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Biomedical subjects

L Feldman

Publications and source records attributed to L Feldman.

At least 127 records · Page 7Linked to original sources
PubMed1980

Echocardiographic determination of contraction and relaxation measurements of the left ventricular wall in normal subjects and patients with muscular dystrophy.

Boys with Duchenne's muscular dystrophy (DMD) usually have a cardiomyopathy characterized by fibrosis of the epicardial half of the left ventricle. This cardiomyopathy is difficult to detect by noninvasive techniques. We report a technique that evaluates incremental left ventricular posterior wall thickening and thinning. High-quality left ventricular posterior wall echoes in 24 boys with DMD and 32 controls were recorded at chordal level two times 1 year apart. Endocardial and epicardial echoes and a timing ECG were digitized and analyzed by minicomputer. Left ventricular wall amplitudes were determined at standardized temporal increments during contraction and relaxation. To compare with this left ventricular assessment technique, systolic ejection times, shortening fraction and mean velocity of circumferenial fiber shortening (Vcf) were also computed in the standard way. Mean year-to-year changes were minor. Mean Vcf, the ratio of preejection period to left ventricular ejection time and shortening fraction during the first year were statistically similar to those of the controls. Shortening fraction decreased slightly during the second year and became significantly different from the control, but remained within the normal range. Left ventricular wall thickness and cavity size were significantly less in boys with DMD than in controls. Therefore, we had to normalize incremental wall thickness to determine if any significant difference occurred. To do this, we evaluated the percentage of maximal wall thickness which occurred at a given percent of systole and diastole. Using this technique, it was shown that thickening during systole was a nearly linear process with respect to time in both groups. However, relaxation was significantly different between the groups. Relaxation was found to be an alinear process, and most thinning occurred in the first 40% of diastole. The major findings of this investigation was that the left ventricular wall of boys with DMD thinned at a slower rate than that of normal subjects. This new technique appears to be sensitive and demonstrates subtle changes in the left ventricular posterior wall.

Adolescent↗
PubMed1979

Surveillance of nosocomial infections by antibiotic monitoring.

Records of all patients receiving intravenous gentamicin sulfate during a 92-day interval were reviewed to detect nosocomial infections that had been missed by routine surveillance. Only 46 of 48 of the 99 treatment courses had been detected. In 96% of cases not detected by routine surveillance, use of gentamicin was considered justified. Of the patients missed by surveillance, 83% were in oncology wards, and 46% had severe neutropenia and fever of unknown origin. Antibiotic surveillance proved a useful adjunct in estimating the incidence of nosocomial infections in such patients.

Anti-Bacterial Agents↗
PubMed1976

Thyroid-stimulating hormone binding to beef thyroid membranes. Role of N-acetylneuraminic acid.

The effect of sugars on 125I-thyroid-stimulating hormone binding to beef thyroid membranes was studied to determine their role in thyroid-stimulating hormone (TSH) binding. At 0.1 M concentration, N-acetylneuraminic acid produced a 3- to 7-fold increase in TSH binding, was the only sugar to enhance TSH binding, and did so whether binding was determined in the cyclase medium or under conditions of optimum binding. The enhanced TSH binding remained after the membranes were removed from the high NeuAc concentration and an effect was observed at concentrations of 10 mM NeuAc. NeuAc did not alter the kinetics of TSH binding but the pH optimum for TSH binding shifted from pH 5.5 to 7.5 in the presence of NeuAc. Incubation of the membranes with increasing concentrations of NeuAc resulted in increased sialic acid content of the membranes. The NeuAc concentration curve of membrane sialic acid and TSH binding were roughly parallel. The capacity of the low affinity site increased from 0.74 to 2.5 nmol/mg of protein in the presence of NeuAc. The apparent affinity (0.88 X 10(6) M-1) of this site was unaffected by NeuAc. With the high affinity site, NeuAc increased both the apparent affinity and capacity from 2.2 X 10(8)M-1 to 5.5 X 10(8) M-1 and 1.6 to 3.1 pmol/mg of protein, respectively. Neuraminidase or neuraminidase plus beta-galactosidase incubation of the membranes removed approximately 60% of the sialic acid from the membranes within 15 to 30 min but did not affect TSH binding. Large quantities of sialic acid were detected in the soluble fractions during isolation of the membranes, 4 to 5% of which was ultrafilterable and not associated with high molecular weight proteins. It is concluded that among the sugars tested, NeuAc exhibits an unique effect on TSH binding that may have physiological significance. The inability to alter TSH binding by enzymatic removal of endogenous sialic acid suggests that either NeuAc resistant to hydrolysis is sufficient to maintain TSH binding or that NeuAc important in TSH binding is removed during membrane preparation but is replaced by incubation with exogenous NeuAc.

Animals↗
PubMed1975

In situ preservation of cadaver kidneys for transplantation: laboratory observations and clinical application.

Many kidneys obtained from cadaver donors undergoing sudden cardiac arrest cannot be transplanted due to the long periods of warm ischemia from the moment of arrest to nephrectomy. A double-ballon-triple-lumen catheter for the rapid in situ preservation of cadaver kidneys has been designed. Used in combination with equipment routinely found in any hospital, it can cool human kidneys in situ to 10-15 C and maintain this temperature until nephrectomy can be performed. Kidenys preserved with this catheter have functioned after transplantation into suitable recipients. This report describes the design and laboratory evaluation of this new device, its clinical effectiveness and technique of insertion.

Adolescent↗
PubMed1974

Squid axon membrane response to white noise stimulation.

The current from a white noise generator was applied as a stimulus to a space-clamped squid axon in double sucrose gap. The membrane current and the voltage response of the membrane were then amplified, recorded on magnetic tape, and the stimulus was cross-correlated with the response. With subthreshold stimuli, a cross-correlation function resembling that obtained from a resonant parallel circuit is obtained. As the intensity of the input noise is increased, the cross-correlation function resembles that obtained from a less damped oscillatory circuit. When the noise intensity is further increased so that an appreciable frequency of action potentials is observed, an additional component appears in the experimental cross-correlogram. The subthreshold cross-correlogram is analyzed theoretically in terms of the linearized Hodgkin-Huxley equations. The subthreshold axon approximates a parallel resonant circuit. The circuit parameters are temperature dependent, with resonant frequency varying from approximately 100 Hz at 10 degrees C to approximately 250 Hz at 20 degrees C. The Q(10) of the resonant frequency is equal to 1.9. These values are in agreement with values found previously for subthreshold oscillations following a single action potential.

Acoustic Stimulation↗