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M C Martínez

Publications and source records attributed to M C Martínez.

At least 19 recordsLinked to original sources
PubMed2006

Cyclic GMP modulates store-operated calcium entry inducing phosphatidylserine translocation at the surface of megakaryocytic cells.

When subjected to stimulation, cells from the vascular compartment show a spontaneous collapse of the plasma membrane phospholipid asymmetry and phosphatidylserine is exposed at the external leaflet. Thus, phosphatidylserine externalization is essential for normal hemostasis and phagocytosis. The mechanism governing the migration of phosphatidylserine to the exoplasmic leaflet is not yet fully understood. We have proposed that store-operated calcium entry (SOCE) constitutes a key step of this process. Here, interaction of [Ca(2+)](i), cAMP and cGMP pathways and phosphatidylserine exposure was examined in human megakaryocytic cells. The membrane permeable cAMP and cGMP analogues, pCPT-cAMP and pCPT-cGMP, enhanced the Ca(2+) signal induced by ionophore and SOCE. Responses to pCPT-cAMP and pCPT-cGMP were independent of protein kinase A, protein kinase G (PKG) or ERK pathways. Inhibition of small G-proteins reduced or abolished the increase of [Ca(2+)](i) induced by pCPT-cAMP or pCPT-cGMP, respectively. pCPT-cGMP but not pCPT-cAMP enhanced the ability of cells to expose phosphatidylserine. This effect was not prevented by the inhibition of PKG or small G-proteins. These results show the differential role of cyclic nucleotides in the Ca(2+)-dependent membrane remodeling. Hence, pCPT-cGMP is another regulatory element for the completion of SOCE-induced phosphatidylserine transmembrane redistribution in HEL cells through a mechanism implicating small G-proteins.

Biological Transport↗
PubMed2006

Origin and biological significance of shed-membrane microparticles.

Microparticles (MPs) are small vesicles released from the membrane surface during eukaryotic cell activation or apoptosis. They originate from various cell types, displaying the typical surface cell proteins and cytoplasmic components of their cell origin. Their procoagulant properties are linked to phosphatidylserine exposed at their surface. Numerous reports have shown that MPs are able to mediate long-range signaling, acting on different targets from those of their own cellular origin. MPs-mediated binding to other cells occurs by integration into the membrane, by adhesion to the cell surface or by ligand-receptor interaction. Elevated levels of circulating MPs have been detected in cardiovascular and immune-mediated diseases. Despite extensive studies of the procoagulant and pro-inflammatory properties of MPs, little is known about their effect on vascular function. MPs accumulate in atherosclerotic plaques and injured vascular wall. Circulating MPs from patients with myocardial infarction induce endothelial dysfunction by impairing the endothelial nitric oxide (NO) pathway, without causing changes in endothelial NO-synthase (eNOS) expression. However, MPs from T-cells may induce endothelial dysfunction, altering gene expression of eNOS and caveolin-1. Moreover, MPs may promote the expression of pro-inflammatory proteins implicated in vascular contractility alterations. This review describes the origin of MPs and their biological role in physiological conditions and in various pathological states, with special reference to the possible linkage between their pro-inflammatory and procoagulant properties and vascular dysfunction.

Animals↗
PubMed2004

Modulation of signal transduction through the cellular prion protein is linked to its incorporation in lipid rafts.

Because expressed at a significant level at the membrane of human T cells, we made the hypothesis that the cellular prion protein (PrPc) could behave as a receptor, and be responsible for signal transduction. PrPc engagement by specific antibodies was observed to induce an increase in cytosolic calcium concentration and led to enhanced activity of Src protein tyrosine kinases. Antibodies to CD4 and CD59 did not influence calcium fluxes or signaling. The effect was maximal after the formation of a network involving avidin and biotinylated antibody to PrPc and was inhibited after raft disruption. PrPc localization was not restricted to rafts in resting cells but engagement was a prerequisite for signaling induction, with concomitant PrPc recruitment into rafts. These results suggest a role for PrPc in signaling pathways, and show that lateral redistribution of the protein into rafts is important for subsequent signal transduction.

Antibodies, Monoclonal↗
PubMed2004

Rho A participates in the regulation of phosphatidylserine-dependent procoagulant activity at the surface of megakaryocytic cells.

Once exposed at the external surface of activated platelets or apoptotic cells, phosphatidylserine, an anionic phospholipid mostly sequestered in the inner leaflet of the plasma membrane, plays essential roles in hemostasis and phagocytosis. The mechanism governing the migration of the phosphatidylserine to the exoplasmic leaflet is not yet fully understood. We have proposed that store-operated calcium entry (SOCE) constitutes a key step of this process. ERK pathway is among the elements modulating SOCE and phosphatidylserine externalization in megakaryocytic HEL cells. Here, we investigated the role of small GTPase Rho A, which may interact with the ERK pathway. Specific inhibitors of Rho A (exoenzyme C3 and toxin B) reduced both SOCE and phosphatidylserine-dependent procoagulant activity. Simultaneous inhibition of Rho A and extracellular signal-regulated kinase (ERK) pathways did not elicit further reduction with respect to each individual one. Rho A can regulate SOCE and phosphatidylserine exposure through the reorganization of actin cytoskeleton, but not through ROCK pathway. Hence, Rho A is another regulatory element for the completion of SOCE-induced phosphatidylserine transmembrane redistribution in HEL cells.

Calcium↗
PubMed2003

Role of lamivudine in the reactivation of hepatitis B virus infection in immunodepressed patients.

INTRODUCTION: hepatitis B virus (HBV) reactivation in immunocompromised states is a well-known event that may be a serious problem in endemic areas of infection. Presently, the investigation of hepatitis B status has been recommended prior to receiving cytotoxic treatment. Lamivudine has been used in the reactivation of HBV in immunocompromised states. We report our corresponding data for lamivudine in the treatment of HBV reactivation after intensive chemotherapy in patients with lymphoma and after kidney transplantation. CLINICAL OBSERVATION: we present two cases of HBV reactivation after chemotherapy for lymphoma and two cases after cadaveric renal transplantation treated with lamivudine (100-150 mg/day). RESULTS: we observed a prompt clinical improvement in all patients after lamivudine treatment. Furthermore, laboratory data showed a rapid biochemical and antiviral response. However, the response in lymphoma patients was quicker than in patients who had post-transplantation reactivation of HBV. Therapy was well tolerated and no relevant side effects appeared during follow-up (twenty four months). The HBV remained negative in three cases. CONCLUSION: lamivudine is effective and safe in the treatment of HBV reactivation in immunodepressed patients. Lamivudine therapy should be considered for the treatment of HBV reactivation in patients with prior hepatitis B or chronic hepatitis B with inactive viral replication.

Adult↗
PubMed2001

Deciphering the plasma membrane hallmarks of apoptotic cells: phosphatidylserine transverse redistribution and calcium entry.

BACKGROUND: During apoptosis, Ca2+-dependent events participate in the regulation of intracellular and morphological changes including phosphatidylserine exposure in the exoplasmic leaflet of the cell plasma membrane. The occurrence of phosphatidylserine at the surface of specialized cells, such as platelets, is also essential for the assembly of the enzyme complexes of the blood coagulation cascade, as demonstrated by hemorrhages in Scott syndrome, an extremely rare genetic deficiency of phosphatidylserine externalization, without other apparent pathophysiologic consequences. We have recently reported a reduced capacitative Ca2+ entry in Scott cells which may be part of the Scott phenotype. RESULTS: Taking advantage of these mutant lymphoblastoid B cells, we have studied the relationship between this mode of Ca2+ entry and phosphatidylserine redistribution during apoptosis. Ca2+ ionophore induced apoptosis in Scott but not in control cells. However, inhibition of store-operated Ca2+ channels led to caspase-independent DNA fragmentation and decrease of mitochondrial membrane potential in both control and Scott cells. Inhibition of cytochrome P450 also reduced capacitative Ca2+ entry and induced apoptosis at comparable extents in control and Scott cells. During the apoptotic process, both control and more markedly Scott cells externalized phosphatidylserine, but in the latter, this membrane feature was however dissociated from several other intracellular changes. CONCLUSIONS: The present results suggest that different mechanisms account for phosphatidylserine transmembrane migration in cells undergoing stimulation and programmed death. These observations testify to the plasticity of the plasma membrane remodeling process, allowing normal apoptosis even when less fundamental functions are defective.

Apoptosis↗
PubMed2001

Potentiation by aminoethylisothiourea of the extra-cellular Ca(2+) component of norepinephrine-induced contraction in rat femoral arteries.

Aminoethylisothiourea (AET) is a potent inhibitor of inducible nitric oxide synthase (NOS). The present study was performed to investigate whether AET and its rearrangement products might modulate vascular contraction independently of its effects as a NOS inhibitor in rat small femoral arteries. AET caused an endothelium-independent increase in contraction induced by norepinephrine (NE). This effect was not affected by either N(omega)-nitro-L-arginine methyl ester, nitro-L-arginine, indomethacin or propanolol, but it was suppressed in Ca(2+)-free medium. AET enhanced extracellular Ca(2+) component of NE-induced contraction, and this effect was prevented by the receptor-mediated Ca(2+) entry blocker, 1-{beta-[3-(p-methoxyphenyl)-propyloxyl]-p-methoxyphenetyl}- 1H-imidaz ole hydrochloride (SK&F 96365), but not by the voltage-dependent Ca(2+) channel blocker, nitrendipine. AET did not alter the response to CaCl(2) in vessels exposed to KCl depolarization. The protein kinase C (PKC) inhibitor, 2-[1-(3-dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl) (GF 109203X), prevented the potentiating effect of AET on the NE response. AET failed to produce an increase in tone in the presence of NE and GTP in permeabilized arteries. Among the AET rearrangement products, mercaptoethylguanidine produced an endothelium-independent increase in the NE response. 2-aminothiazoline had no effect, and guanidinoethyldisulphide produced relaxation. The effect of mercaptoethylguanidine was dependent on extracellular Ca(+) and was prevented by GF 109203X. These results indicate that AET is able to potentiate the contraction to NE in rat femoral resistance arteries independently of its inhibitory effect on either NOS or cyclo-oxygenase. Its effect occurs via an enhancement of SK&F 96365-sensitive Ca(2+) entry. A PKC inhibitor-sensitive mechanism also appears to be involved in the AET effect. Mercaptoethylguanidine potentiates NE response through a mechanism similar to AET.

Animals↗
PubMed2001

Single-step multiplex RT-PCR for simultaneous and colourimetric detection of six RNA viruses in olive trees.

A single-step multiplex RT-PCR was developed for the simultaneous and colourimetric detection of six RNA viruses (Cucumber mosaic virus, Cherry leaf roll virus, strawberry latent ringspot virus, Arabis mosaic virus, Olive latent-1 virus and Olive latent-2 virus) which infect olive trees. Six compatible primer set for one-step RT-PCR amplification in a single closed-tube and 3' digoxigenin labelled probes were designed in optimal, specific and conserved regions. The method has been assessed with 195 Spanish field olive trees, suggesting that approximately 1.5% of the tested material was infected by Cucumber mosaic virus and 0.5% by Cherry leaf roll virus. This method saves time and reagent costs compared with monospecific RT-PCR which needs several reactions for the same number of tests. Using colourimetric detection, it is possible to analyse many samples, it increases sensitivity 10-fold, and whilst facilitating the interpretation of results, it avoids the use of gels and the toxic ethidium bromide. The method could be used routinely for sanitary and certification programmes.

Colorimetry↗
PubMed2001

Distribution of alcohol dehydrogenase mRNA in the rat central nervous system. Consequences for brain ethanol and retinoid metabolism.

The localization of alcohol dehydrogenase (ADH) in brain regions would demonstrate active ethanol metabolism in brain during alcohol consumption, which would be a new basis to explain the effects of ethanol in the central nervous system. Tissue sections from several regions of adult rat brain were examined by in situ hybridization to detect the expression of genes encoding ADH1 and ADH4, enzymes highly active with ethanol and retinol. ADH1 mRNA was found in the granular and Purkinje cell layers of cerebellum, in the pyramidal and granule cells of the hippocampal formation and in some cell types of cerebral cortex. ADH4 expression was detected in the Purkinje cells, in the pyramidal and granule cells of the hippocampal formation and in the pyramidal cells of cerebral cortex. High levels of ADH1 and ADH4 mRNAs were detected in the CNS epithelial and vascular tissues: leptomeninges, choroid plexus, ependymocytes of ventricle walls, and endothelium of brain vessels. Histochemical methods detected ADH activity in rodent cerebellar slices, while Western-blot analysis showed ADH4 protein in homogenates from several brain regions. In consequence, small but significant levels of ethanol metabolism can take place in distinct areas of the CNS following alcohol consumption, which could be related to brain damage caused by a local accumulation of acetaldehyde. Moreover, the involvement of ADH in the synthesis of retinoic acid suggests a role for the enzyme in the regulation of adult brain functions. The impairment of retinol oxidation by competitive inhibition of ADH in the presence of ethanol may be an additional origin of CNS abnormalities caused by ethanol.

Alcohol Dehydrogenase↗
PubMed2000

Relation between phosphatidylserine exposure and store-operated Ca(2+) entry in stimulated cells.

A significant increase in intracellular Ca(2+) is required to trigger the remodeling of the cell plasma membrane. Scott syndrome is an extremely rare inherited disorder of the transmembrane migration of phosphatidylserine toward the exoplasmic leaflet in blood cells. We have recently reported a reduced capacitative Ca(2+) entry in Scott cells [Martínez et al. (1999) Biochemistry 38, 10092-10098]. We have investigated here the links between defective phosphatidylserine exposure and Ca(2+) signaling in Scott cells by focusing on the Ca(2+) entry following the emptying of intracellular stores. After depletion of caffeine- or thapsigargin-sensitive stores, Ca(2+) entry was lower in Scott compared to control lymphoblasts. However, the simultaneous depletion of both types of stores restored a normal Ca(2+) influx across the plasma membrane in Scott cells and phosphatidylserine externalization ability was improved concomitantly with capacitative Ca(2+) entry. These observations point to the essential role of capacitative Ca(2+) entry in the control of phosphatidylserine exposure of stimulated cells.

Aged↗
PubMed2000

Regulation of phosphatidylserine transbilayer redistribution by store-operated Ca2+ entry: role of actin cytoskeleton.

The phosphatidylserine transmembrane redistribution at the cell surface is one of the early characteristics of cells undergoing apoptosis and also occurs in cells fulfilling a more specialized function, such as the phosphatidylserine-dependent procoagulant response of platelets after appropriate activation. Although an increase in cytoplasmic Ca2+ is essential to trigger the remodeling of the plasma membrane, little is known about intracellular signals leading to phosphatidylserine externalization. Here, the role of store-operated Ca2+ entry on phosphatidylserine exposure was investigated in human erythroleukemia HEL cells, a pluripotent lineage with megakaryoblastic properties. Ca2+ entry inhibitors (SKF-96365, LaCl(3), and miconazole) inhibited store-operated Ca2+ entry in A23187- or thapsigargin-stimulated cells and reduced the degree of phosphatidylserine externalization concomitantly, providing evidence for a close link between the two processes. In cells pretreated with cytochalasin D, an agent that disrupts the microfilament network of the cytoskeleton, store-operated Ca2+ entry and phosphatidylserine externalization at the cell surface were inhibited. In a context where most of the key actors remain to be identified, these results provide evidence for the implication of both store-operated Ca2+ entry and cytoskeleton architectural organization in the regulation of phosphatidylserine transbilayer migration.

Actins↗
PubMed2000

Incidence and epidemiology of Citrus tristeza virus in the Valencian community of Spain.

The first outbreak of citrus tristeza disease in Spain caused by Citrus tristeza virus (CTV) was recorded in 1957 in the Valencian Community (VC). In total c. 40 million trees, mainly of sweet orange and mandarin grafted on sour orange rootstocks, declined due to CTV. Large-scale surveys in different municipalities of the VC indicated that the disease spread very fast. Incidence increased from 11% in 1989 to 53% in 1998. Toxoptera aurantii and Aphis spiraecola (inefficient aphid vectors of CTV) predominated before 1985-87. Since then the relatively efficient vector Aphis gossypii has become dominant and induced an epidemic that has been modelled. The large number of A.gossypii that visited each clementine tree (estimated to exceed 97000 per year) explained the difference between the temporal pattern of spread of CTV in clementine which followed the Gompertz model and that in sweet orange (logistic model). The susceptibility of the different citrus species to CTV infection by aphids seems to depend on the number of young, succulent shoots produced. The epidemiological data allowed specific recommendations to be made to growers in order to facilitate a change to a modern citrus industry based on the use of selected varieties grafted on tristeza-tolerant rootstocks produced within a certification scheme. This has been done already in almost 90% of the VC citrus-growing area. The tristeza problem has been solved unless more aggressive isolates are introduced and become prevalent.

Animals↗
PubMed2000

Impact of lactation upon fertility in the New World primate capuchin monkey (Cebus apella).

In the present paper, we have studied the impact of lactation upon fertility in the capuchin monkey, Cebus apella, under laboratory conditions. Nursing females (ten females, 12 postpartum periods) presented lactational amenorrhea (first menses at 159.2 +/- 9.0 vs 42.6 +/- 5.8 days postpartum in five non-nursing females, seven postpartum periods). Plasma estradiol and progesterone concentrations during lactational amenorrhea were lower than those during the follicular phase of the menstrual cycle. Prolactin was higher than in non-nursing females at 31-60 days postpartum. Interbirth interval, studied in three non-nursing (four intervals) and six nursing females (eight intervals) lasted for 349.5 +/- 11.8 and 613.4 +/- 30.8 days, respectively. In non-nursing females, early recovery of the menstrual cycle was followed by a residual infertility (mating but no pregnancy) lasting 152.8 +/- 7.9 days. In nursing females, recovery of the menstrual cycle was followed by an extended residual infertility of 301.5 +/- 22.7 days. Thus, in the capuchin monkey, nursing prolongs the interbirth interval by inducing lactational amenorrhea and extending the residual infertility period.

Amenorrhea↗
PubMed2000

Involvement of protein kinase C, tyrosine kinases, and Rho kinase in Ca(2+) handling of human small arteries.

The mechanisms of Ca(2+) handling and sensitization were investigated in human small omental arteries exposed to norepinephrine (NE) and to the thromboxane A(2) analog U-46619. Contractions elicited by NE and U-46619 were associated with an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), an increase in Ca(2+)-independent signaling pathways, or an enhancement of the sensitivity of the myofilaments to Ca(2+). The two latter pathways were abolished by protein kinase C (PKC), tyrosine kinase (TK), and Rho-associated protein kinase (ROK) inhibitors. In Ca(2+)-free medium, both NE and U-46619 elicited an increase in tension that was greatly reduced by PKC inhibitors and abolished by caffeine or ryanodine. After depletion of Ca(2+) stores with NE and U-46619 in Ca(2+)-free medium, addition of CaCl(2) in the continuous presence of the agonists produced increases in [Ca(2+)](i) and contractions that were inhibited by nitrendipine and TK inhibitors but not affected by PKC inhibitors. NE and U-46619 induced tyrosine phosphorylation of a 42- or a 58-kDa protein, respectively. These results indicate that the mechanisms leading to contraction elicited by NE and U-46619 in human small omental arteries are composed of Ca(2+) release from ryanodine-sensitive stores, Ca(2+) influx through nitrendipine-sensitive channels, and Ca(2+) sensitization and/or Ca(2+)-independent pathways. They also show that the TK pathway is involved in the tonic contraction associated with Ca(2+) entry, whereas TK, PKC, and ROK mechanisms regulate Ca(2+)-independent signaling pathways or Ca(2+) sensitization.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2000

[Detection of Salmonella enteritidis in samples of poultry products for human consumption in the Chilean metropolitan area].

BACKGROUND: Salmonella enteritidis (SE) is a frequent cause of diarrhea, and is transmitted mainly by SE contaminated eggs or poultry meat. The frequency of SE contaminated eggs or chicken meat and the risk for acquiring this pathogen is unknown in Chile. AIM: To measure SE contamination in eggs poultry meat and entrails offered in retail markets in the Metropolitan Area during two consecutive years (1998-1999). MATERIAL AND METHODS: Samples were placed in sterile bags and transported to the laboratory before 4 hours at 4 degrees C. Microbiologic detection was done using a standard procedure and an immunodetection assay. RESULTS: SE was found in one of 1081 egg samples (0.09%). The contaminated sample was offered in a supermarket under their own commercial name. Six percent of 1154 poultry meat samples were contaminated by SE and 2.3% by other Salmonella serotypes. Entrails had even higher rates with 10.2% of 370 samples harboring SE and 2.7% other serotypes. Total Salmonella sp. isolates and SE isolates declined during 1999. Nine SE phagotypes were identified, predominating types 4 and 7. CONCLUSIONS: Eggs and other avian products are contaminated by different SE phagotypes and other Salmonella serotypes, implicating a risk for the consumers (Rev Méd Chile 2000; 128: 1075-83).

Animals↗
PubMed1999

Annexin V counteracts apoptosis while inducing Ca(2+) influx in human lymphocytic T cells.

We have previously shown that when annexin V is present during the execution of a cell death program, apoptosis is delayed. This is reflected by the inhibition of DNA cleavage and of the release of apoptotic membrane particles, and by reduction of the proteolytic processing of caspase-3. Here, we have studied the mechanism(s) through which annexin V counteracts apoptosis in the human CEM T cell line. The degree of apoptosis inhibition was associated with an increase of intracellular Ca(2+) concentration ([Ca(2+)](i)). Reduction of the extracellular Ca(2+) concentration by EGTA abolished the anti-apoptotic effect, suggesting that annexin V favors Ca(2+) influx and that Ca(2+) acts as an inhibitor rather than an activator of apoptosis in CEM T cells. The effects on apoptosis and [Ca(2+)](i) of several modified annexins with different electrophysiological properties indicate that the N-terminal domain of annexin V is necessary for the Ca(2+)-dependent anti-apoptotic action of annexin V. These results suggest that annexin V regulates membrane Ca(2+) permeability and is protective against apoptosis by increasing [Ca(2+)](i) in CEM T cells.

Annexin A1↗