Studies were undertaken in Munich-Wistar rats to assess the influence of changes in filtered bicarbonate (FLHCO3), induced by changes in GFR, on Na+/H+ exchange activity in renal brush border membrane vesicles (BBMV). Whole-kidney and micropuncture measurements of GFR, FLHCO3, and whole-kidney and proximal tubule HCO3 reabsorption (APRHCO3) were coupled with BBMV measurements of H+ gradient-dri...

The variation of kinetic parameters of d-amino acid oxidase from Rhodotorula gracilis with pH was used to gain information about the chemical mechanism of the oxidation of D-amino acids catalysed by this flavoenzyme. d-Alanine was the substrate used. The pH dependence of Vmax and Vmax/Km for alanine as substrate showed that a group with a pK value of 6.26-7.95 (pK1) must be unprotonated and a g...

OBJECTIVES The aim of this study was to evaluate the effect of hypothermia on the in-vivo pharmacokinetics of 4-nitrophenol (4NP) using rat liver homogenate and rat liver perfusion system. METHODS Rat liver homogenate was incubated with 4NP, which is mainly metabolized by cytochrome P450 2E1, at 37, 34, 32 or 28°C. The Michaelis constant (Km ) and maximum elimination velocity (Vmax ) of 4NP w...

The β-glucosidase from almond was immobilized using different strategies: ionic adsorption on aminated (MANAE)-agarose beads at pH 5, 7 and 9, followed by glutaraldehyde pre-activated supports. of the immobilization altered to allow enzyme molecule orientations support surface. concentration exhibited an effect stability free enzyme. Immobilization ion exchange maintained up 80% activity β-gluc...

To investigate the role in catalysis and/or substrate binding of the Walker motif residues of rat testis fructose 6-phosphate, 2-kinase:fructose-2,6-bisphosphatase (Fru 6-P,2-kinase:Fru-2,6-Pase), we have constructed and characterized mutant enzymes of Asp-128, Thr-52, Asn-73, Thr-130, and Tyr-197. Replacement of Asp-128 by Ala, Asn, and Ser resulted in a small decrease in Vmax and a significan...

The phosphotriesterase from Pseudomonas diminuta hydrolyzes a wide variety of organophosphate insecticides and acetylcholinesterase inhibitors. The rate of hydrolysis depends on the substrate and can range from 6000 s-1 for paraoxon to 0.03 s-1 for the slower substrates such as diethylphenylphosphate. Increases in the reactivity of phosphotriesterase toward the slower substrates were attempted ...

Aim: To determine the interaction of over-the-counter (OTC) and illicit psychostimulants at the cytochrome P450 enzyme, CYP2D6. CYP2D6 is responsible for 20% of hepatic Phase I metabolism and is a site of drug-drug interactions, leading to increased drug toxicity. Materials and Methods: We examined the effects the OTC drugs; 1) the prototype H2-antagonist cimetidine (CMT) and 2) the opioid agon...

In a cold dark matter ( CDM) cosmology, the Milky Way accretes satellites into the stellar disc. We use cosmological simulations to assess the frequency of near disc plane and higher inclination accretion events, and collisionless simulations of satellite mergers to quantify the final state of the accreted material and the effect on the thin disc. On average, a Milky Way-sized galaxy has three ...

Dissolved organic nitrogen (DON) makes up a large fraction of the total dissolved nitrogen pool in coastal waters, but is often ignored as a potential nitrogen source for primary producers. In laboratory experiments, we measured the uptake of small, labile DON compounds, urea and a variety of different amino acids, by the common estuarine macroalgae Ulva lactuca and Gracilaria vermiculophylla. ...

The effect of pH on the kinetics of the following transhydrogenation reactions catalyzed by energized and nonenergized submitochondrial particles has been studied: NADH leads to 3-acetylpyridine adenine dinucleotide phosphate (AcPyADP), NADH leads to thionicotinamide adenine dinucleotide phosphate (thioNADP), NADPH leads to AcPyADP, and NADPH leads to thioNADP. The effect of membrane energizati...