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C Montesinos

Publications and source records attributed to C Montesinos.

At least 19 recordsLinked to original sources
PubMed2000

The yeast HAL1 gene improves salt tolerance of transgenic tomato.

Overexpression of the HAL1 gene in yeast has a positive effect on salt tolerance by maintaining a high internal K(+) concentration and decreasing intracellular Na(+) during salt stress. In the present work, the yeast gene HAL1 was introduced into tomato (Lycopersicon esculentum Mill.) by Agrobacterium tumefaciens-mediated transformation. A sample of primary transformants was self-pollinated, and progeny from both transformed and non-transformed plants (controls) were evaluated for salt tolerance in vitro and in vivo. Results from different tests indicated a higher level of salt tolerance in the progeny of two different transgenic plants bearing four copies or one copy of the HAL1 gene. In addition, measurement of the intracellular K(+) to Na(+) ratios showed that transgenic lines were able to retain more K(+) than the control under salt stress. Although plants and yeast cannot be compared in an absolute sense, these results indicate that the mechanism controlling the positive effect of the HAL1 gene on salt tolerance may be similar in transgenic plants and yeast.

Adaptation, Physiological↗
PubMed1998

Altered Na+ and Li+ homeostasis in Saccharomyces cerevisiae cells expressing the bacterial cation antiporter NhaA.

The bacterial Na+ (Li+)/H+ antiporter NhaA has been expressed in the yeast Saccharomyces cerevisiae. NhaA was present in both the plasma membrane and internal membranes, and it conferred lithium but not sodium tolerance. In cells containing the yeast Ena1-4 (Na+, Li+) extrusion ATPase, the extra lithium tolerance conferred by NhaA was dependent on a functional vacuolar H+ ATPase and correlated with an increase of lithium in an intracellular pool which exhibited slow efflux of cations. In yeast mutants without (Na+, Li+) ATPase, lithium tolerance conferred by NhaA was not dependent on a functional vacuolar H+ ATPase and correlated with a decrease of intracellular lithium. NhaA was able to confer sodium tolerance and to decrease intracellular sodium accumulation in a double mutant devoid of both plasma membrane (Na+, Li+) ATPase and vacuolar H+ ATPase. These results indicate that the bacterial antiporter NhaA expressed in yeast is functional at both the plasma membrane and the vacuolar membrane. The phenotypes conferred by its expression depend on the functionally of plasma membrane (Na+, Li+) ATPase and vacuolar H+ ATPase.

Bacterial Proteins↗
PubMed1997

Transfer of the yeast salt tolerance gene HAL1 to Cucumis melo L. cultivars and in vitro evaluation of salt tolerance.

An Agrobacterium-mediated gene transfer method for production of transgenic melon plants has been optimized. The HAL1 gene, an halotolerance gene isolated from yeast, was inserted in a chimaeric construct and joined to two marker genes: a selectable-neomycin phosphotransferase-II (nptII)-, and a reporter-beta-glucuronidase (gus)-. The entire construct was introduced into commercial cultivars of melon. Transformants were selected for their ability to grow on media containing kanamycin. Transformation was confirmed by GUS assays, PCR analysis and Southern hybridization. Transformation efficiency depended on the cultivar, selection scheme used and the induction of vir-genes by the addition of acetosyringone during the cocultivation period. The highest transformation frequency, 3% of the total number of explants cocultivated, was obtained with cotyledonary explants of cv. 'Pharo'. Although at a lower frequency (1.3%), we have also succeeded in the transformation of leaf explants. A loss of genetic material was detected in some plants, and results are in accordance with the directional model of T-DNA transfer. In vitro cultured shoots from transgenic populations carrying the HAL1 gene were evaluated for salt tolerance on shoot growth medium containing 10 gl-1 NaCl. Although root and vegetative growth were reduced, transgenic HAL1-positive plants consistently showed a higher level of tolerance than control HAL1-negative plants.

Acetophenones↗
PubMed1994

[Castleman's disease: description and comments on 3 cases].

Three representative cases of the clinical heterogeneity of Castleman's disease are presented: one localized form with hialine vascular histology (HV) and 2 multicentric forms corresponding to the plasmocellular variety (PC). The asymptomatic patient with HV was treated with surgical resection of one tumor. The 2 patients with the symptomatic PC variant were characterized by the different clinical presentation receiving polychemotherapy and steroids, respectively with good response. The literature is reviewed and the pathogenetic, clinical and therapeutic aspects of the disease, which remains difficult to define as a sole entity, are discussed.

Adult↗
PubMed1994

Coexisting subdural and intercostal haemangiomata.

Haemangioma in the chest wall is a very rare entity, seldom described in the literature. We report the case of a 23 year old woman presenting with independent, cervical subdural and intercostal haemangiomata. She suffered several episodes of recurrent, self-limiting subdural haemorrhage before diagnosis was made by magnetic nuclear resonance, aortography and selective intercostal angiography. Surgical excision was performed in both locations with excellent results.

Adult↗
PubMed1993

Epitope mapping and accessibility of immunodominant regions of yeast plasma membrane H(+)-ATPase.

Immunodominant regions of yeast plasma membrane H(+)-ATPase have been mapped by two different approaches. A rabbit polyclonal antibody was used to screen a library of random fragments of the ATPase gene in a bacterial expression plasmid. In addition, the epitopes recognized by a panel of mouse monoclonal antibodies against the ATPase were mapped by reactions with defined fragments of the enzyme expressed in Escherichia coli. Both methodologies indicated that two regions within the amino-terminal part of the ATPase (at amino acid positions 5-105 and 168-255) contain most of the antigenic determinants. The accessibility of the monoclonal antibodies to their epitopes in native and solvent-perturbed ATPase preparations was investigated by immunofluorescence studies on yeast protoplasts. Cells fixed and permeabilized with formaldehyde were either treated with or without detergents and organic solvents. ELISA competition tests with plasma membrane vesicles and with detergent-purified ATPase incubated in solution with the monoclonal antibodies gave similar results. All the epitopes were accessible in detergent-treated ATPase preparations. In contrast, only the epitopes at amino acids 24-56 were accessible in ATPase preparations not treated with detergents or organic solvents. These epitopes were cytoplasmic because protoplast permeabilization was required for decoration by the reactive monoclonal antibodies.

Amino Acid Sequence↗
PubMed1993

Iron-reducing and free-radical-scavenging properties of apomorphine and some related benzylisoquinolines.

The scavenging and iron-reducing properties of a series of benzylisoquinolines of natural and synthetic origin have been studied. Bulbocapnine, boldine, glaucine, and stepholidine acted as scavengers of hydroxyl radical in the deoxyribose degradation by Fe(3+)-EDTA + H2O2. On the contrary, laudanosoline, apomorphine, protopapaverine, anonaine, and tetrahydroberberine increased deoxyribose degradation by a mechanism related to generation of superoxide anion. Only apomorphine had a stimulating effect in the system using citrate instead of ethylenediaminetetraacetic acid (EDTA) as well as in the absence of chelator. Apomorphine also stimulated DNA damage by Cu2+. The iron-ion reducing ability of apomorphine and laudanosoline was confirmed using cytochrome c. Both compounds scavenged peroxyl radicals in an aqueous medium, while in Fe(3+)-induced microsomal lipid peroxidation apomorphine acted as an inhibitor and laudanosoline stimulated the process. It is suggested that in microsomes the chain-breaking antioxidant properties of apomorphine overcome its possible influence on redox cycling of iron, or prooxidant properties.

Animals↗
PubMed1993

Antioxidant action of benzylisoquinoline alkaloids.

The antioxidant action of a series of benzylisoquinoline alkaloids has been investigated. Laudanosoline, protopapaverine, anonaine, apomorphine, glaucine, boldine, bulbocapnine, tetrahydroberberine and stepholidine produced a dose-dependent inhibition of microsomal lipid peroxidation induced by Fe2+/ascorbate, CCl4/NADPH or by Fe3+ ADP/NADPH. Apomorphine exerted the highest inhibitory effects in the three systems of induction used, with a potency higher than propyl gallate. Laudanosoline was particularly effective in the first system, while bulbocapnine and anonaine were more potent when CCl4/NADPH or Fe3(+)-ADP/NADPH were used as inducers. Laudanosoline, protopapaverine, apomorphine, tetrahydroberberine and stepholidine were also potent inhibitors of nitroblue tetrazolium (NBT) reduction. The presence of a free hydroxyl group or preferably of a catechol group is a feature relevant for inhibition of lipid peroxidation and NBT reduction, nevertheless the antioxidant activity of benzylisoquinoline alkaloids cannot be only ascribed to the formation of phenoxy radicals and other free radical species may be formed during aporphine and tetrahydroprotoberberine oxidation. The influence of this series of compounds on the time course of lipid peroxidation suggests that some of them, like apomorphine and boldine act as chain-breaking antioxidants.

Alkaloids↗
PubMed1993

Effects of coumarin derivatives on superoxide anion generation.

A number of simple coumarins with different patterns of substitution were tested on activated polymorphonuclear leukocyte superoxide generation and superoxide scavenging using the reduction of nitroblue tetrazolium. The most effective compound was fraxetin, which showed a better potency as an inhibitor of superoxide radical generation than as a scavenger. From the structure-activity study it can be deduced the importance of an ortho-dihydroxyl function, especially at the position 7, 8. Blockade of active hydroxyl groups by methylation or glycosylation decreases the activity. None of the coumarins were cytotoxic on leukocytes as assessed by lactic dehydrogenase activity release. Inhibition of superoxide generation in activated neutrophils may play a role in the vasoprotective effects of simple coumarins.

Animals↗
PubMed1992

Imaging of human T-lymphotropic virus type I-associated chronic progressive myeloneuropathies.

We studied magnetic resonance imaging (MRI) of the head and cervical spine and CT of the head in 46 patients (14 men, 32 women) with chronic progressive myeloneuropathy. The findings were correlated with human T-lymphotropic virus type I (HTLV-I) serology, race, country of origin, and age. We found a female predominance of 2:1. Most patients were aged between 30 and 50 years, and most were Caribbean immigrants and black. There were 9 men and 17 women with blood antibody titers to HTLV-I and 7 men and 15 women with cerebrospinal fluid (CSF) titers. All patients with virus or antibodies in blood or CSF were Caribbean immigrants or black. T2-weighted cranial MRI showed scattered areas of high signal intensity in the cerebral white matter, usually in the periventricular and subcortical areas, but not in the posterior cranial fossa. Cranial CT revealed periventricular low density areas, ventricular enlargement, and atrophy MRI of the cervical spine showed atrophy of the cord. Myelography was normal in all 15 patients examined. No imaging differences were observed between the HTLV-I-positive and -negative patients. These findings, although consistent with demyelination, are not specific.

Adolescent↗
PubMed1991

Immunological approaches to the transmembrane topology and conformational changes of the carboxyl-terminal regulatory domain of yeast plasma membrane H(+)-ATPase.

Molecular genetic experiments have suggested that the carboxyl terminus of the Saccharomyces cerevisiae plasma membrane H(+)-ATPase is an inhibitory domain involved in the "in vivo" regulation of the enzyme by glucose metabolism. An antibody prepared against a fusion protein including the last 59 amino acids of the ATPase sequence has been affinity purified to yield a preparation which requires the 18 carboxyl-terminal amino acids for recognition. Antibody binding experiments show that the carboxyl-terminal domain of the ATPase can be selectively exposed by concentrations of the detergent Tween-20 which do not break down the permeability barrier of the plasma membrane to the antibody. Both enzyme-linked immunosorbent assay and immunofluorescence analysis demonstrate that the accessibility of the carboxyl-terminal domain in isolated plasma membranes depends on the physiological state of the cell being increased by glucose metabolism. Immunofluorescence analysis of isolated plasma membrane vesicles, using a dual labeling protocol with concanavalin A and antibody to reveal the orientation of individual vesicles, and colloidal gold immunoelectron microscopy of ultrathin cryosections of whole yeast cells separately demonstrate that the ATPase carboxyl terminus is located in the cytoplasmic compartment. The application of a mutant deleted of the epitope(s) recognized by the affinity purified carboxyl-terminal antibody eliminates the possibility of artifacts arising from nonspecific antibody binding. The accessibility properties and cytoplasmic location of the carboxyl-terminal domain appear to be consistent with its role as a negative regulator of the ATPase.

Blotting, Western↗
PubMed1991

Domains of yeast plasma membrane and ATPase-associated glycoprotein.

In yeast homogenates the plasma membrane H(+)-ATPase and a major surface glycoprotein of about 115 kDa are present in two membrane fractions with peak densities in sucrose gradients of 1.17 and 1.22. Immunogold electron microscopy of frozen yeast sections indicates that the ATPase is exclusively (greater than 95%) present at the surface membrane. Therefore the two ATPase-containing fractions appear to correspond to different domains of the plasma membrane. The 115 kDa glycoprotein is tightly associated with the ATPase during solubilization and purification of the enzyme. However, in a mutant lacking the glycoprotein the activity of the plasma membrane H(+)-ATPase is similar to wild type, suggesting that this association is fortuitous. The ATPase and the glycoprotein are difficult to separate by electrophoresis and therefore binding of concanavalin A to the ATPase cannot be unambiguously demonstrated in wild-type yeast. By utilizing the mutant without glycoprotein it was shown that the ATPase band of 105 kDa binds concanavalin A.

Cell Membrane↗
PubMed1989

Sidedness of yeast plasma membrane vesicles and mechanisms of activation of the ATPase by detergents.

The binding of concanavalin A and of fluorescein 5'-isothiocyanate indicate similar amount of right-side-out and inside-out vesicles in plasma membrane vesicles from either glucose-starved or glucose-fermenting yeast cells. These vesicles contain low-activity and high-activity states of the ATPase, respectively. Unmasking of latent active sites can explain the limited ATPase activation (about 2-fold) produced by several detergents on both kinds of vesicles. On the other hand, lysophosphatidic acid (oleoyl) produces a 7-fold activation of the ATPase in vesicles from glucose-starved cells. This effect is accompanied by a change in Km of the enzyme and probably reflects a direct action of the detergent on the ATPase. A similar activation and Km change can be obtained by sonication of the vesicles, although in this case soybean phospholipids are required for maximal activity. Apparently the low-activity state of the yeast plasma membrane ATPase can be activated not only by glucose metabolism 'in vivo' (mechanism unknown) but also by some detergents and physical treatments 'in vitro'. Experiments with purified ATPase from glucose-starved cells also indicate that lysophosphatidic acid (oleoyl) specifically activates the enzyme. These results suggest a note of caution on considering the usual interpretation of the effects of detergents on membrane enzymes, which only take into account the unmasking of latent active sites.

Adenosine Triphosphatases↗
PubMed1975

Midline sagittal sonographic evaluation of the midbrain.

A technique has been developed for the A-mode display of the upper brain stem using certain bony landmarks to guide transducer placement. Normal findings were substantiated at the time of penumoencephalography and angiography in order to determine the anatomic origin of the ultrasound reflections. Findings in patients with mass lesions distorting the upper brain stem will also be reported.

Adolescent↗