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Biomedical subjects

A M Williamson

Publications and source records attributed to A M Williamson.

33 records · Page 2Linked to original sources
PubMed1989

The influence of diving variables on perceptual and cognitive functions in professional shallow-water (abalone) divers.

Shallow-water diving is regarded as a hazardous occupation due to such dangers as decompression sickness and carbon monoxide poisoning. Recent studies have demonstrated impairments in the neurological and neurobehavioral functioning of professional shallow-water divers, yet the reasons for these deficits are not clear. In this study 80 professional abalone divers were studied using a range of neurobehavioral tests and questioned closely on their diving experience. Multiple linear regression analysis was then performed to determine the extent to which characteristics of the diver's occupation influenced neurobehavioral impairment. The results demonstrated that divers who were at greatest risk of decompression sickness due to their diving technique showed the clearest functional impairments. In particular problems of visual function, psychomotor abilities, and short-term memory were most evident. It appears that professional shallow-water diving is not necessarily a hazardous occupation provided that safe diving practices are observed. However, divers who fail to observe these practices and put themselves at risk of decompression sickness are likely to have impairments in neurobehavioral function which affect their everyday life, and more importantly their responses in emergency situations.

Adult↗
PubMed1987

Neurobehavioural effects of professional abalone diving.

In a study of 33 commercial abalone divers from the Port Lincoln area of South Australia nervous system function was examined using a battery of neurobehavioural tests. Their performance was compared with that of non-diver controls matched for age, sex, education level, job type, language abilities, and cigarette and alcohol consumption. Abalone divers showed significantly poorer vision, learning, and short term memory performance and increased tremor relative to their controls. The reaction time of abalone divers, however, was as fast as or significantly faster than that of controls but their error rates were much higher, indicating that abalone divers were sacrificing speed for accuracy. Despite their apparent risk taking approach to these tests, the performance of abalone divers suggests some impairment of nervous system function.

Adult↗
PubMed1986

Neurobehavioural effects of occupational exposure to lead.

A set of neurobehavioural tests selected on the basis of information processing theory was used to study the effect of low level occupational lead exposure on 59 lead workers compared with a matched control group of the same number. Only one of the lead exposed group had a blood lead concentration above the current threshold limit value of 3.81 mumol/l at the time of testing (mean 2.36 mumol/l, range 1.19-3.92 mumol/l) and none had been detected above that level in the previous three years. Nevertheless, most neurobehavioural functions tested showed some impairment in the lead workers. Visual sensory function was affected and, perhaps as a consequence, sustained attention and psychomotor tasks were performed more slowly by the lead exposed group. Cognitive functions were also impaired, with sensory store memory, short term memory, and learning abilities all showing deficits in lead workers. Such cognitive deficits may also be partly due to initial degradation of the visual input. Long term memory performance compared equally with control levels possibly because of development of a compensatory strategy such as rehearsal by the lead exposed subjects. Multiple linear regression analysis relating to lead workers test performance and their lead exposure showed that performance on the sensory store memory test alone was significantly related to exposure. This was probably due to the homogeneity of the lead exposed group with regard to blood lead concentrations and the use of blood lead as a measure of chronic lead exposure.

Adolescent↗
PubMed1985

Effects of cholinesterase inhibitors on evoked responses in field CA1 of the rat hippocampus.

The anticholinesterases, diisopropylfluorophosphate (DFP) and eserine, were bath applied to submerged rat hippocampal slices. Eserine at concentrations from 100 nM to 100 microM did not produce a significant change in the amplitude of either the orthodromic or antidromic population spike (PS). DFP also produced no significant change in either response at concentrations from 10 nM to 10 microM. In 100 microM DFP, there was a reversible depression in the orthodromic PS but no change in the antidromic response. However, both anticholinesterases elicited a second PS at most concentrations tested. Whereas the second PS elicited by eserine treatment was reversible, the second PS produced by DFP was not reversible. Neither compound elicited spontaneous activity. Application of acetylcholine, carbachol or muscarine produced second PSs which were blocked by the muscarinic antagonists atropine and quinuclidinyl benzylate. Whereas atropine reduced the amplitude of the second PS elicited by 1 microM DFP and 10 microM eserine, neither atropine nor quinuclidinyl benzylate affected the amplitude of the second PS in 10 microM DFP or 100 microM eserine. The nicotinic antagonists, gallamine, hexamethonium and dihydro-beta-erythroidine (10 microM), were ineffective in reversing the second PS elicited by DFP or eserine. The excitatory effects of 10 microM DFP did not resemble those produced by the convulsant, bicuculline methiodide, which produced a large afterdischarge even in the presence of 10 microM DFP. It is concluded that 10 microM DFP and 100 microM eserine have effects in field CA1 that are probably not mediated by cholinergic mechanisms.

Acetylcholine↗
PubMed1982

Occupational mercury exposure and its consequences for behaviour.

Mercury is a known neurotoxin. Evidence from animal studies show behavioural impairment which can be long-lasting, after low-level exposure to mercury. Human research, however, has not been conclusive. Chronic, high-level mercury exposure such as occurred in Japan, and the Middle East, Causes long-lasting and profound neurological damage. However the effects of low-level exposure, such as occurs in occupational exposure, are far from clear. This study used a comprehensive test battery based on an information processing framework to compare a group of twelve chronically mercury-exposed workers with a matched control group. The mercury-exposed group showed poorer psychomotor co-ordination and premature fatigue, although simple motor responses were not affected. General arousal levels also remained unaffected but mercury-exposed workers were superior in sustaining attention. In spite of this, the mercury-exposed group showed clear deficits in short-term memory.

Attention↗
PubMed1980

Activity and T-maze performance in iron deficient rats.

Iron deficient rats were tested in a t-maze to see whether the changes in activity during the onset and progress of the deficiency would affect their performance in the maze. Increased exploratory activity in the initial stages of iron deficiency was reflected in enhanced t-maze learning, whereas the lower activity seen as the deficiency progressed was associated with normal maze-learning. The t-maze task may not be sufficiently sensitive to pick up differences between deficient and control animals due to reduced general activity in the later stages of iron deficiency.

Animals↗
PubMed1978

Intestinal transport of weak electrolytes: Determinants of influx at the luminal surface.

The determinants of weak electrolyte influx into everted segments of rat small intestine have been studied. Preliminary experiments showed that the observed influxes could be described as unidirectional, diffusional fluxes of the nonionized compound uncomplicated by a parallel ionic component. It is shown that the determinants of weak electrolyte influx in this situation may be described in terms of the resistance of the unstirred layer to movement from the bulk phase to the cell surface, the degree of ionization of the weak electrolyte at the cell surface, and the cellular permeability to the nonionized weak electrolyte. Quantitative considerations indicated that the unstirred layer was totally rate-limiting in the cases of some poorly ionized, or highly permeant compounds, but the unstirred layer was not totally rate limiting for most of the compounds studied. Calculation of cellular permeabilities for the nonionized forms of weak electrolytes required assumptions to be made concerning the pH value in the surface fluid layer. A uniform set of permeability data including both weak acids and weak bases was obtained only when it was assumed that the pH in the surface fluid layer was equal to that in the bulk phase, and it was concluded that these studies do not support the concept of a microclimate of distinctive pH at the epithelial surface as a determinant of weak electrolyte transport.

Animals↗
PubMedDate not supplied

The development of a neurobehavioral test battery for use in hazard evaluations in occupational settings.

The interest in, and number of, neurobehavioral test batteries for use in occupational settings has increased markedly over the last decade. While this is a welcome development in furthering the cause for greater acceptance of these methods in hazard evaluation and toxicity testing, there are a number of issues that are not being addressed by many test battery designers and users. Without careful consideration of important issues concerning the use of the test batteries, such as the level of testing needed and the selection of appropriate tests, the specificity and sensitivity of tests chosen, the role of computers in test delivery, and the standardisation and interpretation of test results, it is likely that the credibility and utility of neurobehavioral testing will be jeopardized even at this early stage of development. In this paper, the development of a test battery for use in occupational health will be discussed with particular reference to the degree of success in addressing some of the issues described above. A test battery was designed using an information processing model of behavior generation as a base. A continuing programme of standardisation is being carried out on a range of working populations and current results will be discussed. The battery has also been used to evaluate the effects of occupational exposure to a number of hazardous substances including mercury, lead, and most recently, solvents, and to hazardous environments, specifically, underwater work. These results are summarised in terms of the ability of the test battery to detect the effects of particular hazards.

Behavior↗
PubMedDate not supplied

Historical overview of computerized behavioral testing of humans in neurotoxicology.

Since the early 1970s, when they became more accessible, computers have been used increasingly for behavior measurement over a wide range of purposes, including the detection of neurotoxic effects. Over these relatively few years, the number of computerized tests in use in neurotoxicology has grown from one or two to around 16 major batteries. The development of computerized tests in neurotoxicology has been influenced by a number of drives or influences. Some of these influences have included the push for computerizing traditional paper-and-pencil tests, the moves to develop a standard or core test battery, the emphasis on culture-free tests, and on the pragmatic screening approach to test selection. Lately, there has been more emphasis on the development of tests with stability and reliability. These influences have made, and are still making, some impact on the directions of test and test battery construction. The nature and degree of impact will be discussed in the context of analyzing the development of computerized behavioral testing to its current state.

Behavior↗
PubMedDate not supplied

The role of confounding variables in the assessment of neurobehavioural effects of chronic solvent exposure.

An issue in the assessment of toxic effects on neurobehavioural function in occupational or environmental settings is the presence and relative contribution of confounding variables. Factors such as education level and alcohol use are well-known to exert effects on the performance of neurobehavioural tests. In a prospective study of a cohort of vehicle spray painters, measures of neurobehavioural function, demographic characteristics, daily habits including alcohol-use and general health status were taken from the onset of their exposure on four occasions for three full years. This study provided the opportunity to assess the relative contribution of confounding variables and the study factor, solvent exposure, on neurobehavioural function in a study design which limits the heterogeneity of the study sample. In such a design the effects of confounding would expected to be reduced. Multiple linear regression analysis was used with three confounding variables, education level, alcohol use and occupational experience as well as solvent exposure as predictor variables of neurobehavioural test performance. Although the level of solvent exposure was considerably less than the composite threshold limit value for the solvent mixtures encountered, the results indicated that psychomotor performance deteriorated with increasing solvent exposure, but only on the hand steadiness test. The confounding variables showed even greater influences on performance. Education level affected performance on both psychomotor and cognitive tests in the expected direction. Occupational experience also influenced test performance but only for psychomotor tests. With increasing time in the trade, spray painters showed significantly superior performance on reaction time, hand steadiness and visual pursuit tests. Since training in spray painting focuses on psychomotor coordination, this result would be expected. Alcohol use was associated with mixed effects on neurobehavioural function. Painters who reported using greater amounts of alcohol showed significantly poorer performance on the visual test, critical flicker fusion, but better performance on the short term memory and learning measures of the paired associates test so supporting the findings of previous studies of facilitating effects of lower levels of alcohol on memory. These findings reinforce the importance of separating effects due to confounders from effects due to toxic exposures in studies of neurobehavioural function. They emphasise the dilemma of test selection, choosing tests that are sensitive enough to detect effects due to toxic exposure but which are not affected by confounding variables.

Australia↗