28-day Toxicity Test Research Articles

Evaluation of Short-Term Mussel Test for Estimating Toxicity.

Effect concentrations of ammonia, nickel, sodium chloride, and potassium chloride from short-term 7-day tests were compared to those from standard chronic 28-day toxicity tests with juvenile mussels (fatmucket, Lampsilis siliquoidea) to evaluate the sensitivities of the 7-day tests. The effect concentrations for nickel (59 µg Ni/L), chloride (316-519 mg Cl/L, a range from multiple tests), and potassium (15 mg K/L) obtained from the 7-day tests were within a range of effect concentrations for each corresponding chemical in the 28-day tests (41-91 µg Ni/L, 251->676 mg Cl/L, 15-23 mg K/L), whereas the 7-day ammonia effect concentration (0.40 mg/L total ammonia nitrogen; TAN) was up to 3.3-fold greater than the 28-day effect concentrations (0.12-0.36 mg TAN/L) but with overlapped 95% confidence limits. These results indicate that the 7-day tests produced similar estimates compared to the 28-day tests. Further studies are needed to evaluate the 7-day test sensitivity using additional chemicals with different modes of toxic action. Environ Toxicol Chem 2024;43:2020-2025. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Evaluation of bioaccumulation and toxicity of Tubifex tubifex exposed to contaminated river sediment by potentially toxic elements — A case study of the Middle Black Sea, Turkey

To determine the ecotoxicological assessment of the Black Sea in the seasonal and spatial dimensions, the concentrations of potentially toxic elements (PTEs) in sediment were measured at five sampling sites selected as Kızılırmak (T1), Engiz River (T2), Mert River (T3), Abdal River (T4), and Yeşilırmak (T5). In addition, a 28-day toxicity test was conducted with T. tubifex to evaluate the accumulation and toxicity of the PTEs contamination. The results of PTEs concentration in sediment indicated that the sampling sites are ranked according to the degree of elemental pollution from highly polluted to less polluted as Yeşilırmak > Kızılırmak > Abdal River > Engiz River > Mert River. Both natural and anthropogenic activities including industrial and agricultural effluents, municipal wastewater, and traffic-related pollution were found as the main sources of PTEs. Additionally, the acid volatile sulfide (AVS) – simultaneously extracted metal (SEM) concentrations were measured to determine the potential availability and toxicity of the presence of PTEs. ∑SEM–AVS < 0 were found in 60 % of the samples taken from five different sampling points while ∑SEM– AVS > 0 were observed in 40 % of the samples. Accordingly, the toxicity of PTEs is expected to be limited at 60 % of the samples. The results indicated no mortality in the tested sediment samples. The highest reproduction rate (16.67 ± 1.53) and lowest PTEs content were measured in the Mert River. The results of bioaccumulation factors (BAF) revealed that the most accumulated PTEs were Cu > Zn > Ni > Pb.

Investigation of the nephrotoxicity of 2,6-dichloro-1,4-benzoquinone disinfection by-product in mice through a 28-day toxicity test

In recent years, 2,6-dichloro-1,4-benzoquinone (DCBQ) has become an emerging water disinfection by-product and widely distributed in disinfected water. Although kidney is a potential target of DCBQ, a systematic study of the in vivo nephrotoxicity of DCBQ is rare. In this study, a 28-day oral toxicity test was used to assess the nephrotoxic effects of DCBQ on mice. And the potential mechanisms of nephrotoxicity induced by DCBQ were explored through inflammation, oxidative stress, apoptosis and gut microbiota. The results showed that the kidney indexes of mice were not altered in DCBQ-exposed group in comparison with the control group. The histopathological investigation revealed that DCBQ caused swollen of renal tube, destruction of the renal structure, and infiltration of inflammatory cell in kidney. DCBQ has induced oxidative damage in kidney, as the observation of the increase of the renal superoxide dismutase (SOD) and catalase (CAT) activity. Also, DCBQ has triggered the inflammatory response in kidney through the increased expression of IL-1β, NF-κB and iNOS. Moreover, DCBQ has activated the apoptosis pathway, as indicated by the increased mRNA expression of Caspase-3 and Caspase-9. We eventually found an association between gut microbiota and nephrotoxic variables, demonstrating the importance of gut-kidney axis in DCBQ toxicity. Our results suggested that exposure to DCBQ in disinfected water might be a risk factor for kidney and provided novel insights into the underlying mechanisms of DCBQ–induced kidney injury, contributing to better interpretation of the health impact of the environmentally emerging contaminant DCBQ.

Evaluation of the toxic effects of the aqueous extract of Niprineem tea in mice and rats

Azadirachta indica is an important plant in traditional complementary and alternative medicine with decoctions (tea) being a common mode of administration. Herbal teas are frequently self-administered thus the need to prepare a standardized dosage form for the administration of such decoctions. The leaf of Azadirachta indica was formulated for administration as tea; thus, this study was designed to determine the safety profile of Niprineem tea. Oral acute and sub-chronic toxicity studies of the aqueous extract of Niprineem tea (NTE) were evaluated. The OECD (No 423) limit test was followed to determine the LD50 in Swiss albino mice, while OECD 407 guideline was used for the sub-chronic toxicity studies in Wistar rats. Acute administration of NTE did not cause detectable signs of toxicity in treated animals and no mortality was recorded. In the 28-day toxicity tests, there were no significant (p&lt;0.05) changes in food and water intake, or urine and faecal output. Haematological analysis did not show deleterious effects in treated rats. Biochemical evaluation of indicators for renal and hepatic functions did not show significant changes after treatment with NTE. Likewise, histological tests did not result in structural changes in cells of the tissues of major organs. The results obtained suggest that Niprineem tea is relatively non-toxic and safe at the tested dose.

Preclinical Evaluation of Safety, Pharmacokinetics, Efficacy, and Mechanism of Radioprotective Agent HL-003.

Amifostine is a radioprotector with high efficacy but poor safety, short half-life, no oral formulation, and poor compliance, which limits its application. With the increasing risk of exposure to radiation, the development of new radioprotective agents is critical. We previously synthesized a new amifostine derivative, the small molecule compound HL-003. In this study, we focused on evaluating the radioprotective properties of HL-003. Using the in vitro 2,2-diphenyl-1-picrylhydrazyl assay, we initially confirmed HL-003 as a strong antioxidant and demonstrated that its free radical scavenging activity was stronger than that of amifostine. Then, we performed an acute toxicity test, a 28-day toxicity test, a 30-day survival rate test, and a pharmacokinetic study, all of which provided aggregate evidence that HL-003 functioned as a small molecule radioprotector with high efficacy, a favorable safety profile, a long half-life, and oral administration. The intestinal radioprotective mechanism of HL-003 was explored in male C57 mice after abdominal irradiation by analyzing intestinal tissue samples with hematoxylin-eosin staining, immunohistochemistry, TUNEL staining, and immunofluorescence detection. The results showed that HL-003 protected intestinal DNA from radiation damage and suppressed the expression of phosphorylated histone H2AX, phosphorylated p53, and the apoptosis-related proteins caspase-8 and caspase-9, which contributed to maintaining the normal morphology of the small intestine and provided insights into the mechanism of radioprotection. Thus, HL-003 is a small molecule radioprotector with a potential application in radiation medicine.

The effect of foodborne sertraline on rainbow trout (Oncorhynchus mykiss)

The worldwide consumption of antidepressants is raising as well as their concentrations in the aquatic environment. This increases the risk of food chain contamination and bioaccumulation in aquatic biota. The aim of this study was to describe a potential risk of sertraline as a pollutant from water environment, wherein rainbow trout (Oncorhynchus mykiss) has been chosen as the test organism, because predatory fish are on the top of the food chain in the aquatic environment. The effects of foodborne sertraline were tested on rainbow trout during a 28-day toxicity test according to OECD 215 method. Sertraline was incorporated in commercial feed at a dose of 4.4 µg/kg (environmental concentration), 42 µg/kg and 400 µg/kg. The results confirmed that sertraline has a significant effect on fish behaviour, resulting in suppression of the escape reflex and increased resistance to stress. Moreover, increased Fultońs condition factor was found in fish fed with the highest concentration of sertraline. Haematological analysis revealed a statistically significant increase in the number of neutrophilic bands and neutrophil/lymphocyte ratio, and decreased number of lymphocytes. The results of biochemical examination showed a statistically significant decrease in ammonia and lactate concentrations and histological examination revealed changes in gills and caudal kidney. Although sertraline reduces stress in fish, the decline in nonspecific immunity is a risk to fish population stability.

The effects of subchronic exposure to NeemAzal T/S on zebrafish (Danio rerio)

ABSTRACTThe objective of the study was to investigate the subchronic effects of the insecticidal preparation NeemAzal T/S at concentrations of 3, 10 and 30 mg/L on the mortality, growth and histopathology of juvenile zebrafish (Danio rerio), as well as its related effects on selected indices of oxidative stress during a 28-day toxicity test. The juvenile growth toxicity test was performed according to OECD Guidelines 215 (Fish, Juvenile Growth Test). The results of this study indicate that these tested concentrations of NeemAzal T/S (containing 1% of the active ingredient azadirachtin A) affect fish growth and have a negative influence on the indices of oxidative stress in the juvenile stage of zebrafish, as well as cause mild histopathological changes in liver tissue.

The Effects of Subchronic Exposure to Metribuzin onDanio rerio

The aim of this study was to assess the impact of metribuzin in surface waters on fish under experimental conditions. The effects of subchronic exposure to metribuzin on fish growth and the development of histopathological changes in selected organs (gill, kidney, liver) and on activity of some biochemical markers (CYP450, EROD) in Danio rerio were investigated during a 28-day toxicity test. Juvenile growth tests were performed on D. rerio according to OECD method number 215. Fish at an initial age of 30 days were exposed to a range of metribuzin concentrations (1.5, 5, 16, 33, and 53 mg L−1). Exposure to metribuzin at 53 mg L−1 was associated with increased mortality. Negative effects with regard to total body weight, length, and the inhibition of specific growth rate were induced at concentrations of 33 and 53 mg L−1. Histopathological examination revealed pathological lesions in the liver in pesticide-exposed fish only at the highest concentration of 53 mg L−1 of metribuzin. Based on the results of growth rate, biochemical markers (CYP450, EROD), and histopathological examination, the lowest observed effect concentration (LOEC) value was 33 mg L−1 and the no observed effect concentration (NOEC) value was 16 mg L−1.

New Short Term Prediction Method for Chemical Carcinogenicity by Hepatic Transcript Profiling following 28-Day Toxicity Tests in Rats

We have previously shown the hepatic gene expression profiles of carcinogens in 28-day toxicity tests were clustered into three major groups (Group-1 to 3). Here, we developed a new prediction method for Group-1 carcinogens which consist mainly of genotoxic rat hepatocarcinogens. The prediction formula was generated by a support vector machine using 5 selected genes as the predictive genes and predictive score was introduced to judge carcinogenicity. It correctly predicted the carcinogenicity of all 17 Group-1 chemicals and 22 of 24 non-carcinogens regardless of genotoxicity. In the dose-response study, the prediction score was altered from negative to positive as the dose increased, indicating that the characteristic gene expression profile emerged over a range of carcinogen-specific doses. We conclude that the prediction formula can quantitatively predict the carcinogenicity of Group-1 carcinogens. The same method may be applied to other groups of carcinogens to build a total system for prediction of carcinogenicity.

Discrimination of Carcinogens by Hepatic Transcript Profiling in Rats following 28-day Administration

This study aimed at discriminating carcinogens on the basis of hepatic transcript profiling in the rats administrated with a variety of carcinogens and non-carcinogens. We conducted 28-day toxicity tests in male F344 rats with 47 carcinogens and 26 non-carcinogens, and then investigated periodically the hepatic gene expression profiles using custom microarrays. By hierarchical cluster analysis based on significantly altered genes, carcinogens were clustered into three major groups (Group 1 to 3). The formation of these groups was not affected by the gene sets used as well as the administration period, indicating that the grouping of carcinogens was universal independent of the conditions of both statistical analysis and toxicity testing. Seventeen carcinogens belonging to Group 1 were composed of mainly rat hepatocarcinogens, most of them being mutagenic ones. Group 2 was formed by three subgroups, which were composed of 23 carcinogens exhibiting distinct properties in terms of genotoxicity and target tissues, namely nonmutagenic hepatocarcinogens, and mutagenic and nonmutagenic carcinogens both of which are targeted to other tissues. Group 3 contained 6 carcinogens including 4 estrogenic substances, implying the group of estrogenic carcinogens. Gene network analyses revealed that the significantly altered genes in Group 1 included Bax, Tnfrsf6, Btg2, Mgmt and Abcb1b, suggesting that p53-mediated signaling pathway involved in early pathologic alterations associated with preceding mutagenic carcinogenesis. Thus, the common transcriptional signatures for each group might reflect the early molecular events of carcinogenesis and hence would enable us to identify the biomarker genes, and then to develop a new assay for carcinogenesis prediction.

Tubifex tubifex chronic toxicity test using artificial sediment: methodological issues

The formulation and preparation of artificial sediments to be used in chronic toxicity tests is an important issue in the standardisation process. In the present study, artificial sediment has been used with Tubifex tubifex (Tubificidae, Oligochaeta) in both culture and in 28-day toxicity tests with spiked toxicants, in order to avoid the presence of occasionally important concentrations of some pollutants in sediments from apparently clean sites. The addition of supplementary food to the sediment at the beginning of the test is necessary to get satisfactory reproductive levels at the end of the 28-day chronic test, but this supplement of organic matter also provoked an additional increase of the levels of ammonia. The presence of ammonia at toxic levels in the artificial sediment during the first days after its preparation influences the quality of the water column and interstitial water, affecting the biological results of the test. The behaviour of the worms that escaped from sediment resulted in a reduction of their feeding activity, reproduction, and also mortality during the chronic test. Two different quantities of rations (80 and 160 mg Tetramin® flakes) were compared, combined or not with a weekly renewal of the overlying water. The lowest peak of ammonia in water column and sediment pore-water was measured with 80 mg of Tetramin®. The weekly water renewal did not give better results in survival or reproduction at the end of the 28-day tests. A combination of sediment aeration during two weeks followed by a renewal of water column reduced the levels of ammonia in the water column and interstitial water below 1 mg/l N-NH3. Therefore, this procedure is proposed for the reduction of ammonia, prior a toxicity test is conducted with artificial sediment, in order to avoid the presence of this compound at lethal or sublethal levels that could act as a confounding factor in chronic toxicity tests. The lowest supplement of food (80 mg) in a static exposure regime was chosen as satisfactory for the chronic test. Survival percentage and reproduction (number of cocoons and number of young worms) were comparable with the data reported in tests with natural sediments using Tubifex tubifex, although both adult worm and cocoon biomass values were significantly lower and can not be used as end-points in toxicity tests with artificial sediment as it has been formulated here.

Silver speciation during chronic toxicity tests with the mysid, Americamysis bahia

A 28-day chronic toxicity test and two 7-day chronic estimation toxicity tests were conducted with silver nitrate (AgNO 3) and the marine invertebrate, Americamysis bahia, in 20‰ (parts-per thousand) salinity seawater. One 7-day test was initiated with 7-day-old mysids and the second was initiated with <24-h-old mysids. There was very good agreement between the three toxicity tests. The no-observed-effect concentration (NOEC) values from the 28-day test, the 7-day test initiated with 7-day-old mysids, and the 7-day test initiated with <24-h-old mysids were 34, 65 and 38 μg/l silver, respectively. The 96-h LC50 values from the 28-day toxicity test and the 7-day toxicity test initiated with 7-day old mysids were 260 μg/l, and the 96-h LC50 value from the 7-day toxicity test initiated with <24-h-old mysids was 280 μg/l. Free ionic silver, Ag +, concentrations measured with a silver electrode were in good agreement with concentrations calculated using total dissolved silver and chloride concentrations. Mean measured concentrations of Ag + in the test solutions ranged from 0.99 to 25 ng/l for the dissolved silver concentrations that ranged from 34 to 410 μg/l silver, indicating that free ionic silver varied from 0.003 to 0.006% of the silver dissolved in the 20‰ salinity seawater. Understanding the relationship of salinity and silver speciation, and the effect of this relationship on chronic invertebrate toxicity, will be useful for development of a marine biotic ligand model (BLM) and a water quality criterion for silver. This model could provide an important tool for improving the relationship of laboratory toxicity test results and predicted effects in natural environments, where variations in salinity may act to modify the toxicity of silver and other metals.

Effects of substrate salinity on early seedling survival and growth of Scirpus robustus Pursh and Spartina alterniflora Loisel.

Rooted aquatic plants are being used increasingly to test the toxicity of sediments. However, effects of naturally occurring substrate constituents on most potential test species are not well understood even though their effects could affect the test results. The objective of this study was to determine the effect of substrate salinity (NaCl) on early seedling survival and growth of the emergent macrophytes, Scirpus robustus Pursh and Spartina alterniflora Loisel. Results of four 21- and 28-day toxicity tests, conducted in an artificial sediment, indicated interspecific differences in NaCl sensitivity when based on changes in shoot, root and whole plant dry-weight biomass. Concentrations of 7.8 g NaCl/l and 19.2 g NaCl/l first reduced early seedling biomass of S. robustus and S. alterniflora (P<0.05), respectively, when compared to plants grown in sediment containing no measurable salinity. Seedling survival was not affected at average concentrations of 17.5 g NaCl/l or less for S. robustus and 22.3 g NaCl/l or less for S. alterniflora. The results indicate that substrate salinity is an important consideration in the selection of test species for laboratory phytotoxicity tests conducted with estuarine sediments, particularly if determination of chronic toxicity attributable to anthropogenic contamination is the primary objective.

Synthesis and antifungal activity of new azole derivatives containing an N-acylmorpholine ring.

A series of azole derivatives carrying an N-acylmorpholine ring are described. The compounds were chemically designed to simulate the lanosterol D ring, taking advantage of the conformational preferences of 2-alkyl-1-acylmorpholines. Three structural variables, the nature of the N-benzoyl group, the phenyl substituents, and the degree of oxidation at carbon 2 of the morpholine, were optimized for maximum activity. Only the (5R,6R) isomers showed antifungal activity. Cyclic hemiacetal (-)-39a (UR-9746) and cyclic ether (-)-41 (UR-9751) were selected for further development. In vitro, (-)-41 was clearly more active than (-)-39a and somewhat less active than the acyclic counterpart (-)-7. In vivo activity was assessed by a systemic (mouse) and a vaginal (rat) candidosis model. In the former, (-)-39a, (-)-41, and (-)-7 at 1 mg/kg given 1, 4, and 24 h postinfection displayed 90-100% protection from mortality on day 9. Compound (-)-39a was slightly more potent than (-)-41 and similar in potency to (-)-7. The three compounds were superior in potency to fluconazole and similar in potency in SCH-42427 in this test. In the vaginal model, (-)-39a and (-)-41 given daily during 3 days after infection at 0.5 mg/kg showed high levels of protection on days 10 and 15. At 0.25 mg/kg, (-)-39a was slightly more potent than SCH-42427 and (-)-7 and superior in potency to (-)-41 and fluconazole in this model. Preliminary 28-day toxicity tests at 100 mg/kg/day po in rats indicated no or very mild adverse effects for the two UR compounds.

Sensitivity of brook trout to low pH, low and elevated aluminum concentrations during laboratory pulse exposures

Yolk-sac larvae of brook trout ( Salvelinus fontinalis) were exposed to four sequential low pH and calcium (Ca) pulses, nominally ranging from pH 6.5 to 4.0 in 0.5 pH unit increments, with and without 300 mg/l aluminum (Al) in 28-day toxicity tests. Calcium concentrations during the pulses varied from 0.5 to 1.3 mg/1. Swim-up larvae that had begun to feed were exposed to a single pulse of the same pH and Ca concentrations with 300 mg/l Al. The larvae were allowed to recover for 120-h at circumneutral pH and Ca concentrations that varied from 2.1 to 3.3 mg/l after each pulse exposure. Effects of the pulse exposures on survival, growth, whole-body ion concentrations, and behavioral development were monitored. Mortality of larvae was significant in all low pH and Ca treatments with Al after the first pulse and after the first low pH and Ca pulse at pH 4.0. Growth was significantly reduced among larvae exposed to the low pH and Ca pulses at pH 4.0. In general, growth was most severely affected among larvae exposed to the low pH and Ca pulses with Al at pH 6.1 and lower. Relative to controls, the low pH and Ca pulse exposures with and without Al reduced whole-body Na +, Ca 2+, K +, Mg 2+ P, and Cl −, Wholebody Ca 2+ was most severely reduced followed by Na +, K +, Cl −, P, and Mg 2+. The pulse exposures also caused delayed development and significant reductions in swimming activity and feeding of the larvae. These results support field observations that cyclic pH and Ca depressions, and concurrent increases in Al concentrations may cause mortality and have other adverse effects on natural fish populations.