The fine structure of the odontoblasts in the sting rays, Dasyatis akajei, Dasyatidae, and Urolophus aurantiacus, Urolophidae, was examined using light and transmission electron microscopy. In the dentinogenesis stage, the odontoblasts have been classified into two types, that is, dark cells and light cells, based on differences in their fine ...

Thermoelectric and photoelectric currents were measured in the cuticle of hornets. The spontaneous current in the studied specimens ranged between 30-40 nAmp under conditions of darkness whereas under illumination the current drops to near zero. Upon warming up to 28-29 degrees C, the current rises to 50-200 nAmp but subsequently, ...

Both light and NO3- are necessary for the appearance of nitrate reductase (NR) activity (NRA) in photosynthetic tissues. To define the light effect more precisely, we examined the response to light/dark transitions on NRA, NR protein (NRP), and NR mRNA in 6-d-old maize (Zea mays cv W64A x W182E) seedlings ...

The relative contribution of allocentric and egocentric orientation to place navigation was studied in Long-Evans rats trained in the Morris water maze in permanent light, permanent darkness or flickering light (1 Hz, flash durations 25, 100, 300, 500 and 800 ms). After 3 days of training (nine blocks of four ...

Synechococcus sp. strain RF-1 exhibits a circadian rhythm of N2 fixation when cells are grown under a light-dark cycle, with nitrogenase activity observed only during the dark period. This dark-dependent activity correlated with nif gene transcription in strain RF-1. By using antibodies against dinitrogenase reductase (the Fe protein of the ...

BACKGROUND: In several species there is strong evidence that the retinal dopamine turnover is influenced by retinal dark and light adaptation. In the human retina, dopamine has been found in amacrine and interplexiform cells. METHODS: In the present study, the influence of orally administered levodopa on the human dark adaptation ...

Alpha-terthiophene (alpha-T) and erythrosin-B, the naturally occurring plant secondary metabolites, were tried for their phototoxic properties against Anopheles and Culex larvae under dark, ordinary tube light (1.9-2.4 w/m2) and sun light (680-840 w/m2). LC50 values of alpha-T for Anopheles larvae (4th instar) were found to be 154, 92 and 11 ...

1. Cats were reared in the dark to 3, 5, and 11 mo. We studied the N-methyl-D-aspartate (NMDA) receptor contribution to the visual response in the cortex, defined as the percentage reduction in visual response after application of 2-amino-5-phosphonovaleric acid (APV). We also studied the firing rate in response to ...

The administration of 0.1-0.5% of ethanol produces a slow increase in the transepithelial potential (TEP) of about 2 mV in the bovine pigment epithelium (RPE) under ordinary room lighting. However, virtually no response could be observed when ethanol was administered in the dark. Because of this apparent light sensitivity, the ...

The effects of darkness on quantitative spatial firing characteristics of 235 hippocampal CA1 "complex spike" (CS) cells were studied in young and old Fischer-344 rats during food-motivated performance of a randomized, forced-choice task on an eight-arm radial maze. The room lights were turned on or off on alternate blocks of ...

Myeloid bodies (MBs) are multi-lamellar membrane structures which are widely distributed in the retinal pigment epithelium (RPE) of lower vertebrates. The functional significance of these organelles is not known, but they are believed to be associated with lipid processing in the retina. To determine the nature of the daily changes ...

BACKGROUND AND DESIGN: Fifty-nine melanocytic nevi with eccentric foci of hyperpigmentation ("small dark dots") that measured primarily 1 to 2 mm in diameter were prospectively examined to determine the histologic correlates of the dark dots. RESULTS: Forty-one (69%) of the dark dots were due to increased melanin in epidermal melanocytes ...

Previous studies have typically assessed tonic accommodation (TA) and tonic vergence (TV) by placing subjects in total darkness. However, a recent investigation demonstrated that even under such apparently stimulus-free conditions, subjects' awareness of the proximity of the adjacent surroundings and overall room topography (i.e. surround propinquity) may still influence the ...

The effect of unilateral depletion of retinal dopamine on goldfish visual behavior was studied using a behavioral reflex, the dorsal light reaction (DLR). Retinal dopamine was depleted by intraocular injections of 6-hydroxydopamine (6-OHDA) on two successive days. By 2 weeks postinjection, dopamine interplexiform cells (DA-IPC) were not detected using tyrosine-hydroxylase ...

Psychophysical dark adaptation studies were performed in six patients with Best vitelliform macular dystrophy (BVMD) using a Goldmann-Weekers dark adaptometer. Prebleach thresholds were determined before obtaining a postbleach full recovery curve. Unlike patients with Stargardt macular dystrophy, all patients with BVMD showed a normal time to reach their baseline dark ...

Dark respiration in the light was estimated in leaves of two woody species (Heteromeles arbutifolia Ait. and Lepechinia fragans Greene) using two different approaches based on gas-exchange techniques: the Kok method and the Laisk method. In all cases, dark respiration in the light was lower (P < 0.05) than respiration ...

We examined whether a change in daily light/dark cycle affected DNA synthesis and tumor growth in mouse lung. Both CD-1 and A/J mice, which were treated with urethane and maintained under the short light/dark cycle (6 h light, 6 h dark), developed significantly larger sizes of lung tumors than the ...

Visual field examination is conventionally performed with bright stimuli on a dark background. Dark stimuli on a bright background, however, may provide different information as light increases and decreases are subject to parallel processing in the visual pathway. Twenty five eyes with primary open angle glaucoma and visual field loss ...

PURPOSE: To determine the time course and reproducibility of electroretinogram recovery after short-term (5- to 20-minute) retinal ischemia in the light and in the dark. METHODS: Electroretinogram recovery was measured in Dutch rabbits after 5-, 10-, or 20-minute episodes of ocular ischemia, repeated three times at 1-hour intervals. Results were ...

The theory of the Gordon-Haus effect with application to dark solitons is presented. It is proved analytically that a random frequency shift of a fundamental dark soliton results in a time jitter radical2 times lower than that for bright solitons.

Varying numbers of astrocytes lining the subarachnoid and Virchow-Robin's spaces become stainable by a special silver method in brain sections of rats subjected to a single electroshock of "suitable" parameters immediately before being sacrificed by perfusion fixation. This type of argyrophilia is considered to be induced by some electrically caused ...

Photorefractory castrated male starlings were transferred from a photoperiodic schedule of 18 h light:6 h dark to 1 h light:23 h dark, 5 h light:19 h dark, 8 h light: 16 h dark or 11 h light:13 h dark. Plasma concentrations of LH were measured in blood samples taken at ...

We studied instrument myopia as an overall effect consisting of interactions among the observer's accommodation and resolution during instrument viewing and the manner in which the instrument is focused. Previous investigations of instrument myopia generally have been limited to only one of these variables. Our results are consistent with the ...

Environmental manipulations involving 48 h of light deprivation have been found to produce sparing of function from neglect produced by unilateral destruction of the medial agranular prefrontal cortex (AGm) in rats. The present study is an extension of these findings and examined whether light deprivation would produce recovery in subjects ...

Some patients with age-related changes at the level of Bruch's membrane and good visual acuity report poor vision in dim light, fading vision in bright light, and a central scotoma noticeable in the dark. Ophthalmic examination, scotopic thresholds, and dark adaptation kinetics were recorded in 12 eyes of 12 patients ...

Biliary lipid secretion in conjunction with hepatic cholesterol synthesis was determined in normal male rats at 4, 5, 7, and 9 weeks of age, during a period of linear growth and a near fourfold increase in liver size. Studies were performed both at periods of low (mid-light cycle) and high ...

The distribution and levels of c-fos expression in response to changes in the light/dark cycle were examined in rat retina by in situ hybridization histochemistry. Under a 12 hr light: 12 hr dark cycle (LD 12:12), c-fos mRNA levels in the inner nuclear layer and the ganglion cell layer increased ...

Five zones in the secondary follicles of human tonsils are described, which are distinguished by the phenotype of their constituent cells. Moving from the apex to the base of the follicle the zones are termed: follicular mantle, outer zone, apical light zone, basal light zone and dark zone. The dark ...

We investigated the accommodative hysteresis of the refractive error in the light and also in the dark in 19 healthy young women. We measured refractive error under light and dark conditions using the Nidek Autorefractometer AR 1600 with its target light on or off. Then we measured refractive error in ...

PURPOSE: The authors examined the effects of both light and circadian phase on the synthetic activity of the dopamine producing enzyme, tyrosine hydroxylase (TH), in the retina of the Midas cichlid (Cichlasoma citrinellum). METHODS: TH activity was assayed in the retina-retinal pigment epithelium (RPE) complex of fish entrained to cyclic ...

Perimetric examination of the central visual field with low contrast static dark-on-bright stimuli on a video display unit (VDU) is described. Threshold detection sensitivities to such dark stimuli are determined in normal as well as pathological central visual fields of glaucomatous, diabetic and neuro-ophthalmic patients. The static dark (light decrement ...

The influence of four different intensities of the preadapting light on amplitude and implicit time of the dark-induced oscillation (dark trough) of the electro-oculogram was tested in 10 healthy individuals. The amplitude of the dark trough (normalized to preadapting baseline) was found to be dependent on the intensity of the ...

The inner opercular epithelium of the killifish, Fundulus heteroclitus, may be separated as a single epithelial sheet and mounted in an Ussing-style chamber with the short-circuit current (Isc) approximating chloride secretion. Steady state opercular Isc values in seawater-adapted killifish were higher in tissues removed from fish in the afternoon than ...

Light regulates membrane turnover in vertebrate rod photoreceptor cells. Rods shed membrane-filled tips immediately after light onset, with light inhibiting the dark priming phase but initiating the light induction phase. This study examines the intensities and wavelengths of light that control these two shedding requirements, and demonstrates unexpected situations where ...

Albino rats have recently been reported to have increment thresholds against dim backgrounds that are two log units higher than those of pigmented rats. We, on the other hand, have failed to confirm these differences using electroretinogram b-waves and pupillary light reflexes. This paper reports on experiments using evoked potentials ...

During the light phase of a light/dark cycle, dendrites of teleost cone horizontal cells display numerous finger-like projections, called spinules, which are formed at dawn and degraded at dusk, and are thought to be involved in chromatic feedback processes. We have studied the oscillations of these spinules during a normal ...

Visual pigment, sensitivity, and rhabdomere size were measured throughout a 12-h light/12-h dark cycle in Drosophila. Visual pigment and sensitivity were measured during subsequent constant darkness [dark/dark (D/D)]. MSP (microspectrophotometry) and the ERG (electroretinogram) revealed a cycling of visual pigment and sensitivity, respectively. A visual pigment decrease of 40% was ...

The cellular composition of the dark and light zones of germinal centres in human tonsils was quantitatively determined by electron microscopy. In addition to the well known germinal-centre B-cells, we defined the cleaved blast as a new distinct cell type in the germinal centre. The dark and the light zones ...

We recently described spine-like protrusions (spinules) from the synaptic terminals of mixed rod-cone (Mb) bipolar cells of goldfish retina that invaginated about 5% of the presynaptic amacrine cell processes (Yazulla and Studholme, J Comp Neurol 310:11, 1991). In view of reports of a light/dark dependent-plasticity on the formation of dendritic ...

The behavior of the cockroach Diploptera punctata parasitized with the acanthocephalan Moniliformis moniliformis was examined for parasite-induced alterations. No significant difference in behavior was found between parasitized and unparasitized animals in the following behavioral tests: (1) choice of white/black, horizontal/vertical substrate under light and dark conditions; (2) temporal and directional ...

We determined the disappearance eccentricities of dark and bright stimuli of equal size in the inferonasal central visual field using the oculokinetic perimetry technique at different levels of surrounding illumination. The results suggest that a dark stimulus on a bright background has a smaller 'isoptre' than an equally bright stimulus ...

In the fish retina, connexon densities of gap junctions in the outer horizontal cells are modulated in response to different light or dark adaptation times and wavelengths. We have examined whether the connexon density is a suitable parameter of gap junction coupling under in situ conditions. Short-term light adaptation evoked ...

We developed an electronic endoscope sensitive to light delivered by an infrared laser, which makes it possible to visualize submucosal vessels of the gastrointestinal tract. The system consists of a modified electronic endoscope and an image processing unit. A high output laser diode was chosen as the source of the ...

The effect of bright fluorescent light (115 fc) on oxygen-induced retinopathy in newborn kittens was compared with that of complete darkness and cyclic illumination of 12 hr of bright light (115 fc) and 12 hr of complete darkness. No significant difference was found in the extent of preretinal vasoproliferation and ...

The effects of light:dark transitions on in vitro ecdysteroid synthesis by prothoracic glands (PGs) of male fifth instar Rhodnius have been studied. PGs were rendered arrhythmic by prolonged maintenance of the animals in continuous light (LL). PGs were then explanted and ecdysteroid synthesis was measured hourly by radioimmunoassay. PGs were ...

Administration of diazepam (0.28 mg/kg, IP; 60 min) to male mice or to female mice at oestrus or dioestrus increased the number of transitions made between the light and dark chambers of a test apparatus, a presumed anxiolytic action. However, the same dose of diazepam had no effect on light/dark ...

The major effort in developing pathogenic fungi into potential mycoherbicides is aimed at increasing fungal virulence to weeds without affecting crop selectivity. Specific suppression of biosynthesis of a phytoalexin derived from the shikimate pathway in Cassia obtusifolia L. by a sublethal dose (50 micromolar) of glyphosate increased susceptibility to the ...

Oxygen tension (PO2) was measured with microelectrodes within the retina of anesthetized cats during normoxia and hypoxemia (i.e., systemic hypoxia), and photoreceptor oxygen consumption was determined by fitting PO2 measurements to a model of steady-state oxygen diffusion and consumption. Choroidal PO2 fell linearly during hypoxemia, about 0.64 mmHg/mmHg decrease in ...

The electro-oculogram is variable as a clinical test, but the recording technique has not been standardized, and differences in the protocols for adaptation and stimulation among laboratories may contribute to the variability. To analyze some of these factors, we performed more than 100 electro-oculograms on a single subject under different ...

The objective of this study was to determine whether ocular absorption of topically applied timolol in the pigmented rabbit varied with the time of drop instillation. Twenty-five microliters of a 0.65% timolol maleate solution were instilled in the pigmented rabbit eye at 0600, 0900, 1200, 1500, 1800, 2100, 2400, or ...