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Biomedical subjects

A B Shaw

Publications and source records attributed to A B Shaw.

At least 37 records · Page 2Linked to original sources
PubMed1983

Protein creatinine index and Albustix in assessment of proteinuria.

The protein creatinine index in early morning and random urine specimens was compared with the 24 hour urinary excretion of protein in normal subjects and outpatients with abnormal proteinuria. A protein creatinine index (defined as (mg protein/1 divided by creatinine mmol/1) times 10) below 125 in a random specimen excluded abnormal proteinuria, whereas an index of more than 136 indicated the presence of pathological proteinuria. The index for random specimens provided a useful semiquantitative assessment of the 24 hour excretion of protein (mg protein/24 hours), but the index for early morning specimens was less reliable. Errors with Albustix were partly due to intra and inter observer variations in the interpretation of the colour formed when compared with the chart provided. It is proposed that the protein creatinine index on random urine samples should be used to supplement dipsticks in screening for proteinuria in cases where misclassification would be serious.

Creatine↗
PubMed1980

Cross linking of erythrocyte membrane proteins and phospholipids by chemical probes.

Membrane proteins and phosphatidylethanolamine (PE) in intact red cells and red cell ghosts were reacted with cross-linking probes, which differed in hydrophobicity and charge. Methylacetimidate (MA) cross-links more spectrin bands 1 and 2 in cells than in ghosts. Band 4.1 reacts readily with MA in both cells and ghosts, whereas band 3 and 5 undergo very little linking. However, band 3 and most membrane proteins except band 5 are extensively cross linked by difluorodinitrobenzene (DFDNB). Band 5 reacts with DFDNB more in ghosts than in cells. Isethionyl acetimidate (IA), a nonpenetrating probe, gives very little cross linking of membrane proteins in intact cells, whereas it extensively cross links proteins in ghosts in a similar fashion as does MA. MA reacts extensively with PE in both cells and ghosts. Depending on the concentration of MA, between 47 and 60% of the PE is cross linked to itself. At 20 mM MA, 94% of PE reacts in intact cells, whereas at 20 mM IA only 19% of PE reacts. Furthermore, 66% of the PE that reacts with IA is cross linked to itself. These studies suggest that hydrophilic imidoesters cross link peripheral membrane proteins such as bands 1, 2, and 4.1, but have restricted access to integral proteins such as band 3. However, the hydrophobic probe extensively cross links both integral and peripheral proteins in intact cells except band 5. These data suggest that rearrangement of some membrane proteins occurs when ghosts are prepared.

Chemical Phenomena↗
PubMed1976

Role of Galactolipids in Spinach Chloroplast Lamellar Membranes: II. Effects of Galactolipid Depletion on Phosphorylation and Electron Flow.

A galactolipid lipase from primary bean (Phaseolus vulgaris) leaves has been used to partially deplete spinach chloroplast inner membranes of their galactolipids. Chloroplasts treated with the lipase in the absence of bovine serum albumin lost 91% of their monogalactosyl diglyceride, 83% of their digalactosyl diglyceride, all of their phosphatidyl choline, but none of their sulfolipid. Electron microscopy of this sections revealed that the treated chloroplasts were greatly enlarged and lacked membrane stacking. Linolenic acid had similar effects on the structure of the chloroplasts. Chlorophyll, carotenoids, and coupling factor 1 remained bound to the treated membranes.To minimize the inhibition of phosphorylation and electron flow by fatty acids released by the lipase, bovine serum albumin (15-24 mg/ml) was added to the lipase incubation mixtures. Bovine serum albumin inhibited the extent, but not the initial rate, of fatty acid release by the lipase. Electron microscopy of chloroplasts treated with the lipase in the presence of bovine serum albumin showed that membrane stacking was partially maintained. Chloroplasts treated with lipase under these conditions retained about 30% of their monogalactosyl diglyceride, 50% of their digalactosyl diglyceride and phosphatidyl choline. The sulfolipid and phosphatidyl glycerol contents were unchanged. Electron flow through photosystems I and II with artificial electron donors and acceptors was not affected by lipase treatment in the presence of bovine serum albumin. In contrast, oxygen evolution and phosphorylation were partially inhibited. These reactions are also very sensitive to fatty acids and it is possible that the inhibition is the result of interaction of fatty acids with the membrane prior to their binding to bovine serum albumin.In view of the irreversible inactivation of electron flow and phosphorylation by fatty acids, it is difficult to assess the role of galactolipids in these processes when a specfic lipase is used to deplete the membrane.

Journal Article↗
PubMed1969

Sodium transport in turtle erythrocytes. Apparent stimulation of exchange diffusion by anaerobiosis.

Studies were performed on Na and K transport by red blood cells of the freshwater turtle under anaerobic and aerobic conditions. Although it had previously been assumed that cation transport in turtle red blood cells was dependent on respiration, the present data show greater Na efflux rates in N(2) than in O(2). However, ouabain inhibited Na transport by the same amount quantitatively in O(2) and N(2) gas phases. Thus there was no difference in ouabain-sensitive or "pump" Na transport rates. Na influx rates were higher in nitrogen than in air and potassium influx rates were not significantly different under aerobic and anaerobic conditions. Moreover in the absence of sodium in the bathing medium no difference between air and nitrogen could be discovered. Finally with ethacrynic acid plus ouabain there was an additional decrease in Na efflux but there was a persisting difference between air and nitrogen. These studies do not rule out the existence of a ouabain-insensitive ethacrynic acid-inhibitable flux; however, they suggest that at least part of the activation of Na efflux observed in N(2) was due to increased exchange diffusion.

Adenosine Triphosphate↗