Search results for "Light exposure"
showing 9 items of 9 documents
Circadian Rhythm Variations and Nutrition in Children
2018
AbstractCircadian rhythms are the changes in biological processes that occur on a daily basis. Among these processes are reactions involved in metabolic homeostasis. Circadian rhythms are structured by the central clock in the suprachiasmatic nucleus of the hypothalamus via the control of melatonin expression. Circadian rhythms are also controlled by the peripheral clocks, which are intracellular mechanisms composed of the clock genes, whose expression follows a circadian pattern. Circadian rhythms are impacted by signals from the environment called zeitgebers, or time givers, which include light exposure, feeding schedule and composition, sleeping schedule and pattern, temperature, and phy…
The effects of post-awakening light exposure on the cortisol awakening response in healthy male individuals.
2019
Abstract Background It is assumed that the expression of the cortisol awakening response (CAR) is modulated by light exposure during the peri-awakening period. While initial evidence supports this principal effect, the specific role of the spectral composition of light (brightness and wavelength) is still incompletely understood. Method Two counterbalanced within-subject experiments were conducted in a standardized sleep laboratory setting to investigate the effect of light intensity (study I; two days: dim vs. bright light) and spectral composition (study II; three days: red vs. blue vs. green light) on the CAR. Across studies, light exposure was conducted for one-hour post-awakening and t…
The effects of light exposure on the cortisol stress response in human males.
2020
It is assumed that the production of cortisol is modulated by light exposure. While initial evidence supports this principal effect, the specific effect of light (intensity and wavelength) onto the cortisol stress response is still not completely understood. One between-subject experiment was conducted in a standardized sleep laboratory setting to investigate the effect of light intensity (dim white vs. bright white light) and spectral composition (red vs. blue) on the cortisol response after the Maastricht Acute Stress Test (MAST). 112 healthy young males (24.83 ± 4.10 years of age) were randomly assigned to one of the four light conditions. Across conditions, light exposure was conducted …
Light exposure patterns in schizophrenia
1992
Spontaneous light exposure patterns were studied in 10 chronic schizophrenic patients. Half of our schizophrenic patients exposed themselves to bright light exceeding ordinary indoor illumination. There was a significant positive correlation between the percentage of exposure to bright light and the Brief Psychiatric Rating Scale subscore anergia and a significant negative correlation with depression.
Preoperative factors influencing success in pterygium surgery
2012
Abstract Background To identify preoperative, perioperative and postoperative risk factors that influence the success of pterygium surgery. Methods This is a prospective study of thirty-six patients with primary or recurrent pterygia. A detailed anamnesis and an ophthalmological examination were performed looking for the following factors: age, race, latitude and altitude of the main place of residence, hours of exposure to the sun, use of protective measures against UV-radiation, classification of pterygium, width of the pterygium at limbus, surgical technique (conjunctival autograft plus suturing versus tissue glue), graft alterations (misapposition, granuloma, haemorrhage, oedema, retrac…
Increase in cortisol concentration due to standardized bright and blue light exposure on saliva cortisol in the morning following sleep laboratory
2020
Research studies on LED light exposure and cortisol are inconsistent and not comparable due to different types of light, exposure times, and sample sizes. Therefore, one hour of standardized exposure LED light at different intensities and the spectral composition during the post-awakening phase at 7:30 were compared. A sample of 23 (Study 1) and 26 (Study 2) healthy males were randomly assigned to: 1) bright white light (414 lux) and 2) dim darkened light (2 lux) as well as 3) red light (235 lux) and 4) blue light (201 lux) exposure conditions. Results from repeated measures ANOVA confirm that light exposure affects the cortisol concentration. Study 1 revealed an increase in the saliva cort…
Electroretinographic response in WAG/Rij rats after low-intensity cyclic light exposure.
1993
In order to investigate the combined influence of age and light, the b-wave and oscillatory potentials (OPs) of the electroretinogram (ERG) were recorded in 1.5-, 7- and 12-month-old WAG/Rij rats, reared under homogenous low-intensity cyclic light exposure. Wistar albino rats of the same ages, reared under the same conditions, served as controls. The b-wave amplitude decreased, and its implicit time increased in the older age groups significantly more in WAG/Rij than in Wistar rats. Statistical analysis indicated that the b-wave amplitude is a more suitable parameter than implicit time in differentiating the ERG variations of one rat strain from the other. The added amplitude of the OPs als…
Light exposure of the lower leg as a pathogenetic factor in the occurrence of malignant melanoma.
1992
Of the 1,198 women and men studied in Mainz from 1966 to 1987 there was an approximately fivefold increase in the incidence of melanoma. Among the men melanomas on the trunk (59.9%) predominated, whereas among the women melanomas on the extremities (40.0%) were more common, especially on the lower leg (26.3%). Comparing the decades 1966-1976 and 1977-1987 there was a significant decrease in melanomas affecting women's lower legs (1966-1976: 33%,; 1977-1987: 24.2%). Fashion-dependent sun exposure of this body area might offer an explanation. It could be demonstrated that common stocking materials do not sufficiently protect against UV radiation (average permeability for UV light about 55%), …
The effect of dental chair light exposure duration on shear bond strength of orthodontic brackets : an in vitro study
2018
Background The purpose of this study is to determine if the duration of exposure to the halogen overhead dental chair light has an effect on shear bond strength (SBS) of metal orthodontic brackets. Material and Methods One hundred twenty extracted human lower incisor teeth were divided into six groups (n=20/group). Each group was assigned a predetermined duration of exposure to the halogen dental chair light, set at a fixed distance, before being cured. Light exposure times of 0 minutes (Group 1-Control), 1 minute (Group 2), 2.5 minutes (Group 3), 5 minutes (Group 4), 10 minutes (Group 5), and 15 minutes (Group 6) were tested. Each tooth was subjected to an exclusion criteria examination, s…