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Biomedical subjects

R H Jones

Publications and source records attributed to R H Jones.

At least 217 records · Page 12Linked to original sources
PubMed1985

WHO/FAO Working Team Report: entomology.

A summary of the more important concerns of the Working Team with particular reference to bluetongue (BT) virus (BTV), is as follows: With the exception of Australia, the US, and possibly parts of Africa, there are almost no concrete data that could be used to direct control efforts against the responsible vector(s) of BTV in a specific geographic area. In Australia, a broad plan of attack yielded data that showed that members of the subgenus Avaritia are the primary vector species. It has been clearly shown that Culicoides variipennis (Coq.) is the dominant vector species for most of the US. In the Middle East and certain areas of Africa, isolations from possible vector species indicated that C. imicola K., again probably a species complex and belonging to the subgenus Avaritia, is one of the likely vectors. Except for some subgenera, the taxonomy for much of the Culicoides remains in disarray. The subgenus Oecacta for example still remains a catchall for many species. Although a number of proposals have been made for delineating the species of the C. (Monoculicoides) variipennis species complex, none have been initiated because of the lack of funds. The Working Team strongly feels that the lack of definition of important species complexes is the result of short-term planning that does not consider the fact that efficiency can be increased and a great deal of monies saved by directing control toward the specific species or populations thereof that are responsible for a problem.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Noninvasive assessment of exercise cardiac function before and after pectus excavatum repair.

Surgical correction of pectus excavatum frequently results in subjective improvement of exercise tolerance. Whether or not cardiac function improves after repair remains controversial and has primarily been limited to isolated case reports. The purpose of this investigation was to assess changes in cardiac function during rest and exercise associated with the surgical correction of this deformity. First-pass radionuclide studies during upright rest and bicycle exercise were performed on 13 patients before and at least 6 months after pectus excavatum repair. Operation did not change left ventricular ejection fraction or cardiac index at rest or during exercise. However, the left ventricular end-diastolic volume index and stroke volume index increased at rest after surgical correction. The estimated resting right ventricular end-diastolic volume also increased markedly after operation and was associated with a decrease in right ventricular ejection fraction. These data show no limitation in exercise cardiac function that could be relieved by pectus repair. However, the increase in right and left ventricular volume after operation suggests that some cardiac compression is relieved by operative repair.

Adolescent↗
PubMed1984

A statistical method for determining the breakpoint of two lines.

A method is presented for determining the breakpoint of a line which suddenly changes slope at some unknown point. A statistical test is given for testing whether the broken line is a significantly better fit to the data than a single straight line. An approximate confidence interval can be obtained for the position of the breakpoint.

Alkaline Phosphatase↗
PubMed1984

Effects of covalently linked insulin dimers on receptor kinase activity and receptor down regulation.

Certain covalently linked insulin dimers have previously been found to have a greater ability to bind to the insulin receptor than to stimulate lipogenesis in adipocytes. The present report presents data indicating that the same insulin dimers also have a greater ability to bind to the receptor than to stimulate the kinase activity of the insulin receptor. In particular, one such covalently linked insulin dimer had less than 1% the potency of native insulin in stimulating the receptor kinase although it could bind to the solubilized receptor with 30% the potency of native insulin. In contrast, this dimer could down regulate the insulin receptor with approximately 30% the potency of native insulin. These results suggest that stimulation of the receptor kinase may require more than simple occupancy of the receptor binding site whereas down regulation of the receptor may require only the binding of ligand to the receptor.

Dose-Response Relationship, Drug↗
PubMed1984

Effects of age on radionuclide angiographic detection and quantitation of left-to-right shunts.

The usefulness of quantitative radionuclide angiography (RNA) in detecting left-to-right shunts and estimating shunt size in young children was assessed. The total population of 88 patients was divided into 2 groups: 23 patients 2 years of age and younger (mean 0.8 +/- 0.6 [+/- standard deviation] ) and 65 patients older than 2 years (mean 15 +/- 15 years). The accuracy of 2 different RNA shunt estimation techniques, the gamma variate and the Stewart-Hamilton approach, were compared with the estimations obtained at cardiac catheterization using Fick (88 patients) and indocyanine green dye-dilution techniques (20 patients). Automated data processing algorithms were used to determine the RNA estimations, thereby avoiding the effects of operator judgment and subjectivity on shunt estimation. Of the 88 patients, 16 had no shunt by Fick data (that is, estimation less than 20%) but had a left-to-right shunt demonstrated by cardiac catheterization cineangiocardiography. Nine of these patients had no shunt by RNA (that is, estimation less than 20%). For patients 2 years of age and younger, linear regression analysis of the Fick and gamma variate data provided a slope of 0.63 and a correlation coefficient of 0.82; analysis of the Fick and Stewart-Hamilton data provided a slope of 0.59 and a correlation coefficient of 0.79. For patients older than 2 years, analysis of the Fick and gamma variate data provided a slope of 0.63 and a correlation coefficient of 0.79; analysis of the Fick and Stewart-Hamilton data provided a slope of 0.64 and a correlation coefficient of 0.76.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Prognostic indicators from radionuclide angiography in medically treated patients with coronary artery disease.

The purpose of this investigation was to determine which variables obtained when performing radionuclide angiography predict subsequent survival or total events (cardiovascular death or nonfatal myocardial infarction) in stable patients with symptomatic coronary artery disease (CAD). Univariable and multivariable analyses of 6 variables, including ejection fraction (EF) at rest and exercise, change in EF with exercise, development of ischemic chest pain or electrocardiographic changes, left ventricular (LV) wall motion abnormalities and exercise time were examined in 386 patients followed up to 4.5 years. Univariate analyses revealed that the exercise EF was the variable most closely associated with future events (p less than 0.01), followed by EF at rest, wall motion abnormalities and exercise time. Multivariable analyses revealed that once the exercise EF was known, no other radionuclide variables contributed independent information about the likelihood of future events. Multivariable analyses also revealed that the exercise EF describes much of the prognostic information of coronary anatomy. Our findings suggest that the radionuclide angiogram is useful in predicting future events in patients with stable CAD, although examination in conjunction with other clinical descriptors will be necessary to further quantify this contribution.

Cardiac Output↗
PubMed1984

Covalently-linked insulin dimers: their metabolism and biological effects in vivo as partial competitive antagonists of insulin clearance.

The biological properties of three covalently-linked insulin dimers were studied in greyhounds. Constant infusions showed that the plasma distribution kinetics were slower for the dimers than for insulin. The metabolic clearance rates of the three dimers (10.3 +/- 0.4, 8.8 +/- 0.5, 8.2 +/- 0.5 ml X min-1 X kg-1; mean +/- SEM) were significantly lower than that of insulin (19 +/- 0.8 ml X min-1 X kg-1), and their hypoglycaemic effects (11.2%, 3% and 0.3%) were markedly reduced compared with their lipogenic potencies in vitro (80%, 30% and 13%, respectively). A low dose infusion of insulin or an equipotent dose of one of the dimers significantly prolonged the effects of an insulin bolus on plasma glucose but not on non-esterified fatty acids. The apparent distribution space (106.4 +/- 11.9 ml/kg) and clearance rate (14.7 +/- 0.5 ml X min-1 X kg-1) of an insulin bolus were significantly reduced by one dimer (44.5 +/- 8.4 ml/kg and 10.7 +/- 2.8 ml X min-1 X kg-1) but not by the equipotent insulin infusion (102.7 +/- 8.2 ml/kg and 16.4 +/- 0.07 ml X min-1 X kg-1). The apparent partial competitive antagonism of insulin by the dimers that has been reported in vitro can be observed in vivo, in that antagonism of insulin metabolism was directly demonstrated with one of the dimers.

Animals↗
PubMed1984

Number and affinity of insulin receptors in intact human subjects.

A simple model of the distribution and metabolism of insulin in vivo has been evaluated using data from insulin infusion into a group of normal subjects. The major rate-limiting step for access to degradation pathways is assumed to consist of binding of the ligand to a single population of insulin receptor sites, except that provision is made for the possibility of linear non-receptor-mediated degradation and for the phenomenon of negative cooperativity. The model has been shown to accommodate the non-linearity of insulin metabolism, allows, evaluation of receptor association and dissociation constants and provides for the first time an estimate of total accessible receptor number in the intact organism. For normal fasting man the model predicts 1.00 +/- 0.05 nmol accessible binding sites/kg (mean +/- SD).

Humans↗
PubMed1984

Statistical identification of compartmental models with application to plasma protein kinetics.

A numerical method for fitting linear compartmental models to data is presented which is similar to the method proposed by Jennrich and Bright (R. I. Jennrich and P. B. Bright, Technometrics 18, 385 (1976] and Feldman (H. A. Feldman. Amer. J. Physiol. 233, R1 (1977] but avoids some of the numerical difficulties. The method is direct and does not use numerical integration thereby avoiding time consuming and expensive calculations. Emphasis is on statistical procedures for model selection. In addition to the usual F tests for comparing two models, Akaike's Information Criterion (AIC) is introduced for choosing from among several models. The combined use AIC with an F test, chi-square test, or confidence intervals on estimated parameters gives a practical method to obtain a balance between underfitting and overfitting. Application to models of plasma protein kinetics illustrates the method.

Animals↗
PubMed1984

Mechanism and significance of a decrease in ejection fraction during exercise in patients with coronary artery disease and left ventricular dysfunction at rest.

The purpose of this study was to determine whether an exercise-induced decrease in ejection fraction in patients with coronary artery disease and left ventricular dysfunction at rest represents ischemia or the nonspecific response of a compromised left ventricle to exercise stress. Accordingly, radionuclide ejection fraction responses of 246 patients with coronary artery disease and an ejection fraction at rest of less than 0.50 were compared with those of a "nonischemic" control group of 48 patients with idiopathic dilated cardiomyopathy and a similar degree of ventricular dysfunction. The significance of the ejection fraction response in the group with coronary artery disease was further examined by relating it to the angiographic extent of coronary artery disease, severity of angina, incidence of chest pain and electrocardiographic ST segment depression during exercise and long-term prognosis. The ejection fraction decreased by greater than or equal to 0.01 and greater than or equal to 0.05 during exercise in 48 and 28%, respectively, of the patients with coronary artery disease compared with only 8 and 2%, respectively, of the patients with cardiomyopathy. When exercise was limited by fatigue at a submaximal heart rate, the ejection fraction decreased in 25% of the patients with coronary artery disease but in none of the patients with cardiomyopathy. Patients with coronary artery disease whose ejection fraction decreased during exercise had a significantly higher incidence of three vessel disease, exercise-induced chest pain or ST depression and late mortality than did patients whose ejection fraction did not decrease. These relations were confirmed equally in subgroups of patients with moderate (ejection fraction 0.30 to 0.49) and severe (ejection fraction less than 0.30) left ventricular dysfunction. Thus, in patients with coronary artery disease and left ventricular dysfunction at rest, a decrease in ejection fraction during exercise is more likely to indicate ischemia than a nonspecific left ventricular response to exercise stress. In the individual patient, a decrease of 0.05 or greater, or a decrease during submaximal exercise, appears to be highly specific for ischemia. A decrease in ejection fraction identifies a subgroup of patients with a high prevalence of multivessel coronary artery disease and a high risk of death during long-term follow-up on medical therapy.

Adult↗
PubMed1984

Clinical characteristics and current management of medically refractory unstable angina.

Of 531 patients admitted to the Duke Coronary Care Unit with unstable angina (UA) from June 1981 to September 1982, 100 had persistent angina despite optimal medical therapy of nitrates, propranolol, and nifedipine. At catheterization, 70% of the refractory patients had left main (LM) or three-vessel disease (TVD), 68% had left ventricular end-diastolic pressures of greater than 12 mmHg, and 24% had ejection fractions (EF) of less than 0.40. Twenty-four patients were greater than 65 years of age, and 53 had associated major diseases. Forty-eight patients (Group I) had no evidence of myocardial infarction in the 30 days before catheterization, whereas 52 patients had an infarction precipitating the unstable angina within the preceding 30 days (Group II). Emergent coronary artery bypass grafting was performed in all 100 patients irrespective of ventricular function, hemodynamic status, or coronary anatomy. Management protocols included prompt surgical intervention, preoperative stabilization with the balloon pump in LM or TVD, meticulous myocardial protection, and complete coronary revascularization. An average of 3.6 grafts were placed in each patient. There were two hospital deaths in Group I, and two in Group II. Two-year survival was 90% in Group I and 88% in Group II, and 81% of surviving patients were NYHA Class I or II. Thus, refractory UA denotes particularly severe coronary disease with a high incidence of LM, TVD, and depressed EF. Baseline clinical characteristics, criteria for operation, and expected results in the postinfarction group seem to be similar to the unstable angina group in general. Cardiac anatomic and functional variables no longer constitute operative contraindications. Aggressive operative management is safe, and the current risk may be less dependent on coronary anatomy and ventricular function than previously appreciated.

Adult↗
PubMed1984

Bayesian analysis of data from radionuclide angiocardiograms for diagnosis of coronary artery disease.

A continuous Bayesian model was developed by fitting a beta-function to the frequency distributions of resting ejection fraction, exercise ejection fraction, and change in end-systolic volume during exercise measured by radionuclide angiocardiography in a group of 249 men with coronary artery disease (CAD) and in a group of 56 men without disease. This model, then prospectively applied to 250 men with chest pain, did not increase the overall accuracy of the test but did increase the diagnostic content for individual patients. The diagnostic efficacy of the continuous Bayesian model was compared with previously determined optimal discrete criteria of a positive or negative test. Patients with CAD showed a maximum and mean increase in probability of disease of +0.58 and +0.11, respectively, by the continuous Bayesian model and +0.14 and +0.05, respectively, by discrete criteria. Men without significant disease showed a maximum and mean decrease in probability of disease of -0.73 and -0.38, respectively, by Bayesian analysis and -0.36 and -0.27, respectively, by optimal discrete criteria. Moreover, all 29 patients who died during a 35 month interval after study had a probability of CAD of 0.95 or greater by the continuous Bayesian model. These findings indicate that Bayesian analysis of radionuclide angiocardiographic test results with continuous distributions of left ventricular function measurement enhances the diagnostic and prognostic information for individual patients with symptoms suggestive of CAD.

Adult↗
PubMed1984

Evidence for separate handling in vivo of different regions of the insulin molecule using A14- and B1-labeled insulin tracers.

To compare the metabolic characteristics and degradation of insulin tracers labeled unselectively, selectively at the A14 position (A14-monoiodoinsulin), and selectively at the B1 position (B1-monoiodoinsulin), we have followed the time course of disappearance of intact (immunoprecipitable [IP] and trichloroacetic acid [TCA] precipitable) iodoinsulin after bolus injection into greyhounds. We have used noncompartmental analysis to determine metabolic clearance rate (MCR) and apparent distribution space (DS). We have also measured the appearance of non-IP- and non-TCA-precipitable fragments, and have developed a mathematical model using compartmental analysis to explain the observed differences. B1-Monoiodoinsulin has a significantly higher MCR (16.3 ml/min/kg) than both A14-monoiodoinsulin (10.6 ml/min/kg) and unfractionated tracers (7.6 ml/min/kg) as determined by immunoprecipitation, and reaches the values observed for native insulin in greyhounds. MCR values obtained by TCA precipitation are approximately one-half of those obtained by IP for all 3 tracers. The concentration of non-IP fragments is significantly lower with B1-monoiodoinsulin than with the other tracers. Compartmental analysis suggests this to be due to greater intracellular retention of the B1 moiety during the experimental period. We conclude that: (1) by the criterion of MCR, B1-monoiodoinsulin seems to behave more like native insulin than other preparations tested; (2) the reduced MCR of A14-monoiodoinsulin raises doubts about its validity as a tracer for insulin; (3) a high-molecular-weight product of insulin degradation, which includes both the B1 and the A14-A19 regions of the molecule, is released into the circulation; and (4) smaller fragments containing A14-A19 reappear in the circulation more rapidly than fragments containing B1.(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗
PubMed1984

PERT/CPM network analysis: a management tool for hospital pharmacists involved in strategic planning.

Hospital pharmacists may soon be required to integrate their departmental planning process with strategic plans for the institution. This will necessitate the development of more sophisticated procedures for planning, scheduling, and controlling in order to meet deadlines imposed by the master plan. Program Evaluation and Review Technique/Critical Path Method (PERT/CPM), a network analysis instrument, can be a valuable planning tool. It allows the pharmacist to: (1) visualize the sequence of activities and events (network) in the development of a new service; (2) evaluate activity times; (3) determine those activities which are critical to the completion of the plan; and (4) apply statistical analysis to the anticipated completion date. A PERT/CPM network analysis is described in a format which allows the reader to visualize the use of this tool in the strategic planning process. The case study plan was actually carried out in a 203-bed, acute care hospital. The completion date was within 10 days of the date projected at p = 0.05.

Hospital Bed Capacity, 100 to 299↗
PubMed1984

A gamma camera for medical applications, using a multiwire proportional counter.

A multiwire proportional counter gamma camera, specifically designed for nuclear medicine applications, is portable and weighs less than 50 lb including shielding and collimator. The basic operating characteristics have been investigated with various radioactive sealed sources. The camera demonstrates a peak count rate of 850,000 cps, an intrinsic spatial resolution of 2.5 mm, and excellent image uniformity when used with x-ray sources in the range of 22-81 keV. Tests of the device with Ta-178--a very promising, short half-life (9.3 min), low-energy radionuclide--using 20 mCi injections provided images of quality comparable to those obtained from 15 mCi Tc-99m studies with conventional imaging devices. The camera used with Ta-178 offers particular promise in first-pass nuclear cardiology studies. Considerably improved study quality will likely result in this area because of the increased injectable dose levels offered by Ta-178 combined with the high-count rate capability and improved resolution.

Americium↗