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Biomedical subjects

M Constantin

Publications and source records attributed to M Constantin.

At least 19 recordsLinked to original sources
PubMed2002

Experimental persistence probability for fluctuating steps.

The persistence behavior for fluctuating steps on the Si(111)-(sqrt[3]xsqrt[3])R30 degrees -Al surface was determined by analyzing time-dependent STM images for temperatures between 770 and 970 K. Using the standard persistence definition, the measured persistence probability displays power-law decay with an exponent of theta=0.77+/-0.03. This is consistent with the value of theta=3/4 predicted for attachment-detachment limited step kinetics. If the persistence analysis is carried out in terms of return to a fixed-reference position, the measured probability decays exponentially. Numerical studies of the Langevin equation used to model step motion corroborate the experimental observations.

Journal Article↗
PubMed2001

Acrylic microspheres for oral controlled release of the biguanide buformin.

Spherical microparticles based on methacrylic acid-methyl methacrylate copolymer have been developed. The method chosen for the preparation of such microparticles was suspension radical copolymerization of acrylic comonomers in the presence of the ethyleneglycol dimethacrylate as crosslinking agent. The microparticles obtained were characterised by inverse size exclusion chromatography, scanning electron microscopy, swelling degree and exchange capacity. The porous volume of the microspheres ranged from 0.086 ml/g for the microparticles produced by a methacrylic acid/methyl methacrylate ratio of 1/3 and a 10% degree of crosslinking, to 8.57 ml/g for the microparticles produced by a methacrylic acid/methyl methacrylate ratio of 3/1 and 2% degree of crosslinking (in 0.1 N NaCl in phosphate buffer pH 7.4). Also the pore diameter of the swollen microparticles ranged from a few to 120 A. Buformin tosylate - a classical hypoglycaemic drug - was included in the polymer network of the microparticles during the polymerization process. Due to the water solubility of the drug and its low solubility in the organic phase, the entrapment yield did not exceed 15%. However the amount of encapsulated drug as well as the drug released from the microparticles, was dependent on the methacrylic acid/methyl methacrylate ratio, the degree of crosslinking and solvent/comonomers ratio.

Administration, Oral↗
PubMed2000

[Changes to visual acuity and the visual field in a case of meningioma operated at the anterior level].

It's presented a midline meningioma of anterior level case which preoperative has an importance affectation of the visual acuity and visual field, and postoperative in dynamic is founded the important improvement of visual acuity and visual field. It's discussed visual field topography and atrophy optic pathophysiology. It's a neuro-ophthalmology case example, where the cooperation neurosurgery-ophthalmology permit medical solution and restored in social life of the patient.

Female↗
PubMed1990

Studies on the activity of bepridil as a scavenger of free radicals.

Bepridil, a calcium antagonist with anti-anginal, anti-ischemic, and anti-arrhythmic properties was assessed for its ability to scavenge free radicals. Bepridil reduced the stable free radical 1,1-diphenyl-2-picrylhydrazil (DPPH) in the molar ratio 2:1 and, in this respect, was as active as the reference anti-oxidants hydroquinone and alpha-tocopherol. Allopurinol and SOD inhibited cytochrome c reduction in a hypoxanthine-xanthine oxidase superoxide generating system, whereas bepridil was ineffective. Deoxyribose degradation induced by the .OH radical was prevented by bepridil (IC50 = 0.050 mM). This ability to scavenge .OH was similar to that of dimethyl sulfoxide (DMSO) (IC50 = 0.056 mM) and more potent than that observed with mannitol and allopurinol (IC50 values of 0.74 mM and 0.92 mM, respectively). The powerful .OH scavenging activity of bepridil was confirmed in vivo on alloxan induced diabetes in mice. Bepridil exerted a marked protective effect at 0.150 mmol/kg whilst, ethanol and DMSO were active at the doses of 90 and 94 mmol/kg, respectively. These results demonstrate that bepridil is a potent .OH radical scavenger. This property may contribute to the therapeutic activity of this drug in myocardial ischaemia.

Allopurinol↗
PubMed1985

Cardiotoxicity of high doses of isoproterenol on cardiac haemodynamics and metabolism in SHR and WKY rats.

The haemodynamic and metabolic effects on the heart due to high doses of isoproterenol were compared in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. In baseline conditions, the hypertrophied SHR heart displayed perfectly constant haemodynamics but had fewer energy reserves than the WKY heart. Isoproterenol (2 X 25 mg/kg, s.c.) caused high mortality, myocardial ischaemia, and heart failure in the SHR. These effects were accompanied by anaerobic metabolism. In the WKY rats, on the other hand, isoproterenol caused no changes in ST-segment elevation and no cardiac insufficiency; in addition, aerobic metabolism was maintained. A marked drop in coronary perfusion pressure and excessive accumulation of calcium in the myocardium account, in part, for the effects seen in the SHR. The results indicate that isoproterenol-induced heart failure in the SHR might be a useful model for selecting compounds designed to treat this disease.

Animals↗
PubMed1985

The effect of TP-5 and its analogs on skin grafts in mice.

The immunostimulatory action of oligopeptides RGH-0205 (Arg-Lys-Asp), RGH-0206 (Arg-Lys-Asp-Val) and TP-5 (Arg-Lys-Asp-Val-Try) was measured using the B10LP to C57BL skin graft system and the determination of splenic T cell ratio. While thymectomy increased the period between skin grafting and rejection, each of the oligopeptides increased the number of splenic T cells and in some extent restored the rejection capacity of thymectomised C57Bl mice, presumably by restoration of thymic hormone function.

Adjuvants, Immunologic↗
PubMed1979

Comparative study of oxaflozane urinary metabolism in man, the dog and the rat. Identification of the principal metabolites.

The urinary metabolites of isopropyl-4-(trifluoromethyl-3-phenyl)-2-morpholine (oxaflozane) were compared in man, the dog and the rat using thin-layer chromatography and gas chromatography. In the dog, the tritiated molecule on the morpholine ring was administered to a certain number of animals. The principal metabolites were isolated, purified and identified by IR, RMN spectrometry and mass spectrometry. The principal metabolite in man and the rat was obtained by osaflozane N-dealkylation. In the dog, 2 metabolites formed by cleavage of the morpholine ring were also observed.

Animals↗
PubMed1978

Zipeprol metabolism in man and in the animal.

The urinary metabolism of 1-(2-methoxy-2-phenyl)-ethyl-4-(2-hydroxy-3-methoxy-3-phenyl)-propyl-piperazine dihydrochloride (zipeprol) was studied in man, the dog and the rat. Zipeprol metabolites seemed comparable in man and rat. The principal metabolites isolated from urine were identified by TLC, GLC, IR and mass spectrometry. Zipeprol is partially eliminated untransformed from the body, is mainly metabolised by N-dealkylation, oxidation, hydroxylation and methylation.

Administration, Oral↗
PubMed1978

Pharmacokinetics of amixetrine in the dog. Relation of dose-to-plasma concentration.

N-[(2-Phenyl-2-isoamyloxy)-ethyl-pyrrolidine]-hydrochloride (amixetrine) was administered to dogs at increasing doses, by i.v. and oral routes. Plasma determinations of active principle were carried out by gas liquid chromatography. The sensitivity limits of the method was 0.1 micrograms/ml of plasma. The evolution of the absorption coefficient and variations in half-life as a function of dose, were studied. The results indicate a non-linear, two-compartment open model. A first-pass effect and enzymatic saturation are envisaged.

Administration, Oral↗