Studies of the Protein Requirement of the Neonatal Rat

Czajka-Narins, Dorice M.; Miller, Sanford A.; Browning, Ann M.

doi:10.1093/jn/103.11.1608

Cited by 17 publications

(13 citation statements)

References 15 publications

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“…Feedings were given with a syringe needle fitted with a bulbous tip, which had been used in earlier studies of undemutrition [3,4]. Although nontraumatic to the animals, the feedings are more difficult because, in trying to distend the stomach as much as possible, regurgitation and aspiration into the lungs occasionally occurred.…”

Section: Methodsmentioning

confidence: 99%

“…Although nontraumatic to the animals, the feedings are more difficult because, in trying to distend the stomach as much as possible, regurgitation and aspiration into the lungs occasionally occurred. The formula used in feeding the rats was prepared as follows (in g): nonfat dried skim milk powder, 10; corn oil, 15; vitamin mix, 0.1 (as published in [4], except glucose 417.237); choline, 50; and sterile distilled water, 74. No attempt was made to exactly duplicate rat's milk.…”

Section: Methodsmentioning

confidence: 99%

“…Ideally complete artificial feeding, such as has been used to underfeed rat pups, would best control the intake of the animals and supply information regarding volume of intake [3,4,17]. Attempts to formulate a diet closely simulating rat's milk, which could both be fed in large amounts and be well utilized by the pups, were unsuccessful.…”

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Supplementary Feeding during the Preweaning Period

Czajka-Narins

Hirsch²

1974

Neonatology

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The present study was undertaken to determine if a model system could be established in the rat to produce hypercellularity of adipose tissue by overfeeding the preweaning period comparable to the eating pattern which has been suggested as contributing to one form of human obesity. To produce the hypercellularity, rat pups were given 4 supplementary feedings daily during the preweaning period. Supplementation resulted in significant differences in carcass composition, early in percent of fat (14 and 20 days) and later, in percent of protein (40 and 105 days of age). Although there was no significant difference in cell number between the supplemented and control rats, there were significant differences in cell size, the supplemented animals having larger cells at 40 and 105 days of age. The pattern of cellularity produced by supplementation was, therefore, different than that produced by other techniques of early overnutrition.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Supplementary Feeding during the Preweaning Period

Czajka-Narins

Hirsch²

1974

Neonatology

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“…In most of these studies the effects of protein or energy level have been analyzed independently and by uSing synthetic diets. The importance of considering both nutrients together, as an EPR to allow a better utilization of them, has been recognized (Clarke et al, 1977;NRC, 1978;McCracken, Eddie andStevenson, 1980a, 1980b;and others (Anantharaman, Carpenter & Nesheim, 1968;Czajka-Narins, Miller & Browning, 1973;McCracken, 1975;Berschauer, Close & Stephens, 1981). Some workers have even found a nonlinear response of protein and/or energy retention and their efficiencies, as EPR value of the diet changes (Hartsook, Hershberger & Nae, 1973;Tanaka, Yamaguchi & Kametaka, 1974;McCracken, Eddie & Stevenson, 1980b;Close & Berschauer,1981).…”

Section: Discussionmentioning

confidence: 99%

Energy/protein ratio in natural-ingredient diets for weanling rats. II. Energy and protein retention and efficiency of retention

López

Garcı́a

1984

Lab Anim

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SummaryA 3 x 3 factorial experiment was carried out, in which natural ingredient diets formulated at 3 digestible energy levels (DE) (100, 90 and 80% of NRC, 1978 recommendations) and at 3 energy: protein ratios (EPR) (63, 71 and 79 kJ DE/g crude protein (CP)) were fed to 8 weanling male Wistar rats/group. Half of these animals were sacrificed at the end of the 6-week experimental period and their body composition analyzed. Retentions of protein and energy were assessed by difference from a similar group of 8 rats killed and analyzed at the beginning of the experiment. No interaction was found between the 2 factors studied. Main results showed a decrease in intake and retention of both energy and protein, without affecting the efficiency of retention when energy level of diets was reduced by 20%. An increase in the EPR of the diets led to a decrease in protein intake and to an increase in efficiency of protein retention, without affecting the amount retained. No changes in body composition, nor in composition of live weight gains were found as a result of treatments. It is concluded that a 10% reduction in DE level of the diet is of no consequence, and that an EPR of 79 kJ/g leads to more efficient use of the dietary protein without detrimental effects over any other nutritional indicator.The effects of energy and protein concentration in diets for growing animals has been widely studied in different species. In most of these studies the effects of protein or energy level have been analyzed independently and by uSing synthetic diets. The importance of considering both nutrients together, as an EPR to allow a better utilization of them, has been recognized (Clarke et al., 1977; NRC, 1978; McCracken, Eddie and Stevenson, 1980a, 1980b; and others In a previous report (Lopez & Garcia, 1983) weight gain, intake and intake/weight gain ratio for CP and DE were analyzed, when diets formulated with natural ingredients and differing in DE level and EPR were offered to weanling rats. The EPR value ranged within limits considered as normal by NRC (1978) for such diets. The present work reports on the retention and the efficiency of retention of protein and energy in the body of rats in the same experiment. Materials and methodsThe experiment was conducted as a 3 x 3 factorial, the factors being DE level (IOO, 90 and 80% of NRC, 1978 recommendation, which is 17'5 MJ DE/kg dry matter) and EPR (63, 71 and 79 kJ DE/g CP).. The experimental animals were male weanling Wistar rats. Diets, management and experimental layout were described previously (Lopez & Garcia, 1983). To study the initial carcass composition at the beginning of the experimental period (21 days of age), an extra group of 8 rats were sacrificed with diethylether, just after the animals used for the experiment had been distributed into groups. At the end of the 6-week experimental period, 4 rats/group (the ones that were closest to the average final weight of the group) were sacrificed as described above. In both instances, the bodies were prepared for anal...

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“…Given that gluconeogenesis is high postnatally, what becomes of the nitrogen that is lost from the amino acids? Previous studies done in our laboratory indicated that the young animal tends to conserve nitrogen; nitrogen balance studies with 1-5-day-old rats showed that the rat maintained positive nitrogen balance even on a 0.6% protein diet (8,27).…”

Section: Dietary Amino Acid Utilizationmentioning

confidence: 90%

Utilization of Dietary Amino Acids for Energy Production in Neonatal Rat Liver

White

Miller

1976

Pediatr Res

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Suneroxide dismutase activitv was determined in blood and lung ;issue from adults and varibus infant groups. Enzyme activity in human fetuses and infants was significantly lower than in adults. Similarly, S O D activity was related to age in rats and rabbits with much lower activity found in late fetal animals cornpared with the adult animals. No significant differences in enzyme activity, however, were seen between (I) infants with I R D S / H M D and their premature peers without I R D S / H M D and between (2) premature infants and full term infants.Experiments in which animal lung tissue was exposed either to 80-85% oxygen in vivo or 100% oxygen in vitro demonstrated an enhancement of pulmonary S O D activity in response to this hyperoxic challenge. In the rat, the ability to increase pulmonary S O D activity under hyperoxic conditions was age related, with the maximum effects occurring during the first 18 days of life.These data suggest that S O D is an enzyme for which increasing activity associated with maturation may be obligatory to newborn lung for the provision of protection against the relative hyperoxia of extrauterine life. Pediat. Res. 10: 158-164 (1976) Amino acid metabolism metabolic development glycogen phosphoenolpyruvate carboxykinase activity gluconeogenesis starvation liver Utilization of Dietary Amino Acids for EnergyProduction in Neonatal Rat Liver Departmenl of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, U S AExtract increased from 3 days to 19 days of age, with a decrease to adult levels. Liver glycogen concentration increased from 3 days to 19 The 3-day-old rat has a high basal level of phosphoenolpyruvate days of age, with no additional increase observed at 3 months. There carboxykinase (PEPCK), the activity of which is not increased upon was a decrease with age in the specific activity of liver glycogen starvation. The lower basal activity of the enzyme in 19-day-old rat (from [14C]alanine and [14C]leucine). In fed rats given [14C]alanine, liver can, however, be stimulated by starvation. Serum glucose levels 14C02 expiration tended to decrease with age. The 14C02 produc-

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Studies of the Protein Requirement of the Neonatal Rat

Cited by 17 publications

References 15 publications

Supplementary Feeding during the Preweaning Period

Supplementary Feeding during the Preweaning Period

Energy/protein ratio in natural-ingredient diets for weanling rats. II. Energy and protein retention and efficiency of retention

Utilization of Dietary Amino Acids for Energy Production in Neonatal Rat Liver

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