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Graham C - - 2000
Magnetic field-induced suppression of nocturnal melatonin in humans has been reported in occupational and residential studies, but not in laboratory-based exposure studies. The present study examined whether this contrasting pattern of results might be related to associated differences in exposure duration or to field-induced measurement instability over time. Thirty healthy ...
Kim H E - - 2000
With civilized environments in modern society, since the people tend to depend more on artificial illumination than on natural illumination which makes less discrepancy between day and night life, clarifying the relationship between human life and illumination is necessary. In our previous studies, we found that the subjects dressed faster ...
Lockley S W - - 2000
Although melatonin treatment has been shown to phase shift human circadian rhythms, it still remains ambiguous as to whether exogenous melatonin can entrain a free-running circadian system. We have studied seven blind male subjects with no light perception who exhibited free-running urinary 6-sulphatoxymelatonin (aMT6s) and cortisol rhythms. In a single-blind ...
Lewczuk Bogdan - - 2000
OBJECTIVES: Results of the majority of studies have revealed that diurnal changes in circulating melatonin level in the domestic pig differ from the typical patterns observed in other species. The aim of the present investigation was to study the effect of continuous darkness and continuous illumination on plasma melatonin in ...
Nathan P J - - 2000
It is well known that light is an inhibitor of pineal melatonin secretion in humans. However, the effect of gender on the melatonin suppression by dim and bright light is still controversial. The present study investigated the effect of gender on the suppression of melatonin at five light intensities (0, ...
Walker J F - - 1999
A number of studies have found that cigarette smoking causes an acute increase in resting energy expenditure, but the effect on energy expenditure during light physical activity is less clear. Since both smoking and activity have been shown to increase plasma catecholamines, these could produce additive effects on energy expenditure ...
Firth B T - - 1999
We assessed how chronic exposure to 6-h cryophase temperatures of 15 degrees C in an otherwise 33 degrees C environment entrains the rhythm of blood plasma melatonin rhythms in lizards (Tiliqua rugosa) subjected to constant dark (DD), constant light (LL), and to 12:12-h light-dark cycles (12L:12D). The peak of the ...
Hébert M - - 1999
Ocular light exposure can phase shift circadian rhythms and suppress nocturnal melatonin production. A recent finding suggests that extraocular light can also produce phase shifts in humans. We investigated whether extraocular light could also suppress melatonin secretion in humans. We assayed the salivary melatonin of 16 subjects during a baseline ...
Kazimi N - - 1999
We investigated the time course of circadian system development in zebrafish and the role of environmental light cycles in this process, using a rhythm in melatonin content of embryos and larvae as a marker of circadian function. When zebrafish were raised in a cycle of 14 h light and 10 ...
Green C B - - 1999
The retinal photoreceptors of Xenopus laevis contain a circadian clock that controls the synthesis and release of melatonin, resulting in high levels during the night and low levels during the day. Light is also an important regulator of melatonin synthesis and acts directly to acutely suppress melatonin synthesis during the ...
Funk D - - 1999
Male rats were given 5 min of intermittent footshock, or were not shocked, for 3 or 5 consecutive days in a novel context at the midpoint of the dark phase of a 12:12-h light:dark cycle. Six days later, animals were reexposed to the context without footshock and received either a ...
Martínez-Soriano F - - 1999
In the mammalian pineal gland, synaptic bodies (SBs) are poorly understood organelles. Previous studies in rabbits have shown that the organelles are rather heterogeneous in shape, are few in number during the day and increase in number at night. No studies are currently available on seasonal changes in this species ...
Hätönen T - - 1999
BACKGROUND: In order to clarify the role of light in regulating body functions in sleeping humans, we studied whether the light-sensitive pineal hormone melatonin can be suppressed by facial light exposure in subjects with closed eyelids. METHODS: Eight healthy volunteers participated in 3 nightly sessions: a dim-light control session (< ...
Benloucif S - - 1999
In mammals the phase shifting response of the circadian clock to light can be enhanced by administration of the calcium channel antagonist nimodipine. In the present study we assessed the potential for nimodipine to affect the responsiveness of the human circadian clock to light by measuring the light-induced suppression of ...
Scheer F A - - 1999
The effect of light on the morning-cortisol peak in humans was investigated in fourteen healthy men by exposing them to darkness and to light of 800 lux during a 1-h period on two subsequent mornings. In the early morning, we demonstrated a temporary increase of salivary cortisol levels after awakening, ...
Grace M S - - 1999
Vertebrate retinal photoreceptors periodically shed membrane from their outer segment distal tips; this material is phagocytosed and degraded by the retinal pigmented epithelium. Both a circadian oscillator and the daily light-dark cycle affect disk shedding, and the effects of both may be mediated by melatonin. To clarify melatonin's role in ...
Macías M - - 1999
The unicellular organism Trypanosoma cruzi is an eukaryote whose cell cycle mainly occurs under darkness in the insect gut. The unique external phase corresponds to the metacyclic forms, the forms that are able to infect humans, which appear within the insect deyections. Thus, light may be a powerful stressor in ...
Benloucif S - - 1999
Melatonin and light synchronize the biological clock and are used to treat sleep/wake disturbances in humans. However, the two treatments affect circadian rhythms differently when they are combined than when they are administered individually. To elucidate the nature of the interaction between melatonin and light, the present study assessed the ...
Sabry I - - 1999
In the present study, the pineal gland of the gerbil Gerbillus cheesmani was described for the first time. According to their electron density, two distinct cell types were observed (light and dark pinealocytes). The nuclei were either oval or irregular. Moderate amount of granular endoplasmic reticulum (GER) was observed. Free ...
Lewy A J - - 1999
Several circadian rhythms have been used to assess the phase of the endogenous circadian pacemaker (ECP). However, when more than one marker rhythm is measured, results do not always agree. Questions then inevitably arise. Are there multiple oscillators? Are some markers more reliable than others? Masking is a problem for ...
Heeke D S - - 1999
BACKGROUND AND PURPOSE: A novel light-emitting diode (LED) light source for use in animal-habitat lighting was evaluated. METHODS: The LED was evaluated by comparing its effectiveness with that of cool white fluorescent light (CWF) in suppressing pineal gland melatonin content and maintaining normal retinal physiology, as evaluated by use of ...
Burch J B - - 1999
The effects of geomagnetic disturbances on urinary excretion of the melatonin metabolite, 6-hydroxymelatonin sulfate (6-OHMS), were studied in conjunction with 60 Hz magnetic field (MF) and ambient light exposure in 132 electric utility workers. Geomagnetic activity was assessed using a local (equivalent amplitude or A(K), Boulder, CO) and global (average ...
Okimoto D K - - 1999
The properties of the melatonin-generating system of a tropical teleost, the sailfin molly (Poecilia velifera), were investigated in vitro in a series of experiments using static or perifusion culture techniques. The properties examined included photic entrainment, circadian rhythmicity under continuous light (LL) and continuous darkness (DD), functionality of the melatonin-generating ...
Park S J - - 1999
The effects of bright light exposure during the daytime on circadian urinary melatonin and salivary immunoglobulin A (IgA) rhythms were investigated in an environmental chamber controlled at a global temperature of 27 degrees C+/-0.2 degrees C and a relative humidity of 60%+/-5%. Seven diurnally active healthy females were studied twice, ...
Lucas R J - - 1999
Pineal melatonin production is rapidly suppressed by light. In mammals, the photoreceptors mediating this response are ocular; however, definitive information regarding their nature and precise location is absent. In an attempt to define these photoreceptors, we examined the sensitivity of pineal melatonin production to inhibition by controlled irradiance monochromatic green ...
Visser E K - - 1999
This study investigated whether sensitivity of the nocturnal melatonin suppression response to light depends on the area of the retina exposed. The reason to suspect uneven spatial sensitivity distribution stems from animal work that revealed that retinal ganglion cells projecting to the suprachiasmatic nuclei (SCN) are unequally distributed in several ...
Marchiafava P L - - 1999
Dark-adapted, single photoreceptors isolated from the frog retina produce reactive oxygen species (ROS) after about 1 min of illumination with saturating light that we verified by their oxidation of preloaded dihydrorhodamine 123 (DHR) into the fluorescent rhodamine 123 (RHO). In this preparation we tested the antioxidant effects of vitamin E ...
Sakakibara S - - 1999
To investigate the effects of 8000 lux morning bright light in the elderly, home-based motor activity on sleep was monitored for 5 days in 10 healthy women (mean age: 59.7 years old, range: 50-69 years old). The activity level and movement index on night 4 were significantly lower in bright ...
Takahashi T - - 1999
To estimate the process of re-entrainment we measured the melatonin rhythm on an eastward flight. After the baseline study, 24-hour blood sampling of six male subjects was done on the first and fifth days. During the daytime the subjects were exposed to natural zeitgeber outdoors every day except the blood ...
Zawilska J B - - 1999
Effects of near-ultraviolet light (UV-A; 325-390 nm, peak at 365 nm) on the activity of the pineal serotonin N-acetyltransferase (NAT; a key regulatory enzyme in melatonin biosynthesis) were examined in chicks. Acute exposure of dark-adapted animals to UV-A radiation produced a marked decline in NAT activity of the pineal gland. ...
Partonen T - - 1999
Melatonin may be a key factor in the regulation of seasonal variation in gonadal activity. The circadian disturbances related to reproduction are probably subsequent to the seasonal change. Moreover, melatonin might also be considered essential for both spermatogenesis and folliculogenesis. Exposure to bright light, suppressing the concentration of melatonin in ...
Chen L W - - 1999
HPLC with EC detector was used to study the red light effect on the rhythmicity of catecholamines (NE, DOPAC and dopamine) and indoleamines (NAS, 5-HT, 5-HIAA) in the pineal glands and retinas of the Sprague-Dawley rat. We found the prominent nocturnal elevations of NAS in rat pineal glands and the ...
Apeldoorn E J - - 1999
The effect of melatonin and lighting schedule on energy metabolism in broiler chickens was studied. Eight groups of six female broiler chickens each were assigned to a continuous lighting schedule [23 h light (L):1 h darkness (D)] or an intermittent lighting schedule (1L:3D), and were fed a diet with or ...
Nathan P J - - 1999
Patients with bipolar disorder have been shown to have a supersensitive melatonin suppression to dim white light (200 and 500 lux) compared to normal healthy subjects. Previous studies suggest menstrual cycle dependent changes in the melatonin rhythm, but it is not known if the melatonin sensitivity to light changes during ...
Carskadon M A - - 1999
Circadian timing was assessed with forced desynchrony (FD) in 10 healthy adolescents (five boys, five girls; mean age 13.7 years). Following 10 days of entrainment to a fixed light-dark (LD) schedule at home, participants were studied under dim light (<20 lux) in the laboratory. A 28-h schedule (FD) was imposed ...
Vondrasová-Jelínková D - - 1999
Fifteen human subjects were exposed to natural outdoor summer light from 0415 h until 2000 h for 4 days and then from 0800 h until 1600 h for another 4 days. Following shortening of the natural summer photoperiod, times of the morning salivary melatonin decline and cortisol rise did not ...
Adachi A - - 1999
Our previous study has shown that the phases of circadian rhythms of ocular melatonin and dopamine are always opposite and intraocular melatonin injection suppresses dopamine release. Therefore, it is possible that dopamine rhythms result from inhibitory action of melatonin. We have examined this possibility in the following experiments. In the ...
Rodríguez A B - - 1999
A functional role for melatonin is its relationship to circadian timing mechanisms. In addition, there has recently been assumed to be a functional connection between the pineal gland and the immune system in mammals and birds, with some findings showing melatonin to be a free radical scavenger and general antioxidant. ...
Zeman M - - 1999
In contrast to the situation in mammals, in which circadian melatonin production by the pineal gland does not begin until some time after birth, the development of pineal gland rhythmicity is an embryonic event in the precocial domestic fowl. A distinct melatonin rhythm was found in 19-d-old chick embryos maintained ...
Cardinali D P - - 1999
Melatonin is synthesized and secreted during the dark period of the light/dark cycle. The rhythmic nocturnal melatonin secretion is directly generated by the circadian clock, located within the suprachiasmatic nuclei in mammals and is entrained to a 24-hour period by the light-dark cycle. The periodic secretion of melatonin may be ...
Lewy A J - - 1999
The most useful marker for human circadian phase position is the dim light melatonin onset (DLMO). This is optimally obtained by sampling blood or saliva in the evening at intervals of 30 min or less. Ambient light intensity should not exceed 30-50 lx. For many years, the DLMO was determined ...
Csernus Valér - - 1999
Avian pineals show rhythmic, circadian melatonin secretion pattern also in vitro. The phase of this rhythm can be modified by changing the illumination. Reversed in vitro illumination reverses the phase of the circadian melatonin rhythm in two days. In the present study the effect of the wavelength on the speed ...
Bellavía S L - - 1998
In man, the rate of resting salivary secretion can be influenced by environmental stimuli related to light dark cycles or by noxious stimuli (stressors) of psychological origin. The sympathetic branch of the autonomic nervous system and the adrenal medulla play an important part in homeostatic responses. Previous observations have shown ...
Montgomery M K - - 1998
The symbiotic light organ of the sepiolid squid Euprymna scolopes undergoes significant anatomical, morphological, and biochemical changes during development. Previously we described the embryonic organogenesis and early postembryonic development of the light organ. During embryogenesis, tissues are developed that will promote the onset of an association with Vibrio fischeri, the ...
Nøddegaard F - - 1998
1. In 2 experiments with Single Comb White Leghorn hens, the effects of different light:dark cycles (LD-cycles) upon oviposition patterns and plasma melatonin rhythms were studied. In experiment 1, a 28-h ahemeral LD-cycle (12L:16D) was used. In experiment 2, a normal 24-h LD-cycle (16L:8D) was applied and the effects of ...
Lerchl A - - 1998
Based on findings in various mammalian species, where exposure to electromagnetic fields decreased the nocturnal synthesis of the pineal secretory product melatonin, we investigated the effects of magnetic field (MF) exposure in a teleost fish, the brook trout (Salvelinus fontinalis). Fields were generated by Helmholtz coils (maximum flux density 40 ...
Partonen T - - 1998
A group of specialized photoreceptors are suggested to amplify the weak interaction of the geomagnetic field with a single electron spin to the level of photon detection, resulting in a modulation of the response to light. Under exposure to rotating magnetic field, the size of pinealocytes is bigger at night ...
Mayeda A - - 1998
An indirect lighting protocol was developed to measure nocturnal melatonin suppression by light in normal human subjects. Goals were to minimize both discomfort due to staring intensely at a bright light source, and behavioral variation due to wandering gaze. Subjects sat with a bank of five full-spectrum light sources placed ...
Lewy A J - - 1998
BACKGROUND: According to the phase-shift hypothesis for winter depression, morning light (which causes a circadian phase advance) should be more antidepressant than evening light (which causes a delay). Although no studies have shown evening light to be more antidepressant than morning light, investigations have shown either no difference or morning ...
Arendt J - - 1998
The primary function of melatonin in mammals is to transmit information concerning light-dark cycles for the organization of day length dependent on seasonal functions. There is little evidence for an essential role in circadian organization in mammals, in contrast with lower vertebates. It does, however, appear to reinforce physiological functions ...
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