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At least 1,117 records · Page 62Linked to original sources
PubMed2000

Autonomic nervous system functions in obese children.

Childhood obesity is a complex syndrome, probably due to the multiplicity of contributing factors, contradictory literature information about etiology, prognosis, prevention and treatment. In the recent reports, autonomic nervous system (ANS) dysfunction has been documented in adult obesity. Autonomic nervous system functions in obese children are not clear. This study was planned to investigate autonomic nervous system function in childhood (7-13 years of age) obesity. Study and control groups consisted of 33 simple obese (23 boys and ten girls, mean age 9.5+/-1.4 years) and 30 healthy children (18 boys and 12 girls, mean age 10.1+/-1.8 years), respectively. Four non-invasive autonomic nervous system function tests (Orthostatic test, Valsalva ratio, 30/15 ratio, Heart rate responses to deep breathing) and general ophthalmic examination were performed on both groups. The difference between the obese and control groups was found statistically significant in Valsalva ratio, 30/15 ratio and Heart rate responses to deep breathing (P<0.025), and insignificant in Orthostatic test (P>0.05). Ophthalmic examinations were normal. The result of these tests suggested normal activity of sympathetic, and hypoactivity of parasympathetic nervous system, implying parasympathetic nervous system dysfunction as a risk factor or associated finding in childhood obesity.

Adolescent↗
PubMed2000

Head stability during whole body movements in spastic diplegia.

Head angular stability is essential for postural control in whole body movement. Using the opto-electronic ELITE system, we have studied head orientation during the movements of squatting from the standing position and straightening-up from the squatting position in 12 children with spastic diplegia and 12 age-matched controls. Although no instruction was given regarding the head, diplegic children consistently performed excessive neck flexion in the squatting movement and excessive hyperextension in the straightening-up movement, whereas normal children maintained the initial orientation throughout both movements. We discuss pathophysiological implications.

Cerebral Palsy↗
PubMed1998

Habituation of lower leg stretch responses in Parkinson's disease.

In young healthy subjects, initially large stretch responses in leg muscles are progressively attenuated following a series of identical postural perturbations. We have studied whether this habituation of stretch responses is impaired in Parkinson's disease. Ten patients and 10 elderly controls received 10 serial 'toe-up' rotational perturbations (amplitude 10 degrees) while standing on a supporting forceplate. We recorded posturally destabilizing medium latency (ML) stretch responses from the medial gastrocnemius muscle. Functional habituation across the first few trials occurred in patients, but not in elderly controls. The rate of habituation was influenced by the size of the response to the first perturbation. This observation explained the absence of habituation in elderly subjects because their responses during the first few trials were much smaller compared to patients. These results suggest that habituation of lower leg stretch responses is unimpaired in Parkinson's disease. The presence of initially large and 'unpracticed' responses may partially explain why Parkinson patients fall in response to unexpected postural disturbances that commonly occur in daily life.

Aged↗
PubMed2000

Neurophysiological studies of thin myelinated (A delta) and unmyelinated (C) fibers: application to peripheral neuropathies.

Dysfunction of small fibers may appear in isolation or associated with large fiber lesions. In some acute neuropathies, such as pandysautonomia, small-fiber impairment is relatively pure but it may also appear in disorders with prominent somatic damage, such as Guillain-Barré syndrome, in which autonomic failure worsens the prognosis. At the present time, chronic idiopathic distal small-fiber neuropathy is diagnosed more frequently, and in some prevalent disorders, such as diabetic or amyloidotic polyneuropathies, small-fiber dysfunction is very noticeable. In pure autonomic failure, a peripheral autonomic failure exists, distinguishing it from multiple-system atrophy. Complex regional pain syndrome is a severe condition in which small fibers are responsible for disabling signs and symptoms, and only instrumental recordings lead to the proper treatment. Standard neurophysiological techniques evaluate large myelinated fibers exclusively. Small-fiber polyneuropathy has been considered as a type of somatic neuropathy, but thin myelinated and unmyelinated fibers are responsible not only for temperature and pain perception but also autonomic function. For instance, full autonomic evaluation is needed in some clinical situations such as autonomic failure in the elderly or orthostatic intolerance syndrome. To evaluate small-fiber impairment we need a battery of sensitive, reproducible, specific and noninvasive tests covering somatic and autonomic systems. In this review, we describe and analyze a number of neurophysiological techniques used to diagnose and characterize small-fiber dysfunction in humans. These include cardiovascular monitoring, sudomotor testing, pupillary responses and quantitative sensory tests, and also to some extent thermography and laser evoked potentials. The use of such techniques has proven useful not only for diagnosis, but also to guide adequate therapy and optimize follow-up.

Electrophysiology↗
PubMed1983

Effects of local anesthesia on persistence of peripherally induced postural asymmetries in rats.

Hindlimb flexion induced by direct stimulation of the hindlimb has been observed subsequent to spinal section if an appropriate time interval was allowed to elapse between onset of flexion and spinal cord section. The present series of experiments was conducted to test the possibility that asymmetry persistence is a product of ongoing cutaneous input that continues after stimulation offset and spinal cord section. A local anesthetic (lidocaine) was injected in the general area of stimulation, and its effects on asymmetry were assessed in three experiments. The results generally indicated that ongoing cutaneous input was not a sufficient explanation for persistence of flexion in animals stimulated with intact or severed spinal cords. The data revealed, however, that ongoing cutaneous input may partially explain results of a previous study that employed a "stimulation-wait" preparation to obtain peripherally induced spinal fixation.

Afferent Pathways↗
PubMed2000

Targeted disruption of otog results in deafness and severe imbalance.

Genes specifically expressed in the inner ear are candidates to underlie hereditary nonsyndromic deafness. The gene Otog has been isolated from a mouse subtractive cDNA cochlear library. It encodes otogelin, an N-glycosylated protein that is present in the acellular membranes covering the six sensory epithelial patches of the inner ear: in the cochlea (the auditory sensory organ), the tectorial membrane (TM) over the organ of Corti; and in the vestibule (the balance sensory organ), the otoconial membranes over the utricular and saccular maculae as well as the cupulae over the cristae ampullares of the three semi-circular canals. These membranes are involved in the mechanotransduction process. Their movement, which is induced by sound in the cochlea or acceleration in the vestibule, results in the deflection of the stereocilia bundle at the apex of the sensory hair cells, which in turn opens the mechanotransduction channels located at the tip of the stereo-cilia. We sought to elucidate the role of otogelin in the auditory and vestibular functions by generating mice with a targeted disruption of Otog. In Otog-/- mice, both the vestibular and the auditory functions were impaired. Histological analysis of these mutants demonstrated that in the vestibule, otogelin is required for the anchoring of the otoconial membranes and cupulae to the neuroepithelia. In the cochlea, ultrastructural analysis of the TM indicated that otogelin is involved in the organization of its fibrillar network. Otogelin is likely to have a role in the resistance of this membrane to sound stimulation. These results support OTOG as a possible candidate gene for a human nonsyndromic form of deafness.

Acoustic Stimulation↗
PubMed2005

Neurological and cognitive recovery following abstinence from petrol sniffing.

Anecdotal observations suggest that neurological impairments associated with petrol (gasoline) sniffing resolve with abstinence, although these effects have not been proven empirically. Severe exposure to leaded petrol may induce a lead encephalopathy that extends beyond any acute intoxication and requires emergency hospital treatment. Previously, in chronic petrol sniffers, we showed neurological, saccadic, and cognitive abnormalities that were more severe in petrol sniffers with a history of hospitalization for lead encephalopathy, and that correlated with blood lead levels and the length of time of sniffing petrol. Ex-petrol sniffers showed a qualitatively similar but quantitatively less severe pattern of impairment. Petrol sniffing was stopped completely in one of the study communities by modifying social, occupational, and recreational opportunities. After 2 years, we obtained biochemical and neurobehavioral (neurological, saccade, and cognitive) data from all available participants of the earlier study including 10 nonsniffers and 29 chronic petrol sniffers, with six of these individuals previously receiving hospital treatment for lead encephalopathy. Here, we report that blood lead was reduced and that neurobehavioral impairments improved, and in many cases normalized completely. The most severe petrol-related neurobehavioral impairment was observed among individuals who had longer histories of abuse and higher blood lead levels, and among petrol sniffers with a history of lead encephalopathy. Those with the greatest extent of neurobehavioral impairment showed the greatest degree of improvement with abstinence, but were less likely to recover completely. This is the first direct evidence that neurological and cognitive impairment from chronic petrol sniffing ameliorates with abstinence and may recover completely.

Adolescent↗
PubMed1983

Control of skeletal muscle blood flow during postural changes in acute myocardial infarction.

Central and local regulation of skeletal muscle blood flow in the leg was studied in the acute phase of myocardial infarction. Blood flow was measured by the local 133Xe washout technique in the anterior tibial muscle. The vasoconstrictor response to increase in venous transmural pressure was not present on day 1 after coronary occlusion but gradually returned during days 2, 3 and 7. A normal response to decrease in arterial perfusion pressure was observed, suggesting that intrinsic vascular reactions responsible for autoregulation of blood flow were not affected in the acute phase of myocardial infarction. Passive head-up tilt (30 degrees) induced vasoconstriction in skeletal muscle tissue. There were no differences in this response at any time during the course of acute myocardial infarction. The abolition of the vasoconstrictor response to increase in venous transmural pressure on day 1 is most likely due to centrally elicited increase in sympathetic activity as a normal vasoconstrictor response was obtained the following days. Decrease in baroreceptor activity induced by head-up tilt enabled a marked neurogenically mediated vasoconstriction in skeletal muscle tissue which was almost unaffected during the course of myocardial infarction.

Adult↗
PubMed1984

The influence of acute starvation on the cardiovascular responses to lower body subatmospheric pressure or to standing in man.

The cardiovascular responses to lower body subatmospheric pressure or to standing were measured in the same nine normal male subjects after a 12 h and after a 48 h fast. After the 48 h fast there was a significant reduction in diastolic blood pressure and forearm vascular resistance (relative to the values after a 12 h fast) when subjects were supine. During exposure to lower body subatmospheric pressure, subjects who had fasted for 48 h showed an inability to maintain systolic blood pressure, accompanied by an impairment of forearm vasoconstriction and an exaggerated tachycardia (relative to their responses after a 12 h fast). Similar disorders of cardiovascular homoeostasis were seen on standing. The results are consistent with an inhibition of sympathetic nervous activity after a 48 h fast, but other possibilities are discussed.

Adult↗
PubMed2003

Effects of heat stress on baroreflex function in humans.

INTRODUCTION: Heat stress significantly reduces orthostatic tolerance in humans. The mechanism(s) causing this response remain unknown. The purpose of this review article is to present data pertaining to the hypothesis that reduced orthostatic tolerance in heat stressed individuals is a result of heat stress induced alterations in baroflex function. METHODS: In both normothermic and heat stressed conditions baroreflex responsiveness was assessed via pharmacological and non-pharmacological methods. In addition, the effects of heat stress on post-synaptic vasoconstrictor responsiveness were assessed. RESULTS: Generally, whole body heating did not alter baroreflex sensitivity defined as the gain of the linear portion of the baroreflex curve around the operating point. However, whole body heating shifted the baroreflex curve to the prevailing (i.e. elevated) heart rate and muscle sympathetic nerve activity. Finally, the heat stress impaired vasoconstrictor responses to exogenous administration of adrenergic agonists. CONCLUSION: Current data do not support the hypothesis that reduced orthostatic tolerance associated with heat stress in humans is due to impaired baroreflex responsiveness. This phenomenon may be partially due to the effects of heat stress on reducing vasoconstrictor responsiveness.

Baroreflex↗
PubMed2002

Quantitative analysis of the relative effectiveness of 3 iliotibial band stretches.

OBJECTIVE: To compare the relative effectiveness of 3 common standing stretches for the iliotibial band (ITB): arms at side (stretch A), arms extending overhead (stretch B), and arms reaching diagonally downward (stretch C). DESIGN: Each subject's biomechanics was captured as a 3-dimensional image by using a 4-camera gait acquisition system with a forceplate. SETTING: University biomotion laboratory. PARTICIPANTS: Five male elite-level distance runners. INTERVENTIONS: All participants performed each of the 3 standing stretches for the ITB. MAIN OUTCOME MEASURES: For each stretch, change in ITB tissue length and the force generated within the stretched complex was measured. Data were then combined and analyzed by using kinetic values assessment. RESULTS: All 3 stretches created statistically significant changes in ITB length (P<.05), but stretch B, incorporating overhead arm extension, was consistently most effective both for average ITB length change and average adduction moments at the hip and knee. CONCLUSIONS: Adding an overhead arm extension to the most common standing ITB stretch may increase average ITB length change and average external adduction moments in elite-level distance runners.

Biomechanical Phenomena↗
PubMed1978

The development of the parachute reaction: a visuo-vestibular response.

The development of the parachute reaction as a postural response has been tested under various optic stimuli in normal and statomotorically retarded infants. Complete reaction consists in symmetric extension of the arms with extension and spreading of the fingers on quick approach to visual surface. Using a glass plate with three different sized stimulus patterns the parachute response is scored as complete or incomplete. The complete reaction to large visual surface develops significantly earlier than to small visual surface. The response also requires simultaneously a visual and a vestibular sensory input. The developmental course of the parachute reaction is statistically significant linear correlated in double logarithmic transformation to the stimulus pattern and to the age indicating a complex biological maturating process. When the whole retinal area was stimulated by moving visual scenes similar to normal environmental conditions the reaction starts with about 4 months of age and is fully developed from 9 months onwards. The time of quickest development is around 6.3 months of age, a period where locomotor abilities shift from horizontal postiion to active verticalisation of the body. In statomotorically retarded infants the response develops significantly later according to their active motor behaviour. Brain integration and computing centers of sensory afferent input could be multilevel from reticular formation to cerebral cortex, wherein the latter, probable the parietal lobe should play the major role. It is concluded that the parachute reaction results from a combined visuovestibular mechanism of interaction in connection with sufficient kinesthetic experience in visuo-motor behaviour.

Age Factors↗
PubMed2003

Evaluating the dizzy patient: bedside examination and laboratory assessment of the vestibular system.

Dizziness and imbalance are common presenting complaints to the neurologist. The lack of a systematic approach to the examination and laboratory evaluation of the vestibular system often leads to incorrect diagnoses and suboptimal care. With a basic understanding of vestibular physiology and proper examination techniques, a correct diagnosis can generally be made at the bedside. We review the principles of the neuro-otological examination, including assessment for static vestibular imbalance, dynamic vestibular function, provocative maneuvers, ocular motor examination, and vestibulospinal testing. The use of additional vestibular laboratory testing and neuroimaging is then considered to further localize and quantify abnormalities.

Dizziness↗
PubMed2005

[Syncope].

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Diagnosis, Differential↗