Circadian variation of rectal temperature in newborn sheep.

摘要: In adult animals, body temperature shows a 24 h rhythm that is endogenously generated. We examined the existence of rhythms in 10 newborn sheep. Four newborns, aged 5 to 28 days were kept with their mothers under nycthemeral conditions, and remaining 6 lambs, 21 43 days, constant light from day 3 after birth. Experiments performed both groups lambs laboratory. Additional experiments while they pen rule out artifacts due manipulation or artificial feeding. During done laboratory, blindfolded canvas sling fed baby formula approximately every four hours (lambs conditions) hour (constant lambs). Lights on room during whole experiment. Temperature was maintained at 18 +/- 0.1 degrees C (mean SEM). pen, animals remained mother not controlled. all experiments, rectal hourly measured for thermocouple inserted lamb's rectum connected Philipp Schenk digital recorder. Lambs conditions show variation mean (t degree) period h, fits cosine function (P less than 0.001): Rectal t degree (degree C) = 40.6 + 0.4 cos [15 (t-16.22)]. The mesor 40.6, amplitude 0.4, acrophase expressed 16.22 (n 4). independently whether measurements laboratory pens. acrophases varied widely these when synchronized so theta 2400, showed equation 39.5 0.18 (t-0.23)]. presence its persistence suggests observed lamb true circadian rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)