Search results for "Cuba."
showing 10 items of 340 documents
Modulation of P450 enzymes by Cuban natural products rich in polyphenolic compounds in rat hepatocytes.
2008
This paper reports cytotoxic effects and changes in the P450 system after exposing rat hepatocytes to four polyphenol-rich products widely used in Cuban traditional medicine (Mangifera indica L. (MSBE), Thalassia testudinum (Tt), Erythroxylum minutifolium and confusum extracts). Effects of mangiferin, the main polyphenol in MSBE, were also evaluated. Cytotoxicity was assayed by the MTT test after exposure of cells to the products (50-1000 microg/mL) for 24 or 72 h. The results showed that 500 microg/mL MSBE was moderately cytotoxic after 72 h, while mangiferin was not. Marked reductions in cell viability were produced by Erythroxylum extracts at concentrationsor = 200 microg/mL, whereas onl…
Different deoxyribonucleases in human lymphocytes
1974
Abstract The distribution pattern of deoxyribonuclease activities in human lymphocytes has been examined by micro-disc-electrophoresis. Four groups of deoxyribonuclease activities, differing in their electrophoretic mobility, in the nature of their optimal substrate and in their optimal incubation conditions, are characterized. There are two alkaline DNase-activities. One corresponds to DNase I (EC 3.1.4.5), the other having pH optimum of about pH 9.0, prefers denatured DNA as substrate and is not dependent on divalent cations. The fractions with an acid pH optimum can be subdivided into two groups, which differ in their activity towards native DNA, towards denatured DNA, in their activity …
Effect of genistein added to bull semen after thawing on pronuclear and sperm quality.
2015
The aim of this research was to study the effect of different genistein treatments on bull sperm after thawing on pronuclear formation after in vitro fertilization (IVF) and on different sperm quality variables. Three experiments were performed. In Experiment 1, three treatments (Control, sperm incubation for 1 h at 37 degrees C with or without genistein) and two sperm concentrations during IVF (I or 3 x 10(6) sperm/mL) were evaluated to study the influence of genistein on pronuclear formation (PNF). Sperm incubation for 1 h before IVF reduced PNF regardless of sperm concentration. However, after sperm incubation and with 3 x 10(6) sperm/mL in IVF, the genistein treatment group had greater …
Metabolic activity of fresh and cryopreserved cynomolgus monkey (Macaca fascicularis) hepatocytes
2000
1. The effect of cryopreservation on the metabolic capacity of monkey hepatocytes over 4 h in suspension and 24 h in culture was determined. Hepatocytes were diluted in a buffer containing 10% DMSO and frozen in a computer-controlled chamber. 2. Initial ethoxyresorufin and ethoxycoumarin O-deethylase (ECOD) activities were the same in fresh and cryopreserved (CP) hepatocytes. ECOD activity in suspensions declined over 4 h but was the same in fresh and CP hepatocytes. 3. The formation of testosterone hydroxy (OHT) metabolites (namely 6beta-OHT, 2beta-OHT, 16beta-OHT, 16alpha-OHT, 15beta-OHT, 2alpha-OHT and 6beta-OHT) was unaffected by cryopreservation. The loss of OHT activities over 4 h in …
Effect of acidosis on lipid peroxidation in brain slices.
1991
Acidification of the incubation medium markedly increased lipid peroxidation of cortical brain slices. Lactic acidosis caused a more extensive lipid peroxidation than did phosphoric acidosis (+35% at pH 6 and +81% at pH 5), probably due to the rapid diffusion of the protonated form of lactic acid across cell membranes. These results support the hypothesis that free radical mechanisms may be involved in the cytotoxicity of acidosis.
Formation and release of acetylpyrrolidinecholine (N-methyl, N-acetoxyethylpyrrolidinium) as a false cholinergic transmitter in the myenteric plexus …
1977
1. Longitudinal muscle strips of the guineapig small intestine were incubated with Tyrode solution containing the choline analogue pyrrolidinecholine. At the end of the incubation the concentrations of acetylcholine and its analogue acetylpyrrolidinecholine were determined in the strips by gas chromatography. 2. After 120 min of incubation with 1 mM pyrrolidinecholine, acetylpyrrolidinecholine comprised about 15% of the total amount of acetylcholine plus acetylpyrrolidinecholine. Electrical stimulation (1 Hz) of the strips during the incubation slightly increased the proportion of acetylpyrrolidinecholine to 21%. 3. The acetylcholine content of control strips increased significantly during …
Firm survival: The role of incubators and business characteristics
2015
This paper analyzes the impact of business incubators on firm survival. Using a configurational comparative method, namely fuzzy-set qualitative comparative analysis (fsQCA), the article also examines whether degree of business innovation, size, sector, and export activity affects firm survival. Results show that, when combined with other variables (i.e. sector, technology), business size is a sufficient condition for firm survival. Likewise, incubators alone cannot affect survival. A combination between incubators and other factors is necessary to ensure firm survival. Sin financiación 2.129 JCR (2015) Q2, 40/120 Business UEV
How useful are incubators for new entrepreneurs?
2016
This study examines profiles of incubator tenants who provide the most positive evaluations of the use of advisory services and support from incubators. The study presents an application of qualitative comparative analysis (QCA) to a sample of 54 incubator tenants in Valencia, Spain. The study examines how entrepreneurs' age, gender, education and training, work experience, and family background affect the utility of advice and support from experts at the incubator. The results of the research inform that the incubator tenants who find the services of incubators most useful are young, have good studies, have professional experience, and have family experience.
First-principles study of the electronic structure of cubicGaS: Metallic versus insulating polymorphs
2007
The electronic structure of different polymorphs of gallium sulphide $(\mathrm{GaS})$ with cubic structure is investigated by means of first-principles band structure calculations in connection with experimental reports on a metastable semiconducting cubic form of this material. The expected metallic character of simple cubic phases containing one $\mathrm{GaS}$ group per unit cell (rocksalt or zinc-blende) is confirmed by the calculations. A cubane-based zinc-blende structure is found to exhibit a band gap which is compatible with experimental results but the unit cell parameter is much larger than the reported ones. We have also studied cubic phases containing hydrogen. It is found that t…
Kinetics and isotherm of fibronectin adsorption to three-dimensional porous chitosan scaffolds explored by125I-radiolabelling
2013
In this study, 125I-radiolabelling was explored to follow the kinetics and isotherm of fibronectin (FN) adsorption to porous polymeric scaffolds, as well as to assess the elution and exchangeability of pre-adsorbed FN following incubation in serum-containing culture medium. Chitosan (CH) porous scaffolds with two different degrees of acetylation (DA 4% and 15%) were incubated in FN solutions with concentrations ranging from 5 to 50 µg/mL. The kinetic and isotherm of FN adsorption to CH were successfully followed using 125I-FN as a tracer molecule. While on DA 4% the levels of adsorbed FN increased linearly with FN solution concentration, on DA 15% a saturation plateau was attained, and FN a…