Ecdysone-induced changes in glycoprotein synthesis and puff activities in Drosophila virilis salivary glands

During five hours after the injection of -ecdysone into the hemolymph of D. virilis late third instar larvae the formation of larval glycoproteins in the salivary glands is terminated and the synthesis of a different set of glycoproteins which is characteristic for the prepupal gland is initiated. The data presented suggest that products from early puffs inhibit the formation of larval glycoproteins while the induction of late puffs may be responsible for the appearance of prepupal glycoproteins.     

Snythesis of mucoprotein secretion in the salivary glands of Drosophila melanogaster IIIrd instar larvae]

The process of mucoprotein (glue) accumulation is described. This substance is secreted by salivary glands of the III instar larvae of Drosophila melanogaster. Granules of the secretory substance appear in the glandular cells 90 hrs after egg laying. Its secretion takes place within 120 hrs. The template RNA of glue proteins appears to be synthesized within the range of 72-85 hrs since actinomycin treatment of larvae at this time suppresses the formation of secretory substance. The portion of secretory proteins amounts to 23-32% of the total gland protein. In a mutant, 13tl, deficient by the absence of pupation, no PAS-positive, staining of glands or secretory granules identified under the phase-contrast microscope was found. A possible participation of fat body in the formation of mucoprotein secretory substance is discussed.     

Ecdysterone induced protein synthesis in salivary glands and in fat body of Drosophila melanogaster larvae

Salivary glands of 3rd instar larvae of Drosophila melanogaster were labeled with ³H-leucine in the presence and absence of ecdysterone. Twentysix ecdysterone inducible proteins were detected. Their induction was correlated with puff stage. Synthesis of fifteen proteins commenced during early puff stage (PS2); synthesis of seven others at late puff stages (PS8–10). Synthesis of four proteins was induced between puff stage 3/4 and 7/8. Thus, the hormonal induction of protein synthesis generally reflected the appearance of early and of late puffs as described by Ashburner (1972). Eleven ecdysterone inducible proteins were detected in larval fat body in vitro. Comparison of the fat body to the salivary gland proteins revealed that one of the ecdysterone induced fat body proteins was identical in molecular weight and charge to one of the proteins induced by ecdysterone in salivary glands.     

Structural changes in the salivary glands of Ixodes ricinus larvae

The authors analysed the structure of Ixodes ricinus (L.) larvae in specimens immediately after leaving the egg sheaths, in those which have not fed for 2 months after hatching, and in feeding larvae on the second day of feeding. The results showed that salivary glands in tick larvae are formed by alveoli aligned in strands on both sides of the central nervous system. These alveoli open into central efferent ducts via short ducts. The constituent elements of salivary glands include pyramidal alveoli (with numerous lipid droplets) and granular alveoli of varied structure. It is worth noting that salivary alveoli containing secretory material are present even in the larvae which had just left egg sheaths and were still endowed with deutoplasm.     

Protein synthesis in salivary glands of Drosophila hydei after experimental gene induction.

Several treatments, namely incubation at 37 degrees C, in the presence of arsenite, 2,4-dinitrophenol or vitamin B-6, or release from anaerobiosis induce the same set of puffs in the polythene chromosomes of salivary glands of Drosophila hydei. Analysis of changes in protein-synthetic patterns (as determined by radioautography of sodium dodecyl sulphate-gel electrophoretograms of extracts from [35S]methionine-labelled salivary glands) showed that concomitant with puff induction by these various treatments the same six strongly labelled polypeptide bands appeared. The amount of radioactive label in these peptides accounted for 25% of the total incorporation of [35S]methionine, except during incubation at 37 degrees C when it accounted for about 50%. The rate of synthesis of these peptides was maximal 1 h after the start of the puff-inducing treatment. The rate of decay of the rate of synthesis showed first-order kinetics both after removal of the puff-inducing stimulus or in the presence of actinomycin, with a half-life of approx. 4h.     

Programmed cell death in salivary glands of Drosophila arizonae and Drosophila mulleri

Programmed cell death (PCD) in insect metamorphosis assumes a great diversity of morphology and controlling processes that are still not well understood. With the objective of obtaining information about the PCD process, salivary glands of Drosophila arizonae and D. mulleri were studied during larval-pupal development. From the results, it can be concluded that the type of the PCD that occurs in these organs is morphologically typical of apoptosis (formation of apoptotic nuclei, followed by fragmentation into apoptotic bodies). Histolysis happens in both species, between 22 and 23 h after pupation. There were no significant differences between the species studied. Apoptosis does not occur simultaneously in all cells. Cytoplasmic acid phosphatase activity gradually increases during development, suggesting the existence of acid phosphatases that are only expressed during the apoptotic stage. Twenty hours after pupation, salivary glands already show biochemical alterations relative to nuclear permeability such as acidification, possibly due to the fusion of lysosomes with the nucleus a few hours before apoptosis. Autophagy seems to act together with apoptosis and has a secondary role in cell death.     

Characterisation of histones in the salivary glands of Rhynchosciara americana larvae

The histones from the salivary glands of Rhynchosciara americana larvae were identified. The electrophoretic patterns of the proteins studied resemble that of calf thymus histones, including the H₁ histone, which in Rhynchosciara has a lower electrophoretic mobility in urea/polyacrylamide gels but shows a molecular weight identical to the corresponding histone of calf thymus, as judged by SDS-polyacrylamide gel electrophoresis.