Factors that influence the cutaneous synthesis and dietary sources of vitamin D

The major sources of vitamin D for most humans are casual exposure of the skin to solar ultraviolet B (UVB; 290-315 nm) radiation and from dietary intake. The cutaneous synthesis of vitamin D is a function of skin pigmentation and of the solar zenith angle which depends on latitude, season, and time of day. In order to mimic the natural environment of skin to sunlight exposure, we therefore measured serum 25-hydroxyvitamin D levels in volunteers with different skin types following repeated UV irradiation. Because melanin pigment in human skin competes for and absorbs the UVB photons responsible for the photolysis of 7-dehydrocholesterol to previtamin D3, we also studied the effect of skin pigmentation on previtamin D3 production in a human skin model by exposing type II and type V skin samples to noon sunlight in June when the solar zenith angle is most acute. Vitamin D is rare in food. Among the vitamin D-rich food, oily fish are considered to be one of the best sources. Therefore, we analyzed the vitamin D content in several commonly consumed oily and non-oily fish. The data showed that farmed salmon had a mean content of vitamin D that was approximately 25% of the mean content found in wild caught salmon from Alaska, and that vitamin D2 was found in farmed salmon, but not in wild caught salmon. The results provide useful global guidelines for obtaining sufficient vitamin D3 by cutaneous synthesis and from dietary intake to prevent vitamin D deficiency and its health consequences, ensuing illness, especially, bone fractures in the elderly.     

An evaluation of the vitamin D3 content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D?

It has been suggested that the major source of vitamin D should come from dietary sources and not sun exposure. However, the major fortified dietary source of vitamin D is milk which often does not contain at least 80% of what is stated on the label. Fish has been touted as an excellent source of vitamin D especially oily fish including salmon and mackerel. Little is known about the effect of various cooking conditions on the vitamin D content in fish. We initiated a study and evaluated the vitamin D content in several species of fish and also evaluated the effect of baking and frying on the vitamin D content. Surprisingly, farmed salmon had approximately 25% of the vitamin D content as wild salmon had. The vitamin D content in fish varied widely even within species. These data suggest that the tables that list the vitamin D content are out-of-date and need to be re-evaluated.     

Photorelease of microcystin-LR from resuspended sediments

A series of ten photolysis experiments was conducted with sediments exposed to Microcystis sp. blooms to determine if sunlight is capable of mobilizing the biotoxin microcystin-LR (MC-LR) into the water column. There was a net photorelease of MC-LR in irradiated suspensions in all cases relative to dark controls, ranging from 0.4 to 192 μg L⁻¹ g⁻¹ into the dissolved phase. This should be viewed as a minimum estimate of photorelease due to concurrent photodegradation of dissolved toxin. Dissolved MC-LR concentrations in a sediment suspension increased linearly in the aqueous phase during a six-hour irradiation with simulated sunlight suggesting that longer exposure times produce greater quantities of MC-LR. There was a significant positive correlation between photorelease of toxin and percent organic carbon of the resuspended material, implying that organic-rich sediments yield the greatest photorelease of MC-LR upon exposure to full spectrum sunlight. Samples exposed to photosynthetically active radiation (400 nm–700 nm) were responsible for less than 2% of the photorelease compared to full spectrum exposures. Model calculations indicate that photochemical processing of bloom impacted sediments could be responsible for as much as 100% of the average standing stock of MC-LR in a freshwater pond located in southeastern North Carolina, where surface water concentrations were also measured. Mass spectrometric analysis revealed a new peak in light exposed flasks that appears to be a photo-induced isomerized product of MC-LR. Photoproduction from resuspended sediments therefore represents a significant but previously unrecognized source of highly toxic MC–LR and photoproducts of unknown toxicity and fate to aquatic ecosystems.     

Tolerance of some warm-season turfgrasses to compaction under shade and sunlight conditions in Riyadh,Saudi Arabia

We evaluated the compaction tolerance of some warm-season turfgrasses under shade and sunlight conditions in Riyadh, Saudi Arabia. Hybrid bermudagrass, Cynodon dactylon, cultivars ‘Tifway’ and ‘Tifsport,’ seashore paspalum (Paspalum vaginatum) and its cultivar ‘Sea Isle 2000’ were used. The study area was divided into two sections: one was exposed to sunlight and the other was maintained under 70% shade using a green plastic grille. Turfgrasses were planted using “sods” in beds containing a mixture of sand, silt, and peat moss (4: 1: 1, v/v). The soil was compacted using a locally-made 250 kg cylindrical roll, passing four times over the grown turfgrasses for 3 days/week. The results showed that plant height, leaf area, grass quality and color were decreased by compaction in both the shade and sunlight areas. Plant height in the shaded area with or without compaction was higher than in the sunlight area. Under compaction, ‘Sea Isle 2000’ was the shortest: 8.8 cm in the sunlight and 14.3 cm in the shade. For grasses grown in sunlight, compaction decreased grass height, and height was lowest (4.0 cm) for paspalum ‘Sea Isle 2000’ in January. In the shaded area, paspalum turfgrass retained its high quality (4.0) in April, May, and June. In the sunlight area, the grass quality was highest (4.0) in ‘Sea Isle 2000’ and the lowest (3.0) in ‘Tifsport.’ Paspalum turfgrass showed a higher color degree (4) than bermudagrass (2.5) in April, May, and June. Compaction also led to a decline in leaf area and fresh and dry weights of all grown turfgrasses. The grass density was high for paspalum turfgrasses, indicating that their resistance to compaction was greater than bermudagrasses. It can be concluded that the best compaction and shade-tolerant turfgrasses are ‘Sea Isle 2000’ and seashore paspalum.     

Microhabitat use by the rainbowfish <Emphasis Type="Italic">Melanotaenia duboulayi</Emphasis> in a subtropical Australian stream

Microhabitat use and feeding behavior of the rainbowfish Melanotaenia duboulayi (Castelnau) were investigated in a slow-flowing stream adjacent to riparian forest in south-eastern Queensland, Australia. Fish were more abundant in vegetated areas, but did not enter dense Vallisneria beds, where predators were observed. In sunny conditions shoals of juveniles occurred near the water surface feeding floating material on the surface, but larger fish tended to occur at the bottom near submerged vegetation, often utilizing the overhanging aquatic plant community as a refuge and food source. In the middle of the day, juveniles and small fish seemed to show behavioral thermoregulation at the surface in the warmest site. Under cloudy conditions, however, fish of all sizes preferred deeper water. The present study suggests that in still and sunny pools thermal change caused by sunlight influences the microhabitat choice of small fish. A field experiment using a kingfisher model implies that fish swimming at the surface could escape from aerial predators in sunlit conditions by responding to moving shadows, but could not do so under cloudy conditions. Electronic Publication     

影响中华鳖免疫应答因素的探讨--免疫原(菌苗)与环境条件

通过比较19C-4-2,142G,SL63,Tio63以及Fii32等中华鳖的6个致病菌株的免疫原性,认为T3最强,当它的给予量在50-100×108cfu/mL时,中华鳖的免疫保护率和血清间接凝集抗体效价均达较高水平;低于和高于这个量,中华鳖的免疫应答都会有所降低;当其超过160×108cfu/mL时,则会表现出明显的免疫耐受现象.中华鳖最适宜的免疫温度是25-30℃,水温低于10℃,它的免疫应答反应就大大降低.此外良好的水质,充裕的光照也是提高中华鳖免疫应答水平的一个重要因素.     

Sunlight-driven rapid and facile synthesis of Silver nanoparticles using Allium ampeloprasum extract with enhanced antioxidant and antifungal activity

Green nanotechnology has acquired immense demand due to its cost-effective, eco-friendly and benevolent approach for the synthesis of nanoparticles. Among the biological methods, plants aid as a significant green resource for synthesizing nanoparticles that are safe and non-toxic for human use. In the present investigation, Silver nanoparticles (AgNPs) were synthesized using bulbs extract of Allium ampeloprasum under the influence of sunlight irradiation and characterized using different techniques. Distinct in-vitro assays were performed to test the antioxidant and anticandida potential of the synthesized AgNPs. Results suggested the efficient and rapid sunlight-driven synthesis of AgNPs using A. ampeloprasum extract. UV–Vis spectrum showed absorption peak at 446 nm which confirmed the formation of AgNPs. FTIR analysis suggested the presence of functional groups associated with flavonoids and sulfur compounds in A. ampeloprasum extract. The synthesized AgNPs showed Face Centred Cubic (FCC) structure with an average size of 35 nm. Spherical, quasi spherical, triangular and ellipsoidal morphology of the NPs were observed from the TEM micrograph. The synthesized AgNPs showed pronounced free radical scavenging potential for DPPH, ABTS∙+ and H₂O₂ radicals. The anticandida potency of the synthesized AgNPs was observed as follows: C. albicans ≥ C. tropicalis ≥ C. glabrata ≥ C. parapsilosis ≥ C. krusei. Results showed that sunlight driven nanoparticle synthesis of AgNPs is rapid, facile and exhibit enhanced antioxidant and antifungal activity.     

Vitamin D: its role in cancer prevention and treatment

Vitamin D, the sunshine vitamin, has been recognized for almost 100 years as being essential for bone health. Vitamin D provides an adequate amount of calcium and phosphorus for the normal development and mineralization of a healthy skeleton. Vitamin D made in the skin or ingested in the diet, however, is biologically inactive and requires obligate hydroxylations first in the liver to 25-hydroxyvitamin D, and then in the kidney to 1,25-dihydroxyvitamin D. 25-Hydroxyvitamin D is the major circulating form of vitamin D that is the best indicator of vitamin D status. 1,25-dihydroxyvitamin D is the biologically active form of vitamin D. This lipid-soluble hormone interacts with its specific nuclear receptor in the intestine and bone to regulate calcium metabolism. It is now recognized that the vitamin D receptor is also present in most tissues and cells in the body. 1,25-dihydroxyvitamin D, by interacting with its receptor in non-calcemic tissues, is able to elicit a wide variety of biologic responses. 1,25-dihydroxyvitamin D regulates cellular growth and influences the modulation of the immune system. There is compelling epidemiologic observations that suggest that living at higher latitudes is associated with increased risk of many common deadly cancers. Both prospective and retrospective studies help support the concept that it is vitamin D deficiency that is the driving force for increased risk of common cancers in people living at higher latitudes. Most tissues and cells not only have a vitamin D receptor, but also have the ability to make 1,25-dihydroxyvitamin D. It has been suggested that increasing vitamin D intake or sun exposure increases circulating concentrations of 25-hydroxyvitamin D, which in turn, is metabolized to 1,25-dihydroxyvitamin D(3) in prostate, colon, breast, etc. The local cellular production of 1,25-dihydroxyvitamin D acts in an autocrine fashion to regulate cell growth and decrease the risk of the cells becoming malignant. Therefore, measurement of 25-hydroxyvitamin D is important not only to monitor vitamin D status for bone health, but also for cancer prevention.     

Design Process of an Area-Efficient Photobioreactor

This article describes the design process of the Green Solar Collector (GSC), an area-efficient photobioreactor for the outdoor cultivation of microalgae. The overall goal has been to design a system in which all incident sunlight on the area covered by the reactor is delivered to the algae at such intensities that the light energy can be efficiently used for biomass formation. A statement of goals is formulated and constraints are specified to which the GSC needs to comply. Specifications are generated for a prototype which form and function achieve the stated goals and satisfy the specified constraints. This results in a design in which sunlight is captured into vertical plastic light guides. Sunlight reflects internally in the guide and eventually scatters out of the light guide into flat-panel photobioreactor compartments. Sunlight is focused on top of the light guides by dual-axis positioning of linear Fresnel lenses. The shape and material of the light guide is such that light is maintained in the guides when surrounded by air. The bottom part of a light guide is sandblasted to obtain a more uniform distribution of light inside the bioreactor compartment and is triangular shaped to ensure the efflux of all light out of the guide. Dimensions of the guide are such that light enters the flat-panel photobioreactor compartment at intensities that can be efficiently used by the biomass present. The integration of light capturing, transportation, distribution and usage is such that high biomass productivities per area can be achieved.