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A De Flora

Publications and source records attributed to A De Flora.

144 records · Page 8Linked to original sources
PubMed1968

A new hepatic protein inactivating glucose 6-phosphate dehydrogenase.

Two NADP-cleaving enzymes, namely NADP glycohydrolase and NADP pyrophosphatase, are present in a rat liver extract that inactivates G6PD (glucose 6-phosphate dehydrogenase). The following results suggest that a third G6PD-inactivating protein is present in this extract. (1) Nicotinamide, which selectively inhibits NADP glycohydrolase, enhances the G6PD inactivation under conditions where G6PD activity in control experiments is rather stable. (2) DEAE-cellulose adsorbs the bulk of both NADP glycohydrolase and NADP pyrophosphatase, whereas most of the G6PD-inactivating ability is unadsorbed. (3) Out of 37 liver extracts that were prepared, two were found to lack NADP pyrophosphatase. After removal of NADP glycohydrolase from these extracts by centrifugation, they were still found to inactivate G6PD. (4) Deproteinization of DEAE-cellulose supernatants results in a complete loss of G6PD-inactivating ability; moreover, kinetic experiments performed with the extracts lacking pyrophosphatase strongly support the view that the inactivating protein is an enzyme, although its mechanism is not clear. (5) NADP protects G6PD from inactivation and also reactivates the enzyme completely, thus supporting the view of some action of the inactivating protein on the G6PD-bound NADP.

Animals↗
PubMedDate not supplied

Enhanced antitumor activity of adriamycin by encapsulation in mouse erythrocytes targeted to liver and lungs.

Adriamycin was encapsulated within human and murine (B6D2F1 female mice) erythrocytes using a procedure based on hypotonic hemolysis followed by isotonic resealing and reannealing. Following drug encapsulation the murine erythrocytes were treated with glutaraldehyde to obtain: a) control of Adriamycin efflux from loaded erythrocytes, b) appropriate hepatic and pulmonary targeting of the in vivo re-infused cells. The antitumor effect of equivalent amounts of bolus (i.v.) administered Adriamycin, 1) free, 2) encapsulated within erythrocytes, 3) encapsulated within glutaraldehyde-treated erythrocytes, was compared using an in vivo model of metastasis based on selective hepatic and pulmonary dissemination of intrasplenically injected L1210 cells in B6D2F1 mice. The therapeutic index (TI) of Adriamycin encapsulated within glutaraldehyde-treated erythrocytes increased by more than two-fold over that of the free drug.

Animals↗
PubMedDate not supplied

Human erythrocyte glucose 6-phosphate dehydrogenase. Influence of coenzyme derivatives on thermostability and kinetic properties.

A number of derivatives of NADP(H) were tested with respect to their effectiveness in interacting with tetrameric glucose 6-phosphate dehydrogenase (G6PD) retaining only the fraction of "structural" coenzyme (4 moles NADP). Interaction was probed by two parameters: a) increased thermostability of G6PD activity, measured as the difference in the corresponding transition temperature (Tm) of samples containing and lacking the NADP derivatives, respectively; b) competitive inhibition toward NADP, expressed a Ki values. Protection afforded by the various effectors against thermal denaturation decreased in the following order: NADPH, NADP, PADP-ribose, adenosine 2',5'-P2. Other NADP derivatives, including 2',3' cyclic NADP, NMN, NMNH, nicotinamide, adenosine 2'-P, were uneffective in respect to this property. The kinetically measured affinity was the greatest for NADPH and decreased progressively for the following effectors: PADP-ribose, NADP, NMNH, PADP-glycolaldehyde, adenosine 2',5'-P2, PADP-ribitol, adenosine 2'-P. Nicotinamide and NMN were uneffective on NADP binding. These data show that the adenosine moiety of NADP is more critically involved than the nicotinamide portion in the interaction with human G6PD.

Drug Stability↗
PubMedDate not supplied

Construction of glucose oxidase-loaded human erythrocytes: a model of oxidative cytotoxicity.

Human red blood cells were loaded with Glucose oxidase from Aspergillus niger by a standardized procedure of encapsulation involving transient hypotonic hemolysis followed by isotonic resealing. The amount of loaded enzyme activity, as evaluated by O2 consumption at 5 mM glucose, ranged from 40 to 75 mumoles O2/hr/ml of packed red cells at 37 degrees C. The red cells loaded with Glucose oxidase were found to behave as efficient glucose-consuming bioreactors. Moreover, at 5 mM glucose, no clear mechanism of H2O2-induced damage was apparent, with the exception of a significantly increased formation of methemoglobin (10% approximately) and of a several-fold stimulated intracellular rate of hexose monophosphate shunt activity, indicating glutathione peroxidase-mediated draining of reduced glutathione for removal of bursts of H2O2. The Glucose oxidase-loaded red cells represent a convenient model system for cytotoxicity studies aiming at clarifying the effects of intracellularly formed H2O2.

Aspergillus niger↗