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Biomedical subjects

R H Jones

Publications and source records attributed to R H Jones.

At least 271 records · Page 15Linked to original sources
PubMed1981

Accuracy of diagnosis of coronary artery disease by radionuclide management of left ventricular function during rest and exercise.

Rest and exercise radionuclide angiocardiographic measurements of left ventricular function were obtained in 496 patients who underwent cardiac catheterization for chest pain. Two hundred forty-eight of these patients also had an exercise treadmill test. An ejection fraction less than 50% was the abnormality of resting left ventricular function that provided the greatest diagnostic information. In patients with normal resting left ventricular function, exercise abnormalities that were optimal for diagnosis of coronary artery disease were an injection fraction at least 6% less than predicted, an increase greater than 20 ml in end-systolic volume and the appearance of an exercise-induced wall motion abnormality. The sensitivity and specificity of the test were lower in patients who were taking propranolol at the time of study and in patients who failed to achieve an adequate exercise end point. In the 387 patients with an optimal study, the test had a sensitivity of 90% and a specificity of 58%. Radionuclide angiocardiography was more sensitive and less specific than the exercise treadmill test. The high degree of sensitivity of the radionuclide test suggests that it is most appropriately applied to patient groups with a high prevalence of disease, including those considered for cardiac catheterization.

Adult↗
PubMed1981

Ejection fraction response to exercise in patients with chest pain and normal coronary arteriograms.

In this study we describe the ejection fraction response to upright exercise using first-pass radionuclide angiocardiography in a group of 60 patients with chest pain, normal coronary arteriograms and normal resting ventricular function. A wide range of resting function (heart rate and ejection fraction) and exercise function (heart rate, ejection fraction, peak work load and estimated peak oxygen uptake) were measured. The ejection fraction response to exercise demonstrated wide variation, ranging from a decrease of 23% to an increase of 24%. Six of 22 clinical and radionuclide angiocardiographic variables (resting ejection fraction, peak work load, age, sex, body surface area and the change in end-diastolic volume index with exercise) were significant univariate predictors of the ejection fraction response to exercise. Multivariable analysis identified resting ejection fraction, the change in end-diastolic volume index with exercise and either sex or peak work load as variables that provided significant independent predictive information. These observations indicate that the ejection fraction response to exercise is a complex response that is influenced by multiple physiologic variables. The wide variation in this population suggests that the ejection fraction response to exercise is not a reliable test for the diagnosis of coronary artery disease because of its low specificity.

Adult↗
PubMed1981

Effects of pH and NaCl concentration on binding of covalently-linked insulin dimers to liver plasma membranes.

The effects of NaCl concentration and pH on binding to purified rat liver plasma membranes were compared for labelled insulin and two covalently-linked insulin dimers. Specific binding of both dimers and insulin increased as NaCl concentration increased from 0 to 1M in 0.05M Tris/HCl buffer. The initial rise in binding was much greater for dimers than for insulin. Specific binding of dimers was sensitive to pH changes in 0.029M barbital sodium acetate buffer, but this effect was more marked with insulin, which reached a sharp binding peak at pH 7.7 to 8.0. Both total and non-specific dimer binding were approximately 2-fold greater at pH 5.0 than at pH 8.0. Specific-binding fraction determinations of both dimers relative to insulin have been shown to be critically dependent on the experimental conditions of Na+/Cl- ion concentration and pH. These observations allow a better understanding of the nature of ligand-receptor interaction.

Animals↗
PubMed1981

Acute effects of cigarette smoking on left ventricular function at rest and exercise.

In this study we investigated the acute effects of cigarette smoking on cardiac function during exercise in 12 normal young males. Radionuclide angiocardiography was used to assess cardiac performance at rest and during upright-bicycle exercise on two consecutive days. On the second day each subject smoked three cigarettes. Exercise studies were continued until 85% of age-predicted heart rate for an individual was achieved. At rest cigarette smoking induced significant increases in resting heart rate, blood pressure, and contractility and significant decreases in end-systolic volume and pulmonary transit time. Comparison of hemodynamic data during exercise before and after smoking showed the only significant change to be a decrease in pulmonary transit time. These results suggest that cigarette smoking in healthy young males does not significantly alter cardiac function during submaximal exercise.

Adult↗
PubMed1981

Accuracy of left ventricular end-diastolic dimension determinations obtained by radionuclide angiocardiography.

This study tested the ability of first-pass radionuclide angiocardiography to detect accurately the left ventricular endocardial surface of the intact, conscious, chronically instrumented dog. A spherical phantom was used to define the influence of collimation: with a 1.0-in. collimator, the optimal count threshold was a border at 31% of the image's maximum counts; and with a 1.5-in. collimator, the optimal count threshold was at 21%. These were used to analyze cardioscintigrams obtained in 19 studies of six dogs. The dogs were provided with pulse transit sonomicrometer dimension transducers on the endocardium, right-atrial pacing electrodes, electrocardiographic leads, and catheters in the superior vena cava and right or left atria. The minor-axis dimension of the left ventricle was measured ultrasonically while the cardioscintigram was being stored. The minor-axis dimension and end-diastolic volume obtained by the two techniques had linear correlation coefficients of 0.95 and 0.98. This correlation indicates the inherent accuracy of radionuclide techniques by defining left-ventricular endocardial edges for a large range of volumes in the dog.

Angiocardiography↗
PubMed1981

Effect of valve replacement for chronic mitral insufficiency on left ventricular function during rest and exercise.

In this study we measured left ventricular function at rest and during exercise before and after operation in 18 patients who underwent mitral valve replacement (MVR) for chronic mitral insufficiency. First-transit radionuclide angiocardiography was employed a week before operation and 5 to 19 months after operation to calculate left ventricular ejection fraction, volumes, output, filling, and emptying rates. Preoperatively, left ventricular ejection fraction increased from 0.56 +/- 0.09 (mean +/- S.D.) at rest to 0.62 +/- 0.11 during exercise, and this response was not altered for the group after operation. After valve replacement, there was no consistent change in end-diastolic volume (EDV), and cardiac function was not related to an alteration in filling rates of the left ventricle. After operation, the patient group achieved a maximal ventricular filling rate during exercise comparable to that measured before operation. In addition, postoperative maximal filling rates did not correlate with prosthetic valve size. These data suggest that the hemodynamic changes elicited by MVR for chronic insufficiency are primarily related to the elimination of the regurgitant flow but no attributable to alterations of the myocardium. It is suggested that limitation in exercise performance after operation may be primarily related to the functional status of the myocardium prior to operation.

Adult↗
PubMed1980

The proteinuria of diabetic nephropathy.

The results of an investigation into the nature of the proteinuria of diabetic nephropathy are described. Proteinuria increases quantitatively with deteriorating renal function but there is no consistent qualitative change; even with small amounts of proteinuria the selectivity may be poor and the proportion of albumin to the total excretion constant. These and other findings are discussed in relation to the possible pathogenesis of the glomerular dysfunction in diabetic nephropathy.

Adult↗
PubMed1980

Two dimensional echocardiography in mitral, aortic and tricuspid valve prolapse. The clinical problem, cardiac nuclear imaging considerations and a proposed standard for diagnosis.

The mitral valve prolapse syndrome may present with a variety of clinical manifestations and has proved to be a common cause of nonspecific cardiac symptoms in clinical practice. Primary and secondary forms must be distinguished. Myxomatous degeneration appears to be the common denominator of the primary form. The diagnostic standard of this form has not previously been defined because the detection of mitral leaflet tissue in the left atrium (prolapse) on physical examination or angiography is nonspecific. M mode echocardiography has greatly enhanced the recognition of this syndrome but has not proved to be the best diagnostic standard because of its limited view of mitral valve motion. The advent of two dimensional echocardiography has provided the potential means for specific identification of the mitral leaflet motion in systole and can be considered the diagnostic standard for this syndrome. Primary myxomatous degeneration with leaflet prolapse is not localized to the mitral valve. Two dimensional echocardiography has detected in preliminary studies tricuspid valve prolapse in up to 50 percent and aortic valve prolapse in about 20 percent of patients with idiopathic mitral valve prolapse.

Angiocardiography↗
PubMed1980

Effect of age on the response of the left ventricular ejection fraction to exercise.

To assess the effects of age on the left ventricular ejection fraction (LVEF), we performed radionuclide angiocardiography at rest and during upright bicycle exercise in 77 healthy volunteers 20 to 95 years of age. Radionuclide measurements included left ventricular ejection fraction, end-diastolic volume, and regional wall motion. Age did not appear to influence any of these indexes at rest. However, during exercise the ejection fraction was less than 0.60 in 45 per cent of subjects over age 60 as compared with 2 per cent of younger subjects (P < 0.001). In addition, there was a decline in the change in LVEF (exercise LVEF minus rest LVEF) with increase in age (r = -0.71). Wall-motion abnormalities during exercise occurred with increasing frequency in patients who were 50 and older. In the older subjects these age-related changes in ejection fraction during exercise were not associated with differences in end-diastolic volume or blood pressure.

Adult↗
PubMed1980

Bluetongue and epizootic hemorrhagic disease virus isolation from vertebrate and invertebrate hosts at a common geographic site.

One serotype of bluetongue virus (BTV) and two serotypes of epizootic hemorrhagic disease virus (EHDV) were isolated from vertebrate and invertebrate hosts on a farm in Colorado. The isolations were from blood samples collected a week apart from a dairy heifer with stomatitis and laminitis; EHDV serotypes 1 and 2 were isolated from the first blood sample, and BTV serotype 13 and EHDV serotype 1 were isolated from the second. Antibodies to EHDV and BTV were detected in the serum from this heifer. Both EHDV serotypes and BTV serotype 13 were isolated from pools of female biting gnats (Culicoides variipennis) that had not had a recent blood meal. The BTV insect isolate was biologically transmitted by female gnats from an infected donor sheep to a recipient host sheep. Culicoides variipennis was the predominant insect collected during three nights of light trap captures at the farm.

Animals↗
PubMed1980

Radionuclide measurements of left ventricular function. Their use in patients with aortic insufficiency.

Radionuclide angiocardiography was used to measure left ventricular ejection fraction and end-diastolic volume while at rest and during exercise in 20 patients with severe aortic insufficiency. A second study was performed one year later in ten of these patients who did not undergo aortic valve replacement and in ten patients one year after operation. In patients without aortic valve replacement, the maximum ejection fraction achieved during exercise was 63% +/- 9% during the first study, and decreased to 57% +/- 9% after one year without a change in ejection fraction while at rest. No change in end-diastolic volume either while at rest or during exercise occurred during that period of time. In patients undergoing aortic valve reconstruction, the most striking change after one year was a decrease in end-diastolic volume from 296 +/- 107 to 148 +/- 37 mL at rest and from 306 +/- 92 to 155 +/- 38 mL during exercise. Ejection fraction increased by 10% at rest and 12% during exercise. Therefore, medically treated patients with aortic insufficiency lost the ability to increase ejection fraction during exercise without alteration of the ejection fraction while at rest over the one year of study. In contrast, aortic valve reconstruction resulted in a decrease in end-diastolic volume and an increase in ejection fraction during rest and exercise.

Adolescent↗
PubMed1980

Quantitative radionuclide angiocardiography.

This study introduces a new method for calculating actual left ventricular volumes and cardiac output from data recorded during a single transit of a radionuclide bolus through the heart, and describes in detail current radionuclide angiocardiography methodology. A group of 64 healthy adults with a wide age range were studied to define the normal range of hemodynamic parameters determined by the technique. The normal radionuclide cardiac index averaged 3.25 +/- 0.75 liters/min/m2, the end-diastolic volume index was 62 +/- 16 ml/m2, the stroke volume index was 40 +/- 9 ml/m2, and the ejection fraction was 0.66 +/- 0.07. Radionuclide angiocardiograms were performed in patients undergoing cardiac catheterization to validate the measurements. In 33 patients studied by both techniques on the same day, a close correlation was documented for measurement of ejection fraction (r = 0.89) and end-diastolic volume (r = 0.89). Determination of the linear regression equation for the end-diastolic volumes obtained by the two methods (EDVcath = 1.26 x EDVRN - 7.56) permitted correction of end-diastolic volume and provided an approach for calculation of stroke volume and cardiac output. To validate the method of volumetric cardiac output calculation, 33 simultaneous radionuclide and indocyanine green dye determinations of cardiac output were performed in 18 normal young adults and correlated closely over a range of 4-17 liters/min (r = 0.94). These independent comparisons of radionuclide measurements with two separate methods document that initial transit radionuclide angiocardiography accurately assesses left ventricular function.

Adolescent↗
PubMed1980

Radioimmunoassay of chemically modified insulins.

The reactions between four insulin antisera and eighteen insulin derivatives with modifications at the A1, B1 and B29 positions have been studied using a standard double-antibody radioimmunoassay procedure. The derivatives studied had: a) single modifications at A1, B1 or B29,; b) modifications at two sites with or without a crosslink between them; c) modifications at all three sites with or without a crosslink. Analysis of the results showed a clear difference in the reactivity of the antisera. One antiserum (GP5) was highly sensitive to modifications of the B1 residue and another (Ab1) was sensitive to A1 and B29 modifications. Thus, immunological potencies of insulin analogues derived on the basis of these reactions with the antisera give widely varying results. These antisera were used in discriminatory radioimmunoassays of chemically modified insulins in biological fluids for estimation of in vivo hypoglycaemic potencies by an infusion technique, where the knowledge of the specificity of the antisera was useful in assessing the immunological identity of immunoreactive material in plasma with the analogue infused.

Adipose Tissue↗