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W L Bennett

Publications and source records attributed to W L Bennett.

6 recordsLinked to original sources
PubMed1998

Isolation and characterization of the Saccharomyces cerevisiae LPP1 gene encoding a Mg2+-independent phosphatidate phosphatase.

The DPP1-encoded diacylglycerol pyrophosphate (DGPP) phosphatase enzyme accounts for half of the Mg2+-independent phosphatidate (PA) phosphatase activity in Saccharomyces cerevisiae. The LPP1 (lipid phosphate phosphatase) gene encodes a protein that contains a novel phosphatase sequence motif found in DGPP phosphatase and in the mouse Mg2+-independent PA phosphatase. A genomic copy of the S. cerevisiae LPP1 gene was isolated and was used to construct lpp1Delta and lpp1Delta dpp1Delta mutants. A multicopy plasmid containing the LPP1 gene directed a 12.9-fold overexpression of Mg2+-independent PA phosphatase activity in the S. cerevisiae lpp1Delta dpp1Delta double mutant. The heterologous expression of the S. cerevisiae LPP1 gene in Sf-9 insect cells resulted in a 715-fold overexpression of Mg2+-independent PA phosphatase activity relative to control insect cells. The Mg2+-independent PA phosphatase activity encoded by the LPP1 gene was associated with the membrane fraction of the cell. The LPP1 gene product also exhibited lyso-PA phosphatase and DGPP phosphatase activities. The order of substrate preference was PA > lyso-PA > DGPP. Like the dpp1Delta mutant, the lpp1Delta mutant and the lpp1Delta dpp1Delta double mutant were viable and did not exhibit obvious growth defects. Biochemical analyses of lpp1Delta, dpp1Delta, and lpp1Delta dpp1Delta mutants showed that the LPP1 and DPP1 gene products encoded nearly all of the Mg2+-independent PA phosphatase and lyso-PA phosphatase activities and all of the DGPP phosphatase activity in S. cerevisiae. Moreover, the analyses of the mutants showed that the LPP1 and DPP1 gene products played a role in the regulation of phospholipid metabolism and the cellular levels of phosphatidylinositol and PA.

Animals↗
PubMed1998

Isolation and characterization of the Saccharomyces cerevisiae DPP1 gene encoding diacylglycerol pyrophosphate phosphatase.

Diacylglycerol pyrophosphate (DGPP) is involved in a putative novel lipid signaling pathway. DGPP phosphatase (DGPP phosphohydrolase) is a membrane-associated 34-kDa enzyme from Saccharomyces cerevisiae which catalyzes the dephosphorylation of DGPP to yield phosphatidate (PA) and then catalyzes the dephosphorylation of PA to yield diacylglycerol. Amino acid sequence information derived from DGPP phosphatase was used to identify and isolate the DPP1 (diacylglycerol pyrophosphate phosphatase) gene encoding the enzyme. Multicopy plasmids containing the DPP1 gene directed a 10-fold overexpression of DGPP phosphatase activity in S. cerevisiae. The heterologous expression of the S. cerevisiae DPP1 gene in Sf-9 insect cells resulted in a 500-fold overexpression of DGPP phosphatase activity over that expressed in wild-type S. cerevisiae. DGPP phosphatase possesses a Mg2+-independent PA phosphatase activity, and its expression correlated with the overexpression of DGPP phosphatase activity in S. cerevisiae and in insect cells. DGPP phosphatase was predicted to be an integral membrane protein with six transmembrane-spanning domains. The enzyme contains a novel phosphatase sequence motif found in a superfamily of phosphatases. A dpp1Delta mutant was constructed by deletion of the chromosomal copy of the DPP1 gene. The dpp1Delta mutant was viable and did not exhibit any obvious growth defects. The mutant was devoid of DGPP phosphatase activity and accumulated (4-fold) DGPP. Analysis of the mutant showed that the DPP1 gene was not responsible for all of the Mg2+-independent PA phosphatase activity in S. cerevisiae.

Amino Acid Sequence↗
PubMed1988

Stage I intraoperative adjustment of eye muscle surgery under general anesthesia: consideration of graduated adjustment.

The eyes diverge under general anesthesia. The amount of divergence is predictable; there is a linear relationship between the preoperative and the anesthetized eye position. We have confirmed Apt and Isenberg's regression formula for this relationship (A = 0.8 P + 30). We have previously also reported that adjusting the amount of surgery to be done (stage I adjustment) in cases deviating from this correlation by one standard deviation or more (anomalous) significantly improved our surgical success rate to 85%. Since a fixed arbitrary adjustment of 1 mm more or less surgery had improved our surgical success rate significantly, but still left room for higher success rates, we reviewed our anomalous cases to determine whether a graduated adjustment might be expected to produce even higher success rates. A review of cases including additional ones since our last report failed to support this hypothesis. Satisfactory results in these most recent cases have, however, almost doubled the surgical success rate (in anomalous cases) for our stage I fixed arbitrary 1 mm intraoperative adjustment, from 47% to 90%.

Adolescent↗
PubMed1988

Influence of light optomotor reflex on intraoperative adjustment of eye muscle surgery.

The eyes diverge under general anesthesia. The amount of divergence is predictable: there is a linear relationship between the preoperative and the anesthetized eye position. We recently reported that adjusting the amount of surgery to be done in cases deviating from this correlation significantly improved surgical results. The light optomotor reflex had not, however, been considered in making these measurements. We modified our procedure to eliminate this reflex in our next 100 patients. The measurements were not significantly different from prior studies. We confirmed the prior regression formula of Apt and Isenberg (A = 0.8P + 30) and our previously reported improvement in surgical success rate (from 47% to 88%) following intraoperative adjustment of the amount of surgery to be performed.

Adult↗