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Biomedical subjects

F Müller

Publications and source records attributed to F Müller.

At least 487 records · Page 27Linked to original sources
PubMed1980

Nucleotide sequence of genes coding for tRNAPhe and tRNATyr from a repeating unit of X. laevis DNA.

A cloned 3.18 kb repeating unit of Xenopus laevis DNA, known to contain two tRNA1Met genes, has been partially sequenced. The sequenced region could potentially code for two more tRNA species. One is a phenylalanine tRNA with the same primary sequence as that found in a variety of mammals. The other is a tyrosine tRNA with a 13 bp intervening sequence located immediately adjacent or very close to the 3' nucleotide of the anticodon. The two putative genes have opposite polarity and the sequences encoding the 5' nucleotides of the mature tRNAs are separated by only 72 bp of DNA. Homologous GC-rich sequences of dyad symmetry precede each gene. Neither gene codes for the 3' terminal CCA expected in the nature tRNAs. A short T cluster is present in the noncoding strand 3 bp away from the 3' end of the tRNATyr gene. A similar short T cluster is located 26 bp downstream of the tRNAPhe sequence. The nucleotides in between are very GC-rich and are capable of forming a stable RNA hairpin. The possible significance of these features for tRNA gene evolution, RNA splicing and transcription is discussed.

Animals↗
PubMed1980

Effect of clonidine on growth hormone release in psychiatric patients and controls.

The stimulation of human growth hormone (HGH) release by clonidine (0.15 mg i.v.) was studied as a test of the postsynaptic alpha-receptor sensitivity of psychiatric patients. In this test, endogenous depressives showed a significantly reduced HGH response to clonidine as compared to normal controls, neurotic-reactive depressives, and schizophrenics. However, no differences were found between the endogenous depressives and a group of schizoaffective patients. HGH response to clonidine was not correlated with plasma levels of noradrenaline, serum cortisol, free fatty acids, or blood glucose. Within the group of normal control subjects, a reduced HGH response was found in most postmenopausal women and in some regular users of alcohol. Our findings suggest that patients with endogenous depression are characterized by a subsensitivity of postsynaptic alpha-receptors or of structures related to them. The clonidine test shows promise as an indicator of vulnerability to endogenous depression.

Adult↗
PubMed1979

Fluorescence properties of reduced flavins and flavoproteins.

Fluorescence lifetimes and polarized emission properties of reduced flavin were measured using several model compounds and flavoproteins. Depending on the conditions of solvent and temperature or reduction method the lifetimes vary between 1 and 15 ns. The longer lifetime values are found in several forms of reduced lactate oxidase, in which a good correlation exists between fluorescence intensity and lifetime. In practically all flavoproteins the fluorescence is heterogeneous. Several mechanisms are proposed to explain the observed heterogeneity in lifetimes. The reduced models in glycerol at subzero temperature exhibit high degrees of polarization of the fluorescence, whereas distinct depolarization is encountered in several reduced flavoproteins suggesting a certain mobility of the flavin chromophor.

Flavins↗
PubMed1979

A study of p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens. Improved purification, relative molecular mass, and amino acid composition.

The purification procedure for p-hydroxybenzoate hydroxylase has been modified by replacement of the DEAE-cellulose (DE-32) column in the original procedure by a Sephadex--Cibacron-blue affinity column. In this way the yield of enzyme could be improved from 16% to about 40--50%. Preparative gel chromatography indicated that the enzyme does not exist as a monomeric species as earlier believed but mainly as a dimer. Sodium dodecyl sulfate gel electrophoresis of purified enzyme revealed a minimum relative molecular mass (Mr) of 43000--45000. Analytical gel chromatography, sedimentation equilibrium and sedimentation velocity experiments showed that the enzyme exists in solution mainly as a dimer but also in higher-order quaternary structures (presumably tetramer and hexamer). Temperature dependence of the distribution of the oligomers suggests that the association is of hydrophobic nature. The amino acid composition of the enzyme is also presented. The enzyme contains no disulfide but five sulfhydryl groups. In the native state of the enzyme only one sulfhydryl group is accessible to N-ethylmaleimide or 5,5'-dithiobis(2-nitrobenzoic acid). The iso-electric point of the enzyme was found to be 5.8.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1979

Identification of a low moleculr weight IgM antibody with treponema pallidum specificity in sera of patients with chronic syphilis.

A low-molecular (8S) treponema-specific IgM antibody was isolated by means of Sephadex 200 G gel filtration and/or sucrose gradient ultracentrifugation in 78 of 4,120 sera of patients who had been identified to have had syphilis. The IgM specificity can be shown by indirect immunofluorescence using a mu-chain specific antiserum. The low molecular IgM (LMW-IgM) antibodies are not identical with the 19S-IgM as demonstrated in studies with gel filtration and sucrose gradient methods. They are not identical neither with 7S IgG or IgA. Neither the presence of antinuclear nor rheumatic factor could be shown in the LMW-IgM fraction. In most of the patients with LMW-IgM antibody, there existed a treponema infection of late latency.

Antibodies, Antinuclear↗
PubMed1979

[Results of modern syphilis serology in blood donors, at the same time a contribution to spontaneous healing of syphilis].

261 out of 336 845 blood donors have been shown to had undergone a syphilitic infection. About 52 per cent of these donors have had knowledge of their infection and of specific treatment of the disease. In about 43 per cent of the investigated cases the T. pallidum infection has had probably an inapparent course and healed without treatment, that means spontaneously. In times with an increasing number of infections by T. pallidum blood banks have to look intensively for donors which are in the first stage of primary syphilis. For identification of these people and for the differentiation between antibodies against T. pallidum and apathogenic treponemes the use of a TPHA-ABS test is discussed.

Antibodies↗
PubMed1979

Kinetics and stability of immobilized chicken liver xanthine dehydrogenase.

Xanthine dehydrogenase (EC 1.2.1.37) was isolated from chicken livers and immobilized by adsorption to a Sepharose derivative, prepared by reaction of n-octylamine with CNBr-activated Sepharose 4B. Using a crude preparation of enzyme for immobilization it was observed that relatively more activity was adsorbed than protein, but the yield of immobilized activity increased as a purer enzyme preparation was used. As more activity and protein were bound, relatively less immobilized activity was recovered. This effect was probably due to blocking of active xanthine dehydrogenase by protein impurities. The kinetics of free and immobilized xanthine dehydrogenase were studied in the pH range 7.5-9.1. The Km and V values estimated for free xanthine dehydrogenase increase as the pH increase; the K'm and V values for the immobilized enzyme go through a minimum at pH 8.1. By varying the amount of enzyme activity bound per unit volume of gel, it was shown that K'm is larger than Km are result of substrate diffusion limitation in the pores of the support material. Both free and immobilized xanthine dehydrogenase showed substrate activation at low concentrations (up to 2 microM xanthine). Immobilized xanthine dehydrogenase was more stable than the free enzyme during storage in the temperature range of 4-50 degrees C. The operational stability of immobilized xanthine dehydrogenase at 30 degrees C was two orders of magnitude smaller than the storage stability, t 1/2 was 9 and 800 hr, respectively. The operational stability was, however, better than than of immobilized milk xanthine oxidase (t 1/2 = 1 hr). In addition, the amount of product formed per unit initial activity in one half-life, was higher for immobilized xanthine dehydrogenase than for immobilized xanthine oxidase. Unless immobilized milk xanthine oxidase can be considerable stabilized, immobilized chicken liver xanthine dehydrogenase is more promising for application in organic synthesis.

Animals↗
PubMed1979

Delimitation of a promoter for RNA polymerase III by means of a functional test.

A Xenopus laevis DNA segment containing the structural gene for tRNA1Met and 22 base pairs at the 5' side of the gene is active in tRNA production. The DNA segment was ligated to sea urchin histone DNA and was also inserted into plasmid pCR1. Both recombinant DNAs were shown to produce mature tRNA1Met at a high rate when injected into centrifuged Xenopus oocytes.

Animals↗
PubMed1979

[Comparative studies of the preparation of alpha-gliadin].

alpha-gliadin was prepared from wheat flour by two different methods. The products were compared electrophoretically and by double radial immuno-diffusion. The alpha-gliadin fraction proved to be identical in the immunological test. Only the alpha-gliadin preparation received by ion exchange chromatography is suitable for further purification by multiple gel filtrations.

Electrophoresis, Polyacrylamide Gel↗
PubMed1979

["Old new" problem of the lues risk in transfusion medicine: the effect of the serum and ACD stabilizer at different temperatures on the infectiosity of Treponema pallidium (Nichols strain)].

The portion of warm and fresh blood transfusions had increased obviously. This is accompanied by a decrease of the restrictive period of the former 72 and the presently 48 hours for blood units to be transfused. Therefore, the danger of a symphilis transmitted by transfusion is impending again. This is realized insufficiently and the syphilis may occur, if blood is drawn in the seronegative phase of the primary stage of syphilis and transfused within the restrictive period. Model trials on the infectivity of Treponema pallidum revealed that the syphilis cannot be transmitted by blood and its derivates drawn in the seronegative phase after storage at 4 degrees C for 24 hours. Therefore, the reduction of the restrictive period to 48 hours is justified.

Animals↗
PubMed1979

[Anterior falcate artery in adults: histology of the relation of superior sagittal sinus, dural vein and the arachnoid granulations].

The anterior falcate artery, which is the continuation of the anterior ethmoidal, supplies the dura mater in the region of the superior sagittal sinus as far almost as the coronal suture. Graphic reconstructions show its relationships to the veins, the sinus, and the arachnoid granulations. Histological studies of the artery emphasize its adaptation to longitudinal stretching. The complexity of its relationships suggests a functional significance beyond that of nourishing the dura.

Age Factors↗
PubMed1979

[Relationship between Na+ and monosaccharide influx across the microvilli membrane depending on the energy state of the intestinal mucosa wall].

1. An energy dependence of the Na+ influx and of the "extra-Na+ influx" across the microvilli membrane was demonstrated in an in vitro preparation of the rat jejunum by adjustment of low ATP/ADP quotients. The monosaccharide influx does not show this dependence. 2. The similar relationship of monosaccharide-dependent Na+ influx and Na+ influx without monosaccharide with the energy state in the mucosa cells suggests a common control system. 3. A constant stoichiometry between monosaccharide and "extra-Na+ influx" can be maintained only under constant intracellular conditions. 4. The changes of the Na+ and K+ influxes by so-called Na+ dependently transported monosaccharides correspond to those which can be elicited by lowering the ATP/ADP ratio in the in vitro preparation. 5. A mechanism is discussed in which an ATP-utilizing reaction is stimulated in the microvilli owing to the monosaccharide transport, thus locally discontinuing the condition for uncoupling of an (Na, K)-ATPase and eliciting an "extra-Na+ influx".

Adenosine Diphosphate↗
PubMed1978

[Effects of insulin, glucagon and secretin on intestinal resorption of glucose].

The authors describe a versatile experimental procedure for the study of intestinal digestion and resorption in animals. This procedure is based on the principle of the continuous perfusion of a completely isolated intestinal segment. The results from experiments on glucose absorption from the jejunum of the rabbit serve to demonstrate the great reproducibility of this in vitro technique. No hormonal influence on monosaccharide resorption could be detected by means of this procedure, even in case of unphysiologic dosage of insulin, glucagon and secretin.

Animals↗
PubMed1978

[Effect of alloxan diabetes on (Na+ + K+)-activated ATPase in brush border membrane of the mucosal cell of rat small intestine].

In order to elucidate a possible relationship between (Na+ + K+)-activated ATPase and intestinal absorption of actively transported monosaccharides enzyme activity was measured in mucosal cells from alloxan diabetic rats. The general effect of increasing capacity of active, Na+-dependent transport processes in diabetes mellitus is associated with a significantly enhanced (Na+ +K+)-activated ATPase activity in mucosal homogenate from diabetic animals. To study the localization of these effects within the cell we isolated purified brush borders and their substructures. To enable a comparison to be made between preparation procedures of diabetic and control animals the fractions were controlled by electronmicroscopy and by measuring the sucrase activity. In the purified brush border fraction of alloxan treated rats there was no significant increase in (Na+ + K+)-activated ATPase activity. Based on these results we conclude that the (Na+ + K+)-activated ATPase in the basolateral membranes was increased in alloxan diabetes, and it seems very likely that this enzyme is involved in the regulation of Na+-dependent transport processes.

Animals↗