Iontophoretic release of cyclic AMP and dispersion of melanosomes within a single melanophore.

Selective dispersion of melanosomes was often observed after iontophoretic injection of cyclic adenosine monophosphate (AMP) from a glass microelectrode positioned in a target melanophore in frog skin (as viewed from above through a microscope), with other melanophores in the field serving as controls. Because the skin has orderly arrays of several types of closely spaced cells, it is probable that at times the microelectrode also impales cells other than melanophores. When cyclic AMP injection inside a cell resulted in dispersion of melanosomes from a perinuclear position into dendritic processes, the onset of dispersion was relatively rapid, in many cases less than 4 min (mean time of onset, 5.

Synthesis and structure-activity relationship studies of cytotoxic epoxide derivatives of 7-oxabicyclo[2.2.1]heptane.

Dimethyl exo-5,6-oxido-7-oxabicyclo[2.2.1]hept-2-ene-2,3-dicarboxylate (1) and the 1-methyl homologue 2 were shown to exhibit significant cytotoxicity in the 9KB tissue culture assay.

Cerebral hemodynamic crisis. Physiology, pathophysiology, and approach to therapy.

The physiology and pathophysiology of the cerebral circulation have been discussed in relation to treatment of the cerebral hemodynamic crisis. Data are presented to show how cerebral vascular resistance, the intracranial compartments, and brain metabolic demand may be manipulated to effect internal decompression and raise local perfusion pressures. It is quite apparent that irreversibility occurs rapidly in cases of complete ischemia and therapeutic success is often limited by this fact.

Plasma LH levels in the mare during the oestrous cycle.

Plasma levels of LH were determined by heterologous radioimmunoassay utilizing highly purified equine LH as standard. Samples were taken regularly from eleven mares for twenty-six oestrous cycles over a period of 10 weeks. The mean cycle length was 20-5 +/- 3-1 (S.