Neurotoxicology
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Paclitaxel (Taxol), a chemotherapeutic agent used to treat breast and ovarian tumors, has been reported to induce a predominantly sensory neuropathy. Co-treatment with neurotrophic factors and paclitaxel has been proposed for preventing or reversing paclitaxel-induced peripheral neuropathy. Prosaposin, the precursor of saposins A, B, C and D was recently identified as a neurotrophic factor and was reported to facilitate nerve regeneration in vivo. ⋯ In the short-term high dose study, paclitaxel treated rats lost 10% of their body weight, had reduced erythrocyte counts, hematocrit and hemoglobin concentrations which were not prevented by treatment with prosaptide. TX14(A) did not diminish paclitaxel cytotoxicity of breast cancer cells in vitro. These findings suggest that prosaptide prevents the neurotoxic effects of paclitaxel while not interfering with its anti-tumor activity.
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The effectiveness of paclitaxel (Taxol) in the treatment of different tumors is well-known but, on the other hand, there is little information regarding its neurotoxicity and the mechanism(s) underlying this potentially severe side effect. In this study, using behavioral, neurophysiological, morphological and morphometric methods, we evaluated the effect of intravenous administration of paclitaxel on the rat nervous system. After 2 pilot studies, 40 female Wistar rats were treated with intravenous paclitaxel via a catheter placed in the jugular vein, while 20 animals were used as controls. ⋯ Microtubules seem to be the main target of paclitaxel neurotoxicity, in much the same way as has been described for its antineoplastic activity. Finally, no pathological changes were seen in the neuronal bodies of the spinal cord and dorsal root ganglia. This model may be used for further studies with combination treatments with other antineoplastic or neuroprotective agents.
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Case Reports
The enigma of parkinsonism in chronic borderline mercury intoxication, resolved by challenge with penicillamine.
A 47 year old female dentist suffered from hemiparkinsonism which had started eighteen months earlier and was manifested mainly by resting tremor and cogwheel rigidity. A baseline quantitative urinary mercury excretion was 46 micrograms/day. The patient was treated with chelating agent d-penicillamine for a week. ⋯ After a week chelation therapy was stopped. During a follow-up period of five years, the neurological status remained unchanged after the initial penicillamine-induced improvement. This case may be evidence, therefore, of a rare clinical variant of elemental mercury intoxication associated with parkinsonism, in the absence of most classical neuropsychiatric signs of chronic mercurialism.
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Comparative Study
Quantitation of complex brain function in children: preliminary evaluation using a nonhuman primate behavioral test battery.
The performance of twenty children (3-11 years of age) in a complex operant test battery (OTB) was evaluated. The operant schedules, or tasks, used in the OTB were identical to those originally designed and currently used to assess complex brain function in nonhuman primate laboratory animals (monkeys). The OTB consisted of five operant tasks: 1) Progressive-Ratio [PR]; 2) Conditioned-Position Responding [CPR]; 3) Temporal Response Differentiation [TRD]; 4) Delayed Matching-to-Sample [DMTS] and 5) Incremental Repeated Acquisition [IRA]. ⋯ Of the four 6-yr-olds studied, only those categorized as having either learning disabilities (LD, n = 1) or attention deficit disorders (ADD, n = 2) did not complete the "learning" task. By comparison of human and monkey performance in the OTB, we also hope to validate the use of laboratory animal models in research efforts designed to yield insight into complex human brain function. It is also hoped that assessment of children's performance in the tasks in the OTB will assist in the diagnosis and treatment of certain childhood disorders such as learning disabilities and/or attention deficit disorders.
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Pyridoxine, a water-soluble vitamin, produces a sensory neuronopathy when administered in high doses to dogs. Beagles who received a daily oral dose of 300 mg/kg of pyridoxol hydrochloride developed a swaying gait within 9 days. They eventually became unable to walk, but were not weak. ⋯ Degeneration of sensory nerve fibers in peripheral nerves, dorsal columns of the spinal cord and the descending spinal tract of the trigeminal nerve was apparent. The pathogenesis of these changes is unclear, but may, in part, reflect the selective permeability of blood vessels in the peripheral ganglia. It is apparent that the peripheral neuropathy previously attributed to pyridoxine actually represents a toxic, peripheral sensory neuronopathy.