3,648 research outputs found
Postnatal regulation of myosin heavy chain isoform expression and metabolic enzyme activity by nutrition
No full textDevelopment of muscle is critically dependent on several hormones which in turn are regulated by nutritional status. We therefore determined the impact of mild postnatal undernutrition on key markers of myofibre function: type I slow myosin heavy chain (MyHC) isoform, myosin ATPase, succinate dehydrogenase and α-glycerophosphate dehydrogenase. In situ hybridization, immunocytochemistry and enzyme histochemistry were used to assess functionally distinct muscles from 6-week-old pigs which had been fed an optimal (6 % (60 g food/kg body weight per d)) or low (2 % (20 g food/kg per d)) intake for 3 weeks, and kept at 26°C. Nutritional status had striking muscle-specific influences on contractile and metabolic properties of myofibres, and especially on myosin isoform expression. A low food intake upregulated slow MyHC mRNA and protein levels in rhomboideus by 53 % (P < 0·01) and 18 % (P < 0·05) respectively; effects in longissimus dorsi, soleus and diaphragm were not significant. The oxidative capacity of all muscles increased on the low intake, albeit to varying extents: longissimus dorsi (55 %), rhomboideus (30 %), soleus (21 %), diaphragm (7 %). Proportions of slow oxidative fibres increased at the expense of fast glycolytic fibres. These novel findings suggest a critical role for postnatal nutrition in regulating myosin gene expression and muscle phenotype. They have important implications for optimal development of human infants: on a low intake, energetic efficiency will increase and the integrated response to many metabolic and growth hormones will alter, since both are dependent on myofibre type. Mechanisms underlying these changes probably involve complex interactions between hormones acting as nutritional signals and differential effects on their cell membrane receptors or nuclear receptors
Growth hormone receptor gene expression in porcine skeletal and cardiac muscles is selectively regulated by postnatal undernutrition
No full textDuring mild postnatal undernutrition, growth hormone receptor (GHR) mRNA abundance decreases in liver but increases in longissimus dorsi muscle. We tested the following hypotheses: 1) GHR gene expression is related to the metabolic and contractile characteristics of different muscles, and 2) the GHR response to nutrition depends on muscle type. Eight pairs of littermate pigs were weaned at 3 wk and given an optimal [60 g/(kg·d)] or low [(20 g/(kg·d)] food intake for the next 3 wk. All pigs grew, but at a slower rate in the low food intake group (P 0.10). Compared with the high intake pigs, hepatic GHR mRNA was downregulated in the low intake pigs by 59% (P 0.4); soleus, 65% (P < 0.05); cardiac, 51% (P < 0.05). Moreover, the proportion of skeletal muscle fibers with high oxidative capacity was also greater in the low intake group (P < 0.05). We conclude that postnatal GHR gene expression and its regulation by mild undernutrition are related to the metabolic, contractile and specific functional properties of different muscles
Applicazione di biotecnologie nello studio delle interazioni fra stato nutrizionale ed accrescimento
No full textUrban bias
No full textMost of the world's poor continue to reside in rural areas. Yet, it is often claimed that governments and international development organizations have persistently allocated scarce resources to cities and towns. In a powerful critique of such allocations, Michael Lipton proposed that development exhibited an urban bias. As set out in his book, Why Poor People Stay Poor: A Study of Urban Bias in World Development (1977), Lipton claimed that this bias in favour of cities was both inefficient and inequitable. This chapter examines Lipton's urban bias thesis (UBT), how it has changed with time, its influence on international development thinking, and the criticisms levelled at the original and later iterations
Behavioural Economics and Development Economics
No full textBehavioural economics incorporates insights from psychology to strengthen the explanatory power of microeconomics. As a result of the rapid expansion of behavioural economics in the recent past, it is increasingly becoming part of mainstream economics and its influence on policy formulation is growing. Most of the insights from behavioural economics are universal hence they are also relevant for development economics. While the main principles of behavioural development economics are the same as behavioural economics, the unique circumstances and institutional set-ups in developing countries makes it a distinct sub-discipline in its own right. The increasing use of experimental games in development research is one illustration of the influence of behavioural economics on development economics
Growth hormone receptor gene expression is related to metabolic and contractile properties of muscle
No full text- …
