Cell membrane stabilisation

Prevention of mast cell degranulation membrane stabilisation. 

Adrenaline is used in anaphylactic shock because its mix of actions, cardiovascular and bronchial, provide the best compromise for speed and simplicity of use in an emergency it may also stabilise mast cell membranes and reduce release of vasoactive autacoids (see p. 280). Patients who are taking nonselective p-blockers may not respond to adrenaline (use salbutamol i.v.) and indeed may develop severe hypertension (see below). 

Class I sodium channel blockade. These drugs restrict the rapid inflow of sodium during phase 0 and thus slow the maximum rate of depolarisation. Another term for this property is membrane stabilising activity it may contribute to stopping arrh5dhmias by limiting the responsiveness to excitation of cardiac cells. The class may be subclassified as follows ... 

Sodium cromoglicate is known as a mast cell stabiliser. Its mode of action is not entirely understood but it is thought to act by stabilising mast cell membranes and preventing their degranulation. It counteracts both the early and late response to allergen exposure. 

It has been proposed that the lipophilicity of cholesterol could be used to anchor an oligonucleotide to a cell membrane and might also facilitate cellular uptake and stabilise complexes formed with cellular nucleic acids. An efficient procedure has been developed for the derivati-... 

While linear peptides have been used extensively in the very early stages of lead finding (cf. Chapter 1.4) they found only limited application as therapeutic agents due to their limited protease stability (and thus low plasma stability and bioavailability) and low penetration through cell membranes. To circumvent some of these inherent bioavailability problems associated with linear peptides several approaches have been published to modify and stabilise linear peptides by construction of peptide mimetics. " Figure 2.3.1 schematically summarises these different approaches. 

Also used in surfactant production, betaine is isolated from sugar beet as a value added coproduct from sugar refining. Betaine is used in skincare formulations as a moisturiser and stabiliser for its water binding and cell membrane protecting properties. 

Figure 3.9 Schematic illustrations of lipid membranes in food materials A = double lipid cell membrane, B = nanoparticles bound with simple lipid membrane with lipid phase within the particles, C = liposome bound by double lipid membrane with the aqueous phase inside the particle, D = fat particles stabilised by lamella structure bound by a double lipid membrane and by simple lipid membrane with fat phase inside the particle.

Cholesterol is a steroid which stabilises cell membranes and is also a biosynthetic precursor of steroid hormones and bile salts. The accumulation of plaques on the walls of coronary and carotid arteries which have a high cholesterol content results in a condition... 

Now the polypeptide chain depicted above is in the extended or /3-form and in protein films (and possibly in the protein mono-layers of cell membranes) this form can be stabilised by hydrogen bonding between the carbonyl (> C = O) and imide (HN <) groups of the backbones of parallel orientated polypeptide chains to give a pleated-sheet structure (Fig. 3.3(A)). This is the structure of several fibrous proteins, e.g. j8-keratin. From the primary polypeptide unit of structure, a secondary structure has arisen. 

There is a family of proteins (the Bcl-2 family) that can regulate the potential across the inner mitochondrial membrane, and its permeability. Hence, they can influence apoptosis. Some of this family stabilise the inner membrane and maintain the potential, so that they suppress apoptosis. They are known as cell survival molecules (e.g. the proteins, Bcl-2, Bcl-X). Other members of the family destabilise the mitochondria and decrease the membrane potential which facilitates apoptosis. They are known as cell killer proteins (e.g. the proteins, Bax, Bak). The mechanisms by which they have their effects on mitochondria are not known. They are, of course, of considerable interest for the development and control of growth of tumour cells (See Chapter 21). 

It appears to reduce immune responsiveness. It inhibits the migration of mononuclear cells in area of inflammation. It may also stabilise lysosomal membrane, hence damage to cartilage is prevented. 

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