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PubMed2006

[Electroantennogram and behavioral responses of Monochamus alternatus to the volatiles from Pinus thunbergii with different physiological status].

The volatiles from healthy and pinewood nematode-infested branches of Pinus thunbergii were collected by distillation, and analyzed by using HPLC and GC-MS. Electroantennogram (EAG) and behavioral responses of Monochamus alternatus with different physiological status to the volatiles were investigated respectively. The results showed that unmated beetle had a greater EAG response potential to the volatiles from healthy branch than to those from infested branch, while it was reverse for mated beetle. The EAG response of unmated beetle under 15 days-old to the volatiles from healthy branch increased with its age. "Y" tube olfactory test showed unmated beetle had positive response to the volatiles from healthy branch and negative response to those from infested branch, while mated beetle showed positive response to the volatiles from infested branch and negative response to those from healthy branch. Female beetle with its age from 1 day to 15 days-old and male beetle from 1 day to 9 days-old had an increasing positive response to the volatiles from healthy branch, but the male after 9 days-old showed a negative response. It could be concluded that M. alternatus with different physiological status all had special sensitivity and selectivity to host tree.

Animals↗
PubMed1999

Plant production of volatile semiochemicals in response to insect-derived elicitors.

An increase in the release of volatile compounds by plants in response to insect feeding is triggered by interaction of elicitors in the oral secretions of insect herbivores with damaged plant tissues. This herbivore damage triggers de novo biosynthesis of volatile plant metabolites derived from several different biochemical pathways. Natural enemies of herbivores use these volatile semiochemicals to locate their hosts. Although some volatile compounds are released from storage in plants immediately whenever damage to cells or glands occurs, the induced compounds are only synthesized and released during the light period. This often results in a delay between feeding damage and release of volatiles. Plants release the induced compounds from undamaged as well as damaged leaves. Thus, damage to only a few leaves results in a systemic response and release of volatiles by the entire plant. We propose that plants respond differently to individual herbivore species at least in part due to the composition of insect elicitors that come in contact with the plant. Specialist parasitoids can differentiate the volatile blends released due to damage by hosts from those resulting from non-host damage as well as from mechanical damage, thereby facilitating host location for the parasitoid. Elicitors in the oral secretions of beet armyworm caterpillars have been identified and synthesized.

Animals↗
PubMed1996

[Measurement of expired alcohol concentrations with a new electrochemical sensor. A model investigation to determine interference with volatile anesthetics and clinical application].

UNLABELLED: Absorption of irrigating fluid in transurethral prostatic resection (TURP) and percutaneous nephrolitholapaxy (PNL) into veins or delayed absorption due to fluid extravasation may result in a TURP syndrome. The measurement of end-tidal breath alcohol concentration (et AC) as a monitor of absorption of irrigating fluid labelled with 2% ethanol is limited by the disturbance of infrared sensors by volatile anaesthetics and nitrous oxide (N2O) (Fig. 2). An electrochemical sensor is acceptable for this method. The aim of the present study was the evaluation of breath alcohol measurements using an electrochemical sensor device (Alcomed 3010, Envitec). The stability of the sensor in the presence of volatile anaesthetics was examined using a lung model. In a clinical investigation, the device was then applied to spontaneously breathing or mechanically ventilated patients inhaling volatile anaesthetics during endoscopic urological surgery. METHOD: A two-chamber lung model filled with water for performing noninvasive measurements at the mouth of a patient has already been introduced by Brunner et al. (Fig. 1). With the addition of different amounts of ethanol to the temperature-controlled water, a constant ethanol concentration is achievable in the air above the water that is dependent on adjustments of the ventilator. Increasing concentrations of volatile anaesthetics (isoflurane, enflurane, halothane, and sevoflurane) were added to the fresh gas flow (2 l O2/3 l N2O) and etACs were measured using the manually triggered self-absorbent electrochemical sensor. First, regression equations were established between breath alcohol concentrations and increased volatile anaesthetic concentrations. Regression equations were then established between end-tidal anaesthetic gas concentrations and vaporizer adjustments in order to rule out an influence of ethanol on the anaesthetic gas monitor Ultima V (Datex). In the clinical investigation, 53 intubated and ventilated patients (33 undergoing PNL, 20 undergoing TURP) and 48 patients breathing spontaneously (32 with inhalation anaesthesia, 16 with spinal anaesthesia) were investigated. The etAC was measured with the Alcomed 3010 and compared with gas-chromatographically registered blood alcohol concentrations (BAC). The study had previously been approved by the Ethical Committee of the Medical University of Luebeck. Patients with liver disease and a history of toxic abuse were excluded. Only one value per patient (maximum BAC) was included in the statistics in order to avoid a cluster effect. RESULTS: The lung model experiments demonstrated that the measurement of etAC with an electrochemical sensor is free of interference by volatile anaesthetics (Table 1). The slope of the regression between the measured alcohol concentration and increased concentrations of anaesthetics did not differ significantly from baseline values. The measurement of end-tidal anaesthetic concentrations was not significantly different from vaporizer adjustments in the presence of increased alcohol concentrations (Table 2). During the clinical investigation, a regression between etAC and BAC was determined for both groups. For the group of patients breathing spontaneously, the correlation coefficient was 0.961 and the regression equation revealed etAC = 0.5677*BAC-0.1303 (Fig. 5). However, in the group of ventilated patients a biphasic course was shown that was dependent on BAC (Fig. 6). At BAC < 0.4%, a similar correlation (r = 0.856) to the spontaneously breathing group could be seen (regression equation: etAC = 0.617*BAC-0.020). Above 0.4% BAC there was no acceptable correlation (r = 0.444, regression equation: etAC = 0.202*BAC+0.104). CONCLUSIONS: The tested electrochemical sensor does not interfere with volatile anaesthetics and N2O as demonstrated by a lung model. There is a good correlation between etAC and BAC measurements in patients breathing spontaneously with special regard to the slope of the regression (s = 0.57).

Anesthetics↗
PubMed2005

Volatile anesthetics constrict pulmonary artery in rabbit lung perfusion model.

Volatile anesthetics are generally considered to possess a vasodilator action. Some of their actions on pulmonary vessels, however, are not clearly understood. We examined the effects of various volatile anesthetics on pulmonary vessels using an in situ rabbit isolated-lung perfusion model. We prepared a rabbit constant-flow lung-perfusion model by sending blood to the pulmonary artery and removing blood from the left atrium, and observed the changes in pulmonary arterial perfusion pressure caused by inhalation of 0.5, 1, 2, and 3 minimum alveolar concentration (MAC) volatile anesthetics: halothane, enflurane, isoflurane, and sevoflurane, in random order. These volatile anesthetics increased pulmonary arterial perfusion pressure in a dose-dependent manner and caused the pulmonary arteries to constrict. In particular, halothane at all concentrations induced significantly greater pulmonary vasoconstriction than the other volatile anesthetics. Therefore, it is suggested that volatile inhalation anesthetics induce the pulmonary arteries to constrict, and halothane exhibits the most potent pulmonary vasoconstrictor effect among the volatile anesthetics tested.

Anesthetics, Inhalation↗
PubMed2005

Methyl salicylate, a soybean aphid-induced plant volatile attractive to the predator Coccinella septempunctata.

Induced volatiles provide a signal to foraging predatory insects about the location of their prey. In Iowa, early in the growing season of soybean, Glycine max, many predacious seven-spotted lady beetles, Coccinella septempunctata, were observed on plants with heavy infestations of soybean aphid, Aphis glycines. We studied whether the attraction of this beetle is caused by the release of specific volatile compounds of soybean plants infested by aphids. Volatile compounds emitted by soybean plants infested by aphids were compared with those of undamaged, uninfested, and artificially damaged plants. Gas chromatography-mass spectrometry analyses revealed consistent differences in the profiles of volatile compounds between aphid-infested soybean plants and undamaged ones. Significantly more methyl salicylate was released from infested plants at both the V1 and V2 plant growth stages. However, release patterns of two other induced plant volatiles, (D)-limonene and (E,E)-alpha-farnesene, differed between the two plant growth stages. Gas chromatographic-electroantennographic detection of volatile extracts from infested soybean plants showed that methyl salicylate elicited significant electrophysiological responses in C. septempunctata. In field tests, traps baited with methyl salicylate were highly attractive to adult C. septempunctata, whereas 2-phenylethanol was most attractive to the lacewing Chrysoperla carnea and syrphid flies. Another common lady beetle, the multicolored Asian lady beetle, Harmonia axyridis, showed no preference for the compounds. These results indicate that C. septempunctata may use methyl salicylate as the olfactory cue for prey location. We also tested the attractiveness of some selected soybean volatiles to alate soybean aphids in the field, and results showed that traps baited with benzaldehyde caught significantly higher numbers of aphids.

Animals↗
PubMed2005

Exogenous application of jasmonic acid induces volatile emissions in rice and enhances parasitism of Nilaparvata lugens eggs by the parasitoid Anagrus nilaparvatae.

Jasmonate signaling pathway plays an important role in induced plant defense against herbivores and pathogens, including the emission of volatiles that serve as attractants for natural enemies of herbivores. We studied the volatiles emitted from rice plants that were wounded and treated with jasmonic acid (JA) and their effects on the host-searching behavior of the rice brown planthopper, Nilaparvata lugens (Stål), and its mymarid egg parasitoid Anagrus nilaparvatae Pang et Wang. Female adults of N. lugens significantly preferred to settle on JA-treated rice plants immediately after release. The parasitoid A. nilaparvatae showed a similar preference and was more attracted to the volatiles emitted from JA-treated rice plants than to volatiles from control plants. This was also evident from greenhouse and field experiments in which parasitism of N. lugens eggs by A. nilaparvatae on plants that were surrounded by JA-treated plants was more than twofold higher than on control plants. Analyses of volatiles collected from rice plants showed that JA treatment dramatically increased the release of volatiles, which included aliphatic aldehydes and alcohols, monoterpenes, sesquiterpenes, methyl salicylate, n-heptadecane, and several as yet unidentified compounds. These results confirm an involvement of the JA pathway in induced defense in rice plants and demonstrate that the egg parasitoid A. nilaparvatae exploits plant-provided cues to locate hosts. We explain the use of induced plant volatiles by the egg parasitoid by a reliable association between planthopper feeding damage and egg presence.

Animals↗
PubMed2005

Herbivore-induced plant volatiles mediate in-flight host discrimination by parasitoids.

Herbivore feeding induces plants to emit volatiles that are detectable and reliable cues for foraging parasitoids, which allows them to perform oriented host searching. We investigated whether these plant volatiles play a role in avoiding parasitoid competition by discriminating parasitized from unparasitized hosts in flight. In a wind tunnel set-up, we used mechanically damaged plants treated with regurgitant containing elicitors to simulate and standardize herbivore feeding. The solitary parasitoid Cotesia rubecula discriminated among volatile blends from Brussels sprouts plants treated with regurgitant of unparasitized Pieris rapae or P. brassicae caterpillars over blends emitted by plants treated with regurgitant of parasitized caterpillars. The gregarious Cotesia glomerata discriminated between volatiles induced by regurgitant from parasitized and unparasitized caterpillars of its major host species, P. brassicae. Gas chromatography-mass spectrometry analysis of headspace odors revealed that cabbage plants treated with regurgitant of parasitized P. brassicae caterpillars emitted lower amounts of volatiles than plants treated with unparasitized caterpillars. We demonstrate (1) that parasitoids can detect, in flight, whether their hosts contain competitors, and (2) that plants reduce the production of specific herbivore-induced volatiles after a successful recruitment of their bodyguards. As the induced volatiles bear biosynthetic and ecological costs to plants, downregulation of their production has adaptive value. These findings add a new level of intricacy to plant-parasitoid interactions.

Animals↗
PubMed1984

Aliphatic halogenated hydrocarbons produce volatile Salmonella mutagens.

Production of volatile mutagenic metabolites from 5 halogenated promutagens was examined by a simple modification of the conventional Salmonella/microsome mutagenicity assay. This method incorporates the taping together of 2 agar plates face to face during the initial portion of their incubation at 37 degrees C. By varying the contents of the soft agar in each of the two plates with respect to promutagen, S9 and tester strain cells, mutagenesis due to volatile promutagens and their metabolites could be quantitated separately. Using the taped plate assay, volatile mutagenic metabolites were detected from the promutagens 3-(2-chloroethoxy)-1,2-dichloropropene, the herbicides diallate, triallate and sulfallate, and the flame-retardant tris-(2,3-dibromopropyl) phosphate (Tris-BP). All compounds except Tris-BP were also found to be volatile promutagens. The mutagenic metabolites accounted for 50-80% of the activity of these compounds observed in the standard assay. Morever, our studies suggest that a small, but appreciable percentage of the mutagenic metabolites from all 5 compounds escaped detection in the conventional, untaped assay. Mutagenic activity of the volatile mutagenic metabolites from diallate was quenched by various Salmonella tester strains independent of their responsiveness to diallate mutagenesis. Detection of volatile mutagen formation from diallate was also prevented by cysteine and glutathione, but not by DNA or metyrapone. This taped plate method for the Salmonella assay should facilitate future investigations of the detection, isolation and identification of volatile mutagenic metabolites from other promutagenic compounds or mixtures.

Allyl Compounds↗
PubMed2000

Analysis of volatile organic compounds, using the purge and trap injector coupled to a gas chromatograph/ion-trap mass spectrometer: review of the results in Dutch surface water of the Rhine, Meuse, Northern Delta Area and Westerscheldt, over the period 1992-1997.

Volatile organic compounds are widely introduced into the Dutch aquatic environment. Liquid-liquid extraction and isolation by means of resins give poor recoveries for volatiles. In this study, a method has been developed to analyse these compounds with a purge and trap injection (PTI) coupled to a chromatograph/ion trap mass spectrometer. Volatile compounds are "purged" from the sample by carrier gas flow and transported through a condenser to a cooled trap. The bulk of liquid matrix is condensed in the condenser, while volatile compounds are left unaffected. The compounds of interest are trapped at a low temperature, by liquid nitrogen in the cooled trap of fused silica. Injection takes place by flash heating of the trap. The detection limits of the volatile compounds are in the range of 0.001-0.04 microgram l-1, in full spectrum mode. In this paper a review of the results in Dutch surface water of the Rhine, Meuse, Northern Delta Area and Westerscheldt, over the period 1992-1997, is presented. For calamities causing high levels of volatiles, the method is very useful. The compounds can be monitored over a certain period. In the Meuse, high levels of volatile organic compounds are observed. Diisopropyl ether at a maximum of 592 micrograms l-1.

Chlorobenzenes↗
PubMed2002

Vapour undersaturation in primitive mid-ocean-ridge basalt and the volatile content of Earth's upper mantle.

The analysis of volatiles in magmatic systems can be used to constrain the volatile content of the Earth's mantle and the influence that magmatic degassing has on the chemistry of the oceans and the atmosphere. But most volatile elements have very low solubilities in magmas at atmospheric pressure, and therefore virtually all erupted lavas are degassed and do not retain their primary volatile signatures. Here we report the undersaturated pre-eruptive volatile content for a suite of mid-ocean-ridge basalts from the Siqueiros intra-transform spreading centre. The undersaturation leads to correlations between volatiles and refractory trace elements that provide new constraints on volatile abundances and their behaviour in the upper mantle. Our data generate improved limits on the abundances of carbon dioxide, water, fluorine, sulphur and chlorine in the source of normal mid-ocean-ridge basalt. The incompatible behaviour of carbon dioxide, together with the CO(2)/Nb and CO(2)/Cl ratios, permit estimates of primitive carbon dioxide and chlorine to be made for degassed and chlorine-contaminated mid-ocean-ridge basalt magmas, and hence constrain degassing and contamination histories of mid-ocean ridges.

Journal Article↗
PubMed1997

Volatile anaesthetic effects on calcium conductance of planar lipid bilayers formed with synthetic lipids or extracted lipids from sarcoplasmic reticulum.

Volatile anaesthetics are known to increase leakage of calcium from the light fraction of skeletal sarcoplasmic reticulum (L-SR) which has no calcium release channels. To explore the role of the lipid environment, we have examined the effect of volatile anaesthetics on calcium conductance (gCa) of lipid membranes. Planar lipid bilayers were formed with a mixture of synthetic phospholipids and cholesterol, resembling the composition of SR membranes, or with lipids extracted from skeletal L-SR, gCa was estimated by calculating the calcium transference number (tCa) using diffusion potential measurements. Membranes formed with L-SR-extracted lipids had a higher gCa than membranes formed with synthetic lipids. Volatile anaesthetics increased total conductance and gCa in a dose-dependent manner, but did not affect tCa or membrane specific capacitance. In membranes formed with L-SR-extracted lipids, isoflurane induced the largest increase in gCa (1260 (SEM 304) % increase, n = 4, 0.94 mmol litre-1), followed by enflurane (264 (75)%, n = 5, 1.88 mmol litre-1) and halothane (53 (33)%, n = 5; 1.54 mmol litre-1). In membranes formed with synthetic lipids, volatile anaesthetic-induced increases in gCa followed the same trend but were larger. Volatile anaesthetics increased gCa without changing the ionic selectivity of membranes. However, the magnitude of the increase in gCa in the presence of volatile anaesthetics cannot account for the previously observed calcium leakage from L-SR vesicles. Therefore, the volatile anaesthetic-induced increase in calcium leakage in L-SR vesicles must be mediated via other pathways involving membrane proteins.

Anesthetics, Inhalation↗
PubMed1998

Effects of dietary vitamin E supplementation on lipid oxidation and volatiles content of irradiated, cooked turkey meat patties with different packaging.

A study was conducted to determine the effects of dietary vitamin E supplementation on the storage stability and volatiles production in irradiated cooked turkey meat. Turkeys, raised with diets containing 25, 50, 75, or 100 IU of dl-alpha-tocopheryl acetate (TA)/kg diet from 1 to 105 d of age, were fed with diets containing 25, 200, 400, or 600 IU of TA/kg diet from 105 to 122 d of age. Breast and leg meat patties were prepared, irradiated at 0 or 2.5 kGy dose, cooked to an internal temperature of 78 C, and stored in either vacuum or aerobic packaging. Thiobarbituric acid reactive substance (TBARS) values gradually decreased as the dietary TA increased and > 200 IU TA/kg diet treatments were helpful in maintaining low TBARS values in irradiated breast and leg meat patties during the 7-d storage period. With vacuum-packaging, irradiated cooked breast patties developed more oxidation than nonirradiated patties but the prooxidant effect of irradiation in cooked leg meat patties was not consistent. In aerobic-packaged cooked meat, irradiated patties had lower TBARS than nonirradiated patties in both breast and leg meat stored in oxygen permeable bags for 7 d. Propanal, pentanal, hexanal, 1-pentanol, and total volatiles were highly correlated with the TBARS values of meat. However, hexanal represented the lipid oxidation status of cooked meat better than any other volatiles component. The amount of hexanal and total volatiles in cooked breast and leg meat shows decreasing trends as dietary TA increased. In vacuum packaging, irradiated breast and leg meat had higher hexanal and total volatiles content than nonirradiated meat at both 0 and 7 d of storage. In aerobic packaging, the amount of hexanal and total volatiles greatly increased in both irradiated and nonirradiated meat patties during the 7-d storage periods. The results illustrated that the antioxidant effect of TA was not strong enough to control lipid oxidation and off-odor generation in cooked meat stored under aerobic conditions because the progress of lipid oxidation in cooked meat under aerobic condition is very rapid. However, the combination of dietary TA and vacuum packaging of cooked meat immediately after cooking could be a good strategy to minimize oxidation and volatiles production in cooked meat.

Animal Feed↗
PubMed2001

Modulation of NMDA receptor function by ketamine and magnesium. Part II: interactions with volatile anesthetics.

UNLABELLED: Mg2+ and ketamine interact superadditively at N- methyl-D-aspartate (NMDA) receptors, which may explain the clinical efficacy of the combination. Because patients are usually exposed concomitantly to volatile anesthetics, we tested the hypothesis that volatile anesthetics interact with ketamine and/or Mg2+ at recombinantly expressed NMDA receptors. NR1/NR2A or NR1/NR2B receptors were expressed in Xenopus oocytes. We determined the effects of isoflurane, sevoflurane, and desflurane on NMDA receptor signaling, alone and in combination with S(+)-ketamine (4.1 microM on NR1/NR2A, 3.0 microM on NR2/NR2B) and/or Mg2+ (416 microM on NR1/NR2A, 629 microM on NR1/NR2B). Volatile anesthetics inhibited NR1/NR2A and NR1/NR2B glutamate receptor function in a reversible, concentration-dependent, voltage-insensitive and noncompetitive manner (half-maximal inhibitory concentration at NR1/NR2A receptors: 1.30 +/- 0.02 minimum alveolar anesthetic concentration [MAC] for isoflurane, 1.18 +/- 0.03 MAC for desflurane, 1.24 +/- 0.06 MAC for sevoflurane; at NR1/NR2B receptors: 1.33 +/- 0.12 MAC for isoflurane, 1.22 +/- 0.08 MAC for desflurane, and 1.28 +/- 0.08 MAC for sevoflurane). On both NR1/NR2A and NR1/NR2B receptors, 50% inhibitory concentration for volatile anesthetics was reduced approximately 20% by Mg2+, approximately 30% by S(+)-ketamine, and approximately 50% by the compounds in combination. Volatile anesthetic effects on NMDA receptors can be potentiated significantly by Mg2+, S(+)-ketamine, or-most profoundly-both. Therefore, the analgesic effects of ketamine and Mg2+, are likely to be enhanced in the presence of volatile anesthetics. IMPLICATIONS: Clinically relevant concentrations of volatile anesthetics inhibit functioning of N-methyl-D-aspartate receptors expressed recombinantly in Xenopus oocytes. This inhibition is reversible, concentration-dependent and voltage-insensitive, and results from noncompetitive antagonism of glutamate/glycine signaling. In addition, these effects can be potentiated significantly by co-application of either Mg2+, S(+)-ketamine, or--most profoundly--both.

Analgesics↗
PubMed2001

Absence of direct antioxidant effects from volatile anesthetics in primary mixed neuronal-glial cultures.

BACKGROUND: Volatile anesthetics decrease ischemic brain injury. Mechanisms for this protection remain under investigation. The authors hypothesized that volatile anesthetics serve as antioxidants in a neuronal-glial cell culture system. METHODS: Primary cortical neuronal-glial cultures were prepared from fetal rat brain. Cultures were exposed to iron, H2O2, or xanthine-xanthine oxidase for 30 min in serum-free media containing dissolved isoflurane (0-3.2 mm), sevoflurane (0-3.6 mm), halothane (0-4.1 mm), n-hexanol, or known antioxidants. Cell damage was assessed by release of lactate dehydrogenase (LDH) and trypan blue exclusion 24 h later. Lipid peroxidation was measured by the production of thiobarbituric acid-reactive substances in a cell-free lipid system. Iron and calcium uptake and mitochondrial depolarization were measured after exposure to iron in the presence or absence of isoflurane. RESULTS: Deferoxamine reduced LDH release caused by H2O2 or xanthine-xanthine oxidase, but the volatile anesthetics had no effect. Iron-induced LDH release was prevented by the volatile anesthetics (maximum effect for halothane = 1.2 mm, isoflurane = 1.2 mm, and sevoflurane = 2.1 mm aqueous phase). When corrected for lipid solubility, the three volatile anesthetics were equipotent against iron-induced LDH release. In the cell-free system, there was no effect of the anesthetics on thiobarbituric acid-reactive substance formation in contrast to Trolox, which provided complete inhibition. Isoflurane (1.2 mm) reduced mean iron uptake by 46% and inhibited mitochondrial depolarization but had no effect on calcium uptake. CONCLUSIONS: Volatile anesthetics reduced cell death induced by oxidative stress only in the context of iron challenge. The likely reason for protection against iron toxicity is inhibition of iron uptake and therefore indirect reduction of subsequent intracellular oxidative stress caused by this challenge. These data argue against a primary antioxidant effect of volatile anesthetics.

Anesthetics, Inhalation↗
PubMed1997

De Novo Biosynthesis of Volatiles Induced by Insect Herbivory in Cotton Plants.

In response to insect feeding on the leaves, cotton (Gossypium hirsutum L.) plants release elevated levels of volatiles, which can serve as a chemical signal that attracts natural enemies of the herbivore to the damaged plant. Pulse-labeling experiments with [13C]CO2 demonstrated that many of the volatiles released, including the acyclic terpenes (E,E)-[alpha]-farnesene, (E)-[beta]-farnesene, (E)-[beta]-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, and (E/E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, as well as the shikimate pathway product indole, are biosynthesized de novo following insect damage. However, other volatile constituents, including several cyclic terpenes, butyrates, and green leaf volatiles of the lipoxygenase pathway are released from storage or synthesized from stored intermediates. Analysis of volatiles from artificially damaged plants, with and without beet armyworm (Spodoptera exigua Hubner) oral secretions exogenously applied to the leaves, as well as volatiles from beet armyworm-damaged and -undamaged control plants, demonstrated that the application of caterpillar oral secretions increased both the production and release of several volatiles that are synthesized de novo in response to insect feeding. These results establish that the plant plays an active and dynamic role in mediating the interaction between herbivores and natural enemies of herbivores.

Journal Article↗
PubMed1999

Rhizosphere bacteria enhance selenium accumulation and volatilization by indian mustard

Indian mustard (Brassica juncea L.) accumulates high tissue Se concentrations and volatilizes Se in relatively nontoxic forms, such as dimethylselenide. This study showed that the presence of bacteria in the rhizosphere of Indian mustard was necessary to achieve the best rates of plant Se accumulation and volatilization of selenate. Experiments with the antibiotic ampicillin showed that bacteria facilitated 35% of plant Se volatilization and 70% of plant tissue accumulation. These results were confirmed by inoculating axenic plants with rhizosphere bacteria. Compared with axenic controls, plants inoculated with rhizosphere bacteria had 5-fold higher Se concentrations in roots (the site of volatilization) and 4-fold higher rates of Se volatilization. Plants with bacteria contained a heat-labile compound in their root exudate; when this compound was added to the rhizosphere of axenic plants, Se accumulation in plant tissues increased. Plants with bacteria had an increased root surface area compared with axenic plants; the increased area was unlikely to have caused their increased tissue Se accumulation because they did not accumulate more Se when supplied with selenite or selenomethionine. Rhizosphere bacteria also possibly increased plant Se volatilization because they enabled plants to overcome a rate-limiting step in the Se volatilization pathway, i.e. Se accumulation in plant tissues.

Journal Article↗
PubMed1984

Role of volatile fatty acids in colonization resistance to Clostridium difficile.

The in vitro inhibition of Clostridium difficile by volatile fatty acids was correlated with the pH and concentrations of volatile fatty acids in the ceca of hamsters of different ages. The concentrations of cecal volatile fatty acids increased with the age of the animals. Maximum concentrations of individual volatile fatty acids were attained when the animals were ca. 19 days old, with acetic, propionic, and butyric acids occurring in the highest concentrations (72, 16, and 32 microequivalents/g of cecum, respectively). The cecal pH was approximately the same in hamsters of all ages (pH 6.6 to 7.0). Only butyric acid reached a concentration in the ceca of hamsters which was inhibitory to the in vitro multiplication of C. difficile. This inhibitory concentration was attained when the animals were ca. 19 days of age. When mixtures of volatile fatty acids were prepared at concentrations equal to those present in the ceca of hamsters, there was a direct correlation between the in vitro inhibitory activity of the volatile fatty acids and the susceptibility of hamsters 4 days of age or older to C. difficile intestinal colonization. The resistance of hamsters less than 4 days of age to C. difficile intestinal colonization appears to be due to factors other than volatile fatty acids.

Aging↗
PubMed1989

Neuropsychological consequences of volatile substance abuse: a review.

1. The evidence from studies of the neuropsychological consequences of chronic volatile substance abuse is reviewed. 2. Studies of occupational exposure to solvent vapour are of limited relevance when considering the effects of volatile substance abuse because occupational exposure is normally to small quantities of many different compounds over prolonged periods of time. 3. Many studies of chronic volatile substance abusers suffer from serious shortcomings such as the use of small sample sizes, inadequate controls, failure to exclude the possibility of acute toxic effects and a disregard of other factors which could account for the findings. 4. There is reasonably good evidence that neuropsychological impairment is often present amongst volatile substance abusers with definite neurological abnormalities. 5. Although most studies have found that volatile substance abusers without reported neurological abnormalities obtain lower psychometric test scores than non-abusers, it remains uncertain whether these deficits are best explained in terms of a causal effect of volatile substance abuse, rather than a reflection of other factors associated with volatile substance abuse, such as background, social disadvantages or history of delinquency.

Environmental Exposure↗