Biomedical subjects

F M Veronese

Publications and source records attributed to F M Veronese.

117 records · Page 7Linked to original sources

PubMedDate not supplied

Biopharmaceutical properties of uricase conjugated to neutral and amphiphilic polymers.

A comparative pharmacokinetic and biodistribution investigation of polymer-protein conjugates prepared with various amphiphilic polymers was carried out using uricase as a model. Four polymer-uricase derivatives have been obtained by covalent binding of a similar number of polymer chains of (a) linear poly(ethylene glycol) (Mw 5000 Da); (b) branched poly(ethylene glycol) (Mw 10 000 Da); (c) poly(N-vinylpyrrolidone) (Mw 6000 Da); (d) poly(N-acryloilmorpholine) (Mw 6000 Da). By intravenous administration to Balb/c mice, the conjugates displayed different pharmacokinetic and organ distribution behaviors. (1) The unmodified enzyme and the poly(N-vinylpyrrolidone) conjugate were the enzyme forms with the shortest and the longest permanence in blood respectively (mean residence time 45 and 4378 min). (2) Native uricase was found to localize soon after administration significantly in heart, lungs, and liver from where it was also rapidly cleared. (3) The poly(N-acryloilmorpholine) derivative showed the highest concentration levels in liver (up to 25.5% of the dose) and considerable accumulation took also place in the other considered organs. (4) Poly(N-vinylpyrrolidone)-uricase displayed a relevant tropism for liver but low uptake indexes were found for the other organs. (5) The branched poly(ethylene glycol) derivative accumulated preferentially in liver and spleen. (6) The linear poly(ethylene glycol) conjugate was, among the various uricase forms, the species with the lowest distribution levels in all the examined organs. (7) Finally, all the enzyme forms slowly disposed in kidneys with higher levels for the poly(N-acryloilmorpholine) derivative (15% after 2880 min) and unmodified uricase (14% after 1440 min).

Algorithms↗

PubMedDate not supplied

Drug-protein interaction: 8-methoxy psoralen as photosensitizer of enzymes and amino acids.

For a better insight of the molecular basis of the photobiological effects of furocoumarins, the relevance of proteins oxydation by singlet oxygen produced by these substrates under irradiation with long u. v. light was studied. Complex oligomeric as well as simple monomeric purified enzymes with high or low molecular weight and different properties and simple amino acids were irradiated under oxygen in presence of 8-methoxy-psoralen. The effects on both proteins and amino acids were compared with those obtained under similar conditions with typical photosensitizers as methylene blue and Rose Bengal. The results indicated that the photooxydation of proteins, although possible, appears to play a minor role, if any, in the mechanism of action of furocoumarin.

Amino Acids↗

PubMedDate not supplied

Coupling of monomethoxypolyethyleneglycols to proteins via active esters.

Two alternative methods for the attachment of monomethoxypolyethyleneglycols (PEG) to proteins are proposed; they are based upon the replacement of the hydroxy terminal function of PEG to carboxylate followed by its activation with dicyclohexylcarbodiimide and N-hydroxysuccinimide. The methods, which give more homogeneous product than that employing trichloro-s-triazine as coupling reagent, may also be used for the modification of essential -SH containing enzymes. The attachment of PEG activated via esters was tested with several model proteins and the influence of the extent of modification i. on the biological activity of various enzymes, ii. on the binding capacity for albumin and iii. on the clearance time in rats using superoxide dismutase as model tracer was evaluated. It was also demonstrated that the extent of PEG attachment varies greatly according to the different proteins used.

Animals↗

PubMedDate not supplied

Surface modification of enzymes for therapeutic use: monomethoxypoly (ethylene glycol) derivatization of ribonuclease.

Bovine pancreatic ribonuclease A (RNase) was modified at various extent at the lysine residues by monomethoxypoly(ethylene glycol) (MPEG) activated as active ester. For pharmacokinetic experiments a radioactive adduct was also prepared with tritiated amino acid as spacer between polymer and protein. The modification reduced only slightly the RNase catalytic activity and Km towards the substrate cytidine-2',3'-cyclic monophosphate. On the other hand extensively modified MPEG-RNase samples, showed significant decrease in activity towards ribonucleic acid. The polymer modification did not change the pH activity profile, increased the stability to proteolytic digestion, while the behaviour towards denaturants and heat was not modified. The native and MPEG-RNase administered IV, IM and SC to rats, showed impressive differences in pharmacokinetics: the half-life of the modified enzyme, evaluated in blood by radioactivity, was increased of 40-50 folds with respect to the native form.

Animals↗

PubMedDate not supplied

Evaluation of monomethoxypolyethyleneglycol derivatized superoxide dismutase in blood and evidence for its binding to blood cells.

A method to evaluate in blood free superoxide dismutase (SOD) and SOD covalently bound to monomethoxypolyethylene glycol (MPEG-5000) is reported. The method takes advantage of gel filtration and cationic exchange chromatography to remove substances present in plasma which can interfere with the SOD enzymatic assay. Using this methodology, it was demonstrated that, contrary to free SOD, MPEG-SOD, when added to blood, was not completely recovered in plasma. Binding of MPEG-SOD to blood cell components takes place involving interactions of MPEG chains with cell membranes.

Animals↗

PubMedDate not supplied

General stability of thermophilic enzymes: studies on 6-phosphogluconate dehydrogenase from Bacillus stearothermophilus and yeast.

The thermophilic enzyme 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate:NADP oxidoreductase, decarboxylating, EC 1.1.1.44) from Bacillus stearothermophilus was much more resistant to inactivation under different conditions of temperature, pH, guanidine-hydrochloride, and organic solvents (dioxane, dimethylformamide, acetone) than its mesophilic counterpart from yeast. In addition, the thermophilic enzyme largely withstands proteolysis with trypsin, chymotrypsin, and elastase when compared with the yeast enzyme. It is proposed that thermophilic enzymes are not only thermostable, but also generally more stable to most common protein denaturants than their mesophilic counterparts. Because of their remarkable stability, enzymes isolated from thermophilic microorganisms may be ideally suited for technological applications.

Geobacillus stearothermophilus↗

PubMedDate not supplied

[The modification of Cu, Zn-superoxide dismutase by monomethoxypolyethylene glycol improves the indices of the experimental therapy of the ischemic myocardium in rats].

Mice were used to make a comparative study of the biological distribution of intravenous preparations of native and monomethoxypolyethylene glycol-modified superoxide dismutase isolated from bovine liver, as well as native and aldehyde dextran. The study demonstrated that the biodistribution of the native enzymes from various sources was, however, equal, but in the mouse liver there was a higher accumulation of SOD isolated from the rat liver. AD-SOD was found to have a longer half-life in the blood and in the liver of mice, in particular, while MPEG-SOD showed 10, 15, and 16 times longer in the lungs, blood and heart of the animals examined, respectively. The elevated accumulation of MPEG-SOD in some organs was used for their treatment, particularly for experimental therapy of rat myocardial ischemia. A rat model of ischemia demonstrated that the intravenous bolus administration of MPEG-SOD reduced the size of a myocardial necrotic area by 40% as compared to a 13% decrease when the other compounds were assayed. The findings suggest that the MPEG-SOD preparation is promising for decreasing reperfusion injuries of the cardiovascular system and the lungs.

Animals↗

PubMedDate not supplied

Prevention of ischemia-reperfusion damage with polymerized superoxide dismutase.

The efficacy of preventing ischemia-reperfusion damage by employing native or modified (mPEG-SOD) superoxide dismutase in an experimental model of acute ischemia was tested in the left hind limb of 43 Wistar rats. A significative difference (p=0.004) of the survival leg rate was found in the group treated with mPEG-SOD (86.6%) compared with the control group (30%). This difference was confirmed both clinically and by TEM analysis of muscular specimens.

Animals↗

PubMedDate not supplied

[Polymer biomaterials (polyphosphazenes) in the repair of peripheral nervous system].

Biodegradable polymers gives interesting perspectives of use in making artificial conduits for peripheral nerve reconstruction. Poliphosphazenes are materials highly biocompatible and have a controllable reabsorption rate. According to the substitutes that are introduced in the molecule, they can also be used as a framework for drug release. Conduits obtained with poli [bis(etilalanate) phosphazene] were evaluated as guides for nerve regeneration in an experimental animal model. In six Wistar rats, under general anesthesia and with microsurgical technique, the ischiatic nerve was isolated. On the right side a segment of the nerve was removed in order to create a 10 mm gap. The defect was then repaired using the conduit. On the controlateral limb the nerve continuity was restored using as an autograft the segment removed from the right. Control were performed at 30, 90, 180 days and consisted in histological and electron microscopy investigations. They showed the gradual degradation of the conduit without signs of local and general toxicity. The regeneration of the nerve fibers in the lumen of the conduit was not significantly different from the one obtained with the autologous grafts. So poliphosphazene conduits may be considered effective as a guide for nerve regeneration, above all for the possibility of use the polymer as a carrier for neurite-promoting factors.

Animals↗