Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism
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J. Cereb. Blood Flow Metab. · Aug 2017
Noninvasive optical monitoring of critical closing pressure and arteriole compliance in human subjects.
The critical closing pressure ( CrCP) of the cerebral circulation depends on both tissue intracranial pressure and vasomotor tone. CrCP defines the arterial blood pressure ( ABP) at which cerebral blood flow approaches zero, and their difference ( ABP - CrCP) is an accurate estimate of cerebral perfusion pressure. Here we demonstrate a novel non-invasive technique for continuous monitoring of CrCP at the bedside. ⋯ Measurements of CrCP by optics (DCS) and transcranial Doppler ultrasound (TCD) were carried out in 18 healthy adults; they demonstrated good agreement (R = 0.66, slope = 1.14 ± 0.23) with means of 11.1 ± 5.0 and 13.0 ± 7.5 mmHg, respectively. Additionally, a potentially useful and rarely measured arteriole compliance parameter was derived from the phase difference between ABP and DCS arteriole blood flow waveforms. The measurements provide evidence that DCS signals originate predominantly from arteriole blood flow and are well suited for long-term continuous monitoring of CrCP and assessment of arteriole compliance in the clinic.
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J. Cereb. Blood Flow Metab. · Aug 2017
Posttraumatic therapeutic hypothermia alters microglial and macrophage polarization toward a beneficial phenotype.
Posttraumatic inflammatory processes contribute to pathological and reparative processes observed after traumatic brain injury (TBI). Recent findings have emphasized that these divergent effects result from subsets of proinflammatory (M1) or anti-inflammatory (M2) microglia and macrophages. Therapeutic hypothermia has been tested in preclinical and clinical models of TBI to limit secondary injury mechanisms including proinflammatory processes. ⋯ RT-PCR of M1-associated genes including iNOS and IL-1β was significantly reduced with hypothermia while M2-associated genes including arginase and CD163 were significantly increased compared to normothermic conditions. The injury-induced increased expression of the chemokine Ccl2 was also reduced with PTH. These studies provide a link between temperature-sensitive alterations in macrophage/microglia activation and polarization toward a M2 phenotype that could be permissive for cell survival and repair.
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J. Cereb. Blood Flow Metab. · Aug 2017
Site-specific elevation of interleukin-1β and matrix metalloproteinase-9 in the Willis circle by hemodynamic changes is associated with rupture in a novel rat cerebral aneurysm model.
The pathogenesis of subarachnoid hemorrhage remains unclear. No models of cerebral aneurysms elicited solely by surgical procedures and diet have been established. Elsewhere we reported that only few rats in our original rat aneurysm model manifested rupture at the anterior and posterior Willis circle and that many harbored unruptured aneurysms at the anterior cerebral artery-olfactory artery bifurcation. ⋯ Notably, the level of matrix metalloproteinase-9 associated with interleukin-1β was augmented by the increase in the blood flow volume, suggesting that these molecules exacerbated the vulnerability of the aneurysmal wall. The current study first demonstrates that a site-specific increase in interleukin-1β and matrix metalloproteinase-9 elicited by hemodynamic changes is associated with rupture. Our novel rat model of rupture may help to develop pharmaceutical approaches to prevent rupture.