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At least 1,207 records · Page 67Linked to original sources
PubMed1995

Increase of retinal vessel width in ocular hypertensives with timolol therapy.

PURPOSE: The purpose of this study was to determine whether timolol drops compared to placebo drops had a significant effect on retinal vessel width in ocular hypertensives. METHODS: Thirty-seven ocular hypertensives were randomly assigned to receive placebo or 0.5% timolol drops to both eyes for 18 to 24 months in a double masked clinical trial. Measurements of ocular pressure and retinal vessel width by computerized image analysis from fundus photographs were made at about 3 month intervals for 18 to 24 months of follow-up. RESULTS: None of the subjects developed visual field loss when tested with the Goldmann perimeter by kinetic and static means at six month intervals. Subjects treated with the placebo showed no change in ocular pressure and a significant decrease in retinal vessel width over time especially in the right eye. Subjects treated with timolol had an increase in retinal vessel width compared to the placebo group significant especially for the superior temporal vein. Multivariate analyses indicated that the increase of retinal vessel width was not associated mainly with the ocular pressure on treatment or decrease in ocular pressure on treatment. CONCLUSION: Timolol treatment was associated with an increase of retinal vessel width. The effect of timolol appears to be related primarily to mechanisms other than the decrease in ocular pressure.

Double-Blind Method↗
PubMed2006

Risk factors for conjunctival and retinal vessel alterations in sickle cell disease.

PURPOSE: The aim of this study was to clarify whether the clinical, laboratory and genetic aspects of sickle cell disease (SCD) influence the occurrence of vessel alterations in the conjunctiva and retina. METHODS: A total of 102 SCD patients underwent biomicroscopical and retinal examination, in addition to evaluations of haemoglobin (Hb) and haematocrit (Ht) levels, fetal haemoglobin (HbF) estimations, serum creatinine and albuminuria levels, glomerular filtration rate (GFR) values, phenotypes, beta-globin gene haplotypes and alpha-thalassaemia. The relationship between ocular vessel alterations and clinical, laboratory and genetic features were evaluated using chi-squared or Fisher tests and logistic regression analysis. In 13 patients on enalapril treatment, a second ophthalmological evaluation was performed after a 12-month period to evaluate the longitudinal effect of the drug on ocular vessels. RESULTS: Conjunctival vessel alteration (CVA) was not influenced by age, gender, HbF estimation, serum creatinine and albuminuria levels, GFR values, beta-globin gene haplotypes or alpha-thalassaemia. However, increased frequencies of CVA were found in patients with Hb </= 9.0 g/dl, Ht </= 26.7% and sickle cell anaemia (SS) phenotype. Retinal vessel alteration (RVA) was identified only in patients aged 17 years or older. Enalapril did not demonstrate ocular vessel amelioration after 12-months of daily use. CONCLUSION: The results indicate that lower Hb and Ht levels and SS phenotype are risk factors for CVA, and age over 17 years may be risk factors for RVA in SCD patients.

Adult↗
PubMed2001

Pulsatile blood flow effects on temperature distribution and heat transfer in rigid vessels.

The effect of blood velocity pulsations on bioheat transfer is studied. A simple model of a straight rigid blood vessel with unsteady periodic flow is considered. A numerical solution that considers the fully coupled Navier-Stokes and energy equations is used for the simulations. The influence of the pulsation rate on the temperature distribution and energy transport is studied for four typical vessel sizes: aorta, large arteries, terminal arterial branches, and arterioles. The results show that: the pulsating axial velocity produces a pulsating temperature distribution; reversal of flow occurs in the aorta and in large vessels, which produces significant time variation in the temperature profile. Change of the pulsation rate yields a change of the energy transport between the vessel wall and fluid for the large vessels. For the thermally important terminal arteries (0.04-1 mm), velocity pulsations have a small influence on temperature distribution and on the energy transport out of the vessels (8 percent for the Womersley number corresponding to a normal heart rate). Given that there is a small difference between the time-averaged unsteady heat flux due to a pulsating blood velocity and an assumed nonpulsating blood velocity, it is reasonable to assume a nonpulsating blood velocity for the purposes of estimating bioheat transfer.

Biomechanical Phenomena↗
PubMed2003

Virtual 3D IVUS vessel model for intravascular brachytherapy planning. I. 3D segmentation, reconstruction, and visualization of coronary artery architecture and orientation.

Intravascular brachytherapy (IVB) can significantly reduce the risk of restenosis after interventional treatment of stenotic arteries, if planned and applied correctly. To facilitate computer-based IVB planning, a three-dimensional vessel model has been derived from information on coronary artery segments acquired by intravascular ultrasound (IVUS) and biplane angiography. Part I describes the approach of model construction and presents possibilities of visualization. The vessel model is represented by a voxel volume. Polygonal information about the vessel wall structure is derived by segmentation from a sequence of IVUS images automatically acquired ECG gated during pull back of the IVUS transducer. To detect horizontal, vertical, and radial contours, modified Canny-Edge and Shen-Castan filters are applied on Cartesian and polar coordinate representations of the IVUS tomograms as edge detectors. The spatial course of the vessel wall layers is traced in reconstructed longitudinal IVUS scans. By resampling the sequence of IVUS frames the voxel volume is obtained. For this purpose the frames are properly located in space and augmented with additional intermediate frames generated by interpolation. Their spatial location and orientation is derived from biplane X-ray angiography which is performed simultaneously. For resampling, two approaches are proposed: insertion of the vertices of the rectangular goal grid into the cells of a deformed hexahedral mesh derived from the IVUS sequence, and insertion of the vertices of the hexahedral mesh into the cells of the rectangular grid. Finally, the vessel model is visualized by methods of combined volume and polygon rendering. The segmentation process is verified as being in good agreement with results obtained by manual contour tracing with a commercial system. Our approach of construction of the vessel model has been implemented into an interactive software system, 3D IVUS-View, serving as the basis of a future system for intracoronary brachytherapy treatment planning being currently under development (Part II).

Algorithms↗
PubMedDate not supplied

Evaluation of observer performance in detecting blood vessels on simulated angiographic images.

This paper presents methods for evaluating the effects of technical factors on observers' detection of small blood vessels in angiographic images. A fixed set of physical parameters was used to generate computer-simulated angiographs that contained blood vessels of various diameters. Observers' judgments about each set of images permitted estimation of the receiver operating characteristic (ROC) curves for vessel detection and of the probability of correctly locating the vessels. Both parametric and nonparametric methods were used to characterize the ROC curves. Three different, but theoretically related, measures of vessel detectability varied systematically with changes in the blood vessel's diameter, reflecting changes in observer performance.

Angiography↗
PubMed1995

Investigations of large vessel cooling during interstitial laser heating.

Interstitial laser heating of tissues is influenced by blood flow in the treatment region. Temperature gradients around large blood vessels may result in local underheating of tissues. A three-dimensional, time-dependent finite difference model of interstitial laser heating around large vessels is presented. A thermal conduction model was developed using a transport theory approximation for the energy distribution from an optical line source. Calculated transient temperature profiles and temperature reductions around 0.144 and 0.400 cm diam vessels show qualitative agreement with those measured in a series of tissue phantom studies. Experiments and calculations for a large vessel located approximately 1.0 cm from the optical source indicate that temperature reductions are less than 1 degree C at distances greater than approximately 1.0 cm from the vessel surface. The model also indicates that significant reductions in the extent of a thermal coagulation boundary can occur if a large vessel is situated inside the normal coagulation zone.

Blood Vessels↗
PubMed1993

Occlusion of retinal vessels using targeted delivery of a platelet aggregating agent.

Local laser targeted delivery of a platelet aggregating agent to occlude retinal and choroidal vessels was evaluated in rabbits and rats. Liposomes containing adenosine diphosphate (ADP) were administered intravenously and an argon laser was used to lyse the liposomes in main retinal arteries. Control vessels were treated with the same energy of laser without administering ADP. Fluorescein angiography performed 2 weeks later showed that all the control vessels were perfused. Ninety percent of the ADP-treated arteries showed complete or partial occlusion. Successful occlusion increased with the laser energy and decreased with increasing vessel diameter. Histopathology showed that occlusion was achieved in retinal as well as choroidal vessels. The inner retina remained relatively unaffected at the treatment site but the outer retina was thermally damaged. These preliminary results suggest that targeted delivery of a platelet aggregating agent holds promise for occluding vessels in the fundus.

Adenosine Diphosphate↗
PubMed2000

Evaluation of the Zeiss retinal vessel analyser.

AIM: To investigate the reproducibility and sensitivity of the Zeiss retinal vessel analyser, a new method for the online determination of retinal vessel diameters in healthy subjects. METHODS: Two model drugs were administered, a peripheral vasoconstrictor (the alpha receptor agonist phenylephrine) and a peripheral vasodilator (the nitric oxide donor sodium nitroprusside) in stepwise increasing doses. Nine healthy young subjects were studied in a placebo controlled double masked three way crossover design. Subjects received intravenous infusions of either placebo or stepwise increasing doses of phenylephrine (0.5, 1, or 2 microg/kg/min) or sodium nitroprusside (0.5, 1, or 2 microg/kg/min). Retinal vessel diameters were measured with the new Zeiss retinal vessel analyser. Retinal leucocyte velocity, flow, and density were measured with the blue field entoptic technique. The reproducibility of measurements was assessed with coefficients of variation and intraclass correlation coefficients. RESULTS: Placebo and phenylephrine did not influence retinal haemodynamics, although the alpha receptor antagonist significantly increased blood pressure. Sodium nitroprusside induced a significant increase in retinal venous and arterial diameters (p<0.001 each), leucocyte density (p=0.001), and leucocyte flow (p=0.024) despite lowering blood pressure to a significant degree. For venous and arterial vessel size measurements short term coefficients of variation were 1.3% and 2.6% and intraclass correlation coefficients were 0.98 and 0.96, respectively. The sensitivity was between 3% and 5% for retinal veins and 5% and 7% for retinal arteries. CONCLUSIONS: These data indicate that the Zeiss retinal vessel analyser is an accurate system for the assessment of retinal diameters in healthy subjects. In addition, nitric oxide appears to have a strong influence on retinal vascular tone.

Adrenergic alpha-Agonists↗
PubMed2002

Effects of dopamine on human retinal vessel diameter and its modulation during flicker stimulation.

We performed a randomized, subject-blinded, placebo and time-controlled, two-way crossover study in 12 healthy male subjects. Placebo or dopamine was administered on two separate study days. After saline infusion, dopamine hydrochloride was infused in three consecutive doses (5, 10, and 15 microg x kg(-1) x min(-1)). Plasma levels of dopamine were determined at each perfusion step. Arterial and venous retinal vessel diameters were measured with the use of a Zeiss retinal vessel analyzer. Diffuse luminance flicker stimuli of 8 Hz were applied for 60 s. Blood pressure and pulse rate were monitored continuously. Flicker stimulation (8 Hz) increased retinal vessel diameters under basal conditions. The response to 8-Hz flicker light was significantly reduced by dopamine administration. In addition, dopamine slightly but significantly increased retinal vessel diameters. Dopamine hydrochloride significantly increased systolic but not diastolic or mean arterial pressure. The present study indicates that dopamine has a distinct effect on retinal vessel diameters also attenuating the flicker-induced response reactivity of retinal vessels. This implies a role of dopamine in retinal blood flow hemodynamics.

Adult↗
PubMed2004

Quantitative microcomputed tomography analysis of collateral vessel development after ischemic injury.

Transgenic mouse models are increasingly being used to investigate the functions of specific growth factors or matrix proteins to design therapeutic strategies for controlling blood vessel growth. However, the available methodologies for evaluating angiogenesis and arteriogenesis in these models are limited by animal size, user subjectivity, the power to visualize the three-dimensional vessel networks, or the capability to employ a vigorous quantitative analysis. In this study, we employed contrast-enhanced microcomputed tomography imaging to assess collateral development after induction of hindlimb ischemia in the mouse. The morphological parameters vessel volume, connectivity, number, thickness, thickness distribution, separation, and degree of anisotropy were evaluated in control and surgery limbs 0, 3, and 14 days postsurgery. Results indicate that the vascular volume of the surgically manipulated limb was reconstituted as early as 3 days after femoral artery excision through development of a series of highly connected, small caliber, closely spaced, and isotropically oriented collateral vessels. Parametric analyses were completed to assess the sensitivity of the calculated morphological parameters to variations in image binarization threshold and voxel size. Images taken at the 36-microm voxel size were found to be optimal for evaluating collateral vessel formation, whereas 8- to 16-microm voxel sizes were needed to resolve smaller vascular structures. This study demonstrates the utility of microcomputed tomography as a robust method for quantitative, three-dimensional analysis of blood vessel networks. Whereas these initial efforts focused on the mouse hindlimb ischemia model, the developed techniques may be applied to a variety of model systems to investigate mechanisms of angiogenesis and arteriogenesis.

Animals↗
PubMed1979

In vivo measurement of blood vessel wall thickness.

To understand the mechanical properties of arteries and vascular grafts, it is crucial that the wall thickness in these vessels be known. Unfortunately, all availble methods for measuring this parameter require the removal of the vessel, which precludes the study of such vessels as a function of time. A new radiographic technique for measuring the wall thickness of arteries and vascular grafts in vivo, utilizing contrast materials injected into the vessel lumen and applied to the outer surface of the vessel, is described. Radiographs are obtained with a portable X-ray machine and analyzed using a calibrated microscope. The technique has been successfully applied to the in vivo measurement of wall thickness in canine arteries, veins, and experimental vascular grafts. It is concluded that the method provides better than 95% accuracy in a variety of vessels and that it can be used to study changes in vascular grafts after their implantation into the arterial circulation.

Angiography↗
PubMed1991

Endothelium-dependent vasodilation of canine coronary collateral vessels.

The objective of this study was to determine whether endothelium-mediated relaxation occurs in canine coronary collateral vessels. Responses to endothelium-dependent vasodilators in coronary collateral vessels (250-350 microns) were compared with those obtained in normal native coronary arteries of similar size. Rings of small arteries and collateral vessels were suspended in baths, and tension was recorded. All rings were constricted with prostaglandin F2 alpha (3 microM) and subsequently exposed to cumulative concentrations of acetylcholine or bradykinin. In separate experiments, the procedure was repeated in the presence of 300 microM NG-monomethyl-L-arginine (L-NMMA) to inhibit endothelium-mediated vasodilation. Endothelium-dependent relaxation was further studied in the presence of indomethacin, and endothelium-independent relaxation was examined with sodium nitroprusside. Acetylcholine and bradykinin relaxed both normal native and collateral rings. In preconstricted small arteries and collateral vessels the concentration at 50% of maximal response of acetylcholine was 85.5 +/- 19.5 and 61.0 +/- 14.0 microns, and bradykinin was 11.9 +/- 7.4 and 10.7 +/- 2.1 microns, respectively. L-NMMA attenuated the response to acetylcholine and bradykinin in both groups. The results indicate that endothelium is present and functional in canine coronary collateral vessels. Both small coronary arteries and collateral vessels are equally responsive to endothelium-dependent vasodilators and inhibition of endothelium-dependent relaxing factor.

Acetylcholine↗
PubMed2007

Two distinct types of blood vessels in clear cell renal cell carcinoma have contrasting prognostic implications.

PURPOSE: Intratumoral microvascular density (MVD) has been controversial as an indicator of prognosis in clear cell renal cell carcinoma (CCRCC). Classification of the intratumoral blood vessels based on differential expressions of blood vessel markers has not been correlated with patient prognosis in CCRCC. In this study, we aimed to evaluate the association of different categories of blood vessels with the patients' outcomes. EXPERIMENTAL DESIGN: Seventy-eight CCRCC patients who underwent nephrectomy alone were enrolled. Paraffin-embedded CCRCC tissues, together with 16 nonmalignant kidney cortex tissues, were used in tissue microarray analyses and conventional section analyses. The characteristics of intratumoral blood vessels were identified by multiple blood vessel markers and pericyte markers. A computerized image analysis program was used to quantitatively calculate the vascular density. RESULTS: Two distinct types of microvessels were identified in CCRCC: undifferentiated (CD31(+)/CD34(-)) and differentiated (CD34(+)) vessels. A higher undifferentiated MVD significantly correlated with higher tumor grades and shorter patient survival. In contrast, a higher differentiated MVD significantly correlated with lower tumor grade and longer survival. Multivariate analyses showed that undifferentiated MVD was an independent prognostic factor for patient survival. An inverse correlation between undifferentiated MVD and differentiated MVD was also identified in CCRCC. CONCLUSIONS: This is the first report showing distinct types of vasculature in CCRCC correlated with contrasting prognoses. A refined classification of CCRCC based on vasculature is therefore important for evaluating prognosis, and it may also have therapeutic implications.

Aged↗
PubMed1995

Intramedullary blood vessels of the spinal cord express V1a vasopressin receptors: visualization by a biotinylated ligand.

The neurohypophysial peptide hormone [Arg8]vasopressin (AVP) has well documented pressor effects in the periphery. These are mediated by vasopressin receptors (VPRs) of the V1a subtype, expressed by vascular smooth muscle cells, which induce vascular contraction when activated. AVP also has effects on the vasculature of the brain, where it has been reported to induce both vasodilation and vasoconstriction. The responsiveness of blood vessels of the spinal cord, however, has received little attention. To determine the morphology and distribution of blood vessels within the spinal cord, vessels were vizualised using a mouse anti-rat smooth muscle alpha actin IgG as primary antibody and fluorescein isothiocyanate-conjugated anti-mouse IgG secondary antibodies. A complementary vizualisation strategy which detected the endogenous peroxidase activity of red blood cells within vessels was also utilised. The characteristics of the structures observed using both visualisation strategies were typical of blood vessels. VPRs were localized using recently characterized high affinity biotinylated analogue of AVP (PhAcAL(Btn)VP), which is selective for the V1a subtype of VPR. PhAcAL(Btn)VP:VPR complexes were subsequently visualized by avidin-Texas red. The pharmacological characteristics of these sites were established using selective analogues of vasopressin and oxytocin. This confirmed that V1a receptors were indeed being visualized. The structures observed following visualization of VPRs had the same morphology as the vasculature revealed by the anti smooth muscle alpha-actin antibody. It can therefore be concluded that the blood vessels of the spinal cord express VPRs and are potentially responsive to AVP. Furthermore, VPRs were detected on capillaries of the microvasculature. As these capillaries are devoid of smooth muscle, VPRs must be expressed by endothelial cells as well as by smooth muscle cells. This distribution of VPRs would enable AVP to regulate local blood flow. The source of the AVP could be the general circulation, or perhaps more likely, to be local release from vasopressinergic hypothalamic neurones which are known to innervate specific regions of the spinal cord.

Animals↗
PubMed1983

Blood vessels of the bovine chorioidea. A scanning electron microscopic study.

On corrosion casts of the bovine choroidal vessels, the vascular architecture was investigated by means of scanning and corresponding transmission electron microscopy. Complete filling of the vessels produced close-fitting replicas. Thus, based on different luminal structure, the arteries and veins in the lamina vasculosa could be easily distinguished. The branches of these vessels were followed to the choriocapillaris. The complete pattern of afferent and efferent vessels provided the opportunity to establish a scheme of choroidal microcirculation. The choriocapillaris in the bovine as a freely communicating network is subdivided into star-shaped areas of roughly hexagonal form. On the boundaries of these areas the afferent vessels (arterioles) - arranged at regular distances - join the choriocapillaris, whereas drainage of the choriocapillaris is effected by a single efferent vessel (venule) in the center of each area.

Animals↗
PubMedDate not supplied

Heterogeneous distribution of [3H]alpha,beta-methylene ATP binding sites in blood vessels.

A radioligand binding assay and autoradiographic localisation of P2X-purinoceptors were carried out in several different blood vessels from rat, guinea-pig and rabbit by using [3H]alpha,beta-methylene ATP ([3H]alpha,beta-MeATP) as the radioligand. The radioligand binding assay on rabbit ear artery showed that the binding process was saturable, and a high density of P2X-purinoceptors was observed. Autoradiographic localisation showed that the specific [3H]alpha,beta-MeATP binding sites were only associated with the smooth muscle of the blood vessels. Semi-quantitation of the autoradiographs revealed significant differences in the densities of P2X-purinoceptors amongst the vessels studied. Generally the medium- and small-sized arteries had higher densities of P2X-purinoceptor than the elastic and large muscular arteries. In some large muscular arteries, such as the rabbit carotid, renal, hepatic and mesenteric, the outer region of vessel had a higher density of receptors than the inner region. The veins in this study were sparsely labelled, except portal veins where the longitudinal and circular layers of muscles were found to have different densities of P2X-purinoceptors. The results from this study provide direct evidence for the existence of P2X-purinoceptors in blood vessels; furthermore, the distribution of the P2X-purinoceptors is consistent with known pharmacological responses elicited by ATP in these vessels.

Adenosine Triphosphate↗
PubMed1997

Visualization and flow of platelets and leukocytes in vivo in rat retinal and choroidal vessels.

PURPOSE: To directly visualize the flow of leukocytes in choroidal vessels and the flow of platelets in retinal vessels in a rat without incision by fluorescein leukocyte angiography (FLA) using a scanning laser ophthalmoscope (SLO). METHODS: Blood was withdrawn from a tail vein of a Sprague-Dawley rat with a tuberculin syringe traced with sodium heparin and mixed with sodium fluorescein. The fluorescent plasma layer was diluted with saline solution, centrifuged and then the overlying plasma discarded. The remaining cell suspension was diluted with saline to create the original hematocrit, then infused into the vein of the same rat while performing fluorescein angiography with an SLO. The angiographic image was recorded on a videotape using time-lapsed photography. RESULTS: Fluorescent platelets were detected and the flow within the retinal vessels traced over time. Fluorescent leukocytes in the choroidal vessels were also detected and the flow of a leukocyte was traced and its relative velocities were plotted against the time sequence. The relative size and fluorescence intensities of the platelets and leukocytes in the angiographic image corresponded well with the smear of the blood preparation. CONCLUSIONS: FLA using an SLO can be used to detect the flow of platelets in the retinal vessels and the flow of leukocytes in the choroidal vessels in the experimental rat eye model.

Animals↗
PubMed1997

Compensatory enlargement in coronary and femoral arteries is related to neither the extent of plaque-free vessel wall nor lesion eccentricity. A postmortem study.

Arteries may demonstrate compensatory enlargement in response to plaque accumulation. It has been proposed that enlargement is achieved by the expansion of the nondiseased (plaque-free) vessel wall. In this study, we assessed this hypothesis. Post mortem, 32 atherosclerotic coronary arteries (left anterior descending, n = 10; left circumflex, n = 11; and right coronary, n = 11) and 54 atherosclerotic femoral arteries were pressure fixed. Cross sections (coronary arteries, n = 537; femoral arteries, n = 1602) were obtained for analysis every 2.5 mm for the coronary arteries and every 5.0 mm for the femoral arteries. From these cross sections, we determined the degree of remodeling and an eccentricity index. Finally, we measured the extent of plaque-free vessel wall. The plaque-free vessel wall was defined as (1) no plaque present or (2) plaque thickness < 0.5 mm. A very weak, negative correlation was observed between the degree of remodeling and the extent of the plaque-free vessel wall (coronary arteries: no plaque r2 = .13, P < .01; < 0.5 mm plaque r2 = .15, P < .05; femoral arteries: no plaque r2 = .02, P < .01; < 0.5 mm plaque r2 = 0.04, P < .01). The degree of remodeling did not correlate with the eccentricity index (coronary arteries r2 = .002, P > .05 and femoral arteries r2 = .001, P > .05). Thus, compensatory enlarged segments did not reveal a larger circumference of plaque-free vessel wall compared with segments that failed to enlarge. This study provides no support for the hypothesis that nondiseased vessel-wall expansion is responsible for compensatory enlargement in atherosclerotic arteries.

Aged↗