The yeast IA 3 polypeptide consists of only 68 residues, and the free inhibitor has little intrinsic secondary structure. IA 3 showed subnanomolar potency toward its target, proteinase A from Saccharomyces cerevisiae, and did not inhibit any of a large number of aspartic proteinases with similar sequences/structures from a wide variety of other species. Systematic truncation and mutagenesis of the IA 3 polypeptide revealed that the inhibitory activity is located in the N-terminal half of the sequence. Crystal structures of different forms of IA 3 complexed with proteinase A showed that residues in the N-terminal half of the IA 3 sequence became ordered and formed an almost perfect ␣-helix in the active site of the enzyme. This potent, specific interaction was directed primarily by hydrophobic interactions made by three key features in the inhibitory sequence. Whereas IA 3 was cut as a substrate by the nontarget aspartic proteinases, it was not cleaved by proteinase A. The random coil IA 3 polypeptide escapes cleavage by being stabilized in a helical conformation upon interaction with the active site of proteinase A. This results, paradoxically, in potent selective inhibition of the target enzyme.Aspartic proteinases participate in a variety of physiological processes, and the onset of pathological conditions such as hypertension, gastric ulcers, and neoplastic diseases may be related to changes in the levels of their activity. Members of this proteinase family, e.g. renin, pepsin, cathepsin D, and human immunodeficiency virus-proteinase are generally typecast on the basis of their susceptibility to inhibition by naturally occurring, small molecule inhibitors such as the acylated pentapeptides, isovaleryl-and acetyl-pepstatin. However, the two most recently identified human aspartic proteinases, ␤-site Alzheimer's precursor protein cleavage enzyme and ␤-site Alzheimer's precursor protein cleavage enzyme 2 (1, 2), are not inhibited by this classical type of inhibitor of this family of enzymes. Pepstatins are metabolic products produced by various species of actinomycetes and, as such, are not themselves gene-encoded. Protein inhibitors of aspartic proteinases are relatively uncommon and are found in only a few specialized locations (3). Examples include renin-binding protein in mammalian kidneys which intriguingly has now itself been identified to be the enzyme, N-acetyl-D-glucosamine-2-epimerase (4); a 17-kDa inhibitor of pepsin and cathepsin E from the parasite, Ascaris lumbricoides (5); proteins from plants such as potato, tomato, and squash (6, 7), and a pluripotent inhibitor from sea anemone of cysteine proteinases as well as cathepsin D (8).The IA 3 polypeptide in yeast is an 8-kDa inhibitor of the vacuolar aspartic proteinase (proteinase A or saccharopepsin) that was initially described by Holzer and co-workers (9). The complete sequence of this 68-residue inhibitor has been elucidated (10, 11) and the inhibitory activity of IA 3 has been shown to reside within the N-terminal half of the molecule (10, 12). ...

Plasma testosterone, androstenedione, oestradiol-17β, follicle stimulating hormone (FSH) and luteinizing hormone (LH) were not significantly different in patients with prostatic cancer, with benign prostatic hyperplasia or in patients without prostatic disease. Plasma prolactin concentrations were significantly lower in the patients with benign disease than those with prostatic carcinoma. Endocrine therapy in the form of stilboestrol administration significantly decreased plasma levels of testosterone, oestradiol-17β, FSH and LH within 7 days of the treatment. After 7 days therapy prolactin levels increased significantly in all patients studied. Changes in growth hormone concentrations were more varied in response to stilboestrol, being elevated in several patients and remaining unchanged in others. Treatment of a few prostatic carcinoma patients who were receiving stilboestrol therapy with CB154, an inhibitor of prolactin secretion, brought an immediate decrease in prolactin levels which was sustained. Plasma testosterone, androstenedione and growth hormone were unchanged in these patients but a significant decrease in plasma oestradiol-17β was noted in two patients during CB154 administration.

Oestradiol-17\g=b\,diethylstilboestrol (DES), dl-dihydrodibutylstilboestrol (dl-DHBS) and meso-dihydrodibutylstilboestrol (meso-DHBS) were injected intramuscularly into male Sprague-Dawley rats in a daily dose of 100 \ g=m\ g for a period of 10 days. Oestradiol-17\g=b\ and DES decreased the weight of the prostate and seminal vesicles to the same extent, whereas meso\x=req-\ DHBS was less effective. dl-DHBS was almost inactive. Only oestradiol\x=req-\ 17\g=b\ and DES caused a decrease in the weight of the testes. The adrenal glands increased in weight after administration of either oestradiol-17\g=b\, DES or meso-DHBS.Four hormones in the plasma were measured: testosterone, androstenedi\x=req-\ one, prolactin and interstitial cell-stimulating hormone (ICSH). DES decreased the plasma concentration of both ICSH and testosterone. Oestradiol-17\g=b\ and meso-DHBS administration resulted in a lowering of the plasma testosterone concentration with no effect on ICSH. Oestradiol-17\g=b\, DES and meso-DHBS markedly increased plasma prolactin concentrations. dl-DHBS appeared to have little biological effect causing only very small changes in all the parameters investigated.

Negative ion mass spectra obtained by fast atom bombardment of glycerol solutions of steroid sulphates include the steroid sulphate anion as the single prominent feature. High sensitivity is achieved, with full spectra obtained for samples of less than 15 ng. Differentiation of the isomeric steroids, dehydroepiandrosterone sulphate and testosterone sulphate, is made by comparison of the products of fragmentation of metastable ions. Analyses of biological extracts suffer from poorly-understood matrix effects which may cause partial or complete suppression of the signal attributable to steroid sulphates. Use of an immunoadsorption extraction technique, however, has permitted the detection and approximate quantification (using a (2H2) analogue as internal standard) of dehydroepiandrosterone sulphate in blood plasma. Interference from glycerol background is avoided by preparation of the pentafluorobenzyloxime derivatives.

The effect of Synacthen (β1–24-corticotrophin) on plasma testosterone and 4-androstene-3,17-dione concentrations in untreated patients with prostatic carcinoma, and in patients receiving endocrine therapy is described. An established specific radioimmunoassay was used for the measurement of testosterone, and a radioimmunoassay for 3-androstene-3,17-dione using thin layer chromatography has been developed. Administration of Synacthen resulted in a fall in testosterone in untreated patients, but a rise in 4-androstene-3,17-dione was observed. The plasma concentration of testosterone in all treated patients increased after administration of Synacthen. An increased concentration of plasma 4-androstene-3,17-dione was also observed in these treated patients after Synacthen, but the magnitude of the response was not significantly different from that of untreated patients. The work provides further evidence that in the patient being treated with oestrogen for carcinoma of the prostate a rise in plasma testosterone concentration will result from an increased secretion of ACTH.

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The seminars proved very successful, the liveliest interest being elicited by environmental topics and by considerations of modern techniques in sanipling, purification, chromatography and mass spectrometry. Professor Ballschmiter dealt with sample preparation for capillary GC -MS, and participants appreciated the chance to draw upon his unique expertise in the analysis of almost every class of organic pollutant. Dr. J. D. Baty's seminar dealt with the applications of stable isotope-labelled analogues of drugs as internal standards for quantitative analysis and in the study of metabolic pathways.Environmental analysis by GC -MS was discussed in the seminars conducted by Dr. B. Brookes and Mr. S. J. W. Grigson, while microbore LC -MS was the topic in Dr. D. E. Games's session. Dr. S. J. Gaskell gave a lucid exposition of the analytical capabilities of the various combinations of scanning modes available in modern mass spectrometry systems.i n a Plenary Lecture, Professor C. J. W. Brooks (University of Glasgow) surveyed the role of GC -&IS in the analysis of bio-organic samples, with emphasis on the practical differentiation of closely similar compounds. Examples included (i) the selective analysis of tetrachlorodibenzo-$-dioxins having two chlorine substituents in each benzo ring, based on efficient GLC and on the ion of m / z 176 [C,H,Cl,O,]-• produced via chemical ionisation using oxygen as reagent gas; (ii) the difficulty of distinguishing between sterols with certain structurally or stereochemically isomeric side-chains ; and (iii) the value of appropriate derivatives, and of chemical ionisation, for the characterisation and sensitive detection of prostaglandins and of tlironiboxane B,. The theme was further exemplified by studies in Glasgow in collaboration with Professor T. D. 1'. Lawrie and Mr. J. MacLachlan (Department of Medical Cardiology) on the identification of sterol epoxides in blood plasma.Mr. S. J. \IT. Grigson (Institute of Offshore Engineering, Heriot-Watt University) surveyed the practice and usefulness of analyses of hydrocarbons in marine sediments, exemplified by determinations of triterpanes, steranes and alkylated arenes as indicators of the occurrence and source of oil pollution.Fast atom bombardment (FAB) mass spectrometry was discussed by Dr. R. Large (hl-Scan, Bucks) ; the value of the technique in structural investigations on large biological molecules was well illustrated with reference to peptides, leukotrienes, bleomycins and fungal elicitors of yolygalacturonic acid types, these last compounds yielding molecular ions above nzjz 2 000.

We describe a new, highly selective procedure for the determination of estradiol-17 beta in plasma. Samples are extracted with a micro-cellulose-coupled antiserum to estradiol-17 beta. Conversion of the extracted steroid to the bis(trimethylsilyl) ether is followed by gas chromatography/high-resolution mass spectrometry with selected ion monitoring. Precise quantification is achieved through the use of [2H3]estradiol-17 beta as internal standard.