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Mean F (mean + f)

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Life Sciences100%

Selected Abstracts

Genetic diversity and population structure of indigenous yellow cattle breeds of China using 30 microsatellite markers

ANIMAL GENETICS, Issue 6 2007
G. X. Zhang
Summary Twenty-seven domesticated yellow cattle breeds of China and three introduced cattle breeds were analysed by means of 30 microsatellite markers to determine the level of genetic variation within and among populations as well as the population structure. In all, 480 microsatellite alleles were observed across the 30 breeds with the mean number of alleles per locus of 9.093 for native breeds and 6.885 for the three introduced breeds. Mean F -statistics (0.08) for Chinese native cattle breeds implied that 92% of the total genetic variation was from genetic differentiation within each breed and 8% of the genetic variation existed among breeds. A phylogenetic tree was constructed based on Nei's genetic distances, and three clusters were obtained. According to the tree, the three introduced breeds were distinct from the 27 native breeds. The indigenous cattle breeds were divided into two clusters, one cluster including five humpless breeds and the other cluster containing 22 humped breeds. This study identifies multiple origins of yellow cattle of China from Bos taurus and Bos indicus. Furthermore, population structure analysis implies that there are possibly five independent original domestications for yellow cattle in China. Four of five origins were four different Bos indicus types, mainly in areas of the Chang Jiang, the Zhu Jiang River basin, the Yellow River and the Huai River basin. The other origin was for Bos taurus type of Mongolian descent, mainly located in Northwestern China, the Mongolian plateau and Northeastern China or north of the Great Wall. [source]

Variation in fecal testosterone levels, inter-male aggression, dominance rank and age during mating and post-mating periods in wild adult male ring-tailed lemurs (Lemur catta)

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 12 2007
L. Gould
Abstract In primate species exhibiting seasonal reproduction, patterns of testosterone excretion in adult males are variable: in some species, peaks correlate with female receptivity periods and heightened male,male aggression over access to estrous females, in others, neither heightened aggression nor marked elevations in testosterone have been noted. In this study, we examined mean fecal testosterone ( f,T) levels and intermale aggression in wild adult male ring-tailed lemurs residing in three groups at Beza Mahafaly Reserve, Madagascar. Results obtained from mating and post-mating season 2003 were compared to test Wingfield et al. [1990. Am Nat 136:829,846] "challenge hypothesis", which predicts a strong positive relationship between male testosterone levels and male,male competition for access to receptive females during breeding season. f,T levels and rates of intermale aggression were significantly higher during mating season compared to the post-mating period. Mean f,T levels and aggression rates were also higher in the first half of the mating season compared with the second half. Number of males in a group affected rates of intermale agonism, but not mean f,T levels. The highest-ranking males in two of the groups exhibited higher mean f,T levels than did lower-ranking males, and young males exhibited lower f,T levels compared to prime-aged and old males. In the post-mating period, mean male f,T levels did not differ between groups, nor were there rank or age effects. Thus, although male testosterone levels rose in relation to mating and heightened male,male aggression, f,T levels fell to baseline breeding levels shortly after the early mating period, and to baseline non-breeding levels immediately after mating season had ended, offsetting the high cost of maintaining both high testosterone and high levels of male,male aggression in the early breeding period. Am. J. Primatol. 69:1325,1339, 2007. © 2007 Wiley-Liss, Inc. [source]

Development of respiratory control instability in heart failure: a novel approach to dissect the pathophysiological mechanisms

THE JOURNAL OF PHYSIOLOGY, Issue 1 2006
Charlotte H. Manisty
Observational data suggest that periodic breathing is more common in subjects with low F, high apnoeic thresholds or high chemoreflex sensitivity. It is, however, difficult to determine the individual effect of each variable because they are intrinsically related. To distinguish the effect of isolated changes in chemoreflex sensitivity, mean F and apnoeic threshold, we employed a modelling approach to break their obligatory in vivo interrelationship. We found that a change in mean CO2 fraction from 0.035 to 0.045 increased loop gain by 70 ± 0.083% (P < 0.0001), irrespective of chemoreflex gain or apnoea threshold. A 100% increase in the chemoreflex gain (from 800 l min,1 (fraction CO2),1) resulted in an increase in loop gain of 275 ± 6% (P < 0.0001) across a wide range of values of steady state CO2 and apnoea thresholds. Increasing the apnoea threshold F from 0.02 to 0.03 had no effect on system stability. Therefore, of the three variables the only two destabilizing factors were high gain and high mean CO2; the apnoea threshold did not independently influence system stability. Although our results support the idea that high chemoreflex gain destabilizes ventilatory control, there are two additional potentially controversial findings. First, it is high (rather than low) mean CO2 that favours instability. Second, high apnoea threshold itself does not create instability. Clinically the apnoea threshold appears important only because of its associations with the true determinants of stability: chemoreflex gain and mean CO2. [source]

Variation in fecal testosterone levels, inter-male aggression, dominance rank and age during mating and post-mating periods in wild adult male ring-tailed lemurs (Lemur catta)

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 12 2007
L. Gould
Abstract In primate species exhibiting seasonal reproduction, patterns of testosterone excretion in adult males are variable: in some species, peaks correlate with female receptivity periods and heightened male,male aggression over access to estrous females, in others, neither heightened aggression nor marked elevations in testosterone have been noted. In this study, we examined mean fecal testosterone ( f,T) levels and intermale aggression in wild adult male ring-tailed lemurs residing in three groups at Beza Mahafaly Reserve, Madagascar. Results obtained from mating and post-mating season 2003 were compared to test Wingfield et al. [1990. Am Nat 136:829,846] "challenge hypothesis", which predicts a strong positive relationship between male testosterone levels and male,male competition for access to receptive females during breeding season. f,T levels and rates of intermale aggression were significantly higher during mating season compared to the post-mating period. Mean f,T levels and aggression rates were also higher in the first half of the mating season compared with the second half. Number of males in a group affected rates of intermale agonism, but not mean f,T levels. The highest-ranking males in two of the groups exhibited higher mean f,T levels than did lower-ranking males, and young males exhibited lower f,T levels compared to prime-aged and old males. In the post-mating period, mean male f,T levels did not differ between groups, nor were there rank or age effects. Thus, although male testosterone levels rose in relation to mating and heightened male,male aggression, f,T levels fell to baseline breeding levels shortly after the early mating period, and to baseline non-breeding levels immediately after mating season had ended, offsetting the high cost of maintaining both high testosterone and high levels of male,male aggression in the early breeding period. Am. J. Primatol. 69:1325,1339, 2007. © 2007 Wiley-Liss, Inc. [source]