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Distinguishing arteries from veins in the cerebral cortex is critical for studying hemodynamics under pathophysiological conditions, which plays an important role in the diagnosis and treatment of various vessel‐related diseases. However, due to the complexity of the cerebral vascular network, it is challenging to identify arteries and veins in vivo. Here, we demonstrate an artery–vein separation method that employs a combination of multiple scanning modes of two‐photon microscopy and a custom‐designed stereoscopic fixation device for mice. In this process, we propose a novel method for determining the line scanning direction, which allows us to determine the blood flow directions. The vasculature branches have been identified using an optimized z‐stack scanning mode, followed by the separation of blood vessel types according to the directions of blood flow and branching patterns. Using this strategy, the penetrating arterioles and penetrating venules in awake mice could be accurately identified and the type of cerebral thrombus has been also successfully isolated without any empirical knowledge or algorithms. Our research presents a new, more accurate, and efficient method for cortical artery–vein separation in awake mice, providing a useful strategy for the application of two‐photon microscopy in the study of cerebrovascular pathophysiology. [ABSTRACT FROM AUTHOR]

The deformability of blood vessels in one‐dimensional blood flow models is typically described through a pressure‐area relation, known as the tube law. The most used tube laws take into account the elastic and viscous components of the tension of the vessel wall. Accurately parametrizing the tube laws is vital for replicating pressure and flow wave propagation phenomena. Here, we present a novel mathematical‐property‐preserving approach for the estimation of the parameters of the elastic and viscoelastic tube laws. Our goal was to estimate the parameters by using ovine and human in vitro data, while constraining them to meet prescribed mathematical properties. Results show that both elastic and viscoelastic tube laws accurately describe experimental pressure‐area data concerning both quantitative and qualitative aspects. Additionally, the viscoelastic tube law can provide a qualitative explanation for the observed hysteresis cycles. The two models were evaluated using two approaches: (i) allowing all parameters to freely vary within their respective ranges and (ii) fixing some of the parameters. The former approach was found to be the most suitable for reproducing pressure‐area curves. [ABSTRACT FROM AUTHOR]

Key points: Intrauterine growth restriction (IUGR) increases offspring risk of chronic diseases later in life, including cardiovascular dysfunction.Our prior studies suggest biventricular cardiac dysfunction and vascular impairment in baboons who were IUGR at birth because of moderate maternal nutrient reduction.The current study reveals changes in artery sizes, distensibility, and blood flow pattern in young adult IUGR baboons, which may contribute to cardiac stress.The pattern of abnormality observed suggests that vascular redistribution seen with IUGR in fetal life may continue into adulthood. Maternal nutrient reduction induces intrauterine growth restriction (IUGR), increasing risks of chronic diseases later in life, including cardiovascular dysfunction. Using ultrasound, we determined regional blood flow, blood vessel sizes, and distensibility in IUGR baboons (8 males, 8 females, 8.8 years, similar to 35 human years) and controls (12 males, 12 females, 9.5 years). The measured blood vessels were larger in size in the males compared to females before but not after normalization to body surface area. Smaller IUGR normalized blood vessel sizes were observed in the femoral and external iliac arteries but not the brachial or common carotid arteries and not correlated significantly with birth weight. Mild decrease in distensibility in the IUGR group was seen in the iliac but not the carotid arteries without between‐sex differences. In IUGR baboons there was increased carotid arterial blood flow velocity during late systole and diastole. Overall, our findings support the conclusion that region specific vascular and haemodynamic changes occur with IUGR, which may contribute to the occurrence of later life cardiac dysfunction. The pattern of alteration observed suggests vascular redistribution efforts in response to challenges in the perinatal period may persist into adulthood. Further studies are needed to determine the life course progression of these changes. Key points: Intrauterine growth restriction (IUGR) increases offspring risk of chronic diseases later in life, including cardiovascular dysfunction.Our prior studies suggest biventricular cardiac dysfunction and vascular impairment in baboons who were IUGR at birth because of moderate maternal nutrient reduction.The current study reveals changes in artery sizes, distensibility, and blood flow pattern in young adult IUGR baboons, which may contribute to cardiac stress.The pattern of abnormality observed suggests that vascular redistribution seen with IUGR in fetal life may continue into adulthood. [ABSTRACT FROM AUTHOR]

Purpose: We investigated whether retinal branch arteries in healthy subjects, and non-treated and treated primary open-angle glaucoma (POAG) patients show irregular local patterns during dynamic reaction to acute increases of different magnitudes in intraocular pressure (IOP). Methods: Nine POAG patients and nine age-matched normal volunteers were examined with the retinal vessel analyser (RVA) using a suprasystolic IOP increase (Study 1). Fourteen POAG patients and 13 age-matched controls were examined using a moderate IOP increase for 100 seconds (Study 2). Longitudinal arterial profiles were obtained for the chosen time intervals. The high-frequency waviness (HFW) of these profiles was analysed quantitatively. Results: No significant changes in HFW were found in controls in different phases of the arterial reaction. Significant increases in HFW from baseline to dilation (Study 1, P < 0.03) and from dilation to constriction (Study 2, P < 0.05) were found in POAG patients. High-frequency waviness was higher in POAG patients than in controls during dilation ( P < 0.05) in both studies. Conclusions: Our results indicate a local vessel wall difference in glaucoma patients compared with age-matched controls. Increasing HFW might worsen hydraulic resistance of the vessel segment to blood flow. Significant increase of arterial microirregularities in the POAG retina during vascular dilation might be an indication for vascular endothelial alterations in glaucoma, leading to impaired perfusion in response to IOP increase. [ABSTRACT FROM AUTHOR]

Changes of mean blood flow velocities (MBFV) in the posterior cerebral arteries (PCA) recorded during visual stimulation in a group of 51 healthy, right-handed volunteers are presented. There were 27 (52.9%) males and 24 (47.1%) females, aged 20-59 years (mean age: 36.98 years). Measurements were performed with a hand-held 2 MHz transcranial Doppler (TCD) probe through the temporal window, with the subjects' eyes open and closed, and while they were looking at constant and at flashing white light, In half of the subjects, first the right PCA was insonated and then the left PCA, while in the other half the reverse procedure was used. Statistical analysis was done using Wilcoxon's matched-pair signed-rank test. Mean MBFV value in the left PCA was 41.2±8.6 cm/s (mean ± SD) with eyes open, 27.8±8.5 cm/s with eyes closed, 42.3±9.1 cm/s while looking at constant white light, and 43.0±9.6 cm/s while looking at flashing white light. Mean MBFV value in the right PCA was 41.7±8.9 cm/s with eyes open, 28.2±9.1 cm/s with eyes closed, 42.4±8.8 cm/s while looking at constant white light, and 43.4±9.2 while looking at flashing white light. Value differences for the left PCA, between eyes open and closed and between looking at constant white light and looking at flashing white light, were statistically significant (p<0.001, z= -6.2146, and p<0.001, z= -3.4836, respectively). For the right PCA, a value difference between eyes open and closed, and between looking at constant and flashing white light was statistically significant (p<0.001, z= -6.2146 and p<0.001, z= -3.6928), but there was no significant difference between eyes open and constant white light (p=O.03, z= -2.1693). The results showed that simple visual stimulation had an effect on blood fiow velocities in PCA and that it could be measured with TCD. [ABSTRACT FROM AUTHOR]

Presents abstracts of several studies concerning microvascular remodeling, presented at the Experimental Biology/International Union of Physiological Sciences 2005 Congress held in San Diego, California. "Remodeling of Biaxial Incremental Moduli of RCA in Flow-Overload," by Marisa Garcia and Ghassan Kasab; "Flow Inhibits Inward Remodeling in Cultured Porcine Coronary Resistance Arteries," by Adrian Pistea, Erik N. T. P. Bakker, Spaan A. E. Jos and Ed VanBavel; "NG2 Protoglycan Expression is Dynamically Upregulated by Perivascular Cells Along Venules During Microvascular Remodeling," by Walter Lee Murfee, Shayn M. Pierce and Thomas C. Skalak.

Limb blood flow is widely used as an indicator of the human vascular properties. There are only few non-invasive methods for its measurement such as venous occlusion plethysmography. However, several authors have questioned its validity. The problems appear to be related to the process of venous occlusion. We developed two methods to measure forearm blood flow by plethysmography without venous occlusion in combination with Doppler velocimetry (without imaging). Method 1: the gradient of a tangent drawn on the latter part of the down stroke of the plethysmographic volume pulse is an approximation of venous blood flow in the absence of diastolic blood flow. At equilibrium, it equals the average arterial flow in a cardiac cycle. The Doppler velocity waveform recorded simultaneously allows improvement of this approximation when there is diastolic blood flow. Method 2: the volume pulse detected by a plethysmograph calibrated in absolute volume is used to calibrate the velocity waveform recorded simultaneously to produce an approximation of arterial volumetric flow waveform. Bland-Altman analysis shows both methods have good correlation and agreement with venous occlusion plethysmography at rest. Method 1: mean difference (blood flow measured by venous occlusion minus calculated flow) = 0·10 ml/pulse (±0·18), limits of agreement = −0·41 and 0·61 ml/pulse. Method 2: mean difference = −0·041 ml/pulse (±0·15), limits of agreement = −0·45 and 0·37 ml/pulse. During hyperaemia, venous occlusion plethysmography grossly underestimated relative to the new methods. The new methods are not dependent on venous occlusion and produce consistent results with or without hyperaemia. [ABSTRACT FROM AUTHOR]

1 Choroidal blood vessels, located between the sclera and retina, constitute the principle source of blood flow to ocular structures. The choroid is innervated by vasoconstrictor sympathetic and vasodilator parasympathetic nerves. 2 We have shown previously that sympathetic denervation for 6 weeks leads to significant increases in choroidal thickness, percentage of choroid occupied by vascular lumina, and numbers of choroidal venules, large arterioles and outer retinal capillaries. Sympathetic deafferemation produces similar increases, indicating that loss of sympathetic nerve activity is responsible for increased vascularity after sympathectomy. Thus, sympathetic neurotransmission normally may be important in suppressing vascular proliferation in the adult rodent eye. 3 The aim of the present study was to determine whether sympathetic nerves act by way of adrenergic receptors to maintain normal choroidal vascular integrity. 4 The α-adrenoceptor antagonist, phentolamine (I mg kg[sup-1] day[sup1]), the β-receptor antagonist, propranolol (1 mg kg[sup-1] day[sup-1]), or saline vehicle was infused for 3 weeks using subcutaneously implanted osmotic mintpumps. 5 In phentolamine treated rats, no significant changes were noted relative to saline infused controls. However, propranolol treatment resulted in increases in choroidal thickness, vascular luminal area, and numbers of large choroidal venules and both small and large arterioles, approximating the remodelling seen after chronic sympathectomy. 6 We conclude that sympathetic nerves play a role in maintaining normal choroidal vascular architecture through actions mediated primarily by β-adrenoceptors. [ABSTRACT FROM AUTHOR]

The circulation of the gills has been studied in the perch, trout and eel combining the conventional histological methods and casting techniques. The existence of two blood pathways in each gill arch was confirmed. 1—An arterio-arterial pathway assuming the respiratory function. It includes the afferent branchial artery and in each primary lamella the afferent primary artery, the secondary lamellae capillaries and the primary and branchial efferent arteries. 2—An arterio-venous pathway arising from both the branchial artery, in the gill arch, and the primary arteries in each primary lamella. This pathway includes the central venous sinus of the primary lamella, several small veins and is finally connected with the branchial veins. 3—The lack of connections between afferent primary arteries and cvs in the trout and the perch makes impossible a direct blood flow from the afferent to the efferent artery (shunt). In the eel connections between cvs and both afferent and efferent arteries do not mean that a shunt is operating according to the pressure gradient. [ABSTRACT FROM AUTHOR]

The article explores the implications of the findings of two independent studies published in "The Journal of Physiology" which identified regional differences in cerebral perfusion during acute changes in arterial blood changes. It relates the impact of the findings on the understanding of cerebrovascular control in humans. It explains how the findings affect the way of interpreting data such as changes in blood flow and/or velocity between arteries.

A tree‐like hierarchical branching structure is present in many biological systems, such as the kidney, lung, mammary gland, and blood vessels. Most of these organs form through branching morphogenesis, where outward growth results in smaller and smaller branches. However, the blood vasculature is unique in that it exists as two trees (arterial and venous) connected at their tips. Obtaining this organization might therefore require unique developmental mechanisms. As reviewed here, recent data indicate that arterial trees often form in reverse order. Accordingly, initial arterial endothelial cell differentiation occurs outside of arterial vessels. These pre‐artery cells then build trees by following a migratory path from smaller into larger arteries, a process guided by the forces imparted by blood flow. Thus, in comparison to other branched organs, arteries can obtain their structure through inward growth and coalescence. Here, new information on the underlying mechanisms is discussed, and how defects can lead to pathologies, such as hypoplastic arteries and arteriovenous malformations. Many studies have shown that blood vessel sprouting resembles branching morphogenesis, where smaller branches sprout from larger stems. New work indicates that arteries can also form through inward growth of pre‐specified arterial cells and remodeling. Therefore, the mechanism building hierarchically patterned blood vessel trees might differ between arteries and veins. [ABSTRACT FROM AUTHOR]

The authors discuss research published within the issue concerning stiffness and blood flow problems in downstream and upstream arteries. Topics covered include the effects of the stiffness of large artery on cerebral and skeletal muscle vasculature, greater pulsability of the middle cerebral artery (MCA) compared to the gastrocnemius feed artery and the dependence of MCA on nitrous oxide to elicit dilatation.

The vasomotor function of arterial vessels is impaired in HHcy. Thus we hypothesized that HHcy alters the mediation of flow dependent responses of venules. Thus changes in diameter of pressurized venules (diameter: 250±30/am at 10 mmHg) isolated from normal and HHcy (∼5 weeks methionine diet) rats to increases in perfusate flow were measured. Increases in intraluminal flow elicited dilations of control vessels (max.: 13,4±1%), whereas in HHcy venules flow elicited constrictions (max.: -19±6 %). The NO donor SNP elicited similar magnitude of dilations in both groups. In control venules, the PGH2/TXA2receptor antagonist SQ 29,548 augmented flow-induced dilations, whereas in HHcy venules reversed flow-induced constrictions to dilation. In the presence of SQ 29,548 the NO synthase inhibitor L-NAME significantly decreased flow-induced dilations in control venules, whereas in HHcy the "restored" dilations were not significantly affected. Presence of SOD and CAT did not significantly change flow-induced dilations in control venules, whereas abolished flow-induced constrictions in HHcy venules. Correspondingly, as compared to controls, there was an increased ethidium bromide fluorescence detected in HHcy venules, indicating substantial superoxide production. In conclusion, elevated levels of plasma homocysteine -- in part -- due to an increased production of reactive oxygen species, could reduce the role of NO and increase the role of PGH2/TXA2 in mediation of flow-induced responses of skeletal muscle venules. These changes may impair the regulation of blood flow and favor increased thrombus formation in venules. [ABSTRACT FROM AUTHOR]

We studied the role of MMP-2 and -9 in arterial remodeling in response to blood flow changes in vivo. Normal flow (NF), low flow (LF), and high flow (ilF) were surgically produced in the mesenteric arterial bed of C57 BI-6 (WT), MMP9 or MMP2 null mice (-/-) and maintained for 3 (D3) or 14 days (D14). In situ external arterial diameter (ED) were recorded at the beginning (D0) and at the end (D3 or D14). Ex vivo measurements were performed on histological sections using Image J 1.34s and compared with one-way ANOVA followed by post-hoc analysis or Student's t test in JMP software. Pro- and active MMP-2 and MMP-9 were quantified using gelatin zymography and Quantity One 4.5.2 (Bio-Rad). At D0, mean ED was similar for WT, MMP9-/- and MMP2-/-. In WT, compared to NF, the HF induced a significant mean ED increase, i.e. expansive remodeling and LF induced a mean ED decrease, i.e. constrictive remodeling by D14. In MMP9-/-, LF induced significant inward remodeling at D3 (p<0.032), but mean ED were similar in NF, LF, or HF at D14, indicating remodeling impairment in both LF and HF. In MMP2-/-the constrictive remodeling due to LF was statistically significant at both times (p<0.021) at D3; (p<0.031) at D14, but the outward remodeling in HF did not reach significance. Both MMPs contribute to flow-induced arterial remodeling. MMP-2 contributes to expansive remodeling, but lack of MMP-2 did not impair constrictive remodeling, while MMP-9 seems essential for both expansive and constrictive remodeling. [ABSTRACT FROM AUTHOR]

The article presents a case where ultrasound was used to demonstrate the flow of blood through the ulnar and radial arteries in a patient who was admitted to the intensive care unit. The patient underwent a major abdominal surgery and after the operation, her left hand was found to be slightly cold compared to her right hand. Further examination revealed no sensory or motor deficit. The ultrasound demonstrated the flow through the vessels and prevented further intervention.

With respect to distribution and flow, the Vasa pulmonalia resemble those of the normal grown domestic pig to a great extent. The present article investigates whether, like the human lung (Hayek, 1970), the arrangement of the blood vessels has a function over and above that of directing blood; that is to say, a mechanical function. The arteries through which the blood streams act as flexible supporting structures, and the veins as elastic holding structures, for the quadrupede animal also. [ABSTRACT FROM AUTHOR]