PubMed · 1367542
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J F Dow. 1991. Imaging with simultaneous DIC and fluorescence microscopy.. https://pubmed.ncbi.nlm.nih.gov/1367542/
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Backfiltration of dialysis solution can occur during hemodialysis with highly permeable membranes. A method has recently been developed for determining backfiltration rates in vitro at low dialysate flow rates by measuring changes in the local dialysate concentration of a marker macromolecule via sampling ports added to the hemodialyzer housing. In the present study, the influence of net ultrafiltration on backfiltration rates was determined for five commercial dialyzers containing membranes with different water permeabilities. In vitro experiments were performed (n = 3) using freshly donated whole blood at blood flow rates of 200 and 340 ml/min and at a dialysate flow rate of 100 ml/min. At zero net ultrafiltration, backfiltration rates increased with increasing membrane water permeability and ranged from 0.9 to 6.9 ml/min. At a net ultrafiltration rate of 10 ml/min, backfiltration was eliminated for dialyzers containing membranes with water permeabilities of less than 30 ml/h/mm Hg but remained significant for dialyzers with higher membrane water permeabilities. Therefore, despite a significant net ultrafiltration rate, backfiltration may still occur during hemodialysis with highly permeable membranes.
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The Folch-Pi proteolipid is the most abundant structural protein from the central nervous system myelin. This protein-lipid complex, normally insoluble in water, requires only a small amount of water for solubilization in reverse micelles of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in isooctane. The characterization of the proteolipid-free and proteolipid-containing micelles was undertaken by light scattering and fluorescence recovery after fringe pattern photobleaching (FRAPP) experiments. Quasi elastic light scattering (QELS) was carried out at a high (200 mM) AOT concentration, at low water-to-surfactant mole ratio (Wo = 7) and at increasing protein occupancy. Two apparent hydrodynamic radii, differing tenfold in size, were obtained from correlation functions. The smaller one (RaH = 5.2 nm) remains constant and corresponds to that measured for protein-free micelles. The larger one increases linearly with protein concentration. In contrast, FRAPP measurements of self-diffusion coefficients were found unaffected by the proteolipid concentration. Accordingly, they have been performed at constant protein/surfactant mole ratios. The equivalent RH, extrapolated to zero AOT concentration for protein-free reverse micelles (2.9 nm) and in the presence of the proteolipid (4.6 nm), do not reveal the mode of organization previously suggested by QELS measurements. The complex picture emerging from this work represents a first step in the characterization of an integral membrane protein in reverse micelles.