Calcium regulation in the myometrium of pregnant sheep.

Fractionation of pregnant sheep myometrium has been carried out and the fractions obtained analysed for their marker enzyme content and Ca2+ transporting properties. A fairly pure mitochondrial fraction and a very pure plasma membrane fraction were obtained. Both fractions could accumulate Ca2+ in the presence of ATP but the mechanisms were different, mitochondrial uptake had a high capacity and was inhibited by azide. Plasma membrane uptake was of low capacity and unaffected by azide. The effect of oxalate on plasma membrane suggests that there is an outwardly directed Ca2+ pump in the myometrial cell membrane. Both mitochondria and plasma membrane may be important in the Cas2+ accumulation of relaxation in this muscle.     

Cardiac and uterine hemodynamic responses to ritodrine hydrochloride administration in pregnant sheep.

The changes in the maternal circulation following administration of ritodrine hydrochloride were investigated in chronically prepared pregnant sheep. Low infusion rates of ritodrine (see text) elevated the maternal heart rate and cardiac output and decreased peripheral vascular resistance. Stroke work fell while minute work increased. The distribution of uterine blood flow did not change, as measured with microspheres. Simultaneously measured fetal cardiac output and umbilical blood flow were not altered. When ritodrine infusion rates (see text) were increased there was a slight but significant decrease in uterine perfusion pressure, and an increase in uterine vascular resistance with uterine blood flow decreasing. These changes were observed when the ewes were not in labor, and similar changes were again recovered with ewes in labor despite the simultaneous inhibition of uterine contractions. Selective beta blockade with practolol during ritodrine administration decreased the maternal tachycardia without affecting cardiac output, peripheral vascular resistance, or uterine vascular resistance.     

Effect of cocaine on intracellular calcium regulation in myometrium from pregnant women.

OBJECTIVE: To evaluate the effect of cocaine on intracellular free calcium ([Ca2+]i) regulation in human myometrial cells by determining the sources of Ca2+ it might mobilize, as well as assess the role cocaine might play in the catecholamine's effect on the cell's [Ca2+]i. METHODS: Primary culture of myometrial cells from pregnant women was used as an experimental model. [Ca2+]i relative changes in response to cocaine and norepinephrine were measured with fura-2 fluorometry and analyzed by means of one-way analysis of variance. RESULTS: Cocaine alone (10(-8) to 10(-3) mol/L) increased [Ca2+]i by up to 43 +/- 18% over basal level in a dose-dependent manner. Norepinephrine also elevated [Ca2+]i in a concentration-dependent manner (202 +/- 24% over basal level at 10(-4) mol/L). The norepinephrine-evoked increase was inhibited in Ca(2+)-free media by 48%, whereas the cocaine response was not affected. The Ca(2+)-channel antagonist nifedipine caused decrease in the [Ca2+]i response to 10(-5) mol/L of norepinephrine by 84%, whereas the [Ca2+]i rise to 10(-5) mol/L cocaine was not significantly changed. Inhibitor of the sarcoplasmic reticulum Ca2+ pump, thapsigargin, completely blocked cocaine-evoked increases in [Ca2+]i, whereas norepinephrine responses were greatly reduced. At the same time, cocaine (10(-8) to 10(-3) mol/L) did not potentiate norepinephrine-evoked Ca2+]i increases in the cells. CONCLUSION: These results indicate that cocaine increases [Ca2+]i in pregnant human myometrial cells, primarily by stimulating release of Ca2+ from intracellular stores rather than by direct stimulation of Ca2+ influx.     

Circulatory shock in pregnant sheep. IV. Fetal and neonatal circulatory responses to hypovolemia--influence of anesthesia.

Hemodynamic responses to hypovolemia were investigated in unanesthetized, unstressed fetal lambs and in acute fetal and neonatal preparations. The unstressed fetus tolerated twice the amount of blood loss of the acutely studied fetus or newborn lamb and with a lesser hypotension. Hemodynamic behavior of the newborn lamb and fetus anesthetized with pentobarbital during hypovolemia was markedly different from that of the fetus studied under spinal anesthesia or chronically. Besides tolerating greater blood loss, the unstressed fetus reversed the state of hypovolemic shock rapidly as contrasted to the stressed fetus which was unable to do so even with total blood reinfusion. All animals exhibited bradycardia in response to hypovolemia. The following conclusions were drawn: (a) cardiovascular response to hypovolemia in the perinatal period depends on the initial status of the animal, (b) the fetus tolerates a greater degree of blood loss than a newborn or adult animal, and (c) anesthesia and stress of surgery modify considerably circulatory behavior during blood loss.     

Lack of effect of maternal cocaine administration on myometrial electromyogram and maternal plasma oxytocin concentrations in pregnant sheep at 124-146 days' gestational age.

Although cocaine abuse during human pregnancy is associated with an increased incidence of preterm labor, there are few reports on the effects of cocaine on myometrial activity during pregnancy in experimental animals. Cocaine (0.5, 1, or 2 mg/kg) or vehicle was randomly administered intravenously to 15 pregnant ewes between 124-146 days' gestation (term is 147 days). Neither cocaine nor vehicle administration altered total myometrial electromyographic activity from pre-dose levels 1 or 6 hours after administration. Maternal arterial plasma oxytocin did not change during the study. Using a positive control, we confirmed observations of other investigators that administration of 2 mg/kg cocaine significantly increases maternal arterial blood pressure. The results indicate that cocaine does not stimulate myometrial contractility significantly in late pregnancy in sheep.     

Impaired glucose tolerance in pregnant women with polycystic ovary syndrome.

OBJECTIVE: To determine whether women with polycystic ovary syndrome (PCOS) are more likely to develop gestational diabetes mellitus compared with age- and weight-matched controls. METHODS: This retrospective cohort study compared reproductive-age women with and without PCOS who received prenatal care at the University of North Carolina Hospitals between April 1989 and June 1998. We reviewed the medical charts of 22 women with PCOS diagnosis before pregnancy based on menstrual histories, elevated androgen levels, and LH-FSH ratios greater than 2. These women were compared with 66 women without PCOS matched for age and weight. Gestational diabetes mellitus (GDM) was diagnosed in women if they had abnormal results on a 50-g glucose screening test and at least two abnormal plasma glucose values during a 100-g glucose tolerance test. Medical complications of pregnancy, pregnancy complications, and birth outcomes were compared between women with and without PCOS. RESULTS: Nine of 22 women with PCOS also had GDM diagnosis, compared with two of 66 controls (odds ratio [OR] 22.2; 95% confidence interval [CI] 3.8, 170.0), and these women exhibited increased plasma glucose values for all measurements except fasting. Five of 22 women with PCOS developed preeclampsia compared with one of 66 controls (OR 15.0; 95% CI 1.9, 121.5). CONCLUSION: Women with PCOS are at increased risk of glucose intolerance and preeclampsia during pregnancy.     

Decreased carbohydrate tolerance in pregnant patients with an early menarche.

Carbohydrate tolerance was studied in pregnant patients with no personal or family history suggestive of diabetes, but with a menarche before 12 years of age. The mean disappearance rate constant for glucose (k) in the intravenous glucose tolerance test was 1.68 in the group of patients with an early menarche. This value is essentially the same as that found in patients with the usual criteria for screening for gestational diabetes, where k equaled 1.61. Both values are significantly different from the remaining patients studied, where k was 1.94. The mean fasting blood sugars and the mean 2 hours past-100 Gm. glucose meal blood sugars in patients with a menarche before 12 years of age and the patients with the usual criteria for screening for gestational diabetes were also the same when compared to each other, and significantly different from those of remaining patients studied. There were no apparent reasons for the early menarche group to have a decreased tolerance to glucose except their early menarche.     

Lipopolysaccharide-induced chorioamnionitis is confined to one amniotic compartment in twin pregnant sheep

Background: Chorioamnionitis is a major risk factor for preterm birth in multifetal pregnancies. However, there is little clinical data whether chorioamnionitis is restricted to one amniotic compartment in multifetal pregnancies. Objective: To explore whether chorioamnionitis is confined to the exposed compartment and does not cross to the unaffected fetus in twin pregnancy. Methods: In twin pregnant sheep, one of the twins was exposed to either 2 or 14 days of intra-amniotic lipopolysaccharide (LPS) while the co-twin was exposed to either 2 or 14 days of intra-amniotic saline (n = 3 for each exposure). Singletons were included in this study to compare the grade of inflammation with twins. All fetuses were delivered at 125 days of gestation (term = 150 days). Chorioamnionitis was confirmed by histological examination. Lung inflammation was assessed by cell count in bronchoalveolar lavage. Lung compliance was assessed at 40 cm H(2)O. Results were compared using analysis of variance (ANOVA) with a post-hoc Tukey analysis. Results: Inflammation in placenta, membranes and lung of LPS-exposed twins was significantly higher after 2 and 14 days of exposure when compared to the saline-exposed co-twins. Lung compliance in LPS-exposed twins was significantly increased after 14 days when compared to saline-exposed co-twins. Intrauterine LPS exposure increased lung compliance and inflammation in the membranes, placenta and lung to the same extent in twins as in singletons. Conclusion: In twin pregnant sheep, inflammation of the membranes, placenta and fetal lung was strictly limited to the exposed fetus in the amniotic compartment in which the LPS was injected.     

Systemic and uterine hemodynamic responses to dopamine in pregnant and nonpregnant sheep

The systemic and uterine hemodynamic effects of dopamine were studied in nonpregnant and near-term pregnant, unanesthetized, chronically instrumented sheep. Dopamine was administered by constant intravenous infusion in doses ranging from 2 to 40 microgram per kilogram per minute. A hypertensive effect was consistently observed when doses greater than 5 microgram per kilogram per minute were given. The rise in pressure was accompanied by a rise in the systemic vascular resistance and an increase in the cardiac output; the increment in the latter was greater in the pregnant than in the nonpregnant animals. Uterine blood flow increased consistently despite some rise in uterine vascular resistance; uterine fraction of cardiac output either remained unchanged or increased slightly. Venomotor construction, reflected by a rise in central venous pressure, occurred at all dose levels. These hemodynamic properties of dopamine may be explained partly on the basis of its combined beta- and alpha-mimetic action, as well as through redistributions of flows and resistances among various regional vascular beds.     

Experimental hypertension in pregnant sheep. III. Central hemodynamic alterations in the one-kidney model

Experimental renal hypertension, with use of the one-kidney, one-clip model, was produced in nine pregnant ewes who were then studied during the last one third of gestation. The animals were chronically instrumented for the recording of arterial pressure, heart rate, and cardiac output; blood volume was determined weekly. The studies were carried out in four phases; a control period of 2 weeks, a surgery period of 1 week, a constriction or hypertensive period, and a postpartum period of 2 weeks. We detected no significant changes in heart rate or cardiac output during any phase of the study. The arterial pressure significantly increased during the constriction and postpartum phases (p less than 0.05). Blood volume remained relatively stable during the three pregnancy phases but significantly decreased in the postpartum phase (p less than 0.05). Systemic vascular resistance followed a pattern similar to that of the arterial pressure.     

Hemodynamic effects of indomethacin in chronically instrumented pregnant sheep

Indomethacin administration has produced decreases in uteroplacental blood flow in several animal studies; therefore, it has been suggested that the maintenance of uterine blood flow is critically dependent on the continued synthesis of vasodilating prostaglandins. However, vasoconstriction following indomethacin administration may be due to mechanisms other than reduced prostaglandin synthesis. We administered indomethacin (2, 5, or 10 mg/kg) intravenously to seven unanesthetized sheep in late pregnancy and determined the time courses of the uteroplacental and systemic hemodynamic responses, comparing these to the concurrent changes in circulating prostaglandins. Indomethacin administration resulted in rapid increases in systemic and uteroplacental vascular resistance (80% to 100%) and mean arterial pressure (∼30%) and in decreases in systemic (∼30%) and uteroplacental (0% to 30%) blood flows within 5 minutes. Vasoconstriction was transient, however, and after 60 minutes there was no evidence of uterine or systemic vasoconstriction, although systemic and uterine plasma prostaglandin levels remained reduced for 180 minutes. Thus substantial inhibition of prostaglandin synthesis existed without evidence of concurrent systemic or uteroplacental vasoconstriction, suggesting that uterine blood flow is not directly dependent on maintained prostaglandin synthesis in unstressed pregnant sheep. Furthermore, the transient indomethacin-induced vasoconstriction may not be due to inhibition of prostaglandin synthesis.     

The alloantibody response in the allogeneically pregnant rat. V. Absence of cell-mediated immunity in high responders

Allogeneically pregnant rats have been examined postpartum to determine whether they are sensitized against paternal class I antigens for cell-mediated immunity. This study was undertaken as this point is ambiguous. Since the response of the female to paternal MHC antigens is genetically controlled it is possible that the inability of some investigations to detect cell-mediated immunity against the paternal strain was due to the use of non-responder strain combinations. Cell-mediated immunity was assayed in a strain combination that is an unambiguous high responder, in which 100% of the females respond to the paternal strain by making alloantibodies. Maternal cell-mediated responses to paternal antigens were measured by the assays of DTH and IL-2 secretion under limiting conditions. We were unable to detect any cell-mediated immunity to paternal class I antigens even though the female produced copious quantities of alloantibody.     

Circulatory responses to hypovolemia in the pregnant and nonpregnant sheep after pharmacologic sympathectomy

Circulatory responses to progressive hypovolemia, hypotensive shock, blood reinfusion, and recovery were studied in pregnant and nonpregnant sheep with an intact or pharmacologically ablated sympathetic nervous system produced by administration of 6-hydroxydopamine. These studies also provided an opportunity to assess the contribution of the sympathetic nervous system to the maintenance of vasomotor tone in the pregnant animal at rest. The results show the following: (1) Although there were some differences in the circulatory adjustments to the initial period of blood loss between intact and "sympathectomized" animals, the overall circulatory responses to progressive hypovolemia, shock, blood reinfusion, and recovery were not significantly different in animals with intact or ablated sympathetic nervous systems whether or not they were pregnant. (2) The reasons for the similarity of cardiovascular responses to hypovolemia are the marked increase in catecholamine outputs by the adrenal medulla, which was not affected by 6-hydroxydopamine, and the supersensitivity of the systemic vascular beds of the sympathectomized animal to catecholamines. (3) The contribution of the sympathetic nervous system to the maintenance of the resting vasomotor tone is considerably enhanced during pregnancy, as demonstrated by the chronic effects of adrenergic ablation on the resting arterial pressure. (4) The circulation of the pregnant uterus possesses the ability of autoregulation during chronic changes of perfusing pressure as demonstrated by the differences in the arterial pressure and uteroplacental vascular resistance between intact and sympathectomized animals.     

Amniocentesis in pregnant HIV-infected patients. Absence of mother-to-child viral transmission in a series of selected patients

Objectives

To assess the risk of vertical transmission in HIV-infected pregnant women undergoing diagnostic amniocentesis, and to identify possible predictive factors.

Study design

This was a single center retrospective study. The records of 330 HIV-infected pregnant women booked in our antenatal clinic from 31 January 2001 to 31 January 2006 were analyzed. Women who actually underwent diagnostic amniocentesis (“amniocentesis performed” group) were compared to those eligible for amniocentesis but who did not undergo the procedure (“amniocentesis withheld” group).

Results

During the time period, 318 liveborn babies were delivered (9 HIV infected (2.8%)). Thirty-four women (35 fetuses) were eligible for diagnostic amniocentesis. Amniocentesis was performed in 11 (32.4%) of these women (12 fetuses, none infected among the 9 liveborns) and withheld in 23 (67.6%) women. Among the 19 liveborn babies in this latter group, 1 (5.3%) was infected. There was no statistical difference in vertical transmission rate between the whole cohort of HIV-infected pregnant women and the group of women eligible for amniocentesis; or between the women who actually had or did not have an amniocentesis.The women who did undergo amniocentesis all received highly active antiretroviral combination therapy with three drugs; all but two had an undetectable HIV viral load, only one had immunosuppression and none had HCV co-infection.

Conclusion

No vertical transmission was observed in a group of nine liveborn babies after amniocentesis performed in selected HIV-infected pregnant women. In the presence of high genetic risk during pregnancy, amniocentesis can be considered after proper patient counselling.     

Nitroprusside-induced hemodynamic alterations in normotensive and hypertensive pregnant sheep

It has been suggested that sodium nitroprusside, a potent vasodilator, be used in the management of an acute hypertensive crisis during pregnancy. The present study was designed to evaluate the hemodynamic effects of this agent in the same group of chronically instrumented, unanesthetized pregnant sheep during two experimental periods: (a) normotension with intact kidneys, and (b) one-kidney hypertension. The results demonstrate that (1) nitroprusside is a potent vasodilator which lowers mean arterial pressure; (2) nitroprusside-induced tachycardia was greater in the hypertensive animal; (3) uterine blood flow decreased with the development of hypertension; (4) the hypertensive-induced reduction in uterine blood flow was increased by the infusion of nitroprusside.     

Circulatory and renal effects of beta-adrenergic-receptor stimulation in pregnant sheep

The effects of beta-adrenergic-receptor stimulation with ritodrine on systemic and pulmonary hemodynamics and on renal handling of water and electrolytes were studied in unanesthetized, chronically instrumented pregnant sheep. Each animal was studied during control, ritodrine, and recovery periods, each lasting 60 minutes, with the use of three different modes of hydration. beta-receptor stimulation produced a significant increase in heart rate and cardiac output and a decrease in systemic vascular resistance. Pulmonary arterial and wedge pressures tended to increase. These circulatory effects were similar for the three types of hydration and they persisted after cessation of infusion. In terms of its renal effects, beta-receptor stimulation elicited a profound decrease in urine flow and in the excretions of sodium and potassium, irrespective of the mode of hydration. The antidiuresis and antinatriuresis were accompanied by no changes in plasma osmolality and sodium concentration, whereas plasma potassium levels decreased. All of these effects persisted for 60 minutes after the cessation of infusion. In the water-loaded experiments, the antidiuresis seemed to be related to increased antidiuretic hormone secretion; in the saline-loaded experiments, however, both the antidiuresis and antinatriuresis appeared to be related to increased renal reabsorption. The changes in renal hemodynamics seemed to have an insignificant role. The amount of fluid retained in the body was greater when ritodrine was infused with saline solution than with dextrose solution. These cardiovascular and renal studies suggest that a circulatory overload may be the major factor in the pathogenesis of pulmonary edema observed during beta-adrenergic-receptor stimulation.