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Summary

Nonspecific mitogenicity of Mycoplasma hyopneumoniae membranes for blood lymphocytes (bl) and bronchial lymph node lymphocytes (lnl) from swine was investigated. Additionally, the influence of respiratory tract exposure to the same membrane preparation on responsiveness of these cells was evaluated. Membranes utilized in lymphocyte transformation tests and for inoculation of swine were prepared by osmotic lysis of mycoplasma cells. Conventionally reared and cesarean-derived, colostrum-deprived swine were given membranes intratracheally and responses of bl and lnl to membranes were assessed from postinoculation day 0 to 14. Utilizing a stimulation index of 3 as the cutoff, heated (56 C) M hyopneumoniae membranes exerted moderate nonspecific stimulation of bl 11 of 12 times when bl were collected from normal (control or preinoculation) swine. Similarly, lnl from conventionally reared and control groups of swine were stimulated nonspecifically 4 of 6 times by the same membrane preparations. Exposure of the respiratory tract to membranes appeared to have no influence on stimulation responses of bl at postinoculation days 6 or 13, whereas moderate to marked increases in responsiveness of lnl were detected when collected at necropsy on postinoculation days 7 or 14. These findings indicated that compartmentalization of lymphocyte sensitization in the bronchial lymph nodes resulted from respiratory tract exposure to mycoplasmal membranes. Results obtained confirm that M hyopneumoniae has a moderate nonspecific stimulatory effect on porcine lymphocytes. Nonspecific mitogenicity of M hyopneumoniae on lymphocytes, resulting in altered immune system function, may be a contributing factor in the pathogenesis of mycoplasmal pneumonia of swine.

Free access
in American Journal of Veterinary Research

SUMMARY

Cellular and humoral immune responses of pigs inoculated with Mycoplasma hyopneumoniae were investigated at postinoculation weeks (piw) 2, 4, and 6. The response of blood lymphocytes (bl) and bronchial lymph node lymphocytes (lnl) to stimulation by M hyopneumoniae antigens was evaluated by a lymphocyte-stimulation test. Specific antibodies in serum and lung washing samples were assayed by elisa. Immunoglobulin-positive cells in lungs and bronchial lymph nodes were identified by indirect fluorescent antibody test, using isotype-specific monoclonal antibodies.

At piw 0 to 6, bl from control and M hyopneumoniae-inoculated pigs were stimulated by M hyopneumoniae cells; however, bl from inoculated pigs generally had higher stimulation indices, especially at piw 6. The response of lnl was influenced by previous exposure to M hyopneumoniae, as indicated by higher stimulation indices (P < 0.01) of lnl from inoculated pigs killed at piw 2 and 6. Specific elisa antibodies to M hyopneumoniae in lung washings from inoculated pigs consisted mainly of IgG and IgA isotypes.

Examination of lung sections by indirect immunofluorescence revealed that cells producing IgM and IgA were in controls as well as M hyopneumoniae-inoculated pigs, but IgG-positive cells were only in lungs of inoculated pigs. Resolution of pneumonia appeared to correlate with development of increased sensitization of bl, as well as development of marked increases in immunoglobulins, particularly IgG in lung washings at piw 6.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of clomipramine hydrochloride on heart rate and rhythm in dogs.

Animals—17 healthy Beagles.

Procedures—In experiment 1, 8 dogs received placebo or clomipramine (20 mg/kg of body weight, q 24 h, PO) for 7 days in a 2-way crossover design. In experiment 2, 9 dogs were evaluated for 48 hours before and 24 hours after oral administration of clomipramine (4 or 12 mg/kg) in a 2-way crossover design. Electrocardiogram and heart rate were monitored continuously by use of telemetry.

Results—A significant diurnal rhythm in heart rate was detected; minimum values were recorded at night. Administration of 20 mg of clomipramine/kg induced a significant reduction in heart rate, with peak effect achieved approximately 12 hours after dosing. Administration of 4 or 12 mg of clomipramine/kg did not result in significant changes in heart rate. Sinoatrial and second-degree atrioventricular block and ventricular escape beats were observed during periods of slow heart rate in more dogs that received clomipramine (3 to 4 of 8 dogs), compared with dogs that received placebo (1 to 2 of 8 dogs), but this difference was not significant.

Conclusions and Clinical Relevance—Short-term administration of clomipramine induced benign cardiovascular effects in dogs rather than the potentially dangerous arrhythmias or tachycardia reported following administration of tricyclic antidepressants to humans. Precautions regarding cardiovascular effects may not be needed for the use of clomipramine in healthy dogs. (Am J Vet Res 2000;61:960–964)

Full access
in American Journal of Veterinary Research