No abstract

A number of the important physical and chemical properties of wool are closely associated with the presence of disulfi de cross-linkages between the polypeptide chains of the protein. This conclusion results from a study of the behavior of wool before and after alteration of the mode of linkage of the sulfur by a series of highly specific reactions.The cystine in wool can be readily reduced to cysteine with thioglycolic acid. Strongly alkaline solutions of the reagent have been shown by previous investigators t o dissolve the protein and destroy its fibro us structure. It is now shown that wool can be reduced with thioglycolic acid over a wide range of pH, and that when the reduction is carried out in neutral or acid solution, the fib rous structure of the wool is not destroyed when the disulfide groups are reduced to sulfhydryl groups. T he sulfhydryl groups of fibers reduced in this way react readily with alkyl halides to form thioether groups.Thus reaction of reduced wool with alkyl monohalides, such as methyl iodide, results in permanent rupture of disulfide linkages, and the fibers are greatly increased in extensibility and decreased in strength. Alkylation with aliphatic dihalides, such as methylene iodide or trilnethylene dibromide, introduces hydrocarbon chains between pairs of sulfur atoms of cystine molecules in the fibers. Such fibers are very similar to untreated fibers in physical properties.Wool in which the disulfide linkages have been broken by reduction, or by reduction and alkylation with alkyl monohalides, possesses much higher alkalisolubility t han untreated wool, while wool in which the disulfide cross-linkages have been replaced by new covalent cross-linkages through reduction followed by alkylation with dihalides possesses m uch lower alkali-solubility. Since th!' susceptibility of wool to degradation by alkalies is one of its greatest disadvantages, p rocesses that would make it stable toward alkalies should also enhance its durability. CONTENTS

Wool that has neither been injured mechanically nor modified chemically is completely resistant t o attack by the proteolytic enzymes-pepsin, trypsin, chymotrypsin , and papain. When the cuticle or scale layer of the fib ers is damaged by mecha nical means, the wool becomes susceptible to attack by p epsin and chymotryp sin. Under these conditions only a small portion of the wool is digested, yet the fi bers are considerably weakened and their fibrous structure is partly destroyed.Wool in which the disulfide cross-linkages have been broken, as by r eduction, or by reduction followed by methylation, is almost completely digested by p epsin and chymotrypsin, but is attacked only slightly by trypsin . When the reduced wool is reoxidized and its sulfhydryl groups are converted t o disulfide groups, the wool regains its original sta bility. When the sulfhydryl groups of the reduced wool are converted to bis-thioether groups by the action of an aliphatic dihalide, the stability of the wool toward enzymes is greatly enhanced.

793doses of 200 mg/kg/24 hr produced a fall in tissue C 0 2 and 0 2 tensions, effects due to the increased alveolar ventilation and relatively greater increase of tissue oxygen consumption than tissue perfusion.The Schultz-Dale reaction ( 1,2), which consists of the contraction of smooth muscle from an antigenically sensitized animal on reexposure in vitro to the antigen, has a manipulative simplicity that makes studies of mechanism particularly inviting. The mechanisms that have been proposed fall into 2 overlapping groups: ( 1 ) liberation of a stimulant such as histamine or acetylcholine as a result of the antigen-antibody(3,4,5) and(2) involvement of nerve, a possibility that has been considered both favorably(6) and unfavorably( 7,8,9), without very final evidence either way. The literature concerning the effects of pharmacodynamic agents and enzyme inhibitors on this reaction gives useful preliminary information baring upon questions of mechanism, but the data are scattered and were obtained under a wide variety of experimental conditionls. Therefore a preliminary study was made of the effects of a selected group of drugs and enzyme inhibitors upon the reaction, since it seemed * Supported by a grant from the Helen Hay Whitney Foundation of Sew York. t Mailing address: Southwest Foundation for Research and Education, 8 N O 'Culebra Road, San Antonio, Texas. $ Present address: Caharing Cross Hospital, London, England.likely that indications might be obtained as to which physiological or enzymological systems were involved in the reaction.Gray, Pedrick and Winne( l o ) , using guinea-pig ileum, found that 0.8% ethyl alcohol blocked the Schultz-Dale reaction, which suggested to us that nerve might be involved, and further experiments to test this possibility were performed. Results that support the hypothesis that nerve is involved are presented below.Materials and methods. Guinea pigs weighing about 500 g received intraperitonenlly 2.0 mg of crystalline egg albumin on 2 saccessive days. After 21 to 24 days, the animals were killed, and the ileum was removed and washed with Tyrode's solution.Portions of the ileum about 15 mm long were set up in a muscle bath stirred by aeration and arranged for washing by overflow. It was found important to keep the lumen open at both ends. The bath and all solutions were kept a t 37.5"C. Contractions were recorded with an ink-writing lever that exerted a tension of about 0.5 g, and gave an amplification of 1:4.5. The usual method of testing the effect of a substance of interest upon the action of antigen and other stimulants was to add the substance to the bath containing the ileum, and after 15 minutes, to add the stimby guest on July 24, 2015 ebm.sagepub.com Downloaded from