Vitamins C and E: missing links in preventing preterm premature rupture of membranes?

We propose that generation of reactive oxygen species may be a potentially reversible pathophysiologic pathway leading to preterm premature rupture of the membranes. Reactive oxygen species generated by the body's response to diverse insults such as infection, cigarette smoking, bleeding, or cocaine use can activate collagenolytic enzymes and impair fetal membrane integrity. Vitamin E, a lipid-soluble antioxidant, inhibits membrane-damaging effects of reactive oxygen species-induced lipid peroxidation. Vitamin C, a water-soluble antioxidant in plasma, stimulates and protects collagen synthesis while recycling vitamin E. Prior evidence shows that (1) damage by reactive oxygen species can impair fetal membrane integrity, (2) reduced midgestation levels of vitamin C are associated with preterm premature rupture of membranes, and (3) these vitamins can be safely and effectively absorbed and delivered to gestational tissues. Current prenatal vitamin preparations contain vitamins C and E in concentrations that are less than 1/3 and 1/10, respectively; these levels have been suggested for effective antioxidant protection. We hypothesize that increased dietary consumption or supplementation of vitamins C and E during pregnancy may reduce physiologically the risks of that portion of preterm premature rupture of membranes that is mediated by excessive or undamped peroxidation of fetal membranes. This hypothesis, if confirmed, should stimulate initiation of therapeutic trials to test the efficacy of enhanced supplementation with vitamins C and E during pregnancy to prevent preterm premature rupture of membranes.

Stability of methylecgonidine and ecgonidine in sheep plasma in vitro.

BACKGROUND: Crack smokers are exposed to a pyrolysis product, methylecgonidine (MEG), which can be used as an analytical marker for crack smoking. Ecgonidine (EC), a hydrolytic product of MEG, has been identified in urine of crack smokers. MEG undergoes conversion to EC, complicating analysis and perhaps explaining a lack of forensic blood specimens containing MEG. METHODS: We developed gas chromatography-mass spectrometry (GC-MS) assays for MEG and EC. Plasma was collected from sheep blood containing 0, 0.06, or 0.24 mol/L (0%, 0.25%, or 1%) NaF. MEG was added to these plasmas, and they were incubated at -80, 1, 21, or 37 degrees C to determine whether there were temporal, temperature, or storage effects on MEG stability over 48 h. RESULTS: Decreased temperature and increased NaF concentrations limited MEG degradation and EC formation. MEG stored in plasma at -80 degrees C was stable up to 1 month, even in the absence of NaF. CONCLUSIONS: MEG is stable in sheep plasma collected in commercially available, evacuated blood-collection tubes containing NaF and stored at -80 degrees C. In vitro formation of EC can be minimized with appropriate sample handling, and its in vivo formation may provide a better marker of crack smoking than its parent pyrolysis product.

Pretreatment of human amnion-chorion with vitamins C and E prevents hypochlorous acid-induced damage.

OBJECTIVE: Preterm premature rupture of fetal membranes has been associated with infection, cigarette smoking, and bleeding. Hypochlorous acid (a reactive oxygen species) is central to the body's response to infection, yet it may damage surrounding tissue while destroying pathogens. We examined in vitro the tissue-damaging actions of hypochlorous acid on the amnion-chorion and the protective role provided by pretreatment with vitamins C and E. STUDY DESIGN: Amnion-chorion samples were obtained from 4 term pregnancies, cut into segments, and divided into 6 exposure groups. Half were treated in advance with vitamins C and E (Trolox C) and half were treated with buffer solution alone. After rinsing, amnion-chorion samples were exposed to hypochlorous acid at 1 or 10 mmol/L for 4 hours. Histologic and immunocytochemical evaluations were conducted with antibodies for collagen I and IV. RESULTS: Extensive damage to amniotic epithelium and collagen I but not collagen IV resulted from hypochlorous acid exposure and was dose related. Pretreatment with vitamins C and E prevented this damage in all cases. CONCLUSION: Hypochlorous acid damages the amniotic epithelium and collagen I in the amnion-chorion. The protection against hypochlorous acid-induced damage provided by antioxidant therapy (vitamins C and E) is of therapeutic significance.

Effects of zidovudine (AZT) and dideoxyinosine (ddI) on human trophoblast cells.

The anti-HIV agents AZT (zidovudine) and ddl (dideoxyinosine) are being used clinically during pregnancy. The toxicity of these agents to the fetus and placenta remains a concern because few human pregnancy exposure data are available, and pregnant rodent studies with AZT indicate increased embryonic resorptions and developmental arrest. The current study used a human choriocarcinoma cell line (JAr), which exhibits many characteristics of the early placenta, to assess the effects of a single 24 h exposure of 7.6 or 0.076 mM AZT, and the effects of a single 24 h exposure of 7.6 or 0.076 mM ddI upon cell proliferation and hormone production of human chorionic gonadotropin (hCG), estradiol (E2), and progesterone (P4). The higher concentration of AZT and ddI produced significant (P < 0.025) reductions in cell numbers and growth rate while producing significant increases in hormone production (hCG, E2, and P4). The lower concentration of AZT and ddI produced significant increases in E2 production, but no changes in cell numbers, hCG, or P4. Because placental cells require androgen precursor for E2 synthesis, exogenous androstenedione was added to confirm observations of increased estradiol synthesis after AZT or ddl exposure. These results demonstrate that single 24 h high dose exposures of AZT or ddI produce significant inhibition of cell proliferation and alterations in hormone production in this paradigm of human placental cells.

Cocaine in pregnancy. Recent data on maternal and fetal risks.

Cocaine continues to be abused during pregnancy, creating increased demands on the health care system. Epidemiology and basic science research have identified and confirmed risks of adverse maternal and fetal effects when cocaine is used during pregnancy. These effects of cocaine in pregnant women often are influenced by a number of confounding variables. This article reviews those cocaine effects as well as recent data, which examine in greater detail the risks of adverse outcomes of prenatal cocaine exposure during pregnancy.

Prenatal exposure to amphetamines. Risks and adverse outcomes in pregnancy.

Based on findings in humans and the confirmation of prenatal exposures in animals, amphetamines and methamphetamines increase the risk of an adverse outcome when abused during pregnancy. Clefting, cardiac anomalies, and fetal growth reduction deficits that have been seen in infants exposed to amphetamines during pregnancy have all been reproduced in animal studies involving prenatal exposures to amphetamines. The differential effects of amphetamines between genetic strains of mice and between species demonstrate that pharmacokinetics and the genetic disposition of the mother and developing embryo can have an enormous influence on enhancing or reducing these potential risks. The effects of prenatal exposure to amphetamines in producing altered behavior in humans appear less compelling when one considers other confounding variables of human environment, genetics, and polydrug abuse. In view of the animal data concerning altered behavior and learning tasks in comparison with learning deficits observed in humans, the influence of the confounding variables in humans may serve to increase the sensitivity of the developing embryo/fetus to prenatal exposure to amphetamines. These factors and others may predispose the developing conceptus to the damaging effects of amphetamines by actually lowering the threshold of susceptibility at the sites where damage occurs. Knowledge of the effects of prenatal exposure of the fetus and the mother to designer amphetamines is lacking. Based on the few studies in which designer drugs have been examined in animal models, more questions are raised than answered. Possible reasons why no malformations or significant fetal effects were found in the study by St. Omer include the genetic strain of rat used, the conservative exposure profile, or the fact that the placenta metabolized MDMA before reaching the embryo. These questions underscore the need for further investigations concerning the prenatal exposure effects of designer compounds and the effects of amphetamine and methamphetamine in general.

An introduction to reactive oxygen species and their possible roles in substance abuse.

There is a growing body of information relating diverse diseases and the consequences of injury to generation and toxicity of reactive oxygen species (ROS). Recently, it has been shown that the fetus and its membranes are also vulnerable to this toxicity, suggesting that a number of obstetric diseases may result from exposure to ROS, which are ubiquitous in aerobic organisms. Endogenous antioxidants, including superoxide dismutase, catalase, and glutathione peroxidase are essential for defense against ROS. It is significant that all antioxidants appear to be down-regulated in the fetus and membranes, suggesting the possibility that any process that further depresses their activities or increases the burden of ROS may compromise fetal development or maternal health. When permitted to accumulate, ROS can damage all classes of macromolecules, including lipids, proteins, and nucleic acids. Toxicity includes mutation, protein degradation, and lipid peroxidation, which can severely disturb membrane permeability and alter intracellular calcium and pH. An understanding of the generation and toxicity of ROS should help to define their potential roles in obstetric disease and lead to innovative preventive and therapeutic approaches.

Human placenta does not Reduce AZT (zidovudine) to 3'-amino-3'-deoxythymidine.

Human placental tissue and human trophoblast cells (JAr) were examined after exposure to the anti-HIV nucleoside analog AZT (Zidovudine) for the presence of 3'-amino-3'-deoxythymidine (AMT), a toxic catabolite. Placental cells were exposed to 7.6 mM AZT for 48 hr, and placental lobular tissue was perfused with 3.8 mM AZT for 14 hr. Cell homogenates were prepared, and supernatants were subjected to HPLC analysis. Despite large cellular concentrations of AZT, AMT was not detected in any of the samples analyzed. Exposure of JAr cells to this concentration of AZT produces a 72% inhibition of cell proliferation when compared with unexposed controls. Based upon the results of the current study, AMT was not formed by placental cells exposed to AZT and, thus, not a mechanism for toxicity after in vitro exposure to AZT.

Pharmacokinetic and toxicity studies of AZT (zidovudine) following perfusion of human term placenta for 14 hours.

Multiple exposures to AZT (Zidovudine) for 14 hr were examined in the dually perfused human term placental lobule in order to determine the pharmacokinetics of transfer, as well as several viability parameters of toxicity. In each experiment, three separate additions of AZT at a concentration of 3.8 mM was added to the maternal reservoir, and perfusate samples were obtained from both the maternal and the fetal compartments for determinations of AZT, glucose, lactate, oxygen, and human chorionic gonadotropin (hCG) concentrations. During 14 hr of continuous exposure to this high concentration of AZT, the production of hCG was significantly reduced by 75% when compared to the 2-hr control period before the administration of AZT. In addition, lactate production was reduced by 45% after AZT administration. Such changes in hCG and lactate production were not observed in separate experiments conducted over the same time interval, but with no AZT added. Based upon a lack of total perfusion fluid loss, changes in fetal arterial pressure, and histopathology, placental lobule integrity was maintained throughout the perfusion period. Further, AZT readily crossed the placenta into the fetal compartment reaching equilibrium with maternal levels within 60-90 min after addition of each administration of AZT. Based upon AZT levels in the fetal perfusate, AZT does not accumulate against a concentration gradient and therefore appears to be diffusion limited. Placental tissues obtained from perfused, partially perfused, and nonperfused regions at the conclusion of the experiment were analyzed for AZT levels. Substantial AZT levels in the nonperfused tissues indicated that AZT is a freely diffusible compound. The results of the current study demonstrate that high concentrations of AZT alter placental function resulting in reduced production of hCG and lactate.

Fetal scapular length in the ultrasonographic assessment of gestational age.

A prospective cross-sectional study of 515 singleton fetuses of ages between 15 and 42 weeks' gestation was performed. At gestational ages greater than 26 weeks, only fetuses with a sonographic estimated fetal weight between the 10th and 90th percentiles for growth were included. Scapular length (cm) as a function of gestational age (weeks) was expressed by the regression equation: SL = 0.3289 + 0.9553 (GA) with a Pearson correlation coefficient of R2 = 0.942. This study defines the normal limits of scapular length, demonstrates a high correlation between scapular length, gestational age, and other standard measurements of fetal growth, and indicates that scapular length can predict gestational age in fetuses with normal growth.

Pregnancy enhances cocaine's actions on the heart and within the peripheral circulation.

OBJECTIVE: Our purpose was to determine whether cocaine's enhanced cardiovascular actions in pregnancy are cardiac alone or involve the peripheral vascular system. STUDY DESIGN: Six pregnant and five nonpregnant ewes chronically instrumented for heart rate, blood pressure, cardiac output, and systemic vascular resistance were given cocaine at 1.0 and 2.0 mg/kg and monitored for 60 minutes. Blood samples for cocaine levels were taken at 5, 15, 30, and 60 minutes. RESULTS: Cocaine initially (first 60 seconds) produced increased heart rate, decreased cardiac output, decreased stroke volume, and increased cardiac oxygen consumption, which were greater in pregnant than nonpregnant ewes. After 1 minute recovery of cardiac responses was accompanied by increased systemic vascular resistance, which was greater at each dose in pregnant than nonpregnant ewes. Cocaine levels at 5 minutes for pregnant ewes were eightfold to tenfold higher than for nonpregnant ewes. CONCLUSION: Cocaine produces cardiovascular alterations that are dose and time related but, in each case, enhanced in pregnant ewes. Cocaine metabolism may contribute to this pregnancy-related phenomenon.

Maternal, placental, and fetal pathophysiology of cocaine exposure during pregnancy.

As should be evident from the case reports, epidemiology studies, and animal data, the primary mode of cocaine action is vasoconstriction, whether it occurs on the maternal side or the fetal side of the placenta. Attempts to characterize the fetal effects of cocaine exposure during pregnancy in order to formulate a "fetal cocaine syndrome" has revealed a wide spectrum of fetal effects. Therefore, a well-defined "fetal cocaine syndrome" does not exist. In fact, most fetal defects may be related to vasoconstriction, hypertension, and infarcts at any time during gestation and in any structure. Even the issues of SIDS and seizures may be the result of clinically undetectable vasospasm or hemorrhages. Traditional dogma dictates that a teratogen interferes with normal development of a structure such that the structure is missing, malformed, or dysfunctional. Moreover, since individual structures are formed at specific times during development, these structures are vulnerable to injury at these "time windows." Classical teratogens exert their damaging effects during the organogenesis period. For cocaine, however, exposure during any period in gestation may place any organ or structure at potential risk for damage. While repeated exposures during pregnancy may increase the risk of cocaine-induced damage, it appears that even a single exposure may produce infarction, edema, and tissue necrosis. The site of damage may be related to the tissue level of cocaine and the weakness of the blood vessels at that site. Subsequent loss of vascular supply and tissue necrosis produce fetal damage that is beyond capacity for repair.

Progesterone antagonist mifepristone (RU 486) decreases cardiotoxicity of cocaine.

RU 486, a potent progesterone antagonist, was used to determine whether RU 486 blocks the enhanced cardiotoxicity of cocaine mediated by progesterone upon rat papillary muscles. Groups of nonpregnant rats were pretreated with: progesterone for 3 days (n = 12); progesterone + RU 486 for 3 days (n = 12); progesterone for 3 days + single low dose RU 486, progesterone for 3 days + single high dose RU 486, and RU 486 for 3 days (n = 6); or were untreated (n = 12). Papillary muscles from these groups were electrically paced during exposure to cocaine concentrations ranging from 10(-14) M to 10(-3) M. One group (n = 6) was pretreated with RU 486, but not exposed to cocaine. The results showed that all muscles from rats pretreated with RU 486 for 3 days were functional when exposed to cocaine concentrations one to four orders of magnitude higher than tolerated by muscles from untreated or progesterone-treated rats. As indicated by alterations in contraction response patterns, RU 486 treatment for 3 days reversed progesterone-enhanced cardiotoxicity of cocaine. Single low dose and high dose RU 486 administrations also reversed progesterone's effects upon cocaine-induced cardiotoxicity.

Fetal sacral length in the ultrasonographic assessment of gestational age.

OBJECTIVE: Our purpose was to establish a nomogram of fetal sacral length throughout gestation and to assess its value in cases of abnormal fetal growth. STUDY DESIGN: A prospective cross-sectional study of 506 singleton fetuses with normal growth between 15 and 41 weeks' gestation was performed. Regression analyses were performed on sacral length, gestational age, biparietal diameter, head circumference, and femur length. The sacral length in 80 singleton gestations with abnormal growth (40 > 90th percentile and 40 < 10th percentile for gestational age) were compared with the nomogram. RESULTS: Linear relationships between gestational age and sacral length, biparietal diameter, head circumference, and femur length were demonstrated. Sacral length (centimeters) as a function of gestational age (weeks) was expressed by the regression equation: Sacral length = -0.108 + 0.102 Gestational age, with a Pearson correlation coefficient of R2 = 0.959. The sacral length of all 80 fetuses with abnormal growth demonstrated the same relationship to gestational age as did the 506 normal controls. CONCLUSION: This study defines the normal limits of sacral length; demonstrates a high correlation between sacral length, gestational age, and other standard measurements of fetal growth; and indicates that sacral length can predict gestational age, irrespective of fetal nutritional status.

Pregnancy enhances cardiotoxicity of cocaine: role of progesterone.

Contraction dynamics of isolated papillary heart muscles from nonpregnant, pregnant, and progesterone-treated nonpregnant Long Evans rats were studied during exposure to cocaine. With increasing cocaine concentrations from 10(-16) to 10(-4) M, papillary muscles from nonpregnant rats demonstrated a biphasic pattern of positive, then negative, inotropy. Only negative inotropy with increasing cocaine concentrations was observed in papillary muscles from pregnant and progesterone-treated nonpregnant rats. Papillary muscles from pregnant and progesterone-treated nonpregnant rats became nonfunctional at cocaine concentrations 1-4 orders of magnitude lower than those for nonpregnant rats. These findings demonstrate that pregnancy and progesterone treatment alter cocaine effects upon cardiac papillary muscle function and response patterns and shift the cocaine dose-function curve to the left when compared to the nonpregnant group. We conclude that pregnancy increases the direct cardiotoxicity to cocaine, and progesterone may be responsible for this enhanced cocaine toxicity.

Progesterone increases cardiovascular toxicity to cocaine in nonpregnant ewes.

Cocaine produces a greater hypertensive response in pregnant ewes than in nonpregnant ewes. To determine whether pregnancy-related progesterone levels augmented this cocaine response, six nonpregnant ewes were surgically oophorectomized, implanted with femoral artery and vein catheters, and later administered progesterone 10 mg/kg intramuscularly for 3 days. Consistent responses in blood pressure and heart rate to intravenous norepinephrine 0.4 and 0.6 microgram/kg, before and during progesterone treatment, indicated that progesterone did not increase alpha-adrenergic receptor sensitivity to exogenous norepinephrine. In contrast, intravenous cocaine at either 1.0 or 2.0 mg/kg produced approximately twofold greater increases in blood pressure and threefold greater increases in heart rate during each day of progesterone treatment when compared with responses to the same dose of cocaine before progesterone treatment. These results indicate that progesterone enhances the cardiovascular response to cocaine and does not involve an increase in alpha-adrenergic receptor sensitivity.

Effect of alpha 1 receptor blockade upon maternal and fetal cardiovascular responses to cocaine.

Previous studies in pregnant ewes have demonstrated that intravenous (IV) cocaine produces increased maternal blood pressure and vasoconstriction of the uterine arteries, resulting in decreased uterine blood flow and decreased fetal oxygen levels. To determine whether these responses to cocaine were mediated by alpha 1-adrenergic receptor stimulation, cocaine was administered to four pregnant ewes before and after phenoxybenzamine hydrochloride, an alpha 1 receptor antagonist. Before phenoxybenzamine infusion, cocaine 2.0 mg/kg produced a 53% increase in maternal mean arterial pressure (MAP), a 50% reduction in total uterine blood flow, and a 191% increase in uterine vascular resistance. Cocaine also increased fetal MAP by 24%, increased the fetal heart rate (FHR) by 51%, and reduced fetal PO2 by 29%. Alpha 1 receptor blockade after phenoxybenzamine 5.0 mg/kg was confirmed by a lack of change in uterine blood flow to IV norepinephrine 30 micrograms before cocaine administration. After phenoxybenzamine, cocaine produced no increase in maternal or fetal MAP. However, total uterine blood flow decreased 44%, uterine vascular resistance increased 59%, FHR increased 36%, and fetal PO2 fell 18%. Because the fetal responses mimicked the maternal responses to cocaine both before and after phenoxybenzamine, phenoxybenzamine apparently crossed the placenta to block fetal alpha 1 receptors as well. Alpha 1-adrenergic receptor stimulation is the major mechanism for the maternal and fetal hypertensive responses to cocaine. Although cocaine produces uterine artery vasoconstriction primarily by alpha 1 adrenergic receptor stimulation, its vasoconstrictive effects may involve other vasoactive neurotransmitters, such as dopamine or serotonin.

Pregnancy increases cardiovascular toxicity to cocaine.

The effects of intravenous cocaine on heart rate and blood pressure were studied in pregnant and oophorectomized nonpregnant ewes. In response to intravenous cocaine doses of 1.0 and 2.0 mg/kg, both pregnant and nonpregnant ewes demonstrated dose-dependent increases in systolic, diastolic, mean arterial, and pulse pressures with return to baseline by 30 to 60 minutes after cocaine administration. However, at both doses (1.0 and 2.0 mg/kg) pregnant ewes demonstrated greater increases in mean arterial pressure (+29.6%, +48.7%) than nonpregnant ewes (+15.6%, +27.7%) during the first 5 minutes after cocaine administration. Thereafter the responses were similar. Thus pregnancy increases the cardiovascular toxicity to cocaine.