Dense Cored Vesicles in SAI Merkel Cells and Their Role in Mechano-Electric Transduction

Iggo, A.; Pacitti, Elaine G.; Findlater, Gordon S.

doi:10.1007/978-1-4899-0812-4_34

Cited by 4 publications

(3 citation statements)

References 9 publications

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“…Some investigators have suggested that MCs act as mechanical transducers (for reviews see Iggo and Findlater 1984;Iggo et al 1988;Akaike and Yamashita 1995;Ogawa 1996; also see Tazaki and Iggo 1995;Baumann et al 1996;Chan et al 1996), while others have suggested that MCs do not act as mechanical transducers (Diamond et al 1986Mearow and Diamond 1988;Mills and Diamond 1995). Nevertheless, ultrastructural and immunohistochemical features of MC-neurite complexes suggest that MCs exert a humoral influence on their adjacent nerve terminals (MC-axon terminals).…”

Section: Discussionmentioning

confidence: 95%

Immunohistochemical expression of G protein α-subunit isoforms in rat and monkey Merkel cell-neurite complexes

Tachibana

Endoh

Nawa

2001

Histochem Cell Biol

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The true function of Merkel cells (MCs) is still enigmatic, though the localization of various kinds of neurotransmitter-like substances in MCs has been revealed by immunohistochemistry. Most of the neurotransmitters act on target cells via seven-transmembrane receptors coupled to heterotrimeric G proteins. The heterotrimeric G proteins include various subfamilies that contribute to different signal transduction pathways. Therefore investigation of specific types of G proteins in MCs and related axon terminals (MC-axon terminals) should contribute to the elucidation of the function of MCs. In this study, we investigated the expression patterns of alpha-subunit isoforms of G proteins in MC-neurite complexes of the rat and monkey by enzymatic and fluorescence immunohistochemistry. MC-axon terminals of the rat and monkey showed positive immunoreactions of Galphao and Galphai1. Those of the monkey also showed a weak immunoreaction of Galphas. On the other hand, MCs of both animals showed positive immunoreactions of Galphao, Galphai1, Galphaq, and Galphaz. In addition, MCs of the monkey showed weak immunoreactions of Galphas. Galphao- and Galphai1-like immunoreactions in the MC-axon terminals suggest that MCs suppressively regulate receptive functions of type I mechanosensory nerve terminals. On the other hand, the localization of Galpha-subunits in MCs suggests that these cells are regulated with hormones, neurotransmitter-like substances, or growth factors.

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Section: Discussionmentioning

confidence: 95%

Immunohistochemical expression of G protein α-subunit isoforms in rat and monkey Merkel cell-neurite complexes

Tachibana

Endoh

Nawa

2001

Histochem Cell Biol

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“…Within the thickened epidermis of touch domes, the peripheral terminals of SAIs form expanded disc-like endings that lie in synapse-like apposition to Merkel cells in the basal epidermis (Munger, 1965;Iggo and Muir, 1969). The latter are neural crest-derived neuroendocrine cells (Szeder et al, 2003a) that appear to play an essential role in the transduction of mechanical stimuli into electrical activity of SAI afferents (Findlater et al, 1987;Iggo et al, 1988;Baumann et al, 1990;Ikeda et al, 1994;cf. Nurse and Cooper, 1988;Mills and Diamond, 1995).…”

mentioning

confidence: 99%

Central and peripheral anatomy of slowly adapting type I low‐threshold mechanoreceptors innervating trunk skin of neonatal mice

Woodbury

Koerber

2007

J of Comparative Neurology

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Despite intensive study, our understanding of the neuronal structures responsible for transducing the broad spectrum of environmental energies that impinge upon the skin has rested on inference and conjecture. This major shortcoming motivated the development of ex vivo somatosensory system preparations in neonatal mice in the hope that their small size might allow the peripheral terminals of physiologically identified sensory neurons to be labeled intracellularly for direct study. The present report describes the first such study of the peripheral terminals of four slowly adapting type I low-threshold mechanoreceptors (SAIs) that innervated the back skin of neonatal mice. In addition, this report includes information on the central anatomy of the same SAI afferents that were identified peripherally with both physiological and anatomical means, providing an essentially complete view of the central and peripheral morphology of individual SAI afferents in situ. Our findings reveal that SAIs in neonates are strikingly adult-like in all major respects. Afferents were exquisitely sensitive to mechanical stimuli and exhibited a distinctly irregular, slowly adapting discharge to stimulation of 1-4 punctate receptive fields in the skin. Their central collaterals formed transversely oriented and largely nonoverlapping arborizations limited to regions of the dorsal horn corresponding to laminae III-V. Their peripheral arborizations were restricted entirely within miniaturized touch domes, where they gave rise to expanded disc-like endings in close apposition to putative Merkel cells in basal epidermis. These findings therefore provide the first direct confirmation of the functional morphology of this physiologically unique afferent class.

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“…However, numerous dense-cored granules, which are involved in transduction 11) , were also recognized in the spherical Merkel soma, in addition to the surface cylindrical cytoplasmic processes, suggesting that changes in soma shape do not lead to disappearance of cell function. In other words, it is possible that the dense-cored granules in Merkel cells are released by an appropriate extracellular stimulus.…”

Section: Discussionmentioning

confidence: 99%

Scanning and Transmission Electron Microscopic Observation of Changes in Cylindrical Cytoplasmic Processes of Isolated Single Merkel Cell

Tazaki

Inoue

et al. 2011

Bull. Tokyo Dent. Coll.

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The aim of the present study was to determine the reason isolated single Merkel cells do not respond to mechanical stimulation by fluorescent or histological techniques. Cells identified as Merkel cells by quinacrine fluorescence and measurement of intracellular calcium concentration were observed by transmission electron and scanning electron microscopy. Observations elucidated that the cylindrical cytoplasmic processes of single Merkel cells disappeared with time shortly after isolation. Transmission electron microscopy revealed the presence of numerous dense-cored granules, which may function as sensory receptors in the cytoplasm of the isolated single Merkel cell. Disappearance of the cylindrical cytoplasmic processes impeded reception of mechanical stimulation. The results suggest that an isolated single Merkel cell continues to function as a sensory receptor cell due to the presence of numerous dense-cored granules. Furthermore, the results show that an isolated single Merkel cell is not an appropriate specimen for investigation of mechanically-gated channels.

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Dense Cored Vesicles in SAI Merkel Cells and Their Role in Mechano-Electric Transduction

Cited by 4 publications

References 9 publications

Immunohistochemical expression of G protein α-subunit isoforms in rat and monkey Merkel cell-neurite complexes

Immunohistochemical expression of G protein α-subunit isoforms in rat and monkey Merkel cell-neurite complexes

Central and peripheral anatomy of slowly adapting type I low‐threshold mechanoreceptors innervating trunk skin of neonatal mice

Scanning and Transmission Electron Microscopic Observation of Changes in Cylindrical Cytoplasmic Processes of Isolated Single Merkel Cell

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