Diaminobenzidine Induces Fluorescence in Nervous Tissue and Provides Intrinsic Counterstaining of Sections Prepared for Peroxidase Histochemistry

3,3'-Diaminobenzidine (DAB) is widely used as a chromogen for visualization of horseradish peroxidase activity in neuroanatomical tracing experiments and in immunohistochemistry. The product of the enzymatically catalyzed oxidation of DAB by hydrogen peroxide is brown and nonfluorescent. In frozen sections of formaldehyde fixed rat and mouse brain that had been exposed to DAB either alone or with hydrogen peroxide, we observed strong greenish fluorescence in myelinated nerve fibers and in the somata of some neurons. This fluorescence was not associated with brown coloration and was not due to endogenous peroxidase activity. Extractions, blocking reactions, and other histochemical tests indicate that the fluorescence resulted from the combination of DAB with aldehyde groups that were formed by oxidation of unsaturated linkages in lipids. DAB induced fluorescence provides a simple and useful demonstration of background anatomy in sections that also contain specifically localized deposits of peroxidase activity.     

Who remains childless?

Who are the men and women who are childless in their mid-30s? Life history data for a British cohort born in 1946 show that age at marriage and marital breakdown were clearly associated with childlessness. Women who were only children were more likely to be childless than those with siblings. Further, early menarcheal age, being highly qualified and having a high status occupation were indirectly related to childlessness. For men, particularly amongst those who had experienced a broken marriage, it was the most ambitious, the highly educated and those in professional occupations who were relatively more likely to be childless.