INTRODucnON ... ......... ........... .. . .. ........ ... ........ . .. .. ... .. ... . ......... .. ........ . 238 Structure oj the Cell Envelope.................................................................. 238 Uptake Arross the Outer Membrane.......................................................... 239 Intrinsic,Dejects in Outer Membrane Permeability in So.me Bacteria . .... ..... .. ....

This work tested one aspect of the relations between membrane permeability and fruit ripening. Membrane permeability was measured as [(3)H]water efflux rate from preloaded fruit pericarp disks. Different stages of fruit development were compared between two tomato (Lycopersicon esculentum Mill) strains: the normal Rutgers and the isogenic nonripening rin strain. The first significant increase i...

The medullary thick ascending limb (MTAL) reabsorbs solute without water and concentrates [Formula: see text] in the interstitium without a favorable pH gradient, activities which require low water and NH3 permeabilities. The contributions of different apical and basolateral membrane structures to these low permeabilities are unclear. We isolated highly purified apical and basolateral MTAL plas...

Membrane permeability assays play an important role in assessing drug transport activities across biological membranes. However, in conventional parallel artificial membrane permeability assays (PAMPA), the membrane model used is dissimilar to biological membranes physically and chemically. Here, we describe a microfluidic passive permeability assay using droplet interface bilayers (DIBs). In a...

We examined the mechanism of the neutrophil (PMN)-dependent increase in pulmonary vascular permeability to protein after thrombin-induced pulmonary microembolism. Humoral factors that activate PMNs after thrombin-induced pulmonary microembolism were characterized in pulmonary lymph obtained from unanesthetized sheep challenged with intravenous infusion of alpha-thrombin. Time-dependent increase...

Neurospora crassa conidia incubating in buffer at low water activities (a(w)) release a germination-essential component as well as 260-nm absorbing and ninhydrin-positive materials, regardless of whether an electrolyte or non-electrolyte is used to reduce a(w). Chloroform and antibiotics known to increase cell-membrane permeability have a similar effect. This suggests that membrane damage occur...

The purpose of this review is to demonstrate that an intestine leaky to small molecules can be impermeable to large antigenic molecules. The author proposes that the permeability of the epithelium to very small sugar molecules such as lactulose/mannitol-used for the past 50 years to gauge intestinal permeability-does not necessarily correlate with epithelial permeability to macromolecules. This...

Recently measured water permeability through bilayers of different lipids is most strongly correlated with the area per lipid A rather than with other structural quantities such as the thickness. This paper presents a simple three-layer theory that incorporates the area dependence in a physically realistic way and also includes the thickness as a secondary modulating parameter. The theory also ...

Normally, the gastrointestinal epithelium provides a semi-permeable barrier which allows nutrients to be absorbed while preventing larger, potentially toxic, antigenic, or pathogenic molecules or organisms from crossing into the bloodstream. Pathogenicallyincreased intestinal permeability predisposes the individual to diffusion of antigenic food molecules and translocation of bacteria and/or ye...