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M Müller

Publications and source records attributed to M Müller.

At least 1,027 records · Page 57Linked to original sources
PubMed1992

Whole-body protein parameters in premature infants: a comparison of different 15N tracer substances and different methods.

[15N]glycine, [15N]leucine, and [15N]yeast protein thermitase hydrolysate (YPTH) as tracers for investigating the protein turnover rates in premature infants were studied in nine human milk-fed neonates (born after 32 to 34 wk of gestation) by paired comparison of the tracers. The 15N enrichment of total urinary nitrogen and ammonia after administration of a single oral dose of 15N was measured by emission spectrometry. Flux rates were calculated using a three-compartment model and the ammonia end product method. The mean whole-body protein synthesis rates, as determined by the three-compartment model derived from the three 15N tracers, differed significantly (p less than 0.01) among [15N]glycine (15.9 g/kg/d), [15N] leucine (9.1 g/kg/d), and 15N-YPTH (5.9 g/kg/d). When the corresponding rates were determined from the excretion of label in ammonia, the results showed the opposite tendency; the lowest apparent synthesis rates were found after [15N]glycine (7.5 g/kg/d), followed by [15N]leucine (14.4 g/kg/d), and the highest figure resulted after [15N] YPTH (16.7 g/kg/d). The results of this comparison substantiate the assumption that there are methodologic errors in connection with the use of different tracers and models for the calculation of whole-body protein parameters in preterm infants, with respect to the main requirement for tracer kinetic studies; the tracer nitrogen must be representative of total amino acid nitrogen. Seen in this light, mixtures of completely labeled amino acids such as YPTH may represent the most reliable tracer substance.(ABSTRACT TRUNCATED AT 250 WORDS)

Fungal Proteins↗
PubMed1992

Towards high resolution SEM of biological objects.

The major task of biological high resolution SEM and TEM is to provide structural information for correlating structure and function. It is the only methodology with the inherent power needed to observe structures down to molecular dimensions within the context of complex biological systems. Specimen preparation and imaging techniques should therefore be directed towards the preservation and imaging of the smallest significant details in order to fully exploit this unique, integrating feature of biological electron microscopy, complementing the progress of the techniques used in cell biology, biochemistry, and molecular biology.

Animals↗
PubMed1992

Light microscopical demonstration of non-specific alkaline phosphatase activity with an incubation medium containing cerium and two calcium as the capturing agents. The cerium/calcium-hydrogen peroxide-P-phenylenediamine/pyrocatechol (Ce/Ca-H2O2-PPD/PC) double capture technique.

A new method for the light microscopical demonstration of alPase activity in cryotome sections by using simultaneously cerium and calcium as capturing agents (double capture technique) is described. This method has an increased sensitivity compared with the single cerium-based and the Gomori based-cerium (single calcium and cerium converted) with techniques described previously. Presuming that the enzymatic activity during incubation of sections in the presence of a defined capturing agent is constant, the increased sensitivity after employment of the double capture method could be attributed to a decrease of enzyme inhibition by cerium through the presence of calcium. Based on model experiments it is assumed that calcium phosphate and cerium phosphate are the primary reaction products, the former converting into cerium phosphate already during incubation. The remaining calcium phosphate is converted completely by treatment with cerium citrate solution (conversion reaction). After oxidation with H2O2 the cerium perhydroxyphosphate was visualized in a paraphenylenediamine/pyrocatechol (Hanker-Yates reagent) solution without H2O2 to give a black reaction product. This visualization procedure is superior to the DAB or DAB-Ni mode as published earlier. Some results concerning the mode of inhibition of the pseudoperoxidase activity of the hemoglobin are presented.

Alkaline Phosphatase↗
PubMed1992

Cough induced by ACE-inhibitors. A kinin related phenomenon?

Cough induced by ACE-inhibitors may be related to bronchial hyperreactivity and/or to an accumulation of kinins. In a placebo-controlled, double-blind randomized study in asthmatic and hypertensive patients lung function and bronchial reactivity to histamine and bradykinin remained unaltered although in hypertensive patients with cough, reactivity to histamine tended to be more pronounced and bronchial hyperreactivity to be more frequent than in those without cough. The findings do not support a major role of kinins in ACE inhibitor-induced cough.

Adult↗
PubMed1992

Airway responsiveness and cough induced by angiotensin converting enzyme inhibition.

Dry cough is one of the most common side-effects of angiotensin converting enzyme inhibitors. The mechanism of cough induced by ACE inhibitors is not completely understood and may be related to bronchial hyperreactivity and/or an accumulation of kinins. In a placebo-controlled, double-blind randomised study, the effect of captopril on lung function and bronchial reactivity to histamine and bradykinin was investigated in eight asthmatic and 12 hypertensive patients (six with and six without cough during previous ACE inhibition). Lung function did not change in any patient after a single (25 mg) or short-term (2 x 25 mg for two weeks) administration of captopril. Bronchial reactivity to histamine and bradykinin remained unaltered in all groups. In hypertensive patients with cough, reactivity to histamine tended to be more pronounced and bronchial hyperreactivity to be more frequent than in those without cough. In conclusion, the present results do not support a major role for kinins in cough induced by ACE inhibition. On the other hand, bronchial hyperreactivity may be important in some patients. Additionally, these results demonstrate that treatment with ACE inhibitors is safe in most patients with bronchial asthma.

Adult↗
PubMed1992

[The detection of Alternaria mycotoxins in laboratory culture].

Analytical methods are described for detection of the Alternaria mycotoxins alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT) and tenuazonic acid (TeA) in natural and semisynthetic laboratory cultures. After extraction and purification of the crude extract by column chromatography on silica gel the qualitative and quantitative analyses were carried out by thin layer (TLC)- and high performance liquid chromatography (HPLC). HPLC separations were achieved using a Hypersil ODS column with methanol/water containing a complexing agent as eluent. Detection at 340 nm (AOH, AME, ALT) and 280 nm (TeA), respectively, has proved to be favourably. AME and TeA were produced in high purity and high yields as standard substances by two Alternaria strains. The identity of the toxins could be confirmed by EI-, CI- and FAB-mass spectrometry.

Alternaria↗
PubMed1992

[Toxin-producing ability of molds of the genus Alternaria].

The ability to produce the Alternaria mycotoxins alternariol (AOH), alternariol monomethyl ether (AME) and altenuene (ALT) were studied on 87 Alternaria strains. 50 isolates were studied to produce tenuazonic acid (TeA). The strains were isolated from CCM-maize and stored hay. They were cultured under optimum conditions and analysed by various chromatographic methods for the 4 mycotoxins. All Alternaria strains studied produced AME and TeA, 77 per cent also AOH. A production of ALT was detected only in 18 per cent of the isolates. The concentrations of toxins produced were 0.08-482 (162) ppm for AME, 0.05-1862 (121) ppm for AOH, 0.1-34 (9.1) ppm for ALT and 0.02-42 (11.3) mg/100 ml liquid medium for TeA. The species Alternaria alternata (Fries) Keissler and Alternaria tenuissima (Kunze:Fr.) Wiltshire produced the greatest amounts of all mycotoxins studied.

Alternaria↗
PubMed1992

Selective toxicity of ethacrynic acid towards lymphocytes of chronic lymphocytic leukemia in vitro.

We have used the MTT colorimetric assay to determine the sensitivity to ethacrynic acid of lymphocytes from normal donors and of peripheral blood cells from leukaemia patients. Whereas normal lymphocytes and cells from acute or chronic myeloid leukaemia showed similar sensitivities (median inhibitory dose, ID50 = 20-22 microM), lymphocytes from chronic lymphocytic leukaemia patients were much more sensitive (ID50 = 6 microM). This result was found irrespective of the assay duration.

Cell Survival↗
PubMed1991

Peroxisomal degradation of leukotrienes by beta-oxidation from the omega-end.

Chain shortening via beta-oxidation from the omega-end has been recognized as the major pathway for the degradation of cysteinyl leukotrienes as well as leukotriene B4 (LTB4). The metabolic compartmentation of this pathway was studied using peroxisomes purified from normal and clofibrate-treated rat liver. beta-Oxidation products of omega-carboxy-LTB4, including omega-carboxy-dinor-LTB4 identified by gas chromatography-mass spectrometry, were formed by the isolated peroxisomes. The reaction was dependent on CoA, ATP, and NAD and was stimulated by FAD. NADPH was necessary for the further metabolism of omega-carboxy-dinor-LTB4. Together with microsomes a degradation of omega-carboxy-LTB4 also proceeded in isolated mitochondria in the presence of CoA, ATP, and carnitine. beta-Oxidation of the cysteinyl leukotriene omega-carboxy-N-acetyl-leukotriene E4 was observed only with isolated peroxisomes in combination with lipid-depleted microsomes. Direct photoaffinity labeling using omega-carboxy-[3H] LTB4 and omega-carboxy-N-[3H]acetyl-LTE4 served to identify peroxisomal leukotriene-binding proteins. The bifunctional protein (EC 4.2.1.17 and 1.1.1.35) and 3-ketoacyl-CoA thiolase (EC 2.3.1.16) of the peroxisomal beta-oxidation system were the predominantly labeled polypeptides as revealed by precipitation with monospecific antibodies. In vivo studies with N-acetyl-[3H2]LTE4, N-acetyl-[3H8]LTE4, and N-[14C]acetyl-LTE4 after treatment with the peroxisome proliferator clofibrate indicated formation and biliary excretion of large amounts of metabolites more polar than omega-carboxy-tetranor-N-acetyl-LTE3 including omega-carboxy-tetranor-delta 13-N-acetyl-LTE4 and omega-carboxy-hexanor-N-acetyl-LTE3. Increased formation of beta-oxidized catabolites of N-acetyl-LTE4 and LTB4 was also observed in hepatocytes isolated after clofibrate treatment. Our results indicate that peroxisomes play a major role in the beta-oxidation of leukotrienes from the omega-end. Whereas omega-carboxy-LTB4 was beta-oxidized both in isolated peroxisomes and mitochondria, the cysteinyl leukotriene omega-carboxy-N-acetyl-LTE4 was exclusively degraded in peroxisomes.

Affinity Labels↗
PubMed1991

High-frequency mutagenesis of human cells and characterization of a mutant unresponsive to both alpha and gamma interferons.

2fTGH is a human cell line containing the selectable marker guanine phosphoribosyltransferase regulated by alpha interferon (IFN-alpha). Two IFN-alpha-unresponsive mutants were isolated previously at a low frequency (ca. 10(-8)) by selecting mutagenized 2fTGH cells in selective medium containing 6-thioguanine and IFN-alpha. By using five rounds of mutagenesis, mutants can be isolated at an appreciably higher frequency, greater than 3 x 10(-7). Five new mutants have been isolated, and all are recessive, as are the two mutants we described previously. The seven mutants are in four complementation groups (U1-U4). Since several different types of mutants unresponsive to IFN-alpha have been isolated with high frequency, related approaches may succeed with other cytokines or growth factors. Mutants in the two new complementation groups U3 and U4 are unresponsive to IFN-alpha and, surprisingly, also unresponsive to IFN-gamma. They are also partially defective in response to double-stranded RNA. These results indicate that the signaling pathways for the two types of IFN and double-stranded RNA share common components or that their function depends on common enzymes or transcription factors. IFN receptors are unaffected in mutants U3A and U4A. A major defect appears to be in the synthesis or activation of E, the transcription factor mediating the primary response to type I (alpha/beta) IFNs. Band-shift complementation assays show that U3A contains the E gamma subunit but does not contain an active E alpha subunit after treatment with IFN-alpha.

Aminacrine↗
PubMed1991

Polymerase chain reaction to evaluate antiviral therapy for cytomegalovirus disease.

A sensitive and specific method to monitor suppression of cytomegalovirus (CMV) replication is essential in patients treated with ganciclovir after allogeneic bone-marrow transplantation. In this study, antiviral therapy of eighteen episodes of symptomatic CMV infection in 15 such patients were followed up clinically and by virus culture and polymerase chain reaction (PCR). Clinical improvement, culture, and PCR were assessed for their ability to predict the efficacy of ganciclovir therapy in each patient. In eleven successfully treated episodes of CMV disease (disappearance of symptoms and improvement in biochemical variables) clinical improvement was associated with an effective suppression of virus replication as shown by negative culture and PCR assays of blood and urine specimens obtained after antiviral therapy. 1 patient who did not improve clinically when receiving antiviral therapy remained both culture positive and PCR positive for CMV. 6 patients with early relapse of CMV disease or who died after an initial clinical improvement were PCR positive but culture negative after termination of therapy. Demonstration of CMV in blood and urine by PCR after stopping antiviral therapy (even when culture is negative) points to incomplete suppression of virus replication. The findings show that PCR is a better predictor of the efficacy of antiviral therapy than are culture or clinical assessment.

Adult↗
PubMed1991

ATP-dependent transport of taurocholate across the hepatocyte canalicular membrane mediated by a 110-kDa glycoprotein binding ATP and bile salt.

Direct photoaffinity labeling of liver plasma membrane subfractions enriched in sinusoidal and canalicular membranes using [35S]adenosine 5'-O-(thiotriphosphate) ([35S]ATP gamma S) allows the identification of ATP-binding proteins in these domains. Comparative photoaffinity labeling with [35S]ATP gamma S and with the photolabile bile salt derivative (7,7-azo-3 alpha, 12 alpha-dihydroxy-5 beta-[3 beta-3H]-cholan-24-oyl-2'- aminoethanesulfonate followed by immunoprecipitation with a monoclonal antibody (Be 9.2) revealed the identity of the ATP-binding and the bile salt-binding canalicular membrane glycoprotein with the apparent Mr of 110,000 (gp110). The isoelectric point of this glycoprotein was 3.7. Transport of bile salt was studied in vesicles enriched in canalicular and sinusoidal liver membranes. Incubation of canalicular membrane vesicles with [3H] taurocholate in the presence of ATP resulted in an uptake of the bile salt into the vesicles which was sensitive to vanadate. ATP-dependent taurocholate transport was also observed in membrane vesicles from mutant rats deficient in the ATP-dependent transport of cysteinyl leukotrienes and related amphiphilic anions. Substrates of the P-glycoprotein (gp170), such as verapamil and doxorubicin, did not interfere with the ATP-dependent transport of taurocholate. Reconstitution of purified gp110 into liposomes resulted in an ATP-dependent uptake of [3H]taurocholate. These results demonstrate that gp110 functions as carrier in the ATP-dependent transport of bile salts from the hepatocyte into bile. This export carrier is distinct from hitherto characterized ATP-dependent transport systems.

ATP-Binding Cassette Transporters↗
PubMed1991

Hydrogenosomal succinate thiokinase in Tritrichomonas foetus and Trichomonas vaginalis.

Succinate thiokinase displays a diversity of nucleotide specificity and molecular size throughout Nature. Eukaryotes and Gram-positive bacteria possess distinct 'small' (dimeric) thiokinase enzymes which are specific for adenine (ADP) or guanine (GDP) nucleotides, whereas Gram-negative bacteria contain a single 'large' (tetrameric) enzyme which utilizes both nucleotides. Succinate thiokinase activities, both ADP- and GDP-dependent, were shown to be hydrogenosomal in Tritrichomonas foetus and Trichomonas vaginalis. Surprisingly, the 'small' enzyme was found in T. foetus whereas T. vaginalis contained a 'large' enzyme.

Adenosine Diphosphate↗
PubMed1991

Disease resistance in farm animals.

Genetic variations in disease resistance of farm animals can be observed at all levels of defence against infectious agents. In most cases susceptibility to infections has polygenic origins. In domestic animals only a few instances of a single genetic locus responsible for disease resistance are known. A well-examined example is the Mx1 gene product of certain mice strains conferring selective resistance to influenza virus infections. Attempts to improve disease resistance by gene transfer of different gene constructs into farm animals include the use of monoclonal antibody gene constructs, transgenes consisting of antisense RNA genes directed against viruses and Mx1 cDNA containing transgenes.

Animals↗