When the retinas of some fishes and amphibians are dark-adapted the hyperpolarising response of horizontal cells (HCs) to a light stimulus is suppressed (= dark suppression) but is restored to that of light adaptation when a light stimulus is rapidly repeated (= light potentiation (LP). This phenomenon, which had not ...

BACKGROUND: Psychophysical thresholds, including dark-adaptation functions and increment threshold sensitivities, are useful for the early detection and diagnosis of visual pathologies. However, few instruments have been designed or adapted for their routine clinical measurement. METHODS: Here we describe an instrument prototype designed to meet this need, which we refer to ...

The effect of three forms pyoverdin on mouse liver was studied. Significant increases of alanine amino transferase (ALT) and aspartate amino transferase (AST) were obtained in mice after ingestion of water with forms A and C. The effect on liver was more evident with A than with C. Pyoverdin was ...

We have reported that dark vision is impaired in symptomatic carotid artery disease and that the impairment correlates with internal carotid artery stenosis. To find out whether this impairment is reversible after carotid endarterectomy, dark adaptation was examined pre- and postoperatively. Twenty-one consecutive patients were examined by dark adaptometry. Two ...

The influence of restraint stress (0, 15, 30, or 60 min), uncontrollable footshock (0, 15, 30, or 60 shocks), or intraventricular CCK-8S administration (0, 5, 25, or 50 ng delivered in a 1 microliter volume) were evaluated on transition frequency and cumulative time in light among CD-1 mice in the ...

Nicergoline is an ergot alkaloid derivative acting as a neuroprotective agent. In the present investigation, b-wave time-course recovery profiles under both light- and dark-adapted conditions, were studied in order to evaluate the possible effectiveness of nicergoline in the protection of the rabbit retina. Retinal ischaemia was induced by bilateral occlusion ...

Dark current-voltage (dark I-V) measurements are commonly used to analyze the electrical characteristics of solar cells, providing an effective way to determine fundamental performance parameters without the need for a solar simulator. The dark I-V measurement procedure does not provide information regarding short-circuit current, but is more sensitive than light ...

We examined rhabdom structure and the distribution of filamentous actin in the photoreceptor outer segments of the retina of Octopus bimaculoides. Animals were dark- or light-adapted, fixed, embedded and sectioned for light and electron microscopy. Statistical analyses were used to compare relative cross-sectional areas of rhabdom microvilli and core cytoplasm ...

Cerebral serotonin level influences luteinizing hormone release and, consequently, ovulation. The present study evaluated the effects of precooked maize meal (polenta), a diet almost devoid of tryptophan the serotonin precursor on the alterations of the estrus cycle as measured by vaginal smears analysis in Wistar rats. Several conditions of environmental ...

Receptive field centre profiles of depolarizing (ON-) and hyperpolarizing (OFF-) bipolar cells in dark adapted carp retina were determined by using a narrow slit of light. The spatial decline of the photoresponse was found to consist of double exponential function with small and large length constants, about 100 microns and ...

Sewall Wright's powerful metaphor of rugged adaptive landscapes has formed the basis for discussing evolution and speciation for more than 60 years. However, this metaphor, with its emphasis on adaptive peaks and valleys, is to a large degree a reflection of our three-dimensional experience. Both genotypes and phenotypes of biological ...

Benign paroxysmal positional vertigo (BPPV) is assumed to result from utricular damage, but it is controversial if patients have manifest utricular dysfunction. Therefore, we investigated linear vestibulo-ocular reflexes (LVORs) during lateral whole-body translation in 14 patients with unilateral BPPV. Patients were subjected to linear acceleration steps of 0.24 g along ...

BACKGROUND: Dark adaptation rate, scotopic retinal sensitivity and contrast sensitivity under mesopic conditions, but not visual acuity, have been shown to be directly related to the ability to identify military targets at night. These parameters can be used to select personnel for specific military tasks demanding excellent night vision, as ...

Cyanothece sp. strain ATCC 51142 is a unicellular, diazotrophic cyanobacterium which demonstrated extensive metabolic periodicities of photosynthesis, respiration, and nitrogen fixation when grown under N2-fixing conditions. N2 fixation and respiration peaked at 24-h intervals early in the dark or subjective-dark period, whereas photosynthesis was approximately 12 h out of phase ...

PURPOSE: To characterize the glucose metabolism in the rabbit retina. METHODS: An artery and a vortex vein were cannulated. Arteriovenous differences in oxygen, lactate and glucose concentrations, and blood flow were determined during either 1) darkness and light, or 2) light and 4 Hz flickering light. RESULTS: In darkness, oxygen ...

In the pig eye, oxygen and glucose consumption in the outer retina are reduced in light compared to the consumption in the dark and most of the glucose consumed is metabolized to lactate both in light and in the dark. In the present study, in order to characterize the metabolism ...

PURPOSE: To determine if the pattern of release of neurotensin from the enkephalin-, neurotensin- and somatostatin-like immunoreactive amacrine cells in response to light and dark is the same as that of the enkephalins and somatostatin. METHODS/RESULTS: Both the enkephalins and somatostatin are released at high rates in the dark and ...

Glucose metabolism in the outer retina of pigs was studied in the light and in the dark in pentobarbital anaesthetized pigs. Blood was collected from a vortex vein and an artery, and the arteriovenous concentration differences of lactate, glucose and oxygen were determined in light-adapted eyes. Local blood flows were ...

The interaction between tectonism and erosion produces rugged landscapes in actively deforming regions. In the northwestern Himalaya, the form of the landscape was found to be largely independent of exhumation rates, but regional trends in mean and modal elevations, hypsometry (frequency distribution of altitude), and slope distributions were correlated with ...

We have investigated, through factor analysis, anxiety- and activity-related variables in rats placed in the light/dark box. Thus, vehicle-, diazepam (DZ)-, and chlordiazepoxide (CDP)-treated rats were submitted 30 min later to 5-min light/dark or dark/light tests (initial placements in light or dark, respectively). Following this test, the animals were tested ...

The effect of light stimuli and prolonged darkness on the release of endogenous dopamine was measured in the white perch and hybrid bass retinas. Isolated retinas were superfused and released dopamine was measured using extraction and high-pressure liquid chromatography separation techniques. Potassium-induced release did not depend on the background illumination ...

Ethylene formation was studied in 5- to 6-d-old Chenopodium rubrum seedlings under the following light regimes: continuous light (CL), continuous darkness (CD), and alternating light/darkness (12 h of each). No significant regular oscillations in ethylene formation were found in either the CL or CD groups. In the light/dark regime, pronounced ...

Early experience can affect nervous system development in both vertebrate and invertebrate animals. We have now demonstrated that visual stimulation modifies the size of the optic lobes in the laboratory fruitfly Drosophila melanogaster. Monocular deprivation (painting over one eye) decreases the aggregate volume of the lamina, medulla, and lobula plate ...

Background of the invention: Flat panel liquid crystal displays are important components in display technology. Because of their relatively low cost and high definition, twisted nematic (TN) and supertwisted nematic (STN) cells, ferroelectric liquid crystals and liquid crystal-polymer dispersions have been used in a variety of display applications. Each of ...

The short-term influence of visual experience was studied in the first-order tetrad synapses of the first optic neuropil, or lamina, underlying the compound eye in the housefly (Musca domestica). We report the effects of single light reversals, in which flies reared in constant darkness were exposed to light or those ...

The effect of light deprivation on the levels of dopamine and noradrenaline was studied in the developing rat retina. These transmitters were estimated in three groups of rats: (i) cycling light reared; (ii) dark reared since birth; and (iii) dark reared since birth, but exposed to cycling light for 1 ...

PURPOSE: To determine the roles of oxidation and glycolysis with aerobic and anaerobic lactate formation in the glucose metabolism of the cat outer retina in light and darkness. METHODS: Blood was collected from a choroidal vein and from an artery, and veno-arterial differences in lactate concentration (Lac(v-a) were determined at ...

For assessing monoamine oxidase (MAO-A and -B) activities in the hypothalamus, ovaries and uterus, mature female rats were exposed to either continuous light or dark over 6 weeks. Confirming previous studies, continuous light induced constant estrus in all animals. The majority of animals kept under continuous dark during the six ...

We studied the change of spatial and temporal response properties for cat horizontal (H-) cells during prolonged dark adaptation. H-cell responses were recorded intracellularly in the optically intact, in vivo eye. Spatial and temporal properties were first measured for light-adapted H-cells, followed by a period of dark adaptation, after which ...

We report the observation of incoherently coupled dark-bright spatial soliton pairs in a biased bulk photorefractive crystal. When such a pair is decoupled, the dark component evolves into a triplet structure, whereas the bright one decays into a self-defocusing beam.

Characteristic features of the formation of cylindrical laser-induced thermal steady-state lenses in the dark stripes associated with spatial dark-soliton propagation are analyzed and verified experimentally in an ethanol-dye solution. Positive focusing power perpendicular to the dark stripe is ensured by defocusing along the axis of this stripe and depends strongly ...

Gametogenesis of the green alga Chlamydomonas reinhardtii may be viewed as a two-step process that is controlled by the environmental cues of nitrogen deprivation and blue light. Initiation of gametogenesis is induced by nitrogen deprivation, resulting in mating-incompetent pregametes, when cells are kept in the dark. For the completion of ...

To evaluate the effects of light and darkness on pyroglutamyl peptidase I activity (pGluPI) and its left-right distribution, pGluPI was measured bilaterally in the retina and hypothalamus under selected light-dark schedules. Rats under a 12 h light-dark cycle were divided into four experimental groups. After the end of the 12 ...

A symbiotic pair of dark (second-harmonic) and bright (fundamental frequency) solitons sustain each other and travel locked in second-harmonic generation dominated by group-velocity difference or spatial walk-off. The conditions of existence of the soliton pair are determined, and its stability in the presence of dispersion is discussed.

To measure adaptive changes in the ability to sense tilt after spaceflight, we measured the ability of four astronauts to control roll tilt in the presence of a pseudorandom motion disturbance before and after a 14-day Spacelab mission. The subjects were tested 1) in the dark, 2) with an independent ...

1. It has been reported previously that clonidine can potentiate tyramine-evoked mydriasis on the pain-free side of cluster headache patients. We examined whether a single oral dose of clonidine (200 micrograms) can also potentiate tyramine-evoked mydriasis in healthy subjects, using mydriasis to methoxamine, a directly acting sympathomimetic amine, as a ...

Since high PCO in the dark works like hypoxia in the carotid body chemoreceptors and since hypoxia shows a stimulus interaction with CO2, it is hypothesized that high PCO will show a similar interaction with PCO2 in the chemosensory excitation in the dark. We tested the hypothesis using cat carotid ...

The germinal centres of human palatine tonsils typically have four clearly recognizable compartments. The dark zone is identified by the presence of centroblasts and a thin follicular dendritic cell (FDC) network. The dense FDC network is divided into a CD23(low/-) portion adjacent to the dark zone (the basal light zone) ...

To define the characteristics of the diurnal variation of intraocular pressure (IOP) in eyes of awake rats, ten male brown Norway rats were entrained to a 12-hour light:12-hour dark (12L:12D) lighting schedule and were conditioned to IOP measurement with the TonoPen XL tonometer while awake, using only 0.5% proparacaine HCl ...

Teleost retinas adapted to light show numerous spinules invaginated in the cone pedicles and small nematosomes in the distal horizontal cells. Darkness induces the dissolution of spinules and the presence of large and numerous nematosomes. The aim of this work is to study the influence of optic nerve integrity on ...

Background of the invention: Flat panel liquid crystal displays are important components in display technology. Because of their relatively low cost and high definition, twisted nematic (TN) and supertwisted nematic (STN) cells, ferroelectric liquid crystals and liquid crystal-polymer dispersions have been used in a variety of display applications. Each of ...

Biochemical, physiological and histological data have established that 55-65% of retinal mitochondria are located in the photoreceptor inner segments and suggested that photoreceptors have at least a two-fold greater oxygen consumption (QO2) than the remaining inner retina. QO2 in isolated whole rat retina (QWR), outer retina (QOR) and inner retina ...

PURPOSE: To evaluate whether the characteristics of the oculomotor system are related to the development of late-onset myopia. METHODS: Forty-four college students were followed for 2 to 3 years. When recruited, 33 of the 44 subjects had emmetropia whereas the remainder (N = 11) had late-onset myopia (LOM). For each ...

The purpose of this study was to characterize the form of the pupil in normal human subjects. Using a modified slitlamp, photographs of pupils were taken in steady illumination and 10-20 sec after darkness. Transparencies were projected and digitized, and the pupil margin was represented as a circular Fourier series. ...

Conventional perimeters use bright stimuli. In this study, dark stimuli were also used. Dark stimuli are employed for testing due to their lack of effects of local scatter and are utilized with the purpose of preferentially stimulating the off-system, but their presentation with optical methods is difficult. This problem is ...

Gross observation of testicular parenchyma of 1.5- to 2-yr-old horses reveals both light and dark regions. If this gross, differential shading reflects quantitative differences in the development of spermatogenesis and interstitial cell populations, the horse may prove to be a useful model for study of the paracrine relationships associated with ...

Horizontal cells of the carp retina alter their synaptic connections with cones during dark and light adaptation. At light onset, dendrites of horizontal cells, which are positioned laterally at the ribbon synapse, form "spinules," little processes with membrane densities. Spinules are retracted again during dark adaptation. Spinule retraction is also ...

[3H]Dopamine uptake under acute immobilization stress in adrenal chromaffin cells of mice was examined in vivo during dark (at 06.00 h) and light period (at 18.00 h). In the dark period, acute immobilization suppressed the uptake of [3H]dopamine in adrenal chromaffin cells, while in the light period, when steroid surge ...

Dark respiration in light as well as in dark was estimated for attached leaves of an evergreen (Heteromeles arbutifolia Ait.) and a deciduous (Lepechinia fragans Greene) shrub species using an open gas-exchange system. Dark respiration in light was estimated by the Laisk method. Respiration rates in the dark were always ...

The pitch of a visual field systematically influences the elevation at which a monocularly viewing subject sets a target so as to appear at visually perceived eye level (VPEL). The deviation of the setting from true eye level average approximately 0.6 times the angle of pitch while viewing a fully ...