Electromyographic activity of the nonpregnant and pregnant sheep uterus

Harding, Richard; Poore, E.R.; Bailey, Alan; Thorburn, G. D.; Jansen, C.A.M.; Nathanielsz, Peter W.

doi:10.1016/s0002-9378(16)32389-4

Cited by 111 publications

(70 citation statements)

References 13 publications

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“…The coordination of bursts of impulses across the myometrium takes place gradually over a period of days and there is no evidence that bursts are consistently initiated at one location and then spread throughout the myometrium. This pattern of activity is similar to that recorded throughout late gestation, from day 90 until the start of labour (Hindson and Ward 1973;Harding et al 1982). In late gestation these coordinated contractions raise intra-uterine pressure by O· 67-1 ·07 kPa (5-8 mmHg) and it is probable that the contractions recorded during mid-gestation in this study also caused an increase in intra-uterine pressure.…”

Section: Discussionsupporting

confidence: 88%

“…These were recognized as an increase in frequency superimposed on an irregular background discharge which appeared at two or more sites on the uterus. The bursts recorded in the five ewes had a mean duration of 8· 69± 1 ·68 min (n = 64 data sets) and occurred at a mean frequency of 1· 28±0· 39 h-1 • These values are similar to those recorded from ewes during late gestation (>90 days; duration 7·2 min, frequency 1· 29 h-1 ) by Harding et al (1982). In three of the ewes recordings were made from three or four sites on the dorsal surface of the uterus.…”

Section: Emg Recordingssupporting

confidence: 62%

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Development of Myometrial Electrical Activity during the First Half of Pregnancy in the Sheep

Sigger¹,

Harding²,

Bailey³

1984

Aust. Jnl. Of Bio. Sci.

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Uterine myoelectrical activity was recorded in seven pregnant sheep covering the period between 13 and 75 days post-coitum. Activity in the myometrium was present at day 13 and took the form of intermittent spikes of low amplitude. Bursts of spikes of irregular duration became noticeable between days 25 and 40 but most were not coordinated throughout the myometrium. Coordinated bursts of myoelectrical activity, which could be recorded at several sites simultaneously, first appeared between 40 and 65 days. These bursts had similar characteristics to the myoelectrical activity associated with uterine contractions during the last third of gestation. The myoelectrical activity showed a progressive increase in amplitude during the first half of gestation. There was no relationship between plasma progesterone levels and the increase in amplitude or appearance of coordinated bursts of uterine activity.

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Section: Discussionsupporting

confidence: 88%

Section: Emg Recordingssupporting

confidence: 62%

Development of Myometrial Electrical Activity during the First Half of Pregnancy in the Sheep

Sigger¹,

Harding²,

Bailey³

1984

Aust. Jnl. Of Bio. Sci.

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“…Temporal-specific differences in uterine contractility have been reported during pregnancy in humans, sheep, rats and mice (Harding et al 1982, Bengtsson et al 1984, Buhimschi & Garfield 1996, Buhimschi et al 1997, Hennan & Diamond 1998, Mackler et al 1999. These reports have consistently provided evidence that uterine activity significantly increases just prior to labour.…”

Section: Hsp27 and Myometrial Contractilitymentioning

confidence: 99%

Small heat shock protein 27 (Hsp27) expression is highly induced in rat myometrium during late pregnancy and labour

White¹,

Williams²,

Highmore³

et al. 2005

Reproduction

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The underlying mechanisms that regulate uterine contractions during labour are still poorly understood. A candidate regulatory protein is heat shock protein 27 (Hsp27). It belongs to the small heat shock protein family and can regulate actin cytoskeleton dynamics, act as a chaperone, and may regulate contractile protein activation. As a result, we hypothesized that Hsp27 expression would be highly induced during late pregnancy and labour. Hsp27 mRNA expression was significantly elevated (P < 0.05) on days 17 to 22 of gestation. In addition, immunoblot analysis demonstrated that detection of total Hsp27 increased (P < 0.05) between day 21 and 1 day post-partum (PP) inclusive. Since phosphorylation of Hsp27 has been reported to be a prerequisite for smooth muscle contraction, we examined the temporal and spatial expression of Ser-15 phosphorylated Hsp27. Immunoblot analysis showed that the detection of Ser-15 phosphorylated Hsp27 significantly increased (P < 0.05) between days 19 and 23 (active labour) inclusive, in parallel with detection of total Hsp27. Immunocytochemical analysis of Ser-15 phosphorylated Hsp27 expression in situ demonstrated that phosphorylated Hsp27 in circular muscle became detectable in peri-nuclear and membrane regions on days 19 to 22, but was primarily restricted to the cytoplasm on days 23 to PP. In contrast, phosphorylated Hsp27 in longitudinal muscle was primarily detected in myocyte membranes on days 15 to 22, and then also became detectable in the cytoplasm of myocytes on days 23 and PP. Our results demonstrate that Hsp27 expression is highly upregulated during late pregnancy and labour and suggest that Hsp27 is a potential candidate contraction-associated protein.

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“…The onset of labor in sheep is associated with a clear switch in myometrial contractility patterns from contractures to contractions (Nathanielsz et al 1980, Harding et al 1982. This switch is accompanied by myometrial activation (Lye 1994) involving changes in expression of a collection of contraction-associated proteins, such as estrogen receptor (Wu et al 1995), gap junctions (Garfield 1988, Lye et al 1993) and oxytocin receptor (Fuchs et al 1983, Wu & Nathanielsz 1994, Zingg et al 1995, Chen et al 1996.…”

Section: Introductionmentioning

confidence: 99%

Characterization of two labor-induced genes, DSCR1 and TCTE1L, in the pregnant ovine myometrium

Wen

H²,

Q³

et al. 2003

Journal of Endocrinology

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In the present study we characterized two labor-induced genes, DSCR1 (Down syndrome candidate region 1) and TCTE1L (murine t-complex like), which were identified by suppression subtractive hybridization in the pregnant ovine myometrium. DSCR1 and TCTE1L cDNA sequences were retrieved from a custom-made labormyometrial cDNA library by hybridization screening. The characterized cDNA sequences include 5 -untranslated region (UTR), coding region and 3 -UTR, which are 12 bp, 351 bp and 1716 bp for TCTE1L, and 64 bp, 594 bp and 1539 bp for DSCR1 respectively. The two cDNA sequences encode proteins of 116 and 197 amino acids for TCTE1L and DSCR1 respectively. Northern analysis further confirmed the significant increases of myometrial DSCR1 and TCTE1L mRNA associated with spontaneous term labor (n=6) compared with gestation-matched controls not in labor (n=6). The abundance of DSCR1 and TCTE1L mRNA was attenuated when myometrial contraction was inhibited by Nimesulide (n=6), a specific prostaglandin H synthase 2 inhibitor. Fetal occupancy greatly upregulated DSCR1 and TCTE1L mRNA in the gravid horn during betamethasone-induced premature labor (n=6) compared with the non-gravid horn not in labor (n=3). Estradiol upregulated TCTE1L mRNA, but had no effect on DSCR1 mRNA expression in the non-pregnant sheep myometrium. Progesterone alone had no effect on both DSCR1 and TCTE1L mRNA expression, however progesterone antagonized estradiol's stimulating effect on myometrial TCTE1L mRNA expression in ovariectomized non-pregnant sheep.Upregulation of DSCR1 and TCTE1L in both betamethasone-induced premature labor and spontaneous term labor and inhibition of their expression by Nimesulide suggest a functional role of these two genes in myometrial activation associated with onset of labor. Mechanical stretch, labor and steroids differentially regulated DSCR1 and TCTE1L mRNA in the pregnant and non-pregnant sheep myometrium.

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Electromyographic activity of the nonpregnant and pregnant sheep uterus

Cited by 111 publications

References 13 publications

Development of Myometrial Electrical Activity during the First Half of Pregnancy in the Sheep

Development of Myometrial Electrical Activity during the First Half of Pregnancy in the Sheep

Small heat shock protein 27 (Hsp27) expression is highly induced in rat myometrium during late pregnancy and labour

Characterization of two labor-induced genes, DSCR1 and TCTE1L, in the pregnant ovine myometrium

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