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  • 1990-1994  (2)
  • Acute effect  (1)
  • Cysteamine  (1)
  • 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
    ISSN: 1432-1246
    Keywords: Human skin ; Vibratory sensation Vibration exposure ; Threshold shift ; Acute effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A new, self-recording, vibratory sensation meter measures temporary threshold shifts of vibratory sensation (TTSv) on a finger tip. After exposure to hand-transmitted vibration with exposure frequencies 63 Hz, 200 Hz and 500 Hz, and levels of acceleration 1 g, 2 g, 4 g and 8 g, fingertip measurements were obtained. Temporary threshold shift immediately after the vibratory exposure (TTSVv,0) was estimated for each exposure from the regression analysis by approximation of an exponential function. Time constant (tc) was also estimated at the same time by the analysis. The coefficients of determination were large. Thus, the fit of the exponential function is very good for each exposure. The tc corresponds to the recovering velocity of the temporary shift and implies the half-life period of TTSv. These parameters enable us to examine more generally the relationships of TTSv to the characteristics of exposure vibration, subject and other conditions. On this basis, the estimated TTSv,0 and tc were used to examine the dependency of TTSv on the characteristics of the exposure vibration and the subject. The most effective frequency under the level of 4 g is thought to be between 200 Hz and 500 Hz. TTSv,0 of each subject proportionally increased with power of acceleration. The coefficient of determination on regression analysis was large. This result enables us to estimate TTSv,0 at an arbitrary level of acceleration by use of a regression equation derived from experimental data.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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