Search PubMed⌕ Search

Biomedical subjects

T Weber

Publications and source records attributed to T Weber.

At least 235 records · Page 13Linked to original sources
PubMed1994

Insertion of filamin into lipid membranes examined by calorimetry, the film balance technique, and lipid photolabeling.

The interaction of the actin-binding protein filamin with mixtures of zwitterionic and anionic phospholipids (DMPC, DMPG, PC, PS) was studied in reconstituted lipid monolayers and bilayers. Protein-lipid interactions were investigated by differential scanning calorimetry, the film balance technique, and hydrophobic photoradiolabeling. For calorimetric assays, multilamellar vesicles (MLVs) and large unilamellar vesicles produced by the extrusion technique (LUVETs) were used. With MLVs, filamin induced a pronounced drop in phase transition cooperativity. Mixed DMPC/DMPG LUVETs showed a linear decrease of the main phase transition enthalpy and a significant shift in temperature for the solidus and liquidus lines with increasing mole fractions of reconstituted filamin. The insertion of native filamin into uncharged and negatively charged lipid monolayers was measured in time/area diagrams with the film balance technique. Finally, we have newly synthesized a highly sensitive lipid analogue, [125]TID-PC/16, which selectively labels membrane-embedded hydrophobic domains of proteins, and which proved to label filamin, supporting evidence that this protein partially inserts into the hydrophobic domain of liposomes.

Calorimetry, Differential Scanning↗
PubMed1994

Identification of functional domains in the cytoskeletal protein talin.

The cytoskeletal protein talin potentially plays a key role in actin-membrane linkage. It is able to nucleate actin filament growth in vitro while binding simultaneously to lipid bilayers. Thrombin digestion of human platelet talin yields tow polypeptide domains of 200 kDa and 47 kDa. We have purified these fragments and analyzed their functional properties: the 200-kDa fragment was active in nucleating actin filament formation and reduced the viscosity of filamentous actin, comparable to the effects of the intact protein. The 47-kDa fragment was inactive in this respect. However, the 47-kDa polypeptide, but not the 200-kDa fragment, interacted specifically with large liposomes containing acidic phospholipids. This is demonstrated by selective, hydrophobic photolabeling of the 47-kDa fragment using phosphatidylserine liposomes containing trace amounts of a photoactivable phospholipid analogue and by selective co-sedimentation of this domain with the liposomes. The 200-kDa fragment, whether alone or in conjunction with the small fragment, neither incorporated significant amounts of label nor co-sedimented with the liposomes. We thus are able to attribute specialized functions to distinct domains on the talin molecule. These enable the protein to interact simultaneously with actin filaments and lipid membranes.

Actins↗
PubMed1994

Evidence for H(+)-induced insertion of influenza hemagglutinin HA2 N-terminal segment into viral membrane.

Fusion of influenza virus with target membranes is induced by acid and involves complex changes in the viral fusion protein hemagglutinin. At 0 degree C, in a first kinetically resolvable step, the hemagglutinin polypeptide 2 (HA2) N-terminal segment (fusion peptide) is exposed and inserts into the target membrane (Tsurudome, M., Glück, R., Graf, R., Falchetto, R., Schaller, U., and Brunner, J. (1992) J. Biol. Chem. 267, 20225-20232). We now report studies of the changes taking place at pH 5.0 and 37 degrees C, conditions that result in fusion or, in the absence of a target membrane, in inactivation of the virus' fusion capacity. To this end, we synthesized the new photosensitive phospholipid, 1-palmitoyl-2-[decanedioyl mono-[2-(125I)iodo-4-(3-trifluoromethyl-3H-diazirin-3-yl)-benzyl]e ster]- sn-glycero-3-phosphocholine (specific radioactivity, > 2000 Ci/mmol), and worked out a protocol to incorporate this lipid into the viral membrane. Subsequent photoactivation of the reagent resulted in selective labeling of the C-terminal portion of the HA2 polypeptide chain, in agreement with the membrane topology of hemagglutinin. When, however, prior to reagent activation, the viruses were exposed at pH 5.0, 37 degrees C, both the HA2 C-terminal and the N-terminal regions were labeled, suggesting that the HA2 N-terminal segment (fusion peptide) inserted into the viral membrane. Possible implications for fusion and virus inactivation are discussed.

Animals↗
PubMed1994

Induction of labour by balloon catheter with extra-amniotic saline infusion (BCEAS): a randomised comparison with PGE2 vaginal pessaries.

OBJECTIVE: A new method for induction of labour--balloon catheter with extra-amniotic saline infusion (BCEAS)--is evaluated in randomised comparison with prostaglandin E2 (PGE2) in vaginal pessaries. STUDY GROUP: One-hundred and nine pregnant women with unfavourable cervices. MAJOR OUTCOME MEASURES: The efficiency of inducing vaginal delivery and the level of 'disadvantages following induction of labour' (DisFIL scorings). RESULTS: Overall, BCEAS was less efficient inducing vaginal delivery than vaginal PGE2 (P < 0.01) because of a significant difference among parous women (P < 0.01). In the (larger) primiparous women group, and particularly in the subgroup of these having very low pelvic scores (Lange score, < or = 3), the efficiencies of the two methods were equal (P = 0.06) and P = 0.55, respectively). The levels of DisFIL scorings were not significantly different. However, higher rates of caesarean section followed BCEAS than PGE2 (29% and 10%, respectively; P < 0.05). Serious infectious complications were not recorded following BCEAS. No difference was apparent in the status of the neonates (judging from Apgar scores and umbilical artery pH and SBE). The women, delivering vaginally, commented the two methods equally favourably. CONCLUSION: BCEAS was less efficacious than vaginal PGE2 pessaries, though among primiparous women, especially those with very unfavourable cervices, the difference was not significant. Further refinements of the method are suggested.

Administration, Intravaginal↗
PubMed1994

Conversion of acetyl-coenzyme A into 3-hydroxy-3-methylglutaryl-coenzyme A in radish seedlings. Evidence of a single monomeric protein catalyzing a FeII/quinone-stimulated double condensation reaction.

We solubilized from radish membranes and purified to apparent homogeneity a monomeric protein (55.5 kDa) capable of catalyzing the two-step conversion of acetyl-CoA into 3-hydroxy-3-methylglutaryl(HMG)-CoA. Unlike the situation described for other eukaryotes (yeast, animals), both enzyme activities needed for HMG-CoA synthesis (acetoacetyl-CoA thiolase, AACT and HMG-CoA synthase, HMGS) appear to be localized on a single polypeptide. Thus, the enzyme system is further referred to as AACT/HMGS. The reaction as catalyzed by purified AACT/HMGS is strongly stimulated in vitro in presence of FeII-chelates (namely EDTA) and of quinone cofactors with pyrroloquinoline quinone (PQQ) being by far the most effective one studied so far. Whereas the FeII stimulation is apparently due to a Vmax effect, PQQ increases the affinity of the enzyme system towards acetyl-CoA (1.9 microM vs. 5.9 microM, at 50 microM FeII, 100 microM EDTA, 20 microM PQQ). Stimulation by naphthoquinone (NQ) can be overcome in the presence of halogenated NQ-derivatives, while activation by PQQ remains unaffected, possibly indicating a much more specific-binding of the latter cofactor. Gel filtration experiments of enzyme after preincubation in presence of PQQ indicate that there is no covalent-binding of the quinone cofactor to the enzyme. As is also shown with partially purified enzyme from maize membranes, phenylhydrazine, known to react with PQQ as the prosthetic group of quinoproteins (see van der Meer et al. (1987) FEBS Lett. 221, 299-304), efficiently inhibits the reaction. The data lead us to suggest a reaction mechanism that involves radical formation by the redox couple FeII/PQQ, thereby possibly facilitating the energetically unfavorable Claisen condensation as catalyzed during the first partial (AACT) reaction.

Acetyl Coenzyme A↗
PubMed1994

Comparative analysis of intrathecal antibody synthesis and DNA amplification for the diagnosis of cytomegalovirus infection of the central nervous system in AIDS patients.

We evaluated 49 paired cerebrospinal fluid (CSF) and serum samples of 35 patients infected with the human immunodeficiency virus type 1 (HIV-1) for laboratory evidence of cytomegalovirus (CMV) infection. The patients were grouped according to clinical criteria as probable CMV encephalitis/polyradiculomyelitis, CMV retinitis, cerebral toxoplasmosis, progressive multifocal leukoencephalopathy, HIV-1-related cognitive/motor complex, HIV-1-associated myelopathy, and other neurological diseases. Paired CSF and serum samples were analysed for CMV deoxyribonucleic acid (DNA) by polymerase chain reaction (PCR), quantitative intrathecal synthesis of immunoglobulin G (IgG) antibodies specific for recombinant phosphoprotein 150 (pp150) of CMV and CMV-specific serum IgM. Intrathecal synthesis of pp150-specific IgG was detected in 26% of patients (9/35), serum IgM was found in 23% of patients (8/35), and PCR of CSF was positive in 11% of patients (4/35). Detection of CMV-specific DNA in CSF preceded the intrathecal antibody synthesis in three patients for whom serial samples were available. PCR results of the CSF became negative in one patient with CMV polyradiculomyelitis after successful therapy with 9-[2-hydroxy-1-(hydroxymethyl) ethoxymethyl] guanine (DHPG). PCR has a higher diagnostic specificity in the acute phase of CMV infection than intrathecal antibody synthesis. The serum IgM response to CMV cannot be used to monitor a compartmentalized immune response in the central nervous system while an intrathecal immune response seems to be associated with recovery either spontaneously or as a result of treatment.

AIDS-Related Opportunistic Infections↗
PubMed1994

Analytical quality control in neonatal screening.

This critical review questions the present understanding in monitoring of analytical quality control in neonatal screening. Current status and historical background of the analytical quality control, particularly of the tests intended for the screening of congenital hypothyroidism and some inborn errors of metabolism, is reviewed. The reasons why attempts to standardize immunoassays through the preparation of a so-called "gold standard" (e.g. for thyrotropin) will not resolve noncomparability of results are discussed. The review presents arguments for the necessity of elaboration of international guidelines for methods assessment and comparison with an emphasis on their clinical relevance.

Guidelines as Topic↗
PubMed1994

Specific diagnosis of progressive multifocal leukoencephalopathy by polymerase chain reaction.

Using polymerase chain reaction (PCR), 34 cerebrospinal fluid (CSF) samples from 28 patients with progressive multifocal leukoencephalopathy (PML) were analyzed. As controls, 116 samples were evaluated from 82 human immunodeficiency virus type 1 (HIV-1)-infected patients and 1 HIV-1-negative patient. Of the HIV-1-positive patients, 23 had cerebral toxoplasmosis, 10 had HIV leukoencephalopathy, and 49 had other neurologic complications. Detection of JC virus (JCV) DNA in CSF was increased 10-fold by the addition of carrier DNA before phenol-chloroform-isoamyl alcohol extraction. The primer pair JC 26/29, from the VP1/large T region, had a limit of detection of 10(5) JCV DNA molecules/100 microL. The primer pair JC 36/39, located in the large T gene region, had a 100-fold lower limit of detection. With JC 26/29, the sensitivity was 43% (12/28) and specificity was 100%. Using JC 36/39, sensitivity increased to 82% (23/28), and false-positive results were not observed. Diagnosis of PML is greatly aided by PCR analysis of CSF.

Base Sequence↗
PubMed1994

Progressive multifocal leukoencephalopathy diagnosed by amplification of JC virus-specific DNA from cerebrospinal fluid.

OBJECTIVE: To study the diagnostic sensitivity and specificity of polymerase chain reaction (PCR) for the non-invasive diagnosis of progressive multifocal leukoencephalopathy (PML) in HIV-1-infected individuals. DESIGN: Retrospective analysis of stored cerebrospinal fluid (CSF) samples by PCR of HIV-1-infected patients. METHODS: Results of the PCR analysis of the CSF of three AIDS patients with autopsy-proven PML were compared with the results in 15 neurologically asymptomatic HIV-1-infected patients and with 15 AIDS patients with other opportunistic infections of the central nervous system (CNS). A polyclonal antiserum to simian virus 40 (SV40) cross-reacting with JC virus (JCV) late antigens was used for immunocytochemical confirmation of the diagnosis. Two different primer pairs, one taken from the VP1/large T gene and the other from the large T gene, were used to amplify JCV-specific DNA sequences from CSF. RESULTS: Five CSF samples were analysed and JCV-specific DNA found in three patients with autopsy-proven PML. No JCV-specific DNA was detected in 47 CSF samples, including serial samples from 14 of the 30 non-PML patients. The diagnosis of PML was confirmed in all three cases by immunocytochemistry. CONCLUSION: PML can be diagnosed by PCR analysis of CSF. The sensitivity and specificity of the method depends on the sensitivity of the primers used for amplification. Using a primer pair from the large T gene, JCV-specific DNA was amplified in three cases with PML as early as the day of presentation with the first neurological symptom of PML.

AIDS-Related Opportunistic Infections↗
PubMed1994

Cytokine modulation of basophil histamine release in wasp-venom allergy.

We report the effect of interleukin-3 (IL-3) and of other cytokines on antigen-induced basophil histamine release in wasp-venom-allergic subjects. Leukocytes from 12 patients with documented anaphylactic sensitivity to wasp venom were preincubated in the presence or absence of IL-3, granulocyte/macrophage-colony stimulating factor (GM-CSF), IL-5, IL-8, or stem cell factor (SCF). Washed cells were then exposed to venom and to other secretagogues, and histamine release in the supernatant was measured fluorometrically. Preincubation of leukocytes with IL-3, GM-CSF, or IL-5 (0.02-2 ng/ml), but not with IL-8 and SCF, caused a dose-dependent enhancement of antigen-induced basophilic histamine release in all subjects tested. Mean maximum increase was about 100% for IL-3, IL-5, and GM-CSF. The priming effect of IL-3 was rapid, persisted up to 12 h, and was not accompanied by a change in cellular histamine. IL-3 had a comparable enhancing effect when basophils were triggered with anti-IgE or N-formylmethionylphenylalanine (FMP). By contrast, IL-3 had no effect on substance-P-induced histamine release. The significant enhancement of basophil releasability to antigen in wasp-venom allergy by very low concentrations of IL-3, GM-CSF, and IL-5 suggests that cytokines in the basophil (mast-cell?) microenvironment could be critical factors in determining the variability of sting reactions in Hymenoptera-venom-allergic subjects.

Adolescent↗
PubMed1994

Thyroid autoantibodies in serum samples with abnormal TSH levels.

Serum samples with normal and abnormal levels of thyrotropin (TSH) were tested for thyroid autoantibodies. Thyroid peroxidase (TPO) antibodies were detected by a radioimmunoassay (RIA) and by an agglutination method, and thyroglobulin (Tg) antibodies by an agglutination method. Elevated levels of TPO antibodies were detected in 47% of samples with abnormal and in 12% of samples with normal levels of TSH (p < 0.001). Sixty-one percent of the biochemically hypothyroid and 26% of the biochemically hyperthyroid samples contained these antibodies (p < 0.001). Tg antibodies were only detected together with TPO antibodies. Testing of TPO antibodies from samples with abnormal TSH levels is discussed.

Adult↗
PubMed1994

Acute diffuse leukoencephalitis in HIV-1 infection.

The clinical, neuroradiological, and cerebrospinal fluid findings of a case with acute diffuse leukoencephalitis, a demyelinating disease associated with human immunodeficiency virus infection of the brain, is reported. The patient presented with acute tetraparesis as the primary manifestation of a previously symptom free HIV infection. Cerebrospinal fluid analysis showed enhanced inflammatory abnormalities with high concentrations of P24 antigen. MRI showed diffuse white matter hyper-intensities in both hemispheres. In the follow up over 22 months, the neurological deficits disappeared after antiretroviral treatment in good correlation with improvements in MRI as well as in inflammatory cerebrospinal fluid abnormalities.

AIDS Dementia Complex↗
PubMed1994

Modulation of immunological histamine release from human lung fragments by stem cell factor, IL-3, IL-5 and GM-CSF: comparison with human leukocytes.

Because of the importance of cytokines in the regulation of allergic inflammation, we investigated the effects of SCF, IL-3, IL-5 and GM-CSF on immunological histamine release from sensitized human lung fragments as well as human leukocytes. SCF (0.2-20 ng/ml) caused a concentration-related enhancement of anti-IgE (1/100) induced histamine release from lung fragments reaching maximally 64% at 20 ng/ml. In contrast, enhancement produced by IL-5, IL-3 and GM-CSF (0.2-20 ng/ml) was quite marginal and reached at best around 20% at the higher concentration, IL-5 being slightly more effective than IL-3 and GM-CSF. Further, SCF potentiated histamine release whatever the level of immunological control whereas potentiation by IL-5 primarily occurred when the amount of histamine release induced by the immunological control ranged between 5 and 10%. SCF acted synergistically with IL-5, producing a greater enhancement of histamine release than the sum of each cytokine used alone. Both SCF and, to a lesser extent, IL-5 potentiated anti-IgE-mediated histamine release regardless of passive sensitization of lung fragments. Unlike what was observed with lung fragments, IL-3, GM-CSF and to a lesser extent IL-5, were potent enhancing agents of anti-IgE (1/2,000)-induced histamine release from leukocytes. Maximal enhancement produced by IL-3 (20 ng/ml), GM-CSF (2 ng/ml) and IL-5 (20 ng/ml) reached 92%, 78% and 61%, respectively. By contrast, SCF (0.2-20 ng/ml) was ineffective on human leukocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Serial analysis of circulating adhesion molecules and TNF receptor in serum from patients with multiple sclerosis: cICAM-1 is an indicator for relapse.

We determined the serum levels for circulating adhesion molecules (circulating intercellular adhesion molecule-1 [cICAM-1], circulating endothelial leukocyte adhesion molecule-1 [cELAM-1], and circulating L-selectin [cL-selectin]) and circulating tumor necrosis factor receptor (cTNF-R) p60 in 29 patients with relapsing-remitting MS serially over a period of 12 months. During this period there were 27 relapses in 14 patients (48%). There was progression of disease activity in 12/25 patients (48%), as assessed by the occurrence of new lesions on nonenhancing, T2-weighted MRIs of the head. Clinically active patients with relapse or disease progression on MRI (n = 18) had frequent fluctuations in their serum levels for cICAM-1 if compared to patients with stable MS (n = 11). There were significant differences in the cumulative cICAM-1 production between the two groups (502 +/- 218 ng/ml in active versus 225 +/- 82 ng/ml in stable MS patients; p < 0.001). cTNF-R p60 serum levels were higher in patients with stable compared to active disease (2.3 +/- 0.5 ng/ml versus 1.5 +/- 0.6 ng/ml; p < 0.005). A significant increase in cICAM-1 levels was present at the time of a relapse (799 +/- 263 ng/ml versus 449 +/- 95 ng/ml; p < 0.001), whereas the highest serum levels for cTNF-R p60 occurred 4 weeks after the onset of a relapse (1.8 +/- 0.5 ng/ml at relapse versus 2.3 +/- 0.6 ng/ml 4 weeks after a relapse; p < 0.01). Interestingly, the cL-selectin serum levels in all MS patients were significantly higher than in healthy donors, whereas there were no differences for cELAM-1. These results reflect distinct changes of inflammatory variables in serum of patients with MS and revealed that cICAM-1 is an indicator for disease activity and that high serum levels for cTNF-R p60 are associated with remission.

Adult↗