Alteration in uterine contractility in mares with experimentally induced placentitis

Abstract

An experimental model of ascending placentitis was developed in the mare to characterize the uterine myoelectrical pattern in late gestation and determine how ascending placentitis altered this pattern. In experiment 1, myometrial electrical activity was analyzed during the early morning, late morning and evening hours in four mares in the last 15 days of gestation to identify patterns of activity. In experiment 2, nine mares received intra-cervical inoculations of Streptococcus equi subspecies zooepidemicus. Myoelectrical activity in the early morning and evening hours in these mares was compared with four control mares. In experiment 1, the number of spike burst clusters >30 s was greater in the evening than in the late morning hours (P < 0.04). Spike burst activity (number 3 duration) of mares in experiment 1 was similar during day and night recordings until the last 6 days of gestation when it gradually increased each evening until parturition (P < 0.05). In experiment 2, control mares experienced a gradual increase in the number of small spike burst clusters in the last 6 days (P 5 0.008) and an increase in large and small spike burst clusters in the evening hours in the last 4 days of gestation (P 5 0.03). Mares with experimentally induced placentitis never exhibited a rise in spike burst clusters but had an increase in the mean duration and activity index of large spike burst clusters in the 4 days before parturition (P < 0.04). In conclusion, control mares had a progressive, reversible rise in myoelectrical activity at night in the week preceding parturition. This was not observed in mares with experimentally induced placentitis. They exhibited an increase in the intensity and duration of large spike burst clusters possibly in response to local inflammation.

Hormonal Profiles of Late Gestation Ewes Following Intra-uterine Inoculation With and Without Lux-modified Escherichia coli

“…In support of these observations, intra-amniotic inoculation of pregnant rhesus monkeys with group B Streptococci increased amniotic fluid cytokine concentrations (TNFα IL-1, β and IL-6) followed by sequential increased production of prostaglandins (PGE2 and PGF2α) prior to increases in uterine contractions [18,36]. Similar findings of increased pro-inflammatory cytokine expression in gestational tissue and prostaglandins in allantoic fluid have been reported in the experimentally infected pregnant mare [35] along with increased myometrial activity [38]. The increases in PGE2 and PGF2α observed in the mare study paralleled those of the inflammatory cytokines and were elevated several fold over that observed during spontaneous parturition.…”

Uterine EMG and Cervical LIF - Promising Technologies in Obstetrics

“…9b). Other groups have performed animal uterine EMG studies, and their work also shows that uterine EMG parameters can quantify uterine contractile activity, and/or can characterize changes therein [31][32][33].…”

HORSE SPECIES SYMPOSIUM: A novel approach to monitoring pathogen progression during uterine and placental infection in the mare using bioluminescence imaging technology and lux-modified bacteria1,2

“…The etiology of uterine infectioninduced preterm delivery in pregnant women, mice, and mares involves the release of proinflammatory cytokines, such as tumor necrosis factor a (TNFa), IL-lß, IL-6, and IL-8, among others, from placental and fetal tissues in response to infection (Dudley and Trautman, 1994;Pollard and Mitchell, 1996;Dudley, 1997;Mussalli et al, 1999;LeBlanc et al, 2002). The consequence of the inappropriate expression of these proinflammatory cytokines leads to the initiation of a preterm birth by increasing PG synthesis (Bennett et al, 2000;LeBlanc et al, 2002;McGlothlin et al, 2004). • As in humans, pregnancy loss during late gestation and the death of foals weakened by abnormal periparturient events constitute a large percentage of fetal and neonatal mortality in horses (Vaala and Sertich, 1994), and pluriparous mares are the most commonly afflicted (LeBlanc, 2010).…”

“…However, the application of bioluminescence imaging technology and the ability to modify pathogens with the lux gene provides investigators a unique opportunity to study the etiology of preterm delivery in the mare. The infectious experimental pony mare model developed by McGlothlin et al (2004) was a starting point for our group to explore this approach. It has been proposed that the use of bacteria modified to express light and biohmiinescent imaging technology may offer animal and veterinary researchers a useful means for understanding the pathogenesis of infectious pathogens leading to uterine infections and preterm delivery in the mare (Ryan et al, 2010b).…”