PubMed Health⌕ Search

Biomedical subjects

F Müller

Publications and source records attributed to F Müller.

At least 19 recordsLinked to original sources
PubMed1992

The two main rDNA size classes of Ascaris lumbricoides: comparison of transcription termination and spacer organization.

Structural and functional analyses were carried out to compare transcription termination and intergenic spacer organization between the two heterogeneous ribosomal DNA size classes of Ascaris lumbricoides. By performing mung bean nuclease mapping in vivo, we localized the 3' end of the mature 26S rRNA to the same position in both forms. This site coincides with the in vivo and in vitro transcription termination site of the 40S-precursor rRNA from both rDNA size classes. We demonstrate that the 3' boundary of sequences necessary for faithful transcription termination extends 35 bp beyond the end of the 26S rRNA gene and that these sequences are perfectly conserved within the two size classes. The intergenic spacers of both rDNA size classes have been completely sequenced; they are 2410 bp and 1937 bp long and show a sequence homology of 92.8%. There is no evidence for the presence of reiterated termination sites or promoters within the relatively short intergenic spacers of the two rRNA gene classes.

Animals↗
PubMed1992

How are tRNAs and mRNA arranged in the ribosome? An attempt to correlate the stereochemistry of the tRNA-mRNA interaction with constraints imposed by the ribosomal topography.

Two tRNA molecules at the ribosomal A- and P-sites, with a relatively small angle between the planes of the L-shaped molecules, can be arranged in two mutually exclusive orientations. In one (the 'R'-configuration), the T-loop of the A-site tRNA faces the D-loop of the P-site tRNA, whereas in the other (the 'S'-configuration) the D-loop of the A-site tRNA faces the T-loop of the P-site tRNA. A number of stereochemical arguments, based on the crystal structure of 'free' tRNA, favour the R-configuration. In the ribosome, the CCA-ends of the tRNA molecules are 'fixed' at the base of the central protuberance (the peptidyl transferase centre) of the 50S subunit, and the anticodon loops lie in the neck region (the decoding site) of the 30S subunit. The translocation step is essentially a rotational movement of the tRNA from the A- to the P-site, and there is convincing evidence that the A-site must be located nearest to the L7/L12 protuberance of the 50S subunit. The mRNA in the two codon-anticodon duplexes lies on the 'inside' of the 'elbows' of the tRNA molecules (in both the S-type and R-type configurations), and runs up between the two molecules from the A- to the P-site in the 3' to 5'-direction. These considerations have the consequence that in the S-configuration the mRNA in the codon-anticodon duplexes is directed towards the 50S subunit, whereas in the R-configuration it is directed towards the 30S subunit. The results of site-directed cross-linking experiments, in particular cross-links to mRNA at positions within or very close to the codons interacting with A- or P-site tRNA, favour the latter situation. This conclusion is in direct contradiction to other current models for the arrangement of mRNA and tRNA on the ribosome.

Cross-Linking Reagents↗
PubMed1992

[Acute fatty liver of pregnancy--differential diagnosis and supportive therapy].

A case of clinically diagnosed acute fatty liver of pregnancy (AFLP) is reported. Hypoglycemia and coagulopathy were predominant in the clinical course. Serial studies on blood chemistry, especially blood glucose and coagulation parameters, in association with virus serology and ultrasound, can rule out common causes of jaundice in pregnancy. This contributes to reliability of the clinical diagnosis of AFLP in the absence of liver biopsy, and ensures adequate management of the patient.

Acute Disease↗
PubMed1992

Glutamate receptor expression in the rat retina.

The expression of five genes (GluR A; B; C; D; GluR 5) encoding functional subunits of glutamate receptors was investigated in the rat retina using in situ hybridization with oligonucleotide probes. All five genes are expressed in the retina. All probes label cell bodies in the ganglion cell layer as well as somata in the inner third of the inner nuclear layer (INL), where the amacrine cells are located. In addition GluR 5, B and D, and to a lesser extent also GluR A are found in the middle and outer part of the INL, where bipolar and horizontal cells reside. Different subsets of retinal neurons may thus use glutamate receptors of different subunit composition.

Animals↗
PubMed1992

Unusual features of the retroid element PAT from the nematode Panagrellus redivivus.

The PAT retroid transposable elements differ from other retroids in that they have a 'split direct repeat' structure, i.e., and internal 300bp sequence is found repeated, about one half at each element extremity. A very abundant transcript of about 900 nt, the start of which maps to the preferentially deleted portion of PAT elements, is detected on total Panagrellus redivius RNA bearing Northern blots. A potentially corresponding ORF encodes a protein of 265 residues having a carboxy terminal Cystein motif, believed to be exclusively characteristic of the GAG protein in retoid elements. A much fainter, 1800nt long transcript, is also detected on Northern blots and maps slightly downstream of the first ORF. The predicted protein sequence of this region bears motifs typical of reverse transcriptase and RNaseH, as found in the Pol genes of retroid elements. Peptide motif similarities are greatest with the DIRS-1 element derived from Dictyostelium discoideum. The possibility of using PAT elements as transposon tagging system for Caenorhabditis elegans is discussed.

Amino Acid Sequence↗
PubMed1992

Occurrence and phenotypic properties of verotoxin producing Escherichia coli in sporadic cases of gastroenteritis.

Five verotoxin producing Escherichia coli strains were detected in 405 patients with infectious gastroenteritis and 3 such strains were detected in 11 patients with the hemolytic uremic syndrome in Switzerland. Production of verotoxin 2 was associated with the latter three strains. Four strains reacted with the probe for the virulence plasmid of Escherichia coli O157:H7, and six reacted with a recently described probe for the eae gene of enteropathogenic Escherichia coli. None of the strains was of serotype O157:H7. The methods available at present for detecting toxins or toxin genes will reliably detect all such verotoxin producing strains.

Adult↗
PubMed1992

Release signs in Parkinson's disease with and without dementia.

Release signs have been described in both age-associated diseases and in the healthy elderly. We investigated the palmomental, snout, grasp, corneomandibular and glabellar reflexes in demented and non-demented Parkinson-patients compared to Alzheimer's disease and age-matched controls. The palmomental reflex and a persisting glabellar reflex were linked to parkinsonism irrespective of dementia and were found also in Alzheimer's disease. A corneomandibular reflex was observed more frequently in demented than non-demented Parkinson-patients and in Alzheimer's disease. The snout-reflex was present in nearly all individuals irrespective of diagnosis. Thus, various release signs react quite differentially to degenerative brain disease and dementia.

Aged↗
PubMed1992

Chromatin diminution in nematode development.

Chromatin diminution in Parascaris and Ascaris represents the classical case of a developmentally programmed genome rearrangement. The process is very specific with respect to ontogenetic timing and chromosomal localization, and involves chromosomal breakage, new telomere formation and DNA degradation. Recent evidence from Ascaris lumbricoides var. suum suggests that chromatin diminution might have a function in gene regulation.

Animals↗
PubMed1992

Reactive oxygen intermediates and human immunodeficiency virus (HIV) infection.

HIV infection affects various parts of the immune system, including the CD4+ lymphocytes and mononuclear phagocytes, and causes a progressive immunodeficiency. This renders the patient susceptible to various opportunistic infections and neoplasms. Reactive oxygen intermediates (ROI) are important for the intracellular killing of microorganisms by mononuclear phagocytes and neutrophils. Although data are discrepant, several studies suggest that the generation of ROI is impaired in mononuclear phagocytes, and possibly also in neutrophils, from HIV-infected individuals. This may lead to deficient killing of intracellular microorganisms predisposing the HIV-infected patient to certain opportunistic infections. Recently, in vitro studies have shown that ROI activate the intracellular transcription factor nuclear factor kappa B (NF-kappa B) which stimulates HIV replication. Intracellular antioxidant systems, such as the glutathione system, seem to be of importance for the regulation of ROI levels and thus probably for HIV replication in vitro. However, the role of ROI in regulation of HIV replication in vivo is unknown at present. The role of ROI in HIV infection is thus difficult to assess, both at the cellular and clinical level. Reduced intracellular concentrations of ROI may lead to impaired phagocyte microbicidal functions, thus predisposing HIV-infected patients to various opportunistic infections. On the other hand, increased ROI levels may be associated with a stimulation of HIV replication leading to clinical deterioration.

HIV↗
PubMed1992

Raised serum neopterin levels in patients with primary hypogammaglobulinaemia; correlation to other immunological parameters and to clinical and histological features.

Serum neopterin levels were analysed in 43 patients with primary hypogammaglobulinaemia (25 common variable immunodeficiency (CVI), 12 congenital hypogammaglobulinaemia (CH), six X-linked hypogammaglobulinaemia (XLH)), and in 33 healthy controls. The neopterin values were correlated to lymphocyte subset counts in peripheral blood, lymphocyte mitogen responses and clinical and histological manifestations in the study group. Serum neopterin levels were significantly elevated in all subgroups of patients and particularly in the CVI groups where the highest concentrations were found (P less than 0.001, CVI versus controls). Furthermore, in CVI and CH patients elevated neopterin levels were strongly correlated to decreased number of CD4+ lymphocytes (rs = -0.61, P less than 0.005 and rs = -0.83, P less than 0.001, respectively). In the CVI group high neopterin levels were also significantly correlated to low number of circulatory B (CD19+) lymphocytes (rs = -0.58, P less than 0.05). Both patients with moderately and those with severely depressed lymphocyte mitogen responses had significantly higher neopterin levels than those with normal responses. In addition, high neopterin levels were significantly associated with the occurrence of splenomegaly and nodular intestinal lymphoid hyperplasia. The immunological findings were consistently observed in longitudinal testing, and appeared to be characteristic for the individual patient. High serum neopterin levels are thought to be a marker for hyperactivity in monocytes/macrophages, and dysfunction of these cells may therefore be associated with fundamental immune pathology in some subgroups of primary hypogammaglobulinaemia.

Adolescent↗
PubMed1992

Monoclonal antibodies specific for Clostridium difficile toxin B and their use in immunoassays.

Five mouse monoclonal antibodies (MAbs) against Clostridium difficile toxin B have been raised and characterized. Three of them were immunoglobulin M (IgM) antibodies (6B10, 6G3, and 10B9), and the other two were of the IgG1 isotype (9E5 and 17G2), recognizing specifically two distinct epitopes on the toxin B molecule. No MAb was able to neutralize cytotoxic activity significantly. The two IgG1 MAbs were purified and applied to various immunodiagnostic assays. MAbs coupled to latex beads were used for specific removal of toxin B from cytotoxic samples and for agglutination assay. An indirect sandwich enzyme-linked immunosorbent assay with MAb 9E5 or 17G2 as the capture antibody was established for identification of toxin B with a lower detection limit of 5 ng/ml.

Animals↗
PubMed1992

Nucleotide sequence of PAT, a retroid element with unusual DR organization, isolated from Panagrellus redivivus.

We have isolated several copies of the transposable element PAT of Panagrellus redivivus and sequenced one full length, presumably autonomous, 5514 bp entity. The terminal sequences are found repeated inside the element, probably representing the homologous of the long terminal repeats in common retroid elements. Two major open reading frames are present with features typical of GAG and Pol. Both the structural features and open reading frame characteristics assign PAT to the retroid family of transposable elements, and more precisely to the gypsy class of retroids when putative functional domains of Pol are compared to published sequences.

Amino Acid Sequence↗
PubMed1992

Nonspecific oral immunity in individuals with HIV infection.

Lactoferrin, lysozyme, interferon, and neopterin levels were determined in parotid saliva from 44 individuals with different clinical stages of human immunodeficiency virus (HIV) infection and 19 HIV-seronegative controls. The secretory output of individual components was calculated according to the fluid flow rate. No parotid interferon activity was found in any of the HIV-infected subjects or controls, and no significant differences in parotid lysozyme or neopterin outputs were observed. The lactoferrin output was significantly decreased in HIV-seropositive subjects in parallel with their markedly reduced parotid secretory IgA output. This combined deficiency of parotid lactoferrin and secretory IgA may well contribute to the frequent oral infections seen in subjects with HIV infection.

Adult↗
PubMed1992

[The microbial colonization of implant elements made of plastics and titanium].

12 edentate subjects wearing lower complete dentures stabilized by an IMZ-implant-supported Dolder bar took part in the experiment. Elastic (POM) and titanium connection parts were alternatingly inserted. After the removal of 24 POM and titanium elements from each of the patients, a qualitative analysis of the microbial flora was performed. Except for actinomycetes, aerobic as well as anaerobic microorganisms were found less frequently with titanium than with POM elements.

Actinomycetales↗
PubMed1991

New telomere formation after developmentally regulated chromosomal breakage during the process of chromatin diminution in Ascaris lumbricoides.

During the process of chromatin diminution, which takes place in all presomatic cells of the early Ascaris embryo, the heterochromatic termini of the chromosomes are lost. Here we show that the newly formed ends of the reduced somatic chromosomes carry tandem repeats of the telomeric sequence TTAGGC. Comparison of a cloned somatic telomere with the corresponding germline chromosomal region revealed that these telomeric repeats are not present at or near the chromosomal breakage site. They are most likely added by a telomerase-mediated event. Chromosomal breakage, which precedes the telomere addition process, takes place within a short, specific chromosomal region (CBR); however, it does not occur at a single locus, but rather at many different sites. Altogether, our data show that chromatin diminution in Ascaris is a complex molecular process that includes site-specific chromosomal breakage, new telomere formation, and DNA degradation.

Animals↗
PubMed1991

NMR studies on p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens and salicylate hydroxylase from Pseudomonas putida.

p-Hydroxybenzoate hydroxylase from Pseudomonas fluorescens and salicylate hydroxylase from Pseudomonas putida have been reconstituted with 13C- and 15N-enriched FAD. The protein preparations were studied by 13C-NMR, 15N-NMR and 31P-NMR techniques in the oxidized and in the two-electron-reduced states. The chemical shift values are compared with those of free flavin in water or chloroform. It is shown that the pi electron distribution in oxidized free p-hydroxybenzoate hydroxylase is comparable to free flavin in water, and it is therefore suggested that the flavin ring is solvent accessible. Addition of substrate has a strong effect on several resonances, e.g. C2 and N5, which indicates that the flavin ring becomes shielded from solvent and also that a conformational change occurs involving the positive pole of an alpha-helix microdipole. In the reduced state, the flavin in p-hydroxybenzoate hydroxylase is bound in the anionic form, i.e. carrying a negative charge at N1. The flavin is bound in a more planar configuration than when free in solution. Upon binding of substrate the resonances of N1, C10a and N10 shift upfield. It is suggested that these upfield shifts are the result of a conformational change similar, but not identical, to the one observed in the oxidized state. The 13C chemical shifts of FAD bound to apo(salicylate hydroxylase) indicate that in the oxidized state the flavin ring is also fairly solvent accessible in the free enzyme. Addition of substrate has a strong effect on the hydrogen bond formed with O4 alpha. It is suggested that this is due to the exclusion of water from the active site by the binding of substrate. In the reduced state, the flavin is anionic. Addition of substrate forces the flavin ring to adopt a more planar configuration, i.e. a sp2-hybridized N5 atom and a slightly sp3-hybridized N10 atom. The NMR results are discussed in relation to the reaction catalyzed by the enzymes.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1991

15N- and 13C-NMR investigations of glucose oxidase from Aspergillus niger.

The apoprotein of glucose oxidase from Aspergillus niger was reconstituted with specifically 15N- and 13C-enriched FAD derivatives and investigated by 15N- and 13C-NMR spectroscopy. On the basis of the 15N-NMR results it is suggested that, in the oxidized state of glucose oxidase, hydrogen bonds are formed to the N(3) and N(5) positions of the isoalloxazine system. The hydrogen bond to N(3) is more pronounced than that to N(5) as compared with the respective hydrogen bonds formed between FMN and water. The resonance position of N(10) indicates a small decrease in sp2 hybridization compared to free flavin in water. Apparently the isoalloxazine ring is not planar at this position in glucose oxidase. Additional hydrogen bonds at the carbonyl groups of the oxidized enzyme-bound FAD were derived from the 13C-NMR results. A strong downfield shift observed for the C(4a) resonance may be ascribed in part to the decrease in sp2 hybridization at the N(10) position and to the polarization of the carbonyl groups at C(2) and C(4). The polarization of the isoalloxazine ring in glucose oxidase is more similar to FMN in water than to that of tetraacetyl-riboflavin in apolar solvents. In the reduced enzyme the N(1) position is anionic at pH 5.6. The pKa is shifted to lower pH values by at least 1 owing to the interaction of the FAD with the apoprotein. As in the oxidized state of the enzyme, a hydrogen bond is also formed at the N(3) position of the reduced flavin. The N(5) and N(10) resonances of the enzyme-bound reduced FAD indicate a decrease in the sp2 character of these atoms as compared with that of reduced FMN in aqueous solution. Some of the 15N- and 13C-resonance positions of the enzyme-bound reduced cofactor are markedly pH-dependent. The pH dependence of the N(5) and C(10a) resonances indicates a decrease in sp2 hybridization of the N(5) atom with increasing pH of the enzyme solution.

Aspergillus niger↗