Proceedings of the Japan Academy, Series B

Reviews

The origin of Cretaceous black shales: a change in the surface ocean ecosystem and its triggers

Naohiko OHKOUCHI, Junichiro KURODA, Asahiko TAIRA

2015 Volume 91 Issue 7 Pages 273-291
Published: July 10, 2015
Released on J-STAGE: July 21, 2015

DOIhttps://doi.org/10.2183/pjab.91.273

JOURNAL FREE ACCESS FULL-TEXT HTML

Show abstractHide abstract

Black shale is dark-colored, organic-rich sediment, and there have been many episodes of black shale deposition over the history of the Earth. Black shales are source rocks for petroleum and natural gas, and thus are both geologically and economically important. Here, we review our recent progress in understanding of the surface ocean ecosystem during periods of carbonaceous sediment deposition, and the factors triggering black shale deposition. The stable nitrogen isotopic composition of geoporphyrins (geological derivatives of chlorophylls) strongly suggests that N₂-fixation was a major process for nourishing the photoautotrophs. A symbiotic association between diatoms and cyanobacteria may have been a major primary producer during episodes of black shale deposition. The timing of black shale formation in the Cretaceous is strongly correlated with the emplacement of large igneous provinces such as the Ontong Java Plateau, suggesting that black shale deposition was ultimately induced by massive volcanic events. However, the process that connects these events remains to be solved.

View full abstract

Download PDF (3159K) Full view HTML
Discovery of NKT cells and development of NKT cell-targeted anti-tumor immunotherapy

Masaru TANIGUCHI, Michishige HARADA, Nyambayar DASHTSOODOL, Satoshi KO ...

2015 Volume 91 Issue 7 Pages 292-304
Published: July 10, 2015
Released on J-STAGE: July 21, 2015

DOIhttps://doi.org/10.2183/pjab.91.292

JOURNAL FREE ACCESS FULL-TEXT HTML

Show abstractHide abstract

Natural Killer T (NKT) cells are unique lymphocytes characterized by their expression of a single invariant antigen receptor encoded by Vα14Jα18 in mice and Vα24Jα18 in humans, which recognizes glycolipid antigens in association with the monomorphic CD1d molecule. NKT cells mediate adjuvant activity to activate both CD8T cells to kill MHC-positive tumor cells and NK cells to eliminate MHC-negative tumor at the same time in patients, resulting in the complete eradication of tumors without relapse. Therefore, the NKT cell-targeted therapy can be applied to any type of tumor and also to anyone individual, regardless of HLA type.
Phase IIa clinical trials on advanced lung cancers and head and neck tumors have been completed and showed significantly prolonged median survival times with only the primary treatment. Another potential treatment option for the future is to use induced pluripotent stem cell (iPS)-derived NKT cells, which induced adjuvant effects on anti-tumor responses, inhibiting in vivo tumor growth in a mouse model.

View full abstract

Download PDF (2921K) Full view HTML
Strength and precision of neurotransmission at mammalian presynaptic terminals

Tomoyuki TAKAHASHI

2015 Volume 91 Issue 7 Pages 305-320
Published: July 10, 2015
Released on J-STAGE: July 21, 2015

DOIhttps://doi.org/10.2183/pjab.91.305

JOURNAL FREE ACCESS FULL-TEXT HTML

Show abstractHide abstract

Classically, the basic concept of chemical synaptic transmission was established at the frog neuromuscular junction, and direct intracellular recordings from presynaptic terminals at the squid giant presynaptic terminal have further clarified principles of neurotransmitter release. More recently, whole-cell patch-camp recordings from the calyx of Held in rodent brainstem slices have extended the classical concept to mammalian synapses providing new insights into the mechanisms underlying strength and precision of neurotransmission and developmental changes therein. This review summarizes findings from our laboratory and others on these subjects, mainly at the calyx of Held, with a particular focus on precise, high-fidelity, fast neurotransmission. The mechanisms by which presynaptic terminals acquire strong, precise neurotransmission during postnatal development are also discussed.

View full abstract

Download PDF (9462K) Full view HTML
Mechanism of the calcium-regulation of muscle contraction — In pursuit of its structural basis —

Takeyuki WAKABAYASHI

2015 Volume 91 Issue 7 Pages 321-350
Published: July 10, 2015
Released on J-STAGE: July 21, 2015

DOIhttps://doi.org/10.2183/pjab.91.321

JOURNAL FREE ACCESS FULL-TEXT HTML

Show abstractHide abstract

The author reviewed the research that led to establish the structural basis for the mechanism of the calcium-regulation of the contraction of striated muscles. The target of calcium ions is troponin on the thin filaments, of which the main component is the double-stranded helix of actin. A model of thin filament was generated by adding tropomyosin and troponin. During the process to provide the structural evidence for the model, the troponin arm was found to protrude from the calcium-depleted troponin and binds to the carboxyl-terminal region of actin. As a result, the carboxyl-terminal region of tropomyosin shifts and covers the myosin-binding sites of actin to block the binding of myosin. At higher calcium concentrations, the troponin arm changes its partner from actin to the main body of calcium-loaded troponin. Then, tropomyosin shifts back to the position near the grooves of actin double helix, and the myosin-binding sites of actin becomes available to myosin resulting in force generation through actin-myosin interactions.

View full abstract

Download PDF (13837K) Full view HTML

Register with J-STAGE for free!