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M Soos

Publications and source records attributed to M Soos.

13 recordsLinked to original sources
PubMed2006

Population balance modeling of aggregation and breakage in turbulent Taylor-Couette flow.

An experimental and computational study of aggregation and breakage processes for fully destabilized polystyrene latex particles under turbulent-flow conditions in a Taylor-Couette apparatus is presented. To monitor the aggregation and breakage processes, an in situ optical imaging technique was used. Consequently, a computational study using a population balance model was carried out to test the various parameters in the aggregation and breakage models. Very good agreement was found between the time evolution of the cluster size distribution (CSD) calculated with the model and that obtained from experiment. In order to correctly model the left-hand side of the CSD (small clusters), it was necessary to use a highly unsymmetric fragment-distribution function for breakage. As another test of the model, measurements with different solid volume fractions were performed. Within the range of the solid volume fractions considered here, the steady-state CSD was not significantly affected. In order to correctly capture the right-hand side of the CSD (large aggregates) at the higher solid volume fraction, a modified aggregation rate prefactor was used in the population balance model.

Image Processing, Computer-Assisted↗
PubMed2002

Genetic variants of insulin receptor substrate-1 (IRS-1) in syndromes of severe insulin resistance. Functional analysis of Ala513Pro and Gly1158Glu IRS-1.

AIMS: To define further the role of IRS-1 mutations in human syndromes of severe insulin resistance. METHODS: The IRS-1 gene was scanned for mutations in 83 unrelated affected subjects and 47 unaffected individuals using fluorescent single-strand conformation polymorphism (fSSCP) analysis. A novel heterozygous mutation, Gly1158Glu, was found in one affected subject. Four and two subjects were heterozygous for the previously reported variants Gly972Arg and Ala513Pro, respectively. The previously identified variant Gly819Arg was found in one affected and one unaffected subject. While Gly972Arg has been described to alter the signalling properties of IRS-1, no functional studies of Ala513Pro or Gly1158Glu have been reported. RESULTS: Chinese hamster ovary (CHO) cells stably over-expressing the insulin receptor were transiently transfected with vectors expressing either wild-type, Glu1158 or Pro513 IRS-1. A modest increase in insulin-stimulated tyrosine phosphorylation of Glu1158 IRS-1 was observed. However, this did not result in any significant change in the association of Grb2 or the p85 alpha subunit of PI3-kinase or of PI3-kinase activity. In parallel studies, the Pro513 IRS-1 variant was indistinguishable from wild-type IRS-1. CONCLUSIONS: While subtle effects of these variants cannot be excluded in this system, it is unlikely that these variants are responsible for the extreme insulin resistance seen in the subjects harbouring them. Although IRS proteins play a central role in insulin signalling, functionally significant mutations in the IRS-1 gene are a rare cause of human syndromes of severe insulin resistance.

Animals↗
PubMed2000

Natural variants of human p85 alpha phosphoinositide 3-kinase in severe insulin resistance: a novel variant with impaired insulin-stimulated lipid kinase activity.

AIMS/HYPOTHESIS: Phosphoinositide 3-kinase (PI 3K) plays a central part in the mediation of insulin-stimulated glucose disposal. No genetic studies of this enzyme in human syndromes of severe insulin resistance have been previously reported. METHODS: Phosphoinositide 3-kinase p85 alpha regulatory subunit cDNA was examined in 20 subjects with syndromes of severe insulin resistance by single strand conformational polymorphism and restriction fragment length polymorphism analyses. Insulin-stimulated phosphoinositide 3-kinase activity and recruitment into phosphotyrosine complexes of variants of p85 alpha were studied in transiently transfected HEK293 cells. Phosphopeptide binding characteristics of wild-type and mutant p85 alpha-GST fusion proteins were examined by surface plasmon resonance. RESULTS: The common p85 alpha variant, Met326I1e, was identified in 9 of the 20 subjects. Functional studies of the Met326Ile variant showed it to have equivalent insulin-stimulated lipid kinase activity and phosphotyrosine recruitment as wild-type p85 alpha. A novel heterozygous mutation, Arg409Gln, was detected in one subject. Within the proband's family, carriers of the mutation had a higher median fasting plasma insulin (218 pmol/l) compared with wild-type relatives (72 mol/l) (n = 8 subjects, p = 0.06). The Arg409Gln p85 alpha subunit was associated with lower insulin-stimulated phosphoinositide 3-kinase activity compared with wild-type (mean reduction 15%, p < 0.05, n = 5). The recruitment of Arg409Gln p85 alpha into phosphotyrosine complexes was not significantly impaired. GST fusion proteins of wild-type and mutant p85 alpha showed identical binding to phosphopeptides in surface plasmon resonance studies. CONCLUSION/INTERPRETATION: Mutations in p85 alpha are uncommon in subjects with syndromes of severe insulin resistance. The Met326Ile p85 alpha variant appears to have no functional effect on the insulin-stimulated phosphoinositide 3-kinase activity. The impaired phosphoinositide 3-kinase activity of the Arg409Gln mutant suggests that it could contribute to the insulin resistance seen in this family.

Adult↗
PubMed1997

Differential signaling to glycogen synthesis by the intracellular domain of the insulin versus the insulin-like growth factor-1 receptor. Evidence from studies of TrkC-chimeras.

Insulin and insulin-like growth factor-1 (IGF-1) have similar cell-surface receptors yet subserve different physiological functions. To examine whether these differences relate to intrinsic signaling properties of the intracellular domains of their respective receptors, chimeric receptors were constructed using the extracellular domain of the neurotrophin-3 (NT-3) receptor, TrkC, and the intracellular domain of either the insulin receptor or the IGF-1 receptor. TrkC-IR (TIR) and TrkC-IGF-1R (TIGR) were stably expressed in 3T3-L1 cells. While TIR and TIGR cell lines expressing similar numbers of chimeric receptors showed a similar dose-response relationship in NT-3 stimulated DNA synthesis, NT-3 stimulated glycogen synthesis was greater in TIR than in TIGR cells (maximum TIGR response was 35% of maximum TIR response). Additionally, the concentration of NT-3 at which significant stimulation of glycogen synthesis was seen was 0.1 ng/ml in TIR and 1 ng/ml in TIGR cells. Basal levels of thymidine incorporation but not glycogen synthesis were consistently higher in TIR than in TIGR expressing cells. No detectable basal autophosphorylation of chimeric receptors was seen in any of the cell lines. However, exposure of cell lines to the phosphatase inhibitor bisperoxovanadate resulted in greater basal autophosphorylation of the TIR and endogenous murine IR than the TIGR and endogenous murine IGF-1R. Thus, in this system, the intracellular domain of the IR appears to couple more effectively to glycogen synthesis than that of the IGF-1R, whereas the intracellular domains of both receptors have a similar capacity to stimulate DNA synthesis.

3T3 Cells↗
PubMed1984

A rapid, sensitive two-site immunometric assay for TSH using monoclonal antibodies: investigation of factors affecting optimisation.

Twenty-three monoclonal antibodies specific for human thyrotropin (TSH) have been prepared and characterised. Four different epitopes have been identified, 3 of which are sufficiently distinct to allow simultaneous binding of the corresponding antibodies. Only 1 epitope is expressed on free TSH beta-subunit. The best antibodies have affinities for TSH approaching 10(11) M-1 and cross-reactions with lutropin and chorionic gonadotropin of 0.2% or less. A 2-site immunoradiometric assay for TSH was established using 2 monoclonal antibodies, one of which was absorbed to plastic tubes and the other labelled with 125I. Several parameters affecting assay performance were investigated, including conditions for adsorption of antibodies to various plastics, selection of antibody combinations, concentration of labelled antibody and incubation protocol. The optimised assay covered a working range of 1-60 mU/1 (0.17-10 ng/ml) TSH in a 4 h, single incubation protocol, with no significant interference from other glycoprotein hormones at their maximum physiological or pathological concentrations.

Adsorption↗
PubMed1984

The existence and properties of two dimers of rat liver ecto-5'-nucleotidase.

Immunoaffinity-purified rat liver 5'-nucleotidase contained two subunits of Mr 70 000 (alpha) and 38 000 (beta). Charge-shift electrophoresis and chemical cross-linking revealed that approx. 80% of the solubilized enzyme activity occurred as an alpha alpha-dimer of Mr 140 000. The remaining 20% was an alpha beta-dimer of Mr 108 000. The beta-subunit did not possess enzymic activity. Peptide mapping and immunoblotting with antibodies against the alpha- and beta-subunits showed that the beta-subunit was homologous with a part of the alpha-subunit. Three monoclonal antibodies against rat liver 5'-nucleotidase were characterized as binding to the extracellular domain of the enzyme. All three monoclonal antibodies and concanavalin A bound to the alpha-subunit, but no binding could be detected to the beta-subunit. It was therefore concluded that the beta-subunit was a fragment of an alpha-subunit that had lost an extracellular domain. Both forms of the enzyme occurred in freshly solubilized membrane preparations as well.

5'-Nucleotidase↗
PubMed1983

Characterisation of monoclonal antibodies for human luteinising hormone, and mapping of antigenic determinants on the hormone.

Twelve mouse monoclonal antibodies for human luteinising hormone were produced. The affinities varied from 4 X 10(7) to 1 X 10(10) l/mol. The specificity of each antibody was assessed by determining the relative reactivities with luteinising hormone, thyroid stimulating hormone, follicle stimulating hormone and chorionic gonadotrophin. Six antibodies bound to the alpha-subunit as shown by similar reactivity with all hormones, and the remainder to the beta-subunit as shown by specificity for luteinising hormone. This latter group of antibodies cross-reacted only weakly with thyroid stimulating hormone (approximately 10%) and follicle stimulating hormone (approximately 3%). Three of these antibodies also showed low reactivity towards chorionic gonadotrophin (less than 10%), though the others did not (80-300%). The ability of different antibodies to bind simultaneously to luteinising hormone was examined and it was shown that several distinct antigenic determinants existed on both subunits. The characterisation of monoclonal antibody binding sites is discussed in relation to the use of antibodies in two-site immunoradiometric assays.

Animals↗
PubMed1982

Characterization of monoclonal antibodies directed against human thyroid stimulating hormone.

Monoclonal antibodies directed against human thyroid stimulating hormone (TSH) were obtained from hybrid myelomas, following fusion of mouse NSI myeloma cells with mouse spleen cells. Ten different antibodies were obtained from 4 separate fusions. Eight antibodies were of the IgG1 subclass. Affinities of antibodies for TSH were in the range 2 x 10(8)-5 x 10(10) M-1. Five of the antibodies were specific for TSH and did not react with LH, FSH or hCG. The remaining antibodies reacted with all these hormones and were assumed to recognise their common (alpha) subunit. The 5 specific antibodies fell into 3 subgroups recognising distinct antigenic determinants, whereas the 5 non-specific antibodies recognised a single determinant or closely related set of sites. It is concluded that these antibodies should be valuable reagents for use in sensitive and specific two-site immunoradiometric assays.

Animals↗
PubMed1981

Mapping by gene dosage, using aneuploid human lymphoid cell lines.

Human lymphoblastoid cell lines evolve in vitro by the emergence of successive waves of clones which are often chromosomally marked. This offers the opportunity to compare tissue samples of the same genetic origin but differing in certain defined parts of the karyotype. Using selected sets of lines in which the members of genetically matched pairs differed in the number of copies of 8p or of 12p, levels of GSR and LDH B respectively have been shown to correlate with the specific chromosome aberrations, supporting existing data on the regional assignment of these two structural loci. This approach represents a useful addition to established methods for human gene mapping.

Aneuploidy↗
PubMed1980

Trisomy 8. Report of a mosaic human male with near-normal phenotype and normal IQ, ascertained through infertility.

Trisomy 8, in mosaic or non-mosaic form is an extremely rare chromosomal condition in man. Liveborn subjects usually present with mental retardation, bone and joint anomalies and a variety of other physical anomalies. The mental retardation associated with the condition is, however, usually moderate compared to that found in other viable human autosomal trisomic conditions. The present report describes a trisomy 8 mosaic male subject with normal IQ and near-normal phenotype, ascertained through infertility. Chromosome studies on peripheral blood lymphocytes reveal a pure trisomy 8 constitution; cultured skin fibroblasts show 46,XY/47,XY+8 mosaicism. At meiosis, the extra No. 8 chromosome is missing from the germ line. The testicular histology indicates a germ cell maturation arrest in many spermatocytes and the patient is severely oligospermic. Biochemical studies to assay levels of glutathione reductase, a red cell enzyme, the gene for which resides in chromosome 8, show increased levels in the trisomy 8 patient compared with controls.

Adult↗