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PubMed1987

[Basic studies of the effects of various kinds of tocolytics on uterine contraction in pregnant rats].

The effects of various substances involved in the inhibition of uterine contraction on the uterine muscle of pregnant rats were studied in vitro in terms of uterine contraction and alterations in cyclic nucleotides. 1) The inhibitory effect of 4-aminoantipyrine (4AA) on uterine contraction showed a pattern of decline, being less potent that tranylcypromine. The effect of nifedipine was the most potent, followed by ritodrine, tranylcypromine, RU 486 and 4AA, in that order. The inhibitory effects were diminished by administration of ONO-802.PGF2 alpha. 2) Cyclic nucleotide levels changed according to the potency of each agent in the process of inhibition. Although the level of c-AMP tended to increase and that of c-GMP tended to decrease, there were no changes in their levels when nifedipine was administered. 3) Blood and uterine muscle levels of c-AMP were increased in pregnant rats that had been given ritodrine prior to hysterectomy, and there was no inhibitory effect of ritodrine in comparison with pregnant rats that had not been given the agent. The pregnant rats that had been given ritodrine prior to hysterectomy also showed no significant change in the level of c-AMP in the bath-medium.

Abortifacient Agents↗
PubMed1981

[Studies on the measurement of uterine contraction by the impedance-variance of maternal abdominal wall (author's transl)].

An electronic system for the detection of uterine contractions by impedance measurement of the maternal abdominal wall, where the placenta attached to the anterior uterine wall confirmed by using B-mode ultrasonic method, was evaluated in 74 subjects. Simultaneous recordings of uterine contractive activity with conventional external recording system were made. Impedance recordings were evaluated and compared with the external recordings. The available evidence from this study indicated that 88.31% of uterine contractions were accurately detected and the onset, peak and end of each uterine contractions was reliable parameters of impedance measurement. The uterine contractions which seemed to be weaker in second trimester and difficult to record by the usage of external method were clearly detectable by the method. However on the place of the maternal abdomen where the placenta was not attached, impedance recordings did not show corresponding response with each uterine contractions. It was indicated that impedance recordings on the localization of the placenta mainly represented the change of intraplacental blood volume following by uterine contractions. The advantages of this method consisted in the patients comfort and easy application of the recording electrodes, but the usefulness of the method was limited to the cases of anterior localization of the placenta, namely 50% of the whole pregnant women.

Abdominal Muscles↗
PubMed1984

[The investigations on the effect of daily activity on the uterine contraction during pregnancy].

The present paper is characterized by its uniqueness in that uterine contractions were studied in pregnant women in their own home while engaged in their daily activities. The author, using conventional and newly devised small external tocodynamometers , investigated how daily activities affected uterine contraction during pregnancy and the results are as follows. In normal pregnancy, uterine contractions with a duration of 31-180 sec. were found 1.3-1.5 times per 30 min. in the 6-7th gestational months and 4.8 times in the 10th month. Circadian changes varied according to the number of gestational months. Uterine contractions were easily enhanced by shopping, bath-taking, train-riding, swimming, sexual intercourse, etc. CTG recordings of how they were actually enhanced are shown with statistical data and explanations. Contractions were easily increased by housework activities in patients with threatened preterm labor. When uterine contractions were abnormally strong during pregnancy, the cervix was found to be ripened even before term.

Activities of Daily Living↗
PubMed1991

Parathyroid hormone-related protein inhibits stimulated uterine contraction in vitro.

The effect of parathyroid hormone-related protein (PTHrP) fragments 1-34, 38-64, and 67-86 on acetylcholine-stimulated rat uterine contraction was examined in vitro. In addition, the possibility that PTHrP-(38-64) or (67-86) influenced relaxation caused by PTHrP-(1-34) was also investigated. Contraction of uterine horns was stimulated with 10(-6) or 10(-5) M acetylcholine. PTHrP-(1-34) reduced the magnitude of acetylcholine-stimulated uterine contraction. This effect was dose related over a concentration range of 10(-9)-10(-6) M. Neither PTHrP-(38-64) or PTHrP-(67-86) at concentrations of 10(-8)-10(-6) M affected uterine contraction stimulated by 10(-6) M acetylcholine. These fragments did not affect the relaxation caused by 10(-7) M PTHrP-(1-34). These results demonstrate that (1) PTHrP-(1-34) at 10(-6) M influences contraction of the rat myometrium and (2) the muscle relaxant activity of PTHrP is associated with the first 34 N-terminal amino acids.

Acetylcholine↗
PubMed2006

[Characteristics of uterine contraction and stages of labor under continuous epidural block anesthesia].

OBJECTIVE: To observe the characteristics of uterine contraction and stages of labor during delivery under continuous epidural block anesthesia. METHODS: Totaling 213 parturients in spontaneous labor under epidural block anesthesia with dilated cervical orifice of 3 cm were monitored for the contraction cycle, duration, intensity and curve types of uterine contraction, and recordings were made for 30 min before and 30, 60 and 120 min after the anesthesia took effect, respectively. The duration of the active phase in the first, second and third stages of labor was compared between 421 cases with anesthesia and 237 without anesthesia. RESULTS: Significant difference was noted in the objective indexes of uterine contraction recorded after anesthesia had taken effect (P<0.05) in comparison with those before anesthesia, suggesting significantly attenuated uterine contraction after anesthesia, whereas these indexes underwent no significant further variation as compared between different time points after anesthesia (P>0.05). The average active phase in the first stage was significantly shorter in anesthesia group than that in the control group (P<0.05), but the average duration of the second and third stages of labor differed little between the two groups with appropriate use of oxytocin under strict monitoring (P>0.05). The rates of obstetric forceps utilization and use of oxytocin were higher in anesthesia group than in the control group (P<0.05). CONCLUSION: Epidural block anesthesia produces certain influences on uterine contraction and stages of labor during delivery, for which appropriate treatment measures may prove beneficial.

Adult↗
PubMed1989

Blockade of epidermal growth factor-induced uterine contractions by indomethacin or nordihydroguaritic acid.

Epidermal growth factor (EGF) induces uterine contractions in an in vitro system. As an initial approach to elucidating the cellular mechanism for this action of EGF, we have characterized this effect pharmacologically in uteri from castrate, estrogenprimed mature rats. EGF-induced contractions are observed in both intact tissue and isolated myometrium, are dependent on extracellular calcium and are inhibited by nifedipine and chlorpromazine. Both indomethacin and nordihydroguaritic acid (NGA) inhibit EGF-induced uterine contractions. At the maximum doses which do not affect contractile responses to prostaglandin E2 or carbachol, indomethacin (10 microM) alone or NGA (1 microM) alone only decrease the effect of EGF by 60 to 80%, but indomethacin and NGA in combination abolish totally the response to the growth factor. Arachidonic acid also causes uterine contractions in this system. EGF increases uterine contractions in the presence of a submaximal (1 microM) but not a maximal (10 microM) dose of arachidonic acid. These findings suggest that EGF-induced contractions result from a mobilization of myometrial arachidonic acid, production of intermediates via both lipoxygenase and cyclooxygenase catalyzed pathways and a resultant influx of extracellular calcium.

Animals↗
PubMed1992

Fetal viability and fetal growth after prolonged uterine contractions induced by progesterone withdrawal in late pregnancy in rats.

The hypothesis that sustained uterine contractile activity is the direct cause of fetal death after progesterone withdrawal in late pregnancy in rats was investigated. Pregnant rats were subjected to progesterone withdrawal on day 15 of pregnancy by injecting 2 mg mifepristone (RU 486) kg-1 or by ovariectomy with oestradiol replacement (200 ng day-1). Uterine contractile activity (force and frequency) at 4 h, but not at 2 h, in rats injected with mifepristone was significantly higher than in rats injected with vehicle. The contractile activity in mifepristone-treated rats remained higher than in control rats, at 12, 24 and 48 h. Fetal viability 36 h after mifepristone injection, when uterine contractions had lasted for 32 h, was not significantly different from fetal viability in rats injected with vehicle, but at 42 h after mifepristone injection, fetal viability was significantly reduced. In ovariectomized rats, uterine contractile activity at 12, 24, 36 and 48 h, but not at 8 h, was significantly greater than in ovariectomized rats with progesterone replacement (4 mg day-1). Fetal viability at 42 h after the operation, when uterine contractions had lasted for 30 h, was not significantly reduced, but it was significantly reduced at 48 h. When ovariectomized rats had been left to develop uterine contractions for a period before progesterone was injected, deprivation of progesterone and prolonged uterine contractions for about 30 h did not reduce fetal viability or fetal growth determined on day 18, but it did so 3 days later, on day 21. Administration of 5 mg isoxuprine kg-1 twice a day, which suppressed uterine contractions, improved fetal viability in ovariectomized rats at the earlier stage, but not at the later stage. Nevertheless, isoxuprine did improve fetal growth at the later stage in these ovariectomized rats. It is concluded that increased uterine contractile activity sustained for 32 h or less does not reduce fetal viability, but longer periods of contraction may be the cause of fetal death.

Animals↗
PubMed1988

Association between fetal movements and uterine contractions in the active phase of labor.

Fetal body movements were studied for 40 minutes during the active phase of labor in 15 parturients. The total duration of fetal movements constituted 8.2% of the recording period, with a frequency of 3.8 +/- 2.1 per ten minutes. Of all the movements, 57.3% were associated with uterine contractions, while 40.7% of all uterine contractions were associated with fetal movements. All the fetuses moved in the first 30 minutes of the study period. The fetal movements that were associated with uterine contractions were longer than those not associated with contractions. Similarly, uterine contractions associated with fetal movements were longer than other uterine contractions.

Female↗
PubMed1998

Fetal oxygen saturation and uterine contractions during labor.

Oxygen availability to the fetus during uterine contractions has not been widely reported. We examined whether fetal oxygen saturation (FSpO2) values and signal quality (SQ) were affected by uterine contractions. An intrauterine pressure catheter and a Nellcor FS14 fetal oxygen saturation sensor (Nellcor Puritan Bennett Inc., Pleasanton, CA) were placed transvaginally during the first stage of 17 labors. Fetal SPO2 and SQ units were recorded on a beat-to-beat basis and 10 sec averages of the data calculated over 25 contractions per patient. Five epochs were determined: (1) 30 sec prior to a contraction; (2) during a contraction; (3) 50 sec following completion of a contraction; (4) noncontraction periods, excluding epochs 1 or 3; and (5) equivocal, that is, overlap of epochs 1-3. Mean FSpO2 was lowest during epoch 3 (45.0) and highest during epoch 2 (47.3%) (p <0.001). This small difference is unlikely to be of any clinical significance, however. Mean signal quality was lowest in epoch 1 (42.8 units) and highest in epoch 4 (48.0 units) (p <0.05), that is, in noncontraction periods. We conclude that FSpO2 and SQ were unaffected by uterine contractions.

Female↗
PubMedDate not supplied

NADPH-diaphorase-positive nerves and the role of nitric oxide in CGRP relaxation of uterine contraction.

We previously demonstrated calcitonin gene-related peptide (CGRP) immunoreactivity in sensory nerves in the rat uterus and that CGRP inhibits stimulated uterine contraction in vitro. The present study was undertaken to: 1) examine possible roles nitric oxide (NO) may have in the inhibitory action of CGRP on uterine contraction and 2) identify sites where NO may be synthesized. The relaxing effect of CGRP on SP-stimulated uterine contraction was established in vitro on uterine horns from diethylstilbestrol-treated rats. These experiments were repeated with or without an arginine analog [NG-monomethyl-L-arginine (L-NMMA)] that inhibits NO formation. The localization of the synthetic enzyme for NO production, NO synthase, was accomplished by histochemically staining for NADPH-diaphorase. Calcitonin gene-related peptide (10(-7) M) significantly reduced SP (10(-5) or 10(-6) M)-stimulated uterine contraction. The L-NMMA (10(-3) M) blocked the relaxing action of CGRP on SP-stimulated uterine contraction. The L-NMMA alone had no effect on SP-stimulated uterine contraction. NADPH-diaphorase-positive nerve fibers were located in the myometrium, endometrium, and adjacent to the vasculature. These data demonstrate that: 1) L-NMMA suppresses the relaxant effect of CGRP on myometrial activity and 2) NADPH-diaphorase (indicative of NO synthase) is localized in uterine nerve fibers. These data suggest that the inhibitory action of CGRP may be dependent on NO formation and that the enzyme necessary for NO production is present in nerves in areas optimal to affect myometrial activity.

Animals↗
PubMedDate not supplied

Effects of bPTH fragments (1-34), (3-34) and (7-34) on uterine contraction.

Synthetic bovine parathyroid hormone containing the NH2 terminal 34 amino acids [bPTH-(1-34)] was recently demonstrated to inhibit oxytocin stimulated uterine contraction in vitro. The parathyroid hormone analogues [Nle8, Nle18, Tyr34]bPTH-(3-34)amide [NTA-(3-34)] and [Tyr34]bPTH-(7-34)amide [NTA-(7-34)] have been reported to act as inhibitors of antagonists of parathyroid hormone (PTH) in numerous assays. In the present study the effects of these PTH analogues on uterine contraction and the ability of these analogues to act as antagonists to the uterine inhibitory action of bPTH-(1-34) in vitro were investigated. The NTA-(3-34) fragment had no effect on oxytocin stimulated uterine contractions. However, the NTA-(3-34) fragment was able to alter the ability of bPTH (1-34) to reduce oxytocin stimulated uterine contraction in a dose-related manner. Bovine PTH(1-34) (0.3 microgram/ml) reduced the contractile response obtained with oxytocin (0.5 mU/ml) by 20%. A dose of 15 micrograms/ml) of NTA-(3-34) abolished this inhibitory action of bPTH-(1-34) on oxytocin stimulated uterine contraction. In contrast the NTA-(7-34) caused a change in itself, stimulated contraction of resting uterine horns in a dose-related manner; 3.0 micrograms/ml of NTA-(7-34) caused a change in gram tension of + 1.5 grams. Bovine PTH-(1-34) was able to reduce the uterine contraction stimulated by NTA-(7-34) and 0.3 microgram/ml of bPTH-(1-34) reduced the contractile response obtained with 3.0 micrograms/ml of NTA-(7-34) by as much as 70%.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2000

Uterine contraction patterns and fertility in early postpartum ewes.

Three experiments were conducted to determine: (1) the direction of uterine contractions in Days 32 and 52 postpartum ewes (Experiment 1); (2) the effect of PGF(2alpha) on direction of uterine contractions (Experiment 2); and (3) the effect of PGF(2alpha) on fertility rates in Day 32 postpartum ewes (Experiment 3). In Experiment 1, non-lambing (>90 days postpartum) and lambing ewes (day of lambing=Day 0) received medroxyprogesterone acetate (MAP) vaginal sponges for 8 days and 500 IU of eCG at sponge withdrawal (Days 30 or 50 postpartum). At the time of eCG injection, ewes were divided into the following groups: (1) non-lambing (control; n=29); (2) Day 32 postpartum dry (n=15) and lactating (n=16); and (3) Day 52 postpartum dry (n=14) and lactating (n=16). At estrus or 60h post-eCG, the uterus was exteriorized through a mid-ventral incision, and the origin and direction of uterine contractions were recorded for 10min. In Experiment 2, ewes received MAP sponges on Day 16 postpartum followed by 500 IU of eCG on day of sponge removal (Day 30). At estrus, the ewes were divided into the following treatments: (1) two injections of saline 4h apart (n=10) and (2) 12.5mg of PGF(2alpha) followed by another 12.5mg 4h later (n=7). After the second injection, ewes were laparotomized and uterine contractions were counted. In Experiment 3, estrus was induced in postpartum ewes, and ewes were mated to two rams, then received the same two treatments as described in Experiment 2 (ram+saline; n=32 and ram+PGF(2alpha); n=28). Two days following mating, ewes were laparotomized and the oviducts flushed for recovery of ova. In Experiment 1, lactational status had no effect, therefore, the data were pooled. Control ewes had a greater percentage (p<0.05) of uterine contractions (69%) moving towards the oviducts than did Day 32 (8%) or Day 52 (43%) ewes. In Experiment 2, PGF(2alpha) treatment increased the proportion of contractions (p<0.05) moving toward the oviducts (controls 16%, PGF(2alpha) 42%). Number of PGF(2alpha)-treated ewes (Experiment 3) with fertilized ova were not significantly different from the control ewes (5/32 versus 2/28; respectively). In conclusion, it can be said that the direction of uterine contractions moving toward the oviducts increased as the postpartum interval progressed or if they received PGF(2alpha) injection. PGF(2alpha) treatment did not improve fertility rates in Day 32 postpartum ewes.

Journal Article↗
PubMed2002

Increasing maternal blood pressure with ephedrine increases uterine artery blood flow velocity during uterine contraction.

BACKGROUND: During labor, ephedrine is widely used to prevent or to treat maternal arterial hypotension and restore uterine perfusion pressure to avoid intrapartum fetal asphyxia. However, the effects of ephedrine on uterine blood flow have not been studied during uterine contractions. The purpose of the study was to assess the effects of ephedrine on uterine artery velocities and resistance index using the Doppler technique during the active phase of labor. METHODS: Ten normotensive, healthy parturients with uncomplicated pregnancies at term received intravenous ephedrine during labor to increase mean arterial pressure up to a maximum of 20% above their baseline pressure. Peak systolic and end-diastolic Doppler flow velocities and resistance indices were measured in the uterine artery before and immediately after administration of bolus intravenous ephedrine and after ephedrine washout. Umbilical and fetal middle cerebral arterial resistance indices and fetal heart rate were also calculated. RESULTS: After ephedrine administration, mean arterial pressure increased by 17 +/- 4%. End-diastolic flow velocity in the uterine artery at peak amplitude of uterine contraction was restored to 74% of the value observed in the absence of contraction. The systolic velocity was totally restored, and the uterine resistance index was significantly decreased, compared with the values in the absence of contraction. Between uterine contractions, ephedrine induced similar but less marked effects. Fetal hemodynamic parameters were not altered by ephedrine administration. CONCLUSIONS: Bolus administration of intravenous ephedrine reversed the dramatic decrease in diastolic uteroplacental blood flow velocity and the increase in resistance index during uterine contraction, without altering fetal hemodynamic parameters. This suggests that the increase in uterine perfusion pressure during labor could in part restore uterine blood flow to the placenta during uterine contraction.

Adult↗
PubMed2006

Potential role for oxidative stress in 2,2'-dichlorobiphenyl-induced inhibition of uterine contractions but not myometrial gap junctions.

Previously, we reported that 2,2'-dichlorobiphenyl (2,2'-DCB)-induced decreases of amplitude and synchronization of uterine contractions are dependent on MAPK-induced phosphorylation of Connexin43 (Cx43) and inhibition of myometrial gap junctions. Recent studies show that oxidative stress inhibits uterine contractions and myometrial gap junctions also. The present study examines the hypothesis that 2,2'-DCB-induced modification of uterine contraction is dependent on oxidative stress-mediated inhibition of myometrial gap junctions via activation of mitogen-activated protein kinase (MAPK) and phosphorylation of Cx43. In uterine strips treated with alpha-tocopherol (100 microM), deferoxamine mesylate (Def, 50 microM), or superoxide dismutase (SOD, 1000 U) after a 1-h exposure to 100 microM 2,2'-DCB, modification of uterine contractions reversed 1 h after initiating antioxidant treatment. Treatment of uterine strips with 100 microM 2,2'-DCB for 1 h lowered total SOD activity and also induced a surge of superoxide generation after 5 min of exposure. However, myometrial cells exposed in culture to 100 microM 2,2'-DCB did not produce reactive oxygen species as determined by the lack of superoxide anion generation measured by the cytochrome c reduction assay, reactive species by the formazan assay, hydrogen peroxide by the 2',7'-dichlorofluorescein assay, and lipid peroxidation by the thiobarbituric acid-reactive substance assay. Furthermore, cotreatment with SOD or Def was unable to prevent 2,2'-DCB-induced phosphorylation of Cx43, activation of MAPK, and inhibition of myometrial gap junctions. Although antioxidants reversed 2,2'-DCB-induced inhibition of uterine contraction force and synchronization, the myometrial cell culture experiments failed to support oxidative stress as a mechanistic link between 2,2'-DCB-induced inhibition of myometrial gap junctions and modification of uterine contraction.

Animals↗
PubMed1975

Intervillous space during uterine contractions in human subjects: an ultrasonic study.

Six patients at term were examined by ultrasound during uterine contractions. The length, thickness, and surface of the placental area were found to increase during uterine contraction compared to relaxation. The conclusion is drawn that during uterine contractions the intervillous space is distended. During uterine contraction more maternal blood is available for exchange with the fetal compartment.

Adult↗
PubMed1990

[Changes in arterial uterine blood flow velocity waveform during uterine contraction and relaxation in labor].

The arterial uterine blood flow velocity waveform during uterine contraction and relaxation in labor was measured with ultrasonic continuous wave (CW) Doppler device in 44 pregnant women at 37-41 weeks of gestation. The fetal heart rate (FHR) was also recorded by cardiotocogram during labor in every case. 1. Both the resistance index (RI) and pulsatility index (PI) of the arterial uterine blood flow velocity waveform were significantly higher during uterine contraction than during relaxation (p less than 0.005). These increases in RI and PI during contraction were not influenced by the maternal heart rate. The reverse or interrupted end-diastolic flow was demonstrated in 16.3% of the cases. 2. No abnormal FHR patterns were observed in any of the cases except two with early deceleration or mild variable deceleration in which uterine arterial end-diastolic flow was maintained. The fetal conditions did not seem to be influenced by the reduction of arterial uterine blood flow in our study.

Blood Flow Velocity↗