PubMed Health⌕ Search

Biomedical subjects

J Dancis

Publications and source records attributed to J Dancis.

At least 19 recordsLinked to original sources
PubMed1997

Hypoxia stimulates ecNOS mRNA expression by differentiated human trophoblasts.

Cytotrophoblasts isolated from normal human placenta cultured under normoxic conditions (20% O2, pO2 = 130 mmHg) for 48-72 h differentiate to a form which expresses high levels of hCG and which morphologically resembles syncytiotrophoblast. We had previously shown that hypoxia (0-1% O2, pO2 = 12-14 mmHg) blocks this differentiation process, although trophoblasts exposed to hypoxia for up to 96 h were completely viable. In this article we showed that trophoblast responds to hypoxia by expressing the hypoxia-sensitive DNA binding protein HIF-1. We also showed that in trophoblast cultured under normoxic conditions, expression of endothelial cell nitric oxide synthase (ecNOS) mRNA increases with time, reaching a maximum in 48-72 h. However, in trophoblast maintained under hypoxic conditions for 48 h (after an initial 24 h in normoxia), expression of ecNOS mRNA is greatly reduced. These observations are consistent with the expression of ecNOS by syncytiotrophoblast but not by cytotrophoblast. In contrast, exposure of differentiated trophoblasts to hypoxia for 24 h (after 48-72 h in normoxia) significantly stimulates expression of ecNoS mRNA over that of cells maintained continuously in normoxia. These results suggest that in differentiated trophoblast hypoxia can stimulate ecNOS expression.

Cell Differentiation↗
PubMed1996

Uptake of human immunodeficiency virus envelope protein gp120 by human trophoblast in culture.

OBJECTIVE: Our purpose was to determine whether human trophoblast has a cell surface CD4 antigen that will bind to gp120, the envelope protein of human immunodeficiency virus. STUDY DESIGN: Uptake of iodine 125-labeled gp120 by trophoblast in culture was measured. Particular attention was paid to technical details that may have caused the contradictory results reported by previous investigators: the source of the recombinant gp120, the method of radioiodination, and the isolation procedure of trophoblast to ensure elimination of contaminating cells, particularly macrophages. RESULTS: Uptake of transferrin-free iodine 125-labeled gp120 to trophoblast was unaffected by adding a 200 molar excess of gp120, by preincubating gp120 with soluble CD4 to block the CD4 binding sites on gp120 and by preincubation of trophoblast with a blocking antibody to CD4 (OKT4a). In contrast, uptake of gp120 by CD4-positive H9 human lymphocytes was reduced 79% by a 200 molar excess of gp120 and > 50% by a CD4-blocking antibody. CONCLUSIONS: Uptake of gp120 to trophoblast is by a high capacity, CD4-independent mechanism that is probably nonspecific and may be related to the mechanism for binding other circulating glycoproteins in maternal blood.

Animals↗
PubMed1996

The effect of hypoxia on term trophoblast: hormone synthesis and release.

Isolated trophoblast in culture remained viable when exposed to severe hypoxia (Po2 12-14 mmHg) for at least 72 h as indicated by trypan blue exclusion and the synthesis and secretion of metabolically labelled proteins. However, release of hCG, hPL, progesterone and estradiol was reduced to < 10 per cent when compared to trophoblast in normoxia (Po2 120-130 mmHg). hCG mRNA was also reduced demonstrating interruption of synthesis at transcription. Acute exposure to hypoxia (2 h) suppressed progesterone release but not hCG, whereas inhibitors of oxidative phosphorylation suppressed hCG release but not progesterone. hCG release increases progressively during culture in normoxia, peaking at 72 h. Exposure of trophoblast to hypoxia for 48 h after 24, 48 and 72 h in normoxia interrupted this progression but did not suppress hCG release. Progesterone release, in contrast, was reduced by hypoxia. Exogenous dibutyryl cAMP increased hCG and progesterone release by normoxic trophoblast but not by hypoxic cells. Trophoblast returned to normoxia after 24 h in hypoxia increased hCG and progesterone release, suggesting early recovery. Conservation of oxygen and ATP by reducing hormone synthesis may contribute to survival of trophoblast in hypoxia.

Cell Hypoxia↗
PubMed1995

Drug delivery during pregnancy: evaluation in vitro of new drugs.

Indications for the treatment of the pregnant woman fall into three general categories: mother and infant require treatment, only the mother should be treated, or only the infant. Directing therapy towards the affected subject is an important aspect of good care, although it is not the only one. It is argued that a rational selection of the appropriate drug can be made without endangering mother or infant, with the aid of select laboratory investigations, including placental perfusion, and a knowledge of placental physiology. Examples are presented to support this contention. The intra-amniotic administration of drugs is briefly discussed. A plea is made to develop drugs that are designed specifically for use during pregnancy.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Influence of organic cations on basic amino-acid uptake by human placental villi.

Human placental chorionic villi were incubated for 30 min with [3H]lysine or [3H]arginine and the distribution ratios (intracellular:extracellular concentrations) were determined. The ratios remained unchanged when Na+ in Earle's buffered salt solution was replaced with Li+. When Na+ was replaced with choline there was a significant increase is distribution ratios (lysine 1.34 +/- 0.33 v. 3.99 +/- 0.15, arginine 1.95 +/- 0.37 v. 5.05 +/- 1.16). Leucine, a neutral amino acid with a Na(+)-independent transport system, was unaffected by choline substitution. The distribution ratio for alanine, which is Na(+)-dependent, was reduced (2.50 +/- 0.41 v. 1.45 +/- 0.20). Two other quarternary amines, acetyl-beta-methylcholine and tetraethylammonium chloride (TEA) caused similar increases in the distribution ratios of the basic amino acids. Hordenine, a tertiary amine, was less effective and there was little or no effect with ephedrine, a secondary amine. The choline effect was first observable at concentrations of 105 mM. With TEA, there was a progressive increase in distribution ratios beginning at 29 mM. Lysine efflux was measured after incubation of villi with lysine in Earle's buffer or choline buffer. Lysine was rapidly released to the fresh medium with 25% more retained in choline-exposed villi. The amines may cause alterations in the kinetics of basic amino-acid transporters or may modify other aspects of placental physiology permitting an increase retention of the basic amino acids.

Amino Acids↗
PubMed1995

Lack of effect of cocaine on lysine and alanine uptake in human placental villi or transfer in perfused human placenta.

The effect of cocaine on lysine and alanine uptake in human placental villi and transfer across the dually perfused placenta was studied. Uptake (in terms of the intracellular to extracellular distribution ratio) of alanine and lysine was 2.81 +/- 0.30 (n = 5) and 1.45 +/- 0.24 (n = 5) respectively and was unaffected by cocaine (50-500 ng mL(-1) in the incubation medium. In the dually perfused placenta, the clearance index (ratio of amino acid to antipyrine clearance) was 0.35 +/- 0.03 and 0.30 +/- 0.05 and the transfer index (ratio of amino acid to L-glucose clearance) was 2.20 +/- 0.07 and 1.89 +/- 0.29 for lysine and alanine respectively. Cocaine at concentrations of 100 ng mL(-1) or 250 ng mL(-1) had no effect on the clearance of either amino acid. The results of this study indicate that concentrations of cocaine likely to be encountered in vivo do not affect uptake of lysine or alanine by placental villi or transfer across the perfused placental lobule, in contrast with the report that cocaine reduces uptake of alanine by placental vesicles. Experimental models must be critically evaluated before accepting the results as pertinent to a clinical situation.

Alanine↗
PubMed1995

The effect of zidovudine and 2'3'-dideoxyinosine on human trophoblast in culture.

Trophoblast from term and first trimester placenta, maintained in culture, were exposed to 20 mumoles/l zidovudine or 2'3'dideoxyinosine. Several indices of function were measured and compared to control trophoblast in parallel culture. The results from individual placentas were examined by Student's t-test and cumulative results by ANOVA. Neither zidovudine or 2'3'-dideoxyinosine had statistically significant effects on the function of term trophoblast, following a 48 hr exposure to the drug as indicated by hCG secretion, protein synthesis and glucose consumption. In one of five placentas exposed to zidovudine, progesterone secretion was reduced as compared to its control but remained in the high range. Zidovudine had no significant effect on cultured trophoblast isolated from first trimester placenta even after prolonged exposure to the drug for eleven days. Both term and first trimester trophoblast in culture tolerate prolonged exposure to high concentrations of zidovudine or 2'3'-dideoxyinosine. Human trophoblast in culture provides a safe in vitro model for the screening of drugs intended for use during pregnancy.

Analysis of Variance↗
PubMed1995

Two mechanisms for IgG uptake in cultured human trophoblast: evidence for a novel high affinity Fc receptor.

The mechanism of IgG transport by the placental trophoblast was examined by studying IgG uptake by purified trophoblast maintained in culture. This model retains the ability to bind and endocytose human IgG from human serum. Comparison of the relative IgG uptake by the trophoblast among the four subclasses of both human and mouse IgG indicates that the trophoblast IgG receptor has different affinities from those described for the three known human Fc gamma receptors, FcR gamma I, FcR gamma II, and FcR gamma III. These results suggest the presence of a novel trophoblast Fc gamma receptor. Although Fc gamma RIII has been reported to be present on trophoblasts, immunocytochemical studies failed to detect binding to the cell surface of antibody-specific for Fc gamma RIII, 3G8 MAb. In addition, blocking studies with MAb 3G8 did not interfere with IgG uptake. Scatchard analysis of human IgG uptake revealed a biphasic curve consistent with two distinct mechanisms for the transport of IgG by the trophoblast. The first is a higher affinity system (Ka = 1.7 x 10(7) M-1, 1.7 x 10(4) binding sites/cell) which exhibits IgG subclass and species specificity, and the second is a low affinity system (Ka = 6.9 x 10(3) M-1, 7.5 x 10(7) binding sites/cell).

Animals↗
PubMed1993

Transfer of cocaine by the perfused human placenta: the effect of binding to serum proteins.

OBJECTIVES: Our purpose was to investigate the transfer of cocaine across human placenta and to measure the binding of cocaine to maternal and cord sera and to assess the effect of binding on transfer. STUDY DESIGN: Cocaine transfer by the in vitro perfused human placenta was studied under controlled experimental conditions. Protein binding of cocaine was measured by ultrafiltration in 10 pairs of maternal and cord sera and was compared with 12 sera from nonpregnant females. RESULT: With perfusates of albumin (5 gm/dl) in buffer cocaine clearance was 1.08 +/- 0.52 ml/min, threefold greater than that of the water-soluble marker L-glucose. Transfer was bidirectional and nonsaturable over a concentration of 0.02 to 4000 ng/ml. Cocaine was not detectably metabolized during perfusion. Replacement of albumin-buffer with human serum as maternal perfusate reduced the transfer rate by almost 50%, p < 0.02. Binding of cocaine was greatest by serum from the nonpregnant female > pregnant female (not significant) > cord serum (p < 0.02) = albumin buffer. CONCLUSIONS: Cocaine is rapidly transferred across the placenta by simple diffusion without metabolic conversion. Transfer, although diminished, remains rapid in spite of binding to serum proteins. These several factors plus the poor binding by cord serum conspire to increase fetal exposure to the drug.

Blood Proteins↗
PubMed1993

L. Emmett Holt, Jr.

Explore the source record for details and available documents.

History, 20th Century↗
PubMed1993

Transfer and metabolism of dideoxyinosine by the perfused human placenta.

Dideoxyinosine (DDI) has been recently approved for the treatment of AIDS. In anticipation of its use in HIV-infected women during pregnancy, the transfer and metabolism of DDI by the perfused human placenta have been investigated. Transfer characteristics are those of simple diffusion: clearance is the same as that for L-glucose (transfer index of 0.98 +/- 0.09), it is equivalent in both directions across the placenta, and the transfer rate is proportional to the transplacental gradient over a very broad range (1 to 500 microM). Because of extensive placental metabolism, only about one-half of the cleared DDI (51 +/- 21%) is transferred intact to the fetal circulation. No dideoxyadenine triphosphate, the antiviral product of DDI, could be detected in the placenta following perfusion. Comparison of the pharmacological information on DDI and zidovudine (ZDV) indicates that treatment of HIV-infected women during pregnancy with DDI will expose the fetus to much less drug than if ZDV were used. DDI may therefore be less effective than ZDV in the treatment of the infected fetus. However, the uninfected fetus of an HIV-infected woman will gain by reduced exposure to a drug that is known to be toxic.

Didanosine↗
PubMed1992

Transfer and metabolism of retinol by the perfused human placenta.

The transfer and metabolism of retinol by human placenta was investigated using an in vitro perfusion system with independent maternal and fetal circulations. 3H-retinol bound to albumin added to the maternal perfusate was rapidly taken up and concentrated by the placenta to levels 16.5 +/- 5.28 times the maternal perfusate. Approximately 8% of the retinol retained in the placenta was esterified. No metabolites were detected in the perfusates. Perfusion of placenta with retinol bound to retinol-binding protein (RBP) reduced the placental concentration to 4.4 +/- 1.72 times the maternal concentration and eliminated evidence of metabolism. The transfer rate of RBP:3H-retinol was less than that of albumin:14C-retinol when measured concurrently in three experiments (clearances 0.11 versus 0.75 mL/min, 0.21 versus 1.7 mL/min, and 0.29 versus 0.48 mL/min, respectively). Transfer of the radioactive retinol was more rapid than 125I-RBP or albumin, indicating that retinol was transferred independently of the proteins. The transfer index of retinol (clearance retinol:clearance L-glucose) was 0.73 +/- 0.085 compared to 2.1 +/- 0.36 for thiamin and 3.4 +/- 0.95 for riboflavin, both water-soluble vitamins with active transport systems. The retinol transferred to the fetal perfusate is not bound to RBP, as demonstrated by gel filtration chromatography and chromatography on a transthyretin affinity column, despite the availability of RBP in the cord serum added to the perfusate. The endogenous retinol in the cord serum is bound to RBP.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport, Active↗
PubMed1990

Transfer of zidovudine (AZT) by human placenta.

The transfer of zidovudine (AZT) across human placenta was studied using an in vitro perfusion system with independent maternal and fetal circulations. AZT is transferred toward the fetus more rapidly than L-glucose (transfer index 1.5), a water-soluble molecule smaller than AZT (267 vs. 180 Da) that passively diffuses across the placenta. The transfer rate is proportional to the concentration in the maternal perfusate over a range of 0.03-300 microM. Transfer rate in the reverse direction, toward the maternal perfusate, also exceeds that of L-glucose and fails to show saturability. These observations are consistent with simple diffusion. The partition of AZT and glucose between perfusion buffer and octanol is 1.04 and 0.013, respectively, indicating that AZT is more lipophilic and providing a reasonable explanation for the more rapid transfer. AZT is extensively metabolized by the placenta to more polar and as yet unidentified metabolites that are not released into the perfusate. The possibility that the placental accumulation of such metabolite(s) may exert an antiviral action and may also affect placental function must be considered.

Chromatography, High Pressure Liquid↗
PubMed1989

Bolus tocolysis: treatment of preterm labor with pulsatile administration of a beta-adrenergic agonist.

The treatment of premature labor with beta-adrenergic substances is complicated by side effects. Although most human control mechanisms are pulsatile, therapy is usually administered continuously. We designed a microprocessor-controlled pump to allow pulsatile tocolytic infusion, hoping to reduce the total dose and thus the side effects. In 33 patients pulsatile bolus tocolysis was compared with continuous tocolysis in a control group of 38 patients. Bolus tocolysis required considerably less beta-sympathomimetic agent for comparable therapeutic success (median dosage 3.0 versus 15.9 mg, p less than 0.001). Duration of therapy under bolus tocolysis was also significantly shorter (p less than 0.05). Birth weight was higher after bolus tocolysis (median 3070 versus 2580 gm, p = 0.05). Additional indicators favored bolus tocolysis but were not statistically significant: a longer gestational period, fewer infants weighing less than 2500 gm, and a lower incidence of respiratory distress syndrome. Pulmonary edema occurred in one patient during continuous tocolysis.

Adrenergic beta-Agonists↗