Ultrastructural studies on the effect of heat shock treatment on larval salivary gland cells of Drosophila auraria.

In this study, the effect of heat shock treatment on Drosophila auraria late 3rd instar larval salivary glands was examined. Heat shock treatment was applied on whole animals and on isolated salivary glands. The fine structural changes were examined using transmission electron microscopy, after a temperature rise from normal (25 +/- 1degreesC) to 37 degreesC or 40 degreesC for various periods of time. The AcPace histochemical technique was used to demonstrate the acid phosphatase activity on lysosomal structures and x-ray microanalysis to determine the elemental composition of intramitochondrial granules. Our results indicate that the extent of heat shock damage on salivary gland cells depends on the heat shock intensity (temperature and duration). Three main changes were observed after heat shock treatment: a) appearance of lysosomal structures; b) alteration in the mitochondrial morphology and appearance of intramitochondrial granules and c) morphological alterations of secretory granules. Vesiculation of the Golgi complex and dilation of the rough endoplasmic reticulum were often seen. Irregular structures of unknown function were observed in the cytoplasm, which are referred to as x-structures. Rectangular secretory granules were observed in some cases, for the first time in a Drosophila species. These results are discussed in correlation with the heat shock effect on larval salivary glands of Drosophila.