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F Caron

Publications and source records attributed to F Caron.

34 records · Page 2Linked to original sources
PubMed1987

Neurochemical actions of ethylketocyclazocine and ketocyclazocine in different regions of rat brain.

The effects of ethylketocyclazocine (EKC) and ketocyclazocine (KC), benzomorphan derivatives proposed as kappa opioid receptor agonists, were studied by measuring changes in the levels of dopamine (DA), noradrenaline (NA), 5-hydroxytryptamine (5-HT), and their major metabolites, DOPAC, HVA, MHPG-SO4, 5-HIAA, in different regions of rat brain. Doses ranging from 1 to 10 mg/kg were tested. EKC decreased the levels of DOPAC and HVA in striatum, and increased DA concentrations, EKC markedly increased the levels of MHPG-SO4 in hypothalamus, but not in cortex, midbrain and pons-medulla. There was a non-significant decrease in NA concentrations. EKC increased the levels of 5-HIAA in hypothalamus and also in cortex, midbrain and pons-medulla, while the levels of 5-HT were increased. On the whole, similar neurochemical effects were observed after KC administration. These data were discussed in relation to the behavioral actions caused in rats by EKC and KC, including the increase in food intake, and they raise the possibility that the hypothalamic noradrenergic system participate in feeding behavior of these drugs.

Animals↗
PubMed1987

[Diffusion of 5-fluorocytosine in bronchial secretions in patients with respiratory insufficiency].

The 5-Fluorocytosine bronchial secretion levels of 14 patients with a chronic respiratory disease were determined using a microbiological method. The mean maximal concentrations (7.76 +/- 7 micrograms/ml) were obtained at the end of a single 25 mg/kg i v perfusion over 30 minutes. The level increased when five i v perfusions were performed every 6 hours and bronchial diffusion was higher and faster by concomitant administration of (bromhexin hydrochloride). Therefore, 5-Fluorocytosine was not found in bronchial secretions of four patients in spite of a normal serum levels (21.5 +/- 5 micrograms/ml).

Bronchi↗
PubMed1986

Nucleotide sequence of the Paramecium primaurelia G surface protein. A huge protein with a highly periodic structure.

The complete DNA sequence of the G surface protein of Paramecium primaurelia has been determined. It contains an open reading frame of 8145 nucleotides devoid of introns and coding for a protein of 329,000 Mr. Analysis of the deduced amino acid sequence reveals remarkable features such as important internal homologies and a periodic structure, which could be dictated in part by the rigid scaffolding of cysteine residues. The predicted secondary structure shows a quasi absence of alpha-helix and an abundance of beta-pleated sheets and random coils. The monotony of the amino acid sequence is in favour of a structural role for the protein. Interestingly, homologies with other proteins are limited to surface antigens of trypanosomes. Finally, our data are consistent with a genetic code for paramecium which differs from the "universal" code by the assignment of TAA and TAG codons to glutamine.

Amino Acid Sequence↗
PubMed1986

Isolation and characterization of three monoclonal antibodies to human serum low density lipoprotein apoprotein B.

Human serum low density lipoprotein (LDL) is a large (Mr = 2-3 X 10(6), complex particle composed of lipid, protein and carbohydrate. We obtained about 40 mouse spleen-myeloma hybrid cell lines which produce antibodies against LDL. Three of them, SC2, SC3 and SC10, have been cloned and subcloned and their antibody products characterized. They recognize three non-overlapping epitopes in native LDL. Two of them, SC3 and SC10, also are capable of recognizing very low density lipoprotein, (VLDL), whereas SC2 reacts only weakly with VLDL. All three antigenic determinants remain intact, and accessible to antibodies on the LDL protein apo B, prepared by delipidation in a 'non-denaturing' detergent, sodium deoxycholate. However, apo B prepared by organic solvent, ether-ethanol, or sodium dodecyl sulfate (SDS) delipidation, while reacting strongly with SC10, is only poorly recognized by SC2 or SC3. Proteolysis of LDL with trypsin, chymotrypsin, Staphylococcus aureus protease, papain or thermolysin gives, in each case, several non-identical protein fragments which are separable by SDS-polyacrylamide gel electrophoresis. Upon immunoblotting, some of these fragments are now recognized by either SC3 or SC10 but not SC2, some are recognized by both SC3 and SC10, and others are immunologically unreactive. The protein bands that are separated by SDS gel electrophoresis are composed of several non-identical fragments and contain the antigenic sites to differing degrees. Some of the immunologically reactive fragments do not appear to contain carbohydrate. Reduction and carboxymethylation do not destroy the immunoreactivity of LDL toward any of the antibodies; however, modification of lysine residues by citraconic anhydride markedly diminishes the reactivity of LDL toward SC3. It is likely that the two antibodies SC3 and SC10 are directed against different linear amino acid sequences or very stable domains, whereas the third, SC2, is directed against a more fragile conformational domain of apo B.

Animals↗
PubMed1986

Deviations from the 'universal' genetic code.

Experimental data show that ciliates and mycoplasmas have genetic codes different from the 'universal' code. An evolutionary scheme which could explain the origin of terminators in a genetic code and relate it to the phenomenon of nuclear dimorphism in ciliates is proposed.

Amino Acid Sequence↗
PubMed1985

Macronuclear structure of the G surface antigen gene of Paramecium primaurelia and direct expression of its repeated epitopes in Escherichia coli.

The gene encoding the G surface antigen of Paramecium primaurelia was cloned from a macronuclear DNA library by a screening procedure involving differential hybridization with cDNA probes synthesized from polyadenylated RNAs of cells expressing one of two alternate antigens. S1 mapping experiments and sequencing of the cloned DNA and the mRNA showed that the cloned gene corresponded to the high-molecular-weight mRNA that had been indirectly identified as that of the G surface antigen. Because the genetic code of Paramecium spp. is different from the "universal" code, this mRNA cannot be correctly translated in vitro; direct proof that it encoded the antigenic determinants of this protein was therefore obtained through expression of fragments of the coding sequence in Escherichia coli by using the expression vector lambda gt11. Studies on the structure of this gene revealed that the central part of the coding sequence contained at least five tandem repeats of 222 base pairs, encoding immunogenic domains of the protein. We also showed that, like other surface antigen genes of trypanosomes and paramecia, this gene lay next to a chromosome end and that no rearrangement of its immediate genomic environment was associated with its expression.

Antigens, Protozoan↗
PubMed1979

Characterization of a histone-like protein extracted from yeast mitochondria.

Analysis of proteins isolated by affinity chromatography on DNA-cellulose from highly purified yeast mitochondria shows that these organelles do not contain histones but have in abundance a DNA-binding protein of 20,000 daltons. The purification yield of this protein, called HM, indicates that mitochondria have at least an equal mass of HM relative to DNA. The amino acid composition and its electrophoretic characterization reveal that HM, rich in lysine, is slightly basic and heat stable. HM appears to be coded by the yeast nucleus, as shown by its presence in several "petite" mutants. We have shown that HM, like histones or histone-like proteins, is able to introduce superhelical turns into circular relaxed DNA in the presence of a nicking-closing activity.

Amino Acids↗
PubMed1978

The influence of protein-lipid interactions on the order-disorder conformational transitions of the hydrocarbon chain.

The phases of simple systems involving one type of protein (lysozyme or cytochrome c) and one type of lipid (phosphatidic acid) have been characterized by X-ray crystallography, chemical analysis and spin-labeling technique as a function of temperature. They are of the lamellar type with alternative protein monolayers and lipid bilayers. According to the pH, two types of lamellar phases are obtained, one where the lipid-protein interactions are mainly hydrophobic, the other where they are electrostatic. In both cases, a phase transition occurs as temperature is lowered, between a high temperature phase, where all the lipids are in the liquid-like state, and another phase where some lipid chains are rigid. In the case of the phases with electrostatic interaction, it is shown that the onset of the order-disorder transition is shifted towards low temperature as compared with the homologous lipid-water phase and that the protein content of the phase decreases as the ratio of the liquid to rigid hydrocarbon chains decreases. This leads us to suggest that in the systems studied in this work the proteins interact only with lipid in the liquid-like state. In the case of the phases with hydrophobic interaction, it is shown that the extent of hydrophobic interaction between protein and lipid increases as the unsaturation of the hydrocarbon chains increases. The onset of the order-disorder transition shows a greater shift towards low temperature than the one observed in the case of the phase with electrostatic interaction.

Cytochrome c Group↗
PubMedDate not supplied

Irreversible trapping of DNA during crossed-field gel electrophoresis.

Using an original protocol with a rotating gel electrophoresis apparatus, it is shown that duplex DNA undergoing crossed-field electrophoresis in agarose gets trapped in the gel when the field is increased above a threshold value which decreases with the chain length and depends on the angle between the fields in a non-monotonous manner. This trapping is irreversible, i.e. once trapped at a high field strength, chains are unable to resume their motion when the field is returned to a lower value at which they moved prior to trapping. A model of trapping by "tight knots" is proposed. It predicts a trapping threshold proportional to the inverse square of the electric field, in qualitative agreement with the data. The implications of our results for the separation of large DNA molecules are discussed.

Chromosome Banding↗
PubMedDate not supplied

Does Paramecium primaurelia use a different genetic code in its macronucleus?

It has long been known that messenger RNAs (mRNAs) of ciliates and in particular of Paramecium are not translated well in heterologous in vitro translation systems. Recently, we have demonstrated for Paramecium primaurelia that this phenomenon results from the presence of well-defined blocking sites in the coding sequences of almost all mRNAs, and that these sites are an intrinsic feature of the primary as opposed to the secondary structure of the mRNAs. Here we show that both the gene and the mRNA for the G surface antigen of P. primaurelia contain numerous TAA and TAG codons scattered throughout their coding sequences. We propose that these codons do not represent termination codons in P. primaurelia but instead code for glutamic acid or glutamine and that the in vitro translation of Paramecium mRNAs is blocked by their presence.

Animals↗
PubMedDate not supplied

A method for the amplification of Paramecium micronuclear DNA by polymerase chain reaction and its application to the central repeats of Paramecium primaurelia G surface antigen genes.

This paper describes a method which allows the amplification of Paramecium micronuclear DNA. Amacronucleate cells are first obtained by an appropriate treatment with nocodazole, a microtubule depolymerizing agent which blocks the elongation of the macronucleus and the distribution of the micronuclei at cell division between the two daughter cells; then, DNA from such cells is amplified by the polymerase chain reaction technique. We have applied this method to the problem of the central repeats of the G surface antigen of P. primaurelia (strain 156). The central repeats consist of a 74 amino acid sequence repeated in tandem. The sequence identity of these repeats is also found in the nucleotide sequence even at silent codon positions, suggesting the existence of a mechanism of identity maintenance acting at the nucleotide level. Mechanisms based on RNA secondary structure which are frequently proposed as an explanation of this phenomenon are unlikely to be valid in this case. One can, therefore, imagine that these repeats might originate from one micronuclear sequence through duplicative processes which could occur during the formation of the macronucleus. We have used the described technique to amplify the micronuclear version of the central repeats and showed that it is identical to the macronuclear version, thus ruling out the above hypothesis. Therefore, intragenic recombination appears to be the most likely explanation of the sequence identity of these central repeats.

Amino Acid Sequence↗
PubMedDate not supplied

[Bismuth revisited in Helicobacter pylori gastro-duodenal infection].

The various hypothesis for the explantation of reversible bismuth encephalopathy are reviewed and discussed. Today, this side effect appears to be devoid of mystery, due to uncontrolled and inhibited ingestion of bismuth salts which increased the emergence of genetic and physiopathologic risk factors and brought about the cases of neurotoxicity. Bismuth therapy has shown major efficacy in the treatment of gastroduodenal ulcers. Colloidal bismuth subcitrate is as effective as the H2-receptor antagonists in peptic ulcer. In addition, it offers a lower rate of relapse. This therapeutic benefit has been attributed to a cytoprotective and demulcent action. Moreover bismuth acts as an antimicrobial agent, suppressing the organism Helicobacter pylori which occupies a central place in contemporary views on pathophysiology of ulcer disease. Side effects so far reported have been very infrequent mild and transient when the drug is used at low dosage providing blood-bismuth concentration above toxic values. Colloidal bismuth subcitrate complies to the requirements for a modern drug insofar as it is prescribed in period no longer than 6-8 weeks, followed by 8 weeks bismuth-free intervals.

Bismuth↗