ORCID Profile
0000-0002-7796-5754
Current Organisations
University of St Andrews
,
Xelect Ltd
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Publisher: Cambridge University Press (CUP)
Date: 02-04-2012
DOI: 10.1017/S0007114512000396
Abstract: We investigated postprandial changes in transcript abundance following a single satiating meal in juvenile Atlantic salmon ( Salmo salar L.) (about 70 g body mass) following fasting for 1 week at 12°C. The expression of twenty-three growth-related genes was determined in fast myotomal muscle using quantitative real-time PCR at the following postprandial time points: − 12, 0, 1, 3, 6, 12, 24, 48 and 96 h. The gut was fullest 1–6 h after feeding and emptied within 48–96 h. IGF-I , MyoD1c , MRF4 and myf5 transcripts were sharply up-regulated within 1 h of refeeding and are promising candidate genes involved in a fast-response signalling system that regulates fish myotomal muscle growth. These genes clustered together with MyoD1b and suggest a coordinated regulation to favour resumption of myogenesis as an early response to feeding. Insulin-like growth factor (IGF)-II and the ubiquitin ligase MAFbx/atrogin-1 were initially down-regulated but restored to initial values after 12 h. It is also suggested that local production of IGF-I within the muscle might suppress catabolic pathways depressing MAFbx/atrogin-1.
Publisher: Oxford University Press (OUP)
Date: 15-09-2010
DOI: 10.1093/NAR/GKQ816
Publisher: Springer Science and Business Media LLC
Date: 24-08-2009
Abstract: Many fish species experience long periods of fasting in nature often associated with seasonal reductions in water temperature and prey availability or spawning migrations. During periods of nutrient restriction, changes in metabolism occur to provide cellular energy via catabolic processes. Muscle is particularly affected by prolonged fasting as myofibrillar proteins act as a major energy source. To investigate the mechanisms of metabolic reorganisation with fasting and refeeding in a saltwater stage of Atlantic salmon ( Salmo salar L .) we analysed the expression of genes involved in myogenesis, growth signalling, lipid biosynthesis and myofibrillar protein degradation and synthesis pathways using qPCR. Hierarchical clustering of gene expression data revealed three clusters. The first cluster comprised genes involved in lipid metabolism and triacylglycerol synthesis ( ALDOB , DGAT1 and LPL ) which had peak expression 3-14d after refeeding. The second cluster comprised ADIPOQ , MLC2 , IGF-I and TALDO1 , with peak expression 14-32d after refeeding. Cluster III contained genes strongly down regulated as an initial response to feeding and included the ubiquitin ligases MuRF1 and MAFbx , myogenic regulatory factors and some metabolic genes. Early responses to refeeding in fasted salmon included the synthesis of triacylglycerols and activation of the adipogenic differentiation program. Inhibition of MuRF1 and MAFbx respectively may result in decreased degradation and concomitant increased production of myofibrillar proteins. Both of these processes preceded any increase in expression of myogenic regulatory factors and IGF-I . These responses could be a necessary strategy for an animal adapted to long periods of food deprivation whereby energy reserves are replenished prior to the resumption of myogenesis.
Publisher: Public Library of Science (PLoS)
Date: 14-06-2010
Publisher: The Royal Society
Date: 20-02-2007
Abstract: The reproductive behaviour of the sexually coercive male eastern mosquitofish ( Gambusia holbrooki ) offers an excellent model system for testing the benefits of reversible thermal acclimation responses to mating success. We acclimated male mosquitofish to either 18 or 30°C (14 h light : 10 h dark) for six weeks and tested their ability to obtain coercive copulations in the presence and the absence of male–male competition. Based on the beneficial acclimation hypothesis, we predicted for both sets of experiments that 18°C acclimated males would outperform 30°C acclimated males when tested at 18°C, and vice versa when tested at 30°C. We found that copulation success was greater for acclimated than non-acclimated males at both temperatures when in idual males were tested without competing males. In contrast, when males from the different acclimation treatments were competed against each other for copulations with a single female, the 30°C acclimated males were more aggressive and obtained a greater number of copulations at both test temperatures. Thus, we found a clear benefit for acclimation when fish were tested in a non-competitive environment, but acclimation to cool temperatures was associated with a decrease in aggressive behaviour that reduced mating performance at both test temperatures in a competitive environment. In contrast with the long-held assumption that reversible plasticity is beneficial, the adaptive significance of reversible physiological plasticity is affected by a variety of other ecological factors and is more complex than previously suggested.
Publisher: Springer Science and Business Media LLC
Date: 2009
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Ian Johnston.