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Avian Extended Junctional SR: 3-D Geometry Rendered in Stereo

Published online by Cambridge University Press:  02 July 2020

J.R. Sommer ,
T. High ,
P. Ingram ,
D. Kopf ,
R. Nassar  and
I. Taylor
J.R. Sommer
Affiliation:
Dept. of Pathol., Duke Univ. and VA Med. Ctrs., Durham, NC, 27710
T. High
Affiliation:
Dept. of Pathol., Duke Univ. and VA Med. Ctrs., Durham, NC, 27710
P. Ingram
Affiliation:
RTI, RTP, NC, 27709
D. Kopf
Affiliation:
Dept. of Pathol., Duke Univ. and VA Med. Ctrs., Durham, NC, 27710
R. Nassar
Affiliation:
Dept. of Pediatrics, Duke Univ. Med. Ctr., Durham, NC, 27710
I. Taylor
Affiliation:
Dept. of Pathol., Duke Univ. and VA Med. Ctrs., Durham, NC, 27710
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Extract

Extended junctional sarcoplasmic reticulum (EJSR) is an invariant differentiation of the sarcoplasmic reticulum (SR) in bird cardiac myocytes (CM) and central to excitation-contraction coupling (ECC). EJSR occurs as both continuous and discontinuous extensions of junctional sarcoplasmic reticulum (JSR), and surrounds and pervades the Z/I band as the “ EJSR Z-rete” whose geometry has mechanistic implications for the function of “couplings” in ECC, in general. “Peripheral coupling(s)” (PC) in birds, and the additional “interior coupling(s)” (IC) at transverse tubules (TT) in mammals, are formed by tight apposition to plasmalemma of JSR, a specialized calcium (Ca) store of the SR. Free SR (FSR; i.e. free of JSR/EJSR specializations) is the rest of the smooth, tubular SR network, which connects intercalated patches of EJSR forming the EJSR Z-retes and, elsewhere, displays both longitudinal and transverse geometries in surrounding the contractile material for the purpose of sequestering Ca after each muscle contraction. Except for EJSR having no plasmalemmal contact, morphologically, EJSR and JSR are homologues:1 both have similar sizes; are studded (approx. 32 nm center-to-center) with junctional processes (JP; ryanodine receptor (RyR)/-Ca-release channels);

Type
Imaging Cells and Organelles
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 247 - 248
Copyright
Copyright © Microscopy Society of America 1997

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References

References:

1.Sommer, J. et al. Acta Physiol. Scand. (1991)5.Google Scholar
2.Junker, J. et al. J. Biol. Chem. (1994)1634.Google Scholar
3.Kopf, D. et al. Microbeam Anal. Proc. (1995)317Google Scholar
4. Supported by NIH ROl 12486-27 and the VA Research Service.Google Scholar