An outbreak of avian malaria in captive yellowheads/mohua (Mohoua ochrocephala).

CASE HISTORY: Eight mohua, or yellowheads (Mohoua ochrocephala), were held in a large open aviary over the summer months of 2003-2004, following their capture for captive breeding purposes. Two birds died of transportation trauma shortly after arrival, one became ill and died a month later, and another four died within a 2-week period in February 2004. The eighth bird also became ill at this time but survived for a year following treatment with chloroquine and doxycycline. CLINICAL AND PATHOLOGICAL FINDINGS: The affected birds were depressed, lethargic and dyspnoeic. Necropsy of three birds showed a slightly pale and swollen liver and spleen. Impression smears of the liver of one bird revealed schizonts resembling Plasmodium spp. within the cytoplasm of many hepatocytes, which was confirmed histopathologically. Similar protozoal organisms were seen within splenic histiocytes and pulmonary endothelial cells of 5/6 birds. Electron microscopy identified these as protozoal schizonts containing merozoites of similar size and structure to those of Plasmodium spp. DIAGNOSIS: The birds were infected with a protozoal haemoparasite resembling Plasmodium spp.; asexual stages within hepatocytes and endothelial cells of the lung and spleen were typical of this organism. CONCLUSIONS AND CLINICAL RELEVANCE: The mohua captured from west Otago were highly susceptible to avian malaria as they came from an isolated population that was likely to be naïve and have had no previous contact with this organism. The birds were probably infected by bites from mosquitoes feeding off local populations of blackbirds subsequently found to be infected with Plasmodium spp.

Field investigation of advanced filtration for phosphorus removal from constructed treatment wetland effluents.

Three sorptive media, blast furnace slag, cement clinker, and gravel were investigated for their capacity to remove phosphorus in a subsurface flow constructed treatment wetland post-treatment filter. Three filters were designed: two containing a mixture of either slag and gravel or clinker and gravel, and one with gravel only as the control filter. They were installed as a demonstration polishing treatment step to a constructed treatment wetland treating residential wastewater collected from 137 mobile home units at the Sunny Creek Estates Mobile Home Park. The filters were commissioned during the summer of the field season, with the data gathering taking place over a period of one year. The slag filter consistently had the lowest outflow dissolved phosphorus concentrations (0.27 +/- 0.08 mg l(-1), n=21), whereas the clinker filter had the highest outflow dissolved phosphorus concentrations (0.72 +/- 0.20 mg l(-1), n=23). The clinker filter performed well below expectations based on previous laboratory investigations, possibly due to lower pH conditions encountered in the field study. All of the filters maintained relatively constant outflow concentrations of phosphorus below 1 mg l(-1), despite varying input conditions and environmental factors such as temperature and phosphorus loading, and the occurrence of net export of phosphorus from the wetland. Net export of phosphorus from the filters occurred in the winter months, which was attributed to the decrease in input phosphorus concentrations below the maintained outflow concentrations (leading to phosphorus desorption), rather than cold temperatures or failure of the filter. Although the exact mechanisms of phosphorus removal are still under investigation, the results from this field study allowed for recommendations to be made for improving phosphorus removal at the Sunny Creek Estates constructed treatment wetland, in addition to providing valuable information for new and existing constructed treatment wetlands in cold climate areas.

Laboratory animal medicine education and training in the uniformed services: a brief history.

The history of laboratory animal medicine education and training for uniformed (U.S. Army, U.S. Air Force, and U.S. Public Health Service) veterinarians is reviewed from the beginnings in 1961 at the U.S. Air Force School of Aerospace Medicine. Of the 636 currently listed diplomates of the American College of Laboratory Animal Medicine, at least 208 (32.7%) received specialty training or experience in this discipline while on extended active duty in one of the uniformed services. The evolving "climate" has led to the establishment of the most recent program within the uniformed services at the Uniformed Services University of the Health Sciences in Bethesda, Maryland.

Cryptosporidiosis: an outbreak associated with drinking water despite state-of-the-art water treatment.

OBJECTIVE: To determine the magnitude and source of an outbreak of cryptosporidiosis among persons with human immunodeficiency virus (HIV) infection and to determine whether the outbreak extended into the immunocompetent population. DESIGN: Matched case-control study and environmental investigation. SETTING: Clark County, Nevada. PARTICIPANTS: Adults with HIV infection (36 case-patients with laboratory-confirmed Cryptosporidium parvum infection and 107 controls), matched by physician or clinic and by CD4+ cell count category. MEASUREMENTS: Potential risk factors for infection, death rates, and data on water quality. RESULTS: Review of surveillance and microbiology records identified 3 cases of cryptosporidiosis in 1992 (the first year that cryptosporidiosis was reportable in Nevada), 23 cases in 1993, and 78 cases in the first quarter of 1994. Of the 78 laboratory-confirmed cases in the first quarter of 1994, 61 (78.2%) were in HIV-infected adults. Of these 61 adults, 32 (52.5%) had died by 30 June 1994; at least 20 of the 32 (62.5%) had cryptosporidiosis listed on their death certificates. In the case-control study, persons who drank any unboiled tap water were four times more likely than persons who drank only bottled water to have had cryptosporidiosis (odds ratio, 4.22 [95% Cl, 1.22 to 14.65]; P = 0.02). For persons with CD4+ cell counts less than 100 cells/mm3, the association between tap water and cryptosporidiosis was even stronger (odds ratio, 13.52 [Cl, 1.78 to 102.92]; P = 0.01). Additional data indicate that this outbreak also affected persons who were not infected with HIV. No elevated turbidity values or coliform counts and no Cryptosporidium oocysts were found in testing of source (Lake Mead) or finished (treated) water during the study period, but so-called presumptive oocysts were intermittently found after the investigation in samples of source water, filter backwash, and finished water. CONCLUSIONS: A cryptosporidiosis outbreak was associated with municipal drinking water, despite state-of-the-art water treatment and water quality better than that required by current federal standards. This outbreak highlights the importance of surveillance for cryptosporidiosis and the need for guidelines for the prevention of water-borne-Cryptosporidium infection among HIV-infected persons.

Clinical pathologic findings of Propionibacterium acnes endophthalmitis.

The autors presented two typical cases of patients who were infected with Propionibacterium acnes (P. acnes) after intraocular lens implantation. The patients were treated successfully by the removal of the intraocular lens and the residual lens capsule, and the administration of intravitreal vacomycin. The histopathology illustrated numerous prokaryote bacilli surrounding the lens material without inflammatory reaction. The thickened bacterial cell wall structure may relate to the resistance of P. acnes killing and degradation by the host neutrophils and macrophages. Complete removal of the lens material which may sequester the bacterial growth in the eye is important to eradicate P. acnes endophthalmitis.

Topical anesthetic-induced methemoglobinemia and sulfhemoglobinemia in macaques: a comparison of benzocaine and lidocaine.

Benzocaine (BNZ) and lidocaine (LC) are commonly used topical (spray) anesthetics approved for use in humans. Benzocaine has structural similarities to methemoglobin (MHb)-forming drugs that are current candidates for cyanide prophylaxis, while LC has been reported to increase MHb in man. In this study, we compared MHb and sulfhemoglobin (SHb) production in three groups of Macaques (Chinese rhesus and Indian rhesus (Macaca mulatta) and pig-tailed macaques (Macaca nemestrina)) after exposure to BNZ and LC. Formation of SHb, unlike MHb, is not thought to be reversible and therefore is considered to be of greater toxic significance. Both MHb and SHb levels were measured periodically on a CO-Oximeter. All rhesus macaques (n = 8) were administered an intratracheal/intranasal) dose of 56 mg (low dose) or 280 mg (high dose) of BNZ or 40 mg of LC in a randomized cross-over design (all animals received all three treatments). Pig-tailed macaques (n = 6) were given an intranasal dose of 56 mg of BNZ and 40 mg of LC. As no differences in the peak MHb or time to peak (mean +/- SD) were observed among the three macaque subspecies, the data were pooled. Lidocaine did not cause MHb or SHb formation above baseline in any monkey. In contrast, all monkeys (n = 14) had a significant elevation in peak MHb formation after 56 mg of BNZ, which ranged from 4.0% to 19.4% with an average of 8.6 +/- 4.0% (mean +/- SD), with peak MHb levels reached at 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Marked activation delay caused by ischemia initiated after regional K+ elevation in in situ pig hearts.

BACKGROUND: Conduction mediated by the slow inward (Ca2+) current occurs in vitro under specific experimental conditions but has not been documented in ventricular muscle in vivo during regional myocardial ischemia, perhaps because certain constituents of ischemia (including hypoxia and acidosis) may inhibit the Ca2+ current in this setting. We hypothesized that slow conduction mediated by the Ca2+ current could occur during acute ischemia in situations in which the extracellular K+ rise was more marked relative to the degree of acidosis, as may occur at ischemic boundaries. METHODS AND RESULTS: In open-chest, anesthetized swine, an arterial shunt from the carotid artery to the mid-left anterior descending coronary artery was created through which a solution of KCl was infused to raise extracellular K+ ([K+]e) to approximately 9.4 mmol/L before the initiation of ischemia, which we termed "K(+)-modified ischemia." Ischemia initiated at a normal [K+]e ("unmodified ischemia") resulted in a mean activation delay in the center of the ischemic zone of 55 +/- 26 milliseconds after 5 minutes of ischemia and a decrease in epicardial longitudinal conduction velocity from 53 to 21 cm/s before the onset of conduction block. K(+)-modified ischemia resulted in a mean activation delay in the center of the ischemic zone of 181 +/- 8 milliseconds and a decrease in epicardial longitudinal conduction to less than 10 cm/s. K(+)-modified ischemia was associated with ventricular fibrillation in 85% of episodes compared with 28% of episodes of unmodified ischemia (P < .01). Verapamil prevented the occurrence of marked activation delay during K(+)-modified ischemia, producing local activation block following a maximum activation delay of 74 +/- 25 milliseconds. In two experiments, responses mediated by the slow inward current were produced by regional K+ elevation to 15 to 16 mmol/L, followed by concomitant regional administration of epinephrine (10(-7) mol/L). Regional [K+]e elevation alone to this level resulted in local activation block following a maximum activity delay of 70 to 80 milliseconds, whereas administration of epinephrine in combination with high [K+]e resulted in return of local activation with an activation delay of 160 to 180 milliseconds (ie, similar to that during K(+)-modified ischemia). CONCLUSIONS: Compared with unmodified ischemia, K(+)-modified ischemia resulted in marked activation delay and a high incidence of ventricular fibrillation. Based on measurements of longitudinal conduction velocity, the inhibitory effect of verapamil, and the results of experiments with high [K+]e plus epinephrine, we conclude that the marked activation delay during K(+)-modified ischemia represents conduction mediated by the slow inward current. Because the conditions produced by K(+)-modified ischemia (high [K+]e with minimal acidosis) are similar to conditions in and near ischemic border regions, we hypothesize that responses mediated by the slow inward current may occur in such regions during unmodified ischemia and may participate in the development of reentrant arrhythmias.

Erythrocyte and plasma cholinesterase activity in male and female rhesus monkeys before and after exposure to sarin.

The rhesus monkey (Macaca mulatta) has a menstrual cycle similar to the human. Differences in hormone levels have been demonstrated between the sexes and in females during the menstrual cycle but these differences in terms of organophosphorus toxicity have not been explored. Plasma cholinesterase (ChE/BuChE) and erythrocyte (RBC) acetylcholinesterase (AChE) activity were measured before and after exposure to the organophosphorus compound sarin (11 micrograms/kg, i.v.; 0.75 LD50) in six male and six female rhesus monkeys. After baseline measurements were obtained, sarin was administered to atropinized monkeys to determine in vivo differences between the sexes in their response to sarin. With the baseline values, the intraanimal and intragroup BuChE/AChE variations were found to be minimal. Following sarin intoxication and 2-PAM treatment no significant differences were seen between the sexes in the rate of reactivation of BuChE or AChE by 2-PAM. The rate of aging of sarin phosphonylated RBC AChE between the sexes was also similar. De novo regeneration of RBC AChE and plasma BuChE after sarin intoxication was different between the male and female monkeys. The female plasma BuChE recovery rate was 48% slower than the male recovery rate, while the early (first 63 days) RBC AChE recovery rate was 24.5% faster in the females. In conclusion, there probably are not any clinically significant differences between male and female rhesus monkeys acutely intoxicated with sarin. However, on subsequent exposure clinical differences may be observed due to substantial differences in the rate of de novo synthesis of both plasma BuChE and RBC AChE.

Antiallergic activity of tylogenin, a novel steroidal compound from Tylophora sylvatica.

Tylogenin, a steroidal aglycone generated by acid hydrolysis from two seasonal glycosides occurring in Tylophora sylvatica, inhibits IgE-induced basophil mediator release for allergic reactions. In the rabbit basophil-dependent serotonin release (BDSR) assay system, the inhibitory activity of tylogenin (geom mean IC50 = 39 microM) was significantly (P < 0.05) greater than that of its parent glycosides, tylophoroside (geom mean IC50 263 microM) and acetyltylophoroside (geom mean IC50 331 microM), and that of dexamethasone (geom mean IC50 = 912 microM). The activity of tylogenin was found to increase with the incubation time. In the human leukocyte-dependent histamine release (LDHR) test model, the glycosides had only a minimal activity. In contrast, tylogenin, with a geom mean IC50 = 49 microM, exerted a significantly (P < 0.05) greater potency than dexamethasone (IC50 = 257 microM). These results suggest that tylogenin could represent a new class of antiallergic agents.

Effect of rate on changes in conduction velocity and extracellular potassium concentration during acute ischemia in the in situ pig heart.

INTRODUCTION: The purpose of our study was to determine if the slowing of longitudinal intraventricular conduction in the in situ porcine heart during acute regional no-flow ischemia was rate dependent. Further, we investigated whether any rate dependence could be correlated to a rate-dependent component of the ischemia-induced rise in extracellular potassium concentration, [K+]e. METHODS AND RESULTS: We studied in situ hearts in nine anesthetized open chest pigs in which acute no-flow ischemia was induced by occlusion of the left anterior descending coronary artery. To determine the effects of steady-state rate on the slowing of conduction and rise in [K+]e during ischemia, we varied the rate of stimulation during sequential occlusions from 90 to 150 beats/min. Longitudinal conduction velocity was determined by unipolar electrodes embedded in a plaque that was sutured to the epicardial surface in the center of the ischemic zone. Myocardial [K+]e was determined simultaneously by potassium-sensitive electrodes placed at or within 1 to 2 mm of the epicardium in close proximity to the activation recording electrodes. Conduction velocity decreased more rapidly at the more rapid rates of stimulation although the reduction in conduction velocity occurring prior to the onset of conduction block was similar at both rates. The potassium change was not rate dependent and rose at the same rate regardless of the rate of stimulation. CONCLUSION: Our study demonstrates that the steady-state rate-dependent component of the slowing of intraventricular conduction induced by acute ischemia in the in situ porcine heart occurs in the absence of a rate-dependent component in the rise of [K+]e. Between rates of 90 and 150 beats/min, the rate dependence of the conduction slowing may be attributed to one or more potassium-independent factors such as the rate-dependent changes in resting membrane potential, in Vmax of the action potential upstroke, and in cell-to-cell uncoupling, which have been observed in other models of acute ischemia.

Methemoglobinemia induced by a benzocaine-based topically administered anesthetic in eight sheep.

Benzocaine-based anesthetic sprays are commonly used in sheep to anesthetize the nasal passages and glottis before intubation. Sprays containing benzocaine have been identified as causing methemoglobinemia in dogs, cats, and human beings. Diagnosis of benzocaine-induced methemoglobinemia was made in 8 Dorset-Finn ewes exposed to a 2-second burst of (approx 56 to 112 mg of benzocaine) anesthetic spray. Venous blood samples taken 10 to 20 minutes after intranasal application of the spray revealed methemoglobinemia of 22.6 +/- 1.8% (mean +/- SD) in 9 samples from 8 ewes. Four other ewes intentionally exposed did not have methemoglobinemia. Topical use of benzocaine-containing anesthetics in sheep is not recommended. The high methemoglobin concentration induced by this product may substantially alter the cardiovascular and pulmonary function, blood gas analyses, and exercise capacity, thereby compromising animal health and/or research results. Although it appears that minimal clinical signs are induced in healthy animals, the risks of compromising a subclinically ill animal do not offset the benefits of this product.

Review of the carotid artery loop procedure in sheep.

Carotid loop (CL) surgery involves the permanent externalization of a common carotid artery in a skin tube. The CL facilitates repeated access to the systemic arterial system for blood sampling and blood pressure measurement in laboratory sheep. It eliminates the need for arterial cut-downs and chronic indwelling catheters, reduces the risk of sepsis and infection, and adds flexibility to research protocols. The surgical procedure is aseptically performed under general anesthesia and involves isolation of the common carotid artery, creation of a bipedicled skin tube, and permanent envelopment of the artery in the skin tube. The primary complication is ischemic necrosis with sloughing of the middle of the loop and is usually due to failure to adhere to the critical length-to-width ratio (2.5:1). We have performed 150 CL procedures with an overall success rate of 94%. Nine CL ablations were required, due to necrosis with exposure of the artery (7/9) or stricture formation with loss of patency (2/9). Twenty-two CLs developed complications secondary to partial necrosis, but did not require ablation. Results indicate that the CL is a reliable method to ensure repeated access to the systemic arterial system in sheep. A modification of the standard CL procedure in which the artery is surrounded by a skin tunnel rather than enclosed in a skin loop was performed in 10 sheep. Preliminary results indicate significant reduction in the incidence of complications associated with the standard CL.

Topical anesthetic-induced methemoglobinemia in sheep: a comparison of benzocaine and lidocaine.

Benzocaine induces methemoglobin (MHb) in several species, whereas lidocaine may increase MHb in cats and human. Elevated MHb (greater than 20%) in sheep after benzocaine exposure was recently recognized. MHb decreases blood oxygen-carrying capacity which can complicate interpretation of experimental data. Sheep are used in research which requires tracheal intubation and blood gas analysis. Since benzocaine and lidocaine are used to provide local anesthesia prior to intubation, we compared MHb production by sheep after exposure to these drugs. A dose-response relationship between benzocaine and MHb was investigated. Eight crossbred Dorset ewes were dosed intranasally with benzocaine for 2 sec or with 40 mg of lidocaine in a randomized crossover design. Sheep with elevated MHb after the 2-sec benzocaine dose were later dosed with benzocaine intranasally for 10 sec. MHb levels were measured periodically on a CO-Oximeter. A quantitative MHb response to an indirect MHb former, p-aminopropiophenone (PAPP), by each sheep was determined 15 min after PAPP (0.6 mg/kg iv). MHb levels remained at baseline (1-2%) after lidocaine exposure in all sheep, as well as in four sheep (nonresponders) after the 2-sec benzocaine dose. Four sheep (responders) demonstrated 16.5-26.4% MHb after the 2-sec benzocaine dose. The responders formed 38.2-50.5% MHb after the 10-sec benzocaine dose. All responders developed high MHb after PAPP, while nonresponders developed slightly elevated MHb after PAPP. An N-hydroxy metabolite of benzocaine is the likely active MHb-forming substance. Benzocaine should be replaced by lidocaine when local anesthesia of the nasal or oropharyngeal region in sheep is required.

Day case laparoscopy: a survey of postoperative pain and an assessment of the value of diclofenac.

A randomised, controlled study was undertaken to assess the postoperative pain and side effects experienced by patients undergoing day case diagnostic laparoscopy and laparoscopic sterilisation, and to evaluate the effectiveness in these patients of peroperative diclofenac. Patients undergoing laparoscopic sterilisation had significantly higher pain scores at one hour postoperatively, and at discharge, than patients undergoing diagnostic laparoscopy (p less than 0.01) but there were no significant differences in pain scores 24 hours after discharge. The incidence of postoperative side effects following discharge from hospital was high, but there were no significant differences between the groups. Diclofenac had no significant effect in either group on the severity of postoperative pain, or the incidence of postoperative side effects.

Cardiopulmonary effects of a tiletamine-zolazepam combination in sheep.

To assess the effects on heart and lung function, a tiletamine-zolazepam (TZ) anesthetic combination was evaluated in 10 Dorset-type ewes. Ewes were randomly allotted to 2 equal groups. Ewes of groups 1 and 2 were given a single bolus of TZ (12 and 24 mg/kg of body weight, IV, respectively) at time zero. Hemodynamic, pulmonary, and ventilation variables were measured at 15-minute intervals to 120 minutes. Blood gas variables were evaluated at 5-minute intervals for the first 30 minutes, then at 15-minute intervals to 120 minutes. In all sheep, TZ administration induced rapid, smooth induction, with gradual and unremarkable recovery. Anesthesia duration was not significantly different between groups (mean +/- SD, 39 +/- 5 and 40 +/- 14 minutes for groups 1 and 2, respectively). Immediate drug effects included apnea, decreased mean arterial blood pressure, and arterial hypoxemia. Cardiac output was significantly decreased in both groups at all times after drug administration. Significant changes in group-1 ewes included increased pulmonary and systemic vascular resistances and decreased inspired minute ventilation, tidal volume, and respiratory airflow. Significant changes in group-2 ewes included increased systemic vascular resistance and decreased pulmonary arterial pressure, inspired minute ventilation, and respiratory airflow. Both drug dosages induced apneustic breathing patterns and caused significant changes in arterial and venous blood hemoglobin concentrations and PCV. Tiletamine-zolazepam is useful for intermediate-duration anesthesia in sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of conditioning and maximal incremental exercise on oxygen consumption in sheep.

To assess the suitability of sheep for exercise studies, the effect of incremental exercise and conditioning on oxygen consumption (VO2) was studied. Six sheep were adapted to a treadmill and subsequently trained 8 weeks. The sheep were then studied, in random order, using 3 incremental exercise protocols (EX-1, EX-2, and EX-3). The protocols were chosen to approximate high (EX-1), moderate (EX-2), and low (EX-3) intensity exercise by varying treadmill speed and incline. The sheep were then conditioned for an additional 12 weeks and retested on the EX-2 protocol. During exercise, VO2, gas exchange ratio (R), and rectal temperatures (Tb) were recorded. All 3 protocols resulted in significant increases in VO2, R, and Tb (P less than 0.05). Maximum VO2 for EX-1, 49.9 +/- 5.0 ml/min/kg of body weight, was significantly greater than maximum VO2 for EX-2 and EX-3, 37.8 +/- 6.5 and 42.3 +/- 6.0 ml/min/kg, respectively (P less than 0.05), whereas maximum R and maximum Tb were similar. After the additional 12-week conditioning, time on the treadmill increased 40% from 9.58 +/- 0.87 to 13.4 +/- 0.44 minutes, and maximum VO2 increased 27% to 48.1 +/- 9.1 ml/min/kg. These data indicated that maximum VO2 varied with intensity of the exercise, 12 weeks of maximal exercise conditioning was sufficient to produce a measurable training effect (ie, increase endurance and maximum oxygen consumption) and sheep are suitable for maximal exercise studies where VO2 measurements are desired.

An application of the non-linear bifurcation theory to tumor growth modeling.

The purpose of the work reported in this paper was to understand how a few cancerous cells (either from the primary growth, or as result of breaking away from a tumor and lodging in a different part of the body--metastasis) can grow to form a sizable mass and what decides whether such growth will indeed take place. The intermediate region, lying between the molecular (or micro) level to the fully developed (or macro) level, is not readily accessible to experimental observations. A mathematical model with a firm physiological basis has been proposed to develop a unified field theory that bridges the two regimes. The techniques of non-linear global analysis have been used. The global behavior, (which determines the long-term prognosis), is found to be significantly influenced by the presence or absence of two critical bifurcations. Both of these have practical consequences regarding the inception and the cure of the disease. Several conclusions have been drawn which lead to practical suggestions for experimentation. It is predicted that reducing the food intake immediately after an exposure to carcinogens, would lead to a reduced chance of cancer. A preliminary case has been made to lend support to the idea that an absence of snacking (and even periodic fasting) might work as a preventive measure against cancer.

The cardiovascular response of sheep to tiletamine-zolazepam and butorphanol tartrate anesthesia.

Butorphanol tartrate (0.5 mg/kg intravenously [IV]) was administered to six ewes (group 1), 10 minutes before administration of tiletamine-zolazepam (12 mg/kg IV). In six ewes (group 2), butorphanol tartrate and tiletamine-zolazepam were administered simultaneously. Time of administration of butorphanol did not alter hemodynamics or duration of anesthesia significantly. Anesthesia was adequate for 25 to 45 minutes (mean, 31 min) in group 1. The sheep in group 2 were anesthetized effectively for 25 to 50 minutes (mean, 39 min). Neither dosing regimen caused significant changes in right atrial pressure, heart rate, pulmonary vascular resistance, or pulmonary capillary wedge pressure. Mean arterial blood pressure (MABP) decreased an average of 18% from baseline values of 113 mm Hg to a minimum of 84 mm Hg at minute 60 in group 1, and from 111 mm Hg to 92 mm Hg at minute 75 in group 2. The decrease was significant only for group 1. Cardiac output (CO) was significantly decreased 24% from 6.6 L/min at minute 45 in group 1, and 32% from 6.3 L/min at minute 15 in group 2. Systemic vascular resistance (SVR) was increased significantly at minute 15, 11% in group 1 and 37% in group 2. Mild respiratory acidosis was measured by significant decreases in arterial pO2 and pH and a significant increase in pCO2 without significant changes in HCO3-. Results of this study show that (1) tiletamine-zolazepam and butorphanol tartrate produce adequate anesthesia for 25 to 50 minutes; (2) the cardiovascular and anesthetic effects of the dosing schedules were similar; and (3) tiletamine-zolazepam and butorphanol result in decreased CO and MABP with a concomitant increase in SVR, and mild respiratory acidosis.