The content of eggs and egg white, respectively, in various foods (pastes, mayonnaises, dressings, confections containing egg white, various ready-tocook mixtures, ice creams, omelettes, custards, pie Jillings etc) was assessed by radial immunodiffusion and preferably by rocket immunoelectrophoresis. The problem of partial ovalbumin denaturation during processing of dried eggs or egg white was overcome by using these products for the calibration of the method used. The method may also be applied to assess the degree of egg white contamination in mayonnaises in order to control the yolk and egg tyhite separation during processing.
Milk clotting activity of Mucor miehei proteinase (commercial name Fromase) was determined in combined rennets as the difference between the total activity of combined rennet and the residual activity after inhibition of Fromase by the purified immunoglobulin fraction of a Fromase antiserum. The proposed method is simple, rapid, and makes possible the use of any arbitrary method for assaying milk clotting activity. The application of the immunoglobulin fraction, instead of the whole antiserum, is necessary owing to the presence of nonspecific proteinase inhibitors in blood serum.Immunochemical methods could be of great importance in the analysis of milk clotting enzymes used in cheesemaking, owing to the expanding use of combined rennets containing not only chymosin and bovine pepsin, but also various substitutes such as porcine and chicken pepsin and microbial proteinases produced by Mucor miehei, M. pusillus and Endothia parasitica. A test for determining the composition of such combined rennets is essential.Procedures for the identification and quantification of milk clotting enzymes in combined rennets have been reviewed by Green (1977). Two main approaches to the analysis of combined rennets include an indirect analytical method consisting of selective inactivation of an enzyme by the combination of pH, temperature and time conditions (Mulvihill & Fox, 1977) and an immunochemical method based on rocket immunoelectrophoresis (Rothe et al. 1976;Harboe, 1981).Both these methods have drawbacks: with the former it is difficult to sustain proper conditions for selective enzyme denaturation, with the latter the enzyme concentration assayed does not necessarily correlate with the actual milk clotting activity.In the method described below we have tried to eliminate the above drawbacks by direct measurement of milk clotting activity and by specific inhibition of the selected enzyme on the basis of an immunochemical reaction. The technique was worked out to detect the contribution of Fromase (proteinase from M. miehei) milk clotting activity in combined rennet preparations containing chymosin and bovine, porcine and chicken pepsin.
The use of semisolid medium for the culture and cloning of haematopoietic cells has helped our understanding of their proliferation and differentiation. It has been shown that mixed colonies of granulocytes and macrophages developed, in the presence of colony-stimulating factor (CSF), from their common precursor, granulocyte-macrophage colony-forming cells (GM-CFC). Attempts at recloning these colonies in semisolid medium suggested that granulocytes and macrophages were differentiated cells incapable of further proliferation. However, our studies on cultures of larger numbers of cells demonstrate that while this may be the case for granulocytes, macrophages seem to be capable of long-term proliferation.
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