In this study of the pregnant uterus of the ewe and the pygmy goat, the simultaneous use of real-time ultrasound scanning and electromyography is introduced. In unanaesthetized animals it was ...possible to visualize the uterine wall, the placentomes, parts of the fetal skeleton, the fetal kidneys, different parts of the fetal stomach and several structures of the fetal heart and vascular system. From these features the intra-abdominal position of the fetus could be determined. It was observed that Episodes of Myometrial Electrical Activity (EMEA's), as registered by chronically implanted uterine surface electrodes, coincided with passive displacements of the fetus in the direction of the maternal pelvis. These passive displacements could clearly be discerned from active fetal body movements. In both species the number of active fetal movements was significantly reduced during and/or shortly after an EMEA. In one of the pygmy goats, in which three different types of movement were discerned, this reduction of fetal movements could be studied in more detail. It is concluded that real-time ultrasound scanning of the fetus in small ruminants might contribute to studies of the complex maternal-fetal interactions that exist during late gestation.
To quantify the pattern of myometrial activity during gestation and parturition, one bipolar electrode was implanted on each uterine horn of four bilaterally pregnant pygmy goats between days 102 and ...120 of gestation. After a recovery period, electromyographic recordings were made for at least six hours per day and continuously when parturition was judged to be imminent. During late gestation myometrial activity occurred as discrete episodes of myometrial electrical activity (EMEA) with a mean duration ranging from 6.2 +/- 2.07 to 8.3 +/- 1.60 minutes. The mean interval between two successive EMEAs ranged from 45.8 +/- 19.95 to 74.7 +/- 42.27 minutes. In three of the four goats these characteristics were not significantly different from the two uterine horns. Parturition was preceded by a prolonged period (eight to 12 hours) of myometrial quiescence. It was only from 19 to 15 hours before expulsion of the first kid that total duration of EMG activity increased. This finally resulted in the regular occurrence of bursts which occupied 25 to 30 per cent of the recording time. The results demonstrate that, as in the sheep, cow and pig, the myometrium is active during late pregnancy. It is postulated that luteolysis coincides with the prolonged period of myometrial quiescence which precedes the onset of the parturient pattern of uterine activity.
With electromyography and strain gauges the uterine motility of the sow during the oestrous cycle and early pregnancy was studied. Special attention was paid to characterization of myometrial ...activity at the time of intra-uterine migration of blastocysts. From recordings of 4 animals (3 became pregnant) 3 types of electrical spiking activity (each could be correlated with an elevation of the strain gauge tension) were discerned. Two of them appeared regularly and were suitable for analysis: "High Voltage Slow Acticity" (with relative high amplitude and low frequency of spikes) and "Low Voltage Fast Activity" (with relative low aplitude and high frequency of spikes). The sexual status markedly influenced myometrial activity: during proestrus and oestrus only one type of electrical activity was present whereas the myoelectrical complex (an episode of this activity and the subsequent interval of inactivity) was shorter than 10 min. During dioestrus the myoelectrical complex was longer than 10 min and "High Voltage Slow Activity" (solely on the cervix and bifurcation) and "Low Voltage Fast Activity" occurred simultaneously in episodes which mainly appeared to originate on the bifurcation. The characteristics of uterine activity during pregnancy were similar to those of a cyclic sow until day 12. It was only on day 12 that gestation appeared from an increased frequency of myoelectrical complexes. It is concluded that "Low Voltage Fast Activity" as it was found on the uterine horn at days 8-9 might be involved in the process of intra-uterine migration of blastocysts. In cyclic and in pregnant animals the patterns of "Low Voltage Fast Activity" were similar. Therefore, the occurrence of "Low Voltage Fast Activity" is independent of the actual presence of blastocysts. It seems to be exhibited in dependence on the ovarian hormones.
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