The Effects of Reduced Caloric Intake and Increased Insulin-Induced Caloric Intake on the Cell Growth of Muscle, Liver, and Cerebrum and on Skeletal Collagen in the Postweanling Rat[43]

Abstract

ExtractFollowing weaning, Sprague Dawley rats were given 60% of a normal Purina chow intake until 7 weeks of age. There was a reduced DNA content in the cerebrum at 49 days of age. Previous failure to demonstrate reduced DNA content in rat brain during undernutrition could relate to preoccupation with whole brain analysis. The present study indicates that cerebral DNA increases in normal rats after weaning.T h e cell size or the ratio of protein: DNA increased in the muscle tissues of rats subjected to the caloric restriction, while the ratio of RNA:DNA increased in all tissues studied. These findings are contrary to those found in protein deficiency per se. Carcass weight, fat, and water were below expected levels, but skeletal collagen was less affected.Rats from 26 to 38 days of age, given an increased insulin-induced caloric intake, showed an excess weight gain per gram of food consumed per day and an excess growth of muscle and fat. In contrast, cerebral weight, water, protein, DNA, and RNA content were reduced possibly because of periodic hypoglycemia. SpeculationFollowing weaning, rats subjected to sustained caloric restriction have reduced cell numbers for age and are said not to reach expected cell populations on rehabilitation. With caloric restriction, growth hormone may no longer be effective at the cellular level, but insulin activity continues. Although the ratio of cytoplasm: nucleus is maintained, DNA replication is minimal. Alternatively, since DNA content in the cerebrum decreases, hypothalamic or acidophilic cells may be lost, and growth hormone production may be insufficient for adequate DNA replication and somatic growth.When protein is restricted, the failure of cells to increase in size may be associated with atrophy of the pancreas and a decrease in insulin production.Introduciion nutrition in the sucking pig from 2 weeks to one year of age produced a decrease in DNA synthesis in the Malnutrition is widespread throughout the world. brain, which failed to attain expected levels after reThere have been many studies of metabolic changes in habilitation.

Changes in Enzymes (GOT and GDH) and Metals (Zn, Mn, and Mg) in Liver of Rats During Endocrine Imbalance and Caloric Restriction

“…of trace metal, not just immature levels [6]. Our previIt has been reported that in rats subjected to caloric ous study [6] showed that these trace metals, as well restriction, the DNA content in liver was not increased; as Cu, were reduced in muscle as well as in liver tissue however, the RNA: DNA ratio was excessively high in liver of rats during endocrine imbalance a n d caloric restriction 439 [14]. Activity of GDH and content of Zn, Mn, and Mg per unit of DNA were also increased.…”

“…The methods used for measuring protein, nucleic acids, and water content have been described previously [14]. Student's t test was used to determine the degree of statistical significance between grouped data.…”

“…In contrast, epinephrine inhibits insulin release [26], and the finding of increased GOT activity, together with a failure of protein accretion in liver, is also compatible with our findings. In our previous study [14], intact rats with hyperphagia that were injected with insulin also had reduced GOT activity (p i 0.001), but there was no marked protein accretion.…”

The Action of Insulin, Growth Hormone, and Epinephrine on Cell Growth in Liver, Muscle, and Brain of the Hypophysectomized Rat[39]

“…Body weight, food, and fluid intake were monitored daily. The experimental plan of the control and pair-fed rats to the untreated hypophysectomized rats has been given previously [17]. Both investigations were performed simultaneously.…”

“…The untreated hypophysectomized rat can be compared with intact rats receiving the same diet per 100 g body weight or with rats receiving an ad libitum diet. Data from normal intact rats and pair-fed or calorie-restricted rats have been reported earlier [17].…”