A non-connexon protein (MIP) is involved in eye lens gap-junction formation

1989 ◽  
Vol 93 (3) ◽  
pp. 509-513
Author(s):  
W.T. Gruijters
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Eye Lens ◽  
Specific Interactions ◽  
Domain Specific ◽  
Lens Fibre ◽  
Junction Formation ◽  
New Perspective

New immunolocalization data put the role of the lens MP26 (MIP) protein in a new perspective. During maturation of lens fibre cells, MIP is found to associate specifically with two structures, gap junctions and cell interlocking processes (known as ball and socket domains). It is significant that the zone in which these associations are most striking is discrete, coinciding with the zone of rapidly enlarging junctional plaques and newly forming ball and socket domains. Observation of domain-specific interactions of MIP with forming gap junctions and ball and socket domains suggests that MIP may be involved in the formation of close membrane appositions. Furthermore, previous ambiguities in the literature over the presence of MIP in gap junctions are clarified by the knowledge that, in situ, MIP associates strongly with gap junctions for only a brief period (with less than about 5% of all lens gap junctions at any one time) during the assembly of junctional plaques.

Molecular modulation of calcium oxalate crystallization

2006 ◽  
Vol 291 (6) ◽  
pp. F1123-F1132 ◽  
Author(s):  
James J. De Yoreo ◽  
S. Roger Qiu ◽  
John R. Hoyer
Keyword(s):  
Molecular Modeling ◽  
Calcium Oxalate ◽  
Stone Formation ◽  
Energy Levels ◽  
Critical Role ◽  
Specific Interactions ◽  
Crystal Surfaces ◽  
Site Specific

Calcium oxalate monohydrate (COM) is the primary constituent of the majority of renal stones. Osteopontin (OPN), an aspartic acid-rich urinary protein, and citrate, a much smaller molecule, are potent inhibitors of COM crystallization at levels present in normal urine. Current concepts of the role of site-specific interactions in crystallization derived from studies of biomineralization are reviewed to provide a context for understanding modulation of COM growth at a molecular level. Results from in situ atomic force microscopy (AFM) analyses of the effects of citrate and OPN on growth verified the critical role of site-specific interactions between these growth modulators and individual steps on COM crystal surfaces. Molecular modeling investigations of interactions of citrate with steps and faces on COM crystal surfaces provided links between the stereochemistry of interaction and the binding energy levels that underlie mechanisms of growth modification and changes in overall crystal morphology. The combination of in situ AFM and molecular modeling provides new knowledge that will aid rationale design of therapeutic agents for inhibition of stone formation.

Control of gap junction formation in canine trachea by arachidonic acid metabolites

1986 ◽  
Vol 250 (3) ◽  
pp. C495-C505 ◽  
Author(s):  
R. Agrawal ◽  
E. E. Daniel
Keyword(s):  
Arachidonic Acid ◽  
Gap Junctions ◽  
Gap Junction ◽  
Direct Effects ◽  
Leukotriene C4 ◽  
Lipoxygenase Pathway ◽  
Junction Formation ◽  
Acid Metabolites ◽  
Pg E2

This study examined whether the synthesis of the metabolites of arachidonic acid (AA) was involved in gap junction formation by 4-aminopyridine (4-AP) treatment in vitro in canine trachealis. Studies were made of the effects on gap junction formation of putative inhibitors of the cyclooxygenase and of both this and the lipoxygenase pathway of AA metabolism and the direct effects of prostaglandins (PG) E2 and I2. The number of gap junctions of similar size was increased after brief exposure to 4-AP. After indomethacin (IDM), 4-AP treatment decreased the number of gap junctions but did not affect their size. Pretreatment with 5,8,11,14-eicosatetraynoic acid or nordihydroguiaretic acid, putative inhibitors of cyclooxygenase and lipoxygenase enzymes, inhibited both the 4-AP-induced increase and decrease in the number of gap junctions. FPL 55712, a putative antagonist of leukotriene C4, did not alter either the number or the size of gap junctions when added alone or in combination with IDM. AA alone increased the number of gap junctions, but after IDM, AA decreased the number of gap junctions compared with the controls. Incubation of trachealis strips in vitro for 30 min with PGE2 increased the number of gap junctions by about threefold along with an increase in the size of the gap junctions. Similar incubation with PGI2, however, increased the number of gap junctions by approximately 60% without any change in the size. In the course of some control experiments, an interaction between carbachol and alcohol was observed such that alcohol caused an IDM-sensitive relaxation of carbachol-induced contractions, which was not observed when serotonin was the contractile agent. These results strongly suggest that PGE2 and PGI2 increase the formation of gap junctions in canine trachealis and that these prostanoids are released by 4-AP treatment. Leukotrienes may also be inhibitory in the formation of gap junctions, but FPL 55712 did not affect either the increase or the decrease in gap junctions after 4-AP.

Dissociation of lens fibre gap junctions releases MP70

1988 ◽  
Vol 91 (3) ◽  
pp. 415-421 ◽  
Author(s):  
J. Kistler ◽  
S. Bullivant
Keyword(s):  
Electron Microscope ◽  
Gap Junctions ◽  
Gap Junction ◽  
Plasma Membranes ◽  
Gradient Centrifugation ◽  
Membrane Structures ◽  
Treatment Results ◽  
Double Membrane ◽  
Lens Fibre ◽  
Junction Proteins

MIP and MP70 are putative gap junction components in the plasma membranes of the mammalian lens fibre cells. We show now that MP70 can be solubilized separately from MIP in mild detergent solutions, and that this treatment results in the dissociation of the fibre gap junctions. Solubilized MP70 was isolated as 16.9 S particles by velocity gradient centrifugation and in the electron microscope had the appearance of short double-membrane structures consistent with connexon-pairs. These observations open a new experimental avenue in which to characterize separately the two putative lens gap junction proteins structurally and functionally.

The safety role of gap junctions: A new perspective on atrio-ventricular nodal reentry

2006 ◽  
Vol 67 (5) ◽  
pp. 1253-1254
Author(s):  
Somayeh Mahdavi ◽  
Shahriar Gharibzadeh ◽  
Farzad Towhidkhah ◽  
Mostafa Rezaei-Tavirani
Keyword(s):  
Gap Junctions ◽  
New Perspective

Possible role of gap junctions in activation of myometrium during parturition

1978 ◽  
Vol 235 (5) ◽  
pp. C168-C179 ◽  
Author(s):  
R. E. Garfield ◽  
S. M. Sims ◽  
M. S. Kannan ◽  
E. E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Gap Junctions ◽  
Freeze Fracture ◽  
Normal Pregnancy ◽  
Pregnant Rats ◽  
Junction Formation ◽  
Synchronous Contraction ◽  
Do So

Gap junctions between smooth muscle cells of the myometrium of pregnant rats were found only immediately prior to, during and immediately after parturition by quantitative thin-section and freeze-fracture microscopy. Ovariectomy of 16- to 17-days-pregnant rats resulted in premature termination of pregnancy and the appearance of gap junctions. Methods that prolonged normal pregnancy in rats or maintained pregnancy in ovariectomized animals (progesterone treatment) prevented the appearance of gap junctions. Gap junctions formed in tissues incubated for 24--96 h in vitro without any hormonal influence. We propose that gap junctions are essential for normal labor and delivery for synchronous contraction of the muscle of the uterus. We present a model for control of parturition that may apply to other animals including humans. The model proposes: 1) the possible roles progesterone, prostaglandins, or estrogens may play in initiating gap-junction formation; 2) that the formation of gap junctions is a necessary step in activation of the myometrium leading to labor; and 3) that agents used to stimulate or inhibit labor may do so by affecting gap junctions.

Gap junction formation and regulation in myometrium

1980 ◽  
Vol 239 (5) ◽  
pp. C217-C228 ◽  
Author(s):  
R. E. Garfield ◽  
D. Merrett ◽  
A. K. Grover
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
High Frequency ◽  
Actinomycin D ◽  
Low Frequency ◽  
Synthesis Inhibitor ◽  
Pregnant Rats ◽  
Junction Formation ◽  
Prostacyclin Analog

Myometrial tissues from pregnant rats were examined by electron microscopy for the presence of gap junctions after incubation in vitro with a variety of agents. Gap junctions were present in low frequency or absent prior to incubation in vitro. The junctions were present in control tissues in high frequency after 48 h incubation. The addition of cycloheximide or actinomycin D inhibited the incorporation of [3H]leucine into TCA-precipitable proteins and prevented gap junction formation. A prostacyclin analog (carbacyclin), a thromboxane synthesis inhibitor, and indomethacin also prevented gap junction formation. Oxytocin had no effect on gap junction formation but isoxsuprine decreased their number and increased their size. Isoxsuprine and isoproterenol also produced electron opaque crystals associated with the gap junctions. Dibutyryl cAMP treatment but not monobutyryl cGMP also increased the size of gap junctions. Based upon this and previous studies, we propose at least four sites for regulation of gap junctions and possible control of labor.

scholarly journals Gap junction networks in mushroom bodies participate in visual learning and memory in Drosophila

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Qingqing Liu ◽  
Xing Yang ◽  
Jingsong Tian ◽  
Zhongbao Gao ◽  
Meng Wang ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Learning And Memory ◽  
Visual Learning ◽  
Mushroom Bodies ◽  
Single Pair ◽  
Neural Information ◽  
Neural Information Processing ◽  
Coupling Approach

Gap junctions are widely distributed in the brains across species and play essential roles in neural information processing. However, the role of gap junctions in insect cognition remains poorly understood. Using a flight simulator paradigm and genetic tools, we found that gap junctions are present in Drosophila Kenyon cells (KCs), the major neurons of the mushroom bodies (MBs), and showed that they play an important role in visual learning and memory. Using a dye coupling approach, we determined the distribution of gap junctions in KCs. Furthermore, we identified a single pair of MB output neurons (MBONs) that possess a gap junction connection to KCs, and provide strong evidence that this connection is also required for visual learning and memory. Together, our results reveal gap junction networks in KCs and the KC-MBON circuit, and bring new insight into the synaptic network underlying fly’s visual learning and memory.

scholarly journals Decreased Fast Ripples in the Hippocampus of Rats with Spontaneous Recurrent Seizures Treated with Carbenoxolone and Quinine

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Consuelo Ventura-Mejía ◽  
Laura Medina-Ceja
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
High Frequency Oscillations ◽  
The Mean ◽  
Eeg Recordings ◽  
The Right ◽  
Spontaneous Recurrent Seizures

Background. In models of temporal lobe epilepsy and in patients with this pathology, high frequency oscillations called fast ripples (FRs, 250–600 Hz) can be observed. FRs are considered potential biomarkers for epilepsy and, in the light of manyin vitroandin silicostudies, we thought that electrical synapses mediated by gap junctions might possibly modulate FRsin vivo.Methods. Animals with spontaneous recurrent seizures induced by pilocarpine administration were implanted with movable microelectrodes in the right anterior and posterior hippocampus to evaluate the effects of gap junction blockers administered in the entorhinal cortex. The effects of carbenoxolone (50 nmoles) and quinine (35 pmoles) on the mean number of spontaneous FR events (occurrence of FRs), as well as on the mean number of oscillation cycles per FR event and their frequency, were assessed using a specific algorithm to analyze FRs in intracranial EEG recordings.Results. We found that these gap junction blockers decreased the mean number of FRs and the mean number of oscillation cycles per FR event in the hippocampus, both during and at different times after carbenoxolone and quinine administration.Conclusion. These data suggest that FRs may be modulated by gap junctions, although additional experimentsin vivowill be necessary to determine the precise role of gap junctions in this pathological activity associated with epileptogenesis.

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