Stereologic characteristics of pig small intestine during normal development

Stereologic methods were used to study the behavior of the pig's intestinal wall during periods that are characterized by a high incidence of gastrointestinal disorders. For this purpose conventionally stained transverse and vertical paraffin sections were made of the small intestine (duodenum, jejunum, and ileum) of fetal, neonatal, and weaned pigs. The volumes of the intestinal walls were estimated using Cavalieri's method. Subsequently, the surface density (Sv) of the tunica mucosa and the volume densities (Vv) of the different small intestinal elements were estimated. Finally, the surface and volumes per serosal surface area (Ss and Vs) were calculated. The decrease of Sv can be attributed to the finding that the mucosal surface increases to a lesser extent compared with the volume of the intestinal wall. The Vs of the various layers increased postnatally, illustrating that the intestinal wall thickens. Despite an increasing total mucosal surface, this postnatal thickening causes Ss to decline. Each of these changes is temporally related to dietary changes, an increased antigen load, and an increased need for protection. Additionally, the regional differences of the various parameters match the qualitative descriptions of the small intestine of the pig and relate to region-specific functions.

The ulceration-associated cell lineage (UACL) reiterates the Brunner's gland differentiation programme but acquires the proliferative organization of the gastric gland

The ulceration-associated cell lineage (UACL) develops in the human gastrointestinal mucosa after ulceration; it grows out from the bases of adjacent crypts and ramifies in the lamina propria to form a new gland, finally giving rise to a duct by which the glandular secretion and indeed cells are carried to the surface. Using immunocytochemistry and in situ hybridization with 35S-labelled riboprobes, we have defined the pattern of trefoil peptide gene expression (pS2; human spasmolytic polypeptide, hSP), epidermal growth factor/urogastrone (EGF/URO), and the distribution of cell proliferation during the development of the UACL, as indicated by immunostaining for proliferating cell nuclear antigen (PCNA). Our studies reveal that the morphogenesis of the UACL shows a marked morphological resemblance to developing Brunner's glands; the pattern of trefoil peptide gene expression during UACL development is also very similar. However, trefoil peptide gene expression in the mature UACL complex is unique amongst gastrointestinal cells. The mature UACL shows a distinctive proliferative organization: while the early buds and glands are non-proliferative, apparently being fed by cells from the parent crypts, a definitive proliferative zone develops within the duct. This, of course, corresponds to the location of the gastric gland proliferative zone. We propose that while the UACL shows novel features, it shares its differentiation programme with Brunner's glands, but its pattern of cell renewal eventually is that of the gastric gland.

Perinatal development of Brunner's glands in the rat: morphometrical study

Perinatal changes of the Brunner's glands in rats from fetal day 20 through neonatal day 3 were studied morphometrically and electron-microscopically. Percentage volume of secretory granules of the gland cells did not change from fetal day 20 through neonatal day 1 and increased significantly from neonatal days 1-2; this level was maintained through neonatal day 3. Electron-microscopically, the gland cells during the fetal days were rich in free ribosomes. The Golgi apparatus and rough-surfaced endoplasmic reticulum (RER) were poorly developed during fetal days. After birth, however, the cells showed active formation of secretory granules, which was evidenced by well-developed Golgi apparatus, distended RER and accumulation of granules in the apical cytoplasm. Furthermore, light microscopy revealed that strongly PAS-positive material increased for the first time after birth, indicating remarkable formation of the secretory granules. Thus, the present study indicates that the cell of the Brunner's glands become active in secretory granule formation just after birth by responding to ingested material following birth.