Biomarkers in bivalve mollusks and amphipods for assessment of effects linked to cyanobacteria and elodea: Mesocosm study.

The effects of cyanobacteria (Aphanizomenon flos-aquae (90%), Microcystis aeruginosa) and dense Elodea canadensis beds on the health endpoints of the amphipod Gmelinoides fasciatus and bivalve mollusc Unio pictorum were examined in mesocosms with simulated summer conditions (July-August 2018) in the environment of the Rybinsk Reservoir (Volga River Basin, Russia). Four treatments were conducted, including one control and three treatments with influencing factors, cyanobacteria and dense elodea beds (separately and combined). After 20 days of exposure, we evaluated the frequency of malformed and dead embryos in amphipods, heart rate (HR) and its recovery (HRR) after stress tests in molluscs as well as heat tolerance (critical thermal maximum or CTMax) in both amphipods and molluscs. The significant effect, such as elevated number of malformed embryos, was recorded after exposure with cyanobacteria (separately and combined with elodea) and presence of microcystins (MC) in water (0.17 µg/l, 40% of the most toxic MC-LR contribution). This study provided evidence that an elevated number (>5% of the total number per female) of malformed embryos in amphipods showed noticeable toxicity effects in the presence of cyanobacteria. The decreased oxygen under the influence of dense elodea beds led to a decrease in HR (and an increase in HRR) in molluscs. The notable effects on all studied biomarkers, embryo malformation frequency and heat tolerance in the amphipod G. fasciatus, as well as the heat tolerance and heart rate in the mollusc U. pictorum, were found when both factors (elodea and cyanobacteria) were combined. The applied endpoints could be further developed for environmental monitoring, but the obtained results support the importance of the combined use of several biomarkers and species, especially in the case of multi-factor environmental stress.

Thermal tolerance of Cyclops kolensis lilljeborg, 1901 (Copepoda: Cyclopoida) and its relationships with pessimal to optimal performance.

Cyclops kolensis Lilljeborg, 1901 belongs to the Arctic complex of Palaeoarctic species, yet in the past 20 years, its occurrence has extended to the summer months in waterbodies with high water temperatures. This species is considered one of the most active migrants from the northern waterbodies in the Volga reservoir cascade to the Volga delta. Here, we explored the ranges of the preferred and avoidance temperatures of C. kolensis from two geographically isolated populations. Thermal tolerance was measured in a thermogradient installation and compared to the temperatures at which members of these populations occurred in their source waterbodies. Temperature preference was determined using the "chronic" method. Individuals of C. kolensis possessed a bimodal final temperature preferendum of 2-6 °C and 13-21 °C, which corresponds to the optimal thermal conditions of the species in a pond. These ranges were the same for individuals of both populations irrespective of the geographical location and water temperature of their source waterbodies. The temperature range of normal performance was 2-4 to 21-25 °C, and the pessimal temperature ranges were from 1 - 2 to 3-4 °C and from 22-25 °C to 26-30°Ð¡. These temperature ranges coincide with field observations over a recent 20-year period of temperature conditions under which the species develops in nature. Our results allow us to characterize C. kolensis as an ecologically plastic species, which, despite its strong association with the cold-water Complex species, is adapting to a wider temperature range as global warming occurs.

The preferred and avoidance temperatures of Thermocyclops crassus (Fischer, 1853) and their relation to the temperature of optimal, pessimal and normal performance of the species.

The ranges of the preferred and avoided temperatures in representatives of Thermocyclops crassus (Fischer, 1853) were determined by the results of experimental testing in a thermogradient aparatus and comparison of the obtained values with field observations of the optimal, pessimal and tolerated temperature conditions of development of these populations in nature. Copepods were sampled from pond located near Borok, Yaroslavl region, Russia (58o02'57'' N; 38o14'56'' E). The ambient water temperature was 15.0°Ð¡. Temperature preference was determined by the "chronic" method. The phenology of development of Th. crassus was observed in the field of water bodies in Central and Volga Federal Districts of Russia. The final thermal preferendum (FTP) achievement occurred with an increase in the preferred temperature: when animals were placed at a temperature in the thermal gradient (14.0-15.0°C) that approximated the temperature of the source pond, they moved to warmer water until they chose FTP (26.7°C). Obtained the values of FTP (25-30°C), temperature of normal performance (21-32°C) and pessimal temperatures of 9-20 and 33°Ð¡ well coincide with numerous field observations for temperature conditions of development of species in northern waterbodies of Holarctic and with the temperatures at which populations of Th. crassus thrive in southern waterbodies of Holarctic and in tropical lakes. It is concluded that, despite the historically long existence of the species in the reservoirs of the temperate climatic zone, the northern populations of Th. crassus retained the temperature responses characteristic of their southern sister populations. And although the species has adapted to life in northern reservoirs at lower temperatures, when it becomes possible to choose, cyclops prefer temperatures above 25°C, which are optimal for southern populations living in tropical waters. These data once again confirm that the horizontal thermal gradient method can be used to infer temperature tolerance of freshwater cyclopoid copepods in nature.

Responses of zebra and quagga mussels to copper and tribytiltin exposure: Bioconcentration, metabolic and cardiac biomarkers.

One of the top ecological priorities is to find sensitive indicators for pollution monitoring. This study focuses on the bioconcentration and responses (condition index, survival, oxygen consumption, heart rates, and oxidative stress and neurotoxic effect biomarkers) of mussels from the Volga River basin, Dreissena polymorpha and Dreissena bugensis, to long-term exposure to toxic chemicals such as tributyltin (TBT, 25 and 100 ng/L) and copper (Cu, 100 and 1000 µg/L). We found that TBT was present in the tissues of zebra and quagga mussels in comparable amounts, whereas the bioconcentration factor of Cu varied depending on its concentration in water. Differences in responses between the two species were revealed. When exposed to high Cu concentrations or a Cu-TBT mixture, quagga mussels had a lower survival rate and a longer heart rate recovery time than zebra mussels. TBT treatment caused neurotoxicity (decreased acetylcholinesterase activity) and oxidative stress (increased levels of thiobarbituric acid reactive substances) in both species. TBT and Cu levels in mussel tissues correlated positively with the condition index, but correlated with the level of acetylcholinesterase in the mussel gills. The principal component analysis revealed three main components: the first consists of linear combinations of 14 variables reflecting TBT water pollution, TBT and Cu levels in mussel tissues, and biochemical indicators; the second includes Cu water concentration, cardiac tolerance, and mussel size; and the third combines weight, metabolic rate, and heart rates. Quagga mussels are less tolerable to contaminants than zebra mussels, so they may be used as a sensitive indicator.

Effects of Diclofenac on the Reproductive Health, Respiratory Rate, Cardiac Activity, and Heat Tolerance of Aquatic Animals.

Diclofenac is an important pharmaceutical present in the water cycle of wastewater treatment and one of the most distributed drugs in aquatic ecosystems. Despite the great interest in the fate of diclofenac in freshwaters, the effects of environmentally relevant concentrations on invertebrates are still unclear. Two species of freshwater invertebrates, the amphipod Gmelinoides fasciatus and the bivalve mollusk Unio pictorum, were exposed to diclofenac concentrations of 0.001-2 µg/L (environmentally relevant levels) for 96 h. A set of biological endpoints (survival, fecundity, embryo abnormalities, respiration and heart rates, heat tolerance, and cardiac stress tolerance) were estimated in exposed invertebrates. Effects of diclofenac on amphipod metabolic rate and reproduction (number and state of embryos) and adaptive capacity (cardiac stress tolerance) in both species were evident. The oxygen consumption of amphipods exposed to diclofenac of 0.1-2 µg/L was 1.5-2 times higher than in the control, indicating increased energy requirements for standard metabolism in the presence of diclofenac (>0.1 µg/L). The heart rate recovery time in mollusks after heating to critical temperature (30 °C) was 1.7 and 9 times greater in mollusks exposed to 0.1 and 0.9 µg/L, respectively, than in the control (24 min). A level of diclofenac >0.9 µg/L adversely affected amphipod embryos, leading to an increase in the number of embryos with impaired development, which subsequently died. Thus, the lowest effective concentration of diclofenac (0.1 µg/L) led to increased energy demands of animals while reducing cardiac stress tolerance, and at a level close to 1 µg/L reproductive disorders (elevated mortality of the embryos) occurred. Environ Toxicol Chem 2022;41:677-686. © 2021 SETAC.

Low-dose prednisolone in rheumatoid arthritis: adverse effects of various disease modifying antirheumatic drugs.

OBJECTIVE: To assess the incidence and severity of disease modifying antirheumatic drug (DMARD)-induced adverse effects (AE) in patients with rheumatoid arthritis (RA) taking/not taking glucocorticoids (GC). More specifically, we tested whether GC can prolong the survival time of DMARD in patients receiving combination therapy. METHODS: In a retrospective study of 154 patients with RA, data were examined for DMARD therapy and duration of low-dose GC ((3/4) 7.5 mg prednisone equivalent/day). Patients were followed for 2-62 months, and AE were graded following WHO criteria. RESULTS: GC therapy significantly increased the duration of therapy with sulfasalazine (SSZ) from 10.4 +/- 2.3 to 22.5 +/- 1.9 months and for methotrexate (MTX) from 21.8 +/- 2.9 to 43.3 +/- 2.7 months. Stratifying the withdrawal of DMARD for occurrence of AE and loss of efficacy revealed that GC comedication significantly increased the time until AE for users of MTX (3.0 +/- 0.6 vs 18.8 +/- 1.3 mo; p < 0.05), hydroxychloroquine (HCQ; 34.5 +/- 4.6 vs 54.4 +/- 5.1 mo; p < 0.05), and gold (6.6 +/- 0.9 vs 10.5 +/- 0.9 mo; p < 0.05). In patients taking SSZ the time until cessation due to loss of efficacy increased significantly under GC comedication (16.8 +/- 1.2 vs 31.3 +/- 2.9 mo; p < 0.05). However, in patients taking azathioprine (AZA) the duration of therapy decreased from 44.4 +/- 2.6 to 22.3 +/- 1.6 months under GC due to both time until AE and loss of efficacy. Patients under comedication of MTX + GC, HCQ + GC, and AZA + GC experienced significantly more AE compared to the respective DMARD monotherapy. A highly significant reduction was observed in the frequency of erosive RA in patients with GC comedication (n = 30; 49.1%) compared to patients without low-dose GC (n = 81, 80.4%; OR 4.05, 95% CI 1.91-8.66, p < 0.0001). CONCLUSION: Low-dose GC retard radiological progression of RA and exhibit a differential effect on survival of DMARD and degree of AE due to DMARD. Further studies are warranted to address safety and interactions of chronic low-dose GC in RA patients treated with DMARD.