scholarly journals Freeze-fracture studies of nexuses between smooth muscle cells. Close relationship to sarcoplasmic reticulum.

1977 ◽  
Vol 72 (1) ◽  
pp. 26-34 ◽  
Author(s):  
G N Fry ◽  
C E Devine ◽  
G Burnstock
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Hexagonal Lattice ◽  
Freeze Fracture ◽  
Minimum Size ◽  
Mouse Vas Deferens ◽  
Chicken Gizzard ◽  
Close Relationship ◽  
Fracture Appearance

The freeze-fracture appearance of the nexus was compared in the smooth muscle of guinea pig sphincter pupillac, portal vein, pulmonary artery, taenia coli, uretzr, and vas diferens, mouse vas deferens, chicken gizzard and anterior mesenteric artery, and toad stomach. Nexuses are particularly numerous in the guinea pig sphincter pupillae; they are usually oval and their average area is 0.15 mum2, although some as large as 0.6 mum2 were seen. Small aggregations of particles were observed which would not be recognizable as nexuses in thin section. What constitutes the minimum size of a nexus is discussed. It is estimated that the number of nexuses per cell in this preparation is of the order of tens rather than hundreds. All nexuses examined had 6-9-nm particles in the PF face, with corresponding 3-4-nm pits on the EF face forming a polygonal tending towards a hexagonal lattice. The nexuses are arranged in rows parallel to the main axis of the cell, usually alternating with longitudinal rows of plasmalemmal vesicles. Many nexuses in the guinea pig sphincter pupillae, chicken gizzard, and toad stomach show a close relationship with sarcoplasmic reticulum. The possibility that this may have some role in current flow across this specialized junction is discussed.

Caveolae Intracellulares and Sarcoplasmic Reticulum in Smooth Muscle

1971 ◽  
Vol 8 (3) ◽  
pp. 601-609
Author(s):  
G. GABELLA
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Guinea Pig Ileum ◽  
Intracellular Store ◽  
Similar Role ◽  
Close Relationship

In the smooth-muscle cells from guinea-pig ileum a highly developed sarcoplasmic reticulum has been observed immediately underneath the plasma membrane in close relationship to the caveolae intracellulares. It is suggested that sarcoplasmic reticulum in smooth muscle may play a similar role as in skeletal muscle, constituting the main intracellular store for calcium.

Direct inhibition of contractile apparatus by analogues of amiloride in the smooth muscle of guinea-pig taenia caecum and chicken gizzard

1989 ◽  
Vol 38 (6) ◽  
pp. 915-922 ◽  
Author(s):  
Ozaki Hiroshi ◽  
Moriyama Takahiro ◽  
Karaki Hideaki ◽  
Kohama Kazuhiro ◽  
Edward J. Cragoe
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Contractile Apparatus ◽  
Direct Inhibition ◽  
Chicken Gizzard

scholarly journals Nexuses between the smooth muscle cells of the guinea-pig ileum.

1979 ◽  
Vol 82 (1) ◽  
pp. 239-247 ◽  
Author(s):  
G Gabella ◽  
D Blundell
Keyword(s):  
Smooth Muscle ◽  
Cell Surface ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Muscle Cell ◽  
Packing Density ◽  
Freeze Fracture ◽  
Muscle Cells ◽  
Guinea Pig Ileum ◽  
Average Cell

The circular musculature of the guinea-pig ileum has been studied by freeze-fracture to analyze quantitatively the gap junctions (nexuses) between its smooth muscle cells. The average cell surface area and cell volume are 5,074 micron 2 and 3,260 micron 3. The packing density of nexuses is 48/1,000 micron 2 of cell surface or approximately 244/muscle cell. Nexuses range in area from less than 0.1 to approximately 1.5 micron 2 and they occupy 0.212% of the cell surface. The average packing density of intramembrane particles or pits in nexuses is approximately 7,200/micron 2 of nexal surface, indicating that there may be approximately 77,000 intercellular channels in the full complement of nexuses of one muscle cell.

scholarly journals Membrane particle changes attending the acrosome reaction in guinea pig spermatozoa

1977 ◽  
Vol 74 (2) ◽  
pp. 561-577 ◽  
Author(s):  
DS Friend ◽  
L Orci ◽  
A Perrelet ◽  
R Yanagimachi
Keyword(s):  
Plasma Membrane ◽  
Guinea Pig ◽  
Acrosome Reaction ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Phosphatidylcholine Liposomes ◽  
Acrosomal Membrane ◽  
Large Particles ◽  
Fracture Appearance ◽  
Preparatory Stage

To examine the freeze-fracture appearance of membrane alterations accompanying the preparation of sperm membranes for fusions-the first preparatory stage occurring before physiological release of the acrosomal content, the second afterward-we induced the acrosome reaction in capacitated guinea pig spermatozoa by adding calcium to the mixture. The most common features observed before fusion of the acrosomal and plasma membranes were the deletion of fibrillar intramembranous particles from the E-fracture faces of both membranes, and the clearance of globular particles from the P face of the plasma membrane-events taking place near the terminus of the equatorial segment. Large particles, >12nm, remained not far from the cleared E-face patches. The P face of the outer acrosomal membrane is virtually clear from the outset. In addition, when fusion was completed, occasional double lines of large particles transiently embossed the P face of the plasma membrane (postacrosomal) side of the fusion zone. Behind the line of fusion, another series of particle-cleared foci emerged. We interpreted these postfusion membrane clearances as a second adaptation for sperm-egg interaction. Induction of the acrosome reaction in media containing phosphatidylcholine liposomes resulted in their apparent attachment, incorporation, or exchange in both the originally and secondarily cleared regions. Our observations support the concepts that membranes become receptive to union at particle- deficient interfaces, and that the physiologically created barren areas in freeze-fracture replicas may herald incipient membrane fusion.

Inositol 1,4,5-trisphosphate receptors modulate Ca2+ sparks and Ca2+ store content in vas deferens myocytes

2003 ◽  
Vol 285 (1) ◽  
pp. C195-C204 ◽  
Author(s):  
Carl White ◽  
J. Graham McGeown
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Vas Deferens ◽  
Confocal Imaging ◽  
Time Duration ◽  
Outward Currents ◽  
Inositol 1,4,5 Trisphosphate ◽  
Dependent Pathway ◽  
Spontaneous Transient Outward Currents

Spontaneous Ca2+ sparks were observed in fluo 4-loaded myocytes from guinea pig vas deferens with line-scan confocal imaging. They were abolished by ryanodine (100 μM), but the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) blockers 2-aminoethoxydiphenyl borate (2-APB; 100 μM) and intracellular heparin (5 mg/ml) increased spark frequency, rise time, duration, and spread. Very prolonged Ca2+ release events were also observed in ∼20% of cells treated with IP3R blockers but not under control conditions. 2-APB and heparin abolished norepinephrine (10 μM; 0 Ca2+)-evoked Ca2+ transients but increased caffeine (10 mM; 0 Ca2+) transients in fura 2-loaded myocytes. Transients evoked by ionomycin (25 μM; 0 Ca2+) were also enhanced by 2-APB. Ca2+ sparks and transients evoked by norepinephrine and caffeine were abolished by thimerosal (100 μM), which sensitizes the IP3R to IP3. In cells voltage clamped at –40 mV, spontaneous transient outward currents (STOCs) were increased in frequency, amplitude, and duration in the presence of 2-APB. These data are consistent with a model in which the Ca2+ store content in smooth muscle is limited by tonic release of Ca2+ via an IP3-dependent pathway. Blockade of IP3Rs elevates sarcoplasmic reticulum store content, promoting Ca2+ sparks and STOC activity.

scholarly journals Antagonists of the TMEM16A Calcium-activated Chloride Channel Modulate Airway Smooth Muscle Tone and Intracellular Calcium

2015 ◽  
Vol 123 (3) ◽  
pp. 569-581 ◽  
Author(s):  
Jennifer Danielsson ◽  
Jose Perez-Zoghbi ◽  
Kyra Bernstein ◽  
Matthew B. Barajas ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Potential ◽  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Intracellular Calcium ◽  
Chloride Channel ◽  
Calcium Flux ◽  
Leukotriene D4 ◽  
Peripheral Airways

Abstract Background: Perioperative bronchospasm refractory to β agonists continues to challenge anesthesiologists and intensivists. The TMEM16A calcium-activated chloride channel modulates airway smooth muscle (ASM) contraction. The authors hypothesized that TMEM16A antagonists would relax ASM contraction by modulating membrane potential and calcium flux. Methods: Human ASM, guinea pig tracheal rings, or mouse peripheral airways were contracted with acetylcholine or leukotriene D4 and then treated with the TMEM16A antagonists: benzbromarone, T16Ainh-A01, N-((4-methoxy)-2-naphthyl)-5-nitroanthranilic acid, or B25. In separate studies, guinea pig tracheal rings were contracted with acetylcholine and then exposed to increasing concentrations of isoproterenol (0.01 nM to 10 μM) ± benzbromarone. Plasma membrane potential and intracellular calcium concentrations were measured in human ASM cells. Results: Benzbromarone was the most potent TMEM16A antagonist tested for relaxing an acetylcholine -induced contraction in guinea pig tracheal rings (n = 6). Further studies were carried out to investigate the clinical utility of benzbromarone. In human ASM, benzbromarone relaxed either an acetylcholine- or a leukotriene D4–induced contraction (n = 8). Benzbromarone was also effective in relaxing peripheral airways (n = 9) and potentiating relaxation by β agonists (n = 5 to 10). In cellular mechanistic studies, benzbromarone hyperpolarized human ASM cells (n = 9 to 12) and attenuated intracellular calcium flux from both the plasma membrane and the sarcoplasmic reticulum (n = 6 to 12). Conclusion: TMEM16A antagonists work synergistically with β agonists and through a novel pathway of interrupting ion flux at both the plasma membrane and sarcoplasmic reticulum to acutely relax human ASM.

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