Biomedical subjects

C Richaud

Publications and source records attributed to C Richaud.

At least 19 recordsLinked to original sources

PubMed2002

Bioavailable nitrate detection in water by an immobilized luminescent cyanobacterial reporter strain.

Cyanobacteria are a major group of photosynthetic bacteria that can accumulate in surface water as so-called "blooms" in response to environmental factors such as temperature, light and certain nutrients such as N, P, and Fe. Some species of cyanobacteria produce toxins, causing a considerable danger for human and livestock health. As a consequence, monitoring of bloom formation and toxin production of drinking water supplies has become a major concern. To enable prediction and monitoring of cyanobacterial blooms, tools to detect nutrient bioavailability in water would be advantageous. A whole-cell biosensor was developed for monitoring nitrate (NO(3-)) bioavailability in aquatic ecosystems using the recombinant bioluminescent cyanobacterial strain Synechocystis PCC 6803 harboring an insertion of a luxAB-kmr fusion with nblA1 in its chromosomal DNA, leading to PnblA::luxAB-kmr. This reporter strain was designated N1LuxKm. Cells were immobilized in microtiter plates and showed a dose-dependent response to nitrate deprivation. The resultant CyanoSensor could detect nitrate in the 4-100 micro M concentration range after a sample incubation time of 10 h under continuous illumination (50 micro E m(-2) s(-1)). The optimal temperature for sensor operation was 29 degrees C and the immobilized biosensor could be stored at 4 degrees C in dark for about 1 month without significant loss of sensitivity.

Biological Availability↗

PubMed2001

Nitrogen or sulfur starvation differentially affects phycobilisome degradation and expression of the nblA gene in Synechocystis strain PCC 6803.

Nitrogen (N) limitation in cyanobacteria is well documented: a reduced growth rate is observed, accompanied by a cessation of phycobiliprotein synthesis and an ordered degradation of phycobilisomes (PBS). This leads to a dramatic bleaching phenomenon known as chlorosis. In Synechococcus strain PCC 7942, bleaching due to PBS degradation is also observed under sulfur (S) or phosphorus (P) limitation, and all three are under the control of the nblA gene product, a 59-amino-acid polypeptide which is overexpressed under N, S, and P starvation (J. L. Collier, and A. R. Grossman, EMBO J. 13:1039-1047, 1994). Cyanobase sequence data for Synechocystis strain PCC 6803 indicate the presence of two tandem open reading frames (sll0452 and sll0453) homologous to nblA. We cloned the two genes, identified a unique 5' mRNA end suggestive of a single transcription start site, and studied nblA expression under conditions of N or S starvation by Northern hybridization: transcripts were detected only under N starvation (no signal is detected in replete medium or with S starvation), whether nblA1 or nblA2 was used as a probe. Mutations in nblA1 and nblA2 were constructed by insertion of a kanamycin cassette; both mutations were nonbleaching under N starvation. Synechocystis strain PCC 6803 does not bleach under S starvation, consistent with the absence of nblA induction in these conditions. These results were confirmed by analysis of the PBS components: sequential degradation of phycocyanin and associated linkers was observed only under conditions of N starvation. This indicates differences between Synechocystis strain PCC 6803 and Synechococcus strain PCC 7942 in their regulatory and signaling pathways leading to N- and S-starved phenotypes.

Bacterial Proteins↗

PubMed1998

Accumulation of small heat shock proteins, including mitochondrial HSP22, induced by oxidative stress and adaptive response in tomato cells.

Changes in gene expression, by application of H2O2, O2.- generating agents (methyl viologen, digitonin) and gamma irradiation to tomato suspension cultures, were investigated and compared to the well-described heat shock response. Two-dimensional gel protein mapping analyses gave the first indication that at least small heat shock proteins (smHSP) accumulated in response to application of H2O2 and gamma irradiation, but not to O2.- generating agents. While some proteins seemed to be induced specifically by each treatment, only part of the heat shock response was observed. On the basis of Northern hybridization experiments performed with four heterologous cDNA, corresponding to classes I-IV of pea smHSP, it could be concluded that significant amounts of class I and II smHSP mRNA are induced by H2O2 and by irradiation. Taken together, these results demonstrate that in plants some HSP genes are inducible by oxidative stresses, as in micro-organisms and other eukaryotic cells. HSP22, the main stress protein that accumulates following H2O2 action or gamma irradiation, was also purified. Sequence homology of amino terminal and internal sequences, and immunoreactivity with Chenopodium rubrum mitochondrial smHSP antibody, indicated that the protein belongs to the recently discovered class of plant mitochondrial smHSP. Heat shock or a mild H2O2 pretreatment was also shown to lead to plant cell protection against oxidative injury. Therefore, the synthesis of these stress proteins can be considered as an adaptive mechanism in which mitochondrial protection could be essential.

Adaptation, Physiological↗

PubMed1997

The heme oxygenase gene (pbsA) in the red alga Rhodella violacea is discontinuous and transcriptionally activated during iron limitation.

Heme oxygenase (HO) catalyzes the opening of the heme ring with the release of iron in both plants and animals. In cyanobacteria, red algae, and cryptophyceae, HO is a key enzyme in the synthesis of the chromophoric part of the photosynthetic antennae. In an attempt to study the regulation of this key metabolic step, we cloned and sequenced the pbsA gene encoding this enzyme from the red alga Rhodella violacea. The gene is located on the chloroplast genome, split into three distant exons, and is presumably expressed by a trans-splicing mechanism. The deduced polypeptide sequence is homologous to other reported HOs from organisms containing phycobilisomes (Porphyra purpurea and Synechocystis sp. strain PCC 6803) and, to a lesser extent, to vertebrate enzymes. The expression is transcriptionally activated under iron deprivation, a stress condition frequently encountered by algae, suggesting a second role for HO as an iron-mobilizing agent in photosynthetic organisms.

Amino Acid Sequence↗

PubMed1996

Concentrations of ceftriaxone (1,000 milligrams intravenously) in abdominal tissues during open prostatectomy.

Ceftriaxone concentrations in abdominal tissues were evaluated at different stages of open prostatectomy. Ceftriaxone was administered as antibiotic prophylaxis, and 15 consecutive patients were given a single dose of ceftriaxone (1,000 mg intravenously in 1 min) 30 min before surgery. Ceftriaxone concentrations in tissue were determined at three stages of the surgical procedure; upon the opening of the abdominal cavity, during the prostatectomy, and upon the closure of the abdominal cavity. Samples of the following tissues or sample were assayed: epiploic and abdominal-wall fat; Retzius' space, bladder, and prostate tissue; and urine. During the different stages of the surgical procedure, for all patients, and in the different tested tissues, ceftriaxone concentrations greater than or equal to the cutoff point (4 micrograms/g of tissue) were measured. The highest concentrations were obtained in the bladder (43 +/- 18 micrograms/g) and in the prostate (35 +/- 18 micrograms/g). In fatty tissues, concentrations were between 13 +/- 5 and 22 +/- 8 micrograms/g. All patients (15 of 15) had ceftriaxone levels in tissue greater than the MICs for the potential pathogens (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis). In conclusion, during open prostatectomy and after the use of a single dose of ceftriaxone (1,000 mg), high antibiotic levels were obtained throughout the surgical procedure in the tissues potentially involved in postoperative infection.

Abdominal Muscles↗

PubMed1996

[Kidney cancer and pancreatic metastases. Report of 3 cases].

Simultaneous or secondary pancreatic metastases of primary renal cancer are exceptional and usually delayed. The clinical signs of symptomatic lesions are varied and nonspecific. Computed tomography allows complete investigation and CT angiography visualizes typical hypervascularization, which can be correlated to angiographic examinations. In the light of 3 cases treated surgically with a significant clinical follow-up, the authors review the data of the literature.

Adenocarcinoma↗

PubMed1995

[Manual fragmentation of deep vein thrombosis].

To preserve the venous function after deep vein thrombosis, physical treatment combines elastic stockings, active exercises, lower limbs elevation, ventilatory exercises and manual lymph drainage. When this traditional treatment is not sufficient, we use a new technique. It aims at fragmenting thrombus by compressing it between the physiotherapist's fingers and the patient's bone. In order to define the fragmentation sites we use the Triplex ultrasonography. This technique has been tested on ten patients with serious thrombosis, whom the thromboembolic risk was first controlled. The evaluation was performed by the clinical examination, echography and occlusive impedance plethysmography rheography. The improvement of the subjective and objective signs leads to use our technique. It has to be validated on a larger scale to extend its use.

Female↗

PubMed1993

Directed evolution of biosynthetic pathways. Recruitment of cysteine thioethers for constructing the cell wall of Escherichia coli.

We report that expansion of thioether biosynthesis in Escherichia coli generates sulfur-containing amino acids that can replace meso-diaminopimelate, the essential amino acid used for cross-linking the cell wall. This was accomplished by jointly overexpressing the metB gene coding for L-cystathionine gamma-synthase and disrupting the metC gene, whose product, L-cystathionine beta-lyase, is responsible for the destruction of L-cystathionine and other L-cysteine thioethers. As a result, meso-lanthionine and L-allo-cystathionine were produced endogenously and incorporated in the peptidoglycan, thereby enabling E. coli strains auxotrophic for diaminopimelate to grow in its absence. Thus, current techniques of metabolic engineering can be applied to evolving the chemical constitution of living cells beyond its present state.

Alanine↗

PubMed1993

Physical mapping of the scattered methionine genes on the Escherichia coli chromosome.

Methionine is an important amino acid which acts not only as a substrate for protein elongation but also as the initiator of protein synthesis. The genes of the met regulon, which consists of 10 biosynthetic genes (metA, metB, metC, metE, metF, metH, metK, metL, metQ, and metX), two regulatory genes (metJ and metR), and the methionyl tRNA synthetase gene (metG), are scattered throughout the chromosome. The only linked genes are metK and metX at 63.6 min, metE and metR at 86.3 min, and the metJBLF gene cluster at 89 min. metBL form the only met operon.

Chromosomes, Bacterial↗

PubMed1993

Combination of standard cytology and immunocytology with BL2-10D1 monoclonal antibody for monitoring-treated bladder cancer patients.

Monoclonal antibody BL2-10D1 directed against a tumor-associated antigen of bladder carcinoma was used for monitoring 11 intravesically treated patients. Thirty-three bladder washout specimens were used for standard cytology and immunological staining. Prior to treatment, 9 of 11 cytologic specimens examined with standard cytology were found to be positive. Using BL2-10D1 alone, only 6 were positive but 1 patient negative with standard cytology was positive with the antibody and corresponded to a positive histological control. Thus, before treatment, an increase in positive rate was observed using the combination of the 2 methods from 82 to 91%. At the end of treatment, 9 washout specimens remained positive with standard cytology, whereas 1 case negative in standard cytology was positive in immunocytology. Thus, the positive rate increased from 82 to 91%. One month after the end of treatment, of 11 washout specimens tested, 3 false-negative standard cytologies and 4 false-negative immunocytologies were shown. However, used in combination, the two methods lead to an increase in positive rate from 67 to 89%. In view of these results, BL2-10D1 may be considered as a useful reagent in combination with the standard cytology for the confirmation of the presence of tumor cells before and after immunotherapy.

Antibodies, Monoclonal↗

PubMed1992

Cloning of dapD, aroD and asd of Leptospira interrogans serovar icterohaemorrhagiae, and nucleotide sequence of the asd gene.

Metabolites such as diaminopimelate and some aromatic derivatives, not synthesized in mammalian cells, are essential for growth of bacteria. As a first step towards the design of a new human live vaccine that uses attenuated strains of Leptospira interrogans, the asd, aroD and dapD genes, encoding aspartate beta-semialdehyde dehydrogenase, 3-dehydroquinase and tetrahydrodipicolinate N-succinyltransferase, respectively, were cloned by complementation of Escherichia coli mutants. The complete nucleotide sequence of the asd gene was determined and found to contain an open reading frame capable of encoding a protein of 349 amino acids with a calculated Mr of 38,007. Comparison of this deduced L. interrogans aspartate beta-semialdehyde dehydrogenase amino acid sequence with those of the same enzyme from Saccharomyces cerevisiae and Corynebacterium glutamicum revealed 46% and 36% identity, respectively. By contrast, the identity between the L. interrogans enzyme and the Streptococcus mutans or E. coli enzymes was less than 31%. Highly conserved sequences within aspartate semialdehyde dehydrogenase from the five organisms were observed at the amino and carboxyl termini, and around the cysteine of the active site.

Acyltransferases↗

PubMed1992

Cloning, characterization, and expression of the dapE gene of Escherichia coli.

The dapE gene of Escherichia coli encodes N-succinyl-L-diaminopimelic acid desuccinylase, an enzyme that catalyzes the synthesis of LL-diaminopimelic acid, one of the last steps in the diaminopimelic acid-lysine pathway. The dapE gene region was previously purified from a lambda bacteriophage transducing the neighboring purC gene (J. Parker, J. Bacteriol. 157:712-717, 1984). Various subcloning steps led to the identification of a 2.3-kb fragment that complemented several dapE mutants and allowed more than 400-fold overexpression of N-succinyl-L-diaminopimelic acid desuccinylase. Sequencing of this fragment revealed the presence of two closely linked open reading frames. The second one encodes a 375-residue, 41,129-M(r) polypeptide that was identified as N-succinyl-L-diaminopimelic acid desuccinylase. The first one encodes a 118-residue polypeptide that is not required for diaminopimelic acid biosynthesis, as judged by the wild-type phenotype of a strain in which this gene was disrupted. Expression of the dapE gene was studied by monitoring amylomaltase activity in strains in which the malPQ operon was under the control of various fragments located upstream of the dapE gene. The major promoter governing dapE transcription was found to be located in the adjacent orf118 gene, while a minor promoter allowed the transcription of both orf118 and dapE. Neither of these two promoters is regulated by the lysine concentration in the growth medium.

Amidohydrolases↗

PubMed1992

Scattering of the rRNA genes on the physical map of the circular chromosome of Leptospira interrogans serovar icterohaemorrhagiae.

Leptospira interrogans is a pathogenic bacterium with a low G+C content (34 to 39%). The restriction enzymes NotI, AscI, and SrfI cut the chromosome of L. interrogans serovar icterohaemorrhagiae into 13, 3, and 5 fragments separable by one- and two-dimensional pulsed-field gel electrophoresis (PFGE). The genome is composed of a circular 4.6-Mbp chromosome and a 0.35-Mbp extrachromosomal element. A physical map of the chromosome was constructed for NotI, AscI, and SrfI by using single and double digests, or partial NotI digests obtained at random or by cross-protection of NotI sites by FnuDII methylase, and linking clones. rRNA genes were found to be widely scattered on the chromosome.

Base Sequence↗

PubMed1991

Overproduction and characterization of the iclR gene product of Escherichia coli K-12 and comparison with that of Salmonella typhimurium LT2.

The iclR gene of Escherichia coli K-12, which encodes a regulatory protein (repressor) for the aceBAK operon, is located between that operon and metH in the 91-min region of the chromosome. The iclR gene was cloned and expressed in a coupled T7 RNA polymerase/promoter system and the gene product was identified by specific binding to a fragment containing the aceBAK operator region. The iclR gene product is a polypeptide of 274 amino acids (aa) with a calculated Mr of 29,741. Comparison of the deduced IclR aa sequence to that of Salmonella typhimurium revealed that the two IclR repressors exhibit 89% identity. A possible helix-turn-helix motif characteristic of DNA-binding proteins was found within the IclR sequence. A search in protein data banks revealed that IclR has a score of similarity of 43.7% with GylR, a transcriptional regulator of the glycerol operon of Streptomyces coelicolor.

Acetates↗

PubMed1991

[Björk-Shiley-Monostrut prosthesis of the aortic valve. Mid-term development].

From July 84 to June 88, 100 patients underwent an isolated aortic valve replacement by a Monostrut-Björk-Shiley prosthesis. Fifty-one had calcified aortic stenosis, 24% aortic insufficiency, 25% mixed aortic lesions. Pre-operatively, their mean age was 57 years, 68% were male, 46% were in NYHA class II or IV, 43% had angina, all were in sinus rhythm. Operative mortality was 4%. All the survivors were followed-up for a mean period of 22 months (6 to 58) with a cumulative follow-up of 183 patients-years. All patients were placed on a long-term regimen of anticoagulant therapy. Two late deaths occurred (1 myocardial infarction, 1 cerebral hemorrhage). The 4 years survival rate was 94%. Postoperative functional results were excellent. Nearly all patients were asymptomatic. Concerning valve related complications: the 4 years actuarial rate of patients free from thromboembolism, hemorrhage, valve thrombosis, periprosthetic leakage and endocarditis were respectively 97%, 97%, 100%, 100% and 100%. No patient were reoperated on. Valvular function was evaluated by mean transprothetic gradient on echo-doppler (61 cases) and by the calculation of the valvular area with transseptal catheterization (21 cases). For small sizes prosthesis (annulus diameter of 19 or 21 mm), medium size prosthesis (23 or 25 mm), large size prosthesis (27 to 29 mm), mean transprothetic gradient were respectively 16, 10 and 6.9 mmHg and valvular aortic area were respectively 1.5, 1.9 and 2.4 cm2. Mid term results of the Monostrut-Björk-Shiley prosthesis on aortic position are good with a low rate of valve related complications and good hemodynamic results, even with the small valve size.

Actuarial Analysis↗

PubMed1990

Two genomic species in Borrelia burgdorferi.

A total of 13 Borrelia burgdorferi strains (responsible for Lyme borreliosis) and representatives of 3 other Borrelia species (B. hermsii, B. parkeri, B. turicatae) associated with relapsing fever were studied by DNA/DNA hybridization and rRNA gene-restriction patterns. Two genomic DNA hybridization groups were observed which could be differentiated by rRNA gene-restriction patterns. Moreover, the number and size of restriction fragments suggest the existence of a single set of 16 and 23 S rRNA genes in Borrelia.

Borrelia burgdorferi Group↗

PubMed1990

Cloning of genes required for amino acid biosynthesis from Leptospira interrogans serovar icterohaemorrhagiae.

Leptospira interrogans belongs to a large family of important pathogens, which is part of the order Spirochaetales, a distinct group of eubacteria. In order to obtain a better understanding of the genetic organization of this species, we have constructed a DNA library of the serovar icterohaemorrhagiae, using the Escherichia coli vector pUC13. We have isolated Leptospira DNA fragments containing the genetic information required to complement strains of E. coli with defects in proline and leucine biosynthesis. While a 3.9 kb fragment which complemented proA also complemented proB, a 15 kb fragment complementing leuB could not complement other leu mutations. The L. interrogans origin of the cloned DNA fragments was confirmed by DNA-DNA hybridization. The hydridization was specific to the pathogenic species and was not seen with the saprophytic species L. biflexa.

Amino Acids↗

PubMed1990

[Study of the etiologic mechanism of valvular regurgitation using Doppler echography].

Doppler echocardiography is currently the method of choice for diagnosing and determining the mechanism and etiology of valvular regurgitation. The recent introduction of transesophageal echo coupled with color Doppler has increased the value of these ultrasonic methods. The analysis of the valvular lesion should be particularly precise and accurate in severe mitral insufficiency because of the possibility of surgical valvuloplasty, the indications of which are now much broader than was the case at the beginning of the nineteen eighties.

Aortic Valve Insufficiency↗