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J Besson

Publications and source records attributed to J Besson.

At least 19 recordsLinked to original sources
PubMed1992

Isolation and characterization of sfp: a gene that functions in the production of the lipopeptide biosurfactant, surfactin, in Bacillus subtilis.

The sfp gene is required for cells of Bacillus subtilis to become producers of the lipopeptide antibiotic surfactin. sfp was isolated and its nucleotide sequence was determined. sfp was expressed in Escherichia coli and its putative product was purified for use in antibody production and in amino acid sequence analysis. The gene was plasmid-amplified in B. subtilis, where it conferred a Srf+ phenotype on sfp0 (surfactin non-producing) cells. Overproduction of Sfp in B. subtilis did not cause production of an increased amount of surfactin and resulted in the repression of a lacZ transcriptional fusion of the srfA operon, which encodes enzymes that catalyze surfactin synthesis. We propose that sfp represents an essential component of peptide synthesis systems and also plays a role, either directly or indirectly, in the regulation of surfactin biosynthesis gene expression.

Amino Acid Sequence↗
PubMed1992

One hundred requests for predictive testing for Huntington's disease.

In Grampian region, the first 100 requests for predictive testing for Huntington's disease have been analysed. Forty-five presymptomatic predictive test results have been given, eleven families have made a decision to undergo prenatal exclusion tests, and so far eleven pregnancies have been investigated using chorion villus biopsy. This paper presents the protocol used and a descriptive analysis of those receiving results, those choosing to leave the programme, and those unable to complete it because of an unsuitable family structure or unco-operative relatives.

Adult↗
PubMed1990

Effect of the antiepileptic drug sodium valproate on glutamine and glutamate metabolism in isolated human kidney tubules.

We studied the effects of sodium valproate, a widely used antiepileptic drug and a hyperammonemic agent, on L-[1-14C]glutamine and L-[1-14C]glutamate metabolism in isolated human kidney-cortex tubules. Valproate markedly stimulated glutamine removal as well as the formation of ammonia, 14CO2, pyruvate, lactate and alanine, but it inhibited glucose synthesis; the increase in ammonia formation was explained by a stimulation by valproate mainly of flux through glutaminase (EC 3.5.1.2) and to a much lesser extent of flux through glutamate dehydrogenase (EC 1.4.1.3). By contrast, valproate did not stimulate glutamate removal or ammonia formation, suggesting that the increase in flux through glutamate dehydrogenase observed with glutamine as substrate was secondary to the increase in flux through glutaminase. Accumulation of pyruvate, alanine and lactate in the presence of valproate was less from glutamate than from glutamine. Inhibition by aminooxyacetate of accumulation of alanine from glutamine caused by valproate did not prevent the acceleration of glutamine utilization and the subsequent stimulation of ammonia formation. It is concluded from these data, which are the first concerning the in vitro metabolism of glutamine and glutamate in human kidney-cortex tubules, that the stimulatory effect of valproate is primarily exerted at the level of glutaminase in human renal cortex.

Adult↗
PubMed1988

[Results of myopic keratomileusis. A retrospective clinical study apropos of 40 cases].

The authors report in a retrospective study, the results of myopic keratomileusis. 40 eyes were operated on at the department of ophthalmology of Hotel-Dieu Hospital in Paris, with a range follow-up of 6 to 24 months. The mean pre-operative spherical equivalent was - 15.08 +/- 3.32 D., and the mean post-operative spherical equivalent was - 5.02 +/- 3.75 D. relative to preoperative conditions, best corrected visual acuity were unchanged in 6 cases, improved in 16 cases and diminished in 18 cases. The predictability of results was better for patients with myopia in the range of - 9 to - 16 D. During the first post-operative year, a mean regressive tendency of 3 diopters was noted. Complications are reported and analysed. Myopic keratomileusis is indicated for myopia between - 10 and - 16 D., when correction by contact lenses has failed. Candidates for surgery must be informed and consent about possibilities, limits and risks of the procedure.

Cornea↗
PubMed1987

Characterization of vasoactive intestinal peptide receptors by a photoaffinity label. Site-specific modification of vasoactive intestinal peptide by derivatization of the receptor-bound peptide.

The biological effects of vasoactive intestinal peptide (VIP) are mediated by binding to a membrane-bound receptor. Probes designed to trap this receptor by binding to it in a covalent way may suffer from a greatly reduced affinity. We report here, for the VIP receptor, the use of a photoaffinity probe obtained by derivatization of receptor-bound VIP with para-azidophenylglyoxal. This method protected the parts of the molecule essential for receptor binding. The VIP derivative thus obtained became covalently linked when irradiated. In the dark, however, it exhibited normal VIP-like behavior and retained its biological activity. This derivatization method might be generally applicable when hormone analogues have to be prepared without loss of receptor affinity. Receptor characterization studies on liver plasma membranes showed the presence of high- and low-affinity binding sites with KD = 0.1 and 5 nM, respectively. Treatment of membranes with dithiothreitol causes loss of high-affinity binding. The high-affinity site, trapped by the photoaffinity probe, resolved into two molecular mass forms, 50 and 200-250 kDa. Reduction of the receptor-probe complex left the 50-kDa form intact, whereas the amount of the 200-250-kDa form greatly diminished. We demonstrate the importance of the presence of disulfide bonds in one of the molecular forms involved in high-affinity binding.

Affinity Labels↗
PubMed1987

Autoradiographic localization of vasoactive intestinal peptide (VIP) binding sites in the human term placenta. Relationship with activation of adenylate cyclase.

The presence of vasoactive intestinal peptide (VIP) binding sites and the adenylate cyclase activity in response to VIP were examined in the human term placenta. Slices were used in order to preserve the physicochemical environment and the structural integrity of this heterogeneous organ. 125I-VIP binding to placental slices was saturable. The steady state was reached after 90 min at 37 degrees C and was maintained up to 3 h. Unlabeled VIP was able to compete in a dose-dependent manner with an IC50 value of 5.2 +/- 1.3 x 10(-10) M. Autoradiography and histological analysis showed that VIP binding sites were essentially located on fetal vascularization, especially arteries of stem villi. VIP produced a stimulatory effect on cAMP synthesis at a concentration as low as 10(-10) M. The dose-response curve was monophasic with an ED50 value of 2.9 +/- 1.6 x 10(-9) M. The specificity of the VIP effect was tested with peptides structurally related to VIP such as glucagon, secretin, gastric inhibitory polypeptide and human growth-hormone releasing factor. Only secretin at high concentrations (greater than 10(-6) M) increased cAMP production. Leu-enkephalin or insulin were ineffective. The presence of both VIP binding sites on fetal vascularization and VIP-induced adenylate cyclase activation would seem to suggest a regulatory role of the peptide on fetoplacental blood flow.

Adenylyl Cyclases↗
PubMed1987

[Spheno-ethmoidectomy in recurrent nasal polyposis. Technic, indications, results].

Spheno-ethmoidectomy can be legitimately included within the therapeutic schema for nasosinusal polyposis causing incapacity and resistant to medical treatment. Benefiting from recent technical progress, a very precise medical therapeutic framework and improved knowledge of ethmoid surgical anatomy, a marked reduction in complications of this operation has been observed. Results of a series of 175 ethmoidectomies performed in 90 patients confirm the good results reported in the literature, even though follow up is still insufficient.

Ethmoid Sinus↗
PubMed1986

Characterization and autoradiographic distribution of vasoactive intestinal peptide binding sites in the rat central nervous system.

Biochemical characteristics and topographical distribution of mono-[125I )vasoactive intestinal peptide (VIP) binding sites in rat brain were studied on tissue sections and by quantitative autoradiography. Biochemical investigations show two classes of binding sites with a dissociation constant of 1.03 +/- 0.11 nM and 68 +/- 14 nM and a maximal binding capacity of 43.3 +/- 5.1 fmol/mg protein and 713 +/- 117 fmol/mg protein respectively. The order of potency of various peptides to inhibit 125I-VIP binding to brain sections is: VIP greater than PHI greater than secretin greater than VIP greater than hGRF. Autoradiography reveals the highest densities of binding sites in the pineal gland, the dentate gyrus of the hippocampus, the central amygdaloid nucleus and in various thalamic nuclei such as the mediodorsal, lateral posterior, submedius, dorsolateral and medial geniculate nuclei. Similar high densities are observed in the olfactory bulbs as well as in the suprachiasmatic and dorsomedial nuclei of the hypothalamus and in the superior colliculus. These data together with the distribution of the endogenous peptide suggest a physiological role for VIP both in the regulation of CNS activities and pituitary functions.

Animals↗
PubMed1986

[Estimate of the prevalence of rheumatoid arthritis based on a rheumatology study in the district of Angers].

The prevalence of rheumatoid arthritis is generally estimated to be 1 per cent, despite the marked differences between the various results published according to the survey techniques and the epidemiological criteria employed. The present survey consisted of patients from the target population (the 248,009 inhabitants of Angers over the age of 15 years), who had been examined by one of the hospital or private rheumatologists working in Angers between 1960 and 1984 and who were considered to be suffering from inflammatory rheumatism. The cases of rheumatoid arthritis included in this survey were still alive and were living in Angers between January 1 and June 30 1984 and corresponded to at least two of the New York criteria. The prevalence determined according to this technique was 0.17 per cent for two criteria and 0.11 per cent for three criteria. After discussing the bias and the particular conditions of the study, it appears that these particularly low levels are essentially related to: a recruitment bias due to the limitation of the survey to patients seen by rheumatologists, to the choice of New York criteria and more especially of 3 criteria which increases the specificity of the survey at the expense of the sensitivity, to the long observation (mean of 10.4 years) which contributed to a reduction in the number of false positives. The validity of this study is supported by the comparison with the study by O'Sullivan et al. also based 2 New York criteria with a follow-up of 3 to 5 years, which concluded on a prevalence of 0.24 per cent compared with 0.17 per cent in Angers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Application of iodine-123-labeled isopropylamphetamine imaging to the study of dementia.

Forty-seven patients diagnosed as clinically demented were imaged with 123I isopropylamphetamine (IMP). All of these patients also had a nuclear magnetic resonance (NMR) study. In those patients diagnosed as having senile dementia of the Alzheimer type a bilateral reduction in IMP uptake in the temporo-parieto-occipital region was always seen. The NMR appearances were normal in 64% of these sites. The IMP images of patients with multi-infarct dementia varied from normal to marked focal deficits. There was, however, a much closer agreement between the abnormalities seen on the IMP and NMR images. In alcoholic dementia no focal areas of reduced IMP uptake were seen, although the uptake was generally irregular. In both Korsakoff's psychosis and Huntington's chorea the IMP uptake pattern and the NMR study were normal.

Aged↗
PubMed1985

Ontogeny of vasoactive intestinal peptide and somatostatin in different structures of the rat brain: effects of hypo- and hypercorticism.

The ontogeny of the vasoactive intestinal peptide (VIP) and somatostatin (SRIF) was studied in various structures of the rat central nervous system (CNS), using specific radioimmunoassays. The effect of adrenal corticoids on the concentration of both peptides was investigated during the development of the rat from 3 days before birth to 2 months after birth. The evolution of both peptides was different since SRIF was found before birth in each structure tested while VIP appeared only after birth in the same structures. However, after birth the ontogeny of VIP and SRIF was quite similar and the maximum concentration of both peptides occurred between day 14 and day 21. Hypercorticism (implant of corticosterone) and hypocorticism (Metyrapone injections) modified the postnatal evolution of both peptides, suggesting that corticoids play an important role in the brain developmental patterns of VIP and SRIF.

Adrenal Insufficiency↗