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Biomedical subjects

G Biserte

Publications and source records attributed to G Biserte.

At least 55 records · Page 3Linked to original sources
PubMed1979

Amino acid sequence of rat thymus histone H2B and identification of the in vitro phosphorylation sites.

The amino acid sequence of rat thymus histone obtained in highly purified form by preparative electrophoresis, was determined. This sequence is identical to the sequence of calf thymus histone H2B. The in vitro phosphorylation of the rat histone with a cyclic AMP-dependent protein kinase isolated from rat pancreas led to the identification of four sites of phosphorylation: two major ones, at serine residues 32 and 36, and two minor ones, specific of the rat protein kinase, at serine residues 87 and 91.

Amino Acid Sequence↗
PubMed1979

On the mechanism of the tetrahydropteridine cofactor oxidation in aerobic and H2O2-peroxydase media.

It is commonly postulated that the enzymatic hydroxylation of phenylalanine, tyrosine and tryptophan involves the concomitant oxidation of a tetrahydropteridinic cofactor to an unstable quinonoid product, converted to the initial compound under the catalytic action of dihydropteridine reductase. We now report UV, NMR, mass spectrum and spectroscopic studies of 2-amino-4-hydroxy-6,7-dimethyl-5, 6, 7, 8-tetrahydropteridine oxidation process either by atmospheric O2 or by the H2O2-peroxidase system. No quinonoid form was visualized and, moreover, the spectral characteristics of UV absorbance spectra, initially reported as specific for the quinonoid form, are related to other oxidation products whose formation is explained here.

Hydrogen Peroxide↗
PubMed1979

Cylindrical laminated bodies in nickel-subsulphide-induced rhabdomyosarcoma in rabbits.

The induction of rabbit rhabdomyosarcoma was obtained after intramuscular implantation of a large quantity of very pure nickel subsulphide, though until the present time the rabbit was considered refractory to Ni3S2 tumorigenesis. These tumors are similar to those induced in rats under the same conditions. Four different cell types were observed: small polygonal cells, small elongated cells, giant cells, and mature myofibers. Electron microscopy reveals a complete disorientation of myofibrils in mature myoblasts. Giant cells appear by pluripolar endomitosis and always contain myofibrillar structures, but M-lines and Z-lines are not present in these cells. Cylindrical laminated bodies were observed very often in all four cell types. They are formed of 4 nm fibrils arranged in crossed position in each lamella. Some of these paracrystalline structures were also observed in nuclei. The laminated bodies are considered to be abnormal formations of contractile proteins produced during tumoral myofibrillar differentiation.

Animals↗
PubMed1978

[Biochemical study of the glycosaminoglycan peptides obtained from osteoarthrotic and normal femoral heads (author's transl)].

Glycosaminoglycan peptides prepared by papain hydrolysis of different regions were obtained from osteoarthrotic and normal human femoral heads. Data obtained in these experiments show that in osteoarthrosis a decrease in keratan sulfate and an increase in chondroitin sulfate are observed. Since keratan sulfate appeared to play an important role in proteoglycan aggregation, we suggest that the keratan sulfate decrease is one of the factors involved in the cartilage disorder observed in patients suffering from osteoarthrosis.

Aged↗
PubMed1978

Ultrastructural investigation of NI3S2-induced rhabdomyosarcoma in Wistar rat: comparative study with emphasis on myofibrillar differentiation and ciliar formation.

Nickel-sulfid-induced rhabdomyosarcomas were studied by both light and electron microscopy. The successive stages differentiating tumor cells were described, and two differentiation types of rhabdomyoblasts could be observed 1) with the characteristic pattern of fetal differentiation--i.e., myofilament apparation before Z-line formation--and 2) with synthesis of these elements in the reverse order. An organized T-system is not evident. The sarcoplasmic reticulum is irregular and its cisternae often contain a granular substance or microcrystals. The only well-developed element of tumoral myofibrils is the Z-line; the other zones of sarcomeres are seldom clearly defined. Several unusual granular structures were observed. No virus particles were found. The formation of cilia appears only in interphase rhabdomyoblasts and has to be considered as aberrant and temporary formations from centrioles. They generally possess a "9 + 0" microtubular pattern, but often could be observed as rudimentary forms with a "7 + 2" microtubular arrangement. This case is another example demonstrating the relationship of cilia formation with cell division, especially after suppression of mitotic control. The histology and the electron microscopy results are discussed in relation to the differentiation pattern and the ultrastructural features of embryonic, regenerating and pathological muscle differentiating in vitro.

Animals↗
PubMed1978

Phenylalanine analogues as inhibitors of phenylalanine-hydroxylase from rat liver. New conclusions concerning kinetic behaviors of the enzyme.

The conversion of phenylalanine to tyrosine is catalysed by phenylalanine-hydroxylase. The substrate phenylalanine shows two effects: (1) allosteric transition at low phenylalanine concentrations, (2) excess substration inhibition. The molecular structure of phenylalanine-hydroxylase has not yet been elucidated. However, a tetrameric structure has been proposed. The Kinetic analysis with respect to substrate analogues suggest the existence of three types of sites on each protomer: (1) a catalytic site, (2) a non-competitive inhibitory site, (3) a positive cooperative site. Use of the enzyme's natural cofactor, tetrahydrobiopterin, has been emphasized to ensure good interpretation of the kinetic results of the phenylalanine-hydroxylase effectors.

Allosteric Site↗
PubMed1978

Primary structure of chicken erythrocyte histone H2A.

The complete amino acid sequence (128 residues) of the chicken erythrocyte histone H2A was deduced from the data provided by structural studies on the tryptic peptides from the maleylated histone and of the peptides obtained by thermolysin digestion of the native protein. The sequence of chicken histone H2A differs from the calf homologous histone by the deletion of one residue of histidine at position 123 or 124 and three conservative substitutions: a residue of serine replaces a residue of threonine at position 16, a residue of aspartic acid replaces a residue of glutamic acid at position 121 and a residue of alanine replaces a residue of glycine at position 128.

Amino Acid Sequence↗
PubMed1978

Primary structure of histone H2A from gonad of the sea urchin Psammechinus miliaris.

The complete amino acid sequence (125 residues) of sea urchin histone H2A has been established by structural studies of peptides derived from tryptic and chymotryptic cleavage of the maleylated protein and from thermolysin cleavage of the intact protein. By comparison with calf homologous histone, the basic amino-terminal and carboxy-terminal parts of the protein show 11 substitutions and 4 deletions. The remainder of the sequence, mostly hydrophobic, is almost completely unchanged.

Amino Acid Sequence↗
PubMed1977

Rat alpha-fetoprotein heterogeneity. Comparative chemical study of the two electrophoretic variants and their Ricinus lectin-binding properties.

Two electrophoretic forms of rat alpha-fetoprotein were purified using immunosorbent chromatography and preparative electrophoresis on polyacrylamide gel slabs. Some of their respective chemical properties and their affinity for the Ricinus communis lectin (RCAI) were compared. Electrophoresis on polyacrylamide gradient gel in the presence of sodium dodecyl sulfate indicated a slight difference in molecular 74 000 for the slow alpha-fetoprotein (AFPA) and 72000 for the fat alpha-fetoprotein (AFPB). no significant difference in amino acid composition between AFPA and AFPB was found. A residue of valine was identified at the C-germinal end of both alpha-fetoproteins. The analysis of the CNRr-cleavage products reveals slight differences between AFPS and AFPB. The slow moving alpha-fetoprotein could be further fractionated on RCAI-sepharose column in two components, AFPA1 and AFPA2 differing by their sialic acid content.

Amino Acid Sequence↗