Vertical migration and motility responses in three marine phytoplankton species exposed to solar radiation

Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280-400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280-700 nm), PA (320-700 nm) and P (400-700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV-B displaying a significant decrease in swimming speed and percentage of motile cells after 2-3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub-lethal effects of solar radiation are species-specific and they might have important implications for the aquatic ecosystem.     

Effects on feeding rate and biomarker responses of marine mussels experimentally exposed to propranolol and acetaminophen

Environmental risk assessments of human pharmaceuticals and other ‘emerging contaminants’ should integrate both population-relevant endpoints and biomarkers of potential modes of action in a range of species. Adult Mytilus galloprovincialis were exposed to the beta-adrenergic receptor blocker propranolol or to the anti-inflammatory drug acetaminophen (paracetamol), both commonly used therapeutic drugs present in aquatic ecosystems. Mussels were exposed under semi-static conditions for 10 days to either acetaminophen (CAS number 103-90-2; mean measured concentrations 23 and 403 μg/L) or propranolol hydrochloride (CAS number 318-98-9; mean measured propranolol concentrations 11 and 147 μg/L) at 15 ± 1 °C sea water. Feeding rate was assessed as an indicator of general toxicity. For propranolol, the 10-day no-observed effect concentration (^{feeding rate}NOEC) and lowest observed effect concentration (^{feeding rate}LOEC) were 11 and 147 μg/L, respectively. For acetaminophen, feeding rate was increased at both 23 and 403 μg/L, suggesting a 10-day ^{feeding rate}NOEC of 403 μg/L. Primarily, phase I carboxylesterase (CbE), phase II glutathione S-transferase (GST) and the anti-oxidant catalase activities were evaluated in digestive gland. Gill GST and acetylcholinesterase (AChE) activities were also measured. Lipid peroxidation (LPO) levels were measured in both tissues to assess oxidative stress. Some enzymatic activities in liver were also reduced after propranolol exposure whilst acetaminophen enhanced them (CbE p < 0.05). Acetaminophen exposure significantly increased hepatic LPO levels and inhibited AChE activity in gill (10-day NOEC and LOEC of 23 and 403 μg/L, respectively), whereas propranolol (11 μg/L) enhanced gill GST.     

Physiological responses of Acropora cervicornis to increased solar irradiance

The effects of increased UV radiation (UV-B [280-320 nm] + UV-A [320-400 nm]; hereafter UVR) on the growth, production of photosynthetic pigments and photoprotective mycosporine-like amino acids (MAAs) were studied in the threatened Caribbean coral Acropora cervicornis transplanted from 20 to 1 m depth in La Parguera, Puerto Rico. The UVR exposure by the transplanted colonies was significantly higher than that at 20 m, while photosynthetically active radiation (PAR) only increased by 9%. Photosynthetic pigments, quantified with HPLC, as well as linear extension rates and skeletal densities, were significantly reduced 1 month after transplantation to 1 m depth, while MAAs increased significantly despite immediate paling experienced by transplanted colonies. While these colonies showed a significant reduction in photosynthetic pigments, there were no significant reductions in zooxanthellae densities suggesting photoacclimation of the coral's symbionts to the new radiation conditions. The results suggest that while corals might be able to survive sudden increases in UVR and PAR, their skeletal structure can be greatly debilitated due to a reduction in the photosynthetic capacity of their symbionts and a possible relocation of resources.     

Vesicles to concentrate iron in low-iron media: an attempt to mimic marine siderophores

Amphiphilic catechol-type iron chelators were studied with the aim of mimicking the properties of marine bacterial siderophores. The Fe(III) complexation constants and aqueous solution speciation of L(S10), a sulfonated catechol unit that has a C(10) lipophilic carbon chain connected by an amide linkage, were determined by spectrophotometric titration. The calculated value of pFe3+ is 18.1 at pH 7.4. Cryogenic transmission electron microscopy showed that the tris(catecholate) ferric complex formed at physiological pH initially assembles into micelles, in which the catecholate-iron units stay on the exterior of the micelle. The average diameter of these micelles was estimated to be 4.2 nm. The micelles then slowly rearrange into clusters of different sizes, which leads to the formation of unilamellar and bilamellar vesicles. The reorganization processes are comparable to those observed by Butler et al. for the marinobactin siderophores produced by marine bacteria, but in contrast to the marinobactins, vesicles of the Fe3+-L(S10) complex form without an excess of iron relative to ligand concentration. The time-dependent micelle-to-vesicle transition is discussed herein.     

Photoprotection and long-term acclimation to UV radiation in the marine diatom Thalassiosira weissflogii.

Unialgal cultures of the marine diatom Thalassiosira weissflogii (Grunow) were exposed for 40 days to artificial UV-B radiation in the presence of PAR and UV-A to examine long-term acclimation to UV, PAR and UV-A were supplied 14 h daily, while UV-B (two levels: 0.16 and 0.30 W m(-2) unweighted) was supplied for 4 h/day. Growth rates and photochemical capacity (CFC ratio) both decreased over the first 10-15 days, then recovered. No obvious differences were noted between the responses to the two UV-B treatments. The concentration of the major pigments (chlorophyll a and c(1+2), fucoxanthin and beta,beta-carotene) changed very little with time, except for diatoxanthin. which increased over the first 16 days, decreased over the next 13 days, then increased again from day 29 to the end of the experiment. The concentration of total mycosporine-like amino acids (MAAs) was initially undetectable, then increased from day 16 in the high UV-B treatment and after day 22 in the low UV-B treatment, reaching a maximum on day 29 for both treatments and decreasing afterwards. The synthesis of MAAs proceeded only once photochemical capacity had recovered from the initial UV stress and this recovery likely involved the xanthophyll cycle (diatoxanthin increase). The concentration of MAAs decreased when the cells showed signs of photoinhibition (decrease in CFC ratio). It also showed an inverse trend with diatoxanthin. UV-B alone had little regulatory effect over these responses, except possibly for an earlier synthesis of MAAs under HUV-B conditions. This suggests that the observed changes were due to UV-A rather than to UV-B exposure. The overall response of this coastal diatom to prolonged UV exposure indicates that T. weissflogii is a relatively UV-tolerant species and that its long-term response to UV exposure involves an activation of the xanthophyll cycle followed by the synthesis of MAAs, which may proceed only when photoinhibition is relieved.     

Polybutene-1 pipes exposed to pressurized chlorinated water: Lifetime and antioxidant consumption

Pipes of isotactic polybutene-1 were pressure-tested in chlorinated water at a controlled pH (6.5 ± 0.1), and the lifetime was assessed as a function of temperature (95-115 °C) and chlorine content (≤3 ppm). These data were compared with data from pressure testing in hot water (0 ppm chlorine). The lifetime shortening in chlorinated water was significant even at relatively low chlorine contents, 0.5 ppm. A further increase in chlorine content led only to a moderate shortening of the lifetime. The temperature dependence of the lifetime data obeyed the Arrhenius law. The activation energy obtained for failure data in chlorinated water was ∼140 kJ mol⁻¹, which was greater than the value of 108 kJ mol⁻¹ earlier reported for failure data from hot-water pressure testing. A 0.5-mm thick layer of material at the inner wall in the fractured pipes showed depletion of the antioxidant system and the inner wall displayed a large number of surface cracks, confirming that there was a pronounced chemical degradation of the inner wall material. The decrease in the antioxidant concentration was independent of the chlorine concentration in the range 0.5-1.5 ppm. The time to reach depletion of the antioxidant system could be predicted by linear extrapolation in an oxidation induction time (log scale)-exposure time (linear scale) diagram.     

Distinct responses of chloroplasts to blue and green laser microbeam irradiations in the centric diatom Pleurosira laevis

The centric diatom Pleurosira laevis is a large unicellular alga, in which ca 200 chloroplasts migrate toward the nuclear cytoplasm through the transvacuolar cytoplasmic strands in response to blue-light irradiation and, on the contrary, toward the cortical cytoplasm in response to green-light irradiation. We analyzed these light-induced chloroplast migrations using a scanning laser microbeam provided by a confocal microscope for intracellular irradiation. Spot irradiation of a blue laser microbeam induced rapid assemblage of chroloplasts into the nuclear cytoplasm regardless of the spot position and spot number. On the other hand, one or two spots of green laser microbeam induced chloroplast accumulation at the spots, although increasing spot numbers suppressed chloroplast accumulation at each spot. In our experimental condition, ca 1 min of blue-light irradiation was sufficient to stimulate movement, whereas green-light irradiation required uninterrupted and longer irradiation time (ca 15 min). Chloroplast assemblage induced by blue-light required extracellular Ca2+, and was inhibited by Ca2+ channel antagonists. Furthermore, higher efficiencies of chloroplast migration were obtained when a single beam spot was fragmented and scattered over wider area of plasma membrane. These observations suggested that blue-light induced a response at the plasma membrane, which subsequently activated Ca2+ permeable channels. This sequence of physiological events is identical to what was previously observed with chloroplast movement in response to mechanical stimulation. Furthermore, experiments with the cytoskeleton-disrupting agents, colchicine and cytochalasin D, indicated that blue-light-induced chloroplast movement required microtubules whereas the green-light-induced response to beam spot required actin filaments.     

Synthesis and biological evaluation of two salidroside analogues in the PC12 cell model exposed to hypoglycemia and serum limitation

Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., a traditional Chinese medicinal plant, and has displayed a broad spectrum of pharmacological properties. In this paper, two analogues were prepared with the glucosamine and N-acetylglucosamine as glycosyl donor, 2-(4-hydroxyphenyl)ethanol as glycosyl acceptor. The effects of them over PC12 cell model exposed to hypoglycemia and serum limitation were assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Flow Cytometry and Western blot analysis.     

High irradiance responses involving photoreversible multiple photoreceptors as related to photoperiodic induction of cell division in Euglena

Little is known about the photoreceptors involved in the photoperiodism of unicellular organisms, which we elucidated by deriving their action spectra. The flagellated alga Euglena gracilis exhibits photoperiodism, with a long-day response in cell reproduction. The underlying clock is a circadian rhythm with photoinductive capability, peaking at subjective dusk and occurring at the 26th hour in continuous darkness (DD) when transferred from continuous light (LL); it regulates photoinduction, a high-irradiance response (HIR), of a dark-capability of progressing through cell division. We derived the action spectra by irradiating E. gracilis with monochromatic light for 3h at around the 26th hour; the action maxima occurred at 380, 450-460, 480, 610, 640, 660, 680, and 740nm. Except for the maximum at 450-460nm, which was always a major maximum, the maxima greatly depended on the red (R)/far-red (FR) ratio of the prior LL. The high R/FR ratio resulted in a dominant major peak at 640nm and minor peaks at 480 and 680nm, whereas the low ratio resulted in dominant major peaks at 610 and 740nm and minor peaks at 380 and 660nm; the critical fluence was minimally about 60mmolm(-2). These HIRs resulted from the accumulation of corresponding low-fluence responses (LFRs) because we found that repetition of a 3-min light/dark cycle, with critical fluences of 1mmolm(-2), lasting for 3h resulted in the same photoinduction as the continuous 3-h irradiation. Moreover, these LFRs expressed photoreversibility. Thus, photoperiodic photoinduction involves Euglena-phytochrome (640 and 740nm) and blue photoreceptor (460nm). Although 380, 480, 610, 660, and 680nm may also represent Euglena-phytochrome, a definite conclusion awaits further study.     

Optimization and ecofriendly synthesis of iron oxide nanoparticles as potential antioxidant

The present study involves the use of Box-Behnken design for optimization of the energy-efficient process variables, eco-friendly synthesis of nanoparticles of iron oxide using Coriandrum sativum L. (cilantro) leaf extract. The factors, which significantly influenced mean nanoparticle size, surface charge, and size distribution, were the volume of leaf extract, agitation speed, and temperature. The developed model using Box-Behnken design was validated by synthesizing the iron nanoparticles using optimized operational conditions i.e. 10 ml volume of leaf extract, 1500 rpm agitation speed and 30 °C temperature. This resulted in the formation of highly stable iron oxide nanoparticles with mean particle size 161.5 nm and polydispersity index 0.132 with a zeta potential of −19.5 mV. The free radical inhibitory activity of prepared iron oxide nanoparticles was found comparable to ascorbic acid. These results reveal that iron nanoparticles for a biomedical application can be prepared at ambient temperature in an eco-friendly manner.     

Alterations in osmoregulation, antioxidant enzymes and indole alkaloid levels in Catharanthus roseus exposed to water deficit

Catharanthus roseus (L.) G. Don plants were grown in different water regimes in order to study the drought induced osmotic stress and proline (PRO) metabolism, antioxidative enzyme activities and indole alkaloid accumulation. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress from 30 days after sowing (DAS) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). The drought stressed plants showed increased aminoacid (AA), glycine betaine (GB) and PRO contents and decreased proline oxidase (PROX) and increased γ-glutamyl kinase (γ-GK) activities when compared to control. The antioxidative enzymes like peroxidase (POX) and polyphenol oxidase (PPO) increased to a significant level in drought stressed plants when compared to control. The drought stressed C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to well-watered control plants. Our results suggest that the cultivation of medicinal plants like C. roseus in water deficit areas would increase its PRO metabolism, osmoregulation, defense system and the level of active principles.     

Solution structures and dynamic behaviour of some iron chalcogen derivatives

Summary ¹³C-n.m.r. spectra of (-SR)₂Fe₂(CO)₆, (-SR)₂Fe₂(CO)₅P(n-Bu)₃ and (-X)₂Fe₂(CO)₆ (X=S or Se) show that the solid state structure is maintained in solution. N.m.r. evidence indicates that two isomeric species, not separable by means of the usual physicochemical methods, are present for (-SPh)₂Fe₂(CO)₆ with an overwhelming predominance of theanti form. The phosphine substitutes a COtrans to the iron-iron bond. For any of the iron chalcogen derivatives examined, variable temperature¹³C-n.m.r. spectra show that carbonyl exchange occur in one step. The energy barrier for the exchange of carbon monoxide in the phosphine derivative is lower than that in the unsubstituted complex.     

Primary, secondary metabolites, H2O2, malondialdehyde and photosynthetic responses of Orthosiphon stimaneus Benth. to different irradiance levels

The resource availability hypothesis predicts an increase in the allocation to secondary metabolites when carbon gain is improved relative to nutrient availability, which normally occurs during periods of low irradiance. The present work was carried out to confirm this hypothesis by investigating the effects of decreasing irradiance on the production of plant secondary metabolites (flavonoids and phenolics) in the herbal plant Orthosiphon stamineus, and to characterize this production by carbohydrate, H(2)O(2), and malondialdehyde (MDA) levels, net photosynthesis, leaf chlorophyll content and carbon to nitrogen ratio (C/N). Four levels of irradiance (225, 500, 625 and 900 μmol/m(2)/s) were imposed onto two-week old seedlings for 12 weeks in a randomized complete block design experiment. Peak production of total flavonoids, phenolics, soluble sugar, starch and total non-structural carbohydrate ocurred under low irradiance of 225 μmol/m(2)/s, and decreased with increasing irradiance. The up-regulation of secondary metabolites could be explained by the concomitant increases in H(2)O(2) and MDA activities under low irradiance. This condition also resulted in enhanced C/N ratio signifying a reduction in nitrogen levels, which had established significant negative correlations with net photosynthesis, total biomass and total chlorophyll content, indicating the possible existence of a trade-off between growth and secondary metabolism under low irradiance with reduced nitrogen content. The competition between total chlorophyll and secondary metabolites production, as exhibited by the negative correlation coefficient under low irradiance, also suggests a sign of gradual switch of investment from chlorophyll to polyphenols production.     

Phlorotannin and antioxidant responses upon short-term exposure to UV radiation and elevated temperature in three south Pacific kelps

Rapid adjustments of the photosynthetic machinery and efficient antioxidant mechanisms to scavenge harmful ROS are physiologic adaptions exhibited by intertidal seaweeds to persist in temperate regions. This study examines short-term (3 h) responses of three large kelps from the cold-temperate coast of Chile, normally adapted to water temperatures <16°C, but exposed abruptly to simultaneous high temperatures and UV radiation during low tide in summer. The kelps were exposed in the laboratory to three temperatures (10, 20 and 28°C) with and without UV radiation, and photochemical reactions, concentration of phlorotannins and antioxidant activity were examined. The exposure to elevated temperature (slightly exacerbated by the presence of UV radiation) decreased photochemical processes (measured as fluorescence kinetics) in the three studied species and increased lipid peroxidation in two of them. The concentration of total soluble phlorotannins was variable and correlated with the antioxidant activity in the presence of UV radiation. Insoluble phlorotannins did not change during the exposure. In all, the downregulation of the photochemical machinery, which was expressed as dynamic photoinhibition, and the rapid induction of soluble phlorotannins triggered by UV radiation minimized the effects of oxidative stress and maintained the operation of photochemical processes during short-term thermal stress.     

Comparisons of estimated economic burdens due to insufficient solar ultraviolet irradiance and vitamin D and excess solar UV irradiance for the United States

Vitamin D sufficiency is required for optimal health, and solar ultraviolet B (UVB) irradiance is an important source of vitamin D. UVB and/or vitamin D have been found in observational studies to be associated with reduced risk for over a dozen forms of cancer, multiple sclerosis, osteoporotic fractures, and several other diseases. On the other hand, excess UV irradiance is associated with adverse health outcomes such as cataracts, melanoma, and nonmelanoma skin cancer. Ecologic analyses are used to estimate the fraction of cancer mortality, multiple sclerosis prevalence, and cataract formation that can be prevented or delayed. Estimates from the literature are used for other diseases attributed to excess UV irradiation, additional cancer estimates, and osteoporotic fractures. These results are used to estimate the economic burdens of insufficient UVB irradiation and vitamin D insufficiency as well as excess UV irradiation in the United States for these diseases and conditions. We estimate that 50,000-63,000 individuals in the United States and 19,000-25,000 in the UK die prematurely from cancer annually due to insufficient vitamin D. The U.S. economic burden due to vitamin D insufficiency from inadequate exposure to solar UVB irradiance, diet, and supplements was estimated at $40-56 billion in 2004, whereas the economic burden for excess UV irradiance was estimated at $6-7 billion. These results suggest that increased vitamin D through UVB irradiance, fortification of food, and supplementation could reduce the health care burden in the United States, UK, and elsewhere. Further research is required to confirm these estimates.     

Light histories influence the impacts of solar ultraviolet radiation on photosynthesis and growth in a marine diatom, Skeletonema costatum

Phytoplanktonic species acclimated to high light are known to show less photoinhibition. However, little has been documented on how cells grown under indoor conditions for decades without exposure to UV radiation (UVR, 280-400 nm) would respond differently to solar UVR compared to those in situ grown under natural solar radiation. Here, we have shown the comparative photosynthetic and growth responses to solar UVR in an indoor- (IS) and a naturally grown (WS) Skeletonema costatum type. In short-term experiment (<1 day), Phi(PSII) and photosynthetic carbon fixation rate were more inhibited by UVR in the IS than in the WS cells. The rate of UVR-induced damages of PSII was faster and their repair was significantly slower in IS than in WS. Even under changing solar radiation simulated for vertical mixing, solar UVR-induced higher inhibition of photosynthetic rate in IS than in WS cells. During long-term (10 days) exposures to solar radiation, the specific growth rate was much lower in IS than WS at the beginning, then increased 3 days later to reach an equivalent level as that of WS. UVR-induced inhibition of photosynthetic carbon fixation in the IS was identical with that of WS at the end of the long-term exposure. The photosynthetic acclimation was not accompanied with increased contents of UV-absorbing compounds, indicating that repair processes for UVR-induced damages must have been accelerated or upgraded.     

Plant-derived surfactants as an alternative to synthetic surfactants: surface and antioxidant activities

Biosurfactants have great advantages as an eco-friendly alternative to synthetic surfactants. Surface active properties and antioxidant activity of extracts prepared from Sapindus mukorossi, Verbascum densiflorum, Equisetum arvense, Betula pendula and Bellis perennis have been studied. The extract from Sapindus mukorossi served as a standard because it belongs to the most widely used natural surfactants. The surface active properties of these nonionic surfactants were also compared with the properties of common synthetic surfactants such as sodium lauryl sulfate (SLS) and Tween® 80. In many cases, the plant-derived surfactants showed better properties than the synthetic ones, e.g. minimum critical micelle concentration values were observed for E. arvense (0.033 g L^?1), B. perennis (0.076 g L^?1), or minimum surface tension reached for the extract of B. perennis (36.8 mN m^?1).