Spatial and temporal patterns of nitric oxide diffusion and degradation drive emergent cerebrovascular dynamics.
- 作者列表："Haselden WD","Kedarasetti RT","Drew PJ
:Nitric oxide (NO) is a gaseous signaling molecule that plays an important role in neurovascular coupling. NO produced by neurons diffuses into the smooth muscle surrounding cerebral arterioles, driving vasodilation. However, the rate of NO degradation in hemoglobin is orders of magnitude higher than in brain tissue, though how this might impact NO signaling dynamics is not completely understood. We used simulations to investigate how the spatial and temporal patterns of NO generation and degradation impacted dilation of a penetrating arteriole in cortex. We found that the spatial location of NO production and the size of the vessel both played an important role in determining its responsiveness to NO. The much higher rate of NO degradation and scavenging of NO in the blood relative to the tissue drove emergent vascular dynamics. Large vasodilation events could be followed by post-stimulus constrictions driven by the increased degradation of NO by the blood, and vasomotion-like 0.1-0.3 Hz oscillations could also be generated. We found that these dynamics could be enhanced by elevation of free hemoglobin in the plasma, which occurs in diseases such as malaria and sickle cell anemia, or following blood transfusions. Finally, we show that changes in blood flow during hypoxia or hyperoxia could be explained by altered NO degradation in the parenchyma. Our simulations suggest that many common vascular dynamics may be emergent phenomena generated by NO degradation by the blood or parenchyma.
: 一氧化氮 (NO) 是一种气体信号分子，在神经血管偶联中起重要作用。神经元产生的NO扩散到脑小动脉周围的平滑肌中，驱动血管舒张。然而，血红蛋白中NO降解的速率比脑组织中高几个数量级，尽管这可能如何影响NO信号传导动力学尚不完全清楚。我们使用模拟来研究NO生成和降解的空间和时间模式如何影响皮质中穿透性小动脉的扩张。我们发现NO产生的空间位置和容器的大小在决定其对NO的响应性方面都起着重要作用。血液中NO降解和清除相对于组织而言高得多的速率驱动了紧急的血管动力学。大的血管舒张事件之后可能是由血液增加的NO降解驱动的刺激后收缩，并且也可能产生类似血管运动的0.1-0.3Hz振荡。我们发现，这些动态可以通过血浆中游离血红蛋白的升高来增强，这发生在疟疾和镰状细胞性贫血等疾病中，或输血后。最后，我们发现缺氧或高氧期间血流的变化可以通过改变实质中的NO降解来解释。我们的模拟表明，许多常见的血管动力学可能是由血液或实质不降解产生的紧急现象。
METHODS:BACKGROUND:Thalassemia is one of the most common monogenetic diseases in the south of China and Southeast Asia. Hemoglobin Bart's hydrops fetalis syndrome was caused by a homozygous Southeast Asian deletion (-/-) in the HBA gene. Few studies have proved the potential of screen for Bart's hydrops fetalis using fetal cell-free DNA. However, the number of cases is still relatively small. Clinical trials of large samples would be needed. OBJECTIVE:In this study, we aimed to develop a noninvasive method of target-captured sequencing and genotyping by the Bayesian method using cell-free fetal DNA to identify the fetal genotype in pregnant women who are at risk of having hemoglobin Bart hydrops fetalis in a large-scale study. STUDY DESIGN:In total, 192,173 couples from 30 hospitals were enrolled in our study and 878 couples were recruited, among whom both the pregnant women and their husbands were detected to be carriers of Southeast Asian type (-/αα) of α-thalassemia. Prenatal diagnosis was performed by chorionic villus sampling, amniocentesis, or cordocentesis using gap-polymerase chain reaction considered as the golden standard. RESULTS:As a result, we found that the sensitivity and specificity of our noninvasive method were 98.81% and 94.72%, respectively, in the training set as well as 100% and 99.31%, respectively, in the testing set. Moreover, our method could identify all of 885 maternal samples with the Southeast Asian carrier and 36 trisomy samples with 100% of sensitivity in T13, T18, and T21 and 99.89% (1 of 917) and 99.88% (1 of 888) of specificity in T18 and T21, respectively. CONCLUSION:Our method opens the possibility of early screening for maternal genotyping of α-thalassemia, fetal aneuploidies in chromosomes 13/18/21, and hemoglobin Bart hydrops fetalis detection in 1 tube of maternal plasma.
METHODS:OBJECTIVES:Sickle cell disease (SCD) is a serious illness with disabling acute and chronic pain that needs better therapies, but insufficient patient participation in research is a major impediment to advancing SCD pain management. The purpose of this article is to discuss the challenges of conducting an SCD study and approaches to successfully overcoming those challenges. DESIGN:In a repeated-measures, longitudinal study designed to characterize SCD pain phenotypes, we recruited 311 adults of African ancestry. Adults with SCD completed 4 study visits 6 months apart, and age- and gender-matched healthy controls completed 1 visit. RESULTS:We recruited and completed measures on 186 patients with SCD and 125 healthy controls. We retained 151 patients with SCD with data at 4 time points over 18 months and 125 healthy controls (1 time point) but encountered many challenges in recruitment and study visit completion. Enrollment delays often arose from patients' difficulty in taking time from their complicated lives and frequent pain episodes. Once scheduled, participants with SCD cancelled 49% of visits often because of pain; controls canceled 30% of their scheduled visits. To facilitate recruitment and retention, we implemented a number of strategies that were invaluable in our success. CONCLUSION:Patients' struggles with illness, chronic pain, and their life situations resulted in many challenges to recruitment and completion of study visits. Important to overcoming challenges was gaining the trust of patients with SCD and a participant-centered approach. Early identification of potential problems allowed strategies to be instituted proactively, leading to success.
METHODS:OBJECTIVES:Sickle cell anemia is the commonest genetic disorder in India, and the frequency of the sickle cell gene is very high in the remote tribal areas where facilities are generally limited. Therefore, a rapid and affordable point-of-care test for sickle cell disease is needed. METHODS:The diagnostic accuracy of HemoTypeSC was evaluated against automated high-performance liquid chromatography (HPLC) as the gold standard for its efficacy in a newborn screening program. RESULTS:A total of 1,559 individuals (980 newborns and 579 adults) from four participating centers were analyzed by both methods. HemoTypeSC correctly identified 209 of 211 total hemoglobin (Hb) SS cases, for a 99.1%/99.9% total HbSS sensitivity/specificity. Overall, HemoTypeSC exhibited sensitivity and specificity of 98.1% and 99.1% for all possible phenotypes (HbAA, HbAS, and HbSS) detected. HPLC is relatively expensive and not available in most laboratories in remote tribal areas. CONCLUSIONS:We conclude that the rapid, point-of-care testing device HemoTypeSC test is suitable for population and newborn screening for the HbS phenotype.