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J Menéndez

Publications and source records attributed to J Menéndez.

At least 19 recordsLinked to original sources
PubMed2006

Midbrain neuronal cultures from parkin mutant mice are resistant to nitric oxide-induced toxicity.

Nitric oxide (NO) is a modulator of differentiation and survival of dopamine (DA) neurons. NO may play a role in the pathogenesis of Parkinson's disease (PD) since its levels are increased in parkinsonian brains and it can nitrosylate and alter the function of key proteins involved in the pathogenesis of PD. NO producing neurons are spared in parkinsonian brains suggesting that toxicity by NO can be compensated. Furthermore, the neurotoxic or neurotrophic effects of NO on DA neurons depend on the balance between NO levels and the intracellular levels of glutathione (GSH). We have investigated the effects of NO-donating agents on midbrain neuronal cultures from parkin-deficient mice. Parkin mutations are the most common genetic deficit observed in hereditary parkinsonism. These mice have abnormal DA release and metabolism, increased production of free radicals and a compensatory elevation of GSH. Cultures from parkin knockout (PK-KO) mice were more resistant than those of wild type (WT) to the neurotoxicity by NO, and the difference of susceptibility applied equally to DA, GABA and total number of neurons, and to astrocytes. NO-induced cell death was mainly apoptotic and could be reduced by caspase inhibitors. Cultures from PK-KO had greater levels of GSH than WT and, after treatment with NO, greater levels of S-nitrosoglutathione. The differences in susceptibility disappear when the synthesis of GSH is inhibited or the GSH chelated with diethyl maleate. Our data show that, contrary to the expectations, and related to the enhanced production of GSH in parkin knockout mice, parkin-deficient dopamine neurons are less susceptible to toxicity by NO.

Animals↗
PubMed2006

Suppression of Parkin enhances nigrostriatal and motor neuron lesion in mice over-expressing human-mutated tau protein.

Abnormal deposition of protein tau takes place in the brain of patients with several neurodegenerative diseases. Few of these patients present frontotemporal dementia with parkinsonism and amyotrophy (FTDPA-17), an autosomal dominant tauopathy related to mutations of the gene that codes for protein tau, localized in chromosome 17. The great majority of patients with tauopathies such as Alzheimer's disease, sporadic frontotemporal dementia or progressive supranuclear palsy do not show a Mendelian pattern of inheritance. We have occasionally seen tauopathies in patients with parkin mutations and, therefore, hypothesized that the protein tau interacts with parkin. We have tested that hypothesis in mice with combined genetic modifications of tau (over-expression of human tau with three mutations known to produce FTDPA-17) and parkin (deleted) proteins. Homozygote parkin null or over-expressing mutated-human tau mice have subtle behavioral and molecular abnormalities but do not express a clinical phenotype of neurodegenerative disease. Mice with combined homozygous mutations of these two genes show progressively abnormal walking already noticeable at 3 months of age, loss of dopamine and dopamine markers in striatum, nuclear tau immunoreactive deposits in motor neurons of the spinal cord, abnormal expression of glial markers and enhanced levels of pro-apoptotic proteins; findings that were absent or less pronounced in homozygote animals with deletions of parkin or over-expression of tau. The double transgenic mice do not express normal mechanisms of adaptation to stress such as increased levels of GSH and Hsp-70. In addition, they have reduced levels of CHIP-Hsc70, a complex known to attenuate aggregation of tau and to enhance ubiquitination of phosphorylated tau. We have found high levels of phosphorylated tau in parkin-/-+tau(VLW) mice and a relative decrease of the inactivated pSer9 to total GSK-3 levels. Our data reveal that there are interactions between tau and parkin that could be relevant for the pathogenesis and treatment of tauopathies. Similarly, we hope that the double transgenic parkin-/-+tau(VLW) mice could be useful for testing of compounds with putative therapeutic value in human tauopathies.

Animals↗
PubMed2006

Susceptibility to rotenone is increased in neurons from parkin null mice and is reduced by minocycline.

Parkinson's disease is a neurodegenerative disorder which is in most cases of unknown etiology. Mutations of the Park-2 gene are the most frequent cause of familial parkinsonism and parkin knockout (PK-KO) mice have abnormalities that resemble the clinical syndrome. We investigated the interaction of genetic and environmental factors, treating midbrain neuronal cultures from PK-KO and wild-type (WT) mice with rotenone (ROT). ROT (0.025-0.1 microm) produced a dose-dependent selective reduction of tyrosine hydroxylase-immunoreactive cells and of other neurons, as shown by the immunoreactivity to microtubule-associated protein 2 in PK-KO cultures, suggesting that the toxic effect of ROT involved dopamine and other types of neurons. Neuronal death was mainly apoptotic and suppressible by the caspase inhibitor t-butoxycarbonyl-Asp(OMe)-fluoromethyl ketone (Boc-D-FMK). PK-KO cultures were more susceptible to apoptosis induced by low doses of ROT than those from WT. ROT increased the proportion of astroglia and microglia more in PK-KO than in WT cultures. Indomethacin, a cyclo-oxygenase inhibitor, worsened the effects of ROT on tyrosine hydroxylase cells, apoptosis and astroglial (glial fibrillary acidic protein) cells. N-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, increased ROT-induced apoptosis but did not change tyrosine hydroxylase-immunoreactive or glial fibrillary acidic protein area. Neither indomethacin nor N-nitro-L-arginine methyl ester had any effect on the reduction by ROT of the mitochondrial potential as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Microglial NADPH oxidase inhibition, however, protected against ROT. The roles of p38 MAPK and extracellular signal-regulated kinase signaling pathways were tested by treatment with SB20358 and PD98059, respectively. These compounds were inactive in ROT-naive cultures but PD98059 slightly increased cellular necrosis, as measured by lactate dehydrogenase levels, caused by ROT, without changing mitochondrial activity. SB20358 increased the mitochondrial failure and lactate dehydrogenase elevation induced by ROT. Minocycline, an inhibitor of microglia, prevented the dropout of tyrosine hydroxylase and apoptosis by ROT; the addition of microglia from PK-KO to WT neuronal cultures increased the sensitivity of dopaminergic neurons to ROT. PK-KO mice were more susceptible than WT to ROT and the combined effects of Park-2 suppression and ROT reproduced the cellular events observed in Parkinson's disease. These events were prevented by minocycline.

Animals↗
PubMed2006

[Paraganglioma of the vagus nerve].

Paragangliomas of the vagus nerve are uncommon vascular benign neoplasms of neuroectodermic origin. Initial clinical manifestation is usually as an asymptomatic cervical mass, although sometimes may cause lower cranial nerve palsies. These paragangliomas seldom associate to high levels of circulating catecholamines. Diagnosis is based on the clinics aided by imaging, where CT and MRI play an important role. Angiography is not only diagnostic, but it also allows preoperative embolization of the mass. Most accepted treatment is surgical removal, even though some paragangliomas are suitable for radiation therapy in very specific patients. In this paper we describe a new case of paraganglioma of the vagus nerve in a cervical location, with hypertensive episodes and high catecholamine-levels. The authors review the literature describing the clinical presentation, the diagnosis and the treatment of this rare lesion.

Head and Neck Neoplasms↗
PubMed2005

Differential effects of l-DOPA on monoamine metabolism, cell survival and glutathione production in midbrain neuronal-enriched cultures from parkin knockout and wild-type mice.

l-DOPA is the most effective treatment for Parkinson's disease but in isolated neuronal cultures it is neurotoxic for dopamine (DA) neurones. Experiments in vivo and clinical studies have failed to show toxicity of l-DOPA in animals or patients but that does not exclude the possibility of a toxic effect of l-DOPA on patients with certain genetic risk factors. Mutations of the parkin gene are the most frequent cause of hereditary parkinsonism. Parkin null mice have a mild phenotype that could be modified by different neurotoxins. The aim of this study was to investigate whether the toxic effects of l-DOPA on DA neurones are amplified in parkin null mice. We have measured the effects of l-DOPA on cell viability, tyrosine hydroxylase (TH) expression, DA metabolism and glutathione levels of parkin knockout (PK-KO) midbrain cultures. Neuronal-enriched cultures from PK-KO mice have similar proportions of the different cell types with the exception of a significant increment of microglial cells. l-DOPA (400 microm for 24 h) reduced the number of TH-immunoreactive cells to 50% of baseline and increased twofold the percentage of apoptotic cells in cultures of wild-type (WT) animals. The PK-KO mice, however, are not only resistant to the l-DOPA-induced pro-apoptotic effects but they have an increased number of TH-immunoreactive neurones after treatment with l-DOPA, suggesting that l-DOPA is toxic for neurones of WT mice but not those of parkin null mice. MAPK and phosphatidylinositol-3 kinase signalling pathways are not involved in the differential l-DOPA effects in WT and PK-KO cultures. Intracellular levels of l-DOPA were not different in WT and parkin null mice but the intracellular and extracellular levels of DA and 3-4-dihydroxyphenylacetic acid, however, were significantly increased in parkin null animals. Furthermore, monoamine oxidase activity was significantly increased in parkin null mice, suggesting that these animals have an increased metabolism of DA. The levels of glutathione were further increased in parkin null mice than in controls both with and without treatment with l-DOPA, suggesting that a compensatory mechanism may protect DA neurones from neuronal death. This study opens new avenues for understanding the mechanisms of action of l-DOPA on DA neurones in patients with Park-2 mutations.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2005

Effects of cinnarizine, a calcium antagonist that produces human parkinsonism, in parkin knock out mice.

Cinnarizine, a calcium antagonist that produces parkinsonism in humans, induces behavioural changes such as alopecia, buco-lingual dyskinesia and reduction of motor activity in female parkin knock out (PK-KO) mice but not in wild-type (WT) controls. PK-KO mice have high striatal dopamine levels and increased dopamine metabolism in spite of low reduced tyrosine hydroxylase protein. Cinnarizine, which blocks dopamine receptors and increases dopamine release, further increased dopamine metabolism. PK-KO mice increased GSH levels as a compensatory mechanism against enhanced free radical production related to acceleration of dopamine turnover. Neuronal markers, such as beta-tubulin slightly increased in PK-KO and furthermore with cinnarizine. Astroglial markers were decreased in PK-KO mice, and this effect was potentiated by cinnarizine, suggesting abnormal glia in these animals. Microglia was hyperactivated in PK-KO midbrain, suggesting inflammation in these animals. Proapoptotic proteins were increased by cinnarizine and, to a lesser extent, in PK-KO mice. Our data indicate that mutation of parkin is a risk factor for drug-induced parkinsonism.

Analysis of Variance↗
PubMed2004

The correlation of the spraying volume with herbicide adherence and herbicide penetration in glyphosate treatments.

The relationship between the spraying volume and glyphosate effectiveness has been widely studied over the years. Likewise, the effect of different adjuvants on glyphosate leaf adherence/penetration is currently well understood. However, not much is known about the way spraying volumes may influence these two herbicide properties or, in other words, which factor (adherence or penetration) is the limiting factor when spraying at low or high volumes of treatment. Using grass-weed Lolium rigidum and broad-leaved weed Portulaca oleracea as experimental systems, the effect of low (200 L ha(-1)) and high (800 L ha(-1)) spraying volumes and six commercial adjuvants (poly-l-p-menthene, a mixture of methyl oleate and palmitate, alkylglycol ester, dodecylbenzene ammonium sulphonate, and two paraffinic oils) plus ammonium sulfate on the effectiveness of five commercial glyphosate formulations has been studied under laboratory controlled conditions. Dose-response assays showed significant differences between low and high spraying volume treatments as expected, the former being much more effective than the latter. However, and in all commercial formulations and weed species tested, the best results at low spraying volumes were always obtained when formulating glyphosate with oils or their derivatives, with a minimal improvement observed in glyphosate/surfactant mixtures. On the contrary, both the use of ionic or non-ionic surfactants as glyphosate adjuvants gave the best results at high spraying volumes, with only a marginal success observed on paraffinic oils and fatty acidesters. Data point out glyphosate absorption as being a two-step process made up of adherence first and then penetration, both events being essential for glyphosate effectiveness. Under these terms, high performance glyphosate-rich low spraying volumes succeed by themselves in soaking leaf surfaces, penetration therefore being the main and only limiting factor, while low performance glyphosate-poor high spraying volumes fail to either soak or penetrate leaf cuticles. The use of penetrative agents such as oils is therefore advised as a single method to increase glyphosate effectiveness at low spraying volumes, whereas glyphosate treatments at high spraying volumes are better improved by using surfactant agents or surfactant + oil mixtures.

Biological Transport↗
PubMed2004

Germination requirements and dispersal timing in two heterocarpic weedy asteraceae.

In SW Spain the winter annuals Anacyclus radiatus and Chrysanthemum coronarium (Asteraceae) are found as weeds in diverse crops. Both plant species are heterocarpic, i.e. the peripheral and central achenes of the capitulum are morphologically distinctive. In heterocarpic and heterospermic species the different fruit or seed morphs usually have differential ecological behaviour. In this work we have studied the morphometry, germination and dispersal timing of t he different achene morphs in A. radiatus and C. coronarium. Laboratory germination tests were carried out to evaluate the influence of incubation temperature (light/dark, 27/27, 24/18, 20/10, 15/5, 10/4 degrees C), chilling period (0, 1, 7, 21 and 60 days at 2 degrees C), GA3, nitrate and the dark on the germination percentage and rate (t50). The peripheral achenes of A. radiatus have a significantly broader wing than the central achenes. In this species, germination was inhibited in the dark but viable achenes of both types germinated completely under light exposure irrespective of test conditions. Nevertheless, the peripheral achenes germinated significantly faster compared to the central achenes (t5o 1.04 vs. 1.55 days at 24/18 degrees C). In C. coronarium peripheral achenes have three-winged ribs and are significantly longer, wider and thicker than the central achenes, which have only one- or two-winged ribs. In this species the peripheral achenes showed a much lower germination compared to the central achenes under all conditions tested (0.3-3.5% vs. 41.5-58.0%). Embryos isolated from the pericarp of peripheral achenes germinated quickly in a great extent, and when placed in close contact with a pericarp fragment they did not show any inhibition of germination, suggesting physical dormancy. To determine differences in dispersal timing between achene morphs, we monitored dispersal in a stand of both plant species. In A. radiatus the peripheral achenes were shed first, at the onset of the rainy season in late summer, whereas the central achenes dispersed from late summer to early winter. In contrast, in C. coronarium the central achenes were shed first, from early summer to early autumn, whereas the peripheral achenes dispersed mainly in early autumn. Thus, in both weed species the more dispersible and readier-to-germinate achene morph is dispersed first. The differences in the germination and dispersal behaviour between achene morphs represent an opportunistic, mixed strategy which is favourable under environmental uncertainty, and should be accounted for in order to understand the population dynamics of both weed species.

Asteraceae↗
PubMed2002

Anomalous LO phonon lifetime in AlAs.

The temperature dependence of the frequencies and linewidths of the Raman-active longitudinal optical (LO) phonons in GaAs and AlAs have been measured. The low-temperature lifetime of the LO phonon in AlAs is found to be 9.7 ps, very close to the corresponding GaAs value of 9.5 ps. This contradicts early theoretical predictions. The agreement between theory and experiment can be restored when the accidental degeneracy between the AlAs LO phonon frequency and a feature in the two-phonon density of states is taken into account.

Journal Article↗
PubMed2002

Raman studies of semiconducting oxide nanobelts.

Crystalline nanobelts of ZnO and SnO2 were prepared from a thermal evaporation of oxide powders inside an alumina tube in the absence of catalysts. Typical dimensions of the nanobelt samples ranged from approximately 10 to 100 microns in length, 30 to 300 nm in width, and 6 to 30 nm in thickness. Room temperature Raman spectra were obtained on pressed mats of nanobelt samples and compared with the corresponding spectra of the starting oxide powders and bulk materials. Collectively, our Raman data indicated that the as-prepared nanobelt samples used in this study were oxygen deficient. Upon annealing at 900 degrees C in flowing oxygen for 1 h, the nanobelt samples exhibited Raman features that corresponded to those expected in respective bulk semiconducting oxides. The dimensions of the nanobelts were a bit too large to expect significant quantum size effects on the phonon structure similar to those observed in carbon nanotubes and short-period semiconductor superlattices.

Aluminum↗
PubMed2001

Molecular cloning of an alpha-glucosidase-like gene from Penicillium minioluteum and structure prediction of its gene product.

The dexC cDNA, which is expressed in dextran-containing medium by the filamentous fungus Penicillium minioluteum, was cloned and sequence characterized. The cDNA sequence comprises 1859 bp plus a poly (A) tail, coding for a predicted protein of 597 amino acids. The genomic counterpart was isolated by PCR, finding three introns in its sequence. The dexC gene was located by Southern blot in the same 9-kb fragment that the previously isolated dextranase-encoding gene (dexA). Sequence analysis revealed that the deduced DexC protein belongs to glycosyl hydrolase family 13, showing a high sequence identity (58%) with Aspergillus parasiticus alpha-1,6-glucosidase. In addition, the high sequence identity (51%) between DexC protein and oligo-1,6-glucosidase of Bacillus cereus, with three-dimensional (3D) structure determined, leads us to proposed a 3D model for the structural core of DexC protein.

Amino Acid Sequence↗
PubMed2000

New method for the selection of multicopy transformants of Pichia pastoris, using 3-amino-1,2,4 triazol.

The methylotrophic yeast Pichia pastoris has been successfully used for the expression of many heterologous proteins. The level of expression of some of these proteins depends on the copy number of the gene inserted into the yeast genome. Several methods have been reported in the past few years for the isolation of multicopy transformants. One of these methods used an expression vector that contains the bacterial kanamycin-resistance gene Tn903kanr, which confers resistance to G418. Here, we report a different selection method in a mutant strain of P. pastoris (his3-) based on the resistance to 3-amino-1,2,4 triazol, with a vector containing the HIS3 gene from Saccharomyces cerevisiae. Using this selection method, we isolated here P. pastoris transformants containing several copies of the dextranase gene (dex) from Penicillium minioluteum.

Amitrole↗
PubMed1998

Regulatory regions in the promoters of the Saccharomyces cerevisiae PYC1 and PYC2 genes encoding isoenzymes of pyruvate carboxylase.

We have identified regions in the promoters of the PYC1 and PYC2 genes from Saccharomyces cerevisiae involved in their regulation in different culture conditions. In the case of PYC1, a UAS in the region between -330/-297 and three repressing sequences with the common central core CCGCC at positions -457, -432 and -399 were identified. Specific binding of nuclear proteins to the -330/-214 DNA fragment was abolished in rtg mutants suggesting a role for the RTG genes in the control of PYC1 expression. In the case of the PYC2 promoter, elimination of a fragment from -417 to -291 brings about a two-fold decrease in the expression in repressed conditions and a similar increase in derepression.

Gene Deletion↗
PubMed1998

Isolation of the Pichia pastoris PYC1 gene encoding pyruvate carboxylase and identification of a suppressor of the pyc phenotype.

We have cloned and characterized a gene encoding pyruvate carboxylase from the methylotrophic yeast Pichia pastoris. Disruption of this gene produced inability to grow in minimal medium with glucose as carbon source and ammonium as nitrogen source. Growth was possible with aspartate or glutamate as nitrogen source. The gene PpPYC1 expressed from its own promoter was able to rescue the phenotype of Saccharomyces cerevisiae mutants devoid of pyruvate carboxylase. In a P. pastoris strain carrying a disrupted PpPYC1 gene we have isolated spontaneous mutants able to grow in non-permissive conditions. In a mutant strain grown in glucose several enzymes sensitive to catabolite repression were derepressed. The strain also had elevated levels of glutamate dehydrogenase (NAD) both in repressed and derepressed conditions.

Amino Acid Sequence↗
PubMed1996

Isolation and characterization of mutants as an approach to a transformation system in Kluyveromyces marxianus.

A method to obtain K. marxianus mutants has been developed. Different auxotrophic mutants were isolated by nystatin and snail-enzyme enrichment procedures using an incubation time of 2 h before adding the antibiotic or the enzyme respectively. All his mutants analyzed by complementation tests turned out to belong to the same complementation group. Some of them were transformed and complemented by the S. cerevisiae HIS3 gene. These non-reverting his3 mutants contain no heterologous sequence, which is essential to make them acceptable for application in the food industry.

Genes, Fungal↗