Experimental Mycoplasma pulmonis infection in pathogen-free mice. Models for studying mycoplasmosis of the respiratory tract.

Mice of a Swiss substrain, reared under rigid pathogen-free (PF) conditions, were inoculated intranasally with broth cultures of Mycoplasma pulmonis ranging in dose from 10(1) to 9 x 10(9) colony forming units (CFU). A highly reproducible disease resulted with an LD(50) of 1.3 x 10(8) CFU and a PD(50) (dose producing pneumonia in 50% of mice) of 3.4 x 10(5) CFU. The inoculating dose of M pulmonis was found to be the critical determinant of the severity, duration and pathologic character of the respiratory disease produced. PF mice given 10(4) CFU or less developed a transient illness characterized by low frequencies of rhinitis, otitis media, laryngotracheitis and focal pneumonia. This was proposed as a low dose model. Doses of 10(5) to 10(9) CFU resulted in high frequencies of rhinitis, otitis media, laryngotracheitis and pneumonia. Within the first 10 days the pneumonia often was fatal, being characterized by an outpouring of neutrophils and edema fluid into alveolar spaces, pulmonary congestion and hemorrhage and, occasionally, pleuritis. This high dose-acute disease model was shown to be the result of seeding alveoli with large numbers of organisms at the time of intranasal inoculation. In animals surviving doses of 10(5) to 10(9) CFU beyond approximately 10 days postinoculation, the larger concentration of organisms was present in bronchi and bronchioles, giving rise to a third model, the high dose-chronic disease model. The predominant lesions were chronic suppurative bronchitis and bronchiolitis, marked peribronchial lymphoid cuffing, variable numbers of neutrophils and macrophages in alveoli, and complications such as bronchiectasis and pulmonary abscesses. Identical lesions were observed in axenic mice infected with M pulmonis. The infection in PF mice is considered a highly useful experimental system, both for comparative study of respiratory mycoplasmosis and for investigations directed toward understanding and eliminating the natural disease this agent causes in conventional mice and rats.

HLA-B*27 typing by sequence specific amplification without DNA extraction.

HLA-B27 appears to play a direct role in the pathogenesis of ankylosing spondylitis and almost all patients with this disease have HLA-B27. Therefore, a diagnosis of ankylosing spondylitis can virtually be excluded in the absence of HLA-B27. Many techniques have been used for HLA-B*27 typing. Of these, molecular methods are the most sensitive and specific but require extracted DNA as the testing material. A technique where HLA-B*27 is amplified directly from whole blood using sequence specific primers has been developed. This technique uses small sample volumes, is not restricted by choice of anticoagulant or sample age up to at least six weeks, and can be applied to other clinical polymerase chain reaction based procedures.

The association between murine cytomegalovirus induced hepatitis and the accumulation of oval cells.

The accumulation of oval cells is an early event in the development of hepatocellular carcinoma induced by certain experimental regimes involving hepatocarcinogens. Oval cells have also been observed during chronic hepatitis induced by alcohol and iron overload. In this study, livers of murine cytomegalovirus (MCMV) infected mice were examined to determine whether hepatitis induced by this virus could initiate oval cell proliferation. BALB/c and C57BL/6 mice were infected with MCMV and studied 4, 8, 10 and 12 months later, alongside control (uninfected) mice. The livers were examined histochemically, immunocytochemically and by in situ hybridization to identify oval cells, inflammatory cells and proliferating cells. Oval cells were seen in the periportal regions of livers from MCMV infected BALB/c mice. These increased in number from 4 to 12 months after infection in parallel with increases in the numbers of inflammatory cells, even though cells expressing MCMV antigens were no longer evident in these samples. Proliferating oval cells and hepatocytes were identified by PCNA staining, indicating an increased level of liver regeneration in the infected livers. C57BL/6 mice are less susceptible to persistent MCMV hepatitis and had fewer oval cells than BALB/c mice. Thus the study demonstrates an association between MCMV induced hepatitis, inflammation, and presence of oval cells.

The effectiveness of esophageal stethoscopy in a simulated in-flight setting.

PURPOSE: Previous research has confirmed the inability of flight nurses in an airborne BO-105 helicopter to hear breath sounds using normal or amplified transthoracic stethoscopy. The purpose of this study was to determine whether esophageal stethoscopy enabled effective auscultation of breath sounds in a simulated in-flight environment. METHODS: The cabin-sound environment of an in-flight BO-105 was recorded and recreated in an audiology laboratory, where five flight nurses were evaluated listening to taped breath sounds via an esophageal stethoscope. This audiotape model, validated in a previously published study, used a tape consisting of 24 20-second segments. Each segment, the beginning of which was marked with a beep signal, consisted of 20 seconds of silence or breath sounds. The distal (esophageal) end of the esophageal stethoscope was attached to the tape recorder; the intensity level of breath sounds heard at the stethoscope earpiece was calibrated to equate the sound level of actual esophageal breath sounds recorded on a volunteer. RESULTS: All nurses correctly identified the 24 taped segments as silent or including breath sounds 100% of the time. CONCLUSION: In the simulated environment tested, esophageal stethoscopy enabled 100% accuracy in identification of breath sounds, as compared with previously reported 0% efficacy for standard transthoracic auscultation. Study in the actual patient-care environment is indicated to confirm the usefulness of esophageal stethoscopy in the in-flight setting.