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Biomedical subjects

J A Parker

Publications and source records attributed to J A Parker.

16 recordsLinked to original sources
PubMed1979

Risk assessment of pulmonary embolism by multivariate analysis.

A prospective study of 6,527 hospitalized patients was performed to evaluate the effectiveness of multivariate analysis of risk factors to correctly designate risk for pulmonary embolism. History of previous pulmonary embolism was the single most important factor. In patients without prior history, five factors emerged: inactivity, congestive heart failure, Doppler ultrasound evidence of deep-vein occlusion, female sex, and black race. Used together, these factors permitted a discrimination of risk such that 68.7% of pulmonary embolization was found to occur in 32.2% of the population designated as showing increased risk. Multivariate analysis of clinical factors improved assessment of risk, compared to the use of lower extremity findings alone, and proved to be useful in identifying individuals at increased risk for pulmonary embolism.

Analysis of Variance↗
PubMed1979

Regional ejection fraction: a quantative radionuclide index of regional left ventricular performance.

Radionuclide measurements of regional left ventricular ejection fraction were evaluated as a quantitative index of regional left ventricular function. Left ventricular regional ejection fractions were derived from background-corrected, time-activity curves in 43 patients assessed by both gated equilibrium radionuclide angiocardiography and left ventricular contrast angiography. From a single, modified left anterior oblique projection, the regional change in background corrected counts was determined in each of three anatomic regions. The normal range for regional radionuclide ejection fraction was determined in 10 patients with normal contrast ventriculograms and without obstructive coronary artery disease at coronary arteriography. Regional ejection fraction was compared with percent segmental axis shortening and extent of akinetic segments in corresponding regions of the contrast ventriculogram. Radionuclide and roentgenographic methods were in agreement as to the presence or absence of abnormal wall motion in 83 of 99 left ventricular regions (84%) in 33 patients evaluated prospectively. Comparison of regional ejection fraction demonstrated significant differences between regions with roentgenographically determined normokinesis (75 +/- 3%, mean +/- SEM), hypokinesis (44 +/- 3%, p less than 0.0005) and akinesis (24 +/- 5%, p less than 0.005). We conclude that the left ventricular regional ejection provides a reliable quantitative assessment of regional left ventricular performance.

Adult↗
PubMed1978

Hyperornithinemia and gyrate atrophy of the choroid and retina.

The diagnosis of hyperornithinemia and gyrate atrophy (HOGA) depends upon the presence of five characteristic features: (1) typical chorioretinal lesions, (2) high myopia, (3) cataracts, (4) hyperornithinemia, and (5) autosomal recessive inheritance. We have seen three patients and described four new findings: (1) decreased whole blood glutamic acid, (2) low normal intelligence, (3) hepatic mitochondrial changes, and (4) urinary excretion of ornithine methyl ester. Investigations of amino acid metabolism in vivo are consistent with the presence of a defect in ornithine keto-acid transaminase.

Adult↗
PubMed1978

Assessment of regional myocardial blood flow and regional fractional oxygen extraction in dogs, using 15O-water and 15O-hemoglobin.

A new approach to the assessment of regional myocardial blood flow and fractional oxygen extraction has been developed using 15O-water (H2-15O) and 15O-hemoglobin (15O-Hb). Bolus doses (1 mCi) of H2-15O and 15O-Hb were injected 10 minutes apart into the left main coronary artery of 12 normal dogs. Sequential images of regional myocardial tracer clearance were obtained over 5 minutes with a positron camera. Myocardial blood flow calculated from the monoexponential washout of H2-15O after background correction was 78 +/- 6 (SE) ml/100 g per min. Functional images of regional blood flow in which the image of peak activity was divided by the integrated image of H2-15O washout were derived by computer processing. These images demonstrated homogeneous blood flow in the normal myocardium. Fractional myocardial O2 extraction was determined from an image of initial distribution of O2 used (obtained by extrapolating back to time zero the series of images obtained after 15O-Hb administration), divided by initial distribution of O2 delivered (obtained by back extrapolating H2-15O washout). These functional images showed uniform distribution of fractional O2 extraction in the normal myocardium. Thus, these studies show that regional myocardial blood flow and regional oxygen extraction can be measured simultaneously by sequential imaging after serial intracoronary injections of H2-15O and 15O-Hb.

Animals↗
PubMed1977

Radionuclide left ventriculography with the slant hole collimator.

A 30 degrees slant-hole collimator was used during radionuclide ventriculography of the cardiac blood pool to improve imaging of the heart in both the modified left anterior oblique (MLAO) and right anterior oblique (RAO) views. In the MLAO view, with the holes slanted caudally, good separation between the left atrium and left ventricle was achieved, and the septum was displayed without foreshortening. In the RAO view with the collimator flat against the chest there was better resolution of the cardiac apex. The results of ejection fraction and wall motion analysis in these patients correlated well with contrast ventriculography (r=0.94). Combination of the slant-hole collimator, in vivo red blood cell labeling with stannous pyrophosphate, simultaneous collection of all phases of the cardiac cycle, and cine mode display, provide a practical system for the noninvasive measurement of left ventricular performance parameters.

Coronary Disease↗
PubMed1977

Material and thickness: the important factors in the impact resistance of spectacle lenses.

The identify the population at risk of permanent visual impairment from injuries associated with spectacles, we analysed 446 cases of penetrating ocular injury occurring over a ten year period. Sixteen injuries (3.6%) were due to spectacles; 40% of these were adult male amateur athletes. We used the drop-ball test to determine the important factors in the resistance to impact of 177 used spectacle lenses (29 plastic C39, 40 heat-tempered glass, 108 non-tempered glass). We found that material and thickness were the most important. The plastic lenses were the most impact resistant and non-tempered glass lenses the least, with heat-tempered glass lenses falling between. Plastic lenses of adequate centre thickness mounted in plastic frames are recommended for all children and all adults involved in athletics.

Adolescent↗
PubMed1977

Biosynthesis of proteins by the retina. Inactivation by near-ultraviolet light and the effects of tryptophan, epinephrine, and catalase.

Postmitochondrial supernatant, cytosol, and microsomes were exposed to near-ultraviolet light and assayed for incorporation of (3H)leucine. The results indicate that near-ultraviolet light decreased the incorporation of radioactivity into the aminoacyl-tRNA fraction and into proteins. This effect depended on the wavelength of irradiation and the concentration of exposed protein. Tryptophan and epinephrine potentiated the effect of near-ultraviolet light, but catalase prevented this effect. Hydrogen peroxide decreased protein synthesis when it was added to unirradiated postmitochondrial supernatant. The results suggest that near-ultraviolet light would decrease protein synthesis by generating hydrogen peroxide from tryptophan and epinephrine.

Albumins↗
PubMed1976

Magnification renal scintigraphy in the differential diagnosis of septa of Bertin.

Eight consecutive patients, referred because intravenous urography (IVP) raised the question of hypertrophied septum of Bertin versus a pathologic mass, were examined using 99mTc labeled radiopharmaceuticals with magnification renal scintigraphy. The areas of concern showed a spectrum of activity, from normal to markedly increased, as compared to surrounding tissue. The activity correlated with the size of the mass effect on IVP. Increased resolution provided by pinhole magnification was important in evaluating these patients. We feel that magnification renal scintigraphy is valuable in the evaluation of intrarenal masses.

Adolescent↗
PubMed1976

Stability and precision of a new ampuled quality-control system for pH and blood-gas measurements.

We describe an evaluation of the in-use stability and short-term precision of a three-level ampuled quality-control system for monitoring pH, pCO2, and pO2 measurements on clinical blood-gas analyzers. In three hospital laboratories, 324 such ampuls were opened and allowed to stand with their contents exposed to atmospheric conditions for accurately timed intervals up to 240 s. Contents were then analyzed for pH, pCO2, and pO2. Student's t-test was used to evaluate the significance of differences observed in recoveries after time exposure. At a signifcance level of P less than or equal to 0.05, the only significant changes observed throughout the first minute of exposure were average pO2 increases of 180 Pa (1.4 mmHg) (+ 1.4%) and 230 Pa (1.7 mmHg) (+ 2.9%) at levels of 13.4 and 7.7 kPa kPa (101 and 58 mmHg), respectively. The ampuled system was found to be stable precise convenient, and suitable for use in the routine laboratory.

Autoanalysis↗
PubMed1975

The assessment of near vision.

There are many variables in the physiology of near vision, the end-point criteria, the types available, and the measurements made. I have suggested a hard criterion of the smallest print at the nearest distance. This controls the physiological variables and provides repeatable data for the evaluation of vision, accommodation, and binocular function.

Accommodation, Ocular↗
PubMed1975

Energy: a useful criterion in analysis of human visual evoked response.

Visual evoked responses from a diffuse Xenon flash were studied for seven normal and 14 abnormal subjects. Amplitude and latency measurements of the waveforms were compared with an energy function calculated from the area beneath a curve of the VER voltage squared and summed over the interval from 0 to 125 msec. This energy function proved superior to latency in detecting asymmetrical responses and similar to latency in detecting symmetrically reduced waveforms.

Electrophysiology↗