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Biomedical subjects

N Bernard

Publications and source records attributed to N Bernard.

At least 55 records · Page 3Linked to original sources
PubMed1997

D-2-hydroxy-4-methylvalerate dehydrogenase from Lactobacillus delbrueckii subsp. bulgaricus. II. Mutagenic analysis of catalytically important residues.

Five residues involved in catalysis and coenzyme binding have been identified in D-2-hydroxy-4-methylvalerate dehydrogenase from Lactobacillus delbrueckii subsp. bulgaricus by using biochemical and genetical methods. Enzyme inactivation with diethylpyrocarbonate indicated that a single histidine residue was involved in catalysis. Since H296 is the only conserved histidine in the whole family of NAD-dependent D-2-hydroxyacid dehydrogenases, we constructed the H296Q and H296S mutants and showed that their catalytic efficiencies were reduced 10(5)-fold compared with the wild-type enzyme. This low residual activity was shown to be insensitive to diethylpyrocarbonate. Taken together these data demonstrate that H296 is responsible for proton exchange in the redox reaction. Two acidic residues (D259 and E264) were candidates for maintaining H296 in the protonated state and their roles were examined by mutagenesis. The D259N and E264Q mutant enzymes both showed similar and large reductions in their Kcat/K(m) ratios (200-800-fold, depending on pH), indicating that either D259 or E264 (or both) could partner H296. The conserved R235 residue was a candidate for binding the alpha-carboxyl group of the substrate and it was changed to lysine. The R235K mutant showed a 104-fold reduced Kcat/K(m) due to both an increased K(m) and a reduced Kcat for 2-oxo-4-methylvalerate. Thus R235 plays a role in binding the substrate carboxylate similar to R171 in the L-lactate dehydrogenases. Finally, we constructed the H205Q mutant to test the role of this partially conserved histidine residue (in 10/13 enzymes of the family). This mutant enzyme displayed a 7.7-fold increased Kcat and a doubled catalytic efficiency at pH 5, was as sensitive to diethylpyrocarbonate as the wild-type but showed a sevenfold increased K(m) for NADH and a 100-fold increase in Kd for NADH together with 10-30-fold lower substrate inhibition. The transient kinetic behaviour of the H205Q mutant is as predicted from our previous study on the enzymatic mechanism of D-2-hydroxy-4-methylvalerate dehydrogenase which showed that coenzyme binding is highly pH dependent and indicated that release of the oxidised coenzyme is a significant component of the rate-limiting processes in catalysis at pH 6.5.

Alcohol Oxidoreductases↗
PubMed1997

Incidence of cytomegalovirus disease in the Aquitaine cohort of HIV-infected patients: a retrospective survey, 1987-1993. Groupe d'Epidémilogie Clinique du SIDA en Aquitaine (GECSA).

We estimated the incidence of the first episodes of cytomegalovirus (CMV) disease in the Aquitaine cohort of HIV-infected subjects, south-western France. Cases were retrospectively investigated using standardized definition criteria. Retinitis was confirmed by an ophthalmologist. Gastro-intestinal lesions were confirmed histologically. Encephalitis was histologically confirmed; it was considered possible if TDM or magnetic resonance imaging (MRI) and symptomatology suggested this diagnosis. Pneumopathy was probable in case of hypoxemia, interstitial X-Ray images and response to CMV treatment; it was confirmed if intranuclear inclusions were identified on biopsy or brushing specimen. In the cohort (n = 3525) followed for an average of 46 months, 158 patients had a first episode of CMV disease. The cumulative incidence was 4.5% and the incidence rate (IR) 1.2 per 100 person-years. The IR was higher for homosexuals (2.0) than for heterosexuals (1.0) and intravenous drug users (0.5). Retinitis was the most frequent site (90 cases), followed by digestive system (40), lung (three confirmed and 17 probable) and central nervous system (eight confirmed and three possible). Sixty-eight percent of the patients were at the AIDS stage when CMV disease was diagnosed, with a mean CD4 count of 42/mm3. The cumulative probability of developing CMV disease 2 years after falling below 200 CD4 lymphocytes/mm3 was 8.0%. Retinitis is by far the most common site for CMV disease. Homosexual transmission of HIV, clinical AIDS and low CD4 count are associated with the occurrence of the first episode of CMV disease.

AIDS-Related Opportunistic Infections↗
PubMed1997

[Prevalence of clinical manifestations of allergic reactions in HIV infection. Cross sectional study of 115 subjects].

A cross sectional survey was set up to study the relation between the prevalence of allergic-type reactions during HIV infection course. For each patient, a standardized interview about recent allergic-type manifestations (RATM), skin prick-tests to six common airborne allergens, IgE serum level were done. Among the 115 included patients, the mean CD4 lymphocyte count (CD4) was 214.7/mm3 (range: 0-1328/mm3). RATM were found in 8.8% of patients with CD4 < 50, in 30% of patients with CD4 between 51 and 200, in 36% of patients with CD4 between 201 and 350 and in 11.5% of patients with CD4 < 350 (p = 0.03). The risk of presenting RATM was 4.8 times (95% confidence interval = 1.7-13.5) higher in patients with CD4 between 51 and 350 than in other patients (p = 0.003). The proportion of positive prick-tests did not significantly vary according to the level of CD4. The increased frequency of RATM in patients with CD4 between 51 and 350/mm3 could be due to an allergic predisposition acquired during the course of HIV infection. The mechanisms explaining the reduced frequency of allergic manifestations when immunodeficiency is profound (CD4 < 50/mm3) remain to be explained.

Adult↗
PubMed1997

Mechanical properties of pathological equine superficial digital flexor tendons.

The objective of this study was to mechanically characterise superficial digital flexor tendon (SDFT) lesions. Eight pathological SDFTs, isolated from 6 adult horses, were tested in traction until rupture (at 1 mm/s). The stresses and strains simultaneously undergone by each of the 7 segments of a tendon were determined throughout the test, and the modulus of elasticity of each segment was evaluated from the segmental stress-strain curve thus obtained. These mechanical data were compared to those obtained on 10 normal SDFTs. After the test, the tendinous segments were submitted to a histological examination in order to characterise the tissues. Three lesional categories (I to III, of increasing maturity), as well as the normal tendinous tissue, were defined and assessed quantitatively according to their extent in the histological sections. The most recent and severe lesions (categories I and II) were correlated with a large degree of hypertrophy (often above 200%) of the corresponding segments, with a resulting decrease in the stress at tendon rupture, and a slight decrease in the strain at tendon rupture in spite of a low modulus of elasticity (low stiffness). In contrast, the adjacent areas, less or not injured, underwent compensatory strains. This relative overstraining was especially critical with category III tissue, often present in the transitional areas between sound and severely injured segments. Here the modulus of elasticity was low whereas the hypertrophy was only slight. Therefore, the corresponding segments seemed to be the most fragile sites, and those most predisposed to recurring injury, in an injured SDFT.

Analysis of Variance↗
PubMed1997

[Isolated involvement of the trigeminal nerve of sarcoidosis origin].

Sarcoidosic neurological manifestations are uncommon. Isolated cranial nerve's injury is exceptional. The authors report the case of a 29 year-old woman with a trigeminal nerve tumor. Surgery and anatomopathology led to the diagnosis of sarcoidosic infiltration. No other neurological or extra-neurological localization was found. Cranial fifth nerve injury was observed in 14 cases of the literature. In all cases, trigeminal nerve injury was described as associated with another disease's localization (neurological and/or extra-neurological). This observation seems unusual due to isolated nature of the presentation and complete resolution after surgery. This case illustrated the diagnosis and nosologic difficulties raised by granulomatous lesions, symptomatic or not, in the absence of systemic localization.

Adult↗
PubMed1996

Efficacy of an albendazole slow-release capsule for the control of susceptible or resistant nematode parasites of dairy goats.

The efficacy of albendazole slow release capsules-ASRC- (Proftril-Captec) on gastro-intestinal nematodes of dairy-goats was assessed both for benzimidazole (BZ) susceptible and resistant strains. For BZ susceptible strains, the efficacy of ASRC, assessed by controlled test, ranged from 92% for Trichostrongylus colubriformis to more than 99% for Haemonchus contortus on existing worm burdens. The administration of the ASRC prevented infection with the same strains for 85 to 91 days post treatment. In a dairy goat farm, where both in vitro and in vivo tests indicated a high level of BZ resistance, the efficacy of ASRC on present infections, assessed by Faecal Egg Count Reduction test, ranged from 20 to 60% according to the sampling date (13 to 88 days post treatment). On the same farm the ASRC given at turnout to non infected (primiparous) goats prevented egg shedding up to 72 days (30 for controls). In contrast the ASRC given to infected (multiparous) goats did not prevent egg shedding. The present results show that the ASRC is an efficient device for controlling BZ susceptible nematodes. The ASRC prevents infection with BZ resistant larvae whereas existing infections are not reduced.

Albendazole↗
PubMed1996

Kinetics of appearance of neutralizing antibodies in 12 patients with primary or recent HIV-1 infection and relationship with plasma and cellular viral loads.

HIV-1 primary infection is characterized by a short high titer viremia, which rapidly declines as the immune response emerges. The role of autologous neutralizing antibodies in the decline of viral replication was evaluated in 12 patients with primary or recent HIV-1 infection. Neutralizing antibodies detected for each patient could not generally be observed before several months after isolation of the first obtained HIV isolate. The plasma viral load, as measured by quantitation of the HIV-1 RNA, underwent a global decrease during the first 6 months of the infection, but this decrease did not seem to be associated with the emergence of neutralizing antibodies. The proviral load in peripheral blood mononuclear cells, which was studied by quantitative DNA polymerase chain reaction, exhibited fluctuations and was not as well curtailed as the plasma viremia in the majority of patients.

Adult↗
PubMed1996

Reproducibility of the cardiovascular reactivity to a computerized version of the Stroop stress test in normotensive and hypertensive subjects.

The 1-month reproducibility of haemodynamic and sympathoadrenal responses to a standardized mental stress test was studied in ten normotensive and ten hypertensive individuals. The stress test was a computerized adaptation of the Stroop test and sympathetic activity was evaluated by measuring urinary catecholamine excretion. Three-way analysis of variance (stress, session, blood pressure) revealed significant increases in systolic and diastolic blood pressures and in heart rate during the stress test. Test-retest correlation coefficients for basal stress levels, and stress-induced variations were significant (r from 0.59 to 0.88). The stress test induced a significant increase in urinary noradrenaline excretion with large intra- and interindividual variability. The significant test-retest correlations and the lack of period effect for haemodynamic parameters indicated good temporal stability. However, a slight decrease in stress-induced reactivity was observed. This standardized mental stress test may be useful in epidemiological and therapeutic trials to measure blood pressure and heart rate responses, but measurement of urinary catecholamine excretion does not provide any additional information.

Adult↗
PubMed1996

[Pneumocystis carinii pneumonia in AIDS: retrospective analysis of 80 documented cases (1985-1993)].

Eighty initial episodes of HIV-associated Pneumocystis carinii pneumonia (PCP) diagnosed at Bordeaux hospital between 1985 and 1993 are reported (57 were men and 23 women). PCP revealed HIV infection in 29 patients (36%). Others cases were patients with poor medical follow up (10%), with a CD4+ lymphocyte count above 200/mm3 at last follow-up (9%), non compliant with PCP prophylaxis (9%), or using aerolized pentamidine (AP+) (20%). The main clinical symptoms were fever (90%), dyspnea (68%), non productive (63%) and productive (17%) cough. Radiographic infiltrates were purely interstitial (59%), acinar and interstitial (25%), purely acinar (5%) and absent (11%). Thirty-eight percent of AP+ had upper lobe preferential involvement and 13% a pleural effusion. In all cases, Pneumocystis carinii was detected in bronchoalveolar lavage. Extrapulmonary localizations of pneumocystosis were noticed (eye, liver, spleen, ascitis) in two AP+. Mean CD4+ count was 54/mm3 in patients not having received aerolized pentamidine (AP-) and 22/mm3 in AP+. P24 antigenemia was positive in 53% (AP-) and 88% (AP+). PaO2 LDH and albuminemia were similar in both groups. Antimicrobial therapy (Cotrimoxazole in 91% of the cases) was combined with corticosteroids in 45% and mechanic ventilation in 19%. After 30 days of follow-up, 17 deaths were observed (21%) and 14 attributed to PCP: mortality was worse in AP+ (31%) than in AP- (19%). The main conclusions of our study are the followings: HIV related PCP is still in 1995 frequent and severe; atypical features should not rule out diagnosis; preventive measures are neither sufficient nor efficient. PCP remains in 1995 a priority in HIV related public health and therapeutical research.

AIDS-Related Opportunistic Infections↗
PubMed1996

Increases in CD3+CD4-CD8- T lymphocytes in AIDS patients with disseminated Mycobacterium avium-intracellulare complex infection.

Human immunodeficiency virus type 1 (HIV-1)-infected persons frequently have increased numbers of T cells bearing the gamma delta T cell receptor for antigen (gamma delta TCR). HIV-1-seropositive patients with < 100 CD4+ cells/mm3 were selected and divided into 9 AIDS-defining illness groups. The percentages of CD4+, CD8+, or double-negative CD4-CD8- (DN) T cells (most of the latter expressing the gamma delta TCR) for 8 symptomatic groups were compared with those for a reference group of asymptomatic HIV-1-infected patients. DN T cells were increased only in patients with disseminated Mycobacterium avium-intracellulare complex (MAC) infection, toxoplasmosis, or Kaposi's sarcoma. Multivariate logistic regression analysis revealed that the percentage of DN T cells was a better predictor of MAC infection than was the percentage of CD4+T cells. The increased percentage of DN T cells might have important implications for the understanding of gamma delta T cell physiology and for the early diagnosis and management of MAC infections in AIDS patients.

AIDS-Related Opportunistic Infections↗
PubMed1996

Knockout of the two ldh genes has a major impact on peptidoglycan precursor synthesis in Lactobacillus plantarum.

Most bacteria synthesize muramyl-pentapeptide peptidoglycan precursors ending with a D-alanyl residue (e.g., UDP-N-acetylmuramyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala). However, it was recently demonstrated that other types of precursors, notably D-lactate-ending molecules, could be synthesized by several lactic acid bacteria. This particular feature leads to vancomycin resistance. Vancomycin is a glycopeptide antibiotic that blocks cell wall synthesis by the formation of a complex with the extremity of peptidoglycan precursors. Substitution of the terminal D-alanine by D-lactate reduces the affinity of the antibiotic for its target. Lactobacillus plantarum is a lactic acid bacterium naturally resistant to vancomycin. It converts most of the glycolytic pyruvate to L- and D-lactate by using stereospecific enzymes designated L- and D-lactate dehydrogenases, respectively. In the present study, we show that L. plantarum actually synthesizes D-lactate-ending peptidoglycan precursors. We also report the construction of a strain which is deficient for both D- and L-lactate dehydrogenase activities and which produces only trace amounts of D- and L-lactate. As a consequence, the peptidoglycan synthesis pathway is drastically affected. The wild-type precursor is still present, but a new type of D-alanine-ending precursor is also synthesized in large quantities, which results in a highly enhanced sensitivity to vancomycin.

Anti-Bacterial Agents↗
PubMed1996

[Aortic aneurysms due to Yersinia enterocolitica: three new cases and a review of the literature].

We report three cases of mycotic aortic aneurysms due to Yersinia enterocolitica. In all cases, serogroups are O:9. The three patients more than 70 year-old men with immunodeficiency underlying conditions allowing bacterial graft (neoplasia, diabetes mellitus, dysimmunitary syndrome, hematologic diseases). The six cases of the literature were clinically, biologically and epidemiologically similar. The strains of Y enterocolitica responsible for septicemia are especially serogroups O:9. This is probably due to particular virulence factors in this serogroup (phagocytosis resistance gene: yopH, ypkA et yop E) (yop: Yersinia outer membrane proteins). The presence of a pYV plasmid (plasmid yersinia virulence), found in Yersinia pathogen strains, lead to bacterial proliferation in the tissues. The authors discuss pathophysiological mechanisms involved in arterial bacterial graft following an Y. enterocolitica infection.

Aged↗
PubMed1996

Evolution of tumor necrosis factor-alpha serum concentrations in HIV infected individuals treated with zidovudine.

We studied the evolution of Tumor Necrosis Factor-alpha serum concentration (TNF-alpha) and CD4+ lymphocyte counts (CD4+) in a pilot cohort study of HIV-infected patients during the first year of zidovudine therapy. Data on 17 patients remaining asymptomatic during the one-year follow-up period (non progressors) were analysed. Serum samples were obtained at entry and at each follow-up visit (1, 3, 6, 9 and 12 months). TNF-alpha was quantified in pg/ml using a very sensitive radioimmunoassay (Medgenix). All patients had increased TNF-alpha at entry (median: 26.4 pg/ml). TNF-alpha decreased significantly as soon as the first month of therapy (median: 16 pg/ml). A steady state was then observed until Month 6 (median: 17.5 pg/ml), from which a slow increase appeared, without reaching the initial level (median at Month 9: 21.3, at Month 12: 19.8). During the same time, less sustained changes in CD4+ lymphocytes count and beta-2 microglobulin level were observed. The results of this pilot study suggest that, during HIV infection treated course, TNF-alpha could potentially be an additional surrogate marker to CD4+ lymphocyte count.

Anti-HIV Agents↗
PubMed1995

Prevalence of Onchocerca species and Thelazia lacrimalis in horses examined post mortem in Normandy.

The umbilical skin and ligamentum nuchae of 368 horses were examined post mortem for Onchocerca species. Only four of the horses were infected and pathological changes were observed on the skin of two of them. Thelazia lacrimalis was recovered from 38 (10.3 per cent) of the horses, and animals aged six months to two years were more frequently infected. No ocular lesions were observed. The prevalences of these two nematodes were low when compared with the infection rates reported in the United Kingdom and North America.

Animals↗