9 research outputs found

    Identification of genes involved in Ca(2+ )ionophore A23187-mediated apoptosis and demonstration of a high susceptibility for transcriptional repression of cell cycle genes in B lymphoblasts from a patient with Scott syndrome

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    BACKGROUND: In contrast to other agents able to induce apoptosis of cultured cells, Ca(2+ )ionophore A23187 was shown to elicit direct activation of intracellular signal(s). The phenotype of the cells derived from patients having the hemorrhagic disease Scott syndrome, is associated with an abnormally high proportion of apoptotic cells, both in basal culture medium and upon addition of low ionophore concentrations in long-term cultures. These features are presumably related to the mutation also responsible for the defective procoagulant plasma membrane remodeling. We analyzed the specific transcriptional re-programming induced by A23187 to get insights into the effect of this agent on gene expression and a defective gene regulation in Scott cells. RESULTS: The changes in gene expression upon 48 hours treatment with 200 nM A23187 were measured in Scott B lymphoblasts compared to B lymphoblasts derived from the patient's daughter or unrelated individuals using Affymetrix microarrays. In a similar manner in all of the B cell lines, results showed up-regulation of 55 genes, out of 12,000 represented sequences, involved in various pathways of the cell metabolism. In contrast, a group of 54 down-regulated genes, coding for histones and proteins involved in the cell cycle progression, was more significantly repressed in Scott B lymphoblasts than in the other cell lines. These data correlated with the alterations of the cell cycle phases in treated cells and suggested that the potent effect of A23187 in Scott B lymphoblasts may be the consequence of the underlying molecular defect. CONCLUSION: The data illustrate that the ionophore A23187 exerts its pro-apoptotic effect by promoting a complex pattern of genetic changes. These results also suggest that a subset of genes participating in various steps of the cell cycle progress can be transcriptionally regulated in a coordinated fashion. Furthermore, this research brings a new insight into the defect in cultured Scott B lymphoblasts, leading to hypothesize that a mutated gene plays a role not only in membrane remodeling but also in signal transduction pathway(s) leading to altered transcriptional regulation of cell cycle genes

    Oral cladribine treatment and idiosyncratic drug-induced liver injury in multiple sclerosis

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    Background Oral cladribine (OC) is approved for the treatment of highly active relapsing multiple sclerosis. Postmarketing safety assessments have reported rare, but occasionally severe cases of liver injury in temporal association with OC, with pathophysiologic mechanisms still unknown. In the only detailed case report on this topic, idiosyncratic drug-induced liver injury (iDILI) during OC treatment was well characterised for the first time, but occurred in the context of prior high-dose steroid exposure. Although high-dose steroids are known to induce iDILI in patients with multiple sclerosis with a delay of up to 12 weeks, OC was assumed to be the culprit agent for observed liver injury and the role of steroid exposure was not further investigated.Case Herein, we describe a case of a 35-year-old women treated with high-dose oral prednisolone during the first treatment cycle OC and subsequently developed iDILI. A causality assessment of the role of prednisolone and OC was performed using the updated Roussel Uclaf Causality Assessment Method which also included a negative re-exposure test for OC during the second OC treatment cycle 1 year later.Conclusion Our observations suggest that prednisolone or interactions between prednisolone and OC are more likely to foster development of iDILI rather than OC treatment itself

    Interactive signal transfer between host and pathogen during successful infection of barley leaves by Blumeria graminis and Bipolaris sorokiniana

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    Using ion-selective microprobes, interactive signalling between barley and Blumeria graminis or Bipolaris sorokiniana has been investigated. The question was raised whether a biotrophically growing fungus manipulates the electrical driving forces (membrane potential, transmembrane pH), required for H+ cotransport of energy-rich compounds. Electrodes were positioned in the substomatal cavity of open stomata or on the leaf surface, and pH was measured continuously up to several days during fungal development. We demonstrate that surface and apoplastic fluids are electrically coupled and respond in a similar manner to stimuli. Apoplastic pH, monitored from the moment of inoculation with conidia, reveals several phases: 2–4 h after inoculation of the barley leaf with either fungus, the host displays rapid transient responses after its first contact with the fungal cell wall; apoplastic pH and pCa increases, cytoplasmic pH and pCa decreases. About 1 day after inoculation, the apoplastic pH increases by up to 2 pH units, which is thought to reflect a resistance response against the intruder. Whereas barley leaf cells possess a membrane potential of −152±5 mV, hyphae of B. graminis yield −251±8 mV, indicative of a substantial driving force advantage for the fungus. Although the resting membrane potential of barley remains constant during the first days after inoculation, leaves infected with B. sorokiniana get confronted with an energy problem, indicated by a retarded repolarization following a “light-off” stimulus. Five days after inoculation, apoplastic pH has increased to 5.97±0.47 (n=11) and does no longer respond to “light-off” when measured within lesions. In contrast, it stays at near normal values outside the lesions and responds to “light-off”. It is concluded that biotrophically growing fungi do not manipulate the cotransport driving forces since (i) any change in apoplastic pH would be experienced by both partners; (ii) the resting membrane potential is not changed. It is suggested that measured pH changes reflect defence responses of the host against the fungus rather than fungal action to increase compatibility

    Behavioural responses of indigenous benthic invertebrates (Echinogammarus meridionalis, Hydropsyche pellucidula and Choroterpes picteti) to a pulse of Acid Mine Drainage: A laboratorial study

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    The drainage of abandoned mines leads to several ecological problems, particularly the acidification of surface freshwater systems and heavy metal contamination. In order to study the possibility of using the behavioural early warning responses of Portuguese indigenous benthic invertebrates to detect an acute short-term pulse of Acid Mine Drainage (AMD), experiments with the Multispecies Freshwater Biomonitor MFB (TM) were performed and locomotion and ventilation were measured as endpoints. AMD was collected from the "Sao Domingos" mine (Southeast Portugal) and the following species were selected: Echinogammarus meridionalis (Pinkster, 1973). Hydropsyche pellucidula (Curtis, 1834) and Choroterpes picteti (Eaton, 1870). For simulating the pulsed exposure, AMD was added to river water where invertebrates were collected and pH was lowered until reaching 3.5. The effects of H(+) and heavy metals were discriminated using HCl positive controls. In addition to behaviour, mortality was registered. E. meridionalis was the most sensitive species in terms of mortality and behavioural endpoints, followed by C. picteti and H. pellucidula. E. meridionalis early warning responses consisted of increased locomotion with subsequent increase in ventilation, whereas for C. picteti only an increase in locomotion was observed. H. pellucidula showed no early warning responses. This work demonstrates the suitableness of using benthic invertebrates' behavioural early warning responses for detecting spikes of pollutants like AMD. (C) 2008 Elsevier Ltd. All rights reserved.FCT - SFRH/BM/8677/2002CETERA project - POCTI/BIA/10200/98/200


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