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Biomedical subjects

M Fournier

Publications and source records attributed to M Fournier.

At least 307 records · Page 17Linked to original sources
PubMed1977

Aminoacylation of tRNA Trp from beef liver, yeast and E. coli by beef pancrease tryptophan-tRNA ligase. Stoichiometry of tRNATrp binding.

The Michaelis constants and the maximum velocities in the aminoacylation reaction of tRNATrp from beef liver, yeast and E. coli by pure beef pancreas tryptophan-tRNA ligase show that this mammalian enzyme recognizes and charges the two eucaryotic tRNAs with the same efficiency. The rate of aminoacylation of the procaryotic tRNATrp by the enzyme is three orders of magnitude lower. The pH optimum of aminoacylation is 8 for both eucaryotic tRNAs. The optimum magnesium concentration is different. The rate is maximum when magnesium concentration is stoichiometric to ATP concentration for tRNATrp from beef liver and 10 mM above ATP concentration for tRNATrp from yeast. The number of binding sites on the enzyme for the two eucaryotic tRNAs has been measured by equilibrium filtration on Sephadex G-100 and found equal to two.

Adenosine Triphosphate↗
PubMed1977

Bronchial lymphoepithelial nodules in the rat: morphologic features and uptake and transport of exogenous proteins.

Using morphologic and ultrastructural criteria, the present study in the rat was undertaken to distinguish lymphoepithelial modules from lymphoid aggregates and lymph modes, and to demonstrate the uptake and transport of ferritin and latex particles, instilled in the trachea, by the lymphoepithelium. Unlike lymph nodes or lymphoid aggregates, lymphoepithelial nodules can be distinguished by the following characteristics of the lymphoepithelium: it is flattened and devoid of goblet cells; it contains intracellular and "intercellular" vacuoles; occasional macrophage-like cells infiltrates and surrounding lymphocytes clusters can be observed. At any time, no latex particle was found inside or under the lymphoepithelium, but until 1 hour after local instillation, ferritin particles were localized close to the cilia, at the luminal surface of the epithelium, within vesicles at the surface of some cells, and in the intercellular space. Moreover, ferritin particles were consistently present on both sides of the basement membrane after 1 hour. These results suggest that lymphoepithelial nodules may be considered as original structures capable of uptake and transport across the basement membrane of certain foreign materials.

Animals↗
PubMed1977

[Role of an insoluble thymus fraction in the differentiation of T lymphocytes].

An insoluble thymic fraction, free of both thymocytes and thymic hormone, was injected intraperitoneally to C57B1/6 mice. Following this injection, marked changes were noted in thymocyte populations: these consisted mainly in a significant increase of subcapsular prothymocytes, peaking at day 7. These observations were made by histological examination and confirmed by a study of physical characteristics of thymocyte populations. The possibility that this insoluble thymic fraction might have a biologically active component responsible for prothymocytes recruitment is examined.

Animals↗
PubMed1977

Bronchial lympho-epithelial nodules in the rat: definition and morphological characteristics in optical and electron microscopy.

Three type of structures can be distinguished among the bronchial lymphoid tissue: lymph nodes, lymphoids cells aggregates and lymphoepithelial nodules. Such structures are encountered in many species and may be characterized by flattened epithelium, devoid of mucus producing cells, infiltrated with lymphocytes and containing of few ciliated cells. The lymphoepithelium surrounds the nodules, characterized by a high cellular density. Original structures may be observed, mainly inter and intracellular vacuoles. Peripheral lymphatic vessels and high endothelium veins contribute to the important lymphocyte transfer. Electron microscope, studies support the view that lymphoepithelium has an uptake function of particulate matter; more direct evidence is however attempted. An hypothesis of capacity for antigenic recognition of the lymphoepithelium nodules is discussed.

Animals↗
PubMed1976

Purification of tRNATrp, tRNAVal, and partial purification of tRNAIle and tRNAMfet from beef liver.

tRNATrp from beef lever has been purified by classical chromatographical methods. Total tRNA, prepared on a large scale (total aminoacid acceptance 1280 pmol/A260 unit) was submitted to chromatography on benzoylated-DEAE cellulose, then DEAE Sephadex. The major species accepting tryptophan issued from the second chromatography was aminoacylated with [14C] tryptophan and chromatographed on benzoylated-DEAE cellulose. The tRNA carrying the radioactive label was eluted in the ethanolic region. After stripping, the resulting tRNATrp has an acceptance of 1800 pmol/A260 unit. No isoacceptors could be demonstrated by chromatography of the pure species on RCP 5 in 6 M urea. The yield in pure tRNATrp was currently in the range of 25 to 30 percent of the total tryptophan acceptance of the starting curde tRNA.

Amino Acids↗
PubMed1976

[Bronchial lympho-epithelial nodules in the rat. Definition and morphological characteristics in optical and electron microscopy (author's transl)].

Among the bronchial lymphoid tissue, lympho-epithelial nodules are an original component, easily distinguished from other structures, particularly from lymphoid cell infiltrates. Such structures are encountered in many species and may be characterized by a flattened epithelium, containing a few ciliated cells, devoid of mucus producing cells, and infiltrated with lymphocytes. Inter and intracellular vacuoles are described in the lympho-epithelium and the underlying mucosa. Electron microscope studies support the view that lymphoepithelium has a "trapping" function of particulate matter, more direct evidence is however attempted. Peripheral lymphatic vessels and high endothelium veins contribute to the important lymphocyte transfer. An hypothesis of capacity for antigenic recognition of the lymphoepithelial nodule is discussed.

Animals↗
PubMed1976

Thyrotropin deficiency after polonged high levels of plasma thyroid hormones.

In order to elucidate the mechanism of the Farquharson phenomenon, we studied the thyrotropin function in three groups of patients who had had high plasma levels of thyroid hormones for prolonged period of time : 3 patients (group A) had taken thyroid hormones for several years. One month after discontinuation of the treatment two of them were hypothyroid; in both of them plasma TSH did not increase after injection of TRH. Spontaneous recovery occured in those two patients respectively five and nineteen months after the end of the drug administration. One year after having stopped the treatment the third patient was apparently euthyroid; however, she was proved to have a complete TSH deficiency. Group B consisted of 27 patients who were studied after surgical ablation of toxic adenoma. Four of them were hypothyroid one to four months after surgery and had no response to TRH. Fifteen out of the 23 remaining patients were euthyroid but had such a lack of response to TRH from 5 days to one year after surgery. Group C consisted of forty three patients treated for Graves' disease and who had been euthyroid for at least one year following the treatment. Seven of them exhibited no or a subnormal response to TRH. Finally, thirteen patients (from groups A, B and C) who did not respond to TRH were given 10 mg TRH orally twice a day for two weeks. A normalization of the TRH test was then demonstrated in three patients and a partial recovery in three others. Thus, there is a frequent thyrotropin deficiency after prolonged high levels of plasma thyroid hormones which can disappear spontaneously or after chronic TRH administration.

Administration, Oral↗
PubMedDate not supplied

Suppression of avidin processing and presentation by mouse macrophages after sublethal exposure to dieldrin.

The molecular events in macrophage antigen processing and presentation were examined to determine the possible site(s) of cell-xenobiotic interaction. Antigenic processing by mouse peritoneal macrophages of a single protein antigen, avidin, was significantly suppressed following sublethal exposure of animals to an organochlorine pesticide, dieldrin. Exposure of C57B1/6 female mice to dieldrin affected the in vitro uptake of [methyl-14C]avidin by peritoneal macrophages and markedly decreased phagocytosis of fluorescein-labelled microspheres and Salmonella typhimurium. Release of the processed avidin, determined by immunochemical quantification of immunogenic avidin and by bioassay of immunogenicity of the released antigen, was also markedly affected. Dieldrin markedly affected presentation of avidin on the macrophage surface, observed by cytoimmunochemical staining of the antigen with fluorescent antibody and flow cytometry. Inhibition of the release of processed avidin was dieldrin dose- and time-dependent, following single sublethal intraperitoneal (ip) exposure to the pesticide. The antigenic properties of processed avidin, determined by biological assay using lymphocyte cultures of normal C57B1/6 mice primed with avidin, were proportional to the antigen concentration in supernatants of macrophage cultures, for both vehicle controls and dieldrin-exposed animals. This observation and analysis of the kinetics of release of processed avidin by macrophages from control and dieldrin-exposed animals suggested that the release of processed avidin, but not the immunogenicity of the antigen itself, was affected by the pesticide exposure. Generally, impairment of avidin processing and presentation appeared to be more dramatic than other pesticide-related injuries to macrophages, such as the uptake of the antigen. In conclusion, antigen processing could be a sensitive target for dieldrin-related injury of macrophage functional activities, which, in consequence, could produce suppression of the humoral immune response.

Animals↗