Abstract. Cell cycle progression for postembryonic cells requires the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-R), the enzyme which catalyzes the production of the isoprenoid precursor, mevalonate. In this study, we examine the requirements of HMG-R activity for cell cycle progression during the meiotic and early mitotic divisions using oocytes and dividing embryos from the surf clam, Spisula solidissima. Using two different inhibitors of HMG-R, we find that the activity of this enzyme appears to be required at three distinct points of the cell cycle during meiosis. Depending on the stage at which these inhibitors are added to synchronous clam cultures, a reversible cell cycle block is triggered at the time of activation or at metaphase of either meiosis I or II, whereas there is no block to the mitotic cell cycle. Inhibition of HMG-R activity in activated oocytes does not affect the transient activation of p42 MAPK but results in a block at metaphase of meiosis I that is accompanied by the stabilization of cyclins A and B and p34 ~c2 kinase activity. Our results suggest that metabolites from the mevalonate biosynthetic pathway can act to influence the process of activation, as well as the events later in the cell cycle that lead to cyclin proteolysis and the exit from M phase during clam meiosis.p ROGRESS through the cell cycle of postembryonic cells requires the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-R) t (for reviews see Goldstein and Brown, 1990;Maltese, 1990). HMG-R is a microsomal enzyme which catalyzes the reduction of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) to mevalonate, an essential precursor required for the biosynthesis of several vital end products, which include: cholesterol and other sterols, important for membrane replication and structure; dolichol, required for N-linked protein glycosylation; isopentenyladenine, which is present in some types of tRNAs; and the isoprenoid side-chains of ubiquinone and heme-a, which are involved in electron transport
Ocimum kilimandscharicum Guerke (Lamiaceae), alien to the Indian flora, was discovered in the natural habitat from two locations of different agro-ecological zones of Odisha. After critical review of published literature on distribution, it was earlier known only from Uttarakhand. However, its natural occurrence in Odisha was found to be a new record for peninsular India. A detailed diagnostic description, photographs, ecology and potentiality of the species was provided for easy identification and further economic utilization.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.