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<p>Carpal tunnel syndrome (CTS) is one of the most prevalent work-related musculoskeletal disorders of the upper extremity yet its etiology remains elusive. Nerve hypervascularization has been proposed as a pathophysiological change in CTS and can be measured using high resolution sonography of intraneural blood flow. The purpose of this study was to determine the effects of deviated wrist postures and fingertip force on the intraneural blood flow velocity of the median nerve proximal to the wrist crease. Ten participants experiencing the classic symptoms of CTS and nine healthy volunteers were recruited and underwent qualitative assessments (Phalen’s test, Katz hand diagram, Levine’s CTS questionnaire). Intraneural blood flow velocity was measured in five wrist postures (flexion 30°, flexion 15°, neutral, extension 15°, extension 30°) with and without a middle digit fingertip press (0N, 6N). A control (N=9) group and a CTS symptomatic (N=9) group were determined, in addition to a CTS individual (N=1) that required a separate analysis. A significant main effect of force was found (F_1,16= 28.039, p < 0.0005) with the mean peak velocity being greater with force (3.56 cm/s) than without force (2.81 cm/s). Wrist posture had a main effect (F_4,64= 3.163, p < 0.020) with flow velocity as neutral (2.87 cm/s) was significantly lower than flexion 30° (3.37 cm/s), flexion 15°(3.27 cm/s) and extension 30° (3.29 cm/s). There was no significant difference in peak blood flow velocity between the two experimental groups, CTS symptomatic (3.34 cm/s) and control (3.03 cm/s) (F_1,16= 4.121, p < 0.059). The results suggest that both force and non-neutral wrist postures may acutely induce vascular changes previously associated with CTS. The quantification of reactive median nerve hypervascularity should be investigated further as it has potential to be both a reliable diagnostic technique and a non-invasive assessment of CTS risk.</p> / Master of Science in Kinesiology

<p><h1>ABSTRACT</h1> <h1>Individuals with spinal cord injuries (SCI) are prone to significant alterations in vascular structure and function. This study was designed to examine the effects of osteopathic treatment on mean leg (MLBF) blood flow and skin temperature in the lower extremities of individuals with chronic SCI compared to able-bodied (AB) individuals. Methods: Nine individuals (age 44 ± 17.5 years) with a chronic SCI (C6-T12; AIS A-B; 3.7 ± 4.6 years post-injury) and six AB individuals (38.3 ± 9.7 years) participated. The protocol consisted of 1 interview session and 3 osteopathic treatment sessions. Doppler ultrasound measured the diameter and mean blood velocity in the CFA before (Pre) and after (Post) each session. Skin temperatures were measured using skin thermistors at three different sites on the left leg. Change scores were calculated and measured as post-treatment minus pre-treatment. Results: A two-way ANOVA revealed an increase in flow of 16±2 ml/min within the SCI group and a decrease in flow of 25±2 ml/min in the AB group (p = 0.04). There was also a smaller reduction in skin temperature in individuals within the SCI versus AB (left thigh: SCI, -0.5±0.2° C; AB, -1.2±0.2°C, p(left foot: SCI, -0.1±0.4°C; AB, -1.8±0.4°C, pAll treatments resulted in small increases in MLBF in the SCI group versus small decreases in the able-bodied group and smaller skin temperature decreases in the SCI versus the decreases in the AB group, potentially indicating reduced skin temperature reactivity. These findings emphasize the potential for different physiological responses to interventions in individuals with SCI compared to AB individuals.</h1></p> / Master of Science in Kinesiology

Peripheral artery disease (PAD) affects more than 200 million people worldwide. PAD refers to illness due to a reduction or complete occlusion of blood flow in the artery, especially to the extremities in disease conditions, such as atherosclerosis or diabetes. Critical limb ischemia (CLI) is a severe form of PAD associated with high morbidity and mortality. Currently, no effective and permanent treatments are available for this disease. The current endovascular medications (e.g., angioplasty or stents) only relieve the clinical symptoms while the surgical therapies (e.g., bypass or endarterectomy) require grafting vessels from a healthy organ to the diseased limb of the patient. However, even with these therapeutic techniques, 30% of patients still undergo limb amputation within a year. Thus, understanding of disease mechanism and development of new therapeutic approaches are in urgent needs. Meis1 (myeloid ecotropic viral integration site 1) gene belongs to the three-amino-acid loop extension subclass of homeobox gene families, and it is a highly conserved transcription factor in all eukaryotes. Up to date, little is known about the role of Meis1 in regulating vascular remodeling under ischemic condition. In this study, we aim to investigate the role and underlying mechanism of Meis1 in the regulation of arteriogenesis and angiogenesis using hindlimb ischemia model of transgenic neonatal mice. The long-term goal is to develop a new treatment for patients with PAD. Three separate but related studies were planned to complete the proposed research aims. To better understand the role of Meis1, we reviewed, in the first chapter, all literature relevant to the recent advances of the Meis1 in normal hematopoiesis, vasculogenesis, and heart developments, which were mostly studied in zebrafish and mouse. Briefly, Meis1 is found to be highly expressed in the brain and retina in zebrafish and additional in the heart, nose, and limb in mouse during the very early developmental stage, and remains at a low level quickly after birth. Meis1 is necessary for both primitive and definitive hematopoiesis and required for posterior erythroid differentiation. The absence of Meis1 results in a severe reduction of the number of mature erythrocytes and weakens the heart beats in zebrafish. Meis1 deficiency mouse is dead as early as E11.5 due to the severe internal hemorrhage. In addition, Meis1 is essential in heart development. Knock-down of Meis1 can promote angiotensin II-induced cardiomyocytes (CMs) hypertrophy or CMs proliferation, which can be repressed by a transcription factor Tbx20. Meis1 appears to play a complicated role in the blood vessels. Although the major blood vessels are still normal when global deletion of Meis1, the intersegmental vessel cannot be formed in Meis1 morphants in the zebrafish, and the small vessels are either too narrow or form larger sinuses in Meis1 deficient mouse. The effects of Meis1 on the vascular network under normal and disease (ischemia) condition remain largely unknown, and the existing data in this field is limited. In the second chapter, we developed a method protocol to identify mice of all ages, especially neonates that we faced methodological difficulties to easily and permanently label prior to our major experiments. In this study, single- or 2-color tattooing (ear, tail, or toe or combinations) was performed to identify a defined or unlimited number of mice, respectively. Tail tattooing using both green and red pastes was suitable for identifying white-haired neonatal mice as early as postnatal day (PND) 1, whereas toe tattooing with green paste was an effective alternative approach for labeling black-haired mouse pups. In comparison, single-color (green) or 2-color (green and red) ear tattooing identified both white and black adult mice older than three weeks. Ear tattooing can be adapted to labeling an unlimited number of adult mice by adding the cage number. Thus, tattooing various combinations of the ears, tail, and toes provides an easy and permanent approach for identifying mice of all ages with minimal disturbance to the animals, which shows a new approach than any existing method to identify mouse at all ages, especially the neonatal pups used in the present study (Chapter 4). Various formation of hindlimb ischemia with ligations of femoral artery or vein or both have been reported in the literature. The ischemic severity varies dependent on mouse strains and ligation methods. Due to the tiny body size of our experimental neonatal mice (PND2), it is technically challenging to separate the femoral artery from femoral vein without potential bleeding. In the third chapter, we aimed to explore a suitable surgical approach that can apply to neonatal mice. To this end, we compared the effects of femoral artery/vein (FAV) excision vs. femoral artery (FA) excision on hindlimb model using adult CD-1 mice. We showed during the 4-week period of blood reperfusion, no statistically significant differences were found between FAV and FA excision-induced ischemia regarding the reduction of limb blood flow, paw size, number of necrotic toes, or skeletal muscle cell size. We conclude that FAV and FA excision in CD-1 mice generate a comparable severity of hindlimb ischemia. In other words, FAV ligation is no more severe than FA ligation. These findings provide valuable information for researchers when selecting ligation methods for their neonate hindlimb models. Based on these findings, we selected FAV ligation of hindlimb ischemia approach to study the function of Meis1 in vascular remodeling of neonatal mice. In the fourth chapter (the main part of my dissertation), we investigated the roles of Meis1 in regulating arteriogenesis and angiogenesis of neonatal mouse under the ischemic condition. To this end, endothelial cell-specific deletion of Meis1 was generated by cross-breeding Meis1flox/flox mice with Tie2-Cre mice. Wild-type (WT, Meis1f/f) and endothelial cell-specific knock-out (KO, Meis1ec-/-Tie2-Cre+) C57BL/6 mice at the age of PND2 were used. Under the anesthesia, the pups were subject to hindlimb ischemia by excising FAV. Laser Doppler Imager was used to measure the blood flow pre- and post-surgery up to 28 days. Toe necrosis, skeletal regeneration, and vascular distributions were examined at the end of experiments (PND28 post-ischemia). Surprisingly, during 4-week periods after ischemia, the blood flow ratios (ischemic vs. control limb) in KO mice significantly increased compared to WT on PND14 and PND28, suggesting the inhibitory effects of Meis1 on blood flow recovery under ischemic condition. Meanwhile, WT mice showed more severe necrotic limb (lower ratio of limb length and area, and higher necrotic scores at PND7) than those in the KO mice. Furthermore, significant increases in diameters of Dil-stained arterioles of the skin vessel and the vessels on the ligation site were observed in KO mice, indicating the enhanced arteriogenesis in KO mice. To investigate the underlying mechanism, RNA from the ischemia and control limb was extracted and q-PCR was used to study the potential genes involved in the mechanism. Casp3 and Casp8 were found downregulated showing less apoptosis in the KO mice. On the other hand, endothelial cells (ECs) were isolated from the lungs of 3-5 WT and KO neonates using CD31 Microbeads. CD31+ cells were plated and treated with 0, 0.5, and 1μM doxorubicin for 24 hours and analyzed with various assays. Meis1-KO ECs demonstrated higher cell viability and formed a higher number of vascular tubes than those in WT ECs following 0.5μM Dox treatment, presenting the potential ability of angiogenesis in KO-ECs. Furthermore, the increased viability in KO ECs may be due to the decreased expression or activities of Casp8 and Casp3. In conclusion, my present studies have developed a new methodology to easily and permanently identify all mice at any ages. The insignificant differences between FAV and FA ligations suggest that a relative-easy surgical approach could be used to generate hindlimb ischemic model, which potentially reduces the cost, decreases the surgical time and prevents damage of femoral nerve from surgical tools. More importantly, by using transgenic mice, we found that Meis1-KO dramatically increased blood flow and protected the ischemic hindlimb through vascular remodeling. Obviously, the molecular and cellular mechanisms underlying the above beneficial effects appear complicated and likely to involve multiple cellular remodeling processes and molecular signaling pathways to enhance arteriogenesis and angiogenesis and/or reduce cellular apoptosis through Meis1-mediated pathways. Our study demonstrated that under ischemic condition, knockout of Meis1 increases expression of Hif1a, which then activates Agt or VEGF, thus enhances arteriogenesis or angiogenesis; In addition, knockout of Meis1 activates Ccnd1, which subsequently promotes regeneration of skeletal muscle, and reduces expression of Casp8 and Casp3, thus preventing limb tissue from ischemia-induced apoptosis. Our innovative findings offer great potential to ultimately lead to new drug discovery or therapeutic approaches for prevention or treatment of PAD. / PHD / Peripheral artery disease (PAD), which affects more than 200 million people worldwide, commonly refers to the vascular diseases of legs or feet due to a reduction or even complete occlusion of blood flow to these areas. PAD is usually caused by blockage of main vessels in limbs under certain diseases, such as atherosclerosis. Unfortunately, no effective and permanent treatments are available for this disease. The current medications only relieve the clinical symptoms while the surgical therapy requires grafting vessels from a healthy organ to the diseased limb of the patient. In the present study, we aim to explore a new approach to facilitate the vessel formation in ischemic limb using Meis 1 transgenic mice. Meis 1 (myeloid ecotropic viral integration site 1) gene belongs to homeobox gene families, and it is a highly conserved transcription factor in all eukaryotes. My dissertation aims to understand how Meis 1 affects vascular remodeling in the mouse following induced hindlimb ischemia (to mimic PAD). To better understand the role of Meis 1, we first reviewed the literature studying the Meis 1 function on normal hematopoiesis, vasculogenesis, and heart development in zebrafish and mouse. The studies show that Meis 1 plays a complicated role in the blood vessels. When entirely deleting Meis 1 in the zebrafish, the intersegmental vessels cannot be formed. While in a mammal study, it is found that the major blood vessels are normal while the small vessels are either too narrow or form larger sinuses in Meis 1 deficient mouse. Thus, Mesi1 appears to play an important role in regulating vascular network, but the available information in this field is insufficient. The present projects aimed to study the roles of Meis 1 in regulating vascular remodeling following the hindlimb ischemia induced by ligation of main limb vessels (to mimic PAD). The transgenic mice with the deletion of Meis 1 (called knockout or KO mice) were generated by a Cre-loxP system (a gene manipulation method) to remove Meis 1 only in endothelial cells. The resulting KO mice were subject to the hindlimb ischemia and compared to those mice with the intact Meis 1 (called wild-type, or WT). To this end, the entire experiments contain three separate studies. In the first studies (Chapter 2), we developed an easy, but a permanent method to identify the mice at all age, especially the neonatal mice we used in the projects. Briefly, we used single- or 2-color tattooing to identify a defined or unlimited number of mice, respectively. We labeled our adult mice with ear tattooing combined with cage number and neonatal mice with toe tattooing if necessary to identify the individual animals. Next (Chapter 3), we determined the effects of femoral artery/vein (FAV) ligation vs. femoral artery (FA) ligation alone on hindlimb severities. The purpose of this study was to generate a suitable ligation model for the neonatal mice. Interestingly, no statistically significant differences were found between FAV and FA excision-induced ischemia, suggesting that FAV ligation could be applied to the neonatal hindlimb ischemia model in the rest of study. Upon the establishment of identification and ligation approaches for neonatal mice, we conducted systemic studies at both in vitro and in vivo settings to investigate the biological function of Meis 1 under ischemic condition. Briefly, two groups of Meis 1 mice at ages of postnatal day 2 were used in the study: WT (the normal mice), and endothelial specific knock-out (KO, Meis 1 gene was entirely deleted in endothelial cells). Under anesthesia, the postnatal day 2 pups were induced hindlimb ischemia, and blood flow was measured pre- and post-ischemia up to 4 weeks. Our data demonstrated that the blood flow was significantly higher in KO mice than WT mice, suggesting deletion of Meis 1 in endothelial cells can increase blood perfusion following ischemic injury. Moreover, the KO mice showed less toe damage compared with WT, thus showing protective benefit in rescuing the damaged limb. We also found that deletion of Meis 1 in endothelial cells increased cell viability and induced generation of more numbers of vessels under an induced apoptosis condition. These findings suggested that the deletion of Meis 1 in endothelial cells facilitates vessel formation and prevents the injured limbs from loss or undergoing apoptosis/necrosis, which may lead new drug discovery and development of effective therapy for treatments of PAD.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25273号 / 工博第5232号 / 新制||工||1997(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 小椋 大輔, 教授 原田 和典, 教授 石田 泰一郎 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Es wurde überprüft, ob sich Zusammenhänge zwischen der Tumordurchblutung und Vaskularisation nachweisen lassen, ob Unterschiede in der Durchblutung zwischen malignen und benignen Herdbefunden der Brust gemessen werden können, ob sich aus der Tumordurchblutung und Vaskularisation Aussagen zur Prognose der Patientin ableiten lassen und ob sich die Durchblutung und Vaskularisation unter der präoperativen Chemotherapie bei Mammakarzinomen ändert. Die CD war im direkten Vergleich nicht der Mammographie und der konventionellen B-Bild-Mammasonograpie überlegen. Mit verschiedenen Parametern der Kontrastmittel-Videodensitometrie, wie die Zeiten bis zum maximalen Signalanstieg (Tmax) mit dem Kontrastmittel Levovist(, konnte mit einer Spezifität von bis zu 92% sicher zwischen benignen und malignen Herdbefunden unterschieden werden. Mit der Videodensitometrie war es im Gegensatz zum konventionellen CD möglich, Veränderungen der Durchblutung von Mammakarzinomen unter einer präoperativen Chemotherapie durch die Änderung der Kontrastmittelkinetik zu erkennen. Bei den kleinlumigen Gefäßen korrelierten gefäßmorphologische Parametern mit den klassischen Prognoseparametern (Lymphknotenstatus) und der Durchblutung. Selbst unter einer effektiven Chemotherapie, die auch zu einer histologischen Regression geführt hat, veränderten sich die Vaskularisationsparameter nicht signifikant. / Various qualitative and semi-quantitative blood flow and vascularisation parameters were analyzed for their value in the fields of differential diagnosis, evaluation of prognosis, and of monitoring over the time of preoperative chemotherapy. Color Doppler sonography was not superior to other diagnostic methods for preoperative and prognostic assessment of a breast lesion. In contrast agent videodensitometry the values for Tmax were significantly higher for benign breast than for breast cancer. The combination of contrast agent and subsequent video-densitometry would be able to increase the specificity (92% in this investigation) of the diagnosis of breast cancer. Color Doppler can be used to image the blood supply in the smaller blood vessels. The vascularization and the blood flow of a breast carcinoma permits conclusions to be drawn as to the metastatic lymph-node status of a patient. There were only minimal changes of vascularisation visible even in patients with histological regression of breast cancer after preoperative chemotherapy.

Indiana University-Purdue University Indianapolis (IUPUI) / Atherosclerotic lesions of human beings are common diagnosed in regions of arte- rial branching and curvature. The prevalence of atherosclerosis is usually associated with hardening and ballooning of aortic wall surfaces because of narrowing of flow path by the deposition of fatty materials, platelets and influx of plasma through in- timal wall of Aorta. High Wall Shear Stress (WSS) is proved to be the main cause behind all these aortic diseases by physicians and researchers. Due to the fact that the atherosclerotic regions are associated with complex blood flow patterns, it has believed that hemodynamics and fluid-structure interaction play important roles in regulating atherogenesis. As one of the most complex flow situations found in cardio- vascular system due to the strong curvature effects, irregular geometry, tapering and branching, and twisting, theoretical prediction and in vivo quantitative experimental data regarding to the complex blood flow dynamics are substantial paucity. In recent years, computational fluid dynamics (CFD) has emerged as a popular research tool to study the characteristics of aortic flow and aim to enhance the understanding of the underlying physics behind arteriosclerosis. In this research, we study the hemo- dynamics and flow-vessel interaction in patient specific normal (healthy) and dilated (diseased) aortas using Ansys-Fluent and Ansys-Workbench. The computation con- sists of three parts: segmentation of arterial geometry for the CFD simulation from computed tomography (CT) scanning data using MIMICS; finite volume simulation of hemodynamics of steady and pulsatile flow using Ansys-Fluent; an attempt to perform the Fluid Structure Simulation of the normal aorta using Ansys-Workbench. Instead of neglecting the branching or smoothing out the wall for simplification as a lot of similar computation in literature, we use the exact aortic geometry. Segmen- tation from real time CT images from two patients, one young and another old to represent healthy and diseased aorta respectively, is on MIMICS. The MIMICS seg- mentation operation includes: first cropping the required part of aorta from CT dicom data of the whole chest, masking of the aorta from coronal, axial and saggital views of the same to extract the exact 3D geometry of the aorta. Next step was to perform surface improvement using MIMICS 3-matic module to repair for holes, noise shells and overlapping triangles to create a good quality surface of the geometry. A hexahe- dral volume mesh was created in T-Grid. Since T-grid cannot recognize the geometry format created by MIMICS 3-matic; the required step geometry file was created in Pro-Engineer. After the meshing operation is performed, the mesh is exported to Ansys Fluent to perform the required fluid simulation imposing adequate boundary conditions accordingly. Two types of study are performed for hemodynamics. First is a steady flow driven by specified parabolic velocity at inlet. We captured the flow feature such as skewness of velocity around the aortic arch regions and vortices pairs, which are in good agreement with open data in literature. Second is a pulsatile flow. Two pulsatile velocity profiles are imposed at the inlet of healthy and diseased aorta respectively. The pulsatile analysis was accomplished for peak systolic, mid systolic and diastolic phase of the entire cardiac cycle. During peak systole and mid-systole, high WSS was found at the aortic branch roots and arch regions and diastole resulted in flow reversals and low WSS values due to small aortic inflow. In brief, areas of sudden geometry change, i.e. the branch roots and irregular surfaces of the geom- etry experience more WSS. Also it was found that dilated aorta has more sporadic nature of WSS in different regions than normal aorta which displays a more uniform WSS distribution all over the aorta surface. Fluid-Structure Interaction simulation is performed on Ansys-WorkBench through the coupling of fluid dynamics and solid mechanics. Focus is on the maximum displacement and equivalent stress to find out the future failure regions for the peak velocity of the cardiac cycle.

The importance of coronary microcirculatory perfusion is highlighted by the severe impact of microvascular diseases such as diabetes and hypertension on heart function. Recently, highly-detailed three-dimensional (3D) data on ex vivo coronary microvascular structure have become available. However, hemodynamic information in individual myocardial capillaries cannot yet be obtained using current in vivo imaging techniques. In this thesis, a novel data-driven modelling framework is developed to predict tissue-scale flow properties from discrete anatomical data, which can in future be used to aid interpretation of coarse-scale perfusion imaging data in healthy and diseased states. Mathematical models are parametrised by the 3D anatomical data set of Lee (2009) from the rat myocardium, and tested using flow measurements in two-dimensional rat mesentery networks. Firstly, algorithmic and statistical tools are developed to separate branching arterioles and venules from mesh-like capillaries, and then to extract geometrical properties of the 3D capillary network. The multi-scale asymptotic homogenisation approach of Shipley and Chapman (2010) is adapted to derive a continuum model of coronary capillary fluid transport incorporating a non-Newtonian viscosity term. Tissue-scale flow is captured by Darcy's Law whose coefficient, the permeability tensor, transmits the volume-averaged capillary-scale flow variations to the tissue-scale equation. This anisotropic permeability tensor is explicitly calculated by solving the capillary-scale fluid mechanics problem on synthetic, stochastically-generated periodic networks parametrised by the geometrical data statistics, and a thorough sensitivity analysis is conducted. Permeability variations across the myocardium are computed by parametrising synthetic networks with transmurally-dependent data statistics, enabling the hypothesis that subendocardial permeability is much higher in diastole to compensate for severely-reduced systolic blood flow to be tested. The continuum Darcy flow model is parametrised by purely structural information to provide tissue-scale perfusion metrics, with the hypothesis that this model is less sensitive and more reliably parametrised than an alternative, estimated discrete network flow solution.

Many cerebral diseases are associated with abnormal cerebral hemodynamics and impaired cerebral autoregulation (CA). CA is a mechanism to maintain cerebral blood flow (CBF) stable when mean arterial pressure (MAP) fluctuates. Evaluating these abnormalities requires direct measurements of cerebral hemodynamics and MAP. Several near-infrared diffuse optical instruments have been developed in our laboratory for hemodynamic measurements including near-infrared spectroscopy (NIRS), diffuse correlation spectroscopy (DCS), hybrid NIRS/DCS, and dual-wavelength DCS flow-oximeter. We utilized these noninvasive technologies to quantify CBF and cerebral oxygenation in different populations under different physiological conditions/manipulations. A commercial finger plethysmograph was used to continuously monitor MAP. For investigating the impact of obstructive sleep apnea (OSA) on cerebral hemodynamics and CA, a portable DCS device was used to monitor relative changes of CBF (rCBF) during bilateral thigh cuff occlusion. Compared to healthy controls, smaller reductions in rCBF and MAP following cuff deflation were observed in patients with OSA, which might result from the impaired vasodilation. However, dynamic CAs quantified in time-domain (defined by rCBF drop/MAP drop) were not significantly different between the two groups. We also evaluated dynamic CA in frequency-domain, i.e., to quantify the phase shifts of low frequency oscillations (LFOs) at 0.1 Hz between cerebral hemodynamics and MAP under 3 different physiological conditions (i.e., supine resting, head-up tilt (HUT), paced breathing). To capture dynamic LFOs, a hybrid NIRS/DCS device was upgraded to achieve faster sampling rate and better signal-to-noise. We determined the best hemodynamic parameters (i.e., CBF, oxygenated and total hemoglobin concentrations) among the measured variables and optimal physiological condition (HUT) for detecting LFOs in healthy subjects. Finally, a novel dual-wavelength DCS flow-oximeter was developed to monitor cerebral hemodynamics during HUT-induced vasovagal presyncope (VVS) in healthy subjects. rCBF was found to have the best sensitivity for the assessment of VVS among the measured variables and was likely the final trigger of VVS. A threshold of ~50% rCBF decline was observed which can completely separate subjects with or without presyncope, suggesting its potential role for predicting VVS. With further development and applications, NIRS/DCS techniques are expected to have significant impacts on the evaluation of cerebral hemodynamics and autoregulation.

<p>The human stomach normally contains high levels of bioactive nitric oxide (NO). This NO derives from salivary nitrate (NO₃^-) that is converted to nitrite (NO₂^-) by oral bacteria and thereafter non-enzymatically reduced in the acidic gastric lumen to NO. Nitrate is a common component in vegetables, and after ingestion it is absorbed in the small intestine. Interestingly, circulating nitrate is then concentrated by the salivary glands. Hence, intake of nitrate-rich vegetables results in high levels of NO in the stomach. The physiological effects of the high concentration of NO gas normally present in the gastric lumen have been hitherto unknown, and the present investigations were therefore conducted to address this issue.</p><p>NO produced in the gastric lumen after nitrate ingestion increased gastric mucosal blood flow and the thickness of the firmly adherent mucus layer in the stomach. The blood flow and mucus layer are essential defense mechanisms that protect the mucosa from luminal acid and noxious agents. Nonsteroidal antiinflammatory drugs (NSAID) are commonly prescribed and effective drugs for treating pain and inflammation, but are associated with severe gastrointestinal side effects. We demonstrated that a nitrate-rich diet protects against NSAID-induced gastric damage, as a result of the increased formation of NO in the stomach. We also showed that the gastroprotective effect attributed to nitrate depended completely on conversion of nitrate to nitrite by the bacterial flora colonizing the tongue, and that the oral microflora is therefore important in regulating physiological conditions in the stomach.</p><p>In summary, this thesis challenges the current dogma that nitrate intake is hazardous, and on the contrary suggests that dietary nitrate plays a direct role in regulating gastric homeostasis. It is likely that a sufficient supply of nitrate in the diet together with the oral microflora is essential for preventing pathological conditions in the gastrointestinal tract.</p>