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L W Welling

Publications and source records attributed to L W Welling.

41 records · Page 3Linked to original sources
PubMed1975

Surface areas of brush border and lateral cell walls in the rabbit proximal nephron.

A morphometric technique is used to estimate the absolute and relative surface areas of the brush border microvilli and cell walls bordering lateral intercellular spaces. In isolated, perfused proximal tubule from rabbit, the luminal and lateral surfaces are equal in area. For proximal convoluted tubules (PCT) each surface is 4.1 +/- 0.3 mu2/mu3 of epithelial cell volume or approximately 2.9 X 10(6) mu2/mm of tubule length. In proximal straight tubules (PST) the areas are 2.6 +/- 0.2 mu2/mu3 or 1.2 X 10(6) mu2/mm. Brush border enlarges the apical cell surface 36-fold in PCT and 15-fold in PST. The luminal and lateral cell surfaces each are approximately 20-fold (in PCT) and 10-fold (in PST) greater than the areas of the basal cell surface and tubule basement membrane. These data may be important in the context of an intercellular transport model.

Animals↗
PubMed1975

Pressure-flow-diameter relationships in isolated perfused thin limb of Henle.

To measure directly the relationships between flow rate, tubule diameter, and flow resistance in thin descending limbs of Henle, isolated tubule segments from the rabbit were studied by in vitro microperfusion. Small increases in pressure and flow cause rapid enlargement of the tubule. Flow resistance is inversely related to tubule diameter and, by its effect on transmural pressure, indirectly limits the extent of tubule dilation. In a range of transmural pressures comparable to that in vivo, the tubule is capable of radial dilations as great as 35% and does not reach its structural limit of distensibility. Flow resistance may be approximately by a Poiseuille equation for cylindrical tubules. The effective luminal diameter is approximately a constant fraction of outer tubule diameter and is defined approximately by the innermost projection of semirigid epithelial nuclei.

Animals↗
PubMed1972

Physical properties of isolated perfused renal tubules and tubular basement membranes.

To study the physical properties of renal tubular basement membranes directly, the epithelial layer of single isolated perfused rabbit proximal convoluted, proximal straight, and cortical collecting tubules was removed with sodium desoxycholate. Tubular segments were perfused using micropipets. The distal end of each segment was occluded in order to simplify the measurement of transmembrane water flow. The relation between outer tubular diameter and applied transmural pressure was identical in intact tubules and their respective isolated tubular basement membranes indicating that the basement membrane determines tubular distensibility. Young's modulus for basement membranes from all tubular segments corresponded to that of tendon collagen. Membrane hydraulic conductivity was measured in two ways: (a) from the rate of transmural flow in response to an applied difference in hydrostatic pressure and, (b) from the rate of transmural flow in response to a difference in colloid osmotic pressure. The hydraulic conductivity of tubular basement membranes was 300-800 times greater than that of the intact epithelial layer. Basement membrane hydraulic conductance was similar to that of peritubular and glomerular capillaries in vivo. The hydrostatic conductance of tubular basement membranes exceeded the osmotic conductance by 3-10-fold owing largely to the fact that the membranes were moderately permeable to the osmotic solute (albumin). In view of these findings we suggest that oncotic and hydrostatic pressure may play an important role in the movement of tubular absorbate from the epithelial compartment into the renal interstitium.

Albumins↗