Membrane fluidity, change

Leifert WR, Jahangiri A, McMurchie EJ. Membrane fluidity changes are associated with the antiarrhythmic effects of docosahexaenoic acid in adult rat cardiomy-ocytes. J Nutr Biochem. 2000 I 1 38—44. 

The mechanism by which albumin (in many cases bovine serum albumin BSA) promotes capacitation in mammalian sperm is intriguing as it is believed to function during capacitation in vitro as a sink for the removal of cholesterol from the sperm plasma membrane (Go and Wolf, 1985 Langlais and Roberts, 1998 Cross, 1998). The association between cholesterol removal from the sperm plasma membrane, albumin, and capacitation was first proposed by Davis and colleagues (1980). Removal of this sterol likely accounts for the membrane fluidity changes observed during capacitation (Wolf et al., 1986). The consequence of the removal of this sterol is that the cholesterol to phospholipid ratio in the membrane decreases, and such changes in... 

D. Georgescauld and H. Dulochier, Transient Fluorescent Signals from Pyrene Labeled Pike Nerves During Action Potential. Possible Implications for Membrane Fluidity Changes, Biochem. Biophys. Res. Commun. 85, 1186-1191 (1978). 

The primary site of action is postulated to be the Hpid matrix of cell membranes. The Hpid properties which are said to be altered vary from theory to theory and include enhancing membrane fluidity volume expansion melting of gel phases increasing membrane thickness, surface tension, and lateral surface pressure and encouraging the formation of polar dislocations (10,11). Most theories postulate that changes in the Hpids influence the activities of cmcial membrane proteins such as ion channels. The Hpid theories suffer from an important drawback at clinically used concentrations, the effects of inhalational anesthetics on Hpid bilayers are very small and essentially undetectable (6,12,13). 

BE Schaeffer, JA Zadunaisky. (1979). Stimulation of chloride transport by fatty acids in corneal epithelium and relation to changes in membrane fluidity. Biochim Biophys Acta 556 131-143. 

Havaux, M. and W.I. Gruszecki. 1993. Heat- and light-induced chlorophyll a fluorescence changes in potato leaves containing high or low levels of the carotenoid zeaxanthin Indications of a regulatory effect of zeaxanthin on thylakoid membrane fluidity. Photochem. Photobiol. 58 607-614. 

Biological membranes fluidity order parameters lipid-protein interactions translational diffusion site accessibility structural changes membrane potentials complexes and binding energy-linked and light-induced changes effects of additives location of proteins lateral organization and dynamics... 

Recently, the effect of the lipid composition on the permeability in PAMPA was investigated [129], By varying the phosphate head group and the saturation degree of the acyl chain, differences in transport were observed for a set of five model compounds, which was due to changes in membrane fluidity and ion pairing [129],... 

Stoll S, Scheuer K, Pohl 0, Muller WE. (1996). Ginkgo biloba extract (EGb 761) independently improves changes in passive avoidance learning and brain membrane fluidity in the aging mouse. Pharmacopsychiatry. 29(4) 144-49. 

Fluid membrane hypothesis Anesthetics stabilize, or rather immobilize the cell membrane, hampering membrane fluidity, which produces changes in the ion channel action. 

Alterations In membrane fluidity, especially of neurons, can produce profound changes In cellular function. 

The answer is E. Anesthetics are highly lipid-soluble and experiments with isolated membranes indicate that these molecules can dissolve in the hydrophobic center of the membrane bilayer. This causes a measurable increase in the membrane fluidity by disrupting the packed structure of phospholipids tails. This is considered to be the main, direct mechanism by which this class of drugs inhibits neurotransmission (pain sensations) in neurons. Hallucinogens and opiates may also affect membrane fluidity, but their effects occur by indirect mechanisms, resulting from changes in the protein or lipid composition of the membranes. 

The inhalation anesthetics belong to diverse chemical classes. There main indication is the maintenance of anesthesia after intravenous induction. There are no suggestions that they interact with pharmacologically-defined receptors like some of the injectable anesthetics do and they have no specific site of action. Apparently they cause physical changes in cells such as changes in cell membrane fluidity. 

Inhibitors of HMG-CoA reductase activity (for example compac-tin240), or compounds that lower the levels of the enzyme (including a number of oxygenated cholesterol derivatives,241- 24 la such as 25-liy-droxycholesterol), not only decrease the formation of polyprenyl diphosphate, but also affect the formation of cholesterol and the polyprenyl side-chains of coenzyme Q. Consequently, prolonged treatment with such compounds may cause side effects, for example, changes in membrane fluidity (see also, Section III,5), decreased activity of membrane enzymes,1214,2,3 and inactivation of membrane transport systems,246 and, therefore, indirectly prevent glvcosvlation of proteins. 

Lipid-free (Na+, K+)-ATPase is incapable of hydrolyzing ATP or p-nitrophenyl phosphate. The precise role of the lipid and the specificity for the lipid have not yet been determined. The addition of lipid to the delipidated enzyme brings about conformational changes, with phosphatase activity regenerated before ATPase activity.51 It seems evident that the lipid will affect the conformation of the enzyme and determine membrane fluidity, which is relevant to conformational change. 

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