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Prostaglandins Ej and Fja play major roles in the initiation and maintenance of parturition. There is evidence that they also prime the uterus prior to parturition. Diets high in n3 fatty acids have been reported to be associated with impaired parturition, whereas uterine infection by the intracellular pathogen Chlamydia psiltaci is associated with abortion and premature labour. In each case the course of disruption of normal parturition is unknown, however, impaired or excessive 2-series prostaglandin production has been postulated to play an important part. The effect of high dietary n3 and n6 fatty acid intake on uterine fatty acid composition and metabolism by desaturase, elongase, phospholipase and cydooxygenase enzymes was investigated. The effect of C. psittaci infection on 2-series prostaglandin production and its control was also studied. The uterine fatty acid content of rats maintained on diets high in n6 and n3 essential fatty acids (EFA) for various periods was analysed and compared with a control group fed a normal pelleted diet. Rapid changes in uterine n6 and n3 fatty acid content were observed after three weeks feeding. However, in all three diet groups conservation of arachidonic acid was observed, which was highest in rats fed the n6 fatty acid diet and lowest in rats fed the n3 fatty acid diet. The 20C and 22C EFA were incorporated into phospholipids to a greater extent than into neutral lipids. The distribution of EFA in the individual lipid classes in the three diet groups indicated selective release of arachidonic acid and eicosapentaenoic acid into the free fatty acid pool. Phosphatidylethanolamine arachidonic acid levels were more susceptible to changes in dietary fatty acid content than those of phosphatidycholine and phosphatidylinositol. Analysis of prostaglandins produced by uteri of rats on the three diets, by mass spec-trometry, demonstrated an inhibitory effect of the n3 fatty acids on total prostaglandin production, and the synthesis of the 3-series prostaglandins E and F was detected. Pregnant sheep experimentally infected with an ovine abortion strain of C. psittaci were found to prematurely release prostaglandin Ej (PGEj) into the amniotic and allantoic fluids. Impaired release of PGE3 into the utero-ovarian vein was also detected in infected sheep. The plasma oestradiol-17/3 also increased earlier than that of control sheep. The study detected competitive inhibition of uterine n6 EFA metabolism at the level of esterification, chain elongation, desaturation and cyclooxy-genase metabolism by the dietary n3 EFA. In infectious abortion, abnormalities in PGEj and oestradiol-170 were detected. The first evidence of 3-series prostaglandin production by uterine tissue is presented.

Saline extracts were made from desanguinated human placentae, and histaminase was purified from these extracts by salt fractionation, ion-exchange chromatography on cellulosic adsorbents, and by gel filtration on Sephadex G-200. The Specific Activity of the preparation increased approximately 800- fold from Stage 1 to Stage 6, part of this increase being due to the removal of enzyme inhibitors. Further attempts to resolve Stage 6 enzyme by ion-exchange chromatography and re-cycling gel filtration removed some of the remaining contaminants, but did not result in further increases in Specific Activity. Starch gel electrophoresis of the purest preparation revealed that the enzyme had not been separated from high-molecular weight haptoglobin-methaemoglobin species. A new spectrophotometric test for histaminase was developed from Kapeller-Adler 's (1951) indigo test, which proved unsuitable for the present work. The new test was about 50 times more sensitive than any previous method measuring a common product of oxidative deamination of all substrates. Extinction changes after 24. hr. incubation were linearly related to enzyme concentration. Zeller's criticisms of indigo tests (1956, 1965) could not be substantiated. The new indigo test gave very similar results to the method of Holmstedt and Tham (1959) in almost all applications. Although the oxidation of substrate and the production of hydrogen peroxide proceeded immediately, indigometric assays were subject to an initial delay in indigo oxidation, lasting several hours. The oxidation of indigo by synthetic hydrogen peroxide was not subject to any delayj the mechanisms of indigo oxidation by synthet c hydrogen peroxide and by hydrogen peroxide produced in the enzyme-substrate reaction were not the same. More than the stoichiometric amount of indigo was oxidised in tests using synthetic or enzymic hydrogen peroxide, due to oxidation by atmospheric oxygen, catalysed by substrates and products of the indigo test. No way was found to eliminate, or correct results for, hyper-stoichiometric indigo oxidation, and therefore rates of oxidation of indigo could not be translated into conventional expressions of enzymic activity. The specificity of the purest preparations of placental histaminase was found to resemble that of hog kidney and pea seedling DAO, With supporting evidence from mixed-substrate experiments, it was concluded that histaminase oxidised not only the aliphatic diamines, but also agmatine, benzylamine and histamine. Activity towards histamine could not have been due to any known contaminant. The Michaelis constants for the oxidation of several substrates by placental histaminase were determined. Km for putrescine, and the appearance of an optimal substrate concentration, varied with the assay method employed. The histamine concentration giving optimal activity was lower than that for hog kidney DAO. The pH optima for the activity of placental histaminase towards several substrates were determined. The inhibitor specificity of placental histaminasa resembled that of hog kidney and pea seedling DAO, but was distinct from that of benzylamine oxidase or monoamine oxidase (MAO). Activity towards the aliphatic diamines, but not towards histamine, tended to diminish as the enzyme was purified, unless EDTA wa3 added to the working buffers. The possible significance of metal ions in the activation and inhibition of histaminase was discussed, and it was suggested that discrepancies in earlier reports on the specificity of hog kidney DAO might be due to contamination of enzyme solutions by metal ions. Contamination of the purest preparation by other proteins precluded detailed study of the cofactors of placental histaminase, but the possible involvement of copper and pyridoxal phosphate was discussed. The molecular weight of histaminase x*as probably at least 200,000. The enzyme was much more thermolabile than hog kidney MO, but it was extremely stable at low temperatures in dilute borate buffer, pH 8.6. Priorities for future work were considered to be: (a) Development of a satisfactory assay method for oxidative deamination, (b) Separation of histaminase from haptoglobin-methaemoglobin. (c) Study of the metabolism of aliphatic diamines in normal and pregnant human subjects.