In cultured eucaryotic cells, heat treatments specifically induced the rapid synthesis of the so-called heat-shock polypeptides. To ascertain the physiological importance of this phenomenon for highly differentiated organisms, we attempted to determine whether the heat-shock response occurs in a living endothermic organism at extreme temperatures, and if so, whether the response is organ specific. We developed a procedure to label proteins efficiently in 5-to 18-day-old chicken embryos. Heat-shock polypeptides of identical sizes of 85,000, 70,000, and 25,000 daltons were synthesized predominantly in chicken embryo fibroblasts and in many different organs of 18-day-old embryos at 42.5 to 44°C.The heat-shock response, whereby a new set of proteins, the heat-shock proteins (HSPs), are synthesized at slightly elevated temperatures, is of widespread occurrence and has been studied in simple organisms and cultured cells (2,7,8,15). Until recently, with the exception of the early Drosophila organ studies (26), little work had been done on organ-specific or whole-animal responses to heat shock in higher eucaryotes.We chose the classical embryonated chicken egg, used elegantly in the study of through the shell. The hole was then sealed with wax, and the eggs were incubated at the temperatures indicated below for 2 to 3 h. Embryos were subsequently removed from the eggs and dissected. Isolated organs were washed in phosphate-buffered saline and Dounce homogenized in 1 ml of sample buffer (11).The samples were boiled for 4 min, and 2-to 10-p.l portions of each sample were diluted into 40 p.1 of sample buffer and electrophoresed on 10o acrylamide gels. Gels were subjected to fluorography (13) and exposed for 1 to 7 days.
479on April 27, 2019 by guest