Aop: 16

Title

A descriptive phrase which references both the Molecular Initiating Event and Adverse Outcome.It should take the form “MIE leading to AO”. For example, “Aromatase inhibition leading to reproductive dysfunction” where Aromatase inhibition is the MIE and reproductive dysfunction the AO. In cases where the MIE is unknown or undefined, the earliest known KE in the chain (i.e., furthest upstream) should be used in lieu of the MIE and it should be made clear that the stated event is a KE and not the MIE. More help

Acetylcholinesterase inhibition leading to acute mortality

Short name
A name that succinctly summarises the information from the title. This name should not exceed 90 characters. More help
AChE inhibition - acute mortality

Graphical Representation

A graphical representation of the AOP.This graphic should list all KEs in sequence, including the MIE (if known) and AO, and the pair-wise relationships (links or KERs) between those KEs. More help
Click to download graphical representation template Explore AOP in a Third Party Tool
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Authors

The names and affiliations of the individual(s)/organisation(s) that created/developed the AOP. More help

CHRISTINE L. RUSSOM (1), DANIEL L. VILLENEUVE* (2), VIRGINIA HENCH (3), CATAIA IVES (3), VIRGINIA C. MOSER (1), CARLIE A. LALONE (2), STEPHEN EDWARDS (3), KRISTIE SULLIVAN (4), and GERALD T. ANKLEY (2)

(1) U.S. Environmental Protection Agency (Retired)

(2) National Health and Environmental Effects Research Laboratory, Office of Research and Development, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA

(3) Research Computing Division, RTI International, Research Triangle Park, North Carolina, USA

(4) Physicians Committee for Responsible Medicine, Washington, DC, USA

  • Corresponding author for wiki entry (Villeneuve.dan@epa.gov)

Point of Contact

The user responsible for managing the AOP entry in the AOP-KB and controlling write access to the page by defining the contributors as described in the next section.   More help
Dan Villeneuve   (email point of contact)

Contributors

Users with write access to the AOP page.  Entries in this field are controlled by the Point of Contact. More help
  • Dan Villeneuve
  • Ginnie Hench
  • Cataia Ives
  • Kristie Sullivan

Status

Provides users with information concerning how actively the AOP page is being developed, what type of use or input the authors feel comfortable with given the current level of development, and whether it is part of the OECD AOP Development Workplan and has been reviewed and/or endorsed. OECD Status - Tracks the level of review/endorsement the AOP has been subjected to. OECD Project Number - Project number is designated and updated by the OECD. SAAOP Status - Status managed and updated by SAAOP curators. More help
Author status OECD status OECD project SAAOP status
Under Development: Contributions and Comments Welcome Under Development 1.3 Included in OECD Work Plan
This AOP was last modified on June 04, 2021 10:24

Revision dates for related pages

Page Revision Date/Time
Increased Mortality July 08, 2022 07:32
Acetylcholinesterase (AchE) Inhibition April 29, 2020 17:21
Acetylcholine accumulation in synapses June 26, 2020 13:06
Respiratory distress/arrest December 20, 2019 15:42
Increased Cholinergic Signaling December 20, 2019 17:32
Dysregulation of heart rate and vascular tone December 20, 2019 16:02
Decrease, Population growth rate July 08, 2022 07:40
AchE Inhibition leads to Increased Cholinergic Signaling December 20, 2019 11:07
AchE Inhibition leads to ACh Synaptic Accumulation December 19, 2019 15:57
ACh Synaptic Accumulation leads to Increased Cholinergic Signaling December 20, 2019 09:16
AchE Inhibition leads to Respiratory distress/arrest December 20, 2019 11:47
Increased Cholinergic Signaling leads to Respiratory distress/arrest December 20, 2019 09:51
AchE Inhibition leads to Cardiovascular dysregulation December 20, 2019 14:56
Increased Cholinergic Signaling leads to Cardiovascular dysregulation December 20, 2019 15:05
Cardiovascular dysregulation leads to Respiratory distress/arrest December 19, 2019 16:16
Respiratory distress/arrest leads to Increased Mortality December 20, 2019 10:26
AchE Inhibition leads to Increased Mortality December 20, 2019 17:33
Increased Mortality leads to Decrease, Population growth rate July 08, 2022 08:29
AchE Inhibition leads to Decrease, Population growth rate December 20, 2019 16:49

Abstract

A concise and informative summation of the AOP under development that can stand-alone from the AOP page. The aim is to capture the highlights of the AOP and its potential scientific and regulatory relevance. More help

The contents of this AOP page represent an interconnected network of AOPs linking the MIE of acetylcholinesterase inhibition to the AO of acute mortality. Both AOPs include the KE of acetylcholine accumulation at the synapses, which results in excessive signaling from cholinergic neurons on a broad range of tissues throughout the body. Respiratory failure is the predominant mechanism leading to acute mortality in humans (Satoh, 2006). While these two AOPs are represented on the basis of their most plausible linkages to acute mortality, other known symptoms of acetylcholinesterase inhibition mediated through actions on other receptors and tissues may also play a role (see Russom et al. 2014). Overall, there is strong evidence supporting the linkage of acetylcholinesterase inhibition and acetylcholine accumulation with acute mortality, but the precise contribution of the different organ-level effects across different species isn’t completely understood. This network of AOPs as a whole, including the indirect KERs depicted, supports the potential utility of in vitro or short-term in vivo measures of acetylcholinesterase inhibition for identifying chemicals with potential to cause acute mortality across a broad range of species. Caution is needed when interpreting the in vitro results, however, because well known chemical initiators of these AOPs are known to require metabolic activation, which can result in false negatives. In contrast, detoxification of these compounds is sometimes deficient in the young resulting in life stage differences in response to different chemicals that act through this mechanism. Toxicokinetics is also variable across species making this a major determinant of species sensitivity. At present, quantitative understanding is not sufficiently complete to accurately predict apical outcomes or potency from in vitro measurements alone, and the chemical-specific ADME and toxicokinetic considerations will be strong determinant of quantitative outcomes.

AOP Development Strategy

Context

Used to provide background information for AOP reviewers and users that is considered helpful in understanding the biology underlying the AOP and the motivation for its development.The background should NOT provide an overview of the AOP, its KEs or KERs, which are captured in more detail below. More help

Strategy

Provides a description of the approaches to the identification, screening and quality assessment of the data relevant to identification of the key events and key event relationships included in the AOP or AOP network.This information is important as a basis to support the objective/envisaged application of the AOP by the regulatory community and to facilitate the reuse of its components.  Suggested content includes a rationale for and description of the scope and focus of the data search and identification strategy/ies including the nature of preliminary scoping and/or expert input, the overall literature screening strategy and more focused literature surveys to identify additional information (including e.g., key search terms, databases and time period searched, any tools used). More help

Summary of the AOP

This section is for information that describes the overall AOP. The information described in section 1 is entered on the upper portion of an AOP page within the AOP-Wiki. This is where some background information may be provided, the structure of the AOP is described, and the KEs and KERs are listed. More help

Events:

Molecular Initiating Events (MIE)
An MIE is a specialised KE that represents the beginning (point of interaction between a prototypical stressor and the biological system) of an AOP. More help
Key Events (KE)
A measurable event within a specific biological level of organisation. More help
Adverse Outcomes (AO)
An AO is a specialized KE that represents the end (an adverse outcome of regulatory significance) of an AOP. More help
Type Event ID Title Short name
KE 10 Acetylcholine accumulation in synapses ACh Synaptic Accumulation
KE 39 Increased Cholinergic Signaling Increased Cholinergic Signaling
KE 445 Respiratory distress/arrest Respiratory distress/arrest
KE 1703 Dysregulation of heart rate and vascular tone Cardiovascular dysregulation
AO 351 Increased Mortality Increased Mortality
AO 360 Decrease, Population growth rate Decrease, Population growth rate

Relationships Between Two Key Events (Including MIEs and AOs)

This table summarizes all of the KERs of the AOP and is populated in the AOP-Wiki as KERs are added to the AOP.Each table entry acts as a link to the individual KER description page. More help

Network View

This network graphic is automatically generated based on the information provided in the MIE(s), KEs, AO(s), KERs and Weight of Evidence (WoE) summary tables. The width of the edges representing the KERs is determined by its WoE confidence level, with thicker lines representing higher degrees of confidence. This network view also shows which KEs are shared with other AOPs. More help

Prototypical Stressors

A structured data field that can be used to identify one or more “prototypical” stressors that act through this AOP. Prototypical stressors are stressors for which responses at multiple key events have been well documented. More help

Life Stage Applicability

The life stage for which the AOP is known to be applicable. More help
Life stage Evidence
All life stages High

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available. More help

Sex Applicability

The sex for which the AOP is known to be applicable. More help
Sex Evidence
Unspecific High

Overall Assessment of the AOP

Addressess the relevant biological domain of applicability (i.e., in terms of taxa, sex, life stage, etc.) and Weight of Evidence (WoE) for the overall AOP as a basis to consider appropriate regulatory application (e.g., priority setting, testing strategies or risk assessment). More help

Domain of Applicability

Addressess the relevant biological domain(s) of applicability in terms of sex, life-stage, taxa, and other aspects of biological context. More help
Life Stage Applicability

The key molecular target is the AChE enzyme, which appears to be available in all life stages of vertebrate and invertebrate species, although studies have found that AChE activity increases as the organism develops.

    • AChE can be inhibited by stressors from early in development throughout aging.  AChE inhibition has been measured in rat fetuses when the dam was dosed with chlorpyrifos (Lassiter et al., 1999), and also in aged rats up to 2 years of age treated with either carbaryl or methomyl (Moser et al., 2015).

    • In many species, sensitivity to stressors is greater in the young.  There are several factors that influence these age-related differences.  Intake from food and water is higher on a body weight basis, and in children, certain behaviors (crawling, hand-to-mouth) can also increase intake.  More importantly, considerable evidence shows that immature detoxification in the young account for much of the age differences. AChE inhibitors are metabolized or detoxified through a number of pathways, including hydrolysis by or binding to various esterases, and microsomal metabolism.  This leads to life-stage differences that are highly dependent on the stressor and the individual kinetic profile of each (Moser, 2011)

    • AChE in developing precocial birds were found to level off at the embryo life stage, while in altricial species the AChE activity increased as the bird developed until it reached a steady state at adulthood (Grue et al., 1981).

    • A study examining the acetylcholine and cholinesterase levels in developing brains of Sprague-Dawley rats found that acetylcholine synthesis was significantly lower in neonate and juveniles when compared to the adult levels, and the neonate cholinesterase levels were significantly lower than adult levels of activity (Karanth and Pope 2003). When exposed to either parathion or chlorpyrifos, the researchers found differences in peak inhibition of cholinesterase with neonates seeing the greatest impact early in the exposure (4-24 hrs), while juveniles and adults saw the most severe impacts at 96 hrs of exposure (Karanth and Pope 2003). Exposure to pesticides did not seem to impact acetylcholine production in the rats regardless of life stage, but researchers thought the pesticides may be altering other biochemical process (e.g., choline acetyltransferase) which might ultimately impact the measures of acetylcholine (Karanth and Pope 2003).

    • In Drosophila, changes in AChE activity in the developing organism were observed, with egg stages displaying the lowest activity, and maximum activity at the pupae life stage (Parkash and Kaur 1982).

    • In mammals and birds, studies have determined that skeletal muscles of immature birds and mammals contain both butyrylcholinesterase and AChE, with butyrylcholinesterase decreasing and AChE increasing as the animal develops (Tsim et al. 1988; Berman et al, 1987).

    • Another study found that changes in AChE within the developing pig brain were dependent on the area of the brain and life stage of the animal, with significant decreases in activity within the pons and hippocampus from birth to 36 months, and no significant change in activity in the cerebellum, where activity increased up to four months of age, leveling off thereafter (Adejumo and Egbunike, 2004).

    • Evidence exists that immature life stages in mammals and birds may be more sensitive to OP pesticides (see Grue et al., 1997; Grue et al., 1983; Grue et.al; 1981), although this may be related to the amount of pesticide ingested in relation to body size (Ludke et al, 1975).

    • Researchers reported that frog (Bufo arenarum Hensel) embryos were more tolerant to parathion exposure than frog larvae, and associated this with the ability of the embryo AChE to recover to baseline levels faster than the larval life stage (Anguiano et al, 1994).

Taxonomic Applicability

Although AChE enzyme is found in all vertebrate and invertebrate species, the activity within taxa varies.

    • An examination of the STRING (V9.0 http://string-db.org), which is a database of known and predicted protein interactions, finds that the AChE enzyme is well conserved across vertebrate and invertebrate species.

    • A pattern of species sensitivity for OPs using terrestrial species found birds to be highly sensitive, mammals moderately sensitive, and fish and amphibians of lower sensitivity (Wallace 1992).

    • Taxonomic differences as they relate to key events within the AOP may be due to a number of factors. For instance, the organism’s habitat (e.g., sediment, water, and grass), diet, body size, behavior, mobility, and skin/exoskeleton permeability could all affect the level of exposure and the ability of the chemical to reach the molecular target. A complicating factor when identifying relative species sensitivities are differences in routes of exposure which may impact the time it takes for the substance to reach the molecular target, and impacts to adsorption, distribution, metabolism, and elimination (ADME) within the organism.

    • Phase I metabolism of phosphorothioates and phosphorodithioates by mixed function oxidases results in the more toxic oxon, which is the form that binds to AChE. Differences in species sensitivity may be impacted by the rate at which this reaction occurs, as would any mechanism related to detoxification of the oxon form. For instance, in mammals the oxon form undergoes an ester detoxification pathway which is not present in insect species, resulting in insects having a higher susceptibility to OPs than mammals (Ecobichon 2001). Similarly for procarbamates, invertebrates are able to convert the substance to the active form, while vertebrate species lack this metabolic mechanism (Stenersen 2004).

    • Studies have provided evidence that differences in the AChE enzyme across taxa may better explain differences in species sensitivity. Evidence suggests that the relative activity of AChE is linked to the hydrophobic and electronic configuration of the enzyme, which directly impacts the speed and/or efficiency that a substance can bind to the enzyme, and could impact the ability/speed of the enzyme to reactivate to its normal state (Wallace, 1992; Wallace and Kemp 1991). For instance, taxonomic differences in the electronic and steric properties of the esteratic site, nucleophilic strength of the enzyme center, the distance between the anionic and esteratic sites, and the electronic/steric properties of the anionic site may all impact the relative binding efficiency of the enzyme to the pesticide (O’Brien 1963; Monserrat and Bianchini 2001; Wallace, 1992; Wallace and Kemp 1991).

    • Baseline levels of the enzyme can significantly vary depending on species, strains, age class, sex, season, reproductive and nutritional status, and disease state (Cowman and Mazanti, 2000; Hill 1988; Rattner and Fairbrother 1991).

    • There are specific differences in the genes that code for the cholinergic AChE enzyme. In vertebrate species, AChE is encoded by a single gene (Ace) resulting in a conserved enzyme across the taxonomic group (Lu et al., 2012; Taylor 2011). AChE is encoded in the Diptera suborder Brachycera (e.g., Drosophila, common house fly) by the gene Ace2, while in other insects both an Ace1 and Ace2 gene encode AChE (Lu et al., 2012). The Ace1 gene produces an AChE with a cysteine residue, which is not found in vertebrate AChE, or in the AChE from the Ace2 gene form. Acetylcholinesterase from Ace1 is associated with neurotransmissions within the insect, while AChE from the Ace2 gene is responsible for non-cholinergic activity such as embryonic development, growth, and reproduction (Lu et al., 2012).

    • Comparisons of susceptibility of Xenopus laevis and human forms of AChE to OP and carbamate pesticides found that the enzyme in frog embryos has a much higher resistance to these pesticides than the human form of the enzyme (Shapira et al., 1998).

    • Acetylcholinesterase is found in presynaptic membranes of motor neurons in the spinal cord, cranial nerves within skeletal muscle, and preganglionic sympathetic and postganglionic parasympathetic neurons of vertebrates (Mileson et al., 1998). In invertebrates, AChE appears to be associated with sensory, brain, and other muscle activity (Fulton and Key, 2001; Habig and Di Giulio 1991; Mileson et al. 1998; Ware and Whitacre 2004).

    • In plants, the function of AChE is not well understood, but levels of acetylcholine appear to be involved in the regulation of membrane permeability, and the ability of a leaf to unroll (Tretyn and Kendrick 1991).

Sex Applicability

No studies were located reporting significant differences in AChE activity between male and female organisms.

Essentiality of the Key Events

The essentiality of KEs can only be assessed relative to the impact of manipulation of a given KE (e.g., experimentally blocking or exacerbating the event) on the downstream sequence of KEs defined for the AOP. Consequently, evidence supporting essentiality is assembled on the AOP page, rather than on the independent KE pages that are meant to stand-alone as modular units without reference to other KEs in the sequence. The nature of experimental evidence that is relevant to assessing essentiality relates to the impact on downstream KEs and the AO if upstream KEs are prevented or modified. This includes: Direct evidence: directly measured experimental support that blocking or preventing a KE prevents or impacts downstream KEs in the pathway in the expected fashion. Indirect evidence: evidence that modulation or attenuation in the magnitude of impact on a specific KE (increased effect or decreased effect) is associated with corresponding changes (increases or decreases) in the magnitude or frequency of one or more downstream KEs. More help
  • There are numerous studies which have shown the blockage or reversibility of downstream events following the administration of pharmacological agents that either bypass acetylcholinesterase activity by directly activating acetylcholine receptors or that act as direct agonists or antagonists of the various types of acetylcholine receptors. Additionally, evidence from experiments with AChR morpholino antisense oligonucleotides have provided additional evidence for an essential role of acetylcholine receptor activation in mediating some of the downstream key events.
  • Based on the current information assembled for this AOP, the essentiality of the key events downstream of acetylcholine accumulation is less clear. While there are several key events that correspond with well known symptoms of acetylcholinesterase inhibition (as characterized through a number of nonadjacent KERs), it is presently unclear which of these are the major driver of lethality across different species. In humans, addressing respiratory failure is routinely used to prevent death from poisoning with chemicals that act on acetylcholinesterase. Data from ecological species suggest that other failure points could be equally important. Given the abundance of literature on acetylcholine signaling and adverse effects associated with acetylcholinesterase inhibition, this is an area of the AOP that warrants further development.

Evidence Assessment

Addressess the biological plausibility, empirical support, and quantitative understanding from each KER in an AOP. More help
  • There is strong evidence that the initial inhibition of the AChE enzyme is required prior to triggering key events that lead to the adverse outcome of mortality (See US EPA 2006; Grue and Shipley 1984).
  • There is strong empirical evidence linking the key events, beginning with the molecular initiating event; AChE inhibition, followed by an increase in the acetylcholine at synapses of muscarinic and nicotinic receptors, and subsequent physiological and biochemical response resulting in cholinergic activity resulting in the death of the organism.
  • Strong evidence based on measured AChE inhibition and statistically-derived acute endpoints (e.g., LC/LD50) demonstrate a correlation of increase in enzyme inhibition and increased lethality. The open literature has many studies reporting these effects across invertebrate and vertebrate species with examples presented below.
  • The overall weight of evidence supporting the indirect relationship between AChE inhibition and mortality is very strong and there are many physiological activities associated with acetylcholine neurotransmission that are plausibly linked with organism survival. However, there remain significant gaps in the current AOP description regarding which specific intermediate events are primarily responsible for the toxicity observed. It is likely that it is a combination of these physiological responses rather than any one alone, and that the key driver is also species dependent.

Known Modulating Factors

Modulating factors (MFs) may alter the shape of the response-response function that describes the quantitative relationship between two KES, thus having an impact on the progression of the pathway or the severity of the AO.The evidence supporting the influence of various modulating factors is assembled within the individual KERs. More help

Quantitative Understanding

Optional field to provide quantitative weight of evidence descriptors.  More help

Considerations for Potential Applications of the AOP (optional)

Addressess potential applications of an AOP to support regulatory decision-making.This may include, for example, possible utility for test guideline development or refinement, development of integrated testing and assessment approaches, development of (Q)SARs / or chemical profilers to facilitate the grouping of chemicals for subsequent read-across, screening level hazard assessments or even risk assessment. More help

References

List of the literature that was cited for this AOP. More help
  • Adejumo, D.O. and G.N. Egbunike. 2004. Changes in acetylcholinesterase activities in the developing and aging pig brain and hypophyses. Int. J. Agric. Rural. Dev. 5: 46-53.

  • Anguiano, O.L., C.M. Montagna, M. Chifflet de Llamas, L. Gauna, and A.M. Pechen de D'Angelo. 1994. Comparative toxicity of parathion in early embryos and larvae of the toad, Bufo arenarum Hensel. Bull. Environ. Contam. Toxicol. 52(5): 649-655.

  • Berman, H.A., M.M. Decker, and J. Sangmee. 1987. Reciprocal regulation of acetylcholinesterase and butyrylcholinesterase in mammalian skeletal muscle. Dev. Biol. 120(1): 154-161.

  • Cowman, D.F. and L.E. Mazanti. 2000. Ecotoxicology of “new generation” pesticides to amphibians. In: D.W. Sparling, G. Linder, and C.A. Bishop (Eds.), Ecotoxicology of Amphibians and Reptiles, pp 233-268, SETAC Press, Pensacola, FL.

  • Ecobichon, D.J. 2001. Toxic effects of pesticides. In: C.D. Klaassen (Ed.), Casarett and Doull’s Toxicology: The Basic Science of Poisons; Sixth Edition. (pp. 763-810). McGraw-Hill, New York, NY.

  • Fukuto, TR. 1990. Mechanism of action of organophosphorus and carbamate insecticides. Environ Health Perspect. 87:245-254.

  • Fulton, M.H. and P.B. Key. 2001. Acetylcholinesterase inhibition in estuarine fish and invertebrates as an indicator of organophosphorous insecticide exposure and effects. Environ. Toxicol. Chem. 20(1): 37-45.

  • Grue, C.E., G.V.N. Powell, and N.L. Gladson. 1981. Brain cholinesterase (ChE) activity in nestling starlings: Implications for monitoring exposure of nestling songbirds to ChE inhibitors. Bull. Environ. Contam. Toxicol. 26: 544-547.

  • Grue, C.E., W.J. Fleming, D.G. Busby, and E.F. Hill. 1983. Assessing hazards of organophosphate pesticides to wildlife. In: Transactions of the 48th North American Wildlife and Natural Resources Conference, The Wildlife Management Institute, Washington, DC. pp. 200-220.

  • Grue, C.E. and B.K. Shipley. 1984. Sensitivity of nestling and adult starling to dicrotophos, and organophosphate pesticide. Environ. Res. 35:454-465.

  • Grue, C.E., P.L. Gibert, and M.E. Seeley. 1997. Neurophysiological and behavioral changes in non-target wildlife exposed to organophosphate and carbamate pesticides: Thermoregulation, food consumption, and reproduction. Amer. Zool. 37: 369-388.

  • Habig, C. and R.T. DiGiulio. 1991. Biochemical characteristics of cholinesterases in aquatic organisms. In: P. Mineau (Ed.), Cholinesterase-inhibiting Insecticides: Their Impact on Wildlife and the Environment. pp. 19-33. Elsevier, Amsterdam, The Netherlands.

  • Hill, E.F. 1988. Brain cholinesterase activity of apparently normal wild birds. J.Wild. Dis. 24(1): 51-61.

  • Karanth, S. and Pope, C. 2003. Age-Related Effects of Chlorpyrifos and Parathion on Acetylcholine Synthesis in Rat Striatum. Neurotoxicol.Teratol. 25[5], 599-606.

  • Lassiter TL, Barone S Jr, Moser VC, Padilla S (1999) Gestational exposure to chlorpyrifos: Dose response profiles for cholinesterase and carboxylesterase activity. Tox. Sci. 52:92-100.

  • Lu, Y., Y. Park, X. Gao, X. Zhang, J. Yoo, Y.-P. Pang, H. Jiang, and K.Y. Zhu. 2012. Cholinergic and non-cholinergic functions of two acetylcholinesterase genes revealed by gene-silencing in Tribolium castaneum. Sci. Rep. 2(Article No. 288):1-7.

  • Ludke, J.L., E.F. Hill, and M.P. Dieter. 1975. Cholinesterase (ChE) response and related mortality among birds fed ChE inhibitors. Arch. Environ. Contam. Toxicol. 3(1): 1-21.

  • Mileson, B.E., J.E. Chambers, W.L. Chen, W. Dettbarn, M. Ehrich, A.T. Eldefrawi, D.W. Gaylor, K. Hamernik, E. Hodgson, A.G. Karczmar, S. Padilla, C.N. Pope, R.J. Richardson, D.R. Saunders, L.P. Sheets, L.G. Sultatos, and K.B. Wallace. 1998. Common mechanism of toxicity: A case study of organophosphorus pesticides. Toxicol. Sci. 41: 8-20.

  • Monserrat, J.M. and A. Bianchini. 2001. Anticholinesterase effect of eserine (physostigmine) in fish and crustacean species. Braz. Arch. Biol. Technol. 44(1): 63-68.

  • Moser VC, Phillips PM, McDaniel KL. (2015) Assessment of biochemical and behavioral effects of carbaryl and methomyl in Brown-Norway rats from preweaning to senescence. Toxicology 331, 1-13.

  • Moser VC. (2011) Age-related differences in acetylcholinesterase inhibition produced by organophosphorus and N-methyl carbamate pesticides, in Pesticides in the Modern World B Pests Control and Pesticides Exposure and Toxicity Assessment (Stoytcheva M, ed). pp 495-506, Intech, Rijeka, Croatia

  • O’Brien, R.D. 1963. Mode of action of insecticides: Binding of organophosphate to cholinesterases. Agric. Food Chem. 11(2): 163-166.

  • Parkash, R. and K. Kaur. 1982. Ontogeny of acetylcholinesterases in hybridizing Drosophila species. Proc. Indian Nat. Sci. Acad. B48(5): 659-666.

  • Rattner, B.A. and A. Fairbrother. 1991. Biological variability and the influence of stress on cholinesterase activity. In: P. Mineau (Ed.), Cholinesterase-inhibiting Insecticides: Their Impact on Wildlife and the Environment. (pp. 89-107). Elsevier, Amsterdam, The Netherlands.

  • Satoh, TETSUO. 2006. “CHAPTER 8 - Global Epidemiology of Organophosphate and Carbamate Poisonings.” In Toxicology of Organophosphate & Carbamate Compounds, edited by Ramesh C. Gupta, 89–100. Burlington: Academic Press. https://doi.org/10.1016/B978-012088523-7/50009-0.

  • Schűűrmann G. 1992. Ecotoxicology and structure-activity studies of organophosphorus compounds. Rational Approaches to Structure, Activity, and Ecotoxicology of Agrochemicals, CRC Press, Boca Raton, FL, USA pp 485-541

  • Shapira, M., S. Seidman, N. Livni, and H. Soreq. 1998. In vivo and in vitro resistance to multiple anticholinesterases in Xenopus laevis tadpoles. Toxicol. Lett. 102-103: 205-209.

  • Sogob MA, Vilanova E. 2002. Enzymes involved in the detoxification of organophosphorus, carbamate and pyrethroid insecticides through hydrolysis. Toxicol Lett 128:215-228.

  • Stenersen, J. 2004. Specific enzyme inhibitors. In: Chemical Pesticides: Mode of action and toxicology. (41 p). CRC Press, Boca Raton, FL.

  • Taylor, P. 2011. Anticholinesterase agents. In: L.J. Brunton (Ed.), Goodman and Gilman’s The Pharmacological Basis of Therapeutics; 12th Edition. (pp. 255-276). McGraw Hill, New York, NY. (Accessed from the web: http://accessmedicine.com/resourceTOC.aspx?resourceID=651).

  • Tretyn, A. and R.E. Kendrick. 1991. Acetylcholine in plants: Metabolism and mechanism of action. Bot. Rev. 57(1): 33-73.

  • Tsim, K.W.K., W.R. Randall, and E.A. Barnard. 1988. Synaptic acetylcholinesterase of chicken muscle changes during development from a hybrid to a homogenous enzyme. EMBO J 7(8): 2451-2456.

  • U.S. Environmental Protection Agency (U.S. EPA). 2006. Organophosphorus Cumulative Risk Assessment – 2006. Update. U.S. EPA, Office of Pesticide Programs, Washington, DC. 522 p.

  • Wallace, K.B., and J.R. Kemp. 1991. Species specificity in the chemical mechanisms of organophosphorus anticholinesterase activity. Chem. Res. Toxicol. 4: 41-49.

  • Wallace, K.B. 1992. Species-selective toxicity of organophosphorus insecticides: A pharmacodynamics phenomenon. In: J. E. Chambers and P. E. Levi, (Eds.), Organophosphates— Chemistry, Fate, and Effects. pp. 79-105. Academic Press, San Diego.

  • Ware, G.W. and D.M. Whitacre. 2004. An Introduction to Insecticides. In: E. B. Radcliffe,W. D. Hutchison and R. E. Cancelado [Eds.], Radcliffe's IPM World Textbook. 34 pp. University of Minnesota, St. Paul, MN. (Accessed from the web: URL: http://ipmworld.umn.edu).