Evaluation of the effects of toluene inhalation on alveolar epithelial permeability by 99mTc-DTPA inhalation scintigraphy in automobile painters

In vivo observations provide insight into roles of eosinophils and epithelial cells in asthma

Observations in vivo in patients, supported by guinea-pig in vivo data, take centre stage in this perspective. Its objective is to highlight dichotomies between asthma features observed in vivo and accepted views involving cell/molecular biology research paradigms. For example, increased bronchial epithelial permeability is now considered a major paradigm and trait of asthma, yet, absorption of inhaled tracers has not been increased in vivo in asthma. Such maintained barrier function in exudative asthma reflects in vivo asymmetry of the epithelial lining as barrier between outside and inside world of molecules and cells. In desquamatory asthma, maintained epithelial tightness may be explained by in vivo demonstrations of exceedingly patchy epithelial loss, prompt creation of plasma-derived provisional barriers, and high-speed epithelial regeneration. Acknowledged protein/peptide secretion by epithelial cells in vitro is contrasted here with a dominant, unidirectional movement in vivo of plasma-derived proteins/peptides (including antimicrobial peptides) to the surface of an intact epithelial lining. Furthermore, longstanding claims that epithelium-produced adenosine is a mediator of asthma are eroded by observations in vivo in asthmatics. Notions concerning activation/fate of mucosal tissue eosinophils illustrate additional distinctions between accepted views and in vivo patient observations. Finally, in vitro-based paradigms preaching defect epithelial regeneration and increased permeability in pathogenesis of asthma are contrasted with experimental in vivo observations of exaggerated epithelial regeneration, which is multipathogenic in its own right. In conclusion, unexpected and challenging in vivo observations in recent decades underpin novel insights into mucosal mechanisms in asthma.

Effects of volatile substance abuse on the respiratory system in adolescents

Aim

Inhalant abuse is a prevalent and often overlooked form of substance abuse in adolescents. Chronic inhalant abuse can damage respiratory, cardiac, renal, hepatic, and neurologic systems. This study aims to determine the physiologic effects of inhaling solvents on the respiratory functions.

Methods

The general health status of the subjects was assessed by history taking, physical examination and a questionnaire which was designed to show the severity of respiratory symptoms. Spirometry, ventilation/perfusion scintigraphy, and high resolution computed tomography (HRCT) were performed to assess pulmonary functions and anatomy.

Results

Thirty-one male volatile substance abusers and 19 control subjects were included in the study. The mean age of onset of inhalant use was 14.6 ± 2.2 (9-18) years and duration of drug use was 3.7 ± 1.7 years. The most common respiratory symptoms in volatile substance abusers were nasal congestion (45.2%), sputum (38.7%), exercise intolerance (32.3%) and cough (22.6%). Results of spirometric studies showed 12 (41.4%) subjects with low FVC values < 80% of predicted, indicative of restrictive ventilatory pattern in the study group. Although the difference was not statistically significant, restrictive ventilatory pattern was higher in the study group. There was no statistically significant correlation between restrictive ventilatory pattern and the age of onset/duration/frequency of inhalant abuse, respiratory symptoms and scintigraphic abnormalities. Subjects who had restrictive pattern in their pulmonary function tests were more likely to have abnormal findings at HRCT (p < 0.01).

Conclusion

This study has shown a positive correlation between volatile substance abuse and the development of restrictive ventilatory pattern, but more comprehensive studies are needed for more precise conclusions.