Effect of anesthetic agents on lavage fluid parameters used as indicators of pulmonary injury

The effect of the anesthetic agent used in killing animals in an in vivo pulmonary toxicity screening test was examined in Fischer-344 rats and in Syrian hamsters. Using animals killed by cervical dislocation with no anesthesia as a baseline, two types of anesthetic agents (halothane, sodium pentobarbital) and carbon dioxide were tested. Carbon dioxide caused the greatest perturbance of baseline lavage fluid and tissue parameters normally used in the screening test. Halothane anesthesia caused the least perturbance in the screening test parameters and was selected as the anesthetic of choice for use in future pulmonary toxicity tests.     

Continuous measurement of gas uptake and elimination in anesthetized patients using an extractable marker gas.

Measurement of pulmonary gas uptake and elimination is often performed, using nitrogen as marker gas to measure gas flow, by applying the Haldane transformation. Because of the inability to measure nitrogen with conventional equipment, measurement is difficult during inhalational anesthesia. A new method is described, which is compatible with any inspired gas mixture, in which fresh gas and exhaust gas flows are measured using carbon dioxide as an extractable marker gas. A system was tested in eight patients undergoing colonic surgery for automated measurement of uptake of oxygen, nitrous oxide, isoflurane, and elimination of carbon dioxide with this method. Its accuracy and precision were compared with simultaneous measurements made with the Haldane transformation and corrected for predicted nitrogen excretion by the lungs. Good agreement was obtained for measurement of uptake or elimination of all gases studied. Mean bias was -0.003 l/min for both oxygen and nitrous oxide uptake, -0.0002 l/min for isoflurane uptake, and 0.003 l/min for carbon dioxide elimination. Limits of agreement lay within 30% of the mean uptake rate for nitrous oxide, within 15% for oxygen, within 10% for isoflurane, and within 5% for carbon dioxide. The extractable marker gas method allows accurate and continuous measurement of gas uptake and elimination in an anesthetic breathing system with any inspired gas mixture.     

常用麻醉剂对麻醉小鼠超声心功能的影响

目的:比较常见的多种麻醉剂对小鼠心脏超声结果的影响。方法:C57BL/6小鼠25只,随机分5组,每组5只。首先在清醒状态下,借助小动物高频超声系统(Vevo2100)评价小鼠心功能,然后分别用戊巴比妥钠、水合氯醛、三溴乙醇、氯胺酮/地西泮及异氟烷麻醉,再次对心功能进行评价。比较6种不同处理情况下,超声反映的小鼠心功能的差异。结果:与清醒状态相比,5种麻醉方式下,小鼠的心率及心功能均有不同程度降低。其中,戊巴比妥钠、水合氯醛、三溴乙醇及异氟烷麻醉组的左心收缩功能显著降低(P0.01),而氯胺酮/地西泮麻醉的小鼠与清醒组相比,收缩功能无明显差异(P0.05),但其余参数也有显著差异(P0.01)。结论:不论何种麻醉方式,都会对小鼠心率及心功能造成一定影响,但其同组内仍具有可比性;因此应根据现实条件及实验需要选择麻醉剂,并贯彻始终,保持试验中麻醉条件的一致性。     

Pleistocene persistence and expansion in tarantulas on the Colorado Plateau and the effects of missing data on phylogeographical inferences from RADseq

Montane species endemic to the “sky islands” of the North American southwest were significantly impacted by changing climates during the Pleistocene. We combined mitochondrial and genomic data with species distribution modelling to determine whether Aphonopelma marxi, a large tarantula from the nearby Colorado Plateau, was similarly impacted by glacial climates. Genetic analyses revealed that the species comprises three main clades that diverged in the Pleistocene. A clade distributed along the Mogollon Rim appears to have persisted in place during glacial conditions, whereas the other two clades probably colonized central and northeastern portions of the species' range from refugia in canyons. Climate models support this hypothesis for the Mogollon Rim, but late glacial climate data appear too coarse to detect suitable areas in canyons. Locations of canyon refugia could not be inferred from genomic analyses due to missing data, encouraging us to explore the effect of missing loci in phylogeographical inferences using RADseq. Results from analyses with varying amounts of missing data suggest that samples with large amounts of missing data can still improve inferences, and the specific loci that are missing matters more than the number of missing loci. This study highlights the profound impact of Pleistocene climates on tarantulas endemic to the Colorado Plateau, as well as the mixed nature of the region's fauna. Some animals recently colonized from nearby deserts as glacial climates receded, whereas others, like tarantulas, appear to have persisted on the Mogollon Rim and in refugia associated with the region's famous river‐cut canyons.     

Development and evaluation of methods to assess populations of black flies (Diptera: Simuliidae) at nests of the endangered whooping crane (Grus americana)

Hematophagous insects can negatively affect the reproductive success of their vertebrate hosts. To determine the influence of hematophagous insects on endangered vertebrates requires specially designed programs that minimize disturbance to the hosts and address problems associated with their small populations. We developed and evaluated a surveillance program for black flies potentially affecting a population of whooping cranes (Grus americana) introduced to central Wisconsin, U.S.A. In one of the few studies to survey host‐seeking female black flies and their immature stages concurrently, we processed nearly 346,000 specimens and documented 26 species, of which only two, Simulium annulus and Simulium johannseni, were attracted to nesting whooping cranes. Attempts to assess black fly populations with artificial nests and real crane eggs were unsuccessful. Carbon‐dioxide traps performed well in describing black fly taxa on the landscape. However, the number of black flies at whooping crane nests was consistently higher than the number captured in carbon‐dioxide traps. The carbon‐dioxide traps poorly described the presence/absence, population fluctuations, and periodicity of black flies at whooping crane nests. The weak performance of the carbon‐dioxide traps might have resulted from microhabitat differences between trap locations and nests or from Simulium annulus and Simulium johannseni using sensory cues in addition to carbon dioxide to find hosts. Choice of trapping techniques, therefore, depends on the information required for the particular study objectives.     

Use of medetomidine-zolazepam-tiletamine with and without atipamezole reversal to immobilize captive California sea lions

From June 1998 to August 1999, 39 California sea lions (Zalophus californianus) were immobilized at a rehabilitation center in northern California (USA) using medetomidine plus zolazepam and tiletamine (MZT), alone and in combination with isoflurane, with atipamezole reversal. Animals were given 70 microg/kg medetomidine with 1 mg/kg of a 1:1 solution of tiletamine and zolazepam intramuscularly. Mean (+/-SD) time to maximal effect was 5+/-3 min. At the end of the procedure, animals were given 200 microg/kg atipamezole intramuscularly. Immobilization and recovery times were, respectively, 28+/-18 and 9+/-7 min for 15 animals maintained with MZT alone and 56+/-47 and 9+/-6 min for 18 animals intubated and maintained with isoflurane. One mortality occurred during anesthesia. Other disadvantages of the MZT combination included some prolonged ataxia, weakness and disorientation during recovery. However, the use of MZT resulted in faster induction and a more reliable plane of anesthesia that was reversible with atipamezole and safer than other previously used intramuscular agents. Physiological parameters including heart rate, respiratory rate, temperature, pulse oximeter saturation, and end-tidal carbon dioxide were monitored.     

Effects of Methadone on the Minimum Anesthetic Concentration of Isoflurane,and Its Effects on Heart Rate,Blood Pressure and Ventilation during Isoflurane Anesthesia in Hens (Gallus gallus domesticus)

The aim of this study was to measure the temporal effects of intramuscular methadone administration on the minimum anesthetic concentration (MAC) of isoflurane in hens, and to evaluate the effects of the isoflurane-methadone combination on heart rate and rhythm, blood pressure and ventilation. Thirteen healthy adult hens weighing 1.7 ± 0.2 kg were used. The MAC of isoflurane was determined in each individual using the bracketing method. Subsequently, the reduction in isoflurane MAC produced by methadone (3 or 6 mg kg^-1, IM) was determined by the up-and-down method. Stimulation was applied at 15 and 30 minutes, and at 45 minutes if the bird had not moved at 30 minutes. Isoflurane MAC reduction was calculated at each time point using logistic regression. After a washout period, birds were anesthetized with isoflurane and methadone, 6 mg kg^-1 IM was administered. Heart rate and rhythm, respiratory rate, blood gas values and invasive blood pressure were measured at 1.0 and 0.7 isoflurane MAC, and during 45 minutes after administration of methadone once birds were anesthetized with 0.7 isoflurane MAC. Fifteen minutes after administration of 3 mg kg^-1 of methadone, isoflurane MAC was reduced by 2 (-9 to 13)% [logistic regression estimate (95% Wald confidence interval)]. Administration of 6 mg kg^-1 of methadone decreased isoflurane MAC by 29 (11 to 46)%, 27 (-3 to 56)% and 10 (-8 to 28)% after 15, 30 and 45 minutes, respectively. Methadone (6 mg kg^-1) induced atrioventricular block in three animals and ventricular premature contractions in two. Methadone caused an increase in arterial blood pressure and arterial partial pressure of carbon dioxide, while heart rate and pH decreased. Methadone, 6 mg kg^-1 IM significantly reduced isoflurane MAC by 30% in hens 15 minutes after administration. At this dose, methadone caused mild respiratory acidosis and increase in systemic blood pressure.     

四种麻醉药物对食蟹猴麻醉效果分析和选择应用

目的分析比对速眠新、氯胺酮、异氟烷和利多卡因4种不同麻醉药对食蟹猴的麻醉效果。方法总结实际工作中分别使用四种不同麻醉药物对食蟹猴作用的麻醉特点。结果速眠新、氯胺酮、异氟烷均能获得较好的麻醉效果,能满足不同手术、采样需要;局麻药利多卡因对食蟹猴麻醉的实际应用不理想。结论食蟹猴的手术及其他侵犯性操作等都应该考虑生物安全和动物福利要求,实行麻醉,但应根据食蟹猴实验内容要求和不同麻醉药特点选择合适的麻醉方法,确保人员和动物安全,实验结果不受影响。     

Ubiquitin metabolism affects cellular response to volatile anesthetics in yeast

To investigate the mechanism of action of volatile anesthetics, we are studying mutants of the yeast Saccharomyces cerevisiae that have altered sensitivity to isoflurane, a widely used clinical anesthetic. Several lines of evidence from these studies implicate a role for ubiquitin metabolism in cellular response to volatile anesthetics: (i) mutations in the ZZZ1 gene render cells resistant to isoflurane, and the ZZZ1 gene is identical to BUL1 (binds ubiquitin ligase), which appears to be involved in the ubiquitination pathway; (ii) ZZZ4, which we previously found is involved in anesthetic response, is identical to the DOA1/UFD3 gene, which was identified based on altered degradation of ubiquitinated proteins; (iii) analysis of zzz1Delta zzz4Delta double mutants suggests that these genes encode products involved in the same pathway for anesthetic response since the double mutant is no more resistant to anesthetic than either of the single mutant parents; (iv) ubiquitin ligase (MDP1/RSP5) mutants are altered in their response to isoflurane; and (v) mutants with decreased proteasome activity are resistant to isoflurane. The ZZZ1 and MDP1/RSP5 gene products appear to play important roles in determining effective anesthetic dose in yeast since increased levels of either gene increases isoflurane sensitivity whereas decreased activity decreases sensitivity. Like zzz4 strains, zzz1 mutants are resistant to all five volatile anesthetics tested, suggesting there are similarities in the mechanisms of action of a variety of volatile anesthetics in yeast and that ubiquitin metabolism affects response to all the agents examined.     

Patterns of univariate and multivariate plasticity to elevated carbon dioxide in six European populations of Arabidopsis thaliana

The impact of elevated carbon dioxide on plants is a growing concern in evolutionary ecology and global change biology. Characterizing patterns of phenotypic integration and multivariate plasticity to elevated carbon dioxide can provide insights into ecological and evolutionary dynamics in future human‐altered environments. Here, we examined univariate and multivariate responses to carbon enrichment in six functional traits among six European accessions of Arabidopsis thaliana. We detected phenotypic plasticity in both univariate and multivariate phenotypes, but did not find significant variation in plasticity (genotype by environment interactions) within or among accessions. Eigenvector, eigenvalue variance, and common principal components analyses showed that elevated carbon dioxide altered patterns of trait covariance, reduced the strength of phenotypic integration, and decreased population‐level differentiation in the multivariate phenotype. Our data suggest that future carbon dioxide conditions may influence evolutionary dynamics in natural populations of A. thaliana.     

Effects of isoflurane concentration on basic echocardiographic parameters of the left ventricle in rats

Transthoracic echocardiography (TTE) has become an important modality for the assessment of cardiac structure and function in animal experiments. The acquisition of echocardiographic images in rats requires sedation/anesthesia to keep the rats immobile. Commonly used anesthetic regimens include intraperitoneal or inhalational application of various anesthetics. Several studies have compared the effects of anesthetic agents on echocardiographic parameters in rats; however, none of them examined the effects of different concentrations of inhalational anesthetics on echocardiographic parameters. Accordingly, the aim of this study was to examine the effects of different concentrations of isoflurane used for anesthesia during TTE examination in rats on basic echocardiographic parameters of left ventricular (LV) anatomy and systolic function. TTE examinations were performed in adult male Wistar rats (n=10) anesthetized with isoflurane at concentrations of 1.5-3 %. Standard echocardiograms were recorded for off-line analysis. An absence of changes in basic echocardiographic parameters of LV anatomy and systolic function was found under isoflurane anesthesia using concentrations between 1.5-2.5 %. An isoflurane concentration of 3 % caused a small, but statistically significant, increase in LV chamber dimensions without a concomitant change in heart rate or fractional shortening. For the purpose of TTE examination in the rat, our results suggest that isoflurane concentrations 相似文献   

Rat aversion to isoflurane versus carbon dioxide

Some experts suggest that sedation of laboratory rodents with isoflurane before euthanasia with carbon dioxide (CO₂) is a humane alternative to euthanasia with CO₂ alone, but little research has compared aversion with these agents. Albino rats were tested in a light–dark box where they had the choice between remaining in a dark compartment filling with isoflurane or CO₂, or escaping to a lit compartment. Experiment 1 validated the procedure by confirming that rats responded to agent and light intensity. In experiment 2, 9/16 and 0/16 rats remained in the dark compartment until recumbent when initially exposed to isoflurane and CO₂, respectively. In experiment 3, more rats remained in the dark compartment until recumbent during initial (10/16) versus re-exposure (1/16) to isoflurane. These results indicate that initial exposure to CO₂ is more aversive than isoflurane, and that re-exposure to isoflurane is more aversive than initial exposure. We conclude that sedation with isoflurane is a refinement over euthanasia with CO₂ alone for rats that have not been previously exposed to inhalant anaesthetics.     

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.     

Elevated ornithine decarboxylase activity in the rat liver following exposure to halothane,enflurane and isoflurane

Exposure of rats to the volatile anesthetics, halothane, enflurane and isoflurane and low FIO₂ (0.8%) for two hours results in a transient induction of ODC appearing maximally four hours after exposure. Without the low oxygen accompanying the anesthetic or the low oxygen alone, no significant induction of ODC occurred. The concentration of anesthetic used to produce the ODC induction were 0.5% halothane, 1.5% enflurane and 1.4% isoflurane. Except for halothane, reducing the anesthetic concentration only slightly reduced the effect on ODC levels to control values. Reduction of halothane concentrations to 0.1% was required to reduce the values to control levels. Pretreatment of the animals with either cycloheximide or actinomycin D delayed the onset of ODC induction. The data support the fact that liver damage can occur in the absence of metabolism of the drug.     

Cues used in host‐seeking behavior by frog‐biting midges (Corethrella spp. Coquillet)

We investigated the role of carbon dioxide and host temperature in host attraction in frog‐biting midges (Corethrella spp). In these midges, females are known to use frog calls to localize their host, but the role of other host‐emitted cues has yet not been investigated. We hypothesized that carbon dioxide acts as a supplemental cue to frog calls. To test this hypothesis, we determined the responses of the midges to carbon dioxide, frog calls, and both cues. A significantly lower number of midges are attracted to carbon dioxide and silent traps than to traps broadcasting frog calls. Adding carbon dioxide to the calls does not increase the attractiveness to the midges. Instead, carbon dioxide can have deterrent effects on frog‐biting midges. Temperature of calling frogs is not a cue potentially available to the midges. Contrary to our hypothesis, there was no supplemental effect of carbon dioxide when presented in conjunction to calls. Midge host‐seeking behavior strongly depends on the mating calls emitted by their anuran host. Overall, non‐acoustic cues such as host body temperature and carbon dioxide are not important in long‐distance host location by frog‐biting midges.     

Vital signs monitoring during injectable and inhalant anesthesia in mice

Selecting the appropriate anesthetic protocol for the individual animal is an essential part of laboratory animal experimentation. The present study compared the characteristics of four anesthetic protocols in mice, focusing on the vital signs. Thirty-two male ddY mice were divided into four groups and administered anesthesia as follows: pentobarbital sodium monoanaesthesia; ketamine and xylazine combined (K/X); medetomidine, midazolam, and butorphanol combined (M/M/B); and isoflurane. In each group, rectal temperature, heart rate, respiratory rate, and O₂ saturation (SPO₂) were measured, and the changes over time and instability in these signs were compared. The anesthetic depth was also evaluated in each mouse, and the percentage of mice achieving surgical anesthesia was calculated. K/X anesthesia caused remarkable bradycardia, while the respiratory rate and SPO₂ were higher than with the others, suggesting a relatively strong cardiac influence and less respiratory depression. The M/M/B group showed a relatively lower heart rate and SPO₂, but these abnormalities were rapidly reversed by atipamezole administration. The pentobarbital group showed a lower SPO₂, and 62.5% of mice did not reach a surgical anesthetic depth. The isoflurane group showed a marked decrease in respiratory rate compared with the injectable anesthetic groups. However, it had the most stable SPO₂ among the groups, suggesting a higher tidal volume. The isoflurane group also showed the highest heart rate during anesthesia. In conclusion, the present study showed the cardiorespiratory characteristics of various anesthetic protocols, providing basic information for selecting an appropriate anesthetic for individual animals during experimentation.     

Molecular genetic analysis of volatile-anesthetic action.

The mechanism(s) and site(s) of action of volatile inhaled anesthetics are unknown in spite of the clinical use of these agents for more than 150 years. In the present study, the model eukaryote Saccharomyces cerevisiae was used to investigate the action of anesthetic agents because of its powerful molecular genetics. It was found that growth of yeast cells is inhibited by the five common volatile anesthetics tested (isoflurane, halothane, enflurane, sevoflurane, and methoxyflurane). Growth inhibition by the agents is relatively rapid and reversible. The potency of these compounds as yeast growth inhibitors directly correlates with their lipophilicity as is predicted by the Meyer-Overton relationship, which directly correlates anesthetic potency of agents and their lipophilicity. The effects of isoflurane on yeast cells were characterized in the most detail. Yeast cells survive at least 48 h in a concentration of isoflurane that inhibits colony formation. Mutants resistant to the growth-inhibitory effects of isoflurane are readily selected. The gene identified by one of these mutations, zzz4-1, has been cloned and characterized. The predicted ZZZ4 gene product has extensive homology to phospholipase A2-activating protein, a GO effector protein of mice. Both zzz4-1 and a deletion of ZZZ4 confer resistance to all five of the agents tested, suggesting that signal transduction may be involved in the response of these cells to volatile anesthetics.     

Antimicrobial efficiency of titanium dioxide‐coated surfaces

Aims: Development and evaluation of an antimicrobially active titanium dioxide coating. Methods and results: For this purpose, titanium dioxide coatings were applied to glass slides by using a sol‐gel method and then exposed to a light source. The antimicrobial efficiency was determined by a count reduction test for selected test strains (Aspergillus niger, Bacillus atrophaeus, Kocuria rhizophila), which were homogenously sprayed onto surface. The bacterial count of K. rhizophila was reduced by up to 3·3 log₁₀ on titanium dioxide samples within 4 h of UV‐A light exposure. Experiments with spore formers did not lead to any significant log reduction. A further aspect of this work was to evaluate the effect of selected parameters (relative humidity, inoculation density, radiation intensity) on the antimicrobial efficiency to gain knowledge for further optimization procedures. At a high relative humidity (85% r.h.), increased inactivation was observed for K. rhizophila (up to 5·2 log₁₀). Furthermore, a dependency of the antimicrobial effect on the radiation intensity and the inoculation density was identified. Conclusions: Antimicrobial surfaces and coatings based on titanium dioxide have the potential to effectively inactivate vegetative micro‐organisms. Significance and impact of the study: Knowledge about the antimicrobial efficiency of titanium dioxide was gained. This is a prerequisite for industrial applications to improve hygiene, food quality and safety.     

Overview movement as an index of anesthetic depth in humans and experimental animals

Anesthesia is used widely in animal research, but there are diverse opinions regarding acceptable anesthetic depth. Excessive anesthesia is associated with increased morbidity and mortality. Traditionally, researchers have been taught that animal movement during surgical and experimental procedures indicates that the animal is 'underanesthetized.' Complex movement, however, can be initiated and propagated within the spinal cord, with little input from supraspinal structures. For example, frogs with high spinal-cord transections still maintain the wiping reflex, whereby the hindlimb can move to the forelimb to wipe away a noxious stimulus. Rats that have been decerebrated can perform complex tasks, such as grooming. Brain-dead humans can have spontaneous movement of the arms, legs, and head. Consistent with these phenomena, emerging evidence suggests that, in anesthetized animals, movement in response to noxious stimulation is abolished primarily via anesthetic action in the spinal cord. When isoflurane, halothane, or thiopental is delivered selectively to the brain circulation in goats, substantially greater anesthetic concentrations in brain are needed to ablate movement, as compared with those required upon delivery of anesthetic to the entire body. Rats that have had a precollicular decerebration require the same isoflurane concentrations to prevent movement as compared to intact rats. Furthermore, data from both humans and animals indicate that memory and awareness are ablated at anesthetic concentrations that are < 50% of those needed to abolish movement. Collectively, these data indicate that animals can be anesthetized at depths that, although they do not abolish movement, still produce unconsciousness and amnesia.     

Anesthetic, preoperative and postoperative considerations for liver transplantation in swine

Perioperative care and anesthetic management of donor and recipient animals are crucial factors in studies involving experimental liver transplantation in the pig. Prevention of unacceptably high morbidity and mortality in the transplant recipients requires meticulous attention to anesthesia, preoperative and postoperative care. Liver transplant surgeries were performed using 15 pairs of pigs. Six of the transplant recipients were anesthetized with halothane plus 50% nitrous oxide (N2O) and oxygen (O2), and nine with isoflurane plus 50% N2O in O2. Arterial blood pressure, total anesthetic time, time of interruption of vena cava blood flow, and fluids administered, as well as length of survival were among the parameters measured and compared for the two groups. No deaths were attributed to either anesthetic technique. However, the isoflurane group had slightly higher blood pressure intraoperatively, better long range survival, and relatively rapid recoveries when compared to the halothane group. Because of these findings and the reported low rate of isoflurane metabolism and low resultant potential for formation of toxic metabolites when compared to halothane metabolism, we have elected to use the isoflurane-50% N2O regimen for this procedure.