Effects of intermolecular thiol-disulfide interchange reactions on bsa fouling during microfiltration

Several studies have shown that one of the critical factors governing protein fouling of microfiltration membranes is the presence of denaturedand/or aggregated protein in the bulk solutions. Experiments were performed to evaluate the role of intermolecular disulfide interchange reactionson protein aggregation and membrane fouling during stirred cell microfiltration of bovine serum albumin (BSA). The flux decline during BSA filtration was quite dramatic due to the formation of a protein deposit thatfully covered the membrane pores. This flux decline could be completely eliminated by capping the free sulfhydryl group present on the BSA with eithera carboxymethyl or cysteinyl group, demonstrating the critical importance of this free thiol in the intermolecular aggregation reactions and, in turn, protein fouling. BSA aggregation during storage could be reduced by the addition of metal chelators (EDTA and citrate) or dithiothreitol, orby storage at lower pH (7.0) these solutions all had a significantly lower rate of fouling upon subsequent filtration. This behavior is completely consistent with the known chemistry of the thiol-disulfide interchange reaction, demonstrating that an understanding of these intermolecular (aggregation) reactions can provide a rational framework for the analysis and control of protein fouling in these membrane systems. (c) 1994 John Wiley & Sons, Inc.

Structural characterization of a "signature" phosphatidylethanolamine as the major 10-hydroxy stearic acid-containing lipid of Cryptosporidium parvum oocysts

A 10-hydroxy stearic acid-containing lipid from Cryptosporidium parvum was purified by thin-layer chromatography and analyzed by infrared spectroscopy, fast-atom bombardment mass spectrometry, 1H and 31P nuclear magnetic resonance spectroscopy, and was identified as phosphatidyl-ethanolamine.

Decreased skin blood flow early in the course of streptozotocin-induced diabetes mellitus in the rat

We have previously used laser Doppler technology to demonstrate that skin blood flow is reduced in Type 1 (insulin-dependent) diabetic patients. The possibility of using the skin as an extremely accessible indicator of diabetic microvascular disease is attractive. The streptozotocin diabetic rat is an appealing potential animal model. We performed measurements of skin blood flow in two rat species, nine Sprague Dawley (SD) rats and nine Wistar Kyoto (WKY) rats, observing early changes following the inception of diabetes. Four of the SD rats and five of the WKY rats were made diabetic, the rest serving as controls. There were no significant differences in skin blood flow between the two rat strains. As in man, there appear to be rat skin sites with primarily nutritive capillary supply and those with arteriovenous anastomotic predominance. The back and base of tail, both hair-covered areas, demonstrated low flow characteristics, consistent with nutritive perfusion. In contrast, the plantar surface of the paw behaved similarly to the finger or toe pulps in man, sites of arteriovenous perfusion, with high basal flow and a marked increment with thermal stimulation. In diabetic rats of both species, there was significantly lower flow at the back and base of tail than in non-diabetic animals. The differences were of the order of 30-40%. As a function of time, the decrease in blood flow at the base of tail parallelled the increase in glycohaemoglobin levels in the diabetic rats. In contrast, blood flow at the plantar surface of the paw was unchanged throughout the 3-month post-streptozotocin observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Skin blood flow in the Wistar-Kyoto rat and the spontaneously hypertensive rat

1. Using laser Doppler techniques in man, we have previously demonstrated differences in skin blood flow properties at sites with primarily nutritive (NUTR) perfusion, such as the elbow or knee, as compared to sites such as the finger pulp, with predominantly arteriovenous anastomotic (AVA) perfusion. 2. Basal and heat stimulated flow is greater at AVA sites. In man, blood pressure changes are reflected primarily by changes at AVA rather than NUTR sites. 3. These blood pressure induced changes affect the red blood cell velocity (VEL) component at AVA sites more than microvascular volume (VOL). 4. Given these findings in man, we decided to compare skin blood flow properties in a suitable animal model. 5. We chose the Wistar-Kyoto (WKY) and Spontaneously Hypertensive Rat (SHR) strains, in view of the marked difference in systemic blood pressure in these two related strains. 6. Skin blood flow varied considerably at different skin sites in the rats. Skin sites with hair covering, on the back and at the base of the tail, showed low basal and heat stimulated blood flow. 7. In contrast, the plantar surface of the paw behaved similarly to the finger or toe pulps in man, with 3-4-fold higher basal flow than the hair covered areas and a 7-8-fold rise with local heating to 44 degrees C. 8. Furthermore, there was a 25% greater blood flow at the plantar paw surface in the SHR rats as compared to the WKY rats, corresponding to the 25% higher systemic blood pressure in these animals. 9. The heat induced increase in flow at the plantar surface of the paw was primarily a result of a marked increase in VEL rather than VOL. 10. The higher flow at this site in SHR as compared to WKY rats was likewise ascribable to an increase in VEL, VOL being equivalent in the two strains.

The effect of increasing temperature on skin blood flow and red cell deformability

Using laser Doppler techniques in nine healthy volunteers, we contrasted the effect of increasing local skin temperature at the elbow, a skin site with nutritive microvasculature, and the finger pulp, with predominantly arteriovenous anastomic (AVA) perfusion). We also assessed flow at the finger dorsum, with contributions of both types of microvasculature. In parallel with the laser Doppler studies, we determined the effect of increasing temperature on the red cell deformability of our subjects, using the new technique of Cell Transit Time Analysis (CTTA). Thermal stimulation produced very large increases in skin blood flow at all three sites tested. However, the magnitude and the pattern of increase were different at the three sites. At the finger pulp, there was a linear approximately threefold increase in flow as temperature increased from the basal level to 44 degrees C. At the elbow, basal flow was considerably lower than at the finger pulp and increased very slowly until skin temperature reached 38 degrees C. From that point, flow increased sharply, reaching tenfold the basal level at 44 degrees C. The thermally induced increase at the finger dorsum was intermediate between the other two sites, with a pattern resembling the elbow more than the finger pulp. These differences among the sites were attributable to substantially different patterns of change in the two components of flow, microvascular volume and velocity. At the finger pulp, there was very little increase in microvascular volume with increasing temperature. The curve was practically flat from basal temperature to 44 degrees C. In contrast, there was a linear increase in red blood cell velocity of about 300%. At the elbow, both microvascular volume and red blood cell velocity exhibited a parallel curvilinear pattern of equivalent increase, on the order of 300% for each. There was only a small increase in both parameters until the temperature reached 38 degrees, at which point there was a sharp increase in both. At the finger dorsum, the situation was intermediate, again resembling the elbow more than the finger pulp. Cell Transit Time Analysis revealed a progressive decrease in red cell transit time (TT), from 3.28 ms at 28 degrees C to 2.48 m at 44 degrees C, an overall change of 24%. The decrease in TT was accompanied by an increase in transit frequency, measured as counts s-1 (C s-1), from 3.1 to 5.3, an overall change of 71%. The changes in both TT and C/S were essentially linear.(ABSTRACT TRUNCATED AT 400 WORDS)