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Biomedical subjects

C K Colton

Publications and source records attributed to C K Colton.

At least 55 records · Page 3Linked to original sources
PubMed1987

Absolute quantitative autoradiography of low concentrations of [125I]-labeled proteins in arterial tissue.

We developed a method for absolute quantitative autoradiographic measurement of very low concentrations of [125I]-labeled proteins in arterial tissue using Kodak NTB-2 nuclear emulsion. A precise linear relationship between measured silver grain density and isotope concentration was obtained with uniformly labeled standard sources composed of epoxy-embedded gelatin containing glutaraldehyde-fixed [125I]-albumin. For up to 308-day exposures of 1 micron-thick tissue sections, background grain densities ranged from about two to eight grains/1000 micron 2, and the technique was sensitive to as little as about one grain/1000 micron 2 above background, which correspond to a radioactivity concentration of about 2 x 10(4) cpm/ml. A detailed statistical analysis of variability was performed and the sum of all sources of variation quantified. The half distance for spatial resolution was 1.7 micron. Both visual and automated techniques were employed for quantitative grain density analysis. The method was illustrated by measurement of in vivo transmural [125I]-low-density lipoprotein [( 125I]-LDL) concentration profiles in de-endothelialized rabbit thoracic aortic wall.

Animals↗
PubMed1983

Transmural [125I]albumin concentration in the rabbit aorta during acute hypoxia.

We have quantified the concentration profile of 125I-labeled rabbit albumin in the avascular intima and media of the rabbit descending thoracic aorta following intravenous injection under control and acute hypoxic conditions in vivo. Our purpose was to determine if alterations occurred in the transmural concentration profiles which could be attributed to hypoxia-induced changes in the permeability of the intimal endothelium to plasma-borne macromolecules. The profiles were obtained with frozen serial sections of the aorta from experiments of 30 min duration. Acute hypoxia was induced by addition of nitrogen to the breathing mixture. The hypoxia resulted in arterial pO2 values of 23--32 mm Hg while the arterial pO2 in the control animals ranged from 80 to 88 mm Hg. All animals were under sodium pentobarbital anesthesia. The results revealed no detectable changes in the concentration profile in the inner media accompanying hypoxia. However, increases in the label concentration in the outer media of the hypoxic animals suggested either dilation or increased permeability of the adventitial blood vessels.

Animals↗
PubMed1983

Rabbit aortic medial thickness under relaxed and specified simulated in vivo conditions.

A method is presented for measuring the thickness of the intima-media layer of the normal rabbit descending thoracic aortic wall under both relaxed (excised) and specified simulated in vivo conditions. The in vivo conditions were simulated by maintaining the aorta in situ at its normal longitudinal extension while perfusing its lumen at the normal mean arterial pressure with a mixture of liquid silicone polymer and a catalyst, thus providing physiological radial distension. After the rubber cured, both relaxed and extended-distended tissue segments were obtained from adjacent sites on the same aorta. These tissue segments were fixed and further processed for measurement of their medial thicknesses by light microscopy. This data was used to estimate the ratio of the medial thickness of the relaxed, excised aorta to that under in vivo conditions, 1.72 +/- 0.15. This information is required for quantitative analysis of data obtained from previous studies of in vivo macromolecular transport across the rabbit thoracic aortic wall.

Animals↗
PubMed1982

The effect of angiotensin II on in vivo albumin transport in normal rabbit aortic tissue.

Angiotensin II and other vasoactive amines may have a direct effect on the permeability of the arterial wall. We have investigated the effect of angiotensin II in vivo albumin transport across the aortic wall in rabbits following intravenous injection of [125I]albumin. Transmural concentration profiles of 125I-labeled albumin across the intima and media of the aorta, generated during 25 min of either angiotensin or saline infusion, were measured by a serial-sectioning technique. The uptake of labeled albumin through the aortic wall was found to be dependent on position and to increase from the descending thoracic up to the arch. Angiotensin infusion increased albumin uptake in the region of the aorta proximal to the first pair of intercostal arteries and magnified the position dependence. Angiotensin infusion did not change the uptake of albumin in the descending thoracic aorta between intercostal arteries. The arterial blood pressure elevation associated with angiotensin infusion was not of prime importance in producing the uptake patterns described above.

Angiotensin II↗
PubMed1979

The development of an implantable electrochemical glucose sensor: response to glucose in bovine serum ultrafiltrate.

A glucose sensor based on organic oxidation reactions at a platinum electrode is being developed as the key component for an implantable artificial beta cell for diabetic patients. Sensitivity of a membrane-covered platinum electrode to changing glucose concentration in bovine serum ultrafiltrate has been demonstrated, with current response as high as 60 microamperes per 100 mg/dl change in glucose concentration. Reproducibility of measurements probably will depend on satisfactory mechanical assembly of the membrane-electrode combination. An approach to selectivity based on multiple current measurements is suggested.

Animals↗
PubMed1979

Distribution of glycosaminoglycans in consecutive layers of the rabbit aorta.

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.

Animals↗
PubMed1978

Purification of acetate kinase by affinity chromatography.

A one-step procedure using affinity chromatography has been shown to purify to apparent homogeneity acetate kinase from a commercially available preparation and to partially purify the enzyme from a crude, cell-free extract. Since the gel's capacity for enzyme adsorption is controlled by the thermodynamics of ligand-enzyme interaction, maximization of the adsorption isotherm was attempted. Enzyme adsorption decreased logarithmically with increasing ionic strength but increased with increasing concentration of MgCl2. These competing effects caused the net adsorption of enzyme to increase to a maximum and then to decrease as the MgCl2 concentration was raised. The results allow a significant improvement in affinity column performance and have important implications for scale-up procedures.

Acetate Kinase↗
PubMed1977

Artificial pancreas using living beta cells:. effects on glucose homeostasis in diabetic rats.

An artificial pancreas consisting of beta cells cultured on synthetic semipermeable hollow fibers was tested in rats with alloxan-induced diabetes. When implanted ex vivo as arteriovenous shunts in the circulatory system these devices lowered concentrations of plasma glucose from 533 to between 110 and 130 milligrams per 100 milliliters, increased concentrations of plasma insulin, and restored intravenous glucose tolerance tests essentially to normal.

Animals↗