Search PubMed⌕ Search

Biomedical subjects

R G Murray

Publications and source records attributed to R G Murray.

At least 91 records · Page 5Linked to original sources
PubMed1983

The systemic and coronary haemodynamic effects of felodipine in patients with coronary heart disease.

The cardiovascular effects of felodipine, a new arteriolar vasodilator, were studied in 22 patients with coronary heart disease. There were significant falls in blood pressure and systemic vascular resistance of 16 and 38% respectively (P = 0.001), thus affecting after-load. Cardiac index and stroke index increased by 35 and 12% respectively. There was reflex tachycardia--from 75 +/- 3 to 85 +/- 3 b.p.m. (P = 0.005). Coronary sinus blood flow increased from 134 +/- 9 to 191 +/- 17 ml/min (P less than 0.005) and myocardial arterio-venous oxygen difference narrowed from 12.1 +/- 0.5 to 9.0 +/- 0.4 vols% (P less than 0.001) indicating less oxygen usage. With the heart rate held constant by atrial pacing, cardiac index and stroke index increased by 30 and 26% (P less than 0.001), whilst systolic blood pressure and systemic vascular resistance fell by 20 and 29% (P less than 0.001). This would suggest that the improved haemodynamics were largely secondary to after-load reduction.

Adult↗
PubMed1983

Diagenesis of metals chemically complexed to bacteria: laboratory formation of metal phosphates, sulfides, and organic condensates in artificial sediments.

Cells of Bacillus subtilis, when suspended in a 5mM metal solution, bind metals tenaciously to their cell walls. These metal-loaded cells, when mixed with a synthetic sediment and put under laboratory conditions to simulate low-temperature sediment diagenesis, nucleate the formation of a mixed assemblage of crystalline metal phosphates, metal sulfides, and polymeric, metal-complexed, organic residues. The sequential series of diagenetic events leading to the formation of authigenic mineral phases was followed by transmission electron microscopy and energy-dispersive X-ray analysis. The minerals quartz (SiO(2)) and calcite (CaCO(3)) were employed in the synthetic sediment. Crystalline magnetite (Fe(2)O(3)) and elemental sulfur were added as redox buffering agents to ensure anoxic conditions. Quartz and magnetite appeared unreactive throughout the experimental conditions. Elemental sulfur interacted with the metal-loaded cells, affected both the eventual chemistry and crystal habit of the metal phosphates, and formed a variety of crystalline metal sulfides. Calcite raised the pH of the fluid phase of the sediment, which influenced phosphate mineralization and inhibited metal sulfide genesis.

Journal Article↗
PubMed1983

Cell division in Deinococcus radiodurans and a method for displaying septa.

The study of sections, freeze-cleaved, and whole-cell preparations of Deinococcus radiodurans supported the contention that septa close assymmetrically and originate from discrete opposing locations on the cell surface. Tetrads and the larger associations (sheets) of cells in some strains were formed by alternate and synchronized divisions in two planes. The polarity initiating the second division in cells of the Sark strain, in particular, was often expressed in slower growing cells before completion of the first division so that the advancing margins of the first septum were diverted towards the nearest new pole; the resulting gap was closed later on, and consequently, the cell compartments of this coccus were in communication for some time after two rounds of nuclear segregation. Freeze cleaving showed that the initial generation of septa involved a short sulcus in the plasma membrane and not a circumferential infolding. The shape and form of the developing septum was inferred from sections but was displayed in whole-cell preparations by a technique which selectively and positively stained a septal component. Positive staining of the septum with uranyl salts was appreciable when the relative stainability of the peripheral wall (mainly peptidoglycan) was reduced by pretreatment with salts of low atomic weight metals (0.01-1.0%, w/v) such as cobalt, copper, iron, or zinc. Examination of these whole-cell preparations by stereoscopy showed that the septal diaphragm closes as a slit or long oval, and the advancing margin shows curvature towards the next axis of division. The mechanism and exact site of this positive staining was not elucidated; vancomycin blocking of the uncross-linked peptides of peptidoglycan was almost as effective as the transition metal salts as a foretreatment for staining septa.

Cell Division↗
PubMed1983

Prolongation of the QT interval during therapeutic starvation: a substrate for malignant arrhythmias.

Retrospective examination of weekly electrocardiograms of 13 patients on zero calorie intake for 97 +/- 25.4 d (mean +/- standard deviation) for morbid obesity demonstrated a significant progressive reduction in QRS voltage by the seventh week. There was a significant prolongation of the QTc interval in the group during the eighth week and in seven patients the QTc had lengthened beyond normal by the end of the fast. The importance of these changes is illustrated by one patient with QTc prolongation who sustained two cardiac arrests due to torsade de pointes. We recommend regular in-patient electrocardiographic monitoring for obese patients on therapeutic starvation.

Adult↗
PubMed1982

Evaluation of digitalis in cardiac failure.

Ten patients in sinus rhythm with symptomatic cardiac failure participated in a study investigating the value of digitalis at rest and during dynamic exercise. A haemodynamic profile and left ventricular ejection fraction were measured before treatment, after intravenous ouabain, and after six weeks of maintenance treatment with digoxin. There was no significant change in the haemodynamic profile or in the left ventricular ejection fraction at rest after either glycoside. During exercise there was a significant reduction in left ventricular filling pressure from 39 +/- 3 mm Hg to 34 +/- 3 mm Hg (p less than 0.05) after ouabain and to 33 +/- 3 mm Hg (p less than 0.02) after digoxin. Cardiac index improved from 33 +/- 0.3 1/min/m2 to 4.0 +/- 0.4 l/min/m2 (p less than 0.01) after ouabain and to 3.8 +/- 0.4 l/min/m2 (p less than 0.01) after digoxin. During exercise stroke volume index and stroke work index also improved significantly with both glycosides. This was accompanied by an increase in left ventricular ejection fraction from 29 +/- 2% to 36 +/- 3% (p less than 0.05) after ouabain and digoxin. In this study both intravenous ouabain and maintenance treatment with oral digoxin exerted a modest positive inotropic effect in patients with cardiac failure in sinus rhythm. The haemodynamic benefit, however, was manifest only during exertion.

Adult↗
PubMed1982

Structure of the regular surface layer of Aquaspirillum serpens MW5.

The structure of the regular surface layer of Aquaspirillum serpens MW5 has been investigated by electon microscopy supplemented by computer image processing and least-squares analysis. The layer has a ribbed appearance, both on the bacterium and in isolated, negatively stained fragments. However, detailed analysis indicated that the layer was composed of two hexagonal sheets having p6mm symmetry and a = 16 nm. One sheet was staggered by one half repeat along a (1,0) line of the p6nm lattice relative to the second so that, in projection, the pattern of the composite layer was a translational moiré, characterized by a series of ribs spaced 16 nm apart. The ribbed layer had cmm symmetry with a = 32 nm and b = 18.5 nm. Analysis of this pattern indicated that the two p6nm hexagonal sheets were unevenly stained, and this was confirmed by using least-squares methods to simulate the observed pattern by combining two hexagonal patterns. The general structure of the layer was consistent with a role as a selective and protective barrier on the cell surface.

Cell Membrane↗
PubMed1982

Cardiovascular effects of prenalterol on rest and exercise haemodynamics in patients with chronic congestive cardiac failure.

?The cardiovascular effects of the cardioselective beta, agonist prenalterol have been studied in nine patients with severe chronic congestive cardiac failure and in six patients with left ventricular dysfunction resulting from previous myocardial infarction. In the patients with cardiac failure intravenous prenalterol in a dosage of 1.5 microgram/kg bodyweight increased the cardiac index from 1.8 +/- 0.1 to 21.+/- 0.1 1/min per m2 and the left ventricular ejection fraction from 22 +/- 3 to 28 +/- 3%. There was a modest but significant increase in heart rate from 76 +/- 3 to 87 +/- 4 beats/min. Systemic vascular resistance fell from 2285 +/- 51 to 2041 +/- 534 dynes s-1 cm-5. On exercise, the left ventricular filling pressure fell from 33 +/- 6 to 26 +/- 3 and both cardiac index and stroke index increased by 13% and 16%, respectively. There was no significant change in heart rate or systemic blood pressure. In the patients with left ventricular dysfunction, coronary sinus blood flow increased from 107 +/- 11 to 133 +/- 12 ml/min but the increase in myocardial oxygen consumption was small and not significant (11.6 +/- 1.2 and 14.5 +/- 1.9 ml/min). In all patients there was no evidence that prenalterol was arrhythmogenic.

Adrenergic beta-Agonists↗
PubMed1981

Bayesian analysis of stress thallium-201 scintigraphy.

The variation of the diagnostic value of stress Tl-201 scintigraphy with prevalence of coronary heart disease (CHD) in the population has been investigated using Bayesian reasoning. From scintigraphic and arteriographic data obtained in 100 consecutive patients presenting with chest pain, the sensitivity of stress Tl-201 scintigraphy for the detection of significant CHD was 90% and the specificity was 88%. From Bayes' Theorem, the posterior probability of having CHD for a given test result was calculated for prevalences of CHD ranging from 1% to 99%. The discriminant value of stress Tl-201 scintigraphy was best when the prevalence of CHD lay between 30% and 70% and maximum for a prevalence of 52%. Thus, stress Tl-201 scintigraphy would be an unsuitable diagnostic test where the prior probability of CHD is low, e.g., population screening programmes, and would add little where the clinical probability of having CHD is already high. However, where the prior probability of having CHD is intermediate stress Tl-201 scintigraphy may provide valuable diagnostic information.

Bayes Theorem↗
PubMed1981

The combination of nifedipine and propranolol in the management of patients with angina pectoris.

1 A double-blind cross over study was carried out to assess the effects of the combination of nifedipine and propranolol in 25 patients with chronic stable angina pectoris at beta-adrenoceptor blockade. 2 Efficacy was judged objectively by a standardized exercise protocol using a bicycle ergometer and subjectively by patient assessment of anginal attack rate. 3 The combination of nifedipine and propranolol was shown to be effective with an increase in exercise time to angina and an increase in physical work capacity expressed in terms of calculated maximal oxygen uptake (VO2 max). There was an associated reduction in anginal attack rate. 4 The synergistic effect was even more pronounced after reduction in propranolol dosage to 50% of the beta-adrenoceptor blocking dose, reflecting the myocardial depressant effects of beta-adrenoceptor blocking drugs in these patients with coronary heart disease, some of whom had poor left ventricular function.

Adult↗
PubMed1981

Cell wall proteins of Aquaspirillum serpens.

The Triton X-100-insoluble wall fraction of Aquaspirillum serpens VHA contained three major proteins: the regularly structured (RS) superficial protein (molecular weight 140,000) and two peptidoglycan-associated proteins (molecular weights, 32,000 and 33,000). The molecular arrangement and interactions of the outer membrane and RS proteins were examined with the use of bifunctional cross-linking reagents. The peptidoglycan-associated and RS proteins were not readily cross-linked in either homo- or heteropolymers. This suggests that the free amino groups are not suitably disposed for cross-linking. Some high-molecular-weight multimers of the RS protein were produced, but the subunit structure of the RS array was not stabilized by cross-linking. The peptidoglycan-associated proteins were cross-linked to high-molecular-weight multimers, but no dimers or trimers were produced. This result suggests that these proteins exist in the outer membrane as multimers larger than trimers.

Bacteria↗
PubMed1981

Isolation and characterization of the plasma membrane and the outer membrane of Deinococcus radiodurans strain Sark.

Deinococcus radiodurans strain Sark, although gram-positive, has a complex cell wall profile that includes an outer membrane-like structure. The outer cell envelope layers formed blebs throughout the growth cycle, which were shed as large vesicles (0.5-3.5 micron m in diameter) from approximately 5% of the cell population. Instability was accentuated by treatment with 10% NaCl, which released the outer membrane from all cells without disrupting the peptidoglycan layer, and provided an outer membrane fraction uncontaminated by plasma membrane. Cells so treated formed protoplasts after sequential treatment with 6 M urea, trypsin, and the supernatant from batch cultures of Lysobacter enzymogenes 495. The plasma membrane was isolated from lysed protoplasts. The absence of presence of catalase activity, and differences in lipid composition, were used to differentiate between plasma membrane and outer membrane.

Bacteria↗
PubMed1981

On-line computer-assisted exercise mapping.

The ability of exercise ECG body surface mapping to detect the presence and distribution of coronary artery disease was investigated in 76 patients presenting with chest pain. The ECG data were recorded from 16 leads regularly placed over the left praecordium. All 16 leads were input simultaneously to a PDP8 computer and 8-second samples were stored at rest, at the termination of symptom-limited exercise, and in the recovery period. ST isopotential surface maps were subsequently constructed. The presence and praecordial projection of ST abnormality were related to the arteriographic distribution of coronary disease. The ECG data were abnormal in 56 of 58 patients with coronary disease and permitted the identification of left anterior descending artery disease in 49 of 53, right coronary artery disease in 39 of 43, and circumflex artery disease in 24 of 30. Mapping separated those with single vessel from those with multiple vessel disease in 91% of patients with coronary disease. These preliminary results suggest that exercise ECG body surface mapping may provide an attractive non-invasive approach to the investigation of patients with coronary disease.

Adult↗
PubMed1980

Defined medium for Aquaspirillum serpens VHL effective in batch and continuous culture.

A defined medium for Aquaspirillum serpens VHL allows the replacement of the complex media now in use. It was developed by batch culture methods but supports growth in continuous culture. A basal salts medium supplemented with L-aspartic acid, L-alanine, and L-glutamic acid provided the best growth (turbidity), as long as ammonium chloride was omitted. Ammonium chloride caused either a lag or a reduction or a complete inhibition of the growth of A. serpens VHL on the above amino acids and other organic supplements depending on the combination used. Ammonium sulfate and ammonium hydroxide with L-glutamic acid allowed growth, but the lag period was increased in shake flask cultures. Vitamins, cysteine hydrochloride, and carbon dioxide had no effect on the growth rate. Viability (less than 50%) was inadequate to maintain continuous culture with L-glutamic acid as the sole source of carbon and nitrogen. Combinations of amino and carboxylic acids were then tested and, of these, L-glutamic acid (1 g/liter) and L-histidine (75 mg/liter) without ammonium chloride in the basal salts medium supported growth in batch and continuous culture. L-Glutamic acid was the limiting substrate for growth.

Alanine↗