Vascular permeability factor/vascular endothelial growth factor stimulates endothelial proliferation, angiogenesis, and increased vascular permeability in vivo. We investigated mechanisms of vascular permeability factor-mediated endothelial monolayer permeability changes in vitro. [ 14 C]Albumin flux across endothelial monolayers was measured following a 90-min exposure to vascular permeability factor (660 pM). Vascular permeability factor increased albumin flux to 3.4 times that of control albumin flux. Endothelial monolayers were also incubated for 90 min with vascular permeability factor plus Gö 6976 (10 nM), staurosporine (1 M), wortmannin (10 nM), AG126 (1 and 2.67 M), and PD98059 (20 M). Vascular permeability factor-mediated permeability was not blocked by Gö 6976, an antagonist of "classical" protein kinase C, staurosporine, a pan-protein kinase C antagonist, nor wortmannin, a PI3-kinase blocker, but was blocked by incubation with AG126 or PD98059, inhibitors of mitogen-activated protein kinase activation. Immunofluorescent staining of the junctional proteins VE-cadherin and occludin showed a loss of these proteins from the endothelial junction that was prevented by co-incubation with AG126 or PD98059. These data demonstrate that vascular permeability factor increases albumin permeability across endothelial monolayers in vitro and suggests that permeability increases through rearrangement of endothelial junctional proteins involving the mitogen-activated protein kinase signal transduction pathway.

No abstract

Studies aimed at elucidating the function of the protein synthesis factor eukaryotic initiation factor 4E (elF-4E) have demonstrated that overexpression of this protein results in marked cell phenotypic and proliferative changes, including neoplastic transformation of cells. These data suggest that elF-4E may somehow participate in the development and progression of tumors in vivo. In order to determine how elF-4E exerts its transforming effects, we examined vascular permeability factor (VPF) levels in cells transfected with an elF-4E vector. Cells overexpressing elF-4E showed an increase in intracellular, and an average 130-fold increase in secreted VPF protein levels (CHO 0.13 f 0.12 ng/ml; CHO-4E 20.5 2 12.5 ng/ml) over control cells. HUVEC growth induction revealed these VPF levels to be biologically active. Northern analysis revealed no difference in VPF transcript between the 2 cell lines. Polysome analysis showed that the VPF message in elf-4E-transfected cells was associated with the heavy polysomal regions, whereas the VPF message was associated with light polysomes in control cells. These data strongly suggest that enhanced VPF expression is achieved through translational regulation rather than transcriptional regulation in cells overexpressing elF-4E. This indicates that elf-4E-induced VPF expression may be an important factor in some forms of tumor angiogenesir and development.

To determine the permeability of canine pleural mesothelium, visceral and intercostal parietal pleura from mongrel dogs was carefully stripped from the underlying tissue and mounted as a planar sheet in a Ussing-type chamber. The hydraulic conductivity (Lp) was determined from the rate of volume flux in response to hydrostatic pressure gradients applied to either the mucosal or serosal surface of the pleural membrane. The diffusional permeability (Pd) of radiolabeled water, sucrose, inulin, and albumin was determined under equilibrium conditions from the unidirectional tracer flux. The Lp of the visceral pleura was 0.39 +/- 0.032 (SE) X 10(-4) ml.s-1.cmH2O-1.cm-2 and that Lp of parietal pleura was 1.93 +/- 0.93 X 10(-4) ml.s-1.cmH2O-1.cm-2 (P less than 0.001). The Pd of the visceral pleura ranged from 12.21 +/- 0.45 X 10(-4) cm/s for 3H2O to 0.34 +/- 0.03 X 10(-4) cm/s for [3H]albumin. The Pd of the parietal pleura for water and sucrose was similar to that of the visceral membrane, whereas its Pd for the larger inulin and albumin molecules was greater than that of visceral pleura (P less than 0.01). A spontaneous potential difference could not be detected across either membrane. The relatively higher parietal pleural Lp and Pd for larger solutes is probably due to the presence of stomata in this membrane. These results indicate that both the parietal and the visceral pleura are extremely permeable tissues which offer little resistance to water and solute flux.

No abstract

No abstract

There is currently no reliably effective drug for preventing or delaying the development of oxygen toxicity in humans. Use of the lowest effective oxygen concentration, the avoidance of certain drugs, and attention to nutritional and metabolic factors remain the best means currently available to avoid or minimize oxygen toxicity. Research is continuing into more effective ways to prevent, diagnose, and treat this disorder.

No abstract