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Biomedical subjects

A Cova

Publications and source records attributed to A Cova.

14 recordsLinked to original sources
PubMed1995

Providing distinct vergence and version dynamics in a bilateral oculomotor network.

Given reported interactions between vergence and version dynamics, ocular reflexes cannot be properly modelled as separate independent subsystems. Using a model structure compatible with known anatomy, we show that a single bilateral system can produce results consistent with observed data both at the central and ocular levels. This model provides for both vergence and conjugate integrators in a single controller, and explains the observed modulation on abducens interneurons and mesencephalic vergence cells during vergence responses. Reported interactions between version and vergence would then be a natural consequence of a shared premotor network. Major implications include: the need to record both eyes in a protocol, since cross-talk is always possible; and adaptation to monocular changes could be distributed in all motor projections to both eyes.

Abducens Nerve↗
PubMed1986

Determination of denzimol, a new anticonvulsant agent, and its main metabolite in biological material by gas chromatography and high-performance liquid chromatography.

Two methods, using gas chromatography (GC) and high-performance liquid chromatography (HPLC), were developed in order to investigate the pharmacokinetics of denzimol hydrochloride, N-[beta-[4-(beta-phenylethyl)phenyl]-beta-hydroxyethyl] imidazole hydrochloride, which is a new anticonvulsant drug, and of its main metabolite, N-[beta-[4-(beta-phenyl-beta(alpha)-hydroxyethyl)phenyl] -beta-hydroxyethyl]-imidazole (referred to as M2), in humans. Both methods involve the use of a homologue of denzimol as an internal standard. The GC method is more sensitive (sensitivity limit 2.5 ng/ml for denzimol and 15 ng/ml for M2) and was utilized for the determination of denzimol and M2 in plasma. The GC method is specific, precise (relative standard deviations are 3.26, 2.12 and 1.72% at 10, 100 and 1000 ng/ml for denzimol and 6.45, 4.17 and 3.38% at 50, 500 and 1000 ng/ml for M2) and accurate (mean recovery +/- S.D. is 102.58 +/- 4.10% for denzimol and 99.72 +/- 7.75% for M2). The HPLC method is very simple and quick to perform. This method has a sensitivity limit of 0.5 micrograms/ml for denzimol and 1 microgram/ml for M2, and allows the determination of both compounds in urine with high selectivity, reproducibility (relative standard deviations are 2.05, 3.50 and 1.02% for denzimol and 2.78, 2.80 and 1.73% for M2, at concentrations of 15, 35 and 70 micrograms/ml) and accuracy (mean recovery +/- S.D. is 103.57 +/- 2.97% for denzimol and 95.91 +/- 1.59% for M2). The common anticonvulsants, when present in plasma, do not interfere with the monitoring of denzimol levels.

Anticonvulsants↗
PubMed1979

Is there a physiological intravascular coagulation in obstetrical cases?

The concentrations of plasmatic fibrinogen and its degradation products (FDPs), and the paracoagulation test using serial dilution of protamine sulphate (SDPS) were determined during the third trimester of pregnancy, labor, and puerperium. Singificant increases in the concentrations of fibrinogen and FDPs were observed throughout the process of pregnancy and birth, combined with both positive and negative SDPS tests. We suggest that these findings do not indicate a process of physiological DIC.

Blood Coagulation Tests↗
PubMed1976

Intravascular coagulation in obstetrics: Serial dilution protamine sulfate test throughout labor.

Serial dilution protamine sulfate tests (SDPS) were performed in 191 women during labor. It was found that 27 per cent of women with uncomplicated pregnancies and 42 per cent with complicated pregnancies had positive SDPS tests, the highest incidence being between three and six hours of labor. These findings support the previous report of a physiologic disseminated intravascular coagulation in pregnancy but make the SDPS test of little value in obstetric cases.

Disseminated Intravascular Coagulation↗
PubMed1975

Flavoxate and 3-methylflavone-8-carboxylic acid. Assay methods in blood and urine, plasma-red cells repartition and stability.

The following assay methods for pharmacokinetic studies on flavoxate (F) and on its main metabolite, i.e. 3-methylflavone-8-carboxylic acid (A), are described. 1. Spectrophotometry for the assay of F and of A in plasma, 2. TLC-Spectrodensitometry and GLC for the assay of A in urine after acid hydrolysis, 3. TLC-Spectrodensitometry for determining the F : A ratio in plasma or in urine. It was found that F hydrolyzes into A. This process depends on the pH and on the medium. In water, at pH 5.0, F is stable, while in phosphate buffer at pH 7.4 the semi-hydrolysis time is 60 min. In a solution with bovine serum albumin, in rat, rabbit, dog or human plasma the semi-hydrolysis times are between 5 and 60 min. Finally the plasma-red cells repartitions of F and of A were studied in vitro in rat, rabbit, dog and human blood and found between 0.8 and 2.0 for F and between 2.1 and 4.6 for A.

Animals↗
PubMed1975

Pharmacokinetics of flavoxate in rats.

The plasma levels, the urinary excretion and the biliary excretion of piperidinoethyl-3-methylflavone-8-carboxylate (flavoxate, F) were studied in rats after i.v. and after oral administration. Parallel experiments were made with 3-methyl-flavone-8-carboxylic acid (M), the main metabolite of F. The substances are found in blood and are excreted in the urine and in the bile. The quantities excreted in the urine after oral administration are similar to those excreted after i.v. administration, showing that the enteric availability of the drugs is almost complete. The end product in urine and in bile is represented by a substance which yields M after a strong acid hydrolysis. There are marked pharmacokinetic differences between F and M, probably related to their physical properties.

Administration, Oral↗
PubMedDate not supplied

In vitro and in vivo tetracycline-controlled myogenic conversion of NIH-3T3 cells: evidence of programmed cell death after muscle cell transplantation.

Ex vivo gene therapy of Duchenne muscular dystrophy based on autologous transplantation of genetically modified myoblasts is limited by their premature senescence. MyoD-converted fibroblasts represent an alternative source of myogenic cells. In this study the forced MyoD-dependent conversion of murine NIH-3T3 fibroblasts into myoblasts under the control of an inducible promoter silent in the presence of tetracycline was evaluated. After tetracycline withdrawal this promoter drives the transcription of MyoD in the engineered fibroblasts, inducing their myogenesis and giving rise to beta-galactosidase-positive cells. MyoD-expressing fibroblasts withdrew from the cell cycle, but were unable to fuse in vitro into multinucleated myotubes. Five days following implantation of engineered fibroblasts in muscles of C57BL/10J mice we observed a sevenfold increase of beta-galactosidase-positive regenerating myofibers in animals not treated with antibiotic compared with treated animals. After 1 week the number of positive fibers decreased and several apoptotic myonuclei were detected. Three weeks following implantation of MyoD-converted fibroblasts in recipient mice, no positive "blue" fiber was observed. Our results suggest that transactivation by tetracycline of MyoD may drive an in vivo myogenic conversion of NIH-3T3 fibroblasts and that, in this experimental setting, apoptosis plays a relevant role in limiting the efficacy of engineered fibroblast transplantation. This work opens the question whether apoptotic phenomena also play a general role as limiting factors of cell-mediated gene therapy of inherited muscle disorders.

3T3 Cells↗