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- Brändström, Helge, et al.
(author)
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Autonomic nerve system responses for normal and slow rewarmers after hand cold provocation : effects of long-term cold climate training
- 2013
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In: International Archives of Occupational and Environmental Health. - : Springer-Verlag New York. - 0340-0131 .- 1432-1246. ; 86:3, s. 357-365
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Journal article (peer-reviewed)abstract
- PURPOSE: Differences among individuals concerning susceptibility to local cold injury following acute cold exposure may be related to function of the autonomic nervous system. We hypothesized that there are differences in heart rate variability (HRV) between individuals with normal or more pronounced vasoconstriction following cold exposure and that there is an adaptation related to prolonged cold exposure in autonomic nervous system response to cold stimuli.METHODS: Seventy-seven young men performed a cold provocation test, where HRV was recorded during cold hand immersion and recovery. Forty-three subjects were re-examined 15 months later, with many months of cold weather training between the tests. Subjects were analyzed as 'slow' and 'normal' rewarmers according to their thermographic rewarming pattern.RESULTS: For the 'pre-training' test, before cold climate exposure, normal rewarmers had higher power for low-frequency (P(LF)) and high-frequency (P(HF)) HRV components during the cold provocation test (ANOVA for groups: p = 0.04 and p = 0.005, respectively). There was an approximately 25 % higher P(HF) at the start in normal rewarmers, in the logarithmic scale. Low frequency-to-high frequency ratio (P(LF)/P(HF)) showed lower levels for normal rewarmers (ANOVA for groups: p = 0.04). During the 'post-training' cold provocation test, both groups lacked the marked increase in heart rate that occurred during cold exposure at the 'pre-training' setting. After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low-frequency and high-frequency HRV components. After winter training, the slow rewarmers showed reduced low-frequency power for some of the cold provocation measurements but not all (average total P(LF), ANOVA p = 0.05), which was not present before winter training.CONCLUSIONS: These HRV results support the conclusion that cold adaptation occurred in both groups. We conclude that further prospective study is needed to determine whether cold adaptation provides protection to subjects at higher risk for cold injury, that is, slow rewarmers.
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| 3. |
- Wright, Dominic, et al.
(author)
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Onset of Sexual Maturity in Female Chickens is Genetically Linked to Loci Associated with Fecundity and a Sexual Ornament
- 2012
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In: Reproduction in domestic animals. - : Blackwell Publishing. - 0936-6768 .- 1439-0531. ; 47:SI, s. 31-36
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Journal article (peer-reviewed)abstract
- Onset of sexual maturation is a trait of extreme importance both evolutionarily and economically. Unsurprisingly therefore, domestication has acted to reduce the time to sexual maturation in a variety of animals, including the chicken. In comparison with wild progenitor chickens [the Red Junglefowl (RJF)], domestic layer hens attain maturity approximately 20% earlier. In addition, domestic layers also possess larger combs (a sexual ornament), produce more eggs and have denser bones. A large quantitative trait loci (QTL) analysis (n = 377) was performed using an F2 intercross between a White Leghorn layer breed and a RJF population, with onset of sexual maturity measured and mapped to three separate loci. This cross has already been analysed for comb mass, egg production and bone allocation. Onset of sexual maturity significantly correlated with comb mass, whilst the genetic architecture for sexual maturity and comb mass overlapped at all three loci. For two of these loci, the QTL for sexual maturity and comb mass were statistically indistinguishable from pleiotropy, suggesting that the alleles that increase comb mass also decrease onset of sexual maturity.
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| 4. |
- Wright, Dominic, 1977-, et al.
(author)
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The genetic architecture of domestication in the chicken: effects of pleiotropy and linkage
- 2010
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In: Molecular Ecology. - Oxford : Blackwell Publishing Ltd. - 0962-1083 .- 1365-294X. ; 19, s. 5140-5156
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Journal article (peer-reviewed)abstract
- The extent of pleiotropy and epistasis in quantitative traits remains equivocal. In the caseof pleiotropy, multiple quantitative trait loci are often taken to be pleiotropic if theirconfidence intervals overlap, without formal statistical tests being used to ascertain ifthese overlapping loci are statistically significantly pleiotropic. Additionally, the degreeto which the genetic correlations between phenotypic traits are reflected in thesepleiotropic quantitative trait loci is often variable, especially in the case of antagonisticpleiotropy. Similarly, the extent of epistasis in various morphological, behavioural andlife-history traits is also debated, with a general problem being the sample sizes requiredto detect such effects. Domestication involves a large number of trade-offs, which arereflected in numerous behavioural, morphological and life-history traits which haveevolved as a consequence of adaptation to selective pressures exerted by humans andcaptivity. The comparison between wild and domestic animals allows the geneticanalysis of the traits that differ between these population types, as well as being ageneral model of evolution. Using a large F2 intercross between wild and domesticatedchickens, in combination with a dense SNP and microsatellite marker map, bothpleiotropy and epistasis were analysed. The majority of traits were found to segregate in11 tight ‘blocks’ and reflected the trade-offs associated with domestication. These blockswere shown to have a pleiotropic ‘core’ surrounded by more loosely linked loci. Incontrast, epistatic interactions were almost entirely absent, with only six pairs identifiedover all traits analysed. These results give insights both into the extent of such blocks inevolution and the development of domestication itself.
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