Biomedical subjects

PD Ward

Publications and source records attributed to PD Ward.

3 recordsLinked to original sources

PubMed2000

Enhancing paracellular permeability by modulating epithelial tight junctions.

The intestinal epithelium is a major barrier to the absorption of hydrophilic drugs. The presence of intercellular junctional complexes, particularly the tight junctions (zona occludens), renders the epithelium impervious to hydrophilic drugs, which cannot diffuse across the cells through the lipid bilayer of the cell membranes. There have been significant advances in understanding the structure and cellular regulation of tight junctions over the past decade. This article reviews current knowledge regarding the physiological regulation of tight junctions and paracellular permeability, and recent progress towards the rational design of agents that can effectively and safely increase paracellular permeability via modulation of tight junctions.

Journal Article↗

PubMed2000

Altered river morphology in south africa related to the permian-triassic extinction

The Permian-Triassic transition in the Karoo Basin of South Africa was characterized by a rapid and apparently basin-wide change from meandering to braided river systems, as evidenced by preserved sedimentary facies. This radical changeover in river morphology is consistent with geomorphic consequences stemming from a rapid and major die-off of rooted plant life in the basin. Evidence from correlative nonmarine strata elsewhere in the world containing fluvial Permian-Triassic boundary sections suggests that a catastrophic terrestrial die-off of vegetation was a global event, producing a marked increase in sediment yield as well as contributing to the global delta(13)C excursion across the Permian-Triassic boundary.

Journal Article↗

PubMed1996

Sudden and Gradual Molluscan Extinctions in the Latest Cretaceous of Western European Tethys

Incompleteness of the fossil record has confounded attempts to establish the role of the end-Cretaceous bolide impact in the Late Cretaceous mass extinctions. Statistical analysis of latest Cretaceous outer-shelf macrofossils from western European Tethys reveals (i) a major extinction at or near the Cretaceous-Tertiary (K-T) boundary, probably caused by the impact, (ii) either a faunal abundance change or an extinction of up to nine ammonite species associated with a regression event shortly before the boundary, (iii) gradual extinction of most inoceramid bivalves well before the K-T boundary, and (iv) background extinction of approximately six ammonites throughout the latest Cretaceous.

Journal Article↗