Daisuke Miki

Behavior of fluorine and chlorine in volcanic ash of Sakurajima volcano, Japan in the sequence of its eruptive activity

At Sakurajima volcano, strombolian eruptions forerun vulcanian explosions, and volcanian explosions are often followed by continuous ash eruptions. Change in the mode of its eruptive activity is drastic and release of volatiles from magma corresponding to its eruptive activity is examined by determination of fluorine and chlorine in volcanic ash. The F contents of all the ash samples are markedly higher than the arithmetic mean value of Japanese volcanic rocks (ca. 300 μg/g). Further, the water-soluble Cl contents of almost all the ash samples are also extremely higher than those of Japanese volcanic rocks (less than 50 μg/g). This is attributed to fixation of F and Cl in hot gas onto the volcanic ash particles in the crater and/or eruption plumes. The differences in those contents among the “strombolian eruption”-, “vulcanian explosion”- and “continuous ash eruption” groups are significant, which implies that hot gas rich in F and Cl are issued during strombolian eruptions, while those halogens are less concentrated in hot gas after strombolian eruptions. The water-insoluble Cl content of the “strombolian eruption” group is significantly higher than those of the other groups. This result implies that Cl and the other volatiles are intensely released from magma during the doming period before vulcanian eruptions.Yet, it is inferred that continuous ash eruption is the final phase of vulcanian one.

CD105 maintains the thermogenic program of beige adipocytes by regulating Smad2 signaling

Beige adipocytes are thermogenic adipocytes with developmental and anatomical properties distinct from those of classical brown adipocytes. Recent studies have revealed several key molecular regulators of beige adipocyte development. CD105, also called endoglin, is a membrane protein composed of TGF-β receptor complex. It regulates TGF-β-family signal transduction and vascular formation in vivo. We report here that CD105 maintains the thermogenic gene program of beige adipocytes by regulating Smad2 signaling. Cd105-/- adipocyte precursors showed augmented Smad2 activation and decreased expression of thermogenic genes such as Ucp1 and Prdm16-which encodes a transcriptional regulatory protein for thermogenesis-after adipogenic differentiation. Smad2 signaling augmentation by the constitutively active form of Smad2 decreased the expression of thermogenic genes in beige adipocytes. Loss of thermogenic activity in Cd105-/- beige adipocytes was rescued by Prdm16 expression. These data reveal a novel function of CD105 in beige adipocytes: maintaining their thermogenic program by regulating Smad2 signaling.