Biomedical subjects

M Hallak

Publications and source records attributed to M Hallak.

At least 55 records · Page 3Linked to original sources

PubMed1998

Effect of parenteral magnesium sulfate administration on excitatory amino acid receptors in the rat brain.

The literature regarding magnesium sulfate central nervous system inhibitory effect will be reviewed. We suggest that its mechanism of action be through the excitatory amino acid receptors. We have demonstrated that magnesium sulfate enters the cerebrospinal fluid and brain after systemic administration. The significant rise in brain magnesium concentration is associated with an elevation of the seizure threshold and a marked resistance of the animal to electrically as well as NMDA stimulated hippocampal seizures. Using autoradiography we have studied the effect of magnesium sulfate on the NMDA receptor-channel complex, as well as on the AMPA and Kainate receptors. The results provide further information on the mechanism by which magnesium' central anticonvulsant activity is mediated in the rat model.

2-Amino-5-phosphonovalerate↗

PubMed1997

Activated protein C resistance (factor V Leiden) associated with thrombosis in pregnancy.

OBJECTIVE: Our purpose was to evaluate activated protein C resistance phenotype and genotype among patients with thrombosis during pregnancy and the puerperium. STUDY DESIGN: This observational study was conducted prospectively during a 2-year period (July 1993 to June 1995) in a preselected population. All patients admitted to our high-risk pregnancy unit with a diagnosis of deep vein thrombosis, pulmonary emboli, transient ischemic attack, and cerebrovascular accident during pregnancy and the puerperium were included. Prothrombin time, partial thromboplastin time, fibrinogen levels, protein C, protein S, antithrombin III, functional test for activated protein C resistance, and factor V Leiden mutation by polymerase chain reaction were performed on each patient. RESULTS: Fifteen patients were included. Seven (46.6%) patients were positive for activated protein C resistance (factor V Leiden). All other coagulation studies were negative for all patients. All patients with activated protein C resistance had a venous thrombotic event, deep vein thrombosis, or pulmonary emboli, and only one had a cerebrovascular accident on the basis of sagittal sinus thrombosis. Only two of the activated protein C resistance-negative patients had venous thrombosis (pulmonary emboli). The remaining six patients had transient ischemic attacks or cerebrovascular accidents. For the subgroup with venous thrombosis during pregnancy and the puerperium, the incidence of activated protein C resistance (factor V Leiden) was 78%. CONCLUSION: This study demonstrates the incidence of factor V Leiden in a selected population in whom thrombotic events developed during pregnancy and the puerperium. This small-scale study provides justification for a large cohort study that will identify women with factor V Leiden and determine their risk for thrombosis during pregnancy and the puerperium. We believe that factor V Leiden should be evaluated in conjunction with thrombotic events in the pregnant woman.

Adult↗

PubMed1997

Ripening and dilatation of the unfavourable cervix for induction of labour by a double balloon device: experience with 250 cases.

OBJECTIVE: To determine the efficacy of the double balloon device (the Atad Ripener Device) in ripening and dilatation of the unfavourable cervix for induction of labour. METHODS: Two hundred and fifty women with unfavourable cervices (Bishop score < or = 4) underwent induction of labour with the Atad Ripener Device. Indications were pregnancy induced hypertension (n = 118), post-dates (n = 69), elective inductions (n = 23), other reasons including nonreassuring nonstress test, intrauterine growth retardation, previous caesarean section and diabetes mellitus (n = 40). The Atad Ripener Device was inserted into the cervix, the uterine balloon inflated in the internal os, and the cervico-vaginal balloon in the external os of the cervix (100 mL of normal saline to each balloon). Pressure produced by the inflated balloons caused gradual dilatation and effacement of the cervix. The Atad Ripener Device was removed 12 h after insertion, the cervix assessed again, and labour managed according to obstetrical criteria. RESULTS: The Atad Ripener Device caused an increase in the Bishop score in all subgroups with a mean change of 4.6 (from 2.0 prior to induction to 6.6 upon removal of the Atad Ripener Device; P < 0.05). The mean time interval from insertion of the Atad Ripener Device to delivery was 18.9 h, and from removal to delivery was 6.9 h. Caesarean section was performed in 39/250 patients (16%), and the others had a normal vaginal delivery. CONCLUSIONS: 1. The double balloon device induces significant ripening and dilatation of the unfavourable cervix. 2. Induction of labour was successfully achieved following removal of the Atad Ripener Device. 3. Our caesarean section rate was low compared with rates reported for women with an unfavourable cervix induced by other methods.

Adult↗

PubMed1997

Supplementing iron intravenously in pregnancy. A way to avoid blood transfusions.

OBJECTIVE: To determine the safety and efficacy of maternal intravenous iron administration to avoid blood transfusion in patients who cannot use oral preparations. METHODS: Patients with persistent iron-deficiency anemia who had one of the following indications were included in this study: severe side effects from oral preparations, lack of improvement despite oral iron intake or history of gastrointestinal operations. The total iron amount needed to regenerate iron stores was calculated according to hemoglobin and the patients' weight. Hemoglobin, hematocrit, mean corpuscular volume, serum iron, transferrin and ferritin were evaluated at the start and conclusion of therapy as well as two weeks afterward. RESULTS: Twenty-six patients were included in the study; four of them delivered during the therapy course. One patient developed mild signs of allergy (urticaria) after the test dose and was excluded from the study. The remaining 21 pregnant patients (mean gestational age 28 weeks) completed the therapy course and received a mean of 1,000 mg of elemental iron. The hemoglobin was increased from 8.4 +/- 1.0 to 10.1 +/- 0.6 g/dL at the start and end of therapy, respectively (P < .01) and continued to rise to 10.9 +/- 0.6 g/dL two weeks later (P < .01). The serum iron was increased from 3.9 +/- 2.0 mumol/L at the start of therapy to 15.5 +/- 7.2 at the end (P < .01). The transferrin was decreased from 47.0 +/- 7.8 to 41.4 +/- 5.3 to 37.1 +/- 11.8 mumol/L at the start of, end of and two weeks after therapy, respectively (P < .01). Ferritin levels were increased from 2.9 +/- 2.7 ng/mL at the start to 122.8 +/- 87.1 at the end of therapy (P < .01) and decreased to 109.4 +/- 90.7 ng/mL two weeks after treatment (not significant). Only mild and transient side effects were occasionally reported. CONCLUSION: Intravenous iron administration during pregnancy is an effective method of regenerating hemoglobin and iron stores. It should be considered for patients with severe iron-deficiency anemia who cannot use oral preparations.

Adult↗

PubMed1997

Determining blood pressure in pregnancy. Positional hydrostatic effects.

OBJECTIVE: To evaluate positional hydrostatic effects on blood pressure determination during pregnancy. STUDY DESIGN: We studied 30 normotensive, pregnant women at 34-41 weeks of gestation. Blood pressures were taken in the sitting, left lateral, right lateral and supine positions with a two-minute stabilization period between positions. The bisacromial diameter was measured. Multivariate analysis of variance for repeated measures was used to evaluate the affect of position on blood pressure. RESULTS: Mean systolic pressure in the right arm was 2.6 mm Hg greater than that in the left arm (P < .05). There was no difference between the arms in diastolic blood pressure. Immediate blood pressure in the lower arm was no greater than in the higher arm in lateral positions, and there were no other significant positional effects. Observed blood pressures were significantly different than those theoretically expected on the basis of hydrostatic effects (P < .0001). CONCLUSION: Positional effects on blood pressure in the lateral positions do not appear immediately (within two minutes), indicating that hydrostatic pressure does not account for these changes. The well-documented blood pressure reduction from longer duration in the lateral position does not appear to be an artifact of hydrostatic effect. Repositioning pregnant women in the supine position to have the cuff at the level of the heart is unnecessary and often undesirable when fetal perfusion is an important consideration. We suggest that American Heart Association blood pressure guidelines stating that all measurements be taken with the cuff at the level of the heart to avoid hydrostatic pressure change be revised for pregnancy.

Adult↗

PubMed1997

Second-trimester membrane rupture. Abortion induced with prostaglandin E2 after oxytocin failure.

OBJECTIVE: To test an effective method of terminating second-trimester pregnancy with ruptured membranes in women who fail to abort from an oxytocin infusion. STUDY DESIGN: Five patients with rupture of membranes during the second trimester of pregnancy and failed to abort using the traditional method of intravenous oxytocin infusion were treated with intrauterine instillation of prostaglandin E2 (PGE2) solution through a double-balloon device. RESULTS: All five patients aborted within 8.8 +/- 4.5 hours from the beginning of PGE2 instillation. No major complications occurred. The only side effect was short-duration pyrexia (less than 48 hours). CONCLUSION: Use of the double-balloon device and intrauterine instillation of PGE2 was effective for termination of pregnancy in patients with rupture of membranes who do not respond to oxytocin.

Abortifacient Agents↗

PubMed1996

A randomized comparison of prostaglandin E2, oxytocin, and the double-balloon device in inducing labor.

OBJECTIVE: To compare the efficacy of three methods for ripening and dilating the unfavorable cervix for induction of labor. METHODS: Pregnant women having an indication for induction of labor with a singleton vertex fetus, intact membranes, and Bishop score of no more than 4 were randomized to one of three induction methods: intravaginal prostaglandin (PG) E2 tablets (3 mg) followed by a second dose if labor did not start; continuous intravenous oxytocin drip; or the Atad Ripener Device, with inflation of both balloons and removal after 12 hours. For all patients, the cervix was assessed by the same investigator before induction and 12 hours later. RESULTS: Thirty subjects were included in the PGE2 group, 30 in the oxytocin group, and 35 in the Atad Ripener Device group. The postpartum course was comparable in all. The change in Bishop score in the PGE2 and Atad Ripener Device groups was significantly better than in the oxytocin group (median and range of 5[0-9] and 5[0-7], respectively, versus 2.5 [0-9]; P < .01). Cervical dilation more than 3 cm was more frequent in the Atad Ripener Device group compared with both the PGE2 and oxytocin groups (85.7 versus 50 and 23.3%, respectively; P < .01). The trial of induction failed in only two patients (5.7%) in the Atad Ripener Device group, compared with six (20%) in the PGE2 and 16 (53.3%) in the oxytocin groups (P < .001). Mean (+/- standard deviation) induction-to-delivery interval was 21.3 +/- 7.0 hours in the Atad Ripener Device group, 23.2 +/- 12.5 hours in the PGE2 group, and 28.2 +/- 14.7 hours in the oxytocin group. The success rate for vaginal delivery was significantly better in the Atad Ripener Device and PGE2 groups compared with the oxytocin group (77.1 and 70%, respectively, versus 26.7%; P < .01). CONCLUSION: The Atad Ripener Device had a significantly better success rate for cervical dilation and a lower failure rate than those for PGE2 and oxytocin. The PGE2 and Atad Ripener Device groups had better results than the oxytocin group in regard to Bishop score change and induction-to-delivery interval. The Atad Ripener Device may be a superior method for cervical ripening and labor induction in patients with unfavorable cervices.

Adult↗

PubMed1996

Effect of magnesium sulfate on excitatory amino acid receptors in the rat brain. II. Kainate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors.

OBJECTIVE: Our purpose was to determine the effect of peripherally administered magnesium sulfate on kainate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors in the rat brain. STUDY DESIGN: Six rats were injected intraperitoneally with 270 mg/kg magnesium sulfate, followed by 27 mg/kg every 20 minutes for 4 hours. Controls (n = 6) received saline solution. Six rats received intraperitoneal injections of magnesium sulfate (270 mg/kg) every 4 hours for 24 hours and six received saline solution. Then 6 rats received intraperitoneal magnesium sulfate (270 mg/kg) every 12 hours for 2 weeks and six received saline solution. Rats were subsequently perfused and killed; their brains were dissected and frozen. Cryostat sections were labeled in vitro for autoradiography assay. The ligands used were tritiated kainate agonist, kainate binding site; tritiated alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid agonist, and tritiated 6-cyano-7-nitroquinoxaline-2,3-dione antagonist, both at the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid binding site. RESULTS: Magnesium sulfate caused decreased binding of the agonist to the kainate receptor recognition site after both short-term and intermediate-term systemic administration, whereas long-term treatment resulted in increased binding. No significant consistent effect on the binding to the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor agonist site was recorded after magnesium administration. The receptor antagonist showed an increased binding after short-term treatment. Long-term administration also resulted in increased binding of the antagonist, an effect that was limited to the hippocampus. CONCLUSIONS: These data suggest down-regulation of the kainate receptor population during short- and intermediate-term magnesium sulfate treatment. However, long-term inhibition by magnesium resulted in up-regulation of the receptor population. The results may also reflect an increased inhibitory effect of magnesium sulfate on the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1996

Effect of magnesium sulfate on excitatory amino acid receptors in the rat brain. I. N-methyl-D-aspartate receptor channel complex.

OBJECTIVE: Our purpose was to determine the effect of peripherally administered magnesium sulfate on the N-methyl-D-aspartate receptor channel complex in the rat central nervous system. STUDY DESIGN: Six rats were injected intraperitoneally with 270 mg/kg magnesium sulfate, followed by 27 mg/kg every 20 minutes for 4 hours. Controls (n = 6) received saline solution. Six rats received intraperitoneal injections of magnesium sulfate (270 mg/kg) every 4 hours for 24 hours and 6 received saline solution. Six rats received intraperitoneal magnesium sulfate (270 mg/kg) every 12 hours for 2 weeks and 6 received saline solution. Rats were subsequently perfused and killed and their brains dissected and frozen. Cryostate sections were taken, labeled in vitro by one of three ligands for autoradiography assay, and mounted on tritium-sensitive film for 4 weeks. The ligands were tritiated glutamate agonist, N-methyl-D-aspartate binding site; tritiated glycine agonist, glycine binding site; and tritiated MK-801 noncompetitive antagonist, channel site. Optical density measurements of binding of 11 brain regions on each section were performed with an image analyzing system. RESULTS: N-methyl-D-aspartate receptor binding in the hippocampus was higher than in all other brain regions in all three experiments. Systemic administration of magnesium sulfate for 24 hours resulted in reduced tritiated glutamate binding, whereas long-term administration (2 weeks) resulted in significantly decreased tritiated glycine binding in all brain regions sampled. Binding of tritiated MK-801 was significantly increased in both short- and intermediate-term administration of magnesium sulfate. CONCLUSIONS: These data suggest that short-term magnesium sulfate administration results in increased inhibition of the ion channel. This effect is also continued with prolonged treatment, along with decreased sensitivity of the N-methyl-D-aspartate receptor channel complex to its agonists glutamate and glycine. This proposed time-dependent, twofold effect may provide insight into the mechanisms of magnesium sulfate's central anticonvulsant effect.

Animals↗

PubMed1996

Hyperemesis gravidarum. Effects on fetal outcome.

OBJECTIVE: To study perinatal outcomes in pregnancies complicated by hyperemesis gravidarum (HG) as compared to controls. STUDY DESIGN: Between 1984 and 1991, 138 patients were diagnosed with HG according to Fairweather's criteria. Subjects were stratified into groups of mild and severe HG according to the presence of at least one of the following criteria: ketonuria, increased blood urea nitrogen and hematocrit, and/or abnormal electrolytes. All patients without HG on whom records were available and who delivered during the study period were included as controls. Multiple gestations and stillbirths were excluded from the analysis. Student's t test and X2 were used for statistical analysis. RESULTS: Demographic data were not significantly different between the groups. Forty patients were diagnosed as having mild HG and 98 patients as having severe; 12,335 patients were defined as controls. Mean fetal birth weights were 3,110, 3,093, and 3,160 g in the mild, severe and control groups, respectively. The incidence of congenital anomalies was 2.5%, 2.0% and 1.6%, respectively. The incidence of prematurity was 17.5%, 11.2% and 10.7% in mild and severe HG and controls, respectively. None of the outcome variables for mild or severe HG were significantly different as compared to the controls. Differences in other neonatal outcomes, including frequency of five-minute Apgar score < 7 and neonatal intensive care unit admissions, were not significantly different between the three groups. CONCLUSION: In contrast to previous reports, this study demonstrated that fetuses of gravidas admitted for HG are not at increased risk of growth retardation, congenital anomalies or prematurity. No beneficial effect on pregnancy outcome was detected.

Adult↗

PubMed1995

Amnionitis and premature delivery with intact amniotic membranes involving Staphylococcus aureus. A case report.

Subclinical infection is suspected to be an important etiologic factor in the initiation of preterm labor in women with intact membranes. We present a case of acute clinical chorioamnionitis followed by preterm labor and fetal distress in a woman with intact membranes. The bacteriologic data on the mother and neonate clearly identified coagulase-positive Staphylococcus aureus as the etiologic factor.

Adult↗

PubMed1994

Constriction of the umbilical cord leading to fetal death. A report of three cases.

Constriction of the umbilical cord is characterized by localized absence of Wharton's jelly, leading to narrowing of the cord, thickening of the vascular walls and narrowing of the vascular lumens. This may result in a compromised fetal blood supply, leading to fetal anoxia and eventual fetal death. Approximately 50 cases have been reported in the world literature over the last three centuries. Three cases of umbilical cord constriction leading to intrauterine fetal demise are reported. Two of the patients presented during the late second trimester with loss of sensation of fetal movements. Intrauterine fetal demise was diagnosed, and autopsy revealed constricted umbilical cords associated with torsion. The third patient is unique in that fetal death was precipitated by a routine, technically uncomplicated, transplacental amniocentesis procedure performed in the early second trimester. At the time of termination of the pregnancy we found marked stenosis with torsion over a 1-cm segment of the umbilical cord juxtaposed against the fetal insertion site. Umbilical cord constriction is a rare, almost invariably fatal condition, usually undiagnosed antenatally. In case 3, disruption of the placenta by amniocentesis may have initiated a terminal event in a fetus already compromised by a cord constriction. Three possible mechanisms could have contributed to the fetal death after amniocentesis in the presence of cord constriction: acute vasospasm, acute oligohydramnios and uterine contraction, or an obliterating thrombus.

Adult↗

PubMed1994

Amnioinfusion: does the choice of solution adversely affect neonatal electrolyte balance?

OBJECTIVE: To determine whether various solutions commonly used in amnioinfusion during labor affect neonatal electrolyte and blood gas values. METHODS: Amnioinfusion for thick meconium or severe variable fetal heart rate decelerations is used at our institution according to a standardized protocol. During alternating 3-week periods, the only solution made available for amnioinfusion was either normal saline or Ringer's lactate. Bolus volume, rate, and duration of infusion were determined by the individual physicians. At delivery, cord blood was collected for electrolyte and blood gas determination. These values were compared between the two solution groups and to a non-infused control group. RESULTS: Complete data on neonatal electrolytes and blood gas values were available on 53 infusion patients (20 Ringer's lactate, 33 normal saline) and 39 non-infusion patients. Comparing infusion to non-infusion patients and those infused with Ringer's lactate to those with normal saline, we found no significant difference in demographics, neonatal outcome variables, duration of labor, neonatal electrolytes, and cord blood gas values. Infusion variables (bolus volume, infusion rate, hours infused, and total volume infused) did not differ between solutions. Total volume and hours of infusion were closely correlated with each other (r = 0.93, P < .001); both were correlated with neonatal chloride (r = 0.38 and r = 0.36, respectively; P < .005). No cases of hypernatremia or hyperchloremia were found in any of the groups. The type of solution used had no effect on the neonatal chloride trend. CONCLUSION: The use of both normal saline and Ringer's lactate for indicated amnioinfusion in labor appears to have no clinically significant effect on neonatal electrolytes.

Adult↗

PubMed1993

Two consecutive hydrolethalus syndrome-affected pregnancies in a nonconsanguinous black couple: discussion of problems in prenatal differential diagnosis of midline malformation syndromes.

Hydrolethalus syndrome is a rare autosomal recessive (AR) disorder characterized by polyhydramnios, CNS abnormalities, cleft lip/palate, micrognathia, and polydactyly. Its molecular basis is unknown and prenatal diagnosis is challenging due to phenotypic overlap with several other midline malformation syndromes. A 34-year-old G3P2, nonconsanguinous, married, African-American woman was referred at 19 weeks of gestation after ultrasound findings of "multiple congenital anomalies." A previous pregnancy had been terminated following ultrasound findings of polyhydramnios, cleft lip/palate, polydactyly, severe hydrocephalus, and a Dandy-Walker malformation (DWM). Level II ultrasound evaluation of the current pregnancy demonstrated all of the anomalies which had been present in her previous pregnancy. Karyotype of amniocytes was 46,XX. Autopsy following pregnancy termination confirmed ultrasound findings. The pedigree, sonographic, and autopsy findings in this case were most consistent with hydrolethalus syndrome, although other AR multiple midline malformation syndromes were considered. Our case was detected by 19 weeks. Confident differential diagnosis is difficult for the geneticist and even more so for the sonologist given the technical limitations of ultrasound. It is uncertain whether these mendelian midline malformation syndromes represent slightly different phenotypic expressions of a common genetic defect or are manifestations of allelic and or locus heterogeneity. We suggest that for prenatal diagnostic purposes, in the absence of knowledge of the molecular basis of these disorders, the fine distinctions are not crucial as long as their mendelian inheritance is recognized and presence or absence of manifestations which make them severe are ascertained.

Abnormalities, Multiple↗

PubMed1993

Accelerated pulmonary maturation from preterm premature rupture of membranes: a myth.

OBJECTIVES: It is widely believed that premature rupture of membranes accelerates fetal pulmonary maturity. The purpose of our study was to determine the duration of premature rupture of the membranes required to achieve this effect. STUDY DESIGN: Retrospective analysis of our database yielded a group of 1395 patients who were delivered between 24 and 35 weeks' gestation and for whom we had complete data. The frequencies of premature rupture of the membranes and respiratory distress syndrome by each gestational week were analyzed with a log linear multiway contingency table analysis. Because gestational age was based on pediatric examination and was therefore somewhat subjective, birth weight was used to confirm results. Additional factors related to respiratory distress syndrome were considered in stepwise discriminant analysis. Results were further verified by the 1980 National Natality Survey data set. RESULTS: When we controlled for either gestational age or birth weight, there was no significant difference in the frequency of respiratory distress syndrome related to premature rupture of the membranes, but there was a suggestion (p < 0.08) that respiratory distress syndrome was actually more frequent after premature rupture of the membranes. Stepwise discriminant analysis revealed that gestational age, birth weight, race, sex, and Apgar score at 1 minute were all more important determinants than duration of premature rupture of the membranes. Duration of premature rupture of the membranes was associated with an increased risk of respiratory distress syndrome. Amnionitis was found to be highly related to the duration of premature rupture of the membranes. The incidence of amnionitis significantly increased 24 hours after premature rupture of the membranes occurred. A multiway frequency contingency table of the National Natality Survey data showed a significant increase in respiratory distress syndrome in association with premature rupture of the membranes. CONCLUSIONS: Pulmonary maturation continues but is not accelerated after premature rupture of the membranes. In fact, there is a strong suggestion that premature rupture of the membranes actually increases the risk of respiratory distress syndrome at a given gestational age.

Adult↗

PubMed1993

Transfer of maternally administered magnesium sulfate into the fetal compartment of the rat: assessment of amniotic fluid, blood, and brain concentrations.

OBJECTIVE: Our purpose was to determine whether parenteral magnesium sulfate crosses the rat placenta and enters the fetal brain. STUDY DESIGN: Twenty-eight pregnant female Long-Evans rats were divided into four groups, seven animals in each group. These groups included the following: single saline solution injection group evaluated after 20 minutes (control), single magnesium sulfate injection (270 mg/kg) evaluated after 20 minutes, and prolonged (2 and 4 hours) serum magnesium elevation (270 mg/kg loading and then 27 mg/kg every 20 minutes for maintenance). Each animal was killed, and maternal and fetal sera, amniotic fluid, and specific brain areas were analyzed for levels of magnesium. Statistical analysis included analysis of variance, multiple comparison procedure, and linear regression analysis. RESULTS: All three regimens of maternal subcutaneous magnesium sulfate resulted in significantly elevated maternal serum magnesium concentrations (p < 0.01). Fetal blood magnesium concentration rose from 3.9 +/- 0.3 to 4.9 +/- 0.1 mg/dl after 2 hours of continuous injections (p < 0.05), and to 5.3 +/- 0.0 mg/dl after 4 hours (p < 0.01). Amniotic fluid magnesium concentrations rose from 4.2 +/- 0.2 to 5.1 +/- 0.1 mg/dl after 4 hours (p < 0.05). Maternal blood magnesium concentrations were significantly correlated with amniotic fluid concentrations (r = 0.59, p < 0.01). Four hours of maternal magnesium sulfate treatment resulted in a 25% increase in magnesium concentrations in the fetal forebrain (38.3 +/- 2.3 to 47.9 +/- 3.5 mg/dl/gm, p < 0.05). No significant changes in magnesium concentrations were detected in hindbrain. CONCLUSION: Magnesium sulfate injected subcutaneously into rats crosses the placenta within 2 hours of sustained magnesium levels, enter the fetal blood-brain barrier, and concentrates in the forebrain.

Amniotic Fluid↗

PubMed1993

Stimulation and inhibition of N-methyl-D-aspartate receptors in rats: developing a seizure model.

OBJECTIVE: The objective of this study was to develop an experimental rat hippocampal seizure model based on the stimulatory effects of N-methyl-D-aspartate and to determine the inhibitory effects of MK-801 on N-methyl-D-aspartate-induced seizures. STUDY DESIGN: Two separate experiments were performed. In the first experiment chemitrode-implanted rats were injected intracranially with increasing doses (5, 10, 20, and 30 micrograms) of N-methyl-D-aspartate into the hippocampus. Various electrophysiologic and behavioral parameters were examined to determine the dose required to reliably elicit hippocampal seizure activity without having toxic effects on the rats. In the second experiment rats were given an intraperitoneal injection of MK-801 (0.5 or 1 mg/kg), followed 20 minutes later by an intracranial injection of N-methyl-D-aspartate (20 or 30 micrograms). The ability of MK-801 to suppress N-methyl-D-aspartate-induced seizure activity was assessed in this experiment. RESULTS: Intrahippocampal injection of 20 micrograms of N-methyl-D-aspartate produced the shortest electrical seizure latency (193 +/- 72 seconds, p < 0.01). At this dose seizure was achieved in 80% (four of five of the animals, and the highest numbers of electrical seizures per animal were produced (2.2 +/- 0.8, p < 0.05). The group that received 30 micrograms of N-methyl-D-aspartate had a shorter latency, a longer duration of behavioral seizure and a higher number of behavioral seizures (p < 0.05). However, this group suffered a 60% (three of five) mortality rate. The addition of MK-801 significantly decreased the number of seizures per animal and the total seizure duration (p < 0.05). MK-801 also reduced the latency period. CONCLUSION: Intracranial injection of 20 micrograms of N-methyl-D-aspartate produced reliable hippocampal seizure activity without mortality. MK-801 at a dose of 1 mg/kg injected intraperitoneally had significant inhibitory effects on this seizure model.

Analysis of Variance↗

PubMed1993

The effects of indomethacin and terbutaline on human fetal umbilical artery velocimetry: a randomized, double-blind study.

OBJECTIVE: Our purpose was to study the effects of indomethacin and terbutaline on umbilical artery impedance as measured by the systolic/diastolic ratio. STUDY DESIGN: Normal, low-risk patients at 26 to 32 weeks' gestation were enrolled. A baseline evaluation of the umbilical artery systolic/diastolic ratio was performed. The patients were then randomized to one of three groups and received a coded capsule that contained either terbutaline (5 mg), indomethacin (50 mg), or placebo. Repeat evaluation of the umbilical artery systolic/diastolic ratio was performed 4 hours later. The ratios before and after administration of the medication were compared in the control and study groups. Analysis of variance and paired Student t test were applied. RESULTS: Fifteen patients received indomethacin, 14 placebo, and 12 terbutaline. Pretreatment and posttreatment systolic/diastolic ratios were 3.2 and 3.1 for the indomethacin group, 3.2 and 3.3 for the placebo group, 3.0 and 2.8 for the terbutaline group, respectively. The changes in the systolic/diastolic ratio in the indomethacin and terbutaline groups, as compared with the placebo group, were not found to be significant. CONCLUSION: Terbutaline and indomethacin do not have a significant effect on the human umbilical artery impedance as measured by the systolic/diastolic ratio.

Diastole↗