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Biomedical subjects

A S Gordon

Publications and source records attributed to A S Gordon.

At least 91 records · Page 5Linked to original sources
PubMed1984

Electrolyte effects on attachment of an estuarine bacterium.

The effect of electrolyte concentration on attachment of Vibrio alginolyticus to hydroxyapatite was determined. Bacterial affinity for attachment to the surface and surface capacity were derived from linearization of bacterial adsorption isotherms. At low concentrations (<0.1 M) the affinity of the bacteria for the surface increased with increasing ionic strength, in agreement with the D.L.V.O. theory of colloid interaction. At higher concentrations, bacterial affinity for the surface decreased with increasing concentration of cations and was not related to ionic strength changes in the medium. These results demonstrate a change in the mechanism by which salts affect bacterial attachment at salt concentrations above 0.1 M. The results are consistent with the relationship between the proportion of attached bacteria and salinity observed in previously published field studies. The results may also resolve differences between various attachment studies carried out in different ionic strength media, utilizing different bacteria, surfaces, and experimental methods.

Journal Article↗
PubMed1984

The effect of methylcellulose on extrarenal erythropoietin production.

The macromolecular polymer, methyl cellulose (MC), is a known hepatosplenomegalic agent which promotes a state of experimental hypersplenism in rats. This is characterized by massive splenomegaly, pancytopenia of the blood elements, medullary hypoplasia, and marked gross and histologic alteration of the liver, kidney, adrenals, and lungs. Massive splenomegaly results from storage of this inert material by splenic macrophages. In the present study, chronic MC administration in rats augmented the hepatic Ep response to hypoxia but did not appreciably affect renal production of Ep. Splenectomy resulted in a decrease in the extrarenal Ep response to hypoxia indicating a possible role of the massively enlarged spleen of these MC-treated rats in extrarenal Ep production. The augmentation of extrarenal Ep elaboration may be attributed to a stimulatory effect of MC on the hepatic and splenic macrophages.

Animals↗
PubMed1984

Erythropoietin secretion by isolated rat Kupffer cells.

Hepatic parenchymal and Kupffer cells were isolated from regenerating rat liver and maintained in primary culture in an attempt to identify the cell type responsible for extrarenal erythropoietin (Ep) production. Conditioned media from Kupffer cell cultures were shown to contain Ep. Kupffer cells were cultured in the presence and absence of serum, but only cultures with serum contained bioactive Ep. The addition of latex beads to Kupffer cell cultures increased the amount of Ep secreted. Parenchymal-cell-conditioned media were negative for Ep activity. Isolated liver macrophages might be useful in vitro for the study of Ep elaboration.

Animals↗
PubMed1984

Hepatic and renal erythropoietin production during various intervals of short-term hypoxia.

Hypoxia stimulates erythropoietin (Ep) production and subsequent stimulation of erythropoiesis. Chronically applied hypoxia results in a variety of physiological alterations including polycythemia, hemoglobinemia, and vascular and metabolic changes. As red cell mass increases to such an extent to allow for adequate tissue oxygenation, plasma Ep levels drop and the rate of erythropoiesis is lowered. In the present work, the precise contribution of the kidney and the liver to the Ep response to acutely administered hypoxia (6-24 hr/0.4 atm) was determined using an in situ tandem perfusion of the liver and kidneys. The results indicate that hepatic and renal Ep production during different intervals of acute hypoxia is not uniform. This alteration may be partially explained by the reported reduction in splanchnic blood flow and a possible redistribution of hepatic microcirculation, which may cause the liver to become more hypoxic than the kidney under the same ambient pO2. The role of the liver becomes more pronounced as the time of acute hypoxic exposure increases, whereas the Ep content of renal perfusates is not drastically altered. At certain intervals during hypoxia, the liver displays a greater potential to elaborate Ep.

Animals↗
PubMed1983

Ethanol modulation of opiate receptors in cultured neural cells.

The mouse neuroblastoma-rat glioma hybrid cell line NG108-15 was used to study the acute and chronic interaction of ethanol with intact neural cells. In the short term, ethanol inhibited opiate receptor binding, but after long-term exposure the cells exhibited an apparent adaptive increase in the number of opiate binding sites; this was reversible when ethanol was withdrawn. High concentrations of ethanol (200 mM) increased opiate binding after 18 to 24 hours, whereas lower concentrations (25 to 50 mM) produced similar changes after 2 weeks. This model system has potential for exploring the cellular and molecular mechanisms underlying ethanol intoxication, tolerance, and withdrawal.

Animals↗
PubMed1983

An anti-acetylcholine receptor monoclonal antibody cross-reacts with phosvitin.

Rabbit and mouse anti-Torpedo acetylcholine receptor antibodies cross-reacted partially with the highly phosphorylated protein, phosvitin. We have selected an anti-Torpedo acetylcholine receptor monoclonal antibody which binds specifically to phosvitin; this binding is inhibited by acetylcholine receptor. These findings suggest that a phosphorylated amino acid residue may be a part of the determinant on the acetylcholine receptor recognized by this monoclonal antibody.

Animals↗
PubMed1983

Phospholipid methylation in myogenic cells.

The biosynthesis of phosphatidylcholine from successive N-methylation of phosphatidylethanolamine has been implicated as a major mechanism for the transduction of several receptor-mediated signals including beta-adrenergic coupling to adenylate cyclase. In this report we demonstrate L-isoproterenol stimulation of adenylate cyclase activity in two myogenic cell lines, L8 and BC3H-1. Using a sensitive high performance liquid chromatography method for qualitative and quantitative determination of phospholipids we found an active membrane phospholipid methylation pathway in these cells. Despite beta-adrenergic simulation of adenylate cyclase no alteration in the transmethylation pathway could be demonstrated.

Adenylyl Cyclases↗
PubMed1983

Activation of acetylcholine receptors causes the partition of hydrophobic cations into postsynaptic membrane vesicles.

In the continued presence of cholinergic ligands, the acetylcholine receptor-channel complex (AChR) in postsynaptic membranes undergoes a sequence of conformational changes. On addition of the ligand, the receptor rapidly changes from a closed channel to an open channel conformation, then slowly changes to a nonconducting state termed desensitization. The lifetime of the open channel conformation and the rate of desensitization are both dependent on the magnitude of the membrane potential, suggesting that the ligand-induced conformational changes in AChR may involve the movement of electrical charges within the membrane. Measurements of charge redistribution in AChR-containing membranes following ligand binding have not been reported. Recently, measurements of changes in the membrane partition coefficient of hydrophobic ions have been used to detect electrostatic changes in both biological and model membranes. We report here that cholinergic ligands induce changes in the partition coefficient of the hydrophobic cation tetraphenylphosphonium (TPP) into AChR-enriched membranes. The extent and time course of these changes in TPP partition coefficient are accounted for in a kinetic model. We conclude that TPP movement is a monitor of a molecular event which may be associated with the slow component of AChR desensitization.

Animals↗
PubMed1983

Interaction of monoclonal antibodies to Torpedo acetylcholine receptor with the receptor of skeletal muscle.

Several monoclonal antibodies (mcAbs) elicited against the nicotinic acetylcholine receptor (AChR) from Torpedo react also with skeletal muscle AChR. Such mcAbs were used to define antigenic determinants on muscle AChR and to elucidate their effect on muscle AChR functions. Primary chick muscle cultures were used as a model for skeletal muscle. Of the four mcAbs studies only mcAb 5.5, which is directed against the cholinergic site in Torpedo AChR, blocks the binding of alpha-bungarotoxin (alpha-Bgt) to AChR in chick muscle cultures and inhibits carbamylcholine-induced sodium transport in these cells. The interaction of mcAb 5.5 with the cholinergic site on muscle AChR demonstrates the conservation of this site. Two mcAbs, 5.5 and 5.34, each of a different antigenic specificity but both directed against conformation-dependent antigenic determinants, accelerate the degradation of AChR in muscle cultures. From the reactivity of the various mcAbs with Triton-solubilized and membranous AChR it appears that there are some antigenic differences between the detergent solubilized and membranous forms of the receptor.

Animals↗
PubMed1983

Identification of a molecular weight 43,000 protein kinase in acetylcholine receptor-enriched membranes.

A photoaffinity ATP ligand is used to identify the protein kinase present in acetylcholine receptor-enriched membranes from Torpedo californica. Incubation of these membranes with 8-azido-[alpha-32P]ATP and subsequent irradiation with UV light resulted in covalent labeling of a major band of Mr 43,000. Alkali-stripped membranes that show a selective reduction in the Mr 43,000 polypeptide also show a corresponding reduction in incorporation of photoaffinity label. In addition, the neutralized alkaline extract also showed one band at Mr 43,000 when labeled with the photoaffinity ligand. After alkali extraction, endogenous protein kinase activity decreased in the membranes in proportion to the loss of Mr 43,000 peptide. Moreover, the alkaline extract was able to phosphorylate casein in an exogenous assay system. These results suggest that a Mr 43,000 polypeptide in acetylcholine receptor-enriched membranes is the acetylcholine receptor kinase.

Animals↗
PubMed1983

Fathers and sons: their relationship and personality characteristics associated with the son's smoking behavior.

The purpose of the present study was to examine the interrelationship of the domains of father personality attributes, father socialization techniques, and adolescent personality attributes, and the son's use of tobacco. A sample of 246 male adolescents and their fathers from intact homes was administered questionnaires. Two main findings emerged. First, each of the three domains was significantly associated with the son's tobacco use despite control on the remaining domains. Second, the effectiveness of the father may interact synergistically with or be mitigated by the son's personality attributes in its association with the son's tobacco use. In concert, the findings support the importance of examining the father-son relationship for a greater understanding of the son's tobacco use.

Adult↗
PubMed1983

Older brother's influence on younger sibling's drug use.

This study examined the sibling relationship "having an older brother" and its effect on the younger sibling's stage of drug use. Sibling effects were examined in the context of the younger sibling's peer group. Data collected on 339 9th and 10th grade students indicated that domains of older sibling and peer factors each had independent lines of relationship to the younger sibling's drug use. The older brother's impact on his younger sibling's drug use varied, depending on friends' drug use, sex of the younger sibling, and whether or not the younger sibling identified with the older brother.

Adolescent↗
PubMed1983

Effects of inorganic particles on metabolism by a periphytic marine bacterium.

Measurements were made of adsorption of a periphytic marine bacterium, glucose, and glutamic acid to inorganic particles in seawater and defined bacterial growth medium. Measurements of the metabolism of bacteria were made in the presence and absence of particles by microcalorimetry and radiorespirometry. It was found that hydroxyapatite adsorbs glutamic acid, but not glucose, from the experimental medium. It was also found that hydroxyapatite adsorbs essentially all of the bacteria from the medium when the bacterial concentration is approximately 6 x 10 bacteria per ml. If the bacterial concentration is approximately 6 x 10, then only a small fraction of cells become attached. It was therefore possible to select bacterial concentrations and organic nutrients so that bacterial attachment, organic nutrient adsorption, or both would occur in different experiments. In this experimental system the metabolism by attached and nonattached bacteria of adsorbing and nonadsorbing organic nutrients was measured. The results show that bacterial activity in this model system was not enhanced by the particles, regardless of whether the bacteria, the organic nutrient, or both were associated with the surface. In fact, the respiratory activity of the attached bacteria was diminished in comparison with that of free bacteria.

Journal Article↗
PubMed1983

Evidence for an erythropoietin-stimulating factor in patients with renal and hepatic disease.

Recently, a factor was discovered in the serum of hepatectomized animals which was capable of augmenting the hepatic erythropoietin response to hypoxia when injected into normal rats. This substance was localized in the liver via an in situ perfusion technique and was termed the hepatic erythropoietic factor (HEF). Patients with kidney disease, liver disease, and combined renal and hepatic disease were studied in this report. Detectable HEF levels were found in the plasma of patients with both liver and kidney disease and were highest in anephric patients with various liver diseases. However, HEF levels were negligible in normal humans or in patients manifesting renal disease with no hepatic involvement. The data suggest that HEF-induced hepatic erythropoietin synthesis may occur in humans as well as in animals.

Adult↗
PubMed1983

Paternal correlates of adolescent marijuana use in the context of the mother-son and parental dyads.

This study was designed to examine the paternal determinants of male adolescent marijuana use in the context of the mother-son and parental relationships. In addition, parental factors affecting experimental vs regular use of marijuana were examined. Two hundred forty-six male college students and their fathers were administered written questionnaires. Results indicated that the father's personality attributes and socialization techniques are associated with the son's use of marijuana despite control on the mother-son relationship. Fathers of marijuana users score higher on measures of psychopathology and unconventionality, and are less likely to have established close relationships with their sons. In addition, marijuana users more than nonusers have unaffectionate mothers and parents with less harmonious marital relations. Also of importance were interactions within the family system. The significance of these second-order effects highlights the importance of examining the father-son relation in the context of mother-son and parental interactions.

Adult↗
PubMed1983

Renal and extrarenal production of erythropoietin following exchange transfusion with plasma or a perfluorocarbon-polyol.

The extrarenal production of erythropoietin (Ep) was measured in young adolescent rats following exchange-transfusion with normal rat plasma or the whole blood replacement fluid, Fluosol-43. In the plasma-transfused anephric groups, the peak extrarenal Ep response to the severe degree of anemic hypoxia represented 23% of that evoked in renal-intact groups. In contrast, the peak extrarenal production of Ep in Fluosol-transfused renoprival groups was almost equal to those serum Ep levels produced in renal-intact groups. Histological studies revealed significant fluorocarbon uptake by hepatic macrophages that coincided with the time of peak production of Ep. Thus, while intense levels of hypoxia are required to stimulate the extrarenal production of Ep, these data suggest that as Fluosol-43 is taken up by the hepatic macrophages, Ep production by these cells is stimulated.

Animals↗