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Biomedical subjects

G S Myers

Publications and source records attributed to G S Myers.

At least 19 recordsLinked to original sources
PubMed1993

Ion chromatographic analysis of glucose, fructose, and sucrose concentrations in raw and processed vegetables.

To meet the demands for improved carbohydrate analysis techniques, a method of sugar extraction and analysis has been developed using ion chromatography. The sample preparation method, which uses filtration and extraction steps, has been shown to adequately isolate glucose, fructose, and sucrose from other food components in raw and processed vegetables. Resulting sample preparations were successfully analyzed by ion chromatography using pulsed amperometric detection, which is a sensitive, rapid, and accurate technique. Sugar concentrations in a number of different vegetable products were successfully determined in this way.

Chromatography, Ion Exchange↗
PubMed1985

Evaluation of aortic stenosis by spectral analysis of the murmur.

A relation between the peak transaortic pressure gradient and the frequency content of the murmur (r = 0.79) was demonstrated in a prospective "test" set of 50 patients with the clinical diagnosis of aortic stenosis. After heart sounds were recorded and digitized, three segments of the systolic murmur were isolated and analyzed by fast Fourier transform technique. An average frequency spectrum was quantitated by a previously described empiric spectral estimator. Clinical data and spectral ratio were correlated with the transaortic pressure gradient and aortic valve area was calculated from cardiac catheterization data. The best prediction of the transaortic pressure gradient was obtained when a 170 ms murmur segment was analyzed and when the predictive algorithm also included the aortic dimension (r = 0.87). The aortic valve area was poorly predicted (r = -0.48) unless estimates of blood flow and valvular calcification were included in the algorithm (r = 0.84). Further refinement of this technique may provide a non-invasive and clinically useful method for the estimation of aortic valve stenosis.

Adult↗
PubMed1983

Detection of aortic porcine valve dysfunction by maximum entropy spectral analysis.

A high-resolution method of spectral analysis, of the class generally called "maximum entropy method," was used in a study of aortic porcine valve closing sounds in 37 patients (ages 19 to 76). Spectra from 27 normal xenografts, implanted from 2 weeks to 61 months previously, were characterized by a dominant frequency peak, F1, at 89 +/- 15 Hz (mean +/- SD), with a lower amplitude peak, F2, at 154 +/- 25 Hz. Eight of nine patients with aortic porcine valve dysfunction were proved surgically to have leaflet degeneration or infection and had either F1 (139 +/- 54 Hz) and/or F2 (195 +/- 74 Hz) significantly higher than normal (p less than .001). In two patients with paravalvar leak but no leaflet abnormality, F1 and F2 were in the normal range. Estimation of F1 and F2 was highly reproducible and was unaffected by duration of implant up to 5 years. Spectral analysis of aortic porcine valve closing sounds by the maximum entropy method may be useful for detection of intrinsic xenograft dysfunction.

Adult↗
PubMed1979

The effect of protein-energy malnutrition on appositional bone growth in the rat.

During protein-energy malnutrition appositional bone growth in the seventh caudal vertebra of the rat slows and finally ceases. During rehabilitation appositional growth begins agains and attains a rate in excess of that of the controls. This may account for alterations in skeletal proportions resulting from malnutrition.

Animals↗
PubMed1978

Myocardial function in hypothyroidism. Relation to disease severity and response to treatment.

Systolic time intervals (ST) were used to evaluate myocardial function prospectively in 29 hypothyroid patients. The patients were divided into three categories of disease severity: (1) severe hypothyroidism, (2) mild hypothyroidism, and (3) decreased thyroid reserve or "prehypothyroidism." Groups 1 and 2 showed decreased myocardial contractility with a prolonged preejection period (PEP), shortened left ventricular ejection time (LVET), and increase PEP/LVET, compared with normal controls. The STI were more abnormal (P less than .05) in group 1 than in group 2, suggesting that the severity of myocardial dysfunction correlates with the severity of the hypothyroidism. Group 3 had normal STI. Ten patients were restudied when euthyroid and showed complete normalization of their STI, supporting the thesis that hypothyroidism was the sole cause of the initial myocardial dysfunction.

Female↗
PubMed1978

Characterization of normal and abnormal pulmonary surface by reflected ultrasound.

The use of reflected ultrasound in the diagnosis of pulmonary disease has been limited due to the strong reflection and high absorption of acoustic energy by alveoli containing air. Our study reports the ultrasonic characteristics of normal and diseased pulmonary surface. Two measurements, the coefficient of pulmonary reflection and the tissue frequency signature, were studied with specially calibrated instuments. The coefficient of pulmonary reflection in 23 normal subjects was - 19.6 +/- 0.1 dB at 5.5 MHz. In ten patients with documented pulmonary emboli, the coefficient of pulmonary reflection was -47.4 +/- 0.1 dB, significantly less than normal (P less than 0.1). The tissue frequency signature in 18 normal subjects was specular at higher and nonspecular at lower frequencies, with a typical dip at 5.2 MHz. In patients with chronic obstructive pulmonary disease, the tissue frequency signature was flat, and the typical dip was absent. In patients with pulmonary emboli, the characteristic shape of the tissue frequency signature was preserved, but there was a generalized loss of magnitude of the reflection. Thus, our preliminary data indicate that reflected ultrasound provides a noninvasive method for differentiating normal from diseased pulmonary surfaces.

Animals↗
PubMed1977

Noninvasive evaluation of cardiac function in hypothyroidism. Response to gradual thyroxine replacement.

Left ventricular performance was studied in 15 patients with severe, primary hypothyroidism (mean serum total thyroxine of 0.8 mug per 100 ml and serum thyrotropin of 160 muU per milliliter). Pretreatment systolic-time intervals were characterized by prolongation of the pre-ejection period (delta PEP = +30) and reduction of the left ventricular ejection period (delta LVET = -23) with a resultant increase in the PEP/LVET ratio (0.47). Nine of 14 patients demonstrated pericardial effusions. These abnormalities were reversed with physiologic thyroxine replacement. Further reductions of the delta PEP and PEP/LVET ratio occurred with supraphysiologic doses (200 to 300 mug per day). During therapy, delta PEP was inversely correlated with serum thyroxine (P less than 0.001) and directly correlated with serum thyrotropin (P less than 0.001). Thus physiologic thyroid hormone replacement, appropriately adjusted to need, appears necessary in hypothyroidism for optimal left ventricular function.

Adult↗
PubMed1977

Interobserver variability in echocardiography.

High-quality echocardiograms were performed on 146 normal individuals whose ages ranged from 3 to 73 years (mean 27 years). Normal values for mitral diastolic excursion and E-F slope, the chamber dimensions of the right ventricle, left atrium, and left ventricle, the aortic root dimension, and thickness of the interventricular septum and left ventricular posterior wall were determined. Each tracing was then read independently by two experienced echocardiographers. The extent of interobserver variability was calculated and expressed as a percent of the mean. The 95 per cent confidence limits for these estimates were calculated. Small but significant interobserver variability was found for all nine of these commonly measured echocardiographic parameters. Observer variability is a small but potentially important consideration in investigative echocardiography.

Adolescent↗
PubMed1977

Echocardiographic spectrum of posterior systolic motion of the mitral valve in the general population.

The prevalence of mitral valve prolapse has been established in selected groups of patients but not in the general population. The present study was designed to define the echocardiographic spectrum of mitral valve motion in a population of young individuals without clinical evidence of significant cardiac disease or hypertension. Echocardiograms were performed on 136 normal volunteers. Six subjects (4.4 per cent) had mitral valve prolapse. Eighteen subjects (13.2 per cent) had a lesser degree of posterior systolic motion of the mitral valve leaflets which was suggestive but not diagnostic of prolapse. Minor degrees of posterior systolic mitral valve motion may represent a variant of normal. Caution should be exercised in making the echocardiographic diagnosis of mitral prolapse until this question is settled.

Adolescent↗
PubMed1977

The value and limitations of echocardiography in recording mitral valve vegetations.

The echocardiographic findings and case reports of three patients with active Streptococcal endocarditis and severe congestive heart failure are presented. All three had pathologically proven vegetations on the mitral valve; however, only the two with calcification of the vegetations were successfully demonstrated on echocardiography. Clinical and pathological differences are highlighted and prior case reports in the literature are reviewed. The nonspecific nature of echoes recorded from valvular vegetation is stressed and factors in their echocardiographic detection are discussed.

Aged↗
PubMed1977

Detection of left atrial myxoma by gated radionuclide cardiac imaging.

Gated radionuclide cardiac blood pool scans (GCS) of end-systole and end-diastole or eight images subtending the entire cardiac cycle were performed on seven patients with left atrial myxomas documented by pulmonary cineangiography with left atrial follow-through. The ethocardiogram was either suggestive or diagnostic in all patients. In addition to demonstration of the tumor (6 patients), the GCS detected three patterns of tumor motion: 1) a defect which moved from the left atrium in end systole to the left ventricle in end diastole (2 patients); 2) a defect which remained within the region of the left atrium but decreased in size between end diastole and end systole (3); and 3) a defect which was observed within the region of the left ventricle in end diastole but disappeared in end systole (1). Thus, the GCS is a noninvasive method for detection and evaluation of motion of left atrial myxomas.

Adult↗
PubMed1977

Hypertrophic cardiomyopathy. Evaluation by gated cardiac blood pool scanning.

The gated radionuclide cardiac blood pool scan (GCS) can be used to visualize the entire profile of the interventricular septum and left ventricular contraction. Twenty-two patients with hypertrophic cardiomyopathy, nine with valvular aortic stenosis and six normals, underwent echocardiography and GCS. All patients with hypertrophic cardiomyopathy had asymmetric septal hypertrophy and 14 of 22 had resting systolic anterior motion of the anterior leaflet of the mitral valve on echocardiogram. In eight patients with aortic stenosis with adequate echocardiograms, two had asymmetric septal hypertrophy and none had systolic anterior motion. The GCS demonstrated disproportionate upper septal thickening in 11; septal flattening in 16; cavity obliteration in 17; and a filling defect in the region of the left ventricular outflow tract in 16 of the 22 patients with hypertrophic cardiomyopathy. In the nine patients with valvular aortic stenosis, two demonstrated septal flattening, two cavity obliteration, two an outflow tract defect, and none disproportionate upper septal thickening. Both patients with cavity obliteration demonstrated asymmetric septal hypertrophy on echocardiogram. One normal control patient had septal flattening. Thus the gated cardiac blood pool scan provides an atraumatic technique for the evaluation of patients with hypertrophic cardiomyopathy which complements the echocardiogram.

Aortic Valve Stenosis↗
PubMed1976

Correlation of echocardiographic and clinical findings in patients with pericardial effusion.

Clinical data and echocardiographic findings were correlated in 20 patients with pericardial effusion. Moderate to large effusions were associated with increased motion of the entire heart within the pericardial sac. A correlation was found between the estimated volume of fluid and the diastolic excursion and velocity of the right ventricular and left ventricular walls (P less than 0.01). For any given volume of fluid as estimated from the echocardiogram neoplastic effusions resulted in greater increments in wall motion (P less than 0.02). Patterns of "pseudo" mitral valve prolapse occurred and were correlated with the extent and timing of cardiac swinging and heart rate. A diminished E-F slope of the mitral valve echo and notch on the right ventricular epicardial echo during early systole were found in all four patients with pericardial tamponade. These preliminary observations suggest that echocardiographic examination of patients with pericardial effusion may provide clues to the presence or absence of tamponade in addition to providing an estimate of the quantity of fluid in the pericardial sac.

Adolescent↗
PubMed1975

Evaluation of carotid stenosis by phonoangiography.

Quantitative spectral (frequency) analyses were performed on 60 carotid bruits in 48 patients with suspected carotid stenosis. The technic was totally noninvasive. Bruits were recorded at the skin surface, analyzed by a minicomputer, and the degree of arterial stenosis estimated using a recently derived theory of sound production by turbulent blood flow. This method has been named phonoangiography. Fifty of the 60 bruits (83 per cent) had spectrums characteristic of turbulent blood flow, and a residual lumen diameter could be calculated. Results from the noninvasvie technic compared well with data obtained from radiographic carotid arteriograms in the 50 bruits with internal carotid artery stenosis. The residual lumen diameter estimated from phonoangiography differed from the radiographic value by less than 1 mm in 83 per cent and less than 1.5 mm in 92 per cent of the studies. Phonoangiography appears to be a useful method for assessment of carotid artery stenosis.

Arteriosclerosis↗