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R Durand

Publications and source records attributed to R Durand.

At least 19 recordsLinked to original sources
PubMed1995

Location by fluorescence microscopy of glycosidases and a xylanase in the anaerobic gut fungi Caecomyces communis, Neocallimastix frontalis, and Piromyces rhizinflata.

beta-D-Glucosidase, beta-D-fucosidase, beta-D-xylosidase, and beta-D-cellobiopyranosidase activities in Caecomyces communis, Neocallimastix frontalis, and Piromyces rhizinflata, located with fluorescent conjugates, occur throughout the whole thallus as from zoospore germination and disappear before sporulation. beta-D-Galactosidase and alpha-L-arabinopyranosidase activities are low or nonexistent. A xylanase, detected by indirect immunofluorescence, was observed at the surface of the vegetative cells, vesicles, or rhizoids. Cross-reactions prove the existence of analogies in structure among the enzymes of these anaerobic gut fungi.

Animals↗
PubMed1995

Characterization of the "promoter region" of the enolase-encoding gene enol from the anaerobic fungus Neocallimastix frontalis: sequence and promoter analysis.

The sequence of the Neocallimastix frontalis enolase gene promoter was determined up to 1800 nucleotides 5' to the major transcriptional start point. The base composition of the enolase upstream sequence revealed a very A + T-rich profile (13.5% G + C) leading to many putative hairpin structures. The functional organization of the N. frontalis enolase promoter was investigated by heterologous transient-expression assays. DNA fragments obtained by the sequential removal of sequences upstream of the translation start codon were fused to the Escherichia coli lacZ gene and the resulting plasmids were used to transform the ascomycetes Aspergillus nidulans and Penicillium roqueforti and the oomycete Saprolegnia monoica. Transient expression of the lacZ reporter gene was observed in regenerating proteoplasts of S. monoica when using the 0.3 kb or 1 kb upstream of the enolase coding region. In contrast no beta-galactosidase activity was detected in ascomycete protoplasts. DNA hybridization analysis revealed the integration of vector DNA in the genomic DNA of S. monoica and the presence of free copies of the transformation plasmid which could be rescued in E. coli. Our results indicate that the transcriptional machinery of the anaerobic chytrid N. frontalis may differ significantly from that of ascomycetes but that enough conservation exists within the lower fungi to allow a transient-driven expression of a reporter gene in an oomycete fungus.

Base Sequence↗
PubMed1995

Neocallimastix frontalis enolase gene, enol: first report of an intron in an anaerobic fungus.

A DNA clone containing a putative enolase gene was isolated from a genomic DNA library of the anaerobic fungus Neocallimastix frontalis. It was deduced from sequence comparisons that the enolase gene was interrupted by a large 331 bp intron. The enolase gene, termed enol, has an ORF of 1308 bp and encodes a predicted 436 amino acid protein. The deduced amino acid sequence shows high identity (71.5-71%) to those of enolases from the yeasts Saccharomyces cerevisiae and Candida albicans. The G+C content of the enolase coding sequence (43.8 mol%) is considerably higher than the G+C content of the intervening sequence (14.2 mol%) or the 5' and 3' non-translated flanking sequences (15.2 and 4.7 mol%, respectively). The codon usage of the N. frontalis enolase gene was very biased as has been found for the highly expressed genes of yeast and filamentous fungi. The gene has all the canonical features (polyadenylation signal, intron splicing boundaries) of genes isolated from aerobic filamentous fungi. Only one enolase gene could be detected in N. frontalis genomic DNA by Southern analysis with a homologous probe. RNA analysis detected a single enolase transcript of about 1.6 kb. When mycelium was grown on glucose, levels of enolase mRNA were markedly increased by comparison with enolase mRNA levels in mycelium grown on cellulose, suggesting that expression of the N. frontalis enolase gene was transcriptionally regulated by the carbon source.

Base Sequence↗
PubMed1995

[Importance of drug carriers in the treatment of visceral leishmaniasis].

Visceral leishmaniasis is caused by hemoflagellate protozoa which are obligatory parasites of the mononuclear phagocyte system. Leishmaniasis causes high morbidity and mortality worldwide. The treatment of choice remains pentavalent antimonials, but high toxicity and failures have been reported. An alternative to conventional treatment is delivery anti-leishmania agents using colloidal carrier systems. Carriers improve drug activity against intracellular disease involving the mononuclear phagocyte system. The principle of drug delivery by carrier systems has been applied successfully for anticancer drugs. Recently complete remission of polyresistant visceral leishmaniasis was obtained by injection of liposomal amphotericin B. At present, no colloidal drug carrier for antimony derivatives is available, but pentamidine can be linked experimentally to methacrylate polymer nano-particles. Drug-loaded nanoparticles have been shown to be effective against amastigote leishmania both in vitro and in vivo. Another colloidal system of major interest for drug delivery, the liposome has already been loaded with amphotericin B and used for human therapy. The concept of particulate drug carriers opens the way for new chemotherapeutic approaches in the field of parasitology.

Amphotericin B↗
PubMed1993

Biochemical consequences of a large deletion in the mitochondrial genome of a Drosophila subobscura strain.

A mutant strain of D. Subobscura possesses two populations of mitochondrial genomes: a population identical to that of the wild strain (20%) and a dominant population (80%) which has lost more than 30% of its coding zone by deletion. Spectrophotometric determination of respiratory complex activities shows that: complex I (5 genes implicated in deletion) presents maximal activity reduced by 40%, whereas that of complex III (concerned by cytochrome b) is lowered by 30%. Nevertheless, polarographic determinations of substrate oxidation show activity of complex I to be reduced by 30%. In contrast, complex III activity is similar to that measured in the wild strain. The predominant use of one part of the respiratory chain may account for the fact that the mutant strain is apparently unaffected by mutation.

Animals↗
PubMed1993

[In vitro study of leishmanicidal agents with drug carriers].

Antileishmanial chemotherapy is hampered by the location of parasites within lysosomal vacuoles of the macrophages which restricts the bioavailability of many potential antileishmanial compounds. In this study, the effectiveness of pentamidine targeted to the infected cells by a linkage to a colloidal drug carrier, methacrylate polymer nanoparticles was explored. In the same way, polyisoalkylcyanoacrylate nanospheres which have, in vitro, trypanolytic properties were also tested. The study was performed in an in vitro model using Leishmania major amastigote stages within the U 937 human monohistiocytic cell line. The antileishmanial activities of unloaded or pentamidine-loaded nanoparticles were compared to those of the free drugs. The 50% effective concentration of targeted pentamidine was 0.10 microgram/ml, while it was up to 2.7 micrograms/ml with the free drug after a 24-hour incubation time. The pentamidine-bound nanoparticles proved to be 25 times more active than the free drug. Unloaded polyisoalkylcyanoacrylate nanoparticles destroyed intracellular amastigote stages (50% EC = 15 micrograms/ml) but at a level close to the cytotoxic concentration.

Cell Line↗
PubMed1992

Sequence of the phosphoenolpyruvate carboxykinase-encoding cDNA from the rumen anaerobic fungus Neocallimastix frontalis: comparison of the amino acid sequence with animals and yeast.

The nucleotide sequence of the cDNA of the phosphoenolpyruvate carboxykinase-encoding gene from the fungus Neocallimastix frontalis, was determined. The deduced amino acid sequence (608 residues) and the predicted protein structure were compared to their counterparts in animals and yeast. Catalytic regions (substrate-binding site and nucleotide-binding domains) are highly conserved among fungal and animal organisms. The yeast sequence showed no similarity to the fungal sequence.

Amino Acid Sequence↗
PubMed1991

Molecular cloning of genes from the rumen anaerobic fungus Neocallimastix frontalis: expression during hydrolase induction.

Glycoside and polysaccharide hydrolase production by the rumen anaerobic fungus, Neocalimastix frontalis is induced by the presence of crystalline cellulose. A differential screening of a cDNA library was used to isolate DNA sequences transcribed at high levels under growth conditions which induce enzyme production. Seven clones were isolated that preferentially hybridized to the induced cDNA probe versus the non-induced cDNA probe. Southern analysis showed that a cDNA clone (118) hybridized to a DNA probe encoding part of the exo-cellobiohydrolase I (CBH I) gene of Trichoderma reesei. Northern analysis demonstrated that the cDNA 118 was transcribed to yield a 2.1 kb RNA. This transcript was induced in the presence of cellulose.

Anaerobiosis↗
PubMed1991

The effect of hydralazine on blood flow and misonidazole toxicity in human tumour xenografts.

The effect of post-irradiation hypoxia induced by 5 or 30 mg/kg hydralazine has been studied in three human tumour xenografts (two rectocolic adenocarcinomas and one melanoma) treated with two doses of misonidazole similar to those used in patients (0.1 and 0.2 mg/g). Only a small sensitization was detected using an in vitro colony assay. These results are in marked contrast to the results obtained with rodent tumours. This difference between human tumour xenografts and rodent tumours might be explained by differences in the reduction of tumour blood flow after hydralazine administration (5 and/or 10 mg/kg). Using the laser Doppler technique, the tumour blood flow reduction was 33% and 25% of the control for NA11 and HRT18 tumours, respectively. In contrast, hydralazine induced a 60-70% reduction in blood flow in the murine SCCVII tumour. Using the fluorescent marker Hoechst 33342, the reduction in perfusion was again more pronounced in the murine tumour as compared to the Na11 and HRT18 xenografts. The differences between human tumour xenografts and rodent tumours are not linked to the mouse strain used (nude versus C3H) nor to a tumour bed effect.

Animals↗
PubMed1990

Evaluating the effect of a human values seminar series on ethical attitudes toward resuscitation among pediatric residents.

A human values seminar series was designed to provide training in medical ethics for residents in pediatrics. Attitudes of residents toward resuscitation of children were surveyed before and after the seminar series. Nonpediatric residents rotating through pediatrics served as control subjects. Although both groups of residents demonstrated a significant change in attitude on six scales at the end of 1 year of training, pediatricians and nonpediatricians differed from each other with respect to only one of these scales. After the seminar series, pediatric residents expressed decreased willingness to resuscitate certain critically ill infants in the emergency room, whereas nonpediatricians expressed more willingness (P less than 0.009). Attitude change in decision making among pediatricians was significantly correlated with the consideration given to societal needs, sanctity of life, and anticipated poor morbidity (P less than 0.05). Among nonpediatricians, attitude change was significantly correlated with poor prognosis for survival (P less than 0.05), morbidity (P less than 0.05), or anticipated poor intellectual outcome (P less than 0.01). Attitude differences between the two groups of residents were unrelated to differences in preexisting attitudes or demographic factors. These findings show that attitudes about ethical decisions are influenced by both "maturation," or progression through a training program, and formal instruction. The finding that clinical attitudes change rapidly as residents progress through training confirms our previous findings and suggests that residency training programs should provide support and formal instruction in ethics during this time of change. The small change caused by this current method of instruction indicates that preliminary studies are needed to delineate the goals and the structure of future ethics courses.

Adult↗
PubMed1989

Gastrointestinal effects of water reuse for public park irrigation.

To investigate the gastrointestinal effects of employing recycled water as an irrigation source for urban public parks, we studied subjects active in parks irrigated with potable water, nonpotable water of wastewater origin, and nonpotable water of runoff origin. Wet grass conditions during activity and elevated densities of common indicator bacteria, but not exposure to nonpotable irrigation water per se, were found associated with an increased rate of gastrointestinal illness.

Adolescent↗
PubMed1986

RNA mapping on Drosophila mitochondrial DNA: precursors and template strands.

Drosophila melanogaster mitochondrial DNA (mtDNA) is closely related to the mammalian and amphibian mtDNA except for gene organization. In Drosophila, genes are distributed in clusters alternatively coded on each strand. Besides the eleven major foreseeable transcripts previously described (MERTEN and PARDUE, 1981, J. Mol. Biol., 153, 1-21), we have characterized two poly A+ transcripts, one major and one minor which could correspond respectively to the ND3 and ND6 reading frames, and 27 poly A+ minor transcripts (0.2 to greater than 3.2 kb) which are distributed along the mtDNA except in the rRNAs, ND 1 and A+ T rich regions. The mapping and length of 25 of these transcripts strongly suggest a precursor role. They would be processed at the level of tRNA or tRNA-like sequences. Most of them are transcribed from the template strand of each gene cluster and their distribution is in agreement with the hypothesis of several transcription origins and terminations located near the extremities of each gene cluster. Quantitatively our results show a large variation in each presumptive mature transcript compared to the other, even in a given gene cluster, suggesting a specific degradation of some of the mature transcripts.

Animals↗
PubMed1986

Longitudinal development in pediatric residents of attitudes toward neonatal resuscitation.

We used Guttman scaling procedures to devise a quantitative, reproducible measure among pediatric residents of attitude change concerning neonatal resuscitation. Preliminary cross-sectional testing of an incoming group of pediatric level 1 residents and graduating pediatric level 3 residents indicated that pediatric level 3 residents were more reluctant to resuscitate high-risk infants. This reluctance was not due to age differences. The pediatric level 1 residents were retested at the completion of each year of training. Residents showed significantly increased reluctance to resuscitate infants at the end of the first year of training and again at the end of the third year of training. These attitude changes were unrelated to gender, marital status, religious preference, or ethnic background. Data acquired both cross-sectionally and longitudinally indicated that attitudes toward neonatal resuscitation changed during residency training.

Attitude of Health Personnel↗
PubMed1986

Translation of polyuridylic acid in lysed mitochondria.

After osmotic shock with 50 mM Tricine buffer (pH 7.9), isolated mitochondria from D. Melanogaster embryos are treated with a low concentration of Triton X-100 (25 micrograms/mg of protein). The lysed mitochondria are still capable of RNA and protein synthesis. While incorporation of labeled precursor is often higher in lysed than in intact mitochondria, neosynthesized proteins exhibit similar electrophoretic patterns. Studies of labeled precursor incorporation in the presence of various effectors indicate a better accessibility to the translation machinery in lysed mitochondria than in intact mitochondria. Such a system has proven capable of translating an exogenous synthetic mRNA, i.e., poly (U).

Animals↗
PubMed1985

Mitochondrial DNA expression in Drosophila melanogaster: neosynthesized polypeptides in isolated mitochondria.

The expression of mitochondrial genome of D. melanogaster in isolated mitochondria was followed by incorporation of 35S methionine in neosynthesized polypeptides. A high level of protein synthesis was obtained after optimization of all the incubation parameters. Two kinds of energy-generating systems were used: an endogenous system where an oxidizable substrate were added for ATP synthesis; an exogenous system with an energy-rich compound for ATP regeneration, the latter proved to be the most effective. The effect of the oxidative phosphorylation uncoupler (Clccp), and an ATPase inhibitor (oligomycine) allow us to postulate the role of the electrochemical potential in the expression of the mitochondrial genome. Electrophoresis and autoradiography of neosynthesized mitochondrial proteins exhibits 18 to 24 protein bands, ranging from 6.5 to 65 Kd; incubation of KC 0% drosophila cells with 35S methionine and cycloheximide gave similar results. Both our results and those published elsewhere suggest that the expression of mitochondrial genome in higher organisms could be more complex than simple translation of the 13 genes presents on these genomes.

Animals↗
PubMed1984

Complex RNA chain elongation kinetics by wheat germ RNA polymerase II.

Kinetics of RNA chain elongation catalyzed by wheat germ RNA polymerase II have been studied using various synthetic DNA templates in the presence of excess dinucleotide monophosphate primers. With single- or double-stranded homopolymer templates, the double reciprocal plots 1/(velocity) as a function of 1/(nucleotide substrate) exhibit positive, negative or no curvature. With poly(dAT) as template, the mechanism of nucleoside monophosphate incorporation into RNA is not the ping-pong kinetic mechanism which was derived for E. coli RNA polymerase (6). Noncomplementary nucleoside triphosphates inhibit RNA transcription allosterically. Cordycepin triphosphate behaves as ATP, and not only inhibits AMP incorporation but also that of UMP and GMP on appropriate templates. The reason for this complex kinetic behavior is not yet understood. Possibilities are raised that there are several nucleoside triphosphate binding sites on wheat germ RNA polymerase II, that additional nucleoside triphosphate dependent enzymatic activities are required for reaction to occur or that the Km value for incorporation of a given nucleoside monophosphate into RNA is dependent on the length of the RNA chain and/or the nucleotide sequence surrounding the complementary base on the DNA template.

Kinetics↗