In vitro protein synthesis by tissues of the fifth instar locust

The preparation of trophocytes from disaggregated fat body of the cockroach (Periplaneta americana)

A method has been developed for disaggregating the fat body of the adult American cockroach, Periplaneta americana, using collagenase. The yield of cells is sensitive to the osmolarity of the dispersing medium and to the age of the cockroaches from which the fat bodies are taken. Trophocytes uncontaminated with other cells were obtained by taking advantage of the low density of these cells which causes them to float to the top of the dispersion medium. In contrast, the mycetocytes and urocytes being denser than the medium sink to the bottom. The trophocytes retain the ability to respond to the synthetic hyperglycaemic hormones, CCI and CCII, as shown by the activation of phosphorylase and the stimulation of trehalose efflux. The trophocytes incorporated leucine into protein secreted by the cells in a time dependent manner.

Juvenile hormone-dependent vitellogenin synthesis in Locusta migratoria fat body: inducibility related to sex and stage

Juvenile hormone (JH)-dependent vitellogenin (Vg) synthesis in the fat body of Locusta migratoria is normally limited to sexually mature adult females. As a step toward examining the basis of this limitation, we have tested female and male locusts in a series of stages after the third larval molt for inducibility of Vg synthesis by the synthetic JH analog, methoprene. We find that in the fourth and fifth larval instars fat body of both sexes can be induced to produce Vg, but in the adult stage females respond strongly while no more than trace amounts can be induced in males. Quantitative assays show relative responsiveness in the order: adult female greater than fifth instar female greater than fifth instar male much greater than adult male. During the fifth instar of both sexes, maximal vitellogenic response was obtained in midinstar. After the larval-adult ecdysis, female fat body was unresponsive during the first 4 days, then responsiveness increased and by Day 8 after ecdysis fat bodies were fully as competent to produce Vg as at Day 14, the usual maximum of the first vitellogenic cycle due to endogenous JH. Larval and adult female fat bodies implanted into male larvae are competent for Vg synthesis after metamorphosis, so that the differences between adult male and female cannot be imposed by the male milieu intérieur during the larval-adult molt. In male and female precocious adults, produced by treatment of fourth instars with precocene, fat body responded to methoprene as in normal adults. We conclude that factors intrinsic to the fat body cells, determined early in development, are responsible for differential gene programing in males and females, which is partially expressed by the fifth instar but fully manifest only after a molt in the absence of JH.