interger) was the most common and occurred in 42 of 92 (46%) Holters included in this study. Concealed trigeminy was observed in 12 of 92 (13%) studies. These Holters also showed ventricular ectopic beats strongly suggestive of parasystole with entrainment. Of 53 Holters reviewed for parasystole 12 were suggestive of, and five indicated this dysrhythmia. We conclude that: 1. Concealed extrasystoles are more common than previously appreciated. 2. Concealed bigeminy and trigeminy appear together and conversion may not always be associated with a change in heart rate. 3. Recognition of this dysrhythmia is uncommon mostly because of inadequate lengths of rhythm strips. 4. Parasystole with entrainment is suggested as a common dysrhythmia when frequent extrasystoles are present.
This case report describes the electrocardiographic features of concealed junctional premature beats. When the junctional premature beats occurred in a bigeminal fashion, pseudo 2:1 AV block occurred. The presence of 2:1 AV block was related to the prematurity (H1-H2) of the junctional extrasystoles, in which coupling intervals less than 425 msec were concealed and those greater than 425 msec were manifest. This report is unusual in that persistent long runs of pseudo 2:1 AV conduction were established. In addition, the extrasystolic beats demonstrated exit block and the interectopic sinus beats (n) followed the formula 2n-1.
An animal model demonstrates the superiority of fluorescein fluorescence over that of standard clinical criteria in determining intestinal viability. It is suggested that fluorescein is a readily available, inexpensive, noninjurious, simple and reliable means of assessing viability of the compromised intestine.
Seven patients with myocardial bridging of the left anterior descending coronary artery were evaluated by mens of thallium-201 exercise scintigraphy. The degree of systolic narrowing was 60-70% in five patients and 75-80% in two patients. All patients had presented with chest pain. The resting electrocardiogram was normal in six patients; there were ST segment and T-wave abnormalities in one patient. No patient complained of chest pain during exercise. The exercise electrocardiogram was negative in six patients and inconclusive in one patient. Exercise myocardial scans were negative in all seven patients. We conclude that no evidence of ischemia was demonstrated in patients with myocardial bridging of the left anterior descending coronary artery as determined by exercise electrocardiography and stress thallium-201 scintigraphy.
Thirty patients with angiographically documented mitral valve prolapse but without associated coronary artery disease, underwent exercise 201thallium myocardial scintigraphy. The resting ECG demonstrated ST segment abnormalities in 15 patients (50 percent). The exercise ECGs were abnormal in two patients (6.7 percent), normal in four (13.3 percent), and inconclusive in 24 patients (80 percent). Two patients (6.7 percent) had abnormal exercise myocardial scintigraphy (both patients had abnormal exercise ECGs). Two additional patients (6.7 percent) had perfusion abnormalities in the rest images that did not change with exercise. Twenty-six patients (86.4 percent) had normal scans. We conclude that the majority of patients with mitral valve prolapse have normal exercise 201thallium images in the absence of associated coronary artery disease and exercise electrocardiography is of limited value in patients with mitral valve prolapse because the results are frequently (80 percent) inconclusive.
In this report, we describe the clinical, hemodynamic, and angiographic findings in three patients with atherosclerotic complete occlusion of the left main coronary artery. This rare entity was only seen in three out of 7,000 coronary angiograms. The three patients had extensive right-to-left collateralization. Two patients underwent saphenous vein bypass surgery and are asymptomatic, while the third patient died awaiting surgery. We suggest that patients with complete left main occlusion must undergo surgery as soon as possible.
The significance of transient exercise-induced Q waves present during treadmill testing was prospectively evaluated and correlated with the findings at cardiac catheterization. Exercise-induced Q waves were present in 14 of 560 patients (2.5 per cent) undergoing treadmill exercise testing. Thirteen patients had Q waves in leads V1 through V3 and one patient had Q waves in leads II, III and aVF. Ten patients underwent cardiac catheterization; six did not have coronary artery disease as determined by angiography. Two patients had a documented anterior myocardial infarction and did not undergo cardiac catheterization. Exercise myocardial perfusion imaging was performed in 10 patients. Six patients without coronary artery disease had no evidence of exercise perfusion defects. In the four patients with coronary artery disease, three patients had an abnormal resting perfusion study without change with exercise and one patient had a new exercise myocardial perfusion defect. We conclude that exercise-induced transient Q waves are not diagnostic of underlying coronary disease. In patients without coronary artery disease the mechanism of exercise-induced Q waves is as yet unclear. In patients with coronary artery disease, the mechanism may also be undefined or secondary to myocardial ischemia.
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A case of malignant islet-cell tumor of the pancreas diagnosed by preoperative percutaneous fine needle aspiration biopsy and confirmed by tissue examination is reported. The cytologic presentation of this neoplasm is described, and the differential diagnosis is discussed.