Role of oxytocin in activation of spontaneous electrical activity of uterine body and uterine tubes in non-pregnant rats

The work studies effects of various doses of oxytocin (0.01, 0.1, 1 and 10 microg/kg) on duration of discharges of spontaneous electrical activity and frequency of spikes in various parts of uterine tubes and of uterine body of non-pregnant rats. Under these conditions, changes in these parameters for ovarian parts of the uterine tubes had similar character unlike those in cervical parts of the tubes and in the middle part of the uterine body, so the latter parts can be grouped together owing to peculiarities of their changes. The longest duration of genesis of electric discharges has been shown for the ovarian part of uterine tubes at a concentration of 10 microg/kg of oxytocin. Morphological experiments revealed that among all studies areas the ovarian parts of uterine tubes were characterized by the highest amount of atypical cells that have the maximally pronounced functional activity.     

Effect of oxytocin on activation of spontaneous electrical activities registered from uterine corpus and uterine tubes in rats

The effects if different concentrations of oxytocin (10(-2), 10(-1), 1 and 10 microg/kg) on burst duration and spikes frequency of spontaneous electrical activity in various parts of uterine horns and uterine corpus in non-pregnant rats have been shown. The changes in given parameters for ovarian parts of horns had similar characters unlike cervical parts of horns and middle part of uterine corpus under these conditions, so the last mentioned areas could be grouped together by the reason of similar changes in their parameters. Oxytocin in a concentration of 10(-1) microg/kg promoted the longest duration of spike electrical activity genesis in ovarian parts of horns. Morphological experiments showed that ovarian parts of horns had a great amount of atypical cells with strongly expressed functional activities.     

Role of acetylcholine in coordination of spontaneous electrical activity of various areas of the rat uterus

Spontaneous electrical activity of myometrium was studied in areas of the uterus body, zone of its connection with uterine tube, and cervix at intravenous administration of various acetylcholine concentrations. Under these conditions, changes of the frequency and amplitude characteristics of rhythmogenesis were studied both separately and in their combined active state. The presence of 10^?3 M acetylcholine in the animal blood creates the most optimal conditions for synchronization and coordination of activities of all studied uterus areas.     

Stimulation of fetal hypothalamus induces uterine contractions in pregnant rats at term

The fetal brain is thought to have a role in the onset and progression of labor. Evidence also exists for fetal oxytocin release just before and during parturition. The present study examined whether activation of the fetal brain could induce uterine myometrial contractions through oxytocin receptors in the dam. Under urethane anesthesia, electrical stimulation of the hypothalamus of fetal rats that were still connected with the dams by an intact umbilical cord induced uterine contractions in term pregnant rats. Intraperitoneal injections of synthetic oxytocin in fetuses induced uterine contractions in the dams similar to those induced by electrical stimulation of the fetal hypothalamus. Maternal intravenous injections of an oxytocin antagonist immediately attenuated uterine contractions induced by fetal oxytocin injections and electrical stimulation of the fetal hypothalamus. These findings suggest the possibility that oxytocin released from the fetal hypothalamus is involved in parturition.     

Application of wavelet coherence to the detection of uterine electrical activity synchronization in labor

This paper introduces the use of a method based on wavelet transform to detect the correlation between two uterine electrical activity bursts, recorded at different places on the pregnant abdomen during the same uterine contraction. The method used in this work is called wavelet coherence. The results of this study show that the wavelet analysis can successfully detect and quantify the temporal and spectral interactions between uterine bursts of electrical activity. They also indicate that the coherence is higher in the lower frequencies of the uterine electromyogram signal (EHG), and that it is possible to apply the method to non-segmented uterine signals. We find the method to give promising results permitting to evidence the coherence present in EHGs during a uterine contraction.     

Variation of myometrial activities and steroid sexual hormones following bilateral ovariectomy in the rat at midpregnancy

The effects of bilateral ovariectomy on uterine motility and levels of progesterone, oestradiol, cAMP, adrenaline and PGF2 alpha were studied in the rat at midpregnancy. Animals were randomly divided into two groups, at least 15 rats in each, sham-operated serving as controls and ovariectomized. The spontaneous uterine mechanical activity of Wistar rats was recorded isometrically and the electrical activities were recorded simultaneously by two bipolar electrodes. Within 30 minutes of ovariectomy a significant increase of the amplitude of uterine contractions was observed and the simultaneity of electrical activity was significantly improved; these effects became more pronounced at 1h post-ovariectomy (p less than 0.005). Plasma progesterone levels decreased by 20% (p less than 0.01) at 30 min and by 50% (p less than 0.001) 1h after ovariectomy, whereas oestrogen levels remained unchanged. Levels of adrenaline, cAMP and PGF2 alpha in the uterine tissue 1h following ovariectomy were affected as follows: adrenaline (p less than 0.05) and cAMP (p less than 0.001) were reduced and PGF2 alpha augmented (p less than 0.05). It appears that variation of the ratio oestrogens/progesterone induces precociously the activation of uterine mobility and exerts an effect on some factors involved in the regulation of the rat myometrium at midpregnancy.     

Simulating uterine contraction by using an electro-chemo-mechanical model

Contractions of uterine smooth muscle cells consist of a chain of physiological processes. These contractions provide the required force to expel the fetus from the uterus. The inclusion of these physiological processes is, therefore, imperative when studying uterine contractions. In this study, an electro-chemo-mechanical model to replicate the excitation, activation, and contraction of uterine smooth muscle cells is developed. The presented modeling strategy enables efficient integration of knowledge about physiological processes at the cellular level to the organ level. The model is implemented in a three-dimensional finite element setting to simulate uterus contraction during labor in response to electrical discharges generated by pacemaker cells and propagated within the myometrium via gap junctions. Important clinical factors, such as uterine electrical activity and intrauterine pressure, are predicted using this simulation. The predictions are in agreement with clinically measured data reported in the literature. A parameter study is also carried out to investigate the impact of physiologically related parameters on the uterine contractility.     

产后康复治疗仪使用时机对促进子宫收缩及刺激泌乳的效果观察

目的观察产后康复治疗仪时机对促进产后子宫收缩及刺激泌乳的效果。方法将146例初产妇按住院单双号分为观察组和对照组各73例,观察组产妇在胎儿前肩娩出后即采用产后康复治疗仪对双侧乳房及"气海"穴、"关元"穴进行电刺激,对照组在处理完第三产程后采用产后康复治疗仪对双侧乳房及"气海"穴、"关元"穴进行电刺激,两组产妇低频电刺激强度均以产妇能够耐受为度,观察两组产妇产后1、2h的出血量及产后2h泌乳量情况。结果两组产妇产后1、2h的出血量及产后2h泌乳量比较,差异具有统计学意义(P0.05)。结论在胎儿前肩娩出后即采用产后康复治疗仪对双侧乳房及"气海"穴、"关元"穴进行电刺激,可有效促进子宫收缩,减少产后出血,促进乳汁分泌,有利于产妇恢复及促进母乳喂养。     

Comparison of human uterine cervical electrical impedance measurements derived using two tetrapolar probes of different sizes

Background  

We sought to compare uterine cervical electrical impedance spectroscopy measurements employing two probes of different sizes, and to employ a finite element model to predict and compare the fraction of electrical current derived from subepithelial stromal tissue.     

Improved electrical coupling in uterine smooth muscle is associated with increased numbers of gap junctions at parturition

We have studied some passive electrical properties of uterine smooth muscle to determine whether a change in electrical parameters accompanies gap junction formation at delivery. The length constant of the longitudinal myometrium increased from 2.6 +/- 0.8 mm (X +/- SD) before term to 3.7 +/- 1 mm in tissues from delivering animals. The basis of the change was a 33% decrease in internal resistance and a 46% increase in membrane resistance. Axial current flow in an electrical syncytium such as myometrium is impeded by the cytoplasm of individual cells plus the junctions between cells. Measurement of the longitudinal impedance indicated that the specific resistance of the myoplasmic component was constant at 319 +/- 113 omega . cm before term and 340 +/- 93 omega . cm at delivery. However, a decrease in junctional resistance was apparent from 323 +/- 161 omega . cm to 134 +/- 64 omega . cm at delivery. 1.5-2 d after delivery, the junctional resistance was increased, as was the myoplasmic resistance. Thin-section electron microscopy of some of the same muscle samples showed that gap junctions were present in significantly greater numbers in the delivering tissues. Therefore, our results support the hypothesis that gap junction formation at delivery is associated with improved electrical coupling of uterine smooth muscle.     

Changes in the fast uterine muscle biopotentials in rabbits with chronic hypoxia

Changes of the high-frequency electrical activity in the myometrium after a separate and simultaneous ligation the uterine and ovarian vessels were studied in chronic experiments (137 experiments on 18 non-pregnant rabbits which had already had pregnancies in the past). The highest and most prolonged (up to 45 days) inhibition of the amplitude and frequency of rapid (peak) potentials of the myometrium follows a simultaneous ligation of the uterine and ovarian arteries and veins. The amplitude and frequency of biopotentials is gradually restored with the compensation of blood circulation by the collateral blood channels.     

Inhibition of uterine contraction by synthetic parathyroid hormone fragment

The inhibitory effect of synthetic bovine parathyroid hormone fragment [bPTH-(1-34)] on rat uterine contraction was studied $\text{in vitro}$. Oxytocin, prostaglandin F_2α and acetylcholine produced log dose-related contraction. The addition of bPTH-(1-34) shifted the dose-response curves of the three agonists to the right. Two doses of bPtH-(1-34) were tested. The higher dose (400 ng/ml) caused a greater inhibition of the agonists than did the lower dose (40 ng/ml). bPTH-(1-34) also inhibited the uterine contraction elicited by electrical stimulation of the tissue. We suggest that bPTH-(1-34) has a non-specific depressing effect on the contractile mechanism of the uterine tissue.     

Immunocytochemical localization of galanin in the rat male and female genital tracts and motor effects in vitro

Galanin, a recently discovered neuropeptide, was studied in the rat male and female reproductive tracts by immunocytochemistry and in vitro pharmacology. Nerve fibers containing galanin immunoreactivity were most abundant in the female paracervical tissue, where they surrounded non-immunoreactive ganglion cells. Galanin nerves were also found in the uterus and Fallopian tubes, as well as in the vas deferens. When tested in vitro galanin contracted the smooth muscle of both the uterine horn and cervix. Galanin also slightly potentiated the response to electrical field stimulation in preparations from the uterine cervix and vas deferens, but it had no effect on the seminal vesicle. Galanin-(1–10), an N-terminal residue of galanin, also contracted the uterine horn, though higher concentrations were required. The neurally induced contractions were not influenced by galanin-(1–10) in any of the smooth muscle preparations tested. The muscle receptors mediating the direct contractile effects in the uterine horn seem to require the N-terminus of galanin, while the neuromodulatory effects on the electrically induced contractile activity seem to need the C-terminal part or the whole galanin molecule. Galanin may thus function as a neuromediator in the rat male and female genital organs.     

A comparison of uterine motility in the pregnant and non-pregnant cynomolgus monkey (Macaca fascicularis) and pregnant woman: a manometric and electromyographic study

The use of a combination of manometric and electromyographic methods provided a reliable technique for evaluating variations in uterine activity in conscious macaque monkeys and women. The technique was particularly useful for obtaining data on the influence of steroid hormones. During the spontaneous menstrual cycle of the macaque, uterine motility, after being weak and poorly synchronized during the follicular phase, became still weaker with impaired synchronization during the luteal phase and then much stronger and well-synchronized at the time of menstruation. There was no evidence in vivo of any relationship between the existence of gap junctions in the myometrium of non-pregnant animals and the various patterns of uterine motility. During the last third of pregnancy in macaques, the initiation of electrical activity in various uterine areas was always synchronous with and related to mechanical contraction. The same results were obtained in preparturient women. Thus, improved uterine coordination does not appear to be the mechanism by which the uterine contractile strength increases to expulse the foetus at the end of pregnancy. Apart from the particular situation of non-pregnant animals under progestative influence, in which activity was constantly non-propagated, we could not find any evidence of a general pattern which would indicate only one site for the initiation of activity and its extension to the whole uterus.     

Local and systemic control of myometrial contractile activity during labour in the sheep

The relative contribution of systemic versus local (intrauterine) factors in the activation and stimulation of the sheep myometrium during labour was examined using an in-vivo myometrial explant preparation. Myometrial tissue alone (MYO) or with attached endometrium (ENDO/MYO) was removed from the pregnant uterine horn, sutured to a stainless-steel frame and placed into the omental fat. After 7-10 days the explants developed a pattern of electromyographic activity qualitatively similar to that of the uterine myometrium. Induction of preterm labour by infusion of ACTH (66.6 ng/min for 15 min every 2 h) to the fetus resulted in a reduction in plasma progesterone concentrations and increases in values of oestradiol-17 beta and 13,14-dihydro 15-keto PGF-2 alpha in maternal plasma. The onset of labour, which followed these endocrine changes, was characterized by an increase in EMG burst frequency and reduction in burst duration occurring simultaneously in both the uterine myometrium and in the explants. The response of the uterine and explant myometrium to oxytocin also exhibited a parallel significant increase over the 24-h period leading to delivery. No differences were apparent between the explants containing myometrial tissue alone or those comprising endometrial and myometrial tissue. There was no significant change in uterine or explant EMG activity, or oxytocin responsiveness, after saline administration to the fetus. The pattern of EMG activity changes during spontaneous labour were not distinguishable from those during ACTH-induced labour. As with oxytocin, the responsiveness of the explants to electrical stimulation increased significantly at labour compared to pre-labour. These data suggest that factors within the systemic circulation play a major role in both the onset of labour contractions and the increased response to electrical or hormonal (oxytocin) stimulation during parturition in sheep.     

Storage and Release of Spermatozoa from the Pre-Uterine Tube Reservoir

In mammals, after coitus a small number of spermatozoa enter the uterine tube and following attachment to uterine tube epithelium are arrested in a non-capacitated state until peri-ovulatory signalling induces their detachment. Whilst awaiting release low numbers of spermatozoa continually detach from the epithelium and the uterine tube reservoir risks depletion. There is evidence of attachment of spermatozoa to uterine epithelium in several species which might form a potential pre-uterine tube reservoir. In this study we demonstrate that: (1) dog spermatozoa attach to uterine epithelium and maintain flagellar activity, (2) in non-capacitating conditions spermatozoa progressively detach with a variety of motility characteristics, (3) attachment is not influenced by epithelial changes occurring around ovulation, (4) attachment to uterine epithelium slows capacitation, (5) capacitated spermatozoa have reduced ability to attach to uterine epithelium, (6) under capacitating conditions increased numbers of spermatozoa detach and exhibit transitional and hyperactive motility which differ to those seen in non-capacitating conditions, (7) detachment of spermatozoa and motility changes can be induced by post-ovulation but not pre-ovulation uterine tube flush fluid and by components of follicular fluid and solubilised zona pellucida, (8) prolonged culture does not change the nature of the progressive detachment seen in non-capacitating conditions nor the potential for increased detachment in capacitating conditions. We postulate that in some species binding of spermatozoa to uterine epithelium is an important component of the transport of spermatozoa. Before ovulation low numbers of spermatozoa continually detach, including those which are non-capacitated with fast forward progressive motility allowing the re-population of the uterine tube, whilst around the time of ovulation, signalling from as-yet unknown factors associated with follicular fluid, oocytes and uterine tube secretion promotes the detachment of large numbers of capacitated spermatozoa with hyperactive motility that may contribute to the fertilising pool.     

Characteristics of bovine early puerperal uterine contractility recorded under farm conditions

A non-invasive, digital technique was used to measure and quantify intrauterine pressure (IUP) changes in early postpartum dairy cows kept under farm conditions in order to document physiological changes in uterine contractility after uncomplicated calvings. In addition, possible relationships between characteristics of uterine contractility and blood ionized calcium (Ca(2+))-concentrations were investigated. Recordings of uterine contractility were made by using a transcervically inserted open tip catheter in 12 healthy cows during their first 48h after calving. The IUP recording technique appeared easily applicable under farm conditions. Although mean frequency (FREQ), amplitude (AMP) and area under the curve (AUC) of the myometrial contractions significantly decreased due to time, untreated early postpartum cows showed a high variability in characteristics of uterine contractility. There was no correlation between blood Ca2+ -concentrations and any of the contractility parameters.     

Relationship between the electrical activity of the oviduct and the uterus of the rabbit in vivo.

The electrical activity of the whole genital tract of the rabbit was recorded by means of chronically implanted electrodes after section of the uterotubal junction on one side. When the junction was intact, the activity of the isthmus and that of the proximal uterine horn occurred almost simultaneously, but uterine activity decreased after the junction was cut. During the preovulatory phase and also after administration of HCG, synchronos activity due to adrenergic drugs, smoke or oxytocin persisted on both sides of the uterotubal junction. Hypersensitivity of the isthmus and the proximal segment of the uterine horn was recorded on the cut side after ovariectomy. The concept of a local control mechanism in the region of the uterotubal junction with a positive control of the uterus by the oviduct is suggested.     

Blood supply as a factor regulating pacemaker activity of the rat uterine horn

The effect of ischemia of the uterine artery supplying blood to the main rhythmogenic ovarian zone of the uterine horn in non-pregnant rats was investigated. Parameters of pacemaker activity of the given locus and all the subsequent pacemaker areas up to the cervix were studied under the influence of ischemia. The greatest changes of the amplitude, frequency and burst duration time of spike activities were recorded in the ovarian end of horn. The uterine corpus and cervical end of horn were less affected by ischemia. However, amplitude of the slow-wave oscillations increased by more than one and a half in these conditions. Data obtained allow us to state about presence of certain connection between the ovarian end of horn and uterine cervix. Morphological studies revealed strong vascularization of the upper part of uterine horn.