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W. E. GREER, J. D. ROUSSEL and C. R. AUSTIN

Monkey semen characteristically coagulates during ejaculation, and samples obtained by electrical stimulation consist wholly or largely of a rubbery mass. Some spontaneous dissolution occurs when the ejaculate is held in vitro at room or body temperature, but more than half the mass, usually about 75%, remains unchanged. Use of monkey semen for laboratory studies or for artificial insemination is hampered by this feature. To some extent, the trouble can be remedied by the use of proteolytic enzymes, of which trypsin seems to be the least deleterious to sperm viability (Roussel & Austin, 1967), but the presence of trypsin raises problems for many biochemical studies. Accordingly, the possibility was investigated that surgical removal of the coagulum-producing gland from the male tract might result in the ejaculation of coagulum-free semen, without seriously interfering with the volume and other semen charac

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J. E. Norman, L. M. Ward, W. Martin, A. D. Cameron, J. C. McGrath, I. A. Greer and I. T. Cameron

The purpose of this study was to determine the relaxant effects in vitro of two nitric oxide donors, glyceryl trinitrate and sodium nitroprusside, which are currently available for use in vivo, on contractions of non-labouring myometrium from pregnant women. Since nitric oxide also mediates relaxation by increasing the concentration of cGMP, sensitivity to 8-bromo-cGMP (a cGMP analogue) was also determined. The effects of the K+-channel opener lemakalim and of the Ca2+-channel blocker nifedipine were studied for comparison. After the addition of glyceryl trinitrate (0.1–100 μmol l−1), sodium nitroprusside (0.1–100 μmol l−1) or 8-bromo-cGMP (0.001–3 mmol l−1), the spontaneous rhythmic contractility of myometrial strips was inhibited in a concentrationdependent manner: the maximum inhibition produced by the highest tested concentration of each drug was 40 ± 7%, 53 ± 8% and 39 ± 8% of the original degree of contraction, respectively. Myometrial contractions were completely abolished by lemakalim and by nifedipine and verapamil at concentrations of ≥ 10−5 mol l−1. The nitric oxide donors, glyceryl trinitrate and sodium nitroprusside, attenuate myometrial contractions and are therefore useful as tocolytic agents. However, at equimolar concentrations in vitro, the ability of glyceryl trinitrate and sodium nitroprusside to attenuate myometrial contractions is less than that of lemakalin, nifedipine and verapamil. Controlled trials are required to determine the side-effects and clinical efficacy of each of these agents in vivo.