Michelle A Dickinson

Queen's University, Kingston, Ontario, Canada

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Publications (4)15.76 Total impact

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    ABSTRACT: The aim of this study was to characterize the pregnant guinea pig cytokine time course following a maternal inflammatory insult. Pregnant guinea pigs (n = 34) were injected intraperitoneally with 100 microg/kg lipopolysaccharide (LPS) at 70% gestation and euthanized at 24 hours, 48 hours, or 5 days. Control animals were euthanized at 70% gestation without LPS exposure. Interleukin (IL)-6, IL-1beta, and tumor necrosis factor-alpha (TNF-alpha) were quantified in the maternal serum and amniotic fluid by an enzyme-linked immunosorbent assay. IL-6 and IL-1beta concentrations were elevated in the maternal serum at 24 hours and returned to control levels by 5 days. In the amniotic fluid, IL-6 peaked at 48 hours and IL-1beta at 24 hours. TNF-alpha levels were not significantly increased. Maternal intraperitoneal LPS injection produces transient increases in cytokine concentrations in the maternal serum and amniotic fluid within 5 days, further implicating the cytokines as mediators of fetal white matter damage.
    American journal of obstetrics and gynecology 04/2009; 200(5):534.e1-6. · 3.28 Impact Factor
  • Erica L Harnett, Michelle A Dickinson, Graeme N Smith
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    ABSTRACT: This study determined whether a lipopolysaccharide (LPS) dose-dependent increase in fetal brain injury occurs to further characterize the relationship between maternal inflammation and fetal brain injury. Pregnant guinea pigs (n = 59) at 70% gestation were injected intraperitoneally with 1, 5, 25, 50, 100, 200, or 300 microg LPS per kilogram of maternal body weight or an equivalent volume of vehicle. Animals were killed 7 days later. Maternal serum and amniotic fluid samples were assayed for proinflammatory cytokines tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 using enzyme-linked immunosorbent assay kits. Fetal brains (n = 72) were stained for evidence of cell death with NeuroTACS stain. Seven days after LPS injections, cytokine concentrations in maternal serum and amniotic fluid were not different (P > .05) from controls. Levels of cell death in all brain regions examined were highest following the maternal administration of 300 mug/kg LPS (P < .05). The dose effect was brain region-dependent (P < .05). A threshold of maternal infection/inflammation exists, beyond which demonstrable fetal brain injury may result.
    American journal of obstetrics and gynecology 08/2007; 197(2):179.e1-7. · 3.28 Impact Factor
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    ABSTRACT: Damage of the placenta resulting from ischemia-reperfusion is important to the pathophysiology of preeclampsia. Here we investigated whether low concentrations of glyceryl trinitrate (GTN), a nitric oxide mimetic with anti-apoptotic properties, inhibit hypoxia/reoxygenation-induced apoptosis in the syncytiotrophoblast of chorionic villous explants from human placentas. Compared with villi analyzed immediately after delivery or maintained under normoxic conditions, villi exposed to a 6-hour cycle of hypoxia/reoxygenation exhibited greater numbers of syncytiotrophoblasts with terminal dUTP nick-end labeling (TUNEL)-positive nuclei in the syncytiotrophoblast. This increased number of TUNEL-positive nuclei was paralleled by higher levels of 4-hydroxynonenal (marker of lipid peroxidation), nitrotyrosine residues, and active caspase-3 and polyADP-ribose polymerase expression. Morphological analysis of explants exposed to hypoxia/reoxygenation revealed apoptotic and aponecrotic features similar to those of chorionic villi from preeclamptic pregnancies. Treatment with GTN during the hy-poxia/reoxygenation cycle blocked the increases in the number of TUNEL-positive nuclei and in the levels of 4-hydroxynonenal, nitrotyrosine, and active caspase-3. Incubation with GTN also attenuated the hypoxia/reoxygenation-induced polyADP-ribose polymerase expression and the apoptotic and aponecrotic morphological alterations. These results suggest that small concentrations of nitric oxide protect chorionic villi from hypoxia/reoxygenation-induced damage and provide a rationale for the use of low doses of nitric oxide mimetics in the treatment and/or prevention of preeclampsia.
    American Journal Of Pathology 04/2007; 170(3):909-20. · 4.60 Impact Factor
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    ABSTRACT: Pre-eclampsia, a hypertensive disorder of pregnancy, affects 5 to 7% of pregnancies. Oxidative stress-induced placental injury and subsequent release of placental debris into the maternal circulation are key pathogenic events in the progression of pre-eclampsia. Women who smoke cigarettes throughout pregnancy are 33% less likely to develop this disorder than nonsmoking women. We postulated that elevated carbon monoxide concentrations in serum of smoking women inhibits apoptosis and debris shedding of trophoblast cells exposed to ischemia-reperfusion injury because carbon monoxide has cytoprotective effects on endothelial and smooth muscle cells in culture. This may be responsible for the reduced risk of pre-eclampsia in smoking women. To assess the cytoprotective properties of carbon monoxide within placental tissue, carbon monoxide treatments were administered to in vitro hypoxia/reoxygenation-insulted villous explants cultured from term human placenta. Induction of apoptosis was assessed using molecular and morphological approaches. Placental villous explants treated with carbon monoxide demonstrated 60% less hypoxia/reoxygenation-induced apoptosis in the differentiated syncytiotrophoblast layer compared with untreated explants undergoing a similar insult. In addition, retention of intact syncytial membranes was observed in carbon monoxide-treated explants. These observations indicate that carbon monoxide has potent antiapoptotic properties within human placenta and may hold therapeutic potential in the treatment of pre-eclampsia.
    American Journal Of Pathology 10/2006; 169(3):774-83. · 4.60 Impact Factor

Publication Stats

52 Citations
15.76 Total Impact Points

Institutions

  • 2006–2009
    • Queen's University
      • • Department of Anatomy and Cell Biology
      • • Faculty of Health Sciences
      Kingston, Ontario, Canada