Direct demonstration of 25- and 50-microm arteriovenous pathways in healthy human and baboon lungs

Postmortem microsphere studies in adult human lungs have demonstrated the existence of intrapulmonary arteriovenous pathways using nonphysiological conditions. The aim of the current study was to determine whether large diameter (>25 and 50 microm) intrapulmonary arteriovenous pathways are functional in human and baboon lungs under physiological perfusion and ventilation pressures. We used fresh healthy human donor lungs obtained for transplantation and fresh lungs from baboons (Papio c. anubis). Lungs were ventilated with room air by using a peak inflation pressure of 15 cm H(2)O and a positive end-expiratory pressure of 5 cm H(2)O. Lungs were perfused between 10 and 20 cm H(2)O by using a phosphate-buffered saline solution with 5% albumin. We infused a mixture of 25- and 50-microm microspheres (0.5 and 1 million total for baboons and human studies, respectively) into the pulmonary artery and collected the entire pulmonary venous outflow. Under these conditions, evidence of intrapulmonary arteriovenous anastomoses was found in baboon (n = 3/4) and human (n = 4/6) lungs. In those lungs showing evidence of arteriovenous pathways, 50-microm microspheres were always able to traverse the pulmonary circulation, and the fraction of transpulmonary passage ranged from 0.0003 to 0.42%. These data show that intrapulmonary arteriovenous pathways >50 microm in diameter are functional under physiological ventilation and perfusion pressures in the isolated lung. These pathways provide an alternative conduit for pulmonary blood flow that likely bypasses the areas of gas exchange at the capillary-alveolar interface that could compromise both gas exchange and the ability of the lung to filter out microemboli.

A Novel Method for Visualization of Entire Coronary Arterial Tree

The complexity of the coronary circulation especially in the deep layers largely evades experimental investigations. Hence, virtual/computational models depicting structure-function relation of the entire coronary vasculature including the deep layer are imperative. In order to interpret such anatomically based models, fast and efficient visualization algorithms are essential. The complexity of such models, which include vessels from the large proximal coronary arteries and veins down to the capillary level (3 orders of magnitude difference in diameter), is a challenging visualization problem since the resulting geometrical representation consists of millions of vessel segments. In this study, a novel method for rendering the entire porcine coronary arterial tree down to the first segments of capillaries interactively is described which employs geometry reduction and occlusion culling techniques. Due to the tree-shaped nature of the vasculature, these techniques exploit the geometrical topology of the object to achieve a faster rendering speed while still handling the full complexity of the data. We found a significant increase in performance combined with a more accurate, gap-less representation of the vessel segments resulting in a more interactive visualization and analysis tool for the entire coronary arterial tree. The proposed techniques can also be applied to similar data structures, such as neuronal trees, airway structures, bile ducts, and other tree-like structures. The utility and future applications of the proposed algorithms are explored.

VEGF gene therapy for the survival of transplanted fat tissue in nude mice

The objective of this study was to determine the effects of adenovirus-mediated vascular endothelial growth factor (Ad-VEGF) on the angiogenesis and survival of free-fat tissue transplantation in nude mice. Thirty 6-week-old CD-1 nude male mice were injected with 1ml fat tissue (harvested by suction-assisted lipectomy from the breast of humans) in the subcutaneous of scalp and were randomised into three groups of 10 animals each. Group 1 was the study group, in which Ad-VEGF was mixed with transplanted fat tissue and injected into mice. In group 2, adenovirus-mediated green fluorescent protein (Ad-GFP) gene was mixed with transplanted fat tissue and injected into the mice. In group 3, normal saline alone was used. Both group 2 and group 3 are control groups. The animals were euthanised 15 weeks after the procedure. The fat survival weight and volume of the study group were significantly greater than those of two control groups (p<0.05). Light microscopical examination of haematoxylin and eosin-stained slides of the dissected fat 15 weeks after injection was performed in group 1 and group 2. Less cyst formation and fibrosis, indicating improved quality of the injected fat, can be obtained by the addition of Ad-VEGF. Vascular density was evaluated at the microvascular level through the use of light microscopic sections of the central part of the fat tissue at 15 weeks after injection by von Willebrand factor staining. Histological evaluation showed that capillary density increased markedly in the study group mice. Mice of the study group disclosed significantly higher VEGF protein levels detected by ELISA assay of plasma samples obtained from the mice after the fat injection (day 1, 4, 7 and 28; p<0.01) at each time point than the mice of the two control groups. The findings reported in this study indicate that the VEGF gene therapy can enhance the survival and the quality of grafted fat tissue, which may be due to induction of angiogenesis.

Capillary Perfusion and Wall Shear Stress Are Restored in the Coronary Circulation of Hypertrophic Right Ventricle

It has been shown that right ventricle (RV) hypertrophy involves significant compensatory vascular growth and remodeling. The objective of the present study was to determine the functional implications of the vascular growth and remodeling through a full flow analysis of arterial tree down to first capillary segments. A computer reconstruction of RV branches including the proximal right coronary artery to the posterior descending artery was established based on measured morphometric data in arrested, vasodilated porcine heart. The flows were computed throughout the reconstructed trees based on conservation of mass and momentum and appropriate pressure boundary conditions. It was found that the flow rate was significantly increased in large epicardial coronary arteries in hypertrophic as compared with control hearts but normalized in the intramyocardial coronary arteries and smaller vessels in RV hypertrophy primarily because of the significant increase in number of arterioles. Furthermore, the wall shear stress was restored to nearly homeostatic levels throughout most of the vasculature after 5 weeks of RV hypertrophy. The compensatory remodeling in RV hypertrophy functionally restores the perfusion at the arteriolar and capillary level and wall shear stress in most of larger vessels. This is the first full analysis of coronary arterial tree, with millions of vessels, in cardiac hypertrophy that reveals the compensatory adaptation of structure to function.

Regional changes in the masseter muscle of rats after reduction of blood supply

The masticatory musculature is an integral functional part of the stomatognathic system and influences craniofacial morphogenesis and morphology. This animal study aimed to investigate the morphological consequences of restricted regional blood supply to the m. masseter. A total of 20 adult male Wistar rats (Rattus norvegicus Berkenhout) were divided into an experimental group and a control group comprised of 10 animals respectively and kept under standardized conditions. The experimental group underwent a dextrolateral complete surgical ligation of the a. carotis communis and, after 5 weeks, specimens were taken from the masseters. The muscle samples were analyzed immunohistochemically for fiber distribution and capillary density. Analysis revealed a discrete increase in the proportion of type I fibers with a significant increase of capillary number per area. Although no agreement exists on the alterations occurring in chronically ischemic muscles, it may be assumed that chronic ischemia evokes histomorphological adaptation processes similar to endurance training effects.

Microvascular periodontal alterations: A possible relationship between periodontitis and rheumatoid arthritis

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.

Use of capillaries in the construction of an MRI phantom for the assessment of diffusion tensor imaging: demonstration of performance

Although diffusion tensor imaging (DTI) shows great potential for the diagnosis of a variety of pathologies, no consensus for an appropriate assessment standard of DTI exists. This study examined the feasibility of using water-filled arrays of glass capillaries to construct a DTI phantom suitable for making repeated and reproducible measurements required in a quality assessment program. Three phantoms were constructed using arrays of capillaries with three inner diameters (23, 48, and 82 microm). Data were acquired using DTI protocols; the fractional anisotropy (FA), mean apparent diffusion coefficient (ADC) and principal eigenvectors of the diffusion tensors were calculated. This study demonstrated four results: (1) echo-planar images show that susceptibility within the capillary arrays does not lead to substantial differences in precessional frequency in regions containing the arrays and neither do the regions show noticeable image distortion; (2) principal eigenvectors of the diffusion tensors agree to within<10.3 degrees of the array orientations; (3) mean FA values (0.18-0.50) and ADC values (1.40-1.93x10-(3) mm2/s) within specified regions of interest are in general agreement with simulations after a simple noise correction; and (4) these array performance characteristics are observable using a typical clinical DTI protocol.

Temporo-spatial distribution of blood vessels in human lumbar intervertebral discs

While there is consensus in the literature that blood vessels are confined to the outer anulus fibrosus of normal adult intervertebral disc, debate continues whether there is a vascular in-growths into inner parts of the intervertebral disc during degeneration. We therefore tested the hypothesis that vascular in-growth is not a distinct feature of disc degeneration. The specific endothelial cell marker CD 31 (PECAM) was used to immunohistochemically investigate 42 paraffin-embedded complete mid-sagittal human intervertebral disc sections of various ages (0-86 years) and varying extent of histomorphological degeneration. Additionally, 20 surgical disc samples from individuals (26-69 years) were included in this study. In discs of fetal to infantile age, blood vessels perforated the cartilaginous end plate and extended into the inner and outer anulus fibrosus, but not into the nucleus pulposus. In adolescents and adults, no blood vessels were seen except for the outer zone of the anulus fibrosus adjacent to the insertion to ligaments. The cartilaginous end plate remained free of vessels, except for areas with circumscribed destruction of the end plate. In advanced disc degeneration, no vessels were observed except for those few cases with complete, scar-like disc destruction. However, some rim lesions and occasionally major clefts were surrounded by a small network of capillary blood vessels extending into deeper zones of the anulus fibrosus. A subsequent morphometric analysis, revealed slightly "deeper" blood vessel extension in juvenile/adolescent discs when compared to young, mature and senile adult individuals with significantly "deeper" extension in the posterior than anterior anulus. The analysis of the surgical specimens showed that only sparse capillary blood vessels which did not extend into the nucleus pulposus even in major disc disruption. Our results show that vascular invasion deeper than the periphery was not observed during disc degeneration, which supports the hypothesis that vascular in-growth is not a distinct feature of disc degeneration.

Detection of myocardial capillary orientation with intravascular iron-oxide nanoparticles in spin-echo MRI

In mammalian hearts the capillaries are closely aligned with the muscle fibers. We report our observation of a main-field direction-dependent contrast in MR spin-echo (SE) images of the heart in the presence of Ferumoxtran-10, an intravascular iron-oxide nanoparticle contrast agent (CA). We describe a novel MRI method for mapping the preferential orientation of capillaries in the myocardial wall. The eigenvector corresponding to the minimum eigen value of the R2 relaxation rate tensor is consistent with the expected orientation of the capillary network. Preliminary results also demonstrate the feasibility of this method for in vivo application to rodent imaging.

Statistical analysis of reduced pair correlation functions of capillaries in the prostate gland

Blood capillaries are thread-like structures that may be considered as an example of a spatial fibre process in three dimensions. At light microscopy, the capillary profiles appear as a planar point process on sections. It has recently been shown that the observed pair correlation function g(r) of the centres of the fibre profiles on two-dimensional sections may be used to estimate the reduced pair correlation function of stationary and isotropic fibre processes in three dimensions. In the present study, we explored how this approach may be extended to statistical analysis of reduced g-functions of capillaries from multiple specimens of different groups and with replicated observations. The methods were applied to normal prostatic tissue compared with prostate cancer. Confidence intervals for the mean reduced g-functions of groups were estimated for fixed r-values parametrically using the t-distribution, and by bootstrap methods. Each estimated reduced g-function was furthermore characterized in terms of its first maximum and minimum. The mean length of capillaries per unit tissue volume was significantly higher in prostate cancer tissue than in normal prostate tissue. Significant differences between the mean reduced g-functions of malignant and benign lesions could be demonstrated for two domains of r-values. In general, bootstrap-based confidence intervals were slightly wider than parametrically estimated confidence intervals. Falsely negative lower bounds of the intervals, which sometimes arose using the parametric approach, could be avoided by the bootstrap method. Testing of group mean values for significant differences by the bootstrap method yielded more conservative results than multiple t-tests. The functional value of the first maximum of the reduced g-function and a global statistical parameter of short-range ordering was significantly reduced in the carcinoma group. Prostate cancer tissue is more densely supplied with capillaries than normal prostate tissue and the three-dimensional arrangement of the vessels differs with respect to interaction at various distance ranges. In the local approach used here, bootstrap methods can be used as a robust statistical tool for the computation of confidence intervals and group comparisons of mean reduced g-functions at specific ranges of interaction.

The assessment of the gingival capillary density with orthogonal spectral polarization (OPS) imaging

OBJECTIVE

In this study we evaluated the inter-observer agreement in the assessment of gingival capillary density using Orthogonal Polarization Spectral Imaging.

METHODS

In this study gingival capillary density of 100 healthy subjects was determined by 2 independent observers. Agreement was quantified by calculation of the mean differences between the observers and the standard deviation of this difference and the limits of agreement. Reliability was quantified by means of the intraclass correlation coefficient (ICC).

RESULTS

Fifty males and 50 females were included in the study. The mean age for males was 20+/-1.2 years and for females 20+/-1.4. OPS images showed remarkable good quality images of the gingival microcirculation. The interclass correlation between the 2 observers was 0.63 while the interclass correlation for the 6 measurements in observer 1 was 0.95 and 0.94 for observer 2. The mean capillary density for females in observer 1 was 83.69+/-16.4 and 83+/-16.0 in observer 2, versus 60.55+/-12.3 for observer 1 and 60.4+/-12.1 for males. The mean quantitative functional capillary density in male students was 60.48+/-10.7, compared to 83.45+/-13.5 in female students.

CONCLUSIONS

OPS imaging enabled for the first time direct in vivo visualization and quantification of human functional gingival capillary density in healthy medical students. The inter-observer agreement was found to be good to fair on the quantification of gingival capillary density between the two independent observers. The intracorrelation coefficient (0.95) was excellent when assessing the reliability of one observer.

Erythropoietin Enhances Neovascularization of Ischemic Myocardium and Improves Left Ventricular Dysfunction After Myocardial Infarction in Dogs

OBJECTIVES

We investigated the effects of erythropoietin (EPO) on neovascularization and cardiac function after myocardial infarction (MI).

BACKGROUND

Erythropoietin exerts antiapoptotic effects and mobilizes endothelial progenitor cells (EPCs).

METHODS

We intravenously administered EPO (1,000 IU/kg) immediately [EPO(0) group], 6 h [EPO(6h) group], or 1 week [EPO(1wk) group] after the permanent ligation of the coronary artery in dogs. Control animals received saline immediately after the ligation.

RESULTS

The infarct size 6 h after MI was significantly smaller in the EPO(0) group than in the control group (61.5 +/- 6.0% vs. 22.9 +/- 2.2%). One week after MI, the circulating CD34-positive mononuclear cell numbers in both the EPO(0) and the EPO(6h) groups were significantly higher than in the control group. In the ischemic region, the capillary density and myocardial blood flow 4 weeks after MI was significantly higher in both the EPO(0) and the EPO(6h) groups than in the control group. Four weeks after MI, left ventricular (LV) ejection fraction in the EPO(6h) (48.6 +/- 1.9%) group was significantly higher than that in either the control (41.9 +/- 0.9%) or the EPO(1wk) (42.6 +/- 1.2%) group but significantly lower than that in the EPO(0) group (56.1 +/- 2.3%). The LV end-diastolic pressure 4 weeks after MI in both the EPO(0) and the EPO(6h) groups was significantly lower than either the control or the EPO(1wk) group. Hematologic parameters did not differ among the groups.

CONCLUSIONS

In addition to its acute infarct size-limiting effect, EPO enhances neovascularization, likely via EPC mobilization, and improves cardiac dysfunction in the chronic phase, although it has time-window limitations.

Segmentation of volumetric MRA images by using capillary active contour

Precise segmentation of three-dimensional (3D) magnetic resonance angiography (MRA) images can be a very useful computer aided diagnosis (CAD) tool for clinical routines. Level sets based evolution schemes, which have been shown to be effective and easy to implement for many segmentation applications, are being applied to MRA data sets. In this paper, we present a segmentation scheme for accurately extracting vasculature from MRA images. Our proposed algorithm models capillary action and derives a capillary active contour for segmentation of thin vessels. The algorithm is implemented using the level set method and has been applied successfully on real 3D MRA images. Compared with other state-of-the-art MRA segmentation algorithms, experiments show that our method facilitates more accurate segmentation of thin blood vessels.

Some factors affecting pulmonary oxygen transport

Equations governing oxygen transport from alveolar gas to red blood cells flowing through pulmonary capillaries are written down. Some analytical predictions are made on factors affecting the rate at which this process takes place. Numerical simulations are carried out to investigate the effect of red blood cell shape, capillary dimensions, haematocrit and choice of oxygen dissociation curve on pulmonary oxygen transport. These factors all have an effect on pulmonary transport, with the effect being much more marked for simulations with low oxygen levels, typical of those seen in some subjects with respiratory disease.

Hierarchical microimaging for multiscale analysis of large vascular networks

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.

Arterioles' contribution to oxygen supply to the skeletal muscles at rest

We tested the hypothesis that oxygen is supplied to the resting skeletal muscle by arterioles rather than by capillaries. This hypothesis was evaluated in rats and rabbits by combining different approaches (1) determination of the intravascular oxygen tension (PO2) in arterioles of different diameters, (2) measurement of the perfused capillary number in response to changes in tissue PO2, and (3) estimation of the optimum capillary number to provide oxygen efficiently to the surrounding tissue. The intravascular PO2 values of arterioles along the vessels decreased downstream, suggesting that a significant amount of oxygen diffuses from the arterioles to the surrounding tissue. The perfused capillary number decreased as the tissue PO2 level was elevated, and this mutual relationship displayed a nonlinear correlation. The results suggest that a boundary PO2 level affecting the capillary recruitment exists for tissue PO2 of less than 40 mmHg with the capillary blood-flow stops above that PO2 level. At a high PO2 level, therefore, the oxygen is supplied from the arterioles. Furthermore, an estimation of optimum capillary number reveals that the capillary arrangement is constructed to achieve sufficient oxygen supply to the muscle during exercise, rather than at rest. These results suggest that oxygen is supplied from arterioles to the resting skeletal muscle, whereas the oxygen is supplied from the capillaries during exercise.

Microvascular adaptation to growth in rat humeral head

The aim of this work is to investigate the growth of the vasculature in the rat humeral head cartilage after the initial development of the secondary ossification centre until the adult organization. Rats aging from 5 weeks to 12 months were used. Histological observations on humeral heads were implemented with morphometrical analysis. Subsequently, vascular corrosion cast, that permits a three-dimensional observation of the vasculature, were prepared and observed by scanning electron microscopy. In young animals the epiphysis contains thin bone trabeculae and most of the epiphysis is occupied by bone marrow spaces. With age, the bone trabeculae progressively enlarge up to double their thickness. The percentage of bone tissue increases from 33.6 to 58.6% of the entire epiphysis, while the bone marrow spaces tend to increase very little in their mean dimension. Vascular corrosion casts show that the epiphyseal microcirculation is well distinguished from that of the diaphysis, and arises from the vessels present in the capsule and the periosteal networks. In young animals the only capillaries are bone marrow sinusoids and few subchondral capillaries. In adult animals small vessels run between the clusters of sinusoids forming the trabecular circulation. Capillary sprouts from sinusoids are always observed both in the young and adult animals. Thus, in adult rats different proper microcirculatory districts can be distinguished in the epiphysis: (a) the sinusoidal network, that supplies the hematopoiesis of the bone marrow and the adjacent osteogenic tissue; (b) the bone tissue microcirculation, limited to small vessels that supply the metabolism and the remodelling of the bone tissue. The reported microvascular organization and its adaptation to the epiphyseal growth represent the morphological basis for understanding the reciprocal interaction among the different tissues in developing and adult rat epiphysis.

Differential gene and protein expression in abluminal sprouting and intraluminal splitting forms of angiogenesis

In adult skeletal muscle, abluminal sprouting or longitudinal splitting of capillaries can be initiated separately by muscle overload and elevated microcirculation shear stress respectively. In the present study, gene and protein expression patterns associated with the different forms of angiogenesis were examined using a targeted gene array (Superarray), validated by quantitative RT (reverse transcription)-PCR and immunoblots. Sprouting angiogenesis induced large changes in expression levels in genes associated with extracellular matrix remodelling, such as MMP-2 (matrix metalloproteinase-2), TIMP (tissue inhibitor of metalloproteinases), SPARC (secreted protein, acidic and rich in cysteine) and thrombospondin. Changes in neuropilin, midkine and restin levels, which may underpin changes in endothelial morphology, were seen during splitting angiogenesis. Up-regulation of VEGF (vascular endothelial growth factor), Flk-1, angiopoietin-2 and PECAM-1 (platelet/endothelial cell adhesion molecule-1) was seen in both forms of angiogenesis, representing a common angiogenic response of endothelial cells. In conclusion, the present study demonstrates that general angiogenic signals from growth factors can be influenced by the local microenvironment resulting in differing forms of capillary growth to produce a co-ordinated expansion of the vascular bed.

Stereologic Analysis of Microvascular Morphology in the Elderly

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.

Dehydrated form of plasmid expressing basic fibroblast growth factor-polyethylenimine complex is a novel and accurate method for gene transfer to the cornea

PURPOSE

We describe a novel vector system of nonviral gene transfer into the cornea using a dehydrated form of a plasmid expressing basic fibroblast growth factor-polyethylenimine (p-bFGF-PEI) complex to induce angiogenesis.

METHODS

Corneal neovascularization was evaluated in 48 eyes of Sprague-Dawley rats after implantation of a dehydrated form of PEI containing 1 microg green fluorescent protein (p-GFP-PEI; control group), or 10 microg, 1 microg, or 0.1 microg of p-bFGF-PEI introduced by spin vacuum at ambient temperature. Neovascularization was observed and quantified from day 1 to day 45. Eighteen kDa bFGF protein expression was analyzed by Western blot and immunohistochemistry.

RESULTS

Limbal vessels began to sprout on day 3 in the p-bFGF-PEI groups. The dehydrated form of the p-bFGF-PEI complex induced dose-dependent corneal neovascularization, which reached a maximum on days 24-30 in the 10 microg bFGF group, days 18-24 in the 1 microg bFGF group, and days 15-21 in 0.1 microg bFGF group, and then regressed progressively. No neovascularization was observed in the GFP group.

CONCLUSIONS

The dehydrated form of the p-bFGF-PEI complex is a novel and precise method for controlling the dose, localizing the reagents, and avoiding loss of liquid form during transfection into corneal tissue.

A Novel Three-Dimensional Computer-Assisted Method for a Quantitative Study of Microvascular Networks of the Human Cerebral Cortex

OBJECTIVE

Detailed information on microvascular network anatomy is a requirement for understanding several aspects of microcirculation, including oxygen transport, distributions of pressure, and wall shear stress in microvessels, regulation of blood flow, and interpretation of hemodynamically based functional imaging methods, but very few quantitative data on the human brain microcirculation are available. The main objective of this study is to propose a new method to analyze this microcirculation.

METHODS

From thick sections of india ink-injected human brain, using confocal laser microscopy, the authors developed algorithms adapted to very large data sets to automatically extract and analyze center lines together with diameters of thousands of brain microvessels within a large cortex area.

RESULTS

Direct comparison between the original data and the processed vascular skeletons demonstrated the high reliability of this method and its capability to manage a large amount of data, from which morphometry and topology of the cerebral microcirculation could be derived.

CONCLUSIONS

Among the many parameters that can be analyzed by this method, the capillary size, the frequency distributions of diameters and lengths, the fractal nature of these networks, and the depth-related density of vessels are all vital features for an adequate model of cerebral microcirculation.

Validierung von Modellannahmen einer MR-Sauerstoffextraktionsbildgebung mittels einer Phantomstudie

Oxygen supply is an important parameter for the evaluation of tissue viability and therefore of high interest in cancer diagnosis and therapy. One promising approach to extract relevant information from imaging data is the determination of oxygen saturation by means of the BOLD-effect. Using a simple model of tissue structure allows to evaluate the susceptibility difference between tissue and venous blood, from which the blood oxygen extraction fraction can be derived indirectly. The present study tested the validity of two model assumptions needed for exact quantification: the independence of the results of both capillary diameter d and the relative blood volume lambda. For this purpose a phantom was built, which allows the evaluation of susceptibility differences depending on d (27 microm-238 microm) and lambda (3%-12%). In agreement with model assumptions, delta chi(lambda) was widely constant and independent of ) lambda. In contradiction to the model, delta chi (d) showed a positive slope (delta chi range: 0.35-0.57 ppm). The present study suggests that the simple model investigated here has shortcomings in the quantification of oxygen extraction due to insufficient model assumptions.

The three-dimensional detection of microvasculatory bed in the brain of white rat Rattus norvegicus by a Ca2+-ATPase method

A procedure is described which allows for the selective and non-injectional staining of the three-dimensional microvasculatory bed (MVB) in thick sections (60-140 microm) of formalin-fixed brain tissue of white rats Rattus norvegicus. This histochemical method detects ATPase activity and takes place between pH 10.5 and 11.2. Calcium ion is used to capture inorganic phosphate, calcium phosphate is converted to lead phosphate, and subsequently converted to black or dark brown lead sulfide. All vessels are revealed due to a precipitate on the endothelium and smooth muscle cells of arterioles. In some vessels, red blood cells also stain. The background is transparent with no staining of neurons, nerve fibers, glial cells, or nuclei. This allows for clear identification of arterioles, venules, and capillaries, which is difficult using other methods. New observations are described including the presence of webs connecting branching parts of arterioles and constrictions along vessels. This procedure should be useful in investigations of the MVB in rat brain.