Bud formation in leaves, leaf fragments and midrib pieces of Heloniopsis orientalis (Liliaceae)

Isolated leaves, leaf fragments and pieces of the midrib portion devoid of lamina, of Heloniopsis orientalis were grown on an inorganic nutrient medium without organic nutrients and growth regulators in order to investigate their regenerative ability. Bud formation in intact, attached leaves occurs only at the tip, in isolated leaves at the tip and the base, whereas leaf fragments cut transversely at a distance from the tip and isolated midrib pieces form numerous shoot buds in a random distribution. Lamina fragments lacking midrib frequently fail to regenerate even after a long time of culture. It is suggested that endogeneous growth regulators in the leaf, especially the vascular tissues, play an important role in bud initiation. Very young leaves of Heloniopsis are capable forming buds and roots when isolated from the mother plants.

Effect of adrenergic-blocking or -stimulating agents on plasma growth hormone, immunoreactive insulin, and blood free fatty acid levels in man

In order to determine whether an adrenergic mechanism is involved in the secretion of growth hormone and insulin, the effect of adrenergic-blocking or -stimulating agents on plasma human growth hormone (HGH), immunoreactive insulin, blood free fatty acids (FFA), and glucose levels was studied in normal human subjects. The intravenous infusion of propranolol, a beta adrenergic-blocking agent, caused a rise in plasma HGH, a transient decrease in blood FFA, and no significant change in plasma insulin. This increase in plasma HGH was inhibited either by the combined administration of isoproterenol, a beta adrenergic-stimulating agent, along with propranolol or by oral glucose loading immediately before the start of propranolol infusion. The concomitant administration of epinephrine and propranolol brought about a rise in plasma HGH comparable with that produced by propranolol alone, without any significant change in blood FFA. Alpha adrenergic blockade by the intravenous infusion of phenotolamine significantly suppressed plasma HGH responses to insulin-induced hypoglycemia and to arginine infusion, and enhanced plasma insulin response to arginine infusion. It also stimulated lipid mobilization significantly. The intravenous infusion of alpha adrenergic-stimulating agents, phenylephrine and methoxamine, caused an increase in plasma HGH, a slight decrease in blood FFA, and no significant change in plasma insulin. This increase in plasma HGH was significantly inhibited by the simultaneous administration of phentolamine along with methoxamine. On the contrary, a beta adrenergic stimulant, isoproterenol, raised plasma insulin and blood FFA, and abolished the plasma HGH response to propranolol. Another beta stimulator, isoxsuprine, raised blood FFA but not plasma insulin. It is concluded that either beta adrenergic blockade or alpha stimulation enhances HGH secretion and inhibits insulin secretion and fat mobilization, whereas either alpha blockade or beta stimulation stimulates insulin secretion and fat mobilization and inhibits HGH secretion.