Upper Half Of Villi Research Articles

Immunocytochemical heterogeneity of lactase-phlorizin hydrolase in adult lactase deficiency

Background: Adult lactase deficiency may result either from diminished synthesis of precursor lactase-phlorizin hydrolase (phenotype I deficiency) or from altered posttranslational processing of the precursor protein (phenotype II). The aim of this study was to compare the location of lactase-phlorizin hydrolase along the crypt-villus axis in control with adult lactase-deficient subjects. Methods: The immunocytochemical distribution of lactase-phlorizin hydrolase was studied in subjects with adult hypolactasia and in controls with persistent high lactase expression. Results: Duodenal biopsy samples from controls showed increasing intensity of brush border staining from upper crypt to midvillus. Subjects with phenotype I deficiency showed reduced and more patchy reaction product over brush borders. In some, maximal staining was localized over the upper half of the villi. The subject with phenotype II deficiency showed patchy staining but also intracellular accumulations of immunoreactivity within the apex of enterocytes mainly on the upper half of villi. Subsequent immunoelectronmicroscopy showed nearly a fourfold increase in label over the endoplasmic reticulum. Conclusions: These findings support prior observations of diminished enzyme synthesis in phenotype I lactase deficiency and suggest that the alterations in posttranslational processing in phenotype II deficiency involve a partial block in transport from endoplasmic reticulum to Golgi apparatus.

Structure and permeability differ in subepithelial villus and peyer's patch follicle capillaries

Intravenously injected sheep antilaminin immunoglobulin G conjugated with horseradish peroxidase uniformly labeled the basement membrane of mouse villus epithelium but not that of Peyer's patch follicle domes, although laminin is abundant in both. This suggested differences in the permeability of capillaries underlying these epithelia. Therefore, the fine structure of mouse subepithelial villus and follicle capillaries and their permeability to selected macromolecules was compared. Fenestrae, abundant in villus capillaries, were extremely rare in dome capillaries as assessed by electron microscopy of tissue sections and freeze-fracture replicas. Two minutes after IV-injected horseradish peroxidase and 9 minutes after IV-injected hemoglobin, reaction product decorated the pericapillary space of 97% and 95%, respectively, of capillary profiles in the upper half of villi but only 28% and 2%, respectively, of capillary profiles in the upper half of patch domes. Reaction product was intense surrounding most villus capillaries but, when present, was faint in dome capillary adventitia. These results indicate that most subepithelial capillaries in mouse Peyer's patch domes, unlike those in villi, generally lack endothelial fenestrae, and the dome capillary network is less permeable to some macromolecules than that of the villus.

Structure and Permeability Differ in Subepithelial Villus and Peyer’s Patch Follicle Capillaries

Intravenously injected sheep antilaminin immunoglobulin G conjugated with horseradish peroxidase uniformly labeled the basement membrane of mouse villus epithelium but not that of Peyer's patch follicle domes, although laminin is abundant in both. This suggested differences in the permeability of capillaries underlying these epithelia. Therefore, the fine structure of mouse subepithelial villus and follicle capillaries and their permeability to selected macromolecules was compared. Fenestrae, abundant in villus capillaries, were extremely rare in dome capillaries as assessed by electron microscopy of tissue sections and freeze-fracture replicas. Two minutes after IV-injected horseradish peroxidase and 9 minutes after IV-injected hemoglobin, reaction product decorated the pericapillary space of 97% and 95%, respectively, of capillary profiles in the upper half of villi but only 28% and 2%, respectively, of capillary profiles in the upper half of patch domes. Reaction product was intense surrounding most villus capillaries but, when present, was faint in dome capillary adventitia. These results indicate that most subepithelial capillaries in mouse Peyer's patch domes, unlike those in villi, generally lack endothelial fenestrae, and the dome capillary network is less permeable to some macromolecules than that of the villus.

Na+-induced intestinal interstitial hyperosmolality and vascular responses during absorptive hyperemia.

The coupled active transport of Na+ with sugars and amino acids could cause intestinal villus interstitial hyperosmolarity, which contributes to absorptive hyperemia. However, for the villus hyperosmolarity to cause a major vascular response, a mild-to-moderate hyperosmolarity must occur in the vicinity of the major resistance vessels of the submucosa. Interstitial Na+ activity was measured throughout the small intestinal wall of rats with monensin ion-selective electrodes during glucose absorption. In the upper half of villi, the resting [Na+] was 201 +/- 5 (SE) mM and increased to 267 +/- 6 mM during luminal exposure to 25-300 mg/100 ml glucose. The submucosal resting [Na+] was 144 +/- 1 mM and increased to 177 +/- 3 mM during luminal glucose exposure. The time courses of Na+ appearance and submucosal arterial dilation were almost identical. Calculations of tissue osmolarity indicate an increase in villus osmolarity of 150-200 mosM and 79-90 mosM in the submucosa during glucose absorption. The data are interpreted to indicate that villus hyperosmolarity during glucose absorption increased submucosal osmolarity and a naturally occurring osmotic dilatory component of absorptive hyperemia could exist.