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James M Roberts

Publications and source records attributed to James M Roberts.

At least 73 records · Page 4Linked to original sources
PubMed2003

The 677 C-T methylenetetrahydrofolate reductase mutation does not predict increased maternal homocysteine during pregnancy.

OBJECTIVE: To test the hypothesis that, regardless of the presence of the 677 C-T methylenetetrahydrofolate reductase (MTHFR) mutation, maternal homocysteine concentrations will not be significantly different in women who are taking prenatal vitamins containing folic acid, and to test this relationship in preeclampsia because homocysteine concentrations are higher in preeclamptic pregnancies. METHODS: Fifty-seven pregnant white women (control and preeclamptic) with and without the 677 C-T MTHFR mutation were studied. Total plasma homocysteine and plasma folic acid were analyzed. RESULTS: Homocysteine concentrations were not different by MTHFR genotype (wild type 677 CC 8.7 +/- 5.6 microM versus mutant 677 TT 9.0 +/- 5.7 microM, P =.84) in preeclamptic or normal pregnancies. However, mean homocysteine concentrations were significantly increased in preeclamptic pregnancies compared with those in normal pregnancies (10.6 +/- 7.3 microM versus 7.2 +/- 3.0 microM, P <.03) as previously reported. CONCLUSION: The 677 C-T MTHFR polymorphism does not significantly affect maternal homocysteine concentrations in most women taking prenatal vitamins including women with preeclampsia. The increase in plasma folic acid likely affects maternal homocysteine more than the MTHFR genotype. If homocysteine is considered a thrombophilia risk factor, the concentration of the amino acid and not a particular genotype should be determined.

Adult↗
PubMed2003

Multisite phosphorylation by Cdk2 and GSK3 controls cyclin E degradation.

Autophosphorylation-triggered ubiquitination has been proposed to be the major pathway regulating cyclin E protein abundance: phosphorylation of cyclin E on T380 by its associated CDK allows binding to the receptor subunit, Fbw7, of the SCFFbw7 ubiquitin ligase. We have tested this model in vivo and found it to be an inadequate representation of the pathways that regulate cyclin E degradation. We show that assembly of cyclin E into cyclin E-Cdk2 complexes is required in vivo for turnover by the Fbw7 pathway; that Cdk2 activity is required for cyclin E turnover in vivo because it phosphorylates S384; that phosphorylation of T380 in vivo does not require Cdk2 and is mediated primarily by GSK3; and that two additional phosphorylation sites, T62 and S372, are also required for turnover. Thus, cyclin E turnover is controlled by multiple biological inputs and cannot be understood in terms of autophosphorylation alone.

Animals↗
PubMed2003

Telomerase modulates expression of growth-controlling genes and enhances cell proliferation.

Most somatic cells do not express sufficient amounts of telomerase to maintain a constant telomere length during cycles of chromosome replication. Consequently, there is a limit to the number of doublings somatic cells can undergo before telomere shortening triggers an irreversible state of cellular senescence. Ectopic expression of telomerase overcomes this limitation, and in conjunction with specific oncogenes can transform cells to a tumorigenic phenotype. However, recent studies have questioned whether the stabilization of chromosome ends entirely explains the ability of telomerase to promote tumorigenesis and have resulted in the hypothesis that telomerase has a second function that also supports cell division. Here we show that ectopic expression of telomerase in human mammary epithelial cells (HMECs) results in a diminished requirement for exogenous mitogens and that this correlates with telomerase-dependent induction of genes that promote cell growth. Furthermore, we show that inhibiting expression of one of these genes, the epidermal growth factor receptor (EGFR), reverses the enhanced proliferation caused by telomerase. We conclude that telomerase may affect proliferation of epithelial cells not only by stabilizing telomeres, but also by affecting the expression of growth-promoting genes.

Breast↗
PubMed2003

Changes in markers of vascular injury in response to transient hyperhomocysteinemia.

The purpose of this study was to test whether transient increases in homocysteine would promote changes in markers of endothelial injury, cellular fibronectin (cFN), and soluble vascular cell adhesion molecule 1 (sVCAM-1). Homocysteine, cFN, and sVCAM-1 concentrations increased significantly in response to a methionine load by 6 hours in human subjects. However, no correlation was observed between homocysteine and cFN or sVCAM-1. To directly test whether homocysteine can injure endothelial cells, human umbilical vein endothelial cells (HUVEC) were incubated with increasing concentrations of homocysteine, plasma, or serum from hyperhomocysteinemic mice or from the methionine-loaded test subjects. cFN release was increased from endothelial cells cultured with plasma (but not serum) of hyperhomocysteinemic transgenic mice or from methionine-loaded human subjects. These data suggest that very high homocysteine concentrations can promote endothelial injury; however, this effect is likely mediated by secondary effects that include a factor(s) present in plasma that affects endothelial cells.

Adult↗
PubMed2003

Smoking during pregnancy is associated with alterations in markers of endothelial function.

OBJECTIVE: Alterations in endothelial function may explain the reduced risk of preeclampsia that is associated with smoking. We hypothesized that markers of endothelial function increase over pregnancy but decrease with smoking. STUDY DESIGN: Plasma samples were obtained throughout pregnancy from 63 primiparous women with normal pregnancies. The samples were assayed for cellular fibronectin, vascular cell adhesion molecule-1, and intracellular adhesion molecule-1. Smoking status was determined by urinary cotinine concentrations. RESULTS: Mean cellular fibronectin concentrations were different by time (P<.001) and smoking status (P=.01); the lowest concentrations were found in smokers. In contrast, intracellular adhesion molecule-1 was different by smoking status (P=.046); the highest concentrations were found in smokers. Vascular cell adhesion molecule-1 was different over time (P<.001), but not by smoking status. CONCLUSION: Smoking during pregnancy is associated with reduced cellular fibronectin and increased intracellular adhesion molecule-1. These differences may be the result of different aspects of endothelial function or the source of the marker. The explanation for reduced preeclampsia in smokers remains elusive.

Biomarkers↗
PubMed2003

Interleukin-6 promoter -174 polymorphism and spontaneous preterm birth.

OBJECTIVE: We assessed the relationship between interleukin-6 (IL-6) promoter -174 polymorphism and spontaneous preterm birth (sPTB) less than 34 weeks and the relationship of polymorphism status with race. STUDY DESIGN: Polymerase chain reaction was used to evaluate DNA from 156 controls who delivered after spontaneous labor at term and 51 subjects who had sPTB less than 34 weeks. RESULTS: Among the 156 controls, the C/C variant was present in 30 (19.2%). Among the 51 subjects, the C/C variant was present in 2 (6.3%) (odds ratio 0.17, 95% CI 0.04-0.74). Among white women, the C/C variant was present in 30 (27.2%) controls but only 2 (5.2%) cases. No African American women carried the C/C variant. The racial disparity was statistically significant. (P<.001) CONCLUSION: The IL-6 promoter -174 allelic variant C/C is significantly less frequent among women with sPTB less than 34 weeks. There is a dramatic racial disparity in the distribution of allelic variants of this polymorphism.

Black People↗
PubMed2003

Summary of the NHLBI Working Group on Research on Hypertension During Pregnancy.

A Working Group on Research in Hypertension in Pregnancy was recently convened by the National Heart Lung and Blood Institute to determine the state of knowledge in this area and suggest appropriate directions for research. Hypertensive disorders in pregnancy, especially preeclampsia, are a leading cause of maternal mortality worldwide and even in developed countries increase perinatal mortality five-fold. Much has been learned about preeclampsia but gaps in the knowledge necessary to direct therapeutic strategies remain. Oxidative stress is a biologically plausible contributor to the disorder that may be amenable to intervention. Hypertension that antedates pregnancy (chronic hypertension) bears many similarities to hypertension in nonpregnant women but the special setting of pregnancy demands information to guide evidence based therapy. The recommendations of the Working Group are to attempt a clinical trial of antioxidant therapy to prevent preeclampsia that is be complemented by mechanistic research to increase understanding of the genetics and pathogenesis of the disorder. For chronic hypertension clinical trials are recommended to direct choice of drugs, evaluate degree of control and assess implications to the mother and fetus. Recommendations to increase participation in this research are also presented.

Adult↗
PubMed2003

Subclassification of preeclampsia.

Preeclampsia is a heterogeneous disorder, and as with other diseases (e.g., type I and type II diabetes), progress in the understanding of this disorder would be assisted greatly if subtypes could be characterized. We suggest that a first step would be to subdivide preeclampsia into early-onset disease (< 34 + 0 weeks') and late onset disease (> 34 + 0 weeks').

Adult↗
PubMed2003

Maternal serum oestrogen and androgen concentrations in preeclamptic and uncomplicated pregnancies.

BACKGROUND: Epidemiological studies show a substantially reduced risk of breast cancer in adult daughters of preeclamptic pregnancies, and modest risk reductions have been demonstrated for mothers also. Alterations in pregnancy hormone concentrations, particularly lower in utero exposure to oestrogen, are hypothesized to mediate this association. METHODS: Pregnancy hormone concentrations were measured in maternal sera collected at hospital admission for labour and delivery from 86 preeclamptic and 86 uncomplicated, singleton pregnancies matched on length of gestation, maternal age, parity, and type of delivery. RESULTS: Case and control pregnancies were similar in several maternal and pregnancy factors. Serum unconjugated oestradiol, oestrone, and oestriol concentrations were not lower in preeclamptic pregnancies in a matched analysis with adjustment for race and whether blood was collected before or after labour commenced. Serum unconjugated androstenedione (506.3 versus 316.0 ng/dl; P = 0.0007) and testosterone concentrations (214.5 versus 141.9 ng/dl; P = 0.004), however, were significantly higher in preeclamptic compared with control pregnancies, whereas dehydroepiandrosterone (DHEA) and DHEA sulphate did not differ. CONCLUSIONS: These data do not support the hypothesis that cancer risk in mothers and offspring of preeclamptic pregnancies is explained by exposure to lower maternal blood oestrogen concentrations, but raise the possibility that androgens play a role.

Adult↗
PubMed2003

Nutrient involvement in preeclampsia.

Preeclampsia is a pregnancy-specific condition that increases maternal and infant mortality and morbidity. It is diagnosed by new-onset increased blood pressure and proteinuria during gestation; for many years these markers were the sole targets for study. More recently, increased attention to the multisystemic nature of the syndrome with involvement of almost all organs, activation of coagulation and increased sensitivity to pressor agents has expanded understanding of the disorder. The epidemiology of preeclampsia, being more common in poor women, long ago suggested that nutrients might be involved in the disorder. Numerous conflicting hypotheses were advanced but the testing of these hypotheses has either been done poorly or not at all. Review of the available data indicates very few studies that provide useful insights. In many studies the syndrome is poorly defined and in most studies nutritional data (questionnaires or biomarkers) are obtained on women with the clinical syndrome. In overtly preeclamptic women it is impossible to decipher cause from effect. Nonetheless, current concepts of the genesis of preeclampsia that include endothelial dysfunction, inflammatory activation, oxidative stress and predisposing maternal factors provide targets for well-designed nutritional investigation. In this review the current concepts of the pathogenesis of preeclampsia are reviewed and available data are assessed in light of these concepts. Targets for nutritional investigation based on the current knowledge of pathophysiology are suggested.

Blood Pressure↗
PubMed2003

Correlation of serum hormone concentrations in maternal and umbilical cord samples.

Evidence suggests that adult cancer risk of hormonally related tumors may be influenced by the in utero environment, and most speculation on the biological mechanism has focused on the hormonal component. Epidemiological studies investigating the biological nature of pregnancy and maternal factors associated with offspring's cancer risk have relied on maternal hormone measurements. The degree to which maternal hormone levels represent the fetal environment, however, is not widely known. Pregnancy estrogen, androstenedione, testosterone, dehydroepiandrosterone (DHEA), and DHEA-sulfate concentrations were measured in maternal and mixed umbilical cord sera from 86 singleton pregnancies. Spearman correlations between maternal and cord hormone levels generally ranged between 0.2 and 0.3. The correlation was 0.26 for estriol, the estrogen of highest concentration in pregnancy, and 0.27 for estradiol, the most biologically active estrogen. The correlations between mother and offspring for the estrogens and DHEA appeared similar for males and females, whereas there was a suggestion that the maternal-umbilical cord correlations for other androgens varied in magnitude by fetal sex, and all correlations appeared higher in pregnancies lasting <38 weeks compared with longer gestational lengths, although these stratified findings may have been attributable to chance. These data show a moderate degree of correlation in hormone concentrations between the maternal and fetal circulation. Studies using maternal hormone concentrations as a proxy for the fetal environment should consider the misclassification resulting with the use of this marker.

Adult↗
PubMed2003

Estrogen and androgen concentrations are not lower in the umbilical cord serum of pre-eclamptic pregnancies.

Reductions in breast cancer risk observed in daughters of pre-eclamptic pregnancies are hypothesized to be mediated by lower in utero estrogen concentrations. Whereas maternal urinary estriol excretion is generally lower in pre-eclamptic women, results for maternal blood concentrations are equivocal, and little is known about estrogen concentrations in the cord of pre-eclamptic pregnancies. Unconjugated estrogen and androgen concentrations were measured in mixed umbilical cord sera from 86 pre-eclamptic and 86 uncomplicated, singleton pregnancies, matched on length of gestation, maternal age, parity, and type of delivery. Pre-eclamptic and uncomplicated pregnancies were similar in maternal age, prepregnancy weight, maternal height, type of delivery, use and type of anesthesia, and sex of offspring. Estriol, estradiol, estrone, dehydroepiandrosterone, dehydroepiandrosterone-sulfate, androstenedione, and testosterone concentrations measured in cord sera were not significantly different in pre-eclamptics compared with uncomplicated pregnancies. Estriol was 9% lower (P = 0.43), and all of the other hormones were actually higher in pre-eclamptics with testosterone and estradiol approaching statistical significance (P = 0.06 and P = 0.12, respectively). These data do not support the hypothesis that the lower breast cancer risk in daughters of pre-eclamptic pregnancies is explained by lower in utero estrogen exposure.

Adolescent↗
PubMed2002

Influence of the hofmeister series on the retention of amines in reversed-phase liquid chromatography.

The chromatographic behavior of protonated amines in reversed-phase liquid chromatography (RPLC) is influenced markedly by the identity of the mobile-phase anion. For example, retention factor values, k, obtained from protonated nordoxepin, nortriptyline, and amitriptyline increase almost 1 order of magnitude across the following series of anions employed as mobile-phase modifiers: H2PO4- < HCOO- < CH3SO3- < Cl- < NO3- < CF3COO- < BF4- < ClO4- < PF6-. Early eluting primary, secondary, and tertiary benzylamines are retained and resolved using BF4-, ClO4-, and PF6- but elute in or very near the void using all other mobile-phase anions tested. In contrast, a neutral hydrophobic marker, acenaphthene, shows no significant changes in retention with mobile-phase anion identity. Such large differences in amine retention with anion identity can be rationalized via both an ion-pairing model and the Hofmeister effect. Two key findings are reported. First, the dependence of amine retention on mobile-phase anion identity is attributed unambiguously to the Hofmeister effect and is quantified using a simple equation based solely on differences in the solvation of anions. Accurate prediction of k values from the excess chemical potential of anions in water suggests that anion-solvent interactions dominate the retention of amines in RPLC. Thus, controlling amine retention depends critically on judicious selection of mobile-phase anion (in addition to the usual experimental parameters such as organic modifier, temperature, pH, and stationary phase). Second, more lipophilic molecular anions can provide retention and tailing properties comparable to those obtained from traditional amphiphilic ion-pairing reagents such as octanesulfonate, but with the benefit of a superior gradient background and solubility at high concentrations of organic modifier.

Amines↗
PubMed2002

Oscillation sensation.

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Anaphase-Promoting Complex-Cyclosome↗
PubMed2002

The factor V leiden mutation and the risk of venous thromboembolism in gynecologic oncology patients1.

OBJECTIVE: To measure the strength of the association between the factor V Leiden mutation and venous thromboembolism in gynecologic oncology patients. METHODS: We conducted a case-control study of gynecologic cancer patients in a referral center who were group matched for demographics, tumor type, and treatment. The prevalence of the factor V Leiden mutation was determined in both cases and controls, and an odds ratio was calculated. The factor V Leiden mutation was detected using polymerase chain reaction amplification and nucleic acid restriction digest of deoxyribonucleic acid extracted from leukocytes. RESULTS: Seventy-five patients were enrolled in the study. Seventy-four samples were available for analysis. There were no differences between the cases and controls with respect to age, race, body mass index, smoking, cancer type, high stage (III or IV) of cancer, or treatment modality. The odds ratio for having the factor V Leiden mutation in patients with venous thromboembolism was 0.3 (95% confidence interval 0.1, 1.7). CONCLUSION: This study suggests that the factor V Leiden mutation is not associated with an increased risk of venous thromboembolism in gynecologic oncology patients. This contrasts with other studies showing a strong association between the factor V Leiden mutation and venous thromboembolism in cases of previously unexplained venous thromboembolism, and venous thromboembolism associated with other hypercoagulable states, such as pregnancy and oral contraceptive use. The risk of venous thromboembolism due to cancer outweighs the contribution of the factor V Leiden mutation.

Adult↗