PubMed Health⌕ Search

Biomedical subjects

I Frías

Publications and source records attributed to I Frías.

7 recordsLinked to original sources
PubMed1996

A major isoform of the maize plasma membrane H(+)-ATPase: characterization and induction by auxin in coleoptiles.

The plasma membrane (PM) H(+)-ATPase has been proposed to play important transport and regulatory roles in plant physiology, including its participation in auxin-induced acidification in coleoptile segments. This enzyme is encoded by a family of genes differing in tissue distribution, regulation, and expression level. A major expressed isoform of the maize PM H(+)-ATPase (MHA2) has been characterized. RNA gel blot analysis indicated that MHA2 is expressed in all maize organs, with highest levels being in the roots. In situ hybridization of sections from maize seedlings indicated enriched expression of MHA2 in stomatal guard cells, phloem cells, and root epidermal cells. MHA2 mRNA was induced threefold when nonvascular parts of the coleoptile segments were treated with auxin. This induction correlates with auxin-triggered proton extrusion by the same part of the segments. The PM H(+)-ATPase in the vascular bundies does not contribute significantly to auxin-induced acidification, is not regulated by auxin, and masks the auxin effect in extracts of whole coleoptile segments. We conclude that auxin-induced acidification in coleoptile segments most often occurs in the nonvascular tissue and is mediated, at least in part, by increased levels of MHA2.

Amino Acid Sequence↗
PubMed1995

Lignan models as inhibitors of Phanerochaete chrysosporium lignin peroxidase.

The lignan 8,8'-bis-(methylenedioxy)cinnamic acid (BMDCA) is a powerful competitive inhibitor (K1 = 2.0 microM) of the lignin peroxidase (LiP) from Phanerochaete chrysosporium and of the extracellular peroxidase of Phlebia radiata (I0.5 = 10 microM). BMDCA derivatives with the same double bond system also inhibited these enzymes to some extent. If the double bonds were hydrogenated, the inhibitory effect was lost. HRP-VIII and HRP-XI were slightly inhibited by BMDCA (I0.5 > 50 microM) and two plant peroxidases described as efficient lignan synthesizers were unaffected. Liquid cultures of P chrysosporium did not discolour the dve Poly R478 when 250 microM of BMDCA was present.

Anthraquinones↗
PubMed1991

Purification of a new peroxidase catalysing the formation of lignan-type compounds.

A novel peroxidase that catalyses the dimerization of ferulic acid or caffeic acid via oxidative coupling and formation of beta beta'-linkage to the lignan-type compounds 8,8'-bis(caffeic acid) or 8,8'-bis(ferulic acid) respectively was purified from the leaves of Bupleurum salicifolium. The enzyme, for which the name caffeate peroxidase is proposed, was purified 2700-fold. It is a glycoprotein and has an Mr of 38,000 as determined by gel filtration and SDS/PAGE. The Km values for ferulic acid and caffeic acid were 0.24 mM and for H2O2 0.04 mM with caffeic acid and 0.48 mM with ferulic acid. The purified peroxidase does not exhibit activity on other phenylpropanoids tested and has no detectable phenol oxidase or NADPH oxidase activity. The caffeate peroxidase could be involved in the biosynthesis of lignans.

Catalysis↗
PubMed1987

Effect of polyethylene glycol on the in vitro production of L-lactate by rat liver under near physiological conditions.

The effect of polyethylene glycol (PEG) on lactate production from glucose by rat liver postmitochondrial fraction has been examined, using physiological concentrations of substrate and effectors. Addition of 10% polyethylene glycol (Mw 6000) resulted in an increase in lactate production, while the inhibition of lactate production by citrate and ATP was decreased. These results in conjunction with analysis of glycolytic intermediates suggest that PEG exerts its major action on phosphofructokinase.

Adenosine Triphosphate↗
PubMedDate not supplied

[Fatal poisoning by the rupture of intestinal bags of cocaine].

We report a case of rupture of bags filled with cocaine into the digestive apparatus in a young man. He carried into his digestive tract one hundred of small bags containing 40 g of cocaine each one. The initial clinical picture was characterized by sympathetic hyperactivity, rectorrhagia, and psychosis that evolved in 72 h to neurologic coma, convulsions, rhabdomyolysis, hyperthermia, hypocalcemia, hyperdynamic picture with negative blood cultures, arterial hypotension, syndrome of adult respiratory distress, and multiorgan failure. Treatment with propranolol, mechanic ventilation, barbiturates and inotropic agents was ineffective and the patient died 7 days after.

Adult↗