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Biomedical subjects

J N Ross

Publications and source records attributed to J N Ross.

At least 37 records · Page 2Linked to original sources
PubMed1979

Quantification of thallium-201 scintigrams in acute myocardial infarction.

A method has been developed for measurement of myocardial infarct size from thallium-201 scintigrams that depends on computer measurement of levels of radioactivity in the myocardium. In 16 dogs, thallium-201 scintigrams were obtained in the left lateral and left anterior oblique projections 48 hours after ligation of the left anterior descending coronary artery. Scintigraphic results were obtained by two independent observers and were compared with tissue measurements of infarct volume calculated from thallium autoradiograms and nitro-blue tetrazolium (NBT)-stained tissue slices. Infarct volumes derived from tissue measurements were used to develop criteria for the computer scintigraphic technique. There was no significant difference in the scintigraphic measurements made by the two observers. Scintigraphic infarct size in the left lateral and left anterior oblique projections correlated with tissue infarct size with r values of 0.88 and 0.75, respectively, for thallium autoradiography and 0.71 and 0.70, respectively, for NBT tissue staining. The range of infarct volume was 3.3 to 14.8 percent of the left ventricular mass. Results of this study suggest that scintigraphic quantitation of infarct size is feasible in this dog model.

Acute Disease↗
PubMed1976

Oxidized orlon as a blood interface.

Polyacrylonitrile fabric (Orlon) may by oxidized by heating in air, when it becomes black and carbonized. During the heat treatment, the fibers shrink; this shrinkage allows components such as diaphrams to be shaped around molds. Oxidation reduces the tensile strength by about 25% and also reduces the stiffness of the material. The oxidized Orlons was screened in tissue culture for possible cytotoxic effects. Finding none, patches of the material were sutured into the right atrium of dogs and examined after 48 hr. Because of encouraging results, 10 atrial patches, consisting of Dacron velour and oxidized Orlon side-by-side, were implanted into the right atrium of dogs. Five patches were backed with Silastic to render them impervious, and five with segmented polyurethane. The atrial patches were examined after 48 hr, and in all instances the oxidized Orlon part of the patch was coated with a thinner and smoother fibrin layer than was the Dacron velour half. a left ventricular bypass pump was fabricated from oxidized Orlon and spray-coated on the nonblood surface with segmented polyurethane. After 48 hr implantation in the chest cavity of a calf, pumping without systemic anticoagulation, the pump was found covered by a thin, smooth, firmly attached layer of fibrin.

Acrylic Resins↗
PubMed1975

Systolic time intervals in domestic ponies: alterations in a case of coarctation of the aorta.

This report describes the measurement of systolic time intervals in a nine year old female domestic pony which was found at necropsy to show coarctation of the aorta and bilateral ventricular hypertrophy. Electrocardiogram, phonocardiogram and direct arterial blood pressure were recorded from the pony in a standing unmedicated state and systolic time intervals were measured from the resulting tracings. A prolongation of left ventricular ejection time and shortening of the pre-ejection period were observed in comparison to a group of normal ponies similarly examined. Such changes are consistent with outflow tract obstruction. The pony was also hypotensive and this condition was interpreted as a long-term compensation for the obstructive lesion. It is likely that the changes in systolic time intervals were at this stage predominantly affected by the hypotension. The report notes that the existence of such a case of spontaneous cardiovascular disease in the pony population might suggest the utility of the animal as a resource in comparative cardiovascular physiology and medicine.

Animals↗
PubMed1975

Cerebral effects of profound hypothermia (18 degrees C) and circulatory arrest.

Clinical use of profound hypothermia and total circulatory arrest has been accompanied by occasional postoperative neurological abnormalities. In a series of infant baboons, surface cooling to 32 degrees C (brain) followed by perfusion cooling by cardiopulmonary bypass with a membrane oxygenator and heat exchanger to 18 degrees C was carried out, after which the circulation was stopped for 30 minutes. The animal was rewarmed to 35 degrees C. Marked alterations in the regional cerebral circulation were observed during perfusion cooling and rewarming. Regional cerebral ischemia was negatively correlated with jugular outflow (total cerebral blood flow) during rewarming, while regional hyperemia showed positive correlation both following perfusion cooling and after rewarming. A higher degree of ischemia in brain ischemic samples was found during rewarming than during cooling. These alterations in regional cerebral perfusion were associated with lactacidosis and hyperglycemia after rewarming, and may be considered potentially responsible for posthypothermic cerebral dysfunction.

Animals↗