title: Effect of cycloheximide on RNA synthesis in Chironomus polytene chromosomes.
abstract: Modifications in the synthesis of salivary gland RNA were induced by treatments with 10 microgram/ml cycloheximide (CHM) on 4th instar larvae of Chironomus pallidivitattus. After 3, 6 and 24 h CHM treatment, RNA was labeled "in vitro", by incubating the salivary glands in a medium containing H3-uridine. The electrophoretical analyses corresponding to the 3 and 6 h treatment showed a stimulation of the non-ribosomal components of the newly synthesized RNA, while preribosomal RNA synthesis appeared depressed. This fact was also confirmed at cytological level, since autoradiograms made after 3 h of CHM treatment showed a reduced H3-uridine label over the nucleolus and an increase of diffuse labeling over the chromosomes. Longer treatments (24 h) causes a considerable inhibition of the synthesis of all RNA species. The role played by protein synthesis inhibition in the aforementioned effects is discussed.--Some of the morphological implications of CHM treatment, such as modifications of the nucleolar structure (nucleolar segregation) are also reported. The use of a squash technique based on glutaraldehyde fixation of the salivary glands, considerably facilitates such studies.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002466:Cell Nucleolus / Q000187:drug effects; D002875:Chromosomes / Q000187:drug effects*; D003513:Cycloheximide / Q000494:pharmacology*; D004175:Diptera; D007814:Larva; D012313:RNA / Q000096:biosynthesis*; D012469:Salivary Glands / Q000378:metabolism; D013997:Time Factors
chemical_list: D012313:RNA; D003513:Cycloheximide