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Biomedical subjects

G A Jamal

Publications and source records attributed to G A Jamal.

At least 19 recordsLinked to original sources
PubMed2002

A clinical neurological, neurophysiological, and neuropsychological study of sheep farmers and dippers exposed to organophosphate pesticides.

OBJECTIVES: To classify clinical diseases of the subjects with abnormal indices of peripheral neuropathy identified in field studies of sheep farmers and dippers exposed to organophosphate pesticides. To explore what neuropsychological profiles, if any, may be associated with neurophysiological damage in these subjects. METHODS: A case-control study (79 subjects) nested within the cross sectional study (685 subjects) of sheep farmers from the field study. Three groups with no, possible, and probable or definite neuropathy according to field studies were recruited. Investigations comprised symptoms of neuropathy, neurologial signs, motor and sensory nerve conduction, electromyography, quantitative sensory testing, and neuropsychological tests. RESULTS: The incidence of clinical neuropathy increased from 7% in the no neuropathy group to 52% in the probable or definite neuropathy group based on nerve conduction measurements or presence of neurological signs. Sensory abnormalities were found more often than motor deficits. Small diameter nerve fibres were also affected more than large fibres. CONCLUSIONS: The neuropathy is predominantly sensory and is characteristic of distal, chronic neuropathy with no acute features. Small fibre populations are affected more than large fibre populations. Increasing severity of neuropathy was associated with anxiety and depression as measured in the neuropsychological tests.

Adolescent↗
PubMed2002

Clinical validation of methods of diagnosis of neuropathy in a field study of United Kingdom sheep dippers.

OBJECTIVES: To investigate the reproducibility of measured indices of chronic peripheral neuropathy from a field study of sheep dippers when compared with similar measurements carried out in a clinical setting. METHODS: A stratified random sample of field study subjects was invited to attend a clinic. Neuropathy was measured both in the field and at the clinic with a modified version of a standard symptoms questionnaire and quantitative sensory thresholds for hot, cold, and vibration. These were combined into a classification of the likelihood of neuropathy with a neuropathy scoring system. Indicators of sensory abnormality were based on comparison of sensory thresholds to age dependent reference values derived from an external reference group. RESULTS: Only 51% of subjects were assigned similar classifications in the field and clinic based on the neuropathy scoring system. Of the component indices, grouped symptom scores, with 65% of subjects showing exact agreement, proved to be more reproducible than quantitative sensory test indicators. There were biases in the comparison of field and clinic measurements of hot and vibration sensations, but no evidence of greater variation between individual people in sensory thresholds in the field relative to at the clinic. CONCLUSIONS: The neuropathy scoring system proved to be of limited reproducibility, due in a large part to the lack of reproducibility of the indicators of sensory test abnormality caused by inadequate temperature control. However, the symptoms score and measured sensory thresholds could be used separately as indices of neuropathy in exposure-response analyses.

Adult↗
PubMed2001

Characterisation of breathing and associated central autonomic dysfunction in the Rett disorder.

AIM: To investigate breathing rhythm and brain stem autonomic control in patients with Rett disorder. SETTING: Two university teaching hospitals in the United Kingdom and the Rett Centre, Sweden. PATIENTS: 56 female patients with Rett disorder, aged 2-35 years; 11 controls aged 5-28 years. DESIGN: One hour recordings of breathing movement, blood pressure, ECG R-R interval, heart rate, transcutaneous blood gases, cardiac vagal tone, and cardiac sensitivity to baroreflex measured on-line with synchronous EEG and video. Breathing rhythms were analysed in 47 cases. RESULTS: Respiratory rhythm was normal during sleep and abnormal in the waking state. Forced and apneustic breathing were prominent among 5-10 year olds, and Valsalva breathing in the over 18 year olds, who were also most likely to breathe normally. Inadequate breathing peaked among 10-18 year olds. Inadequate and exaggerated breathing was associated with vacant spells. Resting cardiac vagal tone and cardiac sensitivity to baroreflex were reduced. CONCLUSIONS: Labile respiratory rhythms and poor integrative inhibition in Rett disorder suggest brain immaturity. Linking this to an early monoaminergic defect suggests possible targets for the MECP2 gene in clinical intervention. Exaggerated and inadequate autonomic responses may contribute to sudden death.

Adolescent↗
PubMed2001

An epidemiological study of the relations between exposure to organophosphate pesticides and indices of chronic peripheral neuropathy and neuropsychological abnormalities in sheep farmers and dippers.

OBJECTIVES: To investigate the hypothesis that chronic low level exposure to organophosphates (OPs) in sheep dips is related to clinically detectable measures of polyneuropathy. METHODS: The design was a cross sectional exposure-response study of sheep dippers and other non-exposed groups. The study group consisted of 612 sheep dipping farmers, 53 farmers with no sheep dipping experience, and 107 ceramics workers. Retrospective exposure information was obtained by questionnaire based on stable and easily identifiable features of sheep dipping found during the first phase of the study; in particular, estimates of handling concentrate and splashing with dilute dip. Neurological assessments were based on a standard neuropathy symptoms questionnaire, and thermal and vibration quantitative sensory tests. RESULTS: Adjusted for confounders there was a weak positive association between cumulative exposure to OPs and neurological symptoms, the significance of which was dependent on the inclusion of a few individual workers with extremely high exposure. There was no evidence of an association between cumulative exposure and the thermal or vibration sensory thresholds. However, separating the effects of exposure intensity and duration showed a higher prevalence of symptoms, primarily of a sensory type, among sheep dippers who handled the OP concentrate. There was also evidence that sensory and vibration thresholds were higher among concentrate handlers, the highest exposed group of dippers. CONCLUSIONS: The findings showed a strong association between exposure to OP concentrate and neurological symptoms, but a less consistent association with sensory thresholds. There was only weak evidence of a chronic effect of low dose cumulative exposure to OPs. It is suggested that long term health effects may occur in at least some sheep dippers exposed to OPs over a working life, although the mechanisms are unclear.

Adolescent↗
PubMed2000

Complex regional pain syndrome with selective emotional sudomotor failure.

We report a patient with sympathetically maintained pain following a mild limb injury. Only emotional sudomotor failure was found in the painful limb. Thermoregulatory vasomotor function was intact. However, the patient had other target-specific sympathetic lesions, including thermoregulatory vasomotor failure in a different limb, not associated with pain. We hypothesize that the sympathetic failure preceded the symptoms and that the mild injury may have provoked collateral sprouting of emotional sudomotor fibres, coupling them with somatic sensory fibres to cause continuous pain.

Adolescent↗
PubMed1999

Changes in a measure of cardiac vagal activity before and after epileptic seizures.

In previous studies of the relationship between the cardiac autonomic activity and seizures, assessment of autonomic changes has relied on alterations in heart rate or R-R intervals. We have used a recently developed continuous index of cardiac parasympathetic activity (CIPA) to examine 20 seizures in 10 patients during pre-surgical evaluation in a video-telemetry unit. The patients had localization related seizures due to non-progressive pathology and both complex partial seizures (CPS) and complex partial with secondary generalised tonic clonic seizures (STCS) were examined. Mean CIPA prior to the onset of STCS was elevated above normal values and fell significantly to previously established normal values following the seizure. CPS were not associated with elevated mean CIPA pre- or post-seizure. STCS were associated with a reduction in anti-convulsant dosage and with elevation of pre-ictal CIPA. We propose that elevation of cardiac parasympathetic activity pre-ictally may be a marker for secondary generalisation of seizures.

Adult↗
PubMed1999

Cognitive functioning in people with epilepsy plus severe learning disabilities: a systematic analysis of predictors of daytime arousal and attention.

In spite of the high prevalence of epilepsy and the importance of preserving cognitive function in people with learning disabilities, this population has received relatively little research attention. This study sets out systematically to investigate possible predictive factors of inter-ictal states of arousal and attention. The daytime function of 28 people with epilepsy and severe learning disabilities was assessed by performance on a two-choice reaction time vigilance task, behavioural analysis of time-sampled video recordings taken in naturalistic settings, and carer ratings on visual analogue scales. This methodology yielded eight discrete functional measures, from which two further index measures were derived after principal components analysis. A range of clinical and psychosocial assessments was completed and subjects had 36 hour ambulatory EEG and sleep EEG monitoring. Regression models identified significant predictors of cognitive function from a range of potential explanatory variables i.e. demographic, clinical, pharmacological, background EEG rhythms and sleep parameters. Results indicated that greater severity of learning disability, longer bedtime periods, poor sleep efficiency, frequent seizures and antiepileptic drug polytherapy were significant predictor variables. Explained variance (adjusted R2) was greater than 50% for six of 10 outcome variables (range up to 85%). Furthermore, significant regression equations (P < 0.05) were obtained for all but one variable. Thus, these results appear reasonably robust. Results support an interactional model of daytime arousal and attention in people with epilepsy plus severe learning disabilities. Inter-ictal cognitive function appears to be mediated by a combination of organic, circadian (sleep wake), clinical and pharmacological factors.

Adolescent↗
PubMed1999

Periodicity of a noninvasive measure of cardiac vagal tone during non-rapid eye movement sleep in non-sleep deprived and sleep-deprived normal subjects.

Cyclic alternating pattern (CAP) of microarousals reported in EEG studies is now regarded as an integrating mechanism for the different parts of the central nervous system including the autonomic system. A recently developed continuous index of cardiac parasympathetic activity (CIPA) can be time locked to the EEG allowing the relationship between EEG and autonomic changes to be studied in sleep. Eleven normal subjects were studied for evidence of periodicity in CIPA in non-REM sleep, five of whom had been sleep deprived. Fast Fourier's transformation of the CIPA data confirmed its periodicity with four frequency peaks in the range of 0.015 to 0.3 Hz. The frequency peaks previously reported as caused by respiration, Mayer waves and vasomotor thermoregulatory activity, were within what we called the alpha and beta rhythms of CIPA. There was an additional very slow peak not previously described and we called it the gamma rhythm. It covered the frequency range below 0.03 Hz. The gamma rhythm was the largest of all peaks in CIPA rhythms and its magnitude increased further in sleep-deprived subjects, but it invariably decreased during stage 4 sleep in both groups. Bursts of alpha waves in the EEG recorded concomitantly with CIPA in stage 1 sleep were associated with both peaks and troughs of the gamma rhythm. These results support previous proposals that cyclic alternating pattern in the EEG may be an integrating mechanism associated with functions of the central nervous system, and we have shown here its relationship with CIPA. Because cyclic alternating pattern can also be measured in CIPA, clinical exploitation of this phenomenon could include monitoring of epilepsy, studies of the effects of drug therapy, and assessment of other sleep disorders. All these are known to affect cyclic patterns of sleep EEG.

Adult↗
PubMed1998

Sleep deprivation and its effect on an index of cardiac parasympathetic activity in early nonREM sleep in normal and epileptic subjects.

The effect of 24-hour sleep deprivation on cardiac vagal tone during the first 90 minutes of sleep was studied in 16 subjects using a new real-time index of cardiac parasympathetic activity. The level of cardiac vagal tone in subjects who were sleep deprived was more than doubled that in non-sleep-deprived subjects during sleep stage 0 immediately prior to the onset of sleep stage 1. The mean cardiac vagal tone fell significantly (p < 0.01), from a high level of 19.2 arbitrary units of a linear vagal scale (LVS) to 10 units on reaching slow-wave sleep stage 4 in sleep-deprived epileptic subjects, There was a similar fall in cardiac vagal tone from 18.7 units to 12 units in the LVS in sleep-deprived normal subjects, but this was not statistically significant. There was no change in the mean vagal tone of non-sleep-deprived normal subjects. We propose that the cardiac vagal tone can be used as an objective index of sleep propensity.

Adult↗
PubMed1998

Gulf War syndrome--a model for the complexity of biological and environmental interaction with human health.

Since the end of the Gulf War, tens of thousands of American, Canadian and British soldiers who participated in that war have claimed to be suffering from a variety of incapacitating symptoms which are generally termed as Gulf War Syndrome (GWS). The symptoms are multiple but mainly consist of excessive tiredness, muscle and joint pain, loss of balance, sensory symptoms, neurobehavioural manifestations, diarrhoea, bladder dysfunction, sweating disturbances, and respiratory, gastrointestinal, musculoskeletal and skin manifestations. These veterans have been exposed to a variety of damaging or potentially damaging risk factors including environmental adversities, pesticides such as organophosphate chemicals, skin insect repellents, medical agents such as pyridostigmine bromide (NAPS), possible low-levels of chemical warfare agents, multiple vaccinations in combinations, depleted uranium, and other factors. A large number of basic research findings, clinical epidemiological studies, and case control studies are reviewed to try and link them together to produce a coherent picture and to demonstrate the complexity of the interaction of biological systems, environmental and genetic factors, combinations of drugs and toxins with human health. The findings of these studies so far have demonstrated that many of the previous assumptions made about the 'safety' of certain drugs and toxic substances or vaccines must be radically reviewed. Many of the findings have far reaching implications not only in terms of explanation of what might have gone wrong during the Gulf War, but also have wider implications for many occupational groups who are exposed daily to some of these risk factors. More open-mindedness and much less prejudice are required concerning the basic biology of interactions of the above factors and their effects on cell functions and wider intelligent research is urgently required with high priority. This review highlights the importance of intelligent research for answers for a new phenomenon, and demonstrates the necessity for a combination of this approach with high quality epidemiological research. The reader will notice an emerging clear picture that the majority (if not all) of these advances have been achieved from studies funded by independent or charity organizations rather than by the responsible authorities who are supposed and are duty bound to take on this task.

Chemical Warfare Agents↗
PubMed1997

Selective defect of baroreflex blood pressure buffering with intact cardioinhibition in a woman with familial aniridia.

We report a symptomatic failure of the baroreceptor blood pressure (BP) buffering mechanism in a woman with familial aniridia. Her baseline BP oscillated at 0.1 Hz, the frequency of Mayer waves, with increased amplitude on standing without orthostatic hypotension. Although sudomotor function was normal, cutaneous thermoregulatory function and BP response to Valsalva's maneuver were abnormal. The defective BP buffer mechanism suggests Mayer waves could be a sympathetic mediated cardiovascular resonance. Baroreceptor cardioinhibition was intact. We presume that the lesion is in the rostral aspect of the dorsal medulla oblongata.

Adult↗
PubMed1997

Functional evidence of brain stem immaturity in Rett syndrome.

Autonomic activity and respiration were studied in Rett syndrome (RS) and age matched controls. Breathing movements were monitored using a pletysmograph around the chest. Sympathetic activity was monitored by measuring blood pressure (BP) using the Finapres. Cardiac parasympathetic activity was monitored by measuring the cardiac response to baroreflex using the NeuroScope which outputs measure of cardiac vagal tone (CVT) in units of a linear vagal scale (LVS). Resting CVT (means +/- SEM) was 10.5 +/- 0.9 units in the LVS and BP was 94.6 +/- 6.4 mmHg in controls. The BP was 78 +/- 4.33 mmHg and CVT was 3.6 +/- 0.7 units in the LVS in girls with RS, 65% lower than in their age matched controls (p < 0.001), but equal to previously reported level in neonates. Each girl with RS had at least 6 types of breathing dysrhythmias, a sign of instability of the respiratory oscillator. The sympathetic system controlled the HR and BP smoothly during breath holding in control girls, but there were oscillations and rebounds in RS. The HR and BP were under parasympathetic influence during hyperventilation in normal girls but not in RS. The CVT was invariably withdrawn at the height of sympathetic activity during both hyperventilation and breath holding in RS, leading to sympathovagal imbalance with the risk of cardiac arrhythmias and possibly sudden death. Neonatal level of CVT, poor autonomic integration and multiple breathing dysrhythmias shows medullary immaturity in RS. It is the first demonstration of immaturity of the brain which could be used for screening in early childhood and potentially useful for diagnosis and management of RS.

Adolescent↗
PubMed1997

Neurological syndromes of organophosphorus compounds.

In addition to the acute cholinergic poisoning, organophosphorus (OP) compounds are capable of producing several subacute, delayed and chronic neurological, neurobehavioural and psychiatric syndromes. These include the intermediate syndrome, the organophosphate induced delayed neuropathy (OPIDN) and a number of chronic neurological and psychiatric manifestations lumped in this review under the term chronic organophosphate induced neuropsychiatric disorder (COPIND). A critical review of the concept of the neuropathy target esterase (NTE) inhibition and ageing as a marker of OPIDN and the related hen test is presented. It is concluded that the use of the hen test as an exclusive screening test for neurotoxicity of organophosphorus compounds is flawed. A number of recent studies are presented to demonstrate the unreliability of the test and flaws of scientific concepts underlying the hen test which is used to identify OPs as safe and "non-neurotoxic". The components of this new COPIND syndrome are described and the evidence for its existence is reviewed. Studies are in progress to further determine the profile of this syndrome and to define the overlap between its various components. The review also attempts to determine the clinical features so far described of these components and the investigations or markers used to identify and characterize COPIND and the behaviour of these markers. Evidence for chronic neurological/psychiatric effects of OP compounds have come from case studies, clusters of neurological diseases or from epidemiological investigations. New concepts in neurotoxicology are being produced from recent studies which may necessitate a new radical approach to the assessment of neurotoxicity of pesticides before releasing them for widespread use.

Animals↗
PubMed1996

Endogenous cyclo-oxygenase substrates mediate the neuroactivity of evening primrose oil in rats.

The role of cyclo-oxygenase and or its substrate(s) on the neuroactivity of evening primrose oil was investigated on the basis that a blockade of cyclo-oxygenase activity using aspirin would inhibit neuroactivity of primrose oil if this effect was mediated by prostanoids. Streptozotocin diabetic rats and controls were all given large doses of aspirin, but only subgroups of them received primrose oil. Saphenous sensory A- and C-fibre, and sciatic motor conduction velocities were measured to assess neuroactivity of primrose oil. Aspirin enhanced the neuroactivity of primrose oil thus indicating that prostanoids are unlikely to mediate this neuroactivity, but also suggesting that substrates of cyclo-oxygenase are neuroactive. It is likely that cyclo-oxygenase antagonises neuroactivity of primrose oil by competing with the process for substrates. Thickly myelinated sensory A-fibres were most affected by primrose oil suggesting that the predominant sensory symptoms in diabetic neuropathy could be due to the sensitivity of sensory nerves to the metabolic aberration in diabetes. Normal nerve function is probably preserved by cyclo-oxygenase during an influx of neuroactive fatty acids from the gut, since inhibition of the enzyme rendered non-diabetic nerves vulnerable to dietary primrose oil.

Animals↗
PubMed1996

The "Gulf War syndrome". Is there evidence of dysfunction in the nervous system?

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.

Adult↗