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Biomedical subjects

H Schindler

Publications and source records attributed to H Schindler.

At least 109 records · Page 6Linked to original sources
PubMed1982

alpha-Actinin interacts specifically with model membranes containing glycerides and fatty acids.

A method was developed to identify specific protein-lipid interactions of complex lipid mixtures and to assess their effect upon the arrangement of such complexes in monolayers at an air-water interface. Its application to striated muscle alpha-actinin revealed that just two lipids selectively interact with alpha-actinin. One molecule of glyceride and one molecule of fatty acid were found to be associated in a constant stoichiometry with one molecule of the alpha-actinin dimer. In the presence of both glycerides and fatty acids unexpectedly rigid monolayer areas formed. This lipid specificity could be confirmed by brief protease digestion of alpha-actinin liposome mixtures followed by peptide analysis; the peptide patterns of alpha-actinin depended on the presence or absence of only these two lipids. Possible implications of these findings are discussed in the context of Z-line formation.

Actinin↗
PubMed1982

The effect of prostaglandins in the rat ovary: specific or unspecific stimulation of cAMP, cGMP and progesterone?

Ovarian membranes of the rat do not specifically bind prostaglandin E2 at any stage of development. Attachment of [3H]prostaglandin E2 in the presence of an excess of unlabelled prostaglandin E2 increased in a linear fashion and was not saturable. Prostaglandin E2 stimulated cAMP accumulation by ovarian cells of all developmental stages. This effect was not saturable. An effect of prostaglandin E2 on cGMP levels was not observed. At high concentrations of prostaglandin E2 an increase of ovarian progesterone synthesis was detected. In comparison hCG stimulated progesterone synthesis at much lower concentrations. PGF2 alpha increased cellular and extracellular cAMP at 1000-fold higher concentrations than PGE2 and did not affect cGMP levels.

Animals↗
PubMed1981

Matrix protein in planar membranes: clusters of channels in a native environment and their functional reassembly.

Planar bilayers formed from Escherichia coli outer membrane vesicles exhibit conductance properties similar to those previously observed in bilayers reconstituted from aggregates of matrix protein, the major outer membrane protein. Discrete conductance steps are observed, reflecting voltage-dependent transmembrane channels. These exist in clusters which are activated by voltage. After activation, channels close with increasing potentials and reopen reversibly at lower voltage. Depending on the sign of the potential, two distinct closed states of the pores are observed. Cooperative interactions, hysteresis effects, relaxation times, and values of channel conductance depend on cluster size. These properties provide the reference data for the reconstitution of membrane function from individual components. Planar bilayers were formed from vesicles containing either solubilized matrix protein in a homogeneous trimeric state or bacterial glycolipid (lipopolysaccharide), or both. Activation of channel conductance required the presence of glycolipid and the formation of channel clusters, leading to conductance properties of the channels closely resembling those observed in native outer membranes. At very low concentrations of trimers, irreversible association to clusters by lateral diffusion was observed. Nearly quantitative recoveries of channels allowed the assignment of three pores per trimer.

Bacterial Proteins↗
PubMed1981

Impedometric properties of the vulvar and vaginal tissues of ewes during the oestrous cycle.

Tissue electrical conductance (G) and capacitance (C) were measured in vulvar and vaginal tissues of ewes by a spectroimpedographic method at frequencies from 10 Hz to 100 kHz. The calculated specific conductance (mumho/cm) at 100 kHz was 3082 +/- 20 (s.e.m.) in oestrus and 2153 +/- 16 in dioestrus (n = 8) (P < 0.001). The impedance angle and the tissue phase angle increased during oestrus, indicating that cell volume increased and cell density decreased in comparison with dioestrus. The ratio of conductivities at higher and lower frequencies showed that extracellular water content was maximal during oestrus and coincided with standing heat.

Animals↗
PubMed1980

[Treatment of Paget's disease with synthetic human calcitonin (author's transl)].

7 patients with Paget's disease were treated with synthetic human calcitonin over 6 months. 6 patients responded favourably to treatment and showed a marked decrease in serum alkaline phosphatase and urinary hydroxyproline. Subjectively, these patients reported a considerable decrease in pain. 1 patient did not respond to treatment. No side effects requiring premature termination of therapy were recorded. No regression of the radiological findings was achieved, but 3 patients showed a distinct improvement of the scintigrams. The indications for therapy are discussed.

Alkaline Phosphatase↗
PubMed1980

[New aspects on diagnosis and therapy of primary hyperparathyroidism (author's transl)].

26, out of them 20 surgically proven cases of primary hyperparathyroidism are presented. The value of different laboratory, radiographic and scintigraphic analysis is examined. The estimation of calcium and phosphate in serum, the iPTH-determination and fine detail hands radiographs were found to be sufficient to establish diagnosis and indication for surgery. The chloride/phosphate-ratio proved valuable in comparative statistical analysis between pHPT and two control groups. Venous sampling at present seems to be the superior method for preoperative localization of parathyroid disease. It should be performed before second surgical intervention in the cervical region, in elderly (more than 60 years old) and risk patients. Early diagnosis and therapy of pHPT is important as pHPT is a chronic disease with many organ complications. The value of calcium-screening in an age group between 40 and 60 years is discussed.

Aged↗
PubMed1980

Functional acetylcholine receptor from Torpedo marmorata in planar membranes.

Planar bilayer membranes containing functional acetylcholine receptor were formed from vesicles of Torpedo marmorata electric organ without extracting the acetylcholine receptor from its native environment. Native vesicles were transformed into monolayers which subsequently were apposed into planar bilayers. In the absence of agonists the membrane conductance was similar to that of lipid bilayers. Addition of carbamoylcholine or succinylcholine caused increased membrane conductance and this could be competitively inhibited by d-tubocurarine and suppressed by alpha-bungarotoxin. The amplitude of the conductance response was proportional to the number of alpha-bungarotoxin binding sites in the bilayers. Asymmetric membranes could be formed with the ligand binding sites on only one membrane surface. Desensitization of acetylcholine receptor was evident from equilibrium and kinetic data of the carbamoylcholine-activated conductance. Carbamoylcholine-induced membrane permeability was about 7 times higher for K+ and Na+ ions than for Cl-. At low levels of conductance, single-channel fluctuations of 20-25 pS in conductance and 1.3-msec lifetime were resolved in physiological saline containing carbamoylcholine. The ratio of observed channels to alpha-bungarotoxin sites present showed that a significant fraction of acetylcholine receptor in the membrane was functional. The quantitative aspects of the cation channel, the desensitization, and the ligand binding properties were in close agreement with established values. This transformation of natural acetylcholine receptor vesicles to planar bilayers conserves the essential properties of the in vivo receptor.

Animals↗
PubMed1979

Exchange and interactions between lipid layers at the surface of a liposome solution.

Lipid organization and lipid transport processes occurring at the air-water interface of a liposome (lipid vesicle) solution are studied by conventional surface pressure-area measurements and interpreted by an adequate theory. At the interface of a dioleoyl phosphatidylcholine vesicle solution, used for demonstration, a well defined two layer structure selfassembles: vesicles disintegrate at the interface forming a surface-adsorbed lipid monolayer, which prevents further disintegration beyond about 1 dyne/cm surface pressure. A layer of vesicles now assembles in close association with the monolayer. This layer is in vesicle diffusion exchange with the solution and in lipid exchange with the monolayer. The lipid exchange occurs exclusively between the monolayer and the outer lipid layer of the vesicles; it is absent between outer and inner vesicle layers. Equilibration of the lipid density in the monolayer with that in the vesicle outer layer provides a coherent and quantitative explanation of the observed hysteresis effects and equilibrium states. The correspondence between monolayer and vesicle outer layer is traced down to equilibrium constants and rate constants and their dependences on surface pressure, vesicle size and concentration. Other alternate realizations of surface structure and exchange, including induced lipid flip-flop within vesicles or vesicle monolayer adhesion or fusion are potential applications of the proposed analysis.

Kinetics↗
PubMed1978

Matrix protein from Escherichia coli outer membranes forms voltage-controlled channels in lipid bilayers.

Matrix protein from Escherichia coli was integrated into planar lipid bilayers. The incorporated protein generates aqueous channels across these membranes. Channels are induced irreversibly by voltage, and their number is proportional to the protein content of the membrane and stays constant over hours. They are uniform in size, with a diameter of about 1 nm and a single-channel conductance of 0.14 nS in 0.1 M NaCl. In addition to ionic conductance, the channels allow free diffusion of small, uncharged molecules. Channels assume either an open or a closed state. Membrane potentials shift this two-state equilibrium distribution in favor of closed channels, an observation that explains both negative resistance and inactivation at high potentials. Channels are not randomly distributed in the membrane but interact cooperatively within aggregates. The smallest entity inducible consists of three channels.

Cell Membrane↗
PubMed1976

Branched bimolecular lipid membranes.

Branched bimolecular lipid membranes separating three and four aqueous phases have been formed. The procedure is based on the technique of Montal and Mueller generalized to three and four lipid surface films spanning an appropriate aperture. The technique to produce Teflon structures for the mechanical support of branched bilayers is presented. The existence of the branched bilayer was established by measuring the specific capacity, specific resistance, and the gramicidin-induced single channel conductance of each branch. These structures should facilitate the study of transport properties of ionophores and other molecules and may also serve as model systems for the study of cell fusion.

Lipids↗
PubMed1976

Determination of molecular weights by fluctuation spectroscopy: application to DNA.

A method for determining molecular weights of macromolecules by measuring spontaneous concentration fluctuations is described. The method is absolute, rapid, and requires no shearing forces on the molecules. We have applied this technique to the determination of molecular weight of DNA molecules. The molecular weight values obtained for T2 phage DNA (1.14 X 10(8)) and replicating Escherichia coli DNA (3.9 X 10(9)) agree with previous results. By monitoring individual molecules, an estimate of the molecular weight of nuclei and individual chromosomal DNA molecules of Drosophila melanogaster was obtained.

Animals↗