scholarly journals Increased allopregnanolone levels in the fetal sheep brain following umbilical cord occlusion

2004 ◽  
Vol 560 (2) ◽  
pp. 593-602 ◽  
Author(s):  
Phuong N. Nguyen ◽  
Edwin B. Yan ◽  
Margie Castillo-Melendez ◽  
David W. Walker ◽  
Jonathan J. Hirst
Keyword(s):  
Umbilical Cord ◽  
Fetal Sheep ◽  
Sheep 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

scholarly journals Peripheral chemoreflex control of fetal heart rate decelerations overwhelms the baroreflex during brief umbilical cord occlusions in fetal sheep

2020 ◽  
Vol 598 (20) ◽  
pp. 4523-4536 ◽  
Author(s):  
Christopher A. Lear ◽  
Michi Kasai ◽  
Lindsea C. Booth ◽  
Paul P. Drury ◽  
Joanne O. Davidson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Umbilical Cord ◽  
Fetal Heart Rate ◽  
Fetal Heart ◽  
Fetal Sheep ◽  
Peripheral Chemoreflex

Regulation of cytochrome oxidase redox state during umbilical cord occlusion in preterm fetal sheep

2007 ◽  
Vol 292 (4) ◽  
pp. R1569-R1576 ◽  
Author(s):  
Laura Bennet ◽  
Vincent Roelfsema ◽  
Justin M. Dean ◽  
Guido Wassink ◽  
Gordon G. Power ◽  
...  
Keyword(s):  
Cytochrome Oxidase ◽  
Umbilical Cord ◽  
Redox State ◽  
Cerebral Oxygenation ◽  
Cerebral Metabolism ◽  
Electron Flow ◽  
Initial Response ◽  
Severe Hypoxia ◽  
Fetal Sheep ◽  
Severe Hypotension

The preterm fetus is capable of surviving prolonged periods of severe hypoxia without neural injury for much longer than at term. To evaluate the hypothesis that regulated suppression of brain metabolism contributes to this remarkable tolerance, we assessed changes in the redox state of cytochrome oxidase (CytOx) relative to cerebral heat production, and cytotoxic edema measured using cerebral impedance, during 25 min of complete umbilical cord occlusion or sham occlusion in fetal sheep at 0.7 gestation. Occlusion was followed by rapid, profound reduction in relative cerebral oxygenation and EEG intensity and an immediate increase in oxidized CytOx, indicating a reduction in electron flow down the mitochondrial electron transfer chain. Confirming rapid suppression of cerebral metabolism there was a loss of the temperature difference between parietal cortex and body at a time when carotid blood flow was maintained at control values. As occlusion continued, severe hypotension/hypoperfusion developed, with a further increase in CytOx levels to a plateau between 8 and 13 min and a progressive rise in cerebral impedance. In conclusion, these data strongly suggest active regulation of cerebral metabolism during the initial response to severe hypoxia, which may help to protect the immature brain from injury.

Intercellular barriers to and transcellular transfer of albumin in the fetal sheep brain

1997 ◽  
Vol 195 (3) ◽  
pp. 229-236 ◽  
Author(s):  
Y. Balslev ◽  
K. M. Dziegielewska ◽  
K. Møllgård ◽  
N. R. Saunders
Keyword(s):  
Fetal Sheep ◽  
Sheep Brain

Lack of evidence for impaired preload or Bezold-Jarisch activation during brief umbilical cord occlusions in fetal sheep

2021 ◽  
Author(s):  
Christopher A. Lear ◽  
Laura Bennet ◽  
Benjamin S. A. Lear ◽  
Jenny A. Westgate ◽  
Alistair Jan Gunn
Keyword(s):  
Blood Flow ◽  
Umbilical Cord ◽  
Cardiovascular Responses ◽  
Diastolic Filling ◽  
Fetal Sheep ◽  
Blood Flows ◽  
Rapid Fall ◽  
Filling Time ◽  
Cervical Vagotomy ◽  
Femoral Blood

Impaired cardiac preload secondary to umbilical cord occlusion (UCO) has been hypothesized to contribute to intrapartum decelerations, brief falls in fetal heart rate (FHR), through the activation of the Bezold-Jarisch reflex. This cardioprotective reflex increases parasympathetic and inhibits sympathetic outflows triggering hypotension, bradycardia and peripheral vasodilation but its potential to contribute to intrapartum decelerations has never been systematically examined. In this study we performed bilateral cervical vagotomy to remove the afferent arm and the efferent parasympathetic arm of the Bezold-Jarisch reflex. 22 chronically instrumented fetal sheep at 0.85 of gestation received vagotomy (n=7) or sham-vagotomy (control, n=15), followed by three 1-min complete UCOs separated by 4-min reperfusion periods. UCOs in control fetuses were associated with a rapid fall in FHR and reduced femoral blood flow mediated by intense femoral vasoconstriction, leading to hypertension. Vagotomy abolished the rapid fall in FHR (p<0.001), and despite reduced diastolic filling time, increased both carotid (p<0.001) and femoral (p<0.05) blood flow during UCOs, secondary to carotid vasodilation (p<0.01) and delayed femoral vasoconstriction (p<0.05). Finally, vagotomy was associated with an attenuated rise in cortical impedance during UCOs (p<0.05), consistent with improved cerebral substrate supply. In conclusion, increased carotid and femoral blood flows after vagotomy are consistent with increased left and right ventricular output, which is incompatible with the hypothesis that labor-like UCOs impair ventricular filling. Overall, the cardiovascular responses to vagotomy do not support the hypothesis that the Bezold-Jarisch reflex is activated by UCO. The Bezold-Jarisch reflex is therefore mechanistically unable to contribute to intrapartum decelerations.

Repeated isoflurane exposure and neuroapoptosis in the midgestation fetal sheep brain

2016 ◽  
Vol 214 (4) ◽  
pp. 542.e1-542.e8 ◽  
Author(s):  
Olutoyin A. Olutoye ◽  
Fariha Sheikh ◽  
Irving J. Zamora ◽  
Ling Yu ◽  
Adesola C. Akinkuotu ◽  
...  
Keyword(s):  
Fetal Sheep ◽  
Sheep Brain

Effect of chronic hypoxemia on the regulation of nitric-oxide synthase in the fetal sheep brain

1998 ◽  
Vol 111 (2) ◽  
pp. 271-277 ◽  
Author(s):  
Kripamoy Aguan ◽  
Jun Murotsuki ◽  
Robert Gagnon ◽  
Loren P Thompson ◽  
Carl P Weiner
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Fetal Sheep ◽  
Sheep Brain ◽  
Chronic Hypoxemia ◽  
Oxide Synthase

Heat production of fetal sheep brain in utero

1977 ◽  
Vol 43 (4) ◽  
pp. 747-749 ◽  
Author(s):  
R. M. Abrams ◽  
J. F. Clapp ◽  
M. Notelovitz ◽  
T. Tyler ◽  
S. Cassin
Keyword(s):  
Specific Heat ◽  
Heat Production ◽  
Brain Temperature ◽  
Main Pulmonary Artery ◽  
Fetal Brain ◽  
In Utero ◽  
Total Occlusion ◽  
Fetal Sheep ◽  
Sheep Brain ◽  
Near Term

Thermojunctions were implanted in the brains of 10 near term fetal sheep in utero under halothane anesthesia. Brief total occlusion of fetal brachiocephalic artery was followed immediately by an increase in brain temperature (mean +/- SE) of 0.130 +/- 0.014 degrees C-min-1. Occlusion of main pulmonary artery and ascending aorta, simultaneously, led to a brain temperature increase of 0.144 +/- 0.018 degrees C-min-1. Specific heat of three fetal brains was determined to be 0.898 +/- 0.014 cal-g-1. degrees C-1 or 3.76 +/- 0.059 J-g-1. Rate of fetal brain heat production, computed as the product of the higher rate of temperature change and brain specific heat, was 0.129 +/- 0.014 cal-g-1-min-1 or 9.00 +/- 0.98 mW-g-1.

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