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Biomedical subjects

M M Lucas

Publications and source records attributed to M M Lucas.

18 recordsLinked to original sources
PubMed2006

Transgenic Medicago truncatula plants that accumulate proline display nitrogen-fixing activity with enhanced tolerance to osmotic stress.

Legume root nodule nitrogen-fixing activity is severely affected by osmotic stress. Proline accumulation has been shown to induce tolerance to salt stress, and transgenic plants over-expressing Delta(1)-pyrroline-5-carboxylate synthetase (P5CS), which accumulates high levels of proline, display enhanced osmotolerance. Here, we transformed the model legume Medicago truncatula with the P5CS gene from Vigna aconitifolia, and nodule activity was evaluated under osmotic stress in transgenic plants that showed high proline accumulation levels. Nitrogen fixation was significantly less affected by salt treatment compared to wild-type (WT) plants. To our knowledge, this is the first time that transgenic legumes have been produced that display nitrogen-fixing activity with enhanced tolerance to osmotic stress. We studied the expression of M. truncatula proline-related endogenous genes M. truncatulaDelta(1)-pyrroline-5-carboxylate synthetase 1 (MtP5CS1), M. truncatulaDelta(1)-pyrroline-5-carboxylate synthetase 2 (MtP5CS2), M. truncatula ornithine delta-aminotransferase (MtOAT), M. truncatula proline dehydrogenase (MtProDH) and a proline transporter gene in both WT and transgenic plants. Our results indicate that proline metabolism is finely regulated in response to osmotic stress in an organ-specific manner. The transgenic model allowed us to analyse some of the biochemical and molecular mechanisms that are activated in the nodule in response to high salt conditions, and to ascertain the essential role of proline in the maintenance of nitrogen-fixing activity under osmotic stress.

Adaptation, Physiological↗
PubMed2001

Immunolocalization of alkaloids and X-ray microanalysis of elements in lupin seeds.

Immunolocalization of alkaloids in lupin seeds (Lupinus spp.) has been performed by cryofixation and conventional methods. Alkaloids were localized in the protein bodies of the cotyledon cells. Some immunogold particles in the walls of these cells were also observed. There were no differences in the sites of localization between the two mentioned methods. X-ray microanalysis of elements showed the presence of P, Mg, S, and K in the protein bodies of cotyledon cells in lupin seeds. The role of K+ in alkaloids transport is discussed.

Alkaloids↗
PubMed2000

Axillary block in children: single or multiple injection?

The goal of this double-blind prospective study was to compare the effect of a single injection versus multiple fractionated doses on the onset time and quality of motor and sensory block, obtained in 70 children anaesthetized with axillary block alone. The brachial plexus was identified with a peripheral nerve stimulator, and blocked with 0.5 ml.kg-1 of 1.5% lignocaine with adrenaline. In Group S (single injection), the total volume was injected after location of one nerve. In Group M (multiple fractionated doses), two nerves were located, including necessarily one nerve implicated in the surgical territory. Motor and sensory blocks were assessed according to Lanz's scale before surgery by a blinded observer. A block was considered complete if there was no feeling in at least three nerve territories at 30 min. No difference was found between groups for motor and sensory block quality. However the onset time of the block was faster after multiple fractionated doses (Group M, 25+/-7 min vs Group S, 29+/-4 min) and was faster in younger children (5-9 years: M=23+/-7 min vs S=28+/-5 min, 10-15 years: no difference). There was a significant difference in the quality of the sensory blockade of the musculocutaneous nerve: 18 versus 8 complete blocks, 10 versus 14 incomplete blocks, respectively for Group M versus Group S. No adverse effect was observed and analgesia was prolonged for more than 4 h. We can conclude that, unlike adults, fractionated doses in chilren bring no benefit to the quality of sensory and motor block. Selective block of the musculocutaneous nerve is recommended when a surgical procedure takes place in this territory.

Anesthetics, Local↗
PubMed1999

Characterization of a neuronal kappaB-binding factor distinct from NF-kappaB.

Transcription factors that bind kappaB enhancer elements have begun to garner wide attention in neurobiology. Data suggest that activation of kappaB-binding factors in neurons can be protective against various neurotoxins, but other data have connected NF-kappaB to cell death. In electrophoretic mobility shift assays of kappaB-binding activity, we have found that the predominant activity in rat brain tissue, in primary neurons, and in neuronal cell lines has a mobility inconsistent with that of bona fide NF-kappaB (RelA-p50 heterodimer). We have tentatively termed this activity neuronal kappaB-binding factor (NKBF). Competition assays with various DNA probes distinguished NKBF from NF-kappaB. Probes that efficiently bind the p50 homodimer were able to compete with a conventional NF-kappaB probe for NKBF binding, but NKBF did not react with antibodies to p50 (or any other known Rel family members). Furthermore, UV-crosslinking indicated that NKBF is composed of two polypeptides of 82 kDa and 27 kDa. Although NKBF activity can be elevated in a manner independent of new macromolecular synthesis, it does not appear to be modulated by IkappaB. Finally, no NF-kappaB was induced by glutamate in highly enriched neuronal cultures, although it was induced in neuron-glia cocultures. These data suggest that the primary kappaB-binding transcription factor in neurons is a novel protein complex distinct from NF-kappaB.

Animals↗
PubMed1999

Inhibition of the activity of a neuronal kappaB-binding factor by glutamate.

Activation of transcription factors with affinity for kappaB enhancers is generally correlated with enhanced survival of neurons. In an apparent exception, excitotoxic concentrations of glutamate have been reported to elevate the activity of one such factor, nuclear factor-kappaB (NF-kappaB). Our data indicate that the constitutive neuronal kappaB-binding factor (NKBF) is distinct from bona fide NF-kappaB (RelA/p50 heterodimer). Therefore, we analyzed glutamate's effects on KB-binding activity in highly enriched primary neuronal cultures and in mixed neuron/glia cocultures. Electrophoretic mobility shift assays indicated that a 30-60-min exposure to 50-500 microM glutamate reduced NKBF activity by as much as 70%. Subtoxic doses of glutamate had little or no effect on this DNA-binding activity. Selective antagonists of either NMDA or AMPA [(RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate]/kai nat e receptors inhibited the influence of glutamate on NKBF activity. The effect of glutamate was mimicked by calcium ionophore, and it was blocked by lowering extracellular calcium concentrations or by cyclosporin A. Bona fide NF-kappaB was found only in cocultures containing significant numbers of glia, where it could be activated by glutamate. These data suggest that the primary influence of excitatory amino acids on neuronal KB-binding activity is an inhibitory one, strengthening the correlation between this transcriptional parameter and neuronal survival.

Animals↗
PubMed1998

[Severe streptococcal group A infection complicating varicella].

UNLABELLED: Varicella is a common viral infection which is generally benign in infancy and has a good outcome. It may sometimes be complicated by severe group A streptococcal superinfection. CASE REPORT: Three days after the beginning of varicella, a previously healthy 2-year-old girl presented with left leg pain, lameness and edema of all four limbs. Toxic shock syndrome occurred, due to beta-hemolytic group A Streptococcus grown from blood culture. Computerized tomography (CT) scan showed a mild effusion involving both hips. Cefotaxim was administered, but the week after magnetic resonance imaging (MRI) showed a necrotizing fasciitis and a lesion of the left leg leading to a patchy femoral diaphysis consistent with osteomyelitis. Joint aspirate culture did not grow. The left leg was immobilized in plaster for 6 weeks and the child was given cefotaxim and fosfomycin parenterally during 30 days, then followed by 45 days of oral amoxicillin. She recovered without sequelae. CONCLUSION: Group A Streptococcus infection is a dangerous complication of varicella. It must be considered in case of any joint pain occurring during or just after this disease. The choice of the best treatment needs full collaboration between surgeons, radiologists and pediatricians.

Cefotaxime↗
PubMed1997

Comparative hemodynamic depression of sevoflurane versus halothane in infants: an echocardiographic study.

BACKGROUND: The cardiovascular side effects of volatile anesthetics are one of the chief causes of postoperative complications in children, and infants seem to be at the greatest risk for this. This study compared cardiovascular changes at equipotent concentrations of sevoflurane and halothane in infants. METHODS: Thirty infants classified as American Society of Anesthesiologists physical status I or II who required elective surgery were randomized to receive either halothane or sevoflurane for inhalation induction. Cardiovascular and echocardiographic data were recorded in both groups at baseline and at end-tidal concentrations of 1 and 1.5 minimum alveolar concentration (MAC). RESULTS: Sevoflurane did not alter heart rate or cardiac index at all concentrations compared with awake values. Sevoflurane significantly decreased blood pressure and systemic vascular resistance compared with awake values at all concentrations. Shortening fraction and rate-corrected velocity of circumferential fiber shortening decreased at 1.5 but not at 1 MAC. Myocardial contractility assessed by stress-velocity index and stress-shortening index decreased significantly at all concentrations, but did not fall into the abnormal range at any concentration. Halothane caused a greater decrease in heart rate, shortening fraction, stress-shortening index, velocity of circumferential fiber shortening, stress-velocity index, and cardiac index at all concentrations than did sevoflurane. CONCLUSION: Sevoflurane causes a lesser decrease in cardiac output than does halothane in infants.

Anesthetics, Inhalation↗
PubMed1996

Isolation of monoclonal antibodies reacting with the core component of lipopolysaccharide from Rhizobium leguminosarum strain 3841 and mutant derivatives.

Monoclonal antibodies reacting with the core oligosaccharide or lipid A component of Rhizobium lipopolysaccharide (LPS) could be useful for the elucidation of the structure and biosynthesis of this group of macromolecules. Mutant derivatives of Rhizobium leguminosarum 3841 with LPS structures lacking the major O-antigen moiety were used as immunogens, and eight antibodies were selected for further study. All the antibodies reacted with the fast-migrating species known as LPS-2 following gel electrophoresis of Rhizobium cell extracts. For four of these antibodies, reactivity with affinity-purified LPS was lost after mild acid hydrolysis, indicating that they probably recognized the core oligosaccharide component. The four other antibodies still reacted with acid-treated LPS and may recognize the lipid A moiety, which is stable to mild acid hydrolysis. The pattern of antibody staining after gel electrophoresis revealed differences in LPS-2 epitope structure between each of the mutants and the wild type. Furthermore, for each of the mutants the antibodies crossreacted with a minor band that migrated more slowly than LPS-2; we have termed this more slowly migrating form LPS-3. The majority of the antibodies also reacted with LPS from strain CE109, a derivative of Rhizobium etli CE3, confirming that the LPS core antigens can be relatively conserved between strains of different Rhizobium species. One of the antibodies isolated in this study (JIM 32) was unusual because it appeared to react with all forms of LPS from strain 3841 (namely, LPS-1, LPS-2, and LPS-3). Furthermore, JIM 32 reacted positively with the LPS from many strains of Rhizobium tested (excluding the Rhizobium meliloti subgroup). JIM 32 did not react with representative strains from Bradyrhizobium, Azorhizobium or other related bacterial species.

Antibodies, Bacterial↗
PubMed1995

Ionic Stress and Osmotic Pressure Induce Different Alterations in the Lipopolysaccharide of a Rhizobium meliloti Strain.

A halotolerant strain of Rhizobium meliloti was isolated from nodules of a Melilotus plant growing in a salt marsh in Donana National Park (southwest Spain). This strain, EFB1, is able to grow at NaCl concentrations of up to 500 mM, and no effect on growth is produced by 300 mM NaCl. EFB1 showed alterations on its lipopolysaccharide (LPS) structure that can be related to salt stress: (i) silver-stained electrophoretic profiles showed a different mobility that was dependent on ionic stress but not on osmotic pressure, and (ii) a monoclonal antibody, JIM 40, recognized changes in LPS that were dependent on osmotic stress. Both modifications on LPS may form part of the adaptive mechanism of this bacterium for saline environments.

Journal Article↗
PubMed1995

[The use of serological tests for detecting HIV infection in general clinical consultations and hospital consultations].

AIMS: To determine the number and type of HIV tests requested in general practice (GP) and in hospital outpatient clinics, to identify principle risk behaviors, to determine the percentage of HIV positive tests and to identify possible factors associated with the request of HIV tests. METHODS: Cross-sectional, analytical and observational study, involving 80 GPs and 45 hospital specialists in the region of Lisbon. All requests for HIV tests were analysed during a 12 month period. RESULTS: 936 HIV tests were requested, with a mean of 12.47 in GP and 0.69 in the hospital. Risk behaviors observed were mainly heterosexual contacts and intravenous drug abuse (IVDA). The motives of the requests mainly were pregnancy, risk behaviors in GP and the presence of symptoms suggesting HIV infection in the hospital. The initiative of the request came from doctors in 70% of the cases. The percentage of HIV positive tests (ELISA + Western blot) was 4.2% in GP and 32% in the hospital. According to risk behaviors, the percentage of seropositivity was 33% in homo/bisexuals, 13% in IVDA, 7% in heterosexuals with risk behaviors and 0.2% in individuals with unidentified risk behaviors. CONCLUSIONS: The patterns of request of HIV tests differ in hospital and in GP. In a significant percentage of cases, no informed consent was obtained prior to HIV testing, both in hospital and GP. This study may serve as an indicator of the need for information and education programs concerning HIV testing directed to health professionals and the general population.

Adult↗
PubMed1994

Bacterial and plant glycoconjugates at the Rhizobium-legume interface.

Many classes of bacterial and plant glycoconjugate have been shown to be involved in establishing the Rhizobium root nodule symbiosis with peas (Pisum sativum). It was demonstrated, using techniques of molecular genetics, that a group of Rhizobium nodulation genes (nod genes) co-operate to synthesize a lipo-oligosaccharide signal molecule that specifically initiates nodule development on legume hosts. An additional gene function, encoded by nodX, has been found to extend the host range of Rhizobium leguminosarum bv. viciae to include nodulation of a pea mutant, cultivar Afghanistan; the nodX gene product specifies the addition of an acetyl group to the terminal N-acetylglucosamine residue at the reducing end of the pentasaccharide core of this signal molecule. Several other classes of bacterial glycoconjugate have also been shown by genetic analysis to be essential for normal nodule development and function: these include a capsular extracellular polysaccharide; lipopolysaccharide in the outer membrane; and cyclic glucans present in the periplasmic space. Potential functions for these glycoconjugates are discussed in the context of tissue and cell invasion by Rhizobium. Some plant components involved in symbiotic interactions have been identified by the analysis of nodule-specific gene expression (early nodulins). Several of the cDNA clones encoding these early nodulins specify proline-rich proteins that presumably correspond to cell wall glycoproteins or membrane arabinogalactan proteins. Other plant glycoconjugates have been identified using monoclonal antibodies as probes. A plant glycoprotein present in intercellular spaces has been identified as a component of the luminal matrix of infection threads. Because it attaches to the surface of bacteria and is itself susceptible to oxidative cross-linking, this glycoprotein may be involved in limiting the progress of microbial infections. Endocytosis of bacteria into the plant cytoplasm is apparently driven by direct interactions between the bacterial surface and the plasma membrane that is exposed within an unwalled infection droplet; glycoprotein and glycolipid components of the plant membrane glycocalyx have been defined using monoclonal antibodies. Differentiation of endosymbiotic bacteroids is preceded by differentiation of the plant-derived peribacteroid membrane which encloses the symbiosome compartment. Using a monoclonal antibody that identifies a group of plant membrane-associated, inositol-containing glycolipids, we have identified a very early marker for the differentiation of peribacteroid membrane from plasma membrane.

Carbohydrate Sequence↗
PubMed1994

[Pain conduction tracts. From physiology to practice].

Some new theories concerning pain physiology have recently been suggested. Experimental facts show that despite its complexity, neuroplasticity is an established fact. The concept of preemptive analgesia is about to receive clinical applications. Nevertheless, the role of many opioid ligands which are involved in the pain physiology can explain the efficacy of some analgesia techniques. The authors review the physiological process of pain from its periphery to its centre and the ensuing practical applications. They point out the difficulty to apprehend peripheral analgesia, and the necessity of further researches concerning especially NMDA spinal receptors and other specific receptors.

Animals↗
PubMed1993

[Alprazolam as premedication in ophthalmologic surgery].

Oral premedication with alprazolam was studied in 83 patients before eye surgery. Alprazolam appears to be an excellent anxiolytic drug, with minor cardiovascular and respiratory side effects. A double blind study should be carried on to assess these properties.

Administration, Oral↗
PubMed1992

[Complementing loco-regional anesthesia in children].

An accomplishment to loco-regional anesthesia. Yes! but dependent on the age of the child; rather mild general anesthesia than progressive sedation. This should not lead to the neglect of certain basic principles: a faultless technique including the highest security standards without neglecting the psychological aspect. Use of these technique as means of outpatient treatment will be the future outlook.

Anesthesia, Conduction↗
PubMed1990

Levels of representation in the interpretation of anaphoric reference and instrument inference.

The level of representation accessed when inferences are made during sentence comprehension was examined. The inferences investigated included antecedent assignment for both definite noun phrase anaphors and pronouns and also instrument inferences. In making these inferences, a listener must access the inferred element, whether an antecedent or an instrument, in either a linguistic form representation or a discourse model. The level of representation involved in these inferences was determined by exploiting differences in the lexical decision and naming tasks, which were argued to exhibit differential sensitivity to representational levels. In three experiments, the priming of antecedent and instrument targets in the lexical decision task was compared with priming of the same targets in the naming task. Differences in the patterns of activation across the two tasks indicated that all three types of inferences required accessing elements in a discourse model. Three control experiments ruled out simple context or congruity checking as an explanation for our results. The following conclusions were also supported by these studies: (1) Antecedent assignment occurs immediately after processing an anaphor; (2) antecedent assignment involves inhibition for the inappropriate antecedent rather than facilitation for the appropriate antecedent; (3) although subjects do not make instrument inferences when they hear isolated sentences containing verbs that strongly imply certain instruments, the inferences are made when sentences are preceded by a context that mentions the instrument.

Adult↗