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Biomedical subjects

F Bouvier

Publications and source records attributed to F Bouvier.

At least 55 records · Page 3Linked to original sources
PubMed1995

Biochemistry and molecular biology of chromoplast development.

Plant cells contain a unique class of organelles, designated the plastids, which distinguish them from animal cells. According to the largely accepted endosymbiotic theory of evolution, plastids are descendants of prokaryotes. This process requires several adaptative changes which involve the maintenance and the expression of part of the plastid genome, as well as the integration of the plastid activity to the cellular metabolism. This is illustrated by the diversity of plastids encountered in plant cells. For instance, in tissues undergoing color changes, i.e., flowers and fruits, the chromoplasts produce and accumulate excess carotenoids. In this paper we attempt to review the basic aspects of chromoplast development.

Cell Differentiation↗
PubMed1995

[Infarction in the area of the right anterior choroidal artery and minor hemisphere syndrome: clinical and metabolic study using positron-emission tomography].

A 72 year-old right handed woman had a right sided anterior choroidal artery infarction. She presented the triad of hemiplegia, hemianaesthesia, and homonymous hemianopsia, as well as complete non-determinant hemisphere syndrome that combined: disorientation for place and time, anosognosia, hemiasomatognosia, left spatial neglect, constructional apraxia and spatial fabulation concerning both the present time and the weeks that preceded the vascular event. Language and verbal memory were normal. Spatial memory could not be studied because of the severity of the neglect. The clinical course was poor: when tested one and a half year post-onset, the hemiplegia, the hemianaesthesia, and the hemianopsia as well as left spatial neglect remained severe. Vestibular caloric stimulation, carried out with left ear cold water irrigation, resulted in brief but clear-cut alleviation of the spatial neglect. An MRI with both axial and coronal slices showed a right-sided infarct affecting the whole posterior limb of the internal capsule including the genu, the posterior part of the globus pallidus, the anterior third of the cerebral peduncle and the amygdala but sparing the thalamus and the corona radiata. This crescent-shaped lesion transected entirely the thalamo-cortical connection fibers which resulted in a "thalamic exclusion". The measurement of brain glucose utilisation with (18F)-Fluoro-2-Deoxy-D-Glucose and positron emission tomography performed in the chronic phase (3 months post-onset) showed an exceptionally severe and widespread hypometabolism of the right hemisphere, relative to the left hemisphere, which correlated with both the unusual, severe and protracted non-dominant hemisphere syndrome. All the brain regions on the right side were hypometabolic relative to the left including the temporal region (mostly medial temporal), the left cerebellar lobe, the frontal lobe (mostly prefrontal region), the occipital region and the thalamus. The hypometabolism of the basal ganglia, the sensorimotor area and the parietal cortex was less severe. This most uncommon clinical-metabolic presentation presumably reflects a global thalamo-cortical disconnection inducing a diffuse dysfunction of the whole hemisphere.

Aged↗
PubMed1994

Structure and expression of two plant genes encoding chromoplast-specific proteins: occurrence of partially spliced transcripts.

The genes encoding fibrillin and capsanthin-capsorubin synthase are specifically expressed during fruit ripening in Capsicum annuum, leading to the accumulation of these two proteins in chromoplasts. Here, we report for the first time the cloning of genomic DNA fragments encoding these two enzymes, as well as DNA fragments containing upstream regions which are potentially involved in the regulation of the expression of these genes. While the capsanthin-capsorubin synthase gene is uninterrupted, the fibrillin gene is interrupted by two introns, the first one being inefficiently spliced. Occurrence of unspliced transcripts is apparently not related to a post-transcriptional mechanism controlling the synthesis of fibrillin or an alternative polypeptide. This work provides tools for studies on gene activation and intron splicing in plants.

Amino Acid Sequence↗
PubMed1994

Xanthophyll biosynthesis in chromoplasts: isolation and molecular cloning of an enzyme catalyzing the conversion of 5,6-epoxycarotenoid into ketocarotenoid.

The late steps of carotenoid biosynthesis in plants involve the formation of xanthophylls. Little is known about the enzymology of these steps. This paper reports the purification to homogeneity of a xanthophyll biosynthetic enzyme from Capsicum annuum chromoplasts, which catalyzes the conversion of the ubiquitous 5,6-epoxycarotenoids, antheraxanthin and violaxanthin, into capsanthin and capsorubin, respectively. Owing to its bifunctionality, the name capsanthin-capsorubin synthase is proposed for this new enzyme. The purified enzyme is a monomer with a molecular mass of 50 kDa. Antibodies raised against this enzyme allowed the isolation of a full-length cDNA clone encoding a capsanthin capsorubin synthase high molecular weight precursor. The primary deduced structure reveals the presence of a consensus nucleotide binding site. The capsanthin-capsorubin synthase gene is specifically expressed during chromoplast development in fruits accumulating ketocarotenoids, but not in mutants impaired in this biosynthetic step.

Amino Acid Sequence↗
PubMed1993

Expression of the genes encoding the early carotenoid biosynthetic enzymes in Capsicum annuum.

We have shown that both geranylgeranyl pyrophosphate synthase and phytoene synthase from pepper and tomato chromoplasts are very similar in terms of enzymic activity and immunological properties. This enabled us to clone cDNAs specific for phytoene synthase from ripening tomato and pepper fruits and to compare their amino acid sequences with those of bacterial phytoene synthase and yeast squalene synthase. Comparison of the nucleotide sequence of the 3'-untranslated region of the pepper phytoene synthase cDNA suggests that this region was subjected to complex recombination events. RNA gel blot hybridizations revealed that induction of phytoene synthase gene expression is much stronger in tomato than in pepper fruits. In contrast with tomato, 2 phytoene synthase transcripts of different size are present in pepper leaves and fruits. Comparison of the expression pattern of the genes encoding geranylgeranyl pyrophosphate synthase, phytoene synthase and phytoene desaturase revealed that these genes are not co-regulated during pepper fruit ripening.

Alkyl and Aryl Transferases↗
PubMed1991

[Severe amblyopia and Alzheimer' disease].

A 69-year-old woman developed a rapid and severe visual loss and became nearly blind in a few weeks. As she also presented with memory loss and other disturbances of cognitive functions, with progressive deterioration over one year, a probable Alzheimer's disease was diagnosed. Cerebral CT scan and magnetic resonance imaging were normal. However, clinical and electrophysiological (visual evoked potentials) data indicated an impairment of the primary visual pathways rather than a degeneration of the secondary visual cortex. This case is compared with and discussed in relation to recent reports concerning retinal and optic nerve damage in Alzheimer's disease.

Aged↗
PubMed1977

Thymineless death in Escherichia coli dnaB mutants and in a dnaB dnaG double mutant.

The interference of dnaB mutations of Escherichia coli with thymineless death is described. All the isogenic Thy- dnaB mutants of E. coli we have tested show a remarkable immunity towards cell death induced by thymine deprivation at the nonpermissive temperature. We have also constructed and tested an isogenic double dnaB dnaG mutant. It loses its viability in the absence of thymine at both permissive and nonpermissive temperatures. The role of the dnaB gene product is discussed.

DNA, Bacterial↗
PubMed1975

[Lethality of the dnaB thermosensitive mutation of E. coli : comparison with thymine-less death].

In a dnaB thermosensitive mutant of the bacterium E. coli, a shift to non-permissive conditions leads to the immediate cessation of DNA synthesis and results in a sizable loss of viability. Under conditions where protein synthesis is inhibited, either by addition of antibiotics (chloramphenicol, rifampicin) or by amino-acids starvation, there is a marked increase in viability. This is reminiscent of the behavior of thymine-deprived bacteria and suggests that both types of death, induced by a block in the displacement of the DNA-replicative fork, follow the same pattern.

Amino Acids↗
PubMed1975

Interference of dna ts mutations of Escherichia coli with thymineless death.

Thermosensitive mutants of Escherichia coli in which deoxyribonucleic acid replication is inhibited at high temperature have been assayed for their response to thymine deprivation at permissive and nonpermissive temperatures. The survival rate of mutants in which initiation of replication is defective at 42 C (dnaA and dnaC-D) is much higher at nonpermissive temperatures than at 32 C. By contrast, thymineless death is not hindered at 42 C in two elongation mutants (dnaE and dnaG). Bacterial strains belonging to the dnaB class exhibit both types of behavior. These results are in accordance with the model linking thymineless death to a disruption of an active replication fork. We discuss the possibility that the dnaB protein takes part in this process of cell decay.

Chloramphenicol↗
PubMedDate not supplied

780 SE: a new type of hypolipemic agent. Comparative assays in rats.

The effect of 1-(m-trifluoromethylphenyl)-2-(beta-benzoyloxyethyl)-amino- propane hydrochloride (780 SE) on serum lipids, blood glucose and liver weight was studied in 4 experimental models, and compared with that of clofibrate and tiadenol. When rats were given a daily oral dose of 25 mg/kg or 50 mg/kg of 780 SE for 5 days a marked reduction of serum triglycerides and liver weight was observed. The decreases were more pronounced than those in rats treated with 50 mg/kg or 100 mg/kg of clofibrate or tiadenol. On the other hand, a reduction of serum cholesterol was only observed in the groups given clofibrate and tiadenol. These differences could be explained on the basis of the mechanism of action of the different drugs. Only 780 SE induced a decrease in blood sugar level, a reduction of plasma insulin concentration and restored the insulin sensitivity to a normal value in obese animals. There was a significant decrease in liver weight of 780 SE treated rats, whereas clofibrate and tiadenol cause hepatomegaly.

Animals↗