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Biomedical subjects

P Schultheis

Publications and source records attributed to P Schultheis.

3 recordsLinked to original sources
PubMed1995

Tropane alkaloids and toxicity of Convolvulus arvensis.

Horses in a few, localized northern Colorado pastures exhibited weight loss and colic. At post mortem, intestinal fibrosis and vascular sclerosis of the small intestine was identified. The pastures where the affected horses grazed were overrun by field bindweed (Convolvulus arvensis). Bindweed from the pasture was found to contain the tropane alkaloids tropine, pseudotropine, and tropinone and the pyrrolidine alkaloids cuscohygrine and hygrine. Laboratory mice readily ate C. arvensis and exhibited a variety of abnormal clinical signs depending on the amount eaten. Similar alkaloids have been found in other Convolvulus species and cuscohygrine and calystegines (polyhydroxytropanes) have been previously reported from C. arvensis roots. This is the first report of simple tropane alkaloids in C. arvensis, a world wide problem weed. Pseudotropine, the major alkaloid, is known to affect motility and might represent a causative agent for the observed cases of equine intestinal fibrosis.

Animals↗
PubMed1994

Structure-function studies of the Na,K-ATPase.

Na,K-ATPase catalyzes the movement of sodium and potassium ions across the cell membrane utilizing ATP as an energy source. This enzyme is present in almost all tissues of higher organisms but is most abundant in the kidney where it is responsible for reabsorbing sodium ions from the glomerular filtrate. The enzyme is composed of two subunits and serves as the receptor for cardiac glycosides. Utilizing an expression/selection system it has been possible to identify several amino acid residues that affect sensitivity to the cardiac glycoside, ouabain. Those identified to date are located in the first transmembrane region and first extracellular region. The fact that amino acid residues within a transmembrane region affect ouabain sensitivity suggests that the drug is partially internalized in the lipid bilayer. In an effort to determine whether any of the amino acid residues which affect ouabain sensitivity interact with the sugar part of cardiac glycosides, ouabain and ouabagenin were tested in terms of their ability to inhibit enzyme containing substitutions at these positions. The two compounds differ in that ouabagenin lacks a sugar moiety. Interestingly, the ratio of I50's for the substituted enzymes remains the same as the wild type, which suggests that the amino acids identified as determinants of ouabain sensitivity to date are not likely to interact with the sugar. Another set of studies focused on cation binding. It has been proposed that cation transport involves negatively charged residues in one or more transmembrane regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗