Allergic contact dermatitis by ophthalmological medications in Brazil: experience of a dermatology department.

SUMMARY: Topical treatments in ophthalmologic therapy are significant for the development of allergic contact dermatitis (ACD) in the periorbital region. Preservatives, antibiotics, glucocorticoids, and beta-blocker eye drops are defined as drugs with the highest sensitizing potential. The unavailability of patch test batteries containing substances of ophthalmological use makes it difficult for this diagnosis. In the present report, we describe six patients who developed ACD induced by different agents presenting in eye drops, confirmed with the cutaneous patch tests. The ACD diagnosis due to ophthalmic medications can be challenging, since many different agents can cause it, and the sensitivity of these cutaneous tests is low. Thus, early diagnosis is essential to avoid the complications of ACD on the skin and ocular disorders related to chronic periorbital eczema.

Hydrogen metabolism of Azospirillum brasilense in nitrogen-free medium.

Production of H2 by Azospirillum brasilense under N2-fixing conditions was studied in continuous and batch cultures. Net H2 production was consistently observed only when the gas phase contained CO. Nitrogenase activity (C2H2 reduction) and H2 evolution (in the presence of 5% CO) showed a similar response to O2 and were highest at 0.75% dissolved O2. Uptake hydrogenase activity, ranging from 0.3 to 2.5 mumol H2/mg protein per hour was observed in batch cultures under N2. Such rates were more than sufficient to recycle nitrogenase-produced H2. Tritium-exchange assay showed that H2 uptake was higher under Ar than under N2. Uptake hydrogenase was strongly inhibited by CO and C2H2. Cyclic GMP inhibited both nitrogenase and uptake hydrogenase activities.