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Biomedical subjects

W Simon

Publications and source records attributed to W Simon.

At least 91 records · Page 5Linked to original sources
PubMed1977

Ca2+ transport mediated by a synthetic neutral Ca2+ -ionophore in biological membranes.

The effect of a synthetic neutral ligand on the Ca2+ permeability of several biological membranes has been investigated. The ligand had been previously shown to possess Ca2+ -ionophoric activities in artificial phospholipid membranes. The neutral ionophore is able to transport Ca2+ across the membranes of erythrocytes and sarcoplasmic reticulum, when lipophilic anions such as tetraphenylborate and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP) are present, presumably to facilitate the diffusion of the charged Ca2+ -ionophore complex across the hydrophobic core of the membrane. In mitochondria, the neutral ionophore promotes the active transport of Ca2+ in response to the negative membrane potential generated by respiration, in the presence of the specific inhibitor of the natural carrier ruthenium red.

Animals↗
PubMed1977

Review: ion-selective electrodes in clinical chemistry.

The theoretic framework of electrode systems and numerical data for use in serum analysis is given. Original literature and recent applications to serum analysis are compiled for different types of sensors. The interactions of various effects and their relevance in the context of the precision that newer instrumentation offers are discussed. Specifically, the following topics are treated: response to interfering ions (Nicolsky Eq.), concentration to activity conversion (Debye-Hückel formalism), and liquid-junction potentials (Henderson Eq.); Debye-Hückel parameters, selectivity factors, and physiologic activity ranges; solid-state, liquid-membrane, and special electrodes; flow-through systems, precision, and stability.

Blood Chemical Analysis↗
PubMed1977

The translocation of Ca2+ across phospholipid bilayers induced by a synthetic neutral Ca2+ -ionophore.

The effect of a neutral synthetic Ca2+ -ligand, which induces selective Ca2+ transport in electrodialysis experiments in bulk membranes, on the Ca2+ permeability of phospholipid bilayers has been investigated. The ligand is able to promote the transport of Ca2+ across synthetic phospholipid bilayers and can therefore be classified as a Ca2+ -ionophore. Its activity is enhanced by the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). The efficiency of the neutral carrier-mediated Ca2+ transport is rather low as compared with that of the charged Ca2+ -ionophore X537A. The Ca2+ selectivity of the nuetral ionophore is decreased by its incorporation in the low dielectric ambient of the phospholipid bilayer.

Biological Transport, Active↗
PubMed1975

The metabolism of labeled parathyroid hormone. III. Studies in rats.

A series of experiments indicated that 125I-parathyroid hormone administered to the rat i.v. was deposited very rapidly in three organ systems only, bone, kidney and the liver. As indicated by increasing solubility in trichloracetic acid, the hormone seemed to be rapidly metabolized at the sites of deposition. The experiments were in part repeated employing quantitative extraction and gel filtration procedures. It was found that intact hormone predominated (82%) in the circulation but was cleared very rapidly: 91, 97, and 99% having left by 10, 30 and 60 minutes respectively after injection. The intact hormone was found at 10 minutes to be principally in kidney, bone, and liver. Although there was evidence of fragmentation preferentially to polypeptides of molecular weights of 6000, 4500 and 2500 these cannot be claimed to represent real molecular entities. By one hour, only a few per cent of the injected hormone remained intact, the bulk having been degraded to fragments of small molecular weight.

Animals↗