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Biomedical subjects

F Müller

Publications and source records attributed to F Müller.

At least 361 records · Page 20Linked to original sources
PubMed1987

Detection of immunoglobulin M antibodies to Treponema pallidum in a modified enzyme-linked immunosorbent assay.

The indirect enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin M (IgM) antibodies to Treponema pallidum in sera of syphilitic patients is complicated by false positive reactions due to the interference of IgM rheumatoid factor (IgM-RF) activity and the presence of treponemal IgG antibodies. Another source of error producing false negative results is the competition between treponemal IgG and IgM antibodies for the binding sites on the antigen. To avoid these complications in the indirect Treponema pallidum-specific IgM-ELISA, total IgG was immunoprecipitated from sera of syphilitic patients prior to the assay. The IgM-RF from non-precipitated sera reacted in an IgM-RF-ELISA and in the Treponema pallidum-IgM-specific ELISA with identical titers. After precipitation of total IgG no reaction of the IgM-RF in the assay could be demonstrated. Competition between IgG and IgM antibodies can be prevented almost completely by the precipitation procedure. The sensitivity and specificity of the Treponema pallidum-specific IgM-ELISA after immunoprecipitation of total serum IgG were shown to be higher than 97 percent.

Antibodies, Bacterial↗
PubMed1987

Metabolism of leukotriene B4 by polymorphonuclear granulocytes of severely burned patients.

Leukotriene B4 release from polymorphonuclear granulocytes of severely burned patients was reduced as compared to healthy donor cells. This decrease is due to an enhanced conversion of LTB4 into the 20-hydroxy- and 20-carboxy-metabolites and further to a decreased LTB4-synthesis. In addition, studies on the exogenous LTB4-conversion revealed an unidentified compound which was derived from LTB4. Our data suggest a modulation of the enzymatic activities involved in omega-oxidation of LTB4 (isoenzymes of cytochrome P-450).

Adult↗
PubMed1987

Enzymatic synthesis of riboflavin and FMN specifically labeled with 13C in the xylene ring.

The condensation of 3-hydroximino-2-butanone (1) with 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione (2) yields 6,7-dimethyl-8-ribityllumazine (3). At slightly alkaline pH, the carbonyl group of 1 reacts preferentially with the 5-amino group of 2 (regioselectivity, 4:1). Under acidic conditions, the reaction occurs with higher yield and marginal regioselectivity of opposite direction (1:1.4). Appropriately 13C-labeled samples of 1 afford 3 labeled at C-6 alpha, C-6, C-7 or C-7 alpha. [6 alpha, 7 alpha-13C2]-3 was prepared by condensation of 2 with [1,4-13C2]diacetyl. The lumazines 3 were converted to riboflavin by the enzyme, riboflavin synthase, with almost quantitative yield. By this procedure, any C-atom of the carbocyclic moiety of riboflavin can be selectively labeled with 13C at high abundance. Phosphorylation yields the respectively 13C-labeled FMN samples.

Bacillus subtilis↗
PubMed1987

[Studies on the liberation behavior of insulin from polymeric matrices].

The in-vitro and in-vivo liberation of insulin from embeddings in polymeric matrices was investigated dependent on the charging degree, the particle- and pore size, respectively, of the granules and the dissolution behaviour of the hormone. Polyacrylamide, agar-agar, dextrane and Sephadex G-100 were used as ground-mass. These polymers are characterized by a good swelling and a high binding capacity. If these properties quality them for insulin was investigated in model experiments. Information concerning the obtained retention effects of the matrix mould were produced by photochemical methods (application of insulin against citrate phosphate buffer; absorption region of 230 to 320 nm). The in-vitro effects yielded could be confirmed by means of representative in-vivo studies in eumetabolic insulin sensitive rabbits.

Acrylic Resins↗
PubMed1987

Anti-HIV IgM antibody analysis during early manifestations of HIV infections.

In a prospective study we tested the appearance of IgG and IgM positive viral protein bands in Western blots from six people who seroconverted for anti-HIV antibody. Quantification of the immunoblotted bands was performed by reading the Western blot stripes in Camag scanner and analysed on a 350 computer (digital equipment). In the first serum, all people were negative for anti-HIV antibodies. In the second serum, after 16 to 122 days, all people showed IgM HIV-antibodies to p24. IgG HIV-antibodies were detectable in all people after 18 to 114 days after the second collection. Our data clearly demonstrated that for early analysis of HIV infection only the detection of IgM antibodies to viral protein bands of the Western blot technique provides reliable results and that scanning and advanced integration analysis of the Western blot peaks offer the advantage of direct quantitative comparison of the results, not just qualitative description. Further, this direct quantitative comparison of antibodies to HIV virus protein bands can be used as a prognostic marker for disease states.

Adult↗
PubMed1987

Kinetics of piretanide tablets, penbutolol tablets and the fixed combination of both drugs in healthy male subjects after a single oral dose.

In an open-labelled cross-over study, ten healthy males received an oral dose of piretanide (6 mg tablet), penbutolol (40 mg film-coated tablet) or the fixed dose combination (film-coated tablet). Serum pharmacokinetics and 48 h urinary excretion of each drug were determined for the three dose regimens. The serum pharmacokinetics and excretion of penbutolol were unchanged in combination with piretanide. In combination with penbutolol the maximum serum concentration (Cmax) of piretanide was lowered by 40% (p less than 0.05) and time to reach Cmax delayed from 1.0 h to 1.6 h (p less than 0.05). However, areas under the serum concentration-time curves over 12 h and excretion of piretanide were unchanged, and its diuretic effect was undiminished. Thus the bioavailability of piretanide was unaffected by combination with penbutolol. The above changes in the pharmacokinetics of piretanide were explained entirely by differences in dissolution of the conventional and film-coated tablets. The drugs were safe and well tolerated.

Adult↗
PubMed1987

Measurement of tissue catecholamines of obese rats by liquid chromatography and electrochemical detection.

The content and turnover of norepinephrine was measured in the interscapular brown adipose tissue (BAT), white adipose tissue (WAT) and heart of lean and monosodium glutamate treated obese rats (GOR). An HPLC-ECD method was used for efficient separation and sensitive detection of catecholamines with an appropriate sample preparation, especially for lipid rich tissues. The lower basal norepinephrine level and the slower norepinephrine turnover in organs of the glutamate obese rats indicate a diminished activity of the sympathetic nervous system which may be a reason for a reduced thermogenic response and in this way contributes to the development of obesity.

Adipose Tissue, Brown↗
PubMed1987

[Comparative evaluation of the diagnostic value of indirect and reverse ELISA for demonstrations of specific IgM antibodies in toxoplasmosis in man].

Two ELISA techniques were investigated comparatively regarding their IgM sensitivity and specificity in human toxoplasmosis. Results of the fractionated Toxo-IgM-IIF assay were used as a standard for comparison. In 96 of 264 specimens the Toxo-IgM-IIF assay was positive. Positive sera were investigated quantitatively, negative sera only in the serum dilution 1/50 in both the indirect and the reverse Toxo-IgM ELISA. Sensitivity of the indirect technique was calculated greater than 99% and specificity 97%. The corresponding values for the reverse technique were 66% for sensitivity and greater than 99% for specificity.

Enzyme-Linked Immunosorbent Assay↗
PubMed1987

Relation between microvilli membrane potential and glucose transport capacity of rat small intestine.

Transepithelial electrical potential differences induced by glucose were measured in rat small intestine under conditions of experimental diabetes, application of corticosteroids, adrenalectomy, and inhibition of adrenocortical functions. A close linear correlation between the capacity of monosaccharide absorption and the transepithelial potential difference was found. Microelectrode studies indicated that glucose-induced alterations of the transepithelial potential difference are due to depolarization of the potential difference across the microvilli membrane. Changes in the potential difference across the basolateral plasma membrane were not detectable after addition of glucose.

Animals↗
PubMed1986

Properties of the complexes of riboflavin 3',5'-bisphosphate and the apoflavodoxins from Megasphaera elsdenii and Desulfovibrio vulgaris.

Megasphaera elsdenii and Desulfovibrio vulgaris apoflavodoxins have been reconstituted with riboflavin 3',5'-bisphosphate. Several biochemical and biophysical properties of the complexes have been investigated and the results are compared with the properties of the native proteins. The dissociation constant of the modified complex of M. elsdenii flavodoxin is increased by a factor of about 23 by comparison with that of the native protein. The rate constant for the formation of the complex of M. elsdenii flavodoxin is about 26 times lower than that for the native protein. The redox potential of the transition between the oxidized and semiquinone state is similar to that of the native protein. On the other hand, the redox potential of the semiquinone-hydroquinone transition is about 20 mV more negative than that of the native protein. Absorbance and circular dichroic spectra of the protein-bound artificial prosthetic group and the protein-bound natural prosthetic group are very similar. In both the oxidized and in the fully reduced state only minor differences in interaction between the isoalloxazine ring and the apoprotein for the two flavin derivatives are found by 13C and 15N NMR. 31P-NMR studies show that the 5'-phosphate group of the two flavin derivatives is bound in the same way and that it is dianionic in the complex. In contrast, the 3'-phosphate group in riboflavin 3',5'-bisphosphate is monoanionic or even neutral when bound to the protein. The 3'-phosphate group is also close to or on the surface of the protein. Desulfovibrio vulgaris apoflavodoxin has an affinity for riboflavin 3',5'-bisphosphate which is 10 times higher as compared to Megasphaera elsdenii apoflavodoxin (Ka = 10(8) M-1). Also the association rate constant of Desulfovibrio vulgaris apoprotein and riboflavin 3'5'-bisphosphate is found to be 10 times faster than for the Megasphaera elsdenii flavodoxin reaction. The dissociation behaviour of native Desulfovibrio vulgaris flavodoxin measured under identical conditions as for the riboflavin 3',5'-bisphosphate analog gives a value (Kd approximately equal to 0.2 nM) which is considerably lower than reported earlier [Dubourdieu, M., MacKnight, M. L. & Tollin, G. (1974) Biochem. Biophys. Res. Commun. 60, 649-655]. The results are discussed in the light of the existing crystallographic data of flavodoxins and the recently proposed theory on the regulation of the redox potential in flavoproteins [Moonen, C. T. W., Vervoort, J. & Müller, F. (1984) in Flavins and flavoproteins, pp. 493-496, Walter de Gruyter, Berlin].

Apoproteins↗
PubMed1986

Structure and genomic organization of proretrovirus-like elements partially eliminated from the somatic genome of Ascaris lumbricoides.

A clone containing a middle repetitive element next to satellite DNA has been isolated from a germ line genomic library of the chromatin eliminating nematode Ascaris lumbricoides var. suum. The structure of this element has been elucidated by comparison of several clones containing the element in different environments. It is flanked by 256-bp-long terminal repeats (LTRs) and has an internal region of approximately 7 kb. The nucleotide sequences of both the 5' and the 3' LTRs have been determined. The element has a strong structural similarity with retroviral proviruses and related mobile elements. It was therefore named 'Tas', for transposon-like element of Ascaris. Approximately 50 Tas copies are dispersed over approximately 20 different chromosomal sites. Their genomic distribution varies between individuals, indicating that Tas elements are mobile in the Ascaris genome. Two variant forms, Tas-1 and Tas-2, present in a ratio of approximately 2 to 1 in the germ line genome, have been characterized. They differ not only in their restriction pattern, but also in their elimination behaviour. While only about one-fourth of the Tas-1 elements are expelled from the somatic cell lineage, all Tas-2 copies are specifically eliminated and are thus confined to the germ line cells. We have demonstrated that a cloned representative of Tas-1 elements is expelled concomitantly with its flanking DNA sequences during the chromatin elimination process.

Animals↗
PubMed1986

A comparative carbon-13, nitrogen-15, and phosphorus-31 nuclear magnetic resonance study on the flavodoxins from Clostridium MP, Megasphaera elsdenii, and Azotobacter vinelandii.

The flavodoxins from Megasphaera elsdenii, Clostridium MP, and Azotobacter vinelandii were studied by 13C, 15N, and 31P NMR techniques by using various selectivity enriched oxidized riboflavin 5'-phosphate (FMN) derivatives. It is shown that the pi electron distribution in protein-bound flavin differs from that of free flavin and depends also on the apoflavoprotein used. In the oxidized state Clostridium MP and M. elsdenii flavodoxins are very similar with respect to specific hydrogen bond interaction between FMN and the apoprotein and the electronic structure of flavin. A. vinelandii flavodoxin differs from these flavodoxins in both respects, but it also differs from Desulfovibrio vulgaris flavodoxin. The similarities between A. vinelandii and D. vulgaris flavodoxins are greater than the similarities with the other two flavodoxins. The differences in the pi electron distribution in the FMN of reduced flavodoxins from A. vinelandii and D. vulgaris are even greater, but the hydrogen bond patterns between the reduced flavins and the apoflavodoxins are very similar. In the reduced state all flavodoxins studied contain an ionized prosthetic group and the isoalloxazine ring is in a planar conformation. The results are compared with existing three-dimensional data and discussed with respect to the various possible mesomeric structures in protein-bound FMN. The results are also discussed in light of the proposed hypothesis that specific hydrogen bonding to the protein-bound flavin determines the specific biological activity of a particular flavoprotein.

Azotobacter↗
PubMed1986

The microsomal metabolism of pentachlorophenol and its covalent binding to protein and DNA.

The microsomal metabolism of pentachlorophenol (PCP) was investigated, with special attention to the conversion dependent covalent binding to protein and DNA. The two metabolites detected were tetrachloro-1,2- and tetrachloro-1,4-hydroquinone. Microsomes from isosafrole (ISF)-induced rats were by far the most effective in catalyzing the reaction: the rate of conversion was increased 7-fold over control microsomes. All other inducers tested (hexachlorobenzene (HCB), phenobarbital (PB) and 3-methylcholanthrene (3MC) gave 2--3-fold increases over control. There are indications that the 1,2- and 1,4-isomers are produced in different ratio's by various cytochrome P-450 isoenzymes: Microsomes from PB- and HCB-treated rats produced the tetrachloro-1,4- and tetrachloro-1,2-hydroquinone in a ratio of about 2, while microsomes from rats induced with 3 MC and ISF showed a ratio of about 1.3. When PCP was incubated with microsomes from rats treated with HCB, a mixed type inducer of P-450, the ratio between formation of the 1,4- and 1,2-isomers decreased with increasing concentration of PCP, suggesting the involvement of at least two P-450 isoenzymes with different Km-values. The overall apparent Km-value for HCB-microsomes was 13 microM both for the formation of the soluble metabolites and the covalent binding to microsomal protein, suggesting both stem from the same reaction. The covalent binding could be inhibited by ascorbic acid and this inhibition was accompanied by an increase in formation of tetrachlorohydroquinones (TCHQ). Although a large variation was observed in rates of conversion between microsomes treated with different (or no) inducers, the rate of covalent binding to microsomal protein was remarkably constant. A conversion-dependent covalent binding to DNA was observed in incubations with added DNA which was 0.2 times the amount of binding to protein (37 pmol/mg DNA).

Animals↗
PubMed1986

The microsomal metabolism of hexachlorobenzene. Origin of the covalent binding to protein.

The microsomal metabolism of hexachlorobenzene is studied, with special attention to the covalent binding to protein. The metabolites formed are pentachlorophenol and tetrachlorohydroquinone. In addition, a considerable amount of covalent binding to protein is detected (250 pmoles pentachlorophenol, 17 pmoles tetrachlorohydroquinone and 11 pmoles covalent binding in an incubation containing 50 mumoles of hexachlorobenzene). In order to establish the potential role of reductive dechlorination in the covalent binding, the anaerobic metabolism of hexachlorobenzene was investigated. At low oxygen concentrations no pentachlorobenzene was detected, and only very small amounts of pentachlorophenol as well as covalent binding, indicating a relationship between covalent binding and the microsomal oxidation of hexachlorobenzene. Incubations with 14C-pentachlorophenol at low concentrations showed that a conversion-dependent covalent binding occurs to the extent of 75 pmole binding per nmole pentachlorophenol. This is almost enough to account for the amount of label bound to protein observed in hexachlorobenzene incubations. This indicates that less than 10% of the covalent binding occurs during conversion of hexachlorobenzene to pentachlorophenol, and the remainder is produced during conversion of hexachlorobenzene to pentachlorophenol, and the remainder is produced during conversion of pentachlorophenol. The major product of microsomal oxidation of pentachlorophenol is tetrachlorohydroquinone, which is in redox-equilibrium with the corresponding semiquinone and quinone (chloranil). The covalent binding is inhibited by addition of ascorbic acid or glutathione to the hexachlorobenzene incubations. Ascorbic acid decreases the covalent binding with a simultaneous increase in formation of tetrachlorohydroquinone, probably due to a shift in the redox-equilibrium to the reduced side. Glutathione does not act as a reducing agent, since the inhibition of covalent binding is not accompanied by an increase in tetrachlorohydroquinone formation. Instead, glutathione reacts with chloranil, producing at least three stable products, probably in a Michael-type reaction. These results strongly indicate the involvement of chloranil or the semiquinone radical in the covalent binding during microsomal hexachlorobenzene metabolism.

Animals↗