The secretory contents of Paramecium tetraurelia trichocysts: ultrastructural--cytochemical characterization.

Kersken, Helmut; Tiggemann, R.; Westphal, Christel; Plattner, Helmut

doi:10.1177/32.2.6693754

Cited by 22 publications

(9 citation statements)

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“…The MLS displays a longitudinal periodicity of 30 nm (Figure 6), different from that of the paracrystalline matrix (Kerksen et al, 1984). In pretrichocysts matrix components crystallize in the organelle center.…”

Section: Functional Aspectsmentioning

confidence: 99%

Ultrastructural and antigenic preservation of a delicate structure by cryopreparation: identification and immunogold localization during biogenesis of a secretory component (membrane-matrix connection) in Paramecium trichocysts.

Momayezi¹,

Habermann²,

Sokolova³

et al. 1993

J Histochem Cytochem.

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Ultrastructure and antigenicity of the "mesh-like sheath" (MLS), a very delicate structure connecting the membrane and the paracrystalline matrix of Paramecium trichocysts, are well preserved after cryofixation (rapid freezing followed by freeze-substitution in methanol and embedding in Lowicryl KllM at 213K). The MLS is labeled by colloidal (Ab) against trichocyst components obtained by recloning hybridoma cells twice. We prepared Western blots from reduced gels obtained from subfractionated trichocysts. Trichocyst membranes displayed reactive bands of 68-70, 63-66,43, 40 (strongest), and 57 and 54 KD, with a weak band of 38 KD. One of the most abundant protein bands of soluble secretory components (56-57 KD) was also strongly stained on blots. On ultra-thin sections pre-trichocysts disgold-bound antibodies (Ab-Aulom) With primary antibody

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Section: Functional Aspectsmentioning

confidence: 99%

Ultrastructural and antigenic preservation of a delicate structure by cryopreparation: identification and immunogold localization during biogenesis of a secretory component (membrane-matrix connection) in Paramecium trichocysts.

Momayezi¹,

Habermann²,

Sokolova³

et al. 1993

J Histochem Cytochem.

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“…) and similarly electron micrographs have been evaluated by laser diffractometry (Kersken et al. ). Electron microscope (EM) analysis of Paramecium 's trichocysts has shown that such stretching is paralleled by a change in the periodic crossbanding of the trichocyst body matrix (Hausmann , ; Jakus and Hall ).…”

Section: Basic Features Of Trichocyst Structure and Functionmentioning

confidence: 99%

“…Therefore, the rearrangement of the proteins during decondensation takes place in concert with exocytotic membrane fusion (Hausmann ; Kersken et al. ; Plattner et al. ; Sperling et al.…”

Section: Basic Features Of Trichocyst Structure and Functionmentioning

confidence: 99%

“…The periodicity of crossbanding, as measured after different staining methods, either directly on EM micrographs or by their laser diffractometric analysis, results in a stretching factor of ~4 or 7.5, depending on which banding is considered (Kersken et al. ). In addition, longitudinal connections between densely stained crossbands can be recognized (Hausmann et al.…”

Section: Basic Features Of Trichocyst Structure and Functionmentioning

confidence: 99%

“…Using different affinity and immuno‐labeling procedures, calmodulin in the matrix has been identified as a redistribution artifact generated by the unintentional permeabilization of the trichocyst membrane during preparation (Kersken et al. ; Momayezi et al. ).…”

Section: Additional Trichocyst Components and Luminal Phmentioning

confidence: 99%

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Trichocysts—Paramecium's Projectile‐like Secretory Organelles

Plattner

2016

J Eukaryotic Microbiology

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This review summarizes biogenesis, composition, intracellular transport, and possible functions of trichocysts. Trichocyst release by Paramecium is the fastest dense core-secretory vesicle exocytosis known. This is enabled by the crystalline nature of the trichocyst "body" whose matrix proteins (tmp), upon contact with extracellular Ca , undergo explosive recrystallization that propagates cooperatively throughout the organelle. Membrane fusion during stimulated trichocyst exocytosis involves Ca mobilization from alveolar sacs and tightly coupled store-operated Ca -influx, initiated by activation of ryanodine receptor-like Ca -release channels. Particularly, aminoethyldextran perfectly mimics a physiological function of trichocysts, i.e. defense against predators, by vigorous, local trichocyst discharge. The tmp's contained in the main "body" of a trichocyst are arranged in a defined pattern, resulting in crossstriation, whose period expands upon expulsion. The second part of a trichocyst, the "tip", contains secretory lectins which diffuse upon discharge. Repulsion from predators may not be the only function of trichocysts. We consider ciliary reversal accompanying stimulated trichocyst exocytosis (also in mutants devoid of depolarization-activated Ca channels) a second, automatically superimposed defense mechanism. A third defensive mechanism may be effectuated by the secretory lectins of the trichocyst tip; they may inhibit toxicyst exocytosis in Dileptus by crosslinking surface proteins (an effect mimicked in Paramecium by antibodies against cell surface components). Some of the proteins, body and tip, are glycosylated as visualized by binding of exogenous lectins. This reflects the biogenetic pathway, from the endoplasmic reticulum via the Golgi apparatus, which is also supported by details from molecular biology. There are fragile links connecting the matrix of a trichocyst with its membrane; these may signal the filling state, full or empty, before and after tmp release upon exocytosis, respectively. This is supported by experimentally produced "frustrated exocytosis", i.e. membrane fusion without contents release, followed by membrane resealing and entry in a new cycle of reattachment for stimulated exocytosis. There are some more puzzles to be solved: Considering the absence of any detectable Ca and of acidity in the organelle, what causes the striking effects of silencing the genes of some specific Ca -release channels and of subunits of the H -ATPase? What determines the inherent polarity of a trichocyst? What precisely causes the inability of trichocyst mutants to dock at the cell membrane? Many details now call for further experimental work to unravel more secrets about these fascinating organelles.

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Low-Temperature Embedding

Armbruster

Kellenberger

1986

Ultrastructure Techniques for Microorganisms

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The secretory contents of Paramecium tetraurelia trichocysts: ultrastructural--cytochemical characterization.

Cited by 22 publications

References 0 publications

Ultrastructural and antigenic preservation of a delicate structure by cryopreparation: identification and immunogold localization during biogenesis of a secretory component (membrane-matrix connection) in Paramecium trichocysts.

Ultrastructural and antigenic preservation of a delicate structure by cryopreparation: identification and immunogold localization during biogenesis of a secretory component (membrane-matrix connection) in Paramecium trichocysts.

Trichocysts—Paramecium's Projectile‐like Secretory Organelles

Low-Temperature Embedding

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