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James M Roberts

Publications and source records attributed to James M Roberts.

80 records · Page 5Linked to original sources
PubMed2002

Antigen-specific dose-dependent system for the study of an inheritable and reversible phenotype in mouse CD4+ T cells.

The transgenic T-cell receptor in mouse TEa CD4+ lymphocytes recognizes an endogenous peptide, Ealpha52-68, presented in the context of the major histocompatibility complex class II molecule I-Ab. In response to an optimal peptide concentration TEa cells enter the cell cycle and proliferate. However, a single exposure to high doses of the specific peptide diminished cell expansion upon subsequent restimulation. This hyporesponsive, or anergic, phenotype can still be detected after multiple restimulations indicating that the hyporesponsiveness persists despite cell division and it was inherited by daughter cells. Furthermore, we demonstrated that this hypoproliferative response is associated with high p27Kip1 and cyclin E protein levels, and reduced intracellular interleukin-2 (IL-2) expression. Addition of exogenous IL-2 was required to reset p27Kip1 levels in the progeny derived from hyporesponsive TEa cells. Thus, we have established antigen dose-dependent induction of a reversible, inheritable (i.e. epigenetic) phenotype and we have identified at least three components of the network of interactions: p27Kip1 cyclin E, and IL-2 expression.

Animals↗
PubMed2002

Plasma homocysteine and malondialdehyde are correlated in an age- and gender-specific manner.

Homocysteine is an independent risk factor for peripheral vascular and coronary artery disease. The exact mechanism by which homocysteine promotes vascular dysfunction is unclear, but it is speculated to involve oxidative stress. Several studies have investigated the role of homocysteine in promoting oxidative stress and have obtained conflicting results. The age and gender of the subject populations in these studies may have influenced the outcome. Therefore, we investigated whether plasma homocysteine concentrations were correlated with plasma malondialdehyde (MDA, a marker of oxidative stress), and if the subject's age and gender affected this correlation. Plasma homocysteine and MDA were measured in 35 premenopausal women, 14 young men, 38 postmenopausal women, and 18 older men. Homocysteine was significantly higher in men than women (P <.01) and in older subjects versus younger. However, MDA was significantly greater only in the young men (P <.01). Furthermore, there was a significant correlation between homocysteine and MDA only in these young men (R(2) = 0.50, P <.01). Lastly, subjects undergoing a methionine load did not exhibit increased MDA despite significant increases in homocysteine. Since oxidative stress correlates with basal homocysteine only in young men and does not increase with acutely increased homocysteine, it is unlikely to be the result of a direct effect of homocysteine.

Adult↗
PubMed2002

Endothelial junctional protein redistribution and increased monolayer permeability in human umbilical vein endothelial cells isolated during preeclampsia.

OBJECTIVE: To examine monolayer permeability and junctional protein distribution and expression in endothelial cells isolated from women with preeclampsia and from women with normal pregnancies. We hypothesized that increased endothelial monolayer permeability in preeclampsia reflects altered monolayer barrier properties produced by disorganization of endothelial cell junction proteins. STUDY DESIGN: Endothelial cells were isolated from umbilical veins from women with normal pregnancies (n = 9) and from women with preeclampsia (n = 9) immediately after delivery. In the first passage of endothelial cells, the permeability was determined by measurement of horseradish peroxidase passage through confluent cell monolayers grown on transwell filters, and the distribution and protein expression of vascular endothelial cadherin and occludin were evaluated by use of immunofluorescent staining of the proteins and Western blot analysis. The distribution of vascular endothelial cadherin was also evaluated in the second and third passage endothelial cells. Messenger ribonucleic acid expression of vascular endothelial cadherin and occludin were examined by reverse transcriptase polymerase chain reaction. Data were expressed as mean values (+/- SE) and were analyzed by use of an unpaired t test. RESULTS: The relative monolayer permeability was significantly increased in the endothelial cells isolated from women with preeclampsia compared with those isolated from women with normal pregnancies (0.271 +/- 0.049 versus 0.086 +/- 0.031 for DeltaOD(470); P <.05). Vascular endothelial cadherin expression for normal endothelial cells showed a continuous staining of the junctional protein that surrounded cell borders. In comparison, vascular endothelial cadherin in endothelial cells from preeclamptic pregnancies exhibited disorganized staining and vascular endothelial cadherin fibrils were retracted, with gaps present at the cell borders. The expression of occludin showed a pattern similar to that of vascular endothelial cadherin in both normal and preeclamptic conditions. Western blot results for expression of vascular endothelial cadherin and occludin also showed decreased expression of junctional proteins. The altered endothelial cell junctional protein distribution and expression of vascular endothelial cadherin and occludin observed in the first passage of endothelial cells from preeclamptic pregnancies was restored to normal by the time cells reached the third passage in vitro. There was no statistical difference in mRNA expression for the vascular endothelial cadherin and occludin between normal endothelial cells and those from preeclamptic pregnancies. CONCLUSION: In preeclampsia, increased endothelial cell monolayer permeability appears to reflect disorganized and diminished expression of endothelial cell junctional proteins. The latter response is mediated at the posttranscriptional level. These findings provide new insights about the cellular and molecular basis for altered endothelial cell integrity and barrier dysfunction that are associated with preeclampsia.

Antigens, CD↗
PubMed2002

The Preterm Prediction Study: the value of serum alkaline phosphatase, alpha-fetoprotein, plasma corticotropin-releasing hormone, and other serum markers for the prediction of spontaneous preterm birth.

OBJECTIVE: High levels of a number of analytes are found in maternal blood; alkaline phosphatase,alpha-fetoprotein, and corticotropin-releasing hormone have been associated with spontaneous preterm birth. We investigated the relationship between 8 potential blood markers and subsequent spontaneous preterm birth in asymptomatic pregnant women. STUDY DESIGN: We performed a nested case control study that involved 127 women who were enrolled in the preterm prediction study and who had a singleton spontaneous preterm birth at <35 weeks and 127 women who had a term birth and served as matched (age, parity, center) controls. Serum that was collected at 24 and 28 weeks was analyzed for alkaline phosphatase, alpha-fetoprotein, corticotropin-releasing hormone, and 5 other analytes. RESULTS: Alkaline phosphatase, alpha-fetoprotein, and corticotropin-releasing hormone, but not other analytes, were significantly elevated in pregnancies that ended in spontaneous preterm birth. For alkaline phosphatase at 24 weeks, the odds ratio for spontaneous preterm birth at <32 weeks was 6.8 (range, 1.4-32.8) and for spontaneous preterm birth at <35 weeks 5.1 (range, 1.7-15.6). Similar results were found at 28 weeks. For alpha-fetoprotein at 24 weeks, the odds ratio for spontaneous preterm birth at <32 weeks was 8.3 (range,2.2-30.9) and for spontaneous preterm birth at <35 weeks was 3.5 (range, 1.8-6.7). The levels at 28 weeks were still predictive but less so than at 24 weeks. Corticotropin-releasing hormone, at 28 weeks but not at 24 weeks, was predictive for spontaneous preterm birth at <35 weeks, with an odds ratio 3.4 (range, 1.0-10.9). CONCLUSION: Elevated alkaline phosphatase and alpha-fetoprotein are associated with subsequent spontaneous preterm birth in asymptomatic pregnant women at 24 and 28 weeks. Elevated corticotropin-releasing hormone levels at 28 weeks are associated with spontaneous preterm birth at <35 weeks.

Alkaline Phosphatase↗
PubMed2002

MAD1 and p27(KIP1) cooperate to promote terminal differentiation of granulocytes and to inhibit Myc expression and cyclin E-CDK2 activity.

To understand how cellular differentiation is coupled to withdrawal from the cell cycle, we have focused on two negative regulators of the cell cycle, the MYC antagonist MAD1 and the cyclin-dependent kinase inhibitor p27(KIP1). Generation of Mad1/p27(KIP1) double-null mice revealed a number of synthetic effects between the null alleles of Mad1 and p27(KIP1), including embryonic lethality, increased proliferation, and impaired differentiation of granulocyte precursors. Furthermore, with granulocyte cell lines derived from the Mad1/p27(KIP1) double-null mice, we observed constitutive Myc expression and cyclin E-CDK2 kinase activity as well as impaired differentiation following treatment with an inducer of differentiation. By contrast, similar treatment of granulocytes from Mad1 or p27(KIP1) single-null mice resulted in differentiation accompanied by downregulation of both Myc expression and cyclin E-CDK2 kinase activity. In the double-null granulocytic cells, addition of a CDK2 inhibitor in the presence of differentiation inducer was sufficient to restore differentiation and reduce Myc levels. We conclude that Mad1 and p27(KIP1) operate, at least in part, by distinct mechanisms to downregulate CDK2 activity and Myc expression in order to promote cell cycle exit during differentiation.

Animals↗
PubMedDate not supplied

A pilot study of the effects of phytoestrogen supplementation on postmenopausal endometrium.

OBJECTIVE: This study was designed to assess endometrial histology in postmenopausal women not taking hormone replacement therapy, to evaluate side effects and efficacy of phytoestrogens in treating menopause-associated symptoms, and to determine whether 6 months of phytoestrogen supplementation altered endometrial histology. METHODS: We performed a prospective, double-blinded, randomized, placebo-controlled trial comparing the effects of 6 months of dietary phytoestrogen supplementation versus placebo in postmenopausal women. Baseline endometrial biopsies were performed and, if adequate, nonhyperplastic, noncancerous, and nonovulatory, subjects were randomly assigned to receive daily placebo or soy cereal supplementation for 6 months. Study subjects completed baseline and weekly dietary, symptom, and side effect logs. Repeat endometrial biopsies were obtained at 6 months. RESULTS: Subjects were recruited from January 1998 through June 2000. Twenty-seven subjects were randomized, and 19 completed the study. One (3.7%) baseline endometrial sample was weakly proliferative. All other baseline and final biopsies were consistent with atrophic, inactive endometrium. The maximum risk of endometrial stimulation with phytoestrogens is 35%. Hot flushes, night sweats, and vaginal dryness were significantly less severe at the final week of the study compared with baseline in the placebo group. Insomnia was more common in the treated group. There were no other statistically significant differences in symptoms or side effects. CONCLUSION: Phytoestrogens did not cause stimulation of the endometrium. Insomnia was more frequent over the 6-month study in the soy group, whereas hot flushes, night sweats, and vaginal dryness improved from baseline in the placebo group but not in the soy group.

Biopsy↗