bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary arterial compliance in dogs and pigs: the three-element windkessel model revisited
Authors: Segers Patrick , Brimioulle Serge , Stergiopulos Nikos , Westerhof Nico , Naeije Robert , Maggiorini Marco , Verdonck Pascal
Published: December 2017

In six dogs and six weight-matched miniature pigs at baseline and after pulmonary embolization, pulmonary arterial compliance was determined using the pulse pressure method (CPPM), the three-element windkessel model (CWK-3), and the ratio of stroke volume to pulse pressure (SV/PP). CPPM was lower in pigs than in dogs at baseline (0.72 ± 0.23 vs. 1.14 ± 0.29 ml/mmHg, P < 0.05) and after embolism (0.37 ± 0.14 vs. 0.54 ± 0.16 ml/mmHg, P = 0.07) at matched flow, but not at matched flow and pressure. CPPM showed the expected inverse relation with pressure and a direct relation with flow. CWK-3 was closely correlated with CPPM, except for all dogs at baseline where CWK-3 was up to 100% higher than CPPM. Excluding these data, regression analysis yielded CWK-3 = −0.01 + 1.30 ⋅ CPPM( r 2 = 0.97). CWK-3 was found to be unreliable when input impedance first harmonic modulus was close to characteristic impedance, i.e., when reflections were small. SV/PP correlated well with CPPM (SV/PP = −0.10 + 1.76 ⋅ CPPM, r 2 = 0.89). We conclude that 1) CPPM is a consistent estimate of pulmonary arterial compliance in pigs and dogs, 2) CWK-3 and SV/PP overestimate compliance, and 3) CWK-3 is unreliable when wave reflections are small.
Nitric oxide: a modulator, but not a mediator, of neurovascular coupling in rat somatosensory cortex
Authors: Lindauer Ute , Megow Dirk , Matsuda Hiroshi , Dirnagl Ulrich
Published: December 2017

We investigated the role of nitric oxide (NO)/cGMP in the coupling of neuronal activation to regional cerebral blood flow (rCBF) in α-chloralose-anesthetized rats. Whisker deflection (60 s) increased rCBF by 18 ± 3%. NO synthase (NOS) inhibition by N ω-nitro-l-arginine (l-NNA; topically) reduced the rCBF response to 9 ± 4% and resting rCBF to 80 ± 8%. NO donors [ S-nitroso- N-acetylpenicillamine (SNAP; 50 μM), 3-morpholinosydnonimine (10 μM)] or 8-bromoguanosine 3′,5′-cyclic-monophosphate (8-BrcGMP; 100 μM)] restored resting rCBF andl-NNA-induced attenuation of the whisker response in the presence ofl-NNA, whereas the NO-independent vasodilator papaverine (1 mM) had no effect on the whisker response. Basal cGMP levels were decreased to 35% byl-NNA and restored to 65% of control by subsequent SNAP superfusion. Inhibition of neuronal NOS by 7-nitroindazole (7-NI; 40 mg/kg ip) or soluble guanylyl cyclase by 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 100 μM) significantly reduced resting rCBF to 86 ± 8 and 92 ± 10% and whisker rCBF response to 7 ± 4 and 12 ± 3%, respectively. ODQ reduced tissue cGMP to 54%. 8-BrcGMP restored the whisker response in the presence of 7-NI or ODQ. We conclude that NO, produced by neuronal NOS, is a modulator in the coupling of neuronal activation and rCBF in rat somatosensory cortex and that this effect is mainly mediated by cGMP.l-NNA-induced vasomotion was significantly reduced during increased neuronal activity and after restoration of basal NO levels, but not after restoration of cGMP.
Effects of selected endothelium-dependent vasodilators on fetoplacental vasculature: physiological implications
Authors: Amarnani Saral , Sangrat Belinda , Chaudhuri Gautam
Published: December 2017

The endothelium-dependent vasodilators ACh, histamine, and bradykinin were studied in the isolated, perfused human placental cotyledon. Histamine caused a decrease in perfusion pressure that was attenuated by cimetidine. Bradykinin, at lower concentrations (10−20 to 10−14 M), produced a concentration-dependent decrease in perfusion pressure, whereas at higher concentrations it produced an increase in perfusion pressure. ACh was without any effect. The decrease in perfusion pressure observed with bradykinin was potentiated by captopril and was significantly attenuated in the presence of HOE-140, the B2-receptor antagonist, or by pretreatment with an inhibitor of nitric oxide synthase, but not by an inhibitor of cyclooxygenase. The decrease in perfusion pressure observed with bradykinin was potentiated by ANG I but not by ANG II. It is concluded that endothelium-dependent vasodilation can be demonstrated with histamine and bradykinin in the fetoplacental vessels, and at least for bradykinin, this is partly mediated by release of nitric oxide. The potentiation of the bradykinin response in the presence of ANG I may serve to buffer the vasoconstriction produced by ANG II in the fetoplacental circulation.
α2-Adrenoceptor-mediated presynaptic inhibition in bulbospinal neurons of rostral ventrolateral medulla
Authors: Hayar Abdallah , Guyenet Patrice G.
Published: December 2017

The rostral ventrolateral medulla (RVLM) controls sympathetic tone via excitatory bulbospinal neurons. It is also the main target of α2-adrenoceptor (α2-AR) agonists used for treatment of hypertension. In this study, we examined the synaptic mechanisms by which α2-AR agonists may inhibit the activity of RVLM bulbospinal neurons. We recorded selectively from RVLM bulbospinal neurons in brain stem slices of neonate rats (P5–P21) using the patch-clamp technique (holding potential −70 mV). α2-ARs were activated by norepinephrine (NE, 30 μM) in the presence of the α1-adrenoceptor blocker prazosin. NE induced modest outward currents (5–28 pA) in 70% of the cells that were blocked by barium and by the α2-AR antagonist 2-methoxyidazoxan. The magnitude of this current was not correlated with the tyrosine hydroxylase immunoreactivity of the neurons. Mono- and oligosynaptic excitatory postsynaptic currents (EPSCs) or monosynaptic inhibitory postsynaptic currents (IPSCs) were evoked by focal electrical stimulation. In all cells, NE decreased the amplitude of the evoked EPSCs in the absence or presence of barium (49 and 70%) and decreased the amplitude of the evoked IPSCs (64 and 59%). The effect of NE on EPSC amplitude was blocked by 2-methoxyidazoxan. Focal stimulation produced a 1- to 2-s EPSC afterdischarge (probably due to activation of interneurons) that was 53% inhibited by NE. In the presence of tetrodotoxin, NE decreased the frequency of miniature EPSCs by 74%. In short, α2-AR stimulation produces weak postsynaptic responses in RVLM bulbospinal neurons and powerful presynaptic inhibition of both glutamatergic and GABAergic inputs. Thus the inhibition of RVL bulbospinal neurons by α2-AR agonists in vivo results from a combination of postsynaptic inhibition, disfacilitation, and disinhibition.
Peritoneal lymphatic absorption and solute exchange during zymosan-induced peritonitis in the rat
Authors: Carlsson Ola , Rippe Bengt
Published: December 2017

Lymph flow is elevated in most inflammatory conditions. However, a few previous studies have indicated that peritoneal lymph flow may actually fall during acute peritonitis. This study was performed to explore this issue further and to study the pathophysiology of peritoneal exchange during peritonitis. Therefore, we wanted to assess the total peritoneal clearance (Cl) and the clearance from peritoneum to plasma (Cl → P) of125I-labeled albumin (125I-albumin) as well as plasma-to-dialysate clearance (Cl → D) of Evans blue-labeled albumin together with peritoneal ultrafiltration (UF) profiles and mass transfer area coefficients of51Cr-EDTA and glucose in rats after acute peritonitis induced by zymosan. Zymosan incubation of the peritoneal cavity (120 mg) for 4 h generally led to a 4- to 10-fold increase in peritoneal fluid white blood cell count, indicating that acute peritonitis had been induced. Then 16 ml of 3.86% Dianeal and125I-albumin were instilled intraperitoneally, whereas Evans blue-labeled albumin and51Cr-EDTA were given as infusions intravenously. Compared with control, mass transfer area coefficients for glucose and51Cr-EDTA increased markedly from 0.43 ± 0.06 and 0.25 ± 0.04 to 0.91 ± 0.06 and 0.59 ± 0.05 (SE) ml/min, respectively, during peritonitis, whereas Cl and Cl → D increased from 32.8 ± 5.6 and 8.6 ± 1.6 to 74.5 ± 7.3 and 12.9 ± 1.0 μl/min, respectively. The UF profile in peritonitis indicated type I loss of UF (resulting from the increases in permeability-surface area product for glucose). However, the Cl → P declined to 5.9 ± 1.0 μl/min from 7.9 ± 0.8 μl/min ( P < 0.05) in control. In conclusion, despite marked effects on peritoneal solute transport and on UF, conceivably resulting from vasodilatation and increases in capillary permeability, zymosan-induced peritonitis did not cause any acute increases in direct peritoneal lymphatic absorption.
Role of load in regulating eIF-4F complex formation in adult feline cardiocytes
Authors: Tuxworth William J. , Wada Hisayasu , Ishibashi Yuji , McDermott Paul J.
Published: December 2017

This study examined whether cardiocyte load increases eIF-4F complex formation. To increase load in vitro, adult feline cardiocytes were electrically stimulated to contract (1 Hz, 5-ms pulses). eIF-4F complex formation, measured by eIF-4G association with eIF-4E, increased 57 ± 16% after 4 h of contraction compared with controls. eIF-4F complex formation did not increase on electrical stimulation with 2,3-butanedione monoxime (BDM), an inhibitor of active tension. Both insulin and phorbol ester increased eIF-4F complex formation, but these increases were unaffected by BDM. Insulin caused a shift of eIF-4E binding proteins (4E-BPs) into their hyperphosphorylated γ-isoforms and dissociation of 4E-BPs from eIF-4E. Rapamycin inhibited 4E-BP phosphorylation in response to insulin but had no effect on eIF-4F complex formation. Electrically stimulated contraction caused a partial shift of 4E-BP1 and 4E-BP2 into the γ-isoforms, but it had no effect on 4E-BP association with eIF-4E. Rapamycin blocked the increase in eIF-4F complex formation in electrically stimulated cardiocytes and depressed contractility. These data indicate that cardiocyte load causes a tension-dependent increase in eIF-4F complex formation that does not require dissociation of 4E-BPs from eIF-4E.
Radiotelemetric characterization of overweight-associated rises in blood pressure and heart rate
Authors: Rupp Heinz , Maisch Bernhard
Published: December 2017

We addressed the hypothesis that hypercaloric diets induce hyperkinetic hypertension irrespective of day-night cycle and locomotor activity that is associated with altered cardiac myosin isozymes. Normotensive rats with implanted radiotelemetry pressure transducers were fed increasing amounts of coconut fat (8, 16, and 24%, each for 2 wk) corresponding to 20–47% of total calories from fat. Thereafter, increasing amounts of sucrose (16, 32, and 50%) and fructose (50%) were added to the 24% fat diet corresponding to 13–40% of total calories from sugar. In contrast to the fat diets, the 32% and 50% sucrose diets as well as the 50% fructose diets increased ( P < 0.05) blood pressure (systolic maximum +13 mmHg, diastolic maximum +4 mmHg, mean maximum +7 mmHg) and heart rate (maximum +50 beats/min) irrespective of the day-night cycle and the unaltered locomotor activity. Furthermore, body weight increased ( P < 0.05) during the 32% and 50% sucrose feedings. The increased blood pressure and heart rate normalized after rats were fed a regular chow. We concluded that an excessive caloric intake results in hyperkinetic hypertension that increases the myosin V1proportion.
Brain “ouabain” and angiotensin II contribute to cardiac dysfunction after myocardial infarction
Authors: Leenen Frans H. H. , Yuan Baoxue , Huang Bing S.
Published: December 2017

In chronic heart failure (CHF), sympathetic activity increases in parallel with the impairment of left ventricle (LV) function, and sympathetic hyperactivity has been postulated to contribute to the progression of heart failure. In the brain, compounds with ouabain-like activity (“ouabain,” for brevity) and the renin-angiotensin system contribute to sympathetic hyperactivity in rats with CHF after myocardial infarction (MI). In the present studies, we assessed whether, in rats, chronic blockade of brain “ouabain” or the brain renin-angiotensin system inhibits the post-MI LV dysfunction. In rats, an MI was induced by acute coronary artery ligation. At either 0.5 or 4 wk post-MI, chronic treatment with Fab fragments for blocking brain “ouabain” or with losartan for blocking brain AT1 receptors was started and continued until 8 wk post-MI using osmotic minipumps connected to intracerebroventricular cannulas. At 8 wk post-MI, in conscious rats, LV pressures were measured at rest and in response to volume and pressure overload, followed by LV passive pressure-volume curves in vitro. At 8 wk post-MI, control MI rats exhibited clear increases in LV end-diastolic pressure (LVEDP) at rest and in response to pressure and volume overload. LV pressure-volume curves in vitro showed a marked shift to the right. Intravenous administration of the Fab fragments or losartan at rates used for central blockade did not affect these parameters. In contrast, chronic central blockade with either Fab fragments or losartan significantly lowered LVEDP at rest (only in 0.5- to 8-wk groups) and particularly in response to pressure or volume overload. LV dilation, as assessed from LV pressure-volume curves, was also significantly inhibited. These results indicate that chronic blockade of brain “ouabain” or brain AT1 receptors substantially inhibits development of LV dilation and dysfunction in rats post-MI.
Chronic dipyridamole therapy produces sustained protection against cardiac ischemia-reperfusion injury
Authors: Figueredo Vincent M. , Diamond Ivan , Zhou Hui-Zhong , Camacho S. Albert
Published: December 2017

Sustained protection against ischemia-reperfusion injury is not available for patients at risk for myocardial infarction who may require emergent reperfusion therapy. Whereas ischemic preconditioning and adenosinergic agents reduce myocardial injury, they are only effective when given immediately before ischemia or reperfusion. We recently found chronic ethanol exposure, an adenosine uptake inhibitor, produced sustained cardioprotection against ischemia-reperfusion injury. We now ask whether chronic dipyridamole therapy, a clinically usable nucleoside transport inhibitor, induces similar cardioprotection. Perfused hearts from guinea pigs, given dipyridamole (4 mg ⋅ kg−1⋅ day−1) in their water for 2–6 wk ( n= 10 for each group), underwent ischemia-reperfusion. Injury was assessed by recovery of left ventricular developed (LVDP) and end-diastolic (LVEDP) pressures and creatine kinase release. During reperfusion, hearts from dipyridamole-treated animals (6 wk) had 74% higher LVDP, 28% lower LVEDP, and 61% lower creatine kinase release versus controls. Adenosine A1-receptor antagonism (8-cyclopentyl-1,3-dipropylxanthine; 200 nM) abolished the protection of dipyridamole but A2antagonism (3,7-dimethyl-1-propargylxanthine; 10 mM) did not. Dipyridamole therapy produces sustained protection against ischemia-reperfusion injury in guinea pigs. This cardioprotection requires adenosine A1receptor signaling at the time of ischemia.
Altered central nervous system processing of baroreceptor input following hindlimb unloading in rats
Authors: Moffitt J. A. , Schadt J. C. , Hasser E. M.
Published: December 2017

The effect of cardiovascular deconditioning on central nervous system processing of baroreceptor afferent activity was evaluated following 14 days of hindlimb unloading (HU). Inactin-anesthetized rats were instrumented with catheters, renal sympathetic nerve electrodes, and aortic depressor nerve electrodes for measurement of mean arterial pressure, heart rate, renal sympathetic nerve activity (RSNA), and aortic depressor nerve activity (ADNA). Baroreceptor and baroreflex functions were assessed during infusion of phenylephrine and sodium nitroprusside. Central processing of baroreceptor afferent input was evaluated by linear regression relating RSNA to ADNA. The maximum baroreflex-elicited increase in RSNA was significantly reduced in HU rats (122 ± 3.8 vs. 144 ± 4.9% of baseline RSNA), whereas ADNA was not altered. The slope (−0.18 ± 0.04 vs. −0.40 ± 0.04) and y-intercept (121 ± 3.2 vs. 146 ± 4.3) of the linear regression relating increases in efferent RSNA to decreases in afferent ADNA during hypotension were significantly reduced in HU rats. There were no differences during increases in arterial pressure. Results demonstrate that the attenuation in baroreflex-mediated increases in RSNA following HU is due to changes in central processing of baroreceptor afferent information rather than aortic baroreceptor function.
Structural and mechanical factors influencing infarct scar collagen organization
Authors: Zimmerman Scott D. , Karlon William J. , Holmes Jeffrey W. , Omens Jeffrey H. , Covell James W.
Published: December 2017

Although large collagen fibers in myocardial infarct scar are highly organized, little is known about mechanisms controlling this organization. The preexisting extracellular matrix may act as a scaffold along which fibroblasts migrate. Conversely, deformation within the ischemic area could guide fibroblasts so new collagen is oriented to counteract the stretch. To investigate these potential mechanisms, we infarcted three groups of pigs. Group 1 served as infarct controls. Group 2 had the endocardium slit longitudinally to alter local systolic deformation. Group 3had a plug sectioned from ischemic tissue and rotated 90°. The slit altered systolic deformation in the infarcted tissue, changing circumferential strain from expansion to compression and increasing radial strain and shears and the variability of collagen fiber angles but not the mean angle. In the plug pigs, when deformation, matrix orientation, and continuity are altered in the infarct area, the result is complete disarray in the organization of collagen within the infarct scar.
Energetic effects of adenosine on vascular smooth muscle
Authors: Barron John T. , Gu Liping
Published: December 2017

Adenosine (Ado) is a naturally occurring compound that has several important cardiovascular actions, including activation of ATP-sensitive K+ channels in vascular smooth muscle, vasorelaxation, and an effect to alter glucose metabolism of cardiac muscle. The metabolic effects of Ado on vascular smooth muscle have not been defined and were examined in this study. Porcine carotid artery strips were incubated in the presence and absence of 0.5 mM Ado. Compared with the control, Ado had no effect on glucose uptake, glucose oxidation, or fatty acid (octanoate) oxidation. Ado suppressed glycolysis but enhanced glycogen synthesis. Relative to the rate of glycolysis, Ado increased lactate production. Ado stimulated O2 consumption by 52 ± 10%, altered the activities of the tricarboxylic acid cycle and malate-aspartate shuttle, and increased the content of ATP, ADP, AMP, and phosphocreatine. Alteration in the metabolic variables by Ado could not be attributed to diminished energy requirements of reduced resting muscle tone of the arterial strips. Relaxation of the arterial strips in response to Ado were abolished in arteries incubated under hypoxic conditions (95% N2-5% CO2). Hypoxia was associated with increased ADP content. It is concluded that Ado affected glucose metabolism indirectly. The metabolic and energetic effects of 0.5 mM Ado are mediated by alterations in the concentrations of AMP, ATP, and phosphorylation potential (ATP/ADP).
Tyrosine phosphorylation modulates arteriolar tone but is not fundamental to myogenic response
Authors: Spurrell Brian E. , Murphy Timothy V. , Hill Michael A.
Published: December 2017

The present study investigated the role of protein tyrosine phosphorylation in myogenic responsiveness of rat skeletal muscle arterioles. Arteriolar segments were cannulated and pressurized without intraluminal flow. All vessels studied developed spontaneous tone and demonstrated significant myogenic constriction to step changes in pressure with a resultant increase in myogenic tone over an intraluminal pressure range of 50–150 mmHg. Step increases in intraluminal pressure from 50 to 120 mmHg caused a rapid and sustained elevation in intracellular [Ca2+], as measured using fura 2. Vessels with myogenic tone dilated in response to tyrosine kinase inhibitors genistein (10 or 30 μM) and tyrphostin A47 (10 or 30 μM) and constricted to the tyrosine phosphatase inhibitor pervanadate (1 or 10 μM). Despite the dilator effect, myogenic reactivity was not blocked by the inhibitors. Daidzein (10 μM), a compound structurally similar to genistein but without tyrosine kinase-inhibiting activity, did not alter vessel tone or myogenic responses. Preincubation of arterioles with genistein or tyrphostin A47 did not significantly alter baseline arteriolar [Ca2+], and neither drug reduced the increase in [Ca2+] following an acute increase in intraluminal pressure. Constriction induced by pervanadate (10 μM) was not accompanied by a significant increase in intracellular [Ca2+], even though removal of extracellular Ca2+reversed the constriction. Examination of smooth muscle tyrosine phosphorylation, using a fluorescent phosphotyrosine antibody and confocal microscopy, showed that increased intraluminal pressure resulted in an increase in anti-phosphotyrosine fluorescence. Because manipulation of tyrosine kinase activity was found to alter vessel diameter, these data support a role for tyrosine phosphorylation in modulation of arteriolar tone. However, the results indicate that acute arteriolar myogenic constriction does not require tyrosine phosphorylation.
Expression of the β (slow)-isoform of MHC in the adult mouse heart causes dominant-negative functional effects
Authors: Tardiff Jil C. , Hewett Timothy E. , Factor Stephen M. , Vikstrom Karen L. , Robbins Jeffrey , Leinwand Leslie A.
Published: December 2017

α- and β-myosin heavy chain (MHC), the two MHC isoforms expressed in the mammalian heart, differ quantitatively in their enzymatic activities. The MHC composition of the heart can change dramatically in response to numerous stimuli, leading to the hypothesis that changes in cardiac function can be caused by myosin isoform shifts. However, this hypothesis has remained unproven because the stimuli used to generate these shifts are complex and accompanied by many additional physiological changes, including alterations in cardiac mass and geometry. Adult mouse ventricles normally express only α-MHC (the faster motor). To determine whether genetic alteration of the MHC isoform composition in the adult mouse heart would result in changes in cardiac chamber mass and contractility, we established transgenic mouse lines that express a Myc-tagged β-MHC molecule (the slower motor) in adult ventricular tissue, one of which expreses 12% of its myosin as the transgene. There is no evidence of hypertrophy, induction of hypertrophic markers, and no histopathology. Myofibrillar Ca2+-activated ATPase activity is decreased by 23%, and Langendorff preparations demonstrate a significant 15% decrease in systolic function in transgenic hearts. These results suggest that even small shifts in the myosin isoform composition of the myocardium can result in physiologically significant changes in cardiac contractility and could be relevant to cardiovascular disease.
Comparison of local and systemic effects of insulin on myocardial glucose extraction in ischemic heart disease
Authors: McNulty Patrick H.
Published: December 2017

Physiological increases in circulating insulin level significantly increase myocardial glucose uptake in vivo. To what extent this represents a direct insulin action on the heart or results indirectly from reduction in circulating concentrations of free fatty acids (FFA) is uncertain. To examine this, we measured myocardial glucose, lactate, and FFA extraction in 10 fasting men (ages 49–76 yr) with stable coronary artery disease during sequential intracoronary (10 mU/min, coronary plasma insulin = 140 ± 20 μU/ml) and intravenous (100 mU/min, systemic plasma insulin = 168 ± 26 μU/ml) insulin infusion. Basally, hearts extracted 2 ± 2% of arterial glucose and extracted 27 ± 6% of FFA. Coronary insulin infusion increased glucose extraction to 5 ± 3% ( P < 0.01 vs. basal) without changing plasma FFA or heart FFA extraction. Conversion to intravenous infusion lowered plasma FFA by ∼50% and heart FFA extraction by ∼75%, increasing heart glucose extraction still further to 8 ± 3% ( P < 0.01 vs. intracoronary). This suggests the increase in myocardial glucose extraction observed in response to an increment in systemic insulin concentration is mediated equally by a reduction in circulating FFA and by direct insulin action on the heart itself. Coronary insulin infusion increased myocardial lactate extraction as well (from 20 ± 10% to 29 ± 9%, P< 0.05), suggesting the local action may include stimulation of a metabolic step distal to glucose transport and glycolysis.
Protective effects of leukopenia and tissue plasminogen activator in microvascular ischemia-reperfusion injury
Authors: Bertuglia Silvia , Colantuoni Antonio
Published: December 2017

Ischemia shifts the anticoaugulant/procoagulant balance of the endothelium in favor of activation of coagulation. We studied whether cheek pouch microcirculation of leukopenic hamsters was protected by tissue plasminogen activator (tPA) (50 μg/100 g body wt) against ischemia-reperfusion injury. Adherent leukocytes, total perfused capillary length (PCL), permeability increase, and arteriolar and venular red blood cell (RBC) velocity were investigated by fluorescence microscopy. Measurements were made at control, 30 or 60 min of ischemia, and at 30 or 60 min of reperfusion. Hamsters were made leukopenic by treatment with cyclophosphamide (20 mg/100 g body wt ip, 4 days before the experiment), which decreased circulating leukocyte count by 85–90%. Leukopenic hamsters undergoing 30 min of ischemia followed by 30 min of reperfusion showed no significant decrease in PCL or increased permeability. Leukopenic hamsters undergoing 60 min of ischemia followed by 60 min of reperfusion presented a significant decrease in microvascular perfusion where PCL was 28 ± 7% of baseline, low-flow conditions, and increased permeability. In leukopenic hamsters treated with tPA there was complete protection of capillary perfusion with no significant changes in permeability or arteriolar and venular RBC velocity. In conclusion, thrombus formation may be an additional and independent factor that with leukocyte-mediated mechanisms determines ischemia-reperfusion injury.
Platelet-activating factor receptors in lamb lungs are downregulated immediately after birth
Authors: Ibe Basil O. , Sander Fred C. , Raj J. Usha
Published: December 2017

Platelet-activating factor (PAF) is a phospholipid with diverse biological functions mediated by a G protein-coupled receptor. We determined PAF receptor binding in lung membranes of four groups of perinatal lambs. Membrane protein (100 μg/ml) was incubated for 60 min at 30°C with 0.5–24 nM of acetyl-[3H]PAF in 30 mM Tris buffer, pH 7.2, containing 0.25% BSA, 10 mM MgCl2, and 125 mM choline chloride. PAF bound to membrane was isolated and quantified by scintillation spectrometry, followed with Scatchard analysis for receptor density (Bmax). The Bmax(means ± SE, fmol/mg protein) were 445.8 ± 12.3, 244.2 ± 3.3, 250.6 ± 3.6, and 419.9 ± 8.6 for the fetal, 90-min-old, <1-day-old, and 6- to 12-day-old lambs, respectively. The Bmaxfor the 90-min-old and <1-day-old lambs were not different but were significantly lower than those of either the term fetal or 6- to 12-day-old lambs. These data show a significant decrease in PAF binding to its receptor and in PAF Bmaxin lung membranes of immediate newborn lambs. The dissociation constants ( KD, nM) were 7.7 ± 0.52, 11.5 ± 0.34, 6.9 ± 0.48, and 5.0 ± 0.53 for fetal, 90-min-old, <1-day-old, and 6- to 12-day-old newborn lamb lungs, respectively. The KDof the 90-min-old lamb was the highest of all. PAF receptor gene measured by RT-PCR showed a significant downregulation of PAF receptor gene mRNA in lungs of lambs <1 day old, suggesting a transcriptional regulation of PAF receptor gene expression in the immediate newborn period. We speculate that decreased PAF receptor binding immediately after birth will facilitate the fall in pulmonary vascular resistance in the immediate newborn period.
Preeclamptic pregnancy is associated with increased sympathetic and decreased parasympathetic control of HR
Authors: Yang Cheryl C. H. , Chao Te-Chang , Kuo Terry B. J. , Yin Chang-Sheng , Chen Hsing I.
Published: December 2017

Previous work from our laboratory using heart rate variability (HRV) has demonstrated that women before menopause have a more dominant parasympathetic and less effective sympathetic regulations of heart rate compared with men. Because it is still not clear whether normal or preeclamptic pregnancy coincides with alternations in the autonomic functions, we evaluated the changes of HRV in 17 nonpregnant, 17 normotensive pregnant, and 11 preeclamptic women who were clinically diagnosed without history of diabetic neuropathy, cardiac arrhythmia, and other cardiovascular diseases. Frequency-domain analysis of short-term, stationary R-R intervals was performed to evaluate the total variance, low-frequency power (LF; 0.04–0.15 Hz), high-frequency power (HF; 0.15–0.40 Hz), ratio of LF to HF (LF/HF), and LF in normalized units (LF%). Natural logarithm transformation was applied to variance, LF, HF, and LF/HF for the adjustment of the skewness of distribution. We found that the normal pregnant group had a lower R-R value and HF but had a higher LF/HF and LF% compared with the nonpregnant group. The preeclamptic group had lower HF but higher LF/HF compared with either the normal pregnant or nonpregnant group. Our results suggest that normal pregnancy is associated with a facilitation of sympathetic regulation and an attenuation of parasympathetic influence of heart rate, and such alterations are enhanced in preeclamptic pregnancy.
Nitric oxide produced via neuronal NOS may impair vasodilatation in septic rat skeletal muscle
Authors: Gocan Nigel C. , Scott Jeremy A. , Tyml Karel
Published: December 2017

Impaired vascular responsiveness in sepsis may lead to maldistribution of blood flow in organs. We hypothesized that increased production of nitric oxide (NO) via inducible nitric oxide synthase (iNOS) mediates the impaired dilation to ACh in sepsis. Using a 24-h cecal ligation and perforation (CLP) model of sepsis, we measured changes in arteriolar diameter and in red blood cell velocity ( VRBC) in a capillary fed by the arteriole, following application of ACh to terminal arterioles of rat hindlimb muscle. Sepsis attenuated both ACh-stimulated dilation and VRBCincrease. In control rats, arteriolar pretreatment with the NO donors S-nitroso- N-acetylpenicillamine or sodium nitroprusside reduced diameter and VRBCresponses to a level that mimicked sepsis. In septic rats, arteriolar pretreatment with the “selective” iNOS blockers aminoguanidine (AG) or S-methylisothiourea sulfate (SMT) restored the responses to the control level. The putative neuronal NOS (nNOS) inhibitor 7-nitroindazole also restored the response toward control. At 24-h post-CLP, muscles showed no reduction of endothelial NOS (eNOS), elevation of nNOS, and, surprisingly, no induction of iNOS protein; calcium-dependent constitutive NOS (eNOS+nNOS) enzyme activity was increased whereas calcium-independent iNOS activity was negligible. We conclude that 1) AG and SMT inhibit nNOS activity in septic skeletal muscle, 2) NO could impair vasodilative responses in control and septic rats, and 3) the source of increased endogenous NO in septic muscle is likely upregulated nNOS rather than iNOS. Thus agents released from the blood vessel milieu (e.g., NO produced by skeletal muscle nNOS) could affect vascular responsiveness.
Role of intracellular Ca2+ release in histamine-induced depolarization in rabbit middle cerebral artery
Authors: Gokina N. I. , Bevan J. A.
Published: December 2017

The role of Ca2+ mobilization from intracellular stores and Ca2+-activated Cl− channels in caffeine- and histamine-induced depolarization and contraction of the rabbit middle cerebral artery has been studied by recording membrane potential and isometric force. Caffeine induced a transient contraction and a transient followed by sustained depolarization. The transient depolarization was abolished by ryanodine, DIDS, and niflumic acid, suggesting involvement of Ca2+-activated Cl− channels. Histamine-evoked transient contraction in Ca2+-free solution was abolished by ryanodine or by caffeine-induced depletion of Ca2+ stores. Ryanodine slowed the development of depolarization induced by histamine in Ca2+-containing solution but did not affect its magnitude. In arteries treated with 1 mM Co2+, histamine elicited a transient depolarization and contraction, which was abolished by ryanodine. DIDS and niflumic acid reduced histamine-evoked depolarization and contraction. Histamine caused a sustained depolarization and contraction in low-Cl− solution. These results suggest that Ca2+ mobilization from ryanodine-sensitive stores is involved in histamine-induced initial, but not sustained, depolarization and contraction. Ca2+-activated Cl− channels contribute mainly to histamine-induced initial depolarization and less importantly to sustained depolarization, which is most likely dependent on activation of nonselective cation channels.
Coexpression with β1-subunit modifies the kinetics and fatty acid block of hH1αNa+channels
Authors: Xiao Yong-Fu , Wright Sterling N. , Wang Ging Kuo , Morgan James P. , Leaf Alexander
Published: December 2017

Voltage-gated cardiac Na+channels are composed of α- and β1-subunits. In this study β1-subunit was cotransfected with the α-subunit of the human cardiac Na+channel (hH1α) in human embryonic kidney (HEK293t) cells. The effects of this coexpression on the kinetics and fatty acid-induced suppression of Na+currents were assessed. Current density was significantly greater in HEK293t cells coexpressing α- and β1-subunits ( INa,αβ) than in HEK293t cells expressing α-subunit alone ( INa,α). Compared with INa,α, the voltage-dependent inactivation and activation of INa,αβwere significantly shifted in the depolarizing direction. In addition, coexpression with β1-subunit prolonged the duration of recovery from inactivation. Eicosapentaenoic acid [EPA, C20:5(n–3)] significantly reduced INa,αβin a concentration-dependent manner and at 5 μM shifted the midpoint voltage of the steady-state inactivation by −22 ± 1 mV. EPA also significantly accelerated channel transition from the resting state to the inactivated state and prolonged the recovery time from inactivation. Docosahexaenoic acid [C22:6(n–3)], α-linolenic acid [C18:3(n–3)], and conjugated linoleic acid [C18:2(n–6)] at 5 μM significantly inhibited both INa,αβand INa,α.In contrast, saturated and monounsaturated fatty acids had no effects on INa,αβ. This finding differs from the results for INa,α, which was significantly inhibited by both saturated and unsaturated fatty acids. Our data demonstrate that functional association of β1-subunit with hH1αmodifies the kinetics and fatty acid block of the Na+channel.
Hypotonic stress-induced dual Ca2+responses in bovine aortic endothelial cells
Authors: Oike Masahiro , Kimura Chiwaka , Koyama Tetsuya , Yoshikawa Miyuki , Ito Yushi
Published: December 2017

We have investigated the effects of hypotonic stress on intracellular calcium concentration ([Ca2+]i) in bovine aortic endothelial cells. Reducing extracellular osmolarity by 5% to 40% elicited a steep Ca2+transient both in normal Krebs and Ca2+-free solutions. The hypotonic stress-induced Ca2+transient was inhibited by phospholipase C inhibitors (neomycin and U-73122), a P2-receptor antagonist (suramin), and an ATP-hydrolyzing enzyme (apyrase), suggesting that the hypotonic stress-induced Ca2+transient is mediated by ATP. A luciferin-luciferase assay confirmed that 40% hypotonic stress released 91.0 amol/cell of ATP in 10 min. When the hypotonic stress-induced fast Ca2+transient was inhibited by neomycin, suramin, or apyrase, a gradual [Ca2+]iincrease was observed instead. This hypotonic stress-induced gradual [Ca2+]iincrease was inhibited by a phospholipase A2inhibitor, 4-bromophenacyl bromide. Furthermore, exogenously applied arachidonic acid induced a gradual [Ca2+]iincrease with an ED50of 13.3 μM. These observations indicate that hypotonic stress induces a dual Ca2+response in bovine aortic endothelial cells, i.e., an ATP-mediated fast Ca2+transient and an arachidonic acid-mediated gradual Ca2+increase, the former being the predominant response in normal conditions.
Inhibition by nickel of the L-type Ca channel in guinea pig ventricular myocytes and effect of internal cAMP
Authors: Hobai Ion A. , Hancox Jules C. , Levi Allan J.
Published: December 2017

The characteristics of nickel (Ni) block of L-type Ca current ( I Ca,L) were studied in whole cell patch-clamped guinea pig cardiac myocytes at 37°C in the absence and presence of 100 μM cAMP in the pipette solution. Ni block of peak I Ca,L had a dissociation constant ( K d) of 0.33 ± 0.03 mM in the absence of cAMP, whereas in the presence of cAMP, the K d was 0.53 ± 0.05 mM ( P = 0.006). Ni blocked Ca entry via Ca channels (measured as I Ca,L integral over 50 ms) with similar kinetics ( K d of 0.35 ± 0.03 mM in cAMP-free solution and 0.30 ± 0.02 mM in solution with cAMP, P = not significant). Under both conditions, 5 mM Ni produced a maximal block that was complete for the first pulse after application. Ni block of I Ca,L was largely use independent. Ni (0.5 mM) induced a positive shift (4 to 6 mV) in the activation curve of I Ca,L. The block of I Ca,L by 0.5 mM Ni was independent of prepulse membrane potential (over the range of −120 to −40 mV). Ni (0.5 mM) also induced a significant shift in I Ca,Linactivation: by 6 mV negative in cAMP-free solution and by 4 mV positive in cells dialyzed with 100 μM cAMP. These data suggest that, in addition to blocking channel conductance by binding to a site in the channel pore, Ni may bind to a second site that influences the voltage-dependent gating of the L-type Ca channel. They also suggest that Ca channel phosphorylation causes a conformational change that alters some effects of Ni. The results may be relevant to excitation-contraction coupling studies, which have employed internal cAMP dialysis, and where Ni has been used to block I Ca,L and Ca entry into cardiac cells.
Phorbol ester stimulates cyclooxygenase-2 expression and prostanoid production in cardiac myocytes
Authors: Schuette Ralph , LaPointe Margot C.
Published: December 2017

Phorbol-12-myristate- 13-acetate (PMA) has been shown to induce hypertrophy of cardiac myocytes. The prostaglandin endoperoxide H synthase isoform 2 (cyclooxygenase-2, COX-2) has been associated with enhanced growth and/or proliferation of several types of cells. Thus we studied whether PMA induces COX-2 and prostanoid products PGE2and PGF2αin neonatal ventricular myocytes and whether endogenous COX-2 products participate in their growth. In addition, we examined whether PMA affects interleukin-1β (IL-1β) stimulation of COX-2 and PGE2production. PMA (0.1 μmol/l) stimulated growth, as indicated by a 1.6-fold increase in [3H]leucine incorporation. PMA increased COX-2 protein levels 2.8-fold, PGE23.7-fold, and PGF2α2.9-fold. Inhibition of either p38 kinase or protein kinase C (PKC) prevented PMA-stimulated COX-2. Inhibition of COX-2 with either indomethacin or NS-398 had no effect on PMA-stimulated [3H]leucine incorporation. Exogenous administration of PGF2α, but not PGE2, stimulated protein synthesis. Treatment with IL-1β (5 ng/ml) increased COX-2 protein levels 42-fold, whereas cotreatment with IL-1β and PMA stimulated COX-2 protein only 32-fold. IL-1β did not affect control or PMA-stimulated protein synthesis. These findings indicate that: 1) PMA, acting through PKC and p38 kinase, enhances COX-2 expression, but chronic treatment with PMA partially inhibits IL-1β stimulation of COX-2; and 2) exogenous PGF2αis involved in neonatal ventricular myocyte growth but endogenous COX-2 products are not.
Does autonomic blockade reveal a potent contribution of nitric oxide to locomotion-induced vasodilation?
Authors: Sheriff Don D. , Nelson Christopher D. , Sundermann Ryan K.
Published: December 2017

We sought to test the role of nitric oxide (NO) in governing skeletal muscle (iliac) vascular conductance during treadmill locomotion in dogs ( n = 6; 3.2 and 6.4 km/h at 0% grade, and 6.4 km/h at 10% grade). As seen previously, the increase in muscle vascular conductance accompanying treadmill locomotion was little influenced by NO synthase inhibition alone with N ω-nitro-l-arginine methyl ester (l-NAME, 10 mg/kg iv), but the absolute value of conductance achieved during locomotion was reduced. Such ambiguous results provide an unclear picture regarding the importance of NO during locomotion. However, muscle vasodilation is normally restrained by the sympathetic system during locomotion. Thus a significant contribution by NO to the increase in vascular conductance that accompanies locomotion could be masked by partial withdrawal of the competing influence of sympathetic vasoconstrictor nerve activity secondary to the rise in arterial pressure following systemicl-NAME administration. To test this possibility, we compared the rise in muscle vascular conductance before and afterl-NAME treatment while ganglionic transmission was blocked by hexamethonium. Under these conditions, l-NAME significantly reduced both the rise in vascular conductance (by 32%, P < 0.001) and the absolute level of vascular conductance (by 30%, P < 0.001) achieved during locomotion with no effect on blood flow. Thus augmented NO production normally provides a significant drive to relax vascular smooth muscle in active skeletal muscle during locomotion. Potential deficits stemming from the absence of NO following l-NAME treatment are masked by less intense sympathetic restraint when autonomic function is intact.
Phenotypic screening for heart rate variability in the mouse
Authors: Gehrmann Josef , Hammer Peter E. , Maguire Colin T. , Wakimoto Hiroko , Triedman John K. , Berul Charles I.
Published: December 2017

We developed a technology for heart rate (HR) variability (HRV) analysis in the mouse for characterization of HR dynamics, modulated by vagal and sympathetic activity. The mouse is the principal animal model for studying biological processes. Mouse strains are now available harboring gene mutations providing fundamental insights into molecular mechanisms underlying cardiac electrical diseases. Future progress depends on enhanced understanding of these fundamental mechanisms and the implementation of methods for the functional analysis of mouse cardiovascular physiology. By telemetric techniques, standard time and frequency-domain measures of HRV were computed with and without autonomic blockade, and baroreflex sensitivity testing was performed. HR modulation in the high-frequency component is predominantly mediated by the parasympathetic nervous system, whereas the low-frequency component is under the influence of both the parasympathetic and sympathetic systems. The presented technology and protocol allow for assessment of autonomic regulation of the murine HR. Phenotypic screening for HR regulation in mice will further enhance the value of the mouse as a model of heritable electrophysiological human disease.
Determination of EETs using microbore liquid chromatography with fluorescence detection
Authors: Nithipatikom Kasem , Pratt Phillip F. , Campbell William B.
Published: December 2017

Epoxyeicosatrienoic acids (EETs) are cytochrome P-450 metabolites of arachidonic acid involved in the regulation of vascular tone. The method of microbore column high-performance liquid chromatography with fluorescence detection was developed to determine 14,15-EET, 11,12-EET, and the mixture of 8,9-EET and 5,6-EET. Tridecanoic acid (TA) was used as an internal standard. EETs were reacted with 2-(2,3-naphthalimino)ethyl trifluoromethanesulfonate (NT) to form highly fluorescent derivatives. A C18microbore column and a water-acetonitrile mobile phase were used for separation. Samples were excited at 259 nm, and the fluorescence was detected at 395 nm. The overall recoveries were 88% for EETs and 40% for TA. EETs were detected in concentrations as low as 2 pg (signal-to-noise ratio = 3). The method was used to determine the EET production from endothelial cells (ECs). Bradykinin and methacholine (10−6M) stimulated an increase in the production of EETs by ECs two- and fivefold, respectively. This sensitive method may be used for determination of EETs at low concentrations normally detected in complex biological samples.
Coronary microvascular endothelial cells cosecrete angiotensin II and endothelin-1 via a regulated pathway
Authors: Kusaka Yasuko , Kelly Ralph A. , Williams Gordon H. , Kifor Imre
Published: December 2017

Although endothelial cells produce angiotensin II (ANG II) and endothelin-1 (ET-1), it is not clear whether a single cell produces both peptides, with cosecretion in response to stimulation, or whether different subpopulations of endothelial cells secrete one or the other peptide, with secretion in response to different stimuli. Exposure of cultured coronary microvascular endothelial cells to cycloheximide for 60 min had no effect on ANG II or ET-1 secretion. This result suggested the existence of a preformed intracellular pool of ANG II and ET-1, which is a precondition for regulated secretion. Exposure of endothelial cells to isoproterenol, high extracellular potassium, or cadmium, all of which stimulate peptide secretion via different signaling pathways, significantly ( P > 0.001) increased the secretion of both ANG II and ET-1 in a cell size-dependent manner. Sodium nitroprusside and S-nitroso- N-acetyl penicillamine significantly ( P > 0.001) decreased ANG II and ET-1 secretion, whereas Nω-nitro-l-arginine-methyl ester enhanced it. The similar regulation of ANG II and ET-1 secretion and the presence of both peptides around individual endothelial cells indicate that the autocrine/paracrine regulation of cardiovascular function by endothelial cells is accomplished via cosecretion of ANG II and ET-1.
New optical method for analyzing cortical blood flow heterogeneity in small animals: validation of the method
Authors: Schiszler Istvan , Tomita Minoru , Fukuuchi Yasuo , Tanahashi Norio , Inoue Koji
Published: December 2017

In pentobarbital-anesthetized male Sprague-Dawley rats, a small cranial window was trephined, and the cortex was transilluminated with a fine glass fiber inserted into the brain parenchyma. The light intensity at the surface area of 2 × 2 mm was recorded during intracarotid injection of 25 μl of carbon black (CB) solution. The region of interest (ROI) was divided into a 50 × 50 matrix, and the mean transit time of CB transport was calculated in each matrix element. We found rapid transits of CB along the microvasculature, with considerable heterogeneity in the avascular area, and heterogeneous efficiency in autoregulatory capacity in the ROI during hypotension. The method was validated by comparison with laser-Doppler flowmetry. The average mean difference was 0.03 ± 0.05%. Five percent CO2 inhalation increased the flow by 85%, but heterogeneously. We concluded that the technique is exclusively sensitive to indicator transits in a very small area on the brain surface with potential usefulness in detecting regional heterogeneity in blood flow.