Isoflurane leakage from non-rebreathing rodent anaesthesia circuits: comparison of emissions from conventional and modified ports

Chronic exposure to low levels of fluorocarbon-based waste anaesthetic gas (WAG) has been linked to a multitude of human health problems. We have shown that isoflurane exhaust from passive gas-scavenging canisters is often quite high when using conventional rodent anaesthesia protocols and equipment. Another likely source of WAG build-up in rodent procedure rooms is leakage at the interface between the breathing circuit and the animal's face. We evaluated this possibility using three non-rebreathing circuits: traditional Bain, modified Bain, and Mapleson (type E). For the Mapleson E circuit, a conical rodent facemask was attached and used in one of two configurations: normal aperture, or aperture modified with a latex diaphragm (cut from an unpowdered surgical glove) to reduce the orifice diameter and tighten the seal. Adult female Sprague-Dawley rats were anaesthetized with isoflurane (5% for induction, 2% or 3.5% for maintenance) in oxygen (2 L/min for induction, 1 L/min for maintenance). Isoflurane leakage was assessed by real-time spectrophotometry. In 94% of the trials, three configurations - traditional Bain, modified Bain, and Mapleson E with unmodified mask - permitted isoflurane leakage approaching or exceeding 100 ppm at the face/port interface. In contrast, the Mapleson circuit with diaphragm-modified mask emitted significantly (P相似文献   

不同层流净化级别室内微量麻醉气体对医护人员的影响

目的:研究净化级别不同室内麻醉药物残留浓度对医护人员健康的影响,为制定麻醉操作规范提供参考依据。方法:通过Tedlar采样袋采集麻醉医生及麻醉恢复室人员呼出气20 mL,双盲法送30 min内相关人员应用气相色谱法进行分析。结果:不同层流净化级别室内医务人员呼出微量麻醉气体的浓度不同。十万级恢复室内医护人员呼出气体的浓度高于百级和万级手术间。结论:麻醉废气污染对手术室工作人员的心理行为及操作能力产生影响,医护人员应增强自我防护意识,定期监测手术室环境污染的程度,制定预防和减少麻醉废气污染的有效措施。     

Comparison of isoflurane and sevoflurane for anesthesia in beaver

We compared the hemodynamic and respiratory effects, recovery time, and cost of two gas inhalants (isoflurane and sevoflurane) for anesthetic induction and maintenance of beaver (Castor canadensis) during surgery to implant radio transmitters in the peritoneal cavity. Heart rate, respiratory rate, relative hemoglobin saturation with oxygen (SpO2), and body temperature were measured every 5 min for the first 45 min, and arterial blood gas was measured once, 25 min into the anesthetic procedure. Induction for either agent was smooth and rapid. Heart rate and respiratory rate both decreased during the procedure though neither was lower than baseline values reported in the literature for beaver. Relative hemoglobin saturation with oxygen, body temperature, and blood gas variables did not differ between each anesthetic regime. Both inhalants caused slight respiratory acidosis. Recovery time from anesthesia was highly variable (1-178 min) but did not differ statistically between drugs. Sevoflurane costs ($22.30/60 min) were much higher than isoflurane costs ($3.50/60 min). We recommend isoflurane or sevoflurane for anesthetic induction and maintenance of beaver because of the lack of physiologic differences.     

Behavioral characterictics of ISIAH rat strain

This work was performed in hypertensive ISIAH and normotensive WAG rat strains. The latter was used as a control group. The general evaluation of behavior of the ISIAH and WAG rats tested in the open field, in the light-dark test, in the sound stress test, and in the fatigue test showed that the motor and exploratory activity provoked by an unfamiliar environment was much higher in the ISIAH rats as compared to the control WAG strain. Spontaneous locomotor activity of the ISIAH rats in the home cage was significantly lower as compared to the control WAG strain. This finding suggests that the ISIAH rats are hyperreactive in an novel environment. It is concluded that the hypertensive ISIAH rats are significantly different from the control WAG rats not only in the arterial blood pressure level, but also in behavioral patterns.     

Elevated levels of calcitonin mRNA: a marker for the spontaneous development of medullary thyroid carcinoma in rats

The aging WAG/Rij rats (a Wistar derived strain) develop spontaneously medullary thyroid carcinoma with a high frequency (50%). We have studied calcitonin biosynthesis in Wistar and WAG/Rij rats strains in order to determine if early changes in this parameter occurred in the WAG/Rij strain. Thyroidal and plasma CT levels were measured in three months old WAG/Rij and Wistar rats before and after acute calcium challenge. Total RNA was extracted from thyroid glands and specific CT messenger RNA levels estimated by dot and Northern blot analysis with a 32P-labeled probe specific for CT mRNA. The capacity of mRNA to direct synthesis of CT precursor was also measured by translation in an in vitro system. Though mean basal circulating CT levels were equivalent in both strains, CT release after calcium stimulation was much increased in the WAG/Rij rat. CT content of the glands and CT mRNA levels were two fold higher in the WAG/Rij strain. Thus, in this strain, CT biosynthesis and secretion were increased long before the development of a C-cell carcinoma.     

A scavenging double mask to reduce workplace contamination during mask induction of inhalation anesthesia in dogs

Background  

Workplace contamination by the use of volatile anesthetic agents should be kept to a minimum if a potential health hazard is to be minimised. Mask induction of animals is a common procedure. The present study investigates the efficiency of a novel scavenging double mask in reducing waste gas concentrations in the breathing zone of the anesthetist performing this procedure.     

Anesthetic inhibition of firefly luciferase, a protein model for general anesthesia, does not exhibit pressure reversal.

The surprising observation that pressures of the order of 150 atmospheres can restore consciousness to an anesthetized animal has long been central to theories of the molecular mechanisms underlying general anesthesia. We have constructed a high-pressure gas chamber to test for "pressure reversal" of the best available protein model of general anesthetic target sites: the pure enzyme firefly luciferase, which accounts extremely well for animal potencies (over a 100,000-fold range). We found no significant pressure reversal for a variety of anesthetics of differing size and polarity. It thus appears that either firefly luciferase is not an adequate model for general anesthetic target sites or that pressure and anesthetics act at different molecular sites in the central nervous system.     

Chamber response time: A neglected issue in gas exchange measurements

When the dimensions of standard commercial chambers for measuring gas exchange cannot accommodate the object being measured, scientists construct their own chambers. The time needed to reach chamber steady state (chamber response time) depends on net system volume (e.g. chamber and tubing volume) and airflow. Unfortunately, some authors take chamber response time into consideration while others ignore it. We present the formula for calculating chamber response time.     

An improved general amino acid replacement matrix

Amino acid replacement matrices are an essential basis of protein phylogenetics. They are used to compute substitution probabilities along phylogeny branches and thus the likelihood of the data. They are also essential in protein alignment. A number of replacement matrices and methods to estimate these matrices from protein alignments have been proposed since the seminal work of Dayhoff et al. (1972). An important advance was achieved by Whelan and Goldman (2001) and their WAG matrix, thanks to an efficient maximum likelihood estimation approach that accounts for the phylogenies of sequences within each training alignment. We further refine this method by incorporating the variability of evolutionary rates across sites in the matrix estimation and using a much larger and diverse database than BRKALN, which was used to estimate WAG. To estimate our new matrix (called LG after the authors), we use an adaptation of the XRATE software and 3,912 alignments from Pfam, comprising approximately 50,000 sequences and approximately 6.5 million residues overall. To evaluate the LG performance, we use an independent sample consisting of 59 alignments from TreeBase and randomly divide Pfam alignments into 3,412 training and 500 test alignments. The comparison with WAG and JTT shows a clear likelihood improvement. With TreeBase, we find that 1) the average Akaike information criterion gain per site is 0.25 and 0.42, when compared with WAG and JTT, respectively; 2) LG is significantly better than WAG for 38 alignments (among 59), and significantly worse with 2 alignments only; and 3) tree topologies inferred with LG, WAG, and JTT frequently differ, indicating that using LG impacts not only the likelihood value but also the output tree. Results with the test alignments from Pfam are analogous. LG and a PHYML implementation can be downloaded from http://atgc.lirmm.fr/LG.     

Cellulolytic activity in leachate during leach-bed anaerobic digestion of municipal solid waste

The degradation of municipal solid waste (MSW) under mesophilic conditions can be enhanced by exchanging leachate between fresh waste and stabilised waste. The optimum point in time when leachate from an anaerobically digesting waste bed can be used to initiate degradation of another waste bed might occur when the leachate of the digesting waste bed is highly active with cellulolytic and methanogenic bacteria. In this study, the cellulolytic activity of the leachate was measured using the cellulose-azure assay. As products of hydrolysis are soluble compounds, the rate of generation of these compounds was estimated based on a soluble chemical oxygen demand (SCOD) balance around the fresh waste bed. It was found that once the readily soluble material present in MSW was washed out there was very little generation of SCOD without the production of methane, indicating that flushing leachate from a stabilised waste bed resulted in a balanced inoculation of the fresh waste bed. With the onset of sustained methanogenesis, the rate of SCOD generation equalled the SCOD released from the digester as methane. The experimental findings also showed that cellulolytic activities of the leachate samples closely followed the trend of SCOD generation.     

In vitro control analysis of an enzyme system: Experimental and analytical developments

In this paper we describe a flow-through system for reconstituting parts of metabolism from purified enzymes. This involves pumping continuously into a reaction chamber, fresh enzymes and reagents so that metabolic reactions occur in the chamber. The waste products leave the chamber via the outflow so that a steady state can be setup. The system we chose consisted of a single enzyme, lactate dehydrogenase. This enzyme was chosen because it consumes NADH in the chamber which could be monitored spectrophotometrically. The aim of the work was to investigate whether a steady state could be achieved in the flow system and whether a metabolic control analysis could be done. We measured two control coefficients, C_LDH and C_pump for the enzyme flux and NADH concentration and confirmed that the summation theorem applied to this system. The advantage of a flow-through system is that the titrations necessary to estimate the control coefficients can be easily and precisely controlled; this means that accurate estimates for the control coefficients can be obtained. In the paper, we discuss some statistical aspects of the data analysis and some possible applications of the technique, including a method to determine the presence of metabolic channelling between two different enzymes.     

A method for measuring whole plant photosynthesis in Arabidopsis thaliana

Measurement of photosynthesis of intact leaves of Arabidopsis thaliana has been prohibitive due to the small leaf size and prostrate growth habit. Because of the widespread use of Arabidopsis for plant science research it is important to have a procedure for accurate, nondestructive measurement of its photosynthesis. We developed and tested a method for analysis of photosynthesis in whole plants of Arabidopsis. Net carbon assimilation and stomatal conductance were measured with an open gas exchange system and photosynthetic oxygen evolution was determined from chlorophyll fluorescence parameters. Individual plants were grown in 50 cubic centimeter tubes that were attached with an air tight seal to an enclosed gas exchange chamber for measurement of carbon dioxide and water exchange by the whole plant. Chlorophyll fluorescence from intact leaves was simultaneously measured with a pulse modulated fluorometer. Photosynthetic CO₂ assimilation and stomatal conductance rates were calculated with established gas exchange procedures and O₂ evolution was determined from chlorophyll fluorescence measurement of Photosystem II yield. Carbon assimilation and oxygen evolution in response to light intensity and ambient CO₂ concentration was measured and is presented here to demonstrate the potential use of this method for investigation of photosynthesis of Arabidopsis plants in controlled environment conditions.     

能源重化工工业园环境系统动力学仿真与调控

以锦界工业园环境系统为对象,在系统结构分析基础上,构建其系统动力学模型,并确定生产性投资比例、科技投资比例、环保投资比例、污水处理投资率、废气处理投资率、固废处理投资率为调控参数进行仿真。结果表明,当生产性投资比例由0.14提高到0.16,科技投资比例由0.02提高到0.04,环保投资比例由0.04提高到0.08,污水处理投资率由0.4下调为0.36,废气处理投资率由0.2提高到0.34,固废处理投资率由0.4下调为0.3时,园区年均工业总产值增长率达到21%,环境相对污染度年均降幅为8.1%,人口年增长率为4.7%,系统达到相对最优状态。因此,锦界工业园在环境管理中应采取以下措施:一是合理的调整生产、科技和环保的投资比例,适当降低生产性投资比例,增加科技投资和环保投资比例;二是合理的调整污水、废气和固废处理的投资比例,加强三废处理的基础设施建设,为构建完整的三废回收和处理系统奠定基础。     

Field use of isoflurane as an inhalant anesthetic in the American marten (Martes americana)

We evaluated the effectiveness and practicality of using isoflurane as an inhalation anesthetic with oxygen as a gas carrier for American martens (Martes americana) in a field setting. Sixty-eight martens were trapped in the Waswanipi Cree Model Forest (Québec, Canada) from October to November 2005 and anesthetized with isoflurane in 100% oxygen (1 l/min) using a face mask. Induction setting of isoflurane was 3% for all animals. Mean (+/-SD) length of induction was 1.8+/-1.2 min. Maintenance isoflurane settings ranged from 1% to 4%. Procedures lasted an average of 16.4+/-7.1 min and were uneventful. Length of recovery, defined as the interval between the end of the procedure and animal release, was short (6.3+/-2.8 min), and well below reported lengths of recovery using injectable anesthetics (>/=70 min). As compared to open drop administration of isoflurane described in previous studies, the use of an anesthesia machine prevents the risk of potential fatal anesthetic overdose. We conclude that among anesthesia techniques currently available, isoflurane with oxygen as a gas carrier is a safe and useful field anesthetic in martens, when issues with equipment portability can be overcome.     

A Direct Confirmation of the Standard Method of Estimating Intercellular Partial Pressure of CO(2)

The partial pressure of CO₂ inside leaves of several species was measured directly. Small gas exchange chambers were clamped above and below the same section of an amphistomatous leaf. A flowing gas stream through one chamber allowed normal CO₂ and water vapor exchange. The other chamber was in a closed circuit consisting of the chamber, an infrared gas analyzer, and a peristaltic pump. The CO₂ in the closed system rapidly reached a steady pressure which it is believed was identical to the CO₂ pressure inside the leaf, because there was no flux of CO₂ across the epidermis. This measured partial pressure was in close agreement with that estimated from a consideration of the fluxes of CO₂ and vapor at the other surface.     

Respiratory activity of biofilms: measurement and its significance for the elimination of n-butanol from waste gas

A reaction chamber was developed to determine the respiratory activity of microorganisms immobilized on various support materials for waste gas treatment. The volumetric respiration rate was identified as a suitable parameter for estimating the degradative activity of waste gas treatment plants. A laboratory trickle-bed reactor was filled with either granular clay, polyamide beads, or sintered styrofoam. n-Butanol was used as model solvent to determine the efficiency of its elimination from the gas phase. This crucial parameter was correlated with the volumetric degradation rate, determined from the overall material balance under steady-state operating conditions. The volumetric respiration rate of n-butanol was determined with the reaction chamber, and exceeded the volumetric degradation rate of n-butanol determined from the reactor 16- to 26-fold, depending on the support material. The respiration rate was correlated to the degradation rate by the stoichiometry of n-butanol oxidation and a correlation factor of 2.6–4.3. The volumetric respiration rate appeared to be a suitable parameter to determine the degradative activity of the trickle-bed reactor used. The volumetric respiration rate can be ultimately applied to estimate the efficiency of elimination of an organic pollutant and to calculate the dimensions of a reactor required to eliminate a given organic load from waste gas. Received: 20 February 1997 / Received revision: 20 May 1997 / Accepted: 20 May 1997     

Stress, glucocorticoids and absences in a genetic epilepsy model

Although stress can alter the susceptibility of patients and animal models to convulsive epilepsy, little is known about the role of stress and glucocorticoid hormones in absence epilepsy. We measured the basal and acute stress-induced (foot-shocks: FS) concentrations of corticosterone in WAG/Rij rats, non-epileptic inbred ACI rats and outbred Wistar rats. The WAG/Rij strain is a genetic model for absence epilepsy and comorbidity for depression, which originates from the population of Wistar rats and, therefore, shares their genetic background. In a separate experiment, WAG/Rij rats were exposed to FS on three consecutive days. Electroencephalograms (EEGs) were recorded before and after FS, and the number of absence seizures (spike-wave-discharges, SWDs) was quantified. Both WAG/Rij rats and ACI rats exhibited elevated basal levels of corticosterone and a rapid corticosterone increase in response to acute stress. The WAG/Rij rats also displayed the most rapid normalization of corticosterone during the recovery phase compared to that of ACI and Wistar rats. FS had a biphasic effect on SWDs; an initial suppression was followed by an aggravation of the SWDs. By the third day, this aggravation of seizures was present in the hour preceding FS. This increase in SWDs may arise from anticipatory stress about the upcoming FS. Together, these results suggest that the distinct secretion profile of corticosterone found in WAG/Rij rats may contribute to the severity of the epileptic phenotype. Although the acute stressor results in an initial suppression of SWDs followed by an increase in SWDs, stress prior to a predictable negative event aggravates absences.     

A review of tribromoethanol anesthesia for production of genetically engineered mice and rats

Tribromoethanol (TBE) is easy and inexpensive to make in the laboratory from readily available reagents, requires no special equipment for its administration, and is not subject to federal or state drug enforcement agency regulations. Intraperitoneal (i.p.) injection of TBE results in the simple and rapid induction of short-term surgical anesthesia; however, recent adverse reports about the efficacy and safety of TBE make its continued routine use as a rodent anesthetic controversial. The authors review the history and use of TBE as an animal anesthetic and conclude that TBE should be relegated to acute terminal studies when administered i.p.     

Anesthetic Gases and Water Structure : The effect of xenon on tritiated water flux across the gut

Pauling and Miller have independently proposed that the presence of an anesthetic gas in tissue induces a cage-like arrangement of hydrogen-bonded water molecules. The theories recognize that most gas-hydrate crystals would not form at the temperature and pressure that exist during anesthesia and propose that other components of tissue such as protein should have a stabilizing effect. Measurements of the behavior of water, rather than the anesthetic agent, would provide alternative information about the likelihood of hydrate crystal formation and this information could be such as to be applicable to body temperature and to pressures used for anesthesia. If the number of hydrogen-bonded water molecules in tissue is increased, then the movement of an average water molecule should be hindered. Movement of water through the tissue may be measured by tagging it with tritium and the anesthetic gas should then slow the movement of tritiated water through the tissue. The flux of tritiated water through rat cecum is indeed slowed when the cecum is exposed to the anesthetic gas, xenon, which can participate biochemically only by virtue of its van der Waals interaction. The decrement in water flux is in reasonable agreement with what could be expected theoretically from calculations based on the activation energy for the self-diffusion of water and the degree of hypothermia necessary to produce narcosis.     

Productive phenology of tropical montane forests: Fertilization experiments along a moisture gradient

Phenological responses of leaves and roots were studied in the tropical montane forests of Mount Kinabalu, Borneo. Soil nutrient supply, in addition to the supply of light and water, is a potential abiotic factor influencing plant phenology in the tropics. The main objective of this study was to evaluate the contribution of soil nutrient supply to plant productive phenology. Fertilization experiments, including controls, nitrogen fertilized and nitrogen and phosphorus fertilized treatments, were conducted on three vegetation types in different moisture environments. Responses of leaves and roots were compared among treatments and among vegetation types. Leaf flushing was induced by nitrogen fertilization in the upper montane forest, where extremely wet moisture conditions are associated with cloud cover. This induction of leaf flushing by fertilization was not observed in the other forests. Root growth was suppressed by fertilization when leaf flushing was not induced by fertilization. These results indicate that soil pulsed nutrient release could be a cue for leaf flushing in a tropical wet environment, and that leaf phenology could be regulated by external abiotic factors and root phenology could be regulated by internal plant demands.