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Biomedical subjects

F Dubois

Publications and source records attributed to F Dubois.

At least 19 recordsLinked to original sources
PubMed1996

Soluble form of Lamp II in purified rat liver lysosomes.

Lamp II (for lysosomal associated membrane protein II) is an integral type I glycoprotein. It consists of a very large and heavily glycosylated luminal domain, a single transmembrane segment, and a short cytoplasmic tail. We show that in highly purified lysosomes from rat liver, Lamp II, immunodetected with a monoclonal antibody on Western blots, it surprisingly distributed between a membrane bound form and a "soluble" form. The partition of the protein between the membrane and the content of lysosomes is strongly pH dependent. The soluble Lamp II population is sensitive to pH dependent aggregation as it is for many lysosomal content enzymes.

Animals↗
PubMed1996

Phagocytosis by rat liver: relationships between phagosomes and lysosomes.

To study the transfer of phagocytosed components from phagosomes to lysosomes, we have investigated phagocytosis by rat liver of killed Staphylococcus aureus labelled with (125)I tyramine cellobiose. Lysosomes were identified by injecting the animals with Triton WR1339, a non ionic detergent that is endocytosed by the liver and accumulates in lysosomes, causing a marked decrease of their density; that allows these organelles to be well separated from other particles in a density gradient. Bacteria were quickly taken up by the liver; their uptake is followed by a slow degradation as ascertained by the increase of acid-soluble radioactivity in the homogenates with time. Triton WR1339 injection does not affect the uptake and the degradation of the particles. Differential centrifugation of homogenates shows that at any time after injection, most of the radioactivity is recovered in the mitochondrial fractions. Distributions of acid precipitable and acid soluble radioactivities amongst subcellular structures present in mitochondrial fractions were studied by isopycnic centrifugation in sucrose gradients, at increasing times after bacteria injection. Results show that: 1) acid-precipitable radioactivity is quasi-exclusively present in gradient fractions of high density, well separated from the fractions where there are recovered lysosomes; 2) with time, acid-soluble radioactivity is more and more associated with lysosomes, however, a significant proportion can be detected for many hours after injection, in gradient fractions where acid-precipitable radioactivity is located. The most plausible explanation of our observations is that phagocytosed particles are degraded in phagosomes and that the degradation products are delivered to lysosomes, probably by a vesicular process.

Animals↗
PubMed1996

Identification of a tobacco cDNA encoding a cytosolic NADP-isocitrate dehydrogenase.

A cDNA which encodes a specific member of the NADP-dependent isocitrate dehydrogenase (ICDH) multi-isoenzyme family has been isolated from a tobacco cell suspension library, and the expression pattern of ICDH transcripts examined in various plant tissues. To assign this cDNA to a specific ICDH isoenzyme, the major, cytosolic ICDH isoenzyme of tobacco leaves (ICDH1) was purified to homogeneity and its N-terminus as well as several tryptic peptides, representing 30% of the protein, were sequenced. The comparison of these amino acid sequences with the deduced protein sequence of the cDNA confirmed that this clone encodes for ICDH1. The total ICDH specific activity and protein content were higher in vascular-enriched tobacco leaf tissue than in deveined (depleted in midrib and first-order veins) leaves. Taking advantage of antibodies raised against either ICDH1 or the chloroplastic ICDH2 isoenzyme from tobacco cell suspensions, an immuno-cytochemical approach indicated that the ICDH1 isoenzyme, located in the cytosolic compartment of tobacco leaf cells, is responsible for this expression pattern. This observation was confirmed by northern blot analyses, using a specific probe obtained from the 3' non-coding region of the ICDH1 cDNA. A comparison of ICDH protein sequences shows a large degree of similarity between eukaryotes (> 60%) but a poor homology is observed when compared to Escherichia coli ICDH (< 20%). However, it was found that the amino acids implicated in substrate binding, deduced from the 3-dimensional structure of the E. coli NADP-ICDH, appear to be conserved in all the deduced eukaryotic ICDH proteins reported until now.

Amino Acid Sequence↗
PubMed1995

Uptake of exogenous DNA by rat liver: effect of cationic lipids.

We have investigated by using centrifugation methods, the uptake and the intracellular fate of 35S DNA by rat liver and the effect on these processes of N-(1-(2,3-dioleoxyloxy)propyl)-N,N,N,-trimethylammonium-methyl-sul fate(DOTAP, Boehringer, Mannheim, Germany), an artificial cationic lipid frequently used in transfection experiments. Labeled DNA molecules are quickly taken up by the liver but a progressive degradation takes place with time. Subcellular distribution of the radioactivity was established after differential and isopycnic centrifugation. Results indicate that 35S DNA enters liver cells by endocytosis and reaches lysosomes. The uptake of 35S DNA is not modified if the molecule is associated with DOTAP but marked differences are observed after internalization of the macromolecule. When DOTAP is used, radioactive products remain for a long time in low density organelles distinct from lysosomes indicating that the transfer of internalized DNA to these organelles is delayed by the cationic lipid. These results suggest that cationic lipids could favor transfection by preventing the delivery of DNA to lysosomes, allowing these molecules to be kept intact and available for transfer from endosomes to cytosol for a long time.

Animals↗
PubMed1995

Monocotyledonous C4 NADP(+)-malate dehydrogenase is efficiently synthesized, targeted to chloroplasts and processed to an active form in transgenic plants of the C3 dicotyledon tobacco.

Chloroplastic NADP(+)-malate dehydrogenase (cpMDH, EC 1.1.1.82) is a key enzyme in the carbon-fixation pathway of some C4 plants such as the monocotyledons maize or Sorghum. We have expressed cpMDH from Sorghum vulgare Pers. in transgenic tobacco (Nicotiana tabacum L.) (a dicotyledonous C3 plant) by using a gene composed of the Sorghum cpMDH cDNA under the control of cauliflower mosaic virus 35S promoter. High steady-state levels of cpMDH mRNA were observed in isogenic dihaploid transgenic tobacco lines. Sorghum cpMDH protein was detected in transgenic leaf extracts, where a threefold higher cpMDH activity could be measured, compared with control tobacco leaves. The recombinant protein was identical in molecular mass and in N-terminal sequence to Sorghum cpMDH. The tobacco cpMDH protein which has a distinct N-terminal sequence, could not be detected in transgenic plants. Immunocytochemical analyses showed that Sorghum cpMDH was specifically localized in transgenic tobacco chloroplasts. These data indicate that Sorghum cpMDH preprotein was efficiently synthesized, transported into and processed in tobacco chloroplasts. Thus, C3-C4 photosynthesis specialization or monocotyledon-dicotyledon evolution did not affect the chloroplastic protein-import machinery. The higher levels of cpMDH in transgenic leaves resulted in an increase of L-malate content, suggesting that carbon metabolism was altered by the expression of the Sorghum enzyme.

Amino Acid Sequence↗
PubMed1995

Incidence and prevalence of hepatitis B in France.

Reporting of hepatitis B is not compulsory in France, but it is estimated that 8500-9000 acute cases and 100,000 hepatitis B infections occur every year. Seroprevalence studies have been carried out in selected populations. Every blood donation is screened for HBsAg, alanine aminotransferase elevation and anti-HBc antibody. Prevalence of HBsAg has declined from 13.9 positive donations in 1986 per 10,000 to 5.3 in 1991. In pregnant women, overall seroprevalence is estimated at 0.8-1%, which represents more than 5000 children born each year to carrier mothers. Screening of HBsAg for all women when six months pregnant is now compulsory. Heterosexual patients at STD clinics were shown to have a very high risk of being infected with hepatitis B virus, with a chronic carrier rate of 4-5%. In hospital employees before the introduction of vaccination, the overall incidence of hepatitis B was 100-300 acute cases per 100,000 employees per year. Risk varied according to exposure to blood; the highest incidence was found in nurses in dialysis wards. Vaccination against hepatitis B is now compulsory for all hospital and laboratory workers and medical and paramedical students. In preventive medicine consultants, routine medical check-up showed an overall HBV prevalence of 2.2% and a carrier rate of 0.3% in men and 0.1% in women. Immunization of all newborns and adolescents has recently been adopted in France, vaccination at school of adolescents aged 10-11 years being the main target.

Blood Donors↗
PubMed1995

Radioimmunoassay for plasma histamine: a study of false positive and false negative values.

In order to achieve a correct diagnosis of drug anaphylaxis using a radioimmunoassay devoid of interferences, we have studied factors leading to false positive or false negative values of plasma histamine. Different steps in sample collection were studied systematically in 30 normal volunteers. False positive values were found in haemolysed samples, with histamine concentrations being correlated with haemoglobin concentrations, and where plasma was aspirated from the white-cell layer. There was no significant increase when a tourniquet or vacuum tubes were used, or when blood tubes were left at 4 degrees C overnight. In 12 patients who experienced an anaphylactic reaction, histamine disappeared from blood 10 times more slowly than expected. False negative values were found in two pregnant women and one heparinized patient. Histamine was remarkably stable in vitro in blood or plasma samples, whereas it disappeared rapidly when plasma from a pregnant woman or a heparinized patient was added to the sample. We conclude that false positive and false negative values are rare when using this radioimmunoassay.

Adolescent↗
PubMed1995

Immunogenetic determinants and prediction of IDDM in French schoolchildren.

Islet cell antibodies (ICAs) are predictive markers of the disease in first-degree relatives of patients with insulin-dependent diabetes mellitus (IDDM). The large majority of newly diagnosed cases, however, will develop in children with no family history of diabetes. In France, the risk for development of IDDM up to the age of 20 years is 60 times higher in first-degree relatives than in the general population. The aim of this study was to test whether data collected in the first-degree relatives of IDDM patients could be transferred to children for the prediction of overt diabetes. A large population-based cohort of French school-aged children (n = 13,380; ages 6-17 years) were screened for ICAs, and results were compared with those of 1,185 first-degree relatives of IDDM patients. ICA prevalence rates were significantly different in the two populations (5.5% vs. 1.5%; P < 0.0001), with a significantly higher proportion of high ICA titers in first-degree relatives (37%) than in schoolchildren (14%) (P = 0.0005). ICA titers remained remarkably stable in children over 4 years. Insulin autoantibodies (IAAs) were found in 3.4 and 15.4% of ICA+ children and first-degree relatives, respectively. Susceptibility alleles at the human leukocyte antigen (HLA)-DQB1 locus were observed significantly more frequently in children in whom ICA titers > or = 20 Juvenile Diabetes Foundation units (JDF U) were found on two separate occasions (67%) than in ICA- children (52%) (P = 0.05). Five subjects developed overt diabetes during follow-up. ICA titers of > 20 JDF U were found in all of them on the first sample and at follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Antibodies against bovine albumin and other diabetes markers in French children.

OBJECTIVE: Findings in epidemiology and animal experimentation suggest that autoimmunity in insulin-dependent diabetes mellitus (IDDM) may be triggered by dietary cow-milk protein, particularly bovine serum albumin (BSA). Elevated IgG anti-BSA antibodies were found in children from Finland with newly onset diabetes; Finland has the highest incidence of diabetes and cow's milk consumption in the world. We now analyze BSA serology and other diabetes markers in school-age children from France, where diabetes incidence and cow's milk consumption are low. RESEARCH DESIGN: Sera were obtained from three groups: newly diagnosed diabetic (n = 43), islet cell antibody-positive (ICA+) nondiabetic (n = 98), and ICA- healthy control children (n = 267). IgG anti-BSA antibody levels were measured blindly using particle concentration fluoroimmunoassays and analyzed in comparison with ICA titers and human leukocyte antigen-DQB genotypes. RESULTS: There were highly significant differences in BSA antibody levels between all three groups (P < 0.0001). Diabetic patients had elevated anti-BSA levels in 74.4% of cases, compared with 5.5% of control children. In the group of ICA+ non-diabetic children, 20% were anti-BSA-positive. Neither ICA nor BSA antibody titers were significantly related to DQB genotype or sex. ICA titers ( > or = 4 Juvenile Diabetes Foundation units) were present in 84% of diabetic children. Two-thirds of diabetic children were positive for both ICA and anti-BSA antibodies, and none were negative for both markers. CONCLUSIONS: Elevated IgG anti-BSA levels are associated with IDDM in the low-incidence French population. In newly diagnosed diabetic children, these antibodies have similar specificity (95 vs. 98%) and slightly lower sensitivity for IDDM than ICA (74.4 vs. 83.7%). Our results may support an immunological role of BSA in diabetic autoimmunity.

Adolescent↗
PubMed1995

Hepatitis B, C, D, and E markers in rural equatorial African villages (Gabon).

Serologic markers of hepatitis B virus (HBV), including HBV DNA, and of hepatitis delta virus were measured in three villages in Gabon. Of 303 subjects studied, 19% were carriers of hepatitis B surface antigen (HBsAg); 8.5% of these had anti-delta antibodies. No difference among the three villages was observed. All HBV DNA carriers were children less than 11 years of age. In the 2-9-year-old group, 71% of the HBsAg-positive children tested were HBV DNA carriers. These results indicate that HBV prevalence is high in Gabon and emphasize the importance of horizontal transmission of HBV in Africa. Antibodies to hepatitis C virus, assessed in one of the three villages, were found with a prevalence of 35% with a second generation enzyme-linked immunosorbent assay (ELISA) and 24% with a third generation ELISA. None of 35 subjects tested for antibodies to hepatitis E virus was positive.

Adolescent↗
PubMed1995

Clinical impact of drug addiction in alcoholics.

Careful interviewing of alcoholics who wish to undergo alcohol withdrawal programmes reveals that some are past intravenous drug abusers. As these two potentially hepatotoxic types of substance abuse could cause liver disease or influence its clinical course, we studied biological, histological and virological features in 26 alcoholics with a past history of intravenous (i.v.) drug abuse, compared with paired controls (alcoholics without i.v. drug abuse). There were no differences with regard to routine liver test results. In contrast, the former drug abusers had a significantly higher prevalence of serum markers of hepatitis C (76.9%) and hepatitis B viruses (76.9%) than the other patients (16.7 and 12.5%, respectively). Eight patients, all of whom were HBs Ag negative, were positive for serum HBV-DNA; three were former drug abusers and five were not, giving an overall prevalence of HBV markers in the two groups of 80.8 and 25%, respectively. Two former drug abusers had anti-HIV antibodies and one had anti-hepatitis delta virus antibodies. Ten of the 17 former drug abusers who underwent liver biopsy had histological signs of viral infection. These data underline the need for careful interviews of alcoholic patients, together with serological tests for viral infections and histological analysis of the liver, as some will have liver-damaging viral diseases and may be candidates for anti-viral (i.e. interferon) treatment.

Adult↗
PubMed1995

[Laparoscopic cholecystectomy. Technique and complications. Report of 2,665 cases].

Retrospective study of 2,665 laparoscopic cholecystectomies (LC) performed between April 1988 and December 1994 in the French technique with selective intra operative cholangiography. Obesity was present in 13% of patients, respiratory insufficiency in 4%, inflammation in 13% and common bile duct (CBD) stones in 4%. Those cases are now good indications for L.C. A conversion to laparotomy occurred in 52 cases (2%). The rate of post operative complications was 1.6%, including 24 non biliary complications with 2 death and 17 biliary ones concerning the CBD in 6 cases. Those results compare favourably with the ones of open cholecystectomy and the cost is about the half.

Adolescent↗
PubMed1995

[Myocardial infarction following rapid perfusion of corticoids].

The authors report the case of myocardial infarction occurring immediately after rapid intravenous infusion of a high dose of corticosteroids prescribed for a relapse of multiple sclerosis. Ventriculography confirmed the myocardial damage but the coronary arteries were normal. An aetiological investigation was negative. The authors review the cardiac secondary effects which may be very serious and even fatal. Coronary insufficiency is rare (only 3 previously published cases); it is therefore difficult to determine the prognosis. The possible mechanisms of infarction are discussed. Finally, the authors underline the importance of recording an ECG before treatment, of ECG monitoring during the infusion, and the need for repeating the recordings and of prolonging hospital admission when necessary.

Female↗
PubMed1995

[Strongyloides stercoralis myelitis].

A 66 year-old man presented with a myelitis associated with eosinophilia in blood and cerebrospinal fluid. Specific serological procedures in blood and stool examinations led to the diagnosis of myelitis due to Strongyloides stercoralis. Physiopathology of medullary lesions is discussed. To our knowledge, this is the first report of myelitis in the course of Strongyloides infection.

Aged↗
PubMed1994

Development of RT-semi-nested PCR for detection of hepatitis A virus in stool in epidemic conditions.

The purpose of this study was to determine the efficiency of semi-nested PCR in detecting hepatitis A virus (HAV) RNA. During a 2-year period (1990-1991), HAV RNA was searched for in shellfish from the French Brittany coasts using cRNA and vRNA probes. In January 1992, at the time of a hepatitis A outbreak, 28 stool samples were collected from infected patients (18 adults, 10 children) with anti-HAV IgM. Four samples from subjects with negative HAV serology were used as negative controls. Nucleic acid amplification (reverse-transcription-semi-nested PCR) was performed to detect HAV in stool. HAV RNA was purified by phenol-chloroform extraction and converted to cDNA using reverse transcriptase (Mu-MLV). After amplification, PCR products were visualized on an ethidium-bromide-stained gel and confirmed by hybridization with a specific digoxigenin-labelled oligoprobe. Samples were also studied by molecular hybridization with cRNA and vRNA probes. After onset of the illness, HAV RNA was detected over a longer time period by semi-nested PCR (16/28) than by hybridization (0/28). Even though biological diagnosis of hepatitis A will continue to rely on the detection of anti-HAV IgM, PCR should be useful in certain clinical cases (diagnosis of relapse) and for epidemiological and environmental monitoring of viruses.

Adolescent↗