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Title: Environmental neurotoxicity of chemicals and radiation

Abstract

Epidemiologic and societal concerns continue to stimulate studies in the field of environmental neurotoxicology. Although the role of heavy metals, aluminum, and iron are unclear in the etiology of human neurodegenerative disorders, these toxins have provided fertile ground for in vivo and in vitro experimental studies to elucidate their role in neurotoxic injury. Experimental models of clinical syndromes are discussed with special relevance to developmental neurotoxicology. Cycloleucine, tellurium, and 1,3-dinitrobenzene provide models of subacute combined degeneration, primary peripheral nerve demyelination, and thiamine deficiency-like lesions, respectively. Increasing attention is being given to irradiation neurotoxicity, especially in the developing or young central nervous system. A fuller understanding of the pathogenesis of low-dose irradiation injury allows for a clearer understanding of its neurobiology and also provides a more rational approach to understanding an interventional therapy associated with brain irradiation for childhood neoplasia. 43 refs.

Authors:
 [1]
  1. (Univ. of California, Los Angeles (United States))
Publication Date:
OSTI Identifier:
6282349
Resource Type:
Journal Article
Resource Relation:
Journal Name: Current Opinion in Neurology and Neurosurgery; (United States); Journal Volume: 6:3
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; CENTRAL NERVOUS SYSTEM; INJURIES; LOW DOSE IRRADIATION; PATHOGENESIS; TOXICITY; METALS; NERVOUS SYSTEM DISEASES; ETIOLOGY; RADIOTHERAPY; ALUMINIUM; BRAIN; IN VITRO; IN VIVO; IRON; RADIATION INJURIES; TELLURIUM; THIAMINE; TOXIC MATERIALS; TOXINS; AMINES; ANTIGENS; AZINES; AZOLES; BIOLOGICAL EFFECTS; BIOLOGICAL RADIATION EFFECTS; BODY; DISEASES; ELEMENTS; HAZARDOUS MATERIALS; HETEROCYCLIC COMPOUNDS; HYDROXY COMPOUNDS; IRRADIATION; MATERIALS; MEDICINE; NERVOUS SYSTEM; NUCLEAR MEDICINE; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANIC SULFUR COMPOUNDS; ORGANS; PYRIMIDINES; RADIATION EFFECTS; RADIOLOGY; SEMIMETALS; THERAPY; THIAZOLES; TRANSITION ELEMENTS; VITAMIN B GROUP; VITAMINS; 560300* - Chemicals Metabolism & Toxicology; 560151 - Radiation Effects on Animals- Man

Citation Formats

Verity, M.A. Environmental neurotoxicity of chemicals and radiation. United States: N. p., 1993. Web.
Verity, M.A. Environmental neurotoxicity of chemicals and radiation. United States.
Verity, M.A. Tue . "Environmental neurotoxicity of chemicals and radiation". United States. doi:.
@article{osti_6282349,
title = {Environmental neurotoxicity of chemicals and radiation},
author = {Verity, M.A.},
abstractNote = {Epidemiologic and societal concerns continue to stimulate studies in the field of environmental neurotoxicology. Although the role of heavy metals, aluminum, and iron are unclear in the etiology of human neurodegenerative disorders, these toxins have provided fertile ground for in vivo and in vitro experimental studies to elucidate their role in neurotoxic injury. Experimental models of clinical syndromes are discussed with special relevance to developmental neurotoxicology. Cycloleucine, tellurium, and 1,3-dinitrobenzene provide models of subacute combined degeneration, primary peripheral nerve demyelination, and thiamine deficiency-like lesions, respectively. Increasing attention is being given to irradiation neurotoxicity, especially in the developing or young central nervous system. A fuller understanding of the pathogenesis of low-dose irradiation injury allows for a clearer understanding of its neurobiology and also provides a more rational approach to understanding an interventional therapy associated with brain irradiation for childhood neoplasia. 43 refs.},
doi = {},
journal = {Current Opinion in Neurology and Neurosurgery; (United States)},
number = ,
volume = 6:3,
place = {United States},
year = {Tue Jun 01 00:00:00 EDT 1993},
month = {Tue Jun 01 00:00:00 EDT 1993}
}
  • Ultraviolet radiation appears to be toxic to all forms of unpigmented living cells, including bacteria, protozoa, nematodes, arthropods, fish, birds, and mammals. In addition to the direct absorption of solar energy by cellular constituents, toxicity may occur because of the absorption of sunlight by xenobiotics (or by naturally occurring compounds outside the target cell); these may be converted by light or by subsequent light-promoted reactions that induce cellular damage. This article describes the phototoxicity of photodynamic dyes, light-activated synthetic herbicides, petroleum and its constituents, and naturally occurring chemicals from plants. Detoxification mechanisms are also discussed.
  • Lead, aluminum, mercury, and ketones and related solvents are discussed because they represent common problems in the environment and because they demonstrate selective vulnerability, selectively attacking some portions of the nervous system, sparing others. The absorption, excretion, distribution, and toxicologic effects of these chemicals and the diseases they are associated with are reviewed, as is the accuracy of screening procedures for detection of these chemicals.
  • Few of the more than 65,000 chemicals listed in the Environmental Protection Agency (EPA) inventory have been tested for neurotoxicity. The nervous system may be especially vulnerable to toxicants because many compounds can cross the blood-brain barrier and induce irreversible damage. Additionally, the young, the elderly, and other sensitive populations may be particularly susceptible to neurotoxic injury. The EPA has developed guidelines including neurobehavioral, neuropathological, and neurochemical tests for the identification of possible neurotoxicants. In the present review, tests included in the current EPA guidelines for neurotoxicity testing are described and evaluated. The main benefit of the tests is thatmore » regulators are familiar with them, thus facilitating interpretation. Additionally, validation data on these tests are available for many known neurotoxicants. These factors make it difficult to introduce new methods that may include in vitro and other techniques. The current in vivo tests can be costly and prolonged and can involve the use of many laboratory animals, making them inappropriate for generalized use on existing chemicals. It is suggested that alternative tests be incorporated for screening of large numbers of chemicals and that testing priority be given to chemicals on the basis of structure/activity relationships, lipophilicity, bioaccumulation, and extent of exposure. 67 refs.« less
  • Two patients with brain stem gliomas were treated with hyperfractionated radiation therapy (HFR) (7,020 and 7,560 cGy, respectively). Despite initial clinical improvement during irradiation, both patients demonstrated clinical deterioration approximately 3 weeks after completion of radiotherapy. Cranial magnetic resonance imaging (MRI) revealed a progressive increase in distribution of abnormal brain stem signal consistent with either tumor or edema. {sup 18}FDG positron emission tomography (PET) was obtained in one patient and demonstrated a hypermetabolic lesion at diagnosis and a hypometabolic lesion at the time of clinical deterioration postirradiation. Management with a tapering dose of dexamethasone alone resulted in marked clinical (bothmore » patients) and radiographic (one patient) improvement, allowing reduction or discontinuation of this medication. These results suggest that patients with brain stem tumors demonstrating clinical and radiographic evidence of progressive tumor shortly after completion of HFR should be initially managed conservatively with dexamethasone, since these findings may be manifestations of reversible radiation-related neurotoxicity.« less
  • Purpose: To determine the effect of dose and fractionation schedule of prophylactic cranial irradiation (PCI) on the incidence of chronic neurotoxicity (CNt) and changes in quality of life for selected patients with limited-disease small-cell lung cancer (LD SCLC). Methods and Materials: Patients with LD SCLC who achieved a complete response after chemotherapy and thoracic irradiation were eligible for randomization to undergo PCI to a total dose of 25 Gy in 10 daily fractions (Arm 1) vs. the experimental cohort of 36 Gy. Those receiving 36 Gy underwent a secondary randomization between daily 18 fractions (Arm 2) and twice-daily 24 fractionsmore » (Arm 3). Enrolled patients participated in baseline and follow-up neuropsychological test batteries along with quality-of-life assessments. Results: A total of 265 patients were accrued, with 131 in Arm 1, 67 in Arm 2, and 66 in Arm 3 being eligible. There are 112 patients (42.2%) alive with 25.3 months of median follow-up. There were no significant baseline differences among groups regarding quality-of-life measures and one of the neuropsychological tests, namely the Hopkins Verbal Learning Test. However, at 12 months after PCI there was a significant increase in the occurrence of CNt in the 36-Gy cohort (p = 0.02). Logistic regression analysis revealed increasing age to be the most significant predictor of CNt (p = 0.005). Conclusions: Because of the increased risk of developing CNt in study patients with 36 Gy, a total PCI dose of 25 Gy remains the standard of care for patients with LD SCLC attaining a complete response to initial chemoradiation.« less