Статті в журналах: "In weanling rat"

1

Takahashi, M., H. Homma, and M. Matsui. "Developmental changes in the isoelectric variants of rat hepatic hydroxysteroid sulphotransferase." Biochemical Journal 293, no. 3 (August 1, 1993): 795–800. http://dx.doi.org/10.1042/bj2930795.

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Major isoenzymes of androsterone-sulphating sulphotransferase (AD-ST) were isolated from liver cytosols of weanling and young adult female rats and their isoelectric properties were compared. On chromatofocusing the enzyme activity of young adults was eluted over a wider range of pH than was that of weanling rats. The activity at pH 7.8-7.2 (fraction I) is obvious at both ages, whereas the activity eluted over the pH 6.6-5.5 range (fraction II) is much lower in weanlings than in young adults. The AD-ST activities eluted in fractions I and II were separately purified by 3′-phosphoadenosine 5′-phosphate-agarose affinity chromatography at both ages. Two-dimensional gel electrophoresis of the isolated enzyme revealed several subunits with distinct pI values, but with the same molecular mass, namely 30 kDa. The relative levels of the pI 6.7 and pI 7.2 subunits are high and the relative level of the pI 6.1 is low in fraction I. In fraction II, the levels of pI 6.1 and pI 6.7 subunits are high and the level of the pI 7.2 subunit is low. There is no significant difference in the relative levels of the pI variants in each fraction between weanlings and young adults. The N-terminal amino acid sequences of the pI variants are identical within the area determined, irrespective of animal age or pI values. These results demonstrate that the pI variants of AD-ST are derived from the same precursor by post-translational modification or that they are products of closely related, but distinct, genes. The pI 6.1 and 6.7 subunits presumably increased during the development from the weanling stage to adulthood, resulting in the increase in acidic form(s) of AD-ST (fraction II) in adult females.

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2

Martin, A. F., D. C. Robinson, and R. T. Dowell. "Isomyosin and thyroid hormone levels in pressure-overloaded weanling and adult rat hearts." American Journal of Physiology-Heart and Circulatory Physiology 248, no. 3 (March 1, 1985): H305—H310. http://dx.doi.org/10.1152/ajpheart.1985.248.3.h305.

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We examined the relationship between ventricular isomyosin composition and plasma thyroxine (T4) 5 wk after partial constriction of the abdominal aorta in weanling (21 day) and adult (8 wk) rats. Cardiac enlargement in weanling aorta-constricted animals was associated with a significant (P less than 0.001) decrease in %V1 isomyosin in both left (32%) and right ventricles (25%) with a corresponding increase in the %V3 isomyosin and a reduction in plasma T4 levels. However, the ratio of V1/T4 was similar in weanling control (17.8 +/- 0.8) and aorta-constricted (18.0 +/- 1.4) rats. In adult aorta-constricted animals, there was a significant (P less than 0.001) reduction in the %V1 (16%) isomyosin in the left ventricle and a smaller decrease in the right ventricular V1 (8%) with no change in plasma T4 levels. There was also a significant difference in V1/T4 between control (16.1 +/- 0.4) and aorta-constricted (13.9 +/- 0.7) adult rats in contrast to the maintenance of the V1/T4 in weanling aorta-constricted animals. Thus both increased workload and changes in thyroxine levels contribute to the isomyosin redistribution seen in weanling rats subjected to a pressure overload, whereas, in adult hypertrophied hearts, alterations of the ventricular isomyosin composition appear to be due solely to the increased pressure overload.

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3

Dowell, Russell T. "Metabolic and cyclic nucleotide enzyme activities in muscle and nonmuscle cells of rat heart during perinatal development." Canadian Journal of Physiology and Pharmacology 63, no. 1 (January 1, 1985): 78–81. http://dx.doi.org/10.1139/y85-014.

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Enzyme activities related to aerobic metabolism and cyclic nucleotides were evaluated in muscle and nonmuscle cells of rat heart. The perinatal period from weaning to adult was studied. Malate dehydrogenase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase activities of nonmuscle cells equal or exceed muscle cell activities in the weanling heart. Aerobic enzymes remain unchanged in nonmuscle cells during growth; however, muscle cell activities are enhanced. Adenylate cyclase and guanylate cyclase activities are higher in heart homogenates of weanling than adult rats. Despite elevated adenylate cyclase activity, cyclic AMP levels are identical in weanling and adult rats. Cyclic GMP levels are twofold higher in weanling than in adult rats. Muscle cell metabolism and cyclic nucleotide levels are associated with growth-related changes in heart function and cellularity, respectively.

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4

WAMBERG, S., K. ENGEL, and P. KILDEBERG. "Methionine-induced acidosis in the weanling rat." Acta Physiologica Scandinavica 129, no. 4 (December 1987): 575–83. http://dx.doi.org/10.1111/j.1748-1716.1987.tb08099.x.

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5

Bernardis, L. L., J. Medige, R. Gillespie, H. Wu, and I. Ziv. "The Lateral Hypothalamic Syndrome in the Weanling Rat." Physiology & Behavior 67, no. 5 (November 1999): 799–802. http://dx.doi.org/10.1016/s0031-9384(99)00097-9.

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6

BLAKE, H., and S. HENNING. "Basis for lactose aversion in the weanling rat." Physiology & Behavior 35, no. 2 (August 1985): 313–16. http://dx.doi.org/10.1016/0031-9384(85)90355-5.

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7

Rao, R. K., O. Koldovsky, and T. P. Davis. "Inhibition of intestinal degradation of somatostatin by rat milk." American Journal of Physiology-Gastrointestinal and Liver Physiology 258, no. 3 (March 1, 1990): G426—G431. http://dx.doi.org/10.1152/ajpgi.1990.258.3.g426.

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In vitro degradation of 125I-labeled somatostatin-14 (Tyr11) [I-SS-14(Tyr11)] by luminal flushings of rat gastrointestinal segments was studied to characterize the fate of somatostatin in the gastrointestinal lumen. In addition, we evaluated the effect of rat milk as a potential inhibitor of luminal degradation of 125I-SS-14(Tyr11). Degradation of 125I-SS-14(Tyr11) was not detected in stomach flushings from either suckling or weanling rats. Luminal flushings from the small intestine degraded 125I-SS-14(Tyr11), with a gradient increase of activity from duodenum to midjejunum (degradation in suckling rat midjejunum and ileum was about five times lower than that in weanling rat). Degradation of 125I-SS-14(Tyr11) by luminal flushings of suckling rat midjejunum was dose dependently inhibited by rat milk casein and soluble fractions. Inhibitory activity of rat milk soluble fraction was heat labile and several times more potent than that of casein fraction. Casein fraction appeared to be stable at 100 degrees C for up to 30 min of exposure. These studies suggest that somatostatin is stable in the gastric lumen and that milk protects somatostatin from intestinal luminal proteolysis, indicating a possible physiological significance of milk-borne SS-14 for the suckling rat gastrointestinal tract.

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8

Williamson, D. H., and V. Ilic. "Activities of enzymes of acetoacetate metabolism in rat brown adipose tissue during development." Biochemical Journal 231, no. 3 (November 1, 1985): 773–75. http://dx.doi.org/10.1042/bj2310773.

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The activities of two mitochondrial enzymes concerned in the utilization of acetoacetate, namely 3-oxoacid CoA-transferase and acetoacetyl-CoA thiolase, were high throughout the suckling and weanling period in brown adipose tissue of the rat. In contrast, 3-hydroxybutyrate dehydrogenase activity was comparatively low during this period. The activity of cytosolic acetoacetyl-CoA synthetase (involved in lipogenesis) declined after birth and remained low until the pups were weaned. Experiments with brown-adipose-tissue slices from weanling rats indicated that 70% of the [3-14C]acetoacetate utilized was oxidized to 14CO2, and this value was not altered appreciably by the addition of glucose and insulin.

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9

Said, H. M., F. K. Ghishan, and J. E. Murrell. "Ontogenesis of intestinal transport of 5-methyltetrahydrofolate in the rat." American Journal of Physiology-Gastrointestinal and Liver Physiology 249, no. 5 (November 1, 1985): G567—G571. http://dx.doi.org/10.1152/ajpgi.1985.249.5.g567.

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Developmental aspects of the intestinal transport of 5-methyltetrahydrofolate (5-CH3H4-PteGlu) were studied in suckling (14-day-old), weanling (22-day-old), and adult (90-day-old) rats by use of the intestinal everted-sac technique. Mucosal-to-serosal transport of 0.5 microM 5-CH3H4PteGlu was linear with time for 40-min incubation and occurred at a rate of 0.035, 0.032, and 0.010 nmol X g initial tissue wet wt-1 X min-1 for suckling, weanling, and adult rats, respectively. The transport of 5-CH3H4PteGlu in all age groups was pH dependent (maximal at pH 6) and was higher in the jejunum than in the ileum. In all age groups the transport of 5-CH3H4PteGlu occurred by an active carrier-mediated system. The system was saturable; energy, temperature, and Na dependent; inhibited by structural analogues; and capable of accumulating the substrate against a concentration gradient. Kinetic parameters of the transport process, however, showed some difference. A progressive decrease in Vmax was observed from suckling to weanling to adult rats (5.1, 3.7, and 0.8 nmol X g initial tissue wet wt-1 X 30 min-1, respectively), while apparent Kt was similar (2.2, 1.73, and 1.79 microM, respectively). This study demonstrates that the transport system of 5-CH3H4PteGlu in the rat is fully developed at the suckling age. The results also suggest that the activity and/or the number, but not the affinity, of the transport carriers decrease with maturation.

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10

Balamurugan, Krishnaswamy, and Hamid M. Said. "Ontogenic regulation of folate transport across rat jejunal brush-border membrane." American Journal of Physiology-Gastrointestinal and Liver Physiology 285, no. 5 (November 2003): G1068—G1073. http://dx.doi.org/10.1152/ajpgi.00188.2003.

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Folate is an essential micronutrient that in mammals must be obtained from exogenous sources via intestinal absorption. Previous studies from our laboratory and others have demonstrated that folate absorption from the small intestine is mediated via the reduced-folate carrier (RFC). The goal of this study was to determine whether the initial step of folate uptake by intestinal epithelial cells, i.e., transport across the brush-border membrane (BBM) of the polarized enterocytes, is ontogenically regulated, and if so, to determine the molecular mechanism involved. Purified BBM vesicles (BBMV) isolated from suckling, weanling, and adult rats were used in this study. The initial rate of carrier-mediated uptake of a physiological concentration of folic acid (0.1 μM) by jejunal BBMV was found to be significantly ( P < 0.01) higher in suckling compared with weanling rats, which was, in turn, significantly ( P < 0.01) higher than that in adult rats. This decline in carrier-mediated folate uptake with maturation was found to be mediated via a decrease in the maximum velocity of the folate uptake process (6.55 ± 0.87, 2.16 ± 0.10, 0.90 ± 0.16 pmol·mg protein-1·10 s-1 for suckling, weanling, and adult rats, respectively), with no changes in its apparent Km. Western blot analysis of BBM protein and real-time PCR showed RFC protein and mRNA levels, respectively, to be significantly ( P < 0.01 for both) higher in suckling compared with weanling rats, which were in turn significantly ( P < 0.01 for both) higher than that in adult rats. These changes were found by nuclear run-on assay to be associated with a parallel decline in the RFC transcriptional rate in jejunal epithelia with maturation. In situ hybridization showed a similar pattern of RFC message distribution along crypt/villus axis in suckling and adult rat jejunum. These results demonstrate for the first time that folate transport across the intestinal BBM is under ontogenic regulation during early stages of life and that this regulation involves a transcriptional regulatory mechanism(s).

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11

KARLÉN, J. "Renal response to parathyroid hormone in the weanling rat." Acta Physiologica Scandinavica 134, no. 1 (September 1988): 17–21. http://dx.doi.org/10.1111/j.1748-1716.1988.tb08454.x.

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12

Imaida, Katsumi, Mei-Sie Lee, Ching Y. Wang, and Charles M. King. "Carcinogenicity of dinitropyrenes in the weanling female CD rat." Carcinogenesis 12, no. 7 (1991): 1187–91. http://dx.doi.org/10.1093/carcin/12.7.1187.

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13

Raisuddin, K. P. Singh, S. I. A. Zaidi, A. K. Saxena, and P. K. Ray. "Effects of aflatoxin on lymphoid cells of weanling rat." Journal of Applied Toxicology 10, no. 4 (August 1990): 245–50. http://dx.doi.org/10.1002/jat.2550100404.

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14

Henry, Christiani Jeyakumar, Philip R. Payne, and Amal Ghusain-Choueiri. "Relationship between tissue mobilization and storage in the rat." British Journal of Nutrition 78, no. 1 (July 1997): 131–41. http://dx.doi.org/10.1079/bjn19970125.

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The amount of energy mobilized or stored as protein, expressed as a proportion of the total energy stored or mobilized (defined as the P ratio, Payne & Dugdale, 1977), was investigated in the young male (rapid growth) and adult female (slow growth) rat. Energy mobilization was induced by a 3 d fast and the changes in body content of fat and lean tissues were used to estimate the fasting P ratio (Pfast). Tissue storage was subsequently effected by 17 d of refeeding and the corresponding ratio (Prefed) was calculated from the amounts of lean and fat tissue regained. The same experimental protocol was used for measuring Pfast and Prefed in weanling (30d) and adult (130d) rats. Weight-matched individuals were assigned to three groups. All animals in group 1 were killed at the beginning of the experiment. Animals in group 2 were fasted for 3d and then killed. Group 3 animals were first fasted for 3d, then had free access to a stock diet for a further 17 d before being killed. During fasting, a close linear relationship was found between weight change and body energy changes (r 0·985, and r 0·92, P < 0·001 for weanlings and adult rats respectively) and between carcass N loss and urinary N loss (r 0·933, P < 0·001). These relationships were used to estimate the body energy and N content of each animal at the end of the initial fasting period. Hence, both Pfast and Prefed values could be calculated for all individuals at both ages. When Pfast and Prefed were calculated for adult rats, the mean values were similar (0·138 (SE 0·002) and 0·130 (SE 0·006) respectively). Individually, the Pfast, and Prefed values were correlated (r 0·54, P = 0·058). In weanling rats, the mean Prefed value was about 2·5 times the Pfast (0·421 (SE 0·0113) v. 0·156 (SE 0·004)). Despite the differences in Pfast and Prefed, the individual values were again correlated (r 0·668, P < 0·05). These results support the suggestion made by Payne & Dugdale (1977), that particular P- ratio values are characteristic of individuals and describe the extent to which protein is mobilized or stored during fasting or refeeding. These observations are discussed in relation to the predictions made by the Payne-Dugdale model.

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15

Foltzer-Jourdainne, C., J. C. Garaud, E. Nsi-Emvo, and F. Raul. "Epidermal growth factor and the maturation of intestinal sucrase in suckling rats." American Journal of Physiology-Gastrointestinal and Liver Physiology 265, no. 3 (September 1, 1993): G459—G466. http://dx.doi.org/10.1152/ajpgi.1993.265.3.g459.

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The regulatory effect of epidermal growth factor (EGF) on the postnatal maturation of sucrase was investigated in the small intestine of suckling and weanling rats. Administration of EGF (0.5 micrograms.g body wt-1.day-1) to suckling rats caused a slight precocious induction of sucrase expression. In weanling rats EGF markedly stimulated sucrase activity; however, at both ages, the effect of hydrocortisone was more potent. When the glucocorticoid antagonist RU-38486 was administered to sucklings, the precocious induction of sucrase activity by hydrocortisone was inhibited by 80%. However, RU-38486 or adrenalectomy did not prevent the inductive effect of EGF, indicating that EGF acts in a glucocorticoid-independent manner. EGF also potentiated the effect of hydrocortisone and dietary sucrose on the precocious induction of sucrase activity in the sucklings. At weaning, administration of an antiserum specific to rat EGF significantly decreased sucrase activity. This study shows the involvement of EGF in the postnatal maturation of intestinal sucrase in the rat.

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16

Thorne, B. Michael, Art Cook, Tim Donohoe, Steve Lyon, Denis M. Medeiros, and Chris Moutzoukis. "Aluminum toxicity and behavior in the weanling Long-Evans rat." Bulletin of the Psychonomic Society 25, no. 2 (February 1987): 129–32. http://dx.doi.org/10.3758/bf03330305.

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17

Rodriguez-Sargent, C., I. Torres-Negron, J. L. Cangiano, and M. Martinez-Maldonado. "Deoxycorticosterone hypertension in the intact weanling rat without salt loading." Hypertension 15, no. 2_Suppl (February 1, 1990): I112. http://dx.doi.org/10.1161/01.hyp.15.2_suppl.i112.

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18

Lewis, Eric C., Robert H. Glew, James Chambers, Patrick Coyle та Jhon Coppes. "α-1-Antitrypsin metabolism in the protein-deficient weanling rat". British Journal of Nutrition 54, № 1 (липень 1985): 63–77. http://dx.doi.org/10.1079/bjn19850093.

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1. Protein-deficient weanling rats fed on a 30 g casein/kg diet for 3 weeks lost albumin but maintained the level of serum α-1-antitrypsin, the most abundant protease inhibitor in blood.2.α-1-Antitrypsins from malnourished rats and control rats (given 250 g casein/kg diet) differed; the protease inhibitor from protein-deficient animals: (1) was more acidic, (2) appeared slightly larger (57400 v. 56000 daltons) on sodium dodecyl sulphate (SDS)-polyacrylamide gels, (3) had a more acidic Pitype and increased anodal mobility at pH 8.9, (4) bound more concanavalin-A and contained more carbohydrate, specifically two to three extra sialic acid residues. The amino sugar and neutral sugar contents of both preparations of α-1-antitrypsin were the same.3. Analysis of the products of cyanogen-bromide cleavage revealed that α-1-antitrypsin preparations from protein-deficient rats contain an extra glycopeptide that was not present in α-1-antitrypsin from control animals.4. In vivo studies showed that the increased sialic acid content of α-1-antitrypsin of protein-deficient rats did not alter the half-life of the molecule in the blood of control rats. However, the fractional catabolic rate of α-1-antitrypsin from either well-nourished or protein-deficient rats was significantly (P < 0.01) lower in protein- deficient rats than in control rats (0.0247/h v. 0.0406/h).5. The decreased fractional catabolic rate could not be explained by changes in hepatic mannosyl-, galactosyl- or N-acetylhexosaminyl receptors since liver perfusion studies showed that bovine serum albumin, when covalently modified separately with each of these ligands, was extracted from the perfusion medium as rapidly or more rapidly by livers from malnourished animals.6. Perfused livers from protein-deficient rats secrete three times more α-1-antitrypsin than do livers from well-nourished animals.7. The decreased fractional catabolic rate and increased rate of biosynthesis and secretion of the glycoprotein by livers from protein-deficient animals may account for the maintenance of α-1-antitrypsin levels during protein malnutrition.

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19

Gravina, Fernanda S., Clarice K. B. da Silveira, Adriano M. de Assis, Débora K. Rieger, Carolina Guerini, Alexandre P. Müller, Marcelo Farina, Liane N. Rotta та Marcos L. S. Perry. "Experimental Hypothyroidism Inhibits δ-Aminolevulinate Dehydratase Activity in Neonatal Rat Blood and Liver". Experimental Biology and Medicine 232, № 8 (вересень 2007): 1021–26. http://dx.doi.org/10.3181/0703-rm-66.

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The aim of this study was to investigate the potential relationship between hypothyroidism and δ-aminolevulinate dehydratase (δ-ALA-D) activity in rat blood and liver. Experimental hypothyroidism was induced in weanling rats by exposing their mothers to propylthiouracil (PTU) diluted in tap water (0.05% w/ v), ad libitum, during the lactational period (PTU group). Control (euthyroid) group included weanling rats whose mothers received just tap water, ad libitum, during the lactational period. Reverted-hypothyroid group (PTU + 3,3′,5-triiodo-L-thyronine [T3]) included weanling rats whose mothers were exposed to PTU similarly to those in the hypothyroid group, but pups received daily subcutaneous injections of T3 (20 μg/kg, from Postnatal Days 2–20). After the treatment, serum T3 levels were drastically decreased (around 70%) in the PTU group, and this phenomenon was almost reverted by exogenous T3. PTU decreased blood δ-ALA-D activity by 75%, and T3 treatment prevented such phenomena. Erythrocytes and hemoglobin levels were increased by 10% in PTU-treated animals and higher increments (around 25%) were observed in these parameters when exogenous T3 was coadministered. Dithiothreitol did not change blood δ-ALA-D activity of PTU-exposed animals when present in the reaction medium, suggesting no involvement of the enzyme’s essential thiol groups in PTU-induced δ-ALA-D inhibition. PTU did not affect blood δ-ALA-D activity in vitro. These results are the first to show a correlation between hypothyroidism and decreased δ-ALA-D activity and point to this enzyme as a potential molecule involved with hypothyroidism-related hematological changes.

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20

Wedde-Beer, Katrin, Chengping Hu, Maria M. Rodriguez, and Giovanni Piedimonte. "Leukotrienes mediate neurogenic inflammation in lungs of young rats infected with respiratory syncytial virus." American Journal of Physiology-Lung Cellular and Molecular Physiology 282, no. 5 (May 1, 2002): L1143—L1150. http://dx.doi.org/10.1152/ajplung.00323.2001.

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Respiratory syncytial virus (RSV) infection potentiates neurogenic inflammation in rat airways. Because some vascular effects of sensory nerves are mediated by cysteinyl leukotrienes (cysLTs), we studied whether the receptor antagonist montelukast inhibits neurogenic plasma extravasation in RSV-infected rats. Pathogen-free rats were inoculated at 2 wk (weanlings) or 12 wk (adults) of age with RSV or virus-free medium and treated with montelukast or its vehicle starting 1 day before inoculation. Five days postinoculation, we measured the extravasation of Evans blue-labeled albumin in the respiratory tract after stimulation of sensory nerves with capsaicin. Montelukast had no effect in the extrapulmonary airways but abolished albumin extravasation in the intrapulmonary airways of RSV-infected rats, with a larger effect in weanlings than in adults. Increased concentrations of 5-lipoxygenase-encoding mRNA and cysLTs, as well as numerous mast cells, were detected in the lung tissues of RSV-infected weanling rats. These observations suggest that the release of neuropeptides from capsaicin-sensitive sensory nerves and nonneuronal cells in the lungs of RSV-infected young rats increases vascular permeability by promoting the release of leukotrienes from mast cells.

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21

Dugail, I., A. Quignard-Boulange, R. Bazin, X. Le Liepvre, and M. Lavau. "Adipose-tissue-specific increase in glyceraldehyde-3-phosphate dehydrogenase activity and mRNA amounts in suckling pre-obese Zucker rats. Effect of weaning." Biochemical Journal 254, no. 2 (September 1, 1988): 483–87. http://dx.doi.org/10.1042/bj2540483.

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The regulation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression was studied during the onset of obesity in the genetically obese (fa/fa) rat by determination of GAPDH activity and hybridizable mRNA amounts in adipose tissue and liver from suckling and weanling rats. GADPH activity remained low throughout the suckling period, and a burst of activity occurred after weaning in both lean and obese pups. As early as 7 days of age, adipose tissue from pre-obese rats displayed a significant increase in enzyme activity, whereas no difference could be detected in the liver. In both suckling (16 days of age) and weanling (30 days of age) obese rats a proportionate increase in GAPDH activity and mRNA amounts was observed in adipose tissue, but not in liver. It is concluded that the obese genotype influences GAPDH gene expression at a pretranslational level and in a tissue-specific manner. This phenomenon could partly contribute to the hyperactive fat accretion in the obese rat, since glycolysis is the major metabolic pathway for lipogenic substrates in adipose tissue.

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22

Inamdar, Shashita R., Kathleen M. Eyster та Evelyn H. Schlenker. "Selected Contribution: Estrogen receptor-α antisense decreases brain estrogen receptor levels and affects ventilation in male and female rats". Journal of Applied Physiology 91, № 4 (1 жовтня 2001): 1886–92. http://dx.doi.org/10.1152/jappl.2001.91.4.1886.

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We hypothesized that administration of an antisense oligodeoxynucleotide (ODN) to estrogen receptor (ER)-α mRNA decreases the ER protein in the neonatal rat brain, alters the sex-specific ventilatory responses to aspartic acid in rats, and counteracts the effects of testosterone proportionate (TP) in females. One-day-old rat pups were injected intraventricularly with vehicle, antisense ER ODN, or scrambled ODN control. Additional groups of females received TP or vehicle and one of the three treatments. Brain ER protein levels were decreased by 65% at 6 h and 35% at 24 h after antisense ODN. Aspartic acid decreased ventilation in all groups of weanling males and females except ER ODN-treated females and TP-vehicle-treated females. Aspartic acid decreased ventilation in all groups of adult females except those given TP and in males. Weanling ER ODN-treated rats were shorter and weighed less than controls. Only adult ER ODN-treated males exhibited these traits. Thus neonatal ER affects aspartic acid modulation of breathing and body growth in a sex-specific and developmental manner.

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23

Fukuda, Y., and A. Aperia. "Differentiation of Na+-K+ pump in rat proximal tubule is modulated by Na+-H+ exchanger." American Journal of Physiology-Renal Physiology 255, no. 3 (September 1, 1988): F552—F557. http://dx.doi.org/10.1152/ajprenal.1988.255.3.f552.

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This study examines the effect of in vivo modulation of Na+-H+ exchange activity on the development of Na+-K+-ATPase in rat kidney proximal convoluted tubule (PCT) segments. To stimulate Na+-H+ exchanger (major entry pathway for Na in PCT), weanling rats were fed NH4Cl for 4 days to induce metabolic acidosis (MA). In vehicle (Vh)-fed rats PCT Na+-K+-ATPase activity (pmol Pi.mm tubule-1.h-1 +/- SE) increased from 481 +/- 78 at 16 days to 1,122 +/- 119 at 20 days. In 20-day-old chronic MA rats, PCT Na+-K+-ATPase activity was 1,717 +/- 109, i.e., significantly higher (P less than 0.01) relative to controls. Chronic MA had no effect on PCT Mg ATPase activity and on Na+-K+-ATPase in the medullary thick ascending limb (MTAL). To inhibit the Na+-H+ exchanger, weanling rats received amiloride (30 micrograms.100 g body wt-1.day-1) via osmotic minipump for 4 days. In Vh-treated rats PCT Na+-K+-ATPase increased from 481 +/- 78 at 16 days to 1,428 +/- 81 at 20 days. In rats given chronic amiloride, PCT Na+-K+-ATPase was significantly lower (858 +/- 75) at 20 days relative to controls but PCT Mg ATPase and MTAL Na+-K+-ATPase activity was the same as in controls. Chronic MA and amiloride had no significant effect on PCT Na+-K+-ATPase activity in adult rats. Acute MA and acute amiloride injection had no significant effect on PCT Na+-K+-ATPase in weanling rats.(ABSTRACT TRUNCATED AT 250 WORDS)

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24

Cardenas, Silvia, Mario Scuri, Lennie Samsell, Barbara Ducatman, Pablo Bejarano, Alexander Auais, Melissa Doud, Kalai Mathee, and Giovanni Piedimonte. "Neurotrophic and neuroimmune responses to early-life Pseudomonas aeruginosa infection in rat lungs." American Journal of Physiology-Lung Cellular and Molecular Physiology 299, no. 3 (September 2010): L334—L344. http://dx.doi.org/10.1152/ajplung.00017.2010.

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Early-life respiratory infection with Pseudomonas aeruginosa is common in children with cystic fibrosis or immune deficits. Although many of its clinical manifestations involve neural reflexes, little information is available on the peripheral nervous system of infected airways. This study sought to determine whether early-life infection triggers a neurogenic-mediated immunoinflammatory response, the mechanisms of this response, and its relationship with other immunoinflammatory pathways. Weanling and adult rats were inoculated with suspensions containing P. aeruginosa (PAO1) coated on alginate microspheres suspended in Tris-CaCl2 buffer. Five days after infection, rats were injected with capsaicin to stimulate nociceptive nerves in the airway mucosa, and microvascular permeability was measured using Evans blue as a tracer. PAO1 increased neurogenic inflammation in the extra- and intrapulmonary compartments of weanlings but not in adults. The mechanism involves selective overexpression of NGF, which is critical for the local increase in microvascular permeability and for the infiltration of polymorphonuclear leukocytes into infected lung parenchyma. These effects are mediated in part by induction of downstream inflammatory cytokines and chemokines, especially IL-1β, IL-18, and leptin. Our data suggest that neurogenic-mediated immunoinflammatory mechanisms play important roles in airway inflammation and hyperreactivity associated with P. aeruginosa when infection occurs early in life.

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25

Ricketts, Richard R. "Temporary intraabdominal cryptorchidism in the weanling rat leads to irreversible azoospermia." Journal of Pediatric Surgery 27, no. 6 (June 1992): 788. http://dx.doi.org/10.1016/s0022-3468(05)80139-3.

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26

Gulati, S., K. D. Gill, and R. Nath. "Effect of Cadmium on Lipid Composition of the Weanling Rat Brain." Acta Pharmacologica et Toxicologica 59, no. 2 (March 13, 2009): 89–93. http://dx.doi.org/10.1111/j.1600-0773.1986.tb00139.x.

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27

Eifel, Patricia J., Christine M. Sampson, and Susan L. Tucker. "Radiation fractionation sensitivity of epiphyseal cartilage in a weanling rat model." International Journal of Radiation Oncology*Biology*Physics 19, no. 3 (September 1990): 661–64. http://dx.doi.org/10.1016/0360-3016(90)90493-4.

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28

Gratny, Linda L., Kimberly Ringer, Robert T. Hall, and Uri S. Alon. "Salt Supplementation, Growth, and Nephrocalcinosis in the Furosemide-Treated Weanling Rat." Neonatology 71, no. 1 (1997): 37–45. http://dx.doi.org/10.1159/000244395.

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29

Burman, M. A., N. J. Murawski, F. L. Schiffino, J. B. Rosen, and M. E. Stanton. "Factors governing single-trial contextual fear conditioning in the weanling rat." Behavioral Neuroscience 123, no. 5 (October 2009): 1148–52. http://dx.doi.org/10.1037/a0016733.

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30

Kort, Will J., Ineke Hekking-Weijma, and Marcel Vermeij. "Temporary intraabdominal cryptorchidism in the weanling rat leads to irreversible azoospermia." Journal of Surgical Research 51, no. 2 (August 1991): 138–42. http://dx.doi.org/10.1016/0022-4804(91)90084-y.

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31

Lejeune, Helga, and Pierre Jasselette. "DRL performance in the weanling rat: A comparison with adult subjects." Physiology & Behavior 40, no. 3 (January 1987): 271–78. http://dx.doi.org/10.1016/0031-9384(87)90046-1.

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32

Languille, Solène, Paulette Richer, and Bernard Hars. "Abrupt emergence of long-lasting memory in the pre-weanling rat." Behavioural Brain Research 207, no. 2 (March 5, 2010): 515–19. http://dx.doi.org/10.1016/j.bbr.2009.10.035.

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33

Sokol, R. J., S. F. Taylor, M. W. Devereaux, R. Khandwala, N. J. Sondheimer, R. H. Shikes, and G. Mierau. "Hepatic oxidant injury and glutathione depletion during total parenteral nutrition in weanling rats." American Journal of Physiology-Gastrointestinal and Liver Physiology 270, no. 4 (April 1, 1996): G691—G700. http://dx.doi.org/10.1152/ajpgi.1996.270.4.g691.

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Hepatobiliary dysfunction occurs commonly in infants on prolonged parenteral nutrition alimentation; however, the underlying mechanisms causing liver injury are poorly understood. We postulated that oxidant stress played a significant role in parenteral nutrition-induced liver abnormalities and tested this hypothesis in a rat model. Weanling male rats received 8 days of total parenteral nutrition (TPN) through a central venous catheter (TPN group), pair feeding of rat chow and placement of a central venous catheter (sham group), or ad libitum feedings of rat chow (control group). After 8 days of TPN, serum alanine aminotransferase and cholylglycine levels were elevated, hepatocellular steatosis was present, hepatic mitochondria had dilated intracristal spaces, and lipid peroxidation of mitochondria was increased compared with sham and control groups. Hepatic glutathione levels decreased to 16% of control values after 5 days of TPN; this was followed by mitochondrial lipid peroxidation and elevated serum cholylglycine levels after 8 days of TPN. Sham and control rats showed no evidence of mitochondrial lipid peroxidation or liver injury after 8 days. Removal of metabisulfate from TPN solutions and addition of cysteine HCl or choline had no major effect on these findings. Bacterial translocation was not increased in TPN rats. These data suggest that glutathione depletion and oxidant stress are important factors in the pathogenesis of TPN-induced liver abnormalities in the weanling rats.

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34

Bozzini, C., A. C. Barcelo, R. M. Alippi, T. L. Leal, and C. E. Bozzini. "The Concentration of Dietary Casein Required for Normal Mandibular Growth in the Rat." Journal of Dental Research 68, no. 5 (May 1989): 840–42. http://dx.doi.org/10.1177/00220345890680051801.

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To determine a suitable casein concentration for normal, undeformed mandibular growth, we placed weanling male rats on diets containing graded levels of casein between 0% and 30% for 19 days. Some weanlings were killed so that initial values could be established. Ten linear dimensions corresponding to the six skeletal units of the mandible were evaluated so that their growth rates at the end of the experimental period could be established. Other dimensions were also evaluated for study of the growth rate of the bone as a whole. The macroscopic growth of the mandible showed a sigmoidal relationship with dietary casein concentration, most of the measurements reaching a plateau at 20% casein. Within the skeletal units, four dimensions corresponding to the alveolar and symphyseal regions did not change with age and were not affected by the casein content of the diet. The remaining six dimensions-corresponding to condylar, coronoid, angular, and basal regions of the mandible-increased with age and were related positively to dietary casein concentration. Their growth patterns were not uniform, although all of them reached maximal values when the diet contained 20% casein. Therefore, deformation of the mandible appears to occur in rats fed diets with a casein concentration lower than 20%. It appears that a dietary casein concentration of 20% is required for normal, undeformed mandibular growth.

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35

Casasnovas, Jose, Yunhee Jo, Xi Rao, Xiaoling Xuei, Mary E. Brown, and Kok Lim Kua. "High glucose alters fetal rat islet transcriptome and induces progeny islet dysfunction." Journal of Endocrinology 240, no. 2 (February 2019): 309–23. http://dx.doi.org/10.1530/joe-18-0493.

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Offspring of diabetic mothers are susceptible to developing type 2 diabetes due to pancreatic islet dysfunction. However, the initiating molecular pathways leading to offspring pancreatic islet dysfunction are unknown. We hypothesized that maternal hyperglycemia alters offspring pancreatic islet transcriptome and negatively impacts offspring islet function. We employed an infusion model capable of inducing localized hyperglycemia in fetal rats residing in the left uterine horn, thus avoiding other factors involved in programming offspring pancreatic islet health. While maintaining euglycemia in maternal dams and right uterine horn control fetuses, hyperglycemic fetuses in the left uterine horn had higher serum insulin and pancreatic beta cell area. Upon completing infusion from GD20 to 22, RNA sequencing was performed on GD22 islets to identify the hyperglycemia-induced altered gene expression. Ingenuity pathway analysis of the altered transcriptome found that diabetes mellitus and inflammation/cell death pathways were enriched. Interestingly, the downregulated genes modulate more diverse biological processes, which includes responses to stimuli and developmental processes. Next, we performed ex and in vivo studies to evaluate islet cell viability and insulin secretory function in weanling and adult offspring. Pancreatic islets of weanlings exposed to late gestation hyperglycemia had decreased cell viability in basal state and glucose-induced insulin secretion. Lastly, adult offspring exposed to in utero hyperglycemia also exhibited glucose intolerance and insulin secretory dysfunction. Together, our results demonstrate that late gestational hyperglycemia alters the fetal pancreatic islet transcriptome and increases offspring susceptibility to developing pancreatic islet dysfunction.

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36

Myers, B. A., M. A. Dubick, R. D. Reynolds, and R. B. Rucker. "Effect of vitamin B-6 (pyridoxine) deficiency on lung elastin cross-linking in perinatal and weanling rat pups." Biochemical Journal 229, no. 1 (July 1, 1985): 153–60. http://dx.doi.org/10.1042/bj2290153.

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Weanling and perinatal rats were rendered vitamin B-6 (pyridoxine)-deficient. The rat pups were nursed from vitamin B-6-deficient or -sufficient dams and were killed at day 15 after parturition. The weanling rats were fed vitamin B-6-deficient or -sufficient diets and were killed after 5 weeks of treatment. Lung elastin from the groups of rats was then studied with respect to its content of lysine-derived cross-linking amino acids. Lung lysyl oxidase activity was also measured. B-6 deficiency decreased the number of lysine residues in elastin that were converted into the cross-linking amino acid precursor allysine. However, a more significant defect in cross-link formation was an apparent block in the condensation steps leading to the formation of desmosine. Desmosine was decreased, with an increase in the amounts of aldol condensation products (aldol CP) in elastin. It is proposed that the elevation in aldol CP results from the formation of thiazines, which are produced from the reaction between aldehyde and homocysteine. The concentration of homocysteine is significantly elevated in vitamin B-6-deficient rats.

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37

FERVENZA, FERNANDO C., TANNY TSAO, FAY HSU, and RALPH RABKIN. "Intrarenal Insulin-Like Growth Factor-1 Axis after Unilateral Nephrectomy in Rat." Journal of the American Society of Nephrology 10, no. 1 (January 1999): 43–50. http://dx.doi.org/10.1681/asn.v10143.

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Abstract. It has been suggested that insulin-like growth factor-1 (IGF-1) may play a role in early compensatory renal growth. Since IGF-1 action is influenced by IGF binding proteins (IGFBP), this study was conducted to characterize the changes in gene expression not only of IGF-1 and its receptor, but also of IGFBP in the hypertrophying kidney of adult and weanling rats 1 wk after removal of the other kidney. At this time, there were distinct age-dependent changes in the renal IGF-1 axis. In the mature kidney, IGF-1 mRNA levels fell without a change in kidney IGF-1 peptide content. Likewise, although IGFBP-2, -3, and -5 mRNA levels fell, membrane-associated IGFBP did not change. IGF-1 receptor mRNA levels and IGF-1 receptor number both fell. In the weanling kidneys, IGF-1 mRNA and peptide levels and IGF-1 receptor binding were unaltered. However, IGFBP-3, -4, and -5 mRNA levels were increased, as were plasma membrane-associated IGFBP. Although these changes in the intrarenal IGF-1 axis were distinct, it is difficult to conceive how in either the mature or immature rat they could contribute to the ongoing compensatory renal growth that occurs 1 wk after loss of kidney mass unless IGF-1 were acting in a synergistic manner with other growth promoters.

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38

Burrow, Keegan, Wayne Young, Niels Hammer, Sarah Safavi, Mario Scholze, Michelle McConnell, Alan Carne, David Barr, Malcolm Reid, and Alaa El-Din Bekhit. "The Effect of the Supplementation of a Diet Low in Calcium and Phosphorus with Either Sheep Milk or Cow Milk on the Physical and Mechanical Characteristics of Bone using A Rat Model." Foods 9, no. 8 (August 7, 2020): 1070. http://dx.doi.org/10.3390/foods9081070.

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This study assessed the effect of cow milk (CM) and sheep milk (SM) consumption on the micro-structure, mechanical function, and mineral composition of rat femora in a male weanling rat model. Male weanling rats were fed a basal diet with a 50% reduction in calcium and phosphorus content (low Ca/P-diet) supplemented with either SM or CM. Rats were fed for 28 days, after which the femora were harvested and stored. The femora were analyzed by μ-CT, three-point bending, and inductively coupled plasma–mass spectrometry (ICP-MS). The addition of either milk to the low Ca/P-diet significantly increased (p < 0.05) trabecular bone volume, trabecular bone surface density, trabecular number, cortical bone volume, and maximum force, when compared to rats that consumed only the low Ca/P-diet. The consumption of either milk resulted in a significant decrease (p < 0.05) in trabecular pattern factor, and cortical bone surface to volume ratio when compared to rats that consumed only the low Ca/P-diet. The results were achieved with a lower consumption of SM compared to that of CM (p < 0.05). This work indicates that SM and CM can help overcome the effects on bone of a restriction in calcium and phosphorus intake.

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39

Kojima, Sayuri, Christina Catavero, and Linda Rinaman. "Maternal high-fat diet increases independent feeding in pre-weanling rat pups." Physiology & Behavior 157 (April 2016): 237–45. http://dx.doi.org/10.1016/j.physbeh.2016.02.010.

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40

Faber, Christopher N., Warren F. Diven, Abe E. Axelrod, and Robert H. Glew. "Changes in serum lysosomal enzymes in the vitamin B6-deficient weanling rat." Nutrition Research 11, no. 1 (January 1991): 117–28. http://dx.doi.org/10.1016/s0271-5317(05)80156-3.

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41

Robinson, S. "Perinatal Methadone Exposure Affects Dopamine, Norepinephrine, and Serotonin in the Weanling Rat." Neurotoxicology and Teratology 19, no. 4 (July 8, 1997): 295–303. http://dx.doi.org/10.1016/s0892-0362(97)00018-4.

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42

Hasan, Jamal, Kay D. Beharry, Zahra Gharraee, Yuri Stavitsky, Patricia Abad-Santos, Matthew Abad-Santos, Jacob V. Aranda, and Houchang D. Modanlou. "Early postnatal ibuprofen and indomethacin effects in suckling and weanling rat kidneys." Prostaglandins & Other Lipid Mediators 85, no. 3-4 (March 2008): 81–88. http://dx.doi.org/10.1016/j.prostaglandins.2007.10.006.

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43

Jandacek, R. J., E. J. Hollenbach, B. N. Holcombe, C. M. Kuehlthau, J. C. Peters, and J. D. Taulbee. "Reduced storage of dietary eicosapentaenoic and docosahexaenoic acids in the weanling rat." Journal of Nutritional Biochemistry 2, no. 3 (March 1991): 142–49. http://dx.doi.org/10.1016/0955-2863(91)90006-q.

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44

Robinson, Susan E., Qiu Mo, Jennifer R. Maher, Melisa J. Wallace, and Paul M. Kunko. "Perinatal exposure to methadone affects central cholinergic activity in the weanling rat." Drug and Alcohol Dependence 41, no. 2 (June 1996): 119–26. http://dx.doi.org/10.1016/0376-8716(96)01238-0.

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45

Ashby, J., and P. A. Lefevre. "The Weanling Male Rat as an Assay for Endocrine Disruption: Preliminary Observations." Regulatory Toxicology and Pharmacology 26, no. 3 (December 1997): 330–37. http://dx.doi.org/10.1006/rtph.1997.1177.

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46

Pácha, J., та I. Mikšík. "11β-Hydroxysteroid dehydrogenase in developing rat intestine". Journal of Endocrinology 148, № 3 (березень 1996): 561–66. http://dx.doi.org/10.1677/joe.0.1480561.

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Abstract The enzyme 11β-hydroxysteroid dehydrogenase (11β-OHSD) prevents the binding of corticosterone to mineralocorticoid receptors by reversible conversion of biologically active corticosterone to inactive 11-dehydrocorticosterone. To clarify the relationship between high plasma concentrations of corticosterone during weaning and high activity of intestinal transport pathways that are induced by aldosterone in immature intestine, we have studied the distribution, developmental pattern and regulation of 11 β-OHSD in intestinal segments that possess mineralocorticoid target epithelium. Dehydrogenase activity was already high in the caecum, and the proximal and distal colon on the second postnatal day and altered little until adulthood. In contrast, the activity in the ileum was low during the first two weeks of life, rose more than 5-fold in the next 20 days to attain a peak in 30-day-old rats, and thereafter declined to the values of adult animals. There was no significant reductase activity (conversion of 11-dehydrocorticosterone to corticosterone) in any intestinal segment of young and adult rats. The regulation of intestinal 11β-OHSD by corticosteroids and thyroid hormones was studied in the ileum and distal colon. In weanling rats, adrenalectomy or a high-salt diet decreased 11β-OHSD activities in both intestinal segments whereas dexamethasone administration prevented this decline in adrenalectomized rats and administration of deoxycorticosterone acetate led to a significant increase of intestinal 11β-OHSD activities in rats kept on a high-salt diet. Dexamethasone administration to intact adult rats also stimulated 11 β-OHSD activity in the ileum and distal colon. The changes in thyroid status of weanling rats did not change the 11β-OHSD activities. We conclude that (1) the developmental patterns of 11β-OHSD activity in the small and large intestine are not identical and this discrepancy may facilitate the maturation effect of glucocorticoids in the small intestine and the stimulatory effect of aldosterone in the large intestine and (2) corticosteroids but not thyroid hormones can modulate 11β-OHSD activity in the developing intestine. Journal of Endocrinology (1996) 148, 561–566

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47

Flores, C. A., P. M. Brannon, M. A. Wells, M. Morrill, and O. Koldovsky. "Effect of diet on triolein absorption in weanling rats." American Journal of Physiology-Gastrointestinal and Liver Physiology 258, no. 1 (January 1, 1990): G38—G44. http://dx.doi.org/10.1152/ajpgi.1990.258.1.g38.

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To determine the effect of altered dietary fat intake on the rate of fat absorption in the intact animal, we fed male weanling rats either a high fat-low carbohydrate (HF-LC) (calories: 67% fat, 10% carbohydrate, 20% protein) or low fat-high carbohydrate (LF-HC) (calories: 10% fat, 67% carbohydrate, 20% protein) diet for 8 days. Absorption of [14C]triolein was estimated by determining 1) 14CO2 expiration in breath, 2) intestinal triglyceride output using Triton WR-1339, an inhibitor of lipoprotein lipase, and 3) quantitating the disappearance of labeled triolein from the gastrointestinal tract. Changes in the activity of pancreatic lipase and amylase confirmed the adaptation to altered fat and carbohydrate intake. Animals fed the HF-LC diet exhibited approximately twofold greater triolein disappearance, oxidation, and intestinal triglyceride output compared with animals fed LF-HC. There was also a highly significant linear relationship between 14CO2 excretion and intestinal triglyceride output in both diet groups. These data show that high dietary fat content markedly enhances in vivo fat absorption in the weanling rat.

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48

Van Herck, H., J. P. Van Wouwe, M. Veldhuizen, V. Baumans, F. R. Stafleu, and A. C. Beynen. "Clinical examination of weanling rats with early zinc deficiency." Laboratory Animals 23, no. 4 (October 1, 1989): 328–32. http://dx.doi.org/10.1258/002367789780746015.

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In order to gain experience about the detection of adverse effects during a scientific procedure, we carried out a clinical examination of rats with zinc deficiency. In weanling rats fed a zinc-deficient diet (30 μmol zinc/kg) for 10 days, the mean tibial concentration of zinc was reduced by 53% and body weight gain by 73070 when compared with rats fed a diet containing an adequate amount of zinc (150 μmol zinc/kg). In a small open field on day 9 of the experiment, the deficient rats more frequently displayed the posture standing upright with elevated heels. On day 10 of the experiment a clinical examination was carried out at random and 'blind' by three independent assessors. Out of 20 variables scored quantitatively on each individual animal, only body size differed between normal and deficient rats. Other classical signs of zinc deficiency, such as alopecia, dermatitis and diarrhoea, were not detected. It is concluded that in this rat model of zinc deficiency, no evidence for extreme discomfort can be demonstrated.

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49

McHugh, Nansie A., Haydee M. Vercesi, Robert W. Egan, and John A. Hey. "In vivo rat assay: bone remodeling and steroid effects on juvenile bone by pQCT quantification in 7 days." American Journal of Physiology-Endocrinology and Metabolism 284, no. 1 (January 1, 2003): E70—E75. http://dx.doi.org/10.1152/ajpendo.00102.2002.

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Anesthetized Sprague-Dawley weanling rats were scanned for bone mineral density (BMD) values after 7 days of treatment to determine whether resorption/growth at the proximal tibia can be quantified by peripheral quantitative computed tomography scanning techniques. Because the weanling rat is in a rapid growth stage, all groups showed significant increases in change from baseline values of BMD. Bisphosphonate treatment produced significant dose-related changes in BMD with average increases of 195 and 241% (10 and 20 μg/kg) vs. 86% in control rats. We further characterized this model to determine effects of steroids on growing bone. Graded doses of glucocorticoid (3.5, 7.0, 10.5, 14.0, 28.0, and 42.0 mg · kg−1 · wk−1) caused no significant differences in trabecular BMD in 7 days between control and treated rats. Significant decreases in growth (weights) and increases in cortical bone area were observed, indicating that this model may be useful in comparing effects of nonsteroid, anti-inflammatory alternatives on juvenile bone. Although the relevance of this model to adult disease remains to be elucidated, it also provides a tool for mechanistic evaluation of therapeutic modalities or efficacy assessment for dose selection for longerterm models.

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50

Vestey, M. R., S. T. McMurry, and R. L. Lochmiller. "Influence of dietary protein on selected measures of humoral and cellular immunity in the cotton rat Sigmodon hispidus." Canadian Journal of Zoology 71, no. 3 (March 1, 1993): 579–86. http://dx.doi.org/10.1139/z93-079.

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Small-mammal populations are subject to unpredictable and often dramatic fluctuations in numbers, but the mechanisms underlying this phenomenon are largely unclear. It has been suggested that protein is an important nutritional factor limiting survival, so we explored the effect of protein intake on the immunocompetence of cotton rats (Sigmodon hipsidus). In vivo and in vitro measures of both humoral and cell-mediated immunity were examined in a series of four protein-feeding trials (with weanlings, juveniles, subadults, and adults), using animals randomly assigned to an isocaloric diet containing either 4 or 16% crude protein. The response of lymphoid organ mass and cellularity to low dietary protein was variable, the spleen being more sensitive to dietary protein than the thymus. The ability of splenic lymphocytes to respond to in vitro stimulation with mitogens was unaffected by dietary protein, while the capacity of weanling and subadult cotton rats fed 4% protein to mount a delayed-type hypersensitivity response was enhanced. Nonspecific immunity (complement activity) was reduced in juveniles fed 4% protein. Dietary protein did not influence the ability of subadults or adults to generate a specific antibody response. These data suggest that cotton rats are less sensitive to dietary protein level than many inbred strains of laboratory rodents, younger animals may be at greater risk, and nutritional history may influence the response of a population to a reduction in available dietary protein.

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