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(14,17) that at least part of total fl-glucan synthetase activity is subject to rapid turnover in vivo.The aims of the present study were, in part, to assess the potential of the pea extract components to act as synthetasemoderating regulators in vivo. The intent was also to examine their properties, bearing in mind that it might be possible to exploit a natural activator and minimize effects of any destructive agent during tissue homogenization in order to prepare a more effective ,8-glucan synthetase complex for studies in vitro.Brief reports have appeared indicating that crude extracts from pea epicotyl (12,13,20) and lupin hypocotyl (21) contain a heatlabile component which suppresses membrane-bound 81-glucan synthetase activity, and a heat-stable component which enhances it. Little is known of the specificities or modes of action of these factors beyond the observations that they have different effects on the products synthesized from UDP-glucose and GDP-glucose (13), implying specificity, and the labile component appears to act with a pH optimum close to 7 (20). It is possible that these components represent natural regulators of cellulose or callose synthesis in a manner analogous to the role postulated for specific proteases in controlling fungal chitin (3, 9) and f8-1,3-glucan (23) synthetase activities, as well as turnover of numerous other plant enzymes. It is also possible that the net deleterious effect of crude extracts on synthetase activity, which is particularly evident when assays are conducted with tissue slices (13), i.e. cell surface synthetase (15, 18), is responsible in part for the difficulties encountered in achieving rates of f,-glucan synthesis by isolated particulate fractions comparable to those observed in vivo (7,13,15,18 MATERIALS AND METHODSThe source of growing tissue used throughout this study is the apical 10 mm, defined here as a "segment" (about 25 mg fresh wt), cut from the third internode of pea epicotyls. Seedlings were grown as described earlier (15,18). Methods for assaying fB-glucan synthetase activity in this tissue are based on previous results (17,18,20) and basic information on optimal conditions (15

A new form of cytochrome P-450 was partially purified from hepatic microsomes of neonatally imprinted rats (adult male and adult male castrated at four weeks of age). This new form of cytochrome P-450 appears to have an apparent molecular weight of approximately 50,000 daltons as judged by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It appears that this form of cytochrome P-450 is either absent or present in low concentrations in cytochrome P-450 preparations isolated from neonatally nonimprinted rats (adult female and adult male castrated at birth). Reconstitution of testosterone hydroxylase and benzphetamine N-demethylase activities of this partially purified cytochrome P-450 revealed that the presence of testosterone 16 alpha-hydroxylase activity, an imprintable microsomal enzyme, was in parallel with the imprinting status of the animals; a significantly higher activity was detected in the neonatally imprinted than that of the nonimprinted animals. This was in contrast to the nonimprintable benzphetamine N-demethylase, testosterone 7 alpha- and 6 beta-hydroxylase activities which exhibited no correlation with the imprinting status of the animals. We have prepared antisera from rabbits using the partially purified cytochrome P-450 preparations from adult male rats as antigens. These antisera inhibited microsomal testosterone 16 alpha- and 7 alpha-hydroxylase activities in a concentration-dependent manner, without impairing 6 beta-hydroxylase activity. These data suggest that the partially purified cytochrome P-450 from adult male rats consists of both imprintable (16 alpha-) and nonimprintable (7 alpha-) testosterone hydroxylase activities.(ABSTRACT TRUNCATED AT 250 WORDS)