Microwave fixation of water-cooled insect tissues for immunohistochemistry

In this paper a new technique for microwave-accelerated tissue fixation and washing is described. The temperature of the irradiated specimens is controlled by means of a specially designed water-cooling device. Two types of fixation fluids, one of them containing rather concentrated picric acid, and a washing procedure were tested empirically on dissected nervous tissue of the Colorado potato beetle, Leptinotarsa decemlineata (Say). Entire beetles were processed in a similar way. It was shown that specimens could be irradiated as long as was required for good fixation and washing results, without the accumulation of excessive heat. No differences in morphology and immunoreactivity were observed when compared with standard immersion-fixed controls. A considerable reduction in processing time was achieved.