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Biomedical subjects

C Green

Publications and source records attributed to C Green.

At least 271 records · Page 15Linked to original sources
PubMed1983

Isolation and anticoagulant properties of polysaccharides of Typha Augustata and Daemonorops species.

Polysaccharides were isolated from Dragon's Blood (DB), a red resinous secretion from the fruits of Daemonorops species and from pollens of Typha Augustata (TA) by alcohol precipitation followed by deaminoethylaminoethyl (DEAE) cellulose chromatography. The purified polysaccharides of DB and TA gave specific rotations of [alpha]D20 64 and [alpha]D20 of 80 and their molecular weights by membrane osmometry were approximately 25000 and approximately 30000 respectively. The effect of addition of the polysaccharides on coagulation of pooled normal human plasma was investigated. They were found to accelerate the recalcified plasma times at concentrations below 100 micrograms/ml while inhibiting them at higher concentrations. Their procoagulant properties were due to their effects on the activation of Hageman factor (XII) while the anticoagulant effect was mainly directed towards fibrinogen. Studies of the mechanism of the anticoagulant effect showed that addition of TA polysaccharide inhibited the rate of release of fibrinopeptides by thrombin and also the aggregation of fibrin monomers.

Anticoagulants↗
PubMed1983

Interaction between vascular endothelial cells and vascular intimal spindle-shaped cells in vitro.

The interactions between human or bovine vascular endothelial cells and fibroblast-like vascular intimal spindle-shaped cells have been studied in vitro, using species-specific antibodies to identify the different components in mixed cultures. Pure cultures of endothelial cells grow as uniform, nonoverlapping monolayers, but this growth pattern is lost after the addition of spindle cells, probably because the extracellular matrix secreted by the latter causes the endothelial cells to modify the way they are attached to the substrate. The result is a network of tubular aggregates of endothelial cells in a three-dimensional 'polylayer' of spindle-shaped cells. On the other hand, endothelial cells added to growth-inhibited cultures of spindle-shaped cells will grow in sheets over the surface of the culture. Human endothelial cells grown in contact with spindle-shaped cells have a reduced requirement for a brain-derived endothelial growth factor. The interactions of endothelial cells and other connective tissue cells in vitro may be relevant to the mechanisms of endothelial growth and blood vessel formation in vivo, and emphasize the potential importance of extracellular matrix in controlling endothelial cell behaviour.

Animals↗
PubMed1982

Effect of sterol structure on the transfer of sterols and phospholipids from liposomes to erythrocytes in vitro.

Human erythrocytes were incubated for 24 h with liposomes containing [3H]phosphatidylcholine, [14C]cholesterol and one of several other sterols. Of the other sterols, 3-hydroxycholest-3-en-2-one did not appear to be taken up by the cells, sterophenol was taken up at about the same rate as cholesterol, and cholesta-4,6-dien-3-one and 7-oxocholesterol were taken up much more rapidly than cholesterol. Each component of the liposomes was incorporated into the cells independently of the others and the rate of incorporation of the test sterol had little, if any, effect on the rate of incorporation of phospholipid or cholesterol. The results support the proposal that sterol exchange is mediated via the pool of monomers present in the medium rather than by a collision mechanism.

Cholestenones↗
PubMed1981

Reassociation rate limited displacement of DNA strands by branch migration.

Large branched DNA structures are constructed by two-step reassociation of separated complementary strands from restriction fragments of different lengths. The displacement of DNA strands initially annealed to longer complementary DNA sequences, a process mediated by branch migration, is very rapid and has thus far been followed only under conditions which are second order, DNA reassociation rate limiting. The average lifetime of branched DNA leading to displacement of 1.6 Kb strands is estimated to be less than 10 seconds under conditions of DNA reassociation, Tm-25 degrees C. Several DNA-binding drugs, including intercalating dyes, have been tested to determine their influence, if any, on the kinetics of DNA strand displacements by branch migration. Only actinomycin D was found to have significant effect under the conditions we have described. The kinetics of the strand displacement in the presence of low concentrations of actinomycin D remain second order and slower rate of strand displacement must be attributed to decreased rate of reassociation of DNA strands to form the branched intermediates. Consideration is given to the potential manipulation of DNA structures at site-directed branches and the limitations due to rapid strand displacements. The feasibility of constructing sufficiently large branched DNA regions to approach first order, branch migration rate limiting kinetics is also discussed.

Adenoviruses, Human↗
PubMed1981

Handicapped children: let's be more positive and practical.

Handicap tends to be one of the "poor relations" in paediatric practice. With a more positive and practical approach, it can become a most exciting and rewarding area. The needs and feelings of the parents with a handicapped child are discussed and some simple practical ways to help are outlined.

Anger↗
PubMed1980

Use of fluorescent probes in the study of phospholipid--sterol bilayers.

1. The transfer of excitation energy between the fluorescent probes 1,6-diphenylhexa-1,3,5-triene and 12-(9-anthroyl)stearic acid and the cholesterol analogue cholesta-4,6-dien-3-one in phosphatidylcholine liposomes has been investigated. 2. The results indicate that probes and steroid are randomly distributed in the bilayer at steroid concentrations up to 35 mol%. 3. The degree of polarization of diphenylhexatriene fluorescence increases with increasing cholesterol content. Other sterols, differing in structure in the region of the polar group or in the side chain at position-17, produce similar but not identical effects. 4. the results are consistent with the proposal that diphenylhexatriene gives a general picture of the state of the bilayer and that there is no segregation of sterols in liquid-crystalline phosphatidylcholine bilayers.

Cholestenes↗
PubMed1980

Erythrocyte membrane cholesterol levels and their effects on membrane proteins.

The susceptibility of the band 3 protein of the erythrocyte membrane to proteolytic digestion at either surface of the membrane was not altered when the membrane cholesterol level was increased by 65-103%. Cross-linking of the major membrane proteins by o-phenanthroline . Cu, glutaraldehyde, dimethylsuberimidate and dimethyladipimidate was also unaffected.

Cholesterol↗
PubMed1980

Phosphatidylethanolamine distribution and fluidity in outer and inner membranes of the gram-negative bacterium Erwinia carotovora.

1. The distribution of phosphatidylethanolamine, the major lipid of Erwinia carotovora, was investigated in intact bacteria, spheroplasts and outer- and inner-membrane preparations, with the amino-group reagent 2,4,6-trinitrobenzenesulphonic acid. Only 4% was found on the external surface of the outer membrane with 30% on the internal surface, whereas the inner membrane had 27 and 38% on its external and internal surfaces respectively. Some comparative studies were made with three other bacteria. 2. The fluidity of the membranes of E. carotovora was studied by using the fluorescent probe 1,6-diphenylhexa-1,3,5-triene. Results were consistent with the hydrocarbon region of the outer membrane bilayer being less fluid than that of the inner one. 3. On the basis of these and other results a model for the outer- and inner-membrane structures of E. carotovora is proposed.

Cell Membrane↗