Desorption processes of low-molecular-weight compounds from the surface of smectites into the gas phase determine a number of processes, e.g. those involved in drug delivery and the release of herbicides. The desorption has not been investigated thoroughly and is not well understood. The present study was undertaken in order to understand better the factors influencing these desorption mechanisms. Starting with a very pure standard (Na+-rich) montmorillonite (Kunipia-F), which was exchanged against cations with different hydration properties (Ca2+, Li+, phenyltrimethylammonium, hexyltrimethyl-ammonium), the experiments explored the rate of desorption of volatiles with different chemical functionalities (water, ethanol, ethyl acetate, and toluene). The desorption was monitored by thermogravimetry and differential scanning calorimetry under isothermal conditions, and by ramping the temperature at a constant rate. The experiments were compared with numerical calculations based on finite-element methods and with analytical models. These data point to a two-step mechanism where the desorption follows the curve of the equilibrium desorption isotherms of those molecules on the montmorillonite. The bulk-like volatiles (i.e. volatiles with release kinetics close to that of the bulk liquids) were desorbed in a first step. With a decrease in the degree of coverage of the volatile on the montmorillonite, the desorption was increasingly dominated by the strength of interaction between the volatile and the interlayer cations of the montmorillonite.

The simultaneous infestation of a plant by several species of herbivores may affect the attractiveness of plants to the natural enemies of one of the herbivores. We studied the effect of coconut fruits infested by the pests Aceria guerreronis and Steneotarsonemus concavuscutum, which are generally found together under the coconut perianth. The predatory mite Neoseiulus baraki produced lower numbers of offspring on fruits infested with S. concavuscutum and on fruits infested with both prey than on fruits with A. guerreronis only. The predators were attracted by odours emanating from coconuts with A. guerreronis, but not by odours from coconuts with S. concavuscutum, even when A. guerreronis were present on the same fruit. Fewer N. baraki were recaptured on fruits with both prey or with S. concavuscutum than on fruits with only A. guerreronis. Furthermore, the quality of A. guerreronis from singly and multiply infested coconuts as food for N. baraki did not differ. Concluding, our results suggest that N. baraki does not perform well when S. concavuscutum is present on the coconuts, and the control of A. guerreronis by N. baraki may be negatively affected by the presence of S. concavuscutum.

The source of Martian atmospheric methane is unknown. On Earth, hydrothermal mineral deposits contain ancient methane together with a host of chemical and geological lines of evidence for the mechanism of gas production. Such deposits are therefore potentially attractive sampling sites on Mars. In order to evaluate this potential, hydrothermal calcite veins were sampled across the Caithness region of Scotland and analysed for methane by an incremental-crushing mass spectrometry technique that may be adaptable to Mars rovers. Methane was detected in all samples. Variations in the quantity of methane released were found to relate directly to the geological history of the localities. Calcite particle size was found to affect measurements in a systematic and informative way. Oxidative weathering had no discernable effect on methane recoverability. These results suggest that the technique is sensitive and informative enough to deserve consideration for missions to Mars.

The red turpentine beetle (RTB), Dendroctonus valens LeConte, is a destructive invasive forest pest in China. For such tree-killing species, how to initiate a volatile-mediated mass attack is of great importance during the course of establishment. To understand the hindgut volatile production mechanism underlying mass attack initiated by RTB, coupled gas chromatography-mass spectrometry and 13C-labelled precursors were applied to explore the quantitative variation and biosynthesis of volatiles associated with RTB at different attack phases. Five previously described volatiles, trans-verbenol, myrtenol, cis-verbenol, myrtenal and verbenone, were identified and quantified from extracts of female and male hindguts, with the first two compounds as the major components and the latter three as minor constituents. In newly emerged females and males, only minute amounts of these compounds were detected. The quantity of volatiles from female adults significantly increased after they fed on bolts. Male adults also yielded larger quantities of volatiles after they joined females in galleries, which suggested that RTB males could accelerate the mass colonization on host trees. We also confirmed that RTB produced the five volatiles through oxidizing the major host monoterpene, α-pinene, but not synthesized de novo since products were labeled without 13C. The implication of this study in understanding the successful invasion of RTB is discussed.

We tested the chemotactic responses of dauer juvenile stages (DJs) of the insect parasitic nematode Heterorhabditis bacteriophora to a variety of compounds that are known to be highly attractive or highly repellent to Caenorhabditis elegans. While H. bacteriophora DJs respond to alcohols and some aromatic compounds as well as to host metabolites such as uric acid and CO2, the most notable difference in the responses of these two nematodes is that H. bacteriophora DJs are unresponsive to a large number of compounds which C. elegans finds highly attractive. The latter compounds are typical by-products of bacterial metabolism and include aldehydes, esters, ketones and short-chain alcohols. While C. elegans finds long-chain alcohols (e.g. 1-heptanol and 1-octanol) repellent and short-chain alcohols highly attractive, H. bacteriophora DJs are strongly attracted to 1-heptanol, 1-octanol and 1-nonanol and find short-chain alcohols to be only slightly attractive. Parasitic-stage H. bacteriophora nematodes show a very weak chemotactic response to volatile molecules that DJs find highly attractive. Our results suggest that, associated with the adoption of a parasitic mode of life by Heterorhabditis, there was an adaptive change in chemotactic behaviour of the infective stages, resulting in a decreased sensitivity to volatile by-products of bacterial metabolism and an increased sensitivity towards long-chain alcohols and other insect-specific volatiles and possibly also to herbivore-induced plant volatiles.

Background and objective: The safety of hypotension induced by sevoflurane and splanchnic organ blood flow remains to be clarified. The aim was to investigate the effects of sevoflurane-induced hypotension on systemic haemodynamics and splanchnic organ blood flows in dogs.

Methods: Mean arterial pressure was maintained at 60 mmHg by increasing sevoflurane concentrations. The renal, hepatic and pancreatic blood flows were measured by using the hydrogen clearance method.

Results: Hypotension induced by sevoflurane resulted in a 50% decrease of mean arterial pressure due to a 30% reduction in systemic vascular resistance associated with a 30% decrease in cardiac index. The mechanisms causing the lower cardiac index were produced by the decreases in heart rate and left ventricular dP/dtmax. Renal, hepatic and pancreatic blood flow were reduced, but the whole-body oxygen consumption did not change during the hypotensive period.

Conclusions: The haemodynamic changes induced by sevoflurane were caused by the suppression of arterial baroreflexes and myocardial depression, but splanchnic organ blood flows, though reduced, could provide adequate peripheral perfusion to meet the decrease in oxygen supply.

Background and objective Low-flow anaesthesia is economical and less polluting. The purpose of this study was to determine the inspired and end-tidal desflurane concentrations during anaesthesia with a vaporizer setting maintained at 5%, during low-flow anaesthesia after 120 min with fresh gas inflows of 1.0 and 2.0 L min−1.

Methods The study was both prospective and randomized, including 56 patients (28 patients in each group) scheduled for elective surgery of an expected anaesthesia time of at least 120 min. Inspired and end-tidal concentrations of desflurane were measured during low-flow anaesthesia with fresh gas inflows of 1.0 and 2.0 L min−1. The vaporizer setting was fixed at 5% desflurane.

Results The inspired and end-tidal concentrations of desflurane in the 1.0 L min−1 group after 120 min were 4.54% vs. 4.37% (P < 0.001). In the 2.0 L min−1 group, the inspired and end-tidal concentrations of desflurane were 4.76% vs. 4.58% (P < 0.001). The estimated end-tidal/inspired ratios at 120 min of anaesthesia were 0.96 in both groups. At a fresh gas flow of 1.0 L min−1, the end-tidal concentration was 0.87 of the vaporizer setting. Increasing the fresh gas flow to 2.0 L min−1 increased the end-tidal value by 0.05.

Conclusion There is a significant difference between the inspired and end-tidal concentrations of desflurane when fresh gas inflows were 1.0 and 2.0 L min−1, but not for the ratio of inspired/end-tidal.

CH3Cl emissions by freshly harvested tubers of 61 potato cultivars ranged from less than 4 to 650 ng g−1 f. wt d−1. In experiments with Anna, the cultivar displaying the highest release rate, maximum emission of CH3Cl occurred at 20°C but the rate diminished after 48 h, a decrease due in part to inhibition of CH3Cl release by the accumulation of CH3Cl in the headspace. In 1995 and 1996, CH3Cl emission by tubers was first detectable 6 wk before the normal harvest date. If tubers were stored at 20°C immediately following harvest, release attained a maximum of 350 ng g−1 f. wt d−1 about 4 d after harvest, falling to less than 4 ng g−1 f. wt d−1 within 3 wk of harvest. On storage at 6°C post-harvest, maximum release of CH3Cl (c. 600 ng g−1) was delayed until 5 wk after harvest and release fell below 4 ng g−1 f. wt d−1 after 200 d. Release of CH3Cl was not significantly affected by cutting or bruising tuber tissue, and CH3Cl biosynthesis occurred in both core and superficial tissues of the tuber. The S-methyl group of either L- or D-methionine acted as a precursor of CH3Cl in sliced tubers, but the methylating system was specific for Cl−. An isotope dilution technique using C2H3Cl demonstrated that the amount of CH3Cl metabolized by the intact tuber was approximately 36% of the net release. However, investigations with 14CH3Cl showed that only a small proportion (7%) of the CH3Cl metabolized was fixed in involatile form in the tuber. In both skin and core tissues, fixed 14C was located primarily (80%) in the fraction soluble in phosphate buffer, but the specific activity of skin tissue was about twice that of core tissue. Autoradiography demonstrated that 14C fixation in the tuber was greatest within the lenticels, possibly indicating a microflora adapted to use the locally high concentrations of CH3Cl. Significant 14C fixation was also associated with the periderm but was not attributable to labelling of the O-methyl groups of the phenolic components of suberin. Within the core of the tuber, 14C fixation was located primarily in the phloem, pith and medullary rays.

We have investigated the cardiovascular and plasma noradrenaline response to surgical incision under sevoflurane anaesthesia and determined the end-tidal concentration of sevoflurane that blocks the adrenergic response or responses to surgical incision (MACBAR) and changes in mean arterial pressure (MAP) in response to surgical incision (MACBCR) in 50% of women. We randomly assigned 64 female patients, aged 20–49 years, to eight groups according to end-tidal sevoflurane concentration: 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0% and 8.5%. All patients received only sevoflurane anaesthesia. An increase of 10% or more from prestress (incision) values of MAP or plasma noradrenaline concentration was considered a positive response. The probability of no response to stress was analysed using logistic regression to obtain the probability of no response vs. end-tidal sevoflurane concentration and the best-fit curve from the maximum likelihood estimators of the model parameters. MACBAR (mean±SE) was 8.0±0.2%, MACBCR was 7.9±0.2%. However, such high doses of sevoflurane cannot be used clinically because of their high toxicity. It may be preferable to combine sevoflurane with other anaesthetics to reduce haemodynamic responses to strong stimulation.

The effects of controlled hypotension induced with trimethaphan (TMP), nitroglycerin (TNG) or prostaglandin E1 (PGE1) during sevoflurane anaesthesia on hepatic function were studied in 28 patients undergoing spinal fusion surgery. Patients were randomly divided into three groups to receive TMP (group A, n=10), TNG (group B, n=10) or PGE1 (group C, n=8). Anaesthesia was maintained with N2O and sevoflurane. The mean arterial blood pressure was maintained at 60 mmHg for 90 min. Measurements included arterial ketone body ratio (AKBR-acetoacetate/3-hydroxybutyrate), SGOT, SGPT, LDH, blood glucose and blood gases were made. Measurements were taken before hypotension, 60 min and 90 min after starting hypotension, 60 min after recovery from hypotension and on the post-operative day. AKBR showed no significant change. SGOT, SGPT and LDH were within normal limits. Controlled hypotension induced with TMP, TNG or PGE1 under sevoflurane anaesthesia in surgical patients did not cause hepatocellular damage.

Ten patients, predicted to pose a difficult intubation of the trachea, underwent inhalational induction of anaesthesia using sevoflurane. In all 10 cases the airway was secured successfully and the patient proceeded to have the planned operation. In six of the cases the anaesthetist experienced a problem during the induction but in no case did this present any real difficulties or lead to a critical incident. We feel that sevoflurane has a place for inhalational induction in this challenging group of patients.

The isoflurane-saving and CO2-retaining effects of a charcoal filter were compared with a Siemens standard heat and moisture (HME) exchanger and an emptied specimen (dummy). Isoflurane was delivered during the inspiratory phase and consumption investigated at 10, 15 and 25 cycles min−1. The investigation was performed by ventilation with humidified air with a constant end-tidal CO2 and temperature. For a comparison, isoflurane was delivered in a conventional manner via the ventilator. The arrangement with a charcoal filter reduced the isoflurane consumption by a factor of 2.0−2.6, depending on ventilatory rate. Most of the saving was a result of the method of isoflurane delivery (factor 1.4−2.0), while adding the reflector gave a further reduction (factor 1.3−1.5). One circumstance that reduced the net efficiency of the charcoal filter was that it also reflected CO2; consequently, total minute ventilation had to be increased to maintain constant end-tidal CO2.

The dose-response and concentration-response relation of rocuronium infusion was studied in 20 adult surgical patients during propofol-nitrous oxide and isoflurane (1 MAC) -nitrous oxide anaesthesia. Neuromuscular block was kept constant, initially at 90% and then at 50% with a closed-loop feedback controller. At 90% block the steady-state infusion of rocuronium was 0.55 ± 0.16 mg kg−1 h−1 and the corresponding concentration 1714 ± 281 ng mL−1 in patients receiving propofol. At 50% block the corresponding infusion rate was 0.27 ± 0.11 mg kg−1 h−1 and the concentration 1077 ± 244 ng mL−1, respectively. At 50% block isoflurane reduced the rate of infusion by 52% (P < 0.005) and the concentration by 59% (P < 0.001); at 90% block both the mean infusion rate and the concentration of rocuronium were reduced by 35% (P <0.005). The mean rocuronium clearance at 50% block was unaffected by the type of anaesthesia; it was 4.1 ± 1.6 and 4.9 ± 2.7 mL kg−1 min−1 in the groups receiving propofol and isoflurane anaesthesia, respectively. We conclude that isoflurane reduces the infusion requirements of rocuronium by changing the pharmacodynamic behaviour.

There are only limited data on sevoflurane minimum alveolar concentration (MAC) in rats. This study was designed to determine the minimum alveolar concentration value for sevoflurane in younger and older rats. Minimum alveolar concentration determination was performed in spontaneously breathing animals, 9-week-old rats (younger, n = 8) and more than 13-month-old rats (older, n = 8). Rats were instrumented with a silastic catheter in the abdominal aorta via the femoral artery to allow for arterial blood gas sampling. Subsequently, minimum alveolar concentration for sevoflurane was determined in 40 younger and 38 older rats. Minimum alveolar concentration for sevoflurane in younger rats was significantly higher than in the older rats (2.68 ± 0.19 vs. 2.29 ± 0.19, P < 0.001). Subgroup analysis indicated that minimum alveolar concentration for sevoflurane was not affected by the presence of an arterial catheter in the abdominal aorta (younger, 2.75 ± 0.08 vs. 2.67 ± 0.21; older, 2.23 ± 0.19 vs. 2.30 ± 0.18). Minimum alveolar concentration is profoundly affected by the age of the animal, but not by limited instrumentation.

Desflurane is a new inhalation anaesthetic with a low blood/gas solubility which should allow a fast emergence from anaesthesia. In a prospective open randomized study, desflurane was compared with isoflurane paying special attention to recovery and the quality of the post-operative period. The occurrence of pain and post-operative nausea and vomiting (PONV) was recorded during the first 20 post-operative hours. Seventy women ASA Grade I-II scheduled for elective gynaecological laparoscopic procedures were studied. Patients receiving desflurane were extubated earlier than patients receiving isoflurane, 5±1 and 9±1 min respectively (P < 0.05) and the patients anaesthetized with desflurane were able to tell their name and date on average 5 min earlier than those who had received isoflurane; however, time in the recovery room was the same for both groups of patients. Twenty-two of 35 patients receiving desflurane, and 18 of 35 receiving isoflurane required analgesia. PONV was recorded in 18 patients anaesthetized with desflurane and 12 patients anaesthetized with isoflurane. In both groups PONV was more frequently observed in patients after leaving the recovery room. PONV in the recovery room was associated with a delayed discharge, 139 vs. 114 min respectively. Desflurane seems to be an useful alternative to isoflurane for laparoscopic procedures.

The present study was designed to determine the direct effects of halothane, isoflurane and sevoflurane on the bovine epicardial coronary artery as well as their mode of action. We chose serotonin as the vasoconstrictor because it also causes endothelium-dependent relaxation of coronary arteries. Isolated spiral strips of bovine epicardial coronary artery with and without endothelium were suspended for isotonic contraction recordings in Tyrode's solution. KCl (80.4 mm) solution induced maximal contraction, regarded as the reference value (100%). The muscle strips were then exposed to increasing concentrations of serotonin from 10−8 to 10−4 m in the presence and absence of 1.5 MAC halothane, isoflurane or sevoflurane. All three drugs attenuated serotonin-evoked contraction in the coronary artery strips both those strips with and without endothelium (P < 0.05−0.001). However, there were no significant differences in the attenuation of serotonin-induced contraction of the strips, both with and without endothelium, in each drug group. The attenuation potency of halothane was more than that of isoflurane and sevoflurane. The results demonstrate that halothane, isoflurane and sevoflurane attenuate contractile responses evoked by serotonin in bovine epicardial coronary artery both with and without endothelium.