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Biomedical subjects

J E de Peyer

Publications and source records attributed to J E de Peyer.

6 recordsLinked to original sources
PubMed2000

Propylene glycol monomethyl ether (PGME) exposure. 2. Identification of products containing PGME, their importance and their use in Switzerland.

OBJECTIVE: In order to identify users of PGME and potential exposures, a chemical registration database maintained in Switzerland was analysed. METHOD: The database contains information on the composition of products (qualitative and quantitative), the field of use, the year of registration and the domain of commercial applications (public or professional). RESULTS: Identification of potential exposures in Switzerland was carried out. Out of a total of 150,000 products, 2334 were found to contain PGME and most contained between 1% and 10% PGME. There was a great increase in the number of products declared between 1983 and 1991. The principal fields of use were in inks, varnishes and paints.

Consumer Product Safety↗
PubMed1986

Vascular smooth muscle: availability of calcium through alpha-adrenoceptor stimulation.

In strip preparations from the rabbit main pulmonary artery, it was not possible to differentiate convincingly between alpha 1- and alpha 2-adrenoceptors, when selective agonists such as methoxamine, St 587, B-HT 920, and clonidine, as well as selective antagonists such as prazosin and yohimbine were used for receptor characterization. Measurements of the membrane potential of the vascular smooth-muscle cells with intracellular glass micropipettes showed similar depolarizations in response to the alpha 1-selective methoxamine and the alpha 2-selective B-HT 920. These observations suggest the occurrence of a uniform alpha-adrenoceptor population in the rabbit main pulmonary artery. However, in contrast to alpha 1-agonists, contractile responses to alpha 2-agonists differed considerably in their dependence on external Ca, as revealed in Ca withdrawal experiments, as well as by the use of Ca antagonists. Furthermore, inactivation of the guanine nucleotide-binding inhibitory protein (Ni protein) by pertussis toxin impaired vasoconstriction, in response to alpha 2-agonists, but left that to alpha 1-agonists unaffected. It is suggested that alpha 1- and alpha 2-agonists induce two distinct conformational changes in an otherwise uniform alpha-adrenoceptor of the rabbit main pulmonary artery. By the mediation of Ni protein, alpha 2-agonists appear to allow influx of Ca into the vascular muscle cells through a type of Ca channel that is unlikely to be controlled by voltage.

Adrenergic alpha-Agonists↗
PubMed1982

Ca2+ -activated K+ conductance in internally perfused snail neurons is enhanced by protein phosphorylation.

Depolarizing voltage steps induce inward and outward currents in voltage-clamped, internally perfused neurons from the snail Helix roseneri. Addition of the catalytic subunit of cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) to the internal perfusing medium results in an increase in the net outward current, with no apparent effect on the inward current. Catalytic subunit inactivated by 5,5'-dithiobis(2-nitrobenzoic acid) is without effect, indicating that the increase in net outward current results from protein phosphorylation rather than an unspecific effect of protein perfusion. Decreasing the external Ca2+ concentration from 10 to 1 mM eliminates the effect of catalytic subunit, suggesting that Ca2+ plays an important role in this response. This suggestion is supported by the fact that the stimulation by catalytic subunit can be mimicked by increasing the Ca2+ concentration in the internal perfusion medium and can be prevented by intracellular perfusion with 10 mM EGTA. The results are consistent with the hypothesis that cyclic AMP-dependent protein phosphorylation regulates the Ca2+-activated K+ conductance in these cells.

Action Potentials↗
PubMed1980

Divalent cations as charge carriers during two functionally different membrane currents in the ciliate Stylonychia.

We have investigated the ability of various divalent cations to carry current through membrane channels in ciliates activated by mechanical stimulation and by membrane depolarization. Both types of channels are identified as Ca2+ channels. Whereas Ba2+ ions and Sr2+ ions can replace Ca2+ ions as charge carriers during either kind of current, Mg2+ ions can carry the current evoked by mechanical stimulation but not the current elicited by membrane depolarization. Mn2+ ions did not carry either of these currents, and they reduced the currents carried by Ca2+ ions. Our experiments suggest that the mechano-sensitive and the voltage-sensitive channels exhibit different selectivities for divalent cations.

Animals↗
PubMedDate not supplied

Ca2+ channel modulation by 8-bromocyclic AMP in cultured heart cells.

Modulation of ion channels is of increasing interest as it is an important step in the regulation of cellular functions. We have analysed the effect of 8-bromocyclic AMP on Ca2+ channels in cultured cardiac cells by the patch-clamp method and report here that there was a large increase in the probability of opening of the channels. On the basis of a recently proposed kinetic reaction scheme we suggest that cyclic AMP-dependent phosphorylation of Ca2+ channels primarily promotes the forward rate constants which lead to the open state of a Ca2+ channel during depolarization.

8-Bromo Cyclic Adenosine Monophosphate↗