Effects of high and low irradiance excimer light in repigmenting vitiligo: A single-center cross-sectional study

Crossovers in seedling relative growth rates between low and high irradiance: analyses and ecological potential

Background:Vitiligo, a prevalent acquired depigmentation condition, involves a progressive melanocyte loss, posing significant treatment challenges. Excimer light has been employed in vitiligo treatment, while trichloroacetic acid (TCA) has been noted to induce chemical trauma, leading to perifollicular pigmentation and perilesional repigmentation in vitiligo. This study aims to assess and compare the efficacy and safety of using 308 nm monochromatic excimer light alone versus combining it with 50% TCA in treating vitiligo.Methods:A total of 50 patients diagnosed with stable vitiligo were included. Each patient had 2 patches of vitiligo selected, with 1 patch treated using 50% TCA and excimer light, while the other patch received excimer light treatment alone.Results:All patients experienced a notable decrease in the surface area of their vitiligo lesions. However, those treated with excimer light combined with TCA exhibited a greater reduction in lesion size and an increased number of patients showing significant repigmentation compared to lesions treated with excimer light alone. Additionally, patients expressed a higher level of satisfaction with the patches treated with excimer light and TCA compared to those treated with excimer light alone.Conclusion:The combined treatment of excimer light and TCA shows promise as an effective and safe therapy for vitiligo.

Ultraviolet B (UVB) radiation from the sun may lead to photocarcinogenesis of the skin. Sunscreens were used to protect the skin by reducing UVB irradiance, but sunscreen use did not reduce sunburn episodes. It was shown that UVB-induced erythema depends on surface exposure but not irradiance of UVB. We previously showed that irradiance plays a critical role in UVB-induced cell differentiation. This study investigated the impact of irradiance on UVB-induced photocarcinogenesis. For hairless mice receiving equivalent exposure of UVB radiation, the low irradiance (LI) UVB treated mice showed more rapid tumor development, larger tumor burden, and more keratinocytes harboring mutant p53 in the epidermis as compared to their high irradiance (HI) UVB treated counterpart. Mechanistically, using cell models, we demonstrated that LI UVB radiation allowed more keratinocytes harboring DNA damages to enter cell cycle via ERK-related signaling as compared to its HI UVB counterpart. These results indicated that at equivalent exposure, UVB radiation at LI has higher photocarcinogenic potential as compared to its HI counterpart. Since erythema is the observed sunburn at moderate doses and use of sunscreen was not found to associate with reduced sunburn episodes, the biological significance of sunburn with or without sunscreen use warrants further investigation.

Carotenoids are important photoprotectant and light‐harvesting pigments within the photosynthetic apparatus. Little information is available regarding carotenoid physiology in creeping bentgrass (Agrostis stolonifera L.). Research was conducted to investigate relative high and low irradiance adaptation of creeping bentgrass with respect to β‐carotene and xanthophyll composition. ‘Crenshaw’ creeping bentgrass plants were acclimated for 7 d to relative high [47.9 mol m−2 d−1 photosynthetically active radation (PAR)] or low irradiance (4.7 mol m−2 d−1 PAR). After the acclimation period, plants were transferred from high to low (low irradiance treatment) and low to high (high irradiance treatment) irradiance. Clippings were harvested at 0, 24, 72, and 168 h after the acclimation period. Zeaxanthin and antheraxanthin decreased from 5.1 and 3.4 to 0.9 and 0.6 mg 100 g−1 fresh weight (FW), respectively, over 168 h in low irradiance. As the turf adapted to low irradiance, violaxanthin, lutein, and lutein‐5,6‐epoxide (epoxylutein) increased at 24 h, but levels decreased from 24 to 168 h. Zeaxanthin and antheraxanthin increased in high irradiance, while violaxanthin and β‐carotene decreased. Lutein was the predominant carotenoid quantified regardless of irradiance treatment. Cumulative zeaxanthin, antheraxanthin, and violaxanthin increased as a percentage of the total carotenoids as the turfgrass adapted to high irradiance, but decreased in low irradiance. Conversely, neoxanthin and β‐carotene decreased in high irradiance and increased in low irradiance. Creeping bentgrass produces carotenoid amounts comparable to other plant species potentially attributable to selection efforts of more stress‐tolerant varieties.

A 308 nm excimer light is an effective treatment for vitiligo, with fewer treatment times, rapid obvious effects, relatively complete pigment recovery, good patient compliance, and safe and effective treatment for children. The disadvantage of this treatment is that some patients have a plateau during which the skin lesion reduction rate slows down or stalls after multiple treatments. Treatment data were collected from all vitiligo patients in the Dermatology Department, distinguishing between those who underwent 308 nm excimer light treatment alone and those who received a combination of 308 nm excimer light and 2940 erbium laser treatment. Of the 104 patients, 60 were treated with 308 nm excimer light only, and 44 were treated with a combination of a 2940 erbium laser and 308 nm excimer light. In contrast to the treatment of 308 nm excimer light alone, the combined treatment of the 2940 erbium laser and 308 nm excimer light significantly increased the speed and degree of repigmentation in vitiligo. Our study demonstrates that the combination of 308 nm excimer light and 2940 nm erbium laser treatment can improve the treatment response for vitiligo, decrease the occurrence of treatment plateaus associated with 308 nm excimer light, and improve efficacy. ChiCTR2000036712 (24/08/2020).

The marine cyanobacterium Synechococcus elongatus was grown in a continuous culture system to study the interactive effects of temperature, irradiance, nutrient limitation, and the partial pressure of CO2 (pCO2) on its growth and physiological characteristics. Cells were grown on a 14:10 h light:dark cycle at all combinations of low and high irradiance (50 and 300 μmol photons ⋅ m-2 ⋅ s-1 , respectively), low and high pCO2 (400 and 1000 ppmv, respectively), nutrient limitation (nitrate-limited and nutrient-replete conditions), and temperatures of 20-45°C in 5°C increments. The maximum growth rate was ~4.5 · d-1 at 30-35°C. Under nutrient-replete conditions, growth rates at most temperatures and irradiances were about 8% slower at a pCO2 of 1000 ppmv versus 400 ppmv. The single exception was 45°C and high irradiance. Under those conditions, growth rates were ~45% higher at 1000 ppmv. Cellular carbon:nitrogen ratios were independent of temperature at a fixed relative growth rate but higher at high irradiance than at low irradiance. Initial slopes of photosynthesis-irradiance curves were higher at all temperatures under nutrient-replete versus nitrate-limited conditions; they were similar at all temperatures under high and low irradiance, except at 20°C, when they were suppressed at high irradiance. A model of phytoplankton growth in which cellular carbon was allocated to structure, storage, or the light or dark reactions of photosynthesis accounted for the general patterns of cell composition and growth rate. Allocation of carbon to the light reactions of photosynthesis was consistently higher at low versus high light and under nutrient-replete versus nitrate-limited conditions.

Background and aim Vitiligo is a common skin-depigmentation disorder characterized by the absence of melanocytes. The mechanism and etiology of vitiligo is still unknown, so the treatment of vitiligo is challenging. There are several treatment options for vitiligo, such as topical, systemic, phototherapy, and surgical treatment. We aimed to compare between the efficacies of excimer light alone versus excimer light with topical prostaglandin (PGE) in the treatment of facial vitiligo. Patients and methods This is a comparative study that was carried out on 50 patients (their mean age was 29.57 years, 33 patients were females) diagnosed as facial vitiligo. Two patches of vitiligo were chosen in the same patient, one treated with topical latanoprost (—two to three drops once daily with excimer light two sessions per week for 3 months), the other patch treated with excimer light alone two sessions per week for 3 months. Results There was a significant reduction in vitiligo-surface area after application of excimer light with topical PGE. Also, there was a significant reduction in the vitiligo-surface area after application of excimer light alone, with no significant difference between the two methods; however, there was mild reduction in the surface area of vitiligo patches after application of excimer light with topical PGE more than after application of excimer light alone. Conclusion Excimer light with topical PGE can be used as an effective and safe promising topical treatment for vitiligo, especially the facial variant.

Background and aim Vitiligo is a commonly acquired depigmenting disease described by continuing damage of melanocytes. The treatment of vitiligo is a general challenge. Excimer light has been used previously in the treatment of vitiligo. So this clinical trial aimed to evaluate the effectiveness and safety of 308 nm monochromatic excimer light alone versus 308 nm monochromatic excimer light plus 50% trichloroacetic acid (TCA) in the treatment of vitiligo. Patients and methods This clinical trial was carried out on 50 patients with stable vitiligo (diagnosis confirmed with Wood’s light examination). Two patches of vitiligo were chosen in the same patient; one patch was treated with 50% TCA and excimer light, and the other patch was treated with excimer light alone. Results There was a significant reduction in the surface area of the vitiligo lesion in all patients. However, there was more reduction in the surface area of the lesions, as well as an increase in the number of patients with marked repigmentation among lesions treated with excimer light plus TCA. Moreover, patients gave a higher degree of satisfaction to the areas treated with excimer light plus TCA as compared to areas treated with excimer light alone. Conclusion The combination of excimer light plus TCA could be an effective and safe favorable treatment for vitiligo.

Blue light effects on the acclimation of energy partitioning characteristics in PSII and CO2 assimilation capacity in spinach to high growth irradiance were investigated. Plants were grown hydroponically in different light treatments that were a combination of two light qualities and two irradiances,i.e. white light and blue-deficient light at photosynthetic photon flux densities (PPFDs) of 100 and 500 micromol m(-2) s(-1). The CO2 assimilation rate, the quantum efficiency of PSII(PhiPSII) and thermal dissipation activity (F(v)/F(m)-F'(v)/F'(m)) in young, fully expanded leaves were measured under 1,600 micromol m(-2) s(-1) white light. The CO2 assimilation rate and (PhiPSII) were higher, while F(v)/F(m)-F'(v)/F'(m) was lower in plants grown under high irradiance than in plants grown under low irradiance. These responses were observed irrespective of the presence or absence of blue light during growth. The extent of the increase in the CO2 assimilation rate and PhiPSII and the decrease in F(v)/F(m)-F'(v)/F'(m) by high growth irradiance was smaller under blue light-deficient conditions. These results indicate that blue light helps to boost the acclimation responses of energy partitioning in PSII and CO2 assimilation to high irradiance. Similarly, leaf N, Cyt f and Chl contents per unit leaf area increased by high growth irradiance, and the extent of the increment in leaf N, Cyt f and Chl was smaller under blue light-deficient conditions. Regression analysis showed that the differences in energy partitioning in PSIIand CO2 assimilation between plants grown under high white light and high blue-deficient light were closely related to the difference in leaf N.

To investigate the influence of plant productivity on plant—herbivore interactions in stream ecosystems, we varied the productive capacity of algal assemblages by exposing periphyton to three levels of irradiance and two levels of grazing. We studied interactions between algal assemblages (grown from algae obtained from four Oregon streams) and herbivorous snails (Juga silicula) in 15 laboratory streams containing either 250 snails/m2 or no snails. Biomass, production, export, and taxonomic structure of the algal community were measured at intervals throughout the 75—d study. Ingestion rate and assimilation efficiency of snails also were measured on six different dates using dual—isotope labeling, and snail growth was measured at the end of the experiment. Rates of primary production, algal biomass accumulation, and dominance by chlorophytes generally increased with higher irradiance, although these patterns were modified by herbivores. Ungrazed periphyton at low irradiance (photon flux density: 20μmol°m—2°s—1) accumulated little biomass, which was further reduced by grazing snails. At intemediate (100 μmol°m—2°s—1) and high (400μmol°m—2°s—1) irradiance, snails delayed the accumulation of algal biomass but did not affect the final biomass attained. After 43 d, net primary production (NPP) at high irradiance was unaffected by grazing, whereas grazing increased NPP at both low and intermediate irradiance. Algal export increased with both irradiance and the presence of grazers and constituted a significant loss of plant biomass from the streams. Grazing by Juga delayed algal succession and altered algal taxonomic structure and assemblage physiognomy by reducing the relative abundance of erect and non—attached algae, while increasing the abundance of adnate diatoms. Snails grew slowly at low irradiance, due to scant food resources, but had high growth rates at intermediate and high irradiance, probably because food was not limiting. Assimilation efficiencies for snails generally varied from 40 to 70% and were highest at low irradiance. At low irradiance, 90% of benthic production was harvested by grazers, whereas only 10% accumulated as attached biomass or was exported. At higher irradiances, <15% of primary production was harvested by grazers, and >85% persisted as attached algae or was exported. In these stream ecosystems, the biomass and production of grazers were influenced by abiotic constriants placed on algal productive capacity (i.e., the ability of a plant assemblage to generate biomass). The structure and metabolism of algal assemblages were affected, in turn, by consumptive demand of herbivores. The productive capacity of periphyton modified the nature and outcome of plant—herbivore interactions. This capacity therefore has important implications for the operation of stream ecosystems.

Aeschynanthus longicaulis plants are understory plants in the forest, adapting to low light conditions in their native habitats. To observe the effects of the high irradiance on growth and physiology, plants were grown under two different light levels, PPFD 650 μmol·m–2 ·s–1 and 150 μmol·m–2 ·s–1 for 6 months. Plants under high irradiance had significantly thicker leaves with smaller leaf area, length, width, and perimeter compared to the plants grown under low irradiance. Under high irradiance, the leaf color turned yellowish and the total chlorophyll decreased from 5.081 mg·dm−2 to 3.367 mg·dm−2. The anthocyanin content of high irradiance leaves was double that of those under low irradiance. The plants under high irradiance had significantly lower Amax (5.69 μmol·m–2 ·s–1) and LSP (367 μmol·m–2 ·s–1) and higher LCP (21.9 μmol·m–2 ·s–1). The chlorophyll fluorescence parameter F v/F m was significantly lower and NPQ was significantly higher in high irradiance plants. RLCs showed significantly lower ETRmax⁡ and E k in plants under high irradiance. It can be concluded that the maximum PPFD of 650 μmol·m–2 ·s–1 led to significant light stress and photoinhibition of A. longicaulis.

Thaumatococcus daniellii is a rhizomatous monocotyledonous, perennial herb species of the Marantaceae family. The fruit aril contains thaumatin, a sweet protein with sweetness intensity that is about 1,600–3,000 times that of sucrose and is extensively employed as a natural sweetener. The species has potential as an imperative economic crop if cultivated under proper agronomic practices. Phenological development and thermal time requirements are critical to ensuring a high yield. The aim of this study was to determine the phenological stages according to the BBCH scale and growing degree days (GDDs) under different irradiance and fertiliser levels. Seedlings were raised from rhizomes and grown on the field using a randomised complete block design with four treatments and three replications. The study was carried out at the Botanical Garden, Shah Alam, Malaysia, from July 2014 to February 2017. The treatments consisted of combinations of two irradiance and two fertiliser levels, which were designated as high irradiance with either low (T1) or high fertiliser (T2) and low irradiance with either low (T3) or high fertiliser (T4). A detailed phenological development using two‐ and three‐digit coding systems was conducted on 12 clumps (one clump/replicate/treatment). The species has eight principal stages, which include bud and leaf development, formation of side tillering, petiole elongation, emergence of synflorescence, flowering, fruit development and fruit maturity. Both irradiance and fertiliser levels affected certain phenological stages; with leaf, tiller, synflorescence and fruit strongly influenced by irradiance levels. Leaf growth was more vigorous under high irradiances compared with low irradiances and took about 36 to 42 days to attain full maturity. The clump growth or size is a function of tiller numbers. The tiller number increased with increase in clump age. The onset of certain phenological stages was associated with clump age. The clumps commenced production of synflorescence when tiller number was in the range of 30 to 40, and started fruit formation when tiller number reached 70. Both events occurred under a combination treatment of high irradiance with high fertiliser. The GDD requirement of any phenological stage or development of any plant part is contingent upon the duration of a particular stage or process, as measured in days after emergence or transplanting. The longer the duration, the higher the GDD and it varies with treatments. The total GDD required for the completion of the single leaf growth ranged from 852 to 1,022°C, while the emergence of synflorescence under high irradiance occurred with GDD of 5621 (T2) and low irradiance at 9387°C (T3). Fruit formation was observed only under high irradiance with GDD ranging from 9030 (T2) to 13,147°C (T1) during the study period. A description of phenological development according to BBCH scale and GDD requirements in response to differences in irradiance and fertiliser is imperative. It provides a detailed knowledge based on T. daniellii development vis‐à‐vis growth and environmental requirements. This will pave the way for attainment of an efficient crop agronomic practice.

In response to irradiance seasonality, saplings under brighter conditions increased leaf biomass with high photosynthesis to realize high growth, whereas understory saplings depend on photosynthesis during canopy leaf fall, and larger root biomass contributed to storage. We studied the changes in photosynthesis, biomass partitioning, and starch content in Abies firma saplings in a mixed deciduous forest in southwest Japan. Saplings were examined under high, intermediate, and low irradiance levels. The relative irradiance at intermediate and low irradiance levels increased significantly during winter and spring due to leaf fall in the deciduous canopy trees. The maximum photosynthetic rates (P max) under low irradiance were lower than those under high irradiance throughout the year. The needle daily carbon balance in summer was negative under low irradiance, whereas the balance became positive in winter and spring due to increases in irradiance. The needle daily carbon balance in intermediate- and high-irradiance saplings remained positive year-round, although the midday photosynthetic depression suppressed the daily needle carbon gain under high irradiance. The starch content in needles, branches, and roots was higher in spring due to high photosynthetic production, and then decreased in summer under all irradiance levels. Root starch under low irradiance levels may be used to maintain carbon balance during summer, thereby contributing to survival. High needle biomass coupled with a high P max facilitated carbon gain under high and intermediate irradiance, whereas high relative root biomass under low irradiance may enhance storage ability. Overall, A. firma saplings seemed to acclimate to different irradiance levels with seasonal changes through changes in photosynthetic traits, starch storage, and biomass partitioning.

We evaluated the ultrastructural variations occurring during a surface bloom in Microcystis aeruginosa Kützing PCC 7005, by comparing cultures exposed to high incident light irradiance (90 µmol photons m-2 s-1) and to low irradiance (9 µmol photons m-2 s-1). At 12h, and 15 and 30 days in culture, the cells were fixed in glutaraldehyde and subjected to cytochemical assays. Exposure to high irradiance induced structural changes in the cell wall, and differences in the photosynthetic apparatus and granule reserves. After 15 days of high irradiance, the following features were observed: a reduced number of thylakoids and changes in their arrangement; high accumulation of glycogen, poly-beta-hydroxybutyrate, lipid bodies and cyanophycin; conspicuous structural changes in the cell wall. At day 30 of high irradiance, the viable cells had few thylakoids, arranged parallel to each other and perpendicular to the plasma membrane, and abundant glycogen. Nitrogen, calcium and phosphorus, as detected by electron spectroscopic imaging, were present in different sites of cells grown at low and high irradiance. The results of this study, together with previous data on variation in Fe-superoxide dismutase (Canini et al., 2001a), suggest that defense mechanisms against high and prolonged irradiance only operate for a short time.

Crustose coralline algae (CCA) cement reefs and create important habitat and settling sites for reef organisms. The susceptibility of CCA to increasing ocean pCO2 and declining pH or ocean acidification (OA) is a growing concern. Although CCA are autotrophs, there has been little focus on the interaction of elevated pCO2 and irradiance. We examined elevated pCO2 effects on individual CCA and macroalgal benthic communities at high and low irradiance (205–13 µmol photons m−2 s−1) in an aquaria experiment (35 d, June–August 2014) on Little Cayman Island, Caribbean. A dominant Cayman reef wall CCA (Peyssonnelia sp.) in its adult lobed form and individual CCA recruits were used as experimental units. Changes in CCA, fleshy macroalgae (branching and turfs), and microalgae (including microbial biofilm) per cent cover and frequency were examined on macroalgal communities that settled onto plates from the reef. Reef diel cycles of pCO2 and pH were simulated using seawater inflow from a back reef. Although CO2 enrichment to year 2100 levels resulted in 1087 µatm pCO2 in the elevated pCO2 treatment, CaCO3 saturation states remained high (Ωcal ≥ 2.7). Under these conditions, elevated pCO2 had no effect on Peyssonnelia sp. calcification rates or survival regardless of irradiance. Individual CCA surface area on the bottom of settling plates was lower under elevated pCO2, but per cent cover or frequency within the community was unchanged. In contrast, there was a strong and consistent community assemblage response to irradiance. Microalgae increased at high irradiance and CCA increased under low irradiance with no significant pCO2 interaction. Based on this short-term experiment, tropical macroalgal communities are unlikely to shift at pCO2 levels predicted for year 2100 under high or low irradiance. Rather, irradiance and other factors that promote microalgae are likely to be strong drivers of tropical benthic algal community structure under climate change.