Hyperbaric oxygen therapy for beta-radiation-induced scleral necrosis.

BACKGROUND: Beta-radiation has been used since 1950 as a postoperative measure to reduce the recurrence of pterygia. Scleral necrosis has been a major complication after radiotherapy that has led to perforation of the globe, endophthalmitis, and visual loss in some cases. METHOD: A patient is presented in whom scleral necrosis developed 25 days after a pterygiectomy with bare sclera technique followed by 3000 cGy in 3 weekly, divided doses of strontium 90. After a conjunctival graft failure, the patient was treated with hyperbaric oxygen therapy. RESULTS: The sclera revascularized and returned to nearly normal thickness after 14 sessions of hyperbaric oxygen therapy. CONCLUSION: Hyperbaric oxygen therapy may be an effective treatment for acute scleral necrosis after postoperative beta-radiation.

Features of asthma in older adults.

A study compared clinical and functional features of elderly patients with asthma to younger patients at a university medical center. Older patients had a larger than predicted reduction in pulmonary function parameters even though physician-assessed severity, duration of diagnosed asthma, and smoking status were no different between groups. A significant increase in the comorbid diagnosis of chronic obstructive pulmonary disease was noted in older patients with asthma. These two points support the hypothesis that long-standing asthma may lead to irreversible airflow obstruction. Older patients reported better medication compliance and decreases in some respiratory symptoms and demonstrated lower health care utilization.

Interstitial macrophage subpopulations: responsiveness to chemotactic stimuli.

Recent data suggest that interstitial macrophages are a heterogeneous group of cells with several subpopulations. This study was undertaken to determine if there is heterogeneity among rat interstitial macrophage subpopulations ability to respond to chemotactic stimuli. Alveolar macrophages were harvested and separated into density-defined fractions by centrifugation through a continuous iso-osmotic gradient of colloidal silica. Unfractionated and density-defined interstitial macrophages were then characterized as to their ability to migrate towards F-Met-Leu Phen and zymosan activated serum. Interstitial macrophages of density 1.053 and 1.083-1.097 gm/ml were found to have the greatest migrational movement towards F-Met-Leu-Phen which was lower than the unfractionated population. Interstitial macrophage subpopulations migrational movement towards zymosan activated serum exhibited a major peak by macrophages of density 1.053 gm/ml and a minor peak by macrophages of density 1.083-1.097 gm/ml which was lower than the unfractionated population. These results demonstrated that interstitial macrophages are heterogeneous in their migrational ability towards the chemotactic stimuli F-Met-Leu-Phen and zymosan activated serum and that there may be a cooperative interaction between the subpopulations which affects macrophages migrational ability.

Alveolar macrophage subpopulations' responsiveness to chemotactic stimuli.

Recent data suggest that alveolar macrophages are a heterogeneous group of cells with several subpopulations. This study was undertaken to determine if there is heterogeneity among rat alveolar macrophage subpopulations ability to respond to chemotactic stimuli. Alveolar macrophages were harvested by bronchoalveolar lavage and fractionated into density-defined fractions by centrifugation through a continuous isoosmotic gradient of colloidal silica. Unfractionated and density-defined alveolar macrophages were then characterized as to their ability to migrate towards F-Met-Leu-Phen and zymosan-activated serum. Alveolar macrophages of density 1.083-1.097 gm/ml were found to have the greatest migrational movement toward F-Met-Leu-Phen, which was higher than the unfractionated population. In contrast, 2 peaks in alveolar macrophage subpopulations migrational movement towards zymosan-activated serum were noted that were lower than the unfractionated population. These results demonstrated that alveolar macrophages are heterogeneous in their migrational ability towards the chemotactic stimuli F-Met-Leu-Phen and zymosan-activated serum and that there may be a cooperative interaction between the subpopulations that affects macrophage migrational ability.

Re-expansion pulmonary edema. A potential role for free radicals in its pathogenesis.

Re-expansion pulmonary edema (RPE) has been attributed to decreased lung interstitial pressures from a variety of mechanisms. Because some recent studies have implicated mechanisms that increase microvascular permeability in RPE, we tested whether the edema were due to free radical generation during re-expansion and reoxygenation of the collapsed lung. We used a rabbit model of RPE to test the effects of intracellular (dimethylthiourea) or extracellular (catalase) oxygen metabolite scavengers. Allopurinol was administered separately to determine whether xanthine oxidase was an important source of superoxide in this model. Edema was quantitated both gravimetrically and histologically, and lung xanthine oxidase activity was measured using a sensitive fluorometric assay with pterin as substrate. The results suggest indirectly that OH. or H2O2 (derived from O2-) contribute to the well-documented increase in lung permeability in RPE because dimethylthiourea, dimethylthiourea plus catalase, or catalase alone inhibited the edema to various degrees. Further, we observed histologically that increased numbers of neutrophils were present in re-expanded lungs and that neutrophil infiltration appeared to be diminished by antioxidant administration. Allopurinol did not decrease the edema, because xanthine oxidase activity in rabbit lung tissue is extremely low. We speculate that free radical generation in lung tissue contributes to the pathogenesis of RPE, although reinitiation of lung perfusion and ventilation requires a rapid change in intrathoracic pressure.