bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comprehensive Geometric and Hemodynamic Analysis of Complete Microvascular Networks in Rat Gluteus Maximus Muscle: An Integrated Model Derived from Experimental Data
Authors: Farid Zahra , Lemaster Kent , Al Tarhuni Mohammed , Frisbee Jefferson C. , Jackson Dwayne N. , Goldman Daniel 
Published: November 2023

Skeletal muscle microcirculatory networks consist of sets of branching arterioles, which terminate at capillary beds, which subsequently give rise to a branching array of collecting venules. Generally, microcirculationists study each component of the microcirculation in isolation and provide hemodynamic analyses based on their discrete component of study. However, the interconnectivity of arterioles, capillaries, and venules suggests that measuring and predicting accurate hemodynamic outcomes requires collecting data from complete microvascular networks. Having studied blood flow in arteriolar networks both experimentally and computationally, we are now beginning to consider the roles of capillary resistance and venular network geometry. In particular, we are considering how capillaries and venules alter both overall microvascular network resistance and the flow pattern in terminal arterioles (TA's) supplying capillary beds. The venular networks used were reconstructed from intravital videomicroscopy (IVVM) data used previously to reconstruct complete arteriolar geometries, hence there was an exact correspondence between the arteriolar and venular networks. Preliminary work used an arteriolar network consisting of 1657 nodes, ~200 unbranched vessels, and 89 terminal arterioles, as well as an established steady‐state model of plasma and red blood cell (RBC) flow distribution. When resistive elements were added to the TA's to represent downstream capillary beds, overall flow resistance increased by 32% and the coefficient of variation (CVTA, standard deviation/mean) of TA RBC flow decreased by 9%. When the corresponding reconstructed venular network was added to form a complete arteriolar‐venular unit (2589 nodes), flow resistance increased by 69% and CVTA decreased by 10% compared to the arteriolar network alone. Not only was heterogeneity of TA RBC flow altered by adding capillaries and venules, but the ordering of TA's in terms of amount of RBC flow was also affected. Thus, these results imply the importance of considering complete microvascular networks when seeking to understand blood flow resistance and distribution. We believe entire networks will also be key in understanding regulation of local blood flow and its dysregulation in diseases such as type 2 diabetes and the metabolic syndrome.Support or Funding InformationNatural Sciences and Engineering Research Council of Canada (NSERC) grants R4218A03 (DNJ) and R4081A03 (DG)
Dependence of Erythrocyte Deformability on Mechanical Stress and Oxygenation
Authors: Yalcin Ozlem , Ugurel Elif , Saglam Gokay , Erten Ahmet , Aksu Ali Cenk 
Published: November 2023

Mechanical properties of erythrocytes are known to be affected by their oxygenation status. Several studies suggested that cytoskeletal rearrangements are carried out in an oxygen dependent manner. The structure of the cytoskeleton determines the mechanical properties of erythrocyte membrane. However, oxygen‐dependent mechanical characteristics of erythrocyte are poorly studied whether oxygenated state could alter erythrocyte deformability. In this study, we investigated shear stress induced improvements in erythrocyte deformability through their oxygenation status. Venous blood was collected from male, healthy volunteers (n=10) between 25–50 ages. An informed written consent was obtained from each subject participated in the study according to Declaration of Helsinki. The hematocrit of blood samples adjusted to 0.4 l/l with autologous plasma. Whole blood samples were diluted with polyvinylpyrrolidone (PVP) solution (Mechatronics, Hoorn, Netherlands) with a dilution ratio of 1/200. Blood samples were equilibrated with either ambient air or nitrogen gas for at least 10 minutes at room temperature. Erythrocyte deformability was measured by a laser‐assisted optical rotational cell analyzer (LORRCA MaxSis, Mechatronics, Netherlands) applying shear stresses (SS) ranging between 0.3 to 50 Pa. Then, a constant SS of 5, 10 and 20 Pa were applied continuously for 300 seconds and erythrocyte deformability was measured immediately afterwards. Maximal erythrocyte elongation index (EImax) and the SS required for one‐half of this maximal deformation (SS1/2) were calculated by using the linear Lineweaver‐Burke (LB) model. Deoxygenation of blood samples significantly decreased SS1/2 values both before and after SS applications (p < 0.001). EImax was significantly increased in deoxygenated blood before applying 5 Pa SS (p < 0.05). However, there were no significant differences after continuous SS in oxygenated and deoxygenated blood. Deoxygenation significantly decreased SS1/2/EImax values both before and after SS applications (p < 0.01). SS1/2/EImax values in both oxygenated and deoxygenated blood were significantly decreased after 5 and 10 Pa continuous SS applications although they were not significantly decreased after applying 20 Pa SS. Our study showed for the first time that erythrocyte deformability is improved in deoxygenated conditions in contrast to results presented in previous studies. This deformability improvement may control blood flow and consequently erythrocyte distribution within hypoxic tissues. Our study also demonstrated the relationship of oxygenation‐deoxygenation shifts and magnitude of shear stress on erythrocyte deformability.Support or Funding InformationThis study was supported by The Scientific and Technological Research Council of Turkey Grant 214S186.
Protease Inhibition to Optimize the Intestinal Mucosal Barrier to Digestive Enzymes during Hemorrhagic Shock
Authors: DeLano Frank A , Zhang Hongyu , Schmid‐Schönbein Geert W 
Published: November 2023

Our recent evidence indicates that escape of pancreatic digestive enzymes from the lumen into the wall of the intestine after breakdown of the mucosal barrier causes autodigestion and multiorgan failure in hemorrhagic shock. We hypothesize that initial opening of the mucosal barrier in the small intestine is mediated by matrix‐metallo proteinases (MMPs). We determined the level of pancreatic trypsin leakage into the intestine by immunohistochemistry of intestinal sections after hemorrhagic shock (35 mmHg mean arterial pressure for 2 hours). Two forms of protease inhibition were studied, single enteral inhibition with a MMP inhibitor (doxycycline, 5 mg/kg, i.v.) without and with enteral serine protease inhibition (127 mM tranexamic acid in 17 ml distributed uniformly over the small intestine of a 300 gm rat by local injections). As shown previously, the enteral inhibition of protease activity with tranexamic acid served to reduce the entry of pancreatic trypsin (detected with a mAb) across the mucosal barrier into the villi and mucosal tissue. Dual blockade with the MMP inhibitor (i.v.) and enteral serine protease inhibitor reduced the level of pancreatic trypsin in the intestinal wall to a level that was not significantly different from non‐shock controls. We detected a similar level of protection against entry of pancreatic amylase into the wall of the intestine by the combined enteral and i.v. protease inhibition. These results indicate that the irreversible opening of the mucosal barrier in hemorrhagic shock involves multiple proteases and a dual inhibition serves to minimize the leakage of digestive enzymes out of the lumen of the small intestine. The dual blockade of proteases may have clinical utility in shock patients.Support or Funding InformationSupported by GM 85072
Age‐related activation of ADAM17/TNF in adipose tissue leads to remote coronary microvascular dysfunction in obese patients
Authors: Dou Huijuan 
Published: November 2023

A disintegrin and metalloproteinase ADAM17 (TNF‐α converting enzyme) regulates soluble TNF levels. Here, we examined whether age‐related changes in adipose tissue (AT)‐expressed ADAM17 contributes to the development of coronary microvascular dysfunction (CMD) in obesity. Human coronary arterioles (CA,~100 μm) and mediastinal AT were examined in patients who underwent open‐heart surgery. CA and AT were also studied in young (6‐month) and aged (24‐month) mice fed a 12‐week high‐fat‐diet (HFD). We found that bradykinin‐induced dilation in isolated human CA significantly declines with age in obese, but not lean patients. Similarly, CA dilation was reduced in aged HFD mice when compared to young. The impaired CA dilation was accompanied by increased ADAM17 activity in AT and elevated serum TNF levels. Transplantation of AT from aged HFD to young mice increased plasma TNF levels and impaired CA dilation in the young recipient mice. In patients we found an age‐related increase in AT ADAM17 activity, which was attributed to expression of ADAM17 in the vascular endothelium of AT, but not adipocytes. Excess release of TNF from AT arteries in older patients was sufficient to impair vasodilator function in a bioassay in which the AT artery was serially connected to a CA. The present study demonstrates age‐related increases in vascular endothelial ADAM17 activity and soluble TNF release in the human and rodent AT, which may contribute to the development of CMD in older obese patients.Support or Funding InformationAHA16PRE27550006
Water extract of Imperatae Rhizom induces vascular relaxation via NO‐cGMP‐PKG signaling
Authors: Kim Hye Yoom , Ahn You Mee , Jin Xian Jun , Hong Mi Hyeon , Kim Hyun Ju , Yang Sun Nye , Lee Yun Jung , Lee Ho Sub , Kang Dae Gill 
Published: November 2023

The purpose of the present study was to investigate the underlying cellular mechanisms of the nitric oxide (NO)‐mediated property of the aqueous extract of Imperatae Rhizoma (AIR), pronounced anti‐inflammatory herb, in vascular endothelium. The roles of the NO signaling in the AIR‐induced effects were tested in human umbilical vein endothelial cells (HUVECs) and aortic ring. HUVEC treated with AIR produced higher amount of NO compared to control. AIR increased in the expression and phosphorylation levels of eNOS and Akt in HUVECs, which were attenuated by L‐NAME, a NOS inhibitor, and wortmannin, a PI3K inhibitor. mRNA or protein levels of guanosine triphosphate cyclohydrolase I (GTPCH) was upregulated in HUVECs treated with AIR, suggesting a role of eNOS coupling. In addition, AIR‐induced dose‐dependent relaxation of phenylephrine‐precontracted aorta was abolished by removal of functional endothelium. Pretreatment with L‐NAME, and ODQ inhibited the AIR‐induced vasorelaxation. Wortmannin and LY‐294002 an upstream signaling molecule of eNOS, attenuated the AIR‐induced vasorelaxation. Incubation of endothelium‐intact aortic rings with AIR increased the production of cGMP, however, which were attenuated by L‐NAME and ODQ. Two‐kidney‐one‐clip (2K1C) hypertensive rats were established to investigate the hypotensive effect of AIR in renovascular hypertension. 2K1C rats were treated with AIR at dose of 100 mg/kg/day orally for 3 weeks. AIR significantly lowered blood pressure. Interestingly, AIR ameliorated both endothelium‐dependent and independent vascular relaxation in the phenylephrine‐precontracted thoracic aorta. 2K1C‐induced hypertension model increased plasma renin activity, however, AIR attenuated those activities. Taken together, the present study suggests that AIR ameliorates vascular dysfunction via the regulation of renin‐angiotensin system and endothelium‐dependent activation of through the PI3K/Akt‐mediated NO‐cGMP‐PKG signaling.Support or Funding InformationThis work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (2008‐0062484).
Myogenic Oscillations during Alpha‐2 agonist Administration in Humans
Authors: Talke Pekka O , Diab Mohamed 
Published: November 2023

Dexmedetomidine is a highly selective alpha‐2 adrenergic agonist. While studying peripheral vasomotor effects of alpha‐2 agonists in humans, we observed unique, low frequency, large amplitude oscillations in the infrared photoplethysmograph (PPG) signal recorded from fingertips. We observed these oscillations in both awake and anesthetized subject but only during dexmedetomidine infusions. The purpose of this study was to determine if the origin of these vascular oscillations is central or if they are mediated locally in the fingers (i.e. myogenic oscillations). Infrared PPG data were recorded at 62.5 Hz from six surgical patients during nitrous‐narcotic general anesthesia. All patients received a continuous dexmedetomidine (1.4 ± 0.6 μg/kg/hr) infusion as part of the anesthetic. PPG data were recorded simultaneously from distal phalanxes of right and left index, middle and ring fingers throughout surgery. All sensors were optically isolated to prevent crosstalk. Data were analyzed offline. After visual inspection of the PPG data of each subject, a 5 min artifact free epoch during which PPG from all six sensors displayed low frequency oscillations was selected for analysis. For frequency analysis of these oscillations, PPG data were band pass filtered (0.01–0.5 Hz) followed by Chirp Z‐Transform spanning 0–0.25 Hz with 0.0005 Hz resolution. Perfusion index (PI) defined as PI=AC/DC*100% of the PPG was determined for each cardiac pulse. PI data were used to analyze the amplitude of the low frequency oscillations. Low frequency PPG oscillations were recorded from all six sensors of all six subjects during majority of dexmedetomidine infusion. The Chirp Z‐Transform analysis showed two distinct frequency peaks. One was at the frequency of the mechanical ventilator. The second frequency peak had a significantly larger amplitude. It's minimum and maximum frequencies during the study were 0.021 and 0.037 Hz respectively. In each subject these oscillations had similar but different frequencies in all six fingers, i.e. none of the oscillations were synchronous in any of the subjects. The average frequencies of these oscillations from each subject were 0.028 ± 0.005 Hz. The average amplitude (% modulation) of the oscillations was 19 ± 3 %. In conclusion, we observed low frequency, high amplitude PPG oscillations in all six fingers of every subject during dexmedetomidine infusion. Centrally mediated oscillations would have been expected to be bilaterally synchronous and in phase. Oscillations originating from large arteries (brachial, ulnar, radial) would have been expected to show some synchrony within the three sensors in each hand. Thus, the asynchrony of the oscillation suggests local origin (myogenic oscillations).Support or Funding InformationSupported by departmental funds
Amyloid Beta Peptides and Inflammatory Cytokines Depress Human Brain Vascular Smooth Muscle Tonic Contractility: Relevance to Alzheimer's Disease Impaired Cerebral Autoregulation
Authors: Yun J. Winny , Washington Caretia , Minagar Alireza , Alexander J. Steve 
Published: November 2023

Alzheimer's Disease (AD) is a neurodegenerative disorder that is characterized both by the presence of tau protein neurofibrillary tangles and amyloid beta (Aβ) containing extracellular plaques. AD is also a neuroinflammatory condition in which Th1 cytokines are elevated and appear to contribute to the intensification of AD severity. The cleavage of amyloid precursor protein (APP) can result in the release of several different forms of Aβ. Although Aβ toxicity to neurons has been described extensively, stressful effects of Aβ peptides on components of the neurovasculature such as endothelial and smooth muscle cells have been less well characterized despite AD exhibiting impaired vascular properties. In particular, cerebral autoregulation, the process by which blood flow is controlled despite alterations in feeding pressure, is disturbed in AD. The failure of autoregulation in AD may make the brain susceptible to cerebral microbleeds through a reduced capacity to limit blood flow when pressure is increased. Conversely, reduced vasodilation during low flow could also exacerbate tissue hypoxia. Currently, whether and how Aβ peptides and inflammatory cytokines depress brain smooth muscle cell tonic contraction is not known, but could reveal important targets in the preservation of autoregulation which is disturbed in AD. We used a collagen contractility assay to evaluate the influence of Aβ 25–35, Aβ 1–40 and Aβ 1–42 peptides on the contractility of human brain vascular smooth muscle (HBVSM) as an in vitro model of cerebral autoregulation. We found that Aβ 1–42 significantly depressed HBVSM contractility at 5 and 10μM while 5–20μM Aβ 1–40 did not affect contractility. Conversely Aβ 25–35 increased tonic contractility at 1, 5, 10 and 20μM. Interestingly, the inflammatory cytokines TNFα (20ng/ml), IL‐1β (20ng/ml) and IFNγ (1000U/ml) also depressed HBVSM contractility. These data suggest that both the inflammatory milieu seen in AD as well as the abundance of Aβ peptides may lead to autoregulatory failure and susceptibility to cerebral microbleeds which are an important characteristic of AD.Support or Funding InformationSupported by Malcolm Feist Cardiovascular Center Predoctoral Fellowship and Annette Funicello Research Foundation
KATP Channels Mediate CGRP‐Dependent Hyperpolarization of Mouse Pulmonary Artery Smooth Muscle and Endothelium
Authors: Norton Charles E , Segal Steven S 
Published: November 2023

Calcitonin gene related peptide (CGRP) hyperpolarizes membrane potential (Vm) of smooth muscle cells (SMCs) and endothelial cells (ECs) in pulmonary arteries (PAs) (FASEB J. 30, 945.18). In the systemic circulation, protein kinase A (PKA) can phosphorylate ATP‐sensitive potassium channels (KATP) as a mechanism of vasodilation to CGRP. We hypothesized that this signaling pathway is effective in the pulmonary circulation. Intact PAs were isolated (internal diameter, ~150 μm) from male C57BL/6J mice (age, 3 months), cannulated, pressurized to 16 cm H2O, and studied at 37°C. Alternatively, intact endothelial tubes were studied at 32°C following dissociation of SMCs. Vm was recorded continuously using intracellular microelectrodes. At rest, Vm was −43±2 mV for SMCs of intact PAs and −38±1 mV for ECs in endothelial tubes. Increasing concentrations (1 nM to 10 μM) of pinacidil (KATP activator) hyperpolarized SMCs by 38±2 mV (to −80±3 mV) and ECs by 36±3 mV (to −73±3 mV); respective EC50 values were 72 and 40 nM (n=4/group). Hyperpolarization of SMCs and ECs with 10 μM pinacidil was reversed by glibenclamide (KATP inhibitor) in a concentration‐dependent manner, with complete reversal at 1 μM. Increasing [CGRP] from 0.1 nM to 1 μM hyperpolarized SMCs of intact PAs by 17±3 mV (to −52±3 mV) and ECs by 20±4 mV (to −57±3 mV). With no effect on resting Vm, 1 μM glibenclamide attenuated (P<0.05) hyperpolarization of both SMCs (4±1 mV; n=5) and ECs (5±3 mV; n=4) to 1 μM CGRP. Inhibiting PKA with protein kinase inhibitor [PKI (14–22) amide, myristoylated; 10 μM] attenuated hyperpolarization to 1 μM CGRP in SMCs (5±1 mV; n=3) and in ECs (4±2 mV; n=4). In PAs preconstricted to ~50% of resting diameter with 5 μM uridine triphosphate, peak dilation to 1 μM CGRP was 87±4% (n=5) and 1 μM glibenclamide attenuated this effect to 14±5% (n=4). We conclude that CGRP‐dependent hyperpolarization of pulmonary arterial SMCs and ECs is mediated by KATP channel activation via PKA, leading to vasodilation. These findings provide mechanistic insight into therapies for vascular diseases associated with impaired pulmonary perfusion.Support or Funding InformationSupport: NIH R37HL041026
PIP2‐Regulation of Endothelial KIR2.1 Channels in Cerebral Arteries
Authors: Sancho Maria , Welsh Donals G. 
Published: November 2023

In the cerebral circulation, inwardly rectifying potassium (KIR) channels are robustly expressed in both endothelial and smooth muscle cells. This pattern of expression is unusual for vascular cells that are electrically coupled and it suggests that each pool is differentially regulated driving a distinct subset of physiological responses. In this context, this study characterized the electrical/molecular properties of KIR2.x channels in cerebral arteries and ascertained the importance of phosphatidylinositol‐bis‐phosphate (PIP2), a regulatory phospholipid, in modulating each channel pool. Endothelial and smooth muscle cells were freshly isolated from rat cerebral arteries; patch clamp electrophysiology and Q‐PCR were used to ascertain KIR activity and expression, respectively. Our electrophysiological results highlight that a Ba2+‐sensitive KIR current is present and stable in both cell types. Endothelial current density was ~8 fold greater than smooth muscle (−20 vs −2.5 pA/pF at −100mV) and Q‐PCR revealed that KIR2.x mRNA subunits were present in both cell types, albeit it at variable levels. Intriguingly, KIR channels in endothelial but not smooth muscle cells were PIP2 sensitive; neomycin impaired, and exogenous PIP2 elevated channel activity. In summary, our observations indicate that while endothelial and smooth muscle both expressed KIR channels, they are uniquely regulated by PIP2. A complete picture of the expression/regulation of KIR channels within the vascular wall will provide further advances in our understanding of their role in cerebral blood flow control in health and disease.Support or Funding InformationCanadian Institute of Health Research (CIHR)
The Role of NADPH Oxidase in Regulating Cerebral Vascular Myogenic Tone
Authors: Mazumdar Neil , Jalali Hanna , Hashad Ahmed Mohamed , Welsh Donald Gordon 
Published: November 2023

The myogenic response refers to the intrinsic ability of arteries to constrict to elevated pressure. The underlying mechanism has yet to be elucidated but recent evidence suggests that the angiotensin II type 1 receptor (AT1R) is a key mechanosensor, linking intravascular pressure to tone development. One intriguing aspect of this receptor is its ability to activate NADPH oxidase (Nox), an enzyme responsible for the production of reactive oxygen species. The goal of this study was to ascertain the role of Nox in myogenic tone development. Briefly, rat cerebral arteries were mounted in a myograph, pressurized to 60mmHg and diameter monitored prior to and following the application of apocynin (a general Nox inhibitor) or ML171 (a Nox1 specific inhibitor). Myogenic constriction progressively rose as vessels were pressurized from 20 to 60 mmHg. These pressure‐induced responses were attenuated by apocynin in a concentration dependent manner (37% vs 24% at 60 mmHg) irrespective of whether the endothelium was present or absent. ML171 (30μM) was equally effective at moderating the myogenic response (36% vs 24%); control experiments showed no discernible role for Nox2. Similar attenuating effects were observed in human cerebral arteries. These findings indicate Nox1 is expressed in rat cerebral arterial smooth muscle and may be a regulator of pressure‐induced responses. While the precise downstream mechanism has yet to be resolved, the L‐type Ca2+ channel is a likely target of Nox regulation. This work sheds new light on mechanosensation and how unique signaling proteins impact the ability of resistance arteries to respond to intravascular pressure.Support or Funding InformationThis work is supported by an operating grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) for DG Welsh. DG Welsh is a Rorabeck chair in molecular neuroscience and vascular biology at the University of Western Ontario. AM Hashad is a Vanier scholar (CIHR) and was supported by a salary studentship from Alberta Innovates Health solutions (AIHS).