Presence Of Bright Light Research Articles

Towards the Womb of Neonatal Intensive Care.

Within the mother's womb, life finds its first stirrings. The womb shelters the fetus, the growing child within. We recognize the existential traces of a wombed existence when a newborn calms in response to being held; when a newborn stills in response to his or her mother's heartbeat; and, when a newborn startles in the presence of bright light. Yet, how does experiential human life begin within another human being? What are the conditions and paths of becoming for the fetus within the womb? And for the child born early, what "womb" welcomes the premature child in neonatal intensive care?

Neuroprotectin D1 is synthesized in the cone photoreceptor cell line 661W and elicits protection against light-induced stress.

Docosahexaenoic acid (DHA), an omega-3 fatty acid family member, is obtained by diet or synthesized from dietary essential omega-3 linolenic acid and delivered systemically to the choriocapillaris, from where it is taken up by the retinal pigment epithelium (RPE). DHA is then transported to the inner segments of photoreceptors, where it is incorporated in phospholipids during the biogenesis of outer segment disk and plasma membranes. As apical photoreceptor disks are gradually shed and phagocytized by the RPE, DHA is retrieved and recycled back to photoreceptor inner segments for reassembly into new disks. Under uncompensated oxidative stress, the docosanoid neuroprotectin D1 (NPD1), a potent mediator derived from DHA, is formed by the RPE and displays its bioactivity in an autocrine and paracrine fashion. The purpose of this study was to determine whether photoreceptors have the ability to synthesize NPD1, and whether or not this lipid mediator exerts bioactivity on these cells. For this purpose, 661W cells (mouse-derived photoreceptor cells) were used. First we asked whether these cells have the ability to form NPD1 by incubating cells with deuterium (d4)-labeled DHA exposed to dark and bright light treatments, followed by LC-MS/MS-based lipidomic analysis to identify and quantify d4-NPD1. The second question pertains to the potential bioactivity of these lipids. Therefore, cells were incubated with 9-cis-retinal in the presence of bright light that triggers cell damage and death. Following 9-cis-retinal loading, DHA, NPD1, or vehicle were added to the media and the 661W cells maintained either in darkness or under bright light. DHA and NPD1 were then quantified in cells and media. Regardless of lighting conditions, 661W cells acquired DHA from the media and synthesized 4-9 times as much d4-NPD1 under bright light treatment in the absence and presence of 9-cis-retinal compared to cells in darkness. Viability assays of 9-cis-retinal-treated cells demonstrated that 34 % of the cells survived without DHA or NPD1. However, after bright light exposure, DHA protected 23 % above control levels and NPD1 increased protection by 32 %. In conclusion, the photoreceptor cell line 661W has the capability to synthesize NPD1 from DHA when under stress, and, in turn, can be protected from stress-induced apoptosis by DHA or NPD1, indicating that photoreceptors effectively contribute to endogenous protective signaling mediated by NPD1 under stressful conditions.

Evidence for anxiolytic effects of acute caffeine on anxiety-related behavior in male and female rats tested with and without bright light

Male and female PVG/c rats were observed in an open field (OF) and an elevated plus maze (EPM) either with or without a bright light stressor (600–692lx) following an intraperitoneal injection of saline, 25 or 50mg/kg of caffeine. One week later, the same rats were observed under the same drug and lighting conditions but in the opposite apparatus to that experienced earlier. Either the higher or both doses of caffeine decreased anxiety as indicated by increased OF rearing and decreased grooming, immobility and corner occupancy (in the presence of bright light). A similar interpretation applied to caffeine-related increased entries into and observations in the EPM open arms for males only, and increased entries into the open arms for females alone in the presence of bright light. Bright light increased anxiety as shown by longer latencies of emergence into the OF and decreased ambulation and, for males only, decreased center occupancy and increased corner occupancy. Fewer entries into the open arms in the presence of bright light for females only also suggested heightened anxiety. Apart from one OF and one EPM measure, bright light did not appear to markedly influence the effects of caffeine which were concluded to be primarily anxiolytic, with males being more affected than females. Although the central mechanisms responsible for caffeine's anxiolytic action remain to be established, it is possible that antagonism of A2A adenosine receptors might somehow be involved.

Impaired Masking Responses to Light in Melanopsin‐Knockout Mice

There are two ways in which an animal can confine its behavior to a nocturnal or diurnal niche. One is to synchronize an endogenous clock that in turn controls the sleep–wake cycle. The other is to respond directly to illumination with changes in activity. In mice, high illumination levels suppress locomotion (negative masking) and low illumination levels enhance locomotion (positive masking). To investigate the role of the newly discovered opsin‐like protein melanopsin in masking, we used 1h and 3h pulses of light given in the night, and also a 3.5:3.5h light–dark (LD) cycle. Mice lacking the melanopsin gene had normal enhancement of locomotion in the presence of dim lights but an impaired suppression of locomotion in the presence of bright light. This impairment was evident only with lights in the order of 10 lux or brighter. This suggests that melanopsin in retinal ganglion cells is involved in masking, as it is in pupil contraction and phase shifts. Melanopsin is especially important in maintaining masking responses over long periods.

Double Dissociation between the Involvement of the Bed Nucleus of the Stria Terminalis and the Central Nucleus of the Amygdala in Startle Increases Produced by Conditioned versus Unconditioned Fear

The amplitude of the acoustic startle response is reliably enhanced when elicited in the presence of bright light (light-enhanced startle) or in the presence of cues previously paired with shock (fear-potentiated startle). Light-enhanced startle appears to reflect an unconditioned response to an anxiogenic stimulus, whereas fear-potentiated startle reflects a conditioned response to a fear-eliciting stimulus. We examine the involvement of the basolateral nucleus of the amygdala, the central nucleus of the amygdala, and the bed nucleus of the stria terminalis in both phenomena. Immediately before light-enhanced or fear-potentiated startle testing, rats received intracranial infusions of the AMPA receptor antagonist 2, 3-dihydroxy-6-nitro-7-sulphamoylbenzo(F)-quinoxaline (3 microg) or PBS. Infusions into the central nucleus of the amygdala blocked fear-potentiated but not light-enhanced startle, and infusions into the bed nucleus of the stria terminalis blocked light-enhanced but not fear-potentiated startle. Infusions into the basolateral amygdala disrupted both phenomena. These findings indicate that the neuroanatomical substrates of fear-potentiated and light-enhanced startle, and perhaps more generally of conditioned and unconditioned fear, may be anatomically dissociated.

Circulating Melatonin in Man: Episodic Secretion throughout the Light-Dark Cycle

A sensitive and specific RIA for melatonin has been validated for human plasma. Five young adult men had plasma samples obtained every 20 min during two 24-h periods. One was a normal active period and the other a basal period with complete bed rest. Melatonin was found to be secreted episodically throughout the 24 h in each condition, with secretory episodes clearly present during the waking day in the presence of bright light.

See-Saw Nystagmus

Since the first description of see-saw nystagmus in 1914 by Maddox 1 only seven cases have been reported in the literature. The phenomenon is rare but unmistakable; the eyes move vertically, symmetrically, and rhythmically in dissociated fashion, one looking up while the other looks down (hence the appellation "see-saw"). In addition, as the globe rises it intorts, and as it falls it extorts. When the gaze is directed upward, the movements tend to become faster but smaller. The sign is apparently not dependent upon reduction in visual acuity; however, nearly all patients have a bitemporal hemianopsia. Fixation on a near object or the presence of bright light (as from a flood lamp) diminishes or abolishes the sign. 2 Smith points out that the nystagmus is most easily observed by having the patient look down and then noting the lid movements. 3 The responsible lesion appears in most cases to be