Substrate utilization and regulatory mechanisms of metabolism were studied in migratory garden warblers by measuring plasma levels of glucose, free fatty acids (FFAs), beta-hydroxybutyrate, insulin and glucagon in response to oral glucose loads. Three different physiological states were examined: (a) the autumnal migratory period on a high and (b) on a fasted low body mass level, and (c) the postmigratory period with low body mass. Glucose tolerance was better in the postmigratory lean than fat condition. However, total food deprivation of 5-7 days with fat birds reaching their lean body mass further reduced the glucose utilization rate. Initial levels of FFAs were highest in the starved, intermediate in the fat and lowest in the lean condition. Changes in plasma FFAs during glucose tolerance tests were opposite to those of the glucose levels. Ten minutes after the glucose load plasma glucagon levels decreased and insulin increased. These effects were larger in the fat than in the postmigratory lean condition. There were no differences between sexes. It appears that during premigratory and migratory periods glucose utilization may be inhibited by a more favorable oxidation of fatty acids as would be predicted by the glucose fatty acid cycle. However, the inhibition of glucose utilization seems to be counterregulated by stronger responses of insulin and glucagon. These results may be important also in the consideration of food selection during premigratory periods and refueling abilities of birds crossing ecological barriers.
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M. T. JONES, F. R. BRUSH, and R. L. B. NEAME
SUMMARY
Corticosterone was administered intraperitoneally to rats, and the consequent changes in plasma corticosterone concentration traced. Stress (sham bilateral adrenalectomy) was applied at various times when the plasma corticosterone concentration was changing at different rates, and it was shown that there was a critical rate of rise of plasma corticosterone concentration of about 1·3 μg/100 ml plasma/min in excess of which the stress response was inhibited. Rates of rise less than this did not affect the stress response. A state of ' saturation' of the control system was also demonstrated to result from high plasma corticosterone concentrations when the response to stress was not inhibited as above. A model of the system is suggested to explain these and other data.
J D Bailey, J G Berardinelli, T E Rocke, and R A Bessen
that ranges from 8.5 to 9 weeks ( Bessen & Marsh 1992 , Bartz et al . 2000 , 2005 ). In order to determine whether prion-induced alteration of pancreatic function is related to deposition of PrP Sc within the pancreas, we measured fasted and non-fasted
R. J. Reiter, I. Sabry, M. Nordio, M. K. Vaughan, and S. Migliaccio
ABSTRACT
The onset of cessation of oestrous cyclicity and associated organ and hormonal changes were compared in random-bred (RB) and inbred (IB) female Syrian hamsters kept either under short days (8 h light:16 h darkness; 8L:16D) or long days (14L:10D) and given daily afternoon injections of 25 μg melatonin. In response to short-day treatment, 100% of the IB hamsters exhibited vaginal acyclicity within 35 days; by comparison, none of the RB animals were acyclic at this time. The IB hamsters also exhibited other changes associated with exposure to short days, including increased body weight, enlarged ovaries, regressed uteri, elevated pituitary concentrations of FSH, and depressed pituitary and plasma concentrations of prolactin. At this time, only the pituitary FSH levels were increased in the RB animals kept under the same short-day conditions.
In a second experiment, RB and IB female Syrian hamsters were maintained under long days (14L:10D) and the rate of reproductive regression in response to daily afternoon injections of melatonin was compared. After 8 weeks of melatonin injections, 80% of the IB females were anoestrous, while all RB hamsters were still exhibiting 4-day oestrous cycles. Other changes associated with melatonin administration in the IB females included a marked drop in uterine weight and a depression in pituitary and plasma prolactin levels. The RB hamsters, although they were all still cyclic after 8 weeks, had increased body and ovarian weights, increased pituitary concentrations of FSH, and lower pituitary and plasma prolactin levels.
The results show that the IB strain of Syrian hamster, compared with the RB strain, responded more quickly with vaginal acyclicity to both exposure to short days and daily injections of melatonin. On the other hand, the IB hamsters responded more slowly in terms of oestrous acyclicity to melatonin injections than to treatment with short photoperiod.
Journal of Endocrinology (1989) 120, 489–496
Toya M Albury-Warren, Veethika Pandey, Lina P Spinel, Michal M Masternak, and Deborah A Altomare
of Akt3 was inconsequential. Conversely, haplodeficiency of Akt1 in Ak t2 −/− mice resulted in a more severe diabetic phenotype, characterized by fed and fasted hyperglycemia, glucose intolerance, insulin resistance, and hyperinsulinemia
Tetsuya Ito, Hnin ThidarMyint, Takahiro Murata, Hiroaki Inoue, Roel Mata Neyra, and Hideto Kuwayama
et al. 2001 ). In pigs, plasma PYY levels increase after meal intake ( Adrian et al. 1987 ), plasma ghrelin levels rise during fasting ( Salfen et al. 2003 , Govoni et al. 2005 ). In addition, ghrelin infusion has also been shown to increase
Hideyuki Takahashi, Yohei Kurose, Muneyuki Sakaida, Yoshihiro Suzuki, Shigeki Kobayashi, Toshihisa Sugino, Masayasu Kojima, Kenji Kangawa, Yoshihisa Hasegawa, and Yoshiaki Terashima
ghrelin on insulin secretion have not been examined. On the other hand, blood ghrelin levels are affected by nutritional states. Plasma ghrelin levels are increased after fasting and reduced after feeding in humans ( Ariyasu et al. 2001
F Lucio-Oliveira and C R Franci
food ad libitum , those in group II were fasted for 48 h with access to water, and the rats in group III were refed during 2 h with standard food after 48 h of fasting. During the 3 days before the experiment began, the animals were treated with
Sihan Lv, Xinchen Qiu, Jian Li, Jinye Liang, Weida Li, Chao Zhang, Zhen-Ning Zhang, and Bing Luan
glucose and lipid metabolism in response to hormonal signals. Dedicated transcription regulatory network is involved in the hepatic response to fasting. During the fasted state, one of the major circulating hormones required for liver function is glucagon
Bethany P Cummings, Andrew A Bremer, Timothy J Kieffer, David D'Alessio, and Peter J Havel
order: 1) during saline treatment and 2) during dexamethasone treatment (0.25 mg/kg per day i.m. for 7 days). The studies were performed at least 21 days apart. Animals received treatment for 7 days and then were fasted overnight and underwent a feeding
