Flounder intestinal absorptive cells have abundant gap junctions and may be coupled

1984 ◽  
Vol 246 (1) ◽  
pp. C77-C83 ◽  
Author(s):  
R. L. Curtis ◽  
J. S. Trier ◽  
R. A. Frizzell ◽  
N. M. Lindem ◽  
J. L. Madara
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Intestinal Epithelium ◽  
Winter Flounder ◽  
Potential Difference ◽  
Intestinal Cell ◽  
Intramembrane Particles ◽  
Absorptive Cells ◽  
Small Intestinal ◽  
Apical Membranes

We noted that, unlike mammalian intestinal absorptive cells, cells of the winter flounder (Pseudopleuronectes americanus) displayed abundant gap junctions on the lateral plasma membrane. We compared the distribution of gap junctions in winter flounder to that in rabbit intestinal epithelium. We also examined for evidence of gap junction-mediated intercellular coupling by comparing the cell-to-cell variation of electrical potential difference across winter flounder intestinal cell apical membranes with that in rabbit small intestinal epithelium in which gap junctions are rare. Gap junctions were seen in 95% of flounder absorptive cells and were localized largely to the apical third of the lateral membrane. Individual gap junctions often contained several hundred uniform 9-nm intramembrane particles. Gap junction size and structure was independent of the position of individual absorptive cells on mucosal folds. These findings sharply contrasted flounder intestinal absorptive cells with rabbit small intestinal absorptive cells, in which gap junctions were rarely detected and when present consisted of few intramembrane particles. Correlating with this distribution of morphologically detectable gap junctions, rabbit small intestinal epithelial cells demonstrated marked variability in potential difference across their apical membranes, whereas those in flounder small intestine showed little variation in apical membrane potential difference. Thus, in contrast to intestinal epithelium of rabbits, flounder intestinal epithelium demonstrates morphological and functional characteristics, suggesting a substantial degree of electrical coupling.

Gap junctions in the differentiated neural retinae of newly hatched chickens

1976 ◽  
Vol 22 (3) ◽  
pp. 597-606
Author(s):  
H. Fujisawa ◽  
H. Morioka ◽  
H. Nakamura ◽  
K. Watanabe
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Tight Junctions ◽  
Thin Section ◽  
Outer Nuclear Layer ◽  
Double Cone ◽  
Linear Arrays ◽  
Intramembrane Particles ◽  
Plexiform Layers ◽  
Membrane Region

Gap junctions in the neural retinae of newly hatched chickens were examined in thin section and by freeze cleaving. Unusual gap junctions containing linear arrays of intramembrane particles are found between principal and accessory cones which form a double cone at the region of the outer limiting membrane. These unusual gap junctions are often continuous with macular aggregates of hexagonally packed intramembrane particles which are characteristic of a typical gap junction. Typical gap junctions are also found in both the outer and the inner plexiform layers and in the outer nuclear layer, but are not so abundant as in the outer limiting membrane region. The sizes of intramembrane particles and their centre-to-centre spacing within the macular aggregate of a gap junction in differentiated neural retinae are slightly larger than those in undifferentiated neural retinae. Tight junctions are not found in differentiated neural retinae.

Effect of Ag+ on isolated bullfrog gastric mucosa

1985 ◽  
Vol 248 (4) ◽  
pp. G443-G449 ◽  
Author(s):  
P. K. Rangachari ◽  
J. Matthews
Keyword(s):  
Gastric Mucosa ◽  
Potential Difference ◽  
Anion Conductance ◽  
Luminal Side ◽  
Apical Membranes ◽  
Nitrate Solutions

In nitrate solutions, Ag+ added to the luminal side had marked effects on transmucosal conductance and potential difference (PD). Conductance increased quickly (85% within 60 s, 420% by 10 min); PD increased initially (11% within 30 s) and then fell precipitously (58% decreased within 2 min, 85% decreased by 10 min). During this period, no increase in mannitol permeability was found. These changes were essentially similar in histamine-stimulated, spontaneously secreting, and metiamide-inhibited fundic mucosae. Replacement of luminal Na+ by choline had no effect on the changes observed. Similar changes occurred also in the antrum. In SO2-4 media the increases in conductance occurred more slowly (40% within 2 min, 150% after 10 min); PD increased initially for 4-6 min and then slowly declined over 60 min to 74% of control values. After Ag+ treatment, replacement of luminal SO2-4 by nitrate led to an inversion of the PD by up to 20 mV (serosa -ve). Brief exposure of the mucosa (2 min) to Ag+ did not show any obvious damage, although surface cells were damaged following more prolonged exposures. After a 4-min treatment with Ag+, electrical and secretory parameters showed substantial recoveries. Ag+ appears to increase anion conductance; these effects appear to occur on the apical membranes of tubular and/or surface cells of the fundus and antrum.

scholarly journals Two Drosophila Innexins Are Expressed in Overlapping Domains and Cooperate to Form Gap-Junction Channels

2000 ◽  
Vol 11 (7) ◽  
pp. 2459-2470 ◽  
Author(s):  
Lucy A. Stebbings ◽  
Martin G. Todman ◽  
Pauline Phelan ◽  
Jonathan P. Bacon ◽  
Jane A. Davies
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Ectopic Expression ◽  
In Vivo Studies ◽  
Electrophysiological Properties ◽  
Gap Junction Channels ◽  
Overlapping Domains ◽  
In Vitro Data

Members of the innexin protein family are structural components of invertebrate gap junctions and are analogous to vertebrate connexins. Here we investigate two Drosophila innexin genes,Dm-inx2 and Dm-inx3 and show that they are expressed in overlapping domains throughout embryogenesis, most notably in epidermal cells bordering each segment. We also explore the gap-junction–forming capabilities of the encoded proteins. In pairedXenopus oocytes, the injection of Dm-inx2mRNA results in the formation of voltage-sensitive channels in only ∼ 40% of cell pairs. In contrast, Dm-Inx3 never forms channels. Crucially, when both mRNAs are coexpressed, functional channels are formed reliably, and the electrophysiological properties of these channels distinguish them from those formed by Dm-Inx2 alone. We relate these in vitro data to in vivo studies. Ectopic expression ofDm-inx2 in vivo has limited effects on the viability ofDrosophila, and animals ectopically expressingDm-inx3 are unaffected. However, ectopic expression of both transcripts together severely reduces viability, presumably because of the formation of inappropriate gap junctions. We conclude that Dm-Inx2 and Dm-Inx3, which are expressed in overlapping domains during embryogenesis, can form oligomeric gap-junction channels.

scholarly journals Oscillatory Ca2+ Signaling in the Isolated Caenorhabditis elegans Intestine

2005 ◽  
Vol 126 (4) ◽  
pp. 379-392 ◽  
Author(s):  
Maria V. Espelt ◽  
Ana Y. Estevez ◽  
Xiaoyan Yin ◽  
Kevin Strange
Keyword(s):  
Caenorhabditis Elegans ◽  
Intestinal Epithelium ◽  
Oscillation Frequency ◽  
Gene Networks ◽  
Molecular Mechanisms ◽  
Apical Cell ◽  
Intestinal Cell ◽  
C Elegans ◽  
Contrast Gain ◽  
Behavioral Rhythm

Defecation in the nematode Caenorhabditis elegans is a readily observable ultradian behavioral rhythm that occurs once every 45–50 s and is mediated in part by posterior body wall muscle contraction (pBoc). pBoc is not regulated by neural input but instead is likely controlled by rhythmic Ca2+ oscillations in the intestinal epithelium. We developed an isolated nematode intestine preparation that allows combined physiological, genetic, and molecular characterization of oscillatory Ca2+ signaling. Isolated intestines loaded with fluo-4 AM exhibit spontaneous rhythmic Ca2+ oscillations with a period of ∼50 s. Oscillations were only detected in the apical cell pole of the intestinal epithelium and occur as a posterior-to-anterior moving intercellular Ca2+ wave. Loss-of-function mutations in the inositol-1,4,5-trisphosphate (IP3) receptor ITR-1 reduce pBoc and Ca2+ oscillation frequency and intercellular Ca2+ wave velocity. In contrast, gain-of-function mutations in the IP3 binding and regulatory domains of ITR-1 have no effect on pBoc or Ca2+ oscillation frequency but dramatically increase the speed of the intercellular Ca2+ wave. Systemic RNA interference (RNAi) screening of the six C. elegans phospholipase C (PLC)–encoding genes demonstrated that pBoc and Ca2+ oscillations require the combined function of PLC-γ and PLC-β homologues. Disruption of PLC-γ and PLC-β activity by mutation or RNAi induced arrhythmia in pBoc and intestinal Ca2+ oscillations. The function of the two enzymes is additive. Epistasis analysis suggests that PLC-γ functions primarily to generate IP3 that controls ITR-1 activity. In contrast, IP3 generated by PLC-β appears to play little or no direct role in ITR-1 regulation. PLC-β may function instead to control PIP2 levels and/or G protein signaling events. Our findings provide new insights into intestinal cell Ca2+ signaling mechanisms and establish C. elegans as a powerful model system for defining the gene networks and molecular mechanisms that underlie the generation and regulation of Ca2+ oscillations and intercellular Ca2+ waves in nonexcitable cells.

588 Distinct Dendritic Cell Subtypes with Dichotomous Phenotypes Are Associated with the Murine Small Intestinal Epithelium

2009 ◽  
Vol 136 (5) ◽  
pp. A-94
Author(s):  
Leroy W. Wheeler ◽  
Manreet Kaur ◽  
Keely McDonald ◽  
Rodney D. Newberry
Keyword(s):  
Dendritic Cell ◽  
Intestinal Epithelium ◽  
Small Intestinal Epithelium ◽  
Small Intestinal
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