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Biomedical subjects

W Hoss

Publications and source records attributed to W Hoss.

At least 55 records · Page 3Linked to original sources
PubMed1982

Evidence for a noncholinergic nicotine receptor on human phagocytic leukocytes.

A noncholinergic nicotine receptor on human phagocytic leukocytes has been characterized using the binding of 3H-(d,1)-nicotine. The average affinity +/- standard deviation of (d,1)-nicotine for the receptor on neutrophils is 36 +/- 18 nM (n = 6). The binding is saturable with an average of 8.7 x 10(4) sites per neutrophil. Monocytes and to a lesser extent lymphocytes but not erythrocytes also display specific binding. Bound nicotine is dissociable from the receptor and is not metabolized. Only close structural analogs of nicotine bind to the receptor, which is stereoselective for the (d)-isomer. The receptor can be occupied by (1)-nicotine at concentrations present in the blood of smokers. It is suggested that some of the adverse effects of smoking on leukocyte functions may be mediated by a specific nicotine receptor.

Kinetics↗
PubMed1982

Competitive interaction of gallamine with multiple muscarinic receptors.

Gallamine, a cholinergic antagonist at the (nicotinic) neuromuscular junction possesses antimuscarinic potency in several systems. We report here that gallamine inhibited the binding of [3H] quinuclidinyl benzilate (QNB) in a competitive manner in the brainstem and forebrain of the rat. The occupancy curves derived from these studies suggest that gallamine has widely varying affinities for different subpopulations of muscarinic receptors, a finding which sets gallamine apart from classical muscarinic antagonists such as atropine and QNB. The greatest difference in affinities for gallamine occurred in the brainstem, where the data could be satisfactorily fitted to a two-site model, with 77% of the receptors having high affinity (Kd = 25 nM) and 23% low affinity (93 microM). Further, these affinities displayed rank order correlation with those of carbachol (an agonist), although gallamine has not, so far, displayed agonist (or partial agonist) activity. The finding that antagonists as well as agonists can display multiple affinities for muscarinic receptors suggests that there are fundamental differences among subpopulations of these receptors.

Animals↗
PubMed1980

Enhancement of synaptic vesicle attachment to the plasma membrane fraction by copper.

Synaptic vesicles from rat brain were labeled with 125I, and the association of the vesicles with other subcellular components of brain was examined using a centrifugation assay. Copper at micromolar concentrations enhances the binding of the vesicles to the synaptic membrane as well as other fractions. Magnesium, Ca2+, and calmodulin with Ca2+ are ineffective. There is virtually no binding of synaptic vesicles to the microtuble fraction and only a slight enhancement with Cu2+. These findings support the hypothesis that Cu may serve as a bridge between synaptic vesicles and the plasma membrane.

Animals↗
PubMed1977

Conversion between configurational states of the muscarinic receptor in rat brain.

Reductive alkylation of neural membranes by N-ethyl maleimide (NEM) converts muscarinic acetylcholine receptors from a state of low to high affinity for receptor agonists. Interactions of muscarinic antagonists with the receptor are unaffected by this treatment. Muscarinic receptors from the rat telencephalon in the high agonist affinity state are increased from 34.2 to 53.4% of the total receptor population and the Ki for carbamylcholine inhibition of 3-quinuclidinyl benzilate binding is decreased from 1.2 X 10(-4) to 6.9 X 10(-5) M by NEM treatment.

Animals↗
PubMed1977

Binding and immobilization of catecholamines by liposomes.

The polarization of the native fluorescence of dopamine and noradrenaline has been used to measure their binding and immobilization by liposomes suspended in aqueous buffers. Whereas both catecholamines are significantly immobilized by brain phosphatidyl serine and yeast phosphatidyl inositol, phosphatidyl ethanolamine and phosphatidyl inositol from brain are ineffective. Dopamine is immobilized to a greater degree than noradrenaline. The dissociation constants determined from modified Scatchard plots of the polarization data are 1.7 X 10(-4) and 9.6 X 10(-5)M for dopamine with yeast phosphatidyl inositol and brain phosphatidyl serine, respectively. Apomorphine binds to a hydrophobic region of phosphatidyl serine liposomes with a KD value of 69 micrometer. It is suggested that a fraction of dopamine is complexed with membranous phosphatidyl serine in nerve terminals.

Animals↗
PubMed1977

Binding of apomorphine to neural membranes.

The intrinsic fluorescence of apomorphine has been used to measure its binding to neural membranes. A large number of relatively weak binding sites are concentrated in myelin and synaptic membrane fractions. Butyrophenones have the highest affinities for these sites--KD = 43 micrometer for haloperidol--while dopamine and dopamine releasers and reuptake blockers, as well as a variety of other alkaloids, have much lower affinities. The sites are hydrophobic and undergo a phase transition to a highly fluid state near 26 degrees C. Calcium is a noncompetitive inhibitor of apomorphine binding. Some of the actions of neuroleptic drugs may result from binding to these hydrophobic membrane sites in vivo, blocking conduction in small catecholamine axons.

Animals↗
PubMed1976

Kinetics of interfacial ATP adsorption and anionic exchange with a synaptic membrane protein.

A study was conducted on the adsorption of 14C-ATP to a surface film of a hydrophobic protein derived from synaptic membranes isolated from bovine cerebellum. The adsorption of ATP to the protein film followed a rate law based on diffusion and an energy barrier to adsorption, the rate law being generally applicable to the adsorption of ions to a charged interface. Studies were also carried out on the displacement of ATP from the film by the injection of other nucleotides, inorganic phosphates, and other anions. The kinetics conformed to a rate law based on diffusion and displacement. The most important factor in the displacement of ATP was the magnitude of charge of the anion, while steric factors were relatively minor. However, from a consideration of the energy barrier to adsorption it appeared that steric factors play a greater role in the adsorption of ATP. The results are discussed in relationship to the configurational aspects of the surface film as well as their possible significance in synaptic function.

Adenosine Triphosphate↗
PubMed1975

Stereospecific morphine adsorption to phosphatidyl serine and other membranous components of brain.

In the course of investigating various membranous components for morphine binding, it was found that the major substance responsible was phosphatidyl serine. Other acidic lipids, such as phosphatidic acid and phosphoinositides bind to a considerably lesser extent, while neutral lipids, glycolipids and other phosphatides bind slightly or not at all. Total lipid extracts from a number of regions of rat brain exhibited different degrees of binding to (-)-morphine, such regions as the cerebral cortex and thalamus being the greatest. From an examination of the pH curve for binding and the effect of ionic strength, it was concluded that the binging was largely electrostatic. The method employed was the radioactive measurement of 14C-morphine adsorption to surface films of phosphatidyl serine. When the phosphatide was dispersed in a nonionic detergent near the critical micelle concentration, adsorption was maximal, attaining a value of 1 molecule of morphine adsorbed per molecule of phosphatidyl serine in the surface micelle. The relation between binding affinity and biological potency was not consistent. Morphine adsorption occurred with films prepared from a dispersion of the phosphatide and a hydrophobic protein from synaptic membranes. With the use of levorphanol and dextrorphan it could be shown that binding of morphine was stereospecific.

Adsorption↗