Francis P. Chinard

Permeability of novikoff hepatoma cells to water and monohydric alcohols

The permeability coefficients of Novikoff hepatoma ascites cell membranes for tritiated water (3HHO) and for a homologous series of monohydric alcohols (methanol through hexanol) were deduced from linear diffusion coefficients by means of a series-parallel pathway model (Redwood et al. (1974) J. Gen. Physiol. 64, 706-729). Membrane permeability coefficients for 3HHO at 20, 30 and 37 degrees C were (all x 10(-5)) 97, 125, and 163 cm . s-1, respectively, and were significantly smaller than the corresponding values for the alcohols tested. In the alcohols series, ethanol had the lowest permeability coefficient 198 x 10(-5) cm . s-1 at 20 degrees C. The apparent activation energy for water permeation was 6.7 +/- 1.9 S.E. kcal . mol-1. The apparent membrane diffusion coefficients for the alcohols were a complex function of molecular properties with less diffusional membrane resistance to the alcohols in the middle of the homologous series than would have been expected on the basis of oil-water partitioning or molar volume considerations. The conventional parallel aqueous lipophilic pathway model is not consistent with the present data which can be interpreted by consideration of parallel lipophilic pathways through the Novikoff hepatoma cell membrane.

Variations in cellular attenuation and vesicle numerical densities in capillary endothelium and type I epithelium of isolated, perfused dog lungs after acute severe edema formation

Morphometric comparisons of nonedematous and edematous isolated, perfused dog lungs establish that there are significant differences between the degree of cellular attenuation and vesicle numerical densities in endothelial and type I epithelial cells of the alveolar septa after edema production. In nonedematous isolated lungs the extent of endothelial and epithelial attenuation was greater on the thin sides of the septa. In the edematous lungs, the differential of greater thin-side attenuation was maintained for the endothelium but not for the epithelium where the extent of attenuation in the septal thick segments was increased. Vesicle numerical densities were approximately doubled in the cells on both sides of the septa in the edematous lungs. The endothelial vesicle densities were greater in the septal thin segments than in the septal thick segments in both the nonedematous and the edematous isolated lungs. The epithelial vesicle densities, on the other hand, were similar on the thin and thick sides of the septa in the nonedematous and edematous lung preparations. Although the contribution of vesicles to cellular function in the alveolar septa remains uncertain, further evaluation of vesicular transport should include the possible variability of this function with the varying degrees of cellular attenuation on the two anatomically distinct sides of the septa.

Ultrastructural changes of the air-blood barrier after spontaneous development of edema in isolated dog lungs perfused at 15° ☆

Abstract Isolated dog lungs perfused at 37° develop edema with increases of microvascular pressure or with decreases of perfusate macromolecule concentrations. In such preparations, the edema is restricted to thick portions of the septa and is associated with a doubling of the cellular vesicle volume densities in both endothelial and epithelial (Type I) cells ( DeFouw and Berendsen, 1978a , DeFouw and Berendsen, 1979 ). In contrast, preparations perfused at 15° can develop edema but do not show any increase of vesicle densities in either endothelial or epithelial cells. Cooling restricts transendothelial passage of lipophilic substances probably because of a decrease of membrane lipid fluidity which may also inhibit new vesicle formation. The thesis that capillary vesicles are not primarily associated with edema formation is supported by the occurrence of edema without increased vesiculation.

Distribution and Transport of Varied Substances in the Dog Kidney in Vivo: Implications with Regard to Metabolic Activities

Some matters bearing on renal metabolic activities have been reviewed. The distribution of solutes to various regions of the kidneys depends not only on convection by blood and tissue fluid flow but also on diffusion of the solutes in the tissues. Lipid solubility may play a significant role in tissue diffusion in that substances with significant lipid solubility may have access to more direct pathways than strictly hydrophilic substances. Glucose utilization by the kidney is significant. Glucose may contribute as much as 25 per cent and lactate, through decarboxylation, as much as 30 per cent of the renal carbon dioxide production. Together, glucose and lactate may account for about 50 per cent of the total renal carbon dioxide production. There is evidence that there is substantial lactate production by the kidney as well as gluconeogenesis. The conditions for luminal and anti-luminal cell surface interactions with D-glucose differ with regard to configuration, conformation and phlorizin affinity. Possible pathways of entry of glucose into metabolic activities are briefly considered.

Morphometric and physiological studies of alveolar microvessels in dog lungs in vivo after sustained increases in pulmonary microvascular pressures and after sustained decreases in plasma oncotic pressures

Previous investigations from this laboratory of isolated-perfused dog lungs have shown that volume densities of vesicles in both capillary endothelial and type I epithelial cells are substantially increased after acute, severe edema produced by increasing microvascular pressures (D. O. DeFouw and P. B. Berendsen, 1978, Circ. Res. 43, 72-82) and after decreasing macromolecular concentrations of the perfusate (D. O. DeFouw and P. B. Berendsen, 1979, Microvasc. Res. 17, 90-103). The present study provides morphometric evaluations of alveolar vessel endothelium of the lungs of intact dogs after episodes of sustained increased microvascular pressures and after sustained decreases of plasma oncotic pressures. Endothelial vesicular volume densities did not increase in either case. Fluid accumulation was found in the extraalveolar connective tissue spaces (mainly perivascular); no changes of endothelial or interstitial compartmental thicknesses were observed on either the thin or thick sides of the alveolar septa. Thus, if the increased outward filtration to be expected from the increased hydrostatic or decreased oncotic pressures occurred in the microvasculature, it was moderated by increased hydrostatic and decreased oncotic pressures in the tissues or was accommodated by increased lymph flow rates. Our tentative hypothesis that increased septal interstitial pressure plays a role in initiating vesicle formation in alveolar endothelial cells is consistent with these data if the postulated increases of tissue pressure are less than in the isolated perfused preparations. Our data do not provide support for the concept that endothelial vesicles play a major, early role in the development of pulmonary edema.

Alveolar Microvessels in Isolated Perfused Dog Lungs: Structural and Functional Studies after Production of Moderate and Severe Hydrodynamic Edema

We have reported earlier that increased endothelial vesiculation follows the development of septal edema and alveolar flooding in isolated dog lung preparations. In this report, established ultrastructural morphometric analyses are coupled with data from physiologic and indicator-dilution studies to evaluate the stage of edema development at which de novo formation of alveolar microvessel plasmalemmal vesicles occurs. The interpretation that alveolar microvessel plasmalemmal vesicles increase prior to alveolar flooding, the final stage of edema formation, is consistent with the results reported here. Moderate pulmonary edema, characterized by substantial fluid cuffing around extra-alveolar arteries and veins and by fluid accumulation restricted to the thick sides of the alveolar septa, is associated with increased vesiculation in alveolar vessel endothelium. Further, a larger percentage of the vesicle population seen is directly attached to the endothelial luminal or abluminal surfaces. The functional significance of an increased population and an altered intracellular distribution of vesicles remains undetermined. The vesicles may provide a minor defense against excessive septal interstitial fluid accumulation, and subsequent alveolar flooding, by contributing to retrograde transport to the blood. Increased vesiculation, on the other hand, may represent an adaptive cellular response to interstitial fluid accumulation.

The influence of circulatory overload on extraalveolar microvessel endothelium of dog lung in vivo

In an earlier study from this laboratory, morphometric evaluations of the alveolar capillary endothelium of the lungs of intact dogs were recorded after periods of sustained increases of pulmonary microvascular pressures (D. O. DeFouw, W. O. Cua, and F. P. Chinard, 1983, Microvasc. Res. 25, 56-67). In the present study ultrastructural characteristics of the extraalveolar microvessel endothelium of these dog lungs were evaluated. Small (25- to 50-microns luminal diameter) nonmuscular vessels, which adjoin the alveolar capillaries, and larger (51-200 microns) partially muscular and muscular microvessels were assessed. After increased microvascular filtration, to be expected from the increased hydrostatic pressures, fluid accumulation was found only in the connective tissue sleeves of the larger microvessels. The endothelium of these partially muscular and muscular vessels was markedly affected by fluid distension of the periendothelial interstitium. The endothelial response included the appearance of basal (abluminal) surface invaginations, de novo plasmalemmal vesicle formation, and increased numbers of cytoplasmic vacuoles. The small nonmuscular microvessels lacked both the fluid cuffs and the alterations of endothelial ultrastructure. This latter observation is consistent with the previous report from this laboratory that indicated an absence of both alveolar septal edema and increased capillary endothelial vesicle densities in these lungs (DeFouw et al., 1983). Thus, it seems likely that the conformational changes of the endothelium of the larger microvessels were related to the formation of the periendothelial fluid cuffs. The mechanisms responsible for this endothelial response have not been determined but can be explained on the basis of the testable hypothesis that they are secondary to an increase of tissue pressure associated with accumulation of tissue fluid. These changes may thus represent a secondary structural adaptation to the increased tissue pressures and may serve as a potential vesicular-vacuolar pathway across the endothelium.