ABSTRACT
The introduction of nonradioactive labels, such as hapten-like labeled32'39 or fluorochromized40"44 nucleotides and the employment o f high-affinity reagents that allow immunocytochemical detection and amplification o f the nonradioactive signal strength40,43'47 ushered in a new era o f nonisotopic ISH during the late seventies and early eighties. In particular, indirect nonradioactive ISH methods, using haptenized instead o f fluorochromized probes, could be carried out with three types o f reporter molecules to visualize hybridization results depending on the choice o f evaluation at the microscopic level: for fluorescence microscopy fluorochromes like FITC (green), TR ITC (red) and AMCA (blue),48'49 for light or reflection-contrast microscopy cytochemically detectable enzymes (producing colored precipitates) such as peroxidase and alkaline phosphatase50'52 and for electron microscopy electron-dense particles like colloidal gold,53'55 respectively. Together, these technical innova tions have turned this hybridization technique into a simpler and more accessible one as com pared to radioactive ISH. As a result, the appli cation o f nonradioactive ISH technologies has expanded enormously in various fields o f bio logical research.
