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Biomedical subjects

A Ménard

Publications and source records attributed to A Ménard.

At least 19 recordsLinked to original sources
PubMed2006

Individual QTLs controlling quantitative variation in blood pressure inherited in a Mendelian mode.

We studied three possible genotypes at 10 well-defined blood pressure (BP) QTLs using congenic rat lines. The central question was whether the hypertensive or normotensive allele is dominant, or whether there is partial dominance. The congenic strains were employed to investigate the BP effects of alleles originating from normotensive rats in the background of hypertensive Dahl salt-sensitive (DSS) rats. The normotensive alleles at eight QTLs were fully dominant over DSS alleles, which we tentatively interpreted as indicating that DSS rats incurred a loss of function at these loci and that the QTLs produced BP-reducing agents. In contrast, the normotensive allele of only one QTL was recessive over its DSS counterpart, implying a gain of function at this QTL or a null allele involved in generating a BP-elevating agent. Only one locus, C17QTL, had alleles exhibiting partial dominance. These estimates of dominance differ considerably from those obtained by QTL analysis in a F2 cross. This disagreement demonstrates the importance of establishing a cause-effect relationship between a QTL and its phenotypic effect via congenic strains. The dominance relationships suggest pertinent strategies for gene identification and pharmaceutical intervention.

Alleles↗
PubMed2005

Development of a real-time fluorescence resonance energy transfer PCR to identify the main pathogenic Campylobacter spp.

A simple real-time fluorescence resonance energy transfer (FRET) PCR, targeting the gyrA gene outside the quinolone resistance-determining region, was developed to identify Campylobacter jejuni and Campylobacter coli. These species were distinguished easily, as the corresponding melting points showed a difference of 15 degrees C. A second assay using the same biprobe and PCR conditions, but different PCR primers, was also developed to identify the less frequently encountered Campylobacter fetus. These assays were applied to 807 Campylobacter isolates from clinical specimens. Compared to phenotypic identification tests, the FRET assay yielded the same results for all except three of the isolates. Analysis by standard PCR and 16S rDNA sequencing demonstrated that two of these isolates were hippurate-negative C. jejuni strains, resulting in an erroneous phenotypic identification, while the third was an isolate of C. coli that contained a gyrA gene typical of C. jejuni, resulting in misidentification by the FRET assay. The FRET assay identified more isolates than standard PCR, which failed to yield amplification products with c. 10% of isolates. It was concluded that the FRET assays were rapid, reliable, reproducible and relatively cost-efficient, as they require only one biprobe and can be performed directly on boiled isolates.

Amino Acid Sequence↗
PubMed2005

Association of Helicobacter species with hepatitis C cirrhosis with or without hepatocellular carcinoma.

BACKGROUND AND AIMS: Recent studies have suggested that bacterial coinfection with Helicobacter species in patients already infected with hepatitis C virus (HCV) could be involved in the development of cirrhosis and hepatocellular carcinoma (HCC). A retrospective cross sectional study was performed in order to explore the association between Helicobacter species and HCV associated liver diseases. METHODS: The presence of Helicobacter species was tested by polymerase chain reaction on liver samples from four groups of patients. RESULTS: Helicobacter 16S rDNA was found in only 4.2% of liver samples from control patients (n=24) and in 3.5% of liver samples from patients with non-cirrhotic chronic hepatitis C (n=29) while it was found in 68.0% of liver samples from patients with HCV positive cirrhosis without HCC (n=25) as well as in 61.3% of cirrhotic liver samples from patients with HCV positive cirrhosis and HCC (n=31). In addition, when the HCC tumour tissue was tested (n=21), 90.5% of samples were positive. DNA from Helicobacter pylori- and Helicobacter pullorum-like organisms was found. CONCLUSIONS: There is an association between the presence of Helicobacter species DNA in the liver and hepatitis C cirrhosis, with or without HCC. Indeed, the presence of these bacteria could be the result of structural changes in the liver. Alternatively, Helicobacter species could be a co-risk factor in HCV chronic liver diseases. This result warrants prospective studies to determine the possible causal role of these bacteria in the progression of chronic hepatitis C.

Adult↗
PubMed2004

Identification of a genetic marker of Helicobacter pylori strains involved in gastric extranodal marginal zone B cell lymphoma of the MALT-type.

BACKGROUND AND AIMS: Gastric extranodal marginal zone B cell lymphoma of the mucosa associated lymphoid tissue (MALT)-type (MZBL) is a rare complication of Helicobacter pylori infection. Currently, no bacterial factor has been associated with the development of this disease. Our aim was to identify genes associated with lymphoma development. METHODS: We used subtractive hybridisation as a tool for comparative genomics between H pylori strains isolated from a patient with gastric MZBL and from a patient with gastritis only. RESULTS: When gastric MZBL strains were compared with gastritis strains, two open reading frames (ORFs) were significantly associated with gastric MZBL: JHP950 (74.4% v 48.7%, respectively; p = 0.023) and JHP1462 (25.6% v 2.6%, respectively; p = 0.004). The prevalence of JHP950 was 48.8% (p = 0.024) in duodenal ulcer strains and 39.3% (p = 0.006) in gastric adenocarcinoma strains, which makes this ORF a specific marker for gastric MZBL strains. In contrast, the prevalence of JHP1462 was 16% (p = 0.545) and 35.7% (p = 0.429) in duodenal ulcer and adenocarcinoma strains, respectively. These ORFs were present in reference strain J99 but not in reference strain 26695. JHP950 is located in the plasticity zone whereas the other, JHP1462, is located outside. Both encode for H pylori putative proteins with unknown functions. CONCLUSION: Despite its low prevalence, the ORF JHP1462 can be considered a candidate marker for H pylori strains involved in severe gastroduodenal diseases. In contrast, the ORF JHP950 has a high prevalence, and is the first candidate marker for strains giving rise to an increased risk of gastric MZBL strains. Further confirmation in other studies is needed.

Adenocarcinoma↗
PubMed2004

Fasciola hepatica: the growth and larval productivity of redial generations in Galba truncatula subjected to miracidia differing in their mammalian origin.

Experimental infections of Galba truncatula with 4 isolates of Fasciola hepatica miracidia differing by their mammalian origin (cattle, nutrias, rabbits, or sheep) were carried out to determine if parasite origin had an effect on the number of free rediae, their growth, and their larval productivity in each redia category. The mammalian origin of miracidia had a significant influence on the numbers of free rediae (they were higher in cattle-group snails) and the lengths of rediae (they were lower in rabbit groups). The redia category had also a significant effect on body and pharyngeal measurements. In all groups, the majority of cercariae (55.8-63.2%) were produced by the daughter rediae (R2a rediae) originating from the first mother redia. Compared with the other groups, the mean number of cercariae at day 49 postexposure was twice as high in cattle groups. In contrast, the mean number of daughter rediae produced by each second-appearing mother redia or each R2a redia was higher in the nutria, rabbit, and sheep groups. The mammalian origin of F. hepatica miracidia had an effect on the number of live rediae, their length, and their redial and cercarial productivity.

Animals↗
PubMed2003

[Diagnosis of Mycobacterium ulcerans infection by PCR: report of 3 cases observed in French Guiana].

Mycobacterium ulcerans infection is the third most important mycobacterial infection in the world. It has been described in many different countries including French Guiana. The diagnosis of M. ulcerans infection by culture is often difficult because culture is hard to perform in endemic areas and their sensitivity is not reliable. As a result the diagnosis of this infection is often delayed. However, molecular methods are now available to diagnose rapidly infections by M. ulcerans and distinguish it from other mycobacteria. We report three cases of skin infection due to M. ulcerans observed in French Guiana. Diagnosis was initially made by polymerase chain reaction and was confirmed later by culture (in two patients) and inoculation to mice (in one patient). A faster diagnosis of M. ulcerans infection should lead to a better prognosis of this infection.

Adult↗
PubMed2002

Association of a gliotoxic activity with active multiple sclerosis in US patients.

We recently found that cerebrospinal fluid (CSF) from multiple sclerosis (MS) patients contains a gliotoxic activity which induces programmed cell death of astrocytes and oligodendrocytes and could be the main contributing factor to the massive glial cell death seen in MS active lesions. A previous clinical study aimed at evaluating the gliotoxicity of CSF from a cohort of MS patients from France indicated that MS patients with the active form of the disease do indeed present significant CSF gliotoxicity. To extend this observation, the effect of 141 CSFs from United States patients with different neurological diseases (including 71 MS) was tested on immortalized astrocytes. A cell death assay showed that a gliotoxic activity is significantly present in the CSF from MS patients with the active forms. Thus, this gliotoxic activity may represent a critical pathogenic factor in the neuropathology of active MS by playing a role both in demyelinisation and alteration of the blood-brain barrier.

Animals↗
PubMed2001

Nonlinear free energy relationship in the general-acid-catalyzed acylation of rat kidney gamma-glutamyl transpeptidase by a series of gamma-glutamyl anilide substrate analogues.

The gamma-glutamyl transpeptidase (GGT) purified from rat kidney reacts with a series of eight parasubstituted L-glutamyl gamma-anilides, in the presence of Gly-Gly, catalyzing the formation of gamma-Glu-Gly-Gly (pH 8.0, 37 degrees C). The transpeptidation reaction was followed through the discontinuous colorimetric determination of the concentration of released parasubstituted aniline. Steady-state kinetic studies were performed to measure k(cat) and K(M) values for each anilide substrate. A Hammett plot constructed by the correlation of log(k(cat)) and the sigma(-) parameter for each anilide substrate displays statistically significant upward curvature, consistent with a general-acid-catalyzed acylation mechanism in which the geometry of the transition state changes with the nature of the para substituent. Kinetic isotope effects were measured and are consistent with a reaction involving a proton in flight at the rate-limiting transition state. The pH-rate profiles measured over pH 7.0-9.5 are bell-shaped with kinetic pK(a) values that may be attributed to the active site nucleophile (or its general-base catalytic partner) and the active-site general acid. The variation of the latter pK(a) value as a function of temperature is consistent with an enthalpy of ionization expected for an ammonium ion acting as a general acid. Examination of the variation of k(cat) as a function of temperature gave values for the enthalpy and entropy of activation that are similar to those determined for the general-acid-catalyzed breakdown of the tetrahedral intermediate formed during acylation of chymotrypsin by similar amide substrates.

Acylation↗
PubMed2001

Corticospinal control of locomotor pathways generating extensor activities in the cat.

Interneuronal convergence of corticospinal and segmental pathways involved with the generation of extensor activities during locomotion was investigated in decerebrate and partially spinalized cats. L-dihydroxyphenylalanine (L-DOPA) was slowly injected until long-latency, long-lasting discharges could be evoked by the stimulation of contralateral flexor reflex afferents (coFRA) and the group I autogenetic inhibition was reversed to polysynaptic excitation in extensor motoneurons. Under these conditions, we stimulated in alternation the contralateral pyramidal tract (PT), group I afferents from knee and ankle extensor muscles, and both stimuli together. We did the same for the stimulation of PT and of coFRA. Clear polysynaptic EPSPs could be evoked from all three sources in 32 extensor motoneurons. Convergence was inferred from spatial facilitation, which occurred when the amplitude of the EPSPs evoked by the combined stimuli was notably larger than the algebraic sum of the EPSPs evoked by individual stimulation. Spatial facilitation was found between PT and extensor group I inputs in 30/59 tests (51%) in 20 motoneurons and in all cases (6/6) between PT and coFRA in six motoneurons. When fictive locomotion was induced with further injection of L-DOPA, PT descending volleys from the same stimulating site could reset the stepping rhythm by initiating bursts of activity in all extensors. These results indicate that at least some of the corticospinal fibers project onto interneurons shared by the coFRA and the polysynaptic excitatory group I pathways to extensors. The implications of such convergence patterns on the organization of the extensor "half-center" for locomotion are discussed.

Animals↗
PubMed2001

Fasciola hepatica: the characteristics of experimental infections in Lymnaea truncatula subjected to miracidia differing in their mammalian origin.

Experimental infections of Lymaea truncatula, using two susceptible snail populations (Berneuil, or Migné, central France) and four isolates of Fasciola hepatica miracidia differing in their mammalian host of origin (cattle, nutrias, rabbits, or sheep), were performed under laboratory conditions to determine whether the host of origin had an effect on the daily production of cercariae. Snails were each subjected to bimiracidial exposures and were then reared under semi-natural conditions (a constant temperature of 20 degrees C and natural photoperiod). Significantly lower values were noted in the rabbit groups for survival rates at day 30 post-exposure, as well as for prevalences of infection, snail growth. duration of shedding period, and the total numbers of cercariae these snails shed. The total number of cercariae shed by both nutria groups was significantly higher than those recorded in the six other infected groups. In the cattle, rabbit, and sheep (Berneuil only) groups, the peaks in the daily distribution of cercariae occurred between day 2 and day 4 after the first shedding, and the number of cercaria-shedding snails decreased with increasing number of shedding waves. In contrast, in the three other groups, the peaks were only observed between days 20 and 45. Snails shedding their cercariae during nine or more waves were numerous in these last groups. No infradian-type rhythm in the daily distribution of cercarial numbers over the shedding period was noted for any snail group. The highest production of F. hepatica cercariae in both nutria groups would be a consequence of a higher success rate of miracidia when they infected an allopatric population of snails. The absence of an infradian-type rhythm in the distribution of daily cercarial numbers in the eight groups suggests that this rhythm, if it occurs, would only be influenced by temperature and thus be limited to periods with optimal conditions for cercarial shedding.

Animals↗
PubMed2000

Inventory of wild rodents and lagomorphs as natural hosts of Fasciola hepatica on a farm located in a humid area in Loire Atlantique (France).

With the objective of studying the role of wild fauna in the epidemiology of fasciolosis disease, a definitive wild-host inventory was carried out in a french farm where infected domestic hosts (cows) cohabit with wild potential ones. Liver flukes, faecal eggs and antibodies were looked for in lagomorphs (Oryctolagus cuniculus) and rodents (Myocastor coypus, Ondatra zybethicus, Rattus norvegicus, Arvicola sapidus and micromammal species) trapped in the study area. Presence of Fasciola hepatica was detected in two species: O. cuniculus and M. coypus. Infection rates were respectively 34% (42/124) and 55% (106/193). Liver flukes were found in 78 M. coypus (n = 192) and 11 O. cuniculus (n = 35). No other species was infected by F. hepatica. The number of animals shedding fluke eggs was higher in M. coypus (49 out of 127 sampled; 38.6%) than in O. cuniculus (two out of 17 sampled; 11.7%). The results indicate that M. coypus may play a role in the maintenance and the dissemination of F. hepatica in various environments and open a discussion on the role of other natural wild hosts.

Agriculture↗
PubMed2000

New perspectives in multiple sclerosis: retroviral involvement and glial cell death.

Retroviral involvement in the pathogenic cascade in multiple sclerosis (MS) and a cytotoxic activity with narrow specificity towards glial cells have been recently considered as credible working hypotheses to explain some of the complex pathophysiological and neuropathological features of MS. The partial characterization of exogenous retroviral sequences, thought to be associated with MS, has led us to the identification of new human endogenous retroviruses closely related to the extracellular multiple sclerosis associated retrovirus (MSRV). These endogenous retroviruses (HERV-TcR and HERV-7q) have the potential to be transcribed into RNA and proteins. Interestingly, the env domain of HERV-7q could code for a 59.8 kDa secreted glycoprotein (called enverin) with an immunoregulatory region. The presence in various MS biological fluids of a cytotoxic activity able to induce programmed cell death for oligodendrocytes and astrocytes suggests the possibility of a demyelination phenomenon as part of direct glial cell damage. Moreover, both retroviral expression and cytotoxic factor production have been evidenced in MS monocyte/macrophage cultures and MS cerebrospinal fluid. It is now crucial to better characterize the endo/exo retroviruses possibly involved in MS and their pathogenic potential, and to identify the contributing factor(s) to the gliotoxicity found in the MS cerebrospinal fluid or serum, as well as to elucidate the mechanism of induction of the observed programmed glial cell death.

Amino Acid Sequence↗
PubMed1999

The modulation of presynaptic inhibition in single muscle primary afferents during fictive locomotion in the cat.

The aim of this study is to understand the functional organization of presynaptic inhibition in muscle primary afferents during locomotion. Primary afferent depolarization (PAD) associated with presynaptic inhibition was recorded intra-axonally in identified afferents from various hindlimb muscles in L6-L7 spinal segments during fictive locomotion in the decerebrate cat. PADs were evoked by the stimulation of peripheral muscle nerves and were averaged in the different epochs of the fictive step cycle. Fifty-three trials recorded from 39 muscle axons (37 from group I and two from group II) were retained for analysis. The results showed that there was a significant phase-dependent modulation of PAD amplitude (p < 0.05) in a majority of muscle afferents (30 of 39, 77%). However, not all stimulated nerves led to significantly modulated PADs in a given axon (36 of 53 trials, 68%). We also observed that the pattern of modulation (phase for maximum and minimum PAD amplitude and the depth of modulation) varied with each recorded afferent, as well as with each stimulated nerve. We further evaluated the effect of PAD modulation on the phasic transmission of the monosynaptic reflex (MSR) and found that PADs decreased the MSR amplitude in all phases of the fictive step cycle, independent of the PAD pattern in individual group I fibers. We conclude that (1) PAD modulation patterns of all group I fibers contacting motoneurons led to an overall reduction in monosynaptic transmission, and (2) individual PAD patterns could participate in the control of transmission in specific reflex pathways during locomotion.

Animals↗
PubMed1999

Guinea pig liver transglutaminase: A modified purification procedure affording enzyme with superior activity in greater yield.

Tissue transglutaminase purified from guinea pig livers has a very broad substrate specificity in comparison with other members of the transglutaminase family and therefore is useful for substrate analogue kinetic studies. Modifications made in our laboratory to the standard purification protocol (J. E. Folk and S. I. Chung, 1985, Methods Enzymol. 113, 358-364) have yielded a 28% increase in specific activity and 55% increase in overall yield, while reducing the number of steps to the purification. Herein we report some of the highest yields and specific activities for guinea pig liver transglutaminase found in the literature, as well as the use of lyophilization as a solution to the long-standing problem of enzyme stability during storage.

Animals↗
PubMed1998

Detection of a gliotoxic activity in the cerebrospinal fluid from multiple sclerosis patients.

We recently showed that peripheral blood cell supernatants from multiple sclerosis (MS) patients, containing reverse transcriptase activity and retroviral RNA from the newly human identified multiple sclerosis retrovirus (MSRV), also secrete a cytotoxin which induces death of primary mouse cortical glial cells. We have hypothesized that macrophages could release this cytotoxin in the cerebrospinal fluid. The cerebrospinal fluid cytotoxicity from 166 patients with various neurological diseases (including MS patients) was tested on glial cells in vitro. Our bioassay shows that a glial cytotoxic activity is significantly present in cerebrospinal fluid from patients with relapsing-remitting MS at relapse. Since this cytotoxic activity seems to correlate with active cases of MS, it may represent a critical pathogenic factor in the neuropathology of MS.

Adult↗
PubMed1998

A gliotoxic factor and multiple sclerosis.

The pathogenesis of multiple sclerosis (MS) is unknown. Searching for possible toxic factors, it was found that 3-day exposure to heat-treated cerebrospinal fluid (CSF) from MS patients caused apoptotic death of astrocytes and oligodendrocytes, but not fibroblasts, myoblasts, Schwann cells, endothelial cells and neurons, in vitro. CSFs from other inflammatory or non-inflammatory neurological diseases showed no toxicity. Exposure of these glial cells to partially purified MS CSF produced DNA fragmentation, apoptotic bodies, chromatin condensation, cell shrinkage, and changes in the levels of known cytokines. A cytotoxic factor, called gliotoxin, was characterized chromatographically as a stable 17-kDa glycoprotein. Since this protein is highly cytotoxic for astrocytes and oligodendrocytes, it may represent an initial pathogenic factor, leading to the neuropathological features of MS, such as blood-brain barrier involvement and demyelination.

Animals↗
PubMed1998

Endogenous retroviruses and multiple sclerosis. II. HERV-7q.

The search for new endogenous retroviral sequences, on the basis of sequence homologies with the pol gene of the recently reported multiple sclerosis associated retrovirus (MSRV), allowed us to identify a full length endogenous retrovirus sequence located on the long arm of human chromosome 7. This retrovirus, HERV-7q, includes in its env region, within a single 1,620 bp open reading frame, a 664 bp domain almost identical to a 3' non-coding region of the rab7 gene. Transcripts encompassing both the env and the 3' LTR regions of HERV-7q have already been identified as expressed sequence tags, suggesting that this env-like gene might code for a 538 amino acid long deduced protein.

Amino Acid Sequence↗