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Biomedical subjects

G M Davidson

Publications and source records attributed to G M Davidson.

10 recordsLinked to original sources
PubMed2001

The dynamics of blood-brain barrier breakdown in an experimental model of glial cell degeneration.

This study was undertaken to investigate the dynamics of blood-brain barrier breakdown in an in vivo rat model of selective CNS vulnerability. 1,3-Dinitrobenzene was used to induce rapid glial degeneration in highly defined areas of the brainstem. Leakage of fluorescent dextran was used to demonstrate the breakdown of the blood-brain barrier, and antibodies to glial and neuronal specific proteins to assess the accompanying cell changes. Beginning 18 h after a toxic dose of dinitrobenzene and before loss of glial ensheathment, a sub-population of blood vessels became permeable to fluorescent dextrans below 500,000 mol. wt in size. By 24h most macroglial cells had been lost from within susceptible areas and vascular leakage had reached peak levels. Macrophage invasion was detected three days following dinitrobenzene. Vessels continued to leak up to four days after the lesion was formed, but by six days blood-brain barrier integrity was largely re-established. Multiple tracer injections over time demonstrated that a single sub-population of vessels was leaking during the experimental period. From these findings we conclude that blood-brain barrier breakdown in this model system is highly selective, graded in extent and molecular weight specificity and not a direct consequence of astrocyte degeneration or microglial activation. This system could be useful in modeling human CNS pathological processes with a vascular component and for understanding in vivo glial blood-brain barrier interactions.

Animals↗
PubMed2001

Infusion of volatile flavor compounds into low-density polyethylene.

Supercritical fluids can extract components from some matrixes (e.g., fat and flavors from food) as well as infusing additives into synthetic polymer matrixes. To study the feasibility of infusing flavors into matrixes as a potential flavoring mechanism, a wide range of volatile flavor compounds was infused into a well-defined synthetic polymer (low-density polyethylene) using supercritical carbon dioxide. The polymer was then extracted, and the amount of infused compound was determined. The effects of time, temperature, pressure, rate of depressurization, volatile concentration, and volatile properties on the degree of infusion were studied. Infusion with supercritical carbon dioxide achieved much higher loadings of the polymer (0.01 to 6.87 mg/g LDPE, depending on the volatile molecule being infused) compared to those achieved by static diffusion. Forty-five volatiles were infused, from which a model was developed to predict infusion as a function of certain physicochemical properties.

Chemical Phenomena↗
PubMed1977

Radiation exposure in xeroradiography of the breast.

A survey of the radiation exposure during xeroradiography of the breast for normal clinical exposures is presented. Average values obtained from the measurements made on a number of patients are presented and compared with measurements made by other workers. An estimate of the radiation dose received by the breast during the clinical exposures is also made and the parameters affecting the doses are discussed.

Breast↗
PubMed1977

Intra-operative fluid and electrolyte requirements.

The intravenous administration of Hartmann's solution at a rate sufficient to maintain the hourly urine volume between 0.5 and 1.0 ml/kg/hr is recommended during major operations. Intra-operative extracellular volume expansion followed by the administration of sodium containing fluids for 48 hours postoperatively decreases the incidence of haemodynamic instability and acute renal failure and results in normal water and sodium excretion by the kidney throughout the peri-operative period. Abnormal extracellular volume may exist prior to induction of anaesthesia particularly in patients with pre-existing cardiovascular, renal and hepatic disease. In these patients the suggested fluid regime should be administered with care and may require diuretic therapy. If the operative blood loss in adults is less than one litre, no blood may be necessary. If the loss is between one and 2 litres packed red cells may be sufficient, whereas with a greater loss, filtered whole blood, coagulation factors and platelet infusions may be required. When possible, transfusions of stored autologous blood is recommended for elective operations.

Blood Transfusion↗