bluuebunny/crossref_metadata_2025_split huggingface dataset:
An In Situ Kidney Slice Model for Studying Angiotensin II‐ and TRPC5‐Mediated Calcium Signaling
Authors: Schleifenbaum Johanna , Hennig Grant W. , Nelson Mark T. 
Published: June 2021

Current approaches to study calcium signaling in glomeruli use isolated glomeruli or cultured cells, however the structure and physiology of the tissue is likely to be perturbed by the isolation process in both models. We used kidney slices maintained in physiological solution to better preserve the macroscopic structure of glomeruli and measured the impact of angiotensin II receptor activation and blockade of Transient Potential Receptor Canonical 5 (TRPC5) to examine their possible interaction in a number of pre‐ and intraglomerular cell types using spinning‐disk confocal calcium imaging.Calcium transients and tissue distortion in intact kidney slices of mice expressing genetically modified calcium‐sensors (GCaMP5) in Cx40‐positive cells were recorded and analyzed using particle analysis.We observed spontaneous calcium transients in preglomerular cells located at the vascular pole that were blocked by the SERCA pump inhibitor, cyclopiazonic acid (CPA). Stimulation with angiotensin II increased calcium activity and contraction in these cells and induced calcium transients in distinct populations of intraglomerular cells that were also blocked with CPA. While removal of external calcium did not change angiotensin II‐induced calcium transients in intraglomerular cells, the frequency of calcium transients in preglomerular cells was significantly reduced. In angiotensin II‐preincubated kidney slices, spontaneous calcium transients in the preglomerular area were diminished by the specific TRPC4/5 inhibitor, ML204. If given alone, ML204 completely inhibited all preglomerular calcium transients.Thick kidney slices maintained in vitro appear to better preserve the structure and responses of different cell types in glomeruli as measured using calcium transients and contractions. In our experimental set‐up, angiotensin II induced calcium transients in intraglomerular cells, while its impact on preglomerular cells appeared more indirect. As the TRPC5 antagonist was more effective at inhibiting calcium transients in preglomerular cells when the tissue was not prestimulated with angiotensin II, we suggest that TRPC5‐mediated calcium signaling is at least party modulated by angiotensin II.Support or Funding InformationSupported by Deutsche Forschungsgemeinschaft (DFG)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Renal V1A Receptor Does Not Increase Na+ Excretion in the Rat Isolated Kidney Perfused at Constant Pressure
Authors: Lindstrom Beatriz , Kalina Sara , Wisniewski Kazimierz , Laporte Regent 
Published: June 2021

The effect of arginine vasopressin (AVP) on Na+ excretion has been the subject of many studies and is still a matter of debate. While AVP given at physiological doses was shown to enhance Na+ excretion in water‐loaded rats, others have shown that AVP‐induced natriuresis occurred at doses associated with increases in mean arterial pressure, suggesting that pressure natriuresis may be the underlying mechanism. This natriuresis is thought to be mediated by the V1A receptor (V1AR). To investigate if the renal V1AR mediates natriuresis, we employed the rat isolated kidney perfused at constant pressure to assess the effect of the selective V1AR agonist, [Phe2, Ile3, Orn8]‐vasopressin, on various parameters. Specifically, we sought to test the hypothesis that selective activation of V1AR in the kidney increases urinary excretion of Na+.Each isolated kidney was perfused for a total of 85 min, starting with 10 min for equilibration, and followed by five 15 min‐periods with ascending concentrations of the agonist (0, 30, 100, 300, and 1000 pM). Time‐control kidneys were perfused with media without the agonist for the entire 85 min.We found that the agonist increased renal vascular resistance in a concentration‐dependent manner without changing GFR. At the highest concentrations, the agonist showed antidiuretic activity characterized by decreased urine flow rate and effective water clearance, and increased urine osmolality. Our results further show that although there was an increase in absolute Na+ excretion and fractional excretion Na+, no difference was observed between treated‐ and control‐kidneys, suggesting that the changes in Na+ handling were inherent to perfusion itself rather than activation of the renal V1AR.We conclude that AVP‐induced natriuresis may not be mediated by the renal V1AR, and that AVP may induce natriuresis indirectly through extrarenal factors lacking in the isolated kidney.Support or Funding InformationFerring Research Institute, Inc., San Diego, CAThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Effect of Chronic Lower Limb Heating on Cutaneous Microvascular Function in Aged Humans
Authors: Romero Steven A. , Gagnon Daniel , Adams Amy , Jaffery Manall , Crandall Craig G. 
Published: June 2021

Cutaneous microvascular function is reduced with advancing age. Recent evidence suggests that chronic local heating of a limb improves cutaneous microvascular function in young healthy humans through nitric oxide‐dependent mechanisms. However, exposure to chronic heating of limb has not been studied in aged adults. The purpose of this study was to test the hypothesis that chronic lower limb heating improves nitric oxide‐dependent vasodilation in the cutaneous microvasculature of aged adults. Six healthy aged adults (5 females; age 67 ± 4 years; height 164 ± 3 cm; weight 70 ± 18 kg; mean ± SD) were exposed to 8 weeks of chronic lower limb heating. Subjects immersed their lower limbs ~33 cm into a heated (~ 42°C) and circulated water bath 4 days per week, for 45 min per session. Before and after the 8‐week regimen, cutaneous blood flow (laser Doppler red blood cell flux) was measured in response to 39 °C heating of a discreet area of skin exposed to chronic heating with and without (control) intradermal microdialysis administration of the nitric oxide synthase inhibitor Nω‐nitro‐L‐arginine methyl ester hydrochloride (L‐NAME; 20 mM). Estimated maximal cutaneous blood flow was assessed in response to combined local heating to 43 °C and intradermal infusion of sodium nitroprusside (56 mM). Cutaneous vascular conductance (CVC) was calculated as red blood cell flux divided by mean arterial pressure and expressed as a percentage of maximal vasodilation (%CVCmax), where appropriate. Cutaneous vascular conductance during 39 °C local heating was unchanged following chronic heating (pre 78 ± 5 %CVCmax vs. post 85 ± 7 %CVCmax; P = 0.2). Likewise, nitric oxide‐dependent vasodilation (calculated as the difference between control and L‐NAME sites) did not differ (pre 68 ± 3 % vs. post 64 ± 3 %; P = 0.3). Interestingly, maximal cutaneous vascular conductance increased after chronic heating (pre 1.8 ± 0.1 flux mmHg−1 vs. post 2.4 ± 0.2 flux mmHg−1; P < 0.05). Taken together, chronic lower limb heating does not improve nitric oxide‐dependent cutaneous microvascular function during a local thermal provocation in aged adults, an effect that may be superseded by vascular remodeling as maximal vasodilator capacity was increased after the 8‐week regimen.Support or Funding InformationNational Institutes of Health (GM‐068865 & GM‐117693)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
NO EFFECT OF HEAD UP TILT ON TUMOR PERFUSION IN A RAT PRE‐CLINICAL MODEL OF PROSTATE CANCER
Authors: Rand Taylor , Pyle Joseph , Baumfalk Dryden , Opoku‐Acheampong Alexander , Musch Timothy , Behnke Brad 
Published: June 2021

Previous research has demonstrated an enhanced prostate tumor blood flow and oxygenation associated with the augmented mean arterial pressure during exercise. Further, prostate tumor arterioles lack functional smooth muscle and have a diminished myogenic response. Thus, we tested the hypothesis that with elevations in the heart‐to‐prostate tumor hydrostatic gradient 70° head‐up tilt (HUT) would result in an enhanced perfusion of the prostate tumor. An enhanced tumor perfusion may improve tumor oxygenation and radiation therapy outcomes.MethodsDunning AT‐1 tumor cells (1×104) were injected into the ventral prostate of male Copenhagen rats (n=7) and studies were performed ~ 6 weeks after cell injection. After 5 minutes in each body position, fluorescent microspheres (red and blue/green, ~250,000 spheres per label) were injected via the carotid artery in the level and HUT body positions. Blood flow was determined in the tumor, kidneys and soleus muscle. Vascular conductance was calculated as blood flow divided by mean arterial pressure (MAP). Blood flow and conductance rates were calculated and a two‐tailed paired t‐test was conducted to compare values in the level vs. HUT positions.ResultsAverage tumor weight was 7.1 ± 0.5 g. MAP was not different between level and HUT (p = 0.15). Adequate blood flow distribution, as determined by a <15% difference in flow between the left/right kidney and/or soleus muscle, was achieved in all animals. Tumor blood flow was not different between level and HUT (12.0 ± 1.1 vs. 10.4 ± 0.8 ml/100 g/min, respectively). No difference was observed between body positions in tumor vascular conductance (p>0.05).DiscussionContrary to our hypothesis, we did not see any significant differences in either blood flow or vascular conductance in the tumor with HUT. With HUT, the prostate shows an increase in vascular resistance; thus, the combination of immature and co‐opted host tissue arterioles present in tumors may have resulted in an unchanged perfusion of the tumor with tilt. Specifically, there would be an enhanced vascular resistance of the host‐tissue (prostate) that may counter hydrostatic differences in perfusion pressure. These findings suggest that elevations in the hydrostatic gradient via HUT may not be sufficient to enhance prostate tumor perfusion.Support or Funding InformationAmerican Cancer Society RSG 14‐150‐1‐CCE (BJB)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Endothelium Mediated Dilation Does Not Blunt α1‐adrenergic Vasoconstriction in First Order Arterioles
Authors: Ferguson Brian S. , Kozina Erik , Hill Michael A. , Clifford Philip S. 
Published: June 2021

In contracting skeletal muscle, several vasoactive compounds have been proposed to override sympathetic vasoconstriction, a phenomenon termed functional sympatholysis. Adenosine triphosphate (ATP) has emerged as a candidate molecule capable of mediating these effects, however, the precise source and mechanisms have not been fully elucidated. We tested the hypothesis that endothelium mediated mechanisms are responsible for attenuating α‐adrenergic vasoconstriction. Experiments were conducted on 1A arterioles surgically dissected from the rat cremaster muscle. Sequential sections of arteriole were cannulated on glass micropipettes, pressurized to 70 mmHg, and warmed to 34°C in physiological saline solution. We measured changes in isolated vessel diameter in response to logarithmic concentrations of the α1‐adrenergic receptor specific agonist phenylephrine following dilatory responses to intraluminal flow (flow mediated dilation, n=12), intraluminal adenosine (n=10), or intraluminal ATP (n=11). All vessels tested spontaneously developed myogenic tone (>40% from initial diameter) and displayed functioning endothelium (>40% dilation to acetylcholine). Vessels dilated equally 177±19 μm, 183±10 μm, and 181±22 μm during flow mediated dilation, adenosine, and ATP, respectively. There were no significant differences between treatments following concentration‐response curves generated by phenylephrine administration and the EC50 was not different −5.90±0.02, −6.12±0.18, and −6.00±0.06 for flow mediated dilation, adenosine, or ATP (p=NS). Thus, there was no attenuation of α1‐adrenergic vasoconstriction in response to intraluminal flow mediated dilation, adenosine, or ATP in 1A arterioles. These results suggest that endothelium mediated dilation does not blunt α1‐adrenergic vasoconstriction in first order skeletal muscle arterioles.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Remote Ischemic Conditioning in Rodents: Tourniquet vs. Cuff Occlusion
Authors: El Dabagh Yasmin Sanaya Hauge , Mohanakumar Sheyanth , Hagensen Mette K. , Pedersen Michael 
Published: June 2021

PurposeRemote ischemic conditioning (RIC) implies that transient cycles of ischemia and reperfusion in a limb can activate innate protective responses against ischemia. RIC is usually accomplished in rodents by tightening either a tourniquet or an inflatable cuff on the hind limb. However, the optimal method is not established. Therefore, the purpose of the present study was to perform a comparison of the effects of RIC performed with a tourniquet and an inflatable cuff.MethodsEleven male C57/Bl6 mice were randomized into three groups: sham occlusion (n=3), tourniquet occlusion (n=4) and cuff occlusion at 200 mm Hg (n=4). Animals receiving occlusions were subjected to two cycles of 5 minutes unilateral hind limb occlusion and 5 minutes of reperfusion. Occlusion of blood flow to the hind limb was verified with Near Infrared Fluorescence (NIRF) imaging (figure 1). Motor function of the hind limbs was evaluated using a Rotarod, muscle tissue was harvested for histological analysis, and wet‐to‐dry muscle weight ratio was measured.ResultsNIRF imaging showed that complete occlusion of blood flow to the hind limb was obtained with both tourniquet and cuff occlusion. The tourniquet group scored significantly lower in the motor function tests (p<0.05) compared with the sham and cuff group which did not differ significantly (figure 2). There were no significant histological signs of muscle damage and wet‐to‐dry muscle weight ratio did not imply edema in any groups.ConclusionComplete occlusion of blood flow to the hind limb can be obtained with both a tourniquet and an inflatable blood pressure cuff. Thus, both methods can be used to induce RIC. However, motor function of the hind limb was reduced in animals exposed to tourniquet occlusion indicating that the inflatable cuff should be the preferred method in order to reduce stress on the animals.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Chronic Intermittent Hypoxia Enhances Respiratory Muscle Weakness in Dystrophindeficient mdx Mice
Authors: Burns David P. , Edge Deirdre , Murphy Kevin , O'Halloran Ken D. 
Published: June 2021

Sleep‐disordered breathing (SDB) is a prominent feature of neuromuscular disease, likely due to pharyngeal dilator muscle weakness. Boys with Duchenne muscular dystrophy (DMD) experience nocturnal desaturation during sleep as a result of obstructive and central apnoea. We have previously described maladaptive changes in respiratory muscle structure and function in rodent models of chronic intermittent hypoxia (CIH), a hallmark feature of SDB driving many pathologies. We hypothesized that CIH exacerbates respiratory muscle dysfunction in muscular dystrophy. We sought to explore the effects of CIH on respiratory muscle structure and function in wild‐type (WT) and dystrophin‐deficient mdx mice.Six week old male WT and mdx mice were exposed to CIH, consisting of alternating bouts of hypoxia (90s; 5–6.5% O2 at the nadir) and normoxia (210s, 21% O2) for 12 cycles per hour, 8 hours per day for 14 days. Sham animals were exposed to normoxia in parallel. The diaphragm and sternohyoid (representative pharyngeal dilator) muscles were excised and functional parameters were examined ex vivo.Substantial muscle weakness was observed in dystrophic diaphragm and sternohyoid muscle compared with WT muscles. Exposure to CIH elicited significant muscle weakness in the diaphragm and sternohyoid of WT mice. In mdx mice, exposure to CIH resulted in further weakness in the compromised diaphragm. CIH‐induced potentiation of muscle weakness was less robust in the sternohyoid. We have recently established the essential role of NADPH oxidase in CIH‐induced respiratory muscle weakness. We are currently exploring the molecular mechanisms of CIH‐induced respiratory muscle weakness in WT and mdx mice.Our findings demonstrate that exposure to CIH exacerbates respiratory muscle weakness in the mdx model of muscular dystrophy. Since SDB is a feature of DMD, we reason that SDB may accelerate respiratory insufficiency in DMD. An understanding of the pathogenic factors driving CIH‐induced muscle weakness in mdx may help inform therapeutic strategies that may have relevance to DMD boys.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
α2δ‐1 Is Essential for Angiotensin II‐Induced Sympathoexcitation and NMDA Receptor Hyperactivity in the Hypothalamus
Authors: Ma Huijie , Chen Shao‐Rui , Chen Hong , Zhou Jing‐Jing , Li De‐Pei , Pan Hui‐Lin 
Published: June 2021

Both the sympathetic nervous system and renin‐angiotensin system are critically involved in hypertension development. Although angiotensin II (Ang II) stimulates presympathetic neurons in the hypothalamic paraventricular nucleus (PVN) to increase sympathetic vasomotor tone, the molecular mechanism responsible for this action remains unclear. The glutamate N‐methyl‐D‐aspartate receptor (NMDAR) in the PVN controls sympathetic outflow in hypertension. In this study, we determined how Ang II affects synaptic NMDARs in spinally projecting PVN neurons. Coimmunoprecipitation assays showed that α2δ‐1, commonly known as a voltage‐gated calcium channel subunit, interacted with the NMDAR in the hypothalamus of rats and humans. Ang II increased the synaptic expression level of α2δ‐1–NMDAR complexes. Also, Ang II increased pre‐ and postsynaptic NMDAR activity via AT1 receptors, and such effects were abolished either by treatment with pregabalin, an inhibitory α2δ‐1 ligand, or by interrupting the α2δ‐1–NMDAR interaction with α2δ‐1Tat peptide. In α2δ‐1 knockout mice, Ang II failed to affect the pre‐ and postsynaptic NMDAR activity of PVN neurons. In addition, the α2δ‐1Tat peptide blocked the sympathoexcitatory response to the microinjection of Ang II into the PVN. Our findings indicate that by promoting the synaptic trafficking of α2δ‐1–bound NMDARs, Ang II augments sympathetic vasomotor tone and excitatory glutamatergic input to PVN presympathetic neurons.Support or Funding InformationThis work was supported by the National Institutes of Health (Grant R01 HL131161) and the N.G. and Helen T. Hawkins Endowment (to H.‐L.P.).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
CCL2‐CCR2 Signalling in the Hypothalamic Paraventricular Nucleus Elicits Sympathetic‐Mediated Blood Pressure Elevations Through Monocyte and Lymphocyte Recruitment
Authors: Elsaafien Khalid , Korim Willian Seji , May Clive Newton , Yao Song Tieng 
Published: June 2021

Chemokine C‐C motif ligand 2 (CCL2) is a chemotactic cytokine, which is elevated in the plasma of hypertensive patients. In experimental models of hypertension, CCL2 levels are increased by 3‐fold in the paraventricular nucleus of the hypothalamus (PVN). However, the underlying neural and molecular mechanisms leading to the development of hypertension still remain unknown. Here, we show for the first time that in Sprague‐Dawley rats activation of receptors for CCL2 (i.e. CCR2) in the PVN elicited biphasic blood pressure (BP) responses and changes in renal sympathetic nerve activity (RSNA), consisting of early reductions followed by long‐lasting increases in RSNA and mean arterial pressure (MAP). These responses were abolished by prior CCR2 blockade with the antagonist RS‐102895. Purinergic transmission between astrocytes and neurons mediated the initial sympathoinhibition, whereas monocyte and lymphocyte infiltration into the PVN were involved in the subsequent sympathoexcitation. Our anatomical results support these findings by showing that CCR2 are predominantly expressed in the membrane of astrocytes, which make close appositions with PVN neurons projecting to the rostral ventrolateral medulla (RVLM) ‐ where cardiovascular sympathetic premotor neurons are found. Finally, in renovascular hypertensive rats (2 kidney ‐ 1 clip) plasma and cerebrospinal fluid levels of CCL2 were elevated with an onset occurring on the first week ‐ prior to the development of hypertension. Microglia activation and lymphocyte infiltration in the PVN were also evident by the second week, when animals were still pre‐hypertensive. The results here suggest that CCL2 upregulation, microglia activation, and lymphocyte infiltration in the PVN precede the sustained increases in sympathetic activity and blood pressure observed in hypertension.Support or Funding InformationDepartment of Health, Australian Government | National Health and Medical Research Council (NHMRC): Song T Yao, GNT1079680. Rebecca L Cooper Medical Foundation: Willian S Korim. Australian Government Research Training Program Scholarships: Khalid Elsaafien. Department of Industry, Innovation, Science, Research and Tertiary Education, Australian Government | Australian Research Council (ARC): Song T Yao, FT170100363.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.