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Biomedical subjects

F Martin

Publications and source records attributed to F Martin.

At least 145 records · Page 8Linked to original sources
PubMed1998

The expression of a symbiosis-regulated gene in eucalypt roots is regulated by auxins and hypaphorine, the tryptophan betaine of the ectomycorrhizal basidiomycete Pisolithus tinctorius.

A full-length cDNA coding for a symbiosis-regulated transcript, EgHypar, was isolated by differential screening from a Eucalyptus globulus bicostata--Pisolithus tinctorius ectomycorrhiza. The sequence of this clone revealed a protein with an estimated molecular mass of 25.5 kDa that exhibited a high degree of homology (66%) with plant auxin-induced glutathione-S-transferases. Expression of the EgHypar gene in seedlings was confined largely in roots and it is drastically increased by ectomycorrhiza development. The concentration of EgHypar transcripts was similarly up-regulated in roots incubated in media supplemented with P. tinctorius cell-free extracts, indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid or hypaphorine (tryptophan betaine), the major indolic compound secreted by P. tinctorius. The latter fungal alkaloid concomitantly induced a decrease in root hair elongation in eucalypt seedlings. Up-regulation of EgHypar expression by auxins and fungal metabolites suggests that this symbiosis-regulated gene could be involved in the morphological changes taking place in plants roots upon symbiosis development. To our knowledge, these results provide the first molecular evidence that gene expression of the host plant is altered by molecules produced by the ectomycorrhizal mycobiont.

Amino Acid Sequence↗
PubMed1998

Oral contraceptive use and smoking are risk factors for relapse in Crohn's disease. The Canadian Mesalamine for Remission of Crohn's Disease Study Group.

BACKGROUND & AIMS: Lifestyle factors have been shown to influence prognosis in Crohn's disease. The purpose of this study was to prospectively assess the effects of smoking and oral contraceptive use on clinical relapse rates. METHODS: Placebo-treated patients formed a prospective cohort, followed up for 48 weeks or until relapse. The influence of smoking and the use of oral contraceptives on relapse risk was examined by life-table analysis (log rank tests) and Cox proportional hazards modeling, taking into account demographic and disease characteristics. RESULTS: Of 152 patients, 61 (40%) had a relapse. Univariate analysis showed unfavorable outcomes for women (P = 0.05), current smokers (P = 0.005), and use of oral contraceptives (P = 0.001). Recent surgery was associated with a decreased risk of relapse (P = 0.02). The Cox model retained current smoking vs. never smoking (hazard ratio, 2.1; 95% confidence interval, 1.1-4.2), oral contraceptive use (hazard ratio, 3.0; 95% confidence interval, 1.5-5.9), and medical compared with surgical induction of remission (hazard ratio, 2.1; 95% confidence interval, 1.0-4.2) as predictors of relapse. Ex-smokers did not have an increased risk. Finally, sex, age, time in remission, disease location, and disease duration were not significant predictors. CONCLUSIONS: Oral contraceptive use and smoking are associated with an increased risk of relapse in patients with Crohn's disease.

Adult↗
PubMed1998

A novel immunoglobulin superfamily junctional molecule expressed by antigen presenting cells, endothelial cells and platelets.

The architecture of lymphoid microenvironments depends upon complex interactions between several stromal cell types. We describe in this report the cloning of a cDNA which encodes a novel membrane molecule containing two external Ig-like domains. It is expressed at the junction between endothelial cells including HEV. It is also expressed by platelets and MHC class II+ antigen presenting cells in thymic medulla and T-cell areas in peripheral lymphoid organs. These cells which lack in RelB-deficient mice include tissue-derived dendritic, epithelial cells and macrophages. Thus, this molecule might contribute to the organization of cell junctions in different microenvironments.

Amino Acid Sequence↗
PubMed1998

Expression of bovine activin-A and inhibin-A in recombinant baculovirus-infected Spodoptera frugiperda Sf 21 insect cells.

Currently, bioactive activin and inhibin for investigative purposes are obtained either by purification from bovine or porcine follicular fluid or have been kindly supplied in limited amounts by Genentech. The latter are recombinant formulations produced in cultured monkey kidney CV-1 cells. The aims of this study were to assess the potential of the baculovirus expression system as an alternative means to produce recombinant activin and inhibin. Towards these goals, two recombinant baculoviruses, AcBovACTA and AcBovINHA, were constructed. AcBovACTA contains a contiguous copy of the bovine beta A-inhibin/activin structural gene encoding the beta A-preproprotein whereas AcBovINHA contains contiguous copies of the bovine alpha-inhibin and beta A-inhibin/activin structural genes encoding the alpha- and beta A-preproproteins, respectively. Western blot analyses, using monoclonal antibodies specific for the mature portions of the alpha-inhibin and beta A-inhibin/activin subunits, demonstrated that Spodoptera frugiperda Sf21 cells infected with either recombinant virus secreted mature homodimeric activin-A into the medium. In addition, Sf21 cells infected with the recombinant AcBovINHA virus were found also to produce substantial amounts of the alpha-inhibin precursor protein. However, the mature portion of the latter is not secreted into the medium but is retained within infected cells in an incompletely processed form(s). The recombinant activin-A secreted by Sf21 cells infected with the AcBovACTA virus was shown to possess activin bioactivity when analysed by in vitor bioassay and, therefore, provides an alternative route to mammalian cell expression for the production of recombinant activin-A.

Activins↗
PubMed1998

Functional coupling of a recombinant human 5-HT5A receptor to G-proteins in HEK-293 cells.

1. We have cloned, expressed and pharmacologically characterized the Human 5-HT5A receptor. 2. We have shown that ligand activation of the Human 5-HT5A receptor results in functional coupling to G-proteins in HEK-293 cells. 3. Stimulation of the receptor with 5-CT (5-carboxamidotryptamine) resulted in a dose-dependent increase in the % [35S]-GTPgammaS binding over the basal level. This is the first study to describe such G-protein activation for the Human 5-HT5A receptor in any cell. 4. A dose-dependent inhibition of cyclic AMP accumulation was observed in the recombinant Human 5-HT5A receptor cell line, suggesting a functional coupling to a G alpha i, G-protein in the HEK-293 cell line. 5. A ligand-stimulated reduction in the detectable level of the catalytic domain of protein kinase A (PKA) in nuclear extracts isolated from Human 5-HT5A expressing cells was observed. This observation was consistent with the reduction in the level of cyclic AMP accumulation, in response to receptor activation.

Amino Acid Sequence↗
PubMed1998

Cancer cell sensitization to fas-mediated apoptosis by sodium butyrate.

Cancer cells often resist Fas-mediated apoptosis even when the Fas receptor is expressed at the cell surface. We show here that human and rat colon cancer cells undergo massive apoptosis when they are exposed to soluble Fas ligand in the presence of sodium butyrate, an agent that induces by itself only a low rate of apoptosis. Sodium butyrate potentiates Fas-dependent apoptosis in seven out of eight colon cancer cell lines. Sodium butyrate does not increase Fas receptor cell surface expression and does not modify cell levels of Bcl-2, Bcl-xL, Bcl-xS and Bax. Sodium butyrate also induces tumor cell sensitization to the apoptotic effect of the combination of TNF-alpha and IFN-gamma, but it does not modify the level of the FADD/Mort1 adaptator molecule, at the connection between Fas- and TNF-dependent apoptosis pathways. Because the clinical toxicity of butyrate is low, its ability to enhance Fas-signal delivery in cancer cells could be of therapeutic interest.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Aetiology of childhood proptosis.

OBJECTIVE: To retrospectively analyse causes of childhood proptosis and their investigations and treatment. METHODOLOGY: The records of children under 15 years of age presenting with proptosis to The Children's Hospital, Camperdown, Sydney, were reviewed for the period 1983-93 inclusive. RESULTS: Fifty-seven cases of proptosis were found. In order of frequency the causes were; orbital cellulitis 22, thyroid eye disease 8, optic nerve +/- optic chiasm glioma 8, orbital rhabdomyosarcoma 7, metastatic neuroblastoma 4, orbital neurofibroma 3, orbital haemangioma 2, metastatic Ewing's sarcoma 2 and orbital dermoid cyst 1. Treatment depended on the cause (antibiotics, antithyroid drugs, chemotherapy, radiotherapy, surgery) and was multidisciplinary. CONCLUSIONS: The most common cause of proptosis in children presenting to The Children's Hospital, Camperdown, Sydney, was infective orbital cellulitis. The most useful initial investigation was an orbital computed tomography scan. Treatment depended on the cause of the proptosis and was multidisciplinary.

Adolescent↗
PubMed1998

Visual and brainstem auditory evoked potentials and maximal aerobic exercise: does the influence of exercise persist after body temperature recovery?

Transversal studies have shown a strong correlation between specific evoked potential (EP) values and specific physical activities, as well as between EP values and the amount of training. Prior to longitudinal studies investigating the effect of training in EPs, it is mandatory to determine whether a recent training session could interfere with regular EP recording. Exercise-induced hyperthermia is known to modify EP values. The purpose of the study was to determine whether an acute exercise can induce EP modification persisting after body temperature recovery. We measured two sets of visual evoked potentials (VEPs) and brainstem auditory evoked potentials (BAEPs) in 16 males (8 cyclists and 8 sedentary peers), one before and the other after a maximal cycloergometric graded exercise test. The second test was performed immediately after body temperature recovery. We chose to test cyclists, as their specific training corresponded to the exercise test we performed on a cycloergometer. The repeated measures before and after the exercise test showed no significant differences, neither in VEPs nor in BAEPs, for any subject of the study. Recording VEPs and BAEPs in cyclists, we observed no difference related to this particular sport training. This study showed that VEP and BAEP values were similar to those measured before a maximal exercise when body temperature returned to pre-exercise value. This original work demonstrated that VEP and BAEP recordings can be reliably performed after a recent training session, provided body temperature has returned to basal level.

Adolescent↗
PubMed1998

Engineering, characterization and phage display of hepatitis C virus NS3 protease and NS4A cofactor peptide as a single-chain protein.

The polyprotein encoded by hepatitis C virus (HCV) genomic RNA is processed into functional polypeptides by both host- and virus-encoded proteases. The HCV-encoded NS3 protease and its cofactor peptide NS4A form a non-covalent complex, which participates in processing the viral polyprotein. This proteolytic activity is believed to be essential for virus proliferation and thus the NS3 protease is a prime target for developing anti-HCV pharmacological agents. Recent X-ray crystallography structural studies have revealed the nature of this non-covalent complex between NS3 protease and the 'active' central segment of NS4A, providing the opportunity to design a single-chain polypeptide. To this end, the DNA sequence encoding for the NS4A peptide (residues 21-34) was genetically fused via a short linker, capable of making a beta-turn, to the N-terminus of the NS3 protease domain. This engineered single-chain NS3-protease (scNS3) is fully active with kinetic parameters virtually identical with those of the NS3/ NS4A non-covalent complex. Moreover, the scNS3 protease can be displayed on filamentous phage and affinity selected using an immobilized specific inhibitor. The scNS3 expressed as a soluble protein and in a phage-display format facilitates enzyme engineering for further structural studies and in vitro selection of potential drug-resistant mutants. These are important steps towards developing effective anti-protease compounds.

Amino Acid Sequence↗
PubMed1998

Eucalypt NADP-dependent isocitrate dehydrogenase. cDNA cloning and expression in ectomycorrhizae.

NADP-dependent isocitrate dehydrogenase (NADP-ICDH) activity is increased in roots of Eucalyptus globulus subsp. bicostata ex Maiden Kirkp. during colonization by the ectomycorrhizal fungus Pisolithus tinctorius Coker and Couch. To investigate the regulation of the enzyme expression, a cDNA (EgIcdh) encoding the NADP-ICDH was isolated from a cDNA library of E. globulus-P. tinctorius ectomycorrhizae. The putative polypeptide sequence of EgIcdh showed a high amino acid similarity with plant NADP-ICDHs. Because the deduced EgICDH protein lacks an amino-terminal targeting sequence and shows highest similarity to plant cytosolic ICDHs, it probably represents a cytoplasmic isoform. RNA analysis showed that the steady-state level of EgIcdh transcripts was enhanced nearly 2-fold in ectomycorrhizal roots compared with nonmycorrhizal roots. Increased accumulation of NADP-ICDH transcripts occurred as early as 2 d after contact and likely led to the observed increased enzyme activity. Indirect immunofluorescence microscopy indicated that NADP-ICDH was preferentially accumulated in the epidermis and stele parenchyma of nonmycorrhizal and ectomycorrhizal lateral roots. The putative role of cytosolic NADP-ICDH in ectomycorrhizae is discussed.

Amino Acid Sequence↗
PubMed1998

Carbohydrate and amino acid metabolism in the eucalyptus globulus-pisolithus tinctorius ectomycorrhiza during glucose utilization

The metabolism of [1-13C]glucose in Pisolithus tinctorius cv Coker & Couch, in uninoculated seedlings of Eucalyptus globulus bicostata ex Maiden cv Kirkp., and in the E. globulus-P. tinctorius ectomycorrhiza was studied using nuclear magnetic resonance spectroscopy. In roots of uninoculated seedlings, the 13C label was mainly incorporated into sucrose and glutamine. The ratio (13C3 + 13C2)/13C4 of glutamine was approximately 1.0 during the time-course experiment, indicating equivalent contributions of phosphoenolpyruvate carboxylase and pyruvate dehydrogenase to the production of alpha-ketoglutarate used for synthesis of this amino acid. In free-living P. tinctorius, most of the 13C label was incorporated into mannitol, trehalose, glutamine, and alanine, whereas arabitol, erythritol, and glutamate were weakly labeled. Amino acid biosynthesis was an important sink of assimilated 13C (43%), and anaplerotic CO2 fixation contributed 42% of the C flux entering the Krebs cycle. In ectomycorrhizae, sucrose accumulation was decreased in the colonized roots compared with uninoculated control plants, whereas 13C incorporation into arabitol and erythritol was nearly 4-fold higher in the symbiotic mycelium than in the free-living fungus. It appears that fungal utilization of glucose in the symbiotic state is altered and oriented toward the synthesis of short-chain polyols.

Journal Article↗
PubMed1998

Disseminating multimedia protocols over Internet for emergency and catastrophe management.

Over the last years we have developed various computing methods to assist specialized personnel on various aspects of catastrophe and emergency management. New models can address tasks such as patient triage; stabilization, resource coordination and hospital alertness and techniques based on information technologies. In this paper we present various tools (written on Java and C+2) that we created to store, represent, and disseminate practice guidelines and protocols over the World Wide Web. Guidelines and protocols are stored using a standard database program (e.g., Microsoft Access), and represented in a flowchart format linked to multimedia information such as text, pictures, sound, video or external sources of data. Using our JAVA tool, protocols can be disseminated over the Web and viewed with any browser with JAVA compliance. We have implemented 15 emergency protocols that we developed in collaboration with specialized military personnel from the Ministry of Defense, Spain. Users can access remotely those electronic protocols comparing their procedures and methods. Our goal is to enhance agreement and consensus among remote medical centers regarding emergency and catastrophe management, establishing discussions over the network. Our tools have also a potential for training medical and paramedical personnel for emergency situations.

Clinical Protocols↗
PubMed1998

Cytosolic calcium oscillations and insulin release in pancreatic islets of Langerhans.

Stimulation of insulin release by glucose and other nutrients has been attributed to a rise of cytoplasmic Ca2+([Ca2+]i). In intact pancreatic islets, this rise is organized in oscillations. Two types of [Ca2+]i oscillations are mainly detected. Fast oscillations (frequency of approximately equal to 3 min-1) are consistently observed, and their duration depends on glucose concentration. They are due to a bursting of electrical activity and occur synchronously throughout the islet. Slow oscillations (frequency of 0.2 min-1) also appear in response to other nutrient secretagogues (ketoisocaproate, leucine, isoleucine). They most probably constitute the physiological oscillatory pattern because islets perifused with a solution containing a mixture of amino acids and glucose at concentrations found in the plasma of fed animals showed the same oscillatory pattern. Slow [Ca2+]i oscillations may constitute the framework for pulsatile insulin release observed in vivo.

Amino Acids↗
PubMed1998

[The Fas/Fas-ligand system: implications in the antitumor immune response and in the activity of cytotoxic agents].

Interaction of Fas-ligand (Fas-L) with the extracytoplasmic domain of the Fas receptor can induce Fas trimerization and activation of the apoptotic cell death process. Several molecular pathways that lead to apoptosis and some of their regulatory mechanisms have been identified. Fas-related membrane receptors that contain a death domain in their intracytoplasmic domain have been identified. They constitute a death receptor family (DR1 to DR5) whose first member is the TNFR1 receptor for TNF alpha. The Fas/Fas-L system plays a role in the cytotoxic activity of immune cells and the regulation of immune response amplitude. This system could be involved in the immune response to tumor cells and the cytotoxic activity of drugs and radiations. The expression of Fas-L on the plasma membrane of numerous tumor cells allow them, in vitro, to kill Fas-expressing immune cells. This observations has suggested that tumor cells used Fas-L to induce a specific immune tolerance. However, in vivo, Fas-L expression rather induces tumor cell rejection. The quantity of Fas-L expressed on tumor cells could determine whether tumor cells are tolerated or rejected. Cytotoxic drugs and radiations modulate Fas and Fas-L expression on tumor cells. The role of Fas/Fas-L interactions in the cytotoxicity of these agents remains poorly defined. It has been clearly shown, however, that low doses of cytotoxic drugs increase Fas expression on tumor cells, thereby improving their elimination by immune cells. Drug-induced modulation of Fas expression could provide new therapeutic strategies combining chemotherapy with immunotherapy.

Animals↗
PubMed1998

[Amelioration of perioperative somatosensory evoked potentials in the surgery of injuries of the spine].

Somatosensory evoked potentials were performed in 38 patients with traumatic spine pre, per and postoperatively. In 3 cases, the S.E.Ps altered before surgery, were improved after decompression and reduction. This S.E.Ps improvement was associated to clinical improvement. Even though this study was carried out on few cases, it shows prognosis and diagnosis value of intraoperative S.E.Ps in traumatic spine surgery.

Adult↗