Updated diagnostic criteria for neuromyelitis optica spectrum disorder: Similar outcomes of previously separate cohorts.

BACKGROUND: The specificity of the aquaporin-4 antibody to predict recurrent inflammatory central nervous system disease has led to the design of the 2015 neuromyelitis optica spectrum disorder criteria which capture all aquaporin-4 antibody seropositive patients. OBJECTIVE: The purpose of this study was to compare treatment outcomes in aquaporin-4 antibody seropositive patients who met the previous 2006 clinical criteria for neuromyelitis optica with patients who meet the 2015 neuromyelitis optica spectrum disorder criteria. METHODS: The study involved a three-center retrospective chart review of clinical outcomes among aquaporin-4 patients diagnosed with neuromyelitis optica and neuromyelitis optica spectrum disorder. RESULTS: Hazard ratios of relapse during immunosuppressive therapy, relative to pre-therapy, were not significantly different for patients who met the 2006 criteria of neuromyelitis optica versus the 2015 neuromyelitis optica spectrum disorder criteria among those treated with azathioprine ( p = 0.24), mycophenolate mofetil ( p = 0.63), or rituximab ( p = 0.97). CONCLUSION: Reductions in the hazard of relapse during treatment with immunosuppressive therapies, relative to average pre-treatment, were not different for aquaporin-4 antibody seropositive patients categorized using the 2006 criteria of neuromyelitis optica and the 2015 neuromyelitis optica spectrum disorder criteria. These therapeutic findings support the design of the 2015 neuromyelitis optica spectrum disorder criteria which capture all aquaporin-4 antibody seropositive patients.

Requirement for safety monitoring for approved multiple sclerosis therapies: an overview.

During the last two decades, treatment options for patients with multiple sclerosis (MS) have broadened tremendously. All agents that are currently approved for clinical use have potential side effects, and a careful risk-benefit evaluation is part of a decision algorithm to identify the optimal treatment choice for an individual patient. Whereas glatiramer acetate and interferon beta preparations have been used in MS for decades and have a proven safety record, more recently approved drugs appear to be more effective, but potential risks might be more severe. The potential complications of some novel therapies might not even have been identified to their full extent. This review is aimed at the clinical neurologist in that it offers insights into potential adverse events of each of the approved MS therapeutics: interferon beta, glatiramer acetate, mitoxantrone, natalizumab, fingolimod and teriflunomide, as well as recently approved therapeutics such as dimethyl fumarate and alemtuzumab. It also provides recommendations for monitoring the different drugs during therapy in order to avoid common side effects.

Associations between retinal nerve fiber layer abnormalities and optic nerve examination.

OBJECTIVE: Retinal nerve fiber layer (RNFL) abnormalities detected by optical coherence tomography (OCT) are useful markers for axonal loss and visual dysfunction in multiple sclerosis (MS), but their role in routine clinical management is not well-studied. METHODS: Clinical and OCT examinations were performed on 240 patients attending a neurology clinic. Using OCT 5th percentile to define abnormal RNFL thickness, we compared eyes classified by neurologists as having optic atrophy to RNFL thickness, and afferent pupillary defect (APD) to RNFL thickness ratios of eye pairs. RESULTS: Mean RNFL thickness was less in eyes classified by neurologists as having optic atrophy (79.4 ± 21 µm; n=63) vs those without (97.0 ± 15 µm; n=417; p < 0.001, t test) and in eyes with an APD (84.1 ± 16 µm; n=44) than without an APD (95.8 ± 17 µm; n=436; p < 0.001). Physicians' diagnostic accuracy for detecting pallor in eyes with an abnormal RNFL thickness was 79% (sensitivity=0.56; specificity=0.82). Accuracy for detecting a RAPD in patients with mean RNFL ratio (affected eye to unaffected eye) <0.90 was 73% (sensitivity=0.30; specificity=0.86). Ability to detect visual pathway injury via assessment of atrophy and APD differed between neurologists. CONCLUSIONS: OCT reveals RNFL abnormality in many patients in whom eyes are not classified by neurologic examiners as having optic atrophy. Further study is needed to define the role of OCT measures in the context of examinations for optic atrophy and APD by neuroophthalmologists. OCT-measured RNFL thickness is likely to have an important future role in the clinical setting.

Vitamin D status and effect of low-dose cholecalciferol and high-dose ergocalciferol supplementation in multiple sclerosis.

BACKGROUND: Vitamin D is important for bone health and immune regulation, and has been shown to be low in multiple sclerosis (MS). We sought to determine the effect of over the counter low dose cholecalciferol (LDC) and high dose ergocalciferol (HDE) on the vitamin D levels in MS patients. METHODS: We retrospectively evaluated serum 25-hydroxy-vitamin D [25(OH)D] levels of 199 patients (CIS, n = 32; RRMS, n = 115; PPMS, n = 10; SPMS, n = 16; Transverse Myelitis (TM), n = 9; other neurological diseases, n = 16) attending our clinic between 2004 and 2008. We examined the change in 25(OH)D levels in 40 MS patients who took either LDC (< or =800 IU/day) or HDE (50,000 IU/day for 7-10 days, followed by 50,000 IU weekly or biweekly). RESULTS: The average 25(OH)D level was 71 +/- 39 nmol/L (Mean +/- SD), and 167(84%) patients had insufficient levels (< or =100 nmol/L) of 25(OH)D. The patients supplemented with LDC did not have a significant increase in their 25(OH)D levels. However, 25(OH)D levels increased by 42 nmol/L (P = 0.01) in the patients originally taking LDC and then prescribed HDE. Optimal levels (> or =100 nmol/L) were only achieved in less than 40% of patients. CONCLUSIONS: We conclude that large numbers of patients with MS and TM in our cohort are deficient in vitamin D. HDE significantly elevated 25(OH)D levels in MS patients and was more effective at increasing 25(OH)D levels than LDC. Prospective studies are required to determine appropriate dosing regimen to achieve optimal levels in the majority of MS patients and to ascertain the safety, immunological response, and ultimately the clinical efficacy of vitamin D replacement therapy.

Idiopathic transverse myelitis: corticosteroids, plasma exchange, or cyclophosphamide.

Transverse myelitis is a focal disorder of the spinal cord in which an immune-mediated process results in neural injury. In this large retrospective study, we compare patients who received one of four treatments to identify the most effective therapies. We identified subsets of patients who received clinical benefit from plasma exchange or cyclophosphamide being included in their treatment regimen.

Effects of a pre-incubation period on the photoinduced toxicity of polycyclic aromatic hydrocarbons to the luminescent bacterium Vibrio fischeri.

Irradiation of polycyclic aromatic hydrocarbons (PAHs) in aqueous solution with simulated solar radiation (SSR; a light source with a visible light: UV-A:UV-B ratio similar to that of sunlight) can greatly enhance their toxicity. Two microbial toxicity tests with Vibrio fischeri were used to investigate the effect of composition of the growth medium and pre-incubation on the photoinduced toxicity of PAHs. The assays were a short-term test (15 min) and long-term test (18 h). Both assays were carried out in SSR and darkness to examine for photoinduced toxicity of PAHs. For the short-term toxicity assay, inhibition of bacterial luminescence was measured. For the long-term toxicity assay, both inhibition of bacterial luminescence and inhibition of growth were recorded. To broaden this test, V. fischeri cells were pre-incubated with PAHs in medium without a carbon source (minimal medium) for 8 h to facilitate assimilation and photooxidation of the contaminants, and to prevent bacterial growth at the outset of the assay. V. fischeri was more sensitive in minimal medium than in complex medium in both the short- and long-term toxicity assays. Moreover, in the long-term assay, SSR greatly increased toxicity, especially if there was a pre-incubation period in minimal medium. This indicates that both assimilation and photooxidation of PAHs are important to their toxicity to V. fischeri.

Effects of ultraviolet-A exposure on ultraviolet-B-induced accumulation of specific flavonoids in Brassica napus.

Many plant species are able to acclimate to changes in ultraviolet-B radiation (UVB) (290-320 nm) exposure. Due to the wide range of targets of UVB, plants have evolved diverse repair and protection mechanisms. These include increased biosynthesis of UVB screening compounds, elevated antioxidant activity and increased rates of DNA repair. We have shown previously that Brassica napus L. cv Topas plants can acclimate quite effectively to environmentally relevant increases in UVB through the accumulation of specific flavonoids in the leaf epidermis. However, B. napus was found to lose other flavonoids when plants are exposed to ultraviolet-A radiation (UVA) (320-400 nm) and/or UVB (Wilson et al. [1998] Photochem. Photobiol. 67, 547-553). In this study we demonstrate that the levels of all the extractable flavonoids in the leaves of B. napus plants are decreased in a dose-dependent manner in response to UVA exposure. Additionally, the accumulation of the extractable flavonoids was examined following a shift from photosynthetically active radiation (PAR) + UVA to PAR + UVB to assess if preexposure to UVA affected UVB-induced flavonoid accumulation. UVA preexposures were found to impede UVB-induced accumulation of some flavonoids. This down regulation was particularly evident for quercetin-3-O-sophoroside and quercetin-3-O-sophoroside-7-O-glucoside, which is interesting because quercetins have been demonstrated to be induced by UVB and correlated with UVB tolerance in some plant species. The photobiological nature of these UVA-mediated effects on flavonoid accumulation implies complex interactions between UVA and UVB responses.

Synergistic effects of a photooxidized polycyclic aromatic hydrocarbon and copper on photosynthesis and plant growth: evidence that in vivo formation of reactive oxygen species is a mechanism of copper toxicity.

Heavy metals and polycyclic aromatic hydrocarbons (PAHs) are often cocontaminants in industrialized environments, yet little is known about either the extent or mechanisms of their cotoxicity. To address this shortfall, the combined effects of an oxygenated PAH, 1,2-dihydroxyanthraquinone (1,2-dhATQ), and a heavy metal, Cu2+, on photosynthesis and growth of the duckweed (Lemna gibba) were evaluated. Using assays of chlorophyll a fluorescence and photosystem I activity, 1,2-dhATQ inhibited electron transport at the cytochrome b6/f complex. Conversely, Cu2+ alone (at low concentrations) had little effect on photosynthesis. When Cu2+ was combined with 1,2-dhATQ, an increase in transient and steady-state chlorophyll a fluorescence quenching occurred relative to 1,2-dhATQ alone. Treatment of isolated thylakoid membranes with 1,2-dhATQ inhibited whole-chain linear electron transport, measured as O2 consumption using methyl viologen as the electron acceptor. However, Cu2+ plus 1,2-dhATQ resulted in active O2 consumption with or without methyl viologen as an electron acceptor. From these data, we conclude that 1,2-dhATQ renders the plastoquinone pool to a highly reduced state by inhibiting at cytochrome b6/f. Then, Cu2+ is able to mediate the transfer of electrons from reduced plastoquinone to O2, forming reactive oxygen species. At the whole-organism level, when Cu2+ and 1,2-dhATQ were mixed at concentrations that resulted in the above-mentioned impacts on photosynthesis, synergistic inhibition of plant growth was observed. This suggests a catalytic mechanism of toxicity for redox active metals, a process that could be instrumental in explaining their impacts at low concentrations.

Chlorophyll fluorescence as a bioindicator of effects on growth in aquatic macrophytes from mixtures of polycyclic aromatic hydrocarbons.

Chlorophyll-a fluorescence induction is a rapid technique for measuring photosynthetic electron transport in plants. To assess chlorophyll-a fluorescence as a bioindicator of effects of polycyclic aromatic hydrocarbon mixtures, chlorophyll-a fluorescence parameters and plant growth responses to exposure to the wood preservative creosote were examined in the aquatic plants Lemna gibba and Myriophyllum spicatum. Exposure to creosote inhibited growth of L. gibba (EC50 = 7.2 mg/L total polycyclic aromatic hydrocarbons) and M. spicatum (EC50 = 2.6 mg/L) despite differences in physiology. Creosote also diminished maximum PSII efficiency (Fv/Fm) (EC50 = 36 and 13 mg/L for L. gibba and M. spicatum) and the effective yield of photosystem II photochemistry (deltaF/Fm') (EC50 = 13 and 15 mg/L for L. gibba and M. spicatum). The similarity between growth and chlorophyll-a fluorescence EC50s and slopes of the response curves suggests a close mechanistic link between these end points. The predictive power of chlorophyll-a fluorescence as a bioindicator of whole-organism effects applied to complex contaminant mixtures is discussed.

Control of asgE expression during growth and development of Myxococcus xanthus.

One of the earliest events in the Myxococcus xanthus developmental cycle is production of an extracellular cell density signal called A-signal (or A-factor). Previously, we showed that cells carrying an insertion in the asgE gene fail to produce normal levels of this cell-cell signal. In this study we found that expression of asgE is growth phase regulated and developmentally regulated. Several lines of evidence indicate that asgE is cotranscribed with an upstream gene during development. Using primer extension analyses, we identified two 5' ends for this developmental transcript. The DNA sequence upstream of one 5' end has similarity to the promoter regions of several genes that are A-signal dependent, whereas sequences located upstream of the second 5' end show similarity to promoter elements identified for genes that are C-signal dependent. Consistent with this result is our finding that mutants failing to produce A-signal or C-signal are defective for developmental expression of asgE. In contrast to developing cells, the large majority of the asgE transcript found in vegetative cells appears to be monocistronic. This finding suggests that asgE uses different promoters for expression during vegetative growth and development. Growth phase regulation of asgE is abolished in a relA mutant, indicating that this vegetative promoter is induced by starvation. The data presented here, in combination with our previous results, indicate that the level of AsgE in vegetative cells is sufficient for this protein to carry out its function during development.

Fractional simplex designs for interaction screening in complex mixtures.

In mixture experiments, one may be interested in estimating not only main effects but also some interactions. Main effects and significant interactions in a mixture may be estimated through appropriate mixture experiments, such as simplex-centroid designs. However, for mixtures with a large number of factors, the run size for these designs becomes impractically large. A subset of a full simplex-centroid design may be used, but the problem remains regarding which factor-level settings should be selected. In this paper, we propose a solution that considers design points with either one or p individual nonzero factor-level settings. These fractional simplex designs provide a means of screening for interactions and of investigating the behavior of many-component mixtures as a whole while greatly reducing the run size compared with full simplex-centroid designs. The means of construction of the design arrays is described, and designs for < or = 31 factors are presented. Some of the proposed methodology is illustrated using generated data.

Pathway of anthracene modification under simulated solar radiation.

Exposure of polycyclic aromatic hydrocarbons (PAHs) to sunlight results in rapid structural photomodification generally via oxidation reactions. These PAH modification products are in many cases more toxic than their parent compounds. In this study, anthracene (ANT), a rapidly photooxidized PAH, was irradiated with simulated solar radiation (SSR, 100 micromol m(-2) s(-1)) in aqueous solution to examine the photomodification pathway. The photoproducts formed were identified by HPLC. The ANT product profile after 9 h in SSR was very complex, with more than 20 compounds detected. The photoproducts formed were anthraquinones, benzoic acids, benzaldehydes and phenols showing the process to be oxidative in nature. Some of the anthraquinones were themselves subject to photooxidation, and were thus intermediates in the product pathway. The kinetics of ANT photooxidation revealed a pseudo first-order reaction with a half-life of 2 h under the SSR source used. The kinetics of product formation allowed deduction of a probable photomodification pathway. This study indicates that PAH photooxidation products are likely to exist as complex, dynamically changing mixtures in PAH contaminated aquatic environments.

Protection of photosystem II against UV-A and UV-B radiation in the cyanobacterium Plectonema boryanum: the role of growth temperature and growth irradiance.

Plectonema boryanum UTEX 485 cells were grown at 29 degrees C and 150 mumol m-2 s-1 photosynthetically active radiation (PAR) and exposed to PAR combined with ultraviolet-A radiation (UV-A) at 15 degrees C. This induced a time-dependent inhibition of photosystem II (PSII) photochemistry measured as a decrease of the chlorophyll a fluorescence ratio, Fv/Fm, to 50% after 2 h of UV-A treatment compared to nontreated control cells. Exposure of the same cells to PAR combined with UV-A + ultraviolet-B radiation (UV-B) caused only a 30% inhibition of PSII photochemistry relative to nontreated cells. In contrast, UV-A and UV-A + UV-B irradiation of cells cultured at 15 degrees C and 150 mumol m-2 s-1 had minimal effects on the Fv/Fm values. However, cells grown at 15 degrees C and lower PAR irradiance (6 mumol m-2 s-1) exhibited similar inhibition patterns of PSII photochemistry as control cells. The decreased sensitivity of PSII photochemistry of P. boryanum grown at 15 degrees C and 150 mumol m-2 s-1 to subsequent exposure to UV radiation relative to either control cells or cells grown at low temperature but low irradiance was correlated with the following: (1) a reduced efficiency of energy transfer to PSII reaction centers; (2) higher levels of a carotenoid tentatively identified as myxoxanthophyll; (3) the accumulation of scytonemin and mycosporine amino acids; and (4) the accumulation of ATP-dependent caseinolytic proteases. Thus, acclimation of P. boryanum at low temperature and moderate irradiance appears to confer significant resistance to UV-induced photoinhibition of PSII. The role of excitation pressure in the induction of this resistance to UV radiation is discussed.

Intact and photomodified polycyclic aromatic hydrocarbons inhibit photosynthesis in natural assemblages of Lake Erie phytoplankton exposed to solar radiation.

Recently, there has been a trend toward less turbid water and greater light penetration in parts of western Lake Erie. This could lead to greater phototoxicity from sediment-bound polycyclic aromatic hydrocarbons. To test photosynthesis as a bioindicator of contaminant impacts on algae, water samples containing natural assemblages of phytoplankton were collected from the western and central basins of Lake Erie. These samples were incubated with 0.2 to 2 mg L(-1) anthracene or its photomodified product 1, 2-dihydroxyanthraquinone for 60 min in darkness or in 50% sunlight, to mimic exposure of phytoplankton in the photic zone of a mixed water column. Photosynthetic efficiency was determined from filtered phytoplankton immediately after exposure using a pulse-amplitude modulated chlorophyll fluorometer. Phytoplankton incubated with chemicals in the dark demonstrated chlorophyll fluorescence values similar to those of controls. However, exposure to anthracene or 1, 2-dihydroxyanthraquinone in sunlight diminished photosystem II photosynthetic efficiency and photosynthetic quantum yield in a concentration-dependent manner. Anthracene inhibited photosynthesis at lower concentrations than 1,2-dihydroxyanthraquinone, which is consistent with the different modes of action and toxic strengths of these two contaminants. These results demonstrate that phytoplankton in Lake Erie can be subject to phototoxicity from intact and photomodified polycyclic aromatic hydrocarbons after very short exposures. Further, chlorophyll fluorescence was found to be an effective bioindicator in the field for this form of chemical stress.

Ability of polycyclic aromatic hydrocarbons to induce 7-ethoxyresorufin-o-deethylase activity in a trout liver cell line.

Along with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 24 unsubstituted polycyclic aromatic hydrocarbons (PAHs) were evaluated for their ability to induce 7-ethoxyresorufin-o-deethylase (EROD) activity in the rainbow trout liver cell line RTL-W1. When the duration and cell density of exposure were increased, the EC(50) for EROD induction was relatively constant for TCDD, but increased for PAHs. Regardless of exposure conditions, EROD activity was not induced by 9 PAHs: naphthalene, phenanthrene, anthracene, pyrene, perylene, acenaphthylene, acenaphthene, fluorene, and fluoranthene. Two PAHs, benzo[g,h,i]perylene and coronene, induced EROD activity inconsistently. The remaining 13 PAHs consistently induced EROD activity. The EC(50)s for induction exhibited approximately a 110-fold range. The order of potency, from most to least potent, was benzo[k]fluoranthene, dibenzo[a,i]pyrene, dibenzo [a,h]anthracene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo [b]fluoranthene, pentacene, benzo[b]anthracene, benzo[b] fluorene, chrysene, benzo[a]anthracene, benzo[e]pyrene, and triphenylene. When the induction potency was expressed relative to TCDD, the toxic equivalency factors (TEFs) ranged from 0.001 to 0.000 01. When expressed relative to benzo[a]pyrene, the TEFs ranged from 3.44 to 0. 03.

Impacts of structural photomodification on the toxicity of environmental contaminants: anthracene photooxidation products.

The toxicity of polycyclic aromatic hydrocarbons (PHAs) is known to be enhanced by light via photosensitization reactions (production of active oxygen) and photomodification of the chemicals (e.g., oxidation) to more toxic compounds. Anthracene (ANT) toxicity in particular has been found to increase dramatically following photomodification. The objective of this study was to identify the photooxidation products of ANT and assess the toxicity of selected photoproducts. High performance liquid chromatography (HPLC) analysis of anthracene photooxidation revealed a complex array of oxidation products; prevalent among these were anthraquinone (ATQ) and hydroxy-anthraquinones (hATQs). Eleven of these compounds were tested for toxicity using growth inhibition of the duckweed Lemna gibba L. G-3. All but one of the compounds tested were found to be toxic, and when UV radiation was present in the light source toxicity was generally enhanced. The chemicals were also irradiated under SSR prior to toxicity testing. In about half the cases, the ATQ compounds were rapidly photooxidized and the resultant photoproducts were more toxic than the parent compounds. Interestingly, 2-hydroxyanthraquinone, which was not subject to photooxidation, was the most toxic of the compounds tested. As a light stable compound it presents the risk of a persistent environmental hazard.

Ability of 16 priority PAHs to be directly cytotoxic to a cell line from the rainbow trout gill.

Sixteen polycyclic aromatic hydrocarbons (PAHs) were screened for their ability to be directly cytotoxic to a cell line from the rainbow trout gill, RTgill-W1. Exposure times of 2 h or less were sufficient for direct cytotoxicity to be detected, which appeared to be caused by a common mechanism, the general perturbation of membranes. This was judged by the similarity of results obtained for three fluorescent indicator dyes, alamar Blue, 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM) and neutral red. Among the 16 PAHs tested, just two- and three-ring PAHs were found to be directly cytotoxic. These were naphthalene approximately = acenaphthylene approximately = acenaphthene > fluorene approximately = phenanthrene. The results suggest that water solubility and lipophilicity are the critical properties determining the direct cytotoxicity of PAHs and that they do so by influencing PAH accumulation in membranes. Only naphthalene was effective at concentrations well below its water solubility limit. Therefore, direct cytotoxicity is likely to be most environmentally relevant only with naphthalene.

Ability of 16 priority PAHs to be photocytotoxic to a cell line from the rainbow trout gill.

Sixteen polycyclic aromatic hydrocarbons (PAHs) were screened for their ability to be photocytotoxic to a cell line from the rainbow trout gill, RTgill-W1. PAHs could be divided into one of three groups: incapable of being photocytotoxic, able to be both photocytotoxic and directly cytotoxic, or capable of being only photocytotoxic. Photocytotoxicity was distinct from direct cytotoxicity in that EC50 values were lower with the neutral red assay immediately after the PAH/UV treatment than with alamar Blue or CFDA-AM, indicating a more specific action on lysosomes. As well, in photocytotoxicity but not in direct cytotoxicity, the three assays showed increased impairment 24 h after treatment. Most PAHs were found to be strictly photocytotoxic; however, only six compounds were photocytotoxic at concentrations theoretically achievable in water. When photocytotoxic PAHs were ranked relative to fluoranthene to establish fluoranthene equivalent factors (FEFs), benzo[a]pyrene and benzo[g,h,i]perylene were found to be most potent. However, when the water solubility of each compound was taken into account in order to calculate the potential environmental photocytotoxic potency (PEPP), fluoranthene and pyrene appeared to have the most potential to impact fish through photocytotoxicity.

Amelioration of the photo-induced toxicity of polycyclic aromatic hydrocarbons by a commercial humic acid.

The ability of a commercial (Aldrich Chemical Co.) humic acid (AHA) to ameliorate the photo-induced toxicity of polycyclic aromatic hydrocarbons (PAHs) was examined using Lemna gibba L. (G3). Plants were exposed to anthracene and benzo(a)pyrene both with and without AHA and grown under visible light as well as lighting that simulates relative abundances of UV-A and UV-B in natural sunlight (SSR). Modest additions of 1.6 mg.L-1 AHA were sufficient to ameliorate the photo-induced toxicity of 2 mg.L-1 anthracene by improving growth rates to nearly 50% of controls and inducing minor recovery from complete chlorosis in the most highly affected plants. Benzo(a)pyrene induced minor, but significant, chlorosis under SSR, and AHA additions always increased growth rate and chlorophyll content, although to less of a degree than anthracene toxicity under SSR. The protective effects of AHA on anthracene toxicity increased linearly with increases in AHA concentrations up to 6.2 mg.L-1. Slopes of these relationships changed in the presence of UV light relative to visible light treatments; thus UV changed the extent to which AHA mediates PAH toxicity. However, the net effect was still for AHA to ameliorate PAH photo-induced toxicity even though UV has the potential to photooxidize AHA and enhance the production of potentially toxic reactive oxygen species from AHA photosensitization.

Methodology for demonstrating and measuring the photocytotoxicity of fluoranthene to fish cells in culture.

Methodology was developed for quantifying the photocytotoxicity of fluoranthene to a gill cell line from rainbow trout for future use in screening polycyclic aromatic hydrocarbons for their relative photocytotoxicity to fish. Solubilization in a modified culture medium was achieved with and without foetal bovine serum (FBS) and with and without dimethyl sulfoxide (DMSO). FBS caused most of the fluoranthene to remain in solution and blocked photocytotoxicity if present during UV irradiation. DMSO had little effect on fluoranthene distribution in cell cultures but caused cells to be slightly more sensitive to the phototoxicity of fluoranthene. The indicator dyes alamar Blue() and 5-carboxyfluorescein diacetate acetoxymethyl ester were used to quantify cytotoxicity in two different ways-singly in two separate assays, and mixed together in a novel single assay, which saved time and material. With UV irradiation for 2 hr at a photon fluence rate of either 1.4 mumol UV-B/m(2)/sec (UV-A:UV-B, 1.5) or 1.1 mumol UV-B/m(2)/sec (UV-A:UV-B, 9.7), both dyes indicated increasing loss of viability with increasing doses of fluoranthene. EC(50) values ranged from 18 to 44 ng/ml (89-217 nM), with the alamar Blue assay being slightly more sensitive.