Rapid hematogenous dissemination of Aspergillus fumigatus and A. flavus spores in turkey poults following aerosol exposure

Cultures of blood samples taken from 3-week-old turkey poults exposed to aerosolized spores of either Aspergillus fumigatus or A. flavus for 15 min yielded organisms. Aspergillus fumigatus was also isolated from brain and liver tissue samples taken immediately after exposure. Exfoliated cells from the lungs of 10 poults exposed to aerosolized spores of A. fumigatus were allowed to attach to glass slides in tissue culture. Several types of the fixed and stained cells had attached or ingested spores of A. fumigatus. Macrophages were the predominant cell type with ingested spores, although other cell types may be involved in the transport of spores of A. fumigatus into the blood stream after aerosol exposure.     

Exposure of rabbits to spores of Aspergillus fumigatus or Penicillium sp: survival of fungi and microscopic changes in the respiratory and gastrointestinal tracts.

Rabbits were exposed to spores of Aspergillus fumigatus by 1 of 2 routes: exposure to aerosols of dry spores or introduction of liquid suspensions of spores directly into the stomach. Rabbits also were exposed to aerosols containing spores of a Penicillium sp. Cultural and microscopic examinations of tissues from the respiratory and gastrointestinal tracts indicated fungi were distributed throughout the gastrointestinal tract of the rabbits within 1 hour after exposure to aerosols of A fumigatus or Penicillum spores. Viable A fumigatus and Penicillium were detected in lung tissues of rabbits for 2 or 3 weeks after inhalation of spores. Aspergillus fumigatus was isolated from the gastrointestinal tract no more than 1 week after aerosol exposure, and Penicillium, not beyond 48 hours. However, when large numbers of A fumigatus spores were introduced directly into the stomach, fungi were isolated from tissues for as long as 16 days after exposure even though the intestinal contents were negative 4 to 7 days after introduction of spores. Tests for precipitating antibody were negative, with one exception, among 26 rabbits surviving for 2 weeks or more. Microscopic changes were more pronounced in rabbits exposed to spores of A fumigatus than in rabbits exposed to Penicillium spores.     

Pulmonary bacterial deposition and clearance during ascarid larval migration in weanling pigs.

Pulmonary deposition and clearance of bacteria were measured in weanling pigs, half of which had been inoculated at age 31 days with larvated Ascaris suum ova. Seven days later, when breathing signs of larval migration were pronounced, all pigs were exposed to aerosolized Escherichia coli (strain B). Then, either immediately after aerosol exposure (for deposition assessment) or immediately after a 120 minute period in filtered air (for clearance), bacteria in the pigs' lungs were counted. Ascarid ova-inoculated pigs did not differ significantly from control pigs for number of bacteria in the lungs after aerosol exposure, but after the 120 minute clearance period they had 7.2 times more than did the control pigs. Thus, in weanling pigs, the breathing-pattern changes that were evident during ascarid-larval migration did not affect pulmonary deposition of inhaled bacteria significantly, but the presence of ascarid larvae in the lungs was associated with impaired pulmonary bacterial clearance.     

Effects of inhaled fine dust on lung tissue changes and antibody response induced by spores of opportunistic fungi in goats

OBJECTIVE: To investigate the effects of sterile fine dust aerosol inhalation on antibody responses and lung tissue changes induced by Mucor ramosissimus or Trichoderma viride spores following intratracheal inoculation in goats. ANIMALS: 36 weanling Boer-Spanish goats. PROCEDURES: 6 goats were allocated to each of 2 M ramosissimus-inoculated groups, 2 T viride-inoculated groups, and 2 control (tent or pen) groups. One of each pair of sporetreated groups and the tent control group were exposed 7 times to sterilized fine feedyard dust (mean+/-SD particle diameter, <7.72+/-0.69 microm) for 4 hours in a specially constructed tent. Goats in the 4 fungal treatment groups were inoculated intratracheally 5 times with a fungal spore preparation (30 mL), whereas tent control goats were intratracheally inoculated with physiologic saline (0.9% NaCl) solution (30 mL). Pen control goats were not inoculated or exposed to dust. Goats received an IV challenge with equine RBCs to assess antibody responses to foreign antigens. Postmortem examinations were performed at study completion (day 68) to evaluate lung tissue lesions. RESULTS: 5 of 7 deaths occurred between days 18 and 45 and were attributed to fine dust exposures prior to fungal treatments. Fine dust inhalation induced similar lung lesions and precipitating antibodies among spore-treated goats. Following spore inoculations, dust-exposed goats had significantly more spores per gram of consolidated lung tissue than did their nonexposed counterparts. CONCLUSIONS AND CLINICAL RELEVANCE: Fine dust inhalation appeared to decrease the ability of goats to successfully clear fungal spores from the lungs following intratracheal inoculation.     

Primary and anamnestic responses of bovine bronchoalveolar and peripheral blood lymphocyte subsets to aerosolized Pasteurella haemolytica A1

Site-specific responses of bronchoalveolar and peripheral blood lymphocyte subsets were compared during primary and anamnestic immune responses against live Pasteurella haemolytica A1 (Ph1). Eight 1-year old calves were sequentially exposed intrabronchially with aerosolized Ph1 on days 0, 14, and 21, and two calves were sham exposed. Bronchoalveolar and peripheral blood lymphocytes were analyzed before each Ph1 exposure, and on days 3 and 7 post exposure using single and two-color flow cytometry to identify CD2+, CD4+, CD8+, CD21+, CD45R+, CD25+ and gammadelta lymphocyte subsets. Significant differences (p < 0.05) in bronchoalveolar and peripheral blood lymphocyte subsets were observed before Ph1 exposure. Subsequent aerosol exposures, resulted in significant (p < 0.05) changes in bronchoalveolar lymphocyte subsets and the CD4:CD8 bronchoalveolar lymphocyte ratio, but concomitant changes were not observed in peripheral blood lymphocytes. Expression of CD2, CD4 and CD8 lymphocyte differentiation antigens was consistently lower and more heterogeneous on bronchoalveolar lymphocytes. Differential analysis of bronchoalveolar leukocytes revealed a significant increase in bronchoalveolar lymphocytes and neutrophils during anamnestic responses.     

Activity of bleach, ethanol and two commercial disinfectants against spores of Encephalitozoon cuniculi

Encephalitozoon cuniculi is a small protist parasite in the phylum Microspora. Hosts are infected by ingestion or inhalation of spores passed in the urine or feces. Infection with E. cuniculi is usually asymptomatic, except in young or immunocompromised hosts. This study examined the effects of various disinfectants on in vitro infectivity of E. cuniculi spores. Spores of E. cuniculi were exposed to several dilutions of commercial bleach, 70% ethanol and dilutions of commercial disinfectants HiTor and Roccal for 10 min and then loaded onto human fibroblast cells (Hs68 cells). Ten minutes of exposure to these disinfectants was lethal to E. cuniculi spores. Additional exposure time studies were done using dilutions of bleach at 0.1, 1 and 10%, and 70% ethanol. Exposure of E. cuniculi spores to 1 or 10% bleach for 30s rendered them non-infectious for Hs68 cells. Growth of E. cuniculi was observed in Hs68 cells inoculated with spores treated with 0.1% bleach for 30s or 1, 3 and 5 min, but not with spores treated for 7 min or longer. Exposure of E. cuniculi spores to 70% ethanol for 30s rendered them non-infectious for Hs68 cells. Spores of E. cuniculi are more sensitive to disinfectants than are coccidial oocysts and other parasite cysts. The relatively short contact time needed to kill spores indicates that disinfection of animal housing may be a viable means to reduce exposure of animals to E. cuniculi spores.     

In vivo pulmonary response to Aspergillus terreus spores

The fate of intratracheally instilled Aspergillus terreus spores was followed in both rabbits and rats. Phagocytosis of the spores by the pulmonary macrophage was rapid in that approx. 42% of the observed spores were associated with the macrophages immediately after instillation. Direct penetration of the lung architecture by the spores was not observed but spores were seen in the alveolar interstitium at 3 hr after instillation and in the tracheobroncheal lymph nodes at 24 hr. Granulomas formed between 48 hr and 1 week after exposure. In the absence of apparent spore or spore extract toxicity and precipitating antibodies against Aspergillus terreus, the observed reactions preclude the possibility that the lesions were the consequence of hypersensitivity. This model of pulmonary response to fungal spores may be of future value for characterizing further the pathology associated with certain occupational exposures to moldy materials.     

Changes in leukocyte populations in pulmonary lavage fluids of calves after inhalation of Pasteurella haemolytica

The distribution of leukocytes in bovine bronchoalveolar lavage fluids was determined in 15 calves at various times after aerosol exposure to Pasteurella haemolytica. For comparison, 10 calves were exposed to aerosols of phosphate-buffered saline solution; 15 calves, to Staphylococcus epidermidis; and 10 calves, to Salmonella typhimurium endotoxin. At 10 minutes after inhalation exposure for each group, the predominant cell type was the macrophage. Macrophages remained the predominant cell type throughout each lavage interval for calves exposed to phosphate-buffered saline solution and Staph epidermidis. For calves exposed to P haemolytica, there was a decrease in the percentage of macrophages detectable by 30 minutes after exposure, with a corresponding increase in the percentage of neutrophils. Sixty minutes after the inhalation exposure to P haemolytica, the percentages of macrophages and neutrophils in the lavage fluid were equal. By 240 minutes after exposure to P haemolytica, greater than 90% of the cells in the lavage fluids was neutrophils. The increase in the percentage of neutrophils in lavage fluids from calves exposed to S typhimurium endotoxin was similar to that seen for the calves exposed to P haemolytica.     

Pulmonary distribution of aerosolized technetium Tc 99m pentetate after administration of a single dose of aerosolized albuterol sulfate in horses with recurrent airway obstruction.

OBJECTIVE: To determine whether pulmonary distribution of aerosolized technetium Tc 99m pentetate is improved after inhalation of a single dose of albuterol sulfate in horses susceptible to recurrent airway obstruction (heaves). ANIMALS: 6 horses with heaves and 4 horses with normal respiratory tract function. PROCEDURE: Images were obtained during ventilation of horses at baseline (maximal change in pleural pressure during tidal breathing [deltaPpImax] >15 cm H2O) and after aerosolized albuterol sulfate (360 microg) administration, with a 24-hour washout period between experiments. The deltaPpImax was determined prior to the baseline scan, prior to albuterol sulfate administration, and 5 minutes after albuterol sulfate administration. Images were assessed by visual inspection (semi-quantitative scoring system) and histogram analysis. RESULTS: Images obtained from horses with heaves had nonuniform pulmonary distribution of radionuclide characterized by poor penetration in peripheral lung fields and excess deposition in large airways. Histogram analysis of images of the caudal portions of the lungs revealed nonuniform radionuclide deposition in horses with heaves and uniform radionuclide deposition in control horses. CONCLUSION: Administration of a single dose of aerosolized albuterol sulfate improved pulmonary distribution of aerosolized radiolabeled pentetate suspension in horses with heaves but did not alter pulmonary distribution in clinically normal horses. CLINICAL RELEVANCE: Precedent bronchodilator administration may improve pulmonary distribution of aerosolized, surface-active anti-inflammatory preparations.     

Enhancement of urethan-induced adenoma formation in Swiss mice exposed to methylmercury.

Female Swiss mice were exposed to methylmercury in the drinking water for 15 weeks. The mice were administered concentrations of methylmercury ranging from 0 to 2.0 micrograms/mL mercury. After three weeks of the 15 week exposure period, the mice were administered urethan (1.5 mg/g) intraperitoneally. Pulmonary adenoma formation was evaluated 12 weeks later. Methylmercury exposures of 0.2 and 0.5 micrograms/mL did not affect the number of adenomas, but 2.0 micrograms/mL mercury caused a significant increase in adenoma production. A dose-dependent increase in the mean tumor diameter was seen at methylmercury exposures up to 0.5 micrograms/mL. No further increase in diameter was seen at higher exposures (2.0 micrograms/mL). The changes in adenoma production were seen at exposure levels of methylmercury which did not cause any clinical manifestations. Animal weight gains and water consumption were not affected. In addition, urethan-induced sleeping times which reflect the rate of urethan metabolism or excretion remained unchanged.     

Virulence of fungal spores determined by tracheal inoculation of goats following inhalation of aerosolized sterile feedyard dust

OBJECTIVE: To compare the virulence of spores of 7 fungi by tracheal inoculation of goats following exposure of goats to an aerosol of sterilized feedyard dust. Animals-54 weanling Boer-Spanish goats. PROCEDURE: A prospective randomized controlled study was conducted. There were 7 fungal treatment groups, a tent control group, and a pen control group (n = 6 goats/group). Goats in the 7 treatment and tent control groups were exposed to autoclaved aerosolized feedyard dust for 4 hours in a specially constructed tent. Goats in the 7 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas tent control goats were intratracheally inoculated with 30 mL of physiologic saline (0.9% NaCI) solution. These treatments were repeated each week for 6 weeks. RESULTS: Severity of pathologic changes differed significantly among the 7 fungal treatment groups as determined on the basis of gross atelectatic and consolidated lung lesions and histologic lesions of the lungs. Descending order for severity of lesions was Mucor ramosissimus, Trichoderma viride, Chaetomium globosum, Stachybotrys chartarum, Aspergillus fumigatus, Penicillium chrysogenum, and Monotospora lanuginosa. Trichoderma viride spores were the most invasive and were isolated from the bronchial lymph nodes and thoracic fluid of all 6 goats administered this organism. Spores were observed-histologically in lung tissues harvested 72 hours after inoculation from all treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: 4 of 7 fungal spore types induced significantly larger lung lesions, compared with those induced by the other 3 spore types or those evident in control goats.     

Efficacy of salmeterol xinafoate in horses with recurrent airway obstruction.

OBJECTIVE: To determine the onset, magnitude, and duration of bronchodilation after administration of aerosolized salmeterol xinafoate in horses with recurrent airway obstruction. DESIGN: Randomized controlled study ANIMALS: 6 horses with recurrent airway obstruction. Procedure Horses received aerosolized salmeterol (210 microg) or no treatment, using a crossover design. Salmeterol was administered, using a mask designed for aerosol delivery in horses. Subjective rating of airway obstruction (RAO), maximal change in pleural pressure (deltaPplmax), and pulmonary resistance (RL) were determined at baseline; 5, 15, and 30 minutes; and 1, 2, 4, 6, 8, 10, and 12 hours after administration of salmeterol and in horses that did not receive treatment. RESULTS: The deltaPpl and RL were improved 15 minutes through 6 hours after administration of salmeterol, compared with values obtained from horses receiving no treatment. The RAO was improved 15 minutes through 2 hours after administration of salmeterol. The maximal response to salmeterol was evident 30 to 60 minutes after administration and was characterized by a 59 + 19% decrease in deltaPpl and a 56 +/- 13% decrease in RL. The deltaPpl and RL were not different from baseline values 8 hours after salmeterol administration. CONCLUSIONS AND CLINICAL RELEVANCE: Duration of action of salmeterol in these horses was approximately 6 hours. Maximal bronchodilation was somewhat delayed (30 to 60 minutes), and the magnitude of response was similar to that of short-acting beta2-adrenergic agonists. Salmeterol provides moderately sustained bronchodilation in horses with recurrent airway obstruction and may be an effective drug for long-term control of this condition.     

Deposition in the Respiratory Tract of Cattle of Spores of Bacillus subtilis var niger by Inhalation and by Nasal Instillation

Spores of Bacillus subtilis var niger were deposited in the lungs, tracheae and nasal cavities of four calves by aerosol inhalation and in three calves by intranasal instillation. From each calf 20 specimens of lung tissue, each weighing one gm, three of trachea and three of nasal mucosa were examined for spore content. The average numbers of spores per gm of lung tissue from animals exposed to aerosols were 3.05 and 4.84, 2.35 and 2.02 x 10⁴. Lungs from animals exposed intranasally contained only 747, 62 and 1424 spores per gm of tissue respectively. Animals exposed intranasally had a hundred to a thousand fold more spores on nasal mucosa than animals exposed by aerosol and the latter had a thousand fold more spores on tracheal mucosa than calves exposed intranasally. Aerosol inhalation exposed the lung and trachea more densely and uniformly than did intranasal instillation.     

The effect of UV rays on parasitic arthropods. 3. In vitro and in vivo studies of the effect of a fractionated UV irradiation on the development stages of Psoroptes cuniculi (Acaridida: Psoroptidae)

In vitro studies were conducted into Psoroptes (Ps.) cuniculi larvae and nymphs of undefined age and gender. 30 males and females were involved in each of the experiments. Evidence was found the life expectancy of mites exposed to daily UV irradiation for 1, 2, 3, 4 or 5 minutes was reduced with significance, as compared to non-irradiated mites or to those with only one irradiation of the same length. Developmental stages of Ps. cuniculi responded in differentiated ways to the same dose rate, when applied by one single extended or fractionated shorter irradiation. Fractionated irradiation was more often survived by females than one single extended irradiation, whereas earlier death occurred to larvae following exposure to fractionated irradiation. Mange mites were not eliminated from rabbits with moderate ear mange by fractionated locally delimited in vivo irradiation, up to 16 applications of 10 minutes each or 6 or 9 applications of 10, 20 or 40 minutes each, with one-week intervals in between. Ear mange was clinically re-manifested, after irradiations had been discontinued.     

Exercise-induced pulmonary hemorrhage in horses with experimentally induced allergic lung disease.

The lungs of sensitized horses were exposed to aerosolized ovalbumin. Some horses (n = 4) were given ovalbumin in 1 lung only, whereas in others (n = 7), ovalbumin or vehicle were inoculated in the cranial, ventral, and caudal regions of the caudal lung lobe. Horses were exercised 5 hours after ovalbumin exposure. Immediately before exercise, endoscopy failed to reveal any abnormality. After exercise, endoscopic examination of horses subjected to unilateral ovalbumin exposure revealed extensive blood in airways leading to the exposed lung in all horses. Blood was not observed in the airways leading to the control lung. Mean (+/- SEM) minimum volume of the exposed and control lungs was 9.5 +/- 1.5 and 5.5 +/- 1.6 L, respectively; this difference was statistically significant (P less than 0.05). Bronchoscopy of horses subjected to regional ovalbumin or vehicle exposure and exercise revealed a small amount of blood-tinged fluid in the bronchi serving the regions of the lung inoculated with ovalbumin. Minimum volumes of such regions were not significantly different from one another. However, their minimum volume was significantly (P less than 0.05) larger than that of vehicle-inoculated regions. Gross and histologic examination confirmed inflammation and hemorrhage in the ovalbumin-exposed, but not the control lungs or lung regions. Thus, exercise can cause blood from an injured region of lung to appear in the larger airways. Regional differences in lung structure and function do not influence the appearance of blood in the airways.     

纤毛蛋白与绵羊白细胞介素2融合基因工程疫苗对实验动物的体液免疫应答

将转化节瘤拟杆菌（D.nodosus)纤毛蛋白（Pili）和绵羊白细胞介素2（oviIL2)融合基因表达质粒的工程菌BL－21，在含酸苄青霉素营养肉汤培养基中表达，离心获得菌体沉淀物，裂解后配制成Pili-oviIL2融合基因工程疫苗。用加佐剂和不加佐剂的Pili-oviIL2融合基因工程疫苗分别接种2只健康家兔，21天后接种第2次；定期采血，用对流免疫电泳检测试验兔的体液免疫反应。结果发现，加佐剂和不加佐剂的Pili-oviIL2融合基因工程疫苗免疫兔7天即可产生相应抗体，抗体在免疫血清中可维持6个月以上。进一步试验将不加佐剂的Pili-oviIL2融合基因工程疫苗接种3只健康绵羊，同样21天后接种第2次，定期采血，用对流免疫电泳检测试验绵羊的体液免疫反应。同时用Pili基因工程疫苗接种2只绵羊作对照。结果3只绵羊接种Pili-oviIL2融合基因工程疫苗后，分别于7天和14天产生相应的抗体，而接种Pili基因工程疫苗的绵羊于28天产生相应的抗体；被免疫绵羊血清中的抗体可维持6个月以上。用Pili-oviIL2融合基因工程疫苗接种兔和绵羊的免疫试验表明，Pili-oviIL2融合基因工程疫苗具有较好的体液免疫应答反应，重组OviIL2在融合基因工程疫苗中具有良好的佐剂作用。     

Humoral antibody response of rabbits to experimental infection with Encephalitozoon cuniculi

Six female rabbits (Oryctolagus cuniculus) were experimentally infected intravenously with approximately 1.5 X 10(7) live spores of Encephalitozoon cuniculi. Head tilt was observed as the single clinical sign in only one of the six animals. Antibody response was registered over 68 days postinfection using the indirect immunofluorescence test (IFT) for IgM and IgG, and the carbon immunoassay (CIA). IgG titers reached a level of 160-2560 after a latent phase of 13-28 days, followed by a 2-4 week relatively steep increase. The IgM seroconversion was faster than that of IgG and occurred at the beginning of the antibody response. Thus, simultaneous detection of both IgM and IgG allowed the infection to be identified as recent. Long, short, and episodic antibody responses could be distinguished: the IgG titer continued to increase on Day 68 in one animal (long response) and began to decrease between Days 45 and 63 in three other animals (short response). In two additional animals the seroconversion was very short, occurring between Days 13 and 41, and 28 and 52, respectively (episodic response). The CIA proved to be specific, reliable, and simple to perform; titers were slightly higher than in the IFT. Parasite pseudocysts were detected scattered throughout the brain on Day 68 in four of the six rabbits. The persistence of antigen in the brain did not correlate with antibody response, which in most cases was shorter.     

Clinical and serologic evaluations of induced Borrelia burgdorferi infection in dogs

Adult Beagles were used to evaluate clinical signs and serologic response after inoculation with, or exposure to, Borrelia burgdorferi. An indirect immunofluorescent assay (IFA) and 2 ELISA were used to monitor the serologic response to B burgdorferi. Feeding infected ticks on 4 dogs (group 1) failed to cause seroconversion, and SC inoculation with 500 organisms caused minimal seroconversion in 2 of 4 dogs (group 2). At 56 days, approximately 3.01 X 10(8) B burgdorferi organisms were injected IV into group-1 dogs, and intraperitoneally into group-2 dogs. A control group of 4 dogs (group 3) had noninfected ticks feed on them, and then were given IV injection of physiologic saline solution. Increases in immunoglobulin M (IgM) titers were detected in 2 of 4 group-2 dogs approximately 7 days after the initial exposure. These titers returned to negligible values 20 days later. Immunoglobulin G titers increased approximately 10 days after the initial exposure and were mildly increased 56 days later, when dogs were exposed a second time. Both the IV and intraperitoneal injections (second exposures) resulted in increased IgM titers, which in both groups eventually returned to preexposure values after approximately 2 months. Immunoglobulin G titers increased within a week after the second exposure, and in 3 dogs monitored for 8 months, returned to negligible values after the 8-month period. One control dog had a slightly increased IgG titer 24 days after the second inoculation. The possibility of urine transmission is suggested. Clinical status, hemograms, serum biochemical profiles, ECG and results of urinalyses remained normal throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cellular inflammatory response in the lungs of calves exposed to bovine viral diarrhea virus, Mycoplasma bovis, and Pasteurella haemolytica

Three, 5, or 7 days after inoculation with bovine viral diarrhea (BVD) virus (n = 12) or Mycoplasma bovis (n = 12), groups of calves were exposed to aerosols of Pasteurella haemolytica and were euthanatized 4 hours later. Histologic lesions in the lungs and the ratios of neutrophils to alveolar macrophages, collected by bronchoalveolar lavage, were compared with those of clinically healthy calves (n = 8) and calves inoculated with BVD virus only (n = 4), M bovis only (n = 4), or P haemolytica only (n = 2). Inoculation with BVD virus or M bovis did not have a significant (P greater than 0.05) effect on the neutrophil/macrophage ratio in the bronchoalveolar lavage. Aerosol exposure to P haemolytica induced a marked and significant (P less than 0.01) change in the neutrophil/macrophage ratio (from less than 1:9 to greater than 9:1). The reversed neutrophil/macrophage ratio in calves exposed to P haemolytica correlated well with the histologic changes in which small bronchi and bronchioles were plugged with purulent exudate. Inoculation with BVD virus did not induce gross or microscopic lesions in the lungs. Inoculation with M bovis resulted in a severe peribronchial lymphoid hyperplasia with mild exudation of neutrophils and macrophages into the cranioventral parts of the lungs.     

Behaviour of pigs exposed to mixtures of gases and the time required to stun and kill them: welfare implications

Pigs were exposed individually to either 90 per cent argon in air (anoxia), a mixture of 30 per cent carbon dioxide and 60 per cent argon in air (hypercapnic anoxia) or 80 to 90 per cent carbon dioxide in air (hypercapnic hypoxia) and the times to loss of posture, the onset and duration of convulsions, vocalisation and cessation of gagging (respiratory arrest) were determined. The duration of convulsions and the time to onset of respiratory arrest were longer when the pigs were exposed to argon than when they were exposed to the mixture of carbon dioxide and argon or to the high concentration of carbon dioxide in air. A second experiment was carried out under commercial conditions to determine the duration of unconsciousness and insensibility based on the response to a nose prick, and the incidence of death induced by exposing pigs to either 90 per cent argon in air or a mixture of 30 per cent carbon dioxide and 60 per cent argon in air for different periods. The results showed that when pigs were exposed for three minutes to either argon or the mixture of carbon dioxide and argon they should be bled within 25 seconds from the end of exposure to the gas to prevent them regaining consciousness during bleeding. When the pigs were exposed to either argon or the mixture of carbon dioxide and argon for five minutes and bleeding out began within 45 seconds they did not regain consciousness or suffer convulsions while being bled. The majority of the pigs died when they were exposed to argon for seven minutes, and all of them died when they were exposed to the mixture of carbon dioxide and argon for seven minutes.