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Biomedical subjects

J C Weaver

Publications and source records attributed to J C Weaver.

70 records · Page 4Linked to original sources
PubMed1988

Electroporation: high frequency of occurrence of a transient high-permeability state in erythrocytes and intact yeast.

We present the first determinations of population distributions of macromolecule uptake due to electroporation, the percentage of cells which participate and, for the yeast, the subpopulation of cells whose membranes exhibit significant recovery following macromolecule uptake. Flow cytometry is used to measure the uptake of a first test molecule (green fluorescence, FITC-dextran; 70 kDa) and also, for the yeast, the subsequent uptake of a second, much smaller, test molecule (red fluorescence, propidium iodide; 660 Da), which provides a measure of membrane recovery. A dramatic 20% (erythrocytes) to 75% (intact Schizosaccharomyces pombe) of cells can take up the first test molecule within 5 min of a pulse.

Cell Membrane Permeability↗
PubMed1985

Enzyme electrodes and related technologies.

The technical outlook is promising for miniature analytical systems which are internally complex but externally simple. Salient features to be anticipated are: The use of miniature electrodes or other sensors in combination with enzymes or immunological compounds for biochemical specificity. The use of arrays of miniature electrodes or other sensors. Relatively low cost because of adaptation of semiconductor fabrication techniques. The attendant possibility of the devices being disposable. The intimate involvement of real time computation. The use of simultaneous replicate assays, with increased confidence in the accuracy of the assay. Overall, rapid assays. Because of these possibilities, it may be concluded that the technological outlook for conducting clinical chemistry assays nearer the patient is promising.

Chromatography, Gas↗
PubMed1984

Cardiac, thoracic, and abdominal pump mechanisms in cardiopulmonary resuscitation: studies in an electrical model of the circulation.

To investigate alternative mechanisms generating artificial circulation during cardiopulmonary resuscitation (CPR), an electrical model of the circulation was developed. Heart and blood vessels were modeled as resistive-capacitive networks; pressures in the chest, abdomen, and vascular compartments as voltages; blood flow as electric current; blood inertia as inductance; and the cardiac and venous valves as diodes. External pressurization of thoracic and abdominal vessels, as would occur in CPR, was simulated by application of half-sinusoidal voltage pulses. Three modes of creating artificial circulation were studied: cardiac pump (CP), in which the atria and ventricles of the model were pressurized simultaneously; thoracic pump (TP), in which all intrathoracic elements of the model were pressurized simultaneously; and abdominal pump (AP), in which the abdominal aorta and inferior vena cava of the model were pressurized simultaneously. Flow was greatest with the CP, less with the TP, and least with the AP mechanism. However, the AP could be practically combined with either the CP or TP by interposition of abdominal compressions between chest compressions (IAC-CPR). Our model predicts that this combined method can substantially improve artificial circulation, especially when cardiac compression does not occur and chest compression invokes only the thoracic pump mechanism.

Abdomen↗
PubMed1977

Protein, casein, and noncasein protein percentages in milk with high somatic cell counts.

More than 1000 milk samples of individual cows with somatic cell counts ranging from 20,000 to 20,000,000 per ml were analyzed by amido black dye binding for total protein, whey protein, and casein. Ten classes of varying somatic cell counts were established. The mean total protein percentage for normal samples (counts less than 500,000/ml) was 3.2% and different from all the other protein class means, ranging from 3.4 to 3.9%. Total protein content increased with somatic cell count. There was no significant difference among any of the ten classes for casein values. Whey protein percentages for normal samples were different from the rest. Whey protein content increased with somatic cell count.

Animals↗
PubMed1977

Pericardial drainage operations in the management of uremic pericardial effusion.

Because of frequent failures in nonoperative therapy, we have adopted early surgical drainage of the pericardium in the management of uremic pericardial effusion. This series presents the longest follow-up period of any group of patients with uremic pericardial effusion treated by surgical drainage. There have been no intraoperative deaths and no recurrences. The total hospital mortality rate was 8.3 per cent and the late mortality rate over a 72 month period was 25 per cent. Internal pericardiostomy drainage is a simple yet effective surgical solution to the life-threatening problem of uremic pericardial effusion.

Drainage↗
PubMed1976

Experiments and calculations concerning a thermal enzyme probe.

A simple device capable of measuring almost any reactant in an enzyme-catalyzed reaction is created when an enzyme is immobilized onto one thermal sensor of a differential thermometer. Experiments are described in which two thermistors, one bare and one coated with immobilized enzyme, are immersed in a well-stirred solution. The response of this device to increases in glucose-ATP concentration was observed using hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1), and to increases in glucose concentration using glucose oxidase (beta-D-glucose:oxygen 1-oxidoreductase, EC 1.1.3.4). A simple model is presented whose predictions are in reasonable agreement with the experimental results.

Enzymes, Immobilized↗
PubMed1976

Biochemical assay by immobilized enzymes and a mass spectrometer.

By counting the volatile molecules produced by an immobilized-enzyme catalyzed reaction which is interfaced to a mass spectrometer via a semi-permeable membrane, a general approach to biochemical measurement and detection is obtained which offers the potential of high sensitivity, specificity and speed. In combination with molecule microscopy, this method should allow, for example, a mapping of suitable enzyme distributions in non-stained and non-fixed tissue slices. Immobilized urease (urea amidohyrdrolase, EC 3.5.1.5) was used to assay urea using CO2 as the volatile product, and alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) was used to assay NADH using ethanol as the volatile product.

Alcohol Oxidoreductases↗
PubMed1973

The molecule microscope: a new instrument for biological and biomedical research.

We describe a new instrument, the molecule microscope, which reveals directly spatial variations in the rate of evaporation of molecules from surfaces by using neutral molecules instead of light or charged particles used in existing kinds of microscopes. The surface composition of the sample determines the binding energy of the evaporating molecules and, hence, the rate of evaporation, which also depends on permeability of the sample when the molecules come either from within or from the other side. We show first results obtained with our apparatus, discuss the design of an instrument now under construction with approximately 1-mum resolution, and describe briefly some more advanced versions under consideration with approximately 100-A resolution.

Animals↗