Cytoplasmic vacuoles

Vacuolation of sensory ganglion neuron cytoplasm in rats with long-term exposure to organophosphates

Cytoplasmic vacuolation of sensory neurons has been reported to occur within the dorsal root ganglia in studies investigating various neuropathic conditions including the effects of neurotoxic chemicals. In this study, we investigated this lesion in adult (98-119 days old) male Long-Evans rats, after multiple exposures to two organophosphates (tri-ortho-tolyl phosphate [TOTP] and chlorpyrifos) and the modifying effects of concurrent corticosterone. Tri-ortho-tolyl phosphate was administered by gavage (75, 150, or 300 mg/kg) every other day between days 14 and 28 and between days 49 and 63, chlorpyrifos (60 mg/kg) was administered subcutaneously on days 7 and 42, and corticosterone was provided in the drinking water throughout the study at a concentration of 400 microg/mL. Although relatively uncommon, there was an increase in frequency of cytoplasmic vacuoles seen in treatment groups having multiple exposures to TOTP. They were characterized as peripherally located, single-limiting membrane-bound structures in the neuronal perikarya. There was no associated cell death, even when vacuoles were large. This is the initial report of an association of this change following exposure to neurotoxic organophosphates.

The pattern of pyridoxine-induced lesion: difference between the high and the low toxic level

A fundamental prerequisite for the design of neurotoxicological safety studies is the determination of the target areas in the nervous system which are specific for particular kinds of toxicants. The target areas should be identified in special "lesion-pattern-finding" experiments. The pyridoxine-induced lesion is a prototype of the pattern characteristic of a peripheral, primary sensory neuropathy. Depending on the conditions of treatment such as the dosage level and the timing of examination, the structural changes may be more obvious either in the proximal or the distal portion of the neuron, while the functional signs may vary from severe sensory paralysis to quite unremarkable behavior.