Maternal-to-fetal allopurinol transfer and xanthine oxidase suppression in the late gestation pregnant rat.

Fetal brain hypoxic injury remains a concern in high-risk delivery. There is significant clinical interest in agents that may diminish neuronal damage during birth asphyxia, such as in allopurinol, an inhibitor of the prooxidant enzyme xanthine oxidase. Here, we established in a rodent model the capacity of allopurinol to be taken up by the mother, cross the placenta, rise to therapeutic levels, and suppress xanthine oxidase activity in the fetus. On day 20 of pregnancy, Wistar dams were given 30 or 100 mg kg(-1) allopurinol orally. Maternal and fetal plasma allopurinol and oxypurinol concentrations were measured, and xanthine oxidase activity in the placenta and maternal and fetal tissues determined. There were significant strong positive correlations between maternal and fetal plasma allopurinol (r = 0.97, P < 0.05) and oxypurinol (r = 0.88, P < 0.05) levels. Under baseline conditions, maternal heart (2.18 ± 0.62 mU mg(-1)), maternal liver (0.29 ± 0.08 mU mg(-1)), placenta (1.36 ± 0.42 mU mg(-1)), fetal heart (1.64 ± 0.59 mU mg(-1)), and fetal liver (0.14 ± 0.08 mU mg(-1)) samples all showed significant xanthine oxidase activity. This activity was suppressed in all tissues 2 h after allopurinol administration and remained suppressed 24 h later (P < 0.05), despite allopurinol and oxypurinol levels returning toward baseline. The data establish a mammalian model of xanthine oxidase inhibition in the mother, placenta, and fetus, allowing investigation of the role of xanthine oxidase-derived reactive oxygen species in the maternal, placental, and fetal physiology during healthy and complicated pregnancy

Effects of Antenatal Glucocorticoid Therapy on Hippocampal Histology of Preterm Infants

Objective: To investigate if antenatal glucocorticoid treatment has an effect on hippocampal histology of the human preterm newborn. Patients and Methods: Included were consecutive neonates with a gestational age between 24 and 32 weeks, who were born between 1991 to 2009, who had died within 4 days after delivery and underwent brain autopsy. Excluded were neonates with congenital malformations and neonates treated postnatally with glucocorticoids. The brains were routinely fixed, samples of the hippocampus were stained with haematoxylin and eosin and sections were examined for presence or absence of large and small neurons in regions of the hippocampus. Additional staining with GFAP, neurofilament and vimentin was performed to evaluate gliosis and myelination. The proliferation marker Ki67 was used to evaluate neuronal proliferation. Staining with acid fuchsin-thionin was performed to evaluate ischemic damage. Results: The hippocampi of ten neonates who had been treated with antenatal glucocorticoids showed a lower density of large neurons (p = 0.01) and neurons irrespective of size (p = 0.02) as compared to eleven neonates who had not been treated with glucocorticoids. No difference was found in density of small neurons, in myelination, gliosis, proliferation or ischemic damage. Conclusion: We found a significantly lower density of neurons in the hippocampus of neonates after antenata

Parameters affecting water-hammer wave attenuation, shape and timing. Part 2: Case studies

This two-part paper investigates parameters that may significantly affect water-hammer wave attenuation, shape and timing. Possible sources that may affect the waveform predicted by classical water-hammer theory include unsteady friction, cavitation (including column separation and trapped air pockets), a number of fluid–structure interaction effects, viscoelastic behaviour of the pipe-wall material, leakages and blockages. Part 1 of this two-part paper presents the mathematical tools needed to model these sources. Part 2 of the paper presents a number of case studies showing how these modelled sources affect pressure traces in a simple reservoir-pipeline-valve system. Each case study compares the obtained results with the standard (classical) water-hammer model, from which conclusions are drawn concerning the transient behaviour of real systems.Anton Bergant, Arris S. Tijsseling, John P. Vítkovský, Dídia I. C. Covas, Angus R. Simpson and Martin F. Lamber

Oxidative stress in the developing brain: effects of postnatal glucocorticoid therapy and antioxidants in the rat.

In premature infants, glucocorticoids ameliorate chronic lung disease, but have adverse effects on long-term neurological function. Glucocorticoid excess promotes free radical overproduction. We hypothesised that the adverse effects of postnatal glucocorticoid therapy on the developing brain are secondary to oxidative stress and that antioxidant treatment would diminish unwanted effects. Male rat pups received a clinically-relevant tapering course of dexamethasone (DEX; 0.5, 0.3, and 0.1 mg x kg(-1) x day(-1)), with or without antioxidant vitamins C and E (DEXCE; 200 mg x kg(-1) x day(-1) and 100 mg x kg(-1) x day(-1), respectively), on postnatal days 1-6 (P1-6). Controls received saline or saline with vitamins. At weaning, relative to controls, DEX decreased total brain volume (704.4±34.7 mm(3) vs. 564.0±20.0 mm(3)), the soma volume of neurons in the CA1 (1172.6±30.4 µm(3) vs. 1002.4±11.8 µm(3)) and in the dentate gyrus (525.9±27.2 µm(3) vs. 421.5±24.6 µm(3)) of the hippocampus, and induced oxidative stress in the cortex (protein expression: heat shock protein 70 [Hsp70]: +68%; 4-hydroxynonenal [4-HNE]: +118% and nitrotyrosine [NT]: +20%). Dexamethasone in combination with vitamins resulted in improvements in total brain volume (637.5±43.1 mm(3)), and soma volume of neurons in the CA1 (1157.5±42.4 µm(3)) and the dentate gyrus (536.1±27.2 µm(3)). Hsp70 protein expression was unaltered in the cortex (+9%), however, 4-HNE (+95%) and NT (+24%) protein expression remained upregulated. Treatment of neonates with vitamins alone induced oxidative stress in the cortex (Hsp70: +67%; 4-HNE: +73%; NT: +22%) and in the hippocampus (NT: +35%). Combined glucocorticoid and antioxidant therapy in premature infants may be safer for the developing brain than glucocorticoids alone in the treatment of chronic lung disease. However, antioxidant therapy in healthy offspring is not recommended

Perinatal glucocorticoid treatment and perspectives for antioxidat therapy

Pre- and postnatal glucocorticoids are a life-saving therapy for prematurely born infants. However, glucocorticoids also trigger unwanted side effects. In part I we investigated the effects of antenatal glucocorticoids on hippocampal development. First in a mice model using a clinically relevant dose of antenatal dexamethasone. Dexamethasone treatment increased apoptosis in the hippocampus until birth.During the phase with increased apoptosis, proliferation was reduced. The number of proliferative cells was increased postnatally, but was decreased at adult stage. Thereafter, we investigated effects of antenatal glucocorticoid treatment on the human hippocampus. Included were preterms who died during or within 4 days after delivery. We detected a decreased neuronal density in the CA zones of the hippocampus of glucocorticoid treated neonates. Part II focuses on side effects of postnatal glucocorticoid treatment and how to reduce these effects. Accumulating evidence suggests that one pathway by which glucocorticoids may promote their deleterious effects is increasing oxidative stress and decreasing nitric oxide bioavailability. Therefore we combined postnatal dexamethasone treatment with antioxidant therapy (vitamins C and E) in a rat model and investigated effects on brain development at postnatal day 21. Dexamethasone increased indices of oxidative stress in the cortex and decreased brain volume and soma volumes of neurons in the CA 1 and the dentate gyrus of the hippocampus. Combined treatment restored some but not all indices of oxidative stress to control levels and improved brain volume and soma volumes of neurons in the hippocampus. However, vitamins alone also increased indices of oxidative stress in the cortex. In the following chapters, we tested dexamethasone combined with pravastatin using a comparable rat model. In addition to the effects of dexamethasone on brain development that we found in the dexamethasone and vitamins C and E study, dexamethasone treatment led to a fall in plasma NOx concentrations (nitrates and nitrites,well established indices of circulating NO bioavailability), impaired weight gain during treatment followed by accelerated weight gain thereafter, a decreased number of neurons in the cerebral cortex and increased density of GFAP positive cells in the cingulate white matter. Most of these effects were restored to control levels by giving combined dexamethasone and pravastatin treatment. As regards cardiovascular function; dexamethasone increased basal arterial pressure, decreased vascular reactivity and increased the rate pressure product indicating a higher myocardial workload. These effects were ameliorated by combined treatment with pravastatin. Pravastatin treatment alone decreased NOx concentrations, had no effect on brain development but led to a significant fall in vascular relaxation sensitivity. As changes in growth patterns may have consequences for long term health we compared in a retrospective cohort study growth patterns for weight, height and head circumference from birth to age four years, between prematurely born children postnatally treated with dexamethasone or hydrocortisone and a prematurely born reference group. Growth patterns of preterm born infants were affected by glucocorticoid-treatment, effects were observed mainly on growth velocities