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In this study we have investigated the expression of a major family of cytochrome P450, cytochrome P450IA, in human breast carcinoma. Two closely related subfamilies (or forms) of cytochrome P450IA, cytochrome P450IA1 and cytochrome P450IA2 have been identified in rat and similar forms occur in man (Ioannides & Parke, 1990). The murine monoclonal antibody RM3 used in this study recognises rat cytochrome P450IA1 and not rat cytochrome P450IA2 and recognises a single band on immunoblots of human liver

Estimates of juvenile hormone (JH) biosynthesis by isolated corpora allata from adult male Periplaneta americana using a non-discriminatory partition assay suggested glandular activity levels that were comparable with the moderate to highly active rates observed in mid-gonotrophic cycle females. Parallel measurements of endogenous whole body JH titres using micro-derivatization, HPLC and GC-MS showed that male cockroaches contained less than 10% of the amount of hormone found in mid-cycle females. Radio-TLC measurements of the short-term in vitro synthetic performance of male glands failed to reveal any major differences from female corpora allata. Follow-up JH titre studies combined with surgical sectioning of the allatal nerves seemed to indicate that the corpora allata of adult male cockroaches are subject to neural inhibition in vivo.

The endogenous titres of juvenile hormone III (JH III), and the in vitro rates of juvenile hormone biosynthesis by isolated corpora allata have been measured at intervals during the reproductive cycle of adult female Periplaneta americana. There was a close correlation between the rates of JH III biosynthesis and endogenous hormone titres. Only JH III was detected in whole body extracts, and hormone titres reached a peak (mean approximately 29 ng/g) at about the mid-point of the ootheca production cycle.

Radiochemical techniques have been developed for the measurement of juvenile hormone (JH) biosynthesis by isolated corpora allata (CA) from adult female Tenebrio molitor. The method has sufficient sensitivity, using precursor of only approx. 27 mCi/mmole (1 GBq/mmole), to permit measurement on single CA, and can therefore be used to explore the relationship between CA activity and ovarian development in this species. Identification of the hormone, 2E,6E- C 16 JH has been confirmed by a combination of radio-TLC and capillary column radio-GC of the major product of the reaction and its ‘methoxyhydrin’ derivative. No incorporation into either C17- or C18-JH was found. A 1:1 stoichiometry between incorporation of [methyl-14C]-methionine and [3H]-farnesenic acid moieties demonstrates that this amino acid can be used as a mass marker to quantify JH biosynthesis in this species. It has been shown that the rate of hormone biosynthesis is reasonably constant for up to 3 hr after isolation and the influence of pH and methionine concentration have been determined. High rates of hormone production were found when CA were incubated in TC-199, special MEM, and fortified Hanks' basal salt solution, but comparatively low rates of biosynthesis were observed when glands were incubated in Grace's Lepidopteran medium, Schneider's Drosophila medium, and in a medium used by others for the culture of ovaries and prothoracic glands from T. molitor. The CA of adult female T. molitor are activated as early as 48 hr after the pupal-adult moult. Thereafter, high rates of C16JH synthesis can be demonstrated in isolated glands.

Isolated pairs of corpora allata (CA) from adult females of both Schistocerca gregaria and Periplaneta americana incorporate radioactivity from [methyl- 14 C] methionine into C 16 juvenile hormone (JH) when incubated for up to several hours, such that the rate of JH synthesis can be accurately determined. Analysis of the medium shows that CA from P. americana continue to release newly synthesised JH at constant rates for at least 5 hr, whereas those from S. gregaria may show a marked decrease in rate of JH release after 3 hr, particularly in the case of glands having high initial rates of synthesis and release. In both cases the rates of release of JH are strictly proportional to the rates of JH synthesis when measured over a period of 3 hr incubation, independent of the rate of synthesis. It is concluded that the spontaneous level of endocrine activity in glands from both these species can be faithfully quantified by precise radiochemical methods using the short-term incubation procedures described.

The rates of juvenile hormone (JH) biosynthesis have been measured in vitro for individual members of the paired corpora allata (CA) in the cockroach Periplaneta americana during the first two reproductive cycles. A marked similarity of endocrine activity between left and right glands of the majority of animals was observed, even though total JH biosynthesis by the gland pairs can differ up to 200-fold during this period. In a small number of immature females only one gland in the pair had the capacity to synthesize hormone. These results support the use of 'split pairs' of CA from mature, adult female P. americana in short-term in vitro radioassay of potential exogenous and endogenous modulators of JH biosynthesis, such that each sample bioassayed has a valid control. Furthermore, the observations suggest that, after a short postecdysial period (up to 4 days), the CA of this species are controlled by one or more humoral factors.

SUMMARYSeveral of the pathophysiological responses made by the beetle Tenebrio molitor, when infected with metacestodes of Hymenolepis diminuta, may be attributed to a parasite-induced reduction in host juvenile hormone titre. It has been suggested that production of this hormone by the corpora allata may be inhibited in parasitized insects. This hypothesis was tested using an in vitro radiochemical assay to compare the biosynthesis of juvenile hormone by single pairs of corpora allata taken from mated 12- and 15-day-old infected and control female insects. The results demonstrate, however, that there was no difference in hormone production associated with metacestode infection. Other possible mechanisms for parasite interference in this host endocrine system are discussed.

Durch Inkorporation von14C-Methionin in die Corpora allata vonPeriplaneta americana werden wahrend des Eireifungszyklus zwei Aktivitatsmaxima festgestellt und diese als Juvenilhormonsynthese interpretiert.

The discovery by Roller and Dahm (1970) that significant quantities of juvenile hormone could be isolated from cultures in vitro of corpora allata from the adult moth Hyalophora cecropia heralded the approach of a new era of experimental investigations of the physiology of the insect corpus allatum, since it showed that the glands continued to make and release the hormone after removal from the body and therefore might be amenable to direct observation in this way. Standard organ culture procedures for the production of relatively pure preparations of juvenile hormones biosynthesized in vitro, were then employed in conjunction with specially developed analytical procedures by workers in two other laboratories, so as to identify which of the three known juvenile hormone homologs were produced by the corpora allata of the adult female of several insect species (Judy et al., 1973a,b; 1975; Jennings et al., 1975; Muller et al., 1974). K.J. Judy and his co-workers also employed to their advantage in identifying the homologs, the efficient and relatively specific incorporation of radioactivity from the S-methyl group of methionine into the methyl ester of juvenile hormones, previously discovered during experiments on H. cecropia in vivo by Metzler et al. (1971).

Surgical removal of the ovaries from nymphalPeriplaneta americana results in lower than normal corpus allatum activity in the adult insect and an apparent absence of the manifestly cyclic pattern of juvenile hormone biosynthesis found in intact mated females. The results suggest that the presence of synchronously developing ovaries is necessary for the attainment of normal synthetic activity in the corpus allatum of this species.