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Biomedical subjects

T H Chiu

Publications and source records attributed to T H Chiu.

At least 163 records · Page 9Linked to original sources
PubMed1974

Lipoteichoic acids from Streptococcus sanguis.

Two lipoteichoic acids, membrane (MLTA) and wall (WLTA), have been purified from Streptococcus sanguis by Sepharose and Ecteola-cellulose column chromatographies and concanavalin A-conjugated Sepharose affinity column chromatography. The teichoic acids were homogenous as judged by disc gel electrophoresis, column chromatography, and double diffusion tests. Both MLTA and WLTA consisted of glycerol, phosphate, glucose, and fatty acids in the ratios of 0.95:1:0.71:0.046 and 0.99:1:0.79:0.023, respectively. alpha-Glycerol-phosphate was obtained by the partial acid hydrolysis of the lipoteichoic acids suggesting that their backbone structure consists of the glycerol moieties linked by 1, 3-phosphodiester bonds. Both WLTA and MLTA form aggregates, perhaps due to micelle formation, in concentrated solution. The aggregate form of MLTA dissociates to a much greater extent than that of WLTA under similar conditions.

Cell Membrane↗
PubMed1974

Glycerolphosphate-containing cell wall polysaccharides from Streptococcus sanguis.

Six glycerolphosphate-containing tetraheteroglycans, a, b-1, b-2, b-3, b-4, and b-5, have been purified from the formamide extracts of Streptococcus sanguis by alcohol and acetone precipitations, Sephadex G-75, and diethylaminoethyl-cellulose column chromatography. The polysaccharides were judged as at least 95% pure by analytical disc gel electrophoresis and immune double diffusion against rabbit antiserum. They were shown to be cell wall polysaccharides, since they formed a single band of identity in immune double diffusion with partially purified polysaccharide extracted from a purified cell wall preparation of S. sanguis. The polysaccharides were composed of l-rhamnose, d-glucose, and N-acetyl d-glucosamine in a similar molar ratio, but varied in their glycerol and phosphate contents. They exhibited four different mobilities in polyacrylamide disc gel electrophoresis at pH 8.9. When they were treated with formamide at 170 C for 20 min, the faster moving polysaccharide(s) yielded polysaccharides with mobilities corresponding to the other slower moving polysaccharides. These results indicate that the polysaccharides originated from the same cell wall polysaccharide and were produced as a result of breakage in the phosphodiester bonds during the formamide extraction procedure. A preliminary structural study shows that the terminal reducing sugar is l-rhamnose and that the glycerol moiety is probably linked to the polysaccharide through a phosphodiester bond.

Animals↗
PubMed1973

Acetylcholine receptor and ion conductance modulator sites at the murine neuromuscular junction: evidence from specific toxin reactions.

The perhydro derivative of histrionicotoxin reversibly blocks the excitatory ionic transduction system in the synaptic and sarcolemmal membranes of mammalian skeletal muscle cells. The efficacy of perhydrohistrionicotoxin as an antagonist at the post-synaptic membrane is increased by the transient presence of acetylcholine in the endplate of innervated muscles and at extrajunctional receptors in denervated muscles. alpha-Bungarotoxin and [(3)H]monoacetyl-alpha-bungarotoxin block the endplate acetylcholine receptors, each binding to the same extent. The effect of bungarotoxin is partially reversible. These electrophysiological results, together with the effects of perhydrohistrionicotoxin and/or d-tubocurarine on the binding of [(3)H]monoacetyl-alpha-bungarotoxin at endplates of murine diaphragm muscle and on the bungarotoxin-elicited irreversible blockade of neuromuscular transmission, suggest that at least two types of sites participate in the synaptic excitation by acetylcholine. One site, competitively blocked by bungarotoxin and by curare, is presumably the acetylcholine receptor. Binding of bungarotoxin at this site is responsible for an irreversible blockade of neuromuscular transmission. The second site, competitively blocked by bungarotoxin and perhydrohistrionicotoxin, is proposed to be part of the cholinergic ion conductance modulator. Binding of bungarotoxin to this site does not result in an irreversible blockade.

Acetylcholine↗