Valerie Jansen

The transfer and metabolism of corticosteroids in the perfused human placenta.

The transfer and metabolism of cortisol, prednisolone, betamethasone, and dexamethasone were investigated in vitro in the perfused human placenta. Maternal and fetal circuits were established but the steroid was added to the former only. The clearance expressed as a fraction of the antipyrine transfer rate varied from 0.27 to 0.50, but there were no significant differences among the four steroids. All the steroids were metabolized extensively to their respective 11-ketosteroids and again there were no material differences among the steroids. The metabolic conversions of dexamethasone and betamethasone were far greater in the perfused placenta than in minced placenta. From the standpoint of placental transfer and metabolism, as observed in the perfusion studies, none of the four corticosteroids offers a decisive advantage in the antepartum maturation of the fetal pulmonary surfactant system.

Transfer across perfused human placenta. II. Free fatty acids.

Extract: The rate of transfer of palmitic acid across human placenta was measured in an in vitro perfusion system. The rates of transfer from maternal to fetal circulation and in reverse direction were about the same, and were considerably less than those for antipyrine and leucine. The transfer rate for linoleic acid was similar to that for palmitic acid. An estimate of the absolute rate of transfer for free fatty acids was made which yielded a figure of 6.8 mmol/24 hr. which is less than that required for the deposition of fat by the fetus in the last trimester. These calculations indicate that during the period of rapid accumulation of fat the fetus converts glucose and/or amino acids to that purpose.Uptake and metabolism of palmitate by placental slices differs significantly in the human and the guinea pig.Speculation: It has been suggested that the placental capacity for transfer of some nutrients greatly exceeds requirements, whereas with respect to other nutrients, the capacity for transfer is far more limited. A general reduction in placental function may produce selective nutritional deficiencies in the fetus, beginning with those factors transferred with the smallest margin of safety.

Transfer across perfused human placenta. IV. Effect of protein binding on free fatty acids.

Extract: The effect of protein binding on the rate of placental transfer of hexanoic (C 6) and decanoic (C 10) acids was investigated in an in vitro perfusion system of human placenta. As much as 30% of transferred C 6 was converted to more polar compounds; so that the observations related to the combined effects on transfer and metabolism. Less than 10% of C 10 was similarly metabolized. Both fatty acids are soluble in buffered salt solutions at the concentrations used (40 μM) and both are bound to serum albumin, C-10 having higher association constants (K′ for C 6, 1.48 × 104; for C 10, 1.03 × 105). When the placenta is perfused with buffered salt solution, the transfer of C 6 is 22% more rapid than that of C 10. It is suggested that binding within the placenta retards C 10 more than C 6. The addition of 1 g/100 ml bovine serum albumin to the maternal perfusate reduces the transfer rate of C 10 by 80%, whereas 2 g/100 ml serum albumin has a more moderate effect on C 6 (a reduction of 50%). The addition of 1 g/100 ml serum albumin to the fetal perfusate increases transfer rate of both free fatty acids (FFA), C 6 by about 25% and C 10 by about 250%. With equivalent concentrations of serum albumin in maternal and fetal perfusates, the transfer rate of C 10 was reduced by 65%, whereas there was no detectable effect on transfer of C 6 in two of three experiments.The transfer rates of FFA increase logarithmically with progressive shortening of the carbon chain from C 16 to C 8 when maternal and fetal perfusates contain serum albumin. Protein binding is apparently the determining factor. The rate of transfer falls off at C 6 and C 4, even though protein-binding continues to decrease. The determining factor may be the hydrophilic nature of these molecules.Speculation: If the observations on FFA have general applicability, the overall effect of protein binding on placental transfer of a particular substance may relate to its water solubility and protein binding. If water solubility is not a limiting factor, protein binding may decrease transfer rate sharply, as occurs with decanoic acid (C 10). With substances that have very limited water solubility, protein binding may increase transfer by increasing the amount presented to the placenta. Palmitic acid (C 16) appears to be such a compound. The fraction bound to proteins in the perfusate, as measured by equilibrium dialysis, may not be the most significant factor determining rates of transfer. More significant may be the competitive aspects of binding in the perfusate and to the placenta in influencing rates of release and uptake.

A stop codon mutation in COL11A2 induces exon skipping and leads to non‐ocular Stickler syndrome

Mutations in COL11A2 cause a spectrum of phenotypes affecting chondrogenic tissues. We analyzed this gene by conformation sensitive gel electrophoresis (CSGE) and sequencing in a family with non‐ocular Stickler syndrome, and found a heterozygous C → T mutation in exon 57 + 13 in affected members, resulting in Arg893Stop codon. Since heterozygous nonsense mutations in COL11A2 do not usually lead to any obvious phenotype, all exons and exon boundaries of COL11A2 in the sample of the propositus were sequenced. Because no disease‐associated alterations were found, we performed RT‐PCR analysis on the RNA. Analysis showed skipping of exon 57 in one allele, resulting in an inframe deletion of 54 bp or 18 amino acids, which would explain the phenotype observed in the family. Thus, the exon skipping resulted from a nonsense‐associated altered splicing (NAS). This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148‐7299/suppmat/index.html.

α-Thalassemia hydrops fetalis: Clinical and ultrasonographic considerations

Abstract Five pregnant Southeast Asian women presenting during a 14-month period with microcytic anemia, preeclampsia, and size-date discrepancies were all ultimately diagnosed as carrying fetuses with homozygous α-thalassemia hydrops fetalis. The perinatal complications of this hemoglobin disorder are unique to persons of this ethnic background and include uniform fatality for the affected infant, maternal preeclamptic morbidity, and retained placenta. In this report the obstetric ultrasound findings are presented and the clinical manifestations are discussed, with recommendations made to reduce this emerging public health problem in the United States.

Transfer across Perfused Human Placenta. III. Effect of Chain Length on Transfer of Free Fatty Acids

Extract: Human placentas were perfused in vitro with straight chain, even-numbered free fatty acids (FFA) and the transfer rates from maternal to fetal circulation were measured. The transfer rates increased logarithmically as chain length decreased. The clearances, calculated as percentage of clearance of antipyrine were: palmitic acid, 4%; myristic acid, 10%; lauric acid, 16%; decanoic acid, 18%; octanoic acid, 50%; hexanoic acid, 64%.Speculation: Transfer of hydrophobic materials through the placenta is a complex process which is probably affected by many factors. The present studies with FFA suggest that, for these compounds, protein binding may be particularly significant. If so, it may affect transfer rate by influencing release from maternal serum albumin, diffusion through the placenta, and uptake by fetal plasma. These several factors require further analysis.

Cell population density and phenotypic expression of tissue culture fibroblasts from heterozygotes of Lesch-Nyhan's disease (inosinate pyrophosphorylase deficiency)

Radioautographic examination of skin fibroblasts grown in tissue culture from normal donors revealed heavy labeling of almost all cells following incubation with tritiated hypoxanthine. Cells from patients with Lesch-Nyhans disease, lacking inosinate pyrophosphorylase, had only 10 grains or less per cell. When normal and abnormal cells were mixed prior to culture, there was a progressive increase, with culture time, in the percentage of heavily labeled cells so that by 96 hr, when the cells were confluent, over 95% of the cells were heavily labeled. Reduction of cell density by subculture produced a reversion to original values. Cultures from three obligatory heterozygotes revealed the expected mixed population of cells. This appears to be a practical approach to the identification of the heterozygote.

The effect of ouabain on placental transport of 86Rb

Human placental fragments concentrate 86Rb 10--20-fold during a two-hour incubation period. Inhibition of ouabain is dose-dependent, reaching 90 + per cent at a concentration of 5 x 10(-5) M. The clearance index of 86Rb across the perfused human placenta is 0.34 +/- 0.08, comparing to previously reported indices for Na22 and Cl36 of 0.28 and 0.41, respectively. Ouabain in concentrations up to 5 x 10(-5) M had no detectable effect on transfer across the placenta. The clearance index of ouabain is low, averaging 0.07 in 3 experiments. 3H-ouabain is not detectably bound to albumin or placental homogenate.

Genetic screening of prospective oocyte donors

OBJECTIVE To report our experience with genetic screening of oocyte donor candidates and to determine the frequency with which significant genetic issues are identified. DESIGN Prospective genetic screening of oocyte donor candidates. SETTING University hospital oocyte donation program. PATIENT(S) Women presenting consecutively as volunteer oocyte donors. INTERVENTION(S) Genetic screening was performed by pedigree analysis and laboratory studies. MAIN OUTCOME MEASURE(S) Inclusion in the oocyte donor pool based on the results of clinical evaluation and laboratory tests consisting of polymerase chain reaction based mutational analysis for cystic fibrosis carrier status, cytogenetic analysis for karyotype, enzymatic assay for Tay-Sachs disease carrier status, and complete blood count and hemoglobin electrophoresis. RESULT(S) Eight (11%) of 73 oocyte donor candidates were excluded from the donor pool because of a potentially serious genetic finding. Cystic fibrosis mutations were identified in 5 candidates (7%), abnormal karyotypes were found in 2 (3.5%), and an autosomal dominant skeletal dysplasia was identified in 1 (1.4%). CONCLUSION(S) A significant proportion of women who present as candidates for oocyte donation are inappropriate for donation because of their genetic history or genetic testing results. A thorough genetic evaluation, including a history and laboratory screening, is essential to any oocyte donation program to maximize positive outcomes in pregnancies achieved through assisted means.

Carrier screening for Gaucher disease in couples of mixed ethnicity.

With the advent of mutational analysis for Gaucher disease, carrier screening has been incorporated into many Jewish genetic disease screening programs. Frequencies and mutations for Gaucher disease in non-Jewish populations are less well established and the detection rate of carriers are lower. Testing is problematic for resolving residual risk in a couple of mixed ethnicity. We report the testing choices made by 20 consecutive couples of mixed ethnicity where the Ashkenazi Jewish partner was identified to be a Gaucher disease gene carrier. Carrier studies of the non-Jewish partner were elected as follows: DNA studies alone, 5 (25%); enzymatic assay, 2 (10%); both, 6 (30%); no carrier studies, 7 (35%). Of the 7 couples not electing carrier studies, one was not in a pregnancy and 6 elected prenatal diagnosis in lieu of parental testing by enzymatic analysis of amniocytes. One couple elected parental carrier studies as well as prenatal diagnosis. All couples electing prenatal Gaucher determination had amniocentesis for other indications as well (4, advanced maternal age; 4, parental anxiety). We conclude that Gaucher screening is feasible for couples of mixed ethnicity if appropriate counseling and testing are offered.