The human ovary, in particular the corpus luteum, secretes significant amounts of dimeric and therefore biologically active inhibin.

Inhibin is a polypeptide hormone produced by the granulosa cells of the ovary, and is present in body as dimers of vanous sies each compnsng an a-and a-subunit. Free forms of the a-subunit also circulate, and the presently available radioimmunoassay (Monash asy) cannot distinguish these from biologicaly active dimeric inhibin. Recently we described a new two-site enzyme immunoassay able for the first time to measure the kvels of dimeric inhibin throughout the human menstrual cycle. The sensitivity limit of this assay is 2 pg ml-' in human serum with cross-reactivity against activin of 0.05%. The normal range of inhibin in post-menopausal women is <5 pg mll, in pre-menopausal women 2 -80 pg ml (2 -10 pg ml iin the follicular phase, 40 -80 pg ml-' in the luteal phase). This assay was used to determine inhibin levels in sera from 15 (five pre-menopausal and ten post-menopausal) patients with granulosa cell tumours of the ovary. It was raised in a pre-menopausal patient preoperatively (261 pg ml -), in six post-menopausal patients (32, 43, 54, 66, 24

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Cytogenic changes are becoming increasingly important in understanding the pathogenesis of human malignancies. The t(9;22) (q34;q11) translocation is one of the most consistent and generates the Philadelphia chromosome (Ph1) (ref. 1) in chronic myeloid leukaemia (CML); it has also been observed in some acute lymphoblastic leukaemias (ALL) (ref. 2). In CML the breakpoints occur on chromosome 22 in the region designated bcr (ref. 3) and result in the expression of a bcr-abl fusion product of relative molecular mass (MT) 210,000 (210K) with associated in vitro tyrosine kinase activity (P210bcr-abl). In some cases of Ph1-positive ALL, a novel abl-related protein (P190all-abl) of 190K has been shown to have tyrosine kinase activity. In this report we demonstrate that the P190all-abl protein has a bcr determinant from the amino-terminal region, but is lacking a bcr determinant normally found in the P210bcr-abl near the bcr-abl junction. The chimaeric nature of the P190all-abl was confirmed by sequential immunoprecipitation with antisera against abl and bcr peptides.

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