Intermediate Vessels Research Articles

Diameter-dependent classification of dermal vasculature using optical coherence tomography angiography.

Dermal blood vessels beneath the epidermis play critical roles in epidermal homeostasis and are functionally divided into several types, such as capillaries. Optical coherence tomography angiography (OCTA) is a powerful tool for the non-invasive assessment of dermal vasculature. However, the classification of vessel types has been limited. To address this issue, we proposed an algorithm for diameter-dependent classification that preserves three-dimensional (3D) information using OCTA. OCTA data were acquired by a prototype swept-source-type optical coherence tomography (OCT) system, which was processed through several imaging filters: an optical microangiography (OMAG) imaging filter, a vesselness imaging filter, and a diameter map filter. All vessels were visually classified into three types based on their diameters, as micro-vessels, intermediate vessels, and thick vessels. Aging-related alterations and their association with the epidermis were investigated for each vessel type. The measurements were conducted on the cheeks of 124 female subjects aged 20-79 years. The 3D vascular structure was visualized by applying our proposed post-processing filters. Based on visual assessment, the thresholds for the diameters of the micro, intermediate and thick vessels were set at 80 and 160 µm. It was found that micro-vessels were predominantly located in the upper layer of the dermis and thick vessels in the deeper layer. Analysis of vessel metrics revealed that the volume density of the micro-vessels decreased significantly with age (r=-0.36, P<0.001) and was positively correlated with epidermal thickness (r=0.50, P<0.001). In contrast, the volume density of thick vessels significantly increased with age (r=0.2, P<0.05) and was not significantly correlated with epidermal thickness (r=0.13, P≥0.05). In this study, we proposed a 3D quantification method using OCTA for dermal blood vessels and various vessel metrics, such as vessel volume density. This proposed classification will be beneficial for determining the function of the dermal vasculature and its diagnostic applications.

Topographic analysis of retinal and choroidal vascular displacements after macular hole surgery

It has been reported that the retinal vessel and macular region of the retina are displaced after macular hole (MH) surgery. However, there is no detailed information for correlations between retinal and choroidal displacements. We obtained optical coherence tomography angiography (OCTA) and en-face optical coherence tomography (OCT) images from 24 eyes to measure the retinal and choroidal vascular displacement before and after surgery. These images were merged into infrared images using blood vessel patterns. The same vascular bifurcation points were automatically selected for each follow-up image, and the displacements of the bifurcation points were analyzed as a vector unit for prespecified grid regions in a semi-automated fashion. The results showed displacements of the choroidal intermediate vessels and retinal vessels following MH surgery (p = 0.002, p < 0.001). The topographic changes showed inferior, nasal, and centripetal displacement of the retina and inferiorly displaced choroid. The ILM peeling size and basal MH size were significantly associated with the retinal displacement (p < 0.001 and p = 0.010). Additionally, changes in the amount of the choroidal displacement were significantly correlated with that of the retinal displacements (p = 0.002). Clinicians should keep in mind that there might be topographic discrepancies of the displacement between retina and choroid when analyzing them following surgery.

Computational substantiation of technological characteristics of the closure stage of nuclear fuel cycle using code VIZART

There exist different variants of organizing the closure of nuclear fuel cycle (CNFC) depending on fast reactor type, fuel types, station or centralized allocation of closed nuclear fuel cycle stages. One of the ways to verify and estimate engineering solution is mathematical modeling of radiochemical technology which in the end will allow to optimize composite technological process in order to increase effectiveness and reduce cost. In order to calculate the balance of material flows of process circuits and individual production sections in the stationary and dynamic modes, with taking into account the isotopic composition evolution, a software package VIZART (Virtual Plant of Radiochemical Technologies) was developed, allowing the user to assemble the required sequence of operations for any part of the process scheme and perform the calculation of material balance for all flows of the circuit, as well as to optimize the equipment operating modes and provide the necessary data to justify the safety of certain limits and the entire process circuit. The following capabilities of code VIZART for computational substantiation of CNFC technology design and characteristics are considered: material balance calculation, cyclogram creation, determination of the most loaded parts of processing lines, estimation of fissile materials accumulating in devices and intermediate vessels, optimization of productivity of nodes and devices.

Endothelial cell proliferation and vascular patterns in urothelial carcinoma.

The bladder cancer has some characteristics: the sixth most incident neoplasm in the United States, the majority of diagnosed cases in those 55 years of age and older, four times more common in man than women, a reduced five-year survival rate in case of metastatic disease. Despite the beneficial effects of the combination therapy and immunotherapy, the low response rate and drug resistance were reported. The main goal of this work was evaluation of the endothelial cell proliferation from urothelial carcinomas. Fifty-two cases of T2-T4 infiltrative bladder tumors, aged between 46 and 78 years, were investigated. Morphological, simple and cluster of differentiation 31 (CD31)∕Ki67, CD31∕smooth muscle actin (SMA) double immunostaining were performed. In all the analyzed infiltrative bladder tumors, three types of vessels were noticed: immature, intermediate and mature. In the central part of the tumor area, the following distribution of vessel types was noticed: immature (62.25%), intermediate (35.1%), and mature vessels (2.65%). In the peripheral tumor area, the intermediate vessels increase numerically, up to 54% and the mature ones, up to 18.6%. The peritumoral area was characterized by the absence of immature vessels and the presence of intermediate and mature ones only. It was found the presence of endothelial cell nuclei stained for Ki67 only for immature and intermediate vessels, and never for mature ones. The vascular patterns may contribute to a better stratification of the patient subgroups and antiangiogenic treatment algorithms.

Effect of Surgical Sympathectomy in Patients Diagnosed with Thromboangiitis Obliterans Compared to Pharmacotherapy and Bypass Surgery

Background: Thromboangiitis obliterans (TAO) is a vasculopathy involving small and intermediate vessels of extremities with various medical and surgical treatment strategies. Objectives: This cohort study aimed to compare the outcomes of medical and surgical interventions in patients with TAO. Methods: Patients with a definite diagnosis of TAO were enrolled in the study and evaluated on the first day, as well as three and six months follow-up visits. A total of 70 patients with TAO were followed for 30 months. Improvements in the primary complaints (claudication of calves and soles, rest pain, paresthesia, thrombophlebitis migrans, gangrene, scars, Raynaud's phenomenon) were compared between the groups. Results: In terms of gender, 98.6% of participants were male. The mean age of the patients was 43.24± 9.8 years. Based on the results, 37 sympathectomy surgery, 11 amputation surgery, 15 bypass surgery, and 12 medical therapies with ILOPROST were considered for the patients (Medical treatment as combination therapy in patients with severe symptoms). The final results demonstrated that primary complaints were significantly improved in patients who underwent bypass surgery than in others. Conclusion: As evidenced by the obtained results, patients in our study significantly benefited more from bypass surgery than sympathectomy and pharmacotherapy

Neonatal medium-sized vessel vasculitis: A rare case report

Vasculitis is a rare disorder during the neonatal period. We present a term male neonate of consanguineous parents and birthweight of 4 030 g who presented at 11 days of life with an evolving skin rash. There was no history of drug exposure in the neonate except for routine care. On day 7 of life, multiple erythematous plaques with necrotic or pustular centres appeared. There were no signs of mucosal involvement or sepsis and laboratory findings were normal. Skin biopsy revealed small and intermediate vessel vasculitis. At follow-up 2 weeks after discharge from the hospital, the skin lesions persisted, and at age 2 months, the patient presented with features of severe pneumonia and subsequently died. Vasculitis was reported as the cause of death on postmortem biopsy.

Flow management strategies for a connected purification process.

This paper describes different flow management strategies for a connected purification process which includes two polishing steps, virus filtration and tangential flow filtration. Connecting these unit operations avoids introducing large intermediate product pool vessels in small manufacturing facilities. However, a connected-downstream process requires an elaborate control strategy enabling multiple unit operations to function as a single unit. The key strategy to enable the connected-downstream process is a robust management of flow disparities among unit operations. During a typical ultrafiltration step, product concentration increases as mass is added to the retentate tank, leading to a permeate flux decline. In a connected-downstream process, the inlet stream is directly connected to the prior unit operation and any decrease in permeate flow rate could cause a flow disparity. Four different flow management approaches are proposed to manage potential flow disparities and their advantages and challenges are discussed. Bench-scale results of these strategies are presented and evaluated.

Assessing the energy requirements for butanol production using fermentation tanks-in-series operated under vacuum

Abstract The acetone-butanol-ethanol (ABE) fermentation from corn stover was considered. We propose, study and optimise, via process simulation (using MATLAB® and Aspen Plus®) the use of fermentation tanks-in-series and in situ product recovery by vacuum evaporation. As the operating time of continuous fermentation processes is usually limited at less than 500 h, shutdown and start-up of the reactors are considered and optimised. A multi-objective optimisation methodology that considers economics as well as the energy requirements of the process was used. The optimal configuration was found to be five fermentation tanks-in-series where the first and the last reactors are operated at atmospheric pressure, and the intermediate vessels are operated under vacuum. The economic potential using this configuration was found to be 45% higher than that of vacuum fermenters operating in parallel (continuous operating mode). Also, the total fuel requirements for ABE recovery and purification system were as low as 7 MJ kg−1 butanol, a reduction of between 4 and 33% when compared to a parallel configuration of batch, fed-batch or continuous fermenters. The energy efficiency of this recovery and reaction system was as high as 74% when co-generation is considered.

ІНГІБІТОРНА ЕФЕКТИВНІСТЬ І СКЛАД ЕКСТРАКТУ КОРИ ДУБА

Regional and international researchers have proven that natural products, plants and their extracts can be used to reduce the corrosion rate. Such studies are relevant because natural inhibitors are obtained from renewable sources, therefore they are environmentally friendly. Ukrainian scientists have investigated the inhibition effect of oak bark extracts, but no such studies have been performed on cast iron. What is more, it has not been established which substances cause this effect. The purpose of the study is to determine the corrosion resistance of 08kp steel and gray cast iron SCh-15 (common structural materials of food industry equipment) in acidic and neutral environments in presence of oak bark extracts; to define the qualitative composition of the extract. Structure of cast iron and steel samples was studied on a metallographic microscope MMP-14C. The corrosion rate of metals was evaluated by weight. To determine the corrosion potential, we used a setting of a cathode voltmeter, electrodes (test and saturated chloride-silver), an intermediate vessel with a saturated KCl solution and electrolytic keys filled with the test electrolyte and saturated KCl solution (for the comparison electrode). The extract was analyzed on a Shimadzu GCMS-QP2020 gas chromatograph with mass-selective detection. Using weight method, the inhibition effect of oak shavings alcohol extract was proved in acidic and neutral corrosive environments. Under the influence of oak bark extract (5%), the stationary potential of steel 08kp has shifted: in 3% NaCl solution (oxygen depolarization) – towards more negative values; in 5% HCl solution (hydrogen depolarization) – to less negative values. Gas chromatography with mass-selective detection (GC/MS) revealed that the active substance in the extract is a mixture of natural tannins – polyphenolic compounds with a molecular weight of 500 to 3000. The inhibition effect of natural tannins is probably enhanced by siloxane compounds.

Choroidal and retinal displacements after vitrectomy with internal limiting membrane peeling in eyes with idiopathic macular hole

It has been reported that the macular region of the retina is displaced after vitrectomy with internal limiting membrane (ILM) peeling in eyes with macular hole (MH), but the displacements of the deeper layers of the eye, e.g. RPE and choroid are unclear following the surgery. We used optical coherence tomography (OCT) and OCT angiography (OCTA) to obtain 3 mm × 3 mm en face images before, and 2, 4, and 8 weeks following the vitrectomy with internal limiting membrane (ILM) peeling from 22 eyes of 22 patients with a MH. The OCT and OCTA images showed displacements of the fovea and choroidal intermediate vessels postoperatively. The degree of displacement of the choroid was significantly less than that of the retina (P < 0.001). The displacements of the choroidal bifurcations were significantly correlated to their preoperative distance from the optic disc (r = −0.467, P < 0.001) and they were significantly correlated with the retinal displacements (r = 0.535, P < 0.001). The retina was displaced inferiorly and centripetally, but these localized displacements were not observed in the choroid. In conclusion, clinicians need to be aware of these displacements when evaluating the subfoveal choroid following the surgery because the displacement is different between the retina and the choroid.

The impact of arterial injury level on blood supply of distal limb in lower limb trauma

Objective To explore the impact of arterial injury on distal limb blood supply in lower limb trauma. Methods Retrospective analysis of 93 patients with different levels of lower limb arterial injury admitted to our hospital from June 2014 to August 2017. There were 84 males and 9 females aged 43.54±9.90 years (ranging 25-65 years). Revascularization was performed through open reduction. Patients were divided into three groups according to their arterial injury locations. Proximal vessels were along the superficial femoral artery, from its beginning to the point where it was divided into the descending genicular artery and direct periosteal branches. Intermediate vessels were from the dividing point on the superficial femoral artery to the popliteal artery before it was divided into the medial inferior genicular artery. Distal vessels were from the dividing point on the popliteal artery to the distal end of the peroneal artery. The duration from injury to revascularization in the three groups were 13.67±5.99 h, 11.15±4.43 h, and 11.92±5.48 h, respectively. There was no significant difference between groups (F=1.564, P=0.215). ISS in the three groups were 13.00±3.74, 12.77±3.81, and 11.50±3.99, respectively. There was no significant difference between groups (F=1.445, P=0.241). The following items were compared among the three groups, postoperative creatine kinase, arterial blood lactate and limb compartment cut. Results Creatine kinase of the intermediate vascular group was 8 743.15±6 968.48 u/L, proximal vascular group 1 467.67±1 810.27 u/L, distal vascular group 2 893.51±1 304.56 u/L. The data of intermediate vascular group were higher than those of proximal and distal vascular groups with significant difference among the groups (F=22.587, P=0.000). The lactate of the intermediate vascular group was 3.20±1.51 mmol/L, proximal vascular group 1.63±0.46 mmol/L, distal vascular group 1.85±0.69 mmol/L with significant difference among the groups (F=20.612, P=0.000). The compartment cut of the intermediate vascular group was incised in 24, but not in 15. The proximal vascular group was not incised in 18, while 15 was incised and 21 not incised in distal vascular group. The rates of compartment cut were 61.5%, 0 and 41.7%, respectively with significant differences (χ2=19.156, P=0.000). Conclusion In lower limb injuries, the intermediate vascular (from the superficial femoral artery after it is divided into the descending genicular artery and direct periosteal branches to the popliteal artery before it is divided into the medial inferior genicular artery) injury leads to the most severe distal limb ischemia. Key words: Vascular system injuries; Wounds and injuries; Vascular grafting

Experimental research of condensate blockage and mitigating effect of gas injection

Abstract The condensate blockage causes a substantial decrease in well productivity for gas condensate reservoirs. Based on the previous studies, a novel experimental method was designed to evaluate condensate blockage and the mitigating effect of gas injection. The method considers the stacking effect in the near wellbore region and the gas flow in the far wellbore region. There is an intermediate vessel containing condensate gas at the entrance of core holder in the experimental apparatus. In the process of pressure depletion experiment in a long core model, the vessel is connected to the core and the pressure of the vessel remains above the dew point pressure. The seriousness of condensate blockage is investigated by this research. When pressure drops to maximum retrograde condensation pressure, the gas permeability decreases by 80% compared with the initial gas permeability. Contrastive experiments were conducted to study the removal effect of different injection fluids and different injection volumes. The results show that CO2 injection is more effective than methanol in mitigating condensate blockage and the optimal CO2 injection volume is around 0.15 HCPV.

Counting of angiogenesis in colorectal carcinomas using double immunostain.

The aim of the study was to compare the simple immunostains performed with CD31, CD34 and CD105 antibodies, with double-labeling immunostains realized with CD105 (endoglin) and smooth muscle actin antibodies in colorectal carcinomas. Fourty colorectal carcinoma surgical specimens were immunohistochemically studied. Quantification of microvessel density was realized at 400× magnification, in the intratumoral and peritumoral areas and distant from the tumor. With simple immunostains, it was very difficult to identify the type of vessel. With CD105/smooth muscle actin double-labeling stain we determined vessels maturation grade and identified the following types of vessels: isolated endothelial cells, immature, intermediary, mature and activated mature vessels. The density of intermediate vessels was higher in well-differentiated (2 ± 0.03) than in moderately (0.14 ± 0,02) or poorly differentiated colorectal carcinoma (0.07 ± 0.01). Such vessel types could not be identified with simple immunostains, and we believe that this is one reason why double-labeling immunostaining with CD105/smooth muscle actin should be used to study angiogenesis in colorectal carcinoma. We conclude that the density of intermediate vessels, correlated with the histological grade, could indicate the success or failure of the antiangiogenic treatment. Double-labeling immunostaining is indispensable to study vessel maturation grade.

152 Recurrent Cytogenetic Abnormalities in Intravascular Large B-Cell Lymphoma

Intravascular large B-cell lymphoma (ILBCL) is a rare (<1 per 1,000,000) and aggressive extranodal lymphoma characterized by the proliferation of lymphoma cells almost exclusively within the lumina of small and intermediate vessels. While ILBCL has been associated with complex karyotypes, data characterizing its cytogenetic landscape and the presence of recurrent cytogenetic abnormalities are limited. Here, we present the results of the largest pooled dataset to date. An institutional database was queried for cases of ILBCL with complete cytogenetic analysis and a literature search was performed using PubMed to identify all published cases of definitively diagnosed ILBCL for which a complete karyotype was provided. The identified karyotypes were systematically reviewed for the presence of recurrent abnormalities. Four new cases were identified and pooled, with 25 karyotypes previously published in the literature. Twenty of 29 (69%) patients had abnormalities involving chromosome 1. Ten translocations were present in eight patients, six of which involved either p13 or q21. In three additional patients, three rearrangements involving these breakpoints were also present. Thus, nine of 29 patients had rearrangements involving 1p13 or 1q21. 17/29(58.6%) patients had abnormalities involving chromosome 3. The most common rearrangement was a translocation, which was definitively present in eight patients, of which four (50%) involved 3p21. Seventeen of 29 (58.6%) patients had abnormalities involving chromosome 6. In almost all cases, the long arm of chromosome 6 was implicated, including seven patients with additional material of unknown origin and four 6q deletions. Twelve patients (41.4%) had abnormalities involving chromosome 14, nine (31% of total) of which involved rearrangements of 14q32. Sixteen patients (55.2%) had abnormalities of chromosome 18. Ten of 29 total patients (34.5%) had trisomy 18. ILBCL is associated with multiple recurrent cytogenetic abnormalities, the identification of which may facilitate diagnosis. Further research is warranted to determine the prognostic significance of these aberrations.

Morphological quantification of myocardial pathology in the Zucker diabetic fatty rat

&#x0D; &#x0D; &#x0D; Abstract&#x0D; Zucker Diabetic Fatty rat is an animal model that demonstrates disease progression in terms of complications which are similar to those seen in patients with Type 2 diabetes.The objective of the current study was to employ light and electron microscopy to quantify changes to the myocardial microvasculature and cardiomyocytes in the myocardial tissue of ZDF rats and establish a mechanistic basis for alterations in cardiac function. Materials and Methods:ZDF rats and lean Zucker rats (control) were housed in groups according to their breed. The ZDF rats were supplied with diabetogenic chow (Purina 5008) while the lean Zucker rats had access to standard chow as recommended by the supplier. At 12-14 weeks of age, animals were weighed and sacrificed by cervical dislocation. A blood sample was obtained for determination of blood glucose, and lipid profile.Both samples from LAA and the apex of left ventricle were carefully dissected, divided into small sections then fixed, impeded, sectioned, stained and random sections were photographed and the images were assessed and quantified using Image Analyser Pro-Plus software, version 4.1. Arterioles, venules, intermediate sized vessels, and capillaries were directly counted within the highlighted area of myocardium under light microscope. Ultra-thin sections were imaged in a Tecnai 12 Biotwin transmission electron microscope at a magnification of x4200 and photographed by a camera with a black and white film to quantify different structures of myocardium. Results: Significant reductions in the total vessel, intermediate vessel and capillary density of LAA in the ZDF rats compared to controls were noticed (P= 0.03). As well as a significant increase in the transverse diameter of cardiomyocytes in the ZDF rats compared to controls of LV (P= 0.049). There were significant increase in the basement membrane area of distal myocardial capillaries of both left atrium appendage and left ventricle in the ZDF rats compared to controls (P= 0.008).&#x0D; &#x0D; &#x0D; &#x0D; Conclusion: Early evidence of cardiomyocyte hypertrophy with a reduction in atrial vascular density and evidence of early structural changes in myocardial capillaries in the ZDF rats was noticed. These changes indicate the presence of microangiopathy in the heart of ZDF rats which is surprisingly more prominent in the LAA.&#x0D; Keywords: Zucker Diabetic Fatty (ZDF), Type 2 diabetes mellitus, Left Atrial Appendage, Left ventricle, Cardiomyocyte, Myocardial capillaries.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D;

Industrial Electron-Beam Installation L-4 for Melting and Vacuum Refining of Metals and Alloys

Electron-beam melting is the most effective method of refining and degassing metals in vacuum. Equipment for its implementation is produced in Germany, USA, Ukraine, and other countries. The paper discusses the design features and process capabilities of an industrial electron-beam installation of new generation for melting and vacuum refining of metals and alloys with an intermediate vessel or a direct crystallizer developed at the ELTECHMACH Research and Manufacturing Company (Vinnitsa, Ukraine). A distinctive feature of the installation is the ability to melt highly reactive and refractory metals and materials with a high gas content through the use of high-voltage glow discharge guns that operate steadily in relatively low vacuum.

Field measurements of supermarket refrigeration systems. Part I: Analysis of CO2 trans-critical refrigeration systems

This study investigates the refrigeration performance of three CO2 trans-critical solutions based on field measurements. The measurements are carried out in five supermarkets in Sweden. Using the field measurements, low and medium temperature level cooling capacities and COP's are calculated for ten-minute intervals, filtered and averaged to monthly values. The results indicate that the systems using trans-critical booster system with gas removal from the intermediate vessel have relatively the highest total COP. The reasons are higher evaporation temperatures, lower internal and external superheat and higher total efficiency of booster compressors. Another important factor is gas removal from the intermediate vessel which leads to higher COP of low temperature level. Comparing the older and newer installed systems, a trend in energy efficiency improvement has been seen. The study shows this improvement originates from both changes in the system design (e.g. two stage expansion) and components efficiency improvement (e.g. higher total efficiency of compressors - lower internal superheat and higher evaporation temperatures of cabinets).

Devices for transportation and dosing of adhesive compounds at assembly facilities

This article considers questions regarding the relevance of using automated devices to supply adhesives into the technological process of assembly facilities that use adhesives. A description is given of the construction of standard devices and systems of transportation, as well as of dosed application of adhesive compounds equipped with a means of monitoring the dose with respect to time and air pressure in an intermediate vessel.

Time requirements in closed and open batch distillation arrangements for separation of a binary mixture

Abstract Batch time requirements are provided for the separation of binary zeotropic mixtures in two different multivessel columns (with and without vapor bypass), a non-cyclic two-vessel column and a regular batch column based on dynamic simulations. The first three columns are operated as closed (total reflux) systems and the regular batch column is operated as an open (partial reflux) system. We analyze the effects of feed composition, relative volatility and product specification on the time requirements. The multivessel arrangements perform better than the regular batch column, which requires from 4.00 to 34.67% more time to complete a given separation. The elimination of the vapor bypass in the multivessel column is impractical though it has a positive effect on the batch time requirements. Thus, the multivessel column, with the vapor stream bypassing the intermediate vessel, is proposed as the best candidate for a binary zeotropic mixture with low concentration of light component, low relative volatility and high product purity demand. Furthermore, an experimental multivessel column with vapor bypass is built and the corresponding experiments verify the simulations.

Opposite Reactivity of Meningeal versus Cortical Microvessels to the Nitric Oxide Donor Glyceryl Trinitrate Evaluated In Vivo with Two-Photon Imaging

Vascular changes underlying headache in migraine patients induced by Glyceryl trinitrate (GTN) were previously studied with various imaging techniques. Despite the long history of medical and experimental use of GTN, its effects on the brain vasculature are still poorly understood presumably due to low spatial resolution of the imaging modalities used so far. We took advantage of the micrometer-scale vertical resolution of two-photon microscopy to differentiate between the vasodynamic effects of GTN on meningeal versus cortical vessels imaged simultaneously in anesthetized rats through either thinned skull or glass-sealed cranial window. Intermediate and small calibre vessels were visualized in vivo by imaging intravascular fluorescent dextran, and detection of blood flow direction allowed identification of individual arterioles and venules. We found that i.p.-injected GTN induced a transient constriction of meningeal arterioles, while their cortical counterparts were, in contrast, dilated. These opposing effects of GTN were restricted to arterioles, whereas the effects on venules were insignificant. Interestingly, the NO synthase inhibitor L-NAME did not affect the diameter of meningeal vessels but induced a constriction of cortical vessels. The different cellular environment in cortex versus meninges as well as distinct vessel wall anatomical features probably play crucial role in the observed phenomena. These findings highlight differential region- and vessel-type-specific effects of GTN on cranial vessels, and may implicate new vascular mechanisms of NO-mediated primary headaches.