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Biomedical subjects

C A Nelson

Publications and source records attributed to C A Nelson.

At least 109 records · Page 6Linked to original sources
PubMed1984

Evolution of low density lipoprotein structure probed with monoclonal antibodies.

To assess the relationship of apoB structures in different species of animals, the expressions of apoB epitopes in the sera or plasmas of 23 different mammalian species and one marsupial, and on the low density lipoprotein (LDL) from three species of apes, six species of monkeys, and eight non-primates were measured in competitive radioimmunoassays. The abilities of the sera or LDL to compete with 125I-labeled human LDL for binding to seven monoclonal antihuman LDL antibodies immobilized on microtiter plates were determined. LDL of apes bound to most antibodies, while monkey LDL bound to two or three antibodies. Other mammalian LDL bound only weakly to two of the antibodies or to none. The two monoclonal antibodies binding the LDL of more species were those antibodies which also inhibited the binding to and degradation of LDL by human fibroblasts. The rank order of binding of the LDL of a given species to the antibodies correlated with the rank order inhibition of binding and degradation of 125I-labeled human LDL in the human fibroblast system. This suggests that epitopes spatially located near the recognition site of apoB for cellular receptors have a greater tendency to be conserved.

Animals↗
PubMed1983

Human low density lipoprotein structure: correlations with serum lipoprotein concentrations.

Human low density lipoproteins (LDL) were isolated and purified from individuals having widely differing serum lipid concentrations. Very low density lipoproteins (VLDL) and high density lipoproteins (HDL) were also isolated and quantitated. HDL2 and HDL3 were separated by flotation velocity in the analytical ultracentrifuge and their relative weight percent determined. The mean density of LDL from 41 individuals was determined by flotation velocity at two different solvent densities. The mean density of LDL was directly proportional to the triglyceride (r = 0.65) and VLDL (r = 0.50) concentrations and inversely proportional to the HDL (r = -0.55) and HDL2 (r = -0.74) concentrations (all significant at P less than 0.001). The mean molecular weight of LDL from 42 individuals was determined by flotation equilibrium centrifugation. The mean molecular weight of LDL was directly proportional to the HDL (r = 0.49) and HDL2 (r = 0.48) concentrations and inversely proportional to the serum triglyceride (r = -0.60) and VLDL (r = -0.48) concentrations (all significant at P less than 0.005 except triglyceride--P less than 0.001). The molecular weight of LDL was inversely proportional to its density, and thus inversely proportional to its protein/lipid ratio which was confirmed by composition measurements. The density and molecular weight of LDL had no relationship to the concentration of LDL (r = 0.04 and 0.03).

Adult↗
PubMed1983

Effects of cholesterol feeding on primate serum lipoproteins. III. The change in high density lipoprotein components.

Sooty mangabey (Cercocebus atys) monkeys had a lower serum HDL cholesterol concentration than any other Old World monkey species reported. In addition, they had a higher serum Lp(a) concentration than other species. The mangabeys were fed a cholesterol-fat diet for 5 weeks. HDL2 and HDL3 amounts were determined from the two peaks apparent upon analytical ultracentrifugation. In the first 1-3 weeks, 13 of the 14 mangabeys increased 30% (mean) in total HDL, this increase occurring only in the HDL2 fraction. After 5 weeks, HDL and HDL2 decreased markedly. During the cholesterol feeding, HDL3 continually decreased in flotation rate, indicating it was either smaller and/or denser. HDL2 and HDL3 separated well on molecular sieving agarose columns during the diet period, whereas a single symmetrical elution peak was found for chow-fed HDL. Thus on a cholesterol-fat diet, HDL2 and HDL3 increased in difference in molecular size.

Aging↗
PubMed1983

Influence of a levonorgestrel-containing contraceptive vaginal ring on plasma lipids and lipoproteins in cynomolgus monkeys.

The effect of a contraceptive vaginal ring (CVR) containing levonorgestrel on plasma lipid and lipoprotein concentrations and characteristics was assessed in ten cynomolgus monkeys. The animals were fed a diet similar to the average American diet in fat (40% of calories) and cholesterol (0.2 mg/kcal) content. The objective of this study was to determine if changes in lipids and lipoproteins caused by progestogen administration parallel those seen in human females. A parallel pattern would recommend the cynomolgus monkey as a model for studying the effects of progestogens on the atherosclerotic process. Treatment with the CVR resulted in significant decreases in total plasma, VLDL + ILDL + LDL, and HDL cholesterol concentrations and a decrease in the percentage of HDL2 in total HDL. Plasma triglyceride concentrations were low throughout the study and consistent effects of the CVR were not seen. CVR treatment resulted in increases in TPC:HDL-C ratios and in the flotation rate of the LDL particle. The patterns of effects on HDL cholesterol, total plasma cholesterol, and HDL2 concentrations were similar to the progestogen-induced changes observed in human plasma lipids and lipoproteins. Based on these effects, the cynomolgus monkey appears to be a suitable model for the study of progestogen-induced changes in plasma lipids and lipoproteins and their consequent influences on coronary artery atherosclerosis.

Animals↗
PubMed1983

The perception of facial expressions and stimulus motion by two- and five-month-old infants using holographic stimuli.

3 experiments were conducted in which holograms of faces were used in an attempt to expand our current knowledge of infant face perception. 5-month-old infants in the first experiment were asked to discriminate a change in facial expression and pose displayed in a holographic stereogram that either moved or remained stationary. The experimental group did not show evidence of discrimination when compared to a control group. In addition, there was no preference on the part of infants to attend more to the moving face. 2-month-old infants were tested in a second experiment on an identical discrimination task, using only the moving hologram. Unlike the older infants, the 2-month-olds succeeded in discriminating the change in expression/pose. In the final experiment, the contributions of motion to face recognition were explored in 5-month-old infants using the same hologram as in the first 2 experiments. There was again no evidence to suggest that infants preferred (in any absolute sense) the moving face. There was strong evidence, however, that motion contrasts (i.e., the starting and stopping of motion), and not motion per se, facilitate face recognition. These results are discussed, as is the potential of using holography to study face perception and other perceptual skills in infancy.

Child Development↗
PubMed1982

Changes in the distribution and composition of plasma high density lipoproteins after ingestion of fat.

Following ingestion of a fatty meal there is an increase in concentration of phospholipids and proteins in the plasma high density lipoproteins (HDL). To evaluate the resulting changes in HDL subclasses, the plasma HDL of six subjects were analyzed 4 to 8 h after ingestion of 100 ml of corn oil or 80 ml of corn oil with four eggs. Isopycnic density gradient ultracentrifugation of fasting plasma showed two broad components of HDL: a major peak of density (d) 1.11 to 1.17 g/ml (HDL3) and a smaller peak of d 1.07 to 1.11 g/ml (HDL2). Following ingestion of either type of fatty meal, there was an increase in lipoprotein mass in both peaks of HDL and their centers of mass were shifted to lower density (1.140 leads to 1.120 to 1.130 g/ml; 1.095 leads to 1.090 g/ml). Calculation of changes in HDL concentration (lipemic minus fasting) showed that the alterations in density gradient profile were due to a major increase in lipoproteins of d 1.102 to 1.137 g/ml, a smaller increase in a separate lipoprotein peak of 1.080 to 1.102 g/ml, and a small decrease in lipoproteins of d 1.137 to 1.165 g/ml. Redistribution of HDL mass into larger, less dense lipoproteins was also demonstrated by agarose gel chromatography or by minimal spin density gradient ultracentrifugation in a vertical rotor. The increase in mass of 1.080 to 1.102 lipoproteins was largely due to increased concentrations of phospholipid, cholesterol ester, and apoA-I, while the increase in 1.102 to 1.137 lipoproteins was due to increased concentrations of apoA-I, apoA-II, phospholipids, cholesterol, and cholesterol esters. Analytical ultracentrifugation of representative samples within these density intervals showed lipoprotein species with molecular weights and sedimentation coefficients, respectively, of 378,000, 5.8 (d 1.080 to 1.095); 248,000, 3.5 (d 1.110 to 1.120); and 173,000, 1.6 (d 1.135 to 1.150). Polyacrylamide gradient gel electrophoresis showed that the 1.080 to 1.102 lipoproteins contained a single lipoprotein band of diameter approximately 10.7 nm; the 1.102 to 1.137 lipoproteins contained a single band which varied in size fro 10.0 to 9.2 nm: and the 1.137 to 1.165 lipoproteins contained three species of diameters approximately 9.2, 8.8, and 8.2 nm. Within density intervals, the molecular weights, sedimentation coefficients, and diameters of the different lipoproteins were similar in fasting and lipemic plasma. Calculation of average molecular compositions shows that the major incremental HDL of d approximately 1.12 g/ml could be derived by addition of lipids to the largest species of fasting HDL3. Within density intervals, the particle contents of apoA-I and apoA-II were unchanged during lipemia, suggesting that apoprotein transfer causes interconversion of existing HDL species or formation of new particles with the same content of apoA-I and apoA-II as existing species.

Adult↗
PubMed1981

Presence of autoantibody for phospholipase inhibitory protein, lipomodulin, in patients with rheumatic diseases.

The activity of phospholipase inhibitory protein, lipomodulin, partially purified from rabbit neutrophils, was markedly decreased after treatment with sera from patients with rheumatic diseases such as systemic lupus erythematosus, rheumatoid arthritis, and dermatomyositis. The decrease of the protein's inhibitory activity on phospholipase A2 paralleled the amount of [35S]methionine-labeled lipomodulin precipitated by the sera. Absorption of patients' sera with anti-human IgM (mu chain) or protein A-agarose, but not with anti-human IgG (gamma chain), decreased their ability to decrease the activity of lipomodulin on phospholipase A2 or to precipitate the radioactive lipomodulin. The IgM fraction of patients' sera could precipitate [35S]methionine-labeled lipomodulin (40,000 daltons) which comigrated with highly purified lipomodulin on gel electrophoresis with sodium dodecyl sulfate. All of these observations suggest that the sera of many patients with rheumatic diseases contain autoantibody against lipomodulin. A monoclonal antibody against lipomodulin was also obtained. Stimulating human fibroblasts with bradykinin in the presence of monoclonal antilipomodulin antibody markedly enhanced arachidonic acid release due to the activation of phospholipase(s) in the intact cells, and this stimulatory effect was blocked by adding purified lipomodulin. These findings suggest that lipomodulin regulates the activity of phospholipase(s) on the cell surface and that autoantibodies against lipomodulin may play a role in certain symptoms of rheumatic diseases, especially by the formation of prostaglandins and other metabolites of arachidonic acid.

Animals↗
PubMed1979

Recognition of facial expressions by seven-month-old infants.

3 experiments examined 7-month-old infants' ability to discriminate the facial expressions of happy vs. fear. Experiment 1 revealed that infants demonstrated discrimination of happy vs. fear expressions when posed by a single model but that this discrimination was affected by the order of stimulus presentation. In experiment 2 infants were shown 2 models posing the happing and fearful expressions and did not demonstrate generalization of the discrimination of happy versus fear across these models. The third and main experiment varied the test procedure. Here, infants demonstrated reliable generalized discrimination of the 2 expressions across different models. As in experiment 1, however, these results were constrained by the order in which the stimuli were presented. These consistent order effects were not due to the initial salience of the 2 expressions but, instead, appeared to reflect differential rates of habituation to happy vs. fear expressions.

Discrimination Learning↗
PubMed1978

Wanted: strong trustees for strong boards.

Board members hold in trust the welfare of voluntary organizations and are also responsible for the broad direction of the institutions they serve. They must be highly qualified, willing, and capable individuals who can formulate institutional policy in such a way that they eschew the extremes of mere validation on the one hand and usurpation of administrative authority on the other.

Governing Board↗