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Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies have demonstrated two tremorgenic systems that involve separate brain mechanisms and exhibit different peak frequencies. One system (the thalamo-cortical) generates low frequency (4--8 Hz) tremor; the other (the olivo-cerebellar) produces high frequency (10--18 Hz) tremor. Based on this evidence, the present study focused on determining whether one or both of these tremor systems is involved in the high pressure nervous syndrome (HPNS). Specifically, the concern was to identify and to quantify amplitude and frequency characteristics of HPNS tremor in 8 guinea pigs breathing helium-oxygen during compression (40 ft/min) in a chamber dive to 61.6 ATA (2000 fsw) with a bottom time of 1 h. Rectal temperature was recorded and maintained at 39 degrees C +/- 1 degree. Leg tremor was recorded by magnetic inductance and stored on magnetic tape for power spectral analysis. Frequency histograms of the tremor data revealed development of a biphasic response. From surface to about 31.3 ATA (1000 fsw), a low-power, single, 4- to 6-Hz component was evident, which resembled fine or moderate tremor. Between 34.3 ATA (1100 fsw) and 61.6 ATA, a 12- to 18-Hz component emerged abruptly with a dramatic increase in power, which reflected coarse, uncontrollable tremors. In the first 5 to 10 min after the animals arrived at maximum pressure, relative power of the high frequency component dropped to and remained near base-line levels. These results support the hypothesis that HPNS tremor consists of two components and possibly two separate tremor systems.
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PMID:Quantification of high pressure nervous syndrome (HPNS) tremor in the guinea pig. 63 79

The reduction of acetylene to ethylene by stationary (non-shaking) cultures of free-living rhizobia under atmospheric oxygen levels has been demonstrated. Under these conditions the development of the activity is inhibited by 10 mM NH4Cl and about 20% of oxygen is required for maximal activity. When the stationary cultures were shaken, oxygen concentrations of 1% and higher were found to be inhibitory. Specific activities of 20 and 40 nmol of acetylene reduced h-1 mg-1 protein were observed.
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PMID:Reduction of acetylene by stationary cultures of free-living Rhizobium sp. under atmospheric oxygen levels. 96 17

Five subjects were compressed to 1000 ft (31 ATA) for 2 h breathing 3.2 ATA nitrogen, 0.5 ATA oxygen, and the remainder helium. The compression took 33 min with a 10-s stage at 50 ft (2.5 ATA), 1 MIN AT 320 FT (10.7 ATA), and 2 min at 700 ft (22 ATA). Hypothetically, this 1:10 ratio for nitrogen-helium partial pressures should induce neither nitrogen narcosis nor the High Pressure Nervous Syndrome (HPNS). Tests, therefore, were made during the experiment of postural tremor, spontaneous electroencephalogram, psychomotor and intellectual activities, and subjective sensations. One diver worked underwater for 40 min on a simulated engineering assembly while breathing with a closed-circuit breathing apparatus and wearing a battery-heated suit in water at 56 degrees F. Decompression was in 4 d using 0.8 ATA oxygen and helium. The performance tests indicated no narcosis and little or no signs of HPNS. No tremor or EEG changes were seen. The "wet" diver reported sensations of mild euphoria but the other four reported no difficulties. No nausea or dizziness of HPNS was reported. It is concluded that use of a ratio of 1:10::N2:He is effective in the control of narcosis and HPNS during rapid compression to 1000 ft (31 ATA).
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PMID:Optimal use of nitrogen to suppress the high pressure nervous syndrome. 111 94

Under continuous compression with normoxic helium-oxygen mixture up to 100 Ata with the velocity 1 Ata/min, guinea pigs developed successively tremor, myoclonias, seizures of clonic and tonic types. Blood supply of cerebral structures (cortex, black substance, caudate nucleus) during motor disorders increased depending on the stage of development of the high pressure neural syndrome. The role of cerebral circulation in the latter's pathogenesis is discussed.
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PMID:[The local blood supply of the brain in guinea pigs during the development of the high-pressure nervous syndrome]. 133 Jul 49

When human divers and experimental animals are exposed to high pressure of helium-oxygen mixture, they develop the high pressure neurological syndrome, characterized by nausea, vertigo, tremor, myoclonus, EEG modifications and convulsions. Free-moving rats were stereotaxically implanted in the anterior caudate nucleus with a microdialysis probe to measure dopamine, dihydroxyphenylacetic acid and homovanillic acid levels during different phases of a simulated dive up to 5.1 MPa. Compression was found to cause an increase in extracellular dopamine and dihydroxyphenylacetic acid concentrations, but not in homovanillic acid. This represents a specific effect of high pressure on the dopaminergic pathway. Recent findings on D2 autoreceptors, showing a decrease in receptor affinity under pressure, allow us to conclude that pressure increases dopamine synthesis through a direct action on D2 autoreceptors.
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PMID:Effects of high pressure on striatal dopamine release in freely moving rats: a microdialysis study. 149 92

Repeated measurements of regional cerebral blood flow (rCBF) were obtained in 7 patients who underwent a stereotactic thalamic electrode implantation in the nucleus ventralis intermedius (nVIM) of the thalamus for severe hemi-parkinsonian tremor. Using positron emission tomography and oxygen-15 labelled water, rCBF was studied in each patient in two conditions: in absence of tremor, e.g. under nVIM electrical stimulation, and in presence of tremor. X-ray tomograms permitted individual definition of anatomical regions of interest. In presence of tremor, normalized rCBF increases were observed in the following regions: postcentral (13.6 +/- 8.4%, P = 0.0003), precentral (7.7 +/- 8.8%, P = 0.016), paracentral (7.7 +/- 8.4%), supplementary motor (8.2 +/- 10.4%, P = 0.025), caudate nucleus (5.7 +/- 7.6%, P = 0.03), vermis (9.7 +/- 7.3%, P = 0.007), cerebellar grey nuclei (9 +/- 6%, P = 0.016) on the electrode side and on the contralateral vermis (17.8 +/- 7.5%, P = 0.0003) and cerebellar grey nuclei (22 +/- 6.3%, P = 0.0004). These results clearly indicate an activation of the sensory-motor cortex, as well as an involvement of the supplementary motor area and the cortico-cerebellar pathways in Parkinsonian resting tremor (PRT). They demonstrate that PRT shares common network of brain structures with repetitive voluntary movement.
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PMID:Evidence for a common network of brain structures involved in parkinsonian tremor and voluntary repetitive movement. 151 31

1. ICI D7114 is a novel, beta-adrenoceptor agonist which stimulates whole body oxygen consumption in conscious rats, cats and dogs and brown adipose tissue (BAT) activity in conscious rats. Treatment of rats with ICI D7114 stimulated oxygen consumption (ED50, 0.04 mg kg-1, p.o.) and BAT mitochondrial guanosine diphosphate (GDP)-binding (ED50, 0.15 mg kg-1, p.o.) with no chronotropic effects on the heart at these doses. 2. Reference beta-adrenoceptor agonists, isoprenaline and clenbuterol, also stimulated oxygen consumption and BAT activity but were less selective because they also produced effects on heart rate at these doses. 3. Treatment of conscious rats with ICI D7114 did not attenuate the chronotropic effects on the heart of a subsequent isoprenaline challenge. 4. Administration of ICI D7114 or of its acid metabolite had no effect in a cat soleus muscle model of tremor or on blood potassium levels in the conscious dog, indicating lack of effects at beta 2-adrenoceptors. 5. The results indicate that ICI D7114 may have activity at atypical beta-adrenoceptors in brown adipose tissue leading to increased whole body oxygen consumption.
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PMID:ICI D7114 a novel selective beta-adrenoceptor agonist selectively stimulates brown fat and increases whole-body oxygen consumption. 168 10

33 divers exposed to high pressure have been examined in three series. The dynamics of the forced breathing parameters has been studied: I--helio or neon-oxygen medium under pressure of 1.078-3.53 MPa (11-36 kg/m2) with density to 32.7 kg/m3; II--nitrogen-oxygen medium under 0.274-0.882 MPa (2.8-9.0 kg/m2) with density of 11.7 kg/m3; III--under the same conditions, as II, but using bronchospasmolytics (stimulators of 2-adrenoreceptors: astompent, salbutamol, berotec) under hyperbaria. A new phenomenon: high-density breathing syndrome is revealed. It includes appearance of oscillations of respiratory flows against the background of a decrease of forced breathing rate in dense gas medium and has a common mechanism of appearance both during inhale and exhale. High hydrostatic pressure and narcotic qualities of inert gases can have a modulating effect. Evidences are obtained that tremor phenomena observed during high pressure nervous syndrome can influence the biomechanics of forced breathing at hyperbaria. A high correlation between amplitude modulation of electromyograms of breathing muscles and pneumotachogram oscillations within the range, corresponding to the frequency of physiological tremor, allowed assuming that tremor of breathing muscles induced by high-density gas medium action is one of factors responsible for appearance of respiratory flows oscillations.
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PMID:[High density respiratory syndrome: I. Oscillations of flow-volume curves during forced respiration in dense gas media]. 177 49

Neurophysiological interactions between the competitive N-methyl-D-aspartate (NMDA) preferring receptor antagonist, CPP (3-((+-)-2-carboxypiperazine-4-yl)-propyl-1-phosphonate) and the high pressure neurological syndrome (HPNS) have been investigated in the non-human primate Papio anubis. Eight animals were exposed on two occasions to environmental pressures of 81 atmospheres absolute (ATA) in a hyperbaric chamber, using helium and oxygen. One exposure followed pretreatment with CPP (either 5 or 10 mg/kg i.v. plus 5 mg/kg/hr infusion), the other a saline control. Pretreatment with CPP delayed moderate signs of face tremor and myoclonus and abolished severe signs of whole body tremor and seizure activity. By 81 ATA, scores representing severity of HPNS were significantly reduced by CPP to a mean score, reflecting a level of just mild to moderate limb tremoring (P less than 0.001). Changes in the EEG were observed in channels associated with the frontal, parietal and occipital regions of the left cortex. Amplitude and frequency spectra were calculated and changes with pressure in the 4 conventional wavebands were analysed. The most striking change was the complete prevention by CPP of the 100% increase in the amplitude of alpha waves at 81 ATA in the frontal region (P less than 0.001). It is concluded that NMDA transmission has a major role in the expression of HPNS.
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PMID:The effects of the competitive NMDA receptor antagonist CPP on the high pressure neurological syndrome in a primate model. 183 61

When human divers or experimental animals are exposed to high pressure, they develop the High Pressure Neurological Syndrome (HPNS). Male Sprague-Dawley rats were exposed to high pressure in a conventional helium-oxygen breathing mixture to 80 bars. Pressure-induced behavioral motor disturbances including hyperlocomotor activity (HLA), tremor and myoclonia were monitored with a noninvasive piezoelectrical sensor device enabling a without discontinuity long-term analysis. New data were obtained on the development of the HPNS behavioral motor disturbances. Indeed, the present results suggest myoclonia would be more sensitive to constant high pressure exposure, while HLA and tremor would be more sensitive to increasing pressure. Moreover, myoclonia were found to occur significantly later in rats which developed epileptic seizures than in other. The present results constitute the quantitative basis of HPNS motor disturbances for future pharmacological pressure experiments.
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PMID:Quantitative study of behavioral disturbances in rats exposed to high pressure. 191 Mar 48


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