650 research outputs found
Magnetic-Field-Independent Ultrasonic Dispersions in the Magnetically Robust Heavy Fermion System SmOs4Sb12
Elastic properties of the filled skutterudite compound SmOsSb have
been investigated by ultrasonic measurements. The elastic constant
shows two ultrasonic dispersions at 15 K and 53 K
for frequencies between 33 and 316 MHz, which follow a Debye-type
formula with Arrhenius-type temperature-dependent relaxation times, and remain
unchanged even with applied magnetic fields up to 10 T. The corresponding
activation energies were estimated to be = 105 K and = 409 K,
respectively. The latter, , is the highest value reported so far in the
Sb-based filled skutterudites. The presence of magnetically robust ultrasonic
dispersions in SmOsSb implies a possibility that an emergence of a
magnetically insensitive heavy fermion state in this system is associated with
a novel local charge degree of freedom which causes the ultrasonic dispersion.Comment: 5 pages, 4 figure
Potential role of group X secretory phospholipase A2 in cyclooxygenase-2-dependent PGE2 formation during colon tumorigenesis
AbstractAlthough the cyclooxygenase-2 (COX-2) pathway of the arachidonic acid cascade has been suggested to play an important role in colon carcinogenesis, there is little information concerning the identity of phospholipase A2 (PLA2) involved in the arachidonic acid release in colon tumors. Here, we compared the potencies of three types of secretory PLA2s (group IB, IIA and X sPLA2s) for the arachidonic acid release from cultured human colon adenocarcinoma cells, and found that group X sPLA2 has the most powerful potency in the release of arachidonic acid leading to COX-2-dependent prostaglandin E2 (PGE2) formation. Furthermore, immunohistological analysis revealed the elevated expression of group X sPLA2 in human colon adenocarcinoma neoplastic cells in concert with augmented expression of COX-2. These findings suggest a critical role of group X sPLA2 in the PGE2 biosynthesis during colon tumorigenesis
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