scholarly journals Bile canalicular contraction is coincident with reorganization of pericanalicular filaments and co-localization of actin and myosin-II.

1993 ◽  
Vol 41 (3) ◽  
pp. 353-363 ◽  
Author(s):  
N Tsukada ◽  
M J Phillips
Keyword(s):  
Intermediate Filaments ◽  
Actin Filaments ◽  
Brush Border Membrane ◽  
Myosin Ii ◽  
Bile Canaliculus ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border ◽  
Bile Canalicular Contraction ◽  
Myosin Interaction ◽  
Apical Membranes

We examined the relationships between actin-myosin interaction and bile canalicular contraction using a new experimental model: cytoskeleton-enriched canalicular membranes (CCM). In CCM, the bile canaliculus compartment is isolated complete with membrane-attached pericanalicular actin filaments and the surrounding intermediate filament sheath. Immunofluorescence and immunoelectron microscopy showed that actin and myosin-II were distributed over pericanalicular microfilaments that insert into adherens (belt) junctions; intermediate filaments predominantly inserted into desmosomes. The addition of "contraction solution" (1 microM Ca2+, 1 mM ATP) resulted in closure of CCM lumens, which was interpreted as canalicular contraction. Contraction was also associated with shortening and/or twisting of canaliculi. Rearrangement of actin filaments and myosin-II with co-localization of actin and myosin was observed. Evidence is also provided for attachment of actin-myosin-II aggregates to intermediate filaments coincident with contraction, suggesting a key scaffold function for intermediate filaments of the canaliculus. Attention is drawn to the overall similarity of structure-function dynamics in hepatic apical membranes to those described in intestinal brush border membrane preparations. The results are consistent with dynamic actin-myosin interaction with co-localization of actin and myosin-II in filament clumps coincident with canalicular contraction.

Divalent cations and vitamin B12 uptake by intestinal brush-border membrane vesicles

1980 ◽  
Vol 239 (6) ◽  
pp. G452-G456
Author(s):  
R. C. Beesley ◽  
C. D. Bacheller
Keyword(s):  
Vitamin B12 ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Divalent Cations ◽  
Intrinsic Factor ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Tetraacetic Acid ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

Brush-border membrane vesicles from hamster intestine were employed to investigate uptake (binding) of vitamin B12 (B12). Ileal vesicles took up 25 times more B12 than did jejunal vesicles. Uptake of B12 by ileal vesicles was dependent on intrinsic factor (IF) and required Ca2+. Increasing the Ca2+ concentration caused an increase in uptake of B12 reaching a maximum at approximately 8 mM Ca2+. At high Ca2+ concentrations, 6–8 mM, Mg2+ had little effect on uptake of B12. At low Ca2+ concentrations, up to 2 mM, Mg2+ stimulated B12 uptake. Mg2+, Mn2+, and, to a lesser extent, Sr2+ stimulated Ca2+-dependent B12 uptake, but Zn2+, Ba2+, Na+, K+, and La3+ did not. B12 was apparently not metabolized and was bound as IF-B12 complex, which could be removed with (ethylenedinitrilo)tetraacetic acid (EDTA). Our results suggest that two types of divalent cation reactive sites are involved in binding of IF-B12. One is Ca2+ specific. The other is less specific reacting with Mg2+, Mn2+, Sr2+, and perhaps Ca2+ itself, thereby stimulating Ca2+-dependent binding of IF-B12 to its ileal receptor.

scholarly journals Sodium and pH dependent carrier-mediated transport of antibiotic, fosfomycin, in the rat intestinal brush-border membrane.

1990 ◽  
Vol 13 (5) ◽  
pp. 292-300 ◽  
Author(s):  
Takayuki ISHIZAWA ◽  
Akira TSUJI ◽  
Ikumi TAMAI ◽  
Tetsuya TERASAKI ◽  
Kaoru HOSOI ◽  
...  
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border ◽  
Carrier Mediated Transport ◽  
Ph Dependent
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