Expression of Erythropoietin and Its Receptor in the Brain of Late-Gestation Fetal Sheep, and Responses to Asphyxia Caused by Umbilical Cord Occlusion

2005 ◽  
Vol 27 (2-4) ◽  
pp. 220-227 ◽  
Author(s):  
Margie Castillo-Meléndez ◽  
Edwin Yan ◽  
David W. Walker
Keyword(s):  
Umbilical Cord ◽  
Late Gestation ◽  
Fetal Sheep ◽  
The Brain

Effect of intermittent umbilical cord occlusion on fetal respiratory activity and brain adenosine in late-gestation sheep

2002 ◽  
Vol 14 (1) ◽  
pp. 35 ◽  
Author(s):  
Carole S. Watson ◽  
Rachel Schaefer ◽  
Susan E. White ◽  
Jacobus H. Homan ◽  
Laurence Fraher ◽  
...  
Keyword(s):  
Umbilical Cord ◽  
Fetal Brain ◽  
Extracellular Fluid ◽  
Inhibitory Effect ◽  
Late Gestation ◽  
Fetal Sheep ◽  
Arterial Ph ◽  
Tracheal Pressure ◽  
Ovine Fetal ◽  
Arterial Po2

It was hypothesized that intermittent umbilical cord occlusion (UCO) would inhibit ovine fetal breathing movements (FBM) in association with increased cerebral adenosine levels. To test this hypothesis, on two successive days during late gestation (133–134 days; term = 146 days), microdialysis samples were collected from the brains of 10 chronically instrumented fetal sheep during 2-h periods of complete UCO induced every 30 min (Day 1: 2-min UCOs; Day 2: 4-min UCOs). Control fetuses (n = 10) underwent no UCO. Tracheal pressure was measured throughout. This regimen resulted in a decrease in fetal arterial PO2 (PaO2) during each UCO to 7.3 0.8 mmHg (P<0.01; Day 1) and 8.4 1.1 mmHg (P<0.01; Day 2). Throughout each UCO period, fetal arterial pH (pHa) decreased to 7.28 0.02 (P<0.01; Day 1) and 7.11 0.07 (P<0.01; Day 2). The hourly incidence of FBM decreased significantly only on Day 2, from 38.6 4.1% to 4.1 1.6% (P<0.01). The frequency of deep isolated inspiratory efforts increased from 4.7 2.0 h–1 to 17.6 6.1 h–1 (P<0.05; Day 1) and from 2.2 0.9 h–1 to 33.6 4 h–1 (P<0.01; Day 2). The amplitude of both FBM and deep isolated inspiratory efforts increased during the UCO periods on both days. The concentration of cerebral extracellular fluid (ECF) adenosine during UCO increased by 219 215% (P<0.05; Day 1) and 172 107% (P<0.05; Day 2) over the baseline periods. In conclusion, the severity of the inhibitory effect of repeated UCO on FBM depends, in part, on the length of the occlusions. The inhibition of FBM during intermittent UCO may be mediated by the increase in ECF adenosine in the fetal brain. Furthermore, FBM and deep isolated inspiratory efforts appear to be regulated by different mechanisms.

Distribution of calbindin-D28K in the brain of the fetal sheep in late gestation

1995 ◽  
Vol 675 (1-2) ◽  
pp. 303-315 ◽  
Author(s):  
T.J. McDonald ◽  
C. Li ◽  
R.H. Wasserman
Keyword(s):  
Late Gestation ◽  
Fetal Sheep ◽  
Calbindin D28k ◽  
The Brain

Melatonin Provides Neuroprotection in the Late-Gestation Fetal Sheep Brain in Response to Umbilical Cord Occlusion

2005 ◽  
Vol 27 (2-4) ◽  
pp. 200-210 ◽  
Author(s):  
Suzanne L. Miller ◽  
Edwin B. Yan ◽  
Margie Castillo-Meléndez ◽  
Graham Jenkin ◽  
David W. Walker
Keyword(s):  
Umbilical Cord ◽  
Late Gestation ◽  
Fetal Sheep ◽  
Sheep Brain

Impact of chronic hypoxemia on blood flow to the brain, heart, and adrenal gland in the late-gestation IUGR sheep fetus

2015 ◽  
Vol 308 (3) ◽  
pp. R151-R162 ◽  
Author(s):  
Rajan Poudel ◽  
I. Caroline McMillen ◽  
Stacey L. Dunn ◽  
Song Zhang ◽  
Janna L. Morrison
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Adrenal Gland ◽  
Temporal Lobe ◽  
Late Gestation ◽  
Control Group ◽  
Surgical Removal ◽  
Fetal Sheep ◽  
Intrauterine Growth ◽  
The Brain

In the fetus, there is a redistribution of cardiac output in response to acute hypoxemia, to maintain perfusion of key organs, including the brain, heart, and adrenal glands. There may be a similar redistribution of cardiac output in the chronically hypoxemic, intrauterine growth-restricted fetus. Surgical removal of uterine caruncles in nonpregnant ewe results in the restriction of placental growth (PR) and intrauterine growth. Vascular catheters were implanted in seven control and six PR fetal sheep, and blood flow to organs was determined using microspheres. Placental and fetal weight was significantly reduced in the PR group. Despite an increase in the relative brain weight in the PR group, there was no difference in blood flow to the brain between the groups, although PR fetuses had higher blood flow to the temporal lobe. Adrenal blood flow was significantly higher in PR fetuses, and there was a direct relationship between mean gestational PaO2 and blood flow to the adrenal gland. There was no change in blood flow, but a decrease in oxygen and glucose delivery to the heart in the PR fetuses. In another group, there was a decrease in femoral artery blood flow in the PR compared with the Control group, and this may support blood flow changes to the adrenal and temporal lobe. In contrast to the response to acute hypoxemia, these data show that there is a redistribution of blood flow to the adrenals and temporal lobe, but not the heart or whole brain, in chronically hypoxemic PR fetuses in late gestation.

scholarly journals Mechanisms of Melatonin-Induced Protection in the Brain of Late Gestation Fetal Sheep in Response to Hypoxia

2012 ◽  
Vol 34 (6) ◽  
pp. 543-551 ◽  
Author(s):  
Tamara Yawno ◽  
Margie Castillo-Melendez ◽  
Graham Jenkin ◽  
Euan M. Wallace ◽  
David W. Walker ◽  
...  
Keyword(s):  
Late Gestation ◽  
Fetal Sheep ◽  
The Brain

Characterization of 11 beta-hydroxysteroid dehydrogenase activity in fetal and adult ovine tissues

1995 ◽  
Vol 7 (3) ◽  
pp. 377 ◽  
Author(s):  
EK Kim ◽  
CE Wood ◽  
M Keller-Wood
Keyword(s):  
Limit Of Detection ◽  
Adult Life ◽  
Hydroxysteroid Dehydrogenase ◽  
Late Gestation ◽  
Fetal Life ◽  
Fetal Sheep ◽  
Optimum Ph ◽  
Kidney Liver ◽  
The Brain

11 Beta-hydroxysteroid dehydrogenase (11 beta-HSD) converts 11-hydroxycorticosteroids to 11-oxocorticosteroids, thereby influencing the availability of bioactive cortisol or corticosterone in target tissues. The activity of this enzyme was investigated in sheep by: (1) measuring relative 11 beta-HSD activities in kidney, liver and placenta, and in various areas of the brain (hypothalamus, hippocampus, and brainstem); (2) characterizing the optimum pH of activities in the tested tissues; (3) investigating the possible effect of gonadal steroids on 11 beta-HSD activity in adult hypothalamus and kidney; and (4) investigating possible developmental changes in activities in the tested tissues. The optimum pH in liver and placenta was pH 9-10, whereas the optimum pH in kidney was pH 7-8. In tissues from adult ewes, 11 beta-HSD activity was highest in liver (84.6 +/- 3.8%) and kidney (49.8 +/- 11.6%), lower but measurable in pituitary (38.8 +/- 3.7%), and near the limit of detection in hypothalamus and hippocampus (2.7 +/- 0.9% and 3.2 +/- 0.8% respectively). Liver, kidney and pituitary from late-gestation fetal sheep contained activities which were similar to those in the adult (76.9 +/- 4.5%, 66.0 +/- 6.7% and 26.3 +/- 3.0% respectively). Activity in the pituitary was not related to fetal gestational age. Placenta also contained measureable 11 beta-HSD activity (21.4 +/- 4.7%). However, no activity was detected in hypothalamus (-1.7 +/- 0.2%), hippocampus (-0.2 +/- 0.6%) or brainstem (-1.0 +/- 0.6%) in late-gestation fetal or neonatal sheep. Enzyme activities in kidney and hypothalamus did not change significantly when the circulating concentrations of ovarian steroids were altered over a 1-3-week period. It is concluded that the ovine kidney, liver and placenta, but not hypothalamus or cerebral cortex, contain 11 beta-HSD activity. In addition, there is no change in 11 beta-HSD activity between late-gestation fetal life and adult life, and the relative activities are not altered by the ovarian steroid milieu.

scholarly journals Hemodynamic and metabolic responses to moderate asphyxia in brain and skeletal muscle of late-gestation fetal sheep

2000 ◽  
Vol 88 (1) ◽  
pp. 82-90 ◽  
Author(s):  
J. P. Newman ◽  
D. M. Peebles ◽  
S. R. G. Harding ◽  
R. Springett ◽  
M. A. Hanson
Keyword(s):  
Redox State ◽  
Near Infrared ◽  
Metabolic Response ◽  
Hemoglobin Concentration ◽  
Late Gestation ◽  
Significant Drop ◽  
Fetal Sheep ◽  
Internal Iliac ◽  
Near Term ◽  
The Brain

The purpose of this study was to investigate metabolic and hemodynamic responses in two fetal tissues, hindlimb muscle and brain, to an episode of acute moderate asphyxia. Near-infrared spectroscopy was used to measure changes in total hemoglobin concentration ([tHb]) and the redox state of cytochrome oxidase (COX) simultaneously in the brain and hindlimb of near-term unanesthetized fetal sheep in utero. Oxygen delivery (Do 2) to, and consumption (V˙o 2) by, each tissue was derived from the arteriovenous difference in oxygen content and blood flow, measured by implanted flow probes. One hour of moderate asphyxia ( n = 11), caused by occlusion of the maternal common internal iliac artery, led to a significant fall in Do 2to both tissues and to a significant drop inV˙o 2 by the head. This was associated with an initial fall in redox state COX in the leg but an increase in the brain. [tHb], and therefore blood volume, fell in the leg and increased in the brain. These data suggest the presence of a fetal metabolic response to hypoxia, which, in the brain, occurs rapidly and could be neuroprotective.

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