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C K Colton

Publications and source records attributed to C K Colton.

At least 19 recordsLinked to original sources
PubMed1992

Permeability of dialyzer membranes to TNF alpha-inducing substances derived from water bacteria.

Pro-inflammatory cytokine-inducing substances derived from cultured E. coli have previously been shown to pass across low-flux regenerated cellulosic dialyzer membranes. In the present study, a sterile filtrate of Pseudomonas maltophilia grown from standard bicarbonate dialysis fluid was used to test the permeability of various dialyzer membranes (regenerated cellulose, cellulose triacetate, polyacrylonitrile, polysulfone and polyamide) to TNF alpha-inducing bacterial substances. Pyrogen-free tissue culture medium (MEM) was recirculated for 60 minutes in the dialysate compartment of a closed-loop dialysis system, then P. maltophilia filtrate was added and recirculation was continued for a further hour. Samples from the dialysate (MEM) and the blood side (containing 10% human plasma in MEM) were incubated with donor mononuclear cells (MNC) for 18 hours and TNF alpha release was measured in MNC supernatants by radioimmunoassay. Five minutes after the addition of P. maltophilia filtrate, mean TNF alpha-inducing activity in the dialysate increased from (mean +/- SEM) 0.10 +/- 0.02 to 18.2 +2- 1.5 (ng/2.5 x 10(6) MNC/18 hr). TNF alpha-inducing activity in the blood side increased with regenerated cellulose from 0.10 +/- 0.01 to 4.57 +/- 1.55 (N = 8; P less than 0.001); with cellulose triacetate from 0.20 +/- 0.05 to 0.44 +/- 0.10 (N = 5; P less than 0.05), and with polyacrylonitrile from 0.10 +/- 0.02 to 1.16 +/- 0.45 (N = 5; P less than 0.03). No increased TNF alpha-inducing activity was observed in the blood side of polysulfone (N = 5) or polyamide dialyzers (N = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Complement C5a↗
PubMed1992

Topographical mapping of sites of enhanced HRP permeability in the normal rabbit aorta.

The spatial distribution of sites of enhanced permeability to the macromolecule horseradish peroxidase (HRP) in the normal rabbit aorta after one min circulation was studied using image analysis. These sites, referred to as "HRP spots," exhibit a nonuniform distribution that is qualitatively similar in all rabbits studied. The density of HRP spots is highest in the aortic arch, decreases distally, reaches a minimum in the lower descending thoracic aorta, and then increases again in the abdominal aorta. The region of highest spot density follows a clockwise helical pattern in the aortic arch and outside the arch occurs in streaks largely oriented in the bulk flow direction. The streaks in the abdominal aorta localize along the anatomical right lateral wall and occasionally along the left lateral wall proximal to the celiac artery and along the ventral wall between the celiac and superior mesenteric arteries. The density of spots is high in the immediate vicinity of aortic ostia with the most elevated density being distal to ostia in most cases. At a short distance from the ostium edge of the celiac and superior mesenteric branches the proximal density is comparably high, and no preferred spot orientation is observed around the brachiocephalic vessel. These results are consistent with an influence of localizing factors such as detailed hemodynamic phenomena and/or arterial wall structural and/or functional variations.

Animals↗
PubMed1991

Determining molecular weight distributions of antigen-antibody complexes by quasi-elastic light scattering.

Physiological properties of soluble antigen-antibody (Ag-Ab) complexes depend in part on the size of the complexes. In previous work, the size distribution and structure of model Ag-Ab complexes were determined by electron microscopy. In this study, we used constrained regularization analysis of quasi-elastic light scattering data to estimate molecular weight distributions of model Ag-Ab complexes. A conformational model was necessary to determine appropriate correlations between molecular weight and diffusion coefficient, and to estimate particle structure factors. Porod-Kratky theory proved to be an adequate conformational model for these purposes. The molecular weight distributions determined by constrained regularization compared favorably with distributions obtained either by electron microscopy or by thermodynamic modeling.

Animals↗
PubMed1991

Bioengineering in development of the hybrid artificial pancreas.

The hybrid artificial pancreas for treatment of diabetes consists of insulin-secreting pancreatic tissue which is surrounded by a membrane that protects the tissue from rejection by the immune system following implantation. In this paper, we review the alternative therapeutic approaches for diabetes under study and then discuss the technical requirements that must be met by a hybrid device useful to humans. Previous work on intravascular and extravascular immunoisolation devices is reviewed from the standpoint of these requirements, and three critical unresolved issues are discussed: biocompatibility, oxygen supply limitations, and prevention of immune rejection.

Animals↗
PubMed1990

Size and structure of antigen-antibody complexes: thermodynamic parameters.

The role of antigen-antibody (Ag-Ab) complexes in the immune response depends, in part, on the size of the complexes. Previously, we combined electron microscopy with classical and quasi-elastic light scattering to characterize the molecular weight distribution and the conformation of Ag-Ab complexes made from bovine serum albumin (BSA) and pairs of anti-BSA monoclonal antibodies at a single concentration and Ag:Ab molar ratio. In this report, the molecular weight distribution of Ag-Ab complexes was determined by classical light scattering at a single Ag:Ab ratio and over a range of concentrations, and binding of BSA to pairs of MAb was determined by radioimmunoassay at several Ag:Ab molar ratios. A thermodynamic model was developed for the equilibrium size distribution of Ag-Ab complexes formed between a pair of MAb, each with unique affinity and specificity, and an Ag containing a single epitope for each of the pair of MAb. The combined experimental data were used in conjunction with the model to determine the values of cyclization and polymerization constants. Successful determination of the parameters required data from both classical light scattering and electron microscopy. Cyclization constants were lower than those reported in other studies of Ag-Ab complexes; this may be attributable to our use of a protein Ag, as compared to a divalent hapten. In two out of three cases, cyclization constants increased with increasing number of Ab in the complex, in contrast to previous assumptions. The validity of the thermodynamic model was further shown by its ability, in combination with conformational and hydrodynamic model, to predict the hydrodynamic radius of the complexes over a wide range of experimental conditions.

Animals↗
PubMed1989

Low-density lipoprotein transport in blood vessel walls of squirrel monkeys.

Transmural accumulations of low-density lipoprotein (LDL) were examined in the blood vessel walls of four squirrel monkeys. Vascular wall concentrations of LDL were measured using quantitative autoradiography after 125I-labeled LDL circulation for 30 min. Profiles of relative tissue concentration from different sections in the same region were similar to each other, and there was little animal-to-animal variation. Concentrations were highest near the luminal endothelium, lower near the medial-adventitial border, and lowest within the media. Profiles from different regions fell into three groups: 1) aortic samples had steep intimal concentration gradients and near-zero media concentrations; 2) the iliac, femoral, popliteal, and common carotid arteries had higher intimal concentrations than group 1 but had similar concentrations deep within the media; and 3) the cerebral and coronary arteries, inferior vena cava, and pulmonary artery had intimal concentrations that were similar to group 2, but the concentrations deep within the media were greater than either groups 1 or 2. Arterial bifurcation profiles from the inner wall and the outer walls were similar to each other and to profiles from the upstream and downstream areas. Out of 280 total sites examined, 15 examples of profiles with substantially increased concentrations near the luminal endothelium were found scattered throughout the cardiovascular system, demonstrating that there are focal regions throughout the cardiovascular system which have greatly increased 125I-LDL transendothelial permeability.

Animals↗
PubMed1989

Is the rise in plasma beta-2-microglobulin seen during hemodialysis meaningful?

Beta 2-Microglobulin (beta 2M) plasma levels and levels of a second low-molecular-weight protein (myoglobin) were studied during a 2- to 4-hour sham dialysis period (no dialysate flow, no weight loss) and during a 4- to 5-hour hemodialysis (HD) with a Cuprophan capillary dialyzer. While no rise of the beta 2M or myoglobin levels occurred during sham dialysis, a rise of 22.1 +/- (SD) 8.5% (beta 2M) or 19.9 +/- 12.1% (myoglobin) was seen during regular HD. The increases of both molecules showed a significant correlation (r = 0.44; p less than 0.03). Both rises could not be completely abolished using correction factors for hemoconcentration. The rises occurred irrespectively of the dialysate buffer. The results suggest that neither the Cuprophan membrane nor the extracorporeal circuit were responsible for the rise of both molecules during HD. It seems more likely that changes of the extracellular volume and extra- to intracellular water shifts are involved and account for the majority of the rise. However, the possibility of minor increase in the extracellular mass of beta 2M or myoglobin cannot be excluded completely.

Adolescent↗
PubMed1989

Staphylococcal protein A adsorption in neoplastic disease: analysis of physicochemical aspects.

Staphylococcus aureus organisms and immobilized Staphylococcal protein A have been used as extracorporeal immunoadsorbents for the treatment of neoplastic disease. In a significant number of cases, a biologic response has been documented. This review analyzes the experimental results to date, correlates experimental design parameters with response to treatment, and discusses possible mechanisms of action. The evidence implicates protein A as the tumoricidal agent, although bacterial or complement components may act independently or synergistically. A more quantitative and fundamental approach is needed to exploit the potential for protein A immunoadsorption in treating neoplastic disease.

Adsorption↗
PubMed1988

Monoclonal antibodies to bovine serum albumin: affinity and specificity determinations.

A panel of 12 monoclonal antibodies (MAb) to bovine serum albumin (BSA) was developed and characterized as to their physiochemical and immunological properties. Affinity constants of the MAb varied over a wide range from 10(5) to 10(8) M-1. MAb were assembled into several groups of non- or minimally interacting antibodies by analysis of competitive binding experiments, and BSA domain and subdomain specificities of the MAb were assigned by analysis of results of MAb binding to purified BSA fragments. Further fine specificity delineation was accomplished by examination of cross-reactivity patterns to several mammalian albumins. The data suggest that some of the low affinity MAb recognize sites on different portions of the BSA molecule, indicating that similar epitopes exist on different domains of the BSA molecule.

Animals↗
PubMed1988

Quasi-elastic light scattering of antigen-antibody complexes.

Many biological properties of immune complexes (IC) depend upon their size. Quasi-elastic light scattering (QLS) was used to measure a mean equivalent hydrodynamic radius (Rh) and variance of the distribution of model IC composed of bovine serum albumin (BSA) as antigen (Ag) and combinations of two or three well-characterized monoclonal antibodies (MAb) which bound noncompetitively to unique epitopes on BSA. With the molar ratio (X) of each MAb to Ag fixed, Rh increased with concn. Rh was maximal at equivalence (X = 0.5) with two MAb and at slight MAb excess (X = 0.67) with three MAb. The largest Rh with two MAb was about 200 A, and Rh was uniformly different amongst the three combinations of two MAb IC. The largest hydrodynamic radius of individual complexes which formed with two MAb was estimated to be about 400 A; even larger individual complexes were formed with three MAb. Size changes following alteration of solution concns were also followed with QLS. Kinetics of two MAb IC association were too fast to observe; dissociation following large dilution (40-fold) required 5-10 min to attain a new steady state, much less at small dilution. With three MAb, Rh dropped sharply in 5 min and became steady after 1-2 hr. These results suggest that conventional chromatographic and ultracentrifugation techniques for studying IC size, involving large dilution and long measurement time, provide misleading results. Association of three MAb produced a rapid initial increase of Rh in several min, followed by diverse behavior which depended upon concn. From high to low concn, these included (1) exponential growth of Rh with time and appearance of visible macroscopic particles; (2) metastable states for several hr followed by slow growth to large size over several days, leading to formation of particles; and (3) rapid growth to steady state conditions with no visible particles. This heretofore unobserved equilibrium and kinetic behavior of model IC in solution may be reflected in the behavior of more complex, naturally occurring IC.

Animals↗
PubMed1988

Size and structure of antigen-antibody complexes. Electron microscopy and light scattering studies.

Size parameters of model antigen-antibody (Ag-Ab) complexes formed by the interaction of bovine serum albumin (BSA) and pairs of monoclonal anti-BSA antibodies (mAb) were evaluated by quasielastic light scattering, classical light scattering, and electron microscopy (EM). Mean values for the hydrodynamic radius, radius of gyration, and molecular weight were determined by light scattering. Detailed information regarding the molecular weight distribution and the presence of cycles or open chains was obtained with EM. Average molecular weights were calculated from the EM data, and the Porod-Kratky wormlike chain theory was used to model the conformational behavior of the Ag-mAb complexes. Ag-mAb complexes prepared from three different mAb pairs displayed significantly different properties as assessed by each of the techniques employed. Observations and size parameter calculations from EM photomicrographs were consistent with the results from light scattering. The differences observed between the mab pairs would not have been predicted by idealized thermodynamic models. These results suggest that the geometric constraints imposed by the individual epitope environment and/or the relative epitope location are important in determining the average size of complexes and the ratio of linear to cyclic complexes.

Antibodies, Monoclonal↗
PubMed1988

Electrocatalytic glucose sensor.

High surface area platinum subjected to the appropriate electrical potential cycling regimes exhibits considerable electrocatalytic activity towards glucose oxidation. We have developed a special data processing method, the compensated net charge (CNC) method, to take advantage of the electrocatalytic activity of platinum. This method involves the determination of the net oxidation charge during one complete cycle of a cyclic voltammogram applied to the platinum electrode in a potentiodynamic mode. Under these conditions, the electrode response is very sensitive to glucose, completely insensitive to urea, and only moderately sensitive to amino acid concentration changes. Earlier work with other endogenous and exogenous potential co-reactants shows little interference. Data obtained in vitro and in vivo will be presented and discussed.

Animals↗
PubMed1988

Measurement of 125I-low density lipoprotein uptake in selected tissues of the squirrel monkey by quantitative autoradiography.

A recently developed technique of absolute quantitative light microscopic autoradiography of 125I-labeled proteins in biologic specimens was used to measure 125I-low density lipoprotein (125I-LDL) concentration levels in various tissues of the squirrel monkey after 30 minutes of in vivo LDL circulation. Liver and adrenal cortex exhibited high 125I-LDL concentrations, presumably because of binding to specific cell surface receptors and/or internalization in vascular beds with high permeability to LDL. High tissue concentrations of LDL were associated with the zona fasciculata and reticularis of the adrenal cortex and the interstitial cells of Leydig in the testis; significantly lower levels of 125I-LDL were observed in the adrenal medulla, the zona glomerulosa, and germinal centers of the testis. Contrary to previous reports, low 125I-LDL concentrations were observed throughout the gastrointestinal tract and in lymph nodes. In addition, multiple arterial intramural focal areas of high 125I-LDL concentrations were identified in arteries supplying the adrenal gland, lymph node, small bowel, and liver.

Adrenal Glands↗
PubMed1987

Endothelial cell perturbation and low-density lipoprotein. Quantitative autoradiography.

The focal entry and accumulation of LDL within the arterial wall of the normal animal may represent an early stage in the development of the atherosclerotic plaque. Concentrations of LDL 10 to 100 times normal medial concentrations might be difficult to clear from the arterial wall, permitting accumulation of lipid. Elevated LDL concentrations, in proximity to smooth muscle cells, appear to stimulate SMC proliferation. High LDL concentrations might also enhance mononuclear cell adhesion to endothelium. Since LDL has a high affinity for heparin and heparin for growth factors, LDL accumulation may be a mechanism for the concentration of such materials in the intima. The observation of markedly enhanced macromolecular permeability foci could be related to several potential mechanisms of initiation of atherosclerosis. This observation is of particular note when the focal occurrence of atherosclerosis is considered. Although atherosclerosis is seen as a generalized thickening of the intima, it is the focal narrowing of the lumen that is often responsible for the stenosis which produces symptoms such as angina or myocardial infarction.

Animals↗
PubMed1987

Analysis of membrane processes for blood purification.

Physical phenomena play an important role in membrane processes for blood purification. They largely determine the separation performance of these devices and they interact with chemical and biological phenomena to determine their biocompatibility, or lack thereof, in the clinical setting. In the first part of this paper, analyses of physical phenomena which determine the separation and purification characteristics are reviewed for several processes, including hemodialysis, hemofiltration, combined hemodialysis and ultrafiltration, and membrane plasmapheresis with cross-flow microfiltration. Special attention is given to transport of high-molecular weight solutes in hemodialysis, for use in subsequent analyses, and to the factors which determine filtrate flux in membrane plasmapheresis, because recent findings in this area provide an understanding of filtration processes in general. The second part concerns the problem of biocompatibility, especially as manifested in renal prostheses. After reviewing some of the pathways to bioincompatibility, exploratory analyses are presented using relatively simple models. The objective of these analyses is to provide an initial quantitative framework for examining the likelihood of monocyte secretion of interleukin-1 being stimulated by various routes. Issues examined, for which illustrative calculations are presented, include (1) transport of endotoxin fragments across regenerated cellulose and other membranes, (2) anaphylatoxin C5a concentrations in conventional hemodialysis and (3) the effects of equilibrium and reaction phenomena, ultrafiltration, diffusive membrane permeation and membrane adsorption on the disposition of C5a which is generated at the membrane surface.

Animals↗