Iwao Tasaki

Contribution of whole-body protein synthesis to basal metabolism in layer and broiler chickens.

The effect of starvation on whole-body protein synthesis and on the contribution of protein synthesis to basal metabolic rate was investigated in young chickens (Expt 1). Strain differences between layer and broiler chickens in whole-body protein synthesis and degradation rates were examined when the birds were starved (Expt 2). In Expt 1, 15-d-old White Leghorn male chickens were used, while in Expt 2 Hubbard (broiler) and White Leghorn (layer) male chickens at 14 d of age were used. They were starved for 4 d, and heat production was determined by carcass analysis after 2 and 4 d of starvation. Whole-body protein synthesis rates were measured on 0, 2 and 4 d of starvation (Expt 1), and on 0 and 4 d of starvation (Expt 2). The results showed that starving reduced whole-body protein synthesis in terms of fractional synthesis rate and the amount synthesized. Whole-body protein degradation was increased by starvation both in terms of fractional synthesis rate and the amount degraded on a per kg body-weight basis. Reduced fractional synthesis rate of protein in the whole body was accounted for by reductions in both protein synthesis per unit RNA and RNA:protein ratio. In the fed state, whole-body protein synthesis and degradation rates, whether expressed as fractional rates or amounts per unit body-weight, tended to be higher in layer than in broiler chickens. In the starved state, the difference in the rate of protein synthesis between the two strains virtually disappeared, while the degradation rates were higher in layer than in broiler birds.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental fall in whole body protein turnover of chick embryos during incubation

Whole body protein turnover was measured in chick embryos during incubation to investigate whether or not there is a fall in fractional rates of protein synthesis and degradation during development. Stable isotopically labelled [15N]phenylalanine was injected intraperitoneally into embryos on days 12 and 19. From 60 to 90 min after injection the isotope enrichment in free and protein-bound phenylalanine was measured with a selected-ion gas-chromatograph mass-spectrometer. The results showed that from days 12 to 19 of incubation, there was a remarkable reduction in fractional rates of protein synthesis and degradation in the whole body of chick embryos. During embryonic growth, protein synthesis per unit of RNA that is, the minimum amino acid translation rate of RNA, did not change significantly, whereas the RNA:protein ratio was reduced to one-third from days 12 to 19 of incubation. It was concluded, therefore, that the dramatic fall in fractional synthesis rate in chick embryos would be entirely attributable to the rapid increase in protein content, thereby changing the RNA:protein ratio in parallel with the fractional synthesis rate.

Influence of dietary protein intake on whole-body protein turnover in chicks

1. Experiments were conducted to investigate whether or not varying dietary protein intake affects whole-body protein turnover rates in young chicks. 2. Seven-d-old single comb White Leghorn male chicks were fed on diets with protein concentrations of 0, 100, 200 or 400 g/kg diet under conditions of ad libitum or equalised feeding. At the end of the experiments, the rate of protein synthesis and protein degradation in the whole body were measured in vivo. 3. The results showed that both fractional and absolute rates of protein synthesis increased with increasing dietary protein up to 200 g/kg; above this concentration they remained almost constant when feeding was ad libitum. 4. Similar responses were found with equalized feeding except that a significant reduction in protein synthesis was found when dietary protein was increased from 200 to 400 g/kg diet. 5. Less sensitive and almost parallel changes in protein degradation rates were found. 6. It was concluded that adaptation to varied dietary protein intake occurred primarily through changes in protein synthesis, accompanied by parallel alterations in protein degradation in the whole body.

Enhanced whole-body protein synthesis by methionine and arginine supplementation in protein-starved chicks

1. The effect of supplementing with methionine alone or in combination with arginine on whole-body protein synthesis and degradation was studied in protein-starved chicks, fed on a protein-free (PF) diet, by a massive-dose injection of L-[4-3H]phenylalanine. 2. Methionine or methionine and arginine (MA) supplementation reduced body-weight loss and improved N balance compared with unsupplemented controls. 3. Whole-body protein synthesis was significantly increased both in terms of fractional rate and absolute amounts by methionine and MA addition, whereas the fractional degradation rate was unchanged. 4. No significant difference was found between methionine and MA supplementation except for energy balance of the birds. 5. It was concluded that the N-sparing effect of methionine or MA when added to a PF diet was primarily brought about by enhanced whole-body protein synthesis.

Effect of protein starvation on protein turnover in liver, oviduct and whole body of laying hens

1. Whole body protein turnover rates in White Leghorn laying hens were reduced by protein starvation for 7 days, followed by complete restoration by protein repletion for 7 days. 2. Protein starvation considerably reduced fractional and absolute rates of protein synthesis both in the liver and, to a greater extent, in the oviduct. 3. It was suggested that a considerable portion of the reduced whole body protein synthesis could be accounted for by the reduced protein synthesis in these organs when laying hens were subjected to protein starvation.

Effect of low ambient temperature on protein turnover and heat production in chicks

1. Effect of low ambient temperature on protein turnover in the liver and whole body was investigated in chicks together with the contribution of protein synthesis to the total heat production. 2. Both protein synthesis and degradation in the whole body were increased, the latter to a larger extent, at low ambient temperature (LT, 22 degrees C) compared with adequate temperature (AT, 30 degrees C). Liver protein synthesis was not significantly altered by the temperature treatment. 3. The total heat production of LT group was as high as 160% of the AT group. 4. The increased heat production due to enhanced whole-body protein synthesis accounted for only 1.4% of the heat increment in thermogenesis at low ambient temperature, suggesting that protein synthesis would contribute little, if any, to cold-induced thermogenesis in chicks.

Influence of Energy Intake on Growth and Utilisation of Dietary Protein and Energy in Germ-Free and Conventional Chicks

The effect of metabolisable energy (ME) intake on the growth and utilisation of dietary protein and energy in germ-free (GF) and conventional (CV) chicks was investigated in two experiments. In experiment 1 a high energy diet (HED, 14.8 kJ ME/g) and a marginally-adequate energy diet (AED, 11.7 kJ ME/g) were fed to the GF and CV chicks at 240 g/2 birds/10 d. In experiment 2 a diet with 13.7 kJ ME/g was fed at 118 g (low level, LL) or 128 g (high level, HL)/bird/10 d. Body weight gain, protein retention and protein retention rate were similar in GF and CV chicks on both AED and HED in the first experiment, but in the second were higher in GF than in CV chicks. The increased ME intake of the CV chicks in experiment 2 may be too small to compensate for the increased requirement. ME intake was significantly higher in the CV chicks than in the GF chicks, whereas energy retention was similar in both groups.

Influence of the gut microflora on fasting heat production in chicks

1. The influence of the gut microflora on fasting heat production in chicks was investigated. 2. Single Comb White Leghorn chicks were fed on an adequate diet from 2 to 12 d of age and then fasted for 3 d. Fasting heat production was estimated from changes in body composition and energy content of droppings from days 1 to 3 of fasting. Measurements of body temperature and plasma thyroxine concentration were also made. 3. Body fat content was consistently higher in germ-free (GF) chicks than in conventional (CV) counterparts during the starvation period, whereas no difference was found in body protein content. The GF birds had a significantly higher body temperature than the CV controls with no change in plasma thyroxine concentration. 4. It was concluded that estimated fasting heat production of chicks was increased by the absence of the gut microflora.

Effect of methionine sulfoximine on glutamine synthetase activity and blood metabolite levels in the chicken (Gallus domesticus)

Abstract 1. 1. A single injection of 100 mg of methionine sulfoximine (MSM)/kg body wt. resulted in an almost complete inhibition of glutamine synthetase activity in the liver, heart and intestine. 2. 2. Liver glutamine synthetase activity dropped to 7·3 per cent of the pretreatment level 2 hr after the MSM treatment, and the activity at 5 hr after treatment was 3·6 per cent of the pretreatment level. 3. 3. Plasma glutamine concentration rapidly and greatly decreased after the MSM treatment, whereas blood ammonia concentration significantly increased. 4. 4. Plasma uric acid concentration significantly decreased at 3 hr after the MSM treatment, but thereafter the concentration did not change.

A note on the effect of ageing on whole-body protein turn-over in goats

In ruminants a dynamic state of protein turn-over has been poorly understood although the methodology of measuring the rate of protein turn-over has recently been advanced to a great extent (Waterlow, Garlick and Millward, 1978). Available evidence suggests that ruminants such as sheep and cows are no exception among various mammalian species when whole-body protein synthesis of adult animals is compared on a metabolic body-weight basis (Waterlow et al ., 1978; Reeds and Lobley, 1980).