The effect of hypercapnia on a blood‐brain barrier mechanism in foetal and new‐born sheep.

Evans, Chris; Reynolds, James M.; Reynolds, M. L.; Saunders, NR

doi:10.1113/jphysiol.1976.sp011304

Cited by 24 publications

(19 citation statements)

References 17 publications

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“…Likewise, the increases in arterial carbon dioxide tensions in the fetuses at 60% of gestation and in the newborn lambs during the glucose infusions were similar to those during the mannitol infusions (Stonestreet et al, 2006). Although hypercapnia results in increased penetration of sucrose into the brains of fetal and newborn sheep and adult rabbits, the carbon dioxide levels in the previous reports were much higher than during glucose (Table 1) and mannitol hyperosmolality in our studies (Cameron et al, 1969;Evans et al, 1976;Stonestreet et al, 2006). The increases in the arterial carbon dioxide tensions in the fetuses at 60% of gestation and in the newborn lambs were similar and analogous to those we reported during the mannitol infusions (Stonestreet et al, 2006).…”

Section: Discussionsupporting

confidence: 80%

Comparative Effects of Glucose- and Mannitol-Induced Osmolar Stress on Blood—Brain Barrier Function in Ovine Fetuses and Lambs

Stonestreet

Sadowska

Hanumara

et al. 2011

J Cereb Blood Flow Metab

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We examined the effects of hyperglycemic hyperosmolality on blood-brain barrier (BBB) permeability during development. We hypothesized that the barrier becomes more resistant to hyperglycemic hyperosmolality during development, and the immature BBB is more resistant to glucose than to mannitol hyperosmolality. We quantified the BBB response to hyperosmolality with the blood-to-brain transfer constant (K i ) in immature fetuses, premature, and newborn lambs. K i increased as a function of increases in osmolality. A segmented regression model described the relationship between K i and osmolality. At lower osmolalities, changes in K i were minimal but after a threshold, increases were linear. We examined responses of K i to hyperglycemic hyperosmolality by comparing the thresholds and slopes of the second regression segments. Lower thresholds and steeper slopes indicate greater vulnerability to hyperosmolality. Thresholds increased (P < 0.05) during development in pons and superior colliculus. Thresholds were higher (P < 0.05) during glucose than mannitol hyperosmolality in thalamus, superior colliculus, inferior colliculus and medulla of premature lambs, and in cerebrum and cerebellum of newborns. We conclude that BBB permeability increased as a function of changes in glucose osmolality, the barrier becomes more resistant to glucose hyperosmolality in two brain regions during development, and the barrier is more resistant to glucose than to mannitol hyperosmolality in some brain regions of premature and newborn lambs.

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Section: Discussionsupporting

confidence: 80%

Comparative Effects of Glucose- and Mannitol-Induced Osmolar Stress on Blood—Brain Barrier Function in Ovine Fetuses and Lambs

Stonestreet

Sadowska

Hanumara

et al. 2011

J Cereb Blood Flow Metab

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“…The entry of sucrose into the c.s.f. was also increased by hypercapnia (Evans et al 1976). Hochwald et al (1973) found that c.s.f.…”

Section: Discussionmentioning

confidence: 99%

“…production. In previous studies hypercapnia has been found to increase (Ames, Higashi & Nesbett, 1965), decrease (Evans, Reynolds, Reynolds & Saunders, 1976) or have no effect (Hochwald, Malhan & Brown, 1973) on c.s.f. formation.…”

Section: Discussionmentioning

confidence: 99%

Regulation of cerebrospinal fluid bicarbonate by the cat choroid plexus.

Husted¹,

Reed²

1977

The Journal of Physiology

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1. The regulation of cerebrospinal fluid (c.s.f.) bicarbonate concentration was studied using the cat choroid plexus isolated in a chamber in situ. 2. Decreases in plasma bicarbonate concentration caused relatively small changes in the c.s.f. bicarbonate concentration. 3. Alterations in c.s.f. bicarbonate concentration (c.s.f. HCO3‐=9 or 28 m‐equiv/l.) were countered by changes in the bicarbonate concentration of the fluid produced by the plexus or in the rate of bicarbonate transport which returned c.s.f. bicarbonate towards normal. 4. There was significant regulation of pH in the choroid plexus fluid during hypocapnia and hypercapnia. 5. Alterations of plasma acid‐base status did not significantly alter the potential difference across the choroid plexus. However, the potential difference increased when c.s.f. bicarbonate was increased and decreased when c.s.f. bicarbonate was decreased. 6. The data indicate that the bicarbonate concentration in the c.s.f. is actively regulated by the choroid plexus during acid‐base disturbances occurring either systemically or in the c.s.f.

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“…Dziegielewska, Evans, Malinowska, M0llgard, . This permeability is increased under hypercapnic conditions (Evans, Reynolds, Reynolds, & Saunders, 1976;Habgood, 1990 (Sakurada, Kennedy, Jehle, Brown, Carbin & Sokoloff, 1978). These measurements were based on the Fick principle as described by Kety & Schmidt (1945), and the autoradiography techniques were similar to those first described by Reivich, Jehle, Sokoloff & Kety (1969).…”

Section: Introductionmentioning

confidence: 99%

Cerebral blood flow in the anaesthetized immature sheep fetus and the response to hypercapnia

Habgood¹,

Jones²,

Maroni³

et al. 1991

Experimental Physiology

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The effect of hypercapnia on a blood‐brain barrier mechanism in foetal and new‐born sheep.

Cited by 24 publications

References 17 publications

Comparative Effects of Glucose- and Mannitol-Induced Osmolar Stress on Blood—Brain Barrier Function in Ovine Fetuses and Lambs

Comparative Effects of Glucose- and Mannitol-Induced Osmolar Stress on Blood—Brain Barrier Function in Ovine Fetuses and Lambs

Regulation of cerebrospinal fluid bicarbonate by the cat choroid plexus.

Cerebral blood flow in the anaesthetized immature sheep fetus and the response to hypercapnia

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