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Biomedical subjects

M T Parsons

Publications and source records attributed to M T Parsons.

At least 19 recordsLinked to original sources
PubMed1991

Inhibition of oxytocin-induced uterine contractions by an oxytocin antagonist in the pregnant baboon.

Uterine contractions were induced with oxytocin in anesthetized pregnant baboons (Papio anubis) at three stages of pregnancy (days 140, 156, and 169; normal gestation length, 184 days). After the contractile activity was greater than two to three contractions every 10 minutes, beta-mercapto-beta, beta-cyclopentamethylenepropionic acid1-[D-Trp2,Phe3,Ile4,Arg8]-oxytocin, a novel oxytocin antagonist produced in our laboratories, was given simultaneously with the oxytocin for 90 minutes. Contractile force (frequency x mean amplitude) was determined for 30 minutes before and for three 30-minute intervals after the oxytocin antagonist was administered. Animals at 140 days' gestation showed a significant (p less than 0.05) decrease in contractile force in the first 30-minute interval after oxytocin antagonist infusion was initiated, whereas those at days 156 and 169 showed decreases (p less than 0.05) at the second 30-minute interval. In addition, in late gestation a higher dose of oxytocin antagonist per unit of oxytocin was required to prevent uterine contractions. In conclusion, these results suggest (1) that an oxytocin antagonist can inhibit oxytocin-induced uterine contractions in the pregnant baboon and (2) that the interval from oxytocin antagonist administration to significant inhibition of uterine contractions appears to increase with advancing gestational age.

Animals↗
PubMed1991

Forward shift in the initiation of the nocturnal estradiol surge in the pregnant baboon: is this the genesis of labor?

Daily (9 AM and 6 PM) blood samples were obtained from the inferior vena cava during the last trimester of pregnancy in a tethered baboon model. In addition, three 24-hour (hourly blood sampling) studies were performed at days 143 to 147, 158 to 162, and 172 to 177 of pregnancy. Dramatic 24-hour rhythms in progesterone and estradiol were detected, with both steroids surging nocturnally. Early in the third trimester the estradiol surge followed the progesterone surge. However, approximately 10 to 12 days before delivery, the initiation of the nocturnal estradiol surge shifted forward, thus preceding the progesterone surge. This forward shift in the estradiol surge created a daily (3 to 5 hours) window of elevated estradiol-to-progesterone ratio and appears to coincide with the initiation of nocturnal uterine contractions. The nocturnal uterine contractions can be inhibited by an oxytocin antagonist. We hypothesize that this forward shift in the initiation of the estradiol surge induces nocturnal uterine contractions by oxytocin release and/or increase in uterine oxytocin receptors and generates molecular messages that are the genesis for labor and delivery in the baboon.

Animals↗
PubMed1991

Peritoneal closure or non-closure at cesarean.

The value of peritoneal closure at the time of cesarean birth was evaluated prospectively. Two hundred forty-eight women undergoing low transverse cesarean through a Pfannenstiel skin incision were assigned to one of two groups: peritoneum open (N = 127) or peritoneum closed (N = 121). The mean (+/- SEM) surgical time in the open group (48.1 +/- 1.2 minutes) was significantly less than for the closed group (53.2 +/- 1.4 minutes) (P less than .005). There were no postoperative differences between the groups in the incidence of wound infection, dehiscence, endometritis, ileus, and length of hospital stay. Our study suggests that leaving the parietal peritoneum unsutured is an acceptable way to manage patients at cesarean delivery.

Adult↗
PubMed1991

Fetal head molding. Diagnosis by ultrasound and a review of the literature.

Head molding refers to changes in cranial bone relationships that occur in response to external compression force. In the normal term labor with vertex presentation, the suboccipito-bregmatic diameter shortens and the mentovertical diameter lengthens. This is accomplished partially through the unbending or straightening of the parietal bones rather than the frequently taught mechanism of overlapping sutures. The occipital and frontal bones may also contribute by an inward movement of their apex, using their basal portions as a hinge. A locking mechanism may occur in protracted labors as the free edges of the cranial bones are forced into one another, preventing further molding and providing more protection for the fetal brain. The preterm skull has weaker material properties and wider sutures. Thus, more molding at lower pressures is possible and the protective effect of "locking" may not be operational. A case of extreme antenatal preterm fetal head molding discovered at ultrasound is presented as an introduction to review the literature regarding molding.

Adult↗
PubMed1991

Human fetal response to vibroacoustic stimulation as a function of stimulus duration.

The effect of stimulus duration on the initial fetal heart rate (FHR) acceleration response was evaluated by assessing its amplitude and span following a single vibroacoustic stimulation with durations of 0 (sham), 1, 3, or 5 seconds. Statistically significant differences were observed in the mean amplitude and duration of acceleration in groups 3 and 5 when compared with groups 0 and 1 (P less than .05). In addition, groups 3 and 5 demonstrated significantly greater fetal reactivity than group 0 and a decrease in testing time over groups 0 and 1 (P less than .05). Our results suggest that the magnitude of the FHR acceleration response is dependent on the duration of the stimulus. Furthermore, a 3-second sound stimulus appears to be adequate for a shift to the fetal behavioral "awake" state.

Acoustic Stimulation↗
PubMed1990

Inhibition of spontaneous uterine contractions during the last trimester in pregnant baboons by an oxytocin antagonist.

The effect of a potent oxytocin antagonist, produced in our laboratories, on spontaneous uterine contractions in the pregnant baboon was examined. Three types of uterine contractions were studied: immediately after operation, during the nocturnal period, and near or at labor. Bolus intravenous injections of oxytocin antagonist were given and uterine activity was examined +/- 1 hour after the injection. The oxytocin antagonist caused a precipitate decrease (approximately 70%) in contractile force (mean amplitude x frequency) in the first 15 minutes after injection (p less than 0.05); this force diminished to approximately 90% at the end of 1 hour for both nocturnal and labor contractions. In contrast, uterine contractions immediately after operation were diminished by only 60% within 60 minutes after the oxytocin antagonist. These results indicate that the oxytocin antagonist is a potent inhibitor and suggest that oxytocin is a primary regulator of spontaneous nocturnal and labor uterine contractions in the pregnant baboon.

Analysis of Variance↗
PubMed1990

Cocaine use and its effect on umbilical artery prostacyclin production.

Cocaine's association with adverse perinatal outcome has been attributed to its inhibition of norepinephrine uptake. This study examined the effect of cocaine on umbilical artery prostacyclin (PGI2) production. Umbilical arteries from pregnant cocaine users and controls were incubated in vitro and PGI2 levels in the media determined by measuring its stable metabolite, 6-keto-PGF1 alpha, by RIA. Cocaine users showed a significant decrease (p less than .05) in PGI2 production from their umbilical arteries when compared to controls. This appears to be through a direct effect of cocaine, as it decreases PGI2 production when added in vitro to umbilical arteries from controls. In addition, in vitro phospholipase A2 activity is inhibited by cocaine in a dose-dependent manner. These results suggest that the adverse perinatal outcome associated with cocaine use may be due in part to reduced vascular PGI2 production in the fetus.

Cocaine↗
PubMed1990

A new tocolytic agent: development of an oxytocin antagonist for inhibiting uterine contractions.

A potent oxytocin antagonist has been developed and tested on both the rat and human uterus. In the rat the oxytocin antagonist: (1) inhibited in vitro and in vivo uterine contractions in the nonpregnant animal in response to exogenous oxytocin, (2) inhibited milk letdown, and (3) disrupted the progress of labor. In addition, the oxytocin antagonist inhibited the in vitro contractile response to exogenous oxytocin of human myometrial tissue obtained by cesarean section at term. The results of these studies suggest that the oxytocin antagonist can be used to study the role of oxytocin in labor and has the potential of inhibiting preterm labor in humans.

Animals↗
PubMed1989

Pregnancy outcomes in short women.

The pregnancy outcomes in 3,059 women who were 122-152 cm (48-60 in) tall with singleton pregnancies were compared to those of 7,414 women who were 160 cm (63 in) tall. The short women were of lower weight at delivery and had slightly higher parity. There were fewer whites in the short group. The higher parity was associated with a slightly higher occurrence of placenta previa. The pregnancies in the short women were characterized by smaller infants and more frequent delivery by cesarean section, depending on race. For whites the cesarean section rate was 43% in the very-short group (122-136 cm, or 48-53 in), 35% in the short group (137-151 cm, or 54-59 in) and 23% in the control group. The results suggest that women less than 152 cm (60 in) tall are a high-risk group.

Birth Weight↗
PubMed1989

The prevention of meconium aspiration in labor using amnioinfusion.

In an effort to improve maternal and fetal outcome in patients laboring with thick meconium, 85 patients presenting with thick meconium were randomized to receive either amnioinfusion with 1000 mL normal saline initially and every 6 hours until delivery, or routine care. Meconium was discovered on initial examination during labor, after artificial rupture of membranes, through the use of an intrauterine pressure catheter, or on amniocentesis. Labor management was otherwise routine. Forceps operations and cesarean sections were for distress or failure to progress, as indicated. Patients receiving amnioinfusion had significantly fewer low 1-minute Apgar scores, less meconium below the cords, and a significantly lower incidence of operative delivery. The only three cases of meconium aspiration syndrome occurred in infants delivered of patients receiving routine management. No adverse side effects of amnioinfusion were detected. Amnioinfusion is a simple, inexpensive, and safe technique that reduces the incidence of meconium below the cords and improves obstetric outcome in patients laboring with thick meconium.

Adult↗
PubMed1988

Prostaglandin production and contractile response of umbilical arteries in preeclamptic pregnancies with and without intrauterine growth retardation.

Biochemical and biophysical properties of umbilical arteries from normotensive and preeclamptic pregnancies were examined. The production of prostaglandins E and F, 6-keto-PGF1 alpha, and thromboxane B2 by umbilical arteries from normotensive, mildly preeclamptic, and severely preeclamptic pregnancies were measured in incubation media at baseline and after addition of arachidonic acid. The initial baseline values of 6-keto-PGF1 alpha were decreased in the severely preeclamptic patients with intrauterine growth retardation (IUGR) but not in any of the other groups. Addition of arachidonic acid resulted in a significant increase in 6-keto-PGF1 alpha production over initial baseline in all groups except in the severely preeclamptic pregnancies without IUGR. These results suggest a differential defect in the 6-keto-PGF1 alpha metabolic pathway in severely preeclamptic patients with IUGR compared with those without IUGR. The stretch response curve to serotonin was decreased in the severely preeclamptic group with IUGR compared with the control group. The contractile response to individual vasoactive agents (serotonin, prostaglandin F2, norepinephrine, angiotensin II, and arachidonic acid) showed no significant difference between the normotensive and preeclamptic groups.

Angiotensin II↗
PubMed1987

Court-ordered obstetrical interventions.

In a national survey, we investigated the scope and circumstances of court-ordered obstetrical procedures in cases in which the women had refused therapy deemed necessary for the fetus. We also solicited the opinions of leading obstetricians regarding such cases. Court orders have been obtained for cesarean sections in 11 states, for hospital detentions in 2 states, and for intrauterine transfusions in 1 state. Among 21 cases in which court orders were sought, the orders were obtained in 86 percent; in 88 percent of those cases, the orders were received within six hours. Eighty-one percent of the women involved were black, Asian, or Hispanic, 44 percent were unmarried, and 24 percent did not speak English as their primary language. All the women were treated in a teaching-hospital clinic or were receiving public assistance. No important maternal morbidity or mortality was reported. Forty-six percent of the heads of fellowship programs in maternal-fetal medicine thought that women who refused medical advice and thereby endangered the life of the fetus should be detained. Forty-seven percent supported court orders for procedures such as intrauterine transfusions. We conclude from these data that court-ordered obstetrical procedures represent an important and growing problem that evokes sharply divided responses from faculty members in obstetrics. Such procedures are based on dubious legal grounds, and they may have far-reaching implications for obstetrical practice and maternal and infant health.

Attitude of Health Personnel↗
PubMed1987

Thermic effects of tocolytic agents: decreased temperature with magnesium sulfate.

The effect of the tocolytic agents terbutaline and magnesium sulfate on patients' temperatures was examined. Fifty-two women admitted for preterm labor were randomized to a treatment protocol for one of the two agents. Oral temperatures were measured initially and every two hours during treatment. There was no significant difference between the initial temperature and the lowest temperature recorded during treatment in the terbutaline group, but temperature decreased significantly during treatment with magnesium sulfate. This decrease in maternal temperature may have importance in the treatment of preterm labor with magnesium sulfate in patients with an infectious etiology for uterine activity.

Adult↗
PubMed1986

Appendectomy at cesarean section: a prospective study.

Appendectomy was performed on 40 consecutive consenting patients undergoing elective cesarean section in a clinic population. The control group consisted of all other patients undergoing elective cesarean section during the period of study. The populations were similar. Clinical infection, blood loss, gastrointestinal tract recovery rates were equal in both groups. Appendectomy added 15 minutes to the operation time and extended the hospital stay by about one-half day. There were no wound infections or serious morbidity. A fifth of the appendixes removed were abnormal, including two with inflammation and one with a carcinoid tumor. Prophylactic appendectomy does not seem to add to the risk of elective cesarean section.

Anesthesia↗
PubMed1985

Prospective randomized study of x-ray pelvimetry in the primigravida.

A prospective randomized study was performed to determine the usefulness of x-ray pelvimetry before oxytocin induction or augmentation. Two hundred primiparous women were entered into this study. Agreement on pelvic size by the clinical and radiologic assessment occurred in 76.5% of the cases. When the total groups were compared, there were no differences in pregnancy outcome. In the induction of labor subgroups there were less forcep deliveries and lower five-minute Apgar scores in the pelvimetry group. In the augmentation subgroups there were no differences. The subgroup of patients diagnosed clinically to have a borderline pelvis, had a higher incidence of cesarean section (P less than .05) if they had x-ray pelvimetry. These results suggest that the elimination of x-ray pelvimetry in primigravida women does not lead to a compromise in infant outcome when electronic fetal monitoring is used.

Adult↗