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Biomedical subjects

S G Warren

Publications and source records attributed to S G Warren.

At least 37 records · Page 2Linked to original sources
PubMed1989

Xanthelasma: clinical indicator of decreased levels of high-density lipoprotein cholesterol.

The fasting plasma lipid and lipoprotein levels were measured prospectively in 41 consecutive patients with xanthelasma seen over a four-year period. The study group included 25 women and 16 men with mean ages of 60 and 56 years, respectively. Each patient had clinical evaluation for medications or illnesses that might affect plasma lipid levels before entry into the study. The most striking lipid abnormality was the preponderance of decreased levels of high-density lipoprotein cholesterol (HDL-C). In 94% of the study population, HDL-C values were less than the mean values of the age-matched reference population. For men the mean HDL-C level was 30.8 mg/dl (vs 45 mg/dl in the reference population, P less than .001); for women the mean HDL-C level was 33 mg/dl (vs 50 mg/dl, P less than .001). The total cholesterol, low-density lipoprotein, and triglyceride levels of those in the study were not significantly different from those of the patients in the reference population. Evaluation of cardiac risk based solely on HDL-C levels showed 80% of the study population to have three to four times the average risk. This study points out the high probability of decreased HDL-C levels in patients with xanthelasma. Since the level of HDL-C has been shown to be inversely related to the incidence of cardiovascular disease, it may be prudent to evaluate HDL-C levels and do a thorough cardiovascular evaluation in patients with xanthelasma.

Adult↗
PubMed1985

Coronary angioplasty: current concepts.

Percutaneous transluminal coronary angioplasty is a nonsurgical method of dilating stenotic coronary arteries and relieving angina. Successful outcome is directly related to operator experience. Although the complication rate is low, restenosis remains a significant problem. The role of percutaneous transluminal coronary angioplasty is still evolving, but it has already become a reasonable treatment option for many patients with symptomatic ischemic heart disease.

Angioplasty, Balloon↗
PubMed1983

Postpartum pneumopericardium.

Postpartum pneumopericardium has been previously reported in only 4 patients, but it may occur more frequently than is currently recognized. Two patients are presented with pneumopericardium and pneumomediastinum with symptoms appearing on the first and second postpartum days. The second stage of labor was prolonged in both patients and associated with strenuous maternal effort. Both patients were primiparous and developed dyspnea, pleuritic chest pain, and had Hamman sign. Chest x-rays established the diagnosis in both patients. Echocardiography was nondiagnostic in one patient and mimicked pericardial effusion in the other. Although fatal tension pneumopericardium has been reported in association with other causes, the course in these 2 patients and in the other 4 reported patients has been benign. Symptoms resolved spontaneously in these 2 patients by 72 hours after their appearance. A postulated mechanism for postpartum pneumopericardium is presented.

Adolescent↗
PubMed1977

Diagnostic and prognostic significance of electrocardiographic and CPK isoenzyme changes following coronary bypass surgery: correlation with findings at one year.

The incidence of ECG (14 per cent) indication of acute myocardial infarction complicating coronary artery bypass surgery is documented, corroborating the findings of prior series. An additional 32 per cent of patients had appearance of myocardial specific CPK-MB in serum during the immediate postoperative period. All patients surviving to 1 year following surgery (93 of 103) were asked to return for repeat cardiac catheterization to determine the presence and extent of interim ventricular contraction abnormalities. Sixty-five (70 per cent) of the group returned for evaluation. Preoperative and 1 year postoperative left ventriculograms were compared to determine if new contraction abnormalities would confirm the specificity of perioperative QRS and isoenzyme changes, and if the absence of new abnormalities would confirm their sensitivity. The majority of patients (65 per cent) had new areas of asynergy. However, 73 per cent of these were confined to the apex and thus could have been produced by the vent employed during cardiopulmonary bypass. QRS changes were 100 per cent specific and CPK-MB appearance was 78 per cent specific but they were only 20 and 54 per cent sensitive, respectively. Indeed, 46 per cent of those with new asynergy which was non apical had neither QRS change nor CPK-MB appearance. Thus QRS changes were always--and CPK-MB appearance was usually--associated with new asynergy but, in addition, many patients with no perioperative indication of infarction developed new areas of left ventricular contraction abnormality within the first postoperative year.

Angina Pectoris↗
PubMed1977

Ventricular apical vents and postoperative focal contraction abnormalities in patients undergoing coronary artery bypass surgery.

Ventriculograms made 9-15 months after surgery in 48 patients with normal preoperative apical contraction were reviewed to determine the influence of apical venting on apical wall motion in patients undergoing coronary bypass surgery. After interpretation of postoperative apical wall motion, the patients were subdivided into two groups. One group consisted of 34 patients who were vented by inserting a catheter through the apex of the left ventricle and the second group included 14 patients in whom no transventricular vent was made. The two groups were similar clinically and hemodynamically before surgery, and the surgical procedures were similar with the exception of vent site. Following surgery, incidences of graft patency and antegrade flow to the apex were also similar. Nineteen (56%) patients in the apically vented group had apical dyskinesia or akinesia observed on the postoperative ventriculogram while none of the patients who were not apically vented had these findings. None of the patients with apical dyskinesia or akinesia had congestive heart failure following surgery. The postoperative ventriculograms of 12 patients with mitral stenosis who underwent valvulotomy by inserting a Tubbs dilator through the apex were also analyzed. Only one patient (8.5%) had apical dyskinesia or akinesia. Since the patients with mitral stenosis probably did not have significant coronary artery disease, it is possible that the combination of the apical vent and ischemic heart disease was responsible for the focal contraction abnormalities observed.

Cardiac Catheterization↗
PubMed1976

Aortocoronary bypass surgery: Correlation of angiographic symptomatic and functional improvement at 1 year.

Angiographic changes in the coronary circulation were evaluated in 60 patients 1 year after aortocoronary bypass surgery, and their relation to the postoperative clinical status was examined. Of 124 grafts implanted, 26 were closed, 7 stenotic and 91 (74 percent) patent at 1 year. Progression of occlusive disease occurred in 21 of 57 (37 percent) nongrafted and 78 of 123 (63 percent) grafted vessels. On the basis of location and severity of progression, significant lesions bypassed and patency of grafts, postoperative coronary perfusion was considered optimal in 16 patients (Group I), better in 24 (Group III). Complete freedom from chest pain or lessening of pain (improvement by two New York Heart Association functional classes) occurred in 88 and 79 percent of patients in Group III. Positive preoperative treadmill stress tests became negative after surgery in five of six patients in Group I, five of eight in Grojp II and three of eight in Group III. This study demonstrates that when progression of disease, graft patency and extent of revasculariztion are considered in combination, the postoperative angiographic status of the coronary circulation correlates well with clinical improvement at 1 year. These findings support the hypothesis that improved blood supply to ischemic myocardium is a major factor contributing to relief of angina pectoris after saphenous vein bypass surgery.

Coronary Artery Bypass↗
PubMed1976

Long-term propranolol therapy for angina pectoris.

Sixty-three patients with stable, severe typical angina pectoris (New York Heart Association functional class III or IV) were treated with propranolol and studied prospectively with a follow-up period of 5 to 8 years to assess the rate of complications and long-term effectiveness after an initial control period. The patients' mean age was 56 years; the mean daily dose of propranolol was 255 mg. The average yearly mortality rate was 3.8 percent with a cumulative 5 year mortality rate of 19 percent. Patients whose reduction of angina with propranolol was less than 50 percent had a nearly four-fold greater mortality rate than those whose reduction was 50 percent or more (P less than 0.01). Thirty-two percent of patients per year were angina-free with propranolol and 84 percent per year had 50 percent or more reduction in anginal episodes. There was no evidence for tachyphylaxis. Heart failure developed in 25 percent of patients, two thirds of whom had either congestive heart failure with an acute infarction or a prior history of congestive heart failure. All patients whose initial cardiothoracic ratio was greater than 0.5 had heart failure during the first 3 years of propranolol therapy. Of 12 patients who had an acute infarction during therapy, 7 died, 6 with cardiogenic shock; in contrast, 8 of 9 patients who had congestive heart failure without acute infarction survived. Eight percent of patients had other significant side effects, including gastrointestinal symptoms (three patients), hallucinations (one) and postural hypotension (one). The occurrence of asthma in three patients was dose-related and did not require drug discontinuation. Propanolol is an effective form of long-term therapy for severe angina pectoris; it does not induce tachyphylaxis or increase the overall mortality rate, although it may increase the risk of cardiogenic shock in acute myocardial infarction. Previous history of congestive heart failure, a cardiothoracic ratio of more than 0.5 without overt heart failure and mild asthma are relative contraindications. A 50 percent or greater reduction in anginal pain with propranolol predicts a low mortality group.

Adult↗
PubMed1974

Complex of aspartate carbamoyltransferase from Escherichia coli with its allosteric inhibitor, cytidine triphosphate: electron density at 5.9-angstroms resolution.

Following our earlier determination of the three-dimensional structure of aspartate carbamoyltransferase (EC 2.1.3.2; carbamoylphosphate: L-aspartate carbamoyltransferase) to 5.5-A resolution [S. G. Warren, B. F. P. Edwards, D. R. Evans, D. C. Wiley & W. N. Lipscomb (1973) Proc. Nat. Acad. Sci. USA 70, 1117-1121], we report here, from a different crystal form, the three-dimensional structure at 5.9 A of this enzyme complexed with its allosteric inhibitor, cytidine triphosphate. Location of the major binding site of this inhibitor within each of the six regulatory chains is made secure by comparison of these results with those obtained upon binding of 5-iodocytidine triphosphate to the enzyme. Conformational changes in the aspartate carbamoyltransferase molecule when this inhibitor binds are described briefly at 5.9-A resolution.

Allosteric Regulation↗
PubMed1973

Aqueous central cavity in aspartate transcarbamylase from Escherichia coli.

A three-dimensional x-ray diffraction study of aspartate transcarbamylase to 5.5-angstrom resolution, with the aid of four isomorphous heavy atom derivatives, indicates the presence of a central aqueous cavity approximating an oblate spheroid about 25 by 50 by 50 angstroms in dimension, within a molecule about 90 by 110 by 110 angstroms in largest dimensions.

Aspartate Carbamoyltransferase↗
PubMed1973

Aspartate transcarbamoylase from Escherichia coli: electron density at 5.5 A resolution.

The allosteric enzyme, aspartate transcarbamoylase (EC 2.1.3.2), has previously been shown in our x-ray diffraction studies to have D(3)-32 symmetry. There are six catalytic (C) and six regulatory (R) chains in the molecular complex (R(6)C(6)). Our three-dimensional x-ray diffraction study of this enzyme (R32, a = 131 A, c = 200 A) at 5.5 A resolution shows a spatial arrangement of the two catalytic trimers C(3) above and below an equatorial belt of three regulatory dimers R(2). The molecule is about 110 x 110 x 90 A in largest dimensions, and is shown here to contain a large central aqueous cavity about 50 x 50 x 25 A in size. Location of the single sulfhydryl of each catalytic chain, and correlation of its reactivity with enzymatic activity in the molecule, suggests that the nearby active sites are most probably accessible from the central cavity, but probably not directly from the external solution. The most obvious access to the central cavity consists of six channels, each about 15 A in diameter, near the regulatory region. A component of the regulatory mechanism may be modulation of access of substrates through these channels.

Allosteric Regulation↗