Neuropathological effect of carbamate molluscicides on the land snail, Eobania vermiculata

Abstract

The present study was designed to investigate the neuropathological effect of the two carbamate pesticides: methomyl and methiocarb on the neurons of the buccal ganglia in the land snail Eobania vermiculata using topical application and baiting technique. Their in vivo effects on acetylcholinesterase (AChE, EC 3.1.1.7) activity were also investigated. Sublethal dose and concentration (1/4 LD(50) and 1/4 LC(50)) of both pesticides were used, and the experiment lasted for 14 days. Histopathological and ultrastuctural alterations in the buccal ganglia were more obvious after the baiting technique treatment than after the topical application method, and methomyl was found to be more toxic than methiocarb. These alterations included shrinkage of the perikarya of neurons, increased cytoplasmic basophilia, and extreme indentation of the plasma membrane. In addition, the nuclei appeared karyolitic, eccentric, and highly shrunken with an irregular nuclear envelope. The most outstanding symptom observed after topical application of methiocarb was a highly vacuolated cytoplasm with a peripheral increase in electron density associated with dense accumulations of free ribosomes. On the other hand, an increased number of lysosomes and autophagosomes were observed after topical application of methomyl. Mitochondrial damage, increased number of lipid droplets, and myelin figures were frequently observed in ganglia treated with either methomyl or methiocarb. Moreover, it was noticed that both compounds induced reductions in AChE activity. However, methomyl exhibited more potency in reducing AChE activity than methiocarb.

Effects of organic pollutants on Eobania vermiculata measured with five biomarkers

“…The results of present study showed important inhibition of AChE activity in snails E. vermiculata exposed to organic pollutants, with the most important reduction detected in the higher exposure concentrations (1 ppm) of the organophosphate insecticides chlorpyrifos and parathion-methyl in the digestive cells. The previous observation is probably related to the particularly fast interaction of these organic substances with AChE, as competitive inhibitors of this enzyme, as it has been also proposed by Essawy et al (2008), after the study of snails E. vermiculata, which is in agreement with Pessah and Sokolove (1983) and Young and Wilkins (1989). The neurotoxic action of organics is owed to the inhibition of AChE activity and the accumulation of acetylcholine in the synaptic connections that can lead to changes of movement ability (Wedgwood and Bailey 1988) and diet (Bailey 1989).…”

Neuropathological studies of chickens following exposure to chlorpyrifos

“…Such vacuoles were regarded as a cellular defense mechanism against injurious substances that segregated in the vacuoles. [11] The second interesting finding in our study is that the cerebral endothelial cells became swollen and blocked the lumen of the capillary [Figure 4]. Higher magnification of cerebral endothelial cells is shown in Figure 5.…”

Neuroplastic and neuropathological changes in the central nervous system of the Gray mussel Crenomytilus grayanus (Dunker) under environmental stress

“…Enhanced autophagy in mussel digestive cells has been considered as a cellular defense against environmentally induced oxidative stress (Moore 2008). Besides, increased number of autophagosomes was found in the CNS of another mollusk species, the land snail Eobania vermiculata, following pesticide treatment in vivo (Essawy et al 2009). …”