ImageCalc: a Microsoft Windows application for quantitative image analysis and comparison.

In this report we describe a Microsoft Windows-based computer program (ImageCalc) for the analysis of gels and autoradiograms and for computation of stand-alone images and images that are related to each other (i.e., images with the same image parameters). The program is able to subtract, add, multiply and divide constant values or full images from another image. It measures the intensity of (part of) an image in two ways: (i) by calculation of the total intensity and the average intensity/pixel and (ii) by line scanning. The program allows importation of all images that are stored in an 8-bit uncompressed format and saves them in a Microsoft Windows bitmap format. Densitometric analysis of gels and autoradiograms, digitized using an ordinary optical scanner, is illustrated for glycosaminoglycans separated by electrophoresis on agarose gels and stained with Azure A silver, and for [32P]phosphatidic acid, separated by thin-layer chromatography. Another application of the program is the analysis of multiple related images that are resolved in time or for which different emission or excitation wavelengths are used (fluorescence microscopy). As an example, the change of cytosolic [Ca2+] is demonstrated in cultured human skeletal muscle cells after stimulation with acetylcholine.