DNA damage, histological changes and DNA repair in larval Japanese medaka (Oryzias latipes) exposed to ultraviolet-B radiation

UVB radiation and amphibian resilience: Analyzing skin color, immune suppression and oxidative stress in Rana kukunoris from different elevations

Ultraviolet-B radiation (UVBR), intensified by ozone depletion and climate change, poses a growing ecological threat to amphibians, particularly in high-elevation regions such as the Qinghai-Tibet Plateau. Endemic to this region, Rana kukunoris spans a wide range of elevations, where distinct populations may have evolved unique strategies and regulatory mechanisms to cope with UVBR. However, specific adaptive responses in adult frogs remain underexplored. This study compared the physiological responses of high- and low-altitude Rana kukunoris populations to UVBR exposure, focusing on dorsal color, immune function, antioxidant capacity, and DNA repair gene expression. High-altitude populations exhibited stable, dark pigmentation-potentially reducing the need for rapid melanin synthesis-alongside a robust immune profile and enhanced antioxidant enzyme activity, collectively conferring resilience against oxidative and immune stress under chronic UVBR exposure. Conversely, low-altitude populations exhibited pronounced UVBR-induced responses, including significant skin darkening, heightened immune activation evidenced by increased white blood cell counts, and increased oxidative damage marked by higher malondialdehyde (MDA) levels, coupled with reduced superoxide dismutase (SOD) and catalase (CAT) activities. Furthermore, tissue-specific upregulation of DNA repair genes in high-altitude populations suggested a stable DNA repair capacity adapted to high-UVBR environments. These findings reveal distinct physiological strategies within the same species for coping with UVBR across altitudinal gradients. Amid global increases in UVBR, this study offers novel insights into amphibian resilience in high-UVBR habitats and informs conservation strategies for populations across varying elevations.

Sublethal consequences of ultraviolet radiation exposure on vertebrates: Synthesis through meta-analysis

Ultraviolet radiation (UVR) from the sun is a natural daytime stressor for vertebrates in both terrestrial and aquatic ecosystems. UVR effects on the physiology of vertebrates manifest at the cellular level, but have bottom-up effects at the tissue level and on whole-animal performance and behaviours. Climate change and habitat loss (i.e. loss of shelter from UVR) could interact with and exacerbate the genotoxic and cytotoxic impacts of UVR on vertebrates. Therefore, it is important to understand the range and magnitude of effects that UVR can have on a diversity of physiological metrics, and how these may be shaped by taxa, life stage or geographical range in the major vertebrate groups. Using a meta-analytical approach, we used 895 observations from 47 different vertebrate species (fish, amphibian, reptile and bird), and 51 physiological metrics (i.e. cellular, tissue and whole-animal metrics), across 73 independent studies, to elucidate the general patterns of UVR effects on vertebrate physiology. We found that while UVR's impacts on vertebrates are generally negative, fish and amphibians were the most susceptible taxa, adult and larvae were the most susceptible life stages, and animals inhabiting temperate and tropical latitudes were the most susceptible to UVR stress. This information is critical to further our understanding of the adaptive capacity of vulnerable taxon to UVR stress, and the wide-spread sublethal physiological effects of UVR on vertebrates, such as DNA damage and cellular stress, which may translate up to impaired growth and locomotor performance. These impairments to individual fitness highlighted by our study may potentially cause disruptions at the ecosystem scale, especially if the effects of this pervasive diurnal stressor are exacerbated by climate change and reduced refuge due to habitat loss and degradation. Therefore, conservation of habitats that provide refuge to UVR stress will be critical to mitigate stress from this pervasive daytime stressor.

Susceptibility of DNA damage recognition activities linked to nucleotide excision and mismatch repair in zebrafish (Danio rerio) early and mid-early embryos to 2.5 to 4.5 °C heat stress

Fish at early life stages are sensitive to temperature change because of their narrower temperature tolerance ranges. Initiated by damage detection, DNA mismatch repair (MMR) and nucleotide excision repair (NER) maintain genome integrity respectively by eliminating mismatched nucleotides and helix-distorting DNA lesions. As discharge of heated effluent from power plants may elevate water temperatures to only 2 to 6 °C higher than ambient, this study explored if temperatures within this range affected MMR and NER-linked damage detection activities in fish embryos using zebrafish (Danio rerio) embryo as a model organism. Exposure of early embryos at 10 h post fertilization (hpf) to a warmer temperature at + 4.5 °C for 30 min enhanced damage recognition activities targeting UV-induced cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts (6-4PPs) that distorted helical structures. Conversely, photolesions sensing activities were inhibited in 24 hpf mid-early embryos under the same stress conditions. A much higher temperature at + 8.5 °C imposed similar effects on UV damage detection. A mild heat stress at + 2.5 °C for 30 min, however, repressed both CPD and 6-4PP binding activities in 10 and 24 hpf embryos. Inhibition of damage recognition under mild heat stress impeded the overall NER capacity evidenced by a transcription-based repair assay. Warmer water temperatures at + 2.5 and + 4.5 °C also inhibited G-T mismatch binding activities in 10 and 24 hpf embryos, but G-T recognition was more sensitive to + 4.5 °C stress. Inhibition of G-T binding partially correlated with a downregulation of Sp1 transcription factor activity. Our results showed the potential of water temperature elevation within 2 to 4.5 °C to disturb DNA damage repair in fish at embryonic stages.

Gadusol is a maternally provided sunscreen that protects fish embryos from DNA damage

Ultraviolet radiation (UVR) and its deleterious effects on living cells selects for UVR-protective mechanisms. Organisms across the tree of life evolved a variety of natural sunscreens to prevent UVR-induced cellular damage and stress. However, in vertebrates, only melanin is known to act as a sunscreen. Here we demonstrate that gadusol, a transparent compound discovered over 40 years ago in fish eggs, is a maternally provided sunscreen required for survival of embryonic and larval zebrafish exposed to UVR. Mutating an enzyme involved in gadusol biosynthesis increases the formation of cyclobutane pyrimidine dimers, a hallmark of UVB-induced DNA damage. Compared to the contributions of melanin and the chorion, gadusol is the primary sunscreening mechanism in embryonic and larval fish. The gadusol biosynthetic pathway is retained in the vast majority of teleost genomes but is repeatedly lost in species whose young are no longer exposed to UVR. Our data demonstrate that gadusol is a maternally provided sunscreen that is critical for early-life survival in the most species-rich branch of the vertebrate phylogeny.

DNA repair genes play a variety of roles in the development of fish embryos

Embryogenesis is one of the most important life stages because it determines an organism's healthy growth. However, embryos of externally fertilizing species, such as most fish, are directly exposed to the environment during development and may be threatened by DNA damaging factors (pollutants, UV, reactive oxygen species). To counteract the negative effects of DNA fragmentation, fish embryos evolved complex damage response pathways. DNA repair pathways have been extensively studied in some fish species, such as zebrafish (Danio rerio). Our literature review, on the other hand, revealed a paucity of knowledge about DNA damage response and repair in non-model aquaculture fish species. Further, several pieces of evidence underlie the additional role of DNA repair genes and proteins in organogenesis, spatiotemporal localization in different tissue, and its indispensability for normal embryo development. In this review, we will summarize features of different DNA repair pathways in course of fish embryo development. We describe how the expression of DNA repair genes and proteins is regulated during development, their organogenetic roles, and how the expression of DNA repair genes changes in response to genotoxic stress. This will aid in addressing the link between genotoxic stress and embryo phenotype. Furthermore, available data indicate that embryos can repair damaged DNA, but the effects of early-life stress may manifest later in life as behavioral changes, neoplasia, or neurodegeneration. Overall, we conclude that more research on DNA repair in fish embryos is needed.

Evaluation of UV-B protective properties of leaves and seeds of Achyranthes aspera in Asian catfish Clarias batrachus (Linn.)

The ultraviolet-B (UV-B) radiation is harmful to the aquatic organisms. The UV-B protective properties of leaves and seeds of herb Achyranthes aspera were evaluated in Clarias batrachus. Fish were fed with four diets-EFL1, EFL2 containing 0.25 and 0.5% leaves, EFS containing 0.5% seeds and control, CF. After 83 days of feeding, fish were exposed to UV-B (157 µW/cm²) for 7 days at the rate of 15 min/day. One batch of fish in each treatment was kept unexposed. Significantly higher final weight was found in EFS followed by EFL2 and EFL1 treatments. It was higher in unexposed fish compared to the exposed ones. Among exposed fish, significantly higher lysozyme was found in EFS and myeloperoxidase in EFS and EFL2 compared to others. Nitric oxide synthase and superoxide dismutase levels were significantly higher in liver and head kidney of EFS diet fed fish compared to others. Thiobarbituric acid reactive substances (TBARS) and carbonyl protein levels were minimum in EFS followed by EFL2. The independent sample t-test showed that nitric oxide synthase was significantly higher and myeloperoxidase and TBARS levels were significantly lower in unexposed group compared to the exposed fish in respective treatment. There were up-regulations of TNF-α, iNOS, NF-kB, BAX, Cytochrome c, SOD-c, Caspase 3, Caspase 9, BCL2 in liver and head kidney of leaves and seeds incorporated diets fed fish compared to control. Supplementation of A. aspera seeds and leaves at 0.5% level in diets gave UV-B protection to the fish.

The Effect of an Anthropogenic Magnetic Field on the Early Developmental Stages of Fishes-A Review

The number of sources of anthropogenic magnetic and electromagnetic fields generated by various underwater facilities, industrial equipment, and transferring devices in aquatic environment is increasing. These have an effect on an array of fish life processes, but especially the early developmental stages. The magnitude of these effects depends on field strength and time of exposure and is species-specific. We review studies on the effect of magnetic fields on the course of embryogenesis, with special reference to survival, the size of the embryos, embryonic motor function, changes in pigment cells, respiration hatching, and directional reactions. We also describe the effect of magnetic fields on sperm motility and egg activation. Magnetic fields can exert positive effects, as in the case of the considerable extension of sperm capability of activation, or have a negative influence in the form of a disturbance in heart rate or developmental instability in inner ear organs.

UVA-induced neurotoxicity in Japanese medaka (Oryzias latipes)

Ultraviolet radiation-induced neurodegeneration has been studied in the early stages of development in fish, but not extensively in the adult stage. The present study aimed at investigating the effects of ultraviolet radiation-A (UVA) in adult Japanese medaka (Oryzias latipes). The brain, spinal cord, and retina were examined histopathologically as nervous system target organs. Japanese medaka fish were exposed to 15, 30, and 60 min day-1 UVA for 3 days, and samples were obtained 24 h and 14 days after UVA exposure. Neurohistopathological alterations in brain tissue included vacuoles, blood congestion, degeneration of neuropils, and pyknotic nuclei in neurons. Alterations in the spinal cord included neuronal cell degeneration, reduction in the spinal cord area, and degeneration of Mauthner cells. Retinal tissue showed vacuolation in the nerve fiber layer (NFL), pyknotic nuclei in the ganglion cell layer (GCL), and decreased cell populations particularly in the inner nuclear layer (INL) and GCL. The degree of degeneration was dependent on the duration of UVA exposure. The signs of degeneration decreased gradually and disappeared completely after the 14-day recovery period. In addition, p53-deficient medaka fish were more tolerant than were wild-type (Hd-rR) Japanese medaka. In conclusion, UV radiation induced neurodegeneration in the brain, spinal cord, and retina of adult Japanese medaka (Oryzias latipes) but their normal histological architecture reappeared in these tissues after 14 days.

The Power of Fish Models to Elucidate Skin Cancer Pathogenesis and Impact the Discovery of New Therapeutic Opportunities

Animal models play important roles in investigating the pathobiology of cancer, identifying relevant pathways, and developing novel therapeutic tools. Despite rapid progress in the understanding of disease mechanisms and technological advancement in drug discovery, negative trial outcomes are the most frequent incidences during a Phase III trial. Skin cancer is a potential life-threatening disease in humans and might be medically futile when tumors metastasize. This explains the low success rate of melanoma therapy amongst other malignancies. In the past decades, a number of skin cancer models in fish that showed a parallel development to the disease in humans have provided important insights into the fundamental biology of skin cancer and future treatment methods. With the diversity and breadth of advanced molecular genetic tools available in fish biology, fish skin cancer models will continue to be refined and expanded to keep pace with the rapid development of skin cancer research. This review begins with a brief introduction of molecular characteristics of skin cancers, followed by an overview of teleost models that have been used in the last decades in melanoma research. Next, we will detail the importance of the zebrafish (Danio rerio) animal model and other emerging fish models including platyfish (Xiphophorus sp.), and medaka (Oryzias latipes) in future cutaneous malignancy studies. The last part of this review provides the recent development and genome editing applications of skin cancer models in zebrafish and the progress in small molecule screening.

Ultraviolet absorbing compounds provide a rapid response mechanism for UV protection in some reef fish

The external mucus surface of reef fish contains ultraviolet absorbing compounds (UVAC), most prominently Mycosporine-like Amino Acids (MAAs). MAAs in the external mucus of reef fish are thought to act as sunscreens by preventing the damaging effects of ultraviolet radiation (UVR), however, direct evidence for their protective role has been missing. We tested the protective function of UVAC's by exposing fish with naturally low, Pomacentrus amboinensis, and high, Thalassoma lunare, mucus absorption properties to a high dose of UVR (UVB: 13.4W∗m(-2), UVA: 6.1W∗m(-2)) and measuring the resulting DNA damage in the form of cyclobutane pyrimidine dimers (CPDs). For both species, the amount of UV induced DNA damage sustained following the exposure to a 1h pulse of high UVR was negatively correlated with mucus absorbance, a proxy for MAA concentration. Furthermore, a rapid and significant increase in UVAC concentration was observed in P. amboinensis following UV exposure, directly after capture and after ten days in captivity. No such increase was observed in T. lunare, which maintained relatively high levels of UV absorbance at all times. P. amboinensis, in contrast to T. lunare, uses UV communication and thus must maintain UV transparent mucus to be able to display its UV patterns. The ability to rapidly alter the transparency of mucus could be an important adaptation in the trade off between protection from harmful UVR and UV communication.

Exposure to fluorescent light triggers down regulation of genes involved with mitotic progression in Xiphophorus skin

We report RNA-Seq results from skin of X. maculatus Jp 163 B after exposure to various doses of "cool white" fluorescent light (FL). We show that FL exposure incites a genetic transcriptional response in skin nearly as great as observed for UVB exposure; however, the gene sets modulated due to exposure to the two light sources are quite different. Known light responsive genes involved in maintaining circadian cycling (e.g., clock, cry2a, cry1b, per1b, per2, per3, and arntl1a) exhibited expected shifts in transcriptional expression upon FL exposure. Exposure to FL also resulted in down-regulated transcription of many genes involved with cell cycle progression (e.g., cdc20, cdc45, cdca7b, plk1, cdk1, ccnb-3, and cdca7a) and chromosome segregation (e.g., cenpe, cenpf, cenpi, cenpk, cenpo, cenpp, and cenpu; cep70; knstrm, kntc, mcm2, mcm5; smc2). In addition, several DNA replication and recombination repair genes (e.g., pola1, pole, rec52, rad54l, rpa1, and parpbp) exhibit reduced expression in FL exposed X. maculatus skin. Some genes down modulated by FL are known to be associated with DNA repair and human diseases (e.g., atm2, brip1, fanc1, fancl, and xrcc4). The overall suppression of genes involved with mitotic progression in the skin of adult fish is consistent with entry into the light phase of the circadian cycle. Current efforts are aimed at determining specific wavelengths that may lead to differential expression among the many genes affected by fluorescent light exposure.

Hematotoxic and biochemical effects of UVA on the Egyptian toad (Bufo regularis)

PURPOSE

To study the adverse impacts of ultraviolet radiation-A (UVA 320-400 nm) on some hematological and biochemical parameters of Bufo regularis was considered.

MATERIALS AND METHODS

Samples were classified into four groups: (i) Control; (ii) ultraviolet radiation (UVR)-treated group (for 3 days/for 15 min/day); (iii) UVR-treated group (for 3 days/for 30 min/day); and (iv) (for 3 days/for 60 min/day). The destructive effects of UVA radiation was evaluated by red blood cells (RBC) count, hemoglobin content (Hb), hematocrite (Ht), erythrocytic indices, white blood cells (WBC) count, total protein, glucose, aspartic amino transferase (AST), alanine amino transferase (ALT), alkaline phosphatase (ALP), lactate dehyderogenase (LDH), glucose-6-phosphate dehyderogenase (G6PDH) and total bilribuin.

RESULTS

No mortality was observed. However, some physiological effects after the exposure to UVA were reported. The UVA-induced malformations recorded in the red blood cells included crenated cells (Cr), Acanthocytes (Ac), tear drop-like cells (Tr) and sickle cells (Sk).

CONCLUSION

The present study revealed the exposure to UVA from 15-60 min/day for three days could promote several biochemical and physiological disturbances as well as some changes in RBC.

Negative impacts of ultraviolet-A radiation on antioxidant and oxidative stress biomarkers of African catfish Clarias gariepinus

The present study was carried out to evaluate the ultraviolet-A (UVA) effects on biochemical, oxidative stress and antioxidant changes using aquatic species.

Beyond xeroderma pigmentosum: DNA damage and repair in an ecological context. A tribute to James E. Cleaver

The ability to repair DNA is a ubiquitous characteristic of life on Earth and all organisms possess similar mechanisms for dealing with DNA damage, an indication of a very early evolutionary origin for repair processes. James E. Cleaver's career (initiated in the early 1960s) has been devoted to the study of mammalian ultraviolet radiation (UVR) photobiology, specifically the molecular genetics of xeroderma pigmentosum and other human diseases caused by defects in DNA damage recognition and repair. This work by Jim and others has influenced the study of DNA damage and repair in a variety of taxa. Today, the field of DNA repair is enhancing our understanding of not only how to treat and prevent human disease, but is providing insights on the evolutionary history of life on Earth and how natural populations are coping with UVR-induced DNA damage from anthropogenic changes in the environment such as ozone depletion.

DNA repair activity in fish and interest in ecotoxicology: a review

The knowledge of DNA repair in a target species is of first importance as it is the primary line of defense against genotoxicants, and a better knowledge of DNA repair capacity in fish could help to interpret genotoxicity data and/or assist in the choice of target species, developmental stage and tissues to focus on, both for environmental biomonitoring studies and DNA repair testing. This review focuses in a first part on what is presently known on a mechanistic basis, about the various DNA repair systems in fish, in vivo and in established cell lines. Data on base excision repair (BER), direct reversal with O⁶-alkylguanine transferase and double strand breaks repair, although rather scarce, are being reviewed, as well as nucleotide excision repair (NER) and photoreactivation repair (PER), which are by far the most studied repair mechanisms in fish. Most of these repair mechanisms seem to be strongly species and tissue dependent; they also depend on the developmental stage of the organisms. BER is efficient in vivo, although no data has been found on in vitro models. NER activity is quite low or even inexistent depending on the studies; however this lack is partly compensated by a strong PER activity, especially in early developmental stage. In a second part, a survey of the ecotoxicological studies integrating DNA repair as a parameter responding to single or mixture of contaminant is realized. Three main approaches are being used: the measurement of DNA repair gene expression after exposure, although it has not yet been clearly established whether gene expression is indicative of repair capacity; the monitoring of DNA damage removal by following DNA repair kinetics; and the modulation of DNA repair activity following exposure in situ, in order to assess the impact of exposure history on DNA repair capacity. Since all DNA repair processes are possible targets for environmental pollutants, we can also wonder at which extent such a modulation of repair capacities in fish could be the base for the development of new biomarkers of genotoxicity. Knowing the importance of the germ cell DNA integrity in the reproductive success of aquatic organisms, the DNA repair capacity of such cells deserve to be more studied, as well as DNA repair capacities of established fish cell lines. The limited amount of available data, which shows low/slow DNA repair capacities of fish cell lines compared with mammalian cell lines, concerned mainly the NER system; thus this point merits to be explored more deeply. Additionally, since some of the DNA repair systems appear more efficient in embryo larval stages, it would be of interest to consider embryonic cell lineages more closely.

Effect of sub-lethal exposure to ultraviolet radiation on the escape performance of Atlantic cod larvae (Gadus morhua)

The amount of ultraviolet (UV) radiation reaching the earth's surface has increased due to depletion of the ozone layer. Several studies have reported that UV radiation reduces survival of fish larvae. However, indirect and sub-lethal impacts of UV radiation on fish behavior have been given little consideration. We observed the escape performance of larval cod (24 dph, SL: 7.6±0.2 mm; 29 dph, SL: 8.2±0.3 mm) that had been exposed to sub-lethal levels of UV radiation vs. unexposed controls. Two predators were used (in separate experiments): two-spotted goby (Gobiusculus flavescens; a suction predator) and lion's mane jellyfish (Cyanea capillata; a "passive" ambush predator). Ten cod larvae were observed in the presence of a predator for 20 minutes using a digital video camera. Trials were replicated 4 times for goby and 5 times for jellyfish. Escape rate (total number of escapes/total number of attacks ×100), escape distance and the number of larvae remaining at the end of the experiment were measured. In the experiment with gobies, in the UV-treated larvae, both escape rate and escape distance (36%, 38±7.5 mm respectively) were significantly lower than those of control larvae (75%, 69±4.7 mm respectively). There was a significant difference in survival as well (UV: 35%,

CONTROL

63%). No apparent escape response was observed, and survival rate was not significantly different, between treatments (UV: 66%,

CONTROL

74%) in the experiment with jellyfish. We conclude that the effect and impact of exposure to sub-lethal levels of UV radiation on the escape performance of cod larvae depends on the type of predator. Our results also suggest that prediction of UV impacts on fish larvae based only on direct effects are underestimations.

UV-B exposure causes DNA damage and changes in protein expression in northern pike (Esox lucius) posthatched embryos

The ongoing anthropogenically caused ozone depletion and climate change has increased the amount of biologically harmful UV-B radiation, which is detrimental to fish in embryonal stages. The effects of UV-B radiation on the levels and locations of DNA damage manifested as cyclobutane pyrimidine dimers (CPDs), heat shock protein 70 (HSP70) and p53 protein in newly hatched embryos of pike were examined. Pike larvae were exposed in the laboratory to current and enhanced doses of UV-B radiation. UV-B exposure caused the formation of CPDs in a fluence rate-dependent manner, and the CPDs were found deeper in the tissues with increasing fluence rates. UV-B radiation induced HSP70 in epidermis, and caused plausible p53 activation in the brain and epidermis of some individuals. Also at a fluence rate occurring in nature, the DNA damage in the brain and eyes of pike and changes in protein expression were followed by severe behavioral disorders, suggesting that neural molecular changes were associated with functional consequences.

Effects of ultraviolet A on the activity of two metabolic enzymes, DNA damage and lipid peroxidation during early developmental stages of the African catfish, Clarias gariepinus (Burchell, 1822)

Many ultraviolet-A (UVA)-induced biochemical and physiological changes are valid as biomarkers using aquatic species for detection of the degree of stress. Changes in the concentration and activities of enzymes, such as glucose-6-phosphate dehyderogenase (G6PDH), lactate dehyderogenase (LDH), DNA damage and lipid peroxidation (LPO), can be used as biomarkers to identify possible environmental contamination in fish. This study aimed to investigate the impact of UVA on the activity of the selected enzymes, DNA damage and LPO during early developmental stages of the African catfish Clarias gariepinus. Embryo hemogenates were used for measurements of G6PDH, LDH, DNA damage and LPO concentrations and activities spectrophotometrically at 37 degrees C. The normal ontogenetic variations in enzyme activities, DNA damage and LPO of the early developmental stages (24-168 h-PFS; hours-post fertilization stage) were studied. There was a significant decrease in the activity of G6PDH till 120 h-PFS. Then after 120 h-PFS, the activity of such enzymes insignificantly increased toward higher stages. The LDH activity was recorded with a pattern of decrease till 96 h-PFS, followed by a significant increase toward 168 h-PFS. The polynomial pattern of variations in DNA damage and LPO was also evident. The patterns of the enzyme activities, corresponding DNA damage and LPO of the early ontogenetic stages under the influence of three different UVA doses (15, 30 and 60 min), were recorded. The pattern of variations in G6PDH activity in UVA-induced groups was similar to that of the control group with variation in the magnitude of such activity. In all treated groups, LDH activity decreased till 96 h-PFS, then increased till 168 h-PFS. Within each of the embryonic stages, the increase in UVA led to a significant increase in DNA damage. A significant increase in lipid peroxidation under UVA doses was recorded. The variability in number and molecular weight of proteins under exposure to UVA was evident, reflecting some of the genetic and transcriptional changes during exposure and development.

Effects of environmental and artificial UV-B radiation on freshwater prawn Macrobrachium olfersi embryos

The recent decrease of the stratospheric ozone has resulted in an increase of ultraviolet-B (UV-B) radiation reaching the Earth's surface. In freshwater ecosystems with transparent water, UV-B rays easily penetrate and potentially cause harmful effects to organisms. In this study, embryos of the prawn Macrobrachium olfersi were used to evaluate the impact of UV-B rays in freshwater environments. We observed three groups of embryos: the first was to assess whether UV-B radiation produced morphological defects and/or biochemical impairments in the laboratory. The second was to check whether embryos with the same impairments as those observed in the laboratory were found in their environment, under natural solar radiation. The third group was the non-irradiated control. The embryos irradiated with 310 mW cm(-2) UV-B for 30 min showed morphological alterations similar to those observed in embryos from the environmental control group. The most important effects of the UV-B radiation observed in M. olfersi embryos were morphological (1.2% of the total number of embryos from the environment and 2.8% of the total number of irradiated embryos), pigmentation changes in the eyes (78.0% of the total number of embryos from the environment and 98.9% of the total number of irradiated embryos), and disruption of the chromatophores (46.9% of the total number of embryos from the environment and 95.5% of the total number of irradiated embryos). We also observed an increase in egg volume, which was accompanied by a significant increase in water content in UV-B irradiated groups when compared with aquaria control embryos. In addition, a significant decrease in the mitotic index in eggs exposed to UV-B radiation was detected (0.17 for the embryos from the aquaria control, 0.10 for the embryos of the environmental control, and 0.04 for the irradiated groups). The low levels of NPSH and high levels of TBARS indicated that UV-B rays directly compromised the antioxidant function of the embryonic cells, leading to oxidative stress. Our combined morphological and biochemical analyses revealed important effects induced by UV-B on M. olfersi embryos, and the results suggest that the recent changes in global conditions may have injurious effects, at least on the embryos of freshwater prawns.

Protein expression profiling

Protein expression profiling is defined in general as identifying the proteins expressed in a particular tissue, under a specified set of conditions and at a particular time, usually compared to expression in reference samples. This information is useful in drug discovery and diagnosis as well as in understanding response mechanisms at the protein level. We may identify all the proteins responding to a particular stimulus and select those whose expression changes most. Or we may isolate significant protein variables and then identify them. These definitive sets of proteins (protein expression signatures; PES) are specific to diseases, toxicants, physical stresses, and to degrees of stress severity. Here we describe a method, based on machine learning, for isolating the sets of proteins, before identifying them by name, which classify accurately the treatment classes in a study. The principle in this chapter is that if proteins associated with known classes of interest can be used to identify unknown classes then the proteins are definitive for diagnosis.The proteins in each class, including controls, are converted to digital data and serve as input to artificial neural network (ANN) models. Multiple two-dimensional electrophoresis (2DE) gel patterns are included in each treatment class. A training subset of digitized individual, not composite, gel images is used to construct an ANN model which is then applied to a test set of images. Successful classification of the unknown (test) data confirms that the variables included in the model are indeed significant in discrimination among the classes. In the study described here the misclassifications were 5% or less using the ANN models. The ANN method seems to be a useful complement to image analysis, described in Chapter "Troubleshooting Image Analysis in 2DE". The reduction in protein variables permits multivariable statistics such as cluster and discriminant analyses.

Ultraviolet radiation-A (366 nm) induced morphological and histological malformations during embryogenesis of Clarias gariepinus (Burchell, 1822)

Exposure to ultraviolet radiation has been associated with variety effects in many organisms ranging from molecular and tissue damage to population level effects. The exposure of embryos of the catfish, Clarias gariepinus (Burchell, 1822) to 366nm UVA at different doses 15, 30 and 60 min resulted in the hatching time delayed to 29 h-post-fertilization stage (29 h-PFS) in comparison with normal hatching time of 22h-PFS at 29 degrees C. In embryos exposed to 15 min/UVA, 30 min/UVA and 60 min/UVA the total percentage of hatched embryos/fertilized eggs were 90%, 89% and 85%, respectively, while in control was 95% at 29 h-PFS. The total percentage of mortality/ hatched embryos were (1-14)%, (2-22)%, (2-23)% and (3-40)% for control, 15 min, 30 min and 60 min groups, respectively, at 40 h-PFS. Also as a result some morphological malformations; (yolk sac oedema, body curvature, fin blistering, and dwarfism) were revealed. These destructive effects were also confirmed by histopathological changes in gills, eyes, intestinal tract, spinal cord, notochord, liver, skin and kidney. The results confirm that exposure to UVA caused an exposure time-dependent delay in hatching rate and reduced the percentage of the hatched embryos but the mortality rate increased with increase of the exposure time to UVA.

Long-term UVB irradiation affects the immune functions of carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss)

The effects of long-term, low-dose ultraviolet B (UVB) radiation on immune functions of two fish species representing different taxonomic groups, carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss), were assessed in this study. The fish were exposed to 7, 20 or 60 mJ cm(-2) UVB three times per week, for 6 weeks. In carp, UVB exposure affected the respiratory burst activity of blood and head kidney phagocytes, differential blood leukocyte counts and blood chemistry. Phytohemagglutinin (PHA)-stimulated in vitro proliferation responses of blood and head kidney lymphocytes, however, remained unchanged. Rainbow trout tolerated the irradiations with fewer alterations, but significant changes were detected in blood chemistry and hematocrits of the irradiated fish. These results indicate that long-term exposure to low doses of UVB induces immunomodulation in fish, and that there are species-specific differences in sensitivity to irradiation.

Combined effects of cadmium and ultraviolet radiation on mortality and mineral content in common frog (Rana temporaria) larvae

The combined effects of UV with Cd(2 +) exposure on the mortality and mineral content of common frog larvae was investigated. Tadpoles were raised in increasing concentrations of Cd(2 +) (0-2000 microg x L(-1)). Additionally the larvae were exposed to biologically effective doses of UV-A (0.24 kJ x m(- 2)) and UV-B (2.71 kJ x m(- 2)). Parallel groups were grown in the same ionic concentrations in the absence of UV. In the second experiment larvae were exposed to sublethal doses of Cd(2 +) (1000 microg x L(-1)) for 3 days. Then the larvae were submitted to 4 weeks of recovery in clean water. Cd, Cu, Zn, Ca, Mg, Fe, Na, K contents and Na/K ratio were measured. In tadpoles exposed exclusively to Cd(2 +) the 96 h LC50 = 3155 microg x L(-1). By contrast in tadpoles exposed to Cd(2 +) and UV for 96 hours the LC50 = 710 microg x L(-1). More cadmium was accumulated in UV-exposed tadpoles. On the other hand tadpoles exposed to UV radiation removed cadmium more efficiently than non-irradiated larvae. Cu, Na, and K were positively correlated with Cd content while Mg was negatively correlated with Cd. Animals exposed to combined stressors had lower Mg, Fe, Ca, Na, Zn contents, lower Na/K ratio and higher Cu and K contents than animals exposed exclusively to cadmium. Our studies indicate that cadmium ions combined with UV significantly increase mortality of common frog tadpoles. This may be related to higher cadmium uptake, disturbances in the content of essential metals and ionic imbalance.

COMBINED EFFECTS OF ULTRAVIOLET RADIATION AND TEMPERATURE ON MORPHOLOGY, PHOTOSYNTHESIS, AND DNA OF ARTHROSPIRA (SPIRULINA) PLATENSIS (CYANOPHYTA)(1)

Natural levels of solar UVR were shown to break and alter the spiral structure of Arthrospira (Spirulina) platensis (Nordst.) Gomont during winter. However, this phenomenon was not observed during summer at temperatures of ∼30°C. Since little has been documented on the interactive effects of solar UV radiation (UVR; 280-400 nm) and temperature on cyanobacteria, the morphology, photosynthesis, and DNA damage of A. platensis were examined using two radiation treatments (PAR [400-700 nm] and PAB [PAR + UV-A + UV-B: 280-700]), three temperatures (15, 22, and 30°C), and three biomass concentrations (100, 160, and 240 mg dwt [dry weight] · L(-1) ). UVR caused a breakage of the spiral structure at 15°C and 22°C, but not at 30°C. High PAR levels also induced a significant breakage at 15°C and 22°C, but only at low biomass densities, and to lesser extent when compared with the PAB treatment. A. platensis was able to alter its spiral structure by increasing helix tightness at the highest temperature tested. The photochemical efficiency was depressed to undetectable levels at 15°C but was relatively high at 30°C even under the treatment with UVR in 8 h. At 30°C, UVR led to 93%-97% less DNA damage when compared with 15°C after 8 h of exposure. UV-absorbing compounds were determined as negligible at all light and temperature combinations. The possible mechanisms for the temperature-dependent effects of UVR on this organism are discussed in this paper.

Different sensitivity of carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) to the immunomodulatory effects of UVB irradiation

In order to study the sensitivity of two fish species, carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss), to the immunomodulatory effects of ultraviolet B (UVB) radiation, the fish were exposed to a single UVB dose of 50, 250, 500 or 1,000 mJ cm(-2). These species represent different phylogenetic groups of fish, and they differ also in their behaviour inhabitating often dark and turbid (carp) or clear and transparent waters (salmonids). Immune responses were studied on day 1 post-irradiation. Unexposed fish, and fish exposed to radiation depleted of UV wavelengths served as controls. UVB irradiation markedly enhanced the blood respiratory burst and cytotoxic activity in carp, but in the head kidney these parameters were significantly suppressed. Rainbow trout respiratory burst was affected only after exposure with the highest dose of UVB. Lymphopenia and granulophilia were noted in both fish blood after exposure. This study indicates that UVB irradiation modulates immune functions in both fish species studied, and that rainbow trout is more tolerant than carp against UVB. Fish are clearly adapted to the environmental UVB levels prevailing in their usual living habitats, but are also a target of undesired effects of UVB on immune functions whenever exposed to increased radiation levels.

Ultraviolet (280-400 nm)-induced DNA damage in the eggs and larvae of Calanus finmarchicus G. (Copepoda) and Atlantic cod (Gadus morhua)

In previous work, we evaluated the effects of ultraviolet (UV = 280-400 nm) radiation on the early life stages of a planktonic Calanoid copepod (Calanus finmarchicus Gunnerus) and of Atlantic cod (Gadus morhua). Both are key species in North Atlantic food webs. To further describe the potential impacts of UV exposure on the early life stages of these two species, we measured the wavelength-specific DNA damage (cyclobutane pyrimidine dimer [CPD] formation per megabase of DNA) induced under controlled experimental exposure to UV radiation. UV-induced DNA damage in C. finmarchicus and cod eggs was highest in the UV-B exposure treatments. Under the same spectral exposures, CPD loads in C. finmarchicus eggs were higher than those in cod eggs, and for both C. finmarchicus and cod embryos, CPD loads were generally lower in eggs than in larvae. Biological weighting functions (BWF) and exposure response curves that explain most of the variability in CPD production were derived from these data. Comparison of the BWF revealed significant differences in sensitivity to UV-B: C. finmarchicus is more sensitive than cod, and larvae are more sensitive than eggs. This is consistent with the raw CPD values. Shapes of the BWF were similar to each other and to a quantitative action spectrum for damage to T7 bacteriophage DNA that is unshielded by cellular material. The strong similarities in the shapes of the weighting functions are not consistent with photoprotection by UV-absorbing compounds, which would generate features in BWF corresponding to absorption bands. The BWF reported in this study were applied to assess the mortality that would result from accumulation of a given CPD load: for both C. finmarchicus and cod eggs, an increased load of 10 CPD Mb(-1) of DNA due to UV exposure would result in approximately 10% mortality.