Exposure to a short photoperiod improved the thermogenic capacity, and cold resistance of Djungarian hamsters increased respiratory power their brown adipose tissue. long caused decrease in measurements. This thermotropic action was detectable only during late summer fall. A similar response could be elicited by implanting with melatonin, indicating that pineal may involved photoperiodic control thermoregulatory effectors.

Evidence has recently begun to accumulate that photoperiodic responses of mammals and birds may affect the control energy balance thermoregulation. Exposure short photoperiod can lower set point for body temperature regulation in mammals, as well voluntarily selected ectothermic lizards. This decrease is accompanied by a reorganization circadian or ultradian rhythms temperature, particularly an increase periods spent at rest with minimum temperatures. Short also used environmental cue...

The Per1 and Per2 genes are components of the mammalian circadian clock. Mutations in these alter phase resetting response to a nocturnal light pulse, mutant mice known become arrhythmic constant darkness. We show that under conditions, exhibit robust activity rhythms as well body temperature with period length is less than 24 h. In mutants, both longer h light. mutants prolong their (tao) when illuminance increased, whereas shorten endogenous period. Additionally, authors pattern gene...

Abstract We investigated the influence of ambient temperature (T a ) and food availability on seasonal timing extent physiological responses to short photoperiod (SP), in particular daily torpor, Djungarian hamsters ( Phodopus sungorus ). Exposure cold = 5°C), relative warm T (23°C), resulted in:(1)a significant advance P < 0.05) first occurrence torpor among cold‐exposed (days 52–97 vs. days 83–99 SP); (2) higher 0.01) incidence (48% 20% torpid animals/day);(3) degree molt into winter...

Recent studies on mice with mutations in the Clock gene have shown that this mutation disrupts oestrus cyclicity and interferes successful pregnancy. In order to determine whether two other molecular components of main clock, namely period genes, Per1 Per2, an effect length oestrous cycle reproductive success, we used Per1- Per2-deficient females. We show although fecundity young adult Per mutant females does not differ from wild-type females, middle-aged are characterised by lower success...

Abstract In nature Siberian hamsters utilize the decrement in day length following summer solstice to implement physiological adaptations anticipation of forthcoming winter, but also exploit an intrinsic interval timer initiate recrudescence winter solstice. However, information is lacking on temporal dynamics natural photoperiod photoperiodically regulated genes and their relationship adaptations. To address this, male born maintained outdoors were sampled every month over course one year....

The purpose of the present studies using artificial light was to determine how timing and duration exposure influence light‐induced suppression pineal melatonin levels in hamsters. An 8‐min 0.186 μW/cm 2 cool white fluorescent caused a continued depression even when animals were returned darkness. In addition, gland does not appear change its sensitivity throughout night. A 20‐min 0.019 did significantly suppress during any time peak, whereas capable always suppressing melatonin....

The Djungarian hamster displays photoperiodic variations in gonadal size synchronized to the seasons by nightly secretion of pineal hormone melatonin. In short photoperiod (SP), gonads regress size, and circulating sex steroids levels decline. Thus, brain is subject seasonal both melatonin steroids. Tanycytes are specialized glial cells located ependymal lining third ventricle. They send processes either meninges or blood vessels medio-basal hypothalamus. Furthermore, they known locally...

Klante G, Brinschwitz T, Secci K, Wollnik F, Steinlechner S. Creatinine is an appropriate reference for urinary sulphatoxymelatonin of laboratory animals and humans. J. Pineal Res. 1997; 23:191–197. © Munksgaard, Copenhagen Abstract In our studies on diurnal 6‐sulphatoxymelatonin (aMT6s) rhythms in various species, we have sometimes obtained fluctuating patterns. most these, the volume individual urine fractions was not accurately measured because methodological problems. Here, report a...

Stress causes a rise in body temperature laboratory animals (stress-induced hyperthermia). However, the direct effect of common stressors animal research, i.e. transportation between holding and test rooms or isolation animals, on has not been investigated to its full extent. To address this question, it is important have reliable simple monitoring technique, which does induce stress itself. In present study, we stress-related changes F344/Hw rats after (1) moving cage within room, (2) from...

Torpor is a physiological state characterized by controlled lowering of metabolic rate and core body temperature, allowing substantial energy savings during periods reduced food availability or harsh environmental conditions. The hypothalamus coordinates homeostasis thermoregulation plays key role in directing torpor. We recently showed that mice lacking the orphan G protein-coupled receptor Gpr50 readily enter torpor response to fasting have now used these conduct microarray analysis...

The timing of growth in seasonal mammals is inextricably linked to food availability. This exemplified the Siberian hamster ( Phodopus sungorus ), which uses annual cycle photoperiod optimally programme energy expenditure anticipation fluctuations resources. During autumn, progressively minimised by physiological adaptations, including a 30% reduction body mass, comprising both fat and lean tissues. However, mechanistic basis this adaptation still unexplained. We hypothesised that hormone GH...