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E. Koch and F. Ellendorff

Summary. After preincubation of lymphocytes in serum of non-pregnant pigs and using a standard anti-pig-lymphocyte serum the upper limit of the 99·9% confidence interval of rosette inhibition titres (RIT) for pig serum was calculated to be 11·4 and all titres >12 were defined as a proof of early pregnancy factor (EPF)-activity. The reproducibility of the RITs with serum samples of pregnant pigs was considered satisfactory (interassay coefficient of variation 23·8%), whereas their reproducibility was considered good with sera taken from non-pregnant animals (interassay coefficient of variation 6·5%).

Problems of the test were particularly evident due to the absence of increased RITs after previous incubation of lymphocytes in serum of pregnant pigs. Therefore, all EPF-negative samples were reanalysed up to two times; pregnancy was then correctly diagnosed for 88·7% of sows. There were 8·6% false positive results (N = 70) and 12·2% false negative results (N = 205).

During the first half of pregnancy RITs displayed periodic fluctuations which resembled the physiological cycle interval of the pig. Between Weeks 5 and 9 of pregnancy greater numbers of EPF-negative sows were detected. Subsequently, a continuous increase of mean RITs occurred, which then declined gradually from Day 80 of pregnancy. Similar changes were observed for progesterone values in the dialysed serum samples. However, highest progesterone concentrations always followed elevated RITs with a delay of 1 ·5–4 days. A subthreshold cyclicity of ovarian and luteal function probably persists despite pregnancy.

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E. Koch and F. Ellendorff

Summary. Incubation of normal pig lymphocytes in serum samples collected from 10 sows immediately before, and at daily intervals after mating with a vasectomized boar significantly elevated the rosette inhibition titre (RIT) of a standard antilymphocyte serum in 6 animals on the first but not on the 2nd and 3rd day after copulation. Infusion of seminal plasma without mating into 5 sows induced an obvious, but not statistically significant, transient rise of titres in 3 pigs. Neither sodium chloride infusion (N = 5), nor sham copulation with diverted penis (N = 5) influenced serum RITs. Porcine seminal plasma showed an inherent rosette-inhibiting property. A depression of rosette formation was evident in a concentration-dependent fashion up to a dilution of 1 in 320. Similarly, preincubation of lymphocytes in serial dilutions of seminal plasma in a non-pregnancy serum sample led to an amplification of the rosette inhibiting capacity of the antilymphocyte serum. Non-specific activation of the eggs to release a signal which induces the production of early pregnancy factor (EPF) or the resorption of seminal plasma components into the blood circulation are considered as possible explanations for the EPF-like activity after mating with a vasectomized boar.

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The effect of cyproterone acetate on the duration of pregnancy and the number of embryos (normal, hypertrophied or degenerated) was investigated. Pregnant NMRI-strain albino mice were injected on Days 1 to 10, or Days 10 to 15 with either 0·5 or 5·0 mg cyproterone acetate (CA) or the vehicle (V). In the CA-treated animals, no parturitions occurred up to Day 21 of pregnancy. The number of offspring did, in general, not differ between the CA-treated animals and the controls. The number of normal offspring was less and the number of abnormal embryos was larger in the CA-treated animals compared with the controls. Hormonal induction of parturition showed positive results after oestrogen—oxytocin administration. The effect of CA was attributed (a) to its progestational activities, and (b) to possible direct effects on the development of the embryos.

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R. Claus, F. Ellendorff and C. Hoang-Vu

Summary. Two experiments were carried out to monitor influences on the uterine electromyographic activity (EMG) in cyclic gilts with chronic uterine EMG electrodes. In Exp. 1 the EMG was recorded continuously from Day − 1 for 24 days and was evaluated for frequency, duration and amplitude. Progesterone and oestradiol in peripheral plasma were measured daily. As high amounts of oestrogens are characteristic for boar semen, in Exp. 2 the influence of seminal oestrogens on uterine contractions at Day 0 (first day of standing reflex) was investigated in gilts with chronic intrauterine catheters. They were infused with 10 ml saline (N = 4) or saline with physiological amounts of oestrogens (5 μg oestradiol + 2 μg oestrone + 4·5 μg oestrone sulphate; N = 4). Sham-treated gilts (infusion catheters, no infusion; N = 5) served as controls. The EMG was recorded for 2 h before and 9 h after infusion.

In Exp. 1 the maximal amplitude (2040 + 98 μV) and duration (32 ± 1·7 sec) but the lowest frequency (15·8 ± 2·1 contractions/h) were found on Day 0. With decreasing oestrogen and increasing progesterone concentrations the frequency increased continuously until Day 5 (63·5 ± 1·0 contractions/h) while the amplitude (183 ± 13 μV) and duration (3·3 ± 0·7 sec) decreased. During Days 6–13 the EMG activity was not detectable. The reverse pattern was found from the onset of luteolysis until the following Day 0. On Day 0 a significant correlation between oestradiol and the duration (r = 0·81; P < 0·01; n = 10) but not the frequency was observed.

In Exp. 2 no significant change in contractile activity was found for the saline-infused group and the controls over the 11-h recording periods. After infusion of saline with oestrogens the frequency increased significantly (P < 0·001) from 14·0 ± 3·1 contractions/h during the first hour up to a maximum of 31·2 ± 3·9/h at 2 h after infusion. Compared to the pretreatment period the frequency remained significantly elevated during the 3rd (28·7 ± 2·3/h; P < 0·05) and 4th (20·2 ± 3·9/h; P < 0·05) hour after infusion. Seminal oestrogens therefore stimulate uterine contractions at Day 0 and may play a physiological role for sperm transport.

Keywords: electromyography; seminal oestrogens; gilt; uterine contractions; cycle

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Sexual maturity can be advanced in the sow by hormonal treatment (Schahidi, 1968; Majerciak, Smidt, Schahidi & Harms, 1969) but has not been tried successfully in the boar. Ten boars were investigated under the normal conditions of the experimental station (Roth, 1969). Table 1 shows the age and treatment schedule. The following substances were used: fsh(nih-fsh-p1), lh(nih-lh-b6), and Testoviron (Testoviron®—Depot, Schering AG Berlin). Biopsies were taken at the intervals shown in Table 1. Castration was performed on the 53rd day of the experiment. The following aspects of sexual behaviour were studied: sexual excitement, indicated by aggressiveness towards other boars, frothing from the mouth, and interest in sows in oestrus, as shown by mounting and erection of the penis with and without protrusion from the prepuce. In order to evaluate gonadal
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Halle Morton, D. J. Morton and F. Ellendorff

Summary. The occurrence of early pregnancy factor in the pig has been established by the rosette inhibition test and by the criteria that gel filtration of serum resulted in a number of peaks of activity similar to those observed in other species. In the pig EPF is present virtually to the end of pregnancy, with a biphasic production in which the titres of EPF decline markedly in mid-pregnancy. Free EPF-A appears concurrently with EPF in the first 3 weeks of pregnancy in some but not all pigs. The presence of excess EPF-A has an inhibitory effect in the rosette inhibition test and modifications, including an initial serum dialysis step, have been introduced into the test to take account of this inhibitory effect.

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F. Ellendorff, M. Forsling, N. Parvizi, H. Williams, M. Taverne and D. Smidt

Summary. A single i.m. injection of 5 mg PGF-2α evoked a significant elevation of plasma oxytocin values in sows 6 days post partum and during dioestrus. Plasma vasopressin levels in dioestrous sows were not significantly affected by PGF-2α. It is concluded that circulating steroid levels do not interfere with the response of oxytocin levels to PGF-2α.