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  • 1
    ISSN: 1432-1351
    Keywords: Circadian rhythm ; Suprachiasmatic nucleus ; Cysteamine ; Somatostatin ; Brain slice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Somatostatin is synthesized in the suprachiasmatic nucleus (SCN), a circadian pacemaker in mammals. To explore the functional significance of somatostatin in the circadian system, we examined rhythms of rat locomotor activity and electrical firing rate of SCN neurons in the brain slice after temporal depletion of somatostatin levels in the SCN. Intraperitoneal administration of cysteamine (200 mg/kg), a somatostatin depletor, significantly reduced somatostatin level in the in vivo SCN 5 min after injection and kept low level as long as 3 to 4 days. This administration, on the other hand, induced significant phase advances of about 51 min in the subsequent free-running rhythm of locomotor activity of the rat. A marked phase advance in the circadian rhythm of firing rate in the SCN was also observed after administration of cysteamine in coronal hypothalamic slices. These persistent phase shifts after administration of a somatostatin depletor may suggest that the change of somatostatin level in the SCN have a feedback influence on the circadian pacemaker.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 68 (1996), S. 255-261 
    ISSN: 1432-1246
    Keywords: Key words Vibratory sensation ; Local vibration exposure ; Temporary threshold shift ; Broad-band vibration ; Vibration syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eight healthy subjects were exposed to three 1/3 octave-band vibrations (63, 200, and 500 Hz) by hand clasping a vibrated handle in a soundproof and thermoregulated room. The vibratory sensation threshold at 125 Hz was measured before and after the vibration exposure at an exposed fingertip. According to a preceding study, we first determined the relationship between the acceleration of the vibration and the temporary threshold shift of vibratory sensation immediately after the vibratory exposure (TTSv,0) induced by 1/3 octave-band vibration. We then measured TTSv after the exposure to a composite vibration composed of two 1/3 octave-band vibrations that might induce an equal magnitude of TTSv,0 on the basis of the above relationship. The TTSv,0 induced by the composite vibration was not larger than the TTSv,0 induced by the component vibrations. This result suggests that the component of the vibration inducing the largest TTSv,0 determines the TTSv,0 by broad-band random vibration.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 69 (1996), S. 45-52 
    ISSN: 1432-1246
    Keywords: Key words Vibratory sensation ; Vibration exposure ; Threshold shift ; Temporary threshold shift ; Gripping force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract ⋅Objective This study examines the effect of the force with which a vibrating handle is gripped on the temporary threshold shift of vibratory sensation (TTSv) induced by hand-arm vibration. ⋅  Methods Six healthy subjects gripped a handle vibrating with a 1/3 octave-band vibration, with a central frequency of 200 Hz and an intensity of 39.2 m/s2. Exposure was for 1 min and 10 min, respectively. Gripping forces for the 1-min exposure were 5 N, 10 N, 40 N and 80 N, respectively, with 0 N push-pull force. Gripping forces for the 10-min exposure were the same as for the 1-min exposure, but omitting 80 N. The vibratory sensation threshold at 125 Hz was measured before and after exposure of an exposed fingertip to vibration. The differences measured determine TTS v,t at time t. TTS v,t determines TTSv,0, that is, the temporary threshold shift of vibratory sensation immediately after exposure to vibration according to the estimate made on the basis of the preceding study. The same experimental conditions were repeated 3 times on different days in a soundproof and thermoregulated room. ⋅  Results Our findings show that TTSv increases significantly with increasing gripping force. We also determined the quantitative relationships between TTSv,0 and gripping force as described by the equation where k f and c f are constants and F is gripping force. ⋅  Conclusion This study revealed the importance of ergonomic design in reducing the force with which a vibrating handle is gripped to prevent an adverse effect of local vibration. The equation devised may help in the quantitative assessment of the effect of reduced gripping force.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 68 (1996), S. 255-261 
    ISSN: 1432-1246
    Keywords: Vibratory sensation ; Local vibration exposure ; Temporary threshold shift ; Broad-band vibration ; Vibration syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eight healthy subjects were exposed to three 1/3 octave-band vibrations (63, 200, and 500 Hz) by hand clasping a vibrated handle in a soundproof and thermoregulated room. The vibratory sensation threshold at 125 Hz was measured before and after the vibration exposure at an exposed fingertip. According to a preceding study, we first determined the relationship between the acceleration of the vibration and the temporary threshold shift of vibratory sensation immediately after the vibratory exposure (TTSv, 0) induced by 1/3 octave-band vibration. We then measured TTSv after the exposure to a composite vibration composed of two 1/3 octave-band vibrations that might induce an equal magnitude of TTSv, 0 on the basis of the above relationship. The TTSv, 0 induced by the composite vibration was not larger than the TTSv, 0 induced by the component vibrations. This result suggests that the component of the vibration inducing the largest TTSv, 0 determines the TTSv, 0 by broad-band random vibration.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 64 (1993), S. 499-502 
    ISSN: 1432-1246
    Keywords: Salivary cortisol ; Circadian rhythm ; Shiftwork
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To examine the validity of salivary cortisol for monitoring circadian rhythm variation in adrenal activity during shiftwork, saliva and blood samples were collected at 4-h intervals in experimental short-term shifts, i.e., day (work 0830–1600 h; sleep 0030–0800 h), evening (work 1630–2400 h; sleep 0430–1200 h), and night (work 0030–0800 h; sleep 1230–2000 h) shifts over 2 days. Cortisol levels, determined by radioimmunoassay, and the circadian profiles of saliva and sera were compared. The salivary cortisol showed relatively low levels, the 2-day mean value being 3.1%–3.3% that of serum total cortisol through all shifts. Significant differences in the serum to saliva cortisol ratios were noted among shifts and subjects. When expressed as a relative percentage of a 2-day mean value, however, salivary cortisol paralleled the modified circadian profiles of serum total cortisol of the evening and night shifts, with no significant time lag and no difference in magnitude. The cosinor analysis supported this finding. Thus, salivary cortisol appears to be an excellent measure for monitoring circadian rhythm variation in adrenal activity in healthy individuals during shiftwork.
    Type of Medium: Electronic Resource
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