Effect Of Blue Light Exposure Research Articles

Prolonged Blue Light Exposure Does Not Elicit Adverse Changes to Physical Activity in Male Mice

Color plays a role in human and animal circadian rhythm patterns, behaviors, and emotional responses. Environments containing blue colors improve information storage in humans and reproductive success in animals; however, environments containing blue light influence behavioral and emotional responses in rodents and humans in adverse ways. Exposure to blue light alters sleeping patterns, induces the stress response, and elicits depressive behaviors. These initial responses then affect awake time functionality and productivity. Under normal physiological conditions, mice, when provided access to an in-cage running wheel, exhibit high levels of nocturnal physical activity behavior. It is unknown if this nocturnal behavior changes after prolonged blue light exposure. Therefore, this project's hypothesis is wheel running utilization decreases after exposure to blue light during the diurnal restful period in the normally nocturnal mouse. The purpose of this study was to expose mice to overhead blue LED lights during the daytime rest period and to examine nighttime physical activity patterns. Daily wheel running distance, duration, and speed monitoring in C57BL/6j male mice (n=12) occurred for 21 days. During the second week of the study, an experimental group (n=6) underwent blue light-emitting diode (LED) light exposure, and a control group (n=6) experienced white LED light exposure at the same intensity. The lights were on a 12-hour light/dark cycle at full brightness during the exposure period. Differences in wheel running distance, duration, and speed following exposure to blue LED light were assessed via individual two-way (group by phase of study) ANOVAs. Blue LED light exposure did not appear to affect average daily wheel running distance [F=0.42, p=0.57], duration [F=0.79, p=0.42], or speed [F=0.08, p=0.87]. Following exposure to blue LED light during the restful diurnal period, wheel running remained stable. This lack of effect indicates that mechanisms may exist to protect mice from the adverse effects associated with blue light exposure, especially as it pertains to participating in routine physical activity. These postulated mechanisms may allow robust participation in physical activity-related behaviors in these animals and represent a potential biological regulator that could aid in mitigating the adverse effects of blue light exposure experienced in humans. All funding for this research was provided by the Union University Department of Biology. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of Blue Light on Puberty and Ovary in Female Rats

This study was designed to examine the effect of blue light exposure and exposure time on puberty in an animal model. Eighteen 21-day-old female Sprague Dawley rats were divided into three equal groups which were: control group (CG); blue light-6 hours (BL-6); and blue light-12 hours (BL-12). CG rats were maintained with 12/12-hour light-dark cycles. The animals in BL-6 and BL-12 were exposed to blue light of wavelength 450-470 nm and intensity of 0.03 uW/cm2 for 6 and 12 hours, respectively. Exposure to blue light continued until the first signs of puberty. Serum follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol, testosterone, dehydroepiandrosterone sulfate (DHEA-S), leptin and melatonin were measured. Subsequently the ovaries and uterus were examined histomorphologically. The median day of puberty start was 38, 32 and 30 for the CG, BL-6, and BL-12 groups, respectively (p=0.001). FSH, testosterone, DHEA-S, and leptin concentrations of all groups were similar. However, LH and estradiol concentrations in BL-6 were higher compared to CG (p=0.02). There was a negative correlation between blue light exposure, exposure time, and melatonin concentrations (r=-0.537, p=0.048). Ovarian tissue was compatible with puberty in all groups. As blue light exposure time increased, capillary dilatation and edema in the ovarian tissue increased. Prolonged exposure was associated with polycystic ovary-like (PCO) morphological changes and apoptosis in granulosa cells. These results suggest that exposure to blue light and the duration of exposure induced earlier puberty in female rats. As the duration of blue light exposure increased, PCO-like inflammation, and apoptosis were detected in the ovaries.

Is blue light exposure a cause of precocious puberty in male rats?

Our study aimed to examine the effects of blue light exposure on prepubertal male rats' puberty and testis tissue. Eighteen 21-day-old male Sprague Dawley rats were divided into three groups consisting of six rats in each group: Control Group (CG), Blue Light-6 hours (BL-6), and Blue Light-12 hours (BL-12). CG rats were maintained with 12/12-hour light-dark cycles. The rats of BL-6 and BL-12 were exposed to blue light (450-470nm/irradiance level 0.03uW/cm2) for 6 hours and 12 hours, respectively. Rats were exposed to blue light until the first signs of puberty. The ELISA method was used to analyze the serum levels of FSH, LH, testosterone, DHEA-S, leptin, ghrelin, melatonin, glutathione, glutathione peroxidase, and malondialdehyde. Testes were dissected for histomorphological examination. The medians of the pubertal entry days of the CG, BL-6, and BL-12 were 38th, 30th, and 28th days, respectively. (p:0.001) The FSH, LH, and testosterone concentrations of all groups were similar. The FSH concentration increased as the LH concentration increased (r: 0.82 p: 0.001). The serum LH concentration increased as serum testosterone, and DHEAS decreased, respectively (r: -0.561, p: 0.01) (r:-0.55 p:0.01). Testicular lengths and weights of the BL groups were smaller compared to CG (p: 0.03),(p: 0.04). GPx was higher for BL-6 and BL-12 than the CG (p:0.021, p:0.024). Testis tissue was compatible with the pubertal period in all groups. As the blue light exposure time increased, spermatogenesis was suppressed, and capillary dilatation and edema in the testis tissue increased. Our study is the first to show the effects of blue light exposure on male rats' puberty process. And we showed that exposure to blue light and the duration of exposure lead to precocious puberty in male rats. The blue light exposure suppressed spermatogenesis, marked vasodilatation in the interstitial area of the testis, and disrupted the integrity of the basement membrane. These findings intensified with increasing exposure time.

Determination of intensity and spread of light to the surrounding in conventional phototherapy and comparison with novel converging photo unit — an observational study

BackgroundBlue light phototherapy used extensively in the management of hyperbilirubinemia has many side effects like dry eyes, blurring, headache, and altered circadian rhythm. Healthcare providers working around the phototherapy are unduly exposed to these side effects. Altered circadian rhythm results in disruption in the sleep-wake cycle affecting healthcare providers particularly working during the night shift. The constant glare of the blue light interrupts in clinical observation of the baby on phototherapy. With the intent of providing effective phototherapy with minimal exposure of blue light to healthcare providers, a light source called the photo unit was designed and developed.The objective of this study was to estimate the intensity and spread of blue light to the surrounding in conventional phototherapy and to compare the same with newly developed converging photo unit.ResultsThe therapeutic range of irradiance was noted up to 22 inch in diameter with conventional phototherapy compared to only 7 inch with our photo unit. The light spread with a conventional phototherapy unit was seen beyond 50 inch in all directions whereas was confined to 19-inch diameter with photo unit.ConclusionPhoto unit developed by the authors has minimal divergence of light to the surrounding, thereby mitigating the side effects of blue light exposure to the people working in the vicinity. Multiple of these photo units can be used to make a phototherapy device.

Effect of blue light and nanosilver on vase life, antioxidant enzymes and some other physiologic parameters of Alstroemeria ‘Napoli’ cut flowers

The effects of postharvest blue light exposure have never been studied on cut flowers, so the present study aimed to explore the effects of blue light exposure duration (6, 12, 18, and 24 h) and silver nanoparticle (SNP) application (5, 10, 15, and 20 mg l−1) on the quantitative and qualitative traits of cut Alstroemeria ‘Napoli’ flowers. The control flower received distilled water without blue light exposure. The longest vase life (22.66 days) was related to 10 mg l−1 SNP, not differing from 12 h of blue light exposure (22.00 days) and 20 mg l−1 SNP (21.66 days), significantly. The highest water uptake and total chlorophyll and the lowest ethylene were obtained from the flowers treated with 10 mg l−1 SNP or exposed to 12 h of blue light. These two treatments outperformed the control in reducing MDA accumulation too. APX activity was significantly higher in the flowers treated with 12 h of blue light exposure, 18 h of blue light exposure, or 15 mg l−1 SNP. Except for the blue light exposure for 6 h, all treatments reduced stem-end bacteria versus the control. The lowest bacterial population (57.3 Log10 CFU ml−1) belonged to the flowers treated with 15 mg l−1 SNP. Blue light outperformed SNP in stopping the growth of Gram-positive bacteria and yeast. Based on the results, blue light is introduced as a physical factor to improve the quantitative and qualitative traits of cut Alstroemeria ‘Napoli’ flowers.

Age-dependent effects of blue light exposure on lifespan, neurodegeneration, and mitochondria physiology in Drosophila melanogaster

Blue light is a predominant component of light emitting devices (LEDs), which are increasingly present in our environment. There is already accumulating evidence that blue light exposure causes damage to retinal cells in vitro and in vivo; however, much less is known about potential effects of blue light on non-retinal cells. That blue light may be detrimental at the organismal level independent from retinal effect was recently shown by findings that it reduces lifespan in worms and also in flies with genetically ablated retinas. Here, we investigated the effects of blue light exposure across the fly lifespan and found that susceptibility to blue light stress is strongly age-dependent. The blue light of the same intensity and duration reduced survival and increased neurodegeneration more significantly in old flies than in young flies. These differences appear to be caused, at least in part, by impairments of mitochondrial respiratory function. We report that blue light significantly reduces the activity of Complex II in the electron transport system and decrease the biochemical activity of succinate dehydrogenase in both young and old flies. In addition, complex I and complex IV activities are reduced by age, as are ATP levels. We therefore propose that older flies are more sensitive to blue light because the light-induced mitochondrial damage potentiates the age-related impairments in energy metabolism that occurs even in darkness. Taken together, our results show that damaging effects of blue light at the organismal level are strongly age dependent and are associated with reduced activity of specific components of energy producing pathways in mitochondria.

P76. Blue Light Exposure Results in Quicker Decision Time Without Sacrificing Accuracy in a Two-Armed Bandit Task

Exposure to blue light has been shown to enhance several aspects of cognitive performance, including faster response times when participants must make a decision. This study investigated the effect of blue light exposure on response times to a modified two-armed bandit task in which the likelihood of positive and negative outcomes alternate between arms throughout the task and must be determined through trial and error.

Blue Light Induces Impaired Autophagy through Nucleotide-Binding Oligomerization Domain 2 Activation on the Mouse Ocular Surface.

In this study, we investigated the effects of blue light exposure on nucleotide-binding oligomerization domain 2 (NOD2) expression on the mouse ocular surface and evaluated the role of NOD2 activation in light-induced cell death. Mice were divided into wild-type (WT), NOD2-knock out (KO), WT + blue light (WT + BL), and NOD2-KO + blue light (NOD2-KO + BL) groups, and the mice in the WT+BL and NOD2-KO + BL groups were exposed to blue light for 10 days. After 10 days of blue light exposure, increased reactive oxygen species and malondialdehyde were observed in the WT + BL and NOD2-KO + BL groups, and the WT + BL group showed a higher expression of NOD2 and autophagy related 16 like 1. Although both WT+BL and NOD2-KO + BL groups showed an increase in the expression of light chain 3-II, NOD2-KO + BL mice had a significantly lower p62 expression than WT + BL mice. In addition, NOD2-KO+BL mice had significantly lower corneal epithelial damage and apoptosis than WT + BL mice. In conclusion, blue light exposure can induce impaired autophagy by activation of NOD2 on the ocular surface. In addition, the reactive oxygen species (ROS)–NOD2–autophagy related 16 like 1 (ATG16L) signaling pathway may be involved in the blue-light-induced autophagy responses, resulting in corneal epithelial apoptosis.

Long-Term Blue Light Exposure Changes Frontal and Occipital Cerebral Hemodynamics: Not All Subjects React the Same.

In modern society, we are increasingly exposed to numerous sources of blue light, including screens (e.g., TVs, computers, laptops, smartphones, tablets) and light from fluorescent and LED lamps. Due to this wide range of applications, the effects of blue light exposure (BLE) on the human physiology need to be thoroughly studied. To investigate the impact of long-term BLE on frontal and occipital human cerebral hemodynamics and oxygenation using functional near-infrared spectroscopy (fNIRS) neuroimaging. 32 healthy right-handed subjects (20 females, 12 males; age: 23.8±2.2years) were exposed to blue LED light for 15minutes. Before (baseline, 8min) and after (recovery, 10min) the BLE, subjects were in darkness. We measured the concentration changes of oxyhemoglobin ([O2Hb]) and deoxyhemoglobin ([HHb]) at the prefrontal cortex (PFC) and visual cortex (VC) by fNIRS during the experiment. Subjects were then classified into different groups based on their hemodynamic response pattern of [O2Hb] at the PFC and VC during BLE. On the group level (32 subjects), we found an increase in [O2Hb] and a decrease in [HHb] at both cortices during BLE. Evoked changes of [O2Hb] were higher at the VC compared to the PFC. Eight different hemodynamic response patterns were detected in the subgroup analysis, while an increase of [O2Hb] in both cortices was the most common pattern (8 out of 32 cases, 25%) during BLE. Our study showed that the hemodynamic and oxygenation changes at the PFC and VC during BLE (i) were generally higher in the VC compared to the PFC, (ii) showed an intersubject variability with respect to their magnitudes and shapes, and (iii) can be classified into eight groups. We conclude that blue light affects humans differently. It is essential to consider this when assessing the impact of the BLE on society.

Blaulichtgefährdung der Augen durch Lichtemittierende Dioden (LED)?

Blue light from light-emitting diodes (LED): a risk to the eyes? Background: In occupational and domestic environments people are increasingly exposed to artificial light from light-emitting diodes (LEDs). LEDs have peak emission in the blue range. In this review, we summarise the current knowledge of the possible effects of blue light exposure on ocular health. Effects of blue light on the regulation of physiological functions will be considered elsewhere. Methods: We performed a narrative review. We included preclinical data as well as epidemiological studies. We searched MEDLINE, Pubmed, the Cochrane Library and International Standard Randomised Controlled Trial Number (ISRCTN)-Register clinical trial registers from 01 January 2014 to 31 May 2019. Results: The accumulated experimental evidence obtained from different experimental models has indicated that excessive exposure to blue light can induce damage in the retinal pigment epithelium (RPE), in photoreceptors and ganglion cells. Previous epidemiological findings are equivocal regarding any causal links between blue light exposure and the development of macular degeneration (AMD). In vitro and in vivo evidence suggests that blue light exposure may influence the progression of uveal melanoma. Conclusions: Long-term effects of LEDs on ocular health cannot be definitively assessed on the basis of current knowledge. Susceptibility to blue light damage varies among the different species. The severity of light-induced retinal damage changes with the time of the day and depends on the diet and genetic background. Additional studies on the safety of long-term exposure to low levels of blue light are needed to determine the safety of LEDs for ocular health. Keywords: blue light – light-emitting diode – macular degeneration – uveal melanoma

Oxidative stress and endoreduplication induced by blue light exposure to CHO cells

Blue light is commonly used for the treatment of Neonatal Jaundice and as a photodynamic therapy for cancer. In comparison to ultraviolet light, blue light has a lower toxicity due to the differences in photon energies. However, blue light can still be mutagenic to cells. The proposed mechanism suggests blue light exposure induces reactive oxygen species inducing oxidative stress. In this study, we examined how blue light exposure caused genotoxic effects utilizing Chinese hamster ovary (CHO) cells and UV135 cells when exposed to fluorescent blue light. Cytotoxic effects of blue light exposure were quantified through cellular oxidative stress analysis, cell survival assay, and in cell cycle arrest experiments. Genotoxicity was studied in sister chromatid exchange (SCE) only, and endoreduplication formation. Following blue light exposure, an increase of cell cycle arrest, oxidative stress, and cytotoxicity was observed. Blue light treatment also produced an increased amount of SCE, and more importantly, induced endoreduplicated chromosomes. In conclusion, exposure to blue light resulted in significant genotoxicity of the treated cells.

The Impact of Cumulative Exposure to Blue Light during The Developmental Period of Melanopsin ipRGCs

Previous study revealed that exposure to blue light during postnatal period decrease the function of NIF in mice. However, duration effect of blue light exposure during the developmental period of melanopsin ipRGCs is still unknown. Twenty four Swiss-Webster pregnant mice exposure to 470 nm blue light spectrum of the LED lights and sunlight. As a control group pregnant mice was keep in no light condition. The length of exposure was varies based on the stage of development: (1) from gestation day 9 (E9) up to 18 days of gestation (E18), (2) newborn to 6 days old, (3) from gestation day 9 until aged 6 days old. At 6 days old, selected mice pups were performed for negative phototaxis using cylindrical bore assay. The sunlight mice groups showed that the fastest response occur on longer exposure. However, on blue light mice groups, the longer the exposure actually decreases the activity more compare to only postnatal exposure. These conditions maybe due to interference on synaptogenesis during developmental period of melanopsin ipRGCs. Thus it can be concluded that exposure to blue light since in utero until neonatal is harmful especially to NIF response behavior.

Evoke of The Motoric Brain Waves of Driver in Car Simulator at Night by Blue Light Exposure and Visual Distraction

Driving at night need high levels of concentration for respond any visual stimulation by motoric coordination. Such concentration while driving can be mounted using blue light inside the car’s compartment, since it can inhibit the secretion of melatonin hormone, to increase drivers’ alertnessand prevent drowsiness at night. This study was aimed to evaluate the effect of blue light exposure on µ brain waves while driving at night in the simulator as a response to visual distraction. Brain waves data were recorded using electroencephalograph in brain motor areas from 7 men with predetermined criteria. Data were taken at night (7-9 pm) for 330 seconds in dark condition and blue light exposure, followed by the appearance of visual distraction automatically at 120 and 270 seconds and should be responded by braking. In blue light condition, µ brain waves were fluctuated in both motor areas since the first appearance of blue light exposure and was significantly different when compared to dark condition (p<0.05). It is concluded that blue light exposure at night in a driving simulator may increase drivers’ brain activity in the motor areas when responding to visual distraction, especially in the first appearance.

Blue Light Exposure and Visual Distraction Effect of The Cognition Brain Waves of Driver in Car Simulator at Night

Driving is a complex activity and driver must respond quickly and accurately to any visual distraction. Accidents are high while driving at night, may due to drivers’ drowsiness which is caused by the environmental light that affect the circadian rhythm. Blue light is a component of the solar spectrum and inhibit the secretion of melatonin hormone that can prevent drowsiness at night. This study is aimed to evaluate the effect of blue light exposure on β brain waves while driving at night in the simulator as a response to visual distraction. Brain waves data were obtained from electroencephalograph in brain cognition area from 7 men with predetermined criteria. Data were taken from 7–9 pm for 330 seconds in dark condition and blue light exposure followed by the appearance of visual distraction automatically at 120 and 270 seconds and should be responded by braking. The result showed than β brain waves increased under blue light which was associated with area of cognition and was significantly different when compared to dark condition (p<0.05). It is concluded that blue light exposure at night driving in simulator increase drivers’ alertness and attention when responding to visual distraction, especially in the first appearance.

Effects of blue light spectra on retinal stress and damage in goldfish (Carassius auratus).

There have been a number of studies on the negative effects of blue light exposure in various species; however, little information is available on the impacts of blue light intensity and duration on fish. We investigated the effects of blue light spectra on stress in the retinas of goldfish, using a blue (460nm) light-emitting diode (LED) at three intensities (0.5, 1.0, and 1.5W/m2). The experiment was conducted for 4weeks, and sampling was performed at intervals of 1week. We measured changes in the expression of cortisol, and the concentrations of hydrogen peroxide (H2O2), melanin-concentrating hormone receptor (MCH-R), and caspase-3 in the retinas of goldfish. In addition, we measured histological changes in the retina. We used a transferase dUTP nick end labeling (TUNEL) assay to evaluate the apoptotic response to blue LED spectra. Levels of cortisol, H2O2, MCH-R, and caspase-3 increased with exposure time and light intensity. Histological analysis revealed that the thickness of melanin granules increased with exposure time and light intensity. The progressive TUNEL assay revealed many apoptotic cells after exposure to blue LED light, increasing with exposure time and light intensity. Irradiation with blue light for longer than 1week induced increased retinal stress and may induce apoptosis in the retinas of goldfish, even at a low intensity.

Blue light-induced immunosuppression in Bactrocera dorsalis adults, as a carryover effect of larval exposure.

Detrimental effects of ultraviolet (UV) light on living organisms are well understood, little is known about the effects of blue light irradiation. Although a recent study revealed that blue light caused more harmful effects on insects than UV light and blue light irradiation killed insect pests of various orders including Diptera, the effects of blue light on physiology of insects are still largely unknown. Here we studied the effects of blue light irradiation on cuticular melanin in larval and the immune response in adult stage of Bactrocera dorsalis. We also evaluated the effects of blue light exposure in larval stage on various age and mass at metamorphosis and the mediatory role of cuticular melanin in carryover effects of larval stressors across metamorphosis. We found that larvae exposed to blue light decreased melanin contents in their exoskeleton with smaller mass and delayed metamorphosis than insects reared without blue light exposure. Across metamorphosis, lower melanotic encapsulation response and higher susceptibility to Beauveria bassiana was detected in adults that had been exposed to blue light at their larval stage, thereby constituting the first evidence that blue light impaired adult immune function in B. dorsalis as a carryover effect of larval exposure.

Nrf2 protects photoreceptor cells from photo-oxidative stress induced by blue light

Oxidative stress plays a key role in age-related macular degeneration and hereditary retinal degenerations. Light damage in rodents has been used extensively to model oxidative stress-induced photoreceptor degeneration, and photo-oxidative injury from blue light is particularly damaging to photoreceptors. The endogenous factors protecting photoreceptors from oxidative stress, including photo-oxidative stress, are continuing to be elucidated. In this study, we evaluated the effect of blue light exposure on photoreceptors and its relationship to Nrf2 using cultured murine photoreceptor (661W) cells. 661W cells were exposed to blue light at 2500 lux. Exposure to blue light for 6–24 h resulted in a significant increase in intracellular reactive oxygen species (ROS) and death of 661W cells in a time-dependent fashion. Blue light exposure resulted in activation of Nrf2, as indicated by an increase in nuclear translocation of Nrf2. This was associated with a significant induction of expression of Nrf2 as well as an array of Nrf2 target genes, including antioxidant genes, as indicated by quantitative reverse transcription PCR (qRT-PCR). In order to determine the functional role of Nrf2, siRNA-mediated knockdown studies were performed. Nrf2-knockdown in 661W cells resulted in significant exacerbation of blue light-induced reactive oxygen species levels as well as cell death. Taken together, these findings indicate that Nrf2 is an important endogenous protective factor against oxidative stress in photoreceptor cells. This suggests that drugs targeting Nrf2 could be considered as a neuroprotective strategy for photoreceptors in AMD and other retinal conditions.

082 Effect of blue light overexposure on normal human keratinocytes and ex vivo skin, in vivo objectivation

In the visible spectrum, blue light (400-495 nm) represents the High Energy Visible (HEV) light associated with high photon energy. The majority of blue light comes from the sun, but it appears that we are more and more exposed to artificial light sources, including light-emitting electronic devices that emit significant amounts of blue light. Recently, opsin receptor expression has been reported in human epidermal cells, with three of them being sensitive to blue light. The role of blue light overexposure on the physiological skin condition has been poorly described. The aim of the present study was to evaluate the effect of blue light exposure on Normal Human Keratinocytes (NHK) using LED irradiation. Exposure conditions generating Reactive Oxygen Species (ROS) accumulation were first determined in NHKs. In these conditions, the levels of opsins OPN1 SW, OPN2 and OPN3 were observed to have decreased at specific wavelengths of blue LED. We also treated NHKs with a peptidic extract of Cocoa porcelana and observed a partial preservation of keratinocyte photoreceptors after blue LED exposure. Moreover, ex vivo studies on skin biopsies showed the effects of blue LED overexposure on the elastic fiber network and its preservation associated with the application of the extract. To evaluate the positive effect of a peptidic extract of Cocoa porcelana on the visible signs of aging linked to prolonged exposure to blue light, an in vivo study was performed on the faces of 20 volunteers. At the end of the treatment, wrinkle parameters were observed to have decreased significantly on the treated side compared to the placebo side. Taken together, our results showed that the expression of opsin receptors could be disrupted by blue LED overexposure in NHKs, associated with an oxidative stress response. Moreover, the in vivo study showed an association with an observed decrease in wrinkle appearance. These studies represent a new approach regarding skin sensitivity to blue light through opsin receptors.

Chinese bayberry fruit treated with blue light after harvest exhibit enhanced sugar production and expression of cryptochrome genes

The effect of blue light exposure on sugar metabolism and cryptochrome gene expression in postharvest Chinese bayberry fruit was investigated. Results showed blue light treatment significantly increased the contents of sucrose, fructose, and glucose in bayberries during storage. Expression analysis revealed that transcripts of three sucrose phosphate synthase (MrSPS1, MrSPS2, and MrSPS3) were markedly induced by blue light treatment throughout the storage period, but increases in expression of two acid invertase genes (MrINV2 and MrINV3) were detected only at the beginning of storage. Meanwhile, a hexokinase gene (MrHXK1) and two genes of cryptochrome (MrCRY1 and MrCRY2) were isolated from bayberry fruit. The expression levels of MrHXK1 and MrCRY1 were up-regulated during blue light exposure only at the end of storage; however, significantly higher amounts of MrCRY2 transcripts were found in blue light exposed-fruit throughout the storage period. Results suggest that blue light treatment increases the sugar content in postharvest bayberries during storage by regulating the expression levels of genes involved in sugar metabolism. Additionally, the enhancement of transcripts of MrCRY1 and MrCRY2 might also be associated with the increase in sugar content in blue light exposed fruit.

OSL and photo-transferred TL of quartz single crystals sensitized by high-dose of gamma-radiation and moderate heat-treatments

This study investigates the optically stimulated luminescence (OSL) and the photo-transferred thermoluminescence (PTTL) signals in quartz single crystals showing a strong TL peak near 300°C after being sensitized by irradiation with 25kGy of gamma rays and heating at 400°C. Natural and sensitized samples were prepared from two crystals with different sensitivity levels in the 300°C TL region. Continuous-wave (CW) and linearly-modulated (LM) OSL signals were stimulated with blue light-emitting diodes during 40 and 1000s, respectively. Two components were isolated from the CW-OSL signals of sensitized samples. These components were clearly seen in LM-OSL measurements together with two long-term components. LM-OSL showed that the sensitization process considered in this study sensitized an ultrafast OSL component of these crystals. The similar behavior found for the thermal stabilities of OSL and TL signals and the dependence of these signals with sample origins suggested that the trapping site related to the ultrafast component is also related to the TL process of the sensitized peak. The PTTL signal induced by blue LEDs increased the intensity of the sensitized glow peak. On the other hand, a remarkable reduction in the intensity of this peak as a result of the accumulated effect of blue light exposure was clearly seen in both kinds of crystals. These results were explained by a mechanism of competition between optically unstable deep traps and trap levels responsible to the sensitized TL peak.