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Tumor heterogeneity complicates the quantification of tumor microvascular characteristics assessed by dynamic contrast-enhanced MRI (DCE-MRI). To address this issue a novel approach was developed that combines DCE-MRI with diffusion-based multispectral (MS) analysis to quantify the microvascular characteristics of specific tumor tissue populations. Diffusion-based MS segmentation (feature space: apparent diffusion coefficient, T(2) and proton density) was performed to identify tumor tissue populations and the DCE-MRI characteristics were determined for each tissue class. The ability of this MS DCE-MRI technique to detect microvascular changes due to treatment with an antibody (G6-31) to vascular endothelial growth factor-A (VEGF) was evaluated in a tumor xenograft mouse model. Anti-VEGF treatment resulted in a significant reduction in K(trans) for the MS viable tumor tissue class (-0.0034 +/- 0.0022 min(-1), P < 0.01) at 24 hr posttreatment that differ significantly from the change observed in the control group (0.0002 +/- 0.0025 min(-1)). Viable tumor K(trans) for the anti-VEGF group was also reduced 62% relative to the pretreatment values (P < 0.01). Necrotic tissue classes were found to add only noise to DCE-MRI estimates. This approach provides a means to measure physiological parameters within the viable tumor and address the issue of tumor heterogeneity that complicates DCE-MRI analysis., ((c) 2008 Wiley-Liss, Inc.)

This review briefly summarizes what is known about the dynamic morphology of the hepatic microvascular system that includes all vessels in the liver with a diameter less than 300 microm and various morphological sites within these vessels that regulate the distribution of blood flow. The latter include the various segments of the afferent portal venules and hepatic arterioles, the sinusoids, and central and hepatic venules. Sinusoids are unique exchange vessels lined by fenestrated endothelial cells which have important endocytotic functions and phagocytic Kupffer cells which are important for host defense. These are encircled by extraluminal stellate cells that are specialized pericytes containing fat droplets that store vitamin A. The principle sites for regulating blood flow are in the sinusoidal network with stellate and endothelial cells playing a major role in regulating the diameters of sinusoids and the distribution of blood flow in individual sinusoids, lobules, or segments of lobules. The sinusoidal endothelial cells are a sensitive and early target for several toxicants. For example, as early as 30 minutes after the administration of acetaminophen, the endothelial cells become swollen and begin to lose the ability to endocytose ligands. Within 2 hr, gaps through the cytoplasm appear formed by the destruction and/or coalescence of fenestrae which permit red blood cells to penetrate into the space of Disse. Subsequently, the sinusoid may collapse or disintegrate reducing blood flow.

Background: This study presents a detailed three- and four-dimensional appraisal of the arterial and venous anatomy and perfusion of the anterolateral thigh flap using a novel computed tomographic technique., Methods: Eighteen anterolateral thigh flaps harvested from fresh Western cadavers were used. Four-dimensional computed tomographic angiography with injection of iodinated contrast medium into isolated perforators and their venae comitantes was used to investigate the arterial and venous anatomy and flap perfusion. Additional perforators were injected to investigate the vascular connections within the flap. Changes in flap perfusion after thinning and adipofascial flap harvest were also examined, and contrast density within each flap plexus with respect to the perforator was examined., Results: Large-diameter linking vessels at the suprafascial level enabled perfusion of adjacent vascular territories and of the subdermal plexus between angiotomes. Thinning reduced the size of the vascular territory by ligating recurrent vessels at the level of the suprafascial plexus. Adipofascial flap harvest prevented perfusion of the recurrent vessels, demonstrating the role of the subdermal plexus in recurrent flow. Three distinct perforator complex patterns were found with relevance to flap thinning. A superficial venous system perfused the venae comitantes of the descending branch of the lateral femoral circumflex artery and the long saphenous vein., Conclusions: A reduction in vascular territory occurs in the anterolateral thigh flap after thinning and is attributable to ligation of vessels within the suprafascial plexus. Recurrent flow through the subdermal plexus was seen dynamically for the first time and appears to be an important mechanism for skin perfusion.

Background and Purpose: This study uses T(2)* weighted imaging (T2*WI) to measure the temporal evolution of cerebral angiogenesis in rats subjected to embolic stroke up to 6 weeks after stroke onset with or without sildenafil treatment. Method- Male Wistar rats were subjected to embolic stroke and treated with saline (n=10) or with sildenafil (n=11), with treatment initiated at 24 hours and continued daily for 7 days after onset of ischemia. T2*WI measurements were performed at 24 hours after embolization and weekly up to 6 weeks using a 7-Tesla system. Histological measurements were obtained at 6 weeks after MRI scans., Results: Using T2*WI, cerebral angiogenesis was detected starting from 4 weeks and from 2 weeks after onset of embolic stroke in saline and sildenafil treated rats, respectively. Significant differences in the temporal and spatial features of angiogenesis after embolic stroke up to 6 weeks after onset of stroke were found between saline and sildenafil treated rats and were identified with T2*WI. MRI permeability parameter, K(i), complementarily detected angiogenesis after ischemia in embolic stroke rats. Sildenafil treatment of stroke rats significantly enhanced the angiogenesis, as confirmed histologically., Conclusions: T2*WI can quantitatively measure the temporal evolution of angiogenesis in rats subjected to embolic stroke. Compared to control rats, sildenafil treatment significantly increased angiogenesis in treated animals up to 6 weeks after stroke.

Background: The vascular anatomy of the thoracodorsal artery perforator flap, which has not previously been elucidated, was examined using three- and four-dimensional computed tomographic angiography and venography., Methods: Twenty-five thoracodorsal artery perforator flaps were harvested from fresh cadavers from the Western population. Dynamic static computed tomographic angiography using iodinated contrast media was performed following cannulation of the largest perforator from the descending branch of the thoracodorsal artery and its vena comitans in 10 flaps. Imaging was repeated subsequent to flap thinning between the deep and superficial adipose layers. Colored latex injections and flap dissections were performed in a further 15 flaps to establish the location, caliber, and intramuscular length of the thoracodorsal artery perforators., Results: Two distinct perforator complex types were described. Flap thinning can be safely performed between the deep and superficial adipose layers without significantly affecting flap vascularity, provided that a safety zone about the perforator is respected. The superficial venous system consisted of large veins arranged in a polygonal pattern situated at the subdermal level and was connected to the deep system by the venae comitantes of the thoracodorsal artery perforators. Perforators from the descending branch of the thoracodorsal artery were found in reliable locations., Conclusions: Using a novel dynamic three-dimensional imaging technique, perfusion of the arterial and venous system of the thoracodorsal artery perforator flap was elucidated. Although the flap is inherently thin, it can be safely thinned between the superficial and deep adipose layers. This study identified important advantages of the thoracodorsal artery perforator flap for use in reconstruction.

Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements on local area with small size microvessels. Instead, the mean flux response is generally compared between before and after stimulus. In this study, we proposed a new dimension for comparing the LDF signals. The flux rise time (FRT), a time index with absolute physical quantity, was extracted from noisy LDF signals using a pulsatile-based synchronized-averaging method. We investigated the changes of FRT and its relation to the microvascular resistance (MVR) under the selective effects of angiotensin II (Ang II) on the kidney and the plantar palm. Ang II was infused into anesthetized Wistar Kyoto rats via the femoral vein for 1 h. Using the heartbeat as a self-trigger, we calculated the FRT and MVR from the renal cortical flux, plantar palm flux, and abdominal aortic blood pressure recorded before, during, and after Ang II infusion. The control FRT values were similar in the two vascular beds. Ang II decreased the renal cortical flux but significantly increased the FRT and MVR of both beds. The effects on the renal FRT and renal MVR were selectively larger than those on the palm FRT and palm MVR. The results indicate that the changes of FRT and MVR are similarly physiologically linked with microvascular structures. As an MVR-related absolute physical quantity, the FRT could be developed as a monitoring tool in physiological, pathological, and pharmacological investigations.

Studies on human brain microcirculation have thus far yielded few quantitative data, preventing the closest possible interpretation of functional imaging methods such as fMRI and PET that necessarily rely on robustly delineated morphology of haemodynamic systems. Inadequate data in this area can lead to severe underestimation of the spatial specificity of the BOLD response. We took thick sections of Indian ink injected human brain and, using confocal laser microscopy and a novel three-dimensional computer-assisted method we extracted and analyzed hundreds of thousands of vascular segments within a large area of cortex. From this database the global densities, the statistical distributions of diameters and lengths were analysed, separating the tree-like and the net-like parts of the microcirculation. Furthermore, our analysis included variations in volume density along the cortical depth and along vectors parallel to the cortical surface. These morphometric parameters are all key requirements for a sound model of cerebral microcirculation.

Background: Detailed knowledge of the pattern of origin of the anterior spinal artery is critical as surgical and endovascular procedures involving the area of the ventral medulla and the vertebrobasilar junction are commonplace. We conducted a detailed microanatomical study to elucidate the site and pattern of origin of this critically important artery., Method: Nine adult cadaveric heads (18 sides) were examined after injection of colored silicon. In every specimen, the site of origin of the rami of the anterior spinal artery, their course, branching pattern and anastomoses, external diameters, and the distance from neighbor critical vessels were recorded. The dissections were performed with the aid of both the surgical microscope and a 0 degree endoscope., Findings: The pattern and site of origin of the anterior spinal artery show great variability. Also the distance of the origin of the two rami (right and left) forming the anterior spinal artery from the vertex of the vertebrobasilar junction and from the origin of the posterior inferior cerebellar artery is highly variable., Conclusions: Knowledge of the different pattern of origin and course of the proximal portion of the anterior spinal artery is critically important when planning and executing endovascular and surgical procedures involving the distal vertebral artery, the vertebrobasilar junction and the ventral medulla. On the basis of our and other authors' findings, we propose an overall classification of the pattern of origin and distribution of the proximal anterior spinal artery, which has clinical repercussions.

Activin receptor-like kinase 1 (ALK1) is an endothelial-specific type I receptor of the TGFbeta receptor family that is implicated in angiogenesis and in the pathogenesis of the vascular disease, hereditary hemorrhagic telangiectasia (HHT). In the absence of a specific ligand, ALK1 cellular functions have been mainly studied through the use of a constitutively active form of this receptor (ALK1ca) and are still debated. We previously reported that ALK1ca inhibits proliferation and migration of human endothelial cells suggesting that ALK1 plays an important role in the maturation phase of angiogenesis (Lamouille et al., 2002, Blood 100: 4495-4501). In the present work, we further analyzed the role of ALK1 in the migration of human dermal microvascular endothelial cell (HMVEC-d) and observed that silencing endogenous ALK1 expression with siRNAs accelerates endothelial cell migration in the wound assay. Further, we demonstrate that ALK1-induced inhibition of migration is Smad-independent. Using a panel of kinase inhibitors, we found that HMVEC-d wound closure was completely inhibited by a JNK inhibitor and to a lower degree by an ERK kinase inhibitor. Further, HMVEC-d wounding induced activation of both JNK and ERK, and these were inhibited by ALK1ca expression. Taken together, these results support a significant role for ALK1 as a negative regulator of endothelial cell migration and suggest the implication of JNK and ERK as mediators of this effect.

Knowledge of the morphometric quantities of the coronary arteries in neonates is an increasingly vital component in the management of congenital and acquired heart disease. Because of the considerable heterogeneity of coronary vasculature, what is considered atypical and aberrant or insignificant anatomy is often unclear. The purpose of our present study is to define the normal anatomy of neonates. This was done by focusing on segment analysis of the coronary arteries, which was used to obtain accurate definitions of the length and diameter of the coronary network. The lengths, widths and numbers of collateral branches of the coronary arteries of neonates were measured. The coronary vessels of 50 neonate hearts were visualised post mortem by injection of the coronary arteries with opaque X-ray dye for the imaging study. Black ink cast and silver impregnation specimens were also studied. The longest segment of the circumflex branches of the left coronary arteries was the first, the lengths measuring 7188.5 +/- 839.6 microm and the diameters 850 +/- 90.8 mum. The lengths of segments II, III and IV were 5780 +/- 1182.7 microm, 5397.5 +/- 2070.2 microm and 6932.8 +/- 2236.5 microm and the diameters were 680 +/- 90.8 microm, 510 +/- 90.8 microm and 408 +/- 77.58 microm respectively. The longest segment of the anterior interventricular branches of the left coronary arteries was the first, with lengths of 10151.4 +/- 1298.6 microm and diameters of 1141.9 +/- 82.1 microm. The lengths of segments II, III and IV were 8208.5 +/- 1222.3 microm, 3278.5 +/- 602.4 microm and 5370 +/- 1657.6 mum and the diameters were 971 +/- 82.1 microm, 801.42 +/- 82.1 microm and 631.4 +/- 82.1 microm respectively. The lateral branches were increased in number in the fourth segment. Its diameters ranged from 157.8 +/- 31.7 microm to 655.7 +/- 99.7 microm. The main branch of the right coronary artery was short at the base of the heart. In the newborn the lateral branches of the right coronary artery were short, scattered and curved. Analysis of the data suggests a new anatomical system for classifying the vasculature of the coronary arteries in neonates.

Both high spatial resolution and high temporal resolution are desirable for contrast-enhanced magnetic resonance angiography (CE-MRA) in order to depict the arterial vasculature. In this work a fast MR pulse sequence (spiral time-resolved imaging with contrast kinetics (Spiral-TRICKS)) with spiral readout in-plane and Cartesian slice encoding was developed whereby the slices are partitioned into multiple regions and acquired in the order used with the TRICKS sequence. The combination of highly efficient spiral sampling with TRICKS acquisition significantly reduced imaging time requirements. A unit second temporal reconstructed frame rate could be achieved for three-dimensional (3D) CE-MRA without undersampling of the spiral trajectories. Image quality was improved through spiral trajectory measurement and field-map correction. Phantom and volunteer studies were performed to demonstrate the feasibility of this technique., (Copyright (c) 2007 Wiley-Liss, Inc.)

Axial patterning in embryonic skeletogenesis associates with coordinated programming of somitogenesis and angiogenesis. As seen in endochondral bone formation, skeletogenesis is closely related to angiogenesis during development. PlexinD1 is a member of plexin family, is expressed in central nervous system and endothelium, and plays a role in blood vessel patterning and endothelium positioning during embryonic development. Here, we examined the effects of PlexinD1 deficiency on skeletogenesis. Three-dimensional micro CT examination revealed that PlexinD1 deficiency resulted in axial skeletal patterning defects including malformation in vertebral body and rib bone shape. Histological examination of the vertebral bodies and long bones showed that PlexinD1 deficiency altered the development of cartilage. PlexinD1 deficiency did not affect the levels of von Willebrand factor staining in relatively large vessels not attached but close to the vertebral body of mice. However, PlexinD1 deficiency reduced the von Willebrand factor (vWf) staining in most of the microvasculatures attached to the vertebral bone. PlexinD1 was expressed in osteoblastic cells and bone tissues of newborn and adult mice. As most of the homozygous knockout mice did not survive, we examined the role of PlexinD1 in bone formation in heterozygous adult mice subjected to bone marrow ablation. However, PlexinD1 heterozygous knockout did not reveal defects in new bone formation. In conclusion, PlexinD1 is involved in the patterning of axial skeletogenesis.

The aim of this study was to observe the microcirculation characteristics of the human interdental papilla in healthy patients in vivo. Twenty healthy patients were examined. Capillaroscopy was used to investigate the characteristics of microcirculation of the human periodontal mucosa. Visibility, course, tortuosity, as well as the average caliber of the capillary loops and the number of visible capillary loops per square millimeter were evaluated for each patient. The investigation of gingival mucosa revealed capillary loops with a course both parallel and perpendicular to the surface. Our study has pointed out that capillaroscopy is a reliable method to study periodontal microcirculation in vivo. This method could be applied to the study of microcirculation in periodontal diseases. Future studies might evaluate whether microcirculation in that area is compromised or not during systemic pathologies involving peripheral microcirculation alterations.

The urinary bladder is an unusual organ in that its normal function includes filling and emptying with alternating changes in internal pressure. Although fluctuations in blood flow to the bladder wall are known to accompany these changes, detailed descriptions of the bladder microvasculature are sparse. The present study uses vascular corrosion casting and scanning electron microscopy to describe the three-dimensional anatomy of the microvasculature of the urinary bladder of the dog. Specialized features of that microvasculature, including collateral circulation, vessel folding, vessel orientation, the presence of valves and sphincters, and mucosal capillary density, that may enhance and control blood flow during normal bladder function, are described and discussed.

To date there has been no satisfactory research method for imaging microvascular anatomy in three dimensions (3D). In this article we present a new technique that allows both qualitative and quantitative examination of the microvasculature in 3D. In 10 fresh cadavers (7 females, 3 males, mean age 68 years), selected arteries supplying the abdominal wall and back were injected with a lead oxide/gelatin contrast mixture. From these regions, 30 specimens were dissected free and imaged with a 16-slice spiral computed tomographic (CT) scanner. Using three-dimensional CT (3D-CT) angiography, reconstructions of the microvasculature of each specimen were produced and examined for their qualitative content. Two calibration tools were constructed to determine (1) the accuracy of linear measurements made with CT software tools, and (2) the smallest caliber blood vessel that is reliably represented on 3D-CT reconstructions. Three-dimensional CT angiography produced versatile, high quality angiograms of the microvasculature. Correlation between measurements made with electronic calipers and CT software tools was very high (Lin's concordance coefficient, 0.99 (95% CI 0.99-0.99)). The finest caliber of vessel reliably represented on the 3D-CT reconstructions was 0.4 mm internal diameter. In summary, 3D-CT angiography is a simple, accurate, and reproducible method that imparts a much improved perception of anatomy when compared with existing research methods. Measurement tools provide accurate quantitative data to aid vessel mapping and preoperative planning. Further work will be needed to explore the full utility of 3D-CT angiography in a clinical setting.

Object: The authors studied the microsurgical anatomy of the ophthalmic artery (OphA), paying particular attention to its possibly dangerous anastomoses with the middle meningeal artery (MMA)., Methods: The microsurgical anatomy of the OphA and its anastomoses with the MMA were studied in 14 vessels from seven adult cadaveric heads. The origination order of the OphA branches varies in relation to whether the artery, along its intraorbital course, crosses above or below the optic nerve (ON). The central retinal artery is the first branch to course from the OphA when it crosses over the ON, and it is the second branch to course from the OphA when the artery crosses under the ON. Anastomoses between branches of the MMA and the OphA were present in the majority of the specimens examined., Conclusions: Detailed knowledge of the microanatomy of the OphA and recognition of anastomoses between the external carotid artery and the OphA are critically important in avoiding disastrous complications during endovascular procedures.

Background: Microvascular involvements represent one of the first steps in many autoimmune diseases such as rheumatoid arthritis (RA). The aim of this study was to investigate the differences in periodontal microcirculation between healthy subjects and patients suffering from RA., Methods: Thirty healthy subjects and 30 patients suffering from RA were examined. The patients who showed conditions known to compromise microcirculation, such as diabetes, hypertension, pharmacological treatments, were not included in the group of healthy patients. All the patients were non-smokers. Periodontal capillaroscopy was used to investigate the characteristics of microcirculation. Visibility, course, tortuosity, as well as the possible presence of microhemorrhages, the average caliber of the capillary loops and the number of visible capillary loops per square millimeter were evaluated for each patient., Results: Microcirculation architecture in the healthy and in the RA patients was characterized by a network of capillaries in polygonal mesh with parallel orientation as regards the surface. In patients suffering from RA, it was possible to observe a reduced caliber of capillaries, as well as a greater number and elongated capillaries. No significant differences relating to oral capillaroscopic pattern were detected between RA patients that were rheumatoid factor, ANA, RANA positive and RA patients that were rheumatoid factor, ANA, RANA negative., Conclusions: This study shows that capillary alterations in patients suffering from RA occur in periodontal microcirculation; such evidence could be extremely important, suggesting that microvascular periodontal alterations may play a crucial part in the complex activity associated with periodontal disease in AR patients.

Functional photoacoustic microscopy (fPAM) is a hybrid technology that permits noninvasive imaging of the optical absorption contrast in subcutaneous biological tissues. fPAM uses a focused ultrasonic transducer to detect high-frequency photoacoustic (PA) signals. Volumetric images of biological tissues can be formed by two-dimensional raster scanning, and functional parameters can be further extracted from spectral measurements. fPAM is safe and applicable to animals as well as humans. This protocol provides guidelines for parameter selection, system alignment, imaging operation, laser safety and data processing for in vivo fPAM. It currently takes approximately 100 min to carry out this protocol, including approximately 50 min for data acquisition using a 10-Hz pulse-repetition-rate laser system. The data acquisition time, however, can be significantly reduced by using a laser system with a higher pulse repetition rate.

The branching pattern and geometry of coronary microvessels are of high interest to understand and model the blood flow distribution and the processes of contrast invasion, ischemic changes and repair in the heart in detail. Analysis is performed on high resolution, 3D volumes of the arterial microvasculature of entire goat hearts, which are acquired with an imaging cryomicrotome. Multi-scale vessel detection is an important step required for a detailed quantitative analysis of the coronary microvasculature. Based on visual inspection, the derived lineness filter shows promising results on real data and digital phantoms, on the way towards accurate computerized reconstructions of entire coronary trees. The novel lineness filter exploits the local first and second order multi-scale derivatives in order to give an intensity-independent response to line centers and to suppress unwanted responses to steep edges.

We assessed histological characteristics and sex related differences in morphometric parameters of healthy persons' peritoneal blood vessels. Eighteen samples of parietal peritoneum were collected from 11 healthy persons with elective abdominal surgery, 6 males and 5 females, age range 44-58. Tissue samples were prepared for light and transmission electron microscopy. Morphometric parameters of peritoneal blood vessels were determined by analySIS 3.1 Soft Imaging System GMbH. We directly measured outer and lumen diameter, and outer and lumen surface on blood vessels transversal sections. Wall thickness, lumen diameter-wall thickness ratio, blood vessels numerical density and peritoneal tissue surface under blood vessels were calculated subsequently. Results were statistically analysed with Student T test. Mostly true and venous capillaries were observed. Endothelial citoplasm showed numerous mitochondria, ribosomes and pinocytotic vesicles, prominent rough endoplasmic reticulum, well-developed Golgi complex, and predominantly euchromatic nuclei. No statistically significant differences were found between male and female subjects in any of the investigated variables, rphometric characteristics of pelvic peritoneal blood vessels did not show gender related differences.

The aim of this study was to evaluate the relationship between the cisternal segment of the oculomotor nerve and the posterior cerebral artery and its branches. The oculomotor nerve and the posterior cerebral artery of 15 cadaver brains (30 hemispheres) were examined using a surgical microscope. The dorsal portion of the cisternal segment of the oculomotor nerve had a close relationship with the P(1) and P(2) segments of the posterior cerebral artery in 100% of cases, the thalamoperforating arteries in 97%, the collicular arteries in 97%, the short circumferential arteries in 33% and the posterior medial choroidal arteries in 20%. The proximal portion of the nerve had a close relationship with the P(1) segment of the posterior cerebral artery, the thalamoperforating arteries, the collicular arteries and the short circumferential arteries, whereas the distal portion had a close relationship with the P(2) segment of the posterior cerebral artery and the posterior medial choroidal arteries. The oculomotor nerve was perforated by various arteries in different portions. These arteries were the thalamoperforating arteries in 10% of the hemispheres, the collicular arteries in 16% and the short circumferential arteries in 11%. It can be concluded that the dorsal portion of the cisternal segment of the oculomotor nerve has a close relationship with the branches arising from the P(1) and P(2) segments of the posterior cerebral artery. These arteries supply the cisternal segment of the oculomotor nerve.

Recently, cerebral blood flow changes were re-discussed to contribute to tissue protection after preconditioning. In the present study, we demonstrate increased vessel diameters of the leptomeningeal anastomoses after hypoxic preconditioning by visualization of the brain angioarchitecture using the latex perfusion technique. This finding may display the anatomical correlate to previously described perfusion changes after preconditioning.

The design of the microvasculature of cerebellum and nontegmental rhombencephalic areas was studied in eight adult Acipenser ruthenus L. by scanning electron microscopy of vascular corrosion casts and three-dimensional morphometry. Gross vascularization was described and diameters and total branching angles of parent and daughter vessels of randomly selected arterial and capillary bifurcations (respectively, venous mergings) were measured. With diameters ranging from 15.9 +/- 1.9 microm (cerebellum; mean +/- S.D.) to 15.9 +/- 1.7 mm (nontegmental rhombencephalon; mean +/- S.D.) capillaries in Acipenser were significantly (p > or = .05) smaller than in cyclostomes (18-20 microm) but significantly thicker than in higher vertebrates and men (6-8 microm). With the exception of the area ratio beta (i.e., sum of squared daugther diameters divided by squared diameter of parent vessel) of the venular mergings in the nontegmental rhombencephalon, no significant differences (p > or = .05) existed between the two brain areas. Data showed that arteriolar and capillary bifurcations and venular mergings are optimally designed in respect to diameters of parent vessel to daughter vessels and to branching (merging) angles. Quantitative data are discussed both in respect to methodical pitfalls and the optimality principles possibly underlying the design of vascular bifurcations/mergings in selected brain areas of a nonteleost primitive actinopterygian fish.

We present real-time vascular visualization methods, which extend on illustrative rendering techniques to particularly accentuate spatial depth and to improve the perceptive separation of important vascular properties such as branching level and supply area. The resulting visualization can and has already been used for direct projection on a patient's organ in the operation theater where the varying absorption and reflection characteristics of the surface limit the use of color. The important contributions of our work are a GPU-based hatching algorithm for complex tubular structures that emphasizes shape and depth as well as GPU-accelerated shadow-like depth indicators, which enable reliable comparisons of depth distances in a static monoscopic 3D visualization. In addition, we verify the expressiveness of our illustration methods in a large, quantitative study with 160 subjects.

There is a wide range of diseases and normal physiological processes that are associated with alterations of the vascular system in organs. Ex vivo imaging of large vascular networks became feasible with recent developments in microcomputed tomography (microCT). Current methods permit to visualize only limited numbers of physically excised regions of interests (ROIs) from larger samples. We developed a method based on modified vascular corrosion casting (VCC), scanning electron microscopy (SEM), and desktop and synchrotron radiation microCT (SRmicroCT) technologies to image vasculature at increasing levels of resolution, also referred to as hierarchical imaging. This novel approach allows nondestructive 3D visualization and quantification of large microvascular networks, while retaining a precise anatomical context for ROIs scanned at very high resolution. Scans of entire mouse brain VCCs were performed at 16-microm resolution with a desktop microCT system. Custom-made navigation software with a ROI selection tool enabled the identification of anatomical brain structures and precise placement of multiple ROIs. These were then scanned at 1.4-microm voxel size using SRmicroCT and a local tomography setup. A framework was developed for fast sample positioning, precise selection of ROIs, and sequential high-throughput scanning of a large numbers of brain VCCs. Despite the use of local tomography, exceptional image quality was achieved with SRmicroCT. This method enables qualitative and quantitative assessment of vasculature at unprecedented resolution and volume with relatively high throughput, opening new possibilities to study vessel architecture and vascular alterations in models of disease.

Transcription factors link changes in the extracellular environment with alterations in gene expression. As such, these molecules serve as attractive targets for intervention in pathological settings. Since JUN has been linked with microvascular disease in humans, we hypothesised that small interfering RNA (siRNA) targeting this immediate-early gene may be useful agents that suppress endothelial growth and neovascularisation. Here we show that Jun siRNA inhibits Jun mRNA and protein expression in murine microvascular endothelial cells, blocks cell proliferation and suppresses migration in a scratch-wound assay. It also inhibits three-dimensional tubular formation on basement membrane extracts and reduces angiogenesis in mice bearing Matrigel plugs as subcutaneous implants. Single intravitreal administration of Jun siRNA reduces neovascularisation in a murine model of proliferative retinopathy, and suppresses endothelial JUN and matrix metalloproteinase-2 (MMP-2) immunoreactivity in retinal vessels, data supported by its repression of MMP-2 expression and gelatinolytic activity in vitro. Co-administration of TGFbeta with the siRNA reverses this neovascular inhibitory effect, which is in turn abrogated by cis-9-octadecenoyl-N-hydroxylamide, consistent with the involvement of a metalloproteinase such as MMP-2. Thus, JUN siRNA can serve as a specific inhibitor of aberrant endothelial and neovascular growth.

The aim of this study was to describe all levels of the intermesenteric communications because of their importance in vascular diseases of the colon. The connections of superior and inferior mesenteric networks are very important in cases of acute or chronic obstruction to prevent ischemia and necrosis. Angiograms of mesenteric arteries were studied (40), cadaverous large intestine samples with mesentery and feeding vessels were dissected (36) or injected with India ink solution (24) or methylmetacrylate Mercox (41). In 7.9 % of cases an intermesenteric connection was described, named anastomosis intermesenterica accessoria and classified according to Pikkieff's(1) proposal. The marginal artery in the left colic flexure forms an arch called Riolan's arcade(2) or Haller's anastomosis(3) and is present in 95 % of cases. Infrequent anastomosis between straight vessels and mighty plexuses in the intestinal wall were registered. There are no regional differences when compared to the rest of colon.

The microangioarchitecture of the thalamus and metathalamus in common tree shrew (Tupaia glis) was studied using vascular corrosion cast/stereomicroscope and SEM technique. The arterial supply of the thalamus and metathalamus was found to originate from perforating branches of the posterior communicating artery, the posterior cerebral artery, the middle cerebral artery, and the anterior choroidal artery. These perforating arteries gave rise to numerous bipinnate arterioles which in turn, with decreasing vessel diameters, branched into a non-fenestrated capillary bed. Venous blood from the superficial parts of the thalamus and metathalamus was collected into the thalamocollicular vein, whereas venous blood from internal aspects of the thalamus was conveyed to the internal cerebral vein. Some venous blood from the most rostral part of the thalamus flowed into tributaries of the middle cerebral vein before draining into the cavernous sinus. Further, the thalamic and metathalamic vascular arrangement was found to be of centripetal type. In addition, thalamic arterial anastomosis was rarely observed. Thus, obstruction of thalamic blood supply could easily lead to thalamic infraction.

This work describes the formation, perfusion, and maturation of three-dimensional microvascular tubes in vitro. These tubes consisted of confluent monolayers of human endothelial cells that lined open, cylindrical channels within collagen gels. Perivascular cells could be directly embedded within the gels or added after endothelial cells grew to confluence. The tubes spanned the entire 5-7 mm extent of the gels; their diameters initially ranged from 55 to 120 microm and increased to 75-150 microm after maturation. Endothelial tubes displayed a strong barrier function over 5 days, resisted adhesion of leukocytes, and reacted quickly to inflammatory stimuli by breakdown of the barrier and support of leukocyte adhesion. These tubes resembled venules and "giant" capillaries in both their cellular organization and function, and we believe that they will serve as useful in vitro models of inflammation under constant perfusion.

Objectives: The cell-free layer between the erythrocyte column and the vessel wall is an important determinant of hydrodynamic resistance in microcirculatory vessels. The authors report a method for continuous measurement of the width of this layer., Methods: The light intensity of a linear array of pixels perpendicular to the vessel axis is continuously determined from a video image of a microcirculatory vessel. A threshold level based on Otsu's method is used to establish the interface between the cell-free layer and the erythrocyte column. To test the method, video images at 750-4500 frames/s were obtained from venules and arterioles in rat spinotrapezius muscle at normal and reduced arterial pressures before and after induction of erythrocyte aggregation with Dextran 500. The current measurements were compared to manual measurements of the same images., Results: Values obtained by the manual and the new methods were in agreement within the 95% confidence limit by the Bland-Altman analysis and within 90-95% range by the correlation coefficient (R2). The more frequent measurements reveal substantial, rapid variations in cell-free layer width and changes in mean values with alteration of arterial pressure and red cell aggregability., Conclusions: A new, computer-based technique has been developed that provides measurements of rapid, time-dependent variations in the width of the cell-free layer in the microcirculation.

The pulmonary airway, arterial, venous and capillary networks are vast complex branching and converging systems that are mechanically coupled to the surrounding lung tissue. Early studies that examined vascular or airway geometry relied on measurements from casts, but medical imaging now enables measurement of the lung in vivo, at controlled lung volumes. The high-quality data that imaging provides have prompted development of increasingly sophisticated models of the geometry of the airway and pulmonary vascular trees. The accurate spatial relationships between airway, vessel and tissue in these imaging-derived models are necessary for computational analysis that aims to elucidate regional airway-vessel-tissue interactions. Predictions of blood flow through multiscale imaging-derived models of the pulmonary arteries and capillary bed reveal geometry-dependent patterns of perfusion in response to gravity and lung orientation that cannot be predicted with simplified, summary representations of the pulmonary transport trees. Validation of such predictions against measures from functional imaging holds significant potential for explaining and differentiating normal and disease-related heterogeneity in regional blood flow calculated using perfusion imaging.

The aim of this study was to observe the microcirculation characteristics of the human filiform papillae in healthy patients in vivo. Twenty healthy patients were examined using lingual capillaroscopy to investigate the characteristics of microcirculation of the human filiform papillae. Visibility, course, tortuosity, as well as the possible presence of microhemorrhages, the average caliber of the capillary loops and the number of visible capillary loops per square millimeter were evaluated for each patient. The investigation was simple, non-invasive and repeatable for each patient. Microcirculation architecture was characterized by a network of capillaries in polygonal mesh with parallel orientation in regard to the surface. Rare microhemorrhages were observed. The caliber of visible capillary loops was 12.50 +/- 1.46 microm (mean +/- SD). The number of visible capillaries was 9.88 +/- 1.06 (mean +/- SD). Our study shows that capillaroscopy of lingual filiform papillae is a practicable method. Future studies might evaluate whether microcirculation in that area is compromised or not during systemic pathologies involving peripheral microcirculation alterations. This method could also be applied to the study of microcirculation in pathologies which strictly pertain to the dental stomatological field.

The presence of microvascular changes has been documented both in brain aging and Alzheimer disease (AD), although the relationship between the morphometry of brain capillaries and cognitive impairment is still unknown. We performed an analysis of capillary morphometric parameters and AD-related pathology in 19 elderly individuals with variable degrees of cognitive decline. Cognitive status was assessed prospectively using the Clinical Dementia Rating (CDR) scale. Total capillary lengths and numbers as well as mean length-weighted diameter, total neurofibrillary tangle (NFT) and neuron numbers, and amyloid volume were estimated in entorhinal cortex and the CA1 field. Total capillary numbers and mean diameters explained almost 40% of the neuron number variability in both the CA1 and entorhinal cortex. Total capillary length and numbers in the CA1 and entorhinal cortex did not predict cognitive status. Mean capillary diameters in the CA1 and entorhinal cortex were significantly related to CDR scores, explaining 18.5% and 31.1% of the cognitive variability, respectively. This relationship persisted after controlling for NFT and neuron numbers in multivariate regression models. Consistent with the growing interest about microvascular pathology in brain aging, the present data indicate that changes in capillary morphometric parameters may represent independent predictors of AD-related neuronal depletion and cognitive decline.

The importance of the sinus node as the cardiac pacemaker is well known. The aim of the present study was to investigate the microangioarchitecture at the level of the sinus node. Ten human adult hearts were injected with India ink in the initial segments of the coronary arteries. Pieces were drawn and diaphanized. The results of the study can be summarized: (1) the sinus node is rather an irregularly shaped structure, with peripheral strands intermingling with strands of the atrial myocardium; at this level two vascular patterns can be recognized: (a) the myocardial capillary networks that parallels the muscular bundles, and (b) the peripheral nodal networks built upon dichotomizing arterioles; (2) it seems that while the thick and large sinus node artery does not branch in the nodal tissue, the blood supply of this tissue is ensured by the peripheral nodal networks; (3) characteristically, in the periphery of the nodal tissue are largely present glomeruli made by capillaries with pericellular dispositions. The results strongly suggest that the nodal tissue is mainly supplied from its periphery and the sinus node artery is rather a scaffold than a supplier of that tissue.

The aim of the present study was to bring macroscopic and microscopic evidence on the left papillary muscles blood supply in human hearts. For the study were used human adult hearts from patients without clinically known cardiac ischemic history. Ten hearts were used for injecting China ink in the coronary arteries and other twenty hearts were dissected to evidence the characteristics of the main arteries of the left papillary muscles. Pieces - left papillary muscles - were drawn from the injected hearts and diaphanised. In all dissected hearts the left anterolateral papillary muscles were supplied by the left coronary system: anterior interventricular artery, second diagonal branch and left (obtuse) marginal artery. In 70% the left posteromedial papillary muscles were supplied by the right coronary system (posterior interventricular artery, left retroventricular artery) and in 30% by the left coronary system (circumflex artery). The left papillary muscles were supplied each by one or two main arteries that penetrated the muscles longitudinally. The ventricular wall attaching the papillary muscles was supplied by the subepicardial vessel sending the main arteries of the papillary muscles but also by neighbor subepicardial vessels distributed in that wall. The mural vessels were finer than the papillary muscles main arteries. Injected papillary muscles presented each with two systems of blood perfusion: one represented by segmental centers of arterial branching and distribution of the main arteries of the muscle and other represented by capillary extensions of the mural networks at that level. From the segmental branching centers were perfused the neighbor segments of the papillary muscles and intrasegmental anastomoses were recognized. The microvascular study of the left papillary muscles proves the usual overlapping of sources for segmental supply; this overlapping is reinforced by the high capillary density to ensure the vascularisation of the papillary muscles.

The porcine ameroid model of chronic myocardial ischemia has been widely used for the evaluation of coronary collateralization development. The impact of target vessel occlusion on the presence of myocardial ischemia, and the relationship between morphological, functional, and hemodynamic measurements in the context of therapeutic angiogenesis studies, however, has not been studied thus far. The authors therefore performed a systematic analysis of 94 animals undergoing ameroid constrictor placement around the left circumflex coronary artery (LCX) and, furthermore, a comprehensive evaluation including echocardiography and coronary angiography 26 +/- 1 (mean +/- SEM) days after ameroid placement. Complete LCX occlusion was observed in 34/94 animals (36%) and identified those with myocardial ischemia of the lateral wall, both at rest and under pharmacological stress. By applying a set of angiographic criteria (TIMI or= 1), another 27/94 animals with myocardial ischemia under conditions of pharmacological stress conditions could be identified. Interestingly, echocardiographic parameters of regional and global myocardial function were not correlated with myocardial blood flow or the degree of ischemia. There was no relationship between the extent of coronary collateralization, as assessed by angiography, echocardiographic parameters, or myocardial blood flow. The authors therefore conclude that complete occlusion of the ameroid instrumented coronary artery is not a prerequisite for successfully establishing the pathophysiology of myocardial ischemia. Defined angiographic criteria are important in identifying ischemic animals, thus reducing total animal numbers. Angiographic assessment of the degree of coronary collateralization, however, is not associated with myocardial blood flow or function and should not be used as a primary outcome measure of therapeutic angiogenesis studies in this model.

Microcirculation is the functional end of the coronary circulation and it plays a key role in the regulation of coronary blood flow, both on the local and global scales. A good understanding of its function under physiological and pathophysiological conditions is crucial but, because of its micro-scale, access to this part of the coronary circulation is extremely difficult and requires a considerable amount of innovation and new technologies. Dynamics of the coronary circulation provide the true vehicle by which blood supply reaches the myocardium- coronary vasculature is only the conducting component of that vehicle. It is highly unlikely that the pulsatile nature of the flow, the capacitance of the conducting vessels and the constant pounding of coronary vasculature by surrounding tissue are not part of the design, regulation, and function of the coronary circulation. Interventions, whether to assess or to correct coronary stenosis, continue to be the main clinical avenue to dealing with coronary heart disease. Clinical decisions rely heavily on the ability to determine the true morphology of an occlusive lesion, to predict the future course of that lesion and to assess the functional toll on coronary blood supply which it will inflict at each stage.

Vessel systems and the microvascular unit may be studied by a variety of morphological techniques which enable improved structure-function analyses. Two-dimensional light and electron microscopic sectioning techniques with and without specific markers are complemented by 3D vascularisation and perfusion study techniques. Static ex vivo modalities still prevail, however, the future will be dominated by intravital high-resolution techniques.

Purpose: To determine the histologic basis of perfusion parameters measured at functional computed tomography (CT) and to examine the relationship between changes in perfusion and changes in histologic parameters after antiangiogenic therapy in a rat model., Materials and Methods: This study had institutional animal care and use committee approval. Among 20 Fischer rats with implanted FN13762 tumors in the liver, 10 were treated with SU5416, a tyrosine kinase inhibitor of vascular endothelial growth factor receptor, and 10 were treated with the diluent only as control rats. Six rats chosen at random from each group underwent functional CT for the measurement of tumor blood flow, blood volume, mean transit time, and permeability-surface area product. Tumor tissue slides corresponding to functional CT sections were examined to measure tumor microvascular density, number of luminal vessels, vascular perimeter, and vascular area. Two-tailed Student t testing was used to determine differences in growth, numbers of metastases to major organs, vascularity, and perfusion between SU5416-treated and control tumors. Pearson correlation coefficients were used to investigate relationships between vascular parameters., Results: Mean tumor volume and number of metastases, respectively, were lower in SU5416-treated rats than in control rats (1580 mm3 +/- 830 [standard deviation] vs 2330 mm3 +/- 960 and 22.4 +/- 11.0 vs 35.2 +/- 17.3); however, these differences were not significant (P = .084 and P = .079). Mean tumor microvascular density was significantly lower in SU5416-treated rats than in control rats (6.4 vessels per field +/- 4.6 vs 17.2 vessels per field +/- 7.5, P < .001); however, vessel perimeter and vessel area, respectively, were significantly larger in treated rats than in control rats (470 microm per field +/- 320 vs 360 microm per field +/- 270, P = .02; and 4010 microm2 per field +/- 2990 vs 2230 microm2 per field +/- 1750, P = .001). Significant correlations were observed between microvascular density and vessel perimeter and area (r = 0.59 and r = 0.25, respectively; P < .01 for both) in SU5416-treated tumors but not control tumors. Blood flow, blood volume, and permeability-surface area product at functional CT were significantly higher in SU5416-treated tumors than in control tumors (P < .001 for all)., Conclusion: These results validate the idea that functional CT can help quantify the perfusion function of mature vessels but not changes in microvessel density in antiangiogenic therapy., (RSNA, 2005)

The characteristic of confocal microscopy (CM) vascular data is that it contains many tiny vessels with branching and complex structure. In this work, an automated method for quantitative analysis and reconstruction of cerebral vessels from CM images is presented in which the extracted centerline of the vessels plays the key role. To assess the efficiency and accuracy of different centerline extraction methods, a comparison among three fully automated approaches is given. The centerline extraction methods studied in this work are a snake model, a path planning approach, and a distance transform-based method. To evaluate the accuracy of the quantitative parameters of vessels such as length and diameter, we apply the method to synthetic data. These results indicate that the snake model and the path planning method are more accurate in extracting the quantitative parameters. The efficiency of the approach in clinical applications is then confirmed by applying the method to real CM images. All three methods investigated in this work are accurate enough to correctly distinguish between normal and stroke brain data, while the snake model is the fastest for clinical applications. In addition, three-dimensional visualization, reconstruction, and characterization of CM vascular images of rat brains are presented.

Regional anatomical variations in the nasal vasculature have not been studied histologically. Immunohistochemistry performed using marker for CD34 antigen on vascular endothelium biopsied from 5 sites on the lateral nasal wall and compared with one septal biopsy. No significant regional variations in microvascular architecture over the lateral wall of the nose were found. * Lateral wall measurements were significantly different to the septal measurements (P = 0.0003, 0.01). Suggests biopsies can be taken from any site on the lateral wall and give a representative sampling of the vascularity for research purposes.

We have developed and established a zoom endoscopy technique based on visualization of the mucosal microvascular architecture in units as small as the capillary in the normal stomach and early gastric cancer. With regard to the microvascular architecture of the normal stomach, the findings differed according to the section of the stomach. The gastric body showed a honeycomb-like subepithelial capillary network pattern with collecting venule, whereas the gastric antrum showed a coil-shaped subepithelial capillary network pattern. Regarding early gastric cancer, the following findings seemed to be specific for differentiated carcinoma: (1) a demarcation line between the cancerous and the noncancerous mucosa, (2) the disappearance of the regular subepithelial capillary network pattern, and (3) the presence of an irregular microvascular pattern. These findings, which were visualized by magnified observation, could be useful in clinical practice when we attempt to make a correct endoscopic diagnosis of flat reddened lesions (gastritis vs cancer) and when we attempt to determine the precise horizontal margin of early gastric cancer. This could help us to perform successful endoscopic resection based on endoscopic findings alone. In conclusion, our zoom endoscopy for visualizing the microvascular architecture in gastric mucosa could be a new system for diagnosing early gastric cancer.

Background: Scarce information about the anatomy of the subependymal arteries (SEAs) is present in the scientific literature., Methods: Twenty cerebral hemispheres with injected arteries were microdissected, and the magnetic resonance imaging scans of 100 patients with lacunar infarcts were examined., Results: The SEAs were found to range in diameter from 40 to 490 microm (mean, 149 microm) and in number between 3 and 12 (average, 5.2). Of these, numbers from 1 to 3 originated from the anterior choroidal artery (AChA), between 1 and 10 from the lateral posterior choroidal artery (LPChA), 1 from the medial posterior choroidal artery (MPChA), and 1 from the internal carotid artery. The SEAs most often arose from the choroidal branches (90%) and less frequently from the thalamic (30%), caudate (35%), or thalamocaudate twigs (20%). The SEAs of the AChA supplied the walls of the temporal horn (100%), the occipital horn (85%), and the atrium (35%). Those of the LPChA perfused the walls of the occipital horn (15%), the atrium (65%), the body of the ventricle (100%), and partially the frontal horn. The SEAs of the MPChA partially nourished the body and the frontal horn (10%). The SEAs may also occasionally supply the caudate nucleus (20%) and the stria terminalis. The anastomoses involving the SEAs were absent. In spite of this, ischemia in the territory of a single SEA was noticed in only 1% of our patients., Conclusions: The SEAs are tiny vessels that supply the walls of the lateral ventricle, as well as the caudate nucleus and the stria terminalis occasionally. The obtained anatomic data can have important neurosurgical implications in intraventricular operations.

Rationale and Objective: Structure of the brain is generally thought to remain stationary over the course of young adulthood. However, there is some evidence that microstructural changes of the brain do occur during this period. Magnetic resonance diffusion tensor imaging (DTI) provides quantitative measures of structural changes in the brain. We used DTI to detect possible age-related structural changes in the brains of young adults., Materials and Methods: Twenty-five healthy adults in their 20s and 30s were studied using DTI. Maps of mean diffusivity and fractional anisotropy (FA) were created for subsequent histogram and region-of-interest analyses, and the results were correlated with the respective ages of the subjects., Results: The histogram analysis revealed a significant increase in the mean FA value (r = 0.407, P < .05) and a significant decrease in FA peak height (r = -0.578, P < .002) with increasing age. No age-related changes were observed in indices derived from mean diffusivity maps. Region-of-interest analysis showed no focal white matter regions with significant FA change., Conclusion: Quantitative DTI revealed age-related structural changes in the brains of young adults. Changes on FA histograms observed in this study were considered to be related to changes in the relative volumes of gray and white matter and may represent maturational changes.

Compensating crural anastomoses develop in patients with multi-level occlusion of the calf arteries in the course of atherosclerosis, arteriitis, diabetes, and in vascular malformations of the limbs. The peroneal artery is frequently the only patent calf vessel, especially in diabetic patients who have advanced tibial occlusive disease. The purpose of this study was to identify different types of compensating crural anastomoses in chronic critical limb ischaemia. Using combined anatomical-radiographic and statistical methods, 86 compensating crural anastomoses were studied in 59 specimens of lower limbs (amputated at the thigh) in the course of chronic critical ischaemia. Three types of compensating crural anastomosis and their components were identified. The most common type (55.8%) was the posterior tibioperoneal anastomosis. Less common (23.3%) was the intertibial anastomosis and least common (20.9%) the anterior tibioperoneal anastomosis. The posterior tibioperoneal anastomosis was concurrent with anterior tibioperoneal anastomosis in 26.3% of cases and with the intertibial anastomosis in 15.3% of cases. The great importance of the peroneal artery in the formation of natural crural collateral circulation should encourage vascular surgeons to consider peroneal bypasses.

Our views regarding the origins and functions of splenic marginal zone B cells have changed considerably over the past few years. Perspectives regarding the development and function of these cells vary considerably between investigators studying human and rodent immunology. Marginal zone B cells are now recognized to constitute a distinct naive B lymphoid lineage. Considerable progress has been made regarding the mechanisms involved in marginal zone B cell development in the mouse. Many of the molecular events that participate in the retention of this lineage of B cells in the marginal zone have been identified. Here, we discuss the functions of these cells in both innate and adaptive immunity. We also attempt to reconcile differing viewpoints regarding the generation and function of marginal zone B cells in rodents and primates.