Base de dados : MedCarib
Pesquisa : D01.268.150.075.328 [Categoria DeCS]
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Fotocópia
Id: 14620
Autor: Millward, David J.
Título: Protein turnover in skeletal muscle. I. The measurement of rates of synthesis and catabolism of skeletal muscle protein using [14C]Na2CO3 to label proteins
Fonte: Clin Sci;39(5):577-90, Nov. 1970.
Idioma: En.
Resumo: The turnover of rat skeletal muscle protein was studied using [75Se]selenomethionine, [6-14C]arginine and [14C]Na2CO3 to label protein. In rats labelled with both [75Se]selonomethionine and [14C]Na2CO3 the 14C activity of mixed skeletal muscle protein fell rapidly with a half-life of 6.0 days for the specific activity and 10.5 days for the total activity. There was no loss of 75Se activity from muscle protein during the 12 days of the experiment. Following the injection of [6-14C]arginine both sarcoplasmic and myofibrillar proteins continued to incorporate label for 6 days after which time the label was lost fairly rapidly. Following injection of [14C]Na2CO3 muscle protein was maximally labelled by 6h, at which time specific activity of the free amino acids had fallen to a very low level. Aspartate and glutamate in particular had lost over 99 percent of their maximum activity by this time in comparison to arginine which was still highly labelled after 24h. 14C activity was lost more rapidly from aspartate and glutamate isolated from sarcoplasmic and myofibrillar protein than from other labelled amino acids. The half-lives of the two protein fractions were 3.9 and 7.2 days from the specific activity curves and 6.0 and 19.0 days from the total activity curves. The differences between the half lives of muscle proteins labelled with amino acids are discussed in terms of the effects of reutilization of the labelled amino acids used. It is postulated that aspartate and glutamate labelled by the injection [14C]CO3= are only reutilized to a very small extent and therefore afford the means by which the rates of protein synthesis and catabolism in skeletal muscle can be measured with reasonable accuracy (Summary)
Responsável: JM3.1 - Médical Library
JM3.1; R31.C56


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Fotocópia
Id: 12131
Autor: Golden, Michael H. N; Waterlow, John C.
Título: The in vivo measurement of protein synthesis
Fonte: Am J Clin Nutr;30(8):1353-4, Aug. 1977.
Idioma: En.
Resumo: Methods of measuring in vivo protein synthesis are briefly reviewed. Methods involving incorporation of label into protein are more appropriate for mixed proteins. The major difficulty is the definition of the precursor for protein synthesis. The only data available on the effect of infection on protein synthesis are open to criticism on the grounds that the precursor pool was not sampled. (AU)
Responsável: JM3.1 - Médical Library
JM3.1; RC620.A1A4


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Fotocópia
Id: 10402
Autor: Reeds, P. J.
Título: The catabolism of valine in the malnourished rat: studies in vivo and in vitro with different labelled forms of valine
Fonte: Br J Nutr;31(2):259-70, Mar., 1974.
Idioma: En.
Resumo: 1. The catabolism of valine was estimated in vivo by measurement of the production of labelled CO2 for 2 h after the oral administration of either [U-14C] valine. It was also estimated in vitro in homogenates of liver and muscle incubated with labelled valine. Experiments were performed in rats given diets providing either 215 g (HP) or 25 g (LP) protein per kg diet. 2. The proportion of [U-14C] valine excreted as 14 CO2 was not reduced in rats given the LP diet for 16 d but the excretion of 14 CO 2 from [1-14C] valine was reduced by 40 percent in these animals. When rats were transferred from the HP diet to the LP diet there was a reduction in the excretion of 14CO2 from [1-14C] valine; when the diet was changed from LP to HP output of 14CO2 increased to control values. 3. Homogenates of muscle and liver catabolized valine to CO2. Both liver and muscle from rats fed on the LP diet catabolized less [1-14C] valine than tissues from control animals. 4. Valine aminotransferase activity was higher in muscle than in liver, and did not change in tissues from rats fed on the LP diet. In these animals 2-ketoisovaleric acid dehydrogenase activity was reduced in both liver and muscle. 5. The production of 14CO2 was lower with [U-14C] valine as the substrate than with [1-14C]-valine and there was no difference between tissues from rats fed on the HP and LP diets. 6. The results with [1-14C] valine suggest that both liver and muscle from protein-depleted rats catabolize valine at a reduced rate. The reason for the discrepancy between these results and those with [U-14C] valine is not clear. It is concluded that the results with [U-14C] valine in vitro are affected by dilution of the label before the formation of 14CO2, but that this does not hold in vivo (AU)
Responsável: JM3.1 - Médical Library
JM9.1; QP141.A1B7



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