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Biomedical subjects

B Courtois

Publications and source records attributed to B Courtois.

At least 19 recordsLinked to original sources
PubMed2000

Production of a glucoglucuronan by a rhizobia strain infecting alfalfa. Structure of the repeating unit.

The Rhizobium sp. T1 strain. which induces nodule formation on alfalfa and clover roots, produces, during growth, an extracellular polysaccharide composed of D-glucose and D-glucuronic acid noted glucoglucuronan. During the bacterial growth, the pH of the medium decreases slightly. The control of pH in the growth medium slightly reduces the glucoglucuronan production. Under the conditions tested in the present work, the weight-average molecular weight of the polymers produced with or without pH control are similar: Mw approximately 2 x 10(6); the repeating unit determined by chemical and NMR analyses corresponds to the disaccharide: --> 3)-beta-D-GlcpA-(1-->4)-beta-D-Glcp-(1 -->.

Biopolymers↗
PubMed2000

Increase of the ATP-dependent phosphoenolpyruvate carboxykinase activity in Sinorhizobium meliloti (Rhizobium meliloti) during hypothermic environmental conditions.

Sinorhizobium meliloti growth is affected when the incubation temperature is lower than 22 degrees C. In culture media containing glucose or fructose (1%, w/v), the doubling time at 19 degrees C was about 6.25 h during the exponential growth phase, while it was 2.75 h at 30 degrees C; at 17 degrees C it was three-fold higher than at 30 degrees C. Modifications in the bacterial metabolism explain the doubling time increase when bacteria are incubated at low temperature. We determine here, the phosphoenolpyruvate carboxykinase (PEPCK) activity increases when S. meliloti cells first grown at 30 degrees C are shifted at 17 degrees C and incubated for 10 h at this low temperature; we noted the PEPCK activity was three-fold higher in cells incubated in media containing glucose and shifted from 30 to 17 degrees C than in cells maintained at 30 degrees C, while it was only 1.5-fold higher in cells grown in media containing fructose.

Cold Temperature↗
PubMed2000

Quantitative trait loci for root-penetration ability and root thickness in rice: comparison of genetic backgrounds.

Drought is the major abiotic stress limiting rice (Oryza sativa) production and yield stability in rainfed lowland and upland ecosystems. Root systems play an important role in drought resistance. Incorporation of root selection criteria in drought resistance improvement is difficult due to lack of reliable and efficient screening techniques. Using a wax-petrolatum layer system simulated to compacted soil layers, root traits were evaluated in a doubled haploid (DH) population derived from the cross between 'IR64' and 'Azucena'. Twelve putative QTLs (quantitative trait loci) were detected by interval mapping comprising four QTLs for root-penetration ability, four QTLs for root thickness, two QTLs for penetrated root number, and two QTLs for total root number. These QTLs individually explained 8.4% to 16.4% of the phenotypic variation. No QTL was detected for maximum penetrated root length by interval mapping. One QTL located between RG104 and RG348 was found to influence both root-penetration ability and root thickness. QTLs for root-penetration ability and root thickness were compared across two populations, 'IR64'-'Azucena' and 'CO39'-'Moroberekan', and different testing conditions. The identified consistent QTLs could be used for marker-assisted selection for deep and thick roots with high root-penetration ability in rice.

Oryza↗
PubMed1998

In vivo 13C-NMR studies of polymer synthesis in rhizobium meliloti M5N1 strain

The use of in vivo 13C-NMR approach for the monitoring of the synthesis of various polymers within cells of Rhizobium meliloti (M5N1 strain) is reported. Significant differences in polymer biosynthesis have been shown as a function of the metabolic state of the cells and the labeled carbon source used. Consumption of carbon source and produced glycogen was complete with mid-exponential phase harvested cells. This was not the case with stationary phase harvested cells, for which polyhydroxybutyrate synthesis was higher and gluconate synthesis was lower than the former. [1-13C]fructose-grown cells produced more exopolysaccharide and polyhydroxybutyrate, but less beta-(1,2) glucan and gluconate than [1-13C]glucose-grown cells. This approach offers a suitable tool to examine the kinetics of polymer biosynthesis by Rhizobia. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗
PubMed1997

Mechanism of gluconate synthesis in Rhizobium meliloti by using in vivo NMR.

The dehydrogenation of [1-(13)C]- and [2-(13)C]glucose into gluconate was monitored by NMR spectroscopy in living cell suspensions of two Rhizobium meliloti strains. The synthesis of gluconate was accompanied, in the cellular environment, by the formation of two gluconolactones, a gamma-lactone being detected in addition to the expected delta-lactone. These lactones--as well as the gluconate--could be further metabolized by the cells. The delta-lactone was utilized faster than the gamma-lactone. The presence--in significant amounts--and the relative stability of the lactones raise the question of their possible physiological significance.

Alkalies↗
PubMed1997

Identification of glucuronan lyase from a mutant strain of Rhizobium meliloti.

The Rhizobium meliloti M5N1CS (NCIMB 40472) mutant strain wich induces nodule formation on alfalfa roots, produces a (1 --> 4)-beta-D-glucuronan partially acetylated. During fermentation under specific conditions, the molecular weight of the polymer decrease, the presence of polysaccharide degrading enzyme was suspected. A glucuronan lyase was identified, this new bacterial lyase produces d.p. 4 oligoglucuronans, substituents (acetates) present on the substrate reduced the enzyme activity.

Acetylation↗
PubMed1995

Study of parameters affecting poly(3-hydroxybutyrate) quantification by gas chromatography.

Poly(3-hydroxybutyrate) (PHB) quantification has been developed mostly using acidic methanolysis followed by GC analysis of the 3-hydroxybutyrate methyl ester. However, under our experimental conditions, only 62% of the ester was detected by GC analysis. Following the study of the different steps involved in this method (i.e., hydrolysis, esterification, and recovery of the ester), the recovery was shown to be limiting. Addition of water to the organic phase, required for its purification before injection, led to the partition of the ester between the organic and the aqueous phase. The influence of the length of acidic methanolysis time on the amount of ester detected was also investigated. NMR analysis was used to show that secondary products were absent in both phases, regardless of heating time. Moreover, increasing acid concentration and the use of lyophilized cells were shown to lead to the decrease of the treatment time. Concerning internal standard choice, methyl benzoate was found to meet all the requirements to correct injection volume errors or to follow organic phase volume changes as a function of acid and water concentrations. The validity of the method was checked on Rhizobium meliloti M5N1 cells, which are shown to produce about 60% PHB (w/w) when cultivated with fructose as the carbon source.

Chromatography, Gas↗
PubMed1995

Effects of salts on production and on O-acetylation of glucuronan excreted by the Rhizobium meliloti M5N1 CS strain.

Acetylation determined by 1H-nuclear magnetic resonance spectroscopy and production of the glucuronan excreted by the Rhizobium meliloti M5N1CS strain during cultivation in RCS medium with and without added magnesium salts have been studied. These salts induce an increase in the degree of substitution and the molar ratio of 2,3-di-O-acetyl residues. A decrease in production is observed after 75 h of fermentation as the magnesium salt concentration increases. The presence of manganese and sodium salts in the culture induces inhibition of exopolysaccharide (EPS) production. However, the structure of the EPS is similar to that of the EPS produced by standard fermentation, without modification in the degree of substitution.

Acetylation↗
PubMed1995

Cyclic (1-->2)-beta-D-glucans excreted by the glucuronan-producing strain Rhizobium meliloti M5N1CS (NCIMB 40472) and by the succinoglycan-producing strain Rhizobium meliloti M5N1.

During fermentation, the mutant strain Rhizobium meliloti M5N1CS, which induces nodule formation on alfalfa roots, produces a partially acetylated (1-->4)-beta-D-glucuronan. In addition to this exopolysaccharide of high molecular weight, the mutant strain produces oligoglucoronates and cyclic (1-->2)-beta-D-glucans with degrees of polymerization from 17 to 30. Under the conditions applied, magnesium has no effect on cyclic glucan production by the mutant strain, but the succinoglycan production by the wild-type strain Rhizobium meliloti M5N1 increases.

Acetylation↗
PubMed1994

Physicochemical properties of extracellular (1-->4)-beta-D-glucuronan produced by the Rhizobium meliloti M5N1CS strain during fermentation: evidence of degradation by an exoenzyme activated by Mg2+.

The mutant Rhizobium meliloti M5N1CS (NCIMB 40472) produced a partially acetylated (1-->4)-beta-D-glucuronan during fermentation. The polysaccharide (EPS) extracted from broth during fermentation by microfiltration and ultrafiltration (using a 100 kDa cut-off membrane) was characterized by size exclusion chromatography. The weight-average molecular weight (Mw) of the EPS decreased from 7.5 x 10(5) to 5 x 10(5) between 27 and 75 h of fermentation. When MgSO4.7H2O (0.8 gl-1 per day) was present in the medium during the same period, the Mw of the EPS decreased to 1.5 x 10(5). Since EPS degradation was detected after microfiltration of the fermentation medium supplemented with magnesium, the Mw decrease of the EPS extracted during fermentation may be explained by enzymic degradation of the polymer activated by Mg2+ ions.

Bacterial Proteins↗
PubMed1994

[Flaps for covering extensive losses of cutaneous substance on the upper limb. Apropos of 15 cases].

The authors report on their recent experience concerning flap treatment of upper limb complex trauma, based on 15 cases. Proper wound care, and the use of healthy, well vascularised tissues for coverage is of paramount importance for good results, whose quality mostly depends on the severity of initial lesions. The results of this series are encouraging and appear to be a consequence of the great possibilities offered by the cutaneous or muscular flaps used.

Adult↗
PubMed1994

[Traumatic atlanto-axial dislocation in children: 7 cases].

Seven cases of atlantoaxial rotatory dislocation in children are reported. The CT scan permitted differentiation of the lesions in all the cases. Analysis of the results has led us to introduce two modifications for Fielding's classification: a distance between the atlas and odontoid of less than 5 mm is normal. sagittal dislocation must be included in the same classification. We propose the following therapeutic protocol: rotatory luxation without tears of the transverse ligament should receive orthopedic treatment, rotatory luxation with tears of the transverse ligament should have surgical treatment if orthopaedic treatment fails. sagittal luxation with or without rotatory fixation needs surgical treatment.

Adolescent↗
PubMed1993

Structural characterization and rheological properties of an extracellular glucuronan produced by a Rhizobium meliloti M5N1 mutant strain.

The mutant strain M5N1 C.S. (NCIMB 40472) of Rhizobium meliloti M5N1 is able to produce during fermentation a partially acetylated extracellular (1-->4)-beta-D-glucuronan. At low concentration (1 g.l-1), in the presence of monovalent cations, this new glucuronate behaves as a thickening agent, whereas at higher concentration a thermoreversible gel is obtained. With such divalent cations as Ca2+, a thermally stable gel can be formed.

Carbohydrate Sequence↗
PubMed1993

[Controlled mobilisation after suture of extensor tendons of the hand. Apropos of 30 consecutive cases].

From January 1988 to May 1991, 30 patients (mean age: 27 years old; range: 15 to 45) sustained 57 tendon injuries in 49 fingers. They were treated by primary repair with assisted post-operative mobilisation by a dynamic splint. Adhesion of extensor apparatus rate was 12 p. cent but only one had a functional impairment. No other complications were noted. At the thumb level (3 out of 49 fingers) the Kapandji-test was respectively at 8.8 and 9/10 without any extensor lack. At the long fingers level TAM was excellent in 91 p. cent of cases, good in 4 p. cent, fair and poor in 2 p. cent. According to Allieu classification results were good and excellent in 9 p. cent of cases. These results were better when injury was localised to or up to zone 5 according to Verdan's classification, and when there was no associated bone nor articular injuries or cutaneous defects. Subjective results were less good (70 p. cent of satisfactory results) because of pain, grip strength lack or disability. Assisted mobilisation allowed intrinsic healing and avoided adhesion when application date and rehabilitation protocol were respected. It was more beneficial for distal and complex injuries.

Adolescent↗
PubMed1992

[Osteoid osteoma of the femoral neck in children: diagnostic problems].

The authors report a case of an osteoid osteoma of the femoral neck in a child, aged 3 1/2. This is a benign bone tumor, frequently painful with variable relief obtained with salicylates. Clinical latency is not exceptional in children, owing to the delayed diagnosis. When located in the femoral neck it is usually discovered after a delay, owing to the misleading clinical signs and the frequently normal standard x rays. The only treatment for cure is the excision of the nidus, which is usually difficult because of the anatomical location and the perioperative adjustment.

Child, Preschool↗
PubMed1991

Anatomical basis of neurotisation of the median nerve in the hand by the radial nerve.

The sensory sequelae after lesions of the median nerve cause difficulties in treatment since few sensory transfers are available. Neurotisation of the median by sensory branches of the radial nerve have aroused little interest although they have already been used by some authors after anastomosis at the wrist or through the first or second interosseous spaces. Based on what was originally a purely anatomic study, our interest was directed to the possibilities of performing more distal neurotisation for the treatment of sensory disorders of limited extent. The chief object was to obtain faster sensory reinnervation. 30 hands were dissected and a radial branch was defined as suitable for neurotisation whose diameter approximated that of its palmar digital homolog. Only those findings constantly observed in analysis of the hands studied were taken into account. It is therefore possible to reliably define the type and site of the routes of approach as well as the sensory branches suitable for neurotisation.

Hand↗