Mitogen-activated protein kinase (MAPK) is a conserved eukaryotic signaling factor that mediates various signals, cumulating in the activation of transcription factors. Extracellular signal-regulated kinase (ERK), a MAPK, is activated through phosphorylation by the kinase MAPK/ERK kinase (MEK). To elucidate the extent of the involvement of ERK in various aspects of animal development, we searched for a Drosophila mutant which responds to elevated MEK activity and herein identified a lace mutant. Mutants with mild lace alleles grow to become adults with multiple aberrant morphologies in the appendages, compound eye, and bristles. These aberrations were suppressed by elevated MEK activity. Structural and transgenic analyses of the lace cDNA have revealed that the lace gene product is a membrane protein similar to the yeast protein LCB2, a subunit of serine palmitoyltransferase (SPT), which catalyzes the first step of sphingolipid biosynthesis. In fact, SPT activity in the fly expressing epitope-tagged Lace was absorbed by epitope-specific antibody. The number of dead cells in various imaginal discs of a lace hypomorph was considerably increased, thereby ectopically activating c-Jun N-terminal kinase (JNK), another MAPK. These results account for the adult phenotypes of the lace mutant and suppression of the phenotypes by elevated MEK activity: we hypothesize that mutation of lace causes decreased de novo synthesis of sphingolipid metabolites, some of which are signaling molecules, and one or more of these changes activates JNK to elicit apoptosis. The ERK pathway may be antagonistic to the JNK pathway in the control of cell survival.

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Many industrial products or building equipments are standardized but not always designed taking user ' s sense to ease − ofLuse 血 to account ． The final objective of this research is to establish design system for user friendly engineering produCts ． In the paper， possibility of utilization of electro myoelectric potential in enginee 血 g design is investigated ． Electromyogram( EMG ) occurred in stand ・ up motion f 甘 om sitting position on chair under different hand 岨 iI conditions is measured ． Two per 丘 )rmance index， median frequency and total sum of spectrum of EMG are examined ． They show tendency for load level or degree of fatigue ． Some results show effectiveness of usage ofEMG information in enginee 血 g design or evaluation ． Key Words ： Myoelectric potential ， Electromyogram ， Median frequency ， Total spectrum sum ， Engineei皿 g design