Differences between matched heterosexual and non-heterosexual college students on defense mechanisms and psychopathological symptoms.

Differences between heterosexual and non-heterosexual college students on measures of defense mechanisms and psychopathological symptoms were examined. Fifty-six (28 heterosexual, 28 non-heterosexual) subjects were drawn from a larger study of college student adjustment. Non-heterosexual subjects were matched to a heterosexual peer on several demographic variables as well as on attachment security/insecurity.

Fathers and preschool behavior problems.

Fathers have seldom been the focus of research investigating the causes and correlates of early behavior problems. Two studies examined fathers of preschool boys with and without clinic-referred behavior problems. Six domains of risk were examined: life stress, social support, psychological symptoms, parenting attitudes, positive involvement, and harsh discipline.

Dim background light and Cerenkov radiation from 32P block reversal of rhodopsin phosphorylation in intact frog retinal rods.

The phosphorylation of photoexcited rhodopsin (Rho*) is thought to inactivate this receptor by inhibiting its interaction with the GTP-binding protein transducin (Gt). Here we report that the time course of phosphorylation-dephosphorylation after bright illumination of intact rod outer and inner segments (ROS-RIS) incubated in 33Pi can be altered if the ROS-RIS are first exposed to levels of dim illumination that cause light adaptation in these ROS-RIS. The dephosphorylation of greater than 10(7) phosphorylated rhodopsin molecules/ROS following a bright flash can be blocked by prior dim continuous illumination (generating 10(3) Rho*/ROS/s) that cumulatively bleaches approximately 10(5) rhodopsin molecules/ROS.

Light activation of one rhodopsin molecule causes the phosphorylation of hundreds of others. A reaction observed in electropermeabilized frog rod outer segments exposed to dim illumination.

A rhodopsin phosphorylation reaction that occurs with high-gain is observed if measurements are made in electropermeabilized frog rod outer segments (ROS) stimulated by a dim flash of light in the operating range of the photoreceptor. Flashes of light exciting 1000 or fewer of the 3 x 10(9) rhodopsins present/ROS results in the incorporation of 1400 phosphates from ATP into the rhodopsin pool for each excited rhodopsin (Rho*). This amplification decreases with increasing light intensity, falling most sharply after each disk has absorbed one photon.

Transducin activation in electropermeabilized frog rod outer segments is highly amplified, and a portion equivalent to phosphodiesterase remains membrane-bound.

An electropermeabilized preparation of frog retinal rod outer segments (ROS) has been developed to examine the light sensitivity and amplification of visual transduction reactions in a minimally disturbed environment. Electropermeabilized ROS are indistinguishable from whole and osmotically intact ROS in the light microscope and retain 3-fold more protein than mechanically disrupted ROS. They differ from mechanically fragmented ROS in several respects.

Light-induced changes in GTP and ATP in frog rod photoreceptors. Comparison with recovery of dark current and light sensitivity during dark adaptation.

Light decreases GTP and ATP levels in purified suspensions of physiologically active frog rod outer segments still attached to their inner segment ellipsoids (OS-IS). (a) The GTP decrease is slower in OS-IS (t1/2 = 40 s) than in isolated outer segments (t1/2 = 7 s), which suggests there is more effective buffering in OS-IS. (b) The GTP decrease becomes detectable only at intensities greater than those required to saturate the photoresponse.

Frog rod outer segments with attached inner segment ellipsoids as an in vitro model for photoreceptors on the retina.

Purified suspensions of frog rod outer segments still attached to the mitochondria-rich inner segment portion of the receptor cell (OS-IS) can be obtained in quantities (0.1 mg/retina) sufficient for chemical analysis. In oxygenated glucose-bicarbonate Ringer's medium with added Percoll, they display normal dark currents, light sensitivity, and photocurrent kinetics for several hours.

Light-induced decreases in cGMP concentration precede changes in membrane permeability in frog rod photoreceptors.

This study examines whether changes in cGMP concentration initiated by illumination of frog rod photoreceptors occur rapidly enough to implicate cGMP as an intermediate between rhodopsin activation in the disc membrane and permeability changes in the plasma membrane. Previous studies using whole retinas or isolated outer segments have provided conflicting evidence on the role of cGMP in the initial events of phototransduction. The rod photoreceptor preparation employed in this work consists of purified suspensions of outer segments still attached to the mitochondria-rich ellipsoid portion of the inner segment.

Influence of light and calcium on guanosine 5'-triphosphate in isolated frog rod outer segments.

Frog rod outer segments contain approximately 0.25 mol of GTP and 0.25 mol of ATP per mol of rhodopsin 3 min after their isolation from the retina.