Cells of Dictyostelium discoideum respond to extracellular cyclic AMP with marked changes in intracellular cyclic GMP levels and light scattering. In this work, defined temporal increases in cyclic AMP were produced by the continuous addition of cyclic AMP to agitated suspensions of cells; concomitant hydrolysis of cyclic AMP by the cells subsequently established a constant, steady state concen...

In alternating 12-hr periods of light and darkness, start of the dark period entrains the hamster's 24-hr clock. Blinding or constant darkness frees the clock of entrainment by allowing it to run faster or slower than 24 hr. Constant light frees the clock from entrainment and permits it to run slower than 24 hr--that is, lengthening its period. Heavy water given in drinking water linearly lengt...

Bacterial luciferase catalyzes the emission of visible light from the reaction of reduced flavin, molecular oxygen, and an n-alkyl aldehyde. The mechanism of the reaction was probed by measuring the electronic effects of various substituents at the 8-position of the flavin ring system. Substituent effects were obtained for CH3-, Cl-, CH3O-, CH3S-, F-, and H- on the rate of formation and decay o...

Erbium co-doped TiO2 /Ag catalysts are synthesized by using a simple, one-step solvothermal method and characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Raman analysis, X-ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. The catalysts exhibit anatase crystal structures with increased visible light absorption co...

The resistances of the horizontal cell syncytium in the vertebrate retina are modulated in a time-dependent fashion during light stimulation. Therefore, the spatial properties of horizontal cells are expected to change with time after the illumination conditions are altered. This study was designed to investigate time- and intensity-dependent changes in the receptive-field properties of L1-type...

It is well known from light microscope studies of potato starch that the granules formed in a constant environment (of light and temperature) have a ring formation indistinguishable from that of granules formed under field conditions. Electron microscope studies have confirmed that normal potato starch granules have a fine shell structure not usually resolved by the light microscope, and also t...

The hypothalamic suprachiasmatic nucleus (SCN) is the locus of a master clock that regulates circadian rhythms in physiology and behavior. Gonadectomy in male mice lengthens the period of circadian rhythms and increases the day-to-day variability of activity onset time. Both of these responses are rescued by the nonaromatizable androgen dihydrotestosterone. Androgen receptors (AR) are localized...

Circadian rhythms in Syrian hamsters can be phase shifted by behavioral arousal during the usual rest phase of the circadian rest-activity cycle. Phase shifts can be greatly potentiated by exposing the animals to constant light for 1 or 2 cycles. This could reflect a change in a specific nonphotic input pathway to the suprachiasmatic nucleus (SCN) circadian pacemaker, or it could be caused by a...