Possible biological growth factors in breast milk and postnatal development of the gastrointestinal tract

Cross-fostering of the tammar wallaby (Macropus eugenii) pouch young accelerates fore-stomach maturation

There are two phases of fore-stomach development during the first 200 days of pouch life in tammar wallaby. For the first 170 days, the mucosa displays an immature gastric glandular phenotype that changes to a cardia glandular phenotype, which remains for the rest of the animal's life. During this 200-day period after birth, the pouch young (PY) is dependent on maternal milk, which progressively changes in composition. We showed previously that PY cross-fostered to host mothers at a later stage of lactation accelerated development. In this study, we investigated whether cross-fostering and exposure to late lactation stage milk affected the transition to cardia glandular phenotype. In fostered PY fore-stomach, there was increased apoptosis, but no change in cell proliferation. The parietal cell population was significantly reduced, and expression of gastric glandular phenotype marker genes (ATP4A, GKN2, GHRL and NDRG2) was down-regulated, suggesting down-regulation of gastric phenotype in fostered PY fore-stomach. The expression of cardia glandular phenotype genes (MUC4, KRT20, CSTB, ITLN2 and LPLUNC1) was not changed in fostered PY. These data suggest that fore-stomach maturation proceeds via two temporally distinct processes: down-regulation of gastric glandular phenotype and initiation of cardia glandular phenotype. In fostered PY, these two processes appear uncoupled, as gastric glandular phenotype was down-regulated but cardia glandular phenotype was not initiated. We propose that milk from later stages of lactation and/or herbage consumed by the PY may play independent roles in regulating these two processes.

β-lactoglobulin as a potential modulator of intestinal activity and morphology in neonatal piglets

Studies were conducted to determine the effects of the whey protein beta-lactoglobulin (blg) on the intestinal development and intestinal morphology in neonatal piglets. Two trials (5 and 28 days) were conducted on piglets in three separate groups. One group served as a control group while the remaining two were experimental groups based on diets. The two experimental diets were a bovine colostrum powder, one with supplementation with blg and the other without. The control group remained suckling on a sow. All groups were weaned on day 20 and placed onto a solid commercial piglet diet. Enzymatic activity, total DNA synthesis, crypt depth, and villus height were all parameters used to evaluate the effect of blg. Piglets fed a diet supplement with blg had the greatest total DNA after 5 days. Sow-reared piglets had the greatest intestinal morphology development with regards to villus height. No significant differences were found in enzymatic activity between treatments.

Dimensions and histologic characteristics of the small intestine of dogs during postnatal development

OBJECTIVE

To quantify dimensions of the small intestine of dogs and describe changes in histologic characteristics of the mucosa during postnatal development.

SAMPLE POPULATION

Gastrointestinal tract tissues obtained from 110 Beagles (15 adult females and 95 puppies of both sexes).

PROCEDURE

Several variables (length, total weight, mucosal weight, and nominal surface area) of the small intestine were measured in puppies at birth but before suckling; 1 day after birth and subsequent suckling, 21, 42, and 63 days after birth, and in the adult dams of the puppies. Tissue structure was examined and quantified at each time point by use of routine histologic examination and ocular micrometry of formalin-fixed specimens stained with H&E.

RESULTS

Small intestinal dimensions increased throughout development with the greatest proportional changes during the first day after birth and onset of suckling. Villus height decreased during suckling but had consistent values from 42 days after birth to maturity, whereas crypt depth increased from birth to maturity. Vacuolated enterocytes were evident from birth to 21 days but not thereafter.

CONCLUSIONS AND CLINICAL RELEVANCE

Increases in intestinal dimensions provide growing dogs with a greater capacity for digestion and absorption. Changes in mucosal architecture and cell populations coincided with shifts in dietary inputs. These findings may assist in the diagnosis of small intestinal diseases and nutritional responses during growth and development of dogs.

Vagal intraganglionic laminar endings and intramuscular arrays mature at different rates in pre-weanling rat stomach

To assess whether vagal afferents in the gastrointestinal (GI) tract mature postnatally and differentiate at different rates, potentially reflecting the changing functional requirements of weaning and independence, the vagal afferent innervation of the stomach was inventoried in pre-weanling and adult rats. Wheatgerm agglutinin-horseradish peroxidase was injected into the nodose ganglia of 9-day-old and adult rats, and after tracer transport, the animals were sacrificed. Their stomachs were prepared as wholemounts and processed with tetramethylbenzidine. Inventories were obtained with a counting grid that was systematically positioned throughout the wholemounts by the use of a sampling template that was adjusted for stomach size and shape. Densities in the gastric antrum, corpus, and forestomach were determined for (1) afferent bundles, (2) individual fibers separated from the bundles and presumably located near their targets, (3) differentiated intraganglionic laminar endings (IGLEs) associated with myenteric ganglia, and (4) differentiated intramuscular arrays (IMAs) situated within the smooth muscle layers. In pre-weanling rats, which were 10 days old at perfusion, the distributions of vagal bundles and fibers were similar to those of adults, suggesting that the basic vagal architecture develops early. Differentiated IGLEs were also distributed in a mature pattern in 10 day olds, whereas few IMAs had yet been distributed and differentiated in the forestomach of the pre-weanlings. The authors hypothesize that these different developmental patterns for the two types of vagal afferents are consistent with their putative functional roles as, respectively, mechanoreceptors (IGLEs) that coordinate rhythmic motor function needed early for the digestion of milk and stretch receptors (IMAs) needed later as the GI tract natures for the transition to solid food at weaning.