8 research outputs found
Multiple Pregnancy after Gonadotropin-Intrauterine Insemination: An Unavoidable Event?
Objective. Determine which factors predict multiple pregnancy in gonadotropin-intrauterine insemination cycles so that cancellation criteria might be developed. Study Design. Retrospective chart review of all patients undergoing gonadotropin-intrauterine insemination over a continuous 36 month period. Results. No factors examined were able to predict the occurrence of multiple pregnancy. Conclusion. Multiple pregnancy is an unavoidable complication of gonadotropin-intrauterine insemination treatment
Regulation of human trophoblast GLUT1 glucose transporter by insulin-like growth factor I (IGF-I)
Glucose transport to the fetus across the placenta takes place via glucose transporters in the opposing faces of the barrier layer, the microvillous and basal membranes of the syncytiotrophoblast. While basal membrane content of the GLUT1 glucose transporter appears to be the rate-limiting step in transplacental transport, the factors regulating transporter expression and activity are largely unknown. In view of the many studies showing an association between IGF-I and fetal growth, we investigated the effects of IGF-I on placental glucose transport and GLUT1 transporter expression. Treatment of BeWo choriocarcinoma cells with IGF-I increased cellular GLUT1 protein. There was increased basolateral (but not microvillous) uptake of glucose and increased transepithelial transport of glucose across the BeWo monolayer. Primary syncytial cells treated with IGF-I also demonstrated an increase in GLUT1 protein. Term placental explants treated with IGF-I showed an increase in syncytial basal membrane GLUT1 but microvillous membrane GLUT1 was not affected. The placental dual perfusion model was used to assess the effects of fetally perfused IGF-I on transplacental glucose transport and syncytial GLUT1 content. In control perfusions there was a decrease in transplacental glucose transport over the course of the perfusion, whereas in tissues perfused with IGF-I through the fetal circulation there was no change. Syncytial basal membranes from IGF-I perfused tissues showed an increase in GLUT1 content. These results demonstrate that IGF-I, whether acting via microvillous or basal membrane receptors, increases the basal membrane content of GLUT1 and up-regulates basal membrane transport of glucose, leading to increased transepithelial glucose transport. These observations provide a partial explanation for the mechanism by which IGF-I controls nutrient supply in the regulation of fetal growth
Timeline of control and experimental perfusions.
<p>A stabilization phase of 30 minutes (open fetal circulation) and 60 minutes (closed fetal circulation) was used in both control and experimental perfusions. Maternal perfusion was started 30 min after the beginning of the fetal circulation. Between 90 and 120 min the intervillous space was perfused with medium containing [<sup>3</sup>H] 3-O-methyl-D-glucose and [<sup>14</sup>C] L-glucose (0.064 and 0.032 ”Ci/ml, respectively) to establish rates of transfer from the maternal to fetal circulation (open fetal circulation). After the initial sampling from the maternal and fetal circulations, the fetal circulation was closed and perfusion was continued for 2 hours. During this period, the fetal perfusate in the experimental perfusions contained IGF-I (100 ng/mL) whereas the control perfusions contained no addition. After another 30-minute phase of perfusion with radiolabeled glucose on the maternal side and open circulation on the fetal side, samples were obtained from both circulations. The fetal circulation was again closed and perfusion was continued for another 2 hours containing IGF-I (experimental) or no addition (control). After a final 30 minute period of perfusion with radiolabeled glucose, perfusions were terminated following the final sampling from fetal and maternal circulations.</p
Placental perfusion.
<p>Placental perfusion was performed as described in the text, according to the protocol in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106037#pone-0106037-g004" target="_blank">Figure 4</a>. (A) <i>Maternal-fetal glucose transport</i>. At tâ=â2, 4.5 and 7 hr., samples were taken from the maternal and fetal circulations and the % maternal-fetal transfer of [<sup>3</sup>H] 3-O-methyl-D-glucose and [<sup>14</sup>C] L-glucose was calculated for the control perfusions and those that were perfused with IGF-I (100 ng/mL). There was a significant linear decrease in the transfer of [<sup>3</sup>H] 3-O-methyl-D-glucose in the control perfusions over time (p<0.01, repeated measures ANOVA, linear trend post test; nâ=â4) whereas there was no change in % transfer in the IGF-I perfusions. In addition, no changes were noted in the diffusional transfer component in either the control or experimental group, shown here as the combined data. (B) <i>GLUT1 protein expression</i>. Immediately prior to perfusion, tissue samples were taken from non-perfused areas for preparation of microvillous and basal membrane fractions (immediate controls). After perfusion, the perfused lobules were dissected out and used for preparation of microvillous and basal membrane fractions. The two membrane fractions were slot-blotted to determine GLUT1 protein expression. The results show the effects of IGF-I on microvillous and basal membrane GLUT1 in the perfusions as a fraction of the GLUT1 protein expression in the respective immediate control samples. In the microvillous and basal samples from control perfusions there was a decrease in GLUT1 relative to the expression prior to perfusion. A similar result was obtained for the basal membrane from the control perfusion, however the basal membrane GLUT1 expression from the IGF-I perfusion was increased (p<0.05, one sample t test, nâ=â4).</p
GLUT1 transport and IGF-I in BeWo cells.
<p>(A) <i>Transepithelial transport</i>: BeWo cell monolayers plated on permeable inserts were treated for 24 hr. with 200 ng/ml IGF-1 following serum-starvation. Measurements of the transepithelial transport of glucose were performed in the presence and absence of 2 mM phloretin (see Methods). Transcellular transport was calculated as the phloretin-inhibitable fraction of transepithelial transport. The results showed that treated cells had an increased rate of transcellular glucose transport (p<0.05, paired t test, nâ=â4). (B) <i>Cellular uptake</i>: BeWo cell monolayers plated on permeable inserts were serum starved then treated for 24 hr. with 200 ng/mL IGF-1. Following treatment, uptake of [<sup>3</sup>H] 2-deoxyâD-glucose into the cells across the apical or basolateral face was measured. The rate of glucose uptake across the apical face was not altered by IGF-I treatment. The rate of uptake across the basolateral face was increased by IGF-I treatment (p<0.01, paired t test, nâ=â4).</p
IGF-I effects on BeWo cells.
<p>(A) <i>Dose-response</i>: Serum-starved BeWo cells were treated for 24 hr. with IGF-I at doses ranging from 5 to 200 ng/mL. Extracted cell samples were used to measure GLUT1 by slot blotting. The graph shows that treated BeWo cells demonstrate a GLUT1 dose response to IGF-I terminating at a level 1.6-fold greater than control; (p<0.05, ANOVA, nâ=â3). (B) <i>Time course</i>: Serum-starved BeWo cells were treated with IGF-1 (200 ng/mL) for times ranging from 6 hr. to 48 hr. Extracted cell samples were used to measure GLUT1 by slot blotting. The graph shows that increased levels of GLUT1 were observed by 12 hr. with maximal levels achieved by 24 hr. (p<0.01, ANOVA, nâ=â3).</p