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Biomedical subjects

A Ubeda

Publications and source records attributed to A Ubeda.

41 records · Page 3Linked to original sources
PubMed1989

Relaxant actions of khellin on vascular smooth muscle.

To clarify the mechanism of the vasodilatory action of khellin on calcium, we have investigated its relaxant action on base line and on K+ and noradrenaline-induced contractile tensions in rat aorta smooth muscle and on spontaneous contractile activity of rat portal vein. Khellin relaxed both of these preparations with a similar potency, which suggests a non-specific inhibition of calcium flux, without any difference related to the specific calcium channels. We have also studied the capacity of khellin to interfere with the loading and release mechanisms of caffeine and noradrenaline-sensitive calcium stores in Ca-free medium. Khellin's Ca2+ loading reduction may be related with its capacity to inhibit calcium influx. Khellin applied during Ca2+ release also caused relaxation. We propose that this drug may enhance calcium extrusion or sequestration rather than the calcium release mechanism. These actions on calcium influx and intracellular mobilization can contribute to its vasorelaxant action.

Animals↗
PubMed1983

Pulse shape of magnetic fields influences chick embryogenesis.

A total of 295 chick embryos was exposed during the first 48 hours of development to pulsed electromagnetic fields of 100 Hz and 0.4 to 104 microTeslas (micro T), and findings were compared with those in 364 control embryos. General morphology was analysed and supplemented by light microscopy studies. Exposure to electromagnetic fields with a pulse rise time of 100 microseconds produced teratogenic changes when intensities of 1.0 and 13.9 micro T were used but not with lower or higher intensities, demonstrating a 'window' effect and ruling out the possible influence of a rise in internal embryonic temperature. Exposure to an electromagnetic field of 1.0 micro T specifically altered organogenesis of the truncal nervous system and drastically reduced the alcian blue-stained components, whereas with an intensity of 13.9 micro T, there were abnormalities in the circulatory system and foregut, altering cell-to-cell contacts in the walls of developing vessels. When embryos were exposed to intensities of 0.4 and 1.0 micro T with 2.0 and 42 microseconds pulse rise times, teratogenic effects were greater and alterations involved all developing systems. The most powerful effects were obtained with 1.0 micro T and 42 microseconds rise time. The findings confirm the sensitivity of chick embryos to electromagnetic fields of extremely low frequency and intensity and indicate that pulse shape may be a decisive parameter determining strong, slight, or no modification of embryonic development. Mechanisms of action of electromagnetic fields are still unclear, but induced alterations in extracellular glycosaminoglycans could be a causal factor in the observed malformations.

Animals↗
PubMedDate not supplied

Protective effects of phenolic compounds on CCl4-induced toxicity in isolated rat hepatocytes.

The protective effects of a series of phenolic compounds, phenolic acids and flavonoids on the cytotoxicity of CCl4 in rat hepatocytes were studied. A number of flavones, 7,8-dihydroxy-flavone, luteolin and hypolaetin-8-glucoside, flavonols, morin, quercetin, robinetin and gossypin, phenolic acids, gallic, caffeic and chlorogenic acids, as well as the flavane (+)-catechin significantly inhibited alanine amine transferase (ALT) release. Catechol groups are determinant for the protective activity of flavonoids and cinnamic acid derivatives, as well as the resorcinol or pyrogallol moieties in the B ring of flavonoids. In benzoic acid derivatives a pyrogallol group is required. This feature is associated with the inhibition of ALT spontaneous release.

Animals↗
PubMedDate not supplied

Antioxidant profile of mono- and dihydroxylated flavone derivatives in free radical generating systems.

A number of free radical generating systems were used to investigate the antioxidant properties and structure-activity relationships of a series of monohydroxylated and dihydroxylated flavones. Ortho-dihydroxylated flavones showed the highest inhibitory activity on enzymic and non-enzymic microsomal lipid peroxidation as well as on peroxyl radical scavenging. Most flavones were weak scavengers of hydroxyl radical, while ortho-dihydroxylated flavones interacted with superoxide anion generated by an enzymic system or by human neutrophils. This series of compounds did not exert cytotoxic effects on these cells. Scavenging of superoxide and peroxyl radicals may determine the antioxidant properties of these active flavones.

Animals↗