Protective effect of placenta extracts against nitrite-induced oxidative stress in human erythrocytes

Aqueous-saline human placenta extract (HPE) is known to possess antioxidant activity due to the high concentration of bioactive substances. This fact allows its application in clinical practice in order to treat oxidation-induced diseases. Extract antioxidant activity is mainly conditioned by proteins. Freezing of extracts has been shown to lead to their antioxidant activity increasing due to protein conformation changes.Different biological models are widely used in order to evaluate efficacy of novel antioxidants and mechanisms of their action. One such model appears to be erythrocytes under nitrite-induced oxidative stress. Nitrite is known to be able to penetrate erythrocyte membrane and to oxidize hemoglobin. In order to investigate whether HPE is able to decrease nitrite-induced oxidative injuries and to evaluate the protein contribution to this process, spectrophotometric and electron spin resonance (ESR) assays were used.Experimental data have revealed that antioxidant activity of extracts and of some of their fractions correlates with methemoglobin concentration lowering. Preliminary erythrocyte incubation with an extract fraction of 12 kDa allows preservation of the structural-dynamic cytosol state the closest to the control.

Acute toxicity of nitrate and nitrite to sensitive freshwater insects, mollusks, and a crustacean

Both point- and nonpoint-sources of pollution have contributed to increased inorganic nitrogen concentrations in freshwater ecosystems. Although numerous studies have investigated the toxic effects of ammonia on freshwater species, relatively little work has been performed to characterize the acute toxicity of the other two common inorganic nitrogen species: nitrate and nitrite. In particular, to our knowledge, no published data exist on the toxicity of nitrate and nitrite to North American freshwater bivalves (Mollusca) or stoneflies (Insecta, Plecoptera). We conducted acute (96-h) nitrate and nitrite toxicity tests with two stonefly species (Allocapnia vivipara and Amphinemura delosa), an amphipod (Hyalella azteca), two freshwater unionid mussels (Lampsilis siliquoidea and Megalonaias nervosa), a fingernail clam (Sphaerium simile), and a pond snail (Lymnaea stagnalis). Overall, we did not observe a particularly wide degree of variation in sensitivity to nitrate, with median lethal concentrations ranging from 357 to 937 mg NO(3)-N/l; furthermore, no particular taxonomic group appeared to be more sensitive to nitrate than any other. In our nitrite tests, the two stoneflies tested were by far the most sensitive, and the three mollusks tested were the least sensitive. In contrast to what was observed in the nitrate tests, variation among species in sensitivity to nitrite spanned two orders of magnitude. Examination of the updated nitrite database, including previously published data, clearly showed that insects tended to be more sensitive than crustaceans, which were in turn more sensitive than mollusks. Although the toxic mechanism of nitrite is generally thought to be the conversion of oxygen-carrying pigments into forms that cannot carry oxygen, our observed trend in sensitivity of broad taxonomic groups, along with information on respiratory pigments in those groups, suggests that some other yet unknown mechanism may be even more important.

Assessment of health hazard associated with nitrogen compounds in water

This paper presents results of analyses of water in the river Mała Panew in South West Poland flowing through a rural area with some chemical industry developed. The aims of the work were to investigate the pollutants level in the river, compare the obtained results with obligatory drinking water standards and determine possible health effects when using the river as a source for drinking water production. Attention was given to nitrogen compounds as nitrate(V) ions (NO(3-)) and nitrite(III) ions (NO(2-)), mostly of anthropogenic origin, were detected in the monitored water. The average concentrations of NO(3-) and NO(2-) were 3.54 and 0.286 mg/dm(3), respectively. The chances for non-carcinogenic effects, namely methemoglobinemia, resulting from possible exposure to the examined chemicals were determined based on the analytical and toxicological data. As infants are the sub-population most susceptible to nitrate-induced methemoglobinemia, the assessment was limited to children aged 0-3 years. The determined values expressed by hazard quotient (HQ) and hazard index (HI) indicate that the water pollutants and their concentrations do not exceed unity; however, in the case of infants, the other nitrate sources should be controlled.

[Study on acute and subchronic toxicity of ammonium dinitramide]

OBJECTIVE

To study the acute, subacute and subchronic toxicity induced by ammonium dinitramide (ADN), and to ascertain the gradation and target organs of acute toxicity induced by AND.

METHODS

According to technical specifications for toxicity determination of chemicals, the oral tests for acute, subacute and subchronic toxicity induced by AND were performed for 90 days.

RESULTS

The oral LDx for mouse and rat was 568.9 mg/kg and 616.6 mg/kg ADN respectively. The gradation of acute toxicity induced by AND was low level. The results of oral subacute and subchronic toxicity tests (for 28 and 90 days) showed that a gain in weight in group exposed to 123 mg/kg AND was significantly lower than that in control group (P<0.05), the TBIL and ALT in group exposed to 61.6 and 123 mg/kg AND significantly increased and the ratio of liver weight to body weight obviously decreased, as compared with control group, the number of animals with hepatic pathological changes in group exposed to 61.6 and 123 mg/kg AND was significantly higher than that in control group (P<0.05).

CONCLUSION

The gradation of acute toxicity induced by ADN was low level. When the exposure dose of AND was 30.8 mg/kg, the adverse effect was not observed, and the target organ was liver.

[Study on mutagenicity and teratogenicity of ammonium dinitramide]

OBJECTIVE

To study the mutagenicity and teratogenicity induced by ammonium dinitramide(ADN).

METHODS

According to technical specifications for toxicity determination of chemicals, Salmonella typhimurium reverse mutation assay (Ames assay), in vivo mammalian erythrocyte micronucleus test, sperm malformation test and teratogenesis test were used to detect the mutagenicity and teratogenicity induced by AND.

RESULTS

When the exposure doses of AND were 8-5000 pg/plate, the result of Ames assay was negative. As compared with control group, the micronucleus rate of mice exposed to 113.8 mg/kg AND significantly increased(P<0.05), the sperm malformation rates of mice exposed to 54.4-272.0 mg/kg AND did not increased significantly. The survival rate of fetuses decreased, the rate of assimilated fetuses increased, the rate of fetus sternum agenesis enhanced in mice exposed to 319 mg/kg AND, as compared with controls. The rates of in the 4th-6th fetus sternum agenesis in groups exposed to 21.3, 79.7 and 319 mg/kg AND were higher than that in control group. The malformation rate of fetus bowels in groups exposed to 319 mg/kg AND was higher than that in control group. The teratogenic index of ADN was 30.

CONCLUSION

AND may be a mutagen and induce the teratogenic effect.

Behavioral responses of the Iberian waterfrog, Pelophylax perezi (Seoane, 1885), to three nitrogenous compounds in laboratory conditions

Several studies have assessed the effects of nitrogenous compounds on amphibian behavior. However, few have focused on the effects of their combination with other stressors or on the variation of the response to pollutants among populations. We analyzed the effect of nitrogenous compounds (NH(4)(+); NO(2)(-); NO(3)(-), both alone and in combination) on larval behavior (activity level and location in the water column) in four populations of Pelophylax perezi naturally exposed to different levels of eutrophication. Larval activity was highest and use of the bottom of the experimental beaker was lowest at lower concentrations of nitrogenous compounds acting singly, these responses being minimal and maximal, respectively, at both control and higher concentrations. This pattern appears to fit to an hormetic response. Additionally, the combination of nitrogenous compounds affected more severely the response variables than when ammonium or nitrite acted singly according to an additive model. Populations inhabiting highly polluted aquatic habitats marginally showed higher activity level than the populations from less polluted environments, especially when larvae were exposed to ammonium or when nitrite appeared in combination with other nitrogen forms. Levels of activity correlated positively with larval final mass. Moreover, for similar levels of activity, larvae from polluted populations had higher growth rates than those coming from reference populations which suggests interdemic differences in behavioral sensitivity to nitrogenous pollutants.

Effects of nitrite exposure on functional haemoglobin levels, bimodal respiration, and swimming performance in the facultative air-breathing fish Pangasianodon hypophthalmus

In this study we investigated nitrite (NO₂⁻) effects in striped catfish, a facultative air-breather. Fish were exposed to 0, 0.4, and 0.9 mM nitrite for 0, 1, 2, 4, and 7 days, and levels of functional haemoglobin, methaemoglobin (metHb) and nitrosyl haemoglobin (HbNO) were assessed using spectral deconvolution. Plasma concentrations of nitrite, nitrate, chloride, potassium, and sodium were also measured. Partitioning of oxygen consumption was determined to reveal whether elevated metHb (causing functional hypoxia) induced air-breathing. The effects of nitrite on maximum oxygen uptake (MO(2max)) and critical swimming speed (U(crit)) were also assessed. Striped catfish was highly tolerant to nitrite exposure, as reflected by a 96 h LC₅₀ of 1.65 mM and a moderate nitrite uptake into the blood. Plasma levels of nitrite reached a maximum after 1 day of exposure, and then decreased, never exceeding ambient levels. MetHb, HbNO and nitrate (a nitrite detoxification product) also peaked after 1 day and then decreased. Only high levels of nitrite and metHb caused reductions in MO(2max) and U(crit). The response of striped catfish contrasts with that seen in most other fish species and discloses efficient mechanisms of combating nitrite threats. Furthermore, even though striped catfish is an efficient air-breather, this species has the ability to sustain aerobic scope and swimming performance without air-breathing, even when faced with nitrite-induced reductions in blood oxygen carrying capacity. Our study is the first to confirm that high levels of nitrite and metHb reduce MO(2max) and thereby aerobic scope, while more moderate elevations fail to do so. Further studies are needed to elucidate the mechanisms underlying the low nitrite accumulation in striped catfish.

The interactive effects of microcystin and nitrite on life-history parameters of the cladoceran Daphnia obtusa

Elevated nitrite and microcystin concentrations co-occur during degradation of Microcystis blooms and are toxic to aquatic organisms. We studied the relative and combined effects of these on Daphnia obtusa life-history. Nitrite and microcystin-LR treatments were: 0, 1, 3 mg L(-1) and 0, 10, 100, 300 μg L(-1), respectively. Experiments were factorial with 12 treatment combinations. Incubations were 15 d and recorded: moult number; time to first batch of eggs; time to first clutch; size at first batch of eggs; size at first clutch; number of clutches per female; number of offspring per clutch; total offspring per female. Interactive effects of the toxins occurred for time to first batch of eggs and time to first clutch. The remaining traits were negatively affected by nitrite: a significant decrease occurred in number of offspring per clutch and total number of offspring per mother (both decreased by ∼ 50%); total clutches per mother; number of moults; mother size at first clutch; and first appearance of eggs (primarily at the highest nitrite concentration). We support the literature, recognising nitrite is toxic, and although Microcystis is toxic to zooplankton, the main threat is not from dissolved microcystin but from degradative products such as nitrite.

Effects of nitrite and toxic Microcystis aeruginosa PCC7806 on the growth of freshwater rotifer Brachionus calyciflorus

Over the last two centuries, anthropogenic activities have increased the nitrogen amount in aquatic ecosystems, which has resulted in increased occurrences of blooms of cyanobacteria. This study investigated the effects of nitrite and the cyanobacterium Microcystis aeruginosa on population growth in the rotifer Brachionus calyciflorus. The rotifer was treated for 12 days with nitrite alone (medium containing 0, 3, 6, 10 mg NO (2)(-) -N L(-1)), M. aeruginosa alone (medium containing 0 mg NO(2)(-)-N L(-1) + 5.0 × 10(5) cell ml(-1) M. aeruginosa precultured at 0, 3, 6, 10 mg NO(2)(-)-N L(-1)), and nitrite in combination with M. aeruginosa (medium containing 3, 10 mg NO(2)(-)-N L(-1) + 5.0 × 10(5) cell ml(-1) M. aeruginosa precultured at corresponding nitrite concentrations). We observed that a nitrite concentration of 10 mg NO(2)(-)-N L(-1) markedly inhibited the growth of B. calyciflorus; however, rotifer growth declined slightly in the presence of M. aeruginosa precultured at 6 mg NO(2)(-)-N L(-1). Furthermore, reduced population growth of B. calyciflorus was observed when it was treated with both nitrite and M. aeruginosa compared to nitrite alone or M. aeruginosa alone. These results suggested that a high tolerance of B. calyciflorus to nitrite levels may be attributed to the absence of specific respiratory structures and pigments; and that the increased toxicity of nitrite in combination with M. aeruginosa may have been due to increased production of microcystin. It is also possible that nitrite and microcystin could act in a synergistic way in causing toxicity.

Intracellular conversion of environmental nitrate and nitrite to nitric oxide with resulting developmental toxicity to the crustacean Daphnia magna

BACKGROUND

Nitrate and nitrite (jointly referred to herein as NO(x)) are ubiquitous environmental contaminants to which aquatic organisms are at particularly high risk of exposure. We tested the hypothesis that NO(x) undergo intracellular conversion to the potent signaling molecule nitric oxide resulting in the disruption of endocrine-regulated processes.

METHODOLOGY/PRINCIPAL FINDINGS

These experiments were performed with insect cells (Drosophila S2) and whole organisms Daphnia magna. We first evaluated the ability of cells to convert nitrate (NO(3)(-)) and nitrite (NO(2)(-)) to nitric oxide using amperometric real-time nitric oxide detection. Both NO(3)(-) and NO(2)(-) were converted to nitric oxide in a substrate concentration-dependent manner. Further, nitric oxide trapping and fluorescent visualization studies revealed that perinatal daphnids readily convert NO(2)(-) to nitric oxide. Next, daphnids were continuously exposed to concentrations of the nitric oxide-donor sodium nitroprusside (positive control) and to concentrations of NO(3)(-) and NO(2)(-). All three compounds interfered with normal embryo development and reduced daphnid fecundity. Developmental abnormalities were characteristic of those elicited by compounds that interfere with ecdysteroid signaling. However, no compelling evidence was generated to indicate that nitric oxide reduced ecdysteroid titers.

CONCLUSIONS/SIGNIFICANCE

Results demonstrate that nitrite elicits developmental and reproductive toxicity at environmentally relevant concentrations due likely to its intracellular conversion to nitric oxide.

Acute toxicity of nitrite and ammonia to Daphnia similoides of different developmental stages: using the modified Gaussian model to describe

To gain an insight into the tolerance of Daphnia to nitrite and ammonia, a modified Gaussian model was used to describe the trends of changes in LC50s of nitrite and ammonia to Daphnia similoides at different developmental stages. LC50s of NO(2)-N and NH(3)-N increased with age before maturation and then decreased at maturation. A modified Gaussian model provided an accurate fit for the changes in LC50s of NO(2)-N and NH(3)-N, in which the parameters have definite biological meanings. From this model, we can gain an insight into the maximum LC50 and the age that has the maximum LC50 and predict LC50s at any specific ages. We suggest that such a model might be used to describe the trend in acute toxicity of some other zooplankton species at different stages.

Effect of nitrite on early-life stages of common carp (Cyprinus carpio L.)

A one-month chronic exposure of common carp larvae and embryos to nitrite revealed significant (p < 0.01) differences in total accumulated mortality in fish exposed to 33, 67, and 330 mg/L NO(2)(-) compared with controls. At the highest concentration, all fish died within 8 d of exposure. On the basis of accumulated mortality in the experimental groups, lethal concentrations of nitrite were estimated at 29 d LC50 = 88 mg/L NO(2)(-); lowest-observed-effect concentration (LOEC) = 28 mg/L NO(2)(-); and no-observed-effect concentration (NOEC) = 7 mg/L NO(2)(-). Fulton's condition factor values were significantly lower in fish from all experimental groups compared with controls. By day 12, fish exposed to 33 and 67 mg/L NO(2)(-) had significantly lower mass and total length compared with controls. No significant negative effects of nitrite at the concentrations tested (0.7-330 mg/L NO(2)(-), at 10 mg/L Cl(-)) on hatching or embryo viability were demonstrated, but significant differences in early ontogeny among groups were noted. Fish from all the concentrations showed a dose-related delay in development compared with the controls. Lordosis, kyphosis, scoliosis, and body shortening were observed at all concentrations and in controls, as was yolk sac deformation and edema, eye deformation, and cardiac edema. The incidence of these malformations was positively correlated with nitrite concentration. Histopathology revealed epidermal spongiosis; edema and hyperplasia of the gill epithelium, including hypertrophy and hyperplasia of eosinophilic granular cells (chloride cells); and interstitial edema of skeletal muscle in fish exposed to 67 mg/L NO(2)(-). Similar, but milder, changes were observed at lower nitrite concentrations.

Detection of DNA damage in fish Oreochromis mossambicus induced by co-exposure to phenanthrene and nitrite by ESI-MS/MS

BACKGROUND, AIM, AND SCOPE

Mutagenic nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) have been known to arise in the environment through direct emissions from combustion sources and nitration of PAHs, primarily in the atmosphere. In the marine environment, PAHs are one of the classic anthropogenic organic pollutants, while nitrite (NO(2)(-)) is produced naturally via various biological processes like imbalance in nitrification/denitrification or eutrophication and subsequent oxygen depletion from an oversupply of nutrients. In this paper, we report the formation of PAH-DNA adducts in fish contaminated with PAHs and exposed to NO(2)(-) in the ambient water. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of the bile of the euryhaline fish Oreochromis mossambicus exposed simultaneously to field relevant sublethal concentrations of phenanthrene and NO(2)(-) and collision-induced dissociation of selected ions revealed the presence of DNA-PAH adducts. The present study indicates that, although several high sensitivity techniques have been developed for the analysis of PAH derived DNA adducts, MS/MS has emerged as a powerful tool in the detection and structure elucidation of DNA adducts.

MATERIALS AND METHODS

Juvenile O. mossambicus from a local estuarine fish farm were used with increasing frequency for carcinogenicity testing and comparative cancer research. The fish were exposed to the alkylating agent phenanthrene in the presence of NO(2)(-). Composite untreated bile samples after dilution with methanol: water (1:1; v/v) were analyzed by ESI-MS.

RESULTS

Several adducts could be evidenced in the bile by MS/MS. Deoxyadenosine/deoxyguanosine having a mass in the range of 450-650 amu is detected. In addition, a segment of modified dinucleotide with a mass that corresponds to a dimer consisting of a modified guanosine and a normal guanosine has also been identified in the bile.

DISCUSSION

The formation of certain types of DNA adducts is a crucial step in the induction of cancer and a primary stage in mutagenesis. Phenanthrene injected by i.p. route led to the transformation of phenanthrene to N-formyl amino phenanthrene-N(6)-deoxyadenosine adduct, whereas the fish co-exposed to phenanthrene and ambient nitrite metabolizes PAH to mono-, di- as well as trinitro derivatives, which then react with DNA leading to the formation of mainly modified guanosine and adenosine adducts. In the present investigation, dinitrophenanthrene diol epoxide (DNPDE) adduct with guanosine (m/z 587) seems to be the dominant adduct in the mixture, and its presence is shown first as a comparatively less stable adduct, which decomposes to give a more stable N(2) adduct (m/z 567).

CONCLUSIONS

MS/MS has proved to be useful in the rapid determination and discrimination of structurally different phenanthrene/derivatives DNA adducts in a complex mixture of fish bile co-exposed to phenanthrene and nitrite. However, the nature of metabolites formed is likely determined by the route of PAH administration, and there is a need to further define the early biochemical events of carcinogenesis in these species.

RECOMMENDATIONS AND PERSPECTIVES

DNA adduct analysis in fish bile offers a promising approach to study the risk of potentiation of anthropogenic chemicals into genotoxic compounds in the presence of nitrite in the marine environment. We believe this is the first report on the formation of DNA-phenanthrene adducts on co-exposure of the fish to PAH and nitrite.

Effects of selenium on the antioxidant enzymes response of Neocaridina heteropoda exposed to ambient nitrite

The effects of dietary Selenium (Se) supplementation on muscle superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) activities and haemolymph superoxide anions (O(2)-) of Neocaridina heteropoda exposed to ambient nitrite were investigated. The results showed supplementation of Se in diet could enhance the resistance of shrimp to low concentration ambient nitrite. The results demonstrated that Se might have a potentially useful role as an effective antioxidant and resistance to aqueous nitrite in shrimp and the effect of the organic Se was better than that of the inorganic Se.

Effects of pulse duration and post-exposure period on the nitrite toxicity to a freshwater amphipod

This research assesses the effects of nitrite pulses and post-exposure periods after nitrite exposures on the survival of the freshwater amphipod Eulimnogammarus toletanus. A toxicity bioassay was performed using three different nitrite concentrations (0.5, 5.0 and 10.0 mg/L NO(2)-N), four pulse exposures (1, 8, 24 and 48 h) for each nitrite concentration, and four post-exposure times until to complete 96 h (i.e., 95, 88, 72 and 48 h, respectively). Our results showed a significant effect of nitrite concentrations, pulses and post-exposure times on the mortality of E. toletanus. The cumulative mortality at the end of pulse and that at the end of post-exposure time (delayed mortality) were different. We conclude that due to the high frequency of intermittent pollution in aquatic ecosystems it is necessary to incorporate the post-exposure effects into the traditional toxicological parameters to achieve a more realistic assessment of toxicants, especially at very short-term exposures.

Acute and chronic toxicity of ammonia, nitrite, and nitrate to the endangered Topeka shiner (Notropis topeka) and fathead minnows (Pimephales promelas)

Toxicity tests with ammonia, nitrite, and nitrate were conducted on the endangered Topeka shiner (Notropis topeka) to determine if current U.S. Environmental Protection Agency (U.S. EPA) water quality criteria are protective of this species. Results from acute lethal and chronic growth tests are reported for both Topeka shiners and fathead minnows (Pimephales promelas). Embryo-larval tests were conducted with only fathead minnows because Topeka shiner embryos were not available. Predicted outcomes for Topeka shiner embryo-larval toxicity endpoints were calculated by comparing relationships between growth tests and embryo-larval tests for fathead minnows and extrapolating those relationships to Topeka shiners. Results show that the U.S. EPA's criterion for total ammonia-nitrogen (TAN), 1.24 mg/L when early life stages are present, would be protective, given that our most sensitive result was a predicted maximum acceptable toxicant concentration (MATC) for Topeka shiners at 5.63 mg/L TAN, calculated from the fathead minnow chronic embryo-larval test. The U.S. EPA's criterion for nitrite (5 mg/L) would not be protective, given that our most sensitive result was a predicted MATC for Topeka shiners of 3.97 mg/L NO2-N, calculated from the fathead minnow chronic embryo-larval test. However, nitrite is generally transient, and unpublished field data show levels far lower than the criterion. Finally, the U.S. EPA's recommendation of a maximum of 90 mg/L NO3-N for the protection of warmwater fishes would protect Topeka shiners but not fathead minnows. For Topeka shiners, the MATC from the 30-d juvenile growth test was 360 mg/L NO3-N, but for fathead minnows, the MATC was 84 mg/L. More field sampling may be needed to determine if levels comply with criteria, especially in Topeka shiner critical habitat.

Populational divergence in the impact of three nitrogenous compounds and their combination on larvae of the frog Pelophylax perezi (Seoane, 1885)

Pollution by nitrogenous compounds is a putative stressful factor that may be causally linked to the decline of amphibians. One way to understand the potentially detrimental consequences of eutrophication on amphibian populations is to investigate variation among populations differing in exposure to nitrogen, this variation potentially indicating evolutionary potential to cope with this stressor. We have examined the effect of nitrogenous compounds (NH(4)(+); NO(2)(-); NO(3)(-), both alone and in combination) on fitness-related larval traits in four populations of Pelophylax perezi naturally exposed to different degrees of eutrophication. The results indicate that both survival and larval final size decrease at higher concentrations of these compounds, either singly or in combination. Additionally, the nitrogenous compounds were more lethal and larval food consumption and final mass were significantly reduced when they were exposed to combinations of compounds. Populations inhabiting highly polluted aquatic environments tolerated higher levels of nitrogenous compounds and showed higher survival rates and larger final size than the populations of less polluted environments, suggesting the potential to adapt to increased nitrogenous contamination in this species.

[Toxicity of nitrification substrates and products to photobacterium]

OBJECTIVE

In this study, we studied the toxic effect of nitrification substrates and products on photobacterium.

METHODS

The acute toxicities of nitrification substrates and products to photobacterium were studied with the 15-min half inhibitory concentration (IC50) as indicator at pH = 7.0.

RESULTS

The results of individual toxicity indicated that the toxicity of nitrification substrates and products to photobacterium increased with increasing concentration and there was a linear correlation. The IC50 values of ammonium, hydroxylamine, nitrite and nitrate were 2180.2 mg/L, 6.2740 mg/L, 1207.2 mg/L and 3140.3 mg/ L, respectively, and their toxic order was hydroxylamine > nitrite > ammonium > nitrate. The combined effects of substrates and products were assayed by equivalent concentration mixing method. The results showed that the combined effects of ammonium and hydroxylamine, ammonium and nitrite, hydroxylamine and nitrite were additive effects, whereas the combined effects of ammonium and nitrate, hydroxylamine and nitrate, nitrite and nitrate were independent effects. The combined effect of all nitrification substrates and productions was also additive effect.

CONCLUSION

According to the correlation of the inhibiting concentration to photobacterium and nitrifying bacterium by nitrification substrates and products, the change of luminous intensity of photobacterium can indicate the inhibition from nitrification substrates and products.

Subchronic exposure to nitrite, potassium and their combination on survival, growth, total haemocyte count and gill structure of juvenile blue swimmer crabs, Portunus pelagicus

Among anthropogenic discharges, nitrite and potassium can simultaneously enter aquatic ecosystems at high loading rates which can threaten marine animals. The sensitivity of early juvenile blue swimmer crabs, Portunus pelagicus, to the subchronic exposure to nitrite, potassium and their combination was evaluated by measuring the survival, growth, total haemocyte count (THC) and gill histopathological changes. In all NaNO(2)-N and KNO(2)-N treatments the survival substantially decreased, many due to "molt death syndrome", along with significantly lower (p<0.01) specific growth rates (SGR). Although fewer deaths occurred in the KCl-K treatments, the SGR at the higher concentrations were significantly less (p<0.05) than the control. The gill histopathological changes following elevated NaNO(2)-N, KNO(2)-N and KCl-K exposure showed drastic but similar damage. In spite of a long term healing response, indicated by a significant hemolymph THC increase (p<0.01) and several gill lamellae modifications, early P. pelagicus juveniles are highly sensitive to elevated NO(2)-N levels.

Effects of subchronic nitrite exposure on rainbow trout (Oncorhynchus mykiss)

Subchronic toxicity of nitrite in rainbow trout (Oncorhynchus mykiss; mean mass ± S.D., 18.9 ± 1.3g) was assessed in a 28-day trial. The influence of nitrite on fish mortality, growth rate, haematology, blood biochemistry, and gill histology was observed. Survival was not affected by exposures up to 1 mg l(-1) NO(2)(-) (at 10 mg l(-1) Cl(-)). On the basis of growth rate inhibition data, the values of NOEC (28 d LC(0)) and LOEC (28 d LC(10)) were estimated at 0.01 and 0.2 mg l(-1) NO(2)(-), respectively. At 0.01 mg l(-1) NO(2)(-) (the lowest concentration tested), there was segmental hyperplasia of the respiratory epithelium of secondary lamellae and elevated glucose and decreased potassium. Elevated nitrite concentrations were found in blood plasma of fish exposed to concentrations of 1.0 mg l(-1) NO(2)(-) and higher, and in muscle tissue at the highest concentration 3.0 mg l(-1) NO(2)(-). Plasma and muscle nitrite levels were lower than those in the ambient water in all experimental groups.

Hyperbaric Oxygenation in the Treatment of Life-Threatening Isobutyl Nitrite-Induced Methemoglobinemia—A Case Report

Methemoglobinemia usually results from exposure to oxidizing substances such as nitrates or nitrites. Iron within hemoglobin is oxidized from the ferrous (Fe2+) state to the ferric (Fe3+) state, resulting in the inability to transport oxygen and carbon dioxide. Clinically, this condition causes functional cyanosis. As methemoglobin levels increase, patients show evidence of cellular hypoxia in all tissues. Death usually occurs when methemoglobin fractions approach 70% of total hemoglobin. We describe the case of a 35-year-old female patient with severe life-threatening isobutyl nitrite-induced methemoglobinemia of 75% of total hemoglobin. Toluidine-blue was administered as first-line antidotal therapy immediately, followed by hyperbaric oxygenation. The patient recovered uneventfully and could be discharged 3 days later.

[Protective role of cobalt complexes of porphyrin and phthalocyanine in acute nitrite intoxication and endotoxic shock in an experiment]

There is currently an active search for effective agents to regulate the content of nitric oxide (NO) in the body. One of the ways of reducing its blood concentration may be the binding of NO by different complexions that comprise the metal complexes of porphyrins and phthalocyanines. The study was undertaken to evaluate the protective effect of synthetic metal complexes of porphyrin and phthalocyanine in acute nitrite intoxication and endotoxic shock. The findings suggest that both study samples of the synthetic metal complexes have not prevented hemolytic anemia in acute nitrite intoxication and endotoxic shock; however, they have shown potential sorption properties against nitrate ions in the blood and brain of experimental animals, which may be the subject of a further study.

Toxicity of un-ionized ammonia, nitrite, and nitrate to juvenile bay scallops, Argopecten irradians irradians

Juvenile bay scallops (7.2-26.4 mm) were exposed for 72 h to different concentrations of un-ionized ammonia, nitrite, or nitrate. Using the Trimmed Spearman Karber method, 50% lethal concentrations (LC(50)) and 95% confidence limits were calculated individually for each. Un-ionized ammonia concentrations above 1.0 mg N-NH(3)/L resulted in 100% scallop mortality within 72 h. The 72-h LC(50) for un-ionized ammonia was calculated at 0.43 mg N/L. At nitrite concentrations of 800 mg N/L or higher 100% mortality was observed. The 72-h LC(50) for nitrite was calculated at 345 mg N/L. Nitrate was the least toxic, with 100% mortality observed at a concentration of 5000 mg N/L. The calculated nitrate 72-h LC(50) was 4453 mg N/L. Our results indicate that un-ionized ammonia is the most lethal nitrogenous waste component to bay scallops.