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PubMed1997

On the Nusselt number in heat transfer between multiple parallel blood vessels.

Arrays of two or more parallel blood vessels in a tissue matrix have been studied extensively in the context of bioheat transfer. The average vessel Nusselt number (based on the difference between the mixed-mean blood temperature and the average vessel surface temperature) is a crucial parameter in such studies. Various workers have noted tht in particular cases the average Nusselt number is identical to that for fully developed flow in a single vessel in an infinite medium. In other words, the Nusselt number is unaffected by the presence of other vessels. It is proven here that this surprising result holds true for arbitrary number, size, flow direction, and velocity profile in the blood vessels, and for very general boundary conditions on the outer tissue boundary. A useful corollary is that the average wall temperature in a particular vessel may be found by evaluating the temperature fields due to the other vessels and the tissue boundaries at a single point, the center of the vessels in question.

Blood Flow Velocity↗
PubMed2005

Changes in the distribution and fine structure of the intralobular blood vessels of the submandibular gland in the postnatally developing mouse.

Previous studies have shown that the blood vessels supplying the endocrine organs and the mucosa of the intestinal canals change in terms of not only their distribution but also their structure with the development and growth of each organ. We examined changes in the distribution and structure of intralobular blood vessels, including capillaries, throughout the postnatal development of the submandibular gland, an exocrine organ. The mouse submandibular gland from days 0 (birth) to 49 was investigated chronologically and ultrastructurally. The capillaries changed from continuous to fenestrated on day 10, coincident with an increase in the number of acini to more than the number of terminal tubules. The number of sections of intralobular blood vessels per unit area gradually decreased with increasing acinar size and was lowest on day 21 when pups were weaned; the same number was maintained from then on. In contrast with the reduction in the number of intralobular blood vessels, the number of capillary pores appeared to increase gradually. Acinar size increased further till day 28. Capillary pore number also increased further, till day 35, apparently in relation to the increasing acinar size. These findings suggest that the changes in distribution and structure of the intralobular blood vessels in the submandibular gland of the postnatally developing mouse are closely related to the development of the parenchymal cells in preparation for weaning and sexual maturity.

Animals↗
PubMed1992

Strain distribution in small blood vessels with zero-stress state taken into consideration.

The active and passive deformation of a blood vessel is related to the stress in it. Any analysis of stress and strain must begin with the zero-stress state. Recent reports on large blood vessels such as the aorta, pulmonary arteries, and vena cava have shown that, at zero-stress state, blood vessels are not tubes, but opens sectors. This report presents data on the zero-stress state of small blood vessels with lumen diameters down to approximately 50 microns. Zero-stress state of a vessel was obtained by cutting the vessel into rings and then the rings into sectors; each sector is characterized by an opening angle, alpha. In rat ileal and plantar arterioles, the opening angles are in the order of 100-250 degrees; those in the venules are in the order of 50-100 degrees. The effect of norepinephrine on the opening angle alpha is minor; it decreases alpha of the superior mesenteric artery, and increases alpha of the ileocecocolic and ileal arteries. EDTA has little effect on alpha of arteries greater than 100 microns in diameter, but decreases alpha of arteries less than 100 microns. The physiological meaning of the opening angle is demonstrated in terms of the residual strains in a vessel at the no-load state and homeostatic strains at normal blood pressure. The strains in real vessels are compared with those in hypothetical vessels having an opening angle of zero. It is shown that ignoring the opening angle will cause a large error in strain evaluation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

[Effects of enalapril on plasma Ang II level and the expression of AT1 in blood vessel and kidney of type 2 diabetic rats].

AIM: To study the plasma angiotensin II (Ang II) levels and the expressions of angiotensin II1 receptor (AT1) in blood vessels and kidneys in diabetic and high fat diet rats, and the effects of enalapril on plasma Ang II levels and the expressions of AT1 in blood vessels and kidneys in diabetic rats. METHODS: The plasma Ang II level was assayed with 125I-Ang II radioimmunoassay, and the expression of AT1 in blood vessel and kidney was analyzed with immunohistochemical technique. RESULTS: The plasma Ang II level was significantly higher in type 2 diabetic rats (241 +/- 49) pg x mL(-1) than that in the control (71 +/- 22) pg x mL , high fat diet group (151 +/- 29) pg x mL(-1) (P < 0.01) , and enalapril-treated groups (136 +/- 25) pg x mL(-1) (P < 0.05). The plasma Ang II levels in high fat diet and in enalapril-treated groups were also significantly higher than that in control group ( P < 0.01 ). With immunohistochemical technique, it was found that the expression of AT1 in endothelial cells of blood vessels, vascular smooth muscle cells, and kidneys in diabetic group increased. The expression of AT1 in endothelial cells of blood vessels, vascular smooth muscle cells, and kidney in enalapril-treated group was similar to that in control group. CONCLUSION: The plasma Ang II levels and the expression of AT1 in type 2 diabetic and high fat diet rats increased. Enalapril was shown to decrease the plasma Ang II level and downregulate the expression of AT1 in blood vessels and kidneys in type 2 diabetic rats.

Angiotensin II↗
PubMed1995

Blood vessel growth in the endometrium.

Angiogenesis, or formation of new blood vessels by sprout formation from existing vessels, is generally considered to be the only mechanism by which blood vessel growth occurs. This traditional concept of angiogenesis has been derived largely from observations of experimental systems. Relatively fewer studies on angiogenesis have been carried out using normal angiogenic situations where vessel growth occurs in a controlled three-dimensional fashion throughout the tissue. Recent advances in the treatment of infertility and outpatient gynecological procedures have led to greater accessibility to normal human endometrium, thus providing new opportunities to study the process of angiogenesis in a physiological context. However, to date, it appears that very little work had been done in relation to endometrial angiogenesis apart from the location of numerous angiogenic and other growth factors with potential to influence angiogenesis in the endometrium, and here there have been few attempts to link these observations with actual angiogenic events. The purpose of this review is to summarize the literature regarding angiogenesis in the endometrium, including work from our own laboratory, and to suggest that blood vessel growth in the endometrium may occur by a mechanism that differs from classical angiogenesis.

Animals↗
PubMed2003

[Endothelium-derived factors in hypertensive blood vessels, especially nitric oxide and hypertension].

Endothelium-dependent relaxation (EDR) in the blood vessels of spontaneously hypertensive rats (SHR) and the role of nitric oxide (NO) in the initiation of hypertension are reviewed. EDR was impaired in blood vessels of SHR depending on age and degree of hypertension when compared with those of normotensive rats. The cause of the impairment varied among the type of blood vessels: a decrease in the production of NO and endothelium-derived relaxing factor (EDRF) and an increase in the production of endothelium-derived contracting factor (EDCF) are the main causes of the impairment in large arteries, while a decrease in endothelium-dependent hyperpolarization and increased release of EDCF are the main causes of the impairment in small arteries. Interactions among these endothelium-derived factors and changes in the interactions are also causes of impairment. Superoxide may be involved in the impairment of EDR by destroying NO. The endothelium depresses smooth muscle contraction, including spontaneous tone developed in vascular smooth muscle, and the depressing effect of the endothelium is impaired in the preparations from SHR. The endothelium of blood vessels of SHR are structurally injured as demonstrated by scanning electron microscopy. Antihypertensive treatment prevented these functional and structural changes. Chronic treatment with inhibitors of NO production in normotensive rats impaired EDR and elevated blood pressure. The impairment of EDR is a secondary change due to continued hypertension, and early initiation of antihypertensive therapy is recommended.

Animals↗
PubMed2001

Study of the distribution of retinal blood vessels in buffaloes (Bos bubalis).

The distribution of retinal blood vessels in the eye of buffalo was studied macroscopically and microscopically in twenty-two eyes of healthy animals. After macroscopic observation, 12 of 22 eyes were used for histological study. Ten eyes were stained with hematoxylin and eosin and two eyes with PAS stain. The present findings revealed that the eye of the buffalo was characterized by the complex network of retinal blood vessels (holangiotic or euangiotic). The central retinal artery and vein pierced the eye through the optic disc and gave off several branches. There were four pairs of primary vessels that were named dorsal, ventral, nasal and temporal retinal arteries and veins. The veins anastmosed with each other at the optic disc to form a somewhat circle. Three patterns of the distribution of blood vessels were described. The distribution of the arteries and veins was the same.

Animals↗
PubMed1995

The angiogenic potentials of the cephalic mesoderm and the origin of brain and head blood vessels.

We have used two molecular markers to label blood vessel endothelial cells and their precursors in the early avian embryo. One marker, called Quek1, is the avian homologue of the mammalian VEGF receptor flk-1 and the other is the MB1/QH1 monoclonal antibody. Quek1 is expressed in a subset of mesodermal cells from the gastrulation stage. Quek1 positive cells later form blood vessel endothelial cells and express the MB1/QH1 antigen which is specific for endothelial and hemopoietic cells of the quail species. These two markers allowed us first to show that the cephalic paraxial mesoderm has angiogenic potentials which are much more extended than its trunk counterpart (the somites). Secondly, the origin of the endothelial cells lining the craniofacial and head blood vessels was mapped on the 3-somite stage cephalic mesoderm via the quail-chick chimera technique, in which well defined mesodermal territories are exchanged between stage-matched embryos of both species in a strictly isotopic manner. We found that the anterior region of the cephalic paraxial mesoderm is largely recruited to provide the forebrain and the upper face with their vasculature. This means that large volumes of tissues are vascularized by a discrete region of the cephalic mesoderm, the fate of which is otherwise to give rise to muscles. The widespread expansion of the angiogenic cells arising from the anterior paraxial mesoderm must be related to the high growth rate of the anterior region of the neural primordium, yielding the telencephalon and of the neural crest-derived facial structures which are themselves devoid of angiogenic potencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Increase of segments of elastic-type blood vessel walls in fetal placental stem villi during pre-eclampsia at term.

In recent studies we described the presence of elastic-type blood vessels within trunci and rami chorii of human placental stem villi. For systemic and pulmonary hypertension it is known that elastic fibres are enhanced in arteries. The aim of our study was, therefore, to examine whether pre-eclampsia may lead to an increase of elastic tissue fibres in blood vessel walls of placental stem villi and whether there are differences in the thickness of blood vessel walls within these villi when compared to normotensive pregnant women. Twenty-six women with uncomplicated pregnancies and 25 patients with pre-eclampsia were investigated. Unfixed cryostat serial sections were processed for conventional orcein staining and for the demonstration of alpha-actin-immunoreactivity. The intensity of orcein staining of stem villus blood vessel walls was evaluated by a semiquantitative score method. Significant higher intensities of orcein staining (P<0.00001) were calculated for blood vessel walls of placentae with pre-eclampsia. The amount of thick stem villus vessels (>41 microm) increased during pre-eclampsia from 39 gestational weeks onwards. Our study demonstrates that segments of thick blood vessel walls and elastic-type vessel walls are increased in placental stem villi of patients with pre-eclampsia. This reaction may protect the fetal placental vessels and avert an increase of the fetal hypertension.

Chorionic Villi↗
PubMed2001

[Advances of construction of tissue engineered blood vessels].

OBJECTIVE: To discuss the approaches of tissue engineered blood vessels (TEBV) reconstruction. METHODS: The recent literatures about TEBV were widely reviewed. We summarized various types of biomaterials served as scaffold for TEBV and evaluated the construction model of TEBV. And the biological properties of some TEBV were compared. RESULTS: Although the final model of construction of TEBV was not clear, reports in the last two years had shown several important advances in this exciting field. CONCLUSION: Mimicry of some or all of the properties of three layers of natural healthy blood vessels has been the strategy of all TEBV approaches.

Biocompatible Materials↗
PubMed1999

alpha-Tocopherol increased nitric oxide synthase activity in blood vessels of spontaneously hypertensive rats.

Antioxidant protection provided by different doses of alpha-tocopherol was compared by determining nitric oxide synthase (NOS) activity in blood vessels of spontaneously hypertensive rats (SHR) treated with alpha-tocopherol. SHR were divided into four groups namely hypertensive control (C), treatment with 17 mg of alpha-tocopherol/kg diet (alpha1), 34 mg of alpha-tocopherol/kg diet (alpha2), and 170 mg of alpha-tocopherol/kg diet (alpha3). Wister Kyoto (WKY) rats were used as normal control (N). Blood pressure were recorded from the tail by physiography every other night for the duration of the study period of 3 months. At the end of the trial, animals were sacrificed. The NOS activity in blood vessels was measured by [3H]arginine radioactive assay and the nitrite concentration in plasma by spectrophotometry at wavelength 554 nm using Greiss reagent. Analysis of data was done using Student's t test and Pearson's correlation. The computer program Statistica was used for all analysis. Results of our study showed that for all the three alpha-tocopherol-treated groups, blood pressure was significantly (P < .001) reduced compared to the hypertensive control and maximum reduction of blood pressure was shown by the dosage of 34 mg of alpha-tocopherol/kg diet (C: 209.56 +/- 8.47 mm Hg; alpha2: 128.83 +/- 17.13 mm Hg). Also, NOS activity in blood vessels of SHR was significantly lower than WKY rats (N: 1.54 +/- 0.26 pmol/mg protein, C: 0.87 +/- 0.23 pmol/mg protein; P < .001). Although alpha-tocopherol in doses of alpha1, alpha2, and alpha3 increased the NOS activity in blood vessels, after treatment only that of alpha2 showed a statistical significance (P < .01). Plasma nitrite concentration was significantly reduced in SHR compared to normal WKY rats (N: 54.62 +/- 2.96 mol/mL, C: 26.24 +/- 2.14 mol/mL; P < .001) and accordingly all three groups showed significant improvement in their respective nitrite level (P < .001). For all groups, NOS activity and nitrite level showed negative correlation with blood pressure. It was significant for NOS activity in hypertensive control (r = -0.735, P = .038), alpha1 (r = -0.833, P = .001), and alpha2 (r = -0.899, P = .000) groups. For plasma nitrite, significant correlation was observed only in group alpha1 (r = -0.673, P = .016) and alpha2 (r = -0.643, P = .024). Only the alpha2 group showed significant positive correlation (r = 0.777, P = .003) between NOS activity and nitrite level. In conclusion it was found that compared to WKY rats, SHR have lower NOS activity in blood vessels, which upon treatment with antioxidant alpha-tocopherol increased the NOS activity and concomitantly reduced the blood pressure. There was correlation of lipid peroxide in blood vessels with NOS and nitric oxide, which implies that free radicals may be involved in the pathogenesis of hypertension.

Animals↗
PubMed2006

A vertical scanning Doppler probe identifies blood vessels during laparoscopic surgery.

BACKGROUND: Using a conventional Doppler probe, it is difficult to identify blood vessels precisely in lymph node dissection during laparoscopic surgery. METHODS: For 26 patients undergoing laparoscopic colectomy and 26 patients undergoing laparoscopic subtotal gastrectomy, we used conventional and vertical scanning Doppler probes to compare their ability to identify invisible blood vessels through differences in power output voltage. RESULTS: The vertical scanning Doppler probe was 100% successful in identifying the target blood vessels regardless of the patient's body mass index (BMI), and also was superior to the conventional Doppler probe in detection sensitivity. The vertical scanning Doppler probe was useful for image training of recently qualified surgeons through real-time monitoring of the probe position and response on the monitor. Furthermore, findings showed that the vertical scanning Doppler probe was applicable to lymph node dissection as a forceps for laparoscopic usage. CONCLUSION: The vertical scanning Doppler could identify the target blood vessels regardless of the patient's BMI. It was verified to be useful as a surgical assistive device apart from being a sensor and may serve in the education of recently qualified surgeons.

Arteries↗
PubMed2004

Freezing by a flat, circular surface cryoprobe of a tissue phantom with an embedded cylindrical heat source simulating a blood vessel.

The effects of a thermally-significant blood vessel, simulated by an embedded acrylic tube, 4.8 mm outer diameter on the freezing field caused by a surface cryoprobe were studied experimentally in a tissue phantom. The flat, 15 mm diameter, circular cryoprobe was operated at a constant cooling rate of -8 degrees C/min by liquid nitrogen down to -60 degrees C. Water flow rates of 30 and 100 ml/min, at a constant temperature of 32.5 degrees C, were maintained in the embedded tube. The latter flow rate is typical to the lower range of blood flows in large arteries in the human body. The phase changing medium (PCM) used was a 30/70% by volume mashed potatoes flakes-water solution. Temperature measurements inside the PCM were performed in one plane perpendicular to the embedded tube, relative to which the cryoprobe was placed at 5 locations in separate experiments. This novel experimental method reduced the perturbation caused by the thermocouple junctions while facilitating rather detailed measurements of the temperature fields developing in the PCM. Results show the development of two hump-like formations on either side of the embedded tube. Freezing was retarded in the region away from the surface cryoprobe and under the tube. This accentuated the dominance of the axial effects, due to the embedded tube, over the radial ones due to the cryoprobe. Results of this study should be considered in designing protocols of cryosurgical procedures performed in the vicinity of thermally-significant blood vessels.

Animals↗
PubMed1983

Conjunctival and episcleral blood vessels are permeable to blood-borne horseradish peroxidase.

The vessels of the conjunctival and episcleral plexuses of Macaca mulatta eye are of the continuous type. Most of the vessels in the conjunctival plexus have the diameter of capillaries, while the vast majority of the vessels in the episcleral plexus are venules. Both types of vessels have a simple wall, which consists of an endothelium and a discontinuous layer of pericytes. The aim of this study was to establish their permeability properties to blood-borne horseradish peroxidase (HRP). After intravenous injection of HRP, in 200 microns chopper sections of the anterior segment of the eye examined with the light microscope, the subconjunctival and episcleral tissues appear intensely and diffusely stained by the reaction product. The electron microscope shows that HRP escapes from the vessels lumen by crossing the interendothelial clefts and, in addition, a great number of pinocytotic vesicles loaded with HRP are present on the luminal, tissue front and in the cytoplasm of the endothelial cells. HRP, which rapidly penetrates the loose connective tissue of the region, reaches the spaces between the cells of the conjunctival epithelium where it is finally blocked by the zonulae occludentes that connect the most superficial epithelial cells. A slow diffusion into the compact tissue of the cornea and of the sclera was also observed. Thus, under normal conditions, blood-borne macromolecules can freely diffuse into the subconjunctival and episcleral loose connective tissues. On the other hand, one can equally expect that the aqueous humor that reaches the episcleral and conjunctival blood plexuses through the canal of Schlemm and collector channels can freely diffuse into the subconjunctival spaces across the walls of these permeable vessels.

Animals↗
PubMed1982

Muscarinic cholinergic receptor sites in cerebral blood vessels.

Muscarinic cholinergic receptor sites in cerebral blood vessels were analyzed directly by using radioligand binding techniques with the specific muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) as ligand. Specific binding of [3H]QNB to membrane preparations from isolated bovine pia-arachnoid vessels was found to be saturable, of high affinity (Kd = 5.4 X 10(-10) M) and selectively inhibited by muscarinic antagonists (atropine) and agonists (acetylcholine, carbachol and methacholine). Scatchard and Hill plot analyses of the data indicated one class of sites for the antagonists, but two independent classes of sites were revealed with the agonists. Interestingly, the high and low affinities of the agonist sites correlated with the concentrations of agonist which have been reported to produce dilation and contraction, respectively, of isolated pial artery segments. A substantial number of specific [3H]QNB binding sites also were measured in isolated bovine cerebral microvessels providing direct evidence for muscarinic receptors in intracerebral vessels. In contrast, specific [3H]QNB binding was barely detectable in mesenteric blood vessels. Choline acetyltransferase (ChAT) activity was measured in parallel with [3H]QNB binding. The relative distribution of choline acetyltransferase was correlated with that for the binding, with the highest values observed in the intracerebral microvessels. This suggests a functional innervation of the cerebrovascular muscarinic receptors.

Animals↗
PubMed2007

Segmentation of blood vessels from red-free and fluorescein retinal images.

The morphology of the retinal blood vessels can be an important indicator for diseases like diabetes, hypertension and retinopathy of prematurity (ROP). Thus, the measurement of changes in morphology of arterioles and venules can be of diagnostic value. Here we present a method to automatically segment retinal blood vessels based upon multiscale feature extraction. This method overcomes the problem of variations in contrast inherent in these images by using the first and second spatial derivatives of the intensity image that gives information about vessel topology. This approach also enables the detection of blood vessels of different widths, lengths and orientations. The local maxima over scales of the magnitude of the gradient and the maximum principal curvature of the Hessian tensor are used in a multiple pass region growing procedure. The growth progressively segments the blood vessels using feature information together with spatial information. The algorithm is tested on red-free and fluorescein retinal images, taken from two local and two public databases. Comparison with first public database yields values of 75.05% true positive rate (TPR) and 4.38% false positive rate (FPR). Second database values are of 72.46% TPR and 3.45% FPR. Our results on both public databases were comparable in performance with other authors. However, we conclude that these values are not sensitive enough so as to evaluate the performance of vessel geometry detection. Therefore we propose a new approach that uses measurements of vessel diameters and branching angles as a validation criterion to compare our segmented images with those hand segmented from public databases. Comparisons made between both hand segmented images from public databases showed a large inter-subject variability on geometric values. A last evaluation was made comparing vessel geometric values obtained from our segmented images between red-free and fluorescein paired images with the latter as the "ground truth". Our results demonstrated that borders found by our method are less biased and follow more consistently the border of the vessel and therefore they yield more confident geometric values.

Algorithms↗
PubMed2003

Incorporation of adult organ-derived endothelial cells into tumor blood vessel.

In this study, we attempted to assess the incorporable potential of vascular endothelial cells derived from adult organ blood vessels into tumor blood vessels. Two kinds of adult organ-derived vascular endothelial cells, human aorta endothelial cells (HAEC) and umbilical vein endothelial cells (HUVEC), were administered into murine tumors inoculated to SCID mice. Many human blood vessel networks were visualized in the murine tumors. These cells in solid tumor not only survived and proliferated, but also incorporated into tumor endothelium. These results suggest that adult organ-derived vascular endothelial cells possess the potential to form the neovascular network in various tissues such as vascular endothelial progenitor-like cells in vivo. We propose that these cells can be regarded as a congenic (autologous) vector for vascular regeneration cell therapy and tumor vascular targeting gene therapy.

Adult↗
PubMed2005

A new strategy to obtain robust markers for blood vessels segmentation by using the watersheds method.

The watersheds method is a powerful segmentation tool developed in mathematical morphology. In order to prevent its over-segmentation, in this paper, we present a new strategy to obtain robust markers for segmentation of blood vessels from malignant tumors. For this purpose, we introduced a new algorithm. We propose a two-stage segmentation strategy which involves: (1) extracting an approximate region containing the blood vessel and part of the background near the blood vessel, and (2) segmenting the blood vessel from the background within this region. The approach effectively reduces the influence of peripheral background intensities on the extraction of a blood vessel region. In this application the important information to be extracted from images is only the number of blood vessels present in the images. The proposed strategy was tested on manual segmentation, where segmentation errors less than 10% for false positives and 0% for false negatives are observed. It is demonstrated by extensive experimentation, by using real images, that the proposed strategy was suitable for our application in the environment of a personal computer.

Algorithms↗