Chemical Clearing and Dehydration of GFP Expressing Mouse Brains

Generally, chemical tissue clearing is performed by a solution consisting of two parts benzyl benzoate and one part benzyl alcohol. However, prolonged exposure to this mixture markedly reduces the fluorescence of GFP expressing specimens, so that one has to compromise between clearing quality and fluorescence preservation. This can be a severe drawback when working with specimens exhibiting low GFP expression rates. Thus, we screened for a substitute and found that dibenzyl ether (phenylmethoxymethylbenzene, CAS 103-50-4) can be applied as a more GFP-friendly clearing medium. Clearing with dibenzyl ether provides improved tissue transparency and strikingly improved fluorescence intensity in GFP expressing mouse brains and other samples as mouse spinal cords, or embryos. Chemical clearing, staining, and embedding of biological samples mostly requires careful foregoing tissue dehydration. The commonly applied tissue dehydration medium is ethanol, which also can markedly impair GFP fluorescence. Screening for a substitute also for ethanol we found that tetrahydrofuran (CAS 109-99-9) is a more GFP-friendly dehydration medium than ethanol, providing better tissue transparency obtained by successive clearing. Combined, tetrahydrofuran and dibenzyl ether allow dehydration and chemical clearing of even delicate samples for UM, confocal microscopy, and other microscopy techniques

Low basal serum cortisol in patients with severe atopic dermatitis: potent topical corticosteroids wrongfully accused

BACKGROUND: Topical corticosteroids are used extensively to treat inflammatory skin disorders including atopic dermatitis (AD). Several studies have described temporary reversible suppression of hypothalamic-pituitary-adrenal function. However, sound evidence of permanent disturbance of adrenal gland function is lacking. OBJECTIVES: To relate basal cortisol levels to prior use of topical corticosteroids and disease activity in patients with moderate to severe AD and to investigate the effect on basal serum cortisol levels of topical corticosteroid treatment during hospitalization. METHODS: Two groups of patients with AD were evaluated: 25 inpatients with severe AD who required hospitalization (group 1) and 28 outpatients with moderate to severe AD (group 2). In group 1, morning basal serum cortisol levels were measured twice, at admission and at discharge; in group 2, morning basal serum cortisol levels were measured once. Use of topical corticosteroids in the 3 months prior to the cortisol measurement was recorded and disease activity was monitored using the Six Area, Six Sign Atopic Dermatitis (SASSAD) score and serum thymus and activation-regulated chemokine (TARC) levels. RESULTS: On admission, basal cortisol levels in group 1 were significantly (P < 0.001) decreased in 80% of the patients. In group 2, the basal cortisol levels were normal in all but three patients. Comparing the two groups, group 1 on admission had a significantly lower cortisol level than that of group 2 (P < 0.001). Disease activity in group 1 on admission was significantly higher than that of group 2 (P < 0.001). There was no difference in use of topical corticosteroids in the 3 months before cortisol measurement. At discharge in group 1 there was a significant increase (P < 0.0001) of basal cortisol levels and a significant (P < 0.001) decrease in disease activity reflected by the decrease in serum TARC levels and SASSAD score. CONCLUSIONS: Disease activity, rather than the use of topical corticosteroids, is responsible for the low basal cortisol values in patients with severe AD