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Biomedical subjects

M G Rumsby

Publications and source records attributed to M G Rumsby.

At least 73 records · Page 4Linked to original sources
PubMed1979

Changes in the inhibition of specific agglutination by plasma due to microvesicles released from human red cells during storage for transfusion.

The progressive appearance of erythrocyte antigenic activity in plasma from donations of human blood taken into acid citrate-dextrose (ACD) and stored at 4 degrees D for transfusion has been studied. It has been shown by specific inhibition tests that A, B, H and P1 activities are associated with membrane-bounded microvesicles which are released from the red cell membrane during the disc-echinocyte-spherocyte shape transformation. Although M group activity appears to be lost from the red cell membrane during storage, significant recovery on the microvesicles is not obtained even though these seem to contain the M and N group intrinsic protein, glycophorin.

ABO Blood-Group System↗
PubMed1978

Solubilization of isolated central-nervous-system myelin preparations by the amniotic detergent sodium dodecyl sulphate.

The mechanism for the solubilization of isolated central-nervous-system myelin by sodium dodecyl sulphate was studied in detail. The release of protein and phospholipid to the 100000 g x 1 h supernatant fraction is dependent on the total amount of detergent relative to the amount of membrane present and on the ionic strength of the solubilization system. Gel-filtration analysis of supernatant fractions indicate that at suboptimal concentrations of detergent these contain lipid-protein complexes. The complete dissociation of the individual protein components from lipid is dependent on the total amount of sodium dodecyl sulphate present in the system. The results indicate that for the analysis of membrane components in sodium dodecyl sulphate it is essential that sufficient detergent is present.

Animals↗
PubMed1978

Interaction of the myelin basic protein with the anionic detergent sodium dodecyl sulphate.

The interaction of the myelin basic protein and two peptides derived from it with the anionic detergent SDS (sodium dodecyl sulphate) was studied. At molar ratios of detergent/protein of up to approx. 20:1 the transient increase in turbidity (as measured by increases in A230) is proportional to the ratio. Between ratios of 30:1 and 100:1 the effect of the detergent is constant and maximal. At molar ratios exceeding 100:1 the transient increase in turbidity decreases with increasing amounts of detergent. With increasing ionic strength the rapid development of turbidity is inhibited, whereas the slow decay of turbidity is not affected. Neither of the peptide fragments produced by cleavage of the myelin basic protein at the single tryptophan residue, nor both when mixed, produce measurable turbidity when mixed with SDS. Under similar conditions poly-L-lysine of similar molecular size to the basic protein shows the increase in turbidity but not the decay. The interaction between the protein and SDS is interpreted in molecular terms, which involve the initial ionic interaction of the detergent with protein resulting in aggregation and turbidity in the solution. Within the aggregated complexes molecules rearrange to maximize hydrophobic interactions.

Animals↗
PubMed1978

Molecular organisation in central nerve myelin.

Pertinent data from the literature and in press is summarised and used to construct a model for the molecular arrangement of lipid and protein in the lamellae of compact central nerve myelin. For the lipid phase of myelin the available data is best interpreted in terms of a bilayer arrangement while physical studies suggest that the lipids are in an intermediate fluid state maintained by the presence of cholesterol and water in the system. Lipids will interact to maintain this condition. The proteins of myelin differ in their membrane locations. The high molecular weight proteins are considered to be intrinsic components with at least part of their polypeptide chains in the lipid phase. The proteolipid protein is also intrinsic and may be completely buried in the lipid phase. The basic protein of myelin is an extrinsic component and must be localised at the surface of the lipid phase at either the external or cytoplasmic face of the lamellae. Present results suggest an elusive location at the cytoplasmic apposition region. The lipid-interacting properties of the basic protein are segregated on the polypeptide chain of the molecule and this may be important for the possible role of the basic protein in bridging adjacent lamellae at the cytoplasmic apposition. It is speculated that association of the proteolipid protein with the basic protein in a 1:1 molar ratio would form an effective lipid-complexing nucleus in the lipid rich myelin lamellae but experimental data to support this idea is lacking at present.

Animals↗
PubMed1978

Covalent probe investigations with isolated central nerve myelin preparations.

The interaction of the covalently reacting probes dansyl chloride, fluorodinitrobenzene and trinitrobenzene sulphonic acid with isolated central nerve myelin sheath preparations has been studied. The three probes interact preferentially with accessible amino groups on lipid and protein in the membrane. With isolated myelin some 13% of the total phosphatidyl ethanolamine is labelled with dansyl chloride while the figure is 66% with fluorodinitro benzene and 47% with trinitrobenzene sulphonic acid. Lower levels of phosphatidyl serine are labelled. Phosphatidyl ethanolamine seems to be more accessible to probes in the myelin sheath than is phosphatidyl serine perhaps because the ethanolamine-containing lipid class is localised partially at the external apposition surfaces of the membrane which are most accessible to the probes. The serine phospholipids may not react so well because they are preferentially distributed at the cytoplasmic surface of the system. Analysis of protein labelling patterns after reaction of intact myelin with dansyl chloride indicates that the high molecular weight proteins and the proteolipid protein is accessible to the probe while the basic protein is not, even though this latter component is readily labelled with dansyl choride in purified form. It is suggested that the inability of the basic protein to react with myelin is perhaps due to the fact that it is occluded from interaction with the probe at the cytoplasmic apposition surfaces of the lamellae.

Animals↗
PubMed1978

On the accessibility and localisation of cerebrosides in central nervous system myelin.

Cerebrosides are concentrated in the myelin sheath where they account for about 20% of the total lipid of the membrane. The present paper is concerned with the role and localisation of these glycolipids in the myelin lamellae. Isolated central nerve myelin preparations have been treated with two probes to investigate cerebroside accessibility in the membrane. The action of galactose oxidase on the galactose headgroups of cerebrosides is followed and quantitated by recovery of the modified glycolipid and resolution of either the 6-aldehydo sugar or galactose remaining by gas-liquid chromatography. With isolated myelin preparations only some 40--50% of the cerebroside galactose is attacked by galactose oxidase at 20 degrees C. With periodate at 20 degrees C over 90% of the galactose headgroups are oxidised in 3 h while the figure is 50--55% over the same time period at 4 degrees C rising to 85% after 22 h. With multilamellar liposomes of mixed myelin lipids only some 20--25% of the available cerebroside is oxidised at 4 degrees C, the reaction being complete in 2 h. The results are discussed in relation to the dispositon of cerebroside in the myelin lamellae. A major location on the external face of the membrane system (intraperiod dense line) is favoured. A role for cerebroside in myelin in terms of increasing the stability and resistance of the lipid phase to ion movement is suggested.

Animals↗
PubMed1978

Changes in the agglutinability of red cells and the inhibition of specific agglutination by plasma from human blood taken into ACD and stored at 4 degrees C.

The effect of storage in ACD at 4 degrees C on red cell agglutinability and the inhibitory properties of the plasma to blood group reagents has been studied. It was found that the variability demonstrated was related to the origin of the reagent used, particularly between human and on-human sources. The significance of these findings with regard to biochemical and morphological changes in blood on storage is discussed.

ABO Blood-Group System↗
PubMed1977

Localization of sites for ionic interaction with lipid in the C-terminal third of the bovine myelin basic protein.

The myelin basic protein from bovine brain tissue was purified and the two peptides obtained by cleavage of the polypeptide chain at the single tryptophan residue were isolated. The interaction of these peptides and the intact basic protein with complex lipids was investigated by following the solubilization of lipid-protein complexes into chloroform in a biphasic solvent system. The C-terminal peptide fragment (residues 117-170) and the intact basic protein both formed chloroform-soluble complexes with acidic lipids, but not with neutral complex lipids. The N-terminal fragment (residues 1-115) did not form chloroform-soluble complexes with either acidic or neutral complex lipids. The molar ratio of lipid to protein that caused a 50% loss of protein from the upper phase to the lower chloroform phase was the same for the intact basic protein as for the smaller C-terminal peptide fragment. Phosphatidylserine and phosphatidylinositol were approximately twice as efficient as sulphatide at causing protein redistribution to the chloroform phase. The results are interpreted as indicating that the sites for ionic interactions between lipid and charged groups on the basic protein of myelin are located in the C-terminal region of the protein molecule.

Amino Acids↗