Differential vasomotor responses to isocapnic hyperoxia: cerebral versus peripheral circulation.

Isocapnic hyperoxia (IH) evokes cerebral and peripheral hypoperfusion via both disturbance of redox homeostasis and reduction in nitric oxide (NO) bioavailability. However, it is not clear whether the magnitude of the vasomotor responses depends on the vessel network exposed to IH. To test the hypothesis that the magnitude of IH-induced reduction in peripheral blood flow (BF) may differ from the hypoperfusion response observed in the cerebral vascular network under oxygen-enriched conditions, nine healthy men (25 ± 3 yr, mean ± SD) underwent 10 min of IH during either saline or vitamin C (3 g) infusion, separately. Femoral artery (FA), internal carotid artery (ICA), and vertebral artery (VA) BF (Doppler ultrasound), as well as arterial oxidant (8-isoprostane), antioxidant [ascorbic acid (AA)], and NO bioavailability (nitrite) markers were simultaneously measured. IH increased 8-isoprostane levels and reduced nitrite levels; these responses were followed by a reduction in both FA BF and ICA BF, whereas VA BF did not change. Absolute and relative reductions in FA BF were greater than IH-induced changes in ICA and VA perfusion. Vitamin C infusion increased arterial AA levels and abolished the IH-induced increase in 8-isoprostane levels and reduction in nitrite levels. Whereas ICA and VA BF did not change during the vitamin C-IH trial, FA perfusion increased and reached similar levels to those observed during normoxia with saline infusion. Therefore, the magnitude of IH-induced reduction in femoral blood flow is greater than that observed in the vessel network of the brain, which might involve the determinant contribution that NO has in the regulation of peripheral vascular perfusion.

Systematization and description of the internal carotid arteries and their main ramifications at the brain base in turtles (Trachemys scripta elegans).

Thirty turtle brains (Trachemys scripta elegans) were injected with latex to systematize and describe the internal carotid arteries and their main ramifications at the brain base. The internal carotid arteries had one intercarotid anastomosis. At the level of the tuber cinereum, the internal carotid artery bifurcated into its terminal branches, the rostral and the caudal branches. The rostral branch emitted the rostral choroid artery, the orbital artery, and a series of middle cerebral arteries. After giving off the last middle cerebral artery, the rostral branch continued as the rostral cerebral artery in the cerebral longitudinal fissure, and had one anastomosis with its contralateral homologous artery, the rostral communicating artery, making the first rostral closure of the cerebral arterial circle. Next, the rostral cerebral arteries anastomosed forming a rostral interhemispheric artery, making the second rostral closure of the cerebral arterial circle. The internal carotid artery, after emitting its rostral branch, continued caudally as the caudal branch. The caudal branch ran caudally along the ventral surface of the mesencephalic tegmentum, emitted the caudal cerebral artery and the mesencephalic artery, and continued caudomedially while progressively narrowing, and anastomosed with its contralateral homologous artery, forming the basilar artery. The narrower portion also emitted the trigeminal artery. The anastomosis of the caudal branches closed the cerebral arterial circle caudally. The internal carotid arteries exclusively supplied the cerebral arterial circle of the turtle. Anat Rec, 299:1090-1098, 2016. © 2016 Wiley Periodicals, Inc.

Pharmacological characterization of the mechanisms involved in the vasorelaxation induced by progesterone and 17ß-estradiol on isolated canine basilar and internal carotid arteries.

Progesterone and 17ß-estradiol induce vasorelaxation through non-genomic mechanisms in several isolated blood vessels; however, no study has systematically evaluated the mechanisms involved in the relaxation induced by 17ß-estradiol and progesterone in the canine basilar and internal carotid arteries that play a key role in cerebral circulation. Thus, relaxant effects of progesterone and 17ß-estradiol on KCl- and/or PGF2α-pre-contracted arterial rings were investigated in absence or presence of several antagonists/inhibitors/blockers; the effect on the contractile responses to CaCl2 was also determined. In both arteries progesterone (5.6-180 µM) and 17ß-estradiol (1.8-180 µM): (1) produced concentration-dependent relaxations of KCl- or PGF2α-pre-contracted arterial rings; (2) the relaxations were unaffected by actinomycin D (10 µM), cycloheximide (10 µM), SQ 22,536 (100 µM) or ODQ (30 µM), potassium channel blockers and ICI 182,780 (only for 17ß-estradiol). In the basilar artery the vasorelaxation induced by 17ß-estradiol was slightly blocked by tetraethylammonium (10mM) and glibenclamide (KATP; 10 µM). In both arteries, progesterone (10-100 µM), 17ß-estradiol (3.1-31 µM) and nifedipine (0.01-1 µM) produced a concentration-dependent blockade of the contraction to CaCl2 (10 µM-10mM). These results suggest that progesterone and 17ß-estradiol produced relaxation in the basilar and internal carotid arteries by blockade of L-type voltage dependent Ca(2+) channel but not by genomic mechanisms or production of cAMP/cGMP. Potassium channels did not play a role in the relaxation to progesterone in both arteries or in the effect of 17ß-estradiol in the internal carotid artery; meanwhile KATP channels play a minor role on the effect of 17ß-estradiol in the basilar artery.

[Correlation between the carotid resistance and functional autonomy of old women]. / Correlaçõ entre resistência carotídea e autonomia funcional de mulheres idosas.

This study had as objective to correlate the resistance of the carotid artery and the functional autonomy of old women. The resistance of the carotid artery was evaluated through the method called Doppler and the functional autonomy through tests related to daily activities (Protocol GDLAM). In the description of the data it was used measures of localization and dispersion. The internal right carotid resistance got mean and pattern deviation respectively (0.71 +/- 0.07) and functional autonomy mean and pattern deviation respectively (30.40 +/- 6.31). The coefficient of the correlation of Spearman showed a strong association between the variation of the study (r = 0.998; p = 0.000). The results suggest that the bigger the table of contents of the resistance of the carotid artery is the bigger will be the difficulty of execution of the daily life tasks.

Correlação entre resistência carotídea e autonomia funcional de mulheres idosas / Correlation between the carotid resistance and functional autonomy of old women

Este estudo objetivou correlacionar resistência da artéria carótida e autonomia funcional de idosas. Avaliou-se a resistência da artéria carótida pelo método de ultra-som Doppler e a Autonomia Funcional por testes relacionados a atividades da vida diária (Protocolo GDLAM). Para a descrição dos dados, calculou-se média e desvio padrão, em que a resistência da carótida interna direita obteve respectivamente (0,71 ± 0,07) e o Índice geral de Autonomia Funcional apresentou (30,40 ± 6,31). O coeficiente de correlação de Spearman mostrou forte associação entre as variáveis do estudo (r = 0,998; p = 0,000). Os resultados sugerem que quanto maior o índice de resistência da artéria carótida, maior será a dificuldade de execução das tarefas da vida diária.

This study had as objective to correlate the resistance of the carotid artery and the functional autonomy of old women. The resistance of the carotid artery was evaluated through the method called Doppler and the functional autonomy through tests related to daily activities (Protocol GDLAM). In the description of the data it was used measures of localization and dispersion. The internal right carotid resistance got mean and pattern deviation respectively (0,71 ± 0,07) and functional autonomy mean and pattern deviation respectively (30,40 ± 6,31). The coefficient of the correlation of Spearman showed a strong association between the variation of the study (r = 0,998; p = 0,000). The results suggest that the bigger the table of contents of the resistance of the carotid artery is the bigger will be the difficulty of execution of the daily life tasks.

Este estudio objetivou correlacionar resistência de la arteria carótida interna derecha Y autonomía funcional de ancianas. Se evaluó la resistência de la arteria carótida por el método de ultra-sonido Doppler e a autonomia funcional a través de testes relacionados la actividad da vida diaria (Protocolo GDLAM). Em la descripción de los datos, se calculou media y desvío padrón, donde la resistência de la arteria carótida interna derecha tuvo respectivamente (0,71 ± 0,07) y em lo índice geral de la autonomía funcional fueron respectivamente (30,40 ± 6,31). Lo coeficiente de la correlación de Spearman mostrou fuerte associación entre las variables de el estudio (r = 0,998; p = 0,000). Los resultados sugerem que cuanto mayor lo índice de la resistência de la arteria carótida, mayor fuerón las dificuldades de execucusión de las actividad de la vida diaria.

Physiological importance of the conjugation of the internal carotid artery and cavernous sinus.

The author considers of utmost importance the anatomical arterial-venous conjugation represented by the internal carotid artery and the cavernous sinus, as well as the carotid venous plexus which covers the internal carotid artery within the petrous portion of the temporal bone. He believes that besides protecting the vascular arterial wall in acute episodes of hypertension, it can also contribute to the mechanism of carotid blood flow. This hypothesis is based on consideration of the physiological conditions of the cavernous sinus in relation to those of other dural venous sinuses, and of the endocranial venous system and its cavernous constitution, which differs from other venous blood canals, which have their own venous physiology and different functions. He attempts to compare it with the rest of the body areas where cavernous plexuses are located and where venous pressure reaches high values, and with other regions without this morphologic constitution. He establishes a correlation resulting from a cerebrovascular resistance mechanism, the participation of which he considers to differ from those of other dural sinuses and encephalic veins. He also emphasizes physiologically the carotid siphon and believes that its participation in the hemodynamics of a hypotensive patient who is lying down, facilitates blood access to the brain, thus avoiding anoxia and brain damage, within certain limits, and constitutes an additional means of body defense.

Long-term neurophysiologic outcome after neonatal extracorporeal membrane oxygenation.

We examined clinical and neurophysiologic measures in 10 children 4 to 9 years after neonatal extracorporeal membrane oxygenation. Electroencephalograms did not correlate with clinical or other neurophysiologic measures of interhemispheric asymmetry. By ultrasound imaging, the right internal carotid artery velocity was approximately 62% of that on the left, and right internal carotid flow was reduced by 74% (p less than or equal to 0.01), whereas an age-matched control group showed no differences. A decrease in the amplitude of the long-latency auditory and somatosensory evoked potentials was noted over the right hemisphere after left-sided stimulation compared with the left hemispheric potentials after right-sided stimulation (p less than or equal to 0.005). No significant differences in hemispheric symmetry were noted in the amplitudes for wave V of the auditory brain-stem response or in the P30 component of the middle-latency auditory evoked potentials. Likewise, latency measures of the evoked potentials were symmetric. We conclude that (1) neonatal extracorporeal membrane oxygenation is associated with long-lasting decreased right internal carotid blood flow with compensatory increased flow through the left carotid system and (2) there is a consistent reduction in the amplitude of right hemispheric long-latency evoked potentials. These latter findings may reflect redirected cerebral blood flow patterns after extracorporeal membrane oxygenation.

Cerebral blood flow velocity in term newborn infants: changes associated with ductal flow.

The effects of ductal closure on range-gated pulsed Doppler cerebral blood flow velocity (CBFV) patterns in the internal carotid, anterior cerebral, and middle cerebral arteries were studied in 10 normal term infants (mean birth weight 3302 +/- 294 g (SD) and mean gestational age 39.6 +/- 1.3 weeks). Pulsatility was calculated from flow velocities and used as an estimate of cerebral blood flow (CBF). Ductal closure was associated with a rise in mean blood pressure from 45.0 +/- 4.2 to 51.3 +/- 6.5 mm Hg (P less than 0.05) and a significant decrease in pulsatility in all three vessels (mean = 0.77 +/- 0.07 vs 0.70 +/- 0.05 (P less than 0.02]. Changes in pulsatility were correlated with changes in mean blood pressure (P less than 0.02), providing evidence that systemic blood pressure may influence postnatal cerebral arterial pulsatility indices. We also noted significant differences in the velocity and pulsatility of individual vessels that were independent of blood pressure, suggesting that Doppler flow studies may be useful in describing regional CBF patterns. The temporal association between ductal closure and decreased pulsatility suggests that CBFV patterns reflect ductal shunting in normal term newborn infants. Diastolic runoff and reduced systemic blood pressure in the presence of ductal shunting appear to reduce diastolic flow velocity and increase CBFV pulsatility in normal term infants during the first days of life. Normal mechanisms of cerebral autoregulation compensate for decreased flow with vasodilation; therefore the increased pulsatility associated with ductal shunting may be due to diastolic runoff rather than increased cerebrovascular resistance.

[Control and regulation of the blood circulation in the vertebro-basilar system. Review of the literature]. / Contrôle e regulação da circulação sanguínea no sistema vértebro-basilar. Revisão de literatura.

The author establishes an analogy between the control mechanism and regulation of the cerebral blood flow and of protection of the vascular wall of the internal carotid constituted by the conjunction "internal carotid-cavernous sinus" with the group represented by the system "vertebro basilar-transverse occipital sinus or basilar" (an extension of the cavernous sinus) in the regulation and control of the encephalic circulation carried out through this latter vessels, together with the protection of its vascular walls. The author believes to be very difficult to demonstrate in practice the functioning of these mechanisms, but it is very logical and easy to reason about them, to value them and to give the importance and meaning or motive which forcibly they should have and not simply consider them as freaks of nature and bizarre anatomical features.