Ionic Mechanisms of Excitation in Paramecium

Eckert, Roger; Brehm, Paul

doi:10.1146/annurev.bb.08.060179.002033

Cited by 261 publications

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“…The voltage-gated channels exist in virtually all living species, and we can find several types of them in bacteria, with the Ca 2ϩ -and K ϩ -selective channels being the most ancient. [2][3][4][5][6][7] The bacteria also evolved the first precursor of the Na ϩ channel, the NaChBac expressed, for example, in Bacillus halodurans. 8 In the eukaryotes, the excitable molecules developed further; in single-cell organisms, the waves of plasmalemmal excitation began to generate through the spreading opening/closures of voltagegated channels.…”

Section: Glial Explosion Forms the Human Brainmentioning

confidence: 99%

Astrocytes in Alzheimer's Disease

et al. 2010

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Summary:The circuitry of the human brain is formed by neuronal networks embedded into astroglial syncytia. The astrocytes perform numerous functions, providing for the overall brain homeostasis, assisting in neurogenesis, determining the micro-architecture of the grey matter, and defending the brain through evolutionary conserved astrogliosis programs.Astroglial cells are engaged in neurological diseases by determining the progression and outcome of neuropathological process. Astrocytes are specifically involved in various neurodegenerative diseases, including Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and various forms of dementia. Recent evidence suggest that early stages of neurodegenerative processes are associated with atrophy of astroglia, which causes disruptions in synaptic connectivity, disbalance in neurotransmitter homeostasis, and neuronal death through increased excitotoxicity. At the later stages, astrocytes become activated and contribute to the neuroinflammatory component of neurodegeneration.

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Section: Glial Explosion Forms the Human Brainmentioning

confidence: 99%

Astrocytes in Alzheimer's Disease

et al. 2010

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“…6. Entries [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are cilia along one line of synchrony but with the analyzed segments at different heights up the cilia . Cilia [21][22][23][24][25][26][27][28][29] are examined near the base and are at various phases of the beat .…”

Section: Central-pair Vectors At Nine Different Sectors (As Defined Amentioning

confidence: 99%

“…A vector from the tubule without the marker to the one with the markers can therefore be drawn unambiguously and its angular changes determined . Furthermore, methods of ionic and genetic manipulations of Paramecium behavior are well established (8,28) . We can therefore investigate this vector and its possible rotation in backward-swimming cells or immobilized cells as well as in the normal forward-swimming cells .…”

mentioning

confidence: 99%

Rotation and twist of the central-pair microtubules in the cilia of Paramecium.

Omoto¹,

Kung²

1980

The Journal of Cell Biology

132

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The orientation and configuration of the central-pair microtubules in cilia were studied by serial thin-section analysis of "instantaneously fixed" paramecia. Cilia were frozen in various positions in metachronal waves by such a fixation . The spatial sequence of these positions across the wave represents the temporal sequence of the positions during the active beat cycle of a cilium . Systematic shifts of central-pair orientation across the wave indicate that the central pair rotates 360°counterclockwise (viewed from outside) with each ciliary beat cycle (C . K. Omoto, 1979, Thesis, University of Wisconsin, Madison; C. K. Omoto and C. Kung, 1979, Nature [Lond .] 279:532-534) . This is true even for paramecia with different directions of effective stroke as in forward-or backward-swimming cells. The systematic shifts of centralpair orientation cannot be seen in Ni"-paralyzed cells or sluggish mutants which do not have metachronal waves. Both serial thin-section and thick-section high-voltage electron microscopy show that whenever a twist in the central pair is seen, it is always left-handed . This twist is consistent with the hypothesis that the central pair continuously rotates counterclockwise with the rotation originating at the base of the cilium . That the rotation of the central pair is most likely with respect to the peripheral tubules as well as the cell surface is discussed . These results are incorporated into a model in which the central-pair complex is a component in the regulation of the mechanism needed for three-dimensional ciliary movement .Cilia (eucaryotic flagella and sperm tails) have been studied to determine the function of the components responsible for generating motion (reviewed in references 4, 14, and 40) . The sliding-microtubule model is now accepted as the fundamental motile mechanism for cilia . In the late 1960's Satir (39) produced the first evidence for sliding rather than contraction as the basis for ciliary motion. The sliding-microtubule hypothesis was given support by the direct demonstration of sliding disintegration in trypsin-treated axonemes by Summers and Gibbons (46) . The force that causes the ciliary microtubules to slide is generated by the pair of dynein arms that project out periodically along the length of each peripheral microtubule doublet (11). Sliding was shown to be unipolar by Sale and Satir (37) in Tetrahymena cilia .Studies indicate some interaction between the radial spokes of the peripheral doublets and the projections from the central pair (47,51) . It is suggested that such an interaction converts sliding to bending, but how sliding of the peripheral doublets is transduced into active coordinated beating of cilia is not known . The functions in motility of such components as the radial spokes and the central-tubule complex are largely un-

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“…In ciliates, normal ciliary beat depends on Ca 2þ [165], as does any change in beat activity. For instance, ciliary beat is reversed when intraciliary [Ca 2þ ] increases by activation of voltage-gated Ca 2þ channels, as described for ciliated protozoa [166], and in ctenophores (comb jellies). In both systems, these channels are restricted to the cilia [84,167].…”

Section: Molecular Targets Of Ca 2þ In Cellsmentioning

confidence: 98%

“…Ca 2þ exerts pleiotropic effects on ciliary activity, especially in ciliated protozoa. The availability of a minimum of cytosolic ionized Ca 2þ is required for ciliary/flagellar activity [165], which can be further modulated by Ca 2þ [166]. In ciliates, normal ciliary beat depends on Ca 2þ [165], as does any change in beat activity.…”

Section: Molecular Targets Of Ca 2þ In Cellsmentioning

confidence: 99%

Inseparable tandem: evolution chooses ATP and Ca²⁺to control life, death and cellular signalling

Plattner

Verkhratsky

2016

Phil. Trans. R. Soc. B

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From the very dawn of biological evolution, ATP was selected as a multipurpose energy-storing molecule. Metabolism of ATP required intracellular free Ca 2þ to be set at exceedingly low concentrations, which in turn provided the background for the role of Ca 2þ as a universal signalling molecule. The early-eukaryote life forms also evolved functional compartmentalization and vesicle trafficking, which used Ca 2þ as a universal signalling ion; similarly, Ca 2þ is needed for regulation of ciliary and flagellar beat, amoeboid movement, intracellular transport, as well as of numerous metabolic processes. Thus, during evolution, exploitation of atmospheric oxygen and increasingly efficient ATP production via oxidative phosphorylation by bacterial endosymbionts were a first step for the emergence of complex eukaryotic cells. Simultaneously, Ca 2þ started to be exploited for shortrange signalling, despite restrictions by the preset phosphate-based energy metabolism, when both phosphates and Ca 2þ interfere with each other because of the low solubility of calcium phosphates. The need to keep cytosolic Ca 2þ low forced cells to restrict Ca 2þ signals in space and time and to develop energetically favourable Ca 2þ signalling and Ca 2þ microdomains. These steps in tandem dominated further evolution. The ATP molecule (often released by Ca 2þ -regulated exocytosis) rapidly grew to be the universal chemical messenger for intercellular communication; ATP effects are mediated by an extended family of purinoceptors often linked to Ca 2þ signalling. Similar to atmospheric oxygen, Ca 2þ must have been reverted from a deleterious agent to a most useful (intra-and extracellular) signalling molecule. Invention of intracellular trafficking further increased the role for Ca 2þ homeostasis that became critical for regulation of cell survival and cell death. Several mutually interdependent effects of Ca 2þ and ATP have been exploited in evolution, thus turning an originally unholy alliance into a fascinating success story.This article is part of the themed issue 'Evolution brings Ca 2þ and ATP together to control life and death'.

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Ionic Mechanisms of Excitation in Paramecium

Cited by 261 publications

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Astrocytes in Alzheimer's Disease

Astrocytes in Alzheimer's Disease

Rotation and twist of the central-pair microtubules in the cilia of Paramecium.

Inseparable tandem: evolution chooses ATP and Ca²⁺to control life, death and cellular signalling

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Ionic Mechanisms of Excitation in Paramecium

Cited by 261 publications

References 0 publications

Astrocytes in Alzheimer's Disease

Astrocytes in Alzheimer's Disease

Rotation and twist of the central-pair microtubules in the cilia of Paramecium.

Inseparable tandem: evolution chooses ATP and Ca2+to control life, death and cellular signalling

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Inseparable tandem: evolution chooses ATP and Ca²⁺to control life, death and cellular signalling