Summary. The brain allatotropic hormone (ATTH) is released in Galleria mellonella from the Median neurosecretory cells located in the pars intercerebralis. These cells show the ability to elicit supernumerary larval molts upon implantation into sensitive host larvae, and the ability to in vitro stimulate the juvenile hormone synthesis in corpora cardiaca-corpora allata glands of G. mellonella. Key words. Median neurosecretory cells; allatotropic hormone; juvenile hormone; corpora cardiaca-corpora allata glands; Galleria mellonella.Neurohormonal regulation of juvenile hormone OH) synthesis in corpora allata (CA) has been widely studied =-5. It has been shown that stimulation of JH synthesis can be mediated by the allatotropic neurohormone (ATTH) and inhibited by the allatostatic neurohormone; both hormones originate in the brain 6-]~ Brain cells in which they are synthetized have not been yet identified in any insect species. Material and methods. Wax moth, Galleria mellonella, was bred as described earlier 3. The material comprised 3-day-old penultimate instar (VI3) and 1-day-old last instar (VIII) larvae either untreated or chilled (in order to stimulate the allatotropic activity of the brain) a= at 0 ~ for 3 h. Immediately after chilling the larvae were transferred back to 30 ~ and used for experiments 18-24 h later.Surgical procedures. Dissection of brain and corpora cardiaca-corpora allata complex (CCCA) as well as implantation of brain was performed as described by Sehnal and Granger 3. Isolation of MNC from brain was carried out in MEM medium (Gibco, cat. no. 072-1300). The brain was sectioned at the level of the deutocerebrum, and the neurolamella was separated from the neuropile by gentle pressing of the brain, starting from the top to the midline. Thereafter 8 bluish-opalescent neurosecretory cells, well visible under a stereoscope, were separated from the surrounding tissue, and with the use of a suction micropipette either transferred to an incubation vial or implanted into G. mellonella VII 1 larva. In order to obtain a brain deprived of MNC, the neurolamella over the pars intercerebralis was sectioned, and the MNC were removed with a thin needle. In each series of experiments the accuracy of the MNC removal was checked by staining some brains with paraldehyde-fuchsin ]3. Most of the brains examined contained no stainable MNC; in only a few cases 1-2 cells were present. The in vivo ATTH assay was performed according to Sehnal and Granger 3. As recipients, water-anesthetized G. mellonella VII1 larvae were used. Implantation was made of: clusters of MNC obtained from 2 or 4 brains of chilled VII~ larvae, 2 or 4 intact brains of chilled VII 1 larvae and 2 or 4 brains deprived of MNC. The in vitro ATTH assay was performed as described earlier TM. The clusters of MNC obtained from 4 or 8 brains of chilled VII I larvae, or 4 or 8 intact brains of chilled VII 1 larvae, or else 4 or 8 brains deprived of MNC were incubated in 200 pl of sterile MEM for 1 h. The post-incubation medium was centrifuged and the sup...
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