Sphingosine 1-phosphate (S-1-P) and lysophosphatidic acid (LPA) stimulated glycogen phosphorylase, a rate-limiting enzyme responsible for glycogenolysis, in association with Ca2+ mobilization and phospholipase C (PLC) activation in rat hepatocytes. S-1-P, but not LPA, also inhibited adenosine 3',5'-cyclic monophosphate accumulation reflecting adenylyl cyclase inhibition. S-1-P-induced PLC activation, Ca2+ mobilization, and phosphorylase activation were markedly enhanced by primary culture of the cells for 24 h, whereas the inhibitory adenosine 3',5'-cyclic monophosphate response was unchanged by increasing culture time. Activation of the PLC-Ca2+ system during primary culture was specific to the lysosphingolipid; PLC and Ca2+ responses to LPA and NaF were unchanged or slightly attenuated by increasing culture time. Pertussis toxin treatment almost completely suppressed the S-1-P-induced inhibition of adenylyl cyclase but hardly influenced the lipid-induced activation of PLC and its cascade reactions. We conclude that S-1-P, through an LPA receptor-independent mechanism, stimulates two signaling pathways, i.e., activation of the PLC-Ca2+ system and inhibition of adenylyl cyclase, through distinct S-1-P receptor-transducer systems, resulting in the modulation of glycogenolysis in rat hepatocytes.

Porous aluminum is lightweight and has good shock absorption properties. Therefore, by joining thermoplastic resin, which has been widely used in recent years, to porous aluminum, it is possible to achieve both strength and weight reduction while providing shock absorption properties. In this study, bonding of porous aluminum and a polycarbonate plate was performed. The polycarbonate plate was pressed against the heated porous aluminum to bond them. From the tensile test of the bonded specimen, it was found that bonded specimen, which was bonded at 400℃ can achieve higher strength than that at 300℃ owing to the anchor effect. The bonded specimen, which was bonded at 400℃, exhibited fracture at the porous aluminum part, while the bonded specimen, which was bonded at 300℃, exhibited fracture at the bonded surface.

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