Nocturnal Vision Research Articles

Mutated mitofusin 2 presents with intrafamilial variability and brain mitochondrial dysfunction

The axonal forms of Charcot-Marie-Tooth (CMT2) disease are a clinically and genetically heterogeneous group of disorders. Mitofusin 2 gene (MFN2) mutations are the most common cause of CMT2. Complex phenotypes have been described in association with MFN2 gene mutations, including CMT2 with pyramidal features (hereditary motor and sensory neuropathy [HSMN V]) and CMT2 with optic atrophy (HMSN VI). To report on the clinical, neurophysiologic, and neuropathologic features of an Italian family with a novel MFN2 gene mutation and investigate brain functional parameters using magnetic resonance spectroscopy (MRS). Three family members, a father and his two sons, were affected by peripheral neuropathy, cognitive impairment, and poor nocturnal vision (also optic neuropathy in one case). A member of this family also showed spastic paraparesis. The MFN2 gene sequence was analyzed. A sural nerve biopsy as well as brain (1)H-MRS and (31)P-MRS were evaluated in two patients. Affected family members carried a novel MFN2 missense mutation, namely R104W, located within the critical GTPase domain of the protein which affects a highly conserved amino acid position. Sural nerve biopsies showed a normal mitochondrial network, particularly at the nodes of Ranvier, upon electron microscopy examination. A significant defect of high energy phosphates (HEPs) in the visual cortex was observed at rest by (31)P-MRS in the adult proband, while his son showed a defective recovery of HEPs after stimulation of the visual cortex. Cognitive impairment may be another feature of the MFN2-related phenotype. The widespread peripheral and CNS involvement, as well as the neurosensorial defects, underline the similarities among MFN2-related and primary mitochondrial disorders.

Visual Reliability and Information Rate in the Retina of a Nocturnal Bee

Nocturnal animals relying on vision typically have eyes that are optically and morphologically adapted for both increased sensitivity and greater information capacity in dim light. Here, we investigate whether adaptations for increased sensitivity also are found in their photoreceptors by using closely related and fast-flying nocturnal and diurnal bees as model animals. The nocturnal bee Megalopta genalis is capable of foraging and homing by using visually discriminated landmarks at starlight intensities. Megalopta's near relative, Lasioglossum leucozonium, performs these tasks only in bright sunshine. By recording intracellular responses to Gaussian white-noise stimuli, we show that photoreceptors in Megalopta actually code less information at most light levels than those in Lasioglossum. However, as in several other nocturnal arthropods, Megalopta's photoreceptors possess a much greater gain of transduction, indicating that nocturnal photoreceptors trade information capacity for sensitivity. By sacrificing photoreceptor signal-to-noise ratio and information capacity in dim light for an increased gain and, thus, an increased sensitivity, this strategy can benefit nocturnal insects that use neural summation to improve visual reliability at night.

Unique adaptaton of rod cell nuclear architecture in nocturnal mammals to nocturnal vision

Unique adaptaton of rod cell nuclear architecture in nocturnal mammals to nocturnal vision

Molecular genetics and protein function involved in nocturnal vision

Congenital stationary night blindness (CSNB) is a group of genetically and clinically heterogeneous retinal disorders. Ten different genes have been shown to be associated with CSNB. Mutations in genes coding for proteins of the phototransduction cascade can lead to this disease. However, to date, the major cause of CSNB results from mutations in two genes, CACNA1F and NYX, which are thought to play a role downstream of the phototransduction cascade in transmitting the signal from the photoreceptors to the adjacent bipolar cells. This review focuses on the different genetic causes of CSNB. It provides an overview of the genetically and clinically heterogeneous disease and describes recent progress in identifying mutations in these ten genes, as well as the potential underlying molecular mechanisms of their products.

A fossil brain from the Cretaceous of European Russia and avian sensory evolution

Fossils preserving traces of soft anatomy are rare in the fossil record; even rarer is evidence bearing on the size and shape of sense organs that provide us with insights into mode of life. Here, we describe unique fossil preservation of an avian brain from the Volgograd region of European Russia. The brain of this Melovatka bird is similar in shape and morphology to those of known fossil ornithurines (the lineage that includes living birds), such as the marine diving birds Hesperornis and Enaliornis, but documents a new stage in avian sensory evolution: acute nocturnal vision coupled with well-developed hearing and smell, developed by the Late Cretaceous (ca 90Myr ago). This fossil also provides insights into previous 'bird-like' brain reconstructions for the most basal avian Archaeopteryx--reduction of olfactory lobes (sense of smell) and enlargement of the hindbrain (cerebellum) occurred subsequent to Archaeopteryx in avian evolution, closer to the ornithurine lineage that comprises living birds. The Melovatka bird also suggests that brain enlargement in early avians was not correlated with the evolution of powered flight.

Changes in the refractive state during prey capture under low light in the nocturnal cardinalfish Apogon annularis

Many nocturnal and crepuscular fish use vision to feed and function under low light levels. However, little is known about their ability to accommodate or their visual acuity under these light levels. We used Infrared Photoretinoscopy to track the refractive state of the eye during prey capture under low light in Apogon annularis, a nocturnal reef fish. Anatomical measurements of the eyes allowed calculations of visual acuity. Changes in the refractive state were observed in ∼75% of the prey capturing strikes, preceding the strikes by 30 ms. These changes were rare between strikes or when prey was absent. Anatomical measurements indicated that the number of photo-detection units in a retinal image greatly exceeded the minimal number needed to detect prey. We conclude that nocturnal vision in A. annularis is sufficiently sensitive to allow accommodation during prey capture.

Food, Poetry, and Borderlands Materiality: Walter Benjamin at the taquería

In a short story entitled The Properties of Magic by Tejano writer Ray Gonzalez (2001) a boy named Augustino wakes up in the middle of the night to find a headless man standing at the foot of his bed. Dressed in an old army uniform, the man reaches into the hole in his neck where once a head stood and to the bewilderment of the child pulls out a donkey pinata just like one the boy's parents had given him for his fifth birthday. Readers quickly learn that this eerie nocturnal vision (we can't be sure it is a dream) is not that unusual in the boy's life. Haunting epiphanies and omens manifested through the appearance of familiar objects out of place saturate Augustino's everyday experience: his play is interrupted by finding a broken rosary on the school playground; the flickering of lights at church startles him; a drawing he brought home from school seems to attract the attention of a bird that flies through the bedroom window; sitting on the porch of his house, he feels observed by blue

The Development of Neuronal Morphology in Insects

Neurons are highly polarized cells with some regions specified for information input--typically the dendrites--and others specialized for information output--the axons. By extending to a specific location and branching in a specific manner, the processes of neurons determine at a fundamental level how the nervous system is wired to produce behavior. Recent studies suggest that relatively small changes in neuronal morphology could conceivably contribute to striking behavioral distinctions between invertebrate species. We review recent data that begin to shed light on how neurons extend dendrites to their targets and acquire their particular branching morphologies, drawing primarily on data from genetic model organisms. We speculate about how and why the actions of these genes might facilitate the diversification of dendritic morphology.

Purified high-dose anthocyanoside oligomer administration improves nocturnal vision and clinical symptoms in myopia subjects

The aim of the present study was to determine the effect of purified high-dose anthocyanoside oligomer administration on nocturnal visual function and clinical symptoms in low-to-moderate myopia subjects. The study was a randomized, double-blind, placebo-controlled trial and involved sixty subjects with asthenopia and refractive errors between -1.00 and -8.00 diopters in both eyes. Thirty subjects were administered a purified high-dose anthocyanoside oligomer (100 mg tablet comprising 85 % anthocyanoside oligomer), and thirty were given a placebo in tablet form twice daily for 4 weeks. Prior to the treatment, the placebo and anthocyanoside groups were similar in terms of age and contrast sensitivity. Before and after treatment, subjects completed a questionnaire to determine their clinical symptoms and were also assessed for nocturnal visual function using contrast sensitivity testing. Questionnaire data analysis showed that, following treatment, twenty-two (73.3 %) anthocyanoside subjects showed improved symptoms, whereas only one placebo subject showed an improvement (Fisher's exact test, P<0.0001). Contrast sensitivity levels according to each cycle per degree significantly improved in the anthocyanoside group and remained stable in the placebo group. The mean contrast sensitivity change in the anthocyanoside group was 2.41 (SD) 1.91, compared with -0.66 (SD) 2.66 dB for the placebo group (unpaired Student's t test, P<0.0001). At all cycle per degree levels, contrast sensitivity changes in the anthocyanoside group were better than in the placebo group (unpaired Student's t test, P<0.05). The present data show that the administration of anthocyanoside oligomer appears to improve subjective symptoms and objective contrast sensitivity in myopia subjects with asthenopia.

Retinal and optical adaptations for nocturnal vision in the halictid bee Megalopta genalis.

The apposition compound eye of a nocturnal bee, the halictid Megalopta genalis, is described for the first time. Compared to the compound eye of the worker honeybee Apis mellifera and the diurnal halictid bee Lasioglossum leucozonium, the eye of M. genalis shows specific retinal and optical adaptations for vision in dim light. The major anatomical adaptations within the eye of the nocturnal bee are (1) nearly twofold larger ommatidial facets and (2) a 4-5 times wider rhabdom diameter than found in the diurnal bees studied. Optically, the apposition eye of M. genalis is 27 times more sensitive to light than the eyes of the diurnal bees. This increased optical sensitivity represents a clear optical adaptation to low light intensities. Although this unique nocturnal apposition eye has a greatly improved ability to catch light, a 27-fold increase in sensitivity alone cannot account for nocturnal vision at light intensities that are 8 log units dimmer than during daytime. New evidence suggests that additional neuronal spatial summation within the first optic ganglion, the lamina, is involved.

Zooplanktivory by a nocturnal coral‐reef fish: Effects of light, flow, and prey density

Visual predation by nocturnal zooplanktivorous fish is assumed to be sufficiently limited to allow the evolution of vertical migration as means for predation avoidance by zooplankton. However, in situ measurements of predation rates by nocturnal fish are lacking. Most of our knowledge of this predation is based on stomach contents and laboratory experiments. Our objectives were to measure the in situ rate of zooplanktivory by a common, nocturnal coral‐reef fish, Apogon annularis, and to assess, through laboratory and field experiments, the effects of light, prey density, and flow on the fish’s predation. In situ, the fish selectively fed on large zooplankton (&gt;1 mm) at a rate of 0.12 prey min−1, or 52% efficiency. Predation rates increased linearly with prey density, with no apparent effects of current speed and light intensity. Flume experiments indicated that feeding rates were saturating at a level corresponding to that found at 3 m depth on a moonless night and were negligible at &gt;18 m. Predation rates by A. annularis were two orders of magnitude lower than those of diurnal fishes; however, the difference in carbon gain was largely offset by the greater size of nocturnal prey. Nocturnal vision in A. annularis is sufficiently sensitive to allow a remarkable detectability of large prey in its natural habitat. If this fish is representative of other nocturnal fishes, reconciliation between the potential for substantial nocturnal predation, as is demonstrated in the present study, and the evolution of vertical migration in large zooplankton could be related to the total abundance of those fishes and their depth distribution. Both parameters are as yet poorly known.

The evolution of flight and echolocation in bats: another leap in the dark

ABSTRACTThe earliest known complete bats, from the Eocene (49–53 Mya), were already capable of flapping flight and echolocation. In the absence of direct fossil evidence there have been many speculative scenarios advanced to explain the evolution of these behaviours and their distributions in extant bats. Theories assuming chiropteran monophyly have generally presumed the ancestral pre‐bat was nocturnal, arboreal and insectivorous. Following this assumption hypotheses can be divided into the echolocation first, flight first and tandem development hypotheses, all of which assume that flight evolved only once in the lineage. In contrast, the chiropteran diphyly hypothesis suggests that flight evolved twice. Evidence supporting and refuting the different hypotheses are reviewed. It is concluded that there are significant problems attached to all the current models. A novel hypothesis is advanced, which starts from the assumption that bats are monophyletic and the ancestral pre‐bat was arboreal, but diurnal and frugivorous. After the evolution of flight it is suggested that these animals were driven into the nocturnal niche by the evolution of raptorial birds, and different groups evolved either specialised nocturnal vision (megachiropterans) or echolocation (microchiropterans). A block on sensory modality transfer has retained this distribution of perceptual capabilities ever since, despite some Megachiroptera evolving rudimentary echolocation, and the dietary convergence of some Microchiroptera with the Megachiroptera. The new hypothesis overcomes many of the problems identified in previous treatments.

Vitamin A deficiency and nocturnal vision in teenagers with cystic fibrosis.

The aim of this study was to document plasma retinol status and nocturnal vision in ten eutrophic adolescents with cystic fibrosis (CF) receiving daily retinol supplementation. Plasma retinol, alpha and beta carotenes and retinol binding protein were measured in ten clinically stable CF patients (mean age: 14.3 years; Shwachman score: 80-100). Nocturnal vision evaluation was performed with a Beyne optometer. Plasma retinol (mean 0.42 +/- 0.16 mg/l), alpha carotene and beta carotene levels were below the lower limit of normal in all but one patient. Five out of ten patients with normal standard opthalmological examination presented a poor (n = 3 patients) or a pathological (n = 2) dark adaptation test. These two patients showed a dramatic increase in nocturnal vision after 1 year of adapted retinol supplementation. Low vitamin A levels occur frequently in clinically stable, eutrophic and retinol supplemented CF adolescents. Since vitamin A deficiency is associated with poor nocturnal vision and since this pattern can be reversed by adapted retinol supplementation, we recommend monitoring plasma vitamin A levels in CF patients and evaluation of dark adaptation in retinol deficient patients.

Daily and circadian rhythms of synaptic frequency in the first visual neuropile of the housefly’s ( Musca domestica L.) optic lobe

Photoreceptors of the fly's compound eye generally show no very obvious daily or circadian rhythms, a lack which prompted us to examine whether their function might be regulated not in the retina, but at the site of transmission in the first visual neuropile, or lamina. Here, photoreceptor terminals (R1-R6) are reciprocally interconnected with one class of lamina monopolar cell, L2: L2 receives input from R1-R6 at so-called tetrad synapses, and in turn is presynaptic to R1-R6 at feedback synapses. We have calculated the mean frequencies of these synaptic profiles in electron micrographs of single lamina sections. L2 feedback synapses were more numerous at night than during the day, whereas the number of tetrads showed only small modulations between day and night. These changes persisted amongst feedback synapses in flies held in constant darkness, and are thus circadian. In contrast to the slow modulations during a 24 h cycle, the number of L2 feedback synapses after 1 h light pulse in flies held in constant darkness showed no clear change, whereas it increased the number of tetrad profiles. These findings support the occurrence of cyclical daily and circadian changes amongst the two lamina synaptic populations, with tetrads showing rather weak modulations in frequency, but more pronounced responses to the light pulse than feedback synapses.

Structural features and adaptive properties of photoreceptors in the skate retina

In the duplex (rod/cone) retinae of most vertebrates, electrical responses associated with nocturnal vision can be recorded in relative isolation only over a limited intensity range before there is encroachment by signals from the cone system; e.g., at mesopic levels of illumination, the rods begin to saturate, and the cone mechanism is brought into play. On the other hand, the retinae of some sub-species of skate appear to contain only one class of photoreceptors, namely rods. Nevertheless, skate photoreceptors, as well as other retinal neurons, are able to respond to incremental stimuli presented on background fields so intense that 90% or more of the available rhodopsin is bleached during the exposure. These and other findings raise some doubts as to whether the skate has, in fact, an all-rod retina. In this paper, we present a body of evidence--based on the results of photochemical, anatomical, and electrophysiological studies--to support the view that only a single class of photoreceptor subserves vision in the skate retina. In addition, recent findings will be described that: a) demonstrate how the visual cells transform from sluggishly responding rods to brisk, cone-like elements, and b) may provide some insight into the functional significance of this unusual adaptive property.

Characteristics of the eye of the Indian mongoose (Herpestes auropunctatus)

The refractive state, optical structure, and intraocular muscles of the eye of the Indian mongoose, Herpestes auropunctatus, were examined using a variety of refractive and anatomical techniques. Additional observations concern the structure and function of the tapetum lucidum and the diurnal activity levels. The mongoose eye is emmetropic (zero refractive error), or nearly so, a surprising finding in view of the small (8.0 mm diameter) size of the eye and the fact that the small-eyed mammals seem to show varying degrees of apparent hyperopia. The optical media, particularly the size, shape, and relative location of the ocular lens, are those of a diurnal species. Accommodation, induced pharmacologically, is of a magnitude (11–13.5 diopters) normally associated with primates. The ciliary muscle consists of large and well-developed fascicles of longitudinal fibres. The iris muscles, especially the sphincter, are much larger, on a relative basis, than those of the human iris. The mongoose eye is characterized by the existence of an obvious bright green tapetum cellulosum located in the choroid. The spectral quality of the tapetal reflection matches spectral radiometric measures made in grasses that the animal inhabits. Activity observations confirm the strict diurnality of the mongoose. Though a tapetum is normally associated with nocturnal vision, the mongoose tapetum may be of use in ensuring that the light reflected by the dense vegetation and incident to the eye stimulates cones with relatively high stimulus thresholds.

Luther and the Ascent of Jacob's Ladder

On the west front of Bath Abbey there are carved two stone ladders stretching from heaven to earth on which twelve angels are climbing, six on each ladder. A tourist who sees the west front of the abbey for the first time is told that the carvings represent the dream of Oliver King, Bishop of Bath and Wells under Henry VII and his former chief secretary. The bishop had a nocturnal vision of angels climbing ladders to heaven. As he stood before the ladders in amazement, he heard voices saying that an olive should establish the crown and that the king should restore the church. He took the reference to olives and kings to be an allusion to his own name and concluded that he, Oliver King, should support the Tudor monarchy and rebuild the ruined abbey at Bath.

Adaptations for cryopelagic life in the antarctic notothenioid fish Pagothenia borchgrevinki

The cryopelagic circumantarctic notothenioid fish Pagothenia borchgrevinki lives near the undersurface of the sea ice in McMurdo Sound, Antarctica. When compared to closely related benthic species (especially Trematomus bernacchii), Pagothenia exhibited substantial morphological differences in a variety of organ systems. The values of the fineness ratio and the indices of trunk shape and flatness suggested streamlining and drag reduction, adaptations to life in the water column. Pagothenia also lacked substrate contact adaptations in the pelvic and anal fins. Silvery reflective layers (strata argentea) beneath the skin and in the iris and choroid of the eye provided camouflage when Pagothenia were viewed against a background of platelet ice. The retina had many cones indicating the eye was adapted to both diurnal and nocturnal vision. During the austral spring Pagothenia fed exclusively on nektonic organisms near the ice-water interface. Dietary diversity was low; copepods and amphipods were the most frequently occurring and amphipods were the most frequently occurring taxa. In conclusion, Pagothenia appear specialized for life in the water column.

The Figure of Constantine the Great in Cynewulf's ‘Elene’

The first two hundred lines of Cynewulf'sElenedeal not with Elene's finding of the Holy Cross but with the events that lead to the conversion of her son, the emperor Constantine. They recount the invasion of his kingdom by a horde of Goths, Huns, and Franks; his fear and despair at the prospect of doing battle with such a vastly superior force; his nocturnal vision of the cross with its famous promise of victory; the crushing defeat he inflicts on the invaders the next day; his triumphant return to Rome, where he learns from his counsellors that the cross is the sign of God; his evangelization by a group of Christians; and his subsequent baptism. Only after all this does the quest for the True Cross get underway, at Constantine's bidding. Although the fifth-centuryInventio Sanctae Crucis, Cynewulf's principal source, narrates these events in a few lines of bare, prosaic Latin, the Old English poet has turned them into the most extensive piece of amplification in the whole work, chiefly, but not entirely, by providing detailed descriptions of the invading and defending armies, and of the battle itself, in recognizably formulaic style with much skillful repetition and variation.

Gross anatomical and microscopic observations on the orbit and its contents in Notomys alexis

The gross anatomical arrangement of the orbit and its contents in N. alexis are described, with observations of these structures with the light microscope and of the retina with the transmission and scanning electron microscope. The eye is large compared with that of other rodents, and, in view of the rod outer segment length (43 �m), may afford sensitive nocturnal vision. It is unlikely that the animal has stereoscopic vision. Behavioural and microscopic evidence suggests that N. alexis has considerable processing of the visual signal at a retinal level, which may facilitate its rapid response to any sudden movement within the wide area of its visual field.