著者

Norikazu MATSUOKA Shin-ichi SAWAGUCHI Kenji YOSHIKAWA

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.77, no.5, pp.276-300, 2004-04-01 (Released:2008-12-25)

参考文献数

62

被引用文献数

11 18

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This report overviews observations on periglacial geomorphology in central Spitsbergen, which have been undertaken by the Japanese geomorphological groups. Focus is given to permafrost-related processes, including solifluction, thermal contraction cracking and pingo growth. Annual freeze-thaw action dominates the ground, resulting in extensive occurrence of solifluction and shallow landslides on soil slopes. Solifluction shows low surface velocity but large volumetric transport, which respectively reflects infrequent diurnal frost creep and deep movement. The latter partly originates from plug-like flow in the basal active layer, where permafrost temperature is low and muddy sediment is thick. Non-sorted polygons with a wide range of diameters develop on lowlands. In colder inland terrains, large polygons (>7m) have ice wedges, whereas smaller polygons have only soil wedges or cracks confined to the active layer. Significant ice-wedge cracking occurs during rapid and intensive cooling in midwinter. In warmer coastal terrains, ice wedges are not common even below large polygons, because higher winter temperature can produce only shallow cracks. Open-system pingos occur in valley bottoms and near shores. Some pingos are still growing under a low artesian pressure fed by constant supply of sub-permafrost water. Following lateral river erosion, a new frost mound emerged at a side of a pingo, reaching 3m high during three years. The observations demonstrate that central Spitsbergen is situated in a High Arctic but relatively warm permafrost environment. The transitional condition between cold and warm permafrost allows diverse periglacial features to coexist within a small area. Even minor climatic change can switch the two thermal regimes, affecting significantly the type and magnitude of periglacial processes.

著者

Naoki Murakami Kenji Yoshikawa Kohei Tsukada Noriaki Kamio Yoshinori Hayashi Suzuro Hitomi Yuki Kimura Ikuko Shibuta Ayaka Osada Shuichi Sato Koichi Iwata Masamichi Shinoda

出版者

Nihon University School of Dentistry

雑誌

Journal of Oral Science (ISSN:13434934)

巻号頁・発行日

pp.21-0483, (Released:2021-12-29)

参考文献数

29

被引用文献数

1

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Purpose: Periodontitis progresses with chronic inflammation, without periodontal pain. However, the underlying mechanisms are not well known. Here, the involvement of butyric acid (BA) in periodontal pain sensitivity in Porphyromonas gingivalis (P. gingivalis)-induced periodontitis was examined.Methods: P. gingivalis was inoculated into the ligature which was tied around the molar (P. gingivalis-L) and the gingival mechanical head withdrawal threshold (MHWT) was measured. Following P. gingivalis-L, the expressions of orphan G protein-coupled receptor 41 (GPR41) in trigeminal ganglion (TG) neurons were examined. The amount of gingival BA was analyzed following the P. gingivalis-L and the changes in the MHWT in complete Freund’s adjuvant (CFA)-injected gingival tissue by gingival BA were examined. The changes in the MHWT following P. gingivalis-L by gingival GPR41 antagonist (HA) were examined.Results: No change in the MHWT was observed, GPR41-immunoreactive TG neurons were increased following P. gingivalis-L. The gingival BA amount increased following P. gingivalis-L, and the gingival BA suppressed the decrease in MHWT following CFA. HA decreased MHWT following P. gingivalis-L.Conclusion: Gingival BA modulates periodontal mechanical nociception via GPR41 signaling in P. gingivalis-L-induced periodontitis.