Neo-Realism and International Public Goods

廣田司朗教授古稀記念特集本稿は，文部省科学研究費一般研究 (C) 「経済学サイドから見た「国際政治経済学」の特質とポスト冷戦秩序シナリオ」 (平成7～9年度， 課題番号　07630037) にもとづく研究成果である

Phylogenetic Insights into RT and Vpx/Vpr

The efficiency of reverse transcription to synthesize viral DNA in infected cells greatly influences replication kinetics of retroviruses. However, viral replication in non-dividing cells such as resting T cells and terminally differentiated macrophages is potently and kinetically restricted by a host antiviral factor designated SAMHD1 (sterile alpha motif and HD-domain containing protein 1). SAMHD1 reduces cellular deoxynucleoside triphosphate (dNTP) pools and affects viral reverse transcription step. Human immunodeficiency virus type 2 (HIV-2) and some simian immunodeficiency viruses (SIVs) have Vpx or Vpr to efficiently degrade SAMHD1. Interestingly, the reverse transcriptase (RT) derived from HIV-1 that encodes no anti-SAMHD1 proteins has been previously demonstrated to uniquely exhibit a high enzymatic activity. It is thus not irrational to assume that some viruses may have acquired or lost the specific RT property to better adapt themselves to the low dNTP environments confronted in non-dividing cells. This adaptation process may probably be correlated with the SAMHD1-antagonizing ability by viruses. In this report, we asked whether such adaptive events can be inferable from Vpx/Vpr and RT phylogenetic trees overlaid with SAMHD1-degrading capacity of Vpx/Vpr and with kinetic characteristics of RT. Resultant two trees showed substantially similar clustering patterns, and therefore suggested that the properties of RT and Vpx/Vpr can be linked. In other words, HIV/SIVs may possess their own RT proteins to adequately react to various dNTP circumstances in target cells

Tide-induced reworking of planktonic foraminifers on the outer shelf and slope off the Miyako Island, southern Ryukyus, Japan: Preliminary results

Significance of sediment reworking to a shallower environment is preliminarily discussed by occurrences and oxygen isotopes of planktonic foraminifer (Globolotalia inflata) tests collected from the sea bottom sediments on the insular shelf to slope, off the Miyako Islands, southern Ryukyus, Japan. The isotopic data and comparison with the present water temperature-depth profile indicate that vertical distribution of G. inflata with size of 300-355µm ranges from 135 to 250m (average 160m). Strong tidal currents between the East China Sea and the Pacific Ocean developed in the study area may induce the transpotation of sediment particles to a shallower environment. This is demonstrated by the occurrences of this species in sediment deposited in depth shallower than inhabiting depth. The analyzed tests were not altered by long-time contact with bottom water because they preserve surface structures and a narrow range of oxygen isotopic composition. Shortly after G. inflata died and settled on sea bottom, the tests were commonly transported to the shallower environment by the upwelling, which may result from strong tidal currents and the topographic feature of the Ryukyu Island Arc