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Biomedical subjects

T Müller

Publications and source records attributed to T Müller.

At least 19 recordsLinked to original sources
PubMed1995

Quantification and mapping of antigenic determinants of serum amyloid A (SAA) protein utilizing sequence-specific immunoglobulins and Eu3+ as a specific probe for time-resolved fluorometric immunoassay.

Serum amyloid A (SAA) protein, the most prominent amongst acute-phase proteins, is the specific precursor protein of secondary reactive amyloidosis. The fact that SAA once released into the circulation as a 'free' protein rapidly associates with lipoproteins of the high-density range indicates a specific role in lipoprotein metabolism. In this study a new sensitive assay for quantification of human SAA protein in biological specimens using affinity-purified polyclonal antibodies and Eu3+ as a specific probe for time-resolved fluorometric immunoassay is presented. Both purified SAA and SAA-rich high-density lipoprotein particles served as reliable standards in the indirect and the direct sandwich dissociation-enhanced lanthanide fluorescence immunoassay (DELFIA). The detection limit of the DELFIA technique presented was 4-10 ng after sample dilution of 1/2500. The intra-assay coefficient of variation averaged 4.3% whereas the inter-assay coefficient of variation averaged 6.2%. Comparison with the nephelometric assay, a widely and commonly used assay for SAA quantification in plasma, revealed correlation coefficients of 0.9428. In addition to polyclonal anti-human SAA antibodies sequence-specific antibodies raised against synthetic peptides corresponding to region; 1-17, 14-30, 27-44, 40-63, 59-72, 68-84, 79-94, and 89-104 of the human SAA amino acid sequence were studied. Sequence-specific antibodies raised against epitopes 27-44, 59-72, 68-84, and 89-104 recognize human SAA protein in the DELFIA assay whereas antibodies raised against epitopes 1-17, 14-30, 40-63 and 79-94 failed to recognize the corresponding epitopes. Results obtained from these studies indicate that the N-terminal domain (1-30) as well as epitopes 40-63 and 79-94 of human SAA are apparently masked by the environment of the lipoprotein particle. From our studies it is proposed that the epitopes 31-39, 64-78, and 95-104 may be responsible for the interaction of SAA-rich high density lipoprotein particles with peripheral cells.

Antibodies, Monoclonal↗
PubMed1995

Expression of c-fos in quiescent Swiss 3T3 cells exposed to aqueous cigarette smoke fractions.

The exposure of quiescent Swiss 3T3 cells to mainstream cigarette smoke (CS) trapped in PBS solution (smoke-bubbled PBS) resulted in the dose-dependent expression of c-fos mRNA and protein. Kinetic investigations revealed that in contrast to mitogens, which strongly but transiently induce the c-fos promoter within minutes, c-fos transcripts in cells exposed to 0.03 puffs (approximately 1 cm3) of CS/ml of medium accumulated slowly but were still seen after 8 h; the maximum expression rates were between 2 and 6 h of exposure. This specific expression pattern appears to be the result of altered posttranscriptional as well as transcriptional regulation, since a strikingly increased stability of the c-fos message (t1/2, > or = 2 h versus < 20 min in serum-stimulated cells) in smoke-treated cells was observed in addition to slight transcriptional activation of the c-fos promoter. CS-dependent DNA damage can be excluded as the only source for this altered expression pattern, since inhibition of DNA strand break formation by either catalase or o-phenanthroline had no detectable effect on the CS-induced c-fos expression. The results described here, and other CS-dependent cellular and biochemical effects, are similar to those induced in vitro by okadaic acid, a specific inhibitor of cell growth-regulatory protein phosphatases 1/2A (PP-1/2A). Hence, the effects of smoke treatment on these key enzymes were compared to those of okadaic acid based on the ability of cell-free extracts to release radiolabeled phosphate from glycogen phosphorylase a, a substrate of PP-1/2A. Results from these experiments indicate that both treatments inhibited PP-1/2A in a concentration- and analogous time-dependent manner. The data presented suggest that PP-1/2A may, at least in vitro, be targeted by water-soluble active compounds present in cigarette smoke.

3T3 Cells↗
PubMed1995

Human interleukin-4 and variant R88Q: phasing X-ray diffraction data by molecular replacement using X-ray and nuclear magnetic resonance models.

The structure of recombinant human interleukin-4 (hIL-4) has been determined by both NMR and X-ray diffraction methods in several laboratories, including ours. The X-ray and NMR structures were successfully applied for solving the X-ray crystal structure by molecular replacement. Due to the small size of the hIL-4 molecule (129 residues) and its lack of structural diversity (4-helix bundle), this task was especially difficult and required special care with rotation function applications. The crucial point was that proper removal of the Patterson origin peaks was indispensable in all cases. All available structures of hIL-4 were checked, in a standardized procedure, for their suitability as templates for molecular replacement. The models derived from the various structures are close to, but not in all loop details identical with, the genuine X-ray structures. The deviations of the X-ray structure-derived models are of the same magnitude as the differences between the original X-ray structures, while the deviations of the NMR structure-derived models are two to three times as large. The hIL-4 variant R88Q is a binding mutant, its affinity to the receptor is decreased by a factor of about 200. Its X-ray structure was determined by molecular replacement using the wild-type X-ray structure determined in our laboratory as a model. The structure of R88Q is virtually identical with that of the wild-type protein. All differences besides the shortened side-chain of residue 88 occur at surface residues with high temperature factors, i.e. at spots where the structure is not well defined. Since the structure is not perturbed, the biological effect of decreased receptor affinity has to be attributed to the loss of a single positive charge in the surface area of the main receptor contact.

Computer Simulation↗
PubMed1995

Molecular cloning and functional expression in yeast of a human cAMP-specific phosphodiesterase subtype (PDE IV-C).

We have recently reported increased survival of dopaminergic substantia nigra neurons by inhibition of phosphodiesterase type IV enzymes. As a first step to unravel the involvement of PDE IV subtypes in this process, we isolated phosphodiesterase type IV cDNAs from human substantia nigra. One isolated partial cDNA clone was most homologous to the partially cloned rat and human PDE IV-C isogene. Distribution analysis revealed that the enzyme is expressed in various tissues but not in cells of the immune system. Isolation of the full-length human PDE IV-C isogene cDNA and expression in a PDE-deficient yeast strain resulted in functional complementation of the yeast heat shock response. Inhibition of the enzymatic activity by rolipram characterized this enzyme as a typical type IV phosphodiesterase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1995

Effects of aspartame on 45Ca influx and LDH leakage from nerve cells in culture.

Aspartame (ASM), an artificial sweetener, was shown to dose dependently increase 45Ca-influx into and lactate dehydrogenase (LDH) leakage from murine brain cell cultures. Astrocytes were more resistant than neurones to the effects of ASM. In cerebellar granule neurones, a 20% increase in calcium was found after an incubation time of 22 h in the presence of 0.1 mM ASM; at 0.5 mM concentration, calcium influx increased 40% compared with control cultures. At a concentration of 10 mM, influx was increased 13-fold after 5 h. Morphological appearance as judged by phase contrast microscopy was first visibly affected after exposure to 1 mM ASM for 22 h. Citrate, another food additive, was included in the study to demonstrate that cerebellar granule neurones could tolerate 10 mM additions to the medium and citrate did not cause 45Ca influx or morphological changes in neurones after 22 h. LDH leakage, a sign of severe cell damage, was observed at 1 mM concentrations of ASM after 22 h. Cerebral astrocytes on the other hand were more resistant and showed morphological changes, increased calcium influx and LDH leakage first at 5 mM concentrations of ASM.

Animals↗
PubMed1995

[Partnership and sex behavior of consumers of illegal drugs: a survey of 654 persons in the "open" drug scene in Zurich].

In the spring of 1991, a survey was carried out in the "open" drug scene in Zürich's Platzspitz area with the objective of studying drug users' behaviour with regard to relationships and sexuality, a random sample of 654 users (both male and female) of illegal drugs being interviewed and the data drawn from these interviews being compared with corresponding data on average young adults aged 17 to 30. The latter data have been continuously collected since 1986 to evaluate Switzerland's strategy to prevent AIDS. About fifty per cent of drug users are in steady relationships, which is a smaller proportion than among average young adults. On the other hand, occasional sexual contacts (whether or not a steady relationship exists) are three times as frequent among drug users. The use of condoms is slightly more frequent here than among the average population, but is not as yet-and especially among those who are HIV-positive-consistent enough by any means. The influence of drug abuse on sexuality is usually felt to be negative (decline in libidinal energy, impotence), and often brings about a decrease in sexual contacts. This is equally true of both opiates and stimulants (cocaine, amphetamine). Promiscuous behaviour is rare as such and does not occur with any greater frequency than among the average population. However, a large proportion of drug users is at some stage exposed to prostitution. In summary, one can say that the preventive strategy continues to be deficient where the sexual activities of drug users are concerned. A greater effort should be made, in this context, to target the following groups: persons already frequenting advice centers, persons who are HIV-positive, and male prostitutes.

Adolescent↗
PubMed1995

A seroepidemiological survey for orthopox virus in the red fox (Vulpes vulpes).

703 blood samples from red foxes (Vulpes vulpes) were investigated to determine the prevalence of antibody against an orthopox virus (vaccinia virus strain Elstree). A blocking-ELISA based on a neutralizing monoclonal antibody was used. In this assay 46 sera (6.5%) were positive with titers of 1:2 to 1:16. ELISA-results were confirmed by the plaque reduction test with 44 of the 46 sera reacting positively. The specificity of antibodies in 21 selected sera was also demonstrated by Western blot analysis.

Animals↗
PubMed1995

Further analysis of the mechanisms underlying the tracheal relaxant action of SCA40.

1. SCA40 (1nM-10 microM), isoprenaline (1-300 nM) and levcromakalim (100 nM-10 microM) each produced concentration-dependent suppression of the spontaneous tone of guinea-pig isolated trachea. Propranolol (1 microM) markedly (approximately 150 fold) antagonized isoprenaline but did not antagonize SCA40. The tracheal relaxant action of SCA40 was unaffected by suramin (100 microM) or 8-(p)-sulphophenyltheophylline (8-SPT; 140 microM). 2. An isosmolar, K(+)-rich (80 mM) Krebs solution increased tracheal tone, antagonized SCA40 (approximately 60 fold), antagonized isoprenaline (approximately 20 fold) and very profoundly depressed the log concentration-effect curve for levcromakalim. Nifedipine (1 microM) did not itself modify the relaxant actions of SCA40, isoprenaline or levcromakalim. However, nifedipine prevented the rise in tissue tone and the antagonism of SCA40 and isoprenaline induced by the K(+)-rich medium. In contrast, nifedipine did not prevent the equivalent antagonism of levcromakalim. 3. Charybdotoxin (100 nM) increased tracheal tone, antagonized SCA40 (approximately 4 fold) and antagonized isoprenaline (approximately 3 fold). Nifedipine (1 microM) prevented the rise in tissue tone and the antagonism of SCA40 and isoprenaline induced by charybdotoxin. 4. Quinine (30 microM) caused little or no change in tissue tone and did not modify the relaxant action of isoprenaline. However, quinine antagonized SCA40 (approximately 2 fold). Nifedipine (1 microM) prevented the antagonism of SCA40 induced by quinine. 5. Tested on spontaneously-beating guinea-pig isolated atria SCA40 (1 nM-10 microM) increased the rate of beating in a concentration-dependent manner. Over the concentration-range 1 microM-10 microM, SCA40 also caused an increase in the force of atrial contraction. 6. Intracellular electrophysiological recording from guinea-pig isolated trachealis showed that the relaxant effects of SCA40 (1 micro M) were often accompanied by the suppression of spontaneous electrical slow waves but no change in resting membrane potential. When the concentration of SCA40 was raised to 10 micro M, its relaxant activity was accompanied both by slow wave suppression and by plasmalemmal hyperpolarization.7. SCA40 (10 nM- 100 micro M) more potently inhibited the activity of cyclic AMP phosphodiesterase (PDE)than that of cyclic GMP PDE derived from homogenates of guinea-pig trachealis. Theophylline(1 micro M- 1O mM) also inhibited these enzymes but was less potent than SCA40 in each case and did not exhibit selectivity for inhibition of cyclic AMP hydrolysis.8. Tested against the activity of the isoenzymes of cyclic nucleotide PDE derived from human blood cells and lung tissue, SCA40 proved highly potent against the type III isoenzyme. It was markedly less potent against the type IV and type V isoenzymes and even less potent against the isoenzymes types I and II.9. It is concluded that the tracheal relaxant action of SCA40 (1 nM- 1 micro M) does not involve the activation of beta-adrenoceptors or P1 or P2 purinoceptors. Furthermore, this action is unlikely to depend upon the opening of BKca channels with consequent cellular hyperpolarization and voltage-dependent inhibition of Ca2+ influx. The tracheal relaxant action of SCA40 (up to 1 micro M) is more likely to depend upon its selective inhibition of the type III isoenzyme of cyclic nucleotide PDE. At concentrations above 1 micro M, SCA40 exerts more general inhibition of the isoenzymes of cyclic nucleotide PDE and may then promote the opening of BKca channels.

Animals↗
PubMed1995

Palinopsia as sensory epileptic phenomenon.

Visual perseveration (VP) is defined as persistence or recurrence of visual images, when the stimulus is no longer present. We report three patients with occipital cortical lesions in the right hemisphere and VP. Electroencephalography showed epileptic abnormalities in all cases. In one patient synchronous electroencephalic recordings during the onset of palinopsia-a subtype of VP-revealed, that VP was associated with a clear cut right occipital seizure with a secondary diffusion of the discharge over both hemispheres, which has not been reported in combination with the onset of palinopsia heretofore. In all three patients sensory seizures have to be considered as probable cause of VP.

Adult↗
PubMed1995

Distorted color discrimination in 'de novo' parkinsonian patients.

We performed the Farnsworth-Munsell 100-hue test in 16 "de novo" patients with Parkinson's disease and 16 age-matched controls to determine their color discrimination ability. The mean total error score in patients was significantly elevated as compared with controls (64.6 in patients versus 16.0 in controls). We conclude that the impairment of color discrimination may be an early sign in Parkinson's disease.

Color Perception↗
PubMed1995

Developmental regulation of ion channels and receptors on glial cells.

The electrophysiological properties of glial precursor cells and oligodendrocytes were studied in an intact tissue preparation, the corpus callosum slice, with the patch-clamp technique. The pattern of voltage-gated currents exhibited by different cell types in this white matter tract was compared with that from cultured cells of the O-2A lineage. Precursor cells from the in vitro and the in situ preparation were strikingly similar in most aspects. In contrast, oligodendrocytes in the intact tissue differed from their culture correlates and displayed the ability to redistribute excess K+. To study glial transmitter receptors in neuronglial interactions during development, Bergmann glial cells were investigated in a slice preparation of the cerebellum.

Animals↗
PubMed1995

Antagonistic mutant proteins of interleukin-4.

Interleukin-4 is a major regulator of the immune system, directing e.g. induction of a TH2 phenotype in T-cells, activation of B-cells and synthesis of IgE type antibodies, which are associated with allergic responses. Site-directed mutagenesis has revealed two sites important for receptor interaction on IL-4: site I mediates binding to the IL-4 receptor alpha subunit, and site II is involved in signal transduction through the receptor complex. Specific mutations in site II produced a series of ligands which bound to the receptor with high affinity, but had little or no agonistic activity and inhibited effects of wild type IL-4. The closely related cytokine IL-13, also a mediator of allergic processes, is antagonized as well. Antagonistic site II mutants of human IL-4 are therefore effective inhibitors with therapeutic potential for IL-4 associated diseases like type I hypersensitivity and asthma.

Amino Acid Sequence↗
PubMed1995

[Is insufflation with carbon dioxide as an ambulatory procedure for evaluating tubal patency obsolete today?].

UNLABELLED: Tubal insufflation with carbon dioxide is one of the ambulatory and non-invasive procedures in use for the evaluation of tubal patency. The aim of the present study was to investigate whether the findings obtained at tubal insufflation are reliable enough to avoid laparoscopy with instillation of dye for its inherent risk of severe operative complications. Diagnostic accuracy, positive and negative predictive value of tubal insufflation were compared with that of the reference method (laparoscopy) in 107 infertile patients of childbearing age without previous pelvic inflammatory disease, tubal or ovarian surgery. No result was obtained from tubal insufflation in 13 patients for intolerance or technical problems. The positive predictive value (percentage of correct positive findings, i.e., tubes patent) was 0.79 (130/165 tubes), the negative predictive value (percentage of correct negative findings) 0.43 (10/23) with an overall diagnostic accuracy (percentage of correct findings) of 0.74. If both tubes were reported patent on insufflation (68 patients), this finding was confirmed in 82% (56/68) on laparoscopy. The remaining 18% also include the rate of false negative findings (tubes falsely reported as occluded) on laparoscopy which may account for up to 10% according to the literature. False negative findings on insufflation were reported at a frequency of 21% (35/165 tubes). COMMENT: The diagnostic accuracy of tubal insufflation with carbon dioxide is definitely inferior to that of laparoscopy. In view of the frequency of false negative findings, its use as a screening procedure should be restricted to young patients with a low probability of tubal occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Cell manipulation and cultivation under a.c. electric field influence in highly conductive culture media.

Extreme miniaturisation of electrodes enabled us to apply high-frequency electric fields (between 100 kHz and several hundred MHz) of field strengths up to 50 kV/m into cell suspensions of high conductivity (several S/m), such as original cell culture media. The active electrode areas were additionally decreased and modified by insulating the terminals and/or coating of the electrodes with thin dielectric layers. Micro scaled electrode structures were fabricated on glass or silicon wafers in semiconductor technology. It could theoretically and experimentally be shown that cells exhibit exclusively negative dielectrophoresis if suspended in highly conductive media. Therefore, they can be repulsed from surfaces by appropriate arrangements of electrodes and easily be manipulated in free solution. Adherently growing animal cells, like mouse fibroblasts (3T3, L929), were cultivated in Dulbecco's Modification of Eagle's Medium (DMEM) or RPMI 1640 under permanent field application (frequency: 10 MHz, field strength: 50-100 kV/m).

3T3 Cells↗
PubMed1994

RAP1 stimulates single- to double-strand association of yeast telomeric DNA: implications for telomere-telomere interactions.

Repressor Activator Protein 1 (RAP1) of Saccharomyces cerevisiae is an abundant nuclear protein implicated in telomere length maintenance, transactivation, and in the establishment of silent chromatin domains. The RAP1 binding site 5' of the yeast HIS4 gene is also a region of hyperrecombination in meiosis. We report here that as RAP1 binds its recognition consensus, it appears to untwist double-stranded DNA, which we detect as the introduction of a negative supercoil in circularization assays. Coincident with the RAP1-dependent untwisting, we observe stimulation of the association of a single-stranded yeast telomeric sequence with its homologous double-stranded sequence in a supercoiled plasmid. This unusual distortion of the DNA double helix by RAP1 may contribute to the RAP1-dependent enhancement of recombination rates and promote non-duplex strand interactions at telomeres.

Base Sequence↗