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M Lyon

Publications and source records attributed to M Lyon.

34 records · Page 2Linked to original sources
PubMed1987

Identification of an extended N-acetylated sequence adjacent to the protein-linkage region of fibroblast heparan sulphate.

The distribution of N-sulphate groups within fibroblast heparan sulphate chains was investigated. The detergent-extractable heparan sulphate proteoglycan from adult human skin fibroblasts, radiolabelled with [3H]glucosamine and [35S]sulphate, was coupled to CNBr-activated Sepharose 4B. After partial depolymerization of the heparan sulphate with nitrous acid, the remaining Sepharose-bound fragments were removed by treatment with alkali. These fragments, of various sizes, but all containing an intact reducing xylose residue, were fractionated on Sephacryl S-300 and the distribution of the 3H and 35S radiolabels was analysed. A decreased degree of sulphation was observed towards the reducing termini of the chains. After complete nitrous acid hydrolysis of the Sepharose-bound proteoglycan, analysis of the proximity of N-sulphation to the reducing end revealed the existence of an extended N-acetylated sequence directly adjacent to the protein-linkage sequence. The size of this N-acetylated domain was estimated by gel filtration to be approximately eight disaccharide units. This domain appears to be highly conserved, being present in virtually all the chains derived from this proteoglycan, implying the existence of a mechanism capable of generating such a non-random sequence during the post-polymeric modification of heparan sulphate. Comparison with the corresponding situation in heparin suggests that different mechanisms regulate polymer N-sulphation in the vicinity of the protein-linkage region of these chemically related glycosaminoglycans.

Acetylation↗
PubMed1987

Patterns of porphyrin accumulation in response to xenobiotics. Parallels between results in chick embryo and rodents.

Our objective was to determine whether patterns of porphyrin accumulation produced by chemicals in chick embryo hepatocyte culture would indicate which enzyme of heme biosynthesis was inhibited. The ferrochelatase-inhibitory potency and porphyrin patterns produced by DDC, TTMS, and their analogues were studied. The protoporphyrin:coproporphyrin ratio observed was found to correlate with ferrochelatase-inhibitory activity. The results obtained in chick embryo with TTMS and DDC parallel those found in rodents. Griseofulvin has been shown to lower ferrochelatase activity and to cause the accumulation of protoporphyrin in rodent liver. In chick embryo liver cell culture, however, coproporphyrin, uroporphyrin, and heptacarboxylic acid porphyrin accumulate and ferrochelatase activity is not lowered. Uroporphyrin, heptacarboxylic acid porphyrin, and coproporphyrin are the major porphyrins to accumulate in response to PAHs (for example, 3,3',4,4'-TCBP in chick embryo liver cell culture). This may be explained by inhibition of UROD, which has been observed in chick embryo and rodent liver. Some chemicals, such as phenobarbital and nifedipine, cause the accumulation of these porphyrins in chick embryo liver cell culture, and this is explained by inhibition of UROD. These chemicals have not been reported to interfere with heme biosynthesis in the intact chick embryo or rodents; possibly protective mechanisms that are not available in the cell culture system are operative in the intact animal. It was concluded that porphyrin patterns may serve as a guide to which enzyme of heme biosynthesis is inhibited in chick embryo liver cell culture. The results obtained in the culture system with certain chemicals, such as DDC and TTMS analogues and PAHs, correspond with results in rodents. In other cases, such as with griseofulvin, the results do not correspond.

5-Aminolevulinate Synthetase↗
PubMed1986

Specific chemical modifications of link protein and their effect on binding to hyaluronate and cartilage proteoglycan.

Specific chemical modifications of amino acid residues were performed on purified, native link protein from bovine articular cartilage. The effects of these on link protein's interactions with hyaluronate and bovine articular cartilage proteoglycan were assayed by gel chromatography. Interaction with hyaluronate was significantly perturbed by modification of lysine, arginine, tyrosine and aspartic/glutamic acid residues, but not histidine and tryptophan residues. No free, accessible sulphydryl group was found on native link protein. The requirement for unmodified lysine and arginine residues resembles that of the hyaluronate-binding site of pig laryngeal cartilage proteoglycan (Hardingham, T.E., Ewins, R.J.F. and Muir, H. (1976) Biochem. J. 157, 127-143). In contrast, proteoglycan binding was only significantly perturbed by the loss of arginine residues. This resistance may reflect hydrophobicity of the binding site or masking of the site from chemical modification by link protein self-association. Amidation of carboxyl groups, which destroyed hyaluronate binding but left proteoglycan binding intact, provides a means of generating a monofunctional link protein molecule of potential use in proteoglycan aggregation studies.

Acetylation↗
PubMed1986

Characterization of two murine monoclonal antibodies (P10, P12) directed against different determinants on human blood platelet thrombospondin.

Thrombospondin, a 450-kDa glycoprotein composed of three disulphide linked chains, is located in human blood platelet alpha-granules and is released from platelets upon stimulation. This glycoprotein is thought to play a major role in platelet aggregation. The aim of this study was to characterize two monoclonal antibodies (P10 and P12) directed against human blood platelet thrombospondin. When the released material obtained after stimulation of platelets with thrombin in the presence of 2 mM calcium was immediately treated with EDTA, labelled with 125I and incubated with monoclonal antibodies P10 and P12, both immunoprecipitated a major labelled protein band with a molecular mass of 160 kDa and a weaker band at 146 kDa, as analysed on reduced dodecyl sulphate/polyacrylamide gels. The major band corresponds in molecular mass to the thrombospondin subunits. If, however, the released material was left in the presence of Ca2+ for 48 h, then the main band was at 130 kDa and in addition one minor protein band (75 kDa) was immunoprecipitated by P10 whereas P12 recognized two minor protein bands (75 and 60 kDa). When P10 and P12 were incubated with 125I-labelled platelet releasates treated for 48 h at 4 degrees C with 10mM EDTA, three major protein bands (160, 146 and 130 kDa) were immunoprecipitated in addition to the minor bands mentioned above. These results indicate that thrombospondin is probably degraded by the endogenous platelet calcium-dependent protease. Investigation of tryptic peptide fragments of thrombospondin isolated by fast protein liquid chromatography showed that 125I-labelled antibody P10 bound to 400-kDa and 120-kDa fragments whereas 125I-labelled P12 only recognized a 400-kDa fragment. Competition studies involving solid-phase antibody binding and double antibody sandwich assays showed that P10 and P12 were directed against different determinants of thrombospondin. Purified thrombospondin, isolated in the presence of calcium, either directly or after treatment with EDTA, haemagglutinated trypsinized, formaldehyde-fixed sheep erythrocytes identically. The haemagglutination activity of EDTA-treated thrombospondin was inhibited by P10 and enhanced by P12. On the other hand, P10 and P12, despite their binding to calcium-treated thrombospondin, had no effect on its haemagglutination activity. Monoclonal antibodies P10 and P12 could be useful tools to investigate the role of thrombospondin in platelet aggregation.

Antibodies, Monoclonal↗
PubMed1986

Stereotyped responding by schizophrenic outpatients: cross-cultural confirmation of perseverative switching on a two-choice task.

Some theoretical implications from amphetamine-based models of psychosis were tested during a study of stereotyped responding by schizophrenic patients. Non-institutionalized Danish schizophrenic outpatients (N = 17) and their matched normal controls were asked to guess on which side (R or L) a cross (+) would appear on a computer screen. The sequence of cross positions was random. Multiple analyses of the patients' responses revealed a significantly greater number of single alterations (RLRL), while the matched controls displayed no such tendency. Controls showed instead, significantly more right side repetitions (RRRR) and more frequent double alterations (RRLL and LLRR). The patient response sequences were similar to those seen in an earlier study by Frith and Done (Psychol Med, 13, 779-786, 1983), but some control group differences emerged. Parallels are drawn between the development of perseverative response switching in schizophrenics and predictions derived from the Lyon-Robbins theory of amphetamine-induced stereotypy.

Adult↗
PubMed1979

Benzodiazepine receptors in the brain as affected by different experimental stresses: the changes are small and not undirectional.

Rats and mice were exposed to several different stress situations to investigate whether brain benzodiazepine receptors were sensitive to altered external or internal environmental circumstances. All stresses were applied for several days. Electrical foot shock and post-natal isolation of newborn pups resulted in small (7--25%; P less than 0.05--0.001) decreases in benzodiazepine receptor binding in some cerebral cortex or hippocampal areas while immobilization stress resulted in a small (9%; P less than 0.05) increase in frontal cortex. Other brain areas (i.e., striatum, cerebellum, pons-medulla, and occipital cortex) and other stress forms (isolation of male mice, forced swimming in cold water, or chronic amphetamine intoxication) did not change receptor binding. The effect of prolonged stress on benzodiazepine receptors is complex and not very pronounced.

Aggression↗
PubMed1978

Evidence for cell loss in corpus striatum after long-term treatment with a neuroleptic drug (flupenithixol) in rats.

The number of nerve cells in two different areas of the corpus striatum (i.e., ventrolateral and dorsomedial) was estimated in rat brain after long-term (36 weeks) treatment with the neuroleptic flupenthixol. Nine rats were given weekly injections of 4 mg/kg flupenthixol dissolved in Viscoleo i.m., and seven rats received Viscoleo alone. Fourteen to 18 weeks after the last drug injection, the animals were decapitated and half of each brain was fixated with formalin for cell-count analysis and the remaining half used for a biochemical analysis (Nielsen, 1977). Separate cell counts in the ventrolateral and dorsomedial corpus striatum yielded a significant cell loss of approximately 10%, but only in the ventrolateral striatum of treated animals. These results suggest at least one concrete anatomical basis for the behavioral and biochemical deficits found in the same animals, as reported earlier. The results further suggest that persistent irreversible anatomical changes can follow long-term neuroleptic treatment. The inconsistencies of results regarding cell loss in the corpus striatum may be due to neglect of dorsal-ventral structural differences in corpus striatum.

Animals↗
PubMed1978

Interactions of Shope papilloma virus with some other DNA viruses.

The interactions of Shope papilloma virus (SPV) with primate and rabbit cells in tissue culture have been investigated. The rabbit cell cultures were derived from normal epidermis, from SPV-infected epidermis, from SPV-induced papillomas, and from an SPV-associated carcinoma. None of these cell cultures, whether infected in vitro with SPV or derived from tissues infected in vivo, ever produced infectious SPV or even detectable viral antigens. Some other DNA viruses behaved differently in cells which had been in previous contact with SPV either in vitro or in vivo. Adenovirus type 5 multiplies better in human cells infected 24 h previously with SPV than in the untreated controls. The production of infectious virions of either herpes simplex virus or Shope fibroma virus is reduced in cells derived from SPV-induced papillomas or carcinoma, due, apparently, to a defect in viral maturation. Of the rabbit cells, only those derived from in vivo infected tissue, or those previously infected in vitro with SPV, could be transformed by SV40. The rabbit cell lines derived from papillomas or carcinoma differed from their counterparts derived either from normal epidermis or from tissue infected 24 hrs before biopsy, in their karyotype, and in their ability to grow in soft agar. Similar karyotypic alterations were induced in cells derived from healthy epidermis by infection in vitro with SPV.

Adenoviruses, Human↗
PubMed1976

[Effects of colchicine, vinblastine and mercury p-hydroxybenzoate on the multiplication of adenovirus 5 in HeLa cells].

After 30 min incubation at 37 with 10(-4) M PHMB (p-hydroxymercuribenzoate), monolayers of HeLa cells are not affected; after 3 h exposure to 10(-5) M colchicin or 2.5 X 10(-5) M vinblastine, HeLa cells are not altered morphologically but the number of cells is decreasing between 1 and 2 days post treatment. When cells are kept in suspension after trypsinization, their ability to adhere to the Petri dishes is not altered with 10(-4) M PHMB but only 50% of the cells are able to attach after treatment with colchicine or vinblastine. Adenovirus type 5 is unsensitive to the effect of colchicine and vinblastine at various concentrations, after 3 h incubation at 37. With 10(-3) M PHMB, the virus is inactivated, infectivity and hemagglutinating activity are almost abolished but the particles are unsensitive to pancreatic DNase, so that the structure of the viral particle is intact. This effect is reduced with 10(-4) M PHMB. The adenovirus 5 multiplication is not affected when HeLa cells are treated with 10(-5) M colchicine or 2.5 X 10(-5) M vinblastine, before and during adsorption of the virus. The viral production decreases after 24 h treatment with colchicine or vinblastine. Treatment with 10(-4) M PHMB does not influence intra- or extracellular viral yield.

Adenoviridae↗
PubMed1975

[Immunofluorescence study of the migration of adenovirus 5 in HeLa cell cytoplasm during the penetration phase].

Using the indirect immunofluorescence technique in presence of anti-adenovirus-5 antibody, fluorescent spots were observed two hours after adsorption at 4 degrees C onto HeLa cells on the surface of the cells. The spots subsequently became intracytoplasmic and persisted about 7 to 8 h. Intense fluorescence was further observed in the whole cytoplasm and in the nucleus 12 h following the injection.

Adenoviridae↗
PubMed1975

A prospective evaluation of the lecithin/sphingomyelin ratio and the rapid surfactant test in relation to fetal pulmonary maturity.

Fetal lung maturity was correlated to the results of amniatic fluid analysis in 578 samples obtained over a 2 1/2 year interval. Lecithin/sphingomyelin (L/S) ratios obtained by planimetric and densitometric methods were compared to the rapid surfactant test (RST). Both the planimetric L/S ratio (P L/S) and the densitometric L/S ratio (D L/S) correlated positively in a highly significant fashion with the RST. Both RST and D L/S were reliable in predicting fetal lung maturity (99 to 100 per cent, respectively). The RST was the most reliable test for fetal lung immaturity (69 per cent). Therefore, this series indicates that the RST could be used as a primary method with the D L/S being useful as an additional indicator of fetal maturity when the RST was intermediate, or the sample contaminated with blood and/or meconium.

Amniotic Fluid↗
PubMedDate not supplied

[Interactions of Shope papilloma virus with SV40 in adult domestic rabbit cell lines derived from normal skin or from Shope papilloma virus infected skin (author's transl)].

Three cell lines from adult domestic rabbit are infected with SV40: LP 17 and LP 45 derived from normal skin and LP 42 PS derived from skin infected for 24 h with Shope papilloma virus. The fibroblastic morphology of the cultures is not changed. SV40 is not recovered and T antigen is only detected in LP 42 PS cell line after 29 passages. To know if Shope papilloma virus facilitates penetration of SV40, cultures of LP 45 are first infected with Shope papilloma virus for 2 h and for 24 h, then superinfected with SV40. There is no cellular alteration, and T antigen induced by SV40 is only detected in cells pretreated for 24 h with Shope papilloma virus, after 20 passages. When cultures LP 45 are infected with Shope papilloma virus neutralized with a high titer antiserum and superinfected with SV40, T antigen is not detected. Superinfected cells containing specific SV40 T antigen do not induce tumors either in new born hamsters or in rabbits but they are able to grow in colonies in soft agar. LP 42 PS cell line and LP 45 cells infected with Shope papilloma virus for 24 h containe Shope papilloma virus genome which is able to modify the permissivity of rabbit cells to SV40.

Animals↗