The growth hormone / insulin-like growth factor-1 (GH/IGF-1) pathway of the somatotropic axis is the major controller for growth rate and body size in vertebrates, but the effect of selection on the expression of GH/IGF-1 somatotropic axis genes and their association with body size and growth performance in farm animals is not fully understood. We analyzed a time series of expression profiles of GH/IGF-1 somatotropic axis genes in two chicken breeds, the Daweishan mini chickens and Wuding chickens, and the commercial Avian broilers hybrid exhibiting markedly different body sizes and growth rates. We found that growth rate and feed conversion efficiency in Daweishan mini chickens were significantly lower than those in Wuding chickens and Avian broilers. The Wuding and Daweishan mini chickens showed higher levels of plasma GH, pituitary GH mRNA but lower levels of hepatic growth hormone receptor (GHR) mRNA than in Avian broilers. Daweishan mini chickens showed significantly lower levels of plasma IGF-1, thigh muscle and hepatic IGF-1 mRNA than did Avian broilers and Wuding chickens. These results suggest that the GH part of the somatotropic axis is the main regulator of growth rate, while IGF-1 may regulate both growth rate and body weight. Selection for growth performance and body size have altered the expression profiles of somatotropic axis genes in a breed-, age-, and tissue-specific manner, and manner, and alteration of regulatory mechanisms of these genes might play an important role in the developmental characteristics of chickens.

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Anesthetics are an indispensable prerequisite for surgical intervention and pharmacological animal studies. The objective of present study was to optimize the dose of ketamine (K) and xylazine (X) along with atropine sulfate (A) in order to achieve surgical tolerance in BALB/c mice. Several doses of ketamine (100, 150, 200 mg/kg) and xylazine (10, 15, 20 mg/kg) were mixed and combination of nine doses (K/X: 100/10, 100/15, 100/20, 150/10, 150/15, 150/20, 200/10,200/15,200/20) were evaluated (n=9 per combination). A constant dose of atropine (0.05 mg/kg) was also used to counter side effect. Timerelated parameters were evaluated on the basis of reflexes. KX at dose 200/20 mg/kg produced surgical tolerance in all nine mice with duration 55.00±6.87 minutes. The induction time 0.97±0.09 minutes, sleeping time 90.67±5.81 minutes and immobilization time (102.23±6.83 minutes) were significantly higher than all combination. However, this combination was considered unsafe due to 11 % mortality. While, KX at dose 200/15 mg/kg results in none of the mortality, so was considered as safe. Moreover, this combination produces surgical tolerance in 89 % mice with duration (30.00±7.45 minutes). It was concluded that KX at dose 200/15 mg/kg along with atropine 0.05 mg/kg is safe for performing surgical interventions in BALB/c mice.

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