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Biomedical subjects

C Monnier

Publications and source records attributed to C Monnier.

At least 19 recordsLinked to original sources
PubMed2000

Submolecular Structures in Dipalmytoylphosphatidylethanolamine Langmuir-Blodgett Films Observed by Scanning Force Microscopy.

Dipalmitoylphosphatidylethanolamine (DDPE) Langmuir films at the air/water interface have been studied. These films exhibit high stability. The resulting films transferred on muscovite have been studied by scanning force microscopy with the contact mode. At the microscopic scale, DDPE Langmuir-Blodgett films appear densely packed with few defects. At molecular resolution the films appear well ordered; the double tail of the lipids has been observed.d Copyright 2000 Academic Press.

Journal Article↗
PubMed1997

Hypothesis: the meeting place model for prion disease.

Prions are responsible for spongiform diseases such as scrapie and bovine spongiform encephalopathy. It is now generally accepted that the disease mechanism involves the conversion from the normal form, PrPC, to the pathogenic form, PrPSc, and that this isoform is infectious. In the case of scrapie, 15 different forms of the disease have been described and some of these different phenotypes can be conferred by infectious prions that are themselves encoded by normal genes. We propose here that a prion with an altered structure has a correspondingly altered preference for lipids; this altered preference creates a proteolipid domain containing different lipids and other factors such as chaperonins and enzymes responsible for post-translational modifications. Normal prions associated with this abnormal domain adopt the conformation dictated by its lipidic composition (and by the other factors present) and so acquire the lipidic preference of the original pathogenic prions. These transformed prions could then create new proteolipid domains. This process may be considered as semi-conservative replication in which prion and lipids are analogous to the Watson and Crick strands and the proteolipid domain to the double helix itself.

Animals↗
PubMed1996

Spatial learning in a Z-maze by cerebellar mutant mice.

Two types of cerebellar mutant mice (staggerer and lurcher) were evaluated during 5-day acquisition of a spatial learning task in a Z-maze filled with water. Although the number of errors and escape latencies decreased in normal mice, the acquisition of the cerebellar mutants was impaired but not abolished. These results indicate that the cerebellum has a role in spatial learning. Mice with cerebellar dysfunction take a more indirect route toward a goal during the course of swimming, when ataxic symptoms are no longer in evidence.

Animals↗
PubMed1995

Elevated (+)-maze and hole-board exploration in lurcher mutant mice.

The behavior of lurcher mice, a mutant with degeneration of cerebellar cells, was compared to that of normal mice for three days in two tests of exploration; an elevated (+)-maze and a 4 x 4 hole-board. In the elevated (+)-maze, lurcher mutants visited fewer closed arms than normal mice only on the first test day. Lurcher mutants were slower to emerge from the first closed arm but did not differ from normal mice for entry latencies into the first open arm. The time spent by the mutants in the open arms was higher than that of normal mice, an indication of decreased inhibition to open spaces. In the hole-board, lurcher mutants visited fewer holes than normal mice only on the first day of testing. In proportion to the total number of holes explored, lurcher mutants visited fewer center holes and fewer holes situated next to each other. These results may be due to a lesion-induced tendency to explore a more restricted region of a novel spatial environment and to explore it in a more haphazard fashion.

Animals↗
PubMed1993

Mutations in two new loci that impair both extracellular protein production and development in Myxococcus xanthus.

Two transposon insertion mutants of Myxococcus xanthus altered in the secretion of protein as determined by the hydrolytic activities of several enzymes during vegetative growth were also unable to complete fruiting body formation and were severely impaired in sporulation. The insertions were located in the same part of the M. xanthus chromosome but were unlinked by transduction and therefore define two distinct loci, called excA and excB. Since both Exc +/- mutants were able to rescue development of an asgB mutation, they do not belong to the Asg- group, despite of the fact that asg mutants are also Exc +/-. Our results sustain the hypothesis of a possible relationship between protein secretion during vegetative growth and development or sporulation.

Bacterial Proteins↗
PubMed1990

Mechanism of integration of the broad-host-range plasmid RP4 into the chromosome of Myxococcus xanthus.

The site-specific recombination mechanism through which the plasmid RP4 has been previously shown to integrate into the chromosome of Myxococcus xanthus has been investigated further. Once integrated in one of the numerous chromosomal sites from two different strains, through a precise site on the plasmid, the latter can be excised either precisely or after a definite 14.5-kb deletion. In some cases, the integration is followed by different DNA rearrangements that yield a higher rate of excision and integration. A model for the site-specific integration and excision of the plasmid is proposed.

Blotting, Southern↗
PubMed1990

Comparison of beta-galactosidase production by two inducible promoters in Myxococcus xanthus.

The inducibility of two promoter systems, one heterologous and one homologous, has been assessed in the Gram-negative bacterium Myxococcus xanthus. The heterologous system involved the hybrid tac promoter and the presence of lacIq, the lac repressor from Escherichia coli. This system is inducible in its natural host with isopropyl-beta-D-thiogalactopyranoside (IPTG). The homologous promoter system involves the light-inducible carQRS promoter, which is normally involved in the expression of the regulators of the light-inducible light-protective carotenoid synthesis regulon in M. xanthus. In each case, promoter activity and strength was assayed using the E. coli gene lacZ. In our constructs, which were present in a single copy in the M. xanthus chromosome, the carQRS promoter yielded at least a 47-fold increase in beta-galactosidase production upon light induction, whilst IPTG increased by 8-fold the amount of enzyme produced under the control of the ptac-lacIq system. Regulation by the latter was significantly higher than that obtained with the unmodified lacZ promoter.

Enzyme Induction↗
PubMed1981

Epidemiology of Duchenne muscular dystrophy in the province of Turin.

An epidemiological investigation on Duchenne muscular dystrophy in Turin and its province has been carried out for the period 1955-974. The incidence of the disease proved to be 24 X 10(-5), and the prevalence 2.15 X 10(-5). The mutation rate was 80 X 10(-6). The data are compared with the literature. Segregation analysis on many families was performed in order to find the theoretical number of carrier among Duchenne mothers. The importance of epidemiology for genetic counselling is stressed.

Child↗
PubMed1978

[Prolonged glomerulonephritis and cyanotic heart disease].

Three children with congenital heart disease presented with more or less severe renal dysfunction. Histologic studies showed signs of membranoproliferative pseudoglomerulonephritis without deposits on immunofluorescence. Surgical correction of the heart defect induced a spectacular functional and histologic improvement.

Adolescent↗
PubMed1978

[Effect of the extrusion process on the availability of proteins].

The extrusion process has grown rapidly as in the preparation of meat-extenders from vegetal proteins as in the fabrication of cocktail-snacks and food for breakfast. The nutritional modifications induced by the thermic shock during the extrusion affect: -the diminution of the content of nutrient: loss in vitamins, destruction and unavailability of amino-acids; -the structural modification of a few compounds: starch gelatinization; -destruction of antinutritional factors: essentially antitrypsic factor. We studied the effect of extrusion with a model-mixture on the availability of amino-acids and particularly lysin. We effected the systematic study of different factors which can interfer in the intensity of the Maillard reaction in relation to the composition of the mixture (presence and nature of sugar, etc.) and to the technological parameters (screw-section, moisture of the mixture, etc.) The model mixture composed of cereal flours shows a global loss of 32 p. 100 in lysin (destruction 18 p. 100, biological unavailability 16 p. 100) after extrusion. When this mixture is added up with 7,2 p. 100 of saccharose the total loss in lysin reaches 40 p. 100. If saccharose is substituted by a more reducing sugar (fructose) the lysin loss approaches 80 p. 100. The addition of 4 p. 100 water at the mixture containing saccharose (total moisture 14 p. 100) limits the lysin loss to 10 p. 100. The modification of other technological parameters does not improve significatively the level of available lysin. The moisture of the mixture before extrusion appears to be a preponderatting factor in the intensity of the Maillard reaction during extrusion.

Amino Acids↗
PubMed1976

Enzyme activities associated with an invertebrate iridovirus: nucleotide phosphohydrolase activity associated with iridescent virus type 6 (CIV).

A nucleoside triphosphate phosphohydrolase activity is firmly associated with a purified invertebrate iridovirus, iridescent virus type 6. The enzyme activity hydrolyzes all the nucleoside triphosphates, but has a high preference for ATP. The products of the reaction are nucleoside diphosphates. Conditions for nucleoside triphosphate phosphohydrolase activity are described.

Adenosine Diphosphate↗