Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0028738 (nystagmus)
 7,431 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In an attempt to investigate some aspects of the high pressure nervous syndrome, the vestibulo-ocular reflex (VOR) gain was measured in two professional divers undergoing a simulated dive at 62 ATA. The aquanauts in a seated position were rotated sinusoidally around the vertical axis at a frequency of about 0.3 Hz over a 20 degrees range. Tests were performed at regular intervals prior to, during, and after the compression/decompression period. The rotations were applied either in total darkness or with a visual target rotating with the chair or with a target fixed to the chair-supporting frame. An infrared photoelectric system monitored eye movements. The results showed no spontaneous nystagmus, but two definite changes in VOR gain: (1) a slight but significant increase related to pressure increase, which may be due to an increase of the vestibular system excitability or a decrease of the cerebellar inhibition exerted upon the vestibular nuclei, and (2) an intermittently appearing increase (VOR gain between 1 and 1.3) during brief periods. The latter finding, not related to pressure, was interpreted as the expression of an underwater-adapted mode that may developed in professional divers submitted to the intensive use of magnifying diving-optical systems.
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PMID:Alterations of the human vestibulo-ocular reflex in a simulated dive at 62 ATA. 95 20

The effects of air, helium-oxygen (6.4 ATA), and ethyl alcohol (40% by volume at a dose of 1.5 ml/kg body weight) were examined on the gain, number of beats, and phase lag of the vestibular ocular reflex (VOR) by means of electronystagmography (n = 7). It was found that hyperbaric air and alcohol, both alone and in combination, produced approximately the same increase in the velocity of the slow phase component of the nystagmus, thereby elevating the gain of the system to unity. Hyperbaric helium-oxygen did not influence the gain. These findings suggest that nitrogen nacrosis differentially impairs the system controlling the VOR. It is proposed that this impairment may help to explain the disorientation sometimes associated with nitrogen narcosis.
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PMID:Nitrogen narcosis and ethyl alcohol increase the gain of the vestibular ocular reflex. 273 65

To investigate the mechanism of barotrauma to the inner ear, we used electrophysiologic methods to evaluate guinea pigs exposed to such trauma, and compared the findings with those observed by scanning electron microscopy (SEM). Guinea pigs with good Preyer's reflexes were studied. In those animals that showed a loss of or decrease in Preyer's reflexes and/or nystagmus following exposure to an increase and decrease in pressures in a high-pressure chamber, we measured compound action potentials (CAPs) and cochlear microphonics (CMs) 7-11 days after the exposure. The pressure was increased from 1 ATA to 2 ATA over 30 sec and maintained for 10 min, then pressure was decreased to 1 ATA over 30 sec. Specimens obtained from animals in which CAPs and CMs could be measured were prepared for SEM examination. CAPs and CMs were measured at decreasing 5 dB increments to the visual threshold level of detection with tone bursts at 1, 2, 4 and 8 kHz. Based on the CAPs measured 7-11 days after exposure, guinea pigs were divided into two groups by CAP thresholds, those with severe damage and those with mild damage. None of the animals showed moderate damage. The group with high CAP thresholds showed severe damage to hair cells on SEM, while the group with low CAP thresholds showed no specific morphological abnormalities on SEM. It appeared that some guinea pigs with normal SEM findings following barotrauma to the inner ear did not achieve complete recovery of hearing. From these results, it was speculated that some animals had sustained reversible damage in the mild group and that these animals had recovered from moderate damage. The elevation of CMs was usually not high compared to that of CAPs in the high frequency area, and 4 animals showed CAP and CM separation above 30 dB at 8 kHz. These findings suggested that the group with severe damage exhibited multiple patterns of injury.
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PMID:[Electrophysiological study of inner ear barotrauma in guinea pigs; comparison with scanning electron microscopic findings]. 910 43