Myoelectrical changes in the uterus of the sheep around parturition

Abstract

Myoelectrical activity in the uterus of late-pregnant sheep was recorded by the chronic implantation of bipolar electrodes in the myometrium. Three distinct patterns of electrical activity were recognizable: irregular trains of action potentials (greater than 120 sec), long spike bursts (7--120 sec), or short spike bursts (less than 7 sec) each exhibiting high (greater than 100 muV) or low (50--100 muV) amplitude. The duration of spike activity was expressed as the myoelectrical index (MI), i.e. the fraction of the hour during which a given category of activity is exhibited. The increase in the overall MI which represents daily average values regardless of the class of amplitude from 72 h pre partum up to parturition was significantly (P less than 0.05) more pronounced in the uterine horn than in the body of the uterus. During the last 6--7 days of gestation high-amplitude irregular trains and long spike bursts were significantly (P less than 0.05) more frequent than these activity patterns with low amplitude. Regardless of the amplitude, the incidence of irregular trains began to decline rapidly 48 h pre partum with an abrupt cessation following parturition. The frequency of long spike bursts increased 72 h pre partum to reach a maximum which coincided with parturition.

Electrical and mechanical activity of the cervix in the ewe during pregnancy and parturition

“…Uterine activity in sheep during pregnancy and around parturition has been extensively described (Hindson, Schofield & Turner, 1968;Naakteboren et al, 1975;Prud'homme & Bosc, 1977;Krishnamurti, Kitts, Kitts & Tompkins, 1982;Harding et al, 1982). In contrast, the possibility of motor activity of the cervix during pregnancy has not been evaluated.…”

Changes in the myoelectrical activity during electrical stimulation of healthy and mastitis-changed mammary glands in dairy cows

“…The value of myoelectrical index (Krishnamurti et al 1982) and the number of spike potential groups per minute (Troedsson et al 1993a;Troedsson et al 1993b;Harding et al 1982;Massmann et al 1991) were calculated. Moreover, the mean duration of the spike potential group, the mean amplitude of the spike discharge, and the mean number of spike discharges in the spike potential group, were calculated to describe the patterns of the udder's myoelectrical activity.…”

Effects of Ritodrine and Fetal Oxygenation after in utero Fetal Surgery in Sheep

“…A catheter was then inserted intra-amniotically and the uterine incision was closed. The common fetal umbilical artery was iso lated through a left-flank incision and a precalibrated electromagnetic blood flow transducer (C & C Instru ments, Culver City, Calif.) was placed [7], Three vinyl-insulated multistranded stainless steel electrode wires (Cooner Sales C o ., Chatsworth, Calif.) were sewn into the fundus o f the pregnant horn o f the uterus [8], The flank, uterine, and abdominal inci sions were closed and all catheters, the electrodes and the blood flow transducer cable were brought subcu taneously to the maternal left flank and secured in a Teflon pocket attached to the skin. The catheters were filled with heparin 1,000 U/cm3 and sealed with a metal plug.…”

“…The cardiovascular variables: heart rate, mean arterial blood pressure, the uterine electromyo graphic activity and mean umbilical blood flow were recorded continuously on a polygraph (model R 411, Beckman Instruments Inc., Fullerton, Calif.). The uterine myoelectric activity was calculated as a myoelectric index, defined as the percent o f the hour that uterine myoelectric activity was present [8],…”

“…Krishnamurti et al [8] reported that uterine myoelectric activity is present 25-30% of the hour in chronically instrumented sheep not near parturition. In our study, we observed an increase in uterine myoelectric activity to 38% o f the hour in the postopera tive period.…”