Transient oxidative shock induced by pretreatment of leaves with H2O2 effectively increased chilling tolerance in mung bean and Phalaenopsis. Seedlings of the chilling-tolerant (V3327) cultivar of mung bean (Vigna radiata L.) were employed to study the mechanism of H2O2-induced chilling tolerance. Pretreatment with 200 mM H2O2 increased survival rates of seedlings chilled at 4 degreesC for 36 h from 30% to 70%. The same treatment also lowered the electrolyte leakage from 86% to 21%. Time-course analysis immediately after the treatment demonstrated that exogenous application of H2O2 did not alter the endogenous H2O2 level of the plants. This observation suggests that the primary receptor for the exogenous H2O2 is localized on the leaf surface or in some other way isolated from the endogenous H2O2 pool. Oxidative shock inhibited the induction of the antioxidant enzymes, ascorbate peroxidase and catalase; however, it substantially increased glutathione content both under chilling and control conditions. Combined pretreatment of mung bean plants with abscisic acid and H2O2 showed no synergistic effect on glutathione content and decreased survival rate relative to treatment with either compound alone. These results suggest that the H2O2-induced chilling tolerance in these plants might be mediated by an elevation of glutathione content and is independent of the ABA mechanism of chilling protection

In non‐photosynthetic cells, evidence for UV (ultraviolet radiation) damage to membranes comes from electron microscopy, chemical analysis and observations of transport processes. Specific perturbations in transport across membranes occur quickly after a relatively low fluence of UV. As an example, irradiation of suspension‐cultured rose cells with 500‐2000 J m−2 (at 254 nm) causes an appearance of K+ in the extracellular medium at the rate of 5 × 10−10μmol cell−1 min−1 for 30 to 60 min and more slowly thereafter. The early, rapid phase of appearance of K+ reflects both an increase in efflux and a decrease in influx. The appearance of K+ is matched by an appearance of HCO−3 in the medium. The HCO−3 comes from respiratory CO2, which hydrates and dissociates in the cytoplasm, leading to a decrease in cytoplasmic pH. Overall, these results not only demonstrate UV damage to membrane function, but also suggest several ways by which UV may alter the general metabolic state of the cell. A demonstration of direct effects of UV on membrane components requires a purified system. At lower fluence, < 1800 J m−2 (254 nm), the ATPase of membrane vesicle preparations is inactivated in a two‐phase process that suggests the presence of enzymes with different UV sensitivities. The existence of two non‐mitochondrial enzymes in rose cell vesicles has been confirmed by solubilizing the vesicle proteins with 1% cholic acid and separating the components on G‐150 Sephadex. One component of relatively high molecular weight is especially sensitive. The fact that it is still sensitive when it is dissolved in cholic acid strongly suggests that its sensitivity is intrinsic and does not depend on sensitization by other membrane components. The action spectrum for the inactivation of the ATPase has a major peak at 290 nm and extends into the UV‐C and UV‐A regions. The physiological effects of UV‐stimulated membrane changes are uncertain. There is little evidence that the UV damage to membranes is responsible for cell death. A UV‐induced loss of K+ from guard cells may result in lower stomatal conductance. UV‐stimulated membrane changes may play a role in the UV‐induced synthesis of anthocyanins.

Preparations of plasma membranes isolated from cultured rose (Rosa damascena Mill. cv Cloire de Cuilan) cells synthesized O,-when incubated with either NADH or NADPH, as measured by an 0,--specific assay based on the chemiluminescence of lucigenin. The activities were strongly dependent on the presence of Triton X-1 00. The K,,, for NADH was 159 pM; that for NADPH was 19 p~. Neither NADH-nor NADPH-dependent activity was inhibited by azide, an inhibitor of peroxidase, nor by antimycin A, an inhibitor of mitochondrial electron transport; both activities were inhibited by 30 to 100 nM diphenylene iodonium, an inhibitor of the mammalian NADPH oxidase. l h e NADH-and NADPH-dependent activities could be distinguished by detergent solubilization and ultracentrifugation: the NADH-dependent activity sedimented more easily, whereas the NADPH-dependent activity remained in suspension.One or both of these enzymes may provide the O,-seen when plant cells are exposed to pathogens or pathogen-associated elicitors; however, plasma membranes from rose cells treated with a Pbytophthora elicitor had the same activity as control cells.The term "active oxygen" refers to chemically reactive species of oxygen, including singlet oxygen, hydroxyl radical, O,-, and H,O,. The generation of these species occurs as a byproduct of severa1 natural processes, such as photosynthesis and respiration. Since the products can destroy sensitive functional molecules, plants and other organisms have evolved detoxifying mechanisms (Foyer et al., 1994).Active oxygen species also play a positive role in normal plant development and in a plant's response to stress. In normal development, H,O, serves as a substrate for the polymerization of lignin, suberin, and possibly other cellwall components (Hahlbrock and Griesbach, 1979;Olson and Varner, 1993). O,-and H,O,, produced in response to bacterial or funga1 attack, are thought to kill the attacking cells and also adjacent host cells, thus limiting the spread of the pathogen. Active oxygen species have been suggested to play a signaling role in inducing other defenses to pathogens (Levine et al., 1994;Price et al., 1994).In past publications, our laboratory has reported that suspension-cultured cells of rose (Rosa damascena) produce a burst of H,O, after they have been treated with UV-C radiation (Murphy and Huerta, 1990). They also produce the same response when they are challenged with a chem- ical elicitor, a cell-wall component isolated from a culture of a Pkytopktkora species originally identified as a parasite on rose (Arnott and Murphy, 1991).The mechanism of synthesis of active oxygen species, and particularly of metabolically required H,O,, is a topic of active discussion. In rose cells, the elicitor-induced H,O, is synthesized exclusively from O,-, as judged by the ability of N,N-diethyldithiocarbamate, an inhibitor of superoxide dismutase, to block the appearance of H,O, in elicitor-stimulated cells (Auh and Murphy, 1995). It has been proposed that apoplastic H,O, synthesized by horseradish roots ...

Fentanyl (1 microgram/kg body weight) was administered intravenously and via a lumbar epidural catheter (in random order) on 2 separate occasions to 6 patients with chronic pain associated with non-terminal disease states. Frequent blood samples were collected from an indwelling intravenous catheter and CSF samples were collected via spinal needles inserted in the cervical (C7-T1 interspace) and lumbar (L3.4 interspace) regions at 0, 5, 10, 20, 30 and 45 min after fentanyl administration. The concentration of fentanyl in blood and CSF samples were quantified by a sensitive and selective gas-liquid chromatography assay. Visual analogue pain scores (VAPS) were recorded every 5 min for the first hour. Coded syringes (one containing the appropriate fentanyl dose while the other contained an equivalent volume of saline) allowed the investigator administering the fentanyl and assessing VAPS to remain blinded as to which route of administration actually contained the fentanyl. There was minimal vascular uptake of fentanyl following epidural administration. Similarly, the permeation of fentanyl into cervical and lumbar CSF following intravenous administration was minimal and erratic such that only 4 of the 60 CSF samples had detectable fentanyl concentrations. In contrast, there was a rapid penetration of fentanyl across the dura mater following lumbar epidural administration. There was significantly fentanyl in lumbar CSF samples by 10 min in 5 patients, and by 20 min in all 6 patients. The mean maximum lumbar CSF concentration was 19.1 ng/ml, while the time associated with these maximum concentrations was 22.5 min. The mean maximum cervical CSF fentanyl concentrations were 10% of the lumbar CSF concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential nerve block from peridural anesthesia was used to determine a) if the pressor response to muscle ischemia in man is caused by stimulation of small sensory nerve fibers and b) if these fibers contribute to cardiovascular-respiratory responses during dynamic exercise. Four men exercised at 50-100 W for 5 min. Muscle ischemia and a sustained pressor response were produced by total circulatory occlusion of both legs beginning 30 s before the end of exercise and continuing for 3 min postexercise. During regression of full motor and sensory block, motor strength recovered while sensory block continued; the pressor response was blocked as long as sensory anesthesia persisted (two subjects). During blockade of the pressor response, cardiovascular-respiratory responses to exercise gradually returned from augmented to normal (preblock) levels. Sensory blockade was incomplete in two subjects and the pressor response was not fully blocked. We conclude that stimulation of small sensory fibers during ischemia elicits the pressor response, but that these fibers appear not to contribute to cardiovascular-respiratory responses during mild dynamic exercise with adequate blood flow.