Detecting hemodynamic changes in the foot vessels of diabetic patients by photoacoustic tomography

Limb perfusion monitoring is critical for diabetes mellitus (DM) patients as they are vulnerable to vascular complications due to prolonged hyperglycemia. However, current clinical approaches are ineffective in vascular imaging and in assessing vascular function in lower limbs. In this work, a concave ultrasound transducer array‐based photoacoustic tomography (PAT) system was used to image the foot dorsal section of a subject, and a total of seven DM patients and seven healthy volunteers were enrolled in this study. Hemodynamic changes in foot vessels during vascular occlusion as well as oxygen saturation (SO₂) in rest were analyzed for both groups. The results obtained showed that DM patients have a unique peripheral hemodynamic response to occlusion and a lower level SO₂, compared to that for healthy subjects. This suggests that PAT has the potential to detect vascular dysfunction in DM patients and to measure the effect of treatment.     

Assessing Endothelial Vasodilator Function with the Endo-PAT 2000

The endothelium is a delicate monolayer of cells that lines all blood vessels, and which comprises the systemic and lymphatic capillaries. By virtue of the panoply of paracrine factors that it secretes, the endothelium regulates the contractile and proliferative state of the underlying vascular smooth muscle, as well as the interaction of the vessel wall with circulating blood elements. Because of its central role in mediating vessel tone and growth, its position as gateway to circulating immune cells, and its local regulation of hemostasis and coagulation, the the properly functioning endothelium is the key to cardiovascular health. Conversely, the earliest disorder in most vascular diseases is endothelial dysfunction.In the arterial circulation, the healthy endothelium generally exerts a vasodilator influence on the vascular smooth muscle. There are a number of methods to assess endothelial vasodilator function. The Endo-PAT 2000 is a new device that is used to assess endothelial vasodilator function in a rapid and non-invasive fashion. Unlike the commonly used technique of duplex ultra-sonography to assess flow-mediated vasodilation, it is totally non-operator-dependent, and the equipment is an order of magnitude less expensive. The device records endothelium-mediated changes in the digital pulse waveform known as the PAT ( peripheral Arterial Tone) signal, measured with a pair of novel modified plethysmographic probes situated on the finger index of each hand. Endothelium-mediated changes in the PAT signal are elicited by creating a downstream hyperemic response. Hyperemia is induced by occluding blood flow through the brachial artery for 5 minutes using an inflatable cuff on one hand. The response to reactive hyperemia is calculated automatically by the system. A PAT ratio is created using the post and pre occlusion values. These values are normalized to measurements from the contra-lateral arm, which serves as control for non-endothelial dependent systemic effects. Most notably, this normalization controls for fluctuations in sympathetic nerve outflow that may induce changes in peripheral arterial tone that are superimposed on the hyperemic response.In this video we demonstrate how to use the Endo-PAT 2000 to perform a clinically relevant assessment of endothelial vasodilator function.Download video file.^{(49M, mov)}     

A simple approach for non‐invasive transcranial optical vascular imaging (nTOVI)

In vivo imaging of cerebral vasculature is highly vital for clinicians and medical researchers alike. For a number of years non‐invasive optical‐based imaging of brain vascular network by using standard fluorescence probes has been considered as impossible. In the current paper controverting this paradigm, we present a robust non‐invasive optical‐based imaging approach that allows visualize major cerebral vessels at the high temporal and spatial resolution. The developed technique is simple to use, utilizes standard fluorescent dyes, inexpensive micro‐imaging and computation procedures. The ability to clearly visualize middle cerebral artery and other major vessels of brain vascular network, as well as the measurements of dynamics of blood flow are presented. The developed imaging approach has a great potential in neuroimaging and can significantly expand the capabilities of preclinical functional studies of brain and notably contribute for analysis of cerebral blood circulation in disorder models.

An example of 1 × 1.5 cm color‐coded image of brain blood vessels of mouse obtained in vivo by transcranial optical vascular imaging (TOVI) approach through the intact cranium.     

Intravital Microscopy of the Mouse Brain Microcirculation using a Closed Cranial Window

This experimental model was designed to assess the mouse pial microcirculation during acute and chronic, physiological and pathophysiological hemodynamic, inflammatory and metabolic conditions, using in vivo fluorescence microscopy. A closed cranial window is placed over the left parieto-occipital cortex of the mice. Local microcirculation is recorded in real time through the window using epi and fluorescence illumination, and measurements of vessels diameters and red blood cell (RBC) velocities are performed. RBC velocity is measured using real-time cross-correlation and/or fluorescent-labeled erythrocytes. Leukocyte and platelet adherence to pial vessels and assessment of perfusion and vascular leakage are made with the help of fluorescence-labeled markers such as Albumin-FITC and anti-CD45-TxR antibodies. Microcirculation can be repeatedly video-recorded over several days. We used for the first time the close window brain intravital microscopy to study the pial microcirculation to follow dynamic changes during the course of Plasmodium berghei ANKA infection in mice and show that expression of CM is associated with microcirculatory dysfunctions characterized by vasoconstriction, profound decrease in blood flow and eventually vascular collapse.Download video file.^{(53M, mov)}     

Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brain

Imaging techniques based on optical contrast analysis can be used to visualize dynamic and functional properties of the nervous system via optical signals resulting from changes in blood volume, oxygen consumption and cellular swelling associated with brain physiology and pathology. Here we report in vivo noninvasive transdermal and transcranial imaging of the structure and function of rat brains by means of laser-induced photoacoustic tomography (PAT). The advantage of PAT over pure optical imaging is that it retains intrinsic optical contrast characteristics while taking advantage of the diffraction-limited high spatial resolution of ultrasound. We accurately mapped rat brain structures, with and without lesions, and functional cerebral hemodynamic changes in cortical blood vessels around the whisker-barrel cortex in response to whisker stimulation. We also imaged hyperoxia- and hypoxia-induced cerebral hemodynamic changes. This neuroimaging modality holds promise for applications in neurophysiology, neuropathology and neurotherapy.     

Automatic and label‐free identification of blood vessels in gliomas using the combination of multiphoton microscopy and image analysis

Currently, the targeted treatment of tumor based on the tumor microenvironment is newly developed. Blood vessels are the key parts in the tumor microenvironment, which is taken as a new visible target for tumor therapy. Multiphoton microscopy (MPM), based on the second harmonic generation and two‐photon excited fluorescence, is available to make the label‐free analysis on the blood vessels in human gliomas. MPM can reveal the vascular morphological characteristics in gliomas, including vascular malformation, intense vascular proliferation, perivascular collagen deposition, perivascular lymphocytes aggregation and microvascular proliferation. In addition, the image analysis algorithms were developed to automatically calculate the perivascular collagen content, vascular cavity area, lumen area, wall area and vessel number. Thus, the vascular morphology, the perivascular collagen deposition and intense vascular proliferation degree can be further quantitatively characterized. Compared with the pathological analysis, the combination of MPM and image analysis has potential advantages in making a quantitative and qualitative analyzing on vascular morphology in glioma microenvironment. As micro‐endoscope and two‐photon fiberscope are technologically improved, this combined method will be a useful imaging way to make the real‐time research on the targeting tumor microenvironment in gliomas.     

Simultaneous in vivo optical quantification of key metabolic and vascular endpoints reveals tumor metabolic diversity in murine breast tumor models

Therapeutically exploiting vascular and metabolic endpoints becomes critical to translational cancer studies because altered vascularity and deregulated metabolism are two important cancer hallmarks. The metabolic and vascular phenotypes of three sibling breast tumor lines with different metastatic potential are investigated in vivo with a newly developed quantitative spectroscopy system. All tumor lines have different metabolic and vascular characteristics compared to normal tissues, and there are strong positive correlations between metabolic (glucose uptake and mitochondrial membrane potential) and vascular (oxygen saturations and hemoglobin concentrations) parameters for metastatic (4T1) tumors but not for micrometastatic (4T07) and nonmetastatic (67NR) tumors. A longitudinal study shows that both vascular and metabolic endpoints of 4T1 tumors increased up to a specific tumor size threshold beyond which these parameters decreased. The synchronous changes between metabolic and vascular parameters, along with the strong positive correlations between these endpoints suggest that 4T1 tumors rely on strong oxidative phosphorylation in addition to glycolysis. This study illustrates the great potential of our optical technique to provide valuable dynamic information about the interplay between the metabolic and vascular status of tumors, with important implications for translational cancer investigations.      

Approach to diagnosis and pathological examination in bronchial Dieulafoy disease: a case series

Background

We previously observed that allergen-exposed mice exhibit remodeling of large bronchial-associated blood vessels. The aim of the study was to examine whether vascular remodeling occurs also in vessels where a spill-over effect of bronchial remodeling molecules is less likely.

Methods

We used an established mouse model of allergic airway inflammation, where an allergic airway inflammation is triggered by inhalations of OVA. Remodeling of bronchial un-associated vessels was determined histologically by staining for α-smooth muscle actin, procollagen I, Ki67 and von Willebrand-factor. Myofibroblasts were defined as and visualized by double staining for α-smooth muscle actin and procollagen I. For quantification the blood vessels were divided, based on length of basement membrane, into groups; small (≤250 μm) and mid-sized (250–500 μm).

Results

We discovered marked remodeling in solitary small and mid-sized blood vessels. Smooth muscle mass increased significantly as did the number of proliferating smooth muscle and endothelial cells. The changes were similar to those previously seen in large bronchial-associated vessels. Additionally, normally poorly muscularized blood vessels changed phenotype to a more muscularized type and the number of myofibroblasts around the small and mid-sized vessels increased following allergen challenge.

Conclusion

We demonstrate that allergic airway inflammation in mice is accompanied by remodeling of small and mid-sized pulmonary blood vessels some distance away (at least 150 μm) from the allergen-exposed bronchi. The present findings suggest the possibility that allergic airway inflammation may cause such vascular remodeling as previously associated with lung inflammatory conditions involving a risk for development of pulmonary hypertension.     

The Effect of Hemodynamic Remodeling on the Survival of Arterialized Venous Flaps

Objective

To evaluate the effect of hemodynamic remodeling on the survival status of the arterialized venous flaps (AVFs) and investigate the mechanism of this procedure.

Materials and Methods

Two 7 x 9 cm skin flaps in each rabbit (n=36) were designed symmetrically in the abdomen. The thoracoepigastric pedicle and one femoral artery were used as vascular sources. Four groups were included: Composite skin grafts group and arterial perfusion group were designed in one rabbit; AVF group and hemodynamic remodeling group by ligation of the thoracoepigastric vein in the middle were outlined in another rabbit. Flap viability, status of vascular perfusion and microvasculature, levels of epidermal metabolite and water content in each group were assessed.

Results

Highly congested veins and simple trunk veins were found using angiography in the AVF group; while a fairly uniform staining and plenty of small vessels were observed in the hemodynamic remodeling group. The metabolite levels of the remodeling group are comparable with those in the arterial perfusion group. There was no statistically significant difference in the percentage of flap survival between the arterial perfusion group and hemodynamic remodeling group; however, significant difference was seen between the AVF group and the hemodynamic remodeling group.

Conclusions

Under the integrated perfusion mode, the AVFs are in an over-perfusion and non-physiological hemodynamic state, resulting in unreliability and unpredictability in flap survival; under the separated perfusion mode produced by remodeling, a physiological-like circulation will be created and therefore, better flap survival can be expected.     

ARF-GTPase as a Molecular Switch for Polar Auxin Transport Mediated by Vesicle Trafficking in Root Development

Polar auxin transport (PAT), which is controlled precisely by both auxin efflux and influx facilitators and mediated by the cell trafficking system, modulates organogenesis, development and root gravitropism. ADP-ribosylation factor (ARF)-GTPase protein is catalyzed to switch to the GTP-bound type by a guanine nucleotide exchange factor (GEF) and promoted for hybridization to the GDP-bound type by a GTPase-activating protein (GAP). Previous studies showed that auxin efflux facilitators such as PIN1 are regulated by GNOM, an ARF-GEF, in Arabidopsis. In the November issue of The Plant Journal, we reported that the auxin influx facilitator AUX1 was regulated by ARF-GAP via the vesicle trafficking system.¹ In this addendum, we report that overexpression of OsAGAP leads to enhanced root gravitropism and propose a new model of PAT regulation: a loop mechanism between ARF-GAP and GEF mediated by vesicle trafficking to regulate PAT at influx and efflux facilitators, thus controlling root development in plants.Key Words: ADP-ribosylation factor (ARF), ARF-GAP, ARF-GEF, auxin, GNOM, polar transport of auxinPolar auxin transport (PAT) is a unique process in plants. It results in alteration of auxin level, which controls organogenesis and development and a series of physiological processes, such as vascular differentiation, apical dominance, and tropic growth.² Genetic and physiological studies identified that PAT depends on efflux facilitators such as PIN family proteins and influx facilitators such as AUX1 in Arabidopsis.Eight PIN family proteins, AtPIN1 to AtPIN8, exist in Arabidopsis. AtPIN1 is located at the basal side of the plasma membrane in vascular tissues but is weak in cortical tissues, which supports the hypothesis of chemical pervasion.³ AtPIN2 is localized at the apical side of epidermal cells and basally in cortical cells.^1,4 GNOM, an ARF GEF, modulates the localization of PIN1 and vesicle trafficking and affects root development.^5,6 The PIN auxin-efflux facilitator network controls root growth and patterning in Arabidopsis.⁴ As well, asymmetric localization of AUX1 occurs in the root cells of Arabidopsis plants,⁷ and overexpression of OsAGAP interferes with localization of AUX1.¹ Our data support that ARF-GAP mediates auxin influx and auxin-dependent root growth and patterning, which involves vesicle trafficking.¹ Here we show that OsAGAP overexpression leads to enhanced gravitropic response in transgenic rice plants. We propose a model whereby ARF GTPase is a molecular switch to control PAT and root growth and development.Overexpression of OsAGAP led to reduced growth in primary or adventitious roots of rice as compared with wild-type rice.¹ Gravitropism assay revealed transgenic rice overxpressing OsAGAP with a faster response to gravity than the wild type during 24-h treatment. However, 1-naphthyl acetic acid (NAA) treatment promoted the gravitropic response of the wild type, with no difference in response between the OsAGAP transgenic plants and the wild type plants (Fig. 1). The phenotype of enhanced gravitropic response in the transgenic plants was similar to that in the mutants atmdr1-100 and atmdr1-100/atpgp1-100 related to Arabidopsis ABC (ATP-binding cassette) transporter and defective in PAT.⁸ The physiological data, as well as data on localization of auxin transport facilitators, support ARF-GAP modulating PAT via regulating the location of the auxin influx facilitator AUX1.¹ So the alteration in gravitropic response in the OsAGAP transgenic plants was explained by a defect in PAT.Open in a separate windowFigure 1Gravitropism of OsAGAP overexpressing transgenic rice roots and response to 1-naphthyl acetic acid (NAA). (A) Gravitropism phenotype of wild type (WT) and OsAGAP overexpressing roots at 6 hr gravi-stimulation (top panel) and 0 hr as a treatment control (bottom panel). (B) Time course of gravitropic response in transgenic roots. (C and D) results correspond to those in (A and B), except for treatment with NAA (5 × 10⁻⁷ M).The polarity of auxin transport is controlled by the asymmetric distribution of auxin transport proteins, efflux facilitators and influx carriers. ARF GTPase is a key member in vesicle trafficking system and modulates cell polarity and PAT in plants. Thus, ARF-GDP or GTP bound with GEF or GAP determines the ARF function on auxin efflux facilitators (such as PIN1) or influx ones (such as AUX1).ARF1, targeting ROP2 and PIN2, affects epidermal cell polarity.⁹ GNOM is involved in the regulation of PIN1 asymmetric localization in cells and its related function in organogenesis and development.⁶ Although VAN3, an ARF-GAP in Arabidopsis, is located in a subpopulation of the trans-Golgi transport network (TGN), which is involved in leaf vascular network formation, it does not affect PAT.¹⁰ OsAGAP possesses an ARF GTPase-activating function in rice.¹¹ Specifically, our evidence supports that ARF-GAP bound with ARF-GTP modulates PAT and gravitropism via AUX1, mediated by vesicle trafficking, including the Golgi stack.¹Therefore, we propose a loop mechanism between ARF-GAP and GEF mediated by the vascular trafficking system in regulating PAT at influx and efflux facilitators, which controls root development and gravitropism in plants (Fig. 2). Here we emphasize that ARF-GEF catalyzes a conversion of ARF-bound GDP to GTP, which is necessary for the efficient delivery of the vesicle to the target membrane.¹² An opposite process of ARF-bound GDP to GTP is promoted by ARF-GTPase-activating protein via binding. A loop status of ARF-GTP and ARF-GDP bound with their appurtenances controls different auxin facilitators and regulates root development and gravitropism.Open in a separate windowFigure 2Model for ARF GTPase as a molecular switch for the polar auxin transport mediated by the vesicle traffic system.     

Jumping ability: A theoretical integrative approach

A theoretical integrative approach is proposed to understand the overall mechanical characteristics of lower extremities determining jumping ability. This approach considers that external force production during push-off is limited by mechanical constraints imposed by both movement dynamics and force generator properties, i.e. lower extremities characteristics. While the velocity of the body depends on the amount of external force produced over the push-off, the capabilities of force production decrease with increasing movement velocity, notably for force generators driven by muscular contraction, such as lower extremities of large animals during jumping from a resting position. Considering the circular interaction between these two mechanical constraints, and using simple mathematical and physical principles, the proposed approach leads to a mathematical expression of the maximal jump height an individual can reach as a function of only three integrative mechanical characteristics of his lower extremities: the maximal force they can produce (), the maximal velocity at which they can extend under muscles action () and the distance of force production determined by their usual extension range (h_PO). These three integrative variables positively influence maximal jump height. For instance in humans, a 10% variation in , or h_PO induces a change in jump height of about 10-15%, 6-11% and 4-8%, respectively. The proposed theoretical approach allowed to isolate the basic mechanical entities through which all physiological and morphological specificities influence jumping performance, and may be used to separate the very first macroscopic effects of these three mechanical characteristics on jumping performance variability.     

Functional changes in the neural retina occur in the absence of mitochondrial dysfunction in a rodent model of diabetic retinopathy

Diabetic retinopathy is a neurovascular diabetes complication resulting in vision loss. A wealth of literature reports retinal molecular changes indicative of neural deficits, inflammation, and vascular leakage with chronic diabetes, but the mechanistic causes of disease initiation and progression are unknown. Microvascular mitochondrial DNA (mtDNA) damage leading to mitochondrial dysfunction has been proposed to drive vascular dysfunction in retinopathy. However, growing evidence suggests that neural retina dysfunction precedes and may cause vascular damage. Therefore, we tested the hypothesis that neural mtDNA damage and mitochondrial dysfunction are an early initiating factor of neural diabetic retinopathy development in a rat streptozotocin‐induced, Type I diabetes model. Mitochondrial function (oxygen consumption rates) was quantified in retinal synaptic terminals from diabetic and non‐diabetic rats with paired retinal structural and function assessment (optical coherence tomography and electroretinography, respectively). Mitochondrial genome damage was assessed by identifying mutations and deletions across the mtDNA genome by high depth sequencing and absolute mtDNA copy number counting through digital PCR. Mitochondrial protein expression was assessed by targeted mass spectrometry. Retinal functional deficits and neural anatomical changes were present after 3 months of diabetes and prevented/normalized by insulin treatment. No marked dysfunction of mitochondrial activity, maladaptive changes in mitochondrial protein expression, alterations in mtDNA copy number, or increase in mtDNA damage was observed in conjunction with retinal functional and anatomical changes. These results demonstrate that neural retinal dysfunction with diabetes begins prior to mtDNA damage and dysfunction, and therefore retinal neurodegeneration initiation with diabetes occurs through other, non‐mitochondrial DNA damage, mechanisms.

     

Implications of Pericardial,Visceral and Subcutaneous Adipose Tissue on Vascular Inflammation Measured Using 18FDG-PET/CT

Objective

Pericardial adipose tissue (PAT) is associated with adverse cardiometabolic risk factors and cardiovascular disease (CVD). However, the relative implications of PAT, abdominal visceral and subcutaneous adipose tissue on vascular inflammation have not been explored.

Method and Results

We compared the association of PAT, abdominal visceral fat area (VFA), and subcutaneous fat area (SFA) with vascular inflammation, represented as the target-to-background ratio (TBR), the blood-normalized standardized uptake value measured using ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography (¹⁸FDG-PET) in 93 men and women without diabetes or CVD. Age- and sex-adjusted correlation analysis showed that PAT, VFA, and SFA were positively associated with most cardiometabolic risk factors, including systolic blood pressure, LDL-cholesterol, triglycerides, glucose, insulin resistance and high sensitive C-reactive proteins (hsCRP), whereas they were negatively associated with HDL-cholesterol. In particular, the maximum TBR (maxTBR) values were positively correlated with PAT and VFA (r = 0.48 and r = 0.45, respectively; both P <0.001), whereas SFA showed a relatively weak positive relationship with maxTBR level (r = 0.31, P = 0.003).

Conclusion

This study demonstrated that both PAT and VFA are significantly and similarly associated with vascular inflammation and various cardiometabolic risk profiles.     

A study by scanning (SEM) and transmission (TEM) electron microscopy of the glomerular capillaries in developing rat kidney

Summary Kidneys of 2 to 10 day-old rats of Wistar and Sprague-Dawley strains were fixed with glutaraldehyde by retrograde vascular perfusion and then prepared for observation in TEM and SEM. In addition methacrylate casts of differentiating glomerular capillaries were examined by SEM. Although the glomerular vascular pattern differs from one glomerulus to another, its differentiation proceeds according to the following general plan. First the glomerular capillary splits longitudinally, finally to form 3 to 5 lobules consisting of a capillary network, sustained centrally by the mesangium.In the present study the differentiation of glomerular capillaries is described in five successive arbitrarily selected stages. At Stage I a capillary loop penetrates between the lower limb and the middle segment of the S-shaped body, the rudimentary nephron. At Stage II the capillary undergoes a first subdivision, establishing the primitive lobulation of the glomerulus. At Stage III the vascular and urinary poles differentiate. At Stage IV the glomerulus assumes the aspect of a spherical body, and the capillaries in each lobule undergo subdivision. In Stage V the glomerular vascular pattern approaches its adult appearance, although the maturation processes continue for an extended period of time. Hence in the 10 day-old rat the best-differentiated glomeruli are half the size of adult glomeruli, and their capillary loops are proportionally less well-developed. The capillaries of adjacent lobules may communicate with each other, but a direct vascular shunt between the afferent and efferent vessels cannot be demonstrated.Presented in part at the 60ème Congrés de l'Association des Anatomistes in Nice (27–30 May 1976) and the 73. Versammlung der Anatomischen Gesellschaft in Innsbruck (12–15 September 1978)The author thanks Miss Morena Ghisletta for excellent technical assistance     

Identification of an apical Cl-/HCO-3 exchanger in rat kidney proximal tubule

SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney proximal tubule and mediates exchange in in vitro expression systems. We hypothesized that PAT1 along with a exchange is present in apical membranes of rat kidney proximal tubules. Northern hybridizations indicated the exclusive expression of SLC26A6 (PAT1 or CFEX) in rat kidney cortex, and immunocytochemical staining localized SLC26A6 on the apical membrane of proximal tubules, with complete prevention of the labeling with the preadsorbed serum. To examine the functional presence of apical exchanger, proximal tubules were isolated, microperfused, loaded with the pH-sensitive dye BCPCF-AM, and examined by digital ratiometric imaging. The pH of the perfusate and bath was kept at 7.4. Buffering capacity was measured, and transport rates were calculated as equivalent base flux. The results showed that in the presence of basolateral DIDS (to inhibit cotransporter 1) and apical EIPA (to inhibit Na⁺/H⁺ exchanger 3), the magnitude of cell acidification in response to addition of luminal Cl^– was 5.0-fold higher in the presence than in the absence of . The Cl^–-dependent base transport was inhibited by 61% in the presence of 0.5 mM luminal DIDS. The presence of physiological concentrations of oxalate in the lumen (200 µM) did not affect the exchange activity. These results are consistent with the presence of SLC26A6 (PAT1) and exchanger activity in the apical membrane of rat kidney proximal tubule. We propose that SLC26A6 is likely responsible for the apical (and Cl^–/OH^–) exchanger activities in kidney proximal tubule. putative anion transporter 1; chloride/formate exchanger; SLC26A6     

Effects of different preservation schemes on isolated rat artery

Allogeneic blood vessels are regarded as one of the best natural substitutes for diseased blood vessels due to their good vascular compliance and histocompatibility. Since the supply and demand of allograft blood vessels do not always match in time and space, a good preservation scheme for isolated blood vessels is essential. The abdominal aortas of 110 male Sprague–Dawley (SD) rats were randomly divided into three groups, including cold storage group (4°C) (CSG), frozen storage group (FSG) and ambient storage group (25 ± 2°C) (ASG). Seven time points of preservation for 1, 3, 5, 7, 14, 30 and 90 days were set for detection. The changes in vascular physiological function were evaluated by MTT test and vasoconstriction ability detection, and the changes in vascular wall structure were evaluated by the tension tolerance test and pathological staining. The vascular function of CSG was better than FSG within first the 7 days, but the result was opposite since the 14th day. The vascular wall structure, collagen and elastic fibres of vessels, in CSG, showed oedema within 30 days, and continuous disintegration and rupture at 90 days. The vessel wall structure of FSG remained intact within 90 days. The tensile strength of the vessels in CSG was better than that in FSG within 5 days, and there was no statistical difference between the two groups between the 7th and 30th day, and then, the FSG was higher than CSG on the 90th day. Both cold storage and frozen storage could be applied as safe and effective preservation schemes for isolated rat artery within first 30 days. Cold storage is recommended when the storage time is <14 days, and then, frozen storage is better.     

Sex and limb-specific ischemic reperfusion and vascular reactivity

With little known regarding sex and limb heterogeneity, we investigated vascular reactivity and ischemic reperfusion (IR) in the upper and lower extremities of 15 healthy men (26 +/- 2 yr) and women (23 +/- 1 yr). Doppler ultrasound was used to evaluate IR and flow-mediated dilation (FMD) after suprasystolic cuff occlusion in both the arm [brachial artery (BA)] and the leg [popliteal artery (PA)]. Cumulative IR [area under the curve (AUC)], normalized for muscle mass, revealed no sex-related differences in either limb (forearm: men 38 +/- 3 and women 44 +/- 4 ml/100 g; lower leg: men 12 +/- 2 and women 14 +/- 2 ml/100 g), while both groups revealed a greater IR per unit of arm muscle mass (AUC) compared with the lower leg (P < 0.05). The BA and PA were smaller in women (BA 0.31 +/- 0.1, PA 0.47 +/- 0.1 cm) than in men (BA 0.41 +/- 0.1, PA 0.6 +/- 0.2 cm). Absolute FMD/shear rate revealed attenuated vascular function in the PA of the women [women 3.3 +/- 0.6, men 5.0 +/- 0.8 (all x10(-6)) cm/s(-1).s] and no sex difference in the BA [women 1.2 +/- 0.2, men 1.6 +/- 0.1 (all x10(-6)) cm/s(-1).s]. In both sexes the PA demonstrated greater vascular reactivity than the BA. Thus vascular reactivity in healthy young people is greater in the legs, regardless of sex, and women have vascular function similar to men in the upper extremities but appear to have poorer vascular function normalized for shear rate in the lower extremities.     

1D simulation of blood flow characteristics in the circle of Willis using THINkS

One-dimensional (1D) simulation of the complete vascular network, so called THINkS (Total Human Intravascular Network Simulation) is developed to investigate changes of blood flow characteristics caused by the variation of CoW. THINkS contains 158 major veins, 85 major arteries, and 77 venous and 43 arterial junctions. THINkS is validated with available in vivo blood flow waveform data. The overall trends of flow rates in variations of the CoW, such as the missing anterior cerebral artery (missing-A1) or missing posterior cerebral artery (missing-P1), are confirmed by in vivo experimental data. It is demonstrated that the CoW has the ability to shunt blood flow to different areas in the brain. Flow rates in efferent arteries remain unaffected under the variation of CoW, while the flow rates in afferent vessels can be subject to substantial changes. The redistribution of blood flow can cause particular vessels to undergo extra flow rate and hemodynamic stresses.     

Conformational isomerism and hydrogen-bonded motifs of anion assisted supramolecular self-assemblies using Cu/Co salts and pyridine-4-acetamide

Six novel metal-organic complex assemblies constructed from a conformation-flexible ligand - pyridine-4-acetamide (PAT) and inorganic Cu^II and Co^II salts have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Crystal structure analysis reveals five types of architectures by variation of metal salts. In {[Cu(PAT)₂Cl₂]}_n (1) and {[Co(PAT)₂Cl₂]}_n (3), PAT ligands bridge metal centers to form one-dimensional chains. The chains are extended to three dimensions with the aid of two types of hydrogen bonded motifs () and (12)). {[Cu(PAT)₂(NO₃)](NO₃)(THF)}_n (5) which exhibits two-dimensional coordinating layers forms open channels filled with solvent molecules. In [Cu(PAT)₂Cl₂] (2), [Co(PAT)₂Cl₂] (4) and [Co(PAT)₄(H₂O)₂](NO₃)₂(THF)₂ (6), PAT is observed as a monofunctional ligand. Complex 2 forms one-dimensional hydrogen bonded chains. Crystal structure of complex 4 has a two-dimensional infinite hydrogen-bonded network with and motifs formed by complementary amide-amide hydrogen bonds. [Co(PAT)₄(H₂O)₂](NO₃)₂(THF)₂ (6) crystallizes in centrosymmetric I4₁/a space group. Complex 6 forms chiral channels which are filled with twisted solvent helices and anion helices. Within each channel the solvent helix and the anion helix have the same handedness; and adjacent channels have opposite handedness. Complexes 1, 2 and complexes 3, 4 illustrate examples of conformational supramolecular isomerism in {[Cu(PAT)₂Cl₂]}_∞ and {[Co(PAT)₂Cl₂]}_∞, respectively. In these complexes, changes of PAT conformations and coordination geometry of metal center induced the structural versatility.     

Dual‐wavelength hybrid optoacoustic‐ultrasound biomicroscopy for functional imaging of large‐scale cerebral vascular networks

A critical link exists between pathological changes of cerebral vasculature and diseases affecting brain function. Microscopic techniques have played an indispensable role in the study of neurovascular anatomy and functions. Yet, investigations are often hindered by suboptimal trade‐offs between the spatiotemporal resolution, field‐of‐view (FOV) and type of contrast offered by the existing optical microscopy techniques. We present a hybrid dual‐wavelength optoacoustic (OA) biomicroscope capable of rapid transcranial visualization of large‐scale cerebral vascular networks. The system offers 3‐dimensional views of the morphology and oxygenation status of the cerebral vasculature with single capillary resolution and a FOV exceeding 6 × 8 mm², thus covering the entire cortical vasculature in mice. The large‐scale OA imaging capacity is complemented by simultaneously acquired pulse‐echo ultrasound (US) biomicroscopy scans of the mouse skull. The new approach holds great potential to provide better insights into cerebrovascular function and facilitate efficient studies into neurological and vascular abnormalities of the brain.