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W D Comper

Publications and source records attributed to W D Comper.

66 records · Page 4Linked to original sources
PubMed1983

A paradigm for axonal transport.

Axonal transport has been extensively studied for a period of 20-30 years, but there is still no general consensus concerning the mechanism by which this transport process operates. An important development in this regard is the recent studies in the physical biochemistry group in the Department of Biochemistry at Monash University where it has been demonstrated that ordered flows may be generated spontaneously in polymer systems under non-equilibrium conditions. The new phenomenon exhibits many novel features, particularly with respect to polymer transport, which bear marked similarity to the behaviour of components in axonal transport. This article sets out to essentially bring to the attention of those in the neurosciences some of the properties of ordered structured flows in polymer solutions. These properties may generate a different view in the understanding of the mechanism of axonal transport.

Adenosine Triphosphate↗
PubMed1978

An estimate of the enthalpic contribution to the interaction between dextran and albumin.

It is demonstrated that exclusion phenomena appear to dominate the interaction of dextran with albumin in aqueous solution. The enthalpic contribution to the interaction coefficient describing dextran/albumin mixtures is small, although its determination was subject to considerable error. These results support the earlier assumptions of the type of interaction between the two polymers. The conclusions are primarily based on the interpretation of the temperature-dependence of the interaction coefficient, as measured by light-scattering in the temperature range 6--33 degrees C. Enthalpy of dilution measurements of dextran/albumin mixtures by microcalorimetry were in qualitative agreement with the light-scattering data.

Calorimetry↗
PubMed1974

Model connective-tissue systems. A study of polyion-mobile ion and of excluded-volume interactions of proteoglycans.

The osmotic pressure of solutions of sulphated proteoglycans isolated from the intervertebral discs of animals of various ages was determined. The behaviour of the solutions in salt-added systems was investigated in terms of the Donnan distribution of the mobile ions. It is evident that this effect is the dominating factor in explaining the observed nonidealities. Although marked variations in the compositions of the proteoglycan, with regard to their chondroitin sulphate and keratan sulphate content and hence charge content, occur with increasing age of parent tissue, the osmotic activities of the various preparations are very similar. This is explained by the ;fixation' of the counterions in such a way as to counteract any change in the charge content of the polyion; an ;osmotic buffering' effect. The swelling behaviour of gelatin gels containing the proteoglycan preparations has been measured. In all cases pressures in excess of the sum of the osmotic pressures of the individual components are observed. However, the magnitude of the excess decreases with increasing age of the parent tissue. It is suggested that the age changes, as reflected by a decrease in water content of the gel system, are not the result of changes in the osmotic properties of the individual components but rather reflect changes in the entropic interaction of the proteoglycan with the gelatin matrix. The relevance of this observation to the situation in vivo is discussed.

Age Factors↗
PubMedDate not supplied

The return of glomerular filtered albumin to the rat renal vein--the albumin retrieval pathway.

BACKGROUND: Recent studies have demonstrated that the normal glomerular capillary wall (GCW) is not charge selective to albumin. This means that albumin flux across the GCW is high. This has been confirmed in studies where albumin uptake by the tubules has been inhibited. Therefore, there must be a high capacity postglomerular retrieval pathway in normal kidneys that returns filtered albumin back to the blood supply. METHODS: This study identifies the presence of glomerular filtered albumin in the renal vein from the analysis of the decrease of radioactivity in the venous effluent after the injection of a pulse of tritium labeled albumin into the renal artery in vivo and in the isolated perfused kidney (IPK). RESULTS: The glomerular filtered albumin is returned to the blood supply by a high capacity pathway that transports this albumin at a rate of 1830+/-292 microg/min rat kidney (n= 14) (mean+/-SEM). This pathway has been identified under physiological conditions in vivo and in the IPK. The pathway is specific for albumin as it does not occur for horseradish peroxidase (HRP). The pathway is inhibited in a non-filtering kidney. The pathway is also inhibited by NH4Cl, an inhibitor of protein uptake. CONCLUSIONS: The high capacity retrieval pathway for albumin is most likely associated with transtubular cell transport. It is also apparent that most albuminuric states could be accounted for by the malfunctioning of this pathway without resorting to any change in glomerular permselectivity.

Albumins↗
PubMedDate not supplied

Sulphated macromolecules produced by in vivo labelling in the rat gastric mucosa.

The aim of this study was to investigate the nature and distribution of sulphated macromolecules of the extracellular matrix in rat gastric mucosa. This was achieved by developing an in vivo labelling system. An intraperitoneal injection of 1 mCi [35S]-sulphate was given for either 4 h (0.01% incorporation into macromolecular fraction) or 8 h (0.13% incorporation). At the end of the labelling period the stomach was removed and the mucosa and submucosa was either taken as a single combined sample or separated into four layers by blunt dissection. Each sample was papain digested and analysed by ion-exchange chromatography. This analysis revealed sulphated species of differing charge existing in differing proportions throughout the mucosa. These sulphated species eluted at NaCl concentrations of approximately 0 (A), 0.19 (B), 0.34 (C) and 0.78 mol/L (D) from a Q-Sepharose ion exchange column. Further analysis by size exclusion chromatography and chemical and enzymatic digestion showed that peaks B and C had molecular weights of 2.4 x 10(5) and 2.8 x 10(5), respectively and were resistant to chondroitinase ABC, heparitinase and nitrous acid digestion. Peak D was found to contain a polydisperse population of molecules with a molecular weight range of approximately 1 x 10(4) to 6 x 10(4). This sample was susceptible to nitrous acid and chondroitinase ABC digestion and was found predominantly in the sample isolated from deeper in the tissue. We have thus developed an in vivo labelling technique for sulphated macromolecules that can be used in the further study of injury to the gastric mucosa.

Animals↗