Filtration Permeability Research Articles

Microscopical determination of the filtration permeability of the mucosal surface of the goldfish intestinal epithelium.

The rate of shrinkage of the mucosal folds of goldfish intestine in response to mucosal hypertonicity was measured by microscopic means. Because of the geometry of the intestinal folds the rate of shrinkage could be directly related to the loss of volume from the fold through the brush border membranes and tight junctions. Experimentally a wide range of velocities was observed, reflecting the difficulty of rapidly establishing a uniform osmotic gradient at the preparation's mucosal surface. The initial velocity of volume loss provided a measure of the filtration permeability (Pf) of the mucosal surface. From the highest velocities observed the filtration permeability was estimated to be approximately 14 X 10(-3) cm/sec related to the folded mucosal surface and 65 X 10(-3) cm/sec related to the straight serosal surface. Consideration of the experimental errors and unstirred layer effects make it probable that the latter value is still an underestimate of the true Pf. The series barriers of the epithelium cause the total tissue Pf to be less than the Pf of the mucosal surface alone. In addition the Pf measured in the presence of an osmotic gradient may differ substantially from the tissue filtration permeability which exists in the absence of a change in osmolarity.

Trace Metal Enrichment on Chemically Modified Filter Papers

Abstract A trace enrichment technique for preconcentration of heavy metals on thiocarbaminate modified filter papers is described. The technique has been studied for Cu2+, Fe2+and3+, Zn2+, Pb2+, Ni2+, As3+, Sb3+, Cd2+, Hg2+, VO2+ and UO2+ 2. Up to 100 μg of metal can be retained within one to two hours on the filter. Effects of filter treatment of flow conditions and pH on filter capacity, filter permeability and recovery have been studied. Best recoveries were obtained in the pH range of 5-6. Considerable improvement on stability of the samples and reproducibility was achieved by subjecting the filters to high pressures prior to measurement. The technique was applied to the analysis of metal traces in ultra pure water samples (lower PPB range) and in organic samples by x-ray fluorescence.

Pulmonary transvascular fluid filtration and microvascular permeability to plasma proteins in awake newborn lambs

Pulmonary transvascular fluid filtration and microvascular permeability to plasma proteins in awake newborn lambs

The filtration characteristics of yeast

The filtration characteristics of yeast cells are reported and the use of the information in process calculations of filtration rates is demonstrated. Comparison is made between filtration properties obtained by vacuum filtration studies and permeability measurements. The kinetics of cell growth are followed by size distribution records.

Filtration and diffusion of water across the blood-brain barrier in man

Water transport across the blood-brain barrier was studied in 15 patients during hypertonic intracarotid injection. The filtration permeability coefficient ( P f) measured in 10 patients was 10.4 × 10 −4 cm sec −1. The diffusion permeability coefficient ( P d) for tracer water measured in 12 patients was 2.4 × 10 −4 cm sec −1, but this value is probably too small due to back diffusion. The P f P d ratio was 4.3 and might therefore be even smaller. The results indicate that pores or slits are not present in the blood-brain barrier and probably all water transport occurs by dissolving in the membrane phase.

Osmotic water movement across the sarcolemma of frog skeletal muscle fibers

The permeability coefficient for osmotically induced water flux across the sarcolemma of frog skeletal muscle fibers was determined. A new method for measuring the fiber volume change was applied, based on the fact that the resting tension of a slightly stretched muscle fiber depends on the bathing solution tonicity. Thus, after a quick change in tonicity, the volume change can be derived from the simultaneously occurring tension change. Fitting a theoretical curve to the experimentally obtained values yielded a filtration permeability coefficient for water of 0.54±0.12 cm4/osmol sec (mean ±sd, n=12). Doubling the driving force did not alter the productPWx membrane area. ThePW value found in the present work is compared with that for muscle fibers and other cells given previously.

The identity of filtration and diffusion permeability coefficients in frog egg membrane.

The filtration permeability coefficientP f for water has been determined on ovarian eggs ofRana temporaria as a function of the temperature. A local maximum was found at 16°C and a minimum at 19°C. This temperature dependence has previously been shown to characterize the cytoplasmic water diffusion coefficient and, since isotope studies have demonstrated that there is no measurable barrier to permeation of water at the surface of ovarian eggs, it is concluded that the previously reported values ofP f for this material are fictitious. Determinations ofP f on body cavity eggs, in which a measurable resistance to water permeation prevails, have given values that are not significantly different from the diffusion permeability coefficientsP d obtained in isotope exchange experiments. With reference to these results, and similar ones reported for other types of membrane, it is concluded that the justification is lacking for the claimP f >P d , on which many speculations on the mechanism of water passage through biological membranes have heretofore been based.

Water, sodium and potassium movements across the rumen wall of sheep.

Saliva was entirely diverted from the rumen of sheep via an oesophageal fistula and usually replaced by infusion of a synthetic saliva of known composition. Water movements in the rumen were measured by the use of soluble markers, and sodium and potassium movements were calculated. Water and various solutions were added to the rumen to vary its osmolality over the range 180–550 m‐osmole/kg.When saliva was not replaced, recovery of the normal rumen osmolality following water loading was very slow indeed. When saliva was replaced by a synthetic solution the rate of water movement across the rumen wall (y, [l./hr]) was a linear function of the osmotic pressure (x, [m‐osmole/kg]), such that y = 0·404–0·001206x (r = ‐0·90). This suggests that the filtration permeability of the rumen wall was similar to that of frogskin or toad bladder.Potassium absorption across the rumen wall was also slow but positively related to the potassium concentration. Sodium absorption appeared to depend on the potassium concentration and the osmotic pressure as well as on the sodium concentration. While moderate levels of potassium increased the rate of sodium absorption, grossly high levels, sufficient to produce a substantial entry of water across the rumen wall, decreased it, sometimes markedly. The rate of potasium and perhaps sodium absorption seemed to depend on the immediate state of nutrition of the animal.

Filtering properties of twin-layer sintered filters

1. At equal filter thickness, twin-layer sintered filters from nonspherical powder have a much superior combination of filtration qualities (permeability and purification fineness) compared with filters made entirely from the same powder. 2. The dependence of permeability on resistance for twin-layer filters obeys Darcy's law within the limits investigated; for short filtration periods, permeability and purification fineness are the same irrespective of which of the two layers faces the oncoming fluid stream. 3. It is shown that the service life (period of operation before clogging) of twin-layer filters is longer when the filters are placed so that their coarse-fraction powder layer faces the fluid stream; filters arranged during operation with their fine-fraction powder layer against the fluid stream were found to exhibit better regeneration characteristics. 4. It is shown that filters from nonspherical powders can very effectively be regenerated by ultrasonic treatment, but not by the method of counter-blowing (at pressure drops of up to 1.5 MN/m2). 5. For a given filtration fineness, a twin-layer filter has a much longer service life (to clogging) than a filter made from powder of one fraction.

Action des deux peptides neurohypophysaires sur le transport actif de sodium et le flux net d'eau à travers la peau de diverses espèces de batraciens anoures

The effect of oxytocin (extracted or synthesized) and of antidiuretic hormone (ADH) on the active transport of sodium (recorded by short-circuit current) and on the net flux of water has been studied in vitro on skins of three species of Anura: Rana esculenta, Rana temporaria and Bufo bufo. In Rana esculenta, at concentrations of 0.15 milliunits/ml or higher, oxytocin greatly increases sodium transport and net flux of water, while ADH has no effect. In Rana temporaria, the influence of oxytocin on the transport of sodium is less marked, but it is still far more clearly discernible than that of ADH. In Bufo bufo, the two hormones are equally effective, both increasing the net flux of sodium and of water. Apart from these differences as regards species, this investigation has demonstrated that the action of the hormones on the active uptake of sodium through the skin and on its filtration permeability go hand in hand, and are closely correlated. At least in Rana esculenta, the clear response to even the lowest doses of oxytocin argues in favour of the role attributed to neurohypophyseal peptides in the control of sodium metabolism. It seems, however, that the hormones physiologically secreted by the lower Vertebrates differ from those extracted from the posterior lobe of the hypophysis of Mammals.