Water permeability effect

Attack of the fungus Fusarium oxysporum on the tomato appears to involve both fusaric acid (10) (a pyridine derivative) and a small peptide, lycomarasmin (11) (Fig. 14.4) (Ballio, 1981 Harbome, 1988). The former compound is linked to chelation of metal ions, whereas the peptide is involved in water-permeability effects (Ballio, 1981). 

Water Permeation and Solute Separation through the Membrane. The measurements of water permeability of the 67 membranes prepared under different conditions were carried out by using an Amicon Diaflo Cell (effective membrane area, 13.9 cm2) under a pressure of 3 kg/cm2 at 25 °C. Some results are listed in Table 1067. It is apparent that much higher water absorption and permeability than the cellulosic membrane are characteristic of the 67 membranes prepared by both the casting polymerization and conventional casting. 

The sensitivity of productivity or flux to transmembrane pressure (TMP) is referred to as the permeability L = flux/transmembrane pressure. TMP refers to a module average. Pure-component permeability (e.g., water permeability) refers to membrane properties while the more industrially relevant process permeability includes fouling and polarization effects. 

Nanofiltration membranes are negatively charged and reject multivalent anions at a much higher level than monovalent anions, an effect described as Donnan exclusion. Nanofiltration membranes have MgS04 retention and water permeability claims. 

The reported (14) mechanisms of action of allelochemlcals Include effects on root ultrastructure and subsequent Inhibition of Ion absorption and water uptake, effects on hormone-induced growth, alteration of membrane permeability, changes In lipid and organic acid metabolism, inhibition of protein synthesis and alteration of enzyme activity, and effects on stomatal opening and on photosynthesis. Reduced leaf water potential Is one result of treatment with ferulic and p-coumaric acids (15). Colton and Einhellig (16) found that aqueous extracts of velvetleaf (Abutllon theophrastl Medic.) Increased diffusive resistance In soybean fGlycine max. (L.) Merr.] leaves, probably as a result of stomatal closure. In addition, there was evidence of water stress and reduced quantities of chlorophyll In Inhibited plants. 

Permeability is a property closely tied to the environment of the epithelial cell surface. There is little point in measuring permeability at pH 1.7, if the microclimate barrier has pH >5 and <8, averaging 6. An in vitro permeability screen based on donor pH 5.0-7.4 and acceptor pH 7.4 seems about right. It will be useful to correct the data for the unstirred water layer effect, using computational methods. 

In situ perfusion studies assess absorption as lumenal clearance or membrane permeability and provide for isolation of solute transport at the level of the intestinal tissue. Controlled input of drug concentration, perfusion pH, osmolality, composition, and flow rate combined with intestinal region selection allow for separation of aqueous resistance and water transport effects on solute tissue permeation. This system provides for solute sampling from GI lumenal and plasma (mesenteric and systemic) compartments. A sensitive assay can separate metabolic from transport contributions. 

Finkelstein, A. and Cass, A. (1967). Effect of cholesterol on the water permeability of thin lipid membranes, Nature, 216, 717-718. 

This condition has been recently used in a vaporization-exchange model for water sorption and flux in phase-separated ionomer membranes. The model allows determining interfacial water exchange rates and water permeabilities from measurements involving membranes in contact with flowing gases. It affords a definition of an effective resistance to water flux through the membrane that is proportional to... 

Ceramide is now included in some skin creams which are claimed to be beneficial to the skin, preventing drying and reducing the effects of ageing. Linoleoyl-ceramide is present in the skin where it restricts water permeability, preventing excessive water loss from the skin. 

Study of the temperature dependence of the salt and water permeabilities through heat treated PVA membranes indicates that the heat treatment effect is expressed mainly in changes in permeability activation energies. The activation parameters for water and salt permeability of PVA membranes following various treatments are presented in Table IV. It is evident that the salt permeability activation energy is increasing about 2-3 times as... 

Figure 9. Effect of the duration of heat treatment at I75°C on salt and water permeabilities of PVA at 30°C (A) salt permeability coefficients (O) water permeability coefficients. Open symbols refer to 100% hydrolyzed, 86,000 mol wt PVA solid symbols refer to ]00%> hydrolyzed, 115,000 mol wt PVA.

Adams SL, Zhang T, Rawson DM (2005) The effect of external medium composition on membrane water permeability of zebrafish (Danio rerio) embryos. Theriogenology 64 1591-1602... 

The large pores (ranging from 0.01 pm to 0.1 pm) are sealed by the continuous polymer film formed in the comatrix of LMM and LMC. Consequently, they show reduced water absorption, water permeability and water vapor transmission over ordinary cement mortar and concrete and this effect increases with an increase in polymer content and polymer-cement ratio (Fig. 6.15). The improved water permeability also improves the resistance to chloride ion entry and hence corrosion mitigation [87]. 

Mechanism of Action A posterior pituitary hormone that increases reabsorption of water by the renal tubules. Increases water permeability at the distal tubule and collecting duct. Directly stimulates smooth muscle in the GI tract. Therapeutic Effect Causes peristalsis and vasoconstriction. 

Almost all diuretics exert their action at the luminal surface of the renal tubule cells. Their mechanism of action includes interaction with specific membrane transport proteins like thiazides, furosemide etc., osmotic effects which prevent the water permeable segments of the nephron from absorbing water like mannitol, and specific interaction with enzyme like carbonic anhydrase inhibitors i.e. acetazolamide, and hormone receptors in renal epithelial cells like spironolactone. 

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