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Biomedical subjects

M Nieto

Publications and source records attributed to M Nieto.

At least 19 recordsLinked to original sources
PubMed2006

Normal cellular senescence and cancer susceptibility in mice genetically deficient in Ras-induced senescence-1 (Ris1).

Oncogenic Ras triggers a permanent cell-cycle arrest known as oncogene-induced senescence (OIS) that constitutes a relevant tumor suppressor mechanism. Ris1 (Ras-induced senescence-1) is a novel gene that was identified in a screen as specifically upregulated during Ras-induced senescence, and that is located at a chromosomal region, 3p21.3, frequently lost in human cancer. Moreover, Ris1 is highly conserved in vertebrates, does not present paralogs, and its sequence does not reveal similarities with other proteins or domains. To analyse the physiological function of Ris1 and test its putative role as a tumor suppressor gene, we have generated mutant mice deficient for this gene. Ris1-null mice are viable, fertile, develop normally and do not display any obvious abnormalities. Of relevance, Ris1-deficient mice had a normal lifespan and did not exhibit predisposition to spontaneous tumors or to tumors induced by chemical carcinogens. Finally, Ris1-deficient embryonic fibroblasts were indistinguishable from wild-type cells regarding their proliferation properties, immortalization, senescence and oncogenic transformation. These findings do not support a role of Ris1 in tumor suppression or in OIS.

Animals↗
PubMed2006

A novel icetexane diterpene, 5-epi-icetexone from Salvia gilliessi is active against Trypanosoma cruzi.

In this work the effect of a novel compound, 5-epi-icetexone (ICTX) obtained from Salvia gilliessi Benth. (Labiatae), is studied on cultured epimastigotes of Trypanosoma cruzi (Tulahuen). It was found that the compound exerts an antiproliferative effect on the parasites at concentrations between 2.8 and 4.2 microM, and similar sensitivity in other strains (Dm28c, CL-Brener and Y-strain). The compound was deleterious at concentrations higher than 4.2 microM, with an estimated IC50 of 6.5+/-0.75 microM, but with low cytotoxicity to mammalian cells. These effects were irreversible, even at short times of exposure to the drug. In solution, ICTX showed to be stable for at least 96 h at 29 degrees C. With cytostatic dose a little percentage of parasites was resistant to the action of ICTX, and they continued growing although with different kinetic. By electron transmission microscopy, at dose of 4.2 microM an external vesiculization was observed on the first day of exposure to the compound, but the parasite cytoplasm became plenty of vacuoles and exhibited nuclear disorganization from the second day of exposure. It was concluded that ICTX is active against T. cruzi and may act by multiple mechanisms. In future, this novel icetexane diterpene may be a good candidate for therapeutic use against Chagas' disease.

Animals↗
PubMed2005

Abnormal Sp1 transcription factor expression in Alzheimer disease and tauopathies.

Sp1 transcription factor expression was examined by immunohistochemistry, immunofluorescence and confocal microscopy in Alzheimer disease (AD), Pick disease (PiD), progressive supranuclear palsy (PSP), Parkinson disease (PD) and Dementia with Lewy bodies (DLB). Sp1 partly co-localizes with hyper-phosphorylated tau deposits in neurofibrillary tangles, dystrophic neurites of senile plaques and neuropil threads in AD, and in neurons, astrocytes and oligodendrocytes bearing hyper-phosphorylated tau in PiD and PSP. Sp1 is not found in alpha-synuclein inclusions in PD and DLB. These modifications are not associated with changes in the total expression levels of Sp1, as revealed with gel electrophoresis and Western blotting of brain homogenates. Furthermore, no co-immunoprecipitation of Sp1 and phospho-tau was observed in AD and PiD cases. Since Sp1 binding sites are present in the promoters of several genes involved in amyloid and tau, and Sp1 is regulated by oxidative stress, the present findings suggest that Sp1 deposition in hyper-phosphorylated tau deposits may have functional consequences in the pathology of AD and other tauopathies.

Alzheimer Disease↗
PubMed2005

Applicability of the Rockall score in patients undergoing endoscopic therapy for upper gastrointestinal bleeding.

BACKGROUND: The Rockall score is used to assess the prognosis of patients with upper gastrointestinal bleeding. AIM: To assess the applicability of the Rockall score in patients undergoing endoscopic therapy for upper gastrointestinal bleeding. METHODS: Retrospective evaluation of the Rockall score in the period 1995-2001. To evaluate the applicability of the Rockall system, two groups were created: group I (Rockall or=6 points). RESULTS: Two hundred and twenty-two patients were included. The median age of patients was 65 +/ -17 years. Hypotension and associated diseases were present in 20 and 50% of patients, respectively. Re-bleeding occurred in 50 patients (23%) whose median score was 7, whereas the median score of patients without re-bleeding was 6 (p=0.14). There were 20 deaths (9%) with a median score of 8, whilst the median score of surviving patients was 6 (p<0.001). Sixteen patients in group I (18.4%) and 34 in group II (25.2%) re-bled (p=0.25). All the patients who died belong to group II with a Rockall score>or=6 (15% versus 0% in groups II and I, respectively, p<0.001). CONCLUSION: The Rockall score can be used in patients who undergo therapeutic endoscopy for upper gastrointestinal bleeding to identify those with high risk for mortality.

Aged↗
PubMed2005

A randomised open-label study of tiagabine given two or three times daily in refractory epilepsy.

Efficacy and tolerability of tiagabine was evaluated in patients with non-controlled partial seizures in a multicentre, open-label, parallel group study. Tiagabine was administered either two (b.i.d.) or three times daily (t.i.d.) as adjunctive therapy and titrated stepwise to a target of 40 mg/day during a 12-week, fixed-schedule titration period; this was followed by a 12-week flexible continuation period. The primary efficacy endpoint was the proportion of patients completing the fixed-schedule titration period. A total of 243 patients were randomised and received treatment, 123 to b.i.d. and 120 to t.i.d. dosing. Fewer patients in the b.i.d. (76 and 62%) than in the t.i.d. (87 and 72%) group completed the fixed-schedule titration period (OR: 0.562; 95% CI: 0.309-1.008; P=0.0532). The median percentage decrease in all types of seizure (excluding status epilepticus) during the fixed schedule titration period was 33.4% for the b.i.d. and 23.8% for the t.i.d. groups (P=0.9634; Van Elteren's test). The proportion of responders was similar for the b.i.d. and t.i.d. groups. There were no significant differences between dosage regimens in the change in median seizure rates from baseline. Adverse events were more frequent during the titration than the continuation period. Most events were mild and related to the central nervous system. Although their incidence was similar between treatment groups, severity was more frequent in the b.i.d. group. Our results suggest that during titration tiagabine is better tolerated with t.i.d. dosing, but during long-term maintenance, a t.i.d. schedule is as effective and well tolerated as b.i.d.

Anticonvulsants↗
PubMed2004

Nitric oxide in the cerebral cortex of amyloid-precursor protein (SW) Tg2576 transgenic mice.

Changes in the amyloid-peptide (Abeta), neuronal and inducible nitric oxide (NO)synthase (nNOS, iNOS), nitrotyrosine, glial fibrillary acidic protein, and lectin from Lycopersicon esculentum (tomato) were investigated in the cerebral cortex of transgenic mice (Tg2576) to amyloid precursor protein (APP), by immunohistochemistry (bright light, confocal, and electron microscopy). The expression of nitrergic proteins and synthesis of nitric oxide were analyzed by immunoblotting and NOS activity assays, respectively. The cerebral cortex of these transgenic mice showed an age-dependent progressive increase in intraneuronal aggregates of Abeta-peptide and extracellular formation of senile plaques surrounded by numerous microglial and reactive astrocytes. Basically, no changes to nNOS reactivity or expression were found in the cortical mantle of either wild or transgenic mice. This reactivity in wild mice corresponded to numerous large type I and small type II neurons. The transgenic mice showed swollen, twisted, and hypertrophic preterminal and terminal processes of type I neurons, and an increase of the type II neurons. The calcium-dependent NOS enzymatic activity was higher in wild than in the transgenic mice. The iNOS reactivity, expression and calcium-independent enzymatic activity increased in transgenic mice with respect to wild mice, and were related to cortical neurons and microglial cells. The progressive elevation of NO production resulted in a specific pattern of protein nitration in reactive astrocytes. The ultrastructural study carried out in the cortical mantle showed that the neurons contained intracellular aggregates of Abeta-peptide associated with the endoplasmic reticulum, mitochondria, and Golgi apparatus. The endothelial vascular cells also contained Abeta-peptide deposits. This transgenic model might contribute to understand the role of the nitrergic system in the biological changes related to neuropathological progression of Alzheimer's disease.

Alzheimer Disease↗
PubMed2004

A simple and reliable method for rapid production and purification of Pseudomonas aeruginosa haemolytic phospholipase C.

AIMS: To design a simple method to produce active recombinant Pseudomonas aeruginosa haemolytic phospholipase C (PLC). METHOD AND RESULTS: Pseudomonas aeruginosa PLC is a virulence factor mainly involved in inflammatory and cytotoxic responses. While ammonium sulphate purification requires large amounts of bacterial suspensions and leads to low yields, production of recombinant protein in Escherichia coli is no more successful because of frequent inclusion bodies and accumulation of inactive PLC in the periplasmic space. Using an inducible system based on the glucose-repressed inv1 promoter in the yeast Schizosaccharomyces pombe, we were able to produce up to 10 IU ml(-1) of pure toxin within 24 h. CONCLUSIONS: This work describes the first method to easily get recombinant haemolytic PLC. SIGNIFICANCE AND IMPACT OF THE STUDY: This method provides a powerful tool to study the mechanisms leading to its cellular toxicity.

Bacterial Toxins↗
PubMed2001

Oxidative stress in Rett syndrome.

The investigation of parameters that might influence the neurological evolution of Rett syndrome might also yield new information about its pathogenic mechanisms. Oxidative stress caused by oxygen free radicals is involved in the neuropathology of several neurodegenerative disorders, as well as in stroke and seizures. To evaluate the free radical metabolism in Rett syndrome, we measured red blood cell antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase) and plasma malondialdehyde, as lipid peroxidation marker in a group of patients with Rett syndrome. No significant differences were observed in erythrocyte glutathione peroxidase, glutathione reductase and catalase activities, between the Rett syndrome patients and the control group. Erythrocyte superoxide dismutase activities were significantly decreased in Rett syndrome patients (P<0.001) compared with the control group. Plasma malondialdehyde concentrations were significantly increased in Rett syndrome patients (P<0.001). An unbalanced nutritional status in Rett syndrome might explain the reduced enzyme activity found in these patients. Our results suggest that free radicals generated from oxidation reactions might contribute to the pathogenesis of Rett syndrome. The high levels of malondialdehyde reflect peroxidative damage of biomembranes that may contribute to progressive dementia, impaired motor function, behavioural changes, and seizures, in Rett syndrome. We found a probable relationship between the degree of oxidative stress and the severity of symptoms, which should be further investigated with a larger number of patients in different disease stages.

Adolescent↗
PubMed2001

Neural bHLH genes control the neuronal versus glial fate decision in cortical progenitors.

We have addressed the role of the proneural bHLH genes Neurogenin2 (Ngn2) and Mash1 in the selection of neuronal and glial fates by neural stem cells. We show that mice mutant for both genes present severe defects in development of the cerebral cortex, including a reduction of neurogenesis and a premature and excessive generation of astrocytic precursors. An analysis of wild-type and mutant cortical progenitors in culture showed that a large fraction of Ngn2; Mash1 double-mutant progenitors failed to adopt a neuronal fate, instead remaining pluripotent or entering an astrocytic differentiation pathway. Together, these results demonstrate that proneural genes are involved in lineage restriction of cortical progenitors, promoting the acquisition of the neuronal fate and inhibiting the astrocytic fate.

Animals↗
PubMed2001

Comparative study of new benzenesulphonamide fluoroquinolones structurally related to ciprofloxacin against selected ciprofloxacin-susceptible and -resistant Gram-positive cocci.

The in vitro activities of benzenesulphonamide fluoroquinolones (BSFQs) I-III, new fluoroquinolones with a p-substituted benzenesulphonyl moiety attached to the C(7) piperazinyl ring of ciprofloxacin, were assessed in comparison with those of N-sulfanilylpiperazinyl fluoroquinolone (NSFQ)-105 and ciprofloxacin for 133 Gram-positive clinical isolates. NSFQ-105 and BSFQ-I were the most active drugs. They were 16- to 64-fold more active than ciprofloxacin against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, including ciprofloxacin-resistant strains, and Streptococcus pneumoniae (eight- to 32-fold). A high degree of correlation was found between the MICs of the new compounds and ciprofloxacin for Staphylococcus spp. and E. faecalis. Staphylococci and enterococci exhibit cross-resistance to BSFQs and ciprofloxacin.

Anti-Infective Agents↗
PubMed2000

The tyrosine kinase PYK-2/RAFTK regulates natural killer (NK) cell cytotoxic response, and is translocated and activated upon specific target cell recognition and killing.

The compartmentalization of plasma membrane proteins has a key role in regulation of lymphocyte activation and development of immunity. We found that the proline-rich tyrosine kinase-2 (PYK-2/RAFTK) colocalized with the microtubule-organizing center (MTOC) at the trailing edge of migrating natural killer (NK) cells. When polyclonal NK cells bound to K562 targets, PYK-2 translocated to the area of NK-target cell interaction. The specificity of this process was assessed with NK cell clones bearing activatory or inhibitory forms of CD94/NKG2. The translocation of PYK-2, MTOC, and paxillin to the area of NK-target cell contact was regulated upon specific recognition of target cells through NK cell receptors, controlling target cell killing. Furthermore, parallel in vitro kinase assays showed that PYK-2 was activated in response to signals that specifically triggered its translocation and NK cell mediated cytotoxicity. The overexpression of both the wt and a dominant-negative mutant of PYK-2, but not ZAP-70 wt, prevented the specific translocation of the MTOC and paxillin, and blocked the cytotoxic response of NK cells. Our data indicate that subcellular compartmentalization of PYK-2 correlates with effective signal transduction. Furthermore, they also suggest an important role for PYK-2 on the assembly of the signaling complexes that regulate the cytotoxic response.

Animals↗
PubMed2000

Icetexane and abietane diterpenoids from Salvia gilliessi.

One icetexane and two abietane diterpenes were isolated from the aerial parts of Salvia gilliesii, and characterized as 5-epi-icetexone; 12-hydroxy-11,14-diketo-6,8,12-abietatrien-19,20-olide and 6 alpha,12,19-trihydroxy-11,14-diketo-8,12-abietadien-20,7 beta-olide, respectively. The structures were established by analysis of their 1H and 13C NMR spectra with the aid of 2D experiments. The triterpene oleanolic acid was isolated from the same source.

Diterpenes↗
PubMed1999

Signaling through CD43 induces natural killer cell activation, chemokine release, and PYK-2 activation.

Natural killer (NK) cell activation is the result of a balance between positive and negative signals triggered by specific membrane receptors. We report here the activation of NK cells induced through the transmembrane glycoprotein CD43 (leukosialin, sialophorin). Engagement of CD43 by specific antibodies stimulated the secretion of the chemokines RANTES, macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta, which was prevented by treatment of cells with the specific tyrosine kinase inhibitor genistein. Furthermore, signaling through CD43 increased the cytotoxic activity of NK cells and stimulated an increase in the tyrosine kinase activity in antiphosphotyrosine immune complexes of NK cell lysates. PYK-2 was identified among the tyrosine kinase proteins that become activated. Hence, PYK-2 activation was observed after 20 minutes of CD43 stimulation, reached a maximum after 45 to 60 minutes, and decreased to almost basal levels after 120 minutes of treatment. Together, these results demonstrate the role of CD43 as an activation molecule able to transduce positive activation signals in NK cells, including the regulation of chemokine synthesis, killing activity, and tyrosine kinase activation.

Antigens, CD↗
PubMed1999

Similarities and differences in RANTES- and (AOP)-RANTES-triggered signals: implications for chemotaxis.

Chemokines are a family of proinflammatory cytokines that attract and activate specific types of leukocytes. Chemokines mediate their effects via interaction with seven transmembrane G protein-coupled receptors (GPCR). Using CCR5-transfected HEK-293 cells, we show that both the CCR5 ligand, RANTES, as well as its derivative, aminooxypentane (AOP)- RANTES, trigger immediate responses such as Ca2+ influx, receptor dimerization, tyrosine phosphorylation, and Galphai as well as JAK/STAT association to the receptor. In contrast to RANTES, (AOP)-RANTES is unable to trigger late responses, as measured by the association of focal adhesion kinase (FAK) to the chemokine receptor complex, impaired cell polarization required for migration, or chemotaxis. The results are discussed in the context of the dissociation of the late signals, provoked by the chemokines required for cell migration, from early signals.

Cell Adhesion Molecules↗
PubMed1999

Cytoskeletal rearrangement during migration and activation of T lymphocytes.

T lymphocytes have an inherent ability to migrate along a chemotactic gradient, which enables them to exit the bloodstream and reach different tissues. Motile T cells display a polarized morphology with two distinct cell compartments: the leading edge and the uropod. During cell polarization, chemoattractant receptors, cell-adhesion molecules and cytoskeletal proteins are redistributed within these cellular compartments. The polarity of T lymphocytes changes during the establishment of antigen-specific cell-cell interactions, and this involves rearrangement of cytoskeletal proteins. This article discusses the regulation of these cytoskeletal rearrangements, and their role in the activation, migration and effector function of T cells.

Cell Membrane↗
PubMed1998

Roles of chemokines and receptor polarization in NK-target cell interactions.

We report that the ability of NK cells to produce chemokines is increased in NK-target cell conjugates. The chemokines produced play a critical role in the polarization and recruitment of NK cells as well as in the NK effector-target cell conjugate formation. Chemokines induce the formation of two specialized regions in the NK cell: the advancing front or leading edge, where chemokine receptors CCR2 and CCR5 cluster, which might guide the cells toward the chemotactic source, and the uropod, where adhesion molecules ICAM-1 and -3 are redistributed. NK cell polarity was intrinsically involved in conjugate formation. The redistribution of both adhesion receptors and CCR was preserved during the formation of NK-target cell conjugates. Time-lapse videomicroscopy studies of the formation of effector-target conjugates showed that morphologic poles are also functionally distinct; while the binding to target cells was preferentially mediated through the leading edge, the uropod was found at the rear of migrating NK cells and recruited additional NK cells to the vicinity of K562 target cells. Inhibition of cell polarization and adhesion receptor redistribution blocked the formation of NK-K562 cell conjugates and the cytotoxic activity of NK cells. We discuss the implication of NK-cell polarization in the development of cytotoxic responses.

Antigens, CD↗