PubMed Health⌕ Search

Biomedical subjects

J Rostgaard

Publications and source records attributed to J Rostgaard.

At least 37 records · Page 2Linked to original sources
PubMed1981

Fluid transport and dimensions of epithelial cells and intercellular spaces in frog gallbladder. Studies in the living state, and during processing for electron microscopy.

Morphologic findings of widely dilated intercellular spaces in fluid transporting epithelia have been claimed as evidence for the existence of an epithelial compartment in which the coupling between solute and water fluxes takes place. The validity of using epithelial geometry in sectioned material as an argument can be questioned. The present report describes the morphological appearance of frog gallbladder epithelium--normal and ouabain-treated--in the living state in vitro and after fixation, dehydration and embedding. Gallbladder segments were photographed in the living state and at the end of each step of the preparative procedure. Direct observations of whole-mounted gallbladder segments were carried out, taking advantage of the possibility of optical sectioning and high resolution by Nomarski-microscopy. The same specimens were then sectioned and examined by conventional light and electron microscopy. The observations were quantitated and showed that the epithelial cells of normal and ouabain-treated gallbladders experienced an average linear shrinkage down to 70% of their length in Ringer's solution, which corresponds to a volume shrinkage down to 35%. Moreover, dilated lateral intercellular spaces appeared during the dehydration and embedding procedure in normal but only very moderately or not at all in ouabain-treated gallbladder specimens.

Animals↗
PubMed1980

Localization of Na+, K+ -ATPase to the inside of the basolateral cell membranes of epithelial cells of proximal and distal tubules in rabbit kidney.

Cysteine-sensitive alkaline phosphatase and/or ouabain-sensitive Na+, K+ -ATPase were studied by ultrastructure cytochemistry in epithelial cells of proximal and distal kidney tubules. Alkaline phosphatase reactivity was confined to the surface of the microvillous luminal cell membrane of proximal tubule cells, whereas distal tubules and collecting ducts were unreactive. The Na+, K+- ATPase reactivity was localized evenly along the cytoplasmic side of the basolateral cell membrane of cells of proximal and distal tubules and in collecting ducts. In the proximal tubules, where the activity was strongest, the Na+, K+- ATPase deposits were also found in the 10--50 nm gap between the cell membrane and the cisternae of tubulo-cisternal endoplasmic reticulum (TER) underlying a major part of the basolateral cell membrane. The restriction of NA+, K+ -ATPase sites, which are involved in extrusion of Na+ from the cell, to a narrow cytoplasmic compartment located between the cell membrane and the cisternae of TER, is consistent with a transport role for the TER.

Animals↗
PubMed1979

Lack of correlation between transepithelial transport capacity and paracellular pathway ultrastructure in Alcian blue-treated rabbit gallbladders.

The effects of mucosal application of 1 mg% Alcian blue (a trivalent cationic phthalocyanine dye) on functional and ultrastructural parameters of the isolated rabbit gallbladder have been studied. Apart from minor changes in the shape of the group of central microvilli observed in thin-section electron microscopy and scanning electron microscopy, the major ultrastructural change induced by Alcian blue was an almost complete collapse of intercellular spaces in the region above the tight junctions up to the bases of the marginal microvilli as revealed by thin-section electron microscopy. Freeze-fracture electron microscopy demonstrated a complete disappearance of intramembrane particles of neighboring cell membranes corresponding to the region of interspace collapse. Transepithelial electrical resistance (RT) increased from 44.5 to 58.7 ohm . cm2 upon treatment with Alcian blue. This increase could be well accounted for by the observed structural changes in the paracellular pathway if this pathway determines the low resistance of the rabbit gallbladder epithelium. Despite the increase in RT, net mucosa-to-serosa fluid transport and the spontaneous mucosa-positive potential difference of 3 mV were unaltered by Alcian blue treatment, supporting the hypothesis that the transepithelial transport mechanism per se is electroneutral. A calculation of the maximal paracellular mucosa-to-serosa waterflow in response to a lateral intercellular space hypertonicity of 20 mosM demonstrates that in the Alcian blue-treated gallbladder the resulting figure is about three orders of magnitude too low to keep up with the unaltered spontaneous transepithelial net fluid transport. It is therefore concluded that the tight junction pathway in rabbit gallbladders does not serve as a route for net fluid transport.

Alcian Blue↗
PubMed1978

Morphological aspects of some sodium transporting epithelia suggesting a transcellular pathway via elements of endoplasmic reticulum.

Electron microscopic studies of sodium transporting epithelia from frog skin, sheep choroid plexus, rabbit gallbladder and small intestine, and rat kidney revealed the presence of a complex intracellular system of tubulo-cisternal endoplasmic reticulum which appeared to connect apical (luminal) and baso-lateral cell surfaces. The system was present in the tight epithelium of frog skin but was most abundant in leaky epithelia with low transepithelial resistance and isotonic transport. The basic structural features of the system and its relationship with some associated components are described. Our result, coupled with preliminary physiological studies, indicate that developmental and seasonal (hormone-induced) changes in the configuration of the tubulo-cisternal endoplasmic reticulum may be closely correlated with specific changes in epithelial permeability. The findings are discussed in the light of the hypothesis that epithelia possess two sodium transporting systems: One based on pump sites in the plasma membrane producing a hypertonic transportate and another located in the membranes of the tubulo-cisternal endoplasmic reticulum which, due to its extensive surface, would be well suited for producing an isotonic transportate.

Animals↗