Juvenile hormone synthesis inhibition

There has been some work suggesting that some synergists, including PBO, may have morphogenic effects similar to juvenile hormone analogues (Bowers. 1968), This has not been substantiated (Red fern et at.. 1969) and it is most likely thaL Lite effect is due to mixed function oxidase inhibition interfering with the terminal steps in juvenile hormone synthesis (Staai. 1986). 

The hypothesis that allatostatins In the brain are transported to the corpora allata (CA) by axons was substantiated by the binding of allatostatln antibodies to corpora cardlaca-CA complexes and by the demonstration of allatostatlc activity In fractions from extract of 6000 pairs of CA that cochromatograph with synthetic allatostatins 1-4 on reverse phase HPLC. These fractions Inhibited Juvenile hormone (JH) synthesis In test CA In an in vitro assay. Two truncated peptides containing only the 6 and 5 C-terminal amino acids of allatostatln 4 (8 amino acids) were 10 and 100 times, respectively, less Inhibitory than the complete peptide. 

Figure 3. Isolation of allatostatin 4 from CA by HPLC on a Cg column. A) Synthetic allatostatin 4 eluted with an acetonitrile gradient (dashed line). B) Extract of 6000 pairs of CA (collected from a C column in the region of allatostatin 4) run immediately following and with the same gradient as that in A. The histogram shows the inhibition of juvenile hormone (JH) synthesis of fractions eluting at the same time and adjacent to allatostatin 4. Fractions were tested on 3-4 CA at 100 CA equiv./CA. Dots indicate SEM.

In the mealworm Tenebrio molitor it was demonstrated that the hormonal regulation of the phenotypic expression of genes controlling the synthesis of cuticu-lar protein is realized on the transcriptional level, and includes the synthesis of new tRNA and the activation of their associated enzymes. The stable RNA for cuticu-lar proteins is synthesized earlier, but is not translated until the action of the juvenile hormone induces a change in the tRNA contents (Ilan and Ilan, 1972). The existence of differential translation of some triplets suggested the possibility of regulation of cell differentiation through the selective activation or inhibition of the stable mRNA stored in the embryonic cells. 

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