Effect of the gel to liquid crystalline phase transition on the osmotic behaviour of phosphatidycholine liposomes

Effects of Silicon on Tolerance to Water Deficit and Heat Stress in Rice Plants (Oryza sativaL.), Monitored by Electrolyte Leakage

“…Temperatureinduced changes in membrane lipids are key factors in the regulation of heat resistance of plant (Somerville and Browse, 1991), but, to our knowledge, the involvement of membrane protein with El in relation to high temperature resistance of plant has not been studied. In general, El caused by high temperature is maximum around the transition temperature at which fluid-phase and solidphase lipids coexist in cell membranes (Blok et al, 1976) . Therefore, the extent of El caused by the hightemperature treatment presumably reflects differences in the properties of leaves, in terms of responses of lipids to temperature.…”

Molecular sieving action of the cell membrane during gradual osmotic hemolysis

“…The addition este:l"ol to a monolayer (Phillips, Kamat and Chapman, 1970) or bilayer (Rand and Luzzati, 1968) of unsaturated phospholipids reduces the area per molecule, restricts the motion of the hydrocarbon chains (Darke et aL, 1972), and decreases liposome permeability (Cohen, 1975b) as expected, If liposomes are maintained at a temperature at which domains of crystalline and liquid-crystalline hydrocarbon coexist or if the temperature is changed so that such domains coexist, the liposomes have increased permeability compared to nearby temperatures where a single phase exists (Blok, van Deenen and De Gier, 1976). This is expected on the basis of the free-volume fluctuation hypothesis as previously mentioned because of the increased compressibility when two phases are present.…”

Effect of glycerol and cholesterol-loaded cyclodextrin on freezing-induced water loss in bovine spermatozoa

“…A dissimilarity between the suprazero and subzero water transport parameters was also found for mouse (Devireddy et al 1999), human (Devireddy et al 2000), horse (Devireddy et al 2002a,b), dog (Thirumala et al 2003) and boar sperm cells. This discrepancy between the membrane permeabilities may be associated with possible changes in the sperm cell plasma membrane during suprazero cooling, including a lipid-phase transition of 0 -4 8C (Noiles et al 1995) and/or cold-shock damage or 'chilling' injury during cooling (Blok et al 1976, Watson 1981, Steponkus 1984. These changes in membrane transport properties might also be associated with solidification in the extracellular medium (phase change) phenomena, including changes in the membrane fluidity (Drobnis et al 1993) and lyotropic (i.e.…”

“…However, Purdy and Graham (2004a) found that when cyclodextrins, or cyclic oligosaccharides of glucose with a hydrophobic center capable of incorporating lipids (Gitler 1972, Klein et al 1995, are preloaded with cholesterol (cholesterol-loaded cyclodextrin (CLC)) and then incubated with bull sperm before cryopreservation, higher percentages of motile and viable cells are recovered after freezing and thawing than with control sperm. This added cholesterol probably benefits cells by eliminating or at least lowering the temperature at which the sperm plasma membranes undergo the lipid-phase transition from the fluid to the gel state as the cells are cooled (Blok et al 1976, Watson 1981, Steponkus 1984, Holt & North 1986, Caffrey 1987, Drobnis et al 1993. More importantly, Purdy and Graham (2004b) also showed that, after freezing and thawing, CLC-treated bovine sperm do undergo capacitation and the acrosome reaction at rates similar to control sperm, and fertilize oocytes in vitro and in vivo similarly well.…”