The action of 2,4-Dichlorophenoxyacetic acid on the isolated heart of insect and amphibia

Prioritizing Pesticides of Potential Concern and Identifying Potential Mixture Effects in Great Lakes Tributaries Using Passive Samplers

To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQs) for chemicals with available US Environmental Protection Agency (USEPA) Aquatic Life Benchmark values. In addition, exposure activity ratios (EAR) were calculated using information from the USEPA ToxCast database. Between 16 and 81 chemicals were detected per site, with 97 unique compounds detected overall, for which 64 could be assessed using TQs or EARs. Ten chemicals exceeded TQ or EAR levels of concern at two or more sites. Chemicals exceeding thresholds included seven herbicides (2,4-dichlorophenoxyacetic acid, diuron, metolachlor, acetochlor, atrazine, simazine, and sulfentrazone), a transformation product (deisopropylatrazine), and two insecticides (fipronil and imidacloprid). Watersheds draining agricultural and urban areas had more detections and higher concentrations of pesticides compared with other land uses. Chemical mixtures analysis for ToxCast assays associated with common modes of action defined by gene targets and adverse outcome pathways (AOP) indicated potential activity on biological pathways related to a range of cellular processes, including xenobiotic metabolism, extracellular signaling, endocrine function, and protection against oxidative stress. Use of gene ontology databases and the AOP knowledgebase within the R-package ToxMixtures highlighted the utility of ToxCast data for identifying and evaluating potential biological effects and adverse outcomes of chemicals and mixtures. Results have provided a list of high-priority chemicals for future monitoring and potential biological effects warranting further evaluation in laboratory and field environments. Environ Toxicol Chem 2023;42:340-366. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Probability that there is a mammalian counterpart of cardiac clock in insects

Whether or not the hyperpolarization-activated cyclic nucleotide-gated nonselective cation channel (HCN or funny current I_f ) is involved in pacemaking - recurrent heartbeat, it is attributed to electrical activities in all excitable cells, including those of invertebrates. In latter group of animals prevailingly the electrical signals and function of heart in terms of chrono- and inotropy are elucidated. Although in simpler models including insects experimental outcomes are reproducible and robust, involvement of "cardiac clock" mechanism in pacemaking is not conclusive. In this assay, the mechanisms of heartbeat are synthesized by focused comparisons between insect and mammalian hearts.

Monitoring of Honey Bee Colony Losses: A Special Issue

In recent decades, independent national and international research programs have revealed possible reasons for the death of managed honey bee colonies worldwide. Such losses are not due to a single factor, but instead are due to highly complex interactions between various internal and external influences, including pests, pathogens, honey bee stock diversity, and environmental change. Reduced honey bee vitality and nutrition, exposure to agrochemicals, and quality of colony management contribute to reduced colony survival in beekeeping operations. Our Special Issue (SI) on ‘’Monitoring of Honey Bee Colony Losses’’ aims to address specific challenges facing honey bee researchers and beekeepers. This SI includes four reviews, with one being a meta-analysis that identifies gaps in the current and future directions for research into honey bee colonies mortalities. Other review articles include studies regarding the impact of numerous factors on honey bee mortality, including external abiotic factors (e.g., winter conditions and colony management) as well as biotic factors such as attacks by Vespa velutina and Varroa destructor.

Mutagenic assessment of Lithobates catesbeianus tadpoles exposed to the 2,4-D herbicide in a simulated realistic scenario

The aim of the current study is to assess possible erythrocyte mutagenic effects on Lithobates catesbeianus tadpoles exposed to water contaminated with 2,4-D. In order to do so, tadpoles were exposed to a predictive and environmentally relevant herbicide concentration (1.97 mg/L), which is likely to be found in lentic environments formed by superficial water runoffs in pasture areas where the herbicide was applied. The micronucleus test, as well as tests for other nuclear abnormalities, was conducted after 3, 5, and 9 days of exposure (d.e.). Changes in the biomass and mouth-cloaca length or interference in the larval development of the animals (in the three evaluated times) were not recorded. However, tadpoles exposed to 2,4-D showed the highest total number of nuclear abnormalities, as well as the highest frequency of binucleated erythrocytes and kidney-shaped nuclei (shortly after 3 d.e.). The micronucleus frequency was also higher in animals exposed to 2,4-D (in the 3rd, 5th, and 9th d.e.), as well as the frequency of binucleated cells (3rd, 5th, and 9th d.e.) presenting notched (9th d.e.) and blebbled (9th d.e.) nuclei in comparison to those of the control, after 5 and 9 days of exposure. Therefore, the current study is a pioneer in showing that 2,4-D has a mutagenic effect on L. catesbeianus tadpoles, even at low concentrations (environmentally relevant) and for a short period of time, a fact that may lead to direct losses in anuran populations living in areas adjacent to those subjected to 2,4-D herbicide application.

Programmed Cell Death in the Honey Bee (Apis mellifera) (Hymenoptera: Apidae) Worker Brain Induced by Imidacloprid

Honey bees are at an unavoidable risk of exposure to neonicotinoid pesticides, which are used worldwide. Compared with the well-studied roles of these pesticides in nontarget site (including midgut, ovary, or salivary glands), little has been reported in the target sites, the brain. In the current study, laboratory-reared adult worker honey bees (Apis mellifera L.) were treated with sublethal doses of imidacloprid. Neuronal apoptosis was detected using the TUNEL technique for DNA labeling. We observed significantly increased apoptotic markers in dose- and time-dependent manners in brains of bees exposed to imidacloprid. Neuronal activated caspase-3 and mRNA levels of caspase-1, as detected by immunofluorescence and real-time quantitative PCR, respectively, were significantly increased, suggesting that sublethal doses of imidacloprid may induce the caspase-dependent apoptotic pathway. Additionally, the overlap of apoptosis and autophagy in neurons was confirmed by transmission electron microscopy. It further suggests that a relationship exists between neurotoxicity and behavioral changes induced by sublethal doses of imidacloprid, and that there is a need to determine reasonable limits for imidacloprid application in the field to protect pollinators.

Gene expression in honey bee (Apis mellifera) larvae exposed to pesticides and Varroa mites (Varroa destructor)

Honey bee (Apis mellifera) larvae reared in vitro were exposed to one of nine pesticides and/or were challenged with the parasitic mite, Varroa destructor. Total RNA was extracted from individual larvae and first strand cDNAs were generated. Gene-expression changes in larvae were measured using quantitative PCR (qPCR) targeting transcripts for pathogens and genes involved in physiological processes, bee health, immunity, and/or xenobiotic detoxification. Transcript levels for Peptidoglycan Recognition Protein (PGRPSC), a pathogen recognition gene, increased in larvae exposed to Varroa mites (P<0.001) and were not changed in pesticide treated larvae. As expected, Varroa-parasitized brood had higher transcripts of Deformed Wing Virus than did control larvae (P<0.001). Varroa parasitism, arguably coupled with virus infection, resulted in significantly higher transcript abundances for the antimicrobial peptides abaecin, hymenoptaecin, and defensin1. Transcript levels for Prophenoloxidase-activating enzyme (PPOact), an immune end product, were elevated in larvae treated with myclobutanil and chlorothalonil (both are fungicides) (P<0.001). Transcript levels for Hexameric storage protein (Hsp70) were significantly upregulated in imidacloprid, fluvalinate, coumaphos, myclobutanil, and amitraz treated larvae. Definitive impacts of pesticides and Varroa parasitism on honey bee larval gene expression were demonstrated. Interactions between larval treatments and gene expression for the targeted genes are discussed.

Residues of Pesticides in honeybee (Apis mellifera carnica) bee bread and in pollen loads from treated apple orchards

Honey bee (Apis mellifera carnica) colonies were placed in two apple orchards treated with the insecticides diazinon and thiacloprid and the fungicide difenoconazole in accordance with a Protection Treatment Plan in the spring of 2007. Pollen and bee bread were collected from combs inside the hives. The residue of diazinon in pollen loads 10 days after orchard treatment was 0.09 mg/kg, and the same amount of residue was found in bee bread 16 days after treatment. In pollen loads 6 days after application 0.03 mg/kg of thiacloprid residues and 0.01 mg/kg of difenoconazole were found on the first day after application. Possible sub-lethal effects on individual honey bees and brood are discussed.

Criticality in the relaxation phase of a spontaneously contracting atria isolated from a frog's heart

We investigate the spontaneous contraction generated by the atria of a frog's heart isolated in a physiological solution. In the relaxation phase, the recorded time series for two different sampling rates possesses an intermittent component similar to the dynamics of the order parameter's fluctuations of a thermal critical system belonging to the mean field universality class. This behavior is not visible through conventional analysis in the frequency space due to the presence of Brownian noise dominating the corresponding power spectrum.

Triazines facilitate neurotransmitter release of synaptic terminals located in hearts of frog (Rana ridibunda) and honeybee (Apis mellifera) and in the ventral nerve cord of a beetle (Tenebrio molitor)

Three triazine herbicides, atrazine, simazine and metribuzine, and some of their major metabolites (cyanuric acid and 6-azauracil) were investigated for their action on synaptic terminals using three different isolated tissue preparations from the atria of the frog, Rana ridibunda, the heart of the honeybee, Apis mellifera macedonica, and the ventral nerve cord of the beetle, Tenebrio molitor. The results indicate that triazines facilitate the release of neurotransmitters from nerve terminals, as already reported for the mammalian central nervous system. The no observed effect concentration, the maximum concentration of the herbicide diluted in the saline that has no effect on the physiological properties of the isolated tissue, was estimated for each individual preparation. According to their relative potency, the three triazines tested can be ranked as follows: atrazine (cyanuric acid), simazine>metribuzine (6-azauracil). The action of these compounds on the cholinergic (amphibians, insects), adrenergic (amphibian) and octopaminergic (insects) synaptic terminals is discussed.