A large prospective investigation of outdoor light at night and obesity in the NIH-AARP Diet and Health Study

BACKGROUND

Research has suggested that artificial light at night (LAN) may disrupt circadian rhythms, sleep, and contribute to the development of obesity. However, almost all previous studies are cross-sectional, thus, there is a need for prospective investigations of the association between LAN and obesity risk. The goal of our current study was to examine the association between baseline LAN and the development of obesity over follow-up in a large cohort of American adults.

METHODS

The study included a sample of 239,781 men and women (aged 50-71) from the NIH-AARP Diet and Health Study who were not obese at baseline (1995-1996). We used multiple logistic regression to examine whether LAN at baseline was associated with the odds of developing obesity at follow-up (2004-2006). Outdoor LAN exposure was estimated from satellite imagery and obesity was measured based on self-reported weight and height.

RESULTS

We found that higher outdoor LAN at baseline was associated with higher odds of developing obesity over 10 years. Compared with the lowest quintile of LAN, the highest quintile was associated with 12% and 19% higher odds of developing obesity at follow-up in men (OR (95% CI) = 1.12 (1.00, 1.250)) and women (1.19 (1.04, 1.36)), respectively.

CONCLUSIONS

Our findings suggest that high LAN exposure could predict a higher risk of developing obesity in middle-to-older aged American adults.

Road lighting density and brightness linked with increased cycling rates after-dark

Cycling has a range of benefits as is recognised by national and international policies aiming to increase cycling rates. Darkness acts as a barrier to people cycling, with fewer people cycling after-dark when seasonal and time-of-day factors are accounted for. This paper explores whether road lighting can reduce the negative impact of darkness on cycling rates. Changes in cycling rates between daylight and after-dark were quantified for 48 locations in Birmingham, United Kingdom, by calculating an odds ratio. These odds ratios were compared against two measures of road lighting at each location: 1) Density of road lighting lanterns; 2) Relative brightness as estimated from night-time aerial images. Locations with no road lighting showed a significantly greater reduction in cycling after-dark compared with locations that had some lighting. A nonlinear relationship was found between relative brightness at a location at night and the reduction in cyclists after-dark. Small initial increases in brightness resulted in large reductions in the difference between cyclist numbers in daylight and after-dark, but this effect reached a plateau as brightness increased. These results suggest only a minimal amount of lighting can promote cycling after-dark, making it an attractive mode of transport year-round.

Chemo-mapping and biochemical-modulatory and antioxidant/prooxidant effect of Galium verum extract during acute restraint and dark stress in female rats

Galium verum is a well-known medicinal plant which is used in various pathologies. G. verum extracts are characterized here using chromatography, where among the rich pool of phenolic acids of flavonoids two known anti-stress modulators, chlorogenic acid and rutin are identified in high quantities. Additionally, the extracts are characterized using a series of in vitro assays (EPR, DPPH, TPC and TEAC). Considering the chemical findings, the potential beneficial effects of the G. verum extract are explored here in a living organism exposed to stress induced oxidative damages. Thus, the biochemical-modulatory and antioxidant roles of two doses of G. verum extract are examined in animals exposed to acute restraint and dark stress (S). The animals were divided in groups [control, S, SG1 (exposed to 25 mg G. verum extract), SG2 (50 mg extract)]. Increased levels of lipid peroxidation (TBARS from 4.43 to 8.06 nmol/mL), corticosterone from 0.43 to 1.96 μg/dL and epinephrine from 44.43 to 126.7 μg/mL, as well as decreased antioxidant enzymes activities (SOD/CAT) were observed in the S group. The G. verum extract afforded a near-normal equilibrium within the biochemical parameters of animals exposed to RS, by reducing oxidative damage (TBARS at a 3.73 nmol/mL; CS at 0.90 μg/dL; EP at 63.72 μg/mL) and by restoring the antioxidant balance.

Using fixed-parameter and random-parameter ordered regression models to identify significant factors that affect the severity of drivers' injuries in vehicle-train collisions

This study attempts to identify significant factors that affect the severity of drivers' injuries when colliding with trains at railroad-grade crossings by analyzing the individual-specific heterogeneity related to those factors over a period of 15 years. Both fixed-parameter and random-parameter ordered regression models were used to analyze records of all vehicle-train collisions that occurred in the United States from January 1, 2001 to December 31, 2015. For fixed-parameter ordered models, both probit and negative log-log link functions were used. The latter function accounts for the fact that lower injury severity levels are more probable than higher ones. Separate models were developed for heavy and light-duty vehicles. Higher train and vehicle speeds, female, and young drivers (below the age of 21 years) were found to be consistently associated with higher severity of drivers' injuries for both heavy and light-duty vehicles. Furthermore, favorable weather, light-duty trucks (including pickup trucks, panel trucks, mini-vans, vans, and sports-utility vehicles), and senior drivers (above the age of 65 years) were found be consistently associated with higher severity of drivers' injuries for light-duty vehicles only. All other factors (e.g. air temperature, the type of warning devices, darkness conditions, and highway pavement type) were found to be temporally unstable, which may explain the conflicting findings of previous studies related to those factors.

[EFFECTS OF LIGHT OR DARK DEPRIVATION ON PERFORMANCE AND LACTATE LEVELS IN RAT BLOOD]

The dynamics of rat's swimming test with a load after 10 daily deprivation of light or dark were investigated. It was established that in the control group in nature illumination daily physical swimming with a load to full exhaustion from the first to the third day of the experiment, there was an increase of active swimming time indicator followed by stabilization. In groups of animals kept before bringing swimming test in a day and night lighting or darkening around the clock, there was an increase in swimming time only on the first day of the experiment, and the next days there was a decrease of efficiency. After a five-day cycle of the swimming load the level of lactate in the blood of control animals was increased, and experienced - has not changed in comparison with the intact, not subjected to any stress.

Effects of light deprivation in physical performance and psychophysiological responses to a time-to-exhaustion exercise test

Studies have shown that there is no effect of light deprivation in closed-loop exercise performance, however less is known about the open-loop exercise performance. Thus, we verified if light deprivation may affect performance and psychophysiological responses to a time-to-exhaustion (TE), constant intensity exercise test. Twelve men performed TE tests (at 80% WPEAK of maximal incremental test) in control and light-deprived condition. Gaseous exchange (VE and VO2), heart rate (HR) and vastus lateralis electromyography (EMG) were continuously assessed, ratings of perceived exertion (RPE) and associative thoughts to exercise (ATE) were obtained every 60s. Responses at absolute time of exercise matched by the shortest time to exhaustion, and responses at exhaustion were compared between conditions (P<0.05). Exhaustion was shortened (5.0 ± 1.6 min vs 6.4 ± 2.4 min) and RPE slope was elevated in light deprivation, when compared to control (P<0.05). Responses of VE, VO2 and RPE were greater at exhaustion in light deprivation TE test than at the equivalent, paired time in control test. However, responses were similar at exhaustion of both TE tests; the exception was the lower EMG when the light was deprived. The light deprivation shortened the exhaustion and increased RPE in TE test, until the attainment of similar maximal psychophysiological responses.

Features of the Vision of Elderly Pedestrians when Crossing a Road

The present study clarifies the mechanism by which an accident occurs when an elderly pedestrian crosses a road in front of a car, focusing on features of the central and peripheral vision of elderly pedestrians who are judging when it is safe to cross the road. For the pedestrian's central visual field, we investigated the effect of age on the timing judgment using an actual car. The results for daytime conditions indicate that the elderly pedestrians tended to make later judgments of when they crossed the road from the right side of the driver's view at high car velocities. At night, for a car with its headlights on high beam, the average car-pedestrian distances of elderly pedestrians on the left side of the driver's view were significantly longer than those of young pedestrians at velocities of 20 and 40 km/h. The eyesight of the elderly pedestrians during the day did not affect the timing judgment of crossing a road. At night, for a car with its headlights on either high or low beam, the average car-pedestrian distances of elderly pedestrians having good eyesight were longer than those of elderly pedestrians having poor eyesight, for all car velocities. The color of the car body in the central visual field did not affect the timing judgment of elderly pedestrians crossing the road. Meanwhile, the car-body color in the elderly pedestrian's peripheral vision strongly affected the pedestrian's awareness of the car.

Ontogeny and adolescent alcohol exposure in Wistar rats: open field conflict, light/dark box and forced swim test

Epidemiological studies have demonstrated that heavy drinking and alcohol abuse and dependence peak during the transition between late adolescence and early adulthood. Studies in animal models have demonstrated that alcohol exposure during adolescence can cause a modification in some aspects of behavioral development, causing the "adolescent phenotype" to be retained into adulthood. However, the "adolescent phenotype" has not been studied for a number of behavioral tests. The objective of the present study was to investigate the ontogeny of behaviors over adolescence/young adulthood in the light/dark box, open field conflict and forced swim test in male Wistar rats. These data were compared to previously published data from rats that received intermittent alcohol vapor exposure during adolescence (AIE) to test whether they retained the "adolescent phenotype" in these behavioral tests. Three age groups of rats were tested (post-natal day (PD) 34-42; PD55-63; PD69-77). In the light/dark box test, younger rats escaped the light box faster than older adults, whereas AIE rats returned to the light box faster and exhibited more rears in the light than controls. In the open field conflict test, both younger and AIE rats had shorter times to first enter the center, spent more time in the center of the field, were closer to the food, and consumed more food than controls. In the forced swim test no clear developmental pattern emerged. The results of the light/dark box and the forced swim test do not support the hypothesis that adolescent ethanol vapor exposure can "lock-in" all adolescent phenotypes. However, data from the open field conflict test suggest that the adolescent and the AIE rats both engaged in more "disinhibited" and food motivated behaviors. These data suggest that, in some behavioral tests, AIE may result in a similar form of behavioral disinhibition to what is seen in adolescence.

Photoinhibition-like damage to the photosynthetic apparatus in plant leaves induced by submergence treatment in the dark

Submergence is a common type of environmental stress for plants. It hampers survival and decreases crop yield, mainly by inhibiting plant photosynthesis. The inhibition of photosynthesis and photochemical efficiency by submergence is primarily due to leaf senescence and excess excitation energy, caused by signals from hypoxic roots and inhibition of gas exchange, respectively. However, the influence of mere leaf-submergence on the photosynthetic apparatus is currently unknown. Therefore, we studied the photosynthetic apparatus in detached leaves from four plant species under dark-submergence treatment (DST), without influence from roots and light. Results showed that the donor and acceptor sides, the reaction center of photosystem II (PSII) and photosystem I (PSI) in leaves were significantly damaged after 36 h of DST. This is a photoinhibition-like phenomenon similar to the photoinhibition induced by high light, as further indicated by the degradation of PsaA and D1, the core proteins of PSI and PSII. In contrast to previous research, the chlorophyll content remained unchanged and the H2O2 concentration did not increase in the leaves, implying that the damage to the photosynthetic apparatus was not caused by senescence or over-accumulation of reactive oxygen species (ROS). DST-induced damage to the photosynthetic apparatus was aggravated by increasing treatment temperature. This type of damage also occurred in the anaerobic environment (N2) without water, and could be eliminated or restored by supplying air to the water during or after DST. Our results demonstrate that DST-induced damage was caused by the hypoxic environment. The mechanism by which DST induces the photoinhibition-like damage is discussed below.

Assessment of a new dynamic light regimen in a nuclear power control room without windows on quickly rotating shiftworkers--effects on health, wakefulness, and circadian alignment: a pilot study

The aim of the study was to test whether a new dynamic light regime would improve alertness, sleep, and adaptation to rotating shiftwork. The illumination level in a control room without windows at a nuclear power station was ~200 lux (straight-forward horizontal gaze) using a weak yellow light of 200 lux, 3000 K (Philips Master TLD 36 W 830). New lighting equipment was installed in one area of the control room above the positions of the reactor operators. The new lights were shielded from the control group by a distance of >6 m, and the other operators worked at desks turned away from the new light. The new lights were designed to give three different light exposures: (i) white/blue strong light of 745 lux, 6000 K; (ii) weak yellow light of 650 lux, 4000 K; and (iii) yellow moderate light of 700 lux, 4000 K. In a crossover design, the normal and new light exposures were given during a sequence of three night shifts, two free days, two morning shifts, and one afternoon shift (NNN + MMA), with 7 wks between sessions. The operators consisted of two groups; seven reactor operators from seven work teams were at one time exposed to the new equipment and 16 other operators were used as controls. The study was conducted during winter with reduced opportunities of daylight exposure during work, after night work, or before morning work. Operators wore actigraphs, filled in a sleep/wake diary, including ratings of sleepiness on the Karolinska Sleepiness Scale (KSS) every 2 h, and provided saliva samples for analysis of melatonin at work (every 2nd h during one night shift and first 3 h during one morning shift). Results from the wake/sleep diary showed the new light treatment increased alertness during the 2nd night shift (interaction group × light × time, p < .01). Time of waking was delayed in the light condition after the 3rd night shift (group × light, p < .05), but the amount of wake time during the sleep span increased after the 2nd night shift (p < .05), also showing a tendency to affect sleep efficiency (p < .10). Effects on circadian phase were difficult to establish given the small sample size and infrequent sampling of saliva melatonin. Nonetheless, it seems that appropriate dynamic light in rooms without windows during the dark Nordic season may promote alertness, sleep, and better adaptation to quickly rotating shiftwork.

Mental health and employment: The SAD story

This paper explores the relationship between health-related quality of life (HRQOL) measures and employment status in light of a constructed index related to Seasonal Affective Disorder that depends only on latitude and day of year. In models including demographic covariates and indicators for state, year, and quarter, more hours of darkness is associated with poorer HRQOL, which in turn is associated with a lower likelihood of employment. The relationships between the darkness index and HRQOL measures are stronger overall for women than for men. Inclusion of both the darkness index and the HRQOL measures in models of employment status determinants provides some evidence that the former operates through the latter in predicting a lower likelihood of employment. When specifying the darkness index as an instrument for HRQOL, each additional day of poor mental health per month leads to a 0.76 percentage point increase in the probability of unemployment among women.

Inner ear morphology in the Atlantic molly Poecilia mexicana--first detailed microanatomical study of the inner ear of a cyprinodontiform species

BACKGROUND

Fishes show an amazing diversity in hearing abilities, inner ear structures, and otolith morphology. Inner ear morphology, however, has not yet been investigated in detail in any member of the diverse order Cyprinodontiformes. We, therefore, studied the inner ear of the cyprinodontiform freshwater fish Poecilia mexicana by analyzing the position of otoliths in situ, investigating the 3D structure of sensory epithelia, and examining the orientation patterns of ciliary bundles of the sensory hair cells, while combining μ-CT analyses, scanning electron microscopy, and immunocytochemical methods. P. mexicana occurs in different ecotypes, enabling us to study the intra-specific variability (on a qualitative basis) of fish from regular surface streams, and the Cueva del Azufre, a sulfidic cave in southern Mexico.

RESULTS

The inner ear of Poecilia mexicana displays a combination of several remarkable features. The utricle is connected rostrally instead of dorso-rostrally to the saccule, and the macula sacculi, therefore, is very close to the utricle. Moreover, the macula sacculi possesses dorsal and ventral bulges. The two studied ecotypes of P. mexicana showed variation mainly in the shape and curvature of the macula lagenae, in the curvature of the macula sacculi, and in the thickness of the otolithic membrane.

CONCLUSIONS

Our study for the first time provides detailed insights into the auditory periphery of a cyprinodontiform inner ear and thus serves a basis--especially with regard to the application of 3D techniques--for further research on structure-function relationships of inner ears within the species-rich order Cyprinodontiformes. We suggest that other poeciliid taxa, or even other non-poeciliid cyprinodontiforms, may display similar inner ear morphologies as described here.

Differences in geometry of pedestrian crashes in daylight and darkness

INTRODUCTION

Previous studies have shown that increased risk in darkness is particularly great for pedestrian crashes, suggesting that attempts to improve headlighting should focus on factors that likely influence those crashes. The current analysis was designed to provide information about how details of pedestrian crashes may differ between daylight and darkness.

METHOD

All pedestrian crashes that occurred in daylight or dark conditions in Michigan during 2004 were analyzed in terms of the variables included in the State of Michigan crash database. Additional analysis of the narratives and diagrams in police accident reports was performed for a subset of 400 of those crashes-200 sampled from daylight and 200 sampled from darkness.

RESULTS

Several differences were found that appear to be related to the characteristic asymmetry of low-beam headlamps, which (in the United States) distributes more light on the passenger's side than the driver's side of the vehicle. These results provide preliminary quantification of the how the photometric differences between the right and left sides of typical headlamps may affect pedestrian crash risk.

IMPACT ON INDUSTRY

The results suggest that efforts to provide supplemental forward vehicle lighting in turns may have safety benefits for pedestrians.

Scotosensitive and Photosensitive Myoclonic Seizures in an Infant with Trisomy 13

We describe a male carrier of trisomy 13 with scotosensitive and photosensitive myoclonic seizures appearing at the age of 8 months and persisting until death at 20 months. The seizures consisted of massive myoclonic jerks induced both by switching the room light suddenly on or off or by IPS with a frequency of 1 s. Spontaneous seizures were absent. The child also presented from the same age with breath-holding spells. This is interesting because it represents a rare example of the co-occurrence of scotosensitive and photosensitive seizures. Furthermore, a possible association to locus on 13q31.3 has been reported for photosensitivity, while for scotosensitivity there is no previous genetic information.

Visual spatial disorientation: revisiting the black hole illusion

Spatial disorientation (SD) is often cited as a contributor to aviation accidents. A specific type of visual SD, the "black-hole illusion" (BHI), occurs on approach to landing at night when the outside view lacks cues to terrain around the lighted runway. Pilots too often confidently proceed with a visual approach despite the impoverished visual conditions; the BHI then causes them to experience glide path overestimation (GPO) so that they initiate an inappropriately steep descent. The result is a shallow approach that lies below the correct glide path for obstacle clearance. This review explores the origins of the BHI and describes several mishaps involving it. Nine possible reasons for pilot misperception leading to GPO are described: constancy of apparent size-shape-depth; conflict between familiar and relative size; overestimation of visual angles in the medial extent; deficient terrain orientation cues; lack of distance cues; disparity between optical and geographical slant; perception of approach lighting systems; tendency toward equidistance; and misperception of slant. Mishaps involving visual SD are not pilot error, but demonstrate a perceptual limitation, and more needs to be learned regarding when and where the BHI may occur. It is already clear, however, pilots should be taught that confidence in their visual capabilities during impoverished viewing conditions greatly exceed their perceptual abilities. With the increase in night flying in military and civilian settings, reduction in landing mishaps will depend in part on inclusion of visual SD scenarios in initial and refresher pilot training with presentation of BHI scenarios in annual flight simulator sessions.

Light deprivation delays morphological differentiation of bipolar cells in the rabbit retina

Bipolar cells are responsible for transmitting light signals from the photoreceptors to the ganglion cells in the vertebrate retina. Their maturation process is not only important for establishing normal visual function, but may also underlie the dendritic remodeling of ganglion cells during development. It is known that light deprivation affects the synaptic connections of ganglion cells in the mammalian retina, but little is known about impact of visual experience on bipolar cell development. We used dye injection and gene gun labeling to identify bipolar cells, and characterized their morphological differentiation in normal-reared and dark-reared rabbits. Our results show that immature bipolar cells can be found as early as P1-3, and most characteristic bipolar cells can be identified during P4-6. More importantly, we found that light deprivation causes a delay rather than a permanent arrest of bipolar cell maturation in the rabbit retina. By eye opening at P10-11, both normal-reared and dark-reared rabbits possessed adult-like bipolar cells. This suggests that visual experience has a facilitating effect on the morphological differentiation of bipolar cells.

Sundowning and circadian rhythm disorders in dementia

Sleep disorders and disruptive nocturnal behaviours are commonly reported in people with senile dementia and present both a significant clinical problem and a cause of increased stress for caregivers. Neuronal degeneration of cholinergic Nucleus basalis Meynert (NBM) neurons promote rest-activity disturbance and Sundowning in Alzheimer's disease. NBM neurons modulate the activity of the mainly cholinergic suprachiasmatic nucleus (SCN) and the induction of NONREM sleep. Sundowning might be explained as a syndrome occurring when arousal is to be processed while the neocortex is already turned "off" to (NONREM) sleep. The therapeutic measures should thus primarily be aimed at the stimulation of the circadian system and enforcing "external Zeitgebers". Pharmacologically, application of cholinergic enhancers i.e. cholinesterase inhibitors and melatonin supports and should stabilize the weakened structures.

Distinct Roles for Spontaneous and Visual Activity in Remodeling of the Retinogeniculate Synapse

Sensory experience and spontaneous activity play important roles in development of sensory circuits; however, their relative contributions are unclear. Here, we test the role of different forms of activity on remodeling of the mouse retinogeniculate synapse. We found that the bulk of maturation occurs without patterned sensory activity over 4 days spanning eye opening. During this early developmental period, blockade of spontaneous retinal activity by tetrodotoxin, but not visual deprivation, retarded synaptic strengthening and inhibited pruning of excess retinal afferents. Later in development, synaptic remodeling becomes sensitive to changes in visually evoked activity, but only if there has been previous visual experience. Synaptic strengthening and pruning were disrupted by visual deprivation following 1 week of vision, but not by chronic deprivation from birth. Thus, spontaneous activity is necessary to drive the bulk of synaptic refinement around the time of eye opening, while sensory experience is important for the subsequent maintenance of connections.

The use of sudden darkness in mice: a behavioural and pharmacological approach

Sudden darkness is a non-invasive behavioural analysis tool which increases motor activity and decreases anxiety in rats. It has been shown in previous studies that in rats, dark test conditions can also modify behavioural responses to drugs acting on the dopaminergic system. The increasing use of transgenic mice in behavioural research has raised interest in developing new tests for phenotyping mice. Hence, the aim of the present study was to adapt the sudden darkness paradigm for mice. In the first part of this study, effects of sudden darkness on the performance of mice in the elevated plus maze test were evaluated. Both genders of two mouse strains (Swiss and Balb/c) were tested either in high light intensity conditions or were exposed to sudden darkness. In the second part, responses to the 5-HT(1A) receptor agonist 8-OH-DPAT (0.5 and 1.0 mg/kg) and 5-HT(2C) receptor agonist mCPP (1.0 and 2.0 mg/kg) were investigated in male Swiss mice. Sudden darkness induced a clear anxiolytic effect in male and female Swiss mice. In Balb/c mice, anxiety-related behaviour was only decreased in females, whereas in males the anxiety state remained unchanged. An increase in motor activity was only observed in male Swiss mice; in the other groups, sudden darkness did not affect locomotion. Depending on the light conditions used, the behavioural response to receptor agonists was more evident: 8-OH-DPAT (1.0 mg/kg) only significantly decreased the anxiety state when mice were tested under high levels of illumination, whereas the anxiogenic effect of mCPP (1.0 and 2.0 mg/kg) was only evident in the dark. This study suggests that the sudden darkness paradigm is also a useful tool for the analysis of mice and can be used to modulate the anxiety level without administering drugs. Depending on the mouse strain tested, the same effects on anxiety and motor activity were observed as have been shown for rats.

Families at high and low risk for depression: a three-generation startle study

BACKGROUND

Anxiety symptoms might be a vulnerability factor for the development of major depressive disorder (MDD). Because elevated startle magnitude in threatening contexts is a marker for anxiety disorder, the present study investigated the hypothesis that enhanced startle reactivity would also be found in children and grandchildren of individuals with MDD.

METHODS

The magnitude of startle was investigated in two tests (anticipation of an unpleasant blast of air and during darkness) in children (second generation) and grandchildren (third generation) of probands with (high risk) or without (low risk) MDD (first generation).

RESULTS

Startle discriminated between the low- and high-risk groups. In the probands' children, the high-risk group showed increased startle magnitude throughout the fear-potentiated startle test. In the probands' grandchildren, a gender-specific abnormality was found in the high-risk group with high-risk girls, but not boys, exhibiting elevated startle magnitude throughout the procedure.

CONCLUSIONS

Increased startle reactivity in threatening contexts, previously found in patients with anxiety disorder and in children of parents with an anxiety disorder, might also constitute a vulnerability marker for MDD. These findings suggest that there might be common biologic diatheses underlying depression and anxiety.

Effects of sibutramine on anxiety-related behaviours in rats

Sibutramine is an anorexiant drug that inhibits the reuptake of noradrenaline and serotonin, a pharmacological property shared with drugs clinically effective in treating anxiety pathologies. However, the effects of this compound on experimental and clinical anxiety have not been assessed yet. In this study, we evaluated the effects of sibutramine on anxiety-related behaviours which have been related to specific anxiety disorders. Acute injection of sibutramine (5, 10 or 20 mg kg(-1); intraperitoneally) in male Wistar rats impaired inhibitory avoidance in the elevated T-maze (ETM) and in the light/dark transition test, indicative of an anxiolytic effect. The drug also inhibited one-way escape in the ETM. Sibutramine, however, was ineffective in changing rat performance in the elevated plus-maze. Therefore, sibutramine decreased the expression of defensive behaviours that have been associated with generalized anxiety disorder (inhibitory avoidance) and with panic disorder (one-way escape). Yet, in contrast to what has been reported with drugs such as the tricyclic anti-depressants that also inhibit monoamine reuptake, the anxiolytic effects of sibutramine were revealed after a single administration.

Acute vigabatrin retinotoxicity in albino rats depends on light but not GABA

PURPOSE

Vigabatrin (VGB) is an irreversible inhibitor of gamma-aminobutyric acid (GABA) transaminase. Its use as an antiepileptic drug (AED) has been limited because it causes retinal dysfunction, leading to visual field defects (VFDs). We performed this study to identify factors contributing to acute VGB retinotoxicity.

METHODS

In ex vivo experiments, Sprague-Dawley rat retinas were isolated and incubated with VGB or GABA in the presence or absence of light. In in vivo experiments, Sprague-Dawley rats were given intraperitoneal injections of VGB and then exposed to light or kept in the dark. The retinas were analyzed histologically by using both light and electron microscopy.

RESULTS

Incubating retinas with 50-500 microM VGB under 20,000 Lux white light for < or = 20 h caused a characteristic time- and dose-dependent degeneration limited to the outer retina. Incubating retinas with 500 microM VGB in darkness for 20 h caused no damage. Five hundred micromolar GABA and 50 microM tiagabine were not toxic in the presence or absence of light. Sprague-Dawley rats exposed to an intense white light for 20 h after a 1,000-mg/kg intraperitoneal injection of VGB showed damage in the outer retina, whereas those kept in the dark did not.

CONCLUSIONS

Direct exposure of the retina to VGB causes acute retinotoxicity that depends on light exposure rather than GABA accumulation.

Influence of visual experience on developmental shift from long-term depression to long-term potentiation in the rat medial vestibular nuclei

The influence of visual experience deprivation on changes in synaptic plasticity during postnatal development was studied in the ventral part of the rat medial vestibular nuclei (vMVN). We analysed the differences in the occurrence, expressed as a percentage, of long-term depression (LTD) and long-term potentiation (LTP) induced by high frequency stimulation (HFS) of the primary vestibular afferents in rats reared in the light (LR) and those in the dark (DR). In LR rats, HFS only induced LTD in the early stages of development, but the occurrence of LTD progressively decreased to zero before their eyes opened, while that of LTP enhanced from zero to about 50%. Once the rats' eyes had opened, LTD was no longer inducible while LTP occurrence gradually reached the normal adult value (70%). In DR rats, a similar shift from LTD to LTP was observed before their eyes opened, showing only a slightly slower LTD decay and LTP growth, and the LTD annulment was delayed by 1 day. By contrast, the time courses of LTD and LTP development in DR and LR rats showed remarkable differences following eye opening. In fact, LTD occurrence increased to about 50% in a short period of time and remained high until the adult stage. In addition, the occurrence of LTP slowly decreased to less than 20%. The effect of light-deprivation was reversible, since the exposure of DR rats to light, 5 days after eye opening, caused a sudden disappearance of LTD and a partial recover of LTP occurrence. In addition, we observed that a week of light deprivation in LR adult rats did not affect the normal adult LTP occurrence. These results provide evidence that in a critical period of development visual input plays a crucial role in shaping synaptic plasticity of the vMVN, and suggest that the visual guided shift from LTD to LTP during development may be necessary to refine and consolidate vestibular circuitry.

Developmental regulation of spine and filopodial motility in primary visual cortex: reduced effects of activity and sensory deprivation

Dendritic protrusions are highly motile during postnatal development. Although spine morphological plasticity could be associated with synaptic plasticity, the function of rapid spine/filopodial motility is still unknown. To investigate the role of spine motility in the development of the visual cortex and its relation with critical periods, we used two-photon imaging of neurons from layers receiving visual input in developing mouse primary visual cortex and compared motility between control and visually deprived animals. Spine and filopodia motility was prominent during early synaptogenesis (P11-P13) but greatly decreased after P15. This "switch" was coincident with a 2.5-fold increase in protrusion density and spine formation. Spine motility was not regulated during the critical period for monocular deprivation (P19-P34). Moreover, delaying the critical period by dark rearing did not delay the normal developmental decrease of spine motility, but caused a modest further reduction in motility at P28-P35. Dark rearing and enucleation also mildly reduced spine motility before eye opening and dark rearing reduced the proportion of filopodia. We conclude that (1) rapid spine motility is not related to critical period plasticity, but is likely to play a role in early synaptogenesis, and (2) neuronal activity stimulates spine motility during synaptogenesis and promotes the appearance of dendritic filopodia.

Anxiolytic properties of the antipsychotic alkaloid alstonine

Anxiolytic properties may be a crucial feature of newer antipsychotics associated with the improvement of negative symptoms in schizophrenic patients. The indole alkaloid alstonine acts as an atypical antipsychotic in behavioral models, but differs in its dopamine and serotonin binding profile. The purpose of this study was to verify if alstonine possesses anxiolytic properties in mice. The hole-board and light/dark models were used; moreover, the participation of D(1), 5-HT(2), NMDA and gamma-aminobutyric acid (GABA) receptors was likewise investigated. Alstonine clearly behaves as anxiolytic in both hole-board and light/dark situations. Pretreatment with the 5-HT(2A/2C) serotonin receptor antagonist ritanserin reverted the effects of alstonine in both the hole-board and light/dark models, suggesting the involvement of these receptors in the alstonine mechanism of action. The involvement of glutamate NMDA receptors should also be considered, given that alstonine partially reversed the increase in locomotion induced by MK-801 in the hole board, as well as MK-801-induced hyperlocomotion in motor activity apparatus.

Zn and Cu alteration in connection with astrocyte metallothionein I/II overexpression in the mouse brain upon physical stress

The distribution of metallothioneins I/II in the mouse brain and their specific area distribution upon physical stress were studied. To induce physical stress, groups of mice were subjected to total darkness for different periods (2 weeks, 1 month, and 2 months). The concentration of metallothioneins, evaluated by immunohistochemistry, as well as area-specific protein expression, were found in the following quantitative order: corpus striatum, cerebellum, mesencephalon, hippocampus with fornix, parts of thalamus, and pons. All other brain areas were marginally affected, or even unaffected, in terms of immunopositive metallothionein reaction. Metallothionein I/II expression was compared with the immunopositivity of glial fibrillary acidic protein (GFAP). It is noteworthy that metallothioneins and GFAP are expressed in different types of astrocytes.

Functional retinal input stimulates expression of astroglial elements in the suprachiasmatic nucleus of postnatal developing rat

Astrocytes are abundant in the hypothalamic suprachiasmatic nucleus (SCN), particularly in the retinorecipient region. Using glial fibrillary acidic protein (GFAP) immunocytochemistry, we investigated the effect of light on the development of astrocytes in the SCN housing under light-dark (LD) or constant dark (DD) conditions after birth. GFAP immunoreactivity in the DD group showed lower levels than those in the LD group at P50. However, there was no difference in density of retinohypothalamic tract (RHT) terminals in the SCN between the DD and LD groups. After the adult pattern of GFAP immunoreactivity was established at P30, transferring rats to different LD conditions produced changes in GFAP immunoreactivity evident when rats were sacrificed at P50. We next examined, using a primary culture of hypothalamic astrocytes, whether neurotransmitters of RHT such as glutamate and pituitary adenylate cyclase activating polypeptide (PACAP) can stimulate GFAP expression directly. PACAP-38 increased the length and number of astrocytic processes but glutamate did not. These findings indicate that the functional aspects of RHT such as the light stimulated release of neurotransmitters is important for the development of astrocytes in rat SCN. Dynamic plasticity of astroglial elements in the SCN occurs even after GFAP shows an adult pattern.

Diurnal variations in human urinary excretion of nicotinamide catabolites: effects of stress on the metabolism of nicotinamide

BACKGROUND

More than 500 enzymes need niacin coenzymes. Therefore, elucidation of the control mechanisms of coenzyme metabolism is fundamentally important.

OBJECTIVE

NAD(+) is involved in ATP production. Because energy expenditure is generally higher during the day than at night, we investigated whether the metabolism of nicotinamide changes at various times of day and whether stress affects nicotinamide metabolism.

DESIGN

Twelve women were housed in the same facility and followed the same schedule for activities of daily living for 12 d. Urinary outputs were collected during 5 specific periods to investigate diurnal variations in nicotinamide metabolism. The effects of cold exposure (physical stress), having to perform arithmetic calculations (mental stress), and dark exposure (emotional stress) on nicotinamide metabolism were investigated.

RESULTS

A diurnal variation in the nicotinamide metabolites N(1)-methylnicotinamide, N(1)-methyl-2-pyridone-5-carboxamide, and N(1)-methyl-4-pyridone-3-carboxamide was observed. Of the stresses studied, cold exposure significantly increased the urinary excretory outputs of the nicotinamide metabolites.

CONCLUSIONS

Diurnal variations in nicotinamide metabolism were found in these women. The biosynthesis of nicotinamide from tryptophan seemed to be increased by cold exposure.

Effects of dark rearing on phosphorylation of neurotrophin Trk receptors

Total lack of visual experience (dark rearing, DR) is known to affect development of mammalian visual cortex (VC) and to prolong the critical period of visual cortical plasticity. Neurotrophins (NTs) have been proposed to play a relevant role in activity dependent processes important for the final shaping of cortical visual connections. Neurotrophin supply or antagonism of endogenous NT action profoundly affect visual cortical development and plasticity; in particular, exogenous supply of NTs counteracts DR effects on VC development. However, the effects of DR on NT expression are still debated and mounting evidence reports a mismatch between BDNF mRNA and protein expression in DR animals. To gain insight into the effects of DR on expression of nerve growth factor (NGF) and the functional state of NT signalling pathways, we assessed the phosphorylation state of Trk receptors in light-reared animals (LR), in dark-reared animals (DR), in DR animals briefly exposed to light and in DR animals with exogenous supply of NTs [NGF, brain-derived neurotrophic factor (BDNF) and NT-4] in the VC. We report that DR increases the expression of NGF but reduces the phosphorylation of TrkA and TrkB receptors with respect to LR; normal phosphorylation is rapidly rescued by a brief exposure to light. Exogenous supply of NGF, BDNF or NT4 in DR animals also rescues the phosphorylation of their receptors.

Effects of stress on the urinary excretory pattern of niacin catabolites, the most reliable index of niacin status, in humans

Urinary output of water-soluble vitamins has been used as an indices for vitamin nutrition. It has been pointed out that the coefficient variance of these values is high, especially for niacin catabolites. Thus, we investigated what kinds of stress affect the catabolism using female subjects. The effects of cold exposure (as a typical physical stress), calculation exercise (a typical mental stress) and dark exposure (a typical emotional stress) on the metabolism of niacin were investigated. Of the stresses, cold exposure significantly increased urinary excretory output of the niacin metabolites. The biosynthesis of nicotinamide from Trp seemed to be increased by cold exposure.

Effect of darkness on inner retinal hypoxia in diabetes

It has been postulated that diabetic retinopathy might be initiated by hypoxia during the hours of darkness. Oscillatory potentials, which reflect inner retinal function, are reduced in diabetic patients. We tested the effect of oxygen inhalation on the amplitude of these oscillatory potentials after dark adaptation in seven patients with type 2 diabetes and eight controls. We found that the decreased oscillatory potentials induced by dark adaptation in the diabetic patients increased during oxygen inhalation to an amplitude that was not significantly different from that of the controls before oxygen. Oscillatory potentials in the controls were unaffected by oxygen. This finding strengthens support for the suggestion that diabetic patients might benefit from sleeping with night-time illumination.

Basal increase in c-Fos-like expression in superior colliculus of Royal College of Surgeons dystrophic rats can be abolished by intraocular injection of tetrodotoxin

In normal rats maintained in the dark, very few cells in the primary visual centers, including the superior colliculus, show Fos-like immunoreactivity. By contrast, in rats presented with flashing lights many Fos-like immunoreactivity cells are observed distributed throughout the visual centers. In the dystrophic Royal College of Surgeons rat, in which there is major loss of photoreceptors over the first 3 months of life, similar numbers of Fos-like immunoreactivity cells are seen on light presentation, but in marked contrast, cell densities in the rats maintained in the dark are many times higher than in non-dystrophic rats maintained under similar conditions. Here we show that this elevated dark response can be abolished by intravitreal injection of the sodium channel blocker tetrodotoxin, indicating that this effect results from changed retinal activity, rather than being centrally generated. We suggest that since Fos-like immunoreactivity is not usually elicited by steady state conditions, the elevated levels in the superior colliculus in these animals reflect the return of waves of activity, first seen in development coursing across the retina, but lost with photoreceptor maturation.

Pattern of REM sleep occurrence in continuous darkness following the exposure to low ambient temperature in the rat

The occurrence of REM sleep episodes, separated by intervals >3 min (single episodes) and < or =3 min (sequential episodes), was determined in the rat during the recovery (ambient temperature (Ta) 23 degrees C, L period of the LD [12 h:12 h]-cycle), which followed the exposure to low Ta (0 and -10 degrees C) during the D period of the previous LD-cycle, either in normal light (DL) or in continuous darkness (DD). Both exposures were characterized by an almost complete disappearance of REM sleep, whilst the recoveries showed an increase in the amount of REM sleep in the form of sequential episodes, which in DD was particularly prominent and concomitant with a decrease in the amount of REM sleep in the form of single episodes. The initial 2 h-rate of REM sleep occurrence was lower following the exposure to Ta -10 degrees C, than to Ta 0 degrees C. In DD, such an effect was due to the large reduction in the occurrence of sequential REM sleep episodes. A functional correlate of this finding is that the accumulation capacity of a second messenger (cAMP) was found to be lower at the end of the exposure to Ta -10 degrees C, with respect to both the control (Ta 23 degrees C) and the end of exposure to Ta 0 degrees C, in the preoptic-anterior hypothalamus, but not in the cerebral cortex.

Light irradiation increases embryotoxicity of photodynamic therapy sensitizers (5-aminolevulinic acid and protoporphyrin IX) in chick embryos

Photodynamic therapy (PDT) of malignant processes is based on the ability of a photosensitizer to first, accumulate in malignant (immature) tissue and second, to be destroyed following light irradiation. Because of the similarity between malignant and embryonic immature tissues, we investigated the deleterious effect of the PDT procedure on day 4 chick embryos in ovo. We compared experimentally the photodynamic effect (light-toxic) and the side effect (dark-toxic) of the clinically attractive photosensitizers 5-aminolevulinic acid (ALA) and protoporphyrin IX (PP IX). The dark and light embryotoxicity (i.e. lethality plus teratogenicity) was determined after intra-amniotic injection of one of a range of dose of each compound. Under dark conditions, PP IX exhibited embryotoxicity at a dose of 10 microg/embryo; however ALA did not exhibit embryotoxicity even at the highest dose (300 microg/embryo). Light irradiation of embryos following injection induced strong embryotoxic effects of both substances even at dark-ineffective doses.

Differential effect of dark rearing on long-term potentiation induced by layer IV and white matter stimulation in rat visual cortex

In the earlier work, we showed that primed-burst stimulation (PBs) is an effective protocol to induce long-term potentiation (LTP) in layer II/III of adult rat visual cortex in vitro. In the present study, we investigated effects of dark rearing on potentiation of layer II/III responses to stimulation of layer IV or the underlying white matter in the visual cortex in vitro. Long-term potentiation was induced by PBs applied to white matter or layer IV of the cortex in light and dark reared rats. Regardless of the stimulation site, layer II/III field potentials consisted of two components. In general, the latency of responses in dark reared rats was shorter than that in light reared ones. Whereas PBs of layer IV produced LTP of two components in both the groups, that of white matter induced an appreciable potentiation of the second component in both groups and the first component only in dark reared rats. These results indicate that PBs of either white matter or layer IV can gain access to the modifiable synapses that are related to the second component of layer II/III responses in light and dark reared visual cortex, but accessibility of the modifiable synapses that are related to first component depends on the tetanization site. The dark rearing enhances accessibility of the modifiable synapses that are related to the first component following PBs of the white matter. It is suggested that the immaturity of inhibitory circuits and/or better function of excitatory ones in the visual cortex of dark reared rats may contribute to the enhanced accessibility of the first component.

Effects of dark-rearing on triphenyl phosphate-induced neuropathy in the visual system of the developing European ferret (Mustela putorius furo)

Results of a previous study in our lab (Tanaka et al., 1994) suggested that the onset of susceptibility to the organophosphorus compound triphenyl phosphite (TPP) in the developing ferret visual system might be closely related to eye opening and the onset of light stimulation. In order to explore this idea further, TPP was administered to ferret kits that had been raised for varying periods of time in total darkness to assess whether a delay in the onset of light stimulation to the visual system might also result in a delay in its susceptibility to TPP. Ferret kits were raised from birth either in total darkness or in open-sided sheds exposed to ambient light, injected subcutaneously with TPP (888 mg/kg body weight) at 5.5, 7.5, 9.5, or 21.5 wk of age, euthanized, and perfused transcardially with a 10% formalin-saline solution 4 d after injection. Brains were sectioned parasagittally at a thickness of 40 microm and subsequently processed with the Fink-Heimer silver impregnation technique to reveal the presence of degenerating axons and terminals, and with cresyl violet stain to delineate nuclear boundaries and cell soma morphology. Comparisons among degeneration patterns present in light-reared and dark-reared kits at the four ages examined revealed that the time of onset, extent, and density of TPP-induced axonal and terminal degeneration seen in the lateral geniculate nucleus and primary visual cortex did not differ significantly between light- and dark-reared groups, with the possible exception of dark-reared kits exposed to TPP at 7.5 wk of age. In addition, neurons in the primary visual cortex showed shrinkage and increased packing densities in kits exposed to TPP in both light and dark environments, as well as in dark-reared non-injected kits. The results of this study indicate that dark-rearing does not delay the onset or lessen the severity of TPP-induced axonal and terminal degeneration in the developing visual system of the ferret. Data suggest that light activation and stimulation of the retino-geniculo-striatal visual pathway is not a necessary prerequisite for the onset of visual system susceptibility to the axonopathic effects of triphenyl phosphite.

Differential expression of immediate-early genes, c-fos and zif268, in the visual cortex of young rats: effects of a noradrenergic neurotoxin on their expression

We investigated the expression pattern of two immediate-early genes, zif268 and c-fos, under various visual conditions using immunohistochemical and northern blot analysis in the visual cortex of young rats. The basal expression of c-fos was low and was further reduced by dark rearing that lasted for one week. A marked and transient increase was induced upon visual stimulation applied immediately after dark rearing. Zif268 showed a relatively high basal level. Its expression was reduced by dark rearing of the animals, but returned rapidly to the basal expression level following the introduction of light. Administration of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, a selective noradrenergic neurotoxin, suppressed the basal expression of c-fos messenger RNA. The response of c-fos to photo-stimulation was also significantly lower in the visual cortex of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine-treated young rats. In contrast, no significant change in zif268 expression was detected between normal and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine-treated animals. These findings suggest that differential expression of these immediate-early genes is involved in the activity-dependent regulation of cortical function. One possibility is that the noradrenergic system controls cortical function, including plasticity, by modifying the expression of c-fos.

The hazard of spatial disorientation during helicopter flight using night vision devices

INTRODUCTION

Night Vision Devices (NVDs) provide an enormous advantage to the operational effectiveness of military helicopter flying by permitting flight throughout the night. However, compared with daytime flight, many of the depth perception and orientational cues are severely degraded. These degraded cues predispose aviators to spatial disorientation (SD), which is a serious drawback of these devices.

METHODS

As part of an overall analysis of Army helicopter accidents to assess the impact of SD on military flying, we scrutinized the class A-C mishap reports involving night-aided flight from 1987 to 1995. The accidents were classified according to the role of SD by three independent assessors, with the SD group further analyzed to determine associated factors and possible countermeasures.

RESULTS

Almost 43% of all SD-related accidents in this series occurred during flight using NVDs, whereas only 13% of non-SD accidents involved NVDs. An examination of the SD accident rates per 100,000 flying hours revealed a significant difference between the rate for day flying and the rate for flight using NVDs (mean rate for daytime flight = 1.66, mean rate for NVD flight = 9.00, p < 0.001). The most important factors associated with these accidents were related to equipment limitations, distraction from the task, and training or procedural inadequacies.

CONCLUSIONS

SD remains an important source of attrition of Army aircraft. The more than fivefold increase in risk associated with NVD flight is of serious concern. The associated factors and suggested countermeasures should be urgently addressed.

Fixation-off (Scoto) sensitivity combined with photosensitivity

A 16-year-old boy of normal intelligence had brief absence and myoclonic jerks since age 7 years. Video-EEG documented the unexpected combination of fixation-off sensitivity (scotosensitivity) with photosensitivity.

Transplant of Schwann cells allows normal development of the visual cortex of dark-reared rats

Visual experience is necessary for the correct development of the visual cortex. Dark-rearing from birth affects normal maturation of the functional properties of mammalian visual cortex: cortical cells show rapid habituation to repeated stimulation, decreased orientation selectivity, and enlarged receptive fields. Spatial resolution and response latency are also impaired. Recent experiments have demonstrated that visual deprivation reduces the expression of neurotrophins in the visual cortex. We formulated the hypothesis that visual experience drives the maturation of functional properties of the visual cortex by regulating cortical levels of neurotrophins. If this hypothesis is correct, exogenous supply of neurotrophins during dark-rearing from birth should prevent, or at least ameliorate, the effects of a lack of visual experience. Since Schwann cells are efficient biological minipumps of neurotrophic factors, we transplanted 1.0 or 1.5 x 10(6) Schwann cells or infused vehicle solution as a control into the lateral ventricles of 13 day old rats reared in total darkness from birth until the end of the critical period (postnatal day 45). Single-cell responses and visual-evoked potentials were recorded from the binocular zone of the primary visual cortex of each group. We found that in Schwann cell-transplanted animals all parameters tested were significantly improved upon those of dark-reared control rats and were in the range of normal adult values. Thus, Schwann cell transplant contributed to the normal development of visual response properties in the visual cortex, compensating for a complete absence of visual experience.

gamma-Aminobutyric acid and somatostatin immunoreactivity in the visual cortex of normal and dark-reared rats

Our previous single unit and ultrastructural studies of visual cortex of dark-reared rats revealed an impairment of intracortical inhibitory mechanisms [2,3,5]. Neurochemical changes in inhibitory neurotransmitter and/or neuropeptides, such as gamma-aminobutyric acid (GABA) and somatostatin (SS), respectively, may contribute to the observed alterations. The present study was designed to measure GABA and SS alterations in the visual cortex of the same dark-reared preparation, as possible neurochemical correlates of the changes seen both physiologically and anatomically in previous companion studies. In the present investigation the mean densities of GABA- and SS-immunoreactive neurons in area 17 of dark-reared rats were determined and compared to the density of those of rats reared in normal lighting conditions. Dark-rearing resulted in a significant decrease in the density of GABA-immunoreactive neurons in all cell layers of area 17 of the rat visual cortex; not limited to the thalamorecipient layer(s). There was also a higher mean density of total cortical cells in dark-reared animals. No differences, however, were seen in the density of SS-immunoreactive neurons. The alterations of GABA-immunoreactive neurons in all cortical layers agree with the altered synaptic ultrastructure and physiological responses seen in all cortical layers as reported in our previous companion studies. Taken together, these studies further support the notion of a deficit in intracortical inhibitory mechanisms in the visual cortex of dark-reared adult rats.

Postnatal development of neuropeptide Y-containing neurons in the visual cortex of normal- and dark-reared rats

The postnatal development of neuropeptide Y (NPY)-immunoreactive neurons in the visual cortical areas (17, 18 and 18a) has been studied in Wistar rats reared under normal lighting conditions or in complete darkness. Immunohistochemistry on paraffin sections at postnatal days (P)7, 14, 21, 30 and 60 showed an overall similarity in laminar distribution of NPY neurons in all 3 visual areas of both normal- and dark-reared animals. The pattern of development of NPY neurons was characterized by an increase in their density from P7 to reach a peak at P21 followed by a decline to 37-47% of peak levels at P60. However, this diminution was not so great in dark-reared rats as in the normal, since the density only decreased to 62-78% of peak levels. At P60 the resulting differences in neuron density were marked in areas 17 and 18, where the dark-reared had 75% more cells than normal, and moderate in area 18a (30% more than normal). These results suggest that the normal decline in NPY neurons is not entirely mediated by visual experience since it takes place, albeit to a modified extent, in its total absence.

Thyroid hormone changes during military field operations: effects of cold exposure in the Arctic

This study examined the effect of prolonged physical activity in a cold environment upon circulating thyroid hormone levels. A secondary focus of the study involved the role of nocturnal habitat upon the thyroidal responses to the physical activity and cold exposure. Military personnel exposed to 10 d of field-based operations in the arctic region of Norway were studied. Blood samples were collected before (day 1), and at days 5 and 10 of the operations. Levels of total T4, free T4, total T3, free T3, and thyroid binding globulin were assessed in all blood samples. The results indicated considerable, significant (p less than 0.05) decreases in total thyroid hormone levels, while relative increases of free fractions of the hormones occur with the 10-d operations in the Arctic. However, no significant influence on thyroidal responses were observed due to the nocturnal habitat that the subjects lived in. The hormonal alterations noted are possibly brought about by the combined effects of physical activity and cold exposure acting synergistically to alter thyroid physiology (e.g., most likely the protein carrier binding affinity).

Long-term effects of dark rearing on a visually guided reaching movement in cats

The existence of long-term effects of dark-rearing on visuo-motor coordination is still controversial. In this study 2 dark-reared (DR) cats were trained, after 5-6 years of recovery, to perform a reaching movement towards a stationary or a moving target. The accuracy, and the reaction and movement times were evaluated. The scores obtained by the DR cats were compared to those of normal subjects after a similar period of training. The results showed that while the accuracy of DR cats was not impaired, the performance of their reaching movements was slower than normal and its triggering was delayed. These data are discussed with regards to electrophysiological and behavioural data obtained on analogous DR cats after long-term recovery.

Manipulations of sleep and phototherapy: nonpharmacological alternatives in the treatment of depression

Manipulations of sleep and light (for winter depression) rapidly improve mood in 60% of depressed patients. These two unconventional treatments for depression may prove useful in patients who do not respond to drug treatments, in patients who prefer nonpharmacological treatments, or as adjuncts to drug treatments. This article reviews research on the parameters of effective sleep and light treatments and their biological mechanisms. The results of recent experiments suggest that the depressant effect of sleep may depend on thermoregulatory adjustments that occur after sleep begins.

Dark-rearing retards the maturation of astrocytes in restricted layers of cat visual cortex

The cat visual cortex develops its mature appearance, i.e., its circuitry and neuronal morphology, during a limited period of postnatal development under the influence of visual experience. The critical period for cortical plasticity, which normally extends from the third to seventh postnatal week, can be prolonged by raising animals in total darkness. The prolongation of the critical period by dark-rearing is restricted to the cortical layers except layer IV. Besides the influence of afferent activity on the physiology of cortical cells and on the interconnectivity of thalamo-cortical afferents, visual experience has also been shown to affect the development of glial cells. The present study investigates the effects of dark-rearing on astroglial characteristics as determined by immunostaining for glial fibrillary acidic protein (GFAP) and the S-100 protein. The data reveal a retardation of astrocytic maturation in dark-reared animals, shown by a reduced presence of GFAP immunoreactivity compared to light-experienced animals. The density of astrocytic cell bodies positive for S-100 is unaffected by dark-rearing, suggesting that astroglial proliferation does not rely on afferent activity. However, punctate S-100 staining in the neuropil, which has been shown to reflect astrocytic processes, was also reduced in certain cortical layers in dark-reared animals. The effects of dark-rearing on the expression of GFAP and S-100 were restricted to the cortical layers except layer IV, i.e., those layers that reveal a prolongation of the critical period for cortical plasticity following dark-rearing. It is concluded that astrocytic maturation in the visual cortex is influenced by neuronal activity.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of ondansetron (GR38032F) in rats and mice treated subchronically with diazepam

Using rat and mouse models of aversive behaviour, we have further investigated the properties of the 5-HT3 receptor antagonist ondansetron (GR38032F) that are relevant to its proposed use as an anxiolytic agent. Tolerance to the disinhibitory properties of diazepam was readily demonstrated in the social interaction test in the rat, but did not occur after subchronic treatment with ondansetron. In both the light/dark exploration test in mice and the social interaction test in rats, withdrawal from subchronic treatment with diazepam increased behavioural suppression, whereas this was not observed with ondansetron. The behavioural suppression and weight loss induced by either the withdrawal of diazepam or the administration of the benzodiazepine receptor antagonist, flumazenil, in animals treated subchronically with diazepam, was prevented or antagonised by diazepam or ondansetron. Buspirone was ineffective. It is concluded that, in rats and mice, tolerance to the disinhibitory effects of ondansetron does not occur, that withdrawal from subchronic treatment with ondansetron is not associated with any behavioural disturbances and that ondansetron is highly effective in preventing the behavioural suppression and weight loss following withdrawal from subchronic diazepam treatment. These data suggest that ondansetron may have major therapeutic advantages over currently available anxiolytic agents, particularly in patients who have previously received prolonged benzodiazepine therapy.

The occurrence of the vection illusion among helicopter pilots while flying over water

U.S. Coast Guard helicopter pilots were questioned on the occurrence of the vection illusion while flying over water under different light and sea conditions. A total of 267 (79.9%) pilots completed the study questionnaire. The illusion of vection was experienced by 248 (92.5%) of these pilots. The majority of the pilots, 209 (84.6%), reported that dark rather than light visual conditions increased the likelihood of experiencing vection. Vection was considered likely to occur over rough seas by more pilots [114 (46.2%)] then over smooth seas [81 (37.8%)]. Several pilots commented that they had responded to the illusion with aircraft movement. The vection illusion is a common experience among helicopter pilots while flying over open water. Low light conditions and rough sea states are conducive to experiencing the vection illusion. Pilots may respond to the illusion with aircraft control movements, which raises flight safety concerns.

Visual display lowers detection threshold of angular, but not linear, whole-body motion stimuli

The influence of a visual display, fixed relative to the subject, on thresholds for detection (at 75% correct) of discrete Y-axis linear movements and of discrete Z-axis angular movements, was determined in a group of 12 subjects. Both the linear and the angular, whole-body, motion stimuli had a cosine bell velocity trajectory with a duration of 2.6 s. Thresholds for the detection of the linear motion stimuli in darkness were not significantly different from those obtained when either a simple LED display or an instrument dial were illuminated; the mean threshold was 0.039 m.s-2. None of the subjects reported apparent movement of the visual display. In contrast, the presence of either visual display lowered angular motion thresholds on average by a factor of 2.7 from that obtained in darkness (1.61 degrees.s-1). All subjects reported apparent movement of the visual display, an oculogyral illusion, at stimulus intensities close to the dark threshold. These findings imply that otolithic afferents, unlike those from the semicircular canals, do not interact with neural centres mediating visual localization.