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H Schindler

Publications and source records attributed to H Schindler.

At least 91 records · Page 5Linked to original sources
PubMed1987

Purified L-type calcium channels: only one single polypeptide (alpha 1-subunit) carries the drug receptor domains and is regulated by protein kinases.

The L-type calcium channel was purified from guinea-pig skeletal muscle T-tubule membranes. The purified preparation retained the binding activity for 1,4 dihydropyridines, phenylalkylamines and d-cis diltiazem. Four polypeptides with apparent molecular masses of 180-190, 150-155, 55-60 and 28-35 kDa (termed alpha 1, alpha 2, beta and gamma subunit) copurified with reversible drug binding. In photoaffinity labeling experiments only the alpha 1 subunit was shown to carry the drug receptors. Phosphorylation and functional reconstitution experiments revealed that the cAMP dependent phosphorylation of the alpha 1 subunit is responsible for calcium channel regulation.

Affinity Labels↗
PubMed1985

Metabolism and motility of turkey (Meleagris gallopavo) spermatozoa in the presence or absence of oxygen, glucose and fructose.

Sugar consumption by turkey spermatozoa for 1 hr at 37 degrees C was similar in the presence or absence of oxygen, and with glucose or fructose in the medium. Motility of the spermatozoa at the end of the above incubation period was lower under anaerobic than aerobic conditions. Fructose enhanced the oxygen uptake of spermatozoa in comparison with that in the glucose-containing medium. Omission of sugar from the medium depressed respiration but not motility of the spermatozoa. The rate of oxygen uptake by the spermatozoa during a 3-hr incubation period was higher in a 3.3-mM than a 15.0-mM glucose medium. Fructose was formed from glucose under aerobic but not under anaerobic conditions. Fructose originating from glucose was used for fructolysis, when the glucose reserve in the medium was almost exhausted.

Aerobiosis↗
PubMed1985

Effects of selenium and vitamin E on incidence of retained placenta.

In a series of experiments over 3 yr, relatively low doses of selenium and vitamin E were injected intramuscularly 3 wk prepartum to pregnant Israeli-Holstein dairy cows in a high-producing herd (9000 kg milk/yr) with a history of retained placenta in 17% of the primiparous and 28% of the multiparous animals, as recorded for the 12 mo preceding the study. Selenium ranged from .035 to .109 ppm in the prepartum diet and from .160 to .200 ppm in the postpartum diet. Doses of selenium ranging from 2.3 to 23.0 mg reduced the incidence of retained placenta in 186 primiparous and in 428 multiparous to 7 and 15%, which was half of that of controls. Low doses of selenium (2.3 to 4.6 mg) tended to be more effective than higher ones. Selenium alone was at least as effective as a combination of selenium and vitamin E. Dosage, timing, mechanism, and interactions of selenium with other factors in reducing the incidence of retained placenta need clarification.

Animals↗
PubMed1984

Further evidence for lack of specific receptors for PGE2 in the rat ovary.

Prostaglandin E2 (PGE2) seems to stimulate cAMP accumulation in ovaries of all mammals. While it acts through specific receptors in some species, our earlier observations (1) suggest absence of PGE2 receptors in the rat ovary. In order to further substantiate this assumption we digested ovarian membranes from the bovine and the rat with various enzymes and measured cAMP after stimulation with PGE2, NaF, and hCG. Pronase, trypsin, and phospholipase C abolished cAMP accumulation completely. Neuraminidase, beta-galactosidase and phospholipase D did not interfere with cAMP formation. After treatment with phospholipase A2, PGE2-mediated cAMP accumulation was abolished in the bovine but not in the rat ovary. Formation of cAMP disappeared after hCG but not after NaF in both species. Furthermore specific binding of PGE2 could not be demonstrated in phospholipase A2-treated bovine ovaries. These findings are consistent with presence of specific PGE2 receptors in the bovine and their absence in the rat ovary.

Adenylyl Cyclases↗
PubMed1984

Different channel properties of Torpedo acetylcholine receptor monomers and dimers reconstituted in planar membranes.

It is demonstrated that the monomeric and dimeric structures of the nicotinic acetylcholine receptor of Torpedo californica electric tissue, reconstituted in planar lipid bilayers, are functionally different. The native dimer D of Mr 500,000 (heavy-form) exhibits a "single" channel conductance about twice as large as that of the monomer M of Mr 250,000 (light form). Under conditions where monomers aggregate, the conductance changes from the level of the monomer M to that of dimers M2. The dimer conductances (D and M2) seem to result from synchronous opening and closing of the two channels in the dimer, giving the impression of "single channel" activity. This channel cooperativity is apparently mediated by noncovalent interactions between the two monomers, since it requires no disulfide linkage between monomers. Both the monomers M and the dimers D and M2 show at least one substate of lower conductivity. The relative population of the two conductance levels depends on the ion type (Na+ and K+), indicating ion-specific channel states. Since the channel conductance of isolated dimers resembles those obtained from unextracted microsacs, the dimer with two synchronized channels appears to be the in vivo predominant gating unit. In the linear association of dimers, observed in the native membrane, channel synchronization may extend to more than two channels as suggested by oligomeric channel cooperativity in associations of monomers and dimers.

Animals↗
PubMed1984

The cromolyn binding protein constitutes the Ca2+ channel of basophils opening upon immunological stimulus.

Ca2+ channel opening has been proposed to be induced in the plasma membrane of mast cells and basophils upon crosslinking their Fc epsilon receptors. Here we report direct conductance measurements on planar lipid bilayers containing membrane components of rat basophils (RBL-2H3 line). These studies identify the Ca2+ channel-forming membrane component as the cromolyn binding protein [CBP, in which cromolyn is the anti-asthmatic drug 1,3-bis(2-carboxy-chromon-5-yloxy)-2-hydroxypropane]. Planar membranes were first formed from lipid vesicles containing unfractionated plasma membrane components prepared from RBL-2H3 cells. Conductance of these bilayers was induced by crosslinking IgE bound to the Fc epsilon receptors of this membrane by a specific polyvalent antigen. Channel conductance in the presence of only Ca2+ ions (2 mM) was 2 pS. When only sodium ions were present (150 mM), conductance was 10 pS. Upon addition of Ca2+ (2 mM) to the Na+ ion-containing solution, the conductance decreased from 10 pS to that of the Ca2+ ions--namely, 2pS. Open channel times were in the range of several hundred milliseconds. Conductance amplitudes and time characteristics were independent of the applied voltage. As our earlier studies revealed the essential role of the CBP in Ca2+ conductance of basophil membranes, we formed planar bilayers containing this isolated protein alone. Crosslinking of the CBP by a monoclonal antibody specific to it resulted in the appearance of channel conductances. All characteristics of these channels exhibited great similarity to those observed in planar membranes containing unfractionated RBL-2H3 membrane components. Moreover, in the latter membranes, the monoclonal anti-CBP antibody induced channel conductances that display an even closer similarity to those observed in membranes containing CBP alone. Conductances of both types of planar membranes, irrespective of the mode of activation used, were inhibited by cromolyn. Furthermore, the conductance induced in RBL membranes by polyvalent antigen was inhibited on dissociation of the crosslinked aggregates by a monovalent hapten. The detailed resemblance in channel behavior observed in experiments with the two types of planar bilayers provides compelling evidence that the CBP is the essential and sufficient component forming Ca2+ channels in basophil plasma membranes.

2,4-Dinitrophenol↗
PubMed1984

Testis cell-specific proteins in testosterone-treated rat ovaries.

Two-dimensional gel electrophoresis of rat gonads in various developmental stages (embryonic days 16, 17, 21; postnatal day 5) reveals an increasing number of polypeptide spots; 0.6%-2% of the polypeptides are gonad-specific and increase from embryonic day 16 onwards. Exposure of newborn rat ovaries to testosterone for 5 days results in the appearance of eight polypeptides. These polypeptides are absent in control ovaries but present in the testis from embryonic day 16 or 17 onwards. Three do not appear in the ovary at any developmental stage. These findings indicate that testosterone plays a physiologic role in normal testicular differentiation. After long-term testosterone treatment, ovaries are depleted of germ cells. This might explain the degeneration of oocytes in the abnormal environment of a testis (e.g., in XX true hermaphrodites).

Animals↗
PubMed1984

Effect of pH on the metabolism and fertility of turkey spermatozoa.

Oxygen uptake during a 4-h incubation period at 37 degrees C, and the motility of the spermatozoa before and after incubation, increased significantly with increasing pH from 6.3 to 8.8. No interaction between buffer and pH was noticed. In a second series of experiments on the aerobic metabolism of turkey spermatozoa, the effect of the pHs 6.8, 7.3 and 7.8 was studied. Fructose was formed from glucose without regard to the pH of the medium. The glucose consumption, i.e. the glucose disappearance minus fructose formation, the lactic acid accumulation, and the oxidation of glucose and of other substances, were higher, although not always statistically, at pH 7.8 than at pH 6.8. The percentage of fertile eggs during the 3rd week of collection after insemination with fresh semen diluted in the pH 7.8 medium was significantly lower than that with semen diluted in the pH 6.8 or 7.3 media. After 4 h of storage at 15 degrees C, the decrease in the fertility of spermatozoa in the high pH medium was apparent from the 1st week of collection.

Animals↗
PubMed1984

[URO-103--a new uroflow measuring device].

A new uroflow measuring instrument produced in the GDR by W. Rentsch , the Uroflow -Recorder URO-103, is presented and compared with thermistor and capacity-measuring apparatuses. The Uroflow -Recorder gives strictly linear measurements and requires extremely little maintainence . Over the test period of 8 months it functioned free from disturbance. The new apparatus is recommended for use, whereby it is suitable for combined urodynamic measurements.

Humans↗
PubMed1983

[Treatment of diabetic patients with Optisulin-Depot CR in comparison with Depot-Insulin Hoechst klar CR--therapeutic progress?].

During a cross-over-study in 12 ambulant patients the effects of Optisulin -Depot CR in comparison to Depot-Insulin Hoechst klar CR were examined. After a period with Depot-Insulin Hoechst klar CR patients got Optisulin -Depot CR in the same dose and with the same diet. A week later patients took Depot-Insulin Hoechst klar CR once again. The different blood-sugar-curves corresponded to each other, but Optisulin -Depot CR showed more initial effect. The use of Depot-Insulin Hoechst klar CR is an advantage, because, Optisulin -Depot CR is neutral and no depot-substances are contained. Therefore, less allergic reactions are expected.

Adult↗
PubMed1983

The periplasmic maltose-binding protein modifies the channel-forming characteristics of maltoporin.

Maltoporin, a protein spanning Escherichia coli outer membranes, modifies electrical conductance of membranes due to its channel-forming properties. This observation was made by conductance measurements across planar bilayers which were derived from unextracted, isolated outer membrane vesicles using a porin-deficient E. coli strain. Alternatively, proteoliposomes reconstituted with detergent-solubilized homogeneous maltoporin and phospholipids were used. With either membrane preparation, channel conductance was observed, although no discrete conductance levels were detected. The presence of lipopolysaccharide, a bacterial glycolipid, was not required, nor did it affect channel activity. In the presence of the water-soluble periplasmic maltose-binding protein, conductance fluctuations occurred in discrete steps, demonstrating opening and closing events of channels. Multiple step sizes (1/3, 2/3 and 1 ns in 1 M KCl) in single channel traces suggest cooperative opening and closing of up to three channels. The action of maltose-binding protein is highly asymmetrical, and its affinity to maltoporin is very high (KD = 1.5 X 10(-7) M). Association of maltose-binding protein to maltoporin shifts, for a given polarity, the equilibrium between open and closed states in favour of closed states. This result matches earlier in vivo studies, and supports the physiological significance of the observations made.

ATP-Binding Cassette Transporters↗
PubMed1983

Electrical impedance monitoring of the wound-healing process.

The healing process was studied of five surgical wounds in sheep caused by the implantation of pacemaker electrodes in the vaginal or vulvar submucosa, while the electrodes were being used for impedometric measurements of the tissue surrounding them. Separate measurements of conductance (G) and capacitance (C) were carried out at frequencies ranging from 10 Hz to 100 kHz. The highest specific conductance at 100 kHz (mumho/cm) was observed on the 3rd postoperative day - 3095 +/- 172 SEM (n = 5), at which time the wound area was considerably swollen. Thereafter, the conductance gradually decreased and stabilized in 17-20 days at 2194 +/- 54 when the healing process was terminated. The decreasing impedance angle and tissue phase angle indicated that during the healing process cell volume decreased and cell density increased.

Animals↗
PubMed1982

[Micro-tip transducer for simultaneous pressure and temperature measurements].

It is reported on a new semiconductor-microtransducer with integrated pressure and temperature sensor for simultaneous intracorporal pressure and temperature measuring. The properties of the pressure and temperature canal are described in short and first clinical applications (pressure measuring of the right heart, determination of cardiac output by means of thermodilution). Further applications are discussed.

Cardiac Catheterization↗
PubMed1982

Proteolipid of adenosinetriphosphatase from yeast mitochondria forms proton-selective channels in planar lipid bilayers.

Proteolipid isolated from yeast mitochondrial adenosinetriphosphatase by butanol extraction is reincorporated into lipid vesicles from which planar membranes are formed. The proteolipid permits electric conductance through the membrane. This conductance occurs through membrane channels which are highly selective for protons. Proton channels in the membrane are directly observed at high proton concentrations in the aqueous phases. Channels open and close independently from each other; their open-state conductances and lifetimes are monodisperse but influenced by the applied voltage (12 pS and 3 s, respectively, at pH 2.2 and 100 mV). Proton channels do not occur in single proteolipid molecules; the conducting structure consists of at least two polypeptide chains since channels form in a (reversible) bimolecular reaction of nonconducting forms of proteolipid. The number of proton channels at a constant proteolipid concentration changes in sharp transitions and by orders of magnitudes upon critical changes of membrane composition and pH. These transitions are caused by transitions of proteolipid organization in the membrane from a dispersed state (equilibrium between channel-forming "dimers" and a large pool of "monomers") to a state of almost complete aggregation of proteolipid which stabilizes large proton-conducting structures (probably associates of channel-forming dimers). This self-association of isolated proteolipid into structures containing proton-selective channels suggests that the six proteolipids in the adenosinetriphosphatase complex exist as a self-associating entity containing most likely three proton channels.

Adenosine Triphosphatases↗