Hepatic microvascular development in relation to the morphogenesis of hepatocellular plates in neonatal rats.

The development of hepatic microvascular heterogeneity after birth, and its temporal relationship to the development of parenchymal cell plates have received little attention. As a result, the morphogenesis of some of the parameters contributing to this heterogeneity in suckling and weaned rats was studied as a function of time between postpartum days 4 and 30 using in vivo light microscopic, electron microscopic, and immunocytochemical methods. During the early suckling period, the sinusoid network is highly anastomotic, with little evidence of zonation, and the parenchymal cell plates contain multiple cells and are irregularly arranged throughout the lobule.

Enteral absorption of erythropoietin in the suckling rat.

Milk contains biologically relevant concentrations of erythropoietin (Epo), the primary hormone responsible for erythrocyte production. In animals, milk-borne Epo stimulates erythropoiesis. Epo receptors have been found in nonerythropoietic tissues including gastrointestinal tract.

Transforming growth factor-alpha delays gastric emptying and small intestinal transit in suckling rats.

Transforming growth factor-alpha (TGF-alpha) is a biologically potent polypeptide detected in the gastrointestinal tract in suckling rats. The major goal of the present study was to test the hypothesis that the administration of TGF-alpha affects gastric emptying and small intestinal transit in suckling rats. Suckling (12-day-old) rats fasted 16 h received rat TGF-alpha subcutaneously (s.

Secretion of insulin-like growth factor-II into bile of rats of different ages.

Bile from rats of different ages (suckling 10-12 days; weanling 30-33 days, and adult 60-70 days) was collected and studied for the presence of immuno- and receptor-assayable insulin-like growth factor-II (IGF-II) concentrations. Concentrations of RIA IGF-II in bile were highest in suckling rats (230 +/- 38 ng/ml) and lowest in adults (47 +/- 7 ng/ml). These concentrations were approximately twice those of the bile IGF-I concentration in sucklings, as measured in a previous study.

Absorption of milk-borne insulin-like growth factor-I into portal blood of suckling rats.

Background: Insulin-like growth factors (IGFs) are potent mitogens that have been implicated in control of growth and development during the perinatal period. These hormones are also present in biologically significant quantities in mammalian milks. Although one site of action of these IGFs may be at the intestinal level, current information about whether they pass intact into the circulation is conflicting.

Milk-borne epidermal growth factor modulates intestinal transforming growth factor-alpha levels in neonatal rats.

Epidermal growth factor (EGF) is present in milk from various mammalian species, but its physiologic function in neonatal development remains unclear. Transforming growth factor-alpha (TGF-alpha) is a peptide structurally related to EGF, and its presence is detected in the developing small intestine of rats. The purpose of the present study was to examine the effect of milk-borne EGF on endogenous production of EGF and TGF-alpha in the small intestine of suckling rats.

Effect of milk on somatostatin degradation in suckling rat jejunum in vivo.

Background: Somatostatin-14 is present in breast milk, and intact somatostatin-14 has been recovered from gastric lumen of infants. Studies have shown that somatostatin-14 is metabolized in the intestinal luminal contents in vitro, which could be prevented by the presence of breast milk. In this study, the effect of milk on stability of somatostatin-14 in suckling rat jejunum in vivo was examined.

The expression of epidermal growth factor and transforming growth factor-alpha mRNA in the small intestine of suckling rats: organ culture study.

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) are associated with regulation of various gastrointestinal functions. In order to better understand their role in developing small intestine EGF, TGF-alpha and EGF-R steady-state mRNA levels and transcript stability were determined. Reverse transcription (RT) competitive-polymerase chain reaction (PCR) revealed that intestinal TGF-alpha mRNA levels were 10-fold higher in comparison with EGF mRNA.

Luminal stability of insulin-like growth factors I and II in developing rat gastrointestinal tract.

Background: Insulin-like growth factors (IGF)-I and -II are present in milk of a number of mammalian species. The stability of IGF-I and -II in the intestinal lumen was investigated by measuring the proteolytic degradation of 125I-labeled IGF-I and IGF-II by rat (suckling and adult) intestinal luminal flushings in vitro.

Methods: Degradation of 125I-labeled IGF-I and IGF-II was assessed by measuring the generation of acid-soluble radioactivity and the reduction of the amounts of peak activity (gel filtration).

Human milk as a potential enteral source of erythropoietin.

In addition to its content of traditional nutrients, milk is a rich source of hormones and peptides, which survive digestion in the neonatal gastrointestinal tract secondary to lower proteolytic activity and increased protein permeability. Previous studies have shown accelerated erythropoiesis or elevated serum erythropoietin (Epo) levels in neonatal (suckling) animals after maternal phlebotomy or maternal hypoxia exposure. We sought to determine whether significant quantities of Epo are present in human milk and whether Epo remains intact under physiologic digestion conditions.

Growth of artificially fed infant rats: effect of supplementation with insulin-like growth factor I.

Insulin-like growth factor I (IGF-I), a potent mitogenic peptide, is present in considerable quantities in most mammalian milks, but its importance for the neonate is unknown. To test the hypothesis that milk-borne IGF-I is an important factor in the regulation of neonatal growth, as well as that of the gastrointestinal tract, rat pups were fed a rat milk substitute (RMS) devoid of growth factors via gastrostomy. These animals were compared with those given RMS supplemented with recombinant human IGF-I added at a concentration of 500 ng/ml.

Organ distribution and biliary excretion of intravenously injected insulin-like growth factor-I in suckling rats.

The organ distribution of intravenously injected 125I-IGF-I at a dose of 2-4 x 10(6) cpm or 5-10 ng/animal was studied in 10- to 12-day-old Sprague-Dawley rats at 5 and 30 min after injection. Results of the study suggest that, although the main portion of intravenous IGF-I remains in the circulation, significant amounts are also found in the carcass, liver and kidney. Blood radioactivity fell by 50% 30 min after injection, but concentrations in the carcass, liver, kidney and skin either remained stable or increased.

Effect of milk-borne epidermal growth factor on the hepatic microcirculation and Kupffer cell function in suckling rats.

Epidermal growth factor (EGF) is contained in breast milk, is transported intact across the gastrointestinal mucosa during the suckling period, retains its biological activity, and affects hepatic growth. Whether or not EGF also influences postnatal hepatic development by affecting nonparenchymal cells or by modifying intrahepatic blood is not clear. As a result, the effect of EGF on the hepatic microvasculature was studied in suckling rats fed rat milk substitute (RMS) with and without EGF (100 ng/ml, i.

The potential physiological significance of milk-borne hormonally active substances for the neonate.

This article reviews the presence and potential physiological significance of hormones and hormonally active substances (including growth factors) in human milk. Human milk has been found to contain several nonpeptide hormones and many peptide hormones and growth factors. In contrast to human breast milk, infant formulae lack some hormonally active peptides.

Nutrient absorption in the preterm neonate.

The majority of what we know about the development of the absorptive process is derived from animal studies, studies in human fetal or stillborn tissues, and epidemiologic investigations derived from clinical experience. One can readily ascertain from this review that the absorption of nutrients in the intestine of the premature infant relates to a dynamic developmental process in which the consecutive stages are pre-programmed but can also be regulated by environmental factors. An understanding of these factors may lead to therapeutic intervention in premature infants, as has been the case for the developing lung and respiratory distress syndrome.

Milk carnitine affects organ carnitine concentration in newborn rats.

Previous studies suggest that exogenous milk carnitine may be necessary during the suckling period to maintain normal fat metabolism. To characterize the relationship between milk carnitine and carnitine in body organs, newborn rats were fed from birth a rat milk substitute with or without 300 micromol/L L-carnitine, corresponding to the concentration present in rat milk, for either 2 or 4 d. Carnitine concentrations in heart, skeletal muscle, liver and small intestine were compared with levels in rat pups that were never fed (d 0) and those that were nursed by their mothers for 4 d.

Epidermal growth factor delays gastric emptying and small intestinal transit in suckling rats.

Suckling (12-d-old) rats that were fasted for 15 h received epidermal growth factor (EGF) s.c. (0.

Diet-induced changes in gene expression of lactase in rat jejunum.

To explore the mechanisms by which jejunal lactase activity is modified by carbohydrate and/or fat intake, mRNA levels and the absolute synthesis rate of lactase-phlorizin hydrolase (LPH) were determined in 6-wk-old rats that were fed either low-starch diets containing long-chain triacylglycerol (LCT, 73% energy as corn oil) or medium-chain triacylglycerol (MCT, 66% energy as MCT, 7% energy as corn oil), or a high-starch diet (70% energy as cornstarch) for 7 days. LPH mRNA levels in the jejunum were similar between LCT-fed and MCT-fed rats, but animals fed the high-starch diet exhibited a greater (2x) LPH mRNA level than other groups. The absolute synthesis rate of LPH, estimated by the flooding dose technique using [3H]phenylalanine, was greater (2.

Fate of insulin-like growth factors I and II administered orogastrically to suckling rats.

Milk-borne insulin-like growth factors I and II (IGF-I and -II) may be of importance in the differentiation of the gastrointestinal tract of the suckling. To test this hypothesis, 10- to 11-d-old suckling rats were given via an orogastric tube 125I-IGF-I (n = 6) or 125I-IGF-II (n = 6) in rat milk and killed 30 min later. The results of this study demonstrated that approximately 40% of the radioactivity administered was detected in the gastrointestinal tract for both 125I-IGF-I and 125I-IGF-II experiments.

The use of poly R-478 as a marker to determine gastric emptying and intestinal propulsive motility in suckling rats.

During our studies on gastrointestinal motility in suckling rats using 51Cr or 51Cr-EDTA as markers, we noticed that these markers--in contrast to studies in adult rats--"adhered" to the gastrointestinal wall of sucklings. We therefore decided to test the use of another non-absorbable marker Poly R-478 (an acetylated anthrapyridone chromophore linked to an polyamino-ethylene-sodium ethylene sulfonate copolymer backbone developed by the Dynapol Corporation (Palo Alto, CA). This new method has appeared to be useful.

Late effects of early nutritional manipulations.

Effects of early neonatal interventions on metabolic parameters later in life (s.c. late effects) were studied in rats using two models; namely, (a) the effects of premature weaning and (b) the effects of "dietary" manipulations during the suckling period (s.

Developmental aspects of lipid metabolism.

It was confirmed that the main source of energy for growth and development in the neonatal period was fat. Considerable attention was paid to the development of both white adipose tissue (WAT) and brown adipose tissue (BAT) in the rat and human newborn. Cholesterol metabolism during development was studied in the liver, the small intestine and both WAT and BAT.

Milk-borne hormones: possible tools of communication between mother and suckling.

Early studies suggested endocrine type mother-pup interaction: 131I administered to suckling rats appeared via the urine of the suckling and mother's milk in the circulation of litter mates who were not injected with iodine; levels of thyroxin in rat milk were influenced by the status of the thyroid gland of the lactating rat. Administration of TRH (thyrotropin releasing hormone) to lactating mothers led to an appearance of unaltered hormones in the milk and stomach content of sucklings. TSH (thyroid stimulating hormone) or ACTH (adrenocorticotropic hormone) when given orogastrically to suckling rats increased thyroid hormones and corticosterone serum levels in suckling rats.

Development of gastrointestinal functions.

Data are summarized about digestion and absorption of carbohydrates, lipids and proteins during mammalian perinatal development including human fetuses. Corresponding with the high fat intake in suckling rats, absorption of triglycerides was found to be approximately 2-3 times higher in suckling than in adult rats. Carnitine contents of the small intestinal mucosa of rats decrease postnatally, reaching adult levels at the time of weaning.

Traditions of Czech and Slovak developmental physiology.

Since the beginning of the 19th century, the comparative and ontogenetic branches of developmental physiology were cultivated in our country. Evidence was given that development of the gastrointestinal tract in tadpoles is dependent on the quality of proteins in their food. A complete metamorphosis of Amblystoma mexicanum, was entirely accomplished by feeding with powderized thyroid gland.