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Biomedical subjects

P W Evans

Publications and source records attributed to P W Evans.

8 recordsLinked to original sources
PubMed1999

Relationship between maternal serum vascular endothelial growth factor concentration in early pregnancy and fetal and placental growth.

Vascular endothelial growth factor (VEGF) has important effects on endothelial cells increasing cell proliferation, permeability and nitric oxide production; concentrations of VEGF in the maternal serum increase during the first 10 weeks of pregnancy. In this study, the relationship of maternal serum VEGF with maternal health during pregnancy and with fetal and placental size at mid-pregnancy and at term was investigated. Serum was obtained from 539 Caucasian women with singleton pregnancies between 8 and 20 weeks of pregnancy (mean 14 weeks). Total serum VEGF concentrations were measured by direct competitive radioimmunoassay. Fetal size and placental volume were measured by ultrasound between 16 and 20 weeks gestation. Birthweight, placental weight and anthropometric measurements of the baby were obtained after delivery. Serum VEGF concentrations were found to be higher in women with a lower weight before pregnancy (P = 0.01) and in those carrying a female fetus (P = 0.002). VEGF concentrations were positively correlated with placental volume (r = 0.17, P = 0.0001) but not with fetal size between 16 and 20 weeks gestation. Serum VEGF concentrations were positively correlated with both birthweight (r = 0.10, P = 0.02) and placental weight at delivery (r = 0.13, P = 0.003). The data presented support the view that VEGF may be one of the factors involved in mediating the maternal cardiovascular adaptation to pregnancy.

Adolescent↗
PubMed1998

A longitudinal study of maternal serum vascular endothelial growth factor in early pregnancy.

Using a competitive radioimmunoassay to measure total immunoreactive vascular endothelial growth factor (VEGF), we describe for the first time longitudinal changes in serum VEGF in early pregnancy. The measurements were obtained from 26 women following the transfer of cryopreserved embryos; 18 singleton and eight twin pregnancies were identified by ultrasound at 6 weeks gestation and subsequently delivered as live births. Subjects did not have corpora lutea and exogenous hormone support was provided for the first 70 days of pregnancy. Serum VEGF increased approximately 30 days after embryo transfer and thereafter continued to rise in both singleton and twin pregnancies over a period of 20-40 days after which concentrations remained elevated. The longitudinal profile of serum VEGF concentrations was characterized by a logistic curve for singleton and twin pregnancies; the profile of VEGF concentrations in the twin pregnancies was significantly higher than in the singleton pregnancies (P < 0.0001). Profiles of the longitudinal concentrations of serum human chorionic gonadotrophin (HCG), oestradiol and progesterone were created by polynomial regression for singleton and twin pregnancies. The VEGF profiles were positively correlated with the profiles of HCG (r = 0.44, P = 0.02) and oestradiol (r = 0.36, P = 0.07) but not progesterone (r = 0.16, P = 0.42). Serum VEGF concentrations in the singleton thawed embryo pregnancies were compared with gestation-matched normal singleton pregnancies with corpora lutea. Concentrations of VEGF were significantly (P = 0.004) greater in the pregnancies with corpora lutea although this difference became less marked with advancing gestation. In addition to its important role in angiogenesis, we speculate that VEGF is involved in mechanisms which control the maternal cardiovascular adaptation to pregnancy.

Chorionic Gonadotropin↗
PubMed1997

Variation in detection of VEGF in maternal serum by immunoassay and the possible influence of binding proteins.

Using radioimmunoassay (RIA) and a polyclonal antibody we have shown that maternal serum vascular endothelial growth factor (VEGF) is elevated during pregnancy. In contrast, a commercial VEGF ELISA utilizing a sandwich two-site immunoassay was unable to detect VEGF in 19 of the 20 maternal serum samples analysed. In addition, the recovery of exogenous VEGF added to the pregnancy samples was low or not recordable with the ELISA. Using RIA, 82-101% of the added VEGF was recovered. These differing results could be explained by the formation of VEGF-protein complexes that are detectable using RIA but undetectable with the ELISA. Our data imply that there is a substantial increase in circulating VEGF binding proteins during pregnancy. The increase in VEGF and its binding proteins during pregnancy may reflect important physiological events in the mother and feto-placental unit.

Blood Proteins↗
PubMed1985

Biochemical studies of human placental microvillous plasma membrane proteins.

Isolated human syncytiotrophoblast microvillous plasma membranes (StMPM) have been examined by electron microscopy, SDS-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional PAGE (2D-PAGE), and immunoblots. Electron microscopy of StMPM pellets revealed populations of membrane-bounded vesicles that disrupted after treatment with the chaotrope 3M KCl for 16 hr; with increasing molarity of another chaotrope (NH4SCN), the vesicles became smaller and more homogeneous. NH4SCN treatment resulted in significant reduction on SDS and 2D-PAGE analysis of only one protein at 80kd, shown by immunoblotting to be transferrin; 3M KCl had little effect and appeared to be a poor chaotrope. Chromogenic silver staining of SDS-PAGE gels demonstrated over 50 StMPM-associated discrete protein components. Immunoblotting revealed transferrin (80kd), albumin (65kd), IgG heavy chain (56kd), and Gc protein (56kd). Alpha-2-macroglobulin (alpha 2M) was identified at 180kd and 95kd; the smaller component may be a proteolytic derivative indicating alpha 2M binding to a trophoblast surface protease. Numerous discrete protein dots, and groups of dots characteristic of charge heterogeneity of individual proteins, were observed on high resolution 2D-PAGE. The most intensely stained proteins were transferrin (80kd), albumin (65kd), placental-type alkaline phosphatase (66kd), and actin (46kd). This 2D-PAGE technique is a superior method for analyzing the trophoblast membrane proteins, and the system described will enable systematic mapping of these components.

Albumins↗
PubMed1982

Oxalosis in infancy.

We describe 3 infants with nephrocalcinosis and terminal renal failure. In all 3 there was widespread oxalate deposition: biochemical evidence of primary hyperoxaluria was sought but the presence of severe renal failure and the lack of established normal values for urinary and plasma oxalate and glycollate in infants made this diagnosis difficult to establish.

Calcium Metabolism Disorders↗
PubMed1979

Preliminary experience with controlled-release aminophylline in asthmatic children: salivary levels and peak flow following a single dose.

Preliminary experience of a controlled-release aminophylline tablet in twenty-five asthmatic children has been gained by measuring salivary theophylline levels and peak flow after a single dose (11 mg/kg). The results were compared with an oral theophylline preparation. Mean salivary levels remained elevated at eight hours following ingestion of controlled-release aminophylline, at which time 58% of the children continued to show an improvement in peak flow. Individual children showed a wide variation in salivary levels and respiratory response. It is recommended that theophylline levels should be monitored in the saliva to ensure maximum benefit from the drug.

Adolescent↗