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At least 415 records · Page 23Linked to original sources
PubMed1981

[Studies on physiological changes due to prolonged standing posture (author's transl)].

In relation to static work, an experiment has been made with intention to examine the influence of maintaining standing posture for a long time on human body. The results are as follows: 1) Fluctuation waves of the body weight were classified into two types: type A, a higher amplitude with slow waves, and type B, a lower amplitude with rapid waves. 2) Spectrum analysis on the fluctuation waves of the body weight indicated that type A showed a gradual lowering in relative power in proportion to the wave frequency with the lapse of time, but type B showed a peak in power at around 10 Hz and it increased with the lapse ot time. 3) Action potentials from the left and right gastrocnemium muscles decreased almost simultaneously with the lapse of time in type A with a significant correlation between the left and right, while in type B there was no certain relation between the left and right as well as with the lapse of time. 4) The body weight tended to concentrate on the heel of the dominant foot with the lapse of time. 5) The brain alpha waves increased with the lapse of time, accompanying with a periodical change. 6) In the relationship between the brain alpha waves and the action potential from the gastrocnemius muscle, there was the same cycle at about 1.5 Hz and no change was seen with the lapse of time. 7) There was no significant change in the function of maintaining concentration (TAF). These results suggest that: 1) Besides the reflex mechanism existed as physiological tremor through the stretch reflex loop in maintaining a standing posture, there is a regulation mechanism working to keep balance of the body through the visual organ. 2) The standing posture itself is not always a big stress factor to human body. 3) On the stress by monotonous work, it is necessary to analyse the physiological and psychological load on human body.

Adolescent↗
PubMed2001

[Study of noninvasive intracranial pressure monitoring by bioelectric impedance method].

The changes of intracranial components and corresponding brain impedance were analyzed while intracranial pressure was increasing, and the relation of intracranial pressure pulse wave and brain impedance pulse wave were discussed. A theory of noninvasive intracranial pressure monitoring by bioelectric impedance was put forward. The result of primary experiment suggested that the theory be feasible.

Animals↗
PubMed1994

A square signal wave method for measurement of brain extra- and intracellular water content.

Brain tissue electrical impedance is a commonly used method to evaluate the dynamics of brain edema. We have found the square wave impedance method simpler and more cost-effective than the currently used sine wave impedance method. This square wave method avoids the necessity for expensive frequency control and amplitude-phase measuring devices as well as simplifying on-line data processing. In our experiments the electrical impulse was generated by a pulse generator of Macintosh data acquisition system. The signal (I = 11 muA, t = 2-20 ms) was delivered every 2-3 s external electrodes of a tetrapolar system through a specially designed isolation-calibration device. This electrode system was inserted into the cerebral cortex of experimental animals (rat). The cerebral cortex was found to have linear electrical properties in the 5-30 muA range. Our impedance measurement system was tested in calibration trials, and showed system reliability and accuracy. The system was also tested in pilot experiments, in vivo, in a rat brain osmotic edema model.

Animals↗
PubMed1992

Electrophysiological study on hydranencephaly.

An electrophysiological study was performed on 2 children with hydranencephaly diagnosed by CT and/or MRI. Case 1 was a 4-month-old boy who had no rostral tissues above the midbrain. Case 2 was a 5-year-old boy in whom CT showed retention of the thalamus. Short latency somatosensory evoked potentials (SSEP) in both cases exhibited the absence of cortical activity (N1 and P4) with the preservation of waves of brain stem origin. However, in case 1, wave component No was not observed, while No was seen in case 2. It was postulated, thus, that the No component of SSEP on median nerve stimulation in children, which corresponds to N16 in adults, may originate in the thalamus.

Child, Preschool↗
PubMed1995

Working memory and preparation elicit different patterns of slow wave event-related brain potentials.

Some event-related brain potential (ERP) studies of working memory have used delayed match-to-sample designs in which a stimulus (S1) is held in memory for comparison with a subsequent stimulus (S2). During the S1-S2 interval, ERP slow negatives varied with both the type and amount of material held in working memory. One interpretation is that these slow waves index working memory operations. An alternative explanation is that they only reflect general preparatory processing for the response to S2. To decide between these explanations, we used two visual processing tasks that required similar preparation for S2. In one task, visual memory rehearsal operations were required. During the S1-S2 interval, there were clear differences between the amplitudes, topographies, and the effect of information load on the slow waves in two tasks, thus ruling out preparation only as an explanation.

Adult↗
PubMed1992

Inconsistencies in the correlation between loss of brain stem auditory evoked response waves and postoperative deafness.

This case underscores the difficulty of predicting postoperative hearing status from brain stem auditory evoked response (BAER) monitoring when wave I is preserved and all later waves are lost. During an operation involving the base of the skull, sudden and irreversible loss of all BAER waves beyond wave I occurred unilaterally. Wave I was preserved, with reduced amplitude and minimal latency shift. There was no permanent postoperative hearing sensitivity loss or speech discrimination loss.

Adolescent↗
PubMed2003

Application of shock waves as a treatment modality in the vicinity of the brain and skull.

OBJECT: Shock waves have not previously been used as a treatment modality for lesions in the brain and skull because of the lack of a suitable shock wave source and concerns about safety. Therefore, the authors have performed experiments aimed at developing both a new, compact shock wave generator with a holmium:yttrium-aluminum-garnet (Ho:YAG) laser and a safe method for exposing the surface of the brain to these shock waves. METHODS: Twenty male Sprague-Dawley rats were used in this study. In 10 rats, a single shock wave was delivered directly to the brain, whereas the protective effect of inserting a 0.7-mm-thick expanded polytetrafluoroethylene (ePTFE) dural substitute between the dura mater and skull before applying the shock wave was investigated in the other 10 rats. Visualizations on shadowgraphy along with pressure measurements were obtained to confirm that the shock wave generator was capable of conveying waves in a limited volume without harmful effects to the target. The attenuation rates of shock waves administered through a 0.7-mm-thick ePTFE dural substitute and a surgical cottonoid were measured to determine which of these materials was suitable for avoiding propagation of the shock wave beyond the target. CONCLUSIONS: Using the shock wave generator with the Ho:YAG laser, a localized shock wave (with a maximum overpressure of 50 bar) can be generated from a small device (external diameter 15 mm, weight 20 g). The placement of a 0.7-mm-thick ePTFE dural substitute over the dura mater reduces the overpressure of the shock wave by 96% and eliminates damage to surrounding tissue in the rat brain. These findings indicate possibilities for applying shock waves in various neurosurgical treatments such as cranioplasty, local drug delivery, embolysis, and pain management.

Animals↗
PubMed2006

Measurement of blast wave by a miniature fiber optic pressure transducer in the rat brain.

Exposure to blast wave that is generated during an explosion may result in brain damage and related neurological impairments. The aim of this study was to investigate pressure changes induced by exposure to blast inside the rat brain. For intracranial pressure measurement we used a miniature optic fiber sensor (o.d. 550 microm) with a computer recording system. The sensor was placed in the third cerebral ventricle of anesthetized rats exposed to 40 kPa blast wave in a pneumatic-pressure driven shock tube. Short pressure waves lasting several ms were detected inside the brain with the magnitude that might result in nervous tissue damage.

Animals↗
PubMed1993

A comparison of N1 of the whole nerve action potential and wave i of the brain-stem auditory evoked response in Mongolian gerbil.

The present study seeks to provide empirical support for the assumption that wave i of the gerbil brain-stem auditory evoked response (BAER) corresponds to N1 of the whole nerve action potential (WNAP) by comparing the latency and amplitude of BAER wave i and WNAP N1. Fourteen 3-month old gerbils were anesthetized with Nembutal and Urethane-Dial. Normothermia was maintained by a homeothermic blanket system. BAERs were recorded with Grass needle electrodes placed subdermally. The WNAP was recorded with a silver wire placed in the round window niche. WNAP and BAER were simultaneously recorded with a passband of 100-10,000 Hz. Responses consisted of 500 sweeps, and two responses were obtained for each condition. Clicks were 25-microseconds electrical pulses. Tonebursts were shaped with a Hanning window, with 1-ms rise and fall times. Toneburst frequencies included 1, 2, 4, 8, and 16 kHz. For each stimulus, responses were obtained at levels of 30, 50, 70, and 90 dB pSPL. SPL was measured near the entrance to the ear canal with an Etymotic ER-7C probe microphone. Dependent variables were the latency and amplitude of N1 of the WNAP and wave i of the BAER. The latencies of wave i and N1 were very similar. Mean (across animal) latencies of N1 and wave i were within 70 microseconds for all six stimuli (clicks, tonebursts) and all four levels. Latency/intensity function slopes for N1 and wave i were also very similar, with both dependent variables showing an increasing latency/intensity function slope with decreasing toneburst frequency. The N1/wave i amplitude ratio was computed.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1980

Brain stem evoked response (wave V) latency to filtered pulses.

BSER-Wave v latencies were obtained to filtered pulses centered at .25, .5, 1, 2, 4, and 6.3 kc/s presented monaurally at a rate of 10/sec to 7 normal-hearing Ss, aged 20-29 yrs, at 50, 40, 30, and 20 db HL. Wave V latencies were measured from the first compression of the stimulus waveform. BSERs were extractable at all frequency and intensity combinations except that they were not recoverable from some Ss at 20 db HL at .25 and .5 kc/s. A decrease in frequency and intensity caused a systematic increase in Wave V latency and a depression in waveform amplitude. Wave V latency shifts due to frequency and intensity changes generally agreed with the results of other investigators.

Acoustic Stimulation↗
PubMed1986

A case of ataxic diplegia, mental retardation, congenital nystagmus and abnormal auditory brain stem responses showing only waves I and II.

A three-year-old boy who had ataxic diplegia, mental retardation, horizontal pendular nystagmus with head nodding and abnormal auditory brain stem responses showing only waves I and II was presented. His clinical features coincided with recent reports in the Japanese literature of cases of a new syndrome that is congenital in origin and seen only in boys.

Auditory Pathways↗