Imaginal disk

Lehner In the embryo, cyclin E is a lousy target for the E2F pathway. It might be different in the imaginal disks. There, up-regulation of cyclin E as a result of E2F overexpression has been reported (Neufeld et al 1998). 

Cullen CF, Milner MJ 1991 Parameters of growth in primary cultures and cell lines established from Drosophila imaginal discs. Tissue Cell 23 29—39 Davis KT, Shearn A 1977 In vitro growth of imaginal disks from Drosophila melanogaster. Science... 

Imaginal disks in a mature larva and the structures they lead to in the adult fly. 

Developmental changes - Much of what is known about development comes from study of the fruit fly Drosophila melanogaster. As the larva of this insect develops, groups of cells are set apart as disklike structures called imaginal disks (Figure 28.45). These groups of cells will form specific parts of the adult fly. As the larva metamorphoses, larval cells are destroyed by autolysis, and each imaginal disk develops into a different portion of the adult. 

Bombyxin, an insect brain peptide (Mr 5 kDa) with structural similarity to insulin. Bombyxin exists in various molecular forms (I-V). The heterodimers of the A and B chains show about 50% and 30% identity to the A and B chains of human insulin. Bombyxin stimulates, together with the prothoracicotropic hormone (PTTH), the synthesis and release of ecdysone. It has been reported that bombyxin is a growth factor for wing imaginal disks in Lepi-doptera [M. Iwami, Zool. Sci. 2000,17,1035 ... 

Mikolajczyk P, Zimowska G, Oberlander H, Silhacek DL. Chitin synthesis in Spodoptera frugiperda wing imaginal disks. Ill Role of the peripodial membrane. Arch. Insea Biochem. Physiol. 1995, 28(2), 173-187. 

This is a general protocol for formaldehyde fixation of a variety of tissues that are too small, delicate, fibrous, or difficult to see to carry through in situ hybridization in a PCR tube. This method has been used to fix Drosophila spermatocytes and spermatids (both mature and immature), imaginal disks, and malpighian tubules, and whole-mount C elegans after dissection of the gonad. 

Note For Drosophila imaginal disks, it is beneficial to include both 0.1% Triton X-100 (Pierce) and 0.1% deoxycholate (Calbiochem) in the dissection buffer, because this mixture of detergents seems to permeabilize the tissue and reduce background in the hybridization. It may be worth testing this detergent mixture on other tissues as well. The tissue must be exposed to the detergents prior to fixation to see any benefit of the treatment. 

Note The brain usually remains attached to the head together with several imaginal disks and the salivary glands. 

Sometimes, polyclonal antisera produce considerable unspecific background staining which can impair the detection of small or weak specific IF signals. In these cases, it is often helpful to preabsorb the antiserum against an unrelated tissue (e.g., imaginal disks, muscles) before staining the nervous system. Since antisera are typically used in surplus of their optimal concentration, the antibody dilutions can be reused for further staining which then often becomes crisper simply because the minor unspecific antibody populations decrease in concentration. If intended for reuse, 0.02 % NaNs should be added to the antibody solution as preservative (reeNote 14). 

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