Béatrice Gulbis

Physiological implications of the materno–fetal oxygen gradient in human early pregnancy

This study evaluates the role of the fetal fluid cavities on materno-fetal oxygen diffusion in early pregnancy. Oxygen tension (pO2) was recorded using a multiparameter sensor inserted inside the exocoelomic cavity (ECC) or in the amniotic cavity. There was no correlation between coelomic pO(2) and gestational age, but a negative correlation was found between amniotic pO(2) and gestational age. The mean (SEM) pO(2) was 19.5 mm Hg (1.83) in the ECC at 7-11 weeks and 15.4 mm Hg (1.36) in the amniotic cavity at 11-16 weeks. The volume of the ECC changed little between 7 and 10 weeks of gestation, indicating that coelomic pO(2) results from passive oxygen diffusion through the placenta and is an indicator of the overall pO(2) inside the gestational sac during the first trimester. By contrast, the amniotic cavity volume increases exponentially, whereas amniotic pO(2) decreases with gestational age, suggesting that the increase in uterine blood flow is not sufficient to compensate for the rapid increase in amniotic fluid volume during the first half of pregnancy.

Chronic maternal smoking and cord blood amino acid and enzyme levels at term

Objective To assess the influence of chronic active maternal smoking on cord blood amino acid and enzyme levels at term. Methods The concentrations of 24 free amino acids, total protein, and five enzymes were measured in samples of maternal and fetal cord venous plasma from 24 nonsmokers who were not exposed to tobacco smoke and 24 chronic smokers. Cotinine levels were also measured in maternal plasma to evaluate fetal tobacco exposure. The pregnancies were between 37 and 40 weeks gestation, were uncomplicated, and were delivered vaginally. Results Fetal weight was significantly (P < .01) lower in the smokers than in controls. A positive significant (P < .001) correlation was found between maternal and umbilical venous cotinine concentrations. Significantly lower concentrations of aspartic acid (P < .01), hydroxyproline (P < .05), threonine (P < .005), alanine (P < .05), &agr;-aminobutyric acid (P < .001), methionine (P < .05), tyrosine (P < .001), phenylalanine (P < .01), and lysine (P < .05) were found in the venous cord plasma of the smokers compared with nonsmokers. The fetomaternal ratios were similar in both groups. The umbilical plasma alkaline phosphatase activity was significantly (P < .01) lower in the smokers than in the controls. Conclusion Chronic maternal smoking is associated with alterations of protein metabolism and enzyme activity in fetal cord blood. These may be secondary to irreversible changes in the cellular functions of the trophoblast and may contribute to fetal growth restriction.

Maternal serum testing for alpha-fetoprotein and human chorionic gonadotropin in high-risk pregnancies

To evaluate the variations and potential clinical use of serial maternal alpha‐fetoprotein (AFP) and human chorionic gonadotropin (hCG) in pregnancies at risk of pregnancy‐induced hypertension (PIH) and/or intrauterine growth retardation (IUGR), we investigated the relationship between placental sonographic findings, uterine artery Doppler measurements, and maternal serum AFP, hCG, and uric acid levels between 20 and 34 weeks of pregnancy. Maternal serum samples were collected from 41 singleton pregnancies with bilateral uterine notches and/or an increased uterine artery pulsatility index at 20–24 weeks. Maternal serum AFP, intact hCG and free α and β subunits, and uric acid circulating levels were measured in all cases at 20–24 weeks and 25–28 weeks. Placental sonographic investigations comprised measurements of thickness and morphology. Twenty pregnancies had a normal outcome and 21 had an adverse outcome, including eight complicated by severe PIH with fetal IUGR, eight by isolated IUGR, three by mild PIH with normal fetal growth, and two by placental abruption. At the time of the first scan, the placental thickness and maternal serum levels of AFP, hCG, and uric acid were significantly increased in pregnancies with adverse outcomes, compared with those with a normal outcome. In subsequent maternal serum examinations, the incidence of elevated hormonal levels fell for AFP, intact hCG, and β‐hCG, whereas it increased for the uric acid level. No difference was found at any stage for the α‐hCG level. Seven out of 11 pregnancies complicated by PIH presented with elevated MSAFP and MShCG and a large heterogeneous placenta at the first visit, whereas no pregnancy with a normal outcome presented with similar features. This study has shown a significant association between abnormal development of the utero‐placental circulation, elevated MSAFP and MShCG at mid‐gestation, and subsequent adverse pregnancy outcome. Serial measurements of MSAFP and MShCG do not provide extra information for the follow‐up of these pregnancies.

Fetal amino acid and enzyme levels with maternal smoking.

OBJECTIVEnTo assess the influence of active maternal smoking on fetal amino acid and enzyme levels in early pregnancy.nnnMETHODSnThe concentrations of 23 free amino acids and total protein, and the activity levels of four enzymes were measured in samples of maternal and fetal plasma from nine nonsmokers who were not exposed to tobacco smoke and nine long-term, heavy smokers matched for gestational age. To determine fetal exposure to smoking, cotinine levels were measured in maternal and fetal plasma and fetal liver samples from both groups. The pregnancies were between 12 and 17 weeks gestation.nnnRESULTSnIn women who smoke, the median cotinine concentrations were 156 mg/mL in maternal plasma and 89 ng/mL in fetal plasma, but only one fetal liver sample contained detectable cotinine. Significantly lower concentrations of serine, proline, alpha-aminobutyric acid, leucine, and arginine were found in smokers compared with nonsmokers, with the lowest in arginine. Fetal plasma amylase activity was significantly higher in smokers than controls. There were no differences in concentrations of other amino acids or activity levels of other enzymes in the two groups.nnnCONCLUSIONnMaternal smoking affected placental and fetal protein metabolism and enzyme activity from at least 12 weeks gestation. That finding indicates that high levels of tobacco exposure in the first trimester might cause irreversible changes in the cellular functions of the villous trophoblastic barrier.

Free amino acid distribution inside the first trimester human gestational sac

The trophoblast functions of nutrient transport and protein synthesis generate high concentrations of amino acids in the placenta and in fetal blood during the second half of pregnancy, but little is known about these metabolic processes in embryonic and early fetal periods. The aim of this study is to compare the distribution of amino acids inside the first trimester gestational sac. Free amino acid concentrations were measured in homogenates of placental villi, in samples of coelomic and amniotic fluid, and in the maternal serum from 17 normal pregnancies between 7 and 11 weeks of gestation. Significant positive relationships between maternal serum and placental tissue were found for 10 amino acids, indicating that active amino acid transport and accumulation by the human syncytiotrophoblast occurs as early as 7 weeks of gestation. The transplacental flux of most amino acid transport from maternal blood to the exocoelomic cavity was against a concentration gradient. The highest placental amino acid concentrations were found for taurine, glutamic acid, glycine and alanine. The amniotic fluid contained lower mean concentration of all amino acids than coelomic fluid and maternal serum. The concentration distribution of individual amino acids in coelomic and amniotic fluid were related indicating a passive transfer through the amniotic membrane. A coelomic-maternal gradient was observed in 19 out of 24 amino acids measured and positive correlations were found between maternal serum and coelomic fluid for concentrations of alpha-aminobutyric acid, tyrosine and histidine, suggesting that these amino acids are only partially retained and/or transferred more rapidly by the early placenta.

Amniotic fluid biochemistry in second-trimester trisomic pregnancies: Relationships to fetal organ maturation and dysfunction

Protein and enzyme patterns were investigated in amniotic fluid samples of 12 trisomy 21 and five trisomy 18, between 11 and 16 weeks and of a control group of 50 chromosomally and anatomically normal pregnancies at the same gestational age. Positive correlations were found between gestational age and the concentration of urea (P<0.05), creatinine (P<0.01), beta2-microglobulin (P < 0.0001), hCG (P < 0.01), ALP (P < 0.001), LAP (P < 0.0001) and GGT (P <0.0005) in the amniotic fluid of euploid pregnancies. There were also significant correlations between the concentrations of the different variables measured except for hCG and AFP. Different protein and enzyme patterns were found in the amniotic fluid of aneuploid pregnancies where only beta2-microglobulin concentration was significantly correlated with advancing gestational age. The beta2-microglobulin concentration was significantly (P <0.05) higher in aneuploid fetuses presenting with hydrops compared to those without. These findings suggest that the changes in amniotic composition found during the fourth month of normal pregnancies reflect mainly the maturation of the fetal renal glomerular function and the arrival of enzymes from the digestive and respiratory tract into the amniotic cavity. In trisomy 21, there is evidence of a delay in the maturation of these organs whereas in trisomy 18, there is a reduced production of most proteins and enzymes.

The origin of α-fetoprotein in first-trimester anembryonic pregnancies

Abstract OBJECTIVE: Our purpose was to evaluate the origin of α-fetoprotein in the maternal circulation and coelomic fluid of pregnancies with an empty gestational sac on first-trimester ultrasonographic examinatin. STUDY DESIGN: The α-fetoprotein level and the affinity of α-fetoprotein for concanavalin A Sepharose was measured between 8 and 11 weeks of gestation in the maternal serum and coelomic fluid of nine pregnancies complicated by an empty gestational sac and of 27 normal pregnancies. RESULTS: The maternal serum α-fetoprotein level in patients with an empty gestational sac was high in seven cases and normal in two cases. In these cases the median level was significantly ( p 50% of α-fetoprotein molecules in the coelomic fluid were of the concanavalin A nonreactive fraction, whereas in one case the coelomic fluid sample contained CONCLUSION: Normal or high maternal serum AFP levels and α-fetoprotein molecules predominantly of yolk sac origin in the coelomic fluid of pregnancies with an empty gestational sac on ultrasonography provide further evidence that the most likely explanation for this feature is the early death of the embryo with persistence of the placental tissue.

Effects of the farnesyltransferase inhibitor UCF-1C/manumycin on growth and p21-ras post-translational processing in NIH3T3 cells

Examination of the effect of the farnesylprotein transferase (FPTase) inhibitor UCF1‐C/manumycin on NIH3T3 cells transfected with a normal N‐ras gene and expressing high levels of the corresponding p21‐ras protein showed that 10 μm UCF1‐C immediately and reversibly inhibited growth in these cells, without modifying cell‐death rate, thus acting as a cytostatic. There was also a 98% reduction of p21‐ras neo‐farnesylation and a 3‐fold decrease in total content in p21‐ras products, yet without gross modification of the relative content in the post‐translational products and without accumulation of the native protein to detectable levels. UCF1‐C likewise reversibly inhibited growth in parental NIH3T3 cells, as well as in sub‐strains expressing a transfected normal or mutated H‐ras gene. Together with the fact that the well‐developed network of actin stress fibers present in the NIH3T3 (N‐ras) cells was not affected by the FPTase inhibitor, these data indicate that its growth‐inhibitory effect is not necessarily in direct relation with that exerted on p21‐ras processing. Alternatively, it might be causally related to the decreased prenylation of other cellular proteins, perhaps included among the 13 proteins, unrelated to p21‐ras, of which the farnesylation was also reduced under UCF1‐C treatment. Some cells transformed by a ras or non‐ras oncogene might exhibit higher susceptibility towards FPTase inhibitors than normal cells, but this might then be attributable to differences in the pattern of expression and/or in the functional importance of non‐ras farnesylated proteins. Int. J. Cancer 76:601–608, 1998.© 1998 Wiley‐Liss, Inc.

Limitations of serum values to estimate glomerular filtration rate during exercise

Objective Glomerular filtration rate (GFR) is part of routine medical practice for clinical assessment of kidney function in health and disease conditions, and is determined by measuring the clearance of creatinine (Cl-Crn) or estimated (eGFR) from equations using serum creatinine (Crn) or cystatin C (Cyst C). Crn and Cyst C methods obviate the need for urine collection but their reliability under non-resting conditions is uncertain. This study compared GFR determined by Cl-Crn, Crn and Cyst C methods under the conditions of rest and after exercise. Methods Twelve young male subjects performed a 30 min treadmill exercise at 80% of the maximal oxygen capacity. Venous blood samples and urine collections were collected before and after exercise and after recovery period. GFR rates were calculated from serum Crn and Cyst C equations, and Cl-Crn measured from serum and urine Crn output. Albumin was also determined for all samples. Results Under resting conditions, eGFR from Crn and Cyst C did not differ from Cl-Crn (p=0.39). Immediately after exercise, GFR decreased significantly, regardless of the method, but more so for Cl-Crn (−30.0%; p<0.05) compared with Crn (−18.2%) and Cyst C (−19.8%). After the recovery period, GFR determined by Cl-Crn was returned to initial values whereas Crn and Cyst C remained reduced. Although eGFR methods accurately estimate GFR at rest, those methods underestimated the change in GFR after acute exercise. Conclusions These results indicate that exercise-induced changes in GFR should be determined by Cl-Crn method.

Biochemical composition of the coelomic fluid in anembryonic pregnancy

OBJECTIVEnOur purpose was to investigate the biochemical composition of the coelomic fluid in first-trimester anembryonic pregnancies.nnnSTUDY DESIGNnCoelomic and maternal serum were obtained from 17 anembryonic pregnancies and 17 apparently normal pregnancies between 7 and 12 weeks of gestation that were matched for gestational age. Electrolytes, total proteins, urea, creatinine, lactate, and human chorionic gonadotropin concentrations and pH were measured.nnnRESULTSnSignificantly higher pH (p < 0.005) and bicarbonate levels (p < 0.001) and significantly lower total protein (p < 0.05), phosphate (p < 0.005), and human chorionic gonadotropin (p < 0.001) levels were found in coelomic fluid from anembryonic pregnancies compared with normal pregnancies. No difference was found for chloride, sodium, potassium, urea, creatinine, and lactate between the study and control groups.nnnCONCLUSIONSnThe fluid collected in anembryonic pregnancies is of exocoelomic origin and its biochemical characteristics reflect a failure of most placental biological mechanisms such as metabolic function, transport function, and endocrine activity.