Measurement of the Rate of Growth of Rodent Hair using Cystine labelled withSulphur-35

Journal/Book: Reprinted from Nature Vol. 206 No. 4979 pp. 108-109 April 3 1965. 1965;

Abstract: Beecham Toiletry Division Brentford Middlesex THE use of radioactive markers for the measurement of rates of wool growth has been described by Downes and Lyne1 2. Cystine labelled with sulphur-35 was injected at intervals of not less than three days and autoradiographs of the wool were prepared using a. stripping film technique. Distances between the regions of incorporation of amino-acid into the wool were measured in order to obtain estimates of rates of wool growth. We have adapted this method for use with the mouse. Since in this animal the growth-cycle lasts approximately three weeks variations in rate from day to day can be of significance and in order to minimize experimental error it is important to locate the leading edge of the zone of incorporation as accurately as possible. Using stripping film or liquid emulsions however this is difficult the presence of hair obscuring the trace. Both techniques have the added disadvantages of being laborious and technically difficult while loss of register may occur during processing owing to swelling and shifting of the stripping emulsion. For routine work involving a large number of hair measurements we find that contact autoradiographs are quickly and readily prepared the resulting autoradiograph being uncomplicated by the presence of the hair. Mice are plucked to induce new hair growth. and intra-peritoneal injections of 1 µc. of cystine labelled with sulphur-35 are given at intervals of at least 24 h commencing the tenth day after plucking. When growth is complete the hair is removed from the animal washed successively in detergent water ethanol acetone and ether and dried. The hairs are then mounted in 0 · 5 per cent gelatine -0 · 05 per cent chrome alum an 4 · in.2 photographic cover glasses. Under Ilford ´904 F' brown safelights the hairs an the cover glass are placed in contact with Ilford ´Contrasty' special lantern plates and the two plates are held together with paper clips. They are placed in a light-proof box exposed for 14 days in the refrigerator separated developed for 12 min in concentrated Kodak 'D19b' developer fixed washed and dried. ... ___MH

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