Pituitary-adrenocortical axis, serum serotonin and biochemical response after halothane or isoflurane anaesthesia in rabbits

To document the changes in serum serotonin, adrenocorticotrophic hormone (ACTH), corticosterone levels and select biochemical parameters in response to inhalant anaesthesia, 20 New Zealand White (NZW) rabbits were assigned to two treatment groups: halothane and isoflurane. Induction of anaesthesia was achieved using a face mask (3.5% halothane and 4.5% isoflurane in oxygen) followed by endotracheal intubation and maintenance of anaesthesia for 30 min (1.5% halothane and 2.5% isoflurane in oxygen). Blood samples were obtained before anaesthetic induction, and at 1, 10, 30, 60, 120 min and 24, 48 and 72 h after endotracheal intubation. Serum serotonin and corticosterone levels were measured by competitive enzyme immunoassay, ACTH by radioimmunoassay. Serum glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), blood urea nitrogen (BUN) and creatinine levels were measured using an automated analyser. Significant increases in serum ACTH and corticosterone levels occurred after halothane administration while serum serotonin levels did not change. An increase in serum corticosterone and serotonin levels occurred in the isoflurane group but no changes in ACTH concentrations were detected. Administration of halothane significantly increased serum glucose, ALT, AST, BUN and creatinine levels. After isoflurane administration, there was a significant increase in serum glucose, AST, BUN and creatinine levels. Based on these results, halothane stimulates the hypothalamic-pituitary-adrenal axis to a greater extent than isoflurane, but isoflurane increases serum serotonin levels. Both anaesthetic agents alter select biochemical parameters. These results should be taken into account when blood samples are evaluated in treated isoflurane or halothane anaesthetized rabbits.     

A modified anaesthetic induction chamber for rats.

The anaesthetic induction chamber for rats described in this paper has been designed for use in conjunction with a controlled delivery of halothane/O2 mixture and an anaesthetic scavenger system. Using this system rapid induction of anaesthesia is achieved using low levels of anaesthetic vapour without risk to the operator.     

Combining Nitrous Oxide with Carbon Dioxide Decreases the Time to Loss of Consciousness during Euthanasia in Mice — Refinement of Animal Welfare?

Carbon dioxide (CO(2)) is the most commonly used euthanasia agent for rodents despite potentially causing pain and distress. Nitrous oxide is used in man to speed induction of anaesthesia with volatile anaesthetics, via a mechanism referred to as the "second gas" effect. We therefore evaluated the addition of Nitrous Oxide (N(2)O) to a rising CO(2) concentration could be used as a welfare refinement of the euthanasia process in mice, by shortening the duration of conscious exposure to CO2. Firstly, to assess the effect of N(2)O on the induction of anaesthesia in mice, 12 female C57Bl/6 mice were anaesthetized in a crossover protocol with the following combinations: Isoflurane (5%)+O(2) (95%); Isoflurane (5%)+N(2)O (75%)+O(2) (25%) and N(2)O (75%)+O(2) (25%) with a total flow rate of 3 l/min (into a 7 l induction chamber). The addition of N(2)O to isoflurane reduced the time to loss of the righting reflex by 17.6%. Secondly, 18 C57Bl/6 and 18 CD1 mice were individually euthanized by gradually filling the induction chamber with either: CO(2) (20% of the chamber volume.min-1); CO(2)+N(2)O (20 and 60% of the chamber volume.min(-1) respectively); or CO(2)+Nitrogen (N(2)) (20 and 60% of the chamber volume.min-1). Arterial partial pressure (P(a)) of O(2) and CO(2) were measured as well as blood pH and lactate. When compared to the gradually rising CO(2) euthanasia, addition of a high concentration of N(2)O to CO(2) lowered the time to loss of righting reflex by 10.3% (P<0.001), lead to a lower P(a)O(2) (12.55 ± 3.67 mmHg, P<0.001), a higher lactataemia (4.64 ± 1.04 mmol.l(-1), P = 0.026), without any behaviour indicative of distress. Nitrous oxide reduces the time of conscious exposure to gradually rising CO(2) during euthanasia and hence may reduce the duration of any stress or distress to which mice are exposed during euthanasia.     

建立新生大鼠吸入麻醉模型及异氟醚对其海马凋亡的影响

目的:建立新生大鼠吸入麻醉模型并探讨吸入麻醉药异氟醚对其海马凋亡的影响。方法:Penlon Prima SP麻醉机、异氟醚挥发罐及自制带进出气口的麻醉小室。共55只7日龄的SD大鼠用于实验。将其中35只大鼠随机分为7组(n=5)。实验组(Ⅰ-Ⅵ组)异氟醚挥发罐刻度分别为0.125%,0.25%,0.5%,1%,1.5%,2%;新生大鼠置于自制密封麻醉小室内,分别通入含上述异氟醚浓度的混合气体。对照组(第Ⅶ组)给予未混合异氟醚的30%的氧气。将小室安放于37℃恒温箱内。调节气体流量2L/min。实验组于通入气体5,10,15,30,90,180,360 min(T1-7)时于小室出口处抽取10mL气体,采用气相色谱法测定麻醉小室内异氟醚浓度。于通入气体360 min(T7)自新生大鼠左心室采血行血气分析;另取SD大鼠20只,随机分为对照组(C组,n=10),1.5%异氟醚组(I组,n=10),按上述方法建立异氟醚吸入麻醉模型,麻醉结束后2h处死大鼠,采用免疫组织化学法观察C组和I组大鼠大脑海马区Active caspase-3的表达。结果:①麻醉小室出口异氟醚浓度(Y)与麻醉机挥发罐异氟醚浓度(X)的直线回归方程为Y=1.5472X-0.0575(r=0.9993)。②血气分析结果显示:Ⅰ-Ⅵ组与Ⅶ组血气分析组间差异无统计学意义(P0.05)。③免疫组化结果显示:与C组相比,I组大鼠海马Active caspase-3明显增加,差异有统计学意义(P0.05)。结论:通过麻醉机、异氟醚挥发罐及自制密封带进出气口的麻醉小室成功建立了新生大鼠异氟醚麻醉模型;为进一步研究异氟醚及相关吸入麻醉药对突触发生期的神经毒性提供了实验基础。     

Long-term anaesthesia using inhalatory isoflurane in different strains of mice-the haemodynamic effects

The aim of this study was to establish a simple and safe method of anaesthesia for intravital microcirculatory observations in small laboratory animals. The usefulness of isoflurane inhalation anaesthesia has been investigated in different strains of mice commonly used in experimental medicine. These were the hairless (hr/hr, n = 12), the BALB/c (n = 12) and the nude mouse (nu/nu, n = 3). Anaesthesia was maintained by mask inhalation of isoflurane vaporized at concentrations of up to 4% in the induction phase, at 1.5% during acute surgical procedures and at 0.8-1.3% during prolonged experimental observations. Isoflurane was vapoured in a N(2)O/O(2) mixture and saturated with 32-36% F(i)O(2). During observations the body temperature was kept constant at 37 degrees C. The tail artery was cannulated for monitoring of mean arterial blood pressure (MAP) and heart rate (HR). To maintain the body fluid balance, isotonic saline was administered at a constant rate of 0.2 ml/h. Arterial blood samples were drawn for blood-gas analysis at the end of the experiments. All animals survived the anaesthesia protocol lasting between 3 and 6.5 h. During isoflurane inhalation, no breathing complications or changes in systemic circulatory parameters were observed. Mean values of MAP and HR were 79+/- 3 mmHg and 486+/- 13 min(-1), respectively, over the entire observation period. A moderate acidosis was recorded in animals under isoflurane anaesthesia, with alterations of arterial blood pH, p(a)O(2) and pCO(2) values (7.29+/- 0.06, 130+/- 19 mmHg and 35.6+/- 4.7 mmHg, respectively). In conclusion, inhalation anaesthesia with isoflurane is useful for experimental studies in the mouse due to (1) the simplicity of administration of the anaesthetic, (2) the rapid induction of anaesthesia, (3) easy control of the depth of anaesthesia, (4) the low percentage of complications, and (5) stable MAP and HR during observations lasting several hours. The proposed technique is especially suitable for observations of the microcirculation under intravital fluorescence microscopy.     

Isoflurane with morphine is a suitable anaesthetic regimen for embryo transfer in the production of transgenic rats

During our initial attempts to produce transgenic rats, we found that an anaesthetic combination typically used for embryo transfer (intramuscular injection of ketamine [90 mg/kg] with xylazine [10 mg/kg]) yielded extensive variation in both the depth and length of anaesthesia. In the present prospective study, we compared the reproductive outcomes afforded by using either isoflurane (5% for induction, 2% for maintenance, carried in 2 l/min of oxygen) with morphine (5 mg/kg s.c., given immediately after isoflurane induction) or ketamine/xylazine in adult (250-300 g), pseudopregnant Sprague-Dawley rats. Each animal was anaesthetized with either isoflurane/morphine or ketamine/xylazine, after which 30 microinjected eggs were transferred into the left uterine horn. The mean pregnancy rate for isoflurane/morphine (15%) was 50% greater than that achieved with ketamine/xylazine (10%). The mean number of live pups (just over five per litter) was comparable for both regimens. All rats given isoflurane/morphine quickly achieved a surgical depth of anaesthesia and experienced a rapid postoperative recovery (3-5 min). In contrast, 25% of rats injected with ketamine/xylazine did not reach a depth of anaesthesia within 10 min that was sufficient for laparotomy, and all that were anaesthetized successfully required an extended postoperative recovery period (60-90 min). These data show that isoflurane/morphine is well tolerated by microinjected embryos and suggest that its use during embryo transfer may provide a means for both reducing the number of pseudopregnant females used and increasing the speed with which rat transgenic projects are completed.     

The haemodynamic and catecholamine response to xenon/remifentanil anaesthesia in Beagle dogs

The noble gas xenon seems to have minimal cardiovascular side-effects and so may be an ideal anaesthetic agent when investigating cardiovascular physiology. In comparison with standard modern anaesthetics, we investigated the haemodynamic and hormonal effects of xenon in Beagle dogs. After a 30 min baseline period, anaesthesia was induced with propofol and maintained with either (1) 1.2% isoflurane/70% nitrous oxide (N(2)O), (2) 0.8% isoflurane/0.5 microg/kg/min remifentanil or (3) 63% xenon/0.5 microg/kg/min remifentanil (n = 6 per group). Haemodynamics were recorded and blood samples taken before and 60 min after induction. Mean arterial blood pressure (MAP) was higher in conscious dogs than during isoflurane/N(2)O (86 +/- 2 vs. 65 +/- 2 mmHg, mean +/- SEM) and isoflurane/remifentanil anaesthesia (95 +/- 2 vs. 67 +/- 3 mmHg), whereas MAP did not decrease significantly in response to xenon/remifentanil anaesthesia (96 +/- 4 vs. 85 +/- 6 mmHg). Bradycardia was present during isoflurane/remifentanil (54 +/- 2/min) and xenon/remifentanil (40 +/- 3/min), but not during isoflurane/N(2)O anaesthesia (98 +/- 3/min, P < 0.05). Xenon/remifentanil anaesthesia induced the highest reduction in cardiac output (CO) (-61%), and the highest increase in systemic vascular resistance (+120%) among all treatment groups (P < 0.05). A simultaneous increase in endogenous adrenaline and noradrenaline concentrations could only be observed in the xenon/remifentanil group, whereas angiotensin II and vasopressin concentrations increased in all groups. In conclusion, xenon/remifentanil anaesthesia maintains MAP but reduces heart rate and CO and is associated with a considerable stimulation of vasopressor hormones in Beagle dogs. Therefore, xenon/remifentanil exerts a new quality of adverse haemodynamic effects different from volatile anaesthetics and may not perform better during studies of cardiovascular physiology.     

Recovery index, attentiveness and state of memory after xenon or isoflurane anaesthesia: a randomized controlled trial

Background

Org 25435 is a new water-soluble alpha-amino acid ester intravenous anaesthetic which proved satisfactory in animal studies. This study aimed to assess the safety, tolerability and efficacy of Org 25435 and to obtain preliminary pharmacodynamic and pharmacokinetic data.

Methods

In the Short Infusion study 8 healthy male volunteers received a 1 minute infusion of 0.25, 0.5, 1.0, or 2.0 mg/kg (n = 2 per group); a further 10 received 3.0 mg/kg (n = 5) or 4.0 mg/kg (n = 5). Following preliminary pharmacokinetic modelling 7 subjects received a titrated 30 minute Target Controlled Infusion (TCI), total dose 5.8-20 mg/kg.

Results

Within the Short Infusion study, all subjects were successfully anaesthetised at 3 and 4 mg/kg. Within the TCI study 5 subjects were anaesthetised and 2 showed signs of sedation. Org 25435 caused hypotension and tachycardia at doses over 2 mg/kg. Recovery from anaesthesia after a 30 min administration of Org 25435 was slow (13.7 min). Pharmacokinetic modelling suggests that the context sensitive half-time of Org 25435 is slightly shorter than that of propofol in infusions up to 20 minutes but progressively longer thereafter.

Conclusions

Org 25435 is an effective intravenous anaesthetic in man at doses of 3 and 4 mg/kg given over 1 minute. Longer infusions can maintain anaesthesia but recovery is slow. Hypotension and tachycardia during anaesthesia and slow recovery of consciousness after cessation of drug administration suggest this compound has no advantages over currently available intravenous anaesthetics.     

异氟醚预处理对小鼠全身缺氧损伤保护作用的量效关系

目的:探讨异氟醚预处理对小鼠耐受全身低氧损伤保护作用的浓度效应关系。方法:6-7wk健康雄性C57小鼠100只(n=20),分成5组:Iso0.5组、Iso1.0组、Iso1.5组、Iso2.0组分别吸入0.5%、1.0%、1.5%和2.0%异氟醚30min;对照组吸入相同时间的空气。预处理后洗脱30min,放入5%O2低氧环境中持续20min,记录在20min内小鼠的生存率和生存时间,测量存活小鼠复氧24h后脑,肺和心的组织含水量。结果:Iso1.0组(70%)和Iso1.5组(75%)的生存率分别与对照组(30%)相比,明显提高(P<0.05);Iso1.5组的生存率明显高于Iso2.0%组(44%()P<0.05);其余各组两两比较无统计学差异。Iso1.0组(17.87min)和Iso1.5组(17.93min)的平均生存时间分别与对照组(13.83min)相比(P<0.05),有显著性差异(P<0.05)。其余各组两两比较,差异不明显。结论:1.0%和1.5%异氟醚预处理可以产生较好的保护作用。     

Anaesthesia and post-operative analgesia following experimental surgery in laboratory rodents: are we making progress?

Current attitudes to the use of animals in biomedical research require that any pain or distress should be minimised. This can often be achieved by the use of appropriate anaesthetic and analgesic regimens. There, is however, little information on the peri-operative regimens used. A literature review was conducted to estimate how commonly analgesics are administered to laboratory rodents, the most widely used species of laboratory animals, and to assess the anaesthetic regimens employed. Studies describing potentially painful experimental procedures involving rodents were identified from peer-reviewed journals published from 1990 to 1992 and from 2000 to 2002. In papers published between 2000 and 2002, if analgesic administration was not specified, the institutional veterinary surgeons or authors of the papers were contacted by e-mail to obtain additional information on analgesic use. From 1992 to 2002, there was an increase in the reported prevalence of analgesic administration to laboratory rodents from 2.7% to 19.8%. Although the use of analgesics has increased over the past ten years, the overall level of post-operative pain relief for laboratory rodents is still low. Anaesthetic methodology changed markedly between the two time-periods sampled. Notably, there was an increase in the use of isoflurane and of injectable anaesthetic combinations such as ketamine/xylazine, whereas the use of ether and methoxyflurane decreased.     

Immobilisation of free-living Weddell seals Leptonychotes weddellii using midazolam and isoflurane

Eleven lactating female Weddell seals were immobilised using inhaled isoflurane and oxygen, having initially been sedated using an intramuscular injection of midazolam. The seals were selected from colonies in Long Fjord, East Antarctica. Isoflurane was delivered using a precision, out-of-circle vaporiser in a portable, heated, semi-closed circle system anaesthetic machine. Induction time (time from injection of midazolam to detected maximal effect of midazolam) ranged from 12 min to 29 min. The maximal effect of midazolam was assessed as being either moderate sedation (n=9) or heavy sedation (n=2), and the maximal effect of inhaled isoflurane and oxygen was assessed as being light anaesthesia (n=11). The level of chemical restraint achieved using this combination allowed attachment of heart rate monitoring units and collection of biological samples. Recovery time ranged from 1 min to 11 min. The anaesthetic regime proved a practical, safe and reliable method for the immobilisation of lactating Weddell seals under conditions of low environmental temperature.     

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   

The use of clove oil to induce anaesthesia,and its effects on blood chemistry,in Lates niloticus from Lake Victoria,Uganda

The efficacy of clove oil as an anaesthetic and its effects on blood parameters in Nile perch Lates niloticus were evaluated in 2010. Clove oil concentrations of 49.3, 73.9 and 98.5?mg l^?1 induced anaesthesia in <3?min, while the average recovery time from anaesthesia was 11?min 22 s. The optimal oil clove oil concentration was 49.3?mg l^?1, inducing anaesthesia in 4?min 33 s, with recovery in 3?min 31 s. No stress response was elicited. Clove oil at a concentration of 24.6?mg l^?1 was an effective sedative, whereas a concentration of 49.3?mg l^?1 was sufficient for measuring fish and stripping gametes. A concentration of 73.9?mg l^?1 induced anaesthesia within 4?min and fish recovered in 10?min. Therefore, clove oil was an effective anaesthetic and sedative for the handling of Nile perch within a mass range of 0.4–12?kg fish^?1.     

Cardiovascular responses of Chinook salmon (Oncorhynchus tshawytscha) during rapid anaesthetic induction and recovery

The effects of three anaesthetics on induction and recovery were compared in Chinook salmon (Oncorhynchus tshawytscha). Heart rate (HR), cardiac output (Q), dorsal aortic pressure (DAP) and stroke volume (SV) were measured in minimally disturbed salmon during 5 min anaesthetic inductions with approximately equi-potent concentrations of MS222 (100 ppm), metomidate (6-10 ppm) and AQUI-S (60 ppm). MS222 induction caused a steady decline in DAP only, while metomidate induction did not affect any cardiovascular variable. AQUI-S caused a biphasic response, and within 2 min had depressed HR, Q, DAP and SV by between 20 and 50%. In the final 3 min HR returned to pre-anaesthesia levels, and Q and SV climbed to greater than pre-anaesthesia levels. Blood samples taken pre- and post-anaesthesia showed all inductions caused hypoxaemia (oxygen partial pressure of dorsal aortic blood (PaO2): MS222 47 mmHg, metomidate 35 mmHg, AQUI-S 21 mmHg). Haematocrit and plasma adrenaline and noradrenaline levels increased slightly in AQUI-S treated fish only. Recovery was monitored for 6 h post-anaesthesia, and was similar for each anaesthetic. All cardiovascular variables had returned to control levels within 5 min with the exception of DAP, which was initially slightly elevated (up to 20%) but returned to control values within 30 min. Anaesthesia is usually preceded by handling. Netting prior to anaesthesia caused significant increases in HR, Q and SV, which masked any anaesthetic dependent effects. Recovery from anaesthesia combined with surgery was also generally anaesthetic independent and recovery was prolonged, compared to anaesthesia alone. These data suggest limiting fish handling/manipulation is more important in minimising cardiovascular disturbance than the choice of anaesthetic.     

Tolazoline antagonises ketamine–xylazine anaesthesia in an endangered Black buck (<Emphasis Type="Italic">Antilope cervicapra</Emphasis>)

Seventy-seven anaesthetic events were carried out in 22 captive adult Black bucks (Antilope cervicapra) of either sex with a combination of 2 mg kg⁻¹ ketamine hydrochloride with 0.25 mg kg⁻¹ xylazine hydrochloride using a dart delivered from a blowpipe. Randomised anaesthetised animals received an intravenous injection of either yohimbine hydrochloride (0.125 or 0.25 mg kg⁻¹) or tolazoline hydrochloride (1 or 2 mg kg⁻¹) after 30–40 min of anaesthesia to antagonise the anaesthetic effects. Ketamine–xylazine induced smooth, rapid and reliable anaesthesia within 5–7 min of darting with no clinical adverse effects and causalities during or post-anaesthesia. Yohimbine failed to antagonise the anaesthetic effects of ketamine–xylazine in the Black buck. On the other hand, tolazoline was found to be very effective in hastening recovery in dose-dependent manner within 0.5–1.5 min. This study documents the first report of ketamine–xylazine anaesthesia and its antagonism by tolazoline in captive Black buck.     

Metomidate, etomidate and fentanyl as injectable anaesthetic agents in mice

Light surgical anaesthesia lasting 12-15 min was produced by metomidate at 50 mg/kg and by etomidate at 30 mg/kg after intraperitoneal injection. Full surgical anaesthesia lasting about 160 min was achieved after subcutaneous injection of a metomidate-fentanyl mixture (60 mg/kg: 0.06 mg/kg) and this proved superior to etomidate-fentanyl given subcutaneously or intraperitoneally. It was concluded that metomidate-fentanyl is superior to pentobarbitone and tribromoethanol as an injectable anaesthetic for mice.     

Analysis of cryoprotectant, cooling rate and in situ dilution using conventional freezing or vitrification for cryopreserving sheep embryos

Two studies were conducted to evaluate the influence of cryoprotectant, cooling rate, container and cryopreservation procedure on the post-thaw viability of sheep embryos. In Study 1, late morula- to blastocyst-stage embryos were exposed to 1 of 10 cryoprotectant (1.5 M, glycerol vs propylene glycol)-plunge temperature treatments. Embryos were placed in glass ampules and cooled at 1 degrees C/min to -5 degrees C, seeded and further cooled at 0.3 degrees C/min to -15, -20, -25, -30 and -35 degrees C before rapid cooling by direct placement in liquid nitrogen (LN(2)). Post-thaw embryo viability was improved (P<0.01) when embryos were cooled to at least -30 degrees C before LN(2) plunging. Although there were no overt differences in embryo viability between cryoprotectant treatments (each resulted in live offspring after embryo transfer), there was a lower (P<0.01) incidence of zona pellucida damage using propylene glycol (4%) compared to glycerol (40%). In Study 2, embryos were equilibrated in 1.5 M propylene glycol or glycerol or a vitrification solution (VS3a). Embryos treated in propylene glycol or glycerol were divided into ampule or one-step((R)) straw treatments, cooled to -6 degrees C at 1 degrees C/min, seeded, cooled at 0.5 degrees C/min to -35 degrees C, held for 15 minutes and then transferred to LN(2). Embryos vitrified in the highly concentrated VS3a (6.5 M glycerol + 6% bovine serum albumin) were transferred from room air to LN(2) vapor, and then stored in LN(2). Propylene glycol- and glycerol-treated embryos in straws experienced lower (P<0.05) degeneration rates (27%) and yielded more (P<0.05) hatched blastocysts (73 and 60%, respectively) at 48 hours of culture and more (P<0.05) trophoblastic outgrowths (67 and 53%, respectively) after 1 week than vitrified embryos (47, 40 and 20%, respectively). In vitro development rate for VS3a-treated embryos was similar (P>0.10) to that of ampule controls, which had fewer (P<0.05) expanded blastocysts compared to similar straw treatments. Live offspring were produced from embryos cryopreserved by each straw treatment (propylene glycol, 3 of 7; glycerol, 1 of 7; VS3a, 2 of 7). In summary, freeze-preservation of sheep embryos was more effective in one-step straws than glass ampules and propylene glycol tended to be the optimum cryoprotectant. Furthermore, these findings demonstrate, for the first time, the biological competence of sheep embryos cryopreserved using the simple and rapid procedure of vitrification.     

Induction of anaesthesia with desflurane and isoflurane in the rabbit

The characteristics of two techniques of face-mask induction of desflurane anaesthesia (rapid or slow) were compared with the effects of slow isoflurane induction in five New Zealand White (NZW) rabbits. Slow induction used stepwise increments in vapour setting of 2% for desflurane and 0.5% for isoflurane at 30 s intervals. All animals were anaesthetized using each technique according to a randomized block design with one week between treatments. Observations were made of the quality of induction (any struggling or periods of apnoea) and the latency to, and the duration of loss of the righting and toe pinch reflexes recorded. Changes in respiratory rate, arterial blood gas and cardiovascular parameters were also recorded. Induction and recovery times were shorter with rapid desflurane induction in comparison to isoflurane (loss of righting reflex: 139+/-27 s cf. 205+/-48 s), but both techniques were associated with struggling and long periods of apnoea (> 1 min) during the first 4 min after administration. During this period a significant degree of bradycardia, hypercapnia and hypoxaemia occurred with both techniques, but these and the subsequent effects of rapid desflurane administration were less severe than with isoflurane. Slow induction with desflurane was tolerated best, with little or no deleterious behavioural or physiological effects, however excessively prolonged induction times (loss of righting reflex 337+/-160 s) limits the application of this method. Desflurane, administered rapidly, appears to be a more suitable agent than isoflurane. However, as with isoflurane, anaesthesia should only be induced following oxygen supplementation.     

A method for hyperthermic treatment of mouse skin.

The Sencar mouse skin system is a recognized model for tumour initiation, promotion and progression. The current interest in the effect of hyperthermia on this multi-stage tumorigenesis model prompted the need for a technique to accurately heat a section of dorsal skin of a large number of mice for 30 min per heat treatment. In the technique described, experimental groups of 25 female Sencar mice were treated at 7-8 weeks of age under general methoxyflurane anaesthesia. Treatment consisted of the application of initiating and/or promoting agents with or without hyperthermia. For hyperthermic skin treatments, each group of mice was placed onto a platform in a water bath so that the dorsal skin of the mice was in contact with 44 degrees C temperature controlled water.     

General anesthesia of infant mice by isoflurane inhalation for medium-duration surgery.

In this report we describe a means of general anesthesia for medium-duration (i.e., 20 to 60 min) surgery of infant mice. We tested isoflurane inhalation (2.0% isoflurane in air or oxygen during induction, and 1.5% after surgical anesthesia) anesthesia of 6-to 10-day-old C57BL/6JJcl mice and obtained safe, effective, and reproducible results.