bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the subcellular location and molecular mobility of human cytosolic sulfotransferase SULT1C1 in living human embryonic kidney 293 cells
Authors: Sheng Jonathan
Published: June 2021

Cytosolic sulfotransferases have been immunochemically localized in different subcellular compartments of human cells in several previous studies. In the current work, the subcellular location of human cytosolic sulfotransferase SULT1C1 was studied in living human cells. A cDNA encoding SULT1C1 was amplified from human hepatic tissues by RT‐PCR and fused with a green fluorescent protein (GFP) coding sequence in a plasmid‐based expression vector. The resulting GFP‐SULT1C1 construct was then transfected into human embryonic kidney 293 (HEK293) cells. By using confocal laser scanning microscopy methods, the fluorescent signal of GFP‐SULT1C1 was localized in the cytoplasm of living HEK293 cells. Furthermore, the molecular mobility of the expressed GFP‐SULT1C1 molecules was also assessed using fluorescence recovery after photobleaching (FRAP) microscopy and the results indicated that a portion of the expressed GFP‐SULT1C1 molecules were immobile. The immobility of these recombinant SULT1C1 molecules suggests that they might either be attached to certain endogenous molecules or form multimeric structures in living HEK293 cells.
Delayed treatment with actinonin, a meprin A inhibitor, protects the renal microcirculation and renal function during sepsis in mice
Authors: Wang Zhen , Herzog Christian , Kaushal Gur P , Mayeux Philip R
Published: June 2021

Meprin A is a matrix metalloproteinase highly expressed in the kidney and thought to play an important role in several causes of acute kidney injury (AKI). To address the role of meprin A in the early and late phases of renal microcirculatory dysfunction associated with sepsis, we treated mice at 30 min prior to or 7 h post cecal ligation and puncture (CLP) with the meprin A inhibitor actinonin (20 mg/kg). Intravital videomicroscopy was utilized to image renal cortical peritubular capillary perfusion and reactive nitrogen species generation (RNS) using dihydrorhodamine 123 (DHR) at 18 h post CLP. Actinonin prevented the fall in renal capillary perfusion and the increase in RNS at 18 h even when administered at 7 h post CLP without affecting systemic NO generation. Importantly, even late administration of actinonin preserved renal function (as measured by BUN). These data suggest that meprin A may play an important role in the microcirculatory failure and oxidative stress associated with sepsis‐induced AKI. Moreover, actinonin should be evaluated further as a possible therapeutic agent because an agent that is protective even after the onset of sepsis would have a great impact on patient outcome. Supported by NIH DK075991.
Aerobic Exercise Enhances The Muscle Protein Anabolic Effect Of A Mixed Meal In Older Adults
Authors: Timmerman Kyle L. , Dhanani Shaheen , Glynn Erin L. , Fry Christopher S. , Drummond Micah J. , Rasmussen Blake B. , Volpi Elena
Published: June 2021

Muscle protein metabolism is resistant to the anabolic effects of mixed feeding and insulin in older adults. Aerobic exercise improves insulin sensitivity of muscle proteins in elders. We tested if an acute bout of aerobic exercise can also overcome the anabolic resistance to a mixed meal in healthy, sedentary older subjects (age: 70±3 yr).

Using a randomized cross‐over design, we measured blood flow and muscle protein kinetics (13C6‐phenylalanine) at baseline and during mixed meal ingestion (20g of essential amino acids + 35g of glucose) on 2 occasions: after rest (CTRL) or after a bout of aerobic exercise (EX). We report preliminary data from 4 subjects. Blood flow (CTRL, basal: 2.09±0.49, meal: 2.52±0.88; EX, basal: 2.47±0.46, meal: 4.06±1.06 ml/min/100 ml leg) and mixed muscle protein synthesis (CTRL, basal: 0.054±0.008, meal: 0.053±0.006; EX, basal: 0.057±0.005, meal: 0.079±0.007 %/h) increased (P<0.05) from baseline during mixed meal ingestion only in EX but not in CTRL. Phenylalanine delivery to the leg increased significantly (P<0.05) in both conditions (CTRL, basal: 137±29, meal: 422±137; EX, basal: 142±17, meal: 714±123, nmol/min/100 ml leg), but the change was larger (P<0.05) in EX.

In conclusion, these preliminary data suggest that a prior bout of aerobic exercise restores the anabolic effects of a mixed meal in older adults. This effect may be partially due to increased blood flow and amino acid delivery.

Supported by NIA R01 AG018311 and P30 AG024832
EFFECT OF TOP‐LOADING A HEMOGLOBIN‐BASED OXYGEN CARRIER (HBOC) ON MEAN ARTERIAL PRESSURE (MAP), ARTERIOLAR DIAMETER AND TISSUE OXYGENATION
Authors: Song Bjorn Kyungsuck , Nugent William N , Golub Alexsander S , Moon‐Massat Paula F , Pittman Roland N
Published: June 2021

This study compared the effects on oxygen (O2) transport of two fluids: a HBOC (HBOC‐201, Biopure Corp., Cambridge, MA) and 5.9% human serum albumin (HSA), a non‐O2 carrying iso‐oncotic solution (volume control). Intravital microscopic measurements were made on the spinotrapezius muscle of anesthetized, male Sprague‐Dawley rats. Interstitial (ISF) PO2 was measured using phosphorescence quenching microscopy at baseline and following top‐loading infusions of HBOC‐201 or 5.9% HSA. The purpose of the present study was to identify a dose‐response relationship for HBOC‐201, in which increasing concentrations of HBOC‐201 were infused to reach target plasma concentrations of 1, 10, 100 and 300 μM. Increasing [HBOC] resulted in changes from baseline in MAP (100±1 to 145±5 mmHg), arteriolar diameter (97±2 to 85±5 μm) and ISF PO2 (72±5 to 63±4 mmHg), while HSA infusion did not elicit significant changes in these variables. Although the total blood hemoglobin concentration increased from 13.3 to 14.3 g/dL due to the addition of HBOC‐201, the decreasing ISF PO2 is believed to be caused by a reduction in blood flow, and therefore O2 delivery, subsequent to arteriolar vasoconstriction.
Low oxygen affinity hemoglobin solution increases oxygenation of partially ischemic tissues during acute anemia
Authors: Cabrales Pedro
Published: June 2021

Maintenance of post‐surgical tissue oxygenation depends on the ability of the specific tissue to recruit perfusion and oxygen (O2) supply. However, when native O2 carrying capacity is lacking, fluids to improve O2 carrying capacity based in hemoglobin (Hb) could prevent partially ischemic tissue hypoxia by increasing O2 release from the remaining red blood cells. Responses to facilitated O2 transport after exchange transfusion with polymerized bovine Hb (PBH) were studied in a chronic partially ischemic tissue model, induced by large feeding arterioles ligation during hamster window chamber model implantation. PBH affects in microvascular perfusion and tissue oxygenation were studied after exchange transfusion of 40% of animal's blood volume. Experimental groups were defined by the concentration of PBH used, namely: PBH at 13g/dl [PBH13], PBH at 4 g/dl in albumin solution to matching colloidal osmotic pressure (COP) [PBH4], and no PBH only albumin solution at matching COP [PBH0]. Restitution of O2 carrying capacity with PBH13 increased blood pressure and produced vasoconstriction compared to PBH4 and PBH0. On the other hand, PBH4 maintained blood pressure without significant vasoconstriction, increased tissue pO2, arteriolar O2 supply and extraction to the partially ischemic tissue compared to PBH0 and PBH13. Results suggest the existence of an optimal concentration of low O2 affinity acellular Hb to increase oxygenation of partially ischemic tissue during anemic conditions. This work was supported by BRP R24‐HL64395 and P01 HL071064.
Modulation of NO bioavailability by temporal variability of cell‐free layer width in the arterioles
Authors: Ong Peng Kai , Jain Swati , Johnson Paul , Kim Sangho
Published: June 2021

The formation of a cell (erythrocyte)‐free layer near the vessel wall during blood flow is capable of attenuating NO consumption by the red blood cells and thus improves the preservation of NO in the smooth muscle for eliciting vasodilatory responses. This study utilized a transient NO transport mathematical model to predict how temporal variability exhibited by the layer width and its relevant transient physiological responses could modulate NO preservation by this diffusion barrier at high pseudoshear rates (291.5 ± 13.5 s−1). Data on cell‐free layer width was experimentally acquired from arterioles (48.4 ± 2.3 μm) of the rat cremaster muscle. We found that a time‐varying diffusion barrier could lead to a slight decrease (2% – 6%) in NO bioavailability and this effect was independent of transient changes in NO scavenging rate in the blood lumen. Conversely, transient changes in wall shear stress and accompanying NO release rate played a dominant role in reversing this decline such that an augmentation in NO bioavailability of between 3% – 15% was found. However this increase was not sufficient to induce any significant change in vascular tone. This study highlighted the importance of accounting for transient wall shear stress effect on NO release rate as mediated by the layer width temporal variability when assessing the physiological implication of the layer on NO bioavailability in arterioles.
A Hematocrit‐Dependent Red Blood Cell Exclusion Zone (“No Fly Zone”) is Present at the Wall of Arterioles
Authors: Yalcin Ozlem , Jivani Manoj , Intaglietta Marcos , Johnson Paul
Published: June 2021

A red blood cell (RBC) exclusion zone at the vessel wall has been reported in capillaries and in arterioles during red cell flow. In the current study we found a hematocrit‐dependent RBC exclusion zone between the vascular wall and flowing RBCs in 30–40 μm arterioles. The width of this “no fly zone” decreased from 2.0 μm at a systemic hematocrit (Hctsys) of 20% to a value of 1.0 to 1.1μm over a wide Hctsys range of 30 to 60%. However, the zone width fell to 0.47μm at 65% and to zero at 70, and 75% Hctsys). Also 16 and 22% of the RBCs nearest the wall were found at the wall at Hctsys levels of 70 and 75% but none at lower hematocrits. An exclusion layer of about 1 μm consisting of an endothelial surface layer (ESL) and a lubrication layer has been reported in capillaries. An ESL of about 1 μm thickness has been suggested in arterioles of dimensions similar to ours. Our findings at 30% Hctsys and above could be due to an ESL with structural properties that effectively resist the centrifugal forces acting on the most peripheral RBCs in the 30–60% Hctsys range but are overcome by these forces at higher Hctsys. In the range 20–30% Hctsys axial migration tendencies rather than the ESL may provide an outer limit to RBC location relative to the vascular wall.
GFP‐actin dynamics during histamine‐induced endothelial barrier dysfunction
Authors: Breslin Jerome W , Maietta Dominique A , Kurtz Kristine M , Doggett Travis M , Souza Flavia M , Worthylake Rebecca A
Published: June 2021

We tested the hypothesis that histamine‐induced endothelial barrier dysfunction is associated with disruption of normal actin dynamics at the endothelial cell periphery. Human umbilical vein endothelial cells (HUVEC) were transfected with GFP‐actin (500 ng vector/5 × 105 cells). Transendothelial resistance (TER) served as an index of barrier function. Time‐lapse image sets were acquired before and after the addition of 10 μM histamine. GFP‐actin expression slightly enhanced histamine‐induced endothelial barrier dysfunction, but did not affect the time course. GFP‐actin was found in cortical fibers moving centrally at a mean rate of 63 nm/min, and in membrane ruffles protruding outward at a mean rate of 1462 nm/min. New cortical fibers formed at a frequency of 0.59/min., and membrane ruffling occurred at a frequency of 0.61 events/min. GFP‐actin also localized in small lamellipodia on the cell periphery. Histamine treatment caused a sudden, coordinated formation of lamellipodia around the cell perimeter, followed by inactivity during the time frame of histamine‐induced barrier dysfunction. Shortly after, lamellepodia and membrane ruffling were restored. The data show that histamine‐indcued barrier dysfunction is associated with a loss of normal cortical actin dynamics in endothelial cells. Supported by NIH RR‐018766 and a grant from the American Heart Association.
The α2 isoform of the Na, K‐pump is involved in synchronization of smooth muscle cells in the arterial wall.
Authors: Aalkjær Christian , Møller‐Nielsen Nina , Matchkov Vladimir
Published: June 2021

We have hypothesized that the ouabain‐sensitive Na, K‐pump can regulate smooth muscle gap junction function. To test this hypothesis and determine the relevant isoform we investigated the effect of downregulation of the α2 isoform of Na, K‐pump.

We transfected cultured smooth muscle cells (SMCs) and rat small mesenteric arteries with siRNA against the α2 isoform of Na, K‐pump and with eGFP siRNA, as a control. Paired SMCs were used as a model for electrical coupling by measuring membrane capacitance and synchronized SMC activity was assessed by measuring isometric force.

Pairs of SMCs had a capacitance of 90.4±9.4pF, n=7 twice that of single cells. SMCs were uncoupled when the Na, K‐pump was inhibited by 10 μM ouabain (46.1±7.2pF). β‐glycyrrhetinic acid (βGA) had no additive effect (41.9±4.9pF). Downregulation of the α2 Na, K‐pump significantly reduced the capacitance of cell pairs (33.4±4.1pF) and made them insensitive to ouabain (34.1±4.2pF). βGA uncoupled residual coupling (28.3±3.0pF). Arteries downregulated for the Na, K‐pump had significant reduced amplitude of noradrenalin‐induced vasomotion. This is consistent with the suggested role of gap junction for synchronization of SMCs in the vascular wall.

We demonstrate the importance of α2 isofom of the Na, K‐pump for intercellular coupling in the vascular wall and its involvement in the regulation of vasomotion.
Key role of Ca2+‐activated K+ channels of small and intermediate conductance in the NO signaling of resistance vessels
Authors: Gaete Pablo S , Figueroa Xavier F
Published: June 2021

Ca2+‐activated K+ channels (KCa) and nitric oxide (NO) play a central role in the control of vasomotor tone in resistance arteries. To evaluate the contribution of KCa channels to NO‐mediated dilation, we analyzed the vasomotor responses and NO production (chemiluminiscence) induced by the endothelium‐dependent vasodilator, acetylcholine (ACh), or the Ca2+ ionophore, ionomycin, in isolated arterial mesenteric bed of rat. ACh (0.01–10μM) elicited a concentration‐dependent vasodilatation. In phenylephrine‐contracted mesenteries, NO synthase (NOS) inhibition with Nω‐nitro‐L‐arginine (L‐NA) reduced the response to ACh. Blockade of KCa channels with tetraethylammonium (TEA) or inward rectifier K+ channels with Ba2+ blunted the response to ACh. L‐NA inhibited the ACh‐induced relaxation in presence of Ba2+, but not TEA. In addition, TEA blocked the NO production induced by ACh. In KCl‐contracted vessels, the relaxation‐elicited by ACh or 1μM ionomycin was abolished by L‐NA and inhibited by TEA or simultaneous blockade of KCa channels of small (SKCa) and intermediate (IKCa) conductance with apamin and TRAM‐34, respectively. Apamin and TRAM‐34 also abolished the NO production activated by 100nM ACh. These results indicate that functional SKCa and IKCa channels are required for Ca2+‐mediated eNOS activation. Membrane hyperpolarization is not involved in the regulation of NO production by these channels.

VRAID 15/2009
Pressor and Baroreflex Effects of Ouabain in (mRen2)27 and mRen2.Lewis Rats
Authors: Logan Exazevia , Johnson Amber , Diz Debra , Aileru Azeez
Published: June 2021

Previous studies show that endogenous ouabain, a cardiac digitalis‐like compound, may play a role in development of elevated pressure. The current study investigated the effect of acute intravenous (i.v.) ouabain on mean arterial blood pressure (MAP) in (mRen2)27 and mRen2.Lewis rats models of hypertension. Non‐invasive blood pressure recordings verified elevated systolic pressure in conscious rats. Under urethane/chloralose anesthesia, MAP was normalized in (mRen2)27 and mRen2.Lewis rats (101 ± 6 mmHg and 84.6 ± 6 mmHg). I.V. ouabain (40 μg/kg/bwt) increased MAP to 25% above baseline in (mRen2)27 and 45% in mRen2.Lewis rats, returning to baseline within 30 minutes. The effect of ouabain on baroreceptor reflex sensitivity (BRS) was measured before and after ouabain treatment. At baseline, BRS was similar in (mRen2)27 and mRen2.Lewis rats (0.49 ± 0.13 vs 0.37 ± 0.08 msec/mm Hg). BRS was decreased following ouabain injections in mRen2.Lewis animals (0.005 ± 0.01 msec/mm Hg; p < 0.05 vs baseline) but was unaffected in (mRen2)27 (0.37 ± 0.07 msec/mm Hg). Thus, an exacerbated pressor response was associated with suppression of the BRS in mRen2.Lewis rats. MD000232, MD002303, HL51952
Attenuated endothelin‐1 (ET‐1) vasoconstrictor responses in cardiometabolic syndrome are attributed to increased ET‐B receptors
Authors: Wallace Deborah , Walsh Katie A , Imig John D
Published: June 2021

Vascular dysfunction is an important complication linking cardiometabolic syndrome with cardiovascular diseases. The objective of the present study was to discover the effect of ET‐1 on mesenteric resistance arteries from a cardiometabolic syndrome disease model and assess the relative contribution of ET‐A and ET‐B receptors. Spontaneously hypertensive obese (SHROB) rats displayed increased blood pressure (154±3 vs. 123±2 mmHg) and body weight (417±7 vs. 270±5 g) compared to WKY rats. Mesenteric arteries were isolated and diameter responses to the vasoconstrictor peptide ET‐1 (0.01–10nM) were determined. Baseline mesenteric resistance artery diameters did not differ between WKY, SHR and SHROB. Mesenteric resistance artery responses to 10 nM ET‐1 were greatly attenuated in SHROB (26±9%) compared to SHR (44±13%) and WKY (69±2%). Addition of either ET‐A antagonist BQ123, or ET‐B agonist sarafotoxin 6c resulted in vasodilation in SHROB (105±2% and 104±2%, respectively) suggesting an enhanced ET‐B receptor mediated response in SHROB. Furthermore, ET‐B receptor protein expression was elevated 32 fold in SHROB compared to WKY, respectively. These results indicate that upregulation of the ET‐B receptor contributes to the greatly diminished ET‐1 vasoconstriction in cardiometabolic syndrome.
Myostatin gene knockout improves endothelium dependent dilation in coronary arteries of obese mice
Authors: Ali Mohammed Irfan , Mintz James D , Hamrick Mark , Fulton David J , Stepp David W
Published: June 2021

Obesity impairs and exercise improves coronary function but mechanistic links remain unclear. Exercising increases muscle mass and decreases myostatin (Ms), a muscle growth inhibitor. Deletion of myostatin improves muscle mass and metabolism which may in turn prevent obesity‐related metabolic and vascular dysfunction. Effects of Ms deletion (KO) on coronary function in obesity are unknown. This study tested the hypothesis that Ms KO improves coronary function in obese mice. Dual KO animals were generated on a C57 Blk/6 background that lacked functional leptin and Ms genes (Lepr−/−/Ms−/−, KK). These mice were compared to lean heterozygous mice (Lepr−/+/Ms−/+, HH), and obese mice (Lepr−/−/Ms−/+, KH). Organ weights and A1c% were assessed. Septal coronary arteries were analyzed in vitro (i.d. < 75 μm). Heart weight was similar in all mice. A1c% was improved in KK vs. KH (6.7±.5 v 9.1±.8%, p<0.05) despite similar visceral adiposity. Endothelium‐dependent dilation to acetylcholine was impaired in KH compared to HH (39±4 v 57±2%, p<0.01) while Ms KO improved dysfunction in KK (63±2 v 39±4%, p<0.01). Vasoconstriction to serotonin was similar in all groups (HH: 37±6; KH: 34±7; KK: 43±2%). These data demonstrate that myostatin deletion prevents metabolic and vascular deficits in obesity. We conclude that inhibition of myostatin may provide a therapeutic target for the complications of obesity (NIH HL76533 and 92447).
A Stochastic Model of Flow Bifurcation Predicts Altered Spatial Flow Distributions in Obese Zucker Rats
Authors: Wu Fan , Frisbee Jefferson C. , Beard Daniel A.
Published: June 2021

A stochastic model of flow bifurcation is introduced to analyze intravascular tracer washout data measured from normal Zucker rats and obese Zucker rats, a peripheral vascular disease (PVD) model. The flow bifurcation model is based on a previous model [Qian and Bassingthwaighte, J. Theor. Biol. 205(2):261–268, 2000], which is extended to account for transport over the whole vascular network instead of a single generation. Model analysis helps explain the observed differences in washout kinetics and increased variability in blood flow in obese Zucker rats compared to control. The altered hemodynamics observed in the obese model is predicted to have significant effects on microvascular transport of substances, including oxygen. Treatment with an adrenoreceptor blocker, phentolamine, largely restores normal flow distribution and associated washout kinetics, but fails to improve fatigue resistance of skeletal muscle in obese Zucker rats. Thus, although flow distribution is apparently improved by this treatment, a mismatch between oxygen supply and demand persists. Further investigation requires mechanistically linking flow distribution, flow auto‐regulation, transport, and metabolism.
The ZDSD, a New Rat Model of Metabolic Syndrome: Evidence of Cardiovascular Disease
Authors: Packer C Subah , Meulen Leeanna M , Boice Alexa M , Coy Kathy , Peterson Richard G
Published: June 2021

A new rat model, the ZDSD, has an intact leptin system while having typical metabolic syndrome biomarkers. The goal was to determine if ZDSD also suffer from cardiovascular disease typical of metabolic syndrome. ZDSD and control SD blood pressures (BP) were monitored for several weeks. Right ventricular to left ventricular plus septum weight ratios, RV/(LV+S), were measured. None of the 6 ZDSD had high systemic BP. Two ZDSD developed systemic hypotension that correlated with severe diabetes and weight loss. ZDSD RV/(LV+S) tended to be higher than SD RV/(LV+S) indicative of RV hypertrophy and pulmonary hypertension. Results suggest that the severely diabetic ZDSD were in end stage congestive heart failure (CHF) resulting from a particularly malignant form of metabolic syndrome. A younger cohort of less severely diabetic ZDSD need to be studied in order to know if systemic hypertension plays a role in development of CHF in this model of metabolic syndrome.

Supported by PreClinOmics. L Meulen and A Boice were 2009 Indy Project SEED Scholars supported by American Chemical Society (ACS), Lilly, DowAgroSciences, IUPUI Indiana Clinical and Translational Sciences Institute (CTSI)
Role of cAMP and cGMP in arachidonic acid and PGE2 ‐induced cerebral vasodilation in newborn pigs
Authors: Kanu Alie Joseph , Leffler Charles W.
Published: June 2021

Arachidonic acid (AA) metabolites of cyclooxygenase (COX) are important regulators of newborn cerebral circulation. PGE2 stimulates cAMP in cultured vascular smooth muscle cells. PGE2 increases cAMP and cGMP. Therefore, AA and PGE2, generated in cerebral vessels may produce dilation by increasing cGMP and cAMP. In this study we address the hypothesis that cAMP and/or cGMP mediate dilation produced by AA and PGE2. Experiments used anesthetized newborn pigs with closed cranial windows. In piglets with PGE2, indomethacin (5mg/k g iv) was administered to inhibit COX. Pial arteriolar responses to AA (10−7 M, 10−5 M), PGE2 (10−7 M, 10−5 M) or vehicle with guanylyl cyclase inhibitor ODQ (2.5 x10−5 M) or adenylyl cyclase inhibitor SQ22536 (10−6 M), or their vehicles were determined. ODQ (2.5 x10−5 M) blocked AA‐ and PGE2‐induced increases in cerebral vasodilation in newborn pigs. SQ 22536 blocked dilation produced by the adenylyl cyclase activator forskolin (10−7M) and also inhibited AA‐ and PGE2‐induced cerebral vasodilation. Both cGMP and cAMP appear to contribute to the dilator effect of AA and PGE2. Since both ODQ and SQ22536 blocked dilations to AA and PGE2, cAMP and cGMP may act in a sequential manner. Research supported by NIH/NHLBI.
Folic Acid Attenuates Vascular Dysfunction in Type‐2 Diabetic Mice
Authors: Lawal Rasheed A , Rodriguez‐Alvarez Walter E , Tyagi Suresh C , Joshua Irving G
Published: June 2021

Diabetes induced hyperhomocysteinemia contributes to endothelial‐myocyte uncoupling and heart failure by activation of matrix metalloproteinase‐9 (MMP‐9). We believe that impairments of arteries in diabetes are associated with endothelial dysfunction mediated by MMP‐9. We hypothesized that folic acid (F) will attenuate vascular dysfunction in type‐2 diabetic mouse (T2D). Diabetes was induced in C57BL/6J mice by feeding a high calorie diet (45% fat). Vascular function (isolated aortic rings) and levels of MMP‐9 (Western blot, and reverse zymography) were determined in thoracic aorta segments of T2D mice and in control (C) mice fed a low calorie diet (10% fat). Mice were regrouped into T2D plus F treatment (T2D+F), and without F treatment (T2D−F). Control groups were also with (C+F) and without (C‐F) treatment. Acetylcholine‐induced relaxation responses were decreased in T2D−F as compared to C‐F, but normalized in T2D+F. The contraction responses to phenylephrine decreased by 40% in aortic rings from T2D−F as compared to C‐F, but were normalized in T2D+F. The sodium nitroprusside‐induced relaxation responses in all groups were not altered. The levels of MMP‐9 were higher in aortic segments from T2D−F as compared to the C‐F, and were significantly reduced in T2D+F. The results suggested that the attenuation of vascular dysfunction in diabetic mice by folic acid is associated with decreased MMP‐9 levels.
Inhibition of T cell Costimulation Prevents the Development of Hypertension
Authors: Vinh Antony , McCann Louise A , Blinder Yelena , Weiss Daiana , Taylor William Robert , Goronzy Jorg J. , Weyand Cornelia M. , Guzik Tomasz J. , Harrison David G.
Published: June 2021

Classically, T cell activation requires antigen recognition by the T cell receptor and costimulation. The latter often involves interaction between B7 ligands (CD80 and CD86) on antigen presenting cells (APCs) with the T cell co receptor CD28. We hypothesized that inhibition of costimulation would reduce hypertension and its associated vascular inflammation. Blockade of B7 dependent costimulation with the human recombinant fusion protein, CTLA4Ig, prevented both Ang II (490 ng/kg/min) and DOCA salt induced hypertension in mice (Ang II: 168 ± 1.5 Vs 139 ± 2.8 mmHg, P<0.001; DOCA: 153 ± 3.2 Vs 135 ± 2.7 mmHg, P<0.001). FACS revealed that circulating T cell activation and vascular T cell infiltration caused by these hypertensive stimuli was completely abrogated by CTLA4Ig. Additionally, B7KO mice were protected from Ang II induced hypertension (154 ± 2.5 Vs 124 ± 3.3 mmHg, P<0.001) and vascular T cell infiltration. Engrafting B7 mice with WT bone marrow restored Ang II induced hypertension. Finally, we found that angiotensin II infusion increased the percent of CD11c+CD86+ cells in lymph nodes, suggesting APC activation in hypertension. These findings indicate that T cells are activated classically in hypertension, suggestive of a possible neoantigen produced by or in response to hypertensive stimuli. This study suggests a novel approach to hypertension treatment. Funded by NIH R01 HL39006 and PPG HL58000.
Agmatine‐mediated rat mesenteric artery relaxation via NO synthesis
Authors: Gadkari Tushar , Acosta Zenith , Tsoukias Nikolaos , Joshi Mahesh S
Published: June 2021

Aim

To determine membrane receptor‐dependent or independent mechanisms of agmatine (decarboxylated arginine) relaxation of rat mesenteric arteries.

Background

In spite of excess levels of intracellular L‐arginine, exogenous L‐arginine still activates cellular synthesis of nitric oxide (NO) in a phenomenon called “arginine paradox”. Our previously published data (PNAS, 104, 9982, 2007) show that L‐arginine or agmatine may be initiating the NO synthesis via receptor binding and release of intracellular Ca+2 in endothelial cells. Here we have tested the same mechanism in isolated rat mesenteric arteries.

Methods

The individual 2nd order mesenteric arteriolar segments from rats (250–300 g male, Sprague‐Dawley) were cannulated at both ends in a vessel chamber that was continuously perfused intraluminally and pre‐constricted with norepinephrine (2 μM) in modified Krebs buffer at 37°C. For internal diameter measurements, the vessel chamber was mounted on the stage of a microscope fitted with a video camera leading to video caliper. Mounted vessels were allowed to stabilize for 60 min before initiating experiment.

Results

The data show that agmatine completely relaxed the vessel with an EC50 of 58.75 ± 12.1 μM (n=4) and this relaxation could be significantly inhibited with nitric oxide synthase inhibitor, L‐NAME (0.5 mM) with EC50 of 315 μM (n=1).

Conclusion

Agmatine dose‐dependently relaxed the rat mesenteric artery and NO mediated the relaxation process.

This work was supported in part by NIH grant SC1HL095101
L‐arginine intake improves tolerance to physical exercise and vascular reactivity in obese trained rats
Authors: Zanesco Angelina , Rojas‐Moscoso Julio , Gómez‐Campos Rossana , da Silva Carmem Valgas , Carneiro Everardo , Antunes Edson , Priviero Fernanda B. M.
Published: June 2021

We assessed the effect of L‐Arg ingestion on tolerance to exercise (EX) and vascular reactivity of rats fed with a hyperlipidic diet (HD) and submitted to EX. Male Wistar rats were divided in sedentary (SD), exercised (EX), SD + L‐Arg (SDLA) and EX + LArg (EXLA). After 4 weeks of HD intake, rats underwent to supplementation and an EX program of running for further 4 weeks. Tolerance to exercise was tested until exhaustion. Concentration‐response curves for acetylcholine (ACh), sodium nitroprusside (SNP) and phenylephrine (PE) were obtained in mesenteric artery (RMA). Plasma MDA and SOD levels were measured. Body weight gain was reduced in EX (30 ± 8 g) and SDLA (Δ: 49 ± 6 g) compared to SD (Δ: 90 ± 11 g). A further reduction was found in EXLA (22 ± 8 g). Tolerance to exercise was higher in EX (15 ± 1 min) compared to SD (7 ± 1 min). L‐Arg raised tolerance to exercise in EXLA (20 ± 2 min) and SDLA (11 ± 1 min). In RMA, L‐Arg increased the potency (pEC50) of ACh in EXLA (7.89 ± 0.07) and SDLA (8.14 ± 0.04), compared to SD (7.65 ± 0.04) as well as the pEC50 of SNP in EXLA (8.07 ± 0.11 vs 7.57 ± 0.13 in EX). Responses to PE were not altered. Neither SOD activity nor MDA levels were altered by L‐Arg or exercise. In conclusion, L‐Arg increased body weight loss and tolerance to exercise in SD and EX. In addition, L‐Arg improved relaxation in RMA of EXLA which was not associated with changes in the redox state.

Financial Support: FAPESP
Vascular relaxation by ethanol extract of Xanthoceras sorbifolia via Akt‐ and SOCE‐eNOS‐cGMP signaling
Authors: Jin Song Nan , Wen Jin Fu , Li Xiang , Kang Dae Gill , Lee Ho Sub , Cho Kyung Woo
Published: June 2021

Objective

Xanthoceras sorbifolia Bunge has long been used as a folk medicine in China. The purpose of the present study was to define the effects of ethanol extract of leaves of X. sorbifolia (EXS) on the vascular tone and the mechanisms by which EXS relaxes vascular smooth muscle in isolated rat aortic rings.

Methods and Results

Experiments were performed in isolated rat aortic rings. Aortic ring was suspended in organ bath and isometric tension was recorded in response to drugs. EXS (0.1–100 ug/ml) produced concentration‐dependent relaxation of aortic rings precontracted with phenylephrine. Endothelium‐denudation abolished the EXS‐induced vasorelaxation. L‐NAME and ODQ blocked the EXS‐induced vasorelaxation. Diltiazem had no effect on the EXS‐induced vasorelaxation. However, Ca2+ ‐free buffer attenuated the EXS‐induced vasorelaxation. Thapsigargin, 2‐APB, and Gd3+, modulators of store‐operated Ca2+ entry (SOCE), and Wortmannin, an inhibitor of Akt, significantly attenuated the EXS‐induced vasorelaxation. However, indomethacin, atropine, and propranolol had no effect on the EXS‐induced vasorelaxation. EXS increased cGMP levels of the aortic rings in a concentration‐dependent manner.

Conclusion

These data demonstrate that EXS relaxes vascular smooth muscle via endothelium‐dependent Akt‐ and SOCE‐eNOS‐cGMP signaling pathways. Supported by NSFC (No30570669; 30971080).
Alteration of guanylyl cyclase‐activated vasorelaxation in thoracic aorta from hyperthyroid rats
Authors: Wen Jin Fu , Jin Song Nan , Wang Yan Li , Zhou Guang Hai , Wang Xin Nong , Cho Kyung Woo
Published: June 2021

Objective

Nitric oxide (NO) and C‐type natriuretic peptide (CNP) activate soluble (sGC) and particulate guanylyl cyclas e (pGC), respectively, and play important roles in the mainte nance of cardiovascular homeostasis. The purpose of the present study was to define the alteration of pGC‐ and sGC‐ac tivated vasorelaxation in the thoracic aorta from hyperthyroid rats.

Methods and Results

Hyperthyroidism was induced by administering L‐thyroxine (T4, 0.05 mg/100 g, sc) daily for 16 days. Experiments were performed in isolated rat aortic rings. CNP (0.1–1000 nM) and SNAP (10‐10000 nM) induced vascular relaxation in a concentration‐dependent manner in aortic rings from eu‐and hyperthyroid rats. The responses were significantly attenuated in aortic rings from hyperthyroid rats. ODQ (10 uM), an inhibitor of sGC, blocked the SNAP ‐induced vasorelaxation of aortic rings from both eu‐ and hyperthyroid d rat. To define the changes in response to cGMP, 8‐Br‐Cgmp (1–100 uM), a cell‐permeable cGMP analog, was used. 8‐Br‐cGMP‐induced vasorelaxation was attenuated in aortic rings from hyperthyroid rats compared to those from euthyroid rats.

Conclusions

These data demonstrate that pGC‐ and sGC‐activated vaso relaxation is attenuated in thoracic aorta from hyperthyroid rats which may be a part of the pathophysiology of the disease. Supported by NSFC (No30570669; 30971080).
Tensorial Description of the geometrical arrangement of Endothelin‐1 in response to the changes of blood pressure in rat's aorta
Authors: Huang Wei , Mak Yi Wah
Published: June 2021

For better studying the vascular remodeling in hypertension, the geometrical arrangement of the cellular molecules, which are the foundation of the physical behavior of the cells and tissues, has to be described quantitatively. Endothelin‐1 (ET‐1) is a vasoconstrictor and mitogenic agent, and has been found in the vascular endothelium, the vascular smooth muscle cells, and the fibroblasts. This study aimed to investigate quantitatively the changes of the geometrical distribution of ET‐1 in blood vessel wall in response to the changes of blood pressure. By clamping one cross section of the rat's abdominal aorta, the blood pressure in the aorta was raised in the portion above the clamp, and lowered in the portion below the clamp. The effects of the raising or the lowering of the blood pressure on these two portions of the aorta simultaneously on the tissue remodeling in the abdominal aortas were studied after aortic banding for 0, 0.5, 4, or 8 days. Aortic cross sections in circumferential and longitudinal directions and En Face were prepared and immunostained with ET‐1 antibody for examination by a fluorescent microscope. Digital images were taken for analysis. The geometrical distributions of ET‐1 in the vessel wall was described by a Molecular configuration tensor, Pij, where the subscripts i, j refer to the Cartesian coordinate axes x1, x2, x3. All components in the molecular configuration tensor of ET‐1 are presented.
Influence of myostatin on skeletal muscle plasticity
Authors: Reisz‐Porszasz Suzanne , Abraham Andrea , Baker Michael , Kovanecz Istvan , Porszasz Janos , Caiozzo Vincent J.
Published: June 2021

The objective of this study was to investigate myostatin (Mst) role in the process of muscle structural and functional changes in adult skeletal muscle. Myostatin (growth and differentiation factor‐8, GDF‐8) regulates skeletal muscle growth and differentiation during embryogenesis, but its function in adult muscle is not understood. Three genetically altered animal (6 month old) models were used for bilateral compensatory overload experiment: Mst‐null (KO) mice, Mst overexpressing transgenic (TG) and conditional Mst overexpressing transgenic (CMOT, first time reported) compared with wild type (WT) males (five animals/group). Plantaris muscles were analyzed for contractile measurement, morphometry, histochemistry and gene expression profile. Plantaris muscle weight increased in all groups, but biggest increase was found in CMOT (200%) and the smallest was in KO (158%) mice. The same tendency was observed in total plantaris muscle cross sectional area changes. Fiber transition from oxidative to glycolytic fiber was identified in each group with the highest rate in KO (17%). Fiber number increased after overload indicating that Mst does not inhibits cell proliferation in adult muscle. We conclude that Mst plays a different role in muscle during adulthood regulating muscle structure, composition, and physical performance.

This study was supported by 1R21AR054101, G12RR030262, and P20MD000545 grants.
Altitude Threshold for Sleep Disturbances During Exposure to Acute Hypobaric Hypoxia
Authors: Beidleman Beth Anne , Muza Stephen R , Fulco Charles S , Jones Juli E , Staab Janet E , Demes Robert , Elliott Sarah , Cymerman Allen
Published: June 2021

To determine the altitude threshold for sleep disturbances during exposure to hypobaric hypoxia, 43 sea‐level (SL) residents (mean±SD, 22±4 yr) completed a one night sleep assessment at SL and during exposure to one of six levels of hypobaric hyoxia (2000 m (N=4), 3000 m (N=5), 3500 m (N=8), 4000 m (N=9), 4300 m (N=12), or 4500 m (N=5)). Each wore a pulse oximeter to measure arterial oxygen saturation (SaO2) and desaturation events (# of > 6% drops in SaO2 for ≥ 8 sec) and a wrist motion detector to estimate sleep quality (awakenings/hr) and quantity (% sleep). Mean sleep SaO2 (%) decreased (P<0.05) from SL (96±1) to 2000 m (92±1), 3000 m (89±2), 3500 m (83±4), 4000 m (73±4), 4300 m (72±4) and 4500 m (71±4). Desaturation events/hr did not increase from SL (0±1) at 2000 m (1±12), 3000 m (12±34) or 3500 m (5±4) but increased (P<0.05) at 4000 m (34±48), 4300 m (56±50) and 4500 m (117±17). Awakenings/hr did not increase from SL (1±1) at 2000 m (1±2), 3000 m (2±2) m, or 3500 m (2±2) but increased (P<0.05) at 4000 m (3±1), 4300 m (6±4) and 4500 m (5±3). The % sleep did not decrease from SL (95±6) at 2000 m (95±21), 3000 m (87±21) and 3500 m (88±22) but decreased (P<0.05) at 4000 m (72±20), 4300 m (54±28) and 4500 m (63±25). These results suggest that although mean sleep SaO2 decreases at moderate altitudes, the threshold for significant sleep disturbances does not occur until 4000 m. Authors′ views; not official U.S. Army or DoD policy.
Physical Activity and the Incidence of Acute Mountain Sickness in United States Antarctic Program Participants Following Rapid Transport to the South Pole: Antarctic Study of Altitude Physiology (ASAP)
Authors: Ceridon M L , Anderson P J , Miller A D , Beck K C , OMalley K A , Johnson J B , Johnson B D
Published: June 2021

Background

Physical activity has been proposed as a risk factor for altitude illness however it is unclear whether the total amount or intensity of activity determines illness.

Purpose

To examine activity patterns relative to the incidence of acute mountain sickness (AMS) in United States Antarctic Program workers rapidly transported to the South Pole (SP, 9303 ft).

Methods

53 medically screened subjects (age=37±10yr, BMI=24±3 kg/m2) were transported by a 3 hour flight from McMurdo Station (sea level, SL) to the SP. Physical activity was monitored at SL and for 3 days after ascent using BodyMedia® activity monitors. Symptoms of AMS were assessed using Lake Louise Questionnaires.

Results

53% of subjects displayed AMS between SP days 1–3 (23% day 1, 43% day 2, 15% day 3). Energy expenditure at SP was 3414±944, 3458±781, & 3543±869 Calories/day for days 1–3, respectively. Steps/day at SP was 12593±4926, 13124±4392, & 12966±4482 for days 1–3, respectively. Overall, more activity at higher intensity (>3 METS) on SP day 1 was associated with higher AMS incidence the next morning (p<0.05). Also, calorie expenditure with activity at >3 METS and time of activity at >6 METS in the first 24 hours after ascent independently increased the odds of AMS on SP day 2 (p<0.05).

Conclusions

With rapid transport to altitude, moderate to intense activity within the first 24 hours of ascent contributes to the incidence of AMS. NSF ANT 0540710
Monocyte Chemoattractant Protein‐1 (MCP‐1) released from alveolar macrophages mediates the systemic inflammation of alveolar hypoxia
Authors: Chao Jie , Donham Paula , Wood John G , Gonzalez Norberto C
Published: June 2021

Alveolar hypoxia (AH) produces widespread systemic inflammation in rats. The inflammation is initiated by a circulating mediator released from alveolar macrophages (AMØ) activated by the low alveolar PO2. The mediator(s) induces mast cell degranulation (MCD) with release of inflammatory agents. Recent data suggest MCP‐1 as a mediator. If this is true: 1) Circulating levels of MCP‐1 should increase with AH in intact rats; 2) AMØ depletion should prevent this increase; 3) Plasma from intact AH rats, but not AMØ‐depleted AH rats, should produce MCD; 4) MCP‐1 added to normoxic plasma or AMØ supernatant should produce MCD.

AH (FIO2 = 0.1 for 60 min) produced a rapid (5 min) and sustained 6‐fold increase in plasma MCP‐1 of intact rats. 2) This increase was abolished by AMØ depletion by tracheal instillation of clodronate‐containing liposomes. 3) Mast cell immersion in plasma from AH intact rats, but not in plasma from AMO‐depleted rats, produced MCD. 4) Dose‐dependent MCD occurred when MCP‐1 was added to normoxic AMØ supernatant or rat plasma, but not when added to normoxic culture medium.

Conclusions

In the intact, conscious rat, AH induces release of MCP‐1 from AMØ, which, in turn, produces MCD and initiates systemic inflammation of AH. To induce MCD, MCP‐1 requires another substance(s) which is present in both normoxic plasma and normoxic AMØ supernatant.

Supported by NIH HL39443‐18, AHA 0815652G and APS Frontiers in Biology
Hypoxic Exercise Training Improved Gardos Channel‐Mediated Erythrocyte Deformability
Authors: Mao Tso‐Yen , Fu Li‐Lan , Wang Jong‐Shyan
Published: June 2021

Erythrocyte deformability is an important player in blood rheology. Gardos channel (Ca2+‐activated K+ channel) regulates erythrocyte deformability by employing the ions‐mediated cytoskeleton proteins. This study investigated whether hypoxic exercise training affects Gardos channel‐mediated erythrocyte deformability and further explores its underlying mechanisms. Ten sedentary males were trained on a bicycle ergometer at 60%VO2max under 15%O2 air condition for 30 minutes per day, 5 days per week for 5 weeks. Erythrocyte deformability was determined by dynamic flow ektacytometer, whereas erythrocyte cell volume, Gardos channel performance, and cytoskeleton protein levels were evaluated by the flow cytometry. Our results demonstrated that at pre‐training stage, acute 12%O2 exercise declined erythrocyte deformability mediated by Gardos channel, which was accompanied by erythrocyte shrinkage and decreases in sprectrin and actin levels of erythrocytes. However, 5 weeks of 15%O2 exercise training enhanced Gardos channel‐mediated erythrocyte deformability and increased erythrocyte cytoskeleton protein levels at rest and following acute 12%O2 exercise. Therefore, we conclude that long‐term moderate‐intensity exercise at 15%O2 environment increases erythrocyte deformability under shear flow, possibly by improving performance of Gardos channel on erythrocyte.
Heat acclimation improves central cardiac function and performance variables in cool environments
Authors: Lorenzo Santiago , Miller Danielle , Halliwill John R. , Sawka Michael N. , Minson Christopher T.
Published: June 2021

The aim of this study was to explore heat acclimation effects on central cardiovascular function and performance variables in cool conditions. Twelve trained cyclist performed a VO2peak test, lactate threshold test, and a 1‐hour time trial in a cool environment (13°C 30% RH) before and after a 10‐day period of heat acclimation. Eight subjects matched the 10‐day exercise in a cool environment to serve as controls. Heat acclimation increased maximal cardiac output (24.6 ± 1.2 vs. 26.9 ± 0.8 L min−1, P = 0.018), VO2peak (66.8 ± 2.1 vs. 70.2 ± 2.3 ml kg−1 min−1; P = 0.004), and maximal power output (369.2 ± 14.5 vs. 380.8 ± 14.5 Watts, P = 0.026). Maximal heart rate remained unchanged. Heat acclimation increased power output at lactate threshold (263.0 ± 16.1 vs. 277.1 ± 14.9 Watts; P = 0.002), and total work done during the time trial (879.8 ± 48.5 vs. 934.7 ± 50.9 kJ, P = 0.005). No differences were found in the control group in any of the variables. Collectively, these data suggest heat acclimation induces cardiopulmonary adaptations that improve performance in trained cyclists in a cool environment. Sponsored by the Eugene and Clarissa Evonuk Memorial Graduate Fellowship.
Influence of Hypercapnia and Skin Temperature on Pulmonary Ventilation in Hyperthermic Humans
Authors: Greiner Jesse G , Walsh Michael L , White Matthew D
Published: June 2021

Hyperthermia potentiates the influence of CO2 on pulmonary ventilation (VE). It remains to be resolved how mean skin (TSK) and core temperatures contribute to elevated exercise ventilation response to CO2.

PURPOSE

To assess influences of TSK and end‐tidal CO2 (PETCO2) on the ventilatory equivalent for oxygen (VE/VO2) during exercise with a hyperthermic rectal temperature (TRE).

HYPOTHESIS

During hyperthermia mean skin temperature will positively interact with PETCO2 in their influence on exercise ventilation.

METHODS

Six participants 1.78 ± 0.13 m (mean ± SD) in height, who weighed 74.7 ± 16.5 kg and were 24.3 ± 2.3 yrs of age performed three 1 h exercise trials on each of 2 days in a climatic chamber. For each exercise session conditions were maintained at an RH of 29.5 ± 8.9 % and ambient temperatures of one of 25, 30, or 35°C. This gave 3 significantly different TSK levels (F=15.8, p=0.001) between ~33 and ~36°C. In each trial the volunteer breathed eucapnic air for 5 min during rest before cycling on an ergometer at either ~50 W (normothermic TRE) or at ~150 W (hyperthermic TRE). Once TRE stabilized the volunteers breathed hypercapnic air twice for ~5 min with PETCO2 elevated to ~+4 and ~+8 mmHg.

RESULTS

In the normothermic TRE condition there was a significant effect of PETCO2 (P<0.05) but no effect of TSK on ventilation. In the hyperthermic TRE condition for VE/VO2 there were main effects of TSK (F=4.0, p=0.06) and PETCO2 (F=13.2, p<0.0001) as well as a significant positive interaction (F=3.7, p=0.01) between TSK and PETCO2.

CONCLUSION

During exercise with a steady state hyperthermic core temperature, skin temperatures and PETCO2 positively interact in their influence on exercise ventilation.

Supported by NSERC, Canadian Foundation for Innovation.