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Kt/V Values (v + value)
Selected AbstractsSubcutaneous Transposition of the Superficial Femoral Artery for Arterioarterial Hemodialysis: Technique and ResultsARTIFICIAL ORGANS, Issue 12 2008Octavio J. Salgado Abstract We report the use of subcutaneous transposition of the femoral artery (STFA) for placement of both inflow and outflow needles in 14 hemodialysis (HD) adult patients with difficult access. Follow-up time was 318 months during which a total of 3215 arterioarterial HD sessions were done. Kt/V values ranged between 0.71 and 1.59. Elevated access recirculation and dialysis outflow pressures were common findings to all patients. Complications were: (i) two episodes of bleeding secondary to puncture-related arterial wall laceration, repaired by stitching; (ii) three episodes of thrombosis in two patients, all successfully declotted; (iii) three puncture-related complications needing placement of a vein interposition graft, namely, aneurysm, pseudoaneurysm, and arterial stenosis; and (iv) one case of arterial ligation because of suppurative puncture site infection, without subsequent distal ischemia signs or claudication. The use of STFA should only be reserved for patients in urgent need for vascular access with no remaining options. [source] Oil and fungal biomass dispersion in a stirred tank containing a simulated fermentation brothJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2001Ma Soledad Córdova-Aguilar Abstract The production of ,-decalactone by the filamentous fungus Trichoderma harzianum involves four phases (oil,water,air,mycelium) and its dispersion is crucial during fermentation. Oil and biomass (when present) dispersion, as a function of the volumetric power drawn (P/V), was characterized, in two; three- and four-phase systems agitated with Rushton turbines. Trichoderma harzianum mycelium was used as the solid phase in the four-phase system. Two stages of the fermentation were simulated: the beginning (15% oil and 1.4,kgm,3 of mycelium) and the end (2% oil and 10.6,kg,m,3 of mycelium). In the two-phase system, the use of exhausted broth achieved higher oil dispersions at low P/V values as compared with distilled water. Aeration decreased the oil dispersion for the high-oil system, but enhanced oil dispersion for the low-oil system. Compared with the P/V used in the actual fermentation (0.2,kW m,3), a high segregation of the system was observed for the high-oil/low-biomass system, due to the difficulty of mixing the thick oil,air emulsion present at the top of the tank. The system simulating the end of the fermentation reached almost complete homogeneity of oil and biomass, a phenomenon due to the high biomass/oil ratio and the biomass acting as an oil carrier. © 2001 Society of Chemical Industry [source] Pressure-exploration of the 33-kDa protein from the spinach photosystem II particleFEBS JOURNAL, Issue 9 2001Kangcheng Ruan The 33-kDa protein isolated from the spinach photosystem II particle is an ideal model to explore high-pressure protein-unfolding. The protein has a very low free energy as previously reported by chemical unfolding studies, suggesting that it must be easy to modulate its unfolding transition by rather mild pressure. Moreover, the protein molecule consists of only one tryptophan residue (Trp241) and eight tyrosine residues, which can be conveniently used to probe the protein conformation and structural changes under pressure using either fluorescence spectroscopy or fourth derivative UV absorbance spectroscopy. The different experimental methods used in the present study indicate that at 20 °C and pH 6, the 33-kDa protein shows a reversible two-state unfolding transition from atmospheric pressure to about 180 MPa. This value is much lower than those found for the unfolding of most proteins studied so far. The unfolding transition induces a large red shift of the maximum fluorescence emission of 34 nm (from 316 nm to 350 nm). The change in standard free energy (,Go) and in volume (,V) for the transition at pH 6.0 and 20 °C are ,14.6 kJ·mol,1 and ,120 mL·mol,1, respectively, in which the ,Go value is consistent with that obtained by chemical denaturation. We found that pressure-induced protein unfolding is promoted by elevated temperatures, which seem largely attributed to the decrease in the absolute value of ,Go (only a minor variation was observed for the ,V value). However, the promotion of the unfolding by alkaline pH seems mainly related to the increase in ,V without any significant changes in ,Go. It was also found that NaCl significantly protects the protein from pressure-induced unfolding. In the presence of 1 m NaCl, the pressure needed to induce the half-unfold of the protein is shifted to a higher value (shift of 75 MPa) in comparison with that observed without NaCl. Interestingly, in the presence of NaCl, the value of ,V is significantly reduced whilst that of ,Go remains as before. The unfolding-refolding kinetics of the protein has also been studied by pressure-jump, in which it was revealed that both reactions are a two-state transition process with a relatively slow relaxation time of about 102 s. [source] Kinetics of inhibition of peroxidase activity of myeloperoxidase by quercetinINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2008Tatjana Momi The inhibition of myeloperoxidase (MPO), isolated from human neutrophils, by quercetin was investigated by following peroxidase activity of the enzyme using o -dianisidine as the substrate. The inhibition parameters (IC50) were obtained by graphical analysis of the inhibition curves. A reaction mechanism, which involved the enzyme inhibition by quercetin and H2O2 in excess, was proposed. The rate and equilibrium constants for the proposed reaction path were calculated from experimental data. Kinetic analysis in noninhibiting H2O2 concentration range in the absence and the presence of quercetin revealed that the reaction mechanism underwent Michaelis,Menten kinetics. K and V values indicated that quercetin was a mixed inhibitor of MPO activity. The initial reaction rates were recalculated using the obtained results. Calculated curves fitted the experimental results within the range of experimental error. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 384,394, 2008 [source] | ||||||||||