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Biomedical subjects

K Mühlethaler

Publications and source records attributed to K Mühlethaler.

At least 19 recordsLinked to original sources
PubMed1992

The skin as a target organ for the investigation of antiallergic drugs: comparison between cetirizine and terfenadine.

Two double-blind clinical pharmacology studies were performed in atopics in order to compare the inhibitory effects of cetirizine (CTZ) 2 HCl and terfenadine (TER) on histamine and antigen-induced skin reactions. In the first study, the subjects took single intakes of CTZ 10 mg and TER 60 mg. In the second study, they took CTZ 10 mg once a day and TER 60 mg b.i.d. for 3 weeks. CTZ was more effective than TER in inhibiting histamine skin reactivity. CTZ and TER were equally effective in inhibiting antigen-induced reactions. There was no tachyphylaxis, either for CTZ or for TER.

Adolescent↗
PubMed1990

[Hyposensitization in pollinosis. Results of a 3-year controlled study with 2 depot-allergoid grass pollen extracts: aluminum hydroxide-adsorbed allergoid and tyrosine-adsorbed allergoid].

For controlled hyposensitization treatment over a period of three years 36 patients with confirmed grass pollen sensitization had been selected in 1986 and randomly distributed to receive preseasonal injection therapy: 23 patients were treated with an average of seven AGD (aluminium-adsorbed allergoid) injections, and 13 patients had received six TA (tyrosine-adsorbed allergoid) injections. Evaluation of the trial data collected during three years of preseasonal treatment showed the following results of tolerance and efficacy: Systemic side-reactions registered during therapy were only mild and transient and occurred in the average after 3% of the AGD injections and after 10% of the TA injections. Local reactions over 5 cm diameter were registered after 7% in the AGD group and after 9% in the TA group. Before therapy there was no significant difference (p greater than 0.05) between the groups; after three years of therapy the AGD injections had resulted in a mean net rise of specific IgG of 220% (significant, p = 0.001); during the same time, TA injections had resulted in a final net increase of 10% (not significant, p greater than 0.05). Both treatment forms did not lead to any statistically relevant changes of specific IgE values. After three years of hyposensitization treatment, patients of both groups had improved; but an advantage was documented for patients treated with AGD on the basis of scores for objective assessment as well as for registered symptom and medication scores.

Adult↗
PubMed1989

[Angioedema caused by enalapril (Reniten)].

Two cases of enalapril(Reniten)-induced angioedema are described. In both patients the time lag between the first manifestation of angio-edema and diagnosis was more than one year, during which several bouts of edema occurred. One patient developed life-threatening swelling of the tongue and the larynx followed by asystole and apnea. The second patient had recurrent edema of the tongue and dyspnea. In general, enalapril-induced edema is not thought to be based on immunological mechanisms. However, in both patients we found elevated titres of antinuclear antibodies, which were reversible upon cessation of enalapril medication. The possible pathomechanisms are discussed.

Angioedema↗
PubMed1989

[Anaphylactic reaction to latex, an immediate-type allergen of increasing significance].

We report on two patients with immediate-type allergy to latex, an allergen that is receiving increasing attention. Both patients presented with anaphylactic symptoms after gynecological examination. In addition, one patient reacted with an anaphylactic shock immediately after insertion of a latex intestinal tube for a Holzknecht test. Of all the cases of immediate-type allergy to latex published so far, 45% had localized urticaria, 43% mucocutaneous reaction, and 10% an anaphylactic shock; 74% of the patients were atopic.

Adult↗
PubMed1983

Localisation of Rhodopseudomonas viridis reaction centre and light harvesting proteins using ferritin-antibody labelling.

Rhodopseudomonas viridis thylakoid membrane polypeptides were characterised by SDS gels, 2 D gels and surface-specific iodination. Four polypeptides with apparent molecular weights of 38 000, 33 000, 27 000, and 24 000 (reaction centre) and three low molecular weight polypeptides 11 000, 8000 and 6000 (probably light harvesting polypeptides) were identified. Antibodies were produced against the polypeptides eluted from SDS gels and tested for specificity by an immunoblotting assay. The antibodies were bound to the membranes and viewed by electron microscopy using a modification of the ferritin labelling technique. It is suggested that antigenic determinants for the 38 000, 33 000, and 27 000 reaction centre polypeptides and the 11 000 and 8000 low molecular weight polypeptides are present on the cytoplasmic membrane surface. The 33 000, 27 000, 11 000 and 6000 polypeptides appear to have surface-located residues which can be iodinated. The photosynthetic membrane of Rps. viridis appears to be a highly asymmetrical membrane.

Antibodies, Bacterial↗
PubMed1982

Isolation and localization of plasma membrane-bound invertase in yeast (Saccharomyces cerevisiae).

Latex spheres of 60 nm diameter (synthesized by aqueous emulsion copolymerization of methacrylate derivatives according to [22]) were coated with bovine serum albumin (BSA) and concanavalin A. By virtue of their size and their high density (1.32-1.35 g/ml) they are well suited as scanning electron microscopy markers and as affinity density perturbation reagents. Yeast protoplasts could be labeled with these spheres and the amount of binding depended upon incubation time and temperature. Isolated and solubilized yeast plasma membranes were incubated with these spheres and by density gradient centrifugation the membrane glycoproteins could be separated from the other proteins by the method of affinity density perturbation. Since the yeast plasma membrane glycoproteins exhibit invertase activity [1, 19] the activity of the different fractions was either detected on gels by staining for invertase activity or measured in vitro and quantified; a 6 to 7fold purification of the enzyme was achieved. Protoplasts labeled with antibodies directed against these glycoproteins exhibited a distribution of ferritin marker molecules that was very similar to that of the intramembranous particles. Antibodies against extracellular invertase cross reacted with the plasma membrane of glycoproteins and showed the same distribution of markers as the antibodies against the glycoproteins. It can therefore be concluded that the yeast plasma membrane glycoproteins exhibit invertase activity and that they are associated with the intramembranous particles.

Cell Fractionation↗
PubMed1981

Isolation and characterization of paracrystalline arrays of the plasma membrane of baker's yeast Saccharomyces cerevisiae.

Yeast plasma membranes were isolated from homogenized cells and analyzed by SDS-PAGE. Two glycoproteins of 160 000 and 240 000 molecular weight were found, both of which exhibited invertase activity (EC 3.2.1.26). By density gradient centrifugation a heavy membrane fraction which consisted of the glycoproteins and two hydrophobic proteins was isolated. Antibody labeling of protoplasts revealed a good correlation between the distribution of binding sites of the antibodies against the heavy fraction and the distribution of the intramembranous particles. The cytoplasmic surface of the yeast plasma membrane was visualized by freeze drying and subsequent platinum/carbon shadowing of membrane vesicles adsorbed to cationized glass and squirted with a hypotonic buffer stream. In contrast to the smooth exoplasmic surface the cytoplasmic surface showed paracrystalline arrays of particles which resembled in size, number and lattice constant the intramembranous particles. Removal of the adsorbed paracrystalline arrays and subsequent SDS-PAGE revealed the same protein pattern as the heavy membrane fraction. It can therefore be concluded that the glycoproteins which show invertase activity and the two hydrophobic proteins are the major components of the paracrystalline arrays. It is proposed that the glucose level of the nutrient medium influences the appearance and disappearance of the paracrystalline arrays, which consist mainly of invertase, because synthesis of invertase is inhibited by glucose levels higher than 1%.

Antibodies↗
PubMed1981

Specific labeling of glycoproteins in yeast plasma membrane with concanavalin A.

The intramembranous particles of yeast Saccharomyces cereisiae plasma membrane form paracrystalline arrays or are randomly distributed as seen by freeze-fracture electron microscopy. Protoplasts with randomly distributed particles and with paracrystalline arrays were isolated and subsequently labeled with 3H-Con A, Con A and ferritin-Con A. The distribution of the Con A or the ferritin-Con A molecules on deep-etched exoplasmic surfaces strongly resembled the distribution of the intramembranous particles. The influence upon labeling of buffer ionic strength was investigated. Binding assays with 3H-Con A and freeze-etch electron microscopy demonstrated that the amount of non-specifically bound lectin molecules decreases by increasing buffer ionic strength. Only partial removal of Con A molecules was achieved by adding various concentrations of the specific sugar Methyl-alpha-D-Mannoside (alpha MM) to labeled protoplasts. By means of analytical ultracentrifugation it was found that alpha MM also promotes the formation of Con A dimers. fixed protoplasts were treated with detergents and 2-chloroethanol at various concentrations and subsequently labeled with 3H-Con A or ferritin-Con A. The amount of Con A bound to extracted cells did not decrease but ultrastructural changes of the deep-etched surfaces were observed. From our data it can be concluded that only the glycoproteins are labeled with Con A and they seem to be associated with the intramembranous particles [15]. Each intramembranous particle seems to bind 36 to 44 Con A molecules and therefore the glycoproteins seem to possess very long sugar chains. This further supports the hypothesis that the intramembranous particles are associated with the membrane-bound invertase.

Cell Membrane↗
PubMed1980

Immunochemical analysis of the plasma membrane from baker's yeast Saccharomyces cerevisiae.

Yeast plasma membranes have been isolated from homogenized yeast cells, identified as pure plasma membrane vesicles which were used as antigens. By crossed immunoelectrophoresis with anti-membrane immunoglobulins, 17 discrete antigens have been detected in Triton X-100 extracts from plasma membranes. Three different immunoabsorption experiments were performed with : a) isolated membranes exposing the cytoplasmic surfaces (PS) and the external surfaces (ES), b) yeast protoplasts exposing only antigenic determinants on the ES, c) lysed protoplasts which had been saturated on the ES with antibodies prior to lysis. These absorption experiments demonstrated that seven of the antigens are expressed on the ES while eight immunogens expose antigenic determinants on the PS. Four of the principal immunoprecipitates are not affected by absorption with surface antigens whereas two of the antigens indicate transmembrane characteristics. Of these 17 immunoprecipitates four were shown by zymograms to possess enzymatic activities: ATPase (EC 3.6.1.3) and NADH-dehydrogenase (EC 1.8.99.3) (three separate components). Three of these enzymes are expressed on the PS, and one NADH-dehydrogenase exposes determinants on the ES of the protoplasts. The presence of antigens on the PS of the plasma membrane could also be demonstrated on micrographs by the indirect ferritin-antibody labeling technique followed by freeze-etching and shadowing of the membranes.

Adenosine Triphosphatases↗
PubMed1979

Hydrophobic membrane protein from chromatophores of Rhodospirillum rubrum. Structural and spectroscopic studies of monolayers and multilayers.

A hydrophobic, lipid- and pigment-free polypeptide from the chromatophore membrane of Rhodospirillum rubrum was spread from chloroform/methanol, pyridine and formic acid solutions at an air-water interface. Surface pressure versus area isotherms of the monolayers formed at the interface were partially dependent upon the spreading solvent used. From the surface area at 20 dynes/cm compression, an average molecular area of 12.9 nm2/molecule was calculated for a polypeptide monolayer spread from chloroform/methanol. Multilayers built up on germanium plates at different surface pressures were subjected to attenuated total reflection infrared spectroscopy. In all cases the amide I and II absorption bands were typical of alpha-helical and random conformations. Electron microscopy of transferred monolayers replicated by rotary platinum shadowing revealed domains of regular texture in specimens prepared at 20 dynes/cm. Such domains were virtually absent in specimens prepared at 10 and 30 dynes/cm. Light optical diffractometry of the ordered arrays yielded a smallest repetitive area of 13.5 nm2 which agrees well with the molecular area obtained from the monolayer surface. Although no drastic changes in secondary structure were detected in the course of this study, some conformational changes are indicated by solvent-dependent differences in the surface pressure versus area isotherms.

Bacterial Chromatophores↗
PubMed1975

Instability of Langmuir-Blodgett layers of barium stearate, cadmium arachidate and tripalmitin, studied by means of electron microscopy and infrared spectroscopy.

Results of an investigation of the stability of n-layers of barium stearate, cadmium arachidate and tripalmitin by means of electron microscopy and attenuated total reflection infrared spectroscopy are reported. Odd and even numbered barium starate n-layers with n - 1,2,3,4,5 are found to rearrange spontaneously from a regular film into ultrastructures of irregular, flat islands of varying thickness. The kinetics of the phase transformation of the first layer depends on the substrate, that of n-layers appears to be dependent on n, the temperature, and the surrounding medium. The kinetic behaviour of odd and even numbered layers is distinctly different. Similar studies on cadmium arachidate layers reveal much slower kinetics of the rearrangement process. In the case of tripalmitin n-layers it is shown that electron microscopy and infrared spectroscopy yield valuable complementary information about ultrastructure and molecular structure of the layers in correlation with the rearrangement process, which also occurs with this system. Consequences of the results of this paper for work published in various fields are briefly discussed.

Barium↗