PubMed Health⌕ Search

Biomedical subjects

R Reuter

Publications and source records attributed to R Reuter.

At least 37 records · Page 2Linked to original sources
PubMed1993

Tuberculosis in wild seals and characterisation of the seal bacillus.

Tuberculosis was diagnosed in 3 otariid seals found dead on beaches at 3 locations on the south coast of Western Australian between May 1990 and March 1991. This confirms that tuberculosis is present in the 2 native seals (Neophoca cinerea and Arctocephalus forsteri) in Western Australian waters. Mycobacterium sp isolated from the lungs of 2 of the seals were studied to determine the similarity of the strains to each other, to the strains isolated during 1986 from Australian sea lions and New Zealand fur seals kept in captivity at a marine park near Perth, Western Australia, and to a strain isolated in 1988 from a seal trainer who worked with the infected captive seals for 3 years. After restriction endonuclease analysis (REA) with the endonucleases Bst EII, Bcl I and Pvu II, one of the wild seal strains appeared to have identical DNA fragment patterns to the strains from the captive seals and the seal trainer. The other wild seal isolate had identical REA profiles using Bst EII and Bcl I, but a minor difference was detected using Pvu II. Differences in these isolates were more clearly seen in restriction fragment length polymorphisms after hybridisation with two DNA probes. The secretory protein MPB70, present in M bovis, was not detected in wild seal isolates using sodium dodecyl sulphate polyacrylamide gel electrophoresis and Western blotting techniques. Analysis of protein and DNA fragment profiles indicated that seal tuberculosis isolates form a unique cluster within the M tuberculosis complex.

Animals↗
PubMed1993

A role for the mesoderm in endodermal migration and morphogenesis in Drosophila.

The endodermal midgut arises from two primordia, the anterior midgut (AMG) primordium and the posterior midgut (PMG) primordium, which are separated by almost the entire length of the Drosophila embryo. To form the midgut, these two parts have to extend towards each other and to fuse laterally on both sides of the yolk. Shortly before and during that movement, AMG and PMG are arranged as mesenchymal cell masses, but later the midgut cells form an epithelium. We show that these two aspects of midgut development, migration of AMG and PMG and transition to an epithelium, depend on the mesoderm. The extension of the midgut primordia is achieved by cell migration along the visceral mesoderm which forms a continuous layer of cells within the germ band. In mutant embryos lacking the entire mesoderm or failing to differentiate the visceral mesoderm, AMG and PMG are formed but do not migrate properly. In addition, they fail to form an epithelium and instead either remain as compact cell masses anterior and posterior to the yolk (in twist and snail mutant embryos) or only occasionally wrap around the yolk before embryogenesis is completed (in tinman-deficient embryos). We conclude that the visceral mesoderm serves as a substratum for the migrating endodermal cells and that the contact between visceral mesoderm and endoderm is required for the latter to become an epithelium.

Animals↗
PubMed1992

Mechanisms of early Drosophila mesoderm formation.

Several morphogenetic processes occur simultaneously during Drosophila gastrulation, including ventral furrow invagination to form the mesoderm, anterior and posterior midgut invagination to create the endoderm, and germ band extension. Mutations changing the behaviour of different parts of the embryo can be used to test the roles of different cell populations in gastrulation. Posterior midgut morphogenesis and germ band extension are partly independent, and neither depends on mesoderm formation, nor mesoderm formation on them. The invagination of the ventral furrow is caused by forces from within the prospective mesoderm (i.e. the invaginating cells) without any necessary contribution from other parts of the embryo. The events that lead to the cell shape changes mediating ventral furrow formation require the transcription of zygotic genes under the control of twist and snail. Such genes can be isolated by molecular and genetic screens.

Animals↗
PubMed1990

Autoantibody production against the U small nuclear ribonucleoprotein particle proteins E, F and G in patients with connective tissue diseases.

The nucleoplasmic U small nuclear ribonucleoprotein particles (snRNP) have a set of seven proteins in common which are designated B', B, D, D', E, F and G. Patients suffering from rheumatoid autoimmune diseases such as systemic lupus erythematosus often develop autoantibodies against the proteins B', B, and D. Here we describe a sensitive immunoassay which allows the specific detection of autoantibodies reacting with the E, F or G snRNP proteins. We were able to identify several patient sera containing autoantibodies against one or more of these proteins. This demonstrates that all snRNP proteins described so far are potentially antigenic in systemic rheumatoid diseases. The characterization of the antibodies showed an immunological cross-reactivity between the snRNP protein G and the 70-kDa protein of U1 snRNP. Several sera contained autoantibodies which were specific for the F snRNP protein.

Antibody Specificity↗
PubMed1990

Expression and function of the homoeotic genes Antennapedia and Sex combs reduced in the embryonic midgut of Drosophila.

Drosophila homoeotic genes control the formation of external morphological features of the embryo and adult, and in addition affect differentiation of the nervous system. Here we describe the morphogenetic events in the midgut that are controlled by the homoeotic genes Sex combs reduced (Scr) and Antennapedia (Antp). The midgut is composed of two cell layers, an inner endoderm and an outer visceral mesoderm that surround the yolk. Scr and Antp are expressed in the visceral mesoderm but not in the endoderm. The two genes are required for different aspects of the midgut morphogenesis. In Scr null mutant embryos the gastric caeca fail to form. Scr is expressed in the visceral mesoderm cells posterior to the primordia of the gastric caeca and appears to be indirectly required for the formation of the caeca. Antp is expressed in visceral mesoderm cells that overlie a part of the midgut where a constriction will form, and Antp null mutant embryos fail to form this constriction. An ultrastructural analysis of the midgut reveals that the visceral mesoderm imposes the constriction on the endoderm and the yolk. The mesodermal tissue contracts within the constriction and thereby penetrates the layer of the midgut endoderm. Microtubules participate in the morphological changes of the visceral mesoderm cells. The analysis of the expression of Scr in Antp mutant embryos revealed a case of tissue-specific regulation of Scr expression by Antp. In the epidermis, Antp has been shown to negatively regulate Scr, but it positively regulates Scr in the visceral mesoderm.

Animals↗
PubMed1990

Homeotic genes regulate the spatial expression of putative growth factors in the visceral mesoderm of Drosophila embryos.

During Drosophila embryogenesis homeotic genes control the developmental diversification of body structures. The genes probably coordinate the expression of as yet unidentified target genes that carry out cell differentiation processes. At least four homeotic genes expressed in the visceral mesoderm are required for midgut morphogenesis. In addition, two growth factor homologs are expressed in specific regions of the visceral mesoderm surrounding the midgut epithelium. One of these, decapentaplegic (dpp), is a member of the transforming growth factor beta (TGF-beta) family; the other, wingless (wg), is a relative of the mammalian proto-oncogene int-1. Here we show that the spatially restricted expression of dpp in the visceral mesoderm is regulated by the homeotic genes Ubx and abd-A. Ubx is required for the expression of dpp while abd-A represses dpp. One consequence of dpp expression is the induction of labial (lab) in the underlying endoderm cells. In addition, abd-A function is required for the expression of wg in the visceral mesoderm posterior to the dpp-expressing cells. The two growth factor genes therefore are excellent candidates for target genes that are directly regulated by the homeotic genes.

Animals↗
PubMed1990

A Drosophila growth factor homolog, decapentaplegic, regulates homeotic gene expression within and across germ layers during midgut morphogenesis.

The decapentaplegic (dpp) gene product, a member of the transforming growth factor-beta family, is required in Drosophila embryos for normal gastrulation and the establishment of dorsal-ventral polarity in the embryo. dpp is also expressed at specific positions in the visceral mesoderm along the developing midgut. We find that mutations that eliminate the visceral mesoderm expression of dpp lead to defects in midgut morphogenesis and alter the spatially localized expression of the homeotic genes Sex combs reduced (Scr), Ultrabithorax (Ubx), and Antennapedia (Antp) in the visceral mesoderm. The extracellular dpp protein migrates from the visceral mesoderm across the apposing endodermal cell layer in a region of the endoderm that expresses the homeotic gene labial (lab). Mesodermal expression of dpp is required for the expression of lab in these endodermal cells indicating that dpp mediates an inductive interaction between the two germ layers. We propose that extracellular dpp protein regulates gut morphogenesis, in part, by regulating homeotic gene expression in the visceral mesoderm and endoderm of the developing midgut.

Animals↗
PubMed1990

Purification and characterization of glucose-6-phosphate dehydrogenase from Pseudomonas W6.

Glucose-6-phosphate dehydrogenase (EC 1.1.1.49) has been purified from methanol grown Pseudomonas W6 by a simple procedure involving dye-ligand affinity chromatography on Cibacronblue F3G-A-Sephadex and Procion Red HE-3B-Sepharose. The purification procedure yielded a homogeneous enzyme with (1) high specific activity of 390 and 500 units/mg with NADP and NAD, respectively, and (2) low concentrations of contaminating activities. The molecular mass of the native enzyme was estimated to be 123 +/- 5 kDa. For the polypeptide chain after SDS denaturation a molecular mass of about 61 kDa was calculated. The kinetic behaviour of glucose-6-phosphate dehydrogenase exhibiting activity with either NADP or NAD was studied with respect to the substrate and coenzyme affinities and to ATP inhibition of enzyme activity. The applicability of prepared glucose-6-phosphate dehydrogenase as an auxiliary enzyme in clinical tests is discussed.

Chromatography, Affinity↗
PubMed1990

Interaction of bacterial glucose-6-phosphate dehydrogenase with triazine dyes: a study by means of affinity partitioning and kinetic analysis.

The interaction of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) from Pseudomonas W6 with 33 triazine dyes bound to poly(ethylene glycol) has been screened by means of affinity partition in an aqueous two-phase system composed of poly-(ethylene glycol) and dextran. Regarding the strength of interaction expressed by the affinity partitioning effect three groups of dyes can be distinguished showing high, medium or low interaction to the enzyme. The different influence of the structurally related dyes Cibacronblue F3G-A, Procion Blue MX-3G and Procion Blue MX-R on the partitioning of glucose-6-phosphate dehydrogenase is discussed. Both coenzymes of this glucose-6-phosphate dehydrogenase, NADP+ and NAD+, are able to diminish the dye-enzyme interactions but to a different extent. In the case of Procion Red HE-3B less than 0.2 mM of NADP+ abolished completely the dye-protein interaction indicating that the dye binding site might be closely related to the nucleotide binding site. This does not hold for a series of other dyes revealing strong interactions to the enzyme. In these cases higher NADP(+)-concentrations are necessary to weaken the dye-enzyme interactions. Only small influences on the interaction between the dye and glucose-6-phosphate dehydrogenase were found with 1 mM NAD+. The different effects of the two coenzymes are discussed with respect to separate binding sites for them and to different conformational states induced. The competition of Procion Red HE-3B with NADP+ and NAD+ for the binding site of glucose-6-phosphate dehydrogenase was also demonstrated by inhibition studies. The Ki-values of Procion Red HE-3B with NAD+ and NADP+, respectively, were calculated.

Bacterial Proteins↗
PubMed1989

Affinity chromatography of bovine heart lactate dehydrogenase using dye ligands linked directly or spacer-mediated to bead cellulose.

A number of reactive dyes coupled to bead cellulose directly or spacer-mediated has been investigated in respect of their interaction with lactate dehydrogenase (LDH; E.C. 1.1.1.28) from heart muscle. The Procion dyes Red HE-7B and Navy H-ER, as well as the Remazol dyes Brilliant Blue R and Brilliant Red 5-BN directly bound to bead cellulose provide high binding of LDH and the adsorbed enzyme is eluted specifically from these affinity adsorbents in high yield. In contrast, under the same conditions no binding of LDH has been found to the Procion dyes Green H-4G, Yellow HE-3G, Scarlet MX-G and Orange MX-G, although an opposite behaviour was expected from the results of affinity partitioning in aqueous two-phase systems. However, immobilizing these dyes via a spacer generated strong binding of the enzyme to the affinity adsorbent. The influence of the length of the spacer was studied in respect of the binding capacity and the yield of the enzyme specifically eluted. The applicability of Procion Scarlet MX-G-(diaminohexyl)-bead cellulose for the purification of LDH from muscle extract in one chromatographic step was demonstrated.

Animals↗
PubMed1989

Mercuric chloride induces autoantibodies against U3 small nuclear ribonucleoprotein in susceptible mice.

Autoantibodies to nucleolar components are a common serological feature of patients suffering from scleroderma, a collagen vascular autoimmune disease. While animal models, which spontaneously develop abundant anti-nucleolar antibodies, have not yet been described, high titers of such antibodies may be induced by treating susceptible strains of mice with mercuric chloride. We have identified the nucleolar autoantigen against which the HgCl2-induced IgG autoantibodies from mice of strain B10.S are directed. It is a protein with an apparent molecular mass of 36 kDa and a pI value of approximately 8.6, which is associated with the nucleolar small nuclear RNA U3, and by these criteria must be identical with a polypeptide called fibrillarin. It is striking that scleroderma patients spontaneously produce autoantibodies against the same U3 ribonucleoprotein (RNP). The HgCl2-induced murine and the scleroderma-specific human anti-U3 RNP autoantibodies were indistinguishable in their reactivities toward fibrillarin. They further resemble each other insofar as both recognize epitopes on the 36-kDa protein, which have been highly conserved throughout evolution. Our results provide a basis to investigate at the molecular level whether similar immunoregulatory dysfunctions may lead to the preferential anti-U3 RNP autoantibody production in the animal model and in scleroderma patients.

Animals↗
PubMed1987

A monoclonal antibody against 2,2,7-trimethylguanosine that reacts with intact, class U, small nuclear ribonucleoproteins as well as with 7-methylguanosine-capped RNAs.

A hybridoma secreting a monoclonal antibody (H-20) that recognizes the 2,2,7-trimethylguanosine(m3G)-containing cap structure of U snRNAs was derived from a mouse which was immunized with a m3G-containing human serum albumin conjugate. The antibody specifically reacts with intact small nuclear ribonucleoprotein particles, U snRNPs, and allows the snRNPs U1 to U6 to be isolated in one step from nuclear extracts of eucaryotic cells by affinity chromatography on a preparative scale. Antibody-bound snRNPs are desorbed from the affinity column by elution with excess of the cross-reactive nucleoside 7-methylguanosine (m7G), which guarantees maintenance of their native structure. The 20 affinity column also allows the snRNPs U1, U2 and U5 to be separated from U4/U6 RNPs by sequential elution of the particles with m7G under differential salt concentrations. As determined by competitive radioimmunoassay and protein-A--Sepharose immunoprecipitation, mAb H-20 crossreacts with intact m7G cap structures. In particular we could show that non-denatured m7G-capped SP6/beta-globin RNA was precipitated efficiently by the antibody while GpppG-capped or non-capped RNAs did not react. Thus the monoclonal antibody H-20 should have a wide application, not only for studying the molecular biology and immunology of the U snRNPs from diverse organisms, but also for the characterization and isolation of m7G-capped transcripts.

Animals↗
PubMed1987

Molecular relationships between U snRNP proteins as investigated by rabbit antisera and peptide mapping.

Each of the major U snRNP polypeptides from human cells was purified by electroelution from SDS-polyacrylamide gels. Rabbit antisera could be obtained against the individual proteins 70K, A, B', B and D, although rabbits failed to elicit antibodies against E, F and G. A strong structural homology was found between proteins B' and B, against which patients with connective tissue diseases produce predominantly anti-Sm autoantibodies. Thus, rabbit antisera against B' strongly crossreact with B and vice versa. Peptide patterns of the proteins B' and B obtained with chymotrypsin are identical with the exception of one fragment in each case. Polypeptide D, the third major Sm-antigenic protein, is structurally distinct from B' and B, as evidenced by the failure of anti-D antisera to crossreact with B' or B and vice versa, as well as by the different peptide patterns observed for proteins D and B' or B. The U1 specific polypeptide A and the U2 specific polypeptide B" share homologous regions, as indicated by the crossreactivity of anti-A antisera with protein B", and the occurrence of common fragments in the peptide patterns of the two proteins. Further homologies between other snRNP protein pairs were not detected.

Animals↗