BACKGROUND: Organic chemicals have been known to cause allergic diseases such as bronchial asthma and hypersensitivity pneumonitis; however, the possibility that they do not cause irreversible pulmonary fibrosis has not been considered. Polyacrylic acid (PAA), an organic chemical, has caused irreversible progressive pulmonary fibrosis in exposed workers, indicating its potential to induce pulmonary inflammation and fibrosis. Although intratracheal instillation studies are commonly used for evaluating lung pathology, traditional methods face challenges with chemical substances, particularly nanoparticles, which tend to aggregate in suspension and prevent uniform pulmonary distribution. Such aggregation alters the qualitative and quantitative responses to lung injury, limiting accurate assessment of lung pathology. To overcome this limitation, we developed a 'molecular dispersion method' that uses pH modification to negative charges to PAA particles, maintaining their dispersion. Using this method, we investigated the effects of PAA on pulmonary inflammation and fibrosis in a rat model. METHODS: F344 rats were intratracheally instilled with PAA using molecular dispersion (0.1 mg/rat, 1.0 mg/rat), PAA without molecular dispersion (1.0 mg/rat), and normal saline (control group). Rats were sacrificed at 3 days, 1 week, 1 month, 3 months, and 6 months after exposure to examine inflammatory and fibrotic responses. RESULTS: PAA caused persistent increases in neutrophil influx in the bronchoalveolar lavage fluid (BALF) from 3 days to 1 month following instillation. In histopathological findings, the group with molecular dispersion had almost no inflammatory masses in the lung tissue compared to the group without molecular dispersion, and exhibited relatively uniform dispersion. CONCLUSION Intratracheal instillation of dispersed PAA induced neutrophil inflammation and fibrosis in the rat lung, suggesting that PAA might have pulmonary inflammogenicity and fibrogenicity. Intrapulmonary dispersion of PAA particles following intratracheal instillation studies using the molecular dispersion method was similar to that following inhalation studies.
Animals ; Rats, Inbred F344 ; Acrylic Resins/adverse effects* ; Rats ; Inhalation Exposure/adverse effects* ; Male ; Pulmonary Fibrosis/pathology* ; Pneumonia/pathology* ; Lung/pathology* ; Bronchoalveolar Lavage Fluid/cytology*

At Nippon Medical School, a "Basic Clinical Training Course" is provided as an introduction to clinical medicine. Medical students undergo initial clinical skills training with simulators. We describe the technique of effective training to acquire clinical skills and the results of student evaluations and a questionnaire survey.1) The training consisted of 8 practicums, including internal examination, funduscopic examination, otoscopic examination, breast examination, auscultation (heart sounds and lung sounds), and collection of blood samples. Medical students moved in rotation once per time period (45 minutes) and performed practical training in each unit, which comprised 2 practicums.2) The training with the prescribed number of 50 students in 4 time periods was efficiently performed for 2 days and required 9 trainers per day. Student evaluations and a questionnaire survey revealed the interest and enthusiasm of medical students and showed they thought highly of the training.3) The training was efficiently performed and was thought to help reduce the teaching load of instructors. The educational effect of the training can be strengthened by increasing the convenience of the clinical simulation laboratory, by reinforcing the education of clinical skills and attitudes in clinical clerkship, and by evaluating these factors after the completion of the clinical clerkship.