Using a mechanical model of the giraffe neck and head circulation consisting of a rigid, ascending, 'carotid' limb, a 'cranial' circulation that could be rigid or collapsible, and a descending, 'jugular' limb that also could be rigid or collapsible, we have analyzed the origin of the high arterial and venous pressures in giraffe, and whether blood flow is assisted by a siphon. When the tubes we...

The effect of high hydrostatic pressure on the lipid bilayer hydration, the mean order parameter, and rotational dynamics of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) cholesterol vesicles has been studied by time-resolved fluorescence spectroscopy up to 1500 bar. Whereas the degree of hydration in the lipid headgroup and inter...

Changes in hydrostatic pressure, at levels as low as 10 mm Hg, have been reported in some studies to alter cell function in vitro; however, other studies have found no detectable changes using similar methodologies. We here investigate the hypothesis that the rate of depressurization, rather than elevated hydrostatic pressure itself, may be responsible for these reported changes. Hydrostatic pr...

PURPOSE The response of cells (e.g., optic nerve head [ONH] cells) to mechanical stress is important in glaucoma. Studies have reported the biological effects of hydrostatic pressure on ONH cells cultured on a rigid substrate. An apparatus, designed to independently vary hydrostatic pressure and gas tension (including oxygen tension) in culture medium, was used to evaluate the effects of pressu...

Human osteosarcoma cells, MG-63, were exposed to a hydrostatic pressure shock of 4.0 MPa for 20 min. Changes in subcellular distribution of the cytoskeletal elements and heat shock protein 70 (hsp70) were followed by indirect immunofluorescence and by avidin-biotin-peroxidase protocols. During recovery, total cellular RNA was determined and actin and aldolase mRNA content was followed using rev...

There is evidence that high hydrostatic pressure can solate and weaken gel-like structures within cells. It was thus of interest to determine its effect on the mechanical properties of the cell surface since it has been suggested that there is a gel-like cortex beneath the plasma membrane which makes a significant contribution to its mechanical properties. The mechanical property measured was t...

Internal waves occur at a variety of temporal and spatial scales and are mechanisms by which momentum, energy, nutrients and biota are transported in lakes, estuaries and coastal oceans. In stratified systems, accurate prediction of water quality effects requires modeling internal wave evolution and propagation. Lake, estuary, and coastal ocean models typically apply the hydrostatic approximati...

The effect of hydrostatic pressure on solid and hollow microsphere optical resonators was investigated. The primary goal was to explore the feasibility of a micro-optical pressure sensor based on whispering gallery modes (WGMs) and to quantify the deleterious effect of environmental pressure changes on other WGM-based sensors. Expressions were developed for WGM shifts due to changes in hydrosta...