1
|
Mattsson JL, Albee RR, Eisenbrandt DL. Neurological Approach to Neurotoxicological Evaluation in Laboratory Animals. ACTA ACUST UNITED AC 2016. [DOI: 10.3109/10915818909019552] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The neurotoxicological potential of a compound is best evaluated with information from a wide variety of tests. Our philosophy is that tests should be applicable across species and emphasize complementarity to neuropathology. Electrophysiologic tests comparable to those in human clinical neurology fulfill these requirements. Animals are not anesthetized but are physically restrained during the tests. Routine tests include flash evoked potentials, auditory brainstem responses to clicks and tone pips, somatosensory evoked responses, and caudal nerve action potentials. Tests can be added (e.g., H-reflex, EMG, or EEG) or deleted as circumstances warrant. A careful clinical examination of all animals (functional observational battery) and, for rats, a test of grip strength are utilized as well. Neuropathology typically includes perfusion fixation and special stains of histological sections from the central and peripheral nervous systems. Approximately half the animals are retained as a recovery group for subsequent tests if warranted by the results of the neurotoxicological evaluation. The neurological approach, in conjunction with standard toxicological studies, provides data with the necessary breadth and depth for a comprehensive evaluation of neurotoxicity.
Collapse
Affiliation(s)
- Joel L. Mattsson
- The Dow Chemical Company Health and Environmental Sciences, 1803 Building Midland, MI 48674
| | - R. R. Albee
- The Dow Chemical Company Health and Environmental Sciences, 1803 Building Midland, MI 48674
| | - D. L. Eisenbrandt
- The Dow Chemical Company Health and Environmental Sciences, 1803 Building Midland, MI 48674
| |
Collapse
|
2
|
Gupta VK, Pal R, Siddiqi NJ, Sharma B. Acetylcholinesterase from Human Erythrocytes as a Surrogate Biomarker of Lead Induced Neurotoxicity. Enzyme Res 2015; 2015:370705. [PMID: 26600946 PMCID: PMC4633554 DOI: 10.1155/2015/370705] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 09/30/2015] [Indexed: 01/08/2023] Open
Abstract
Lead induced neurotoxicity in the people engaged in different occupations has received wide attention but very little studies have been carried out to monitor occupational neurotoxicity directly due to lead exposure using biochemical methods. In the present paper an endeavour has been made in order to assess the lead mediated neurotoxicity by in vitro assay of the activity of acetylcholinesterase (AChE) from human erythrocytes in presence of different concentrations of lead. The results suggested that the activity of this enzyme was localized in membrane bound fraction and it was found to be highly stable up to 30 days when stored at -20°C in phosphate buffer (50 mM, pH 7.4) containing 0.2% Triton X-100. The erythrocyte's AChE exhibited K m for acetylcholinesterase to be 0.1 mM. Lead caused sharp inhibition of the enzyme and its IC50 value was computed to be 1.34 mM. The inhibition of the enzyme by lead was found to be of uncompetitive type (K i value, 3.6 mM) which negatively influenced both the V max and the enzyme-substrate binding affinity. Taken together, these results indicate that AChE from human erythrocytes could be exploited as a surrogate biomarker of lead induced neurotoxicity particularly in the people occupationally exposed to lead.
Collapse
Affiliation(s)
- Vivek Kumar Gupta
- Department of Biochemistry, Faculty of Science, University of Allahabad, Allahabad 211002, India
| | - Rajnish Pal
- Department of Biochemistry, Faculty of Science, University of Allahabad, Allahabad 211002, India
| | - Nikhat Jamal Siddiqi
- Department of Biochemistry, College of Science, King Saud University, P.O. Box 22452, Riyadh 11495, Saudi Arabia
| | - Bechan Sharma
- Department of Biochemistry, Faculty of Science, University of Allahabad, Allahabad 211002, India
| |
Collapse
|
3
|
Abstract
Worldwide, several hundred million tons of organic solvents are used annually in household, industry, and other occupational settings. Millions of workers are regularly exposed to organic solvents considered neurotoxic. Acute neurotoxicity due to high exposure of solvent is usually evident, but the nature of long-term effects, such as chronic solvent encephalopathy (CSE), has raised uncertainty even among experts. Earlier studies were criticized for their methodology, mainly epidemiologic studies or investigations of exposed groups with many possible confounders and inadequate exposure assessment. However, an increasing number of studies have been performed since, also on workers with defined CSE based on differential diagnostics. During the last decade, evidence has emerged to enable identification of CSE, a necessity for the early recognition and prevention of progression of dysfunction and disability. Selected chemicals are presented here due to their widespread use, neurotoxic potential, and ability to cause solvent encephalopathy. Constant introduction of new chemicals may introduce new hazardous chemicals or known chemicals may reveal new health effects. It is important to keep an open mind for new findings of solvent-related neurobehavioral effects.
Collapse
|
4
|
Neurological and neurophysiological examinations of workers exposed to arsenic levels exceeding hygiene standards. Int J Occup Med Environ Health 2014; 27:1013-25. [DOI: 10.2478/s13382-014-0316-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 06/11/2014] [Indexed: 11/20/2022] Open
|
5
|
Abstract
This article schematically reviews the clinical features, diagnostic approaches to, and toxicological implications of toxic encephalopathy. The review will focus on the most significant occupational causes of toxic encephalopathy. Chronic toxic encephalopathy, cerebellar syndrome, parkinsonism, and vascular encephalopathy are commonly encountered clinical syndromes of toxic encephalopathy. Few neurotoxins cause patients to present with pathognomonic neurological syndromes. The symptoms and signs of toxic encephalopathy may be mimicked by many psychiatric, metabolic, inflammatory, neoplastic, and degenerative diseases of the nervous system. Thus, the importance of good history-taking that considers exposure and a comprehensive neurological examination cannot be overemphasized in the diagnosis of toxic encephalopathy. Neuropsychological testing and neuroimaging typically play ancillary roles. The recognition of toxic encephalopathy is important because the correct diagnosis of occupational disease can prevent others (e.g., workers at the same worksite) from further harm by reducing their exposure to the toxin, and also often provides some indication of prognosis. Physicians must therefore be aware of the typical signs and symptoms of toxic encephalopathy, and close collaborations between neurologists and occupational physicians are needed to determine whether neurological disorders are related to occupational neurotoxin exposure.
Collapse
|
6
|
Early effects of long-term neurotoxic lead exposure in copper works employees. J Toxicol 2011; 2011:832519. [PMID: 21776266 PMCID: PMC3135313 DOI: 10.1155/2011/832519] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 03/18/2011] [Indexed: 11/29/2022] Open
Abstract
The situation of exposure in a copper works facility in Germany enabled early lead-induced neurotoxic effects to be investigated in the workers. The aim of the investigation was to study the long-term effects of small doses of lead on psychometric/psychophysiological performance of workers. The study involved 70 male lead exposed workers and 27 male controls with no neurotoxic exposure. All test persons were subjected to the method of investigation involving performance data, physiological strain data, and the subjective state.
It was found that of the psychometric performance parameters, only the mainly motor performance parameters had a potential for being neurotoxic early indicators. Preferably centrally influenced performance parameters were found to be less suitable early indicators. The lead-exposed subjects exhibited a slowed poststrain resetting behaviour of the vegetative nervous system, which correlated with the individual blood lead level. This was attributed to vagus depression, which had already started in the prevailing situation of exposure and was reflected by diminished cardiac phase duration variability. Our results indicate that it is necessary to more critically choose the lead level standards in the air on the working area. Heart rate variability may be affected even at small lead concentration.
Collapse
|
7
|
Effects of occupational exposure to arsenic on the nervous system: Clinical and neurophysiological studies. Int J Occup Med Environ Health 2010; 23:347-55. [DOI: 10.2478/v10001-010-0034-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
8
|
Ademuyiwa O, Ugbaja RN, Rotimi SO, Abam E, Okediran BS, Dosumu OA, Onunkwor BO. Erythrocyte acetylcholinesterase activity as a surrogate indicator of lead-induced neurotoxicity in occupational lead exposure in Abeokuta, Nigeria. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2007; 24:183-188. [PMID: 21783808 DOI: 10.1016/j.etap.2007.05.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 04/29/2007] [Accepted: 05/01/2007] [Indexed: 05/31/2023]
Abstract
Dose-effect and dose-response relationships in occupational neurotoxicology are rarely studied by means of biochemical methods. In order to investigate the potential neurotoxic effects of lead during occupational exposure to this metal, the activity of erythrocyte acetylcholinesterase (AcChE), as well as blood pressure and pulse, were determined in various artisans in Abeokuta, Nigeria, who have been shown to be occupationally exposed to lead, and these were related to blood lead levels. AcChE activity in the artisans was inhibited to varying extents. While AcChE activity was inhibited to the tune of 39% in the male petrol station attendants, the inhibition amounted to 32% in female petrol station attendants. In other artisans, AcChE inhibition ranged from 31% in the welders to 38% in painters. The lowest inhibition of 15% was obtained in the panel beaters. Correlations, as calculated by Pearson's method, revealed a significant (p<0.001) inverse linear relationship between AcChE activity and blood lead levels (r=-0.40; y=-120.38x+13935.59; p<0.001). Blood pressure and pulse were not significantly different between control and lead-exposed subjects. Our findings suggest that erythrocyte AcChE activity could be used as a biomarker of lead-induced neurotoxicity in occupationally exposed subjects.
Collapse
Affiliation(s)
- O Ademuyiwa
- Department of Biochemistry, University of Agriculture, Abeokuta, Nigeria; Toxicokinetics Section, Industrial Toxicology Research Centre, Mahatma Gandhi Marg, Lucknow 226001, India
| | | | | | | | | | | | | |
Collapse
|
9
|
Abstract
Neurologic erectile dysfunction presents a diagnostic and treatment challenge to the internist and urologist. Multiple chronic disease modalities and traumatic etiologies exist. Education regarding these conditions and a detailed and thorough history and office work-up are the best resources for the clinician. Treatment can follow the model of proceeding from the least to most invasive procedure (process of care), taking into account patient and partner satisfaction. Because the psychology of grief and loss may enter into treatment of some neurologic conditions (e.g., erectile dysfunction after radical retropubic prostatectomy, spinal cord injury, or chronic diseases), a whole-patient approach encompassing psychotherapy is warranted.
Collapse
Affiliation(s)
- A Nehra
- Department of Urology, Mayo Medical School, and Mayo Clinic and Foundation, Rochester, Minnesota, USA.
| | | |
Collapse
|
10
|
Fay M, Eisenmann C, Diwan S, de Rosa C. ATSDR evaluation of health effects of chemicals. V. Xylenes: health effects, toxicokinetics, human exposure, and environmental fate. Toxicol Ind Health 1998; 14:571-781. [PMID: 9782568 DOI: 10.1177/074823379801400501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Xylenes, or dimethylbenzenes, are among the highest-volume chemicals in production. Common uses are for gasoline blending, as a solvent or component in a wide variety of products from paints to printing ink, and in the production of phthalates and polyester. They are often encountered as a mixture of the three dimethyl isomers, together with ethylbenzene. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that are of greatest concern for public health purposes. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of the bulk of this profile (ATSDR, 1995) into the mainstream scientific literature. An extensive listing of known human and animal health effects, organized by route, duration, and end point, is presented. Toxicological information on toxicokinetics, biomarkers, interactions, sensitive subpopulations, reducing toxicity after exposure, and relevance to public health is also included. Environmental information encompasses physical properties, production and use, environmental fate, levels seen in the environment, analytical methods, and a listing of regulations. ATSDR, as mandated by CERCLA (or Superfund), prepares these profiles to inform and assist the public.
Collapse
Affiliation(s)
- M Fay
- Agency for Toxic Substances and Disease Registry, Public Health Service, U.S. Department of Health and Human Services, Atlanta, Georgia 30333, USA.
| | | | | | | |
Collapse
|
11
|
Stokes L, Letz R, Gerr F, Kolczak M, McNeill FE, Chettle DR, Kaye WE. Neurotoxicity in young adults 20 years after childhood exposure to lead: the Bunker Hill experience. Occup Environ Med 1998; 55:507-16. [PMID: 9849536 PMCID: PMC1757620 DOI: 10.1136/oem.55.8.507] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES An epidemiological study of young adults was conducted to determine whether environmental exposure to lead during childhood was associated with current adverse neurobehavioural effects. METHODS The exposed group consisted of 281 young adults who had been exposed environmentally to lead as children and the unexposed referent group consisted of 287 age and sex frequency matched subjects. Information on demographics, past and current health, and past exposures to neurotoxicants, and responses to the Swedish Q16 questionnaire were collected by interview. Standard neurobehavioural and neurophysiological tests were administered by computer or trained technicians. K x ray fluorescence was used to estimate tibial bone lead concentrations among the exposed and unexposed groups. Associations were examined between the exposed group and referents and tibial bone lead concentration and the neurobehavioural and neurophysiological outcomes of interest. RESULTS Among the measures of peripheral nerve function, after controlling for confounders, sural sensory nerve evoked response amplitude, peroneal motor nerve compound motor action potential amplitude, vibrotactile thresholds of fingers and toes, and standing steadiness were significantly associated with exposure group. Among the neurobehavioural tests, hand-eye coordination, simple reaction time latency, trails B latency, symbol digit latency, serial digit, and learning error score were also significantly associated with exposure group after controlling for confounders. Exposed subjects had significantly more neuropsychiatric symptoms than the referents. Associations between tibial bone lead concentration and scores for vocabulary, vibrotactile thresholds of the fingers, and vibrotactile thresholds of the toes approached significance. CONCLUSIONS Significant adverse central and peripheral neurological effects were found in a group of young adults 20 years after childhood environmental exposure to lead when compared with non-exposed controls. The absence of a significant association between neurological outcomes and tibial bone lead concentration, and the presence of significant associations between neurological outcomes and exposure group may be due to either the magnitude of measurement uncertainty in K x ray films relative to the actual tibial bone lead concentration in these young non-occupationally exposed subjects, or uncontrolled confounding of the exposure group.
Collapse
Affiliation(s)
- L Stokes
- Epidemiology and Surveillance Branch, Centers For Disease Control and Prevention, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia 30333, USA
| | | | | | | | | | | | | |
Collapse
|
12
|
Luo ZD, Berman HA. The influence of Pb2+ on expression of acetylcholinesterase and the acetylcholine receptor. Toxicol Appl Pharmacol 1997; 145:237-45. [PMID: 9266795 DOI: 10.1006/taap.1997.8172] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This paper examines the influence of inorganic lead (Pb2+) on the presence of acetylcholinesterase (AchE) molecular forms and the acetylcholine receptor (AchR) in two types of excitable tissue, primary cultures of skeletal muscle and neural retina from embryonic chick. Treatment of skeletal muscle with Pb2+ is observed to cause reductions in the 5/7S and 19S but not the 11.4S molecular forms of AchE. The reductions are dose-dependent, requiring submicromolar concentrations, slow in onset, requiring incubation times greater than 24 hr, and tissue specific, being pronounced in skeletal muscle but absent from neural retina. Significantly, the reductions in AchE occur without corresponding reductions in amounts of AchR and without reduction in activity of protein kinase C (PKC). These studies illustrate a tissue-specific action of inorganic lead that is not mediated through PKC.
Collapse
Affiliation(s)
- Z D Luo
- Department of Biochemical Pharmacology, State University of New York at Buffalo, 14260, USA
| | | |
Collapse
|
13
|
Jamal GA, Hansen S, Apartopoulos F, Peden A. The "Gulf War syndrome". Is there evidence of dysfunction in the nervous system? J Neurol Neurosurg Psychiatry 1996; 60:449-51. [PMID: 8774417 PMCID: PMC1073905 DOI: 10.1136/jnnp.60.4.449] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In a pilot study, 14 Gulf War veterans were randomly selected from a large list of those with unexplained illness, to compare the functional integrity of the peripheral and central nervous system with a group of 13 healthy civilian control subjects using predetermined outcome measures. The controls were matched closely for age, sex, handedness, and physical activity. Outcome measures included scoring of symptoms and clinical neurological signs, quantitative sensory testing of heat, cold and vibration sensibilities, motor and sensory nerve conduction studies on upper and lower limbs, needle EMG of distal and proximal muscles and multimodality evoked potential (visual, brainstem, and somatosensory) studies. Three measurements, all related to peripheral nerve function (cold threshold (P = 0.0002), sural nerve latency (P = 0.034), and median nerve sensory action potential (P = 0.030) were abnormal in the veterans compared with the controls. There may be a dysfunction in the veterans but more studies are required to investigate the findings further and to characterise the dysfunction if confirmed.
Collapse
Affiliation(s)
- G A Jamal
- Department of Neurology, Southern General Hospital NHS Trust, Glasgow, UK
| | | | | | | |
Collapse
|
14
|
Laine A, Seppäläinen AM, Savolainen K, Riihimäki V. Acute effects of 1,1,1-trichloroethane inhalation on the human central nervous system. Int Arch Occup Environ Health 1996; 69:53-61. [PMID: 9017435 DOI: 10.1007/bf02630739] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The object of this study was to examine the immediate nervous effects of variable 1,1,1-trichloroethane (TCE) exposure combined with physical exercise. The effects on the quantitative electroencephalography (EEG), visual evoked potentials (VEP) and body sway were analyzed. Nine male volunteers were exposed to either a stable or a fluctuating exposure pattern with the same time-weighted average concentration of 200 ppm (8.1 mumol/l). In both cases, the subjects engaged in physical exercise during the exposures. Exercise alone induced an increase in the dominant alpha frequency in the EEG and, after an initial drop, an increase in the alpha percentage with a concomitant decrease in theta, whereas delta and beta bands remained unaffected. By contrast, exposure to TCI and exercise did not affect the alpha, theta or delta activities but induced changes in beta during the morning recordings at peak exposure to TCE. The body sway tended to decrease slightly during the fluctuating TCE exposure, and the later peaks in VEPs showed slight prolongations. Overall, no deleterious effects of exposure were noted.
Collapse
Affiliation(s)
- A Laine
- Institute of Occupational Health, Helsinki, Finland
| | | | | | | |
Collapse
|
15
|
Yeh JH, Chang YC, Wang JD. Combined electroneurographic and electromyographic studies in lead workers. Occup Environ Med 1995; 52:415-9. [PMID: 7627320 PMCID: PMC1128247 DOI: 10.1136/oem.52.6.415] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVES To evaluate the effects of chronic exposure to lead on the peripheral nervous system in lead workers. METHODS Nerve conduction velocity and electromyographic studies were performed on 31 lead workers of a battery recycling factory and 31 sex and age matched controls. 25 cases with mild distal extensor weakness of the upper limbs were classified as the lead neuropathy subgroup and the rest of the lead workers as the lead exposure subgroup. Blood lead concentrations and haematological and biochemical data were recorded. An index of cumulative exposure to lead was calculated by the summation of multiplying the average blood concentration of lead with the duration of exposure at various jobs. RESULTS Compared with the control group, the distal motor latency of the median nerve was significantly prolonged in the lead neuropathy subgroup, but not in the exposure subgroup. Only six of 31 workers had nerve conduction abnormalities, whereas electromyographic evidence of denervation was found in 93.5% of the lead neuropathy subgroup and 83.5% in the lead exposure subgroup. The electromyographic abnormalities found were neurogenic polyphasic waves in all 29 workers with abnormal electromyographic findings (grade in seven cases and grade ++ in the rest). Spontaneous activity was only recorded in seven workers, with grade + in four and grade ++ in three. There was a positive linear correlation between the index of cumulative exposure to lead and the distal motor latencies of the tibial nerve as well as a negative correlation with conduction velocities of the sural nerve after multivariate analysis and control of potential confounding by age and sex. No correlation could be found between the electrophysiological values and a simple duration of exposure or concentration of blood lead. A non-parametric analysis showed that there was a trend of higher index of cumulative exposure to lead with more severe electromyographic changes. Electromyographic abnormality also occurred in workers with blood lead concentrations between 17.4 and 58 micrograms/dl. CONCLUSION Electromyographic study in the distal extensors of the upper limbs may be used as a tool for biological monitoring of effect in lead workers.
Collapse
Affiliation(s)
- J H Yeh
- Department of Neurology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan, Republic of China
| | | | | |
Collapse
|
16
|
Costa LG, Manzo L. Biochemical markers of neurotoxicity: research strategies and epidemiological applications. Toxicol Lett 1995; 77:137-44. [PMID: 7618127 DOI: 10.1016/0378-4274(95)03283-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A great deal of attention has been given in the past few years to the development and validation of biomarkers for non-cancer endpoints, to be used in human epidemiological studies. In this research, as they apply to the field of neurotoxicology, will be discussed. As biomarkers are often divided into indicators of exposure, effect and susceptibility, one example for each of these classes is presented. Measurements of hemoglobin adducts were developed as a way to monitor exposure to acrylamide (a peripheral neurotoxicant) in animals as well as humans, and have been successfully applied in a field study in occupationally exposed workers. Activity of monoamine oxidase B (MAO-B) in platelets was found to be inversely correlated with the levels of exposure to styrene, suggesting that this biochemical measurement may be a useful effect-related biomarker, though additional studies are needed to understand the mechanistic implications of these findings. Serum paraoxonase activity has been shown in animals to modulate the toxicity of organophosphorus insecticides. Studies in humans have lead to the identification of a genetic polymorphism for this enzyme and to define its underlying molecular basis. Epidemiological studies are needed to determine the relevance of this polymorphism in determining susceptibility to organophosphate toxicity.
Collapse
Affiliation(s)
- L G Costa
- Department of Environmental Health, University of Washington, Seattle 98195, USA
| | | |
Collapse
|
17
|
Vrca A, Bozicević D, Karacić V, Fuchs R, Prpić-Majić D, Malinar M. Visual evoked potentials in individuals exposed to long-term low concentrations of toluene. Arch Toxicol 1995; 69:337-40. [PMID: 7654139 DOI: 10.1007/s002040050180] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
An investigation of visual evoked potentials was carried out in two groups of subjects; 49 workers employed in a printing-prss where toluene has been used exclusively as an organic solvent for the last 30 years, and 59 workers not occupationally exposed to any known neurotoxic substances. The average length of work service in the printing-press was 21.4 years. The level of exposure was assessed by determination of the concentration of toluene in peripheral blood, the concentration of hippuric acid and ortho-cresol in urine in subgroups of subjects chosen at random from both groups. N75, P100 and N145 waves of the pattern reversal visual evoked potentials were analyzed. In the group of exposed subjects, significantly greater amplitudes were found in all waves, with significantly longer latency of the P100 wave.
Collapse
Affiliation(s)
- A Vrca
- Institute for Medical Research and Occupational Health, Zagreb, Croatia
| | | | | | | | | | | |
Collapse
|
18
|
Electrophysiological Analysis of Complex Brain Systems. Neurotoxicology 1995. [DOI: 10.1016/b978-012168055-8/50013-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
19
|
Eisenbrandt DL, Allen SL, Berry PH, Classen W, Bury D, Mellert W, Millischer RJ, Schuh W, Bontinck WJ. Evaluation of the neurotoxic potential of chemicals in animals. Food Chem Toxicol 1994; 32:655-69. [PMID: 8045479 DOI: 10.1016/0278-6915(94)90010-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This review provides a scientific view on how to evaluate effectively the neurotoxic potential of chemicals in order to provide adequate safeguards for human health. Detection of compounds that may cause direct, persistent, adverse effects on the nervous system should be given the most critical attention. Evaluation of the neurotoxic potential of a chemical should include descriptions of functional and morphological effects as well as the determination of the dose response, no-observed-effect level, time course and reversibility of effects. Evaluation of the nervous system in the context of standard toxicity studies that use a variety of species and study durations are appropriate screening tests (Tier 1) for the detection of potential neurotoxicity. Studies specifically designed to assess neurotoxicity (Tier 2) should be performed with chemicals for which there is an indication of neurotoxic potential and where the available data are inadequate for risk assessment. Tier 2 studies should evaluate the function and structure of the nervous system by comprehensive clinical examinations and neuropathological assessment. These studies may be conducted in conjunction with standard toxicity studies so that any potential neurotoxicity can be interpreted in the context of other systemic toxicity. More specific neurotoxicity tests (Tier 3) may be necessary for advanced characterization of discovered neurotoxicants.
Collapse
Affiliation(s)
- D L Eisenbrandt
- European Centre for Ecotoxicology and Toxicology of Chemicals, Brussels, Belgium
| | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Abstract
Lead may be an industrial and an environmental hazard which becomes of greater importance every year. Classical symptoms of plumbism are rare, whenever minor clinical signs increase in frequency. Erythrocyte zinc protoporphyrin and delta-aminolaevulinic acid dehydratase are reliable indicators of the importance of the lead poisoning in individuals. The concentration of lead in blood is also a suitable biological indicator as is EDTA mobilization test. The treatment is based on the use of chelating agents such as calcium EDTA or DMSA, but the only solution is reduction or removal of the sources of lead exposure.
Collapse
Affiliation(s)
- M Klein
- Service de médecine J. CHRU de Nancy, hôpitaux de Brabois, Vandoeuvre-lès-Nancy, France
| | | | | | | |
Collapse
|
21
|
Ruijten MW, Sallé HJ, Kingma R. Comparison of two techniques to measure the motor nerve conduction velocity distribution. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1993; 89:375-81. [PMID: 7507423 DOI: 10.1016/0168-5597(93)90110-b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Hopf's technique to measure the distribution of motor nerve conduction velocities (DMCV) has been compared with the technique introduced by Ingram et al. in the peroneal nerve of 28 healthy subjects 41.2 (S.D. 8.4) years. Twenty subjects were examined twice. Both techniques yielded an equal DMCV and equally reproducible results. Group mean velocities for the slowest examined (MNCV95) motor nerve fibres were 39.0 m/sec (S.D. 3.3) for Ingram's technique and 38.6 (S.D. 3.6) for Hopf's technique. The conventional MNCV was always slower than the velocity of the 5% fastest fibres estimated from the DMCV. Ingram's technique may have a number of merits which may have been obscured by measurement in the peroneal nerve, which may be of advantage in shorter nerve segments or faster nerve fibres. On the basis of our data in the peroneal nerve of healthy subjects no preference can be given for either of the techniques.
Collapse
Affiliation(s)
- M W Ruijten
- Coronel Laboratory, University of Amsterdam, Academic Medical Center, The Netherlands
| | | | | |
Collapse
|
22
|
Mattsson JL, Albee RR, Lomax LG, Beekman MJ, Spencer PJ. Neurotoxicologic examination of rats exposed to 1,1,1-trichloroethane vapor for 13 weeks. Neurotoxicol Teratol 1993; 15:313-26. [PMID: 8277925 DOI: 10.1016/0892-0362(93)90033-k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Large evoked potential and EEG changes occurred in a pilot study in Fisher 344 rats during exposure to 2000 ppm of 1,1,1-trichloroethane (1,1,1-T; a cleaning solvent with anesthetic properties). In the main study, rats were evaluated for persistent nervous system effects the week following exposure to 0, 200, 630, or 2000 ppm 1,1,1-T for 6 h/day, 5 days/week, for 13 weeks. Rats were clinically examined regularly and were given a functional observational battery monthly (FOB, including forelimb and hindlimb grip performance testing). After 13 weeks of exposure, the rats were evaluated by FOB and by visual, auditory, somatosensory, and caudal nerve-evoked potentials. After functional testing, a subgroup of rats had histopathologic examination of brain, spinal cord, peripheral nerves, and limb muscles. There were no post-exposure treatment-related findings in any parameter (FOB observations plus 39 dependent variables) except for a slightly smaller forelimb grip performance in the 2000-ppm exposure group. There was no recognized toxicologic significance for the difference in forelimb grip performance; a lack of findings in any other clinical, evoked potential or morphologic parameter did not support a diagnosis of neurotoxicity.
Collapse
|
23
|
|
24
|
Mattsson JL, Albee RR, Eisenbrandt DL. Neurotoxicologic evaluation of rats after 13 weeks of inhalation exposure to dichloromethane or carbon monoxide. Pharmacol Biochem Behav 1990; 36:671-81. [PMID: 2377667 DOI: 10.1016/0091-3057(90)90273-k] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Male and female Fischer 344 rats were exposed to dichloromethane (methylene chloride, DCM) or carbon monoxide (CO) for 6 hr/day, 5 days/week, for 13 weeks. Since oxidative metabolism of DCM to CO and CO2 is a saturable process, DCM exposure concentrations were selected clearly below saturation (50 ppm), just below saturation (200 ppm), and well above saturation (2000 ppm). At saturation of metabolism, metabolic CO causes about 10% carboxyhemoglobinemia (COHb). Therefore, as a control for CO effects, a separate group of rats was exposed to 135 ppm CO to induce approximately 10% COHb. Postexposure functional tests included an observational battery, hindlimb grip strength, and a battery of evoked potentials (flash, auditory brainstem, somatosensory, caudal nerve). After functional tests were completed, rats from all groups were perfused with fixative and a comprehensive set of nervous tissues from the high DCM exposure group and from controls were examined by light microscopy. Although some miscellaneous functional and morphologic variations were recorded, none were related to treatment. Thus, subchronic exposures as high as 2000 ppm DCM or 135 ppm CO had no deleterious effects on any of the measures of this study.
Collapse
Affiliation(s)
- J L Mattsson
- Dow Chemical Company, Health and Environmental Sciences, Midland, MI 48674
| | | | | |
Collapse
|
25
|
Mattsson JL, Eisenbrandt DL, Albee RR. Screening for neurotoxicity: complementarity of functional and morphologic techniques. Toxicol Pathol 1990; 18:115-27. [PMID: 2195632 DOI: 10.1177/019262339001800117] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Our philosophy is that screening tests should be applicable across species and emphasize complementarity to neuropathology. Within this context, electrophysiological tests comparable to those in human clinical neurology are powerful screening tools. For example, while histopathologic evaluation of the cochlea for ototoxicity is difficult, evoked potential audiometry is fast and easy. In this instance, one might routinely screen for deficits in auditory function, and reserve morphologic techniques for a characterization role rather than one of discovery. Lesions of neurons, axons and myelin are, however, readily assessed by light microscopy. A suitable combination of functional and morphologic screening tests, therefore, enhances the ability to discover neurotoxicity, and these data often are ideal for generation of refined hypotheses for subsequent characterization studies.
Collapse
Affiliation(s)
- J L Mattsson
- Dow Chemical Company, Health and Environmental Sciences, Midland, Michigan 48674
| | | | | |
Collapse
|
26
|
Beritić T. Spinal origin of human lead neuropathy: this paper marks the 150th anniversary of Paralysie de Plomb ou Saturnine by L. Tanquerel des Planches. Am J Ind Med 1989; 15:643-56. [PMID: 2665479 DOI: 10.1002/ajim.4700150604] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
One hundred fifty years ago a young but distinguished French scientist, L. Tanquerel des Planches, published a most comprehensive work dealing with almost every known clinical, epidemiological, and occupational aspect of lead poisoning, Traité des Maladies de Plomb ou Saturnines exposing in its second volume, Paralysie de Plomb ou Saturnine his invaluable experience on lead palsy. Among his ideas, based on a rather unique accumulation of human cases of lead palsy, the theory of the neurotoxic action of lead on the spinal cord is of outstanding importance. This site and the mode of action of lead have long been unsettled, although both the nineteenth century classics in neurology and the classics in industrial medicine of the first half of the twentieth century have contributed to solving the pathophysiology of lead palsy. The contributions from these reports, which concur with Tanquerel's assumptions, are presented and discussed. It must be emphasized, however, that only with the advent of electrophysiology has it become possible definitely to recognize the spinal cord involvement as the cause of lead neuropathy. The hypothesis of the axonal degeneration of the "dying back" variant, starting in the biochemical lesion of perikaria of the anterior horn cells in the spinal cord, is in full agreement with both the electromyographic signs of denervation and the electroneurographic normal range of conduction velocity. This presumptive conclusion confirming the spinal origin of human lead neuropathy is very much in line with the concepts of Tanquerel des Planches.
Collapse
Affiliation(s)
- T Beritić
- Division of Medicine, Yugoslav Academy of Sciences and Arts, Zagreb
| |
Collapse
|