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M Simonsen

Publications and source records attributed to M Simonsen.

At least 19 recordsLinked to original sources
PubMed1992

MHC class II beta-chain expression in the rainbow trout.

A cDNA clone corresponding to the MHC class II beta-chain of the rainbow trout (Oncorhynchus mykiss) has been isolated and used in restriction fragment length polymorphism (RFLP) studies in a family of full siblings of rainbow trout. A very simple RFLP pattern was detected, suggesting segregation of a homozygote AA genotype and a heterozygote AB genotype. The MHC class II beta-chain of the rainbow trout seems to be transcribed in the same type of cells as class II genes of higher vertebrates even though the cDNA clone recognizes atypical messenger sizes of 2.2 kb and 3.6 kb in the analysed family. Surprisingly the transcripts seem to be allele-specific for the assigned genotypes.

Amino Acid Sequence↗
PubMed1992

Kinetics and mechanism of proteinase-binding of pregnancy zone protein (PZP). Appearance of sulfhydryl groups in reactions with proteinases.

Proteinase binding by pregnancy zone protein (PZP), an alpha-macroglobulin involves bait region cleavages, association of dimeric-PZP into tetrameric and reaction of internal gamma-glutamyl-beta-cysteinyl thiol esters of PZP with proteinase side chains. The product is an equimolar enzyme-PZP(tetramer) covalently linked complex with four free sulfhydryl groups. The kinetics of the appearances of sulfhydryl groups during the reaction of PZP with chymotrypsin has been investigated using stopped-flow and conventional mixing techniques over a broad concentration range. Thiol ester cleavages followed double exponential decays corresponding with two steps. The faster one resulted in the appearance of three sulfhydryl groups with an observed rate constant, k(obs) = k1.1 + k1.2 delta E, dependent on the excess concentration of chymotrypsin, delta E, and k1.1 = 0.03 s-1 and k1.2 = 4 x 10(4) M-1 s-1. The last sulfhydryl group appeared in a slower step, with similar concentration dependence and k2.1 approximately 0.003 s-1 and k2.2 approximately 5 x 10(3) M-1s-1. Covalent binding of the enzyme apparently was simultaneous with the faster thiol ester cleavage step. Based on these and previous results a model of the reaction mechanism of the proteinase binding reaction of PZP is proposed. It consists of four major steps: (i) Bait region cleavage of PZP-dimers by the enzyme, (ii) fast association of enzyme-PZP(dimer) species with native PZP or with another enzyme-PZP(dimer) compound resulting in release of one of the associated enzyme molecules (iii) reaction of an average of three thiol esters of the enzyme-PZP(tetramer) intermediate with the associated internal enzyme molecule or with an external one. In this step one enzyme molecule becomes covalently linked to the PZP-(tetramer), three sulfhydryl groups appear and the enzymic activity of the bound enzyme molecule decreases to the level of that of the final complex. (iv) Hydrolysis of the last thiol ester and in the presence of excess enzyme, degradation of enzyme-PZP(tetramer) complexes and formation of fragments some of which are the size of PZP(dimer) with enzyme bound.

Amino Acid Sequence↗
PubMed1991

The "adjuvant effect" of the polymorphic B-G antigens of the chicken major histocompatibility complex analyzed using purified molecules incorporated in liposomes.

The polymorphic B-G region of the chicken major histocompatibility complex has previously been shown to mediate an "adjuvant effect" on the humoral response to other erythrocyte alloantigens. We demonstrate here that B-G molecules purified with monoclonal antibodies exert this adjuvant effect on the production of alloantibodies to chicken class I (B-F) molecules, when the two are in the same liposome. The adjuvant effect may in part be mediated by antibodies, since the antibody response to B-G molecules occurs much faster than the response to B-F molecules, and conditions in which antibodies to B-G are present increase the speed of the response to B-F molecules. We also found that the presence of B-G molecules in separate liposomes results in a lack of response to B-F molecules. In the light of this and other data, we consider the possible roles for the polymorphic B-G molecules, particularly for the generation of B cell diversity, in the immune systems of birds and other animals.

Adjuvants, Immunologic↗
PubMed1990

Increased angiogenesis in diabetes.

Rats with streptozotocin-induced diabetes mellitus showed a 3.4-4.5 times increased angiogenic response following mast-cell activation in situ as compared with age-matched normal controls. The test tissue used was the mesenteric window, which we have previously exploited as a quantitative angiogenesis assay. In the present study two independent techniques for quantifying the angiogenic response showed essentially the same result. The finding of a pathologically increased angiogenic reaction in the diabetic animals is noteworthy since some of the most harmful complications of diabetes in man relate to proliferative vascular lesions.

Animals↗
PubMed1990

MHC-like molecules in some nonmammalian vertebrates can be detected by some cross-reactive xenoantisera.

Rabbit antisera raised to human and chicken MHC molecules were used to immunoprecipitate cross-reactive molecules from biosynthetically and cell surface-labeled spleen and/or blood cells of representative vertebrate species. Five major points emerged: 1) There were many nonspecific cross-reactions using these techniques, so various criteria were developed to distinguish these from true MHC-like molecules. 2) Only very small subpopulations of immunogen-specific antibodies cross-reacted with MHC-like molecules in other nonmammalian species. These subpopulations were different for each species and even within a species, sometimes being so limited as to behave like alloantisera. This led to a very scattered pattern of true cross-reactions that sometimes failed to reflect the properties of the bulk antibody population. 3) Antisera containing antibodies to class II beta- and class I alpha-chains cross-reacted better and more widely than those to B-G, class II alpha and, in general, beta 2-microglobulin. 4) Some cross-reactive antibodies were clearly directed to epitopes on the surface of the mature heterodimers, but many seemed to recognize nonlinear cryptic determinants, presumably in the contact regions between the chains. These latter antibodies recognized biosynthetic intermediates and also a variety of unusual cell surface MHC-like molecules present in reptile and amphibian, but absent in the mammal and chicken cells tested. These included E homodimers whose relationship to chicken B-G molecules is unknown. 5) MHC-like molecules were identified in a bird, three reptiles, and two amphibians, but no molecules with the expected properties were found with these reagents in any of the fish tested.

Amphibians↗
PubMed1990

Effects of a multidisciplinary management program on neurologically impaired patients with dysphagia.

Dysphagia is a major problem in patients with neurologic disorders. Aspiration pneumonia and impaired nutritional status are consequences of dysphagia that result in high morbidity and mortality rates. Assessment and treatment of the dysphagic patient by a multidisciplinary team have been advocated but to date the effects of such an approach have not been demonstrated quantitatively. This prospective study was conducted to determine if a dysphagia program would improve patients' caloric intake and body weight, decrease the instances of aspiration pneumonia, or improve patients' feeding ability. Patients were referred from a 26 bed neurology/neurosurgery unit. A time series design was utilized. The control group consisted of 15 patients (mean age = 46.1 years), managed according to the existing ward routine. Subsequently, nursing staff attended a dysphagia training program. Following this, the treated group of 16 patients, (mean age = 49.3 years) was assessed by the dysphagia team, using bedside and videofluoroscopic examinations to determine the specific swallowing disorder. An individualized treatment program was designed for each patient. The groups were compared on the basis of deviation from their baseline weight, deviation from ideal energy intake, and the incidence of aspiration pneumonia. Statistical analysis revealed that the groups were comparable in age, number of days on the study, and Glasgow Coma Scale score; and that a significant weight gain and increase in caloric intake occurred in the treated group. No incidence of aspiration pneumonia was reported in either group. We speculate that this may have been influenced by the meticulousness of the care delivered in an acute unit as well as greater attention to prevention given in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Pregnancy zone protein, a proteinase-binding macroglobulin. Interactions with proteinases and methylamine.

Human pregnancy zone protein (PZP) is a major pregnancy-associated plasma protein, strongly related to alpha 2-macroglobulin (alpha 2M). Its properties and its reactions with a number of enzymes, particularly chymotrypsin, and with methylamine have been investigated. It is concluded that native PZP molecules are dimers of disulfide-bridged 180-kDa subunits and that proteinase binding results in covalent 1:1 (tetrameric)PZP-enzyme complexes. Native PZP is unstable, and storage should be avoided, but when kept unfrozen at 0 degree C most PZP preparations stay native 1-3 months. The reaction of PZP with chymotrypsin involves (i) proteolysis of bait regions, (ii) cleavage of beta-cysteinyl-gamma-glutamyl thiol ester groups, (iii) some change of the conformation and quaternary structure of PZP, and (iv) the formation of covalent 1:1 chymotrypsin-PZP(tetramer) complexes in which chymotrypsin is active but shows less activity than free chymotrypsin. The emission spectra of intrinsic fluorescence show significant differences between the PZP-chymotrypsin complex and its native components, whereas no differences are observed between methylamine-reacted PZP and native PZP. Methylamine reacts with the beta-cysteinyl-gamma-glutamyl thiol ester groups of PZP in a second-order process with k = (13.6 +/- 0.5) M-1 s-1, pH 7.6, 25 degrees C. The reaction product is PZP(dimers); no PZP(tetramers) are formed. The proteinase-binding specificity of PZP is far more restricted than that of alpha 2M. Certain chymotrypsin-like and trypsin-like enzymes are bound much less efficiently than is chymotrypsin itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Chymotrypsin↗
PubMed1989

Specific molecular interaction between the insulin receptor and a D product of MHC class I.

The density of MHC class I was determined on a murine thymoma cell line (R1), an H-2 negative variant (R1E), and R1E-derived cell lines in which H-2 expression was restored by transfection of various MHC class I genes (Db, Kb, and truncated Db) and/or a beta-2-microglobulin gene (beta 2-m; B2). Appreciable MHC class I expression was found on R1 cells and on the variants in which MHC class I expression was restored by transfection of Db/beta 2-m or Kb/beta 2-m genes. Only approximately 20% difference was observed between the number of Db molecules and Kb molecules on the R1E/B2/Db and on R1E/B2/Kb, respectively. However, specific insulin binding was significantly different between these lines. By using a computer assisted curve fitting program, the insulin binding data for R1 and R1E/B2/Db cell lines best fitted a two-site model (K approximately 6 x 10(-9) M for high-affinity sites and a 2 to 3 x 10(-7) M for low-affinity sites), whereas all other lines only expressed one type of insulin binding site. These sites were unrelated to IGF-I and IGF-II receptors. Cross-linking of 125I-labeled insulin demonstrated specific binding of the ligand to a Mr approximately 130,000 dalton band in all lines. In the R1E/B2/Db cells, insulin also cross-linked to cell membrane molecules with Mr approximately 48,000 and approximately 60,000 Da, which were identified by immunoprecipitation to be the H chain of MHC class I and the heavy chain of MHC class I plus beta 2-m, respectively. It is concluded that the insulin receptors in the cell membrane interact specifically with D-products of MHC class I and that class I molecules of MHC may have a crucial role in insulin receptor expression. This may reflect a more general nonimmunologic role of MHC class I.

Animals↗
PubMed1989

On mast cell-mediated mitogenesis in normal and hyperplastic mesenterial windows in female rats.

The outcome of the mast cell-mediated mitogenesis in hyperplastic membranous mesenterial windows of lactating rats as well as in normal mesenterial windows of age-matched and young virgin female rats was studied quantitatively in vivo and in organ culture. Besides elucidating the effect of age and tissue hyperplasia on mitogenic responsiveness, this approach should provide some insight into the pathogenic mechanics of the previously reported supranormal mast cell-mediated mitogenic reaction that emerges in similarly hyperplastic mesenterial windows of diabetic rats. Mast cell secretion was elicited by Compound 48/80 and the histamine release, which was quantified fluorometrically, was unaffected by lactation. The young female rats showed a statistically significant mast cell-dependent mitogenesis taken as the mitotic index and the fraction of the predominating fibroblasts and mesothelial cells in the (S+G2) cell cycle phases after Feulgen-DNA absorption analysis of the cells in situ. Although there was an age-dependent decrease in mitogenesis, the older lactating and non-lactating virgin control rats also showed mast cell-mediated mitogenesis measured as the specific DNA activity. The hyperplastic mesenterial tissue of the lactating animals showed a virtually normal mitogenic reactivity following local mast cell secretion, but at a lower level than in the age-matched controls. This finding suggests that the supranormal mast cell-mediated mitogenesis previously found in the hyperplastic mesenterial windows of diabetic animals is causally related to the diabetic condition rather than to the hyperplastic state of the test tissue.

Animals↗
PubMed1988

Mixed lymphocyte reactions (MLR) in rainbow trout (Salmo gairdneri) sibling.

Suitable conditions for 2 way MLR were determined in random combinations of commercially cultured trout and were then applied to full siblings in two families reared for experimental purposes. The primary aim of the investigation was to determine whether the immunogenetic predictions from mammalian and avian experiments would apply, i.e. (i) that all full sibs, short of rare intra-MHC recombinants, can be assigned to a maximum of four different MHC genotypes, and (ii) that individuals of the same genotype are mutually histocompatible as tested in MLR. If both predictions apply, five or more siblings tested in all pairwise combinations should invariably display compatible pairs, so that a maximum of four groups of mutually incompatible individuals should emerge. The findings did not fit this model, and two alternative immunogenetic models are discussed.

Animals↗
PubMed1987

Analysis of class II genes of the chicken MHC (B) by use of human DNA probes.

Class II genes of the major histocompatibility complex (MHC) in the chicken have been investigated by Southern blot analysis using human cDNA probes for DQ alpha, DQ beta, DR alpha, and DR beta. Both beta probes but not the alpha probes cross-hybridized well with chicken DNA. The results indicated that the beta probes hybridized with at least two beta genes in the chicken MHC and there was no clear indication of a DQ-DR subdivision of chicken class II beta genes. The possibility of using human beta probes for MHC typing in the chicken was tested by using two homozygous individuals for each of 20 different, serologically defined, MHC (B) haplotypes originating from the domestic breeds of White Leghorn and Rhode Island Red, or from Red Jungle Fowl (the wild ancestral form). Genomic DNA samples from these individuals were digested with any one of the Eco RI and Pvu II restriction enzymes and hybridized with the DR beta probe. Restriction fragment length polymorphism (RFLP) was obtained with Pvu II only, which resolved seven different RFLP types. There was an excellent correlation between these RFLP types and the serological B typing since the RFLP type was identical within each pair of homozygotes. In addition to this broad survey of many haplotypes, a more detailed comparison was carried out on B21-like haplotypes originating from different breeds. No differences in restriction fragment patterns among these haplotypes could be resolved using any of the restriction enzymes Bg1 II, Eco RI, Hind III, Pst I, Pvu II, and Taq I.

Animals↗
PubMed1987

The chicken erythrocyte-specific MHC antigen. Characterization and purification of the B-G antigen by monoclonal antibodies.

Mouse monoclonal antibodies with B-G antigen (major histocompatibility complex class IV) specificity were obtained after immunization with erythrocytes or partially purified B-G antigen. The specificities of the hybridoma antibodies were determined by precipitation of B-G antigens from 125I-labeled chicken erythrocyte membranes (CEM) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. The B-G antigen had an approximate molecular mass of 46-48 kd in reduced samples, depending on the haplotype, and in unreduced samples contained either dimers (85 kd), when labeled erythrocytes were the antigen source, or trimers (130 kd), when B-G was purified and precipitated from CEM. The B-G antigen was unglycosylated as studied by in vitro synthesis in the presence or absence of tunicamycin, binding experiments with lectin from Phaseolus limensis, and treatment of purified B-G antigen with Endoglycosidase-F or trifluoromethanesulfonic acid. Two-way sequential immunoprecipitation studies of erythrocyte membrane extracts with anti-B-G alloantisera and monoclonal antibodies revealed only one population of B-G molecules. Pulse-chase experiments have shown B-G to be synthesized as a monomer, with dimerization taking place after 20-30 min. No change in the monomer's molecular mass due to posttranslational modifications was revealed. The antigen was purified from detergent extract of CEM by affinity chromatography with a monoclonal antibody, and then reduced and alkylated and affinity-purified once more. Finally, reverse-phase chromatography resulted in a pure product. The B-G antigen was identified in the various fractions by rocket immunoelectrophoresis. The final product was more than 99% pure, as estimated by SDS-PAGE analysis followed by silver stain of proteins. The yield from the affinity chromatography step was 3-4 micrograms B-G/ml blood, calculated from Coomassie-stained SDS-PAGE of B-G using ovalbumin standards. The monoclonal antibodies were also used to identify the B-G (class IV) precipitation arc in crossed immunoelectrophoresis. No common precipitate with the B-F (class I) antigen was observed.

Animals↗
PubMed1986

Isolation and characterization of chicken and turkey beta 2-microglobulin.

Chicken and turkey beta 2-m were isolated from citrated plasma in sequential use of three chromatographic steps: affinity chromatography, gel filtration chromatography and anion-exchange chromatography. The purified protein was identified as beta 2-m by reaction with a beta 2-m specific monoclonal antibody and by the ability to recombine with the chicken MHC class I heavy chain. The purity was estimated by SDS-PAGE and IEF. The pI was between 5.1 and 5.3 for chicken beta 2-m and 4.7 and 4.8 for turkey beta 2-m, which fact is reflected in their different electrophoretic mobilities in agarose gel (turkey migrates in the alpha and chicken migrates in the beta region). The mol. wt of both chicken and turkey beta 2-m was 14,500 estimated by SDS-PAGE whereas calculations based on the amino acid compositions gave mol. wts of 11,000. EM280 was 15.9 for chicken beta 2-m and 16.4 for turkey beta 2-m. The amino acid compositions and sequences of the two avian beta 2-m molecules have been compared with earlier data from the literature. The sequence of the 23 N-terminal amino acids was found to be identical in our preparations from both chicken and turkey, namely DLTPKVQVYSRFPASAGTKNVLN, and is incompatible with a previously published sequence also thought to be from turkey beta 2-m. Reasons for our opinion that the molecules isolated and sequenced in this paper are the correct ones are given.

Amino Acid Sequence↗
PubMed1986

The major histocompatibility complex class I heavy chain as a structural subunit of the human cell membrane insulin receptor: implications for the range of biological functions of histocompatibility antigens.

Monoclonal antibodies against some of the monomorphic determinants of major histocompatibility complex (MHC) class I molecules reduce insulin binding and precipitate 125I-labeled insulin receptor preparations. A monoclonal antibody with specificity for the insulin binding site on the cell membrane insulin receptor of human cells was used to precipitate insulin receptors from human cell lines and resulted in distinct bands of Mr approximately 130,000, 90,000, and 45,000. The Mr 45,000 molecules thus precipitated were subjected to NaDodSO4/PAGE, eluted from the gels, and found to react with monoclonal antibodies against monomorphic and a polymorphic MHC class I determinant known to be expressed on the cell line used as receptor source. Moreover, a murine thymoma line (RI) with MHC class I expression bound significant amounts of insulin, whereas a MHC class I-negative variant had low insulin binding capacity. Reduction in the density on human cells of the MHC class I heavy chain was obtained by capping with antibodies to beta 2-microglobulin or to the MHC class I heavy chain and resulted in decreased insulin binding, whereas down-regulation of insulin receptors induced increased density of MHC class I molecules. It is concluded that the MHC class I heavy chain and the tetrameric insulin receptor are structurally associated in the cell membrane and suggested that this association may occur by displacement of beta 2-microglobulin by the insulin receptor.

Antibodies, Monoclonal↗