Effect of isoprenaline on cells in different phases of the mitotic cycle

The effects of isoprenaline on parotid acinar cells in different phases of the mitotic cycle have been investigated. Cells in mitosis at the time of drug administration are not depleted of secretory granules whilst those in other phases are. The drug causes temporary blocks both in metaphase and in the G2 phase. The blocks are prolonged by repeated injections of the drug. Cells continue to undergo DNA synthesis during the period of secretion following the drug. The mitotic delay appears to be specific for the parotid and submaxillary glands.     

A new species of <Emphasis Type="Italic">Mentzelia</Emphasis> section <Emphasis Type="Italic">Bartonia</Emphasis> (Loasaceae) from the Grand Canyon,Arizona

Mentzelia hualapaiensis, a new species of Mentzelia sect. Bartonia, is described from the Grand Canyon region of Arizona. The new species is closely related to M. puberula, which is found west of M. hualapaiensis along the Colorado River, and to M. oreophila, M. polita, and M. tiehmii. It shares with these species a suffrutescent shoot system characterized by a subterranean, branching caudex, multiple annual branches, and similar leaves that have shallowly lobed or toothed to entire laminas. The flowers of M. hualapaiensis differ from those of its closest relatives in having cream-white, linear to narrowly spatulate petals and staminodes, characteristics that are convergent with those of the flowers of the Chihuahuan Desert species M. humilis.