In cultured cells of California poppy formation of benzophenanthridine alkaloids can be triggered by a yeast elicitor preparation independently of the hypersensitive reaction. A plasma membrane (PM) bound phospholipase A (PLA) is likely to play a role in the signalling process: PLA activity was detectable in individual cells, cell suspensions and PM vesicles with the fluorogenic phospholipid bis-BODIPY FL C11-PC and was sensitive to known inhibitors of PLA2. In microscopic assays, enzyme activity increased after elicitor contact of cells that were pretreated with non-saturating concentrations of PLA2 inhibitors. In PM vesicles a PLA2-like protein as well as G alpha- and G beta-proteins were detected immunologically. Anti-G alpha or anti-G beta antisera or mastoparan stimulated PLA activity thus indicating a G-protein-controlled enzyme. Elicitation of alkaloid production was sensitive to aristolochic acid and enhanced by PLA2 products such as lysophosphatidylcholine and linolenic acid. Pretreatment of the cells with the artificial electron acceptors hexabromoiridate(V) or ferricyanide(III) reversibly abolished the effect of subsequent elicitation and reduced the activity of PLA both in intact cells and in PM vesicles. It appears, therefore, that PLA2 is a point of interference of redox control with the signal path.
obJective A pilot study of prophylactic nimodipine and hydroxyethyl starch treatment showed a beneficial effect on facial and cochlear nerve preservation following vestibular schwannoma (VS) surgery. A prospective Phase III trial was undertaken to confirm these results. methods An open-label, 2-arm, randomized parallel group and multicenter Phase III trial with blinded expert review was performed and included 112 patients who underwent VS surgery between January 2010 and February 2013 at 7 departments of neurosurgery to investigate the efficacy and safety of the prophylaxis. The surgery was performed after the patients were randomly assigned to one of 2 groups using online randomization. The treatment group (n = 56) received parenteral nimodipine (1-2 mg/hr) and hydroxyethyl starch (hematocrit 30%-35%) from the day before surgery until the 7th postoperative day. The control group (n = 56) was not treated prophylactically. results Intent-to-treat analysis showed no statistically significant effects of the treatment on either preservation of facial nerve function (35 [ ]) (p = 0.530) 12 months after surgery. Since tumor sizes were significantly larger in the treatment group than in the control group, logistic regression analysis was required. The risk for deterioration of facial nerve function was adjusted nearly the same in both groups ], p = 0.91). In contrast, the risk for postoperative hearing loss was adjusted 2 times lower in the treatment group compared with the control group (OR 0.49 [95% CI 0.18-1.30], p = 0.15). Apart from dosedependent hypotension (p < 0.001), no clinically relevant adverse reactions were observed. coNclusioNs There were no statistically significant effects of the treatment. Despite the width of the confidence intervals, the odds ratios may suggest but do not prove a clinically relevant effect of the safe study medication on the preservation of cochlear nerve function after VS surgery. Further study is needed before prophylactic nimodipine can be recommended in VS surgery.Clinical trial registration no.: 2009-012088-32 (www.clinicaltrialsregister.eu)
SummaryPlant heterotrimeric G-proteins are involved in a variety of signaling pathways, though only one a and a few bc isoforms of their subunits exist. In isolated plasma membranes of California poppy (Eschscholzia californica), the plant-specific Ga subunit was isolated and identified immunologically and by homology of the cloned gene with that of several plants. In the same membrane, phospholipase A 2 (PLA 2 ) was activated by yeast elicitor only if GTPcS (an activator of Ga) was present. From the cholate-solubilized membrane proteins, PLA 2 was co-precipitated together with Ga by a polyclonal antiserum raised against the recombinant Ga. In this immunoprecipitate and in the plasma membrane (but not in the Ga-free supernatant) PLA 2 was stimulated by GTPcS. Plasma membranes and immunoprecipitates obtained from antisense transformants with a low Ga content allowed no such stimulation. An antiserum raised against the C-terminus (which in animal Gas is located near the target coupling site) precipitated Ga without any PLA 2 activity. Using non-denaturing PAGE, complexes of solubilized plasma membrane proteins were visualized that contained Ga plus PLA 2 activity and dissociated at pH 9.5. At this pH, PLA 2 was no longer stimulated by GTPcS. It is concluded that a distinct fraction of the plasma membrane-bound PLA 2 exists in a detergent-resistant complex with Ga that can be dissociated at pH 9.5. This complex allows the Ga-mediated activation of PLA 2 .
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