Biomedical subjects
Publications and source records attributed to T A Massaro.
By virtually all criteria, the American health-care system has the largest and most widely distributed technology base of any in the world. The impact of this emphasis on technology on the cost of care, the rate of health-care inflation, and the well-being of the population is reviewed from the perspective of the patient, the provider, and the public health analyst.
Transmural variations in various glycosaminoglycan (GAG) fractions were determined in adventitia-free thoracic aortas from rabbits. Total glycosaminoglycan concentration decreased from intima to outer media. These data are similar to total GAG concentration in bovine and human aortas as reported by others. There is a marked decrease in the concentration of the combined chondroitin sulfate-dermatan sulfate component with increasing distance from the endothelial surface. These transmural differences are linked to the possible variation of the diffusion coefficient of a diffusing solute as a function of distance, which can affect the concentration profile of the solute.
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Evaluation of a new system, based on gas chromatography, providing arterial blood gas tensions without requiring drawn blood samples is continued in an animal model. A series of in vivo dog experiments is discussed evaluating flow dependence and other performance characteristics. Results confirm the laboratory bench performance reported earlier; clinical trials are now indicated.
The water flux through preparations of porcine aorta has been investigated. After an initial unsteady period a stable flux of approximately 2 mul/cm2-h was reached and this flux rate remained constant for several hours. Under the experimental conditions which were maintained (110 mm Hg pressure drop across a 2 mm thick section of tissue) this total flux corresponds to a hydraulic conductivity of less than or equal to 7.0 X 10(-13) cm4/dyne-sec. Since these data were obtained in tissue samples where the endothelial layer was not intact, they represent values which are in fact larger than the actual in vivo condition where the endothelial barrier would serve as an additional resistance. Thus, they demonstrate that the transmural flux of water across the aorta wall in vitro due to a pressure gradient is extremely small and, therefore, that other mass transfer mechanisms may be significant.
The swelling properties of isolated swine arterial tissue have been studied to determine their effect on diffusion and hydraulic permeability measurements. Tissue potassium and sodium content were also measured to obtain an index of tissue metabolic activity. When oxygen and glucose were present in the incubation medium, a 5% decrease in tissue water content was observed over an incubation period of approximately 3.5 h. Under these conditions the tissue potassium content was higher and the sodium content was lower than when oxygen and/or glucose were omitted from the medium. When both oxygen and glucose were omitted, the potassium and sodium levels were significantly altered, suggesting a disturbance in the sodium-potassium transport system due to depletion of necessary metabolities.
Measurements of the extracellular space (ECS) of the isolated swine thoracic aorta were performed with both [14C]inulin and transient measurements and appeared to have better access to available tissue water than the [14C]sucrose gave more consistent results in available tissue water than the [14C]inulin. With [14C]sucrose as the tracer, no significant difference in the ECS was found when the tissue was incubated for 1.5 h in the presence of oxygen and glucose as compared to an incubation in which both oxygen and glucose were absent. However, the ion contents were markedly altered by this change in incubation medium. When oxygen and glucose were present tissue K+ was significantly higher and tissue Na+ was significantly lower than when these metabolites were deleted from the medium. Thus, significant alteration in ion content did not lead to substantial cell damage or bursting.
A new system providing near continuous arterial p02 and pCO2 measurements without requiring blood samples is described. Based on intra-arterial placement of a closed-tipped 2F catheter with gas chromatographic separation and analysis this system appears capable of providing rapid sensitive data with accuracy and precision equivalent to conventional bench analyzers. The initial in vitro experiments are discussed including flow and temperature dependency studies.
The diffusion coefficients of Ca2+ and H2O in in vitro porcine arterial tissue were determined to provide a measure of vascular permeability. The effect of anatomical location and diet on the magnitude of that permeability was evaluated. The diffusion coefficient of calcium was found to vary focally and, in addition, pulmonary artery was much more permeable than thoracic aorta. Four months feeding of a high lipid diet did not affect diffusive transport.
It has been suggested that the glycosaminoglycans (GAG) influence atherogenesis by regulating the permeability of the arterial wall. For this reason, a study has been made of the diffusive transport of Ca2+ and water across the in vitro porcine artery wall, where particular attention was focused on the influence of GAG content and distribution within the wall on the transport properties. The radioisotop-s 45Ca and 3HHO were used to measure the tracer-diffusion flux in a stirred, two chamber diffusion cell. GAG were isolated, fractionated using a cetyl pyridinium chloride-cellulose column procedure, and assayed using a colorimetric carbazole reaction for uronic acid. The biochemical analyses showed that the pulmonary artery contains significantly more hyaluronic acid and dermatan sulfate than found in two locations in the thoracic aorta. In addition, a significant regression was found for the diffusion coefficient of 45Ca2+ (99% level) and 3HHO (95% level) versus specific GAG fractions. The regression indicated an increase in permeability with increase in the ratio of sulfated: nonsulfated GAG.