Protein Metabolism and Requirements in Pregnancy and Lactation

Blaxter, K. L.

doi:10.1016/b978-1-4832-3210-2.50011-x

Cited by 37 publications

(22 citation statements)

References 123 publications

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“…Therefore, we have limited the comiiparisoni to a few amino acids. Accuinitulation rates in the fetal lamb have been estimated from the known rate of nitrogen accumulation (23) and data on the amino acid composition per gram of nitrogen of fetal calves (24). The use of the latter seems justified, in view of the fact that results of carcass analysis in different species show good agreement.…”

Section: Resultsmentioning

confidence: 99%

Umbilical uptake of amino acids in the unstressed fetal lamb.

Ja¹,

Ew²,

Jones³

et al. 1976

J. Clin. Invest.

267

120

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A B S T R A C T The whole blood concentrations of 22 amino acids were measured in a chronic, unstressed fetal lamb preparation. Samples were taken daily from the umbilical artery, umbilical vein, and maternal artery over the latter quaiter of gestation. 73 sets of samples (from the umbilical artery and vein and the maternal artery) from 13 animals were analyzed for amino acid levels. Oxygen contents were determined simultaneously in 48 sets (umbilical artery and vein) to relate fetal oxygen consumption to amino acid uptake via the umbilical circulation.The results indicate that there is no umbilical uptake of the acidic amino acids, glutamate and aspartate; there is, in fact, a net flux of glutamate out of the fetus into the placenta. As both of these amino acids are major constituents of body proteins, the data indicate that they are formed within the fetus. The umbilical uptake of some neutral and basic amino acids (e.g., valine, leucine, isoleucine, arginine, phenylalanine, and tyrosine) is in considerable excess of estimated growth requirements, suggesting that some amino acids undergo extensive transamination and oxidative degradation in the fetus.Finally, the net uptake of nitrogen, carbon, and calories by the growing ovine fetus in the formn of amino acids, glucose, and lactate is compared to estimated requirements as determined in previous studies.

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Section: Resultsmentioning

confidence: 99%

Umbilical uptake of amino acids in the unstressed fetal lamb.

Ja¹,

Ew²,

Jones³

et al. 1976

J. Clin. Invest.

267

120

View full text Add to dashboard Cite

show abstract

“…Finally, turning back to the differences between species noted earlier, we suggest that these could be related to the fact that pregnancy imposes a relatively small metabolic load in large species such as man, mn which the product is relatively small, or in guinea-pigs in which gestation is unusually long, but constitutes a massive burden on the maternal body in small species such as the rodent (Blaxter, 1964).…”

Section: Discussionmentioning

confidence: 99%

Ornithine decarboxylase activity, nucleic acids and cell turnover in the livers of pregnant rats

Campbell¹,

Fell²,

Mackie³

1974

The Journal of Physiology

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SUMMARY1. Comparisons were made between the livers of pregnant and nonpregnant rats, all of which were fed on a ration of 20 g food per day.2. In the second half of pregnancy there were marked increases in the weight of the liver and in its total content of protein, RNA and DNA. RNA concentration increased from the 15th day of gestation.3. Between the 12th and 18th day of pregnancy liver weight, total RNA, total DNA and mean liver cell nuclear volume increased in parallel at approximately the same rate of 6-10 % per day.4. Ornithine decarboxylase activity was enhanced in pregnancy by the 5th day of gestation and rose to peak activity at the 18th day.5. The mitotic index of hepatic parenchymal cells was elevated in the first and last stages of pregnancy. The later peak in mitosis was associated with a rapid fall in mean nuclear volume.6. There was histological evidence of cell turnover in the liver of pregnant rats; enlargement of the liver was associated with both hyperplasia and cell deletion.

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“…By analogy to adult mammals, Blaxter [31,32] predicted that the weight of the digestive tract of suckling animals would be directly proportional to body weight rather than to metabolic body size (body weight to the power 0.75). The data in table 5 are con sistent with this hypothesis.…”

Section: Comparison O F Newborn Seals With Newborn Terrestrial Mammalsmentioning

confidence: 99%

Effects of Suckling and the Postsuckling Fast on Weights of the Body and Internal Organs of Harp and Hooded Seal Pups

Oftedal

Bowen

Widdowson³

et al. 1989

Neonatology

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The weights of harp seal pups quadruple during 13 days of suckling while hooded seal pups double in weight in a lactation period of just 4 days. Pups of both species then fast for a month or longer. As a first measure of tissue responses to this ‘feast and famine’ pattern, we weighed the body, sculp (blubber and attached skin), core (carcass including viscera) and major internal organs of seal pups at birth, at the end of suckling, and at the end of the fast. When expressed as a percentage of body weight, the weights of the internal organs of newborn harp and hooded seals were within the range reported for newborn land mammals. During suckling, harp and hooded seals gained 2.3 and 6.5 kg/day body weight, respectively, but a large part (64–73 %) of this gain was blubber and skin rather than core. Even though pups were ingesting great quantities of fat, their digestive organs (stomach, small and large intestines, pancreas) were neither particularly large at birth nor did these organs gain in weight or length unusually rapidly. Most organs increased in weight in proportion to the increase in core weight, but the liver and spleen increased proportionately more than the core, and the stomach, heart and kidneys increased proportionately less. At the end of suckling, sculp accounted for more than half of the body weight in both species. The subsequent 4-week fast resulted in weight loss from both the sculp and core, and the liver and spleen decreased in weight by about 70%. The net effect of sequential suckling and fasting was particularly striking in the hooded seal pup, which had a lighter core, heart, liver and spleen at 1 month postpartum than at birth. These data illustrate a remarkable cycle of nutrient deposition and depletion which is undoubtedly central to the survival of young seals in the harsh pack-ice environment.

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Protein Metabolism and Requirements in Pregnancy and Lactation

Cited by 37 publications

References 123 publications

Umbilical uptake of amino acids in the unstressed fetal lamb.

Umbilical uptake of amino acids in the unstressed fetal lamb.

Ornithine decarboxylase activity, nucleic acids and cell turnover in the livers of pregnant rats

Effects of Suckling and the Postsuckling Fast on Weights of the Body and Internal Organs of Harp and Hooded Seal Pups

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