Concentration of free vascular endothelial growth factor and its soluble receptor, sFlt-1 in the maternal and fetal circulations of normal term pregnancies at high and low altitudes.

OBJECTIVE: Vascular endothelial growth factor (VEGF) is regulated by hypoxia that is essential for placental development. It is antagonized by a soluble form of its receptor (sFlt-1). The purpose of this study was to measure these factors in the maternal and the cord bloods, at low and high altitude. METHODS: Samples were collected from full term births normal pregnant women. Free (unbound) VEGF and sFlt-1 levels were measured in plasma samples from cord and maternal blood for each subject by enzyme-linked immunosorbent assay (ELISA) using commercially available kits from R&D systems, UK (Cat # DVE00 and Cat # SVR100B, respectively). RESULTS: At high altitude, the average maternal free VEGF in pg/ml was significantly (p < 0.001) lower than that of the cord level (71.30 ± 282.14 and 431.35 ± 424.31, respectively). On the other hand, the average maternal sFlt-1 was significantly (p < 0.001) higher than that of the cord level (8205.41 ± 6244.72 and 1811.74 + 3469.30, respectively). At low altitude, the average maternal free VEGF was significantly lower than that of the cord level (0.47 ± 0.89 and 483.44 ± 457.31, respectively, p < 0.001). On the other hand, the average maternal sFlt-1 was significantly higher than that of the cord level (9267.82 ± 6345.68 and 958.66 ± 1359.92, respectively, p < 0.001). There were no significant differences by altitude. CONCLUSION: Secretion of sFlt-1 appears to be polarized, in that concentrations are higher in the maternal compartment than on the fetal side at both high and low altitudes. This may be a normal physiological phenomenon to permit angiogenesis in the placenta and fetus while protecting the mother. Chronic exposure to hypobaric hypoxia at high altitude does not affect these distributions.

Concentrations of free vascular endothelial growth factor in the maternal and foetal circulations during pregnancy: a cross-sectional study.

OBJECTIVE: To investigate the concentrations of free plasma vascular endothelial growth factor (VEGF) in the maternal and foetal circulations of normal term pregnancies. METHODS: Free plasma VEGF was measured from plasma of umbilical cord and maternal blood by ELISA for each of 20 normal pregnancies delivering at term at an altitude of 3100 m. Spearman's correlation coefficient was used to test for correlation between values and clinical maternal and neonatal data. Student's 't' test was used to test for differences between samples from male and female neonates. RESULTS: Free plasma VEGF was undetectable from maternal samples, but it was detectable in the cord blood (mean, 560.3775 pg/ml, median, 145.84 pg/ml, range, 22.56-2653.5). No differences were found between neonates sex, and no correlation was found with clinical maternal and neonatal data. CONCLUSION: Circulating VEGF is usually bound to the soluble form of its receptor 1 (sFlt-1). High levels of sFlt-1 are secreted by the syncytiotrophoblast during pregnancy, and so free plasma VEGF is undetectable in the maternal circulation. In contrast, our findings are the first to show free plasma VEGF in the umbilical circulation. We speculate that this free VEGF may promote angiogenesis in the foetus and placenta. Our data imply that sFlt-1 is not present in the cord blood, and that secretion by the syncytiotrophoblast is polarised to its apical surface. Further investigations are required to test this hypothesis.

Diversity of detoxification pathways of ingested ecdysteroids among phytophagous insects.

The metabolic pathways of ingested ecdysteroids have been investigated in three insect species, the aphid Myzus persicae and two Lepidoptera, Plodia interpunctella and Ostrinia nubilalis. M. persicae produces mainly a 22-glucoside conjugate, whereas P. interpunctella eliminates a mixture of 20E and its 3-oxo and 3-epi derivatives, both in free form and as conjugates with various fatty acids. O. nubilalis only produces fatty acyl ester conjugates. These data point out the great diversity of detoxification mechanisms used by phytophagous insects in order to overcome the potential harmful effects of ecdysteroids present in their food.

Within-species variability of the response to 20-hydroxyecdysone in peach-potato aphid (Myzus persicae Sulzer).

Phytoecdysteroids have been proposed as new tools for controlling crop pests because of their endocrine disruption and deterrent effects on insects and nematodes. There is increasing evidence of variability between taxa in sensitivity to phytoecdysteroids, but the genetic variability of this sensitivity within species is unknown. However, knowledge about this intraspecies variability is required for predicting evolution of the pest's response to new control methods. We assessed the variability of the response of the aphid Myzus persicae Sulzer, a major agricultural pest, to 20-hydroxyecdysone (20E). We determined the number of nymphs produced by six clones of M. persicae exposed to various concentrations of 20E and the capacity of these clones to detect 20E in choice experiments. High concentrations of 20E significantly decreased the number of nymphs produced for two clones and both increases and decreases in the number of offspring were detected at low concentrations. Two clones significantly avoided food with 20E, while one significantly preferred it, suggesting that 20E does not always act as a deterrent in this species. We conclude that genetic variability in the response to 20E exists in natural populations of M. persicae. The consequences of this finding on the sustainability of control methods using 20E are discussed.

[Mevalonolactone: a volatile compound produced by Psammotettix alienus (Dhb)]. / La mévalonolactone: un composé volatil produit par Psammotettix alienus (Dhb).

The interaction between the aphid Rhopalosiphum padi (L.) and the leafhopper Psammotettix alienus was investigated in the laboratory. The leafhoppers, when physically separated from aphid but with a common air supply, caused a reduction in aphid offspring production. One of the hypotheses to explain this result is that volatile compounds might be responsible for the effect on the aphid reproduction. To verify this hypothesis, leafhopper static headspace was subjected to GC-MS (gas chromatography-mass spectrometry) analyses. An original compound was identified in the leafhopper headspace as mevalonolactone (Mev) and was found to be produced only by adults. This is the first report of Mev released in the headspace of either an insect or living organisms in general. Two other new compounds in insects were also identified in both leafhopper nymphs and adults: 2-(2-hydroxypropoxy)-1-propanol and 3,3'-oxybis-2-butanol.