Regional brain blood flow and cerebral hemispheric oxygen consumption during acute hypoxaemia in the llama fetus

Llanos, Aníbal J.; Riquelme, Raquel; Sanhueza, Emilia M.; Herrera, Emílio; Cabello, Gertrudis; Giussani, Dino A.; Parer, Julian T.

doi:10.1113/jphysiol.2001.013230

Cited by 21 publications

(9 citation statements)

References 32 publications

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“…Our experiments show that absolute mean brain temperature decreased 0.54°C during prolonged hypoxaemia, indicating lower heat production or an increase in release of heat from the brain. Previous findings show a lowering of brain cortex oxygen consumption in an episode of acute hypoxaemia (1 h) in the llama fetus (Llanos et al 2002), suggesting that a reduction in heat production (beyond the scope of the present study) is probably present during the first hour of hypoxaemia. A reduction in brain heat production has been shown by Hunter et al (2003) in an episode of 30 min hypoxaemia in fetal sheep.…”

Section: Discussionmentioning

confidence: 47%

“…Remarkably, unlike fetuses of lowland species, the llama fetus responds to acute hypoxaemia with only a minor increase in cerebral blood flow (Llanos et al 2003). Furthermore, the fetal llama shows a progressive fall in brain oxygen delivery and cerebral oxygen consumption with progression of the fetal hypoxaemia (Llanos et al 2002). We have shown that the electrocorticogram flattens under these conditions of hypoxaemia, and seizure activity does not occur, which suggests that no hypoxaemic damage occurs (Llanos et al 2003).…”

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confidence: 99%

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Fetal brain hypometabolism during prolonged hypoxaemia in the llama

Ebensperger

Herrera

et al. 2005

The Journal of Physiology

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In this study we looked for additional evidence to support the hypothesis that fetal llama reacts to hypoxaemia with adaptive brain hypometabolism. We determined fetal llama brain temperature, Na + and K + channel density and Na + -K + -ATPase activity. Additionally, we looked to see whether there were signs of cell death in the brain cortex of llama fetuses submitted to prolonged hypoxaemia. Ten fetal llamas were instrumented under general anaesthesia to measure pH, arterial blood gases, mean arterial pressure, heart rate, and brain and core temperatures. Measurements were made 1 h before and every hour during 24 h of hypoxaemia (n = 5), which was imposed by reducing maternal inspired oxygen fraction to reach a fetal arterial partial pressure of oxygen (P a,O 2 ) of about 12 mmHg. A normoxaemic group was the control (n = 5). After 24 h of hypoxaemia, we determined brain cortex Na + -K + -ATPase activity, ouabain binding, and the expression of NaV1.1, NaV1.2, NaV1.3, NaV1.6, TREK1, TRAAK and K ATP channels. The lack of brain cortex damage was assessed as poly ADP-ribose polymerase (PARP) proteolysis. We found a mean decrease of 0.56• C in brain cortex temperature during prolonged hypoxaemia, which was accompanied by a 51% decrease in brain cortex Na + -K + -ATPase activity, and by a 44% decrease in protein content of NaV1.1, a voltage-gated Na + channel. These changes occurred in absence of changes in PARP protein degradation, suggesting that the cell death of the brain was not enhanced in the fetal llama during hypoxaemia. Taken together, these results provide further evidence to support the hypothesis that the fetal llama responds to prolonged hypoxaemia with adaptive brain hypometabolism, partly mediated by decreases in Na + -K + -ATPase activity and expression of NaV channels.

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Section: Discussionmentioning

confidence: 47%

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confidence: 99%

Fetal brain hypometabolism during prolonged hypoxaemia in the llama

Ebensperger

Herrera

et al. 2005

The Journal of Physiology

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“…Characteristically, the fetal llama has a greater total peripheral vascular resistance than the sheep, both in normoxemia and in hypoxemia (28,34). Furthermore, unlike fetuses of lowland species (34), the fetal llama responds to acute hypoxemia with a marked peripheral vasoconstriction and with little or no increase in cerebral blood flow (13,14,27,29). This response to hypoxemia suggests differences in the gain of chemoreflexes or in the balance between endocrine and autocrine vasoconstrictor and vasodilator mechanisms between fetuses of highland and lowland species.…”

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confidence: 92%

Vasodilator tone in the llama fetus: the role of nitric oxide during normoxemia and hypoxemia

Sanhueza¹,

Riquelme²,

Herrera³

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

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The fetal llama responds to hypoxemia, with a marked peripheral vasoconstriction but, unlike the sheep, with little or no increase in cerebral blood flow. We tested the hypothesis that the role of nitric oxide (NO) may be increased during hypoxemia in this species, to counterbalance a strong vasoconstrictor effect. Ten fetal llamas were operated under general anesthesia. Mean arterial pressure (MAP), heart rate, cardiac output, total vascular resistance, blood flows, and vascular resistances in cerebral, carotid and femoral vascular beds were determined. Two groups were studied, one with nitric oxide synthase (NOS) blocker N(G)-nitro-L-arginine methyl ester (L-NAME), and the other with 0.9% NaCl (control group), during normoxemia, hypoxemia, and recovery. During normoxemia, L-NAME produced an increase in fetal MAP and a rapid bradycardia. Cerebral, carotid, and femoral vascular resistance increased and blood flow decreased to carotid and femoral beds, while cerebral blood flow did not change significantly. However, during hypoxemia cerebral and carotid vascular resistance fell by 44% from its value in normoxemia after L-NAME, although femoral vascular resistance progressively increased and remained high during recovery. We conclude that in the llama fetus: 1) NO has an important role in maintaining a vasodilator tone during both normoxemia and hypoxemia in cerebral and femoral vascular beds and 2) during hypoxemia, NOS blockade unmasked the action of other vasodilator agents that contribute, with nitric oxide, to preserving blood flow and oxygen delivery to the tissues.

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“…To this effect, here we emphasize that no information is available on the early morphogenesis of the central nervous system (CNS) during the first trimester of pregnancy. Since the alpaca lives in the high altitude hypoxic environment, the species may represent a particularly interesting translational model for the study of the human adaptation to the same environment (Llanos et al, , ; Ebensperger et al, ; Herrera et al, ; Moraga et al, ).…”

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Mapping of the Early Intrauterine Morphogenesis in the Alpaca (Vicugna pacos): External Features and Development of the Cephalic Vesicle in Comparison with the Progressive Carnegie Scale

Montelli

Stelletta

Ruiz

et al. 2018

The Anatomical Record

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In this study, we characterized the morphological aspects of the early development of the head of the alpaca (Vicugna pacos) and identified the main structures of the central nervous system during the first trimester of pregnancy. The topography and the cytoarchitecture of the fetal brain regions were described by histological analysis of the brain sections. We performed this analysis on alpaca embryos and fetuses presumably aged 20, 30, 45, and 90 days. For the description of the external body structures we considered the shape of the head, the development of the optic primordium, the dorsal curvature of the body, the limb buds, the umbilical cord and relative vessels, and the thickness and transparency of the skin. The prosencephalic, mesencephalic, and the rhomboencephalic vesicles were described by analyzing sagittal sections of the head. The present article provides the first progressive morphological and anatomical description of alpaca brain during early development. A detailed study represents an important basis to further understand the phases of prenatal development in this species, since information about alpaca embryology in incomplete and reproductive failure is a relevant factor. These data are important also for interspecies comparisons and application of reproductive biotechnologies. Anat Rec, 302:1226–1237, 2019. © 2018 Wiley Periodicals, Inc.

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Regional brain blood flow and cerebral hemispheric oxygen consumption during acute hypoxaemia in the llama fetus

Cited by 21 publications

References 32 publications

Fetal brain hypometabolism during prolonged hypoxaemia in the llama

Fetal brain hypometabolism during prolonged hypoxaemia in the llama

Vasodilator tone in the llama fetus: the role of nitric oxide during normoxemia and hypoxemia

Mapping of the Early Intrauterine Morphogenesis in the Alpaca (Vicugna pacos): External Features and Development of the Cephalic Vesicle in Comparison with the Progressive Carnegie Scale

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