Fetal Cerebral Oxygenation: The Homeostatic Role of Vascular Adaptations to Hypoxic Stress

Pearce, William J.; Butler, Stacy M.; Abrassart, Jenna M.; Williams, James M.

doi:10.1007/978-1-4419-7756-4_30

Cited by 15 publications

(14 citation statements)

References 19 publications

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“…Rather, we propose the influence of early-life factors, such as prenatal exposure to high altitude and high physical activity levels during childhood (5) to explain the ability to maintain Cox in elite Kenyan runners. Prenatal exposure to high altitude triggers cerebral vasodilator responses at muscle and endothelium level by stimulating extensive cerebrovascular remodeling that increases wall thickness but decreases overall contractility (25). Many of these adaptations to chronic hypoxia appear to be homeostatic and mediated by vascular endothelial growth factors (VEGF).…”

Section: Discussionmentioning

confidence: 99%

Maintained cerebral oxygenation during maximal self-paced exercise in elite Kenyan runners

Santos-Concejero

Billaut

Grobler

et al. 2015

Journal of Applied Physiology

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The purpose of this study was to analyze the cerebral oxygenation response to maximal self-paced and incremental exercise in elite Kenyan runners from the Kalenjin tribe. On two separate occasions, 15 elite Kenyan distance runners completed a 5-km time trial (TT) and a peak treadmill speed test (PTS). Changes in cerebral oxygenation were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxyhemoglobin (Δ[O2Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI). During the 5-km TT (15.2 ± 0.2 min), cerebral oxygenation increased over the first half (increased Δ[O2Hb] and Δ[HHb]) and, thereafter, Δ[O2Hb] remained constant (effect size, ES = 0.33, small effect), whereas Δ[HHb] increased until the end of the trial (P < 0.05, ES = 3.13, large effect). In contrast, during the PTS, from the speed corresponding to the second ventilatory threshold, Δ[O2Hb] decreased (P < 0.05, ES = 1.51, large effect), whereas Δ[HHb] continued to increase progressively until exhaustion (P < 0.05, ES = 1.22, large effect). Last, the TOI was higher during the PTS than during the 5-km TT (P < 0.001, ES = 3.08; very large effect), whereas nTHI values were lower (P < 0.001, ES = 2.36, large effect). This study shows that Kenyan runners from the Kalenjin tribe are able to maintain their cerebral oxygenation within a stable range during a self-paced maximal 5-km time trial, but not during an incremental maximal test. This may contribute to their long-distance running success.

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Section: Discussionmentioning

confidence: 99%

Maintained cerebral oxygenation during maximal self-paced exercise in elite Kenyan runners

Santos-Concejero

Billaut

Grobler

et al. 2015

Journal of Applied Physiology

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“…On the other hand, in intermittent and chronic hypoxic conditions, eNOS expression and function is reduced and a concomitant treatment with melatonin in the former exerts its protective action by restoring the expression of eNOS and NO bioavailability . Chronic hypoxia during development is affecting vascular NO function in the brain, but still remains as an important area to be further explore .…”

Section: Discussionmentioning

confidence: 99%

Melatonin improves cerebrovascular function and decreases oxidative stress in chronically hypoxic lambs

Herrera

Macchiavello

Montt

et al. 2014

Journal of Pineal Research

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Chronic hypoxia during gestation and delivery results in oxidative stress and cerebrovascular dysfunction in the neonate. We assessed whether melatonin, a potent antioxidant and potential vasodilator, improves the cerebral vascular function in chronically hypoxic neonatal lambs gestated and born in the highlands (3600 m). Six lambs received melatonin (1 mg/kg per day oral) and six received vehicle, once a day for 8 days. During treatment, biometry and hemodynamic variables were recorded. After treatment, lambs were submitted to a graded FiO2 protocol to assess cardiovascular responses to oxygenation changes. At 12 days old, middle cerebral arteries (MCA) were collected for vascular reactivity, morphostructural, and immunostaining evaluation. Melatonin increased fractional growth at the beginning and improved carotid blood flow at all arterial PO2 levels by the end of the treatment (P < 0.05). Further, melatonin treatment improved vascular responses to potassium, serotonin, methacholine, and melatonin itself (P < 0.05). In addition, melatonin enhanced the endothelial response via nitric oxide-independent mechanisms in isolated arteries (162 ± 26 versus 266 ± 34 AUC, P < 0.05). Finally, nitrotyrosine staining as an oxidative stress marker decreased in the MCA media layer of melatonin-treated animals (0.01357 ± 0.00089 versus 0.00837 ± 0.00164 pixels/μm2 , P < 0.05). All the melatonin-induced changes were associated with no systemic cardiovascular alterations in vivo. In conclusion, oral treatment with melatonin modulates cerebral vascular function, resulting in a better cerebral perfusion and reduced oxidative stress in the neonatal period in chronically hypoxic lambs. Melatonin is a potential therapeutic agent for treating cerebrovascular dysfunction associated with oxidative stress and developmental hypoxia in neonates.

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“…It is noteworthy to bear in mind that UA Doppler correlates only with total lumen and wall thickness of placental vessels [19] , standing for purely objective down-flow resistance data. Conversely, cerebral Doppler provides information about the fetal self-perception of the oxygenation received [20] , therefore being a reaction to fetal hypoxemia. Thus, a decrease in the cerebral resistance might be the only information heralding an abnormal outcome [21] .…”

Section: Cerebral Doppler As a Marker Heralding Abnormal Outcomementioning

confidence: 99%

Neonatal Acid-Base Status in Fetuses with Abnormal Vertebro- and Cerebro-Placental Ratios

et al. 2015

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Objective: A low cerebro-placental ratio (CPR) at term suggests the existence of failure to reach growth potential (FRGP) with a higher risk of poor neonatal acid-base status. This study aimed to evaluate whether similar findings were also seen in the vertebral artery (vertebro-placental ratio, VPR), supplying 30% of the cerebral flow. Methods: We studied term fetuses classified into groups according to birth weight (BW), CPR and VPR. BW was expressed in centiles and ratios in multiples of the median (MoM). Subsequently, associations with neonatal pH values were evaluated by means of regression curves and Mann-Whitney tests. Results: VPR MoM correlated with BW centiles (p < 0.0001, R² = 0.042) and its distribution resembled that of CPR MoM (p < 0.001). When both arteries were compared, adequate-for-gestational-age (AGA) fetuses with either low CPR or low VPR had lower neonatal venous pH values (p < 0.05, p < 0.01, respectively). However, in case of small-for-gestational-age (SGA) fetuses, only those with low VPR had significantly lower neonatal arterial and venous pH values (p < 0.05). Conclusions: Blood flow in the vertebral artery mimics that in the middle cerebral artery supporting the FRGP model. Both CPR and VPR identify AGA fetuses with lower neonatal pH values, but only VPR identifies SGA with lower pH values. Hypoxemia might be reflected as a generalized cerebral vasodilation demonstrated as low CPR and VPR.

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Fetal Cerebral Oxygenation: The Homeostatic Role of Vascular Adaptations to Hypoxic Stress

Cited by 15 publications

References 19 publications

Maintained cerebral oxygenation during maximal self-paced exercise in elite Kenyan runners

Maintained cerebral oxygenation during maximal self-paced exercise in elite Kenyan runners

Melatonin improves cerebrovascular function and decreases oxidative stress in chronically hypoxic lambs

Neonatal Acid-Base Status in Fetuses with Abnormal Vertebro- and Cerebro-Placental Ratios

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