首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Mucociliary clearance and retention of monodisperse aerosols of radiolabelled polystyrene particles of both 3.3 microns and 5 microns diameter were investigated in four healthy calves and two sick calves. The effect of the mucolytic agent bromhexine was also assessed at two dosage levels. There were significant differences (P less than 0.05) in clearance rate constant between calves, but similar patterns of clearance for each calf. These characteristics of mechanical lung clearance did not vary over a two month period. Values of clearance rate constant and percentage retention varied significantly (P less than 0.001) between the two different particle sizes, 5 microns particles giving faster clearance and lower retention of particles than 3.3 microns particles. Bromhexine at the recommended dose of 1.6 mg/kg 0.75 caused a significant (P less than 0.05) increase in clearance rate in both healthy and sick calves, but affected percentage retention only in sick calves. This study illustrates the variation in mucociliary clearance rates shown by individuals and also underlines the importance of particle size in aerosols used for studies of pulmonary deposition and clearance. The work also indicates that bromhexine may be of use in the therapy of respiratory disease in calves.  相似文献   

2.
In each of 11 experiments, four calves were exposed first to an aerosol of bovine herpesvirus 1 (BHV1, virus of infectious bovine rhinotracheitis) and second to an aerosol of Pasteurella haemolytica. The interval between aerosols was three to five days. In two other experiments, calves were exposed only to a bacterial aerosol. Climate was controlled for all experiments from the day of viral exposure and for eight of the experiments it was also controlled for four to six days before the first aerosol. The concentration of infectious doses of virus in the aerosols and the number of bacteria in the aerosols of each calf were determined. Macroscopically recognizable rhinitis, tonsillitis, laryngitis, tracheitis and pneumonia of lobar distribution in 42 lobes from 11 calves were seen in five experiments in which bacterial aerosol followed the viral aerosol by at least four days. One calf died with marked respiratory disease in each of four experiments within four days of exposure to the bacterial aerosol. Production of pneumonia was dependent on an interval between aerosols of at least four days but not on the condition of controlled climate on the environmental chamber either before or after the viral aerosol nor on the period of habituation allowed calves of some experiments.  相似文献   

3.
The influence of pulmonary edema, hydrocortisone, immunization against Pasteurella hemolytica and concurrent infection with parainfluenza-3 virus upon pulmonary clearance of aerosolized P. hemolytica was studied in 31 calves. Following the various treatments calves were challenged with an aerosol of P. hemolytica. One control calf was killed immediately after the aerosol and the numbers of bacteria in the lung taken as 100%. Two calves were killed four hours after challenge and the numbers of bacteria in the lungs were compared to the 100% of the control calf. The result was the percentage clearance of bacteria at four hours.

Pulmonary edema was induced by three different methods: by an aerosol of histamine, by intravenous injection of endotoxin and by intravenous injection of croton oil emulsion. The edema impaired the clearance of P. hemolytica, which was reflected in high numbers of P. hemolytica present in the lungs at four hours after challenge: 260% after histamine, 300% and 400% after endotoxin and 92% after croton oil.

Six days of treatment of four calves with high doses of hydrocortisone acetate produced inconsistent results: two calves treated with a higher daily dose (36 mg/kg) had normal clearance whereas two calves treated with a lower dose had pulmonary edema and displayed lowered clearance with 111% and 31% respectively of P. hemolytica retained in the lungs four hours after challenge.

Immunization of calves by three different methods, a subcutaneously injected bacterin of P. hemolytica (2 calves), single aerosol (2 calves) and four aerosols (4 calves) of live P. hemolytica was reflected in an accelerated pulmonary clearance of P. hemolytica (with a mean of 1.55% of bacteria retained at four hours).

Concurrent infection with parainfluenza-3 virus did not lower the clearance of P. hemolytica in the lungs of 12 calves over 15 days except on the first day following the exposure to parainfluenza-3 virus. These calves had hemagglutinating antibodies against P. hemolytica before exposure.

  相似文献   

4.
Two groups of three calves were exposed to monodisperse aerosols of radiolabelled polystyrene spheres measuring 3.3 microns in aerodynamic diameter (SD 0.3 micron). Although the spheres preferentially deposited in the trachea and major bronchi, 72 per cent of the total radioactivity deposited was found in lung tissue beyond the major bronchi. Mean alveolar deposition, estimated from the end retention value after mucociliary clearance, was 34 per cent in the group of bull calves and 52 per cent in the group of heifer calves. Alveolar deposition increased from 47 to 56 per cent (P less than 0.05) in heifer calves treated with oestradiol. Mucociliary clearance of the spheres was unaffected by repeated exposure to the experimental aerosol and the overall mean mucociliary clearance rate constant was 1.28 (+/- 0.43) h-1 (half-life 32 minutes). Clearance curve profiles tended to be characteristic for individual calves but variation in mucociliary clearance rates within calves was high and on occasions clearance rate inexplicably fell to 10 to 50 per cent of the maximum achievable value for the calf. Neither mucociliary clearance rate nor alveolar deposition was affected by a change in climate from 14 degrees C, 87 per cent relative humidity to 5 degrees C, 75 per cent relative humidity. Both alveolar deposition and mucociliary clearance of the spheres could be manipulated using a beta-adrenergic treatment.  相似文献   

5.
Pathological changes in respiratory tracts were studied in 30 calves following exposure to aerosols of Pasteurella multocida or to bovine herpesvirus 1 and P. multocida. Two groups of five calves were exposed to aerosols of one of two types of P. multocida only, which produced lobar pneumonia in one calf of each group. Another five groups of four calves were exposed to aerosols of bovine herpesvirus 1 and four to seven days later to one of the two types or one sub-type of P. multocida. Extensive necropurulent lesions were produced throughout the respiratory tract with each type of P. multocida in all four calves in three groups but none in the remaining two groups. The pathological changes differed from those produced following similar exposures to bovine herpesvirus 1 and P. haemolytica, in that the exudate in air passages and alveoli was more purulent and streaming (oat) cells and large mononuclear eosinophilic granulocytes were absent. This is the first report of experimental respiratory disease in cattle as a result of aerosol exposure to P. multocida alone or in combination with bovine herpesvirus 1.  相似文献   

6.
To investigate the influence of humoral immunity on the severity of disease caused by infection with bovine respiratory syncytial virus (BRSV), an experimentally induced infection study was performed on vaccinated and nonvaccinated calves. Fifteen weanling calves were allotted to 3 groups: 1 group of 6 calves was exposed to 2 live virus aerosols, 35 days apart; another group of 6 calves was vaccinated prior to the same aerosol exposures; and the remaining 3 calves served as controls. Clinical signs of infection were converted to a numerical score for evaluating disease severity. For 14 days after each virus exposure, BRSV-specific IgG and IgM concentrations in serum and BRSV-specific IgA concentration in nasopharyngeal exudate and lung lavage fluid were measured by ELISA. Serum BRSV-specific IgG and IgM and secretory BRSV-specific IgA concentrations did not correlate with disease sign expression. There was a strong correlation between viral isolation and disease scores. Vaccination prior to virus exposure appeared to have little or no effect on severity of the disease, but it did appear to affect disease persistence. Findings indicate that the immunoglobulins evaluated may be primarily protective in nature and do not contribute to disease severity.  相似文献   

7.
In order to study the aerosol transmission of arthropathic and amyloidogenic Enterococcus faecalis strains, preliminary aerosol experiments were performed. The experiments were carried out in empty isolators to assess the yield and viability of E. faecalis and Newcastle disease vaccine virus (NDVV) aerosol particles with time. NDVV was aerosolized because this virus would be used in combination with E. faecalis in a subsequent study. Concentrations of about 10(5) colony-forming units (CFU) of E. faecalis/ml of air were still found 30 min after the aerosol application. At 45 min, however, E. faecalis concentrations dropped below the detection level. The average E. faecalis concentration during the aerosol experiment was estimated at 10(5) CFU/liter. The NDVV aerosol generated an average of 10(4)-10(5) 50% embryo infective dose per liter of air. In these experiments, E. faecalis and NDVV aerosols were successfully generated despite considerable initial particle loss. The bacteria and virus uptakes per chick are discussed in case day-old chicks would be exposed to these aerosols.  相似文献   

8.
OBJECTIVE: To characterize the accuracy of an ultrafine 99m-technetium-labeled carbon dry aerosol for use in assessment of regional ventilation in calves with pulmonary dysfunction. ANIMALS: 7 Belgian White and Blue calves. PROCEDURE: The ultrafine aerosol was assessed by comparing deposition (D) images with ventilation (V) images obtained by use of 81 m-krypton (81mKr) gas via D-to-V ratio (D:V) image analysis in calves during spontaneous breathing (SB) and during experimentally induced pulmonary dysfunction (ePD). RESULTS: Mismatching index (LrTot) calculated on the D:V images revealed a good match (LrTot, 0.96 +/- 0.01) between D and V distribution patterns in calves during SB. Calculation of the ultrafine aerosol penetration index relative to 81mKr (PIRel) revealed preferential distribution of the ultrafine aerosol in lung parenchyma (PIRel, 1.13 +/- 0.11). In ePD, heterogeneity in the D:V distribution was observed (LrTot, 0.78 +/- 0.10) as a result of ultrafine aerosol particles impaction in airways as indicated by PIRel (0.66 +/- 0.16) and a proportion of pixels more radioactive in D images, compared with V images, that was located in the central part of the lung (475 +/- 77% in ePD vs 32.8 +/- 5.7% in SB). However, this central deposition did not prevent visual examination of the entire ventilated lung. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrafine aerosol appears suitable for use in examination of ventilated parts of lungs of cattle, even those with impaired pulmonary function. However, airway impaction of ultrafine aerosol particles impedes the quantification of regional ventilation in cattle with abnormal lung function.  相似文献   

9.
The distribution and variance of respiratory disease produced with aerosols of bovine herpesvirus 1 (BHV-1) and Mannheimia haemolytica in control (183 calves in 44 experiments) and vaccinated calves were studied in experiments conducted at the Animal Diseases Research Institute, Lethbridge, Alberta, from 1975 to 1989. All calves had been born and raised at this institute and exposed similarly for 5 min by means of a face mask to viral and bacterial aerosols produced by a Collison atomizer (particles < 3 microm in diameter). We summarized the macroscopic pathological responses of pneumonia (main end point), tonsillitis, tracheitis, and other microbiologic and experimental variables. We also summarized the lobar distribution of pneumonia in 202 control and 192 vaccinated calves with this disease model and in calves similarly exposed to parainfluenza 3 virus/M. haemolytica or BHV-1/Pasteurella multocida. Pneumonia in control calves began in ventral tissues of all lobes, with lobar preferences, and progressed dorsally, the dorsal parts of both large caudal lobes being least affected. A high variance of pneumonia was evident within and among experiments. From the magnitude of variance observed in the control groups, the number of calves per group required in vaccine-challenge studies using this BHV-1/M. haemolytica disease model was estimated. Such estimates are required for any disease model used in vaccine-challenge studies.  相似文献   

10.
Lung and alveolar macrophage studies were conducted following experimental immunostimulation of calves with Freund's complete adjuvant (FCA). Intravenous administration of FCA to calves 35 days before aerosol exposure to serratia marcescens resulted in a 53.1% reduction in the 2-hour pulmonary mean percent retention of the organism when compared to control calves. FCA treatment increased alveolar macrophage concentration (cells/g lung) by 30.9%. Lymphoid and granulomatous responses were increased in the lungs of treated calves.  相似文献   

11.
Five clinically healthy calves received an intravenous injection of 25 g sodium D-lactate (223 mmol) in 100 ml sterile water and five control calves were given the same volume of 0.9 per cent sodium chloride. Two clinical examiners who were blinded to the status (test or control) of the calves observed that between eight and 40 minutes after the injections the calves that had received sodium-D-lactate could be distinguished with certainty from the control calves on the basis of their clinical signs, for example, an impaired palpebral reflex, somnolence and a staggering gait. One-compartment and two-compartment analyses of the changes in the plasma concentration of D-lactate, and its renal clearance, indicated that the calves metabolised considerable amounts of D-lactate.  相似文献   

12.
Two experiments were conducted. In the first, 16 crossbred Hereford calves were divided into two equal groups. The first group was vaccinated intranasally with a commercial vaccine against bovid herpesvirus 1 and the second group was unvaccinated. The calves were later exposed to an aerosol of bovid herpesvirus 1 (strain 108) for five minutes. Four calves from each group were subjected to transportation and four calves from each group were kept in an environmental chamber for four days. Four days after viral aerosol all calves were exposed to an aerosol of Pasteurella haemolytica and the same subgroups were again transported or held in the chamber for a further four days.

The calves that did not die from pneumonia were necropsied ten days after the final day of transport. Pulmonary lesions were present in both vaccinated and control animals but were less extensive in the vaccinated calves. Six of eight vaccinated but none of the eight control calves survived.

In the second experiment, eight crossbred Hereford calves were divided into two equal groups. One group was vaccinated with bovid herpesvirus 1 (strain 108) and the other acted as controls. Four weeks later all calves were sequentially exposed to aerosols of bovid herpesvirus 1 (strain 108) and P. haemolytica four days apart. Three of the four controls but none of the vaccinates died from pneumonia. Every lobe of the lungs in all the controls was affected by pneumonia while no pulmonary lesions were found in the vaccinated calves. The differences in efficacy of the modes of vaccination and the possible role of transport stress are discussed.

  相似文献   

13.
D.L. Benschop  J.P. Cant   《Livestock Science》2009,122(2-3):177-185
To characterize the effects of diet and age on the post-absorptive use of fermentation end-products, calves were subjected before and after weaning to plasma glucose, β-hydroxybutyrate and acetate clearance tests. Twenty-four one-week old male Holstein calves were assigned to one of four starter feeds, in a complete random design: (1) control; (2) 10% alfalfa; (3) 20% alfalfa; and (4) cracked corn. Starters were fed ad libitum. Starter intake, carcass-adjusted body weight gain and post-weaning rumen pH were higher in calves consuming alfalfa. Final bodyweights of calves fed alfalfa were 9.5 kg higher than calves given the other diets. With 20% alfalfa, papillae in the caudal ventral blind sac of the rumen were taller than with cracked corn and narrower than on the control. Rumen concentrations of volatile fatty acids were not affected by diet but the acetate:butyrate ratio and pH were higher on d 54 with 20% alfalfa compared to the control. Glucose clearance and flux rates increased significantly from d 11 to 39 but were unaffected to d 53. Increases in plasma β-hydroxybutyrate and acetate concentrations with age were accompanied by corresponding increases in BHB and acetate fluxes, respectively, but no change in the clearance rate constants. There was little effect of diet on clearance of the plasma metabolites. By 8 weeks of age, glucose was cleared from plasma at 2%/min, β-hydroxybutyrate at 16%/min, and acetate at 24%/min. Because of relatively low plasma concentrations of β-hydroxybutyrate and acetate due to incomplete rumen development, glucose remained the predominant energy source for all calves at 8 weeks.  相似文献   

14.
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.  相似文献   

15.
A study was undertaken to investigate the effects of the immune response induced by combined aerosol and parenteral vaccination on the lung lesions induced in calves by Pasteurella haemolytica AI. Twenty-four calves, twelve of which had been vaccinated with killed P. haemolytica by aerosol and subcutaneous injection in Freund's complete and incomplete adjuvant were challenged by intratracheal inoculation of live P. haemolytica. Serological response to vaccination was not marked but was best measured by the whole cell agglutination test or by indirect bacterial agglutination rather than by the passive haemagglutination test. Titres of vaccinates were positively correlated with the degree of pneumonic change following challenge while in nonvaccinated controls, titres were negatively correlated with lung lesions. These findings suggest the occurrence of an immunologically mediated hypersensitivity pneumonitis in the lungs of vaccinates and point to the potential efficacy of live bacterial aerosols for stimulation of protective immunity in pneumonic pasteurellosis.  相似文献   

16.
The present study was undertaken to investigate whether sequential exposure to aerosols of parainfluenza-3 virus followed by Pasteurella haemolytica, or P. haemolytica followed by parainfluenza-3 virus, could lead to the production of pulmonary lesions in conventionally-raised calves. Twenty male calves with low serum antibody titres to both organisms were placed in five equal groups. Synergism of parainfluenza-3 virus and P. haemolytica was not demonstrated in any of the sequentially infected groups and pulmonary lesions were mild in all challenged calves. Clinical signs of disease were not present after exposure to parainfluenza-3 virus although the virus was repeatedly isolated from nasal secretions of all inoculated calves. Exposure to P. haemolytica produced a transient response which consisted of increased rectal temperatures and respiratory rates, with a mild neutrophilic leukocytosis and a mild left shift present six hours postinoculation and returning to normal within 24 hours. Results from this study suggest, although do not confirm, that reduced pulmonary clearance of inhaled P. haemolytica in parainfluenza-3 virus infected calves does not necessarily lead to production of severe pulmonary lesions and that previous exposure to aerosols of P. haemolytica may not enhance secondary parainfluenza-3 virus infection.  相似文献   

17.
A study was conducted to characterize the aerosols produced by a medical ultrasonic nebulizer using solutions containing antimicrobials appropriate for therapy of equine lower respiratory bacterial infections (gentamicin sulfate and ceftiofur sodium). Test aerosols were generated using an ultrasonic nebulizer and were analyzed using a laser diffraction aerosol particle analyzer. The aerosol was described in terms of the particle size distribution (volume median diameter), span (sample dispersion), and aerosol density (% volume). The particle size distribution and aerosol density of gentamicin and ceftiofur aerosols were affected by the antimicrobial concentration of the solution. All solutions produced aerosols appropriate for delivery of antimicrobials to the intrathoracic airways of the horse, but the gentamicin (50 mg/ml) and ceftiofur (25 mg/ml) solutions offered the optimal combinations of particle size and aerosol density.  相似文献   

18.
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.  相似文献   

19.
Infection of seronegative Welsh mountain ponies was established by intranasal instillation or exposure to nebulised aerosol of egg grown H3N8 viruses. Pyrexia and coughing were noted following intranasal instillation and high titres of virus were recovered from the nasopharynx. Exposure to aerosol resulted in more severe clinical signs characterised by high temperatures, dyspnoea, anorexia and coughing; lower levels of virus were recovered from the nasopharynx. The severity of clinical signs and the kinetics of virus shedding were dose-related with the minimal infectious dose being 10(2)EID50/ml when ponies were exposed to aerosols produced by nebulisation of 20ml allantoic fluid. Full clinical signs only developed when ponies were exposed to a dose of 10(6)EID50/ml. It was concluded that exposure to nebulised aerosols of egg grown H3N8 viruses was a more reliable method of inducing clinical influenza than intranasal inoculation and would be more suitable for challenge studies.  相似文献   

20.
The effect of various aerosol doses of bovine herpesvirus 1, followed four days later by aerosol exposure to a constant level of Pasteurella haemolytica, was studied in 16 crossbred Hereford range calves. A Collision nebulizer was used to generate aerosols from virus suspensions with concentrations of 10(8.2) (high), 10(5.2) (moderate) or 10(2.2) (low) TCID50/mL. The bacterial suspension contained 10(7) colony forming units/mL. Control calves exposed only to P. haemolytica developed no pulmonary lesions. Calves in the low, moderate and high virus exposure groups developed lobular areas of atelectasis; in addition, one calf in the moderate and all four in the high virus exposure group developed fibrinous pneumonia. One of the latter calves died. The 50% effective dose for fibrinous pneumonia under these experimental conditions was 10(6.0) TCID50 bovine herpesvirus 1/mL of suspension in the nebulizer reservoir, and approximately 10(4.0) infectious units inhaled per calf.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号