Simultaneous in vivo imaging of leukocyte migration: heterogeneity among iris, limbus, and choroid vessels.

PURPOSE: Endothelial cells of different vascular systems may express site-specific adhesion molecules to attract leukocyte subsets. This study describes a method to visualize and compare leukocyte-endothelial interactions in three vascular beds within the same eye in mice. METHODS: Digital in vivo fluorescence microscopy was used to record a trans-corneal iris view, a superficial limbus view, and a trans-scleral anterior choroid view of mouse tissue. Uveitis was induced by intravitreal injection of E. coli endotoxin into BALB/c mice. Leukocytes were labeled systemically with SYTO-16 or rhodamine 6G. Leukocyte rolling and sticking were quantified at baseline and 4, 6, and 24 hours after endotoxin injection. RESULTS: In a normal animal, the limbus had 18 times the number of rolling leukocytes and 6 times the number of sticking leukocytes relative to the iris. All three vascular beds were affected by intravitreal injection of endotoxin. Although they each showed increased numbers of rolling and sticking cells, the levels and kinetics of these increases differed. Rolling peaked at 6 hours in the iris (34-fold increase from baseline) and limbus (7-fold increase) but was maximal in the choroid earlier with a 16-fold increase. Sticking was maximal at 4 hours for iris (96-fold increase) and choroid (19-fold increase) but peaked in the limbus at 6 hours (47-fold increase from baseline). CONCLUSIONS: This study demonstrates that leukocyte-endothelial dynamics are not the same in different vascular beds in the normal mouse eye. Furthermore, site-specific differences in responses to intravitreally injected endotoxin, beyond what can be readily explained by differential distribution of endotoxin, were observed. The methodology can be used to test the hypothesis that endothelial cells within the eye have site-specific patterns of adhesion molecule expression.

Foreign-body pneumonitis associated with tracheostomy.

Foreign-body aspiration in adults is usually associated with asphyxiation after aspiration of food particles. The present report documents a case of foreign-body aspiration that resulted from poor tracheostomy care in an alcoholic patient, and caused fulminant pneumonitis.

Effect of aging on ventilatory response to exercise and CO2.

Studies were performed to determine the effects of aging on the ventilatory responsiveness to two known respiratory stimulants, inhaled CO2 and exercise. Although explanation of the physiological mechanisms underlying development of exercise hyperpnea remains elusive, there is much circumstantial evidence that during exercise, however mediated, ventilation is coupled to CO2 production. Thus matched groups of young and elderly subjects were studied to determine the relationship between increasing ventilation and increasing CO2 production (VCO2) during steady-state exercise and the change in their minute ventilation in response to progressive hypercapnia during CO2 rebreathing. We found that the slope of the ventilatory response to hypercapnia was depressed in elderly subjects when compared with the younger control group (delta VE/delta PCO2 = 1.64 +/- 0.21 vs. 2.44 +/- 0.40 l X min-1 X mmHg-1, means +/- SE, respectively). In contrast, the slope of the relationship between ventilation and CO2 production during exercise in the elderly was greater than that of younger subjects (delta VE/delta VCO2 = 29.7 +/- 1.19 vs. 25.3 +/- 1.54, means +/- SE, respectively), as was minute ventilation at a single work load (50 W) (32.4 +/- 2.3 vs. 25.7 +/- 1.54 l/min, means +/- SE, respectively). This increased ventilation during exercise in the elderly was not produced by arterial O2 desaturation, and increased anaerobiasis did not play a role. Instead, the increased ventilation during exercise seems to compensate for increased inefficiency of gas exchange such that exercise remains essentially isocapnic. In conclusion, in the elderly the ventilatory response to hypercapnia is less than in young subjects, whereas the ventilatory response to exercise is greater.