The injury of membranes by biologically-active agents

Cholesterol, in various proportions, is a natural constituent of most biological membranes, but if the proportion is allowed to increase, membrane function is usually diminished. Thus, the membrane that surrounds the sarcoplasmic reticulum vesicles in muscle progressively loses the calciumtransporting function of its ATPase when cholesterol starts replacing the phospholipids. Similarly, ox-heart mitochondria, when exposed to chole- 

Chlorohexidine (/0.24), a much-used local antiseptic, was found to release the cell contents of coli when these baaeria were placed in a 

I 10 OCX) aqueous solution for 5 minutes at 20°, and most of them died (Rye and Wiseman, 1966). Both tetrachlorosalicylanilide and hexachloro-phane 11.37) released 260 nm-absorbing material (a sign of damage to the cytoplasmic membrane) from bacteria which then died. Both substances are liposoluble skin disinfectants (Woodroffe and Wilkinson, 1966 Joswick, 1961). 

Streptomycin ( C) is initially accumulated by the bacterial cell wall. This local concentration makes the cytoplasmic membrane swell and become porous (Anand, Davis, and Armitage, i960). Streptomycin then enters the cell more easily (cf. the behaviour of dodine, above) and the final site of action is on the ribosomes (see Section 4.1, p. 126). 

A polymer, useful to experimental pharmacologists and known as 48/80 , selectively bursts the membrane of mast cells in living mammals, and so causes the release of histamine in large amounts (Norton, 1934). This substance is a trimer of iV-methylAowoanisylamine and formaldehyde. 

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The injury of membranes by biologically active agents. 603 The preservation of membranes by biologically active agents. 608... 

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