Robert K. Kan

Zebrafish as a model for acetylcholinesterase‐inhibiting organophosphorus agent exposure and oxime reactivation

The current research progression efforts for investigating novel treatments for exposure to organophosphorus (OP) compounds that inhibit acetylcholinesterase (AChE), including pesticides and chemical warfare nerve agents (CWNAs), rely solely on in vitro cell assays and in vivo rodent models. The zebrafish (Danio rerio) is a popular, well‐established vertebrate model in biomedical research that offers high‐throughput capabilities and genetic manipulation not readily available with rodents. A number of research studies have investigated the effects of subacute developmental exposure to OP pesticides in zebrafish, observing detrimental effects on gross morphology, neuronal development, and behavior. Few studies, however, have utilized this model to evaluate treatments, such as oxime reactivators, anticholinergics, or anticonvulsants, following acute exposure. Preliminary work has investigated the effects of CWNA exposure. The results clearly demonstrated relative toxicity and oxime efficacy similar to that reported for the rodent model. This review surveys the current literature utilizing zebrafish as a model for OP exposure and highlights its potential use as a high‐throughput system for evaluating AChE reactivator antidotal treatments to acute pesticide and CWNA exposure.

Vapor inhalation exposure to soman in conscious untreated rats: preliminary assessment of neurotoxicity

Abstract Neurological toxicity and brain injury following vapor inhalation exposure to the chemical warfare nerve agent (CWNA) soman (GD) were examined in untreated non-anesthetized rats. In this study, male Sprague-Dawley rats (300–350 g) were exposed to 600 mg × min/m3 of soman or vehicle in a customized head-out inhalation system for 7 min. Convulsant animals were observed for clinical signs and various regions of the brain (dorsolateral thalamus, basolateral amygdala, piriform cortex, and lateral cortex) were collected for pathological observations 24 h post-exposure. Signs of CWNA-induced cholinergic crises including salivation, lacrimation, increased urination and defecation, and tremors were observed in all soman-exposed animals. Soman-exposed animals at 24 h post-exposure lost 11% of their body weight in comparison to 2% in vehicle-exposed animals. Whole blood acetylcholinesterase (AChE) activity was significantly inhibited in all soman-exposed groups in comparison to controls. Brain injury was confirmed by the neurological assessment of hematoxylin-eosin (H&E) staining and microscopy in the piriform cortex, dorsolateral thalamus, basolateral amygdala, and lateral cortex. Severe damage including prominent lesions, edematous, congested, and/or hemorrhagic tissues was observed in the piriform cortex, dorsolateral thalamus, and lateral cortex in soman-exposed animals 24 h post-exposure, while only minimal damage was observed in the basolateral amygdala. These results indicate that inhalation exposure to soman vapor causes neurological toxicity and brain injury in untreated unanesthetized rats. This study demonstrates the ability of the described soman vapor inhalation exposure model to cause neurological damage 24 h post-exposure in rats.

Determining Optimal Microwave Antigen Retrieval Conditions for Microtubule-Associated Protein 2 Immunohistochemistry in the Guinea Pig Brain

Abstract : The present study examined the efficacy of microwave pretreatment on microtubule-associated protein 2 (MAP-2) immunoreactivity in paraffin-embedded sections of formalin-fixed guinea pig brains using different MAP-2 monoclonal antibodies. Brain sections were boiled in sodium citrate, citric acid, Tris hydrochloride, and EDTA solutions with pH values of 2, 4, 6, and 8 in a microwave prior to MAP-2 immunohistochemical staining. Specific MAP-2 immunoreactivity was observed in brain regions when NeoMarkers MAP-2 antibody (clone AP-18) was used in conjunction with citric acid buffer of pH 6.0 as an antigen retrieval solution. No immunoreactivity of MAP-2 was observed in negative control sections. The results suggest that a lO-min boiling in citric acid solution at pH 6.0 is the optimal microwave-assisted AR method for immunolabeling MAP-2 in formalin-fixed, paraffin-processed guinea pig brain samples using NeoMarkers MAP-2 monoclonal antibody (AP-18). This undoubtedly will have important applications in our efforts to conduct retrospective studies on archival guinea pig brain paraffin blocks, ultimately relaxing the use of additional animals to evaluate changes in MAP-2 expression between chemical warfare nerve agent-treated and control samples.