bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of T- and L-type Ca2+ currents in shark ventricular myocytes
Authors: Maylie J. , Morad M.
Published: December 2017

Two types of Ca2+ currents with characteristics of T- and L-type Ca2+ currents were recorded in ventricular myocytes of dogfish (Squalus acanthias). The T-type Ca2+ current activated near -70 mV and had a peak current density of 9.8 pA/pF at -34 mV. The L-type Ca2+ current activated near -50 mV and had a peak current density of 10.6 pA/pF near 0 mV. The threshold for activation of the T-type Ca2+ current was 20 mV negative to that of the tetrodotoxin-sensitive Na+ current. Inactivation of the T-type Ca2+ current was rapid with a limiting time constant of 5 ms at positive potentials. The T-type Ca2+ current was not modulated by isoproterenol or acetylcholine. In dogfish the T-type Ca2+ channel has current densities equivalent to the L-type channel and is likely to activate before the Na+ channel, contributing significantly to generation of the foot of the action potential.
Conducted vasodilation elevates flow in arteriole networks of hamster striated muscle
Authors: Kurjiaka D. T. , Segal S. S.
Published: December 2017

Our purpose was to investigate blood flow responses to local and conducted vasodilation in arteriole networks supplying the cremaster muscle of anesthetized (pentobarbital sodium) male hamsters. We tested the hypothesis that with local release of a vasodilator onto an arteriole segment, conduction is necessary to increase arteriolar perfusion. The tips (OD, 1-2 microns) of micropipettes containing acetylcholine (ACh; 1.0 M) or sodium nitroprusside (NP; 0.2 M) were positioned approximately 1 mm distal to the origin of a 3A arteriole (resting diameter, 16 +/- 2 microns) originating at a "Y" bifurcation. Responses were monitored (n = 9) at the site of release (local) and at three upstream locations: at the vessel origin, in the parent (2A) arteriole (diameter, 24 +/- 3 microns), and in the paired (3A) daughter branch (diameter, 17 +/- 3 microns). At each upstream site, diameter and red blood cell velocity (Vrbc) were quantified at rest and during the peak of diameter responses; these variables were used to calculate blood flow and wall shear rate (WSR). Microiontophoresis (1 mA, 500 ms) of ACh increased local diameter by 13 +/- 4 microns (P < 0.05); vasodilation was conducted to each of the upstream sites (typical magnitude, 4-6 microns; P < 0.05). Blood flow into branches increased 25-80% above corresponding values at rest without changing Vrbc; thus WSR consistently decreased with dilation (P < 0.05). Microiontophoresis of NP induced similar dilation locally yet had no effect on diameter, blood flow, or WSR in network branches. Thus dilation of a distal arteriole segment alone had no effect on muscle blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)
Fructose-1,6-diphosphate or adenosine attenuate leukocyte adherence in postischemic skeletal muscle
Authors: Akimitsu T. , White J. A. , Carden D. L. , Gute D. C. , Korthuis R. J.
Published: December 2017

The purpose of this study was to determine whether fructose-1,6-diphosphate (FDP) or adenosine (Ado), administered at the onset of reperfusion, would prevent ischemia/reperfusion (I-R)-induced leukocyte adherence and microvascular dysfunction in skeletal muscle. Changes in vascular permeability and tissue neutrophil content were assessed by measurement of the solvent drag reflection coefficient (delta) for total plasma proteins and muscle myeloperoxidase (MPO) activity, respectively, in continuously perfused, isolated canine gracilis muscles and in muscles subjected to I-R alone, I-R + FDP, and I-R + Ado. To determine whether FDP or Ado would attenuate leukocyte-endothelial cell adhesive interactions induced by I-R, leukocyte adherence and emigration were assessed in postischemic mouse cremaster muscles, using intravital microscopy in the presence and absence of FDP or Ado during reperfusion. I-R was associated with a marked increase in microvascular permeability and muscle MPO activity relative to nonischemic controls. These increases were attenuated by FDP and Ado. I-R also increased the number of adherent and emigrated leukocytes relative to control. I-R-induced leukocyte adherence and emigration were significantly attenuated by either FDP or Ado. These results indicate that FDP and Ado attenuate postischemic microvascular barrier dysfunction in skeletal muscle by a mechanism that may be related to their ability to inhibit leukocyte adhesion and emigration.
NMR spectroscopy studies of severe hypokalemia in isolated rat hearts
Authors: Peterson E. W. , Chen K. G. , Elkins N. , Hutchison R. B. , Shapiro J. I.
Published: December 2017

Effects of acute tissue potassium depletion on cellular energy metabolism are poorly understood. To examine this issue, we performed the following studies in an isovolumic isolated perfused heart preparation. Perfusion of isolated hearts with media lacking potassium (K = 0 mmol/l) for 30 min resulted in ventricular fibrillation, rapid decreases in creatine phosphate (PCr) and ATP, and increases in Pi. During reinstitution of normal perfusate potassium, hearts did not resume normal contractions, and no increases in tissue ATP were observed. However, some normalization of PCr and Pi were noted during reinstitution of normal perfusate. Perfusion with media containing K = 2 mmol/l caused significant but less dramatic decreases in tissue ATP concentrations than perfusion with media containing K = 0 mmol/l. Reduction of perfusate calcium from 1.2 (normal) to 0.6 mmol/l in media containing K = 0 mmol/l attenuated the fall in ATP seen with media containing K = 0 mmol/l. Conversely, increasing perfusate calcium to 2.4 mmol/l in media containing K = 2 mmol/l markedly worsened the fall in tissue ATP seen in media containing K = 2 mmol/l. In this subgroup (K = 2 mmol/l, Ca = 2.4 mmol/l), ventricular fibrillation developed approximately one-half of the time. However, no differences in the rate of ATP fall were observed between those hearts that fibrillated and those that did not. During perfusion with media containing K = 0 mmol/l, nuclear magnetic resonance (NMR)-visible tissue potassium concentrations fell rapidly and dramatically. Significant but less severe reductions in NMR-visible potassium were seen during perfusion with media containing K = 2 mmol/l. With K = 2 mmol/l perfusate, the rate of cellular potassium loss was influenced by perfusate calcium concentration. When cardiac mitochondria were examined after perfusion with media containing K = 0 mmol/l, evidence for calcium loading as well as respiratory dysfunction was noted. These data indicate that reductions in perfusate potassium caused dramatic reductions in tissue ATP and NMR-visible potassium concentrations. The abnormal energy metabolism that results from acute cellular potassium depletion appears to be due, at least in part, to impaired energy production by cardiac mitochondria that become calcium loaded.
Reciprocal regulation of endothelin-1 and endothelial constitutive NOS in proliferating endothelial cells
Authors: Flowers M. A. , Wang Y. , Stewart R. J. , Patel B. , Marsden P. A.
Published: December 2017

The expression of endothelin-1 (ET-1) and endothelial constitutive nitric oxide synthase (ecNOS) was assessed in two independent in vitro models: asynchronously differentially proliferating cultures and wounded endothelial cell monolayers. Northern blot analysis of RNA isolated from preconfluent, confluent, and postconfluent cells revealed a fourfold rise in ET-1 mRNA transcripts, whereas levels of ecNOS mRNA transcripts were reduced twofold in proliferating cells. Nuclear run-off analysis demonstrated that increased steady-state ET-1 mRNA content in proliferating cells was mediated, in part, by increased gene transcription. In contrast, ecNOS transcription rates in proliferating cells were not decreased compared with quiescent nonproliferating cells, indicating that mRNA destabilization mediated the decreased ecNOS mRNA levels in proliferating endothelium. Concordant changes in protein expression were documented for both ET-1 and ecNOS. In injured endothelial cell monolayers, in situ cRNA hybridization demonstrated increased mRNA transcript levels for ET-1 in growth fronts of injured endothelial monolayers. These data are taken to indicate that expression of ET-1 and ecNOS is reciprocally regulated in two different models of endothelial cell proliferation.
Relationship between PVA and myocardial oxygen consumption can be derived from thermodynamics
Authors: Denslow S.
Published: December 2017

The pressure-volume area (PVA) has been shown to be an excellent, linear index of myocardial oxygen consumption. The thermodynamic basis for this result, however, has not been elucidated. The present study was undertaken to determine what information could be gained from analyzing the cardiac pressure-volume (P-V) cycle as an approximation to some "ideal" thermodynamic cycle operating under the constraints imposed by cardiovascular anatomy and physiology. The myocardium was approximated as a linear, chemically driven elastance in accordance with the time-varying elastance model. Analysis provided descriptions of a Carnot cycle for myocardium and a suboptimal ideal cycle, including isovolumic phases. Further analysis of the ideal cycle indicated that the end-systolic P-V relationship (ESPVR) is an approximation to the adiabatic P-V trajectory that primarily determines total energy consumption. Analysis also indicated possible explanations of current results that seem to be at odds with the time-varying elastance model. These results suggest that thermodynamic cycle analysis may provide a useful analytic tool for investigation of the cardiac cycle.
Myocardial VO2 of mechanically unloaded contraction of rat ventricular slices measured by a new approach
Authors: Yasuhara S. , Takaki M. , Kikuta A. , Ito H. , Suga H.
Published: December 2017

We instituted a new approach of measuring mechanically unloaded myocardial oxygen consumption (VO2) by using rat left ventricular (LV) slices in an air-tight chamber filled with oxygenated Tyrode solution. Myocardial slices (300 microns in thickness) freely shortened without external load by electrical field stimulation (St). VO2 without St (n = 6) was 1.69 +/- 0.41 ml O2.min-1.100 g LV-1. VO2 with St (n = 6) increased to 2.28 +/- 0.36 ml O2.min-1.100 g LV-1. VO2 in Ca(2+)-free Tyrode solution irrespective of St was nearly equal to VO2 without St in normal Tyrode solution, indicating that all these VO2 correspond to basal metabolic VO2. The increment in VO2 by St (delta VO2) increased up to twice normal with the extracellular Ca2+ concentration up to 4 times normal. Inhibition of cross-bridge cycling by 2,3-butanedione monoxime (5 and 10 mM) did not decrease delta VO2. These results suggest that delta VO2 consists of VO2 primarily for excitation-contraction coupling but not for cross-bridge cycling.
Systemic and subcutaneous microvascular Po2 dissociation during 4-h hemorrhagic shock in conscious hamsters
Authors: Kerger H. , Saltzman D. J. , Menger M. D. , Messmer K. , Intaglietta M.
Published: December 2017

The relationship between systemic and microvascular Po2 in subcutaneous connective tissue and hemodynamics was investigated during 4-h hemorrhagic shock (40 mmHg) in conscious Syrian hamsters (n = 66) fitted with a dorsal skinfold window. Systemic blood gases, metabolic parameters, arteriolar, venular, and tissue Po2, microvascular red blood cell velocity, and blood flow were evaluated in survivors (S) and nonsurvivors (NS). Surviving animals were resuscitated with shed blood. Microvascular and tissue Po2 were measured by phosphorescence decay of Pd-meso-tetra (4-carboxyphenyl) porphyrin (30 mg/kg body wt iv). Shock caused a significant dissociation between systemic arterial and microvascular arteriolar Po2 levels. Arterial Po2 increased from 59.7 +/- 12.0 to 110.8 +/- 19.7 mmHg (S) and from 64.0 +/- 13.7 to 128.5 +/- 10.1 mmHg (NS), whereas Po2 in large arterioles decreased from 56.9 +/- 5.5 (control) to 29.5 +/- 20.1 (S) and 6.0 +/- 5.7 mmHg (NS). Correspondingly, tissue Po2 fell from 24.1 +/- 6.8 (control) to 0.9 +/- 0.6 (S) and 0.4 +/- 0.3 mmHg (NS). Venous Po2 decreased from 28.8 +/- 3.7 to 20.4 +/- 4.1 (S) and from 28.0 +/- 2.9 to 16.3 +/- 0.5 mmHg (NS). Shock outcome and tissue oxygenation were predicted by arterial blood gases and metabolic and microcirculatory conditions but not by central venous Po2.
Novel recombinant serpin, LEX-032, attenuates myocardial reperfusion injury in cats
Authors: Delyani J. A. , Murohara T. , Lefer A. M.
Published: December 2017

We studied the potential cardioprotective effects of the novel recombinant serine protease inhibitor (serpin), LEX-032, which inhibits the serine proteases elastase and cathepsin G. LEX-032 is a recombinant construct of human alpha 1-antichymotrypsin in which six amino acid residues were replaced around the active center with those of human alpha 1-protease inhibitor. Cats were subjected to 90 min of left anterior descending coronary artery (LAD) occlusion and 270 min of reperfusion (MI/R). Either LEX-032 or its vehicle (i.e., phosphate-buffered saline) was administered intravenously 10 min before reperfusion. Control cats were subjected to sham MI/R. Cats treated with LEX-032 demonstrated a marked reduction in cardiac necrosis after MI/R compared with cats receiving only vehicle (10 +/- 3 vs. 31 +/- 3%, P < 0.01). In addition, relaxation of LAD rings to the endothelium-dependent dilators (e.g., acetylcholine and A23187) was greater in the LEX-032-treated group than in cats receiving vehicle (72 +/- 5 vs. 52 +/- 7%, P < 0.05, and 74 +/- 8 vs. 50 +/- 8%, P < 0.05, respectively), indicating that endothelial function was preserved by LEX-032. Moreover, LEX-032 administration resulted in a marked reduction of polymorphonuclear leukocyte (PMN) adherence to ex vivo coronary vascular endothelium compared with vehicle (33 +/- 4 vs. 86 +/- 7 PMNs/mm2, P < 0.01). These data indicate that LEX-032 is a significant cardioprotective agent exerting its protective effect by inhibition of PMN-mediated cellular injury, and this agent represents a novel means of attenuating PMN-mediated reperfusion injury.
Receptor-mediated transcytosis of transferrin through blood-brain barrier endothelial cells
Authors: Descamps L. , Dehouck M. P. , Torpier G. , Cecchelli R.
Published: December 2017

A cell culture model of the blood-brain barrier consisting of a coculture of bovine brain capillary endothelial cells (BBCECs) and astrocytes has been used to examine the mechanism of iron transport to the brain. Binding experiments showed that BBCECs express 35,000 high-affinity (concn at 50% receptor saturation = 11.3 +/- 2.1 nM) transferin (Tf) receptors per cell. In contrast to apo-transferrin (apoTf) we observed a specific transport of holo-transferrin (holoTf) across BBCECs. This transport was inhibited completely at low temperature. Moreover, the anti-Tf receptor antibody (OX-26) competitively inhibited holoTf uptake by BBCECs. Pulse-chase experiments demonstrated that only 10% of Tf was recycled to the luminal side of the cells, whereas the majority of Tf was transcytosed to the abluminal side; double-labeling experiments clearly demonstrated that iron crosses BBCECs bound to Tf. No intraendothelial degradation of Tf was observed, suggesting that the intraendothelial pathway through BBCECs bypasses the lysosomal compartment. These results clearly show that the iron-Tf complex is transcytosed across brain capillary endothelial cells by a receptor-mediated pathway without any degradation.
Effect of 3-aminotriazole on hyperthermia-mediated cardioprotection in rabbits
Authors: Kingma J. G. , Simard D. , Rouleau J. R. , Tanguay R. M. , Currie R. W.
Published: December 2017

Hyperthermia-induced cardioprotection during myocardial ischemia may involve increased activity of antioxidative enzymes. In this study we investigated the effects of 3-amino-1,2,4-triazole (3-AT), an irreversible catalase inhibitor, in heat-shocked (HS) rabbits subjected to ischemia-reperfusion injury. Rabbits underwent whole body hyperthermia at 42 degrees C for 15 min. Twenty-four hours later, rabbits were administered either saline vehicle or 3-AT (1 or 2 g/kg i.p.) 30 min before undergoing 30 min of regional coronary occlusion and 3 h reperfusion. Controls did not undergo whole body hyperthermia and were given either saline or 3-AT. Heart rate and left ventricular pressure were recorded continuously during these experiments. Infarct area (tetrazolium staining) was normalized to anatomic risk zone size (microsphere autoradiography). Expression of HSP 71 was verified using Western blot analysis; myocardial catalase activity was determined in tissue biopsies. Infarct size was significantly reduced in HS rabbits (25.1 +/- 2.8%, P = 0.2; means +/- SE) compared with controls (53.6 +/- 4.7%). Treatment with 1 g/kg 3-AT attenuated HS-mediated cardioprotection (36.9 +/- 4.9%, P = 0.063 vs. HS); protection was abolished with 2 g/kg 3-AT (48.9 +/- 6.6%). Myocardial catalase activities were higher in tissue biopsies from HS rabbits (47.0 +/- 4.5 U/mg protein, P < or = 0.02) compared with controls (33.4 +/- 1.9 U/mg protein); catalase activities were significantly reduced in rabbits treated with 3-AT. In conclusion, whole body hyperthermia increases expression levels of HSP 71; myocardial catalase activity is also significantly increased. Myocardial protection is HS rabbits subjected to ischemia-reperfusion injury was reversed with 3-AT. These data suggest that increased intracellular activities of catalase and possibly other antioxidant enzymes is an important mechanism for hyperthermia-mediated cellular protection.
Effects of ischemia on cerebrovascular responses to N-methyl-D-aspartate in piglets
Authors: Busija D. W. , Meng W. , Bari F. , McGough P. S. , Errico R. A. , Tobin J. R. , Louis T. M.
Published: December 2017

We examined the effects of total global ischemia on cerebral arteriolar responses to N-methyl-D-aspartate (NMDA) in anesthetized newborn pigs. Arteriolar responses to 10(-4) M NMDA were determined before and after 10 to 20 min of ischemia caused by increasing intracranial pressure. Before ischemia, NMDA dilated arterioles by 30 +/- 5% (baseline = 88 +/- 2 microns; n = 6). However, after 10 min of ischemia, arteriolar dilation was reduced to 10 +/- 3% at 1 h (P < 0.05). At 2 and 4 h, NMDA-induced dilation was not different from preischemia values. Twenty minutes of ischemia had similar effects. Coadministration of 100 U/ml of superoxide dismutase did not restore arteriolar dilation to NMDA at 1 h after ischemia. Sodium nitroprusside dilated by 14 +/- 3 and 40 +/- 5% at 10(-6) and 10(-5) M before ischemia, respectively, and arteriolar responsiveness was not changed by ischemia (n = 6). Cortical nitric oxide synthase (NOS) activity, measured by the in vitro conversion of L-[14C]arginine to L-[14C]citrulline, was unaffected by ischemia (n = 12). We conclude that decreases in cerebral arteriolar responsiveness to NMDA are not due to impairment of NOS activity, enhanced degradation or chelation of nitric oxide (NO), or reduced vascular smooth muscle responsiveness to NO.
Effect of dobutamine of ventriculoarterial coupling in acute regional myocardial ischemia in dogs
Authors: Seki H. , Katayama K. , Sakai H. , Yonezawa T. , Kunichika H. , Saeki Y. , Hiro T. , Matsuzaki M.
Published: December 2017

We assessed the effect of dobutamine on left ventricoarterial coupling during acute regional ischemia. Using a conductance catheter, we analyzed the end-systolic pressure-volume relation (ESPVR) in anesthetized dogs. We calculated the slope of ESPVR (Ees), the slope of the end-systolic pressure-stroke volume relation (Ea), (Ea/Ees) and the ratio (work efficiency) of external work to pressure-volume area at base-line during ischemia induced by occlusion of the left anterior descending coronary artery and during low-dose (1-3 micrograms.min-1.kg-1) and high-dose (4-10 micrograms.min-1.kg-1)dobutamine infusions with ischemia. ESPVR shifted to the right without a change in Ees during ischemia. Dobutamine caused dose-dependent increases in Ees but did not affect the intercept of ESPVR. During ischemia, Ea/Ees increased and work efficiency decreased. Low-dose dobutamine was associated with a return in control for Ea/Ees and work efficiency. High-dose dobutamine increased Ees and Ea but produced no further increase in Ea/Ees or work efficiency. Low-dose dobutamine would appear to be the preferable regimen to achieve the optimal ventriculoarterial coupling in acute regional ischemia associated with mismatched ventriculoarterial coupling and depressed left ventricular work efficiency.
Indicial functions of arterial remodeling in response to locally altered blood pressure
Authors: Liu S. Q. , Fung Y. C.
Published: December 2017

We investigated the effect of locally altered blood pressure on the remodeling processes of the cells and extracellular matrices of the splenic and ileal arteries and used an indicial function approach to quantitatively analyze the relationship between the altered blood pressure and the remodeling processes. Blood pressure in these arteries was locally modulated by constricting the aorta at a location between the celiac and mesenteric bifurcations, resulting in a higher blood pressure at the splenic arteries then at the ileal arteries, After the pressure changes, the cross-sectional areas and the fractions of the cells and extracellular matrices of the splenic and ileal arteries were examined by electron microscopy at 2, 6, 10, 20, and 30 days. We found that both arteries remodeled, but the splenic arteries (higher blood pressure) remodeled more rapidly and to a larger degree than the ileal arteries (lower pressure compared with the splenic arteries) of the same animal. To verify whether an identical change in the blood pressure at the splenic and ileal arteries leads to the same remodeling process in these arteries, we created another model by constricting the aorta at a location between the mesenteric and renal bifurcations, resulting in hypertension of the same level at both splenic and ileal arteries. We found that the remodeling processes of the cells and matrices were almost identical in the arteries with similar changes in blood pressure. Thus we conclude that the remodeling processes of cells and matrices of the splenic and ileal arteries are dependent on the local blood pressure in aorta constriction-induced hypertension, and the indicial analysis is a useful approach in the description of the relationship between the blood pressure and the arterial remodeling processes.
Effect of retinoic acid on contractile competence of vascular smooth muscle
Authors: Wright G. , Wang S. , Bailey G. , Reichenbecher V. , Wright G. L.
Published: December 2017

Rat aortic rings cultured for 24 h in protein-free medium showed a significant reduction in the contractile response to potassium (-60%) and to phorbol 12,13-dibutyrate (-65%). The addition of plasma to the medium attenuated the loss in responsiveness, and the supplementation of the plasma-containing medium with all trans-retinoic acid (RA) returned the response to potassium (85%) and phorbol ester (135%) to near normal or supramaximal compared with fresh tissue. Furthermore, the combined additions of plasma and RA resulted in significant preservation of the contractile response (75%) for at least 3 days in organ culture. Removal of the endothelium before organ culture eliminated the enhancement of contraction by plasma and RA. However, the removal of the endothelium from tissues that had been cultured with an intact endothelium or the blockade of nitric oxide synthesis in these tissues before contractile measurements had no effect on the contractile response. Finally, the incubation of tissues with phorbol ester to downregulate protein kinase C resulted in a marked attenuation (-75%) of the contractile response compared with control tissues in culture. The results suggest that circulating factors may be necessary for the maintenance of contractile function of aortic smooth muscle. Based on the opposing actions of RA and phorbol ester, the long-term regulation of contractile function may involve protein kinase C activity.
Activation of vascular thrombin receptors mediates cardiac response to alpha-thrombin in isolated, perfused guinea pig heart
Authors: Damiano B. P. , Mitchell J. A. , Cheung W. M. , Falotico R.
Published: December 2017

alpha-Thrombin alters vascular tone via a cell surface receptor. We used isolated guinea pig hearts perfused with buffer at constant flow to assess the effects of thrombin-receptor activation on coronary perfusion pressure, left ventricular function, and electrocardiogram. alpha-Thrombin produced concentration-dependent (0.03-1 U/ml), transient decreases in perfusion pressure followed by sustained increases. Concurrently, alpha-thrombin markedly reduced ventricular function. SFLLRN, a peptide that directly activates thrombin receptors, had qualitatively similar effects, except that it was less potent (0.1-30 microM). FSLLRN, a structurally similar peptide that does not activate thrombin receptors, had no effect. alpha-Thrombin and SFLLRN also changed S-T segment level and T-wave morphology. Previous alpha-thrombin exposure markedly inhibited the response to a alpha-thrombin but only moderately attenuated the response to SFLLRN. However, previous SFLLRN exposure did not alter subsequent response to alpha-thrombin or SFLLRN. Pretreatment with hirudin (3 U/ml), an inhibitor of thrombin's proteolytic action, prevented alpha-thrombin but not SFLLRN responses. Cromakalim (0.5 microM), a coronary vasodilator, reversed the effects of alpha-thrombin and SFLLRN on ventricular function, suggesting that depression of ventricular function resulted, in part, from vasoconstriction-induced myocardial perfusion deficit. Our results show that alpha-thrombin at physiologically relevant concentrations, has marked effects on coronary vascular resistance and ventricular function in isolated guinea pig hearts that are mediated by the proteolytically activated thrombin receptor.
Cigarette smoke condensate-induced adhesion molecule expression and transendothelial migration of monocytes
Authors: Shen Y. , Rattan V. , Sultana C. , Kalra V. K.
Published: December 2017

Cigarette smoking is clearly linked with increased incidence of atherosclerosis and cardiovascular disease. The adherence of blood monocytes to the endothelium, followed by their migration beneath the endothelium, are initiating events in the formation of foam cells, promoting atherogenesis. We show that cigarette smoke condensate (CSC)-induced surface expression of a subset of cell adhesion molecules (CAM) [intercellular adhesion molecule 1 (ICAM-1), endothelial leukocyte adhesion molecule 1 (ELAM-1), and vascular cell adhesion molecule 1 (VCAM-1)] in human umbilical vein endothelial cells (HUVEC) is associated with an increase in the binding activity of nuclear transcription factor NF-kappa B to the consensus motif common to the CAM genes. Furthermore, CSC (25 microgram/ml) both increases the rate of transendothelial migration of vitamin D3-differentiated monocyte-like cells across the HUVEC monolayer by 200% and causes an approximately 10-fold increases in the phosphorylation of platelet endothelial CAM (PECAM-1), an adhesion molecule located at intercellular junctions and involved in endothelial cell-cell adhesion. Our results show that CSC-induced activation of protein kinase C in endothelial cells initiates a signaling pathways, leading to heightened binding of NF-kappa B to specific DNA sequences, which in turn increases surface expression of the subset of CAMs. Furthermore, our studies demonstrate a link between the phosphorylation of PECAM-1 and the migration of blood monocytes across vascular endothelium.
Rapid cooling contractures in rat skinned myocardium: effects of isoflurane and halothane
Authors: Herland J. , Julian F. J. , Stephenson D. G.
Published: December 2017

Rapid cooling contractures (RCCs) have been elicited in rat ventricular cardiac muscle skinned by saponin (50 micrograms/ml). The size and shape of the RCC in skinned cardiac muscle were similar to those observed in intact cardiac muscle. The ATP-dependent Ca2-uptake pump in the sarcoplasmic reticulum (SR) was active at low temperature and could efficiently load the SR with Ca2+ even at 3 degrees C. Halothane reduced both RCC and caffeine contracture in a dose-dependent way when halothane treatment was applied before either RCC or caffeine. This action is consistent with halothane-induced depletion of the SR Ca2+. Under similar conditions, isoflurane inhibited RCC but had little effect on the caffeine contracture. This may suggest that rapid cooling and caffeine have different modes of action on the SR Ca(2+)-release channel. Our results provide further strong supporting evidence for differential inhibitory actions on a key intracellular organelle in cardiac muscle by two vapor anesthetic agents.
O2 transfer from single microvessels to acinar cells in secretin-stimulated pancreas of rat
Authors: Seiyama A. , Tanaka S. , Kosaka H. , Shiga T.
Published: December 2017

O2 transfer from the inside to the outside of single microvessels in the resting and secretin-stimulated exocrine pancreas of rats was investigated by dual-spot microspectroscopy. Measurements of intravascular hemoglobin (Hb) concentration, O2 saturation of Hb, and velocity of flowing red blood cells were carried out in single microvessels at the edge of the exocrine pancreas of anesthetized rats. The rate of O2 release (Ro2) from a single microvessel wall was constant [approximately 2 nmol.cm-2.s-1] over a wide range of oxyhemoglobin inflow ([HbO2] inflow; 200-700 fmol/s) but decreased almost linearly with an [HbO2] inflow < 200 fmol/s, where [HbO2] inflow is defined as the product of inflowing oxyhemoglobin concentration ([HbO2]) and blood flow rate. When the exocrine pancreas was stimulated with secretin either by superfusion (> or = 0.3 nM) or by intravenous infusion (> or = 0.5 microgram.kg-1.h-1), the Ro2 as well as the pancreatic secretion increased about two times higher than the basal values. With secretin administration, it was found that 1) an inverse relationship between red blood cell velocity and intravascular Hb concentration held and thus 2) [HbO2] inflow was maintained within the basal level (i.e., 200-700 fmol/s). Furthermore, 3) the elevation of Ro2 from single microvessels was accomplished by the increased O2 extraction instead of the increased O2 supply in the microvessels.
Effect of myocardial swelling on residual strain in the left ventricle of the rat
Authors: Lanir Y. , Hayam G. , Abovsky M. , Zlotnick A. Y. , Uretzky G. , Nevo E. , Ben-Haim S. A.
Published: December 2017

Left ventricular (LV) residual strain in the unloaded state was shown previously to affect LV performance. The interrelationship between myocardial swelling and LV residual strain was studied, both experimentally and theoretically. Myocardial swelling was induced by retrograde perfusion of beating, nonworking, isolated rat hearts with perfusate of graded osmolarities (200-420 mosM). The opening angle (an index of residual strain), in radially cut equatorial cross-sectional slices, and their water content were measured in 40 arrested rat LV. Both water content and opening angle decreased significantly with osmolarity from 84.2 +/- 0.45% and 77.2 +/- 9.2 degrees at 200 mosM to 76.5 +/- 1.05% and 36.3 +/- 9.8 degrees at 420 mosM (P < 0.001, respectively). A morphologically based theoretical model was developed and yielded as swelling residual strain relationship, which agrees well with the data. Our results indicate that myocardial swelling is strongly related to LV residual strain, suggesting that swelling, through its effect on residual strain, can affect both LV function and its adaptation to varying loading conditions.
Transport and metabolism of L-glutamate during oxygenation, anoxia, and reoxygenation of rat cardiac myocytes
Authors: Dinkelborg L. M. , Kinne R. K. , Grieshaber M. K.
Published: December 2017

The intracellular glutamate concentration of oxygenated, isolated adult rat heart cells incubated with 0.15 mM glutamate amounts to 2.89 +/- 0.6 mM. Under these conditions the velocity of glutamate transport was 24.3 +/- 1.6 pmol.min-1.mg protein-1 and occurs via a high-affinity carrier characterized by an apparent affinity (K(m)) value of 0.18 +/- 0.03 mM. At high glutamate concentrations ( > 1mM) this high-affinity transport system is superimposed by additional uptake processes of a low affinity but a high capacity for glutamate. The 1.6-fold increased uptake of glutamate observed during 30 min of anoxic incubation of cardiomyocytes does not prevent an intracellular decrease in this amino acid to a concentration of 0.49 mM. After 15 min reoxygenation of cardiomyocytes the intracellular glutamate content increases to the control values of oxygenated cells. Only 2.4% of the glutamate increase after reoxygenation is due to the transport o glutamate from the incubation medium. The competitive inhibitor of transaminases, aminooxyacetate, prevents both the observed intracellular decrease in glutamate during anoxia and the increase in intracellular glutamate after reoxygenation of cardiomyocytes. Half of the amino groups needed for the synthesis of glutamate originate from intracellular alanine, which increases during anoxia and is metabolized during reoxygenation of cardiomyocytes. The velocity of the glutamate uptake of cardiomyocytes incubated in a medium containing 10 mM L-glutamate amounted to 728 +/- 140 pmol.min-1.mg protein-1. During anoxic incubation of cardiomyocytes at this high extracellular glutamate concentration, the intracellular glutamate breakdown may be compensated by a simultaneous uptake of this amino acid via the transport processes characterized by a high capacity
Equine coronary hemodynamics during brief coronary occlusions at three levels of collateral function
Authors: Williams D. O. , Boatwright R. B. , Rugh K. S. , Ross C. R. , Sarazan R. D. , Garner H. E. , Griggs D. M.
Published: December 2017

Adult-grade ponies were surgically instrumented with a Doppler flow probe and pneumatic cuff occluder on the left anterior descending coronary artery (LAD), sonomicrometry crystals and intraventricular micromanometer in the left ventricle, and catheters in the left atrium, anterior interventricular vein, and, in some animals, the LAD. Conscious-animal studies were begun 2 wk after surgery. Measured variables included regional left ventricular systolic function, end-diastolic wall thickness, oxygen extraction, lactate extraction, and hydrogen ion release. Changes in collateral perfusion were deduced from changes in these variables. Serial data were obtained during a 3-min LAD occlusion before stimulation of collateral function by the intermittent coronary occlusion method and during a 10-min LAD occlusion after 14 +/- 2 and 27 +/- 2 days of stimulation. Hemodynamic interpretation of data was based on a model of the equine coronary circulation consisting of collateral and arteriolar resistances in series. It was concluded that 1) chronic stimulation of collateral function leads to the emergence of a time-dependent reduction in total collateral resistance during acute coronary occlusion; 2) with enhancement of collateral function, the major resistance controlling collateral blood flow shifts from the collateral circulation to the recipient vessel arterioles; and 3) at a certain level of enhanced collateral function, coronary occlusion results in a triphasic blood flow response in collateral-dependent myocardium consisting of early hypoperfusion, transient hyperperfusion, and late autoregulated perfusion. This study demonstrates that chronic stimulation of collateral function is accompanied by specific alterations in coronary hemodynamics during acute coronary occlusion that hasten the recovery of ischemic myocardium.
Effect of vasopressin on baroreflex control of lumbar sympathetic nerve activity and hindquarter resistance
Authors: Scheuer D. A. , Bishop V. S.
Published: December 2017

Arginine vasopressin (AVP) has been shown to increase the inhibitory influence of the baroreflex on sympathetic nerve activity by a mechanism involving receptors located in the area postrema. The purpose of these experiments was to study the functional effect of this action of AVP by testing the hypothesis that AVP can buffer its own vasoconstrictor effect by facilitating baroreflex-mediated withdrawal of sympathetic nerve activity. Specifically, we determined 1) if AVP can attenuate increases in hindquarter vascular resistance during the infusion of another vasoconstrictor, phenylephrine, and 2) whether the effects of AVP on vascular resistance are associated with appropriate corresponding changes in lumbar sympathetic nerve activity (LSNA). In pentobarbital-anesthetized New Zealand White rabbits the baroreflex was stimulated by phenylephrine-induced elevations in arterial pressure. Baroreflex-mediated changes in heart rate (HR), calculated hindquarter vascular resistance index (R), and LSNA were determined during the simultaneous intravertebral infusion of AVP (0, 0.5, or 1.0 ng.kg-1, min-1). Intravertebral infusion of AVP alone had no effect on resting mean arterial pressure (MAP) but reduced baseline values for LSNA and HR. Intravenous infusion of phenylephrine alone produced dose-dependent increases in MAP and R and decreases in LSNA and HR. The simultaneous infusion of AVP (0.5 or 1.0 ng.kg-1 min-1) and phenylephrine (1.25, 2.5, 5.0, 7.5, and 10.0 micrograms.kg-1.min-1) had no effect on the increase in MAP but attenuated the increases in R and facilitated the reductions in LSNA at all doses of phenylephrine. The higher dose of AVP also enhanced the phenylephrine-induced reductions in HR. In contrast, the intravenous infusion of AVP (1.0 ng.kg-1.min-1) did not alter baroreflex-mediated changes in R, LSNA, or HR. Therefore, we conclude that the action of AVP to increase baroreflex-mediated sympathoinhibition results in an attenuated rise in hindquarter vascular resistance during the infusion of another vasoconstrictor, phenylephrine.
CPA induces a sustained increase in [Ca2+]i of endothelial cells in situ and relaxes porcine coronary artery
Authors: Higuchi Y. , Nishimura J. , Kobayashi S. , Kanaide H.
Published: December 2017

Using fura 2 fluorometry, we investigated the effect of cyclopiazonic acid (CPA), an inhibitor of Ca2+ pump adenosinetriphosphatase of the endoplasmic reticulum, on cystosolic Ca2+ concentration ([Ca2+]i) and tension in porcine aortic valvular endothelial cells and coronary arterial strips with endothelium. In normal physiological salt solution, CPA induced a sustained increase in [Ca2+]i in the valvular strips, whereas in Ca(2+)-free physiological salt solution, CPA elicited a transient elevation of [Ca2+]i. CPA(30 microM) relaxed coronary strips with endothelium precontracted by 100 nM U-46619; this relaxation was partially inhibited by N omega-nitro-L-arginine (100 microM). These results indicate that the CPA-induced increase in [Ca2+]i depends on the Ca2+ release and the Ca2+ influx in the endothelial cells in situ and that the CPA-induced endothelium-dependent decreases in [Ca2+]i and tension in the smooth muscle are due to the combined effect of N omega-nitro-L-arginine-sensitive and -resistant factors.
Comparison of ANG II with other growth factors on Egr-1 and matrix gene expression in cardiac fibroblasts
Authors: Iwami K. , Ashizawa N. , Do Y. S. , Graf K. , Hsueh W. A.
Published: December 2017

The purpose of the present investigation was to compare the effects of angiotensin II (ANG II) other growth factors implicated to play a role in ventricular hypertrophy on cardiac fibroblast changes associated with cardiac remodeling. These changes included induction of early growth response (Egr-1) gene and increases in message levels of extracellular matrix proteins. ANG II treatment (10(-10)-10(-6) M) of rat cardiac fibroblasts induced 1) Egr-1 and 2) a fourfold (P < 0.02) increase in fibronectin and a twofold (P = 0.05) increase in laminin mRNA levels but no increases in that of collagens I, III, or IV at 24–48 h, and 3) a decrease in AT1-receptor mRNA levels to 26% (P < 0.001) of basal at 4–6 h. These effects were all inhibited by the AT1-receptor blocker, losartan, but not AT2-receptor blockers. Immunostaining of cultured cells with antibody against rat fibronectin demonstrated positive staining of cells in serum-free medium; staining was more intense in cells treated with ANG II (10(-6) M, 48 h). Fluorescent-activated cell sorting using an antibody against rat AT1 receptor demonstrated a receptor signal in cells maintained in serum-free medium; however, the receptor signal was not detectable in ANG II-treated cells. Serum and epidermal growth factor (EGF) also induced Egr-1, but norepinephrine (NE) and endothelin (ET) had no effect. Serum increased fibronectin mRNA levels by twofold (P < 0.05). EGF, NE, and ET had no effect on matrix gene expression. Serum, EGF, and NE also transiently downregulated AT1-receptor mRNA levels at 4–6 h of treatment. These results demonstrate that 1) ANG II both induces protooncogene expression and enhances fibronectin mRNA levels in cultured cardiac fibroblasts, whereas EGF only induces Egr-1, and NE and ET have no effects on either function; 2) ANG II effects are primarily mediated by the AT1 receptor; and 3) growth factors can regulate AT1-receptor mRNA levels. Thus ANG II, relative to NE, ET, and EGF, appears to play a prominent and direct role in fibroblast changes associated with cardiac hypertrophy.
Lymph pump mechanics in the rabbit hind leg
Authors: Ikomi F. , Schmid-Schonbein G. W.
Published: December 2017

The mechanisms that govern fluid uptake by the initial lymphatics and adjustment of lymph flow rates remain to a large degree uncertain. The aim of this study was to examine how passive tissue movement contributes to lymph flow rates. Lymph fluid was collected via a cannula inserted into one of the popliteal prenodal lymphatics in the rabbit hind leg. Lymph flow rates were measured during periodic whole leg rotation and controlled oscillatory massage of the dorsal skin of the foot. Without whole leg rotation, lymph flow remained at low values (< 0.01 ml/h). Introduction of whole leg passive rotation caused a frequency-dependent increase in lymph flow rates, which were increased linearly with the log of frequency between 0.03 and 1.0 Hz. Local skin massage in the region of the initial lymphatics also led to a similar increase of lymph flow rates dependent on frequency as well as amplitude of skin displacement. Lymph flow rates during local skin massage reached a comparable order of magnitude regardless of whether the animal was alive or the heart had been arrested, suggesting that local lymph flow rates can be adjusted by periodic tissue motion independently of capillary fluid filtration pressures. The results indicate that periodic expansion and compression of initial lymphatics provide a mechanism for lymph pumping.
Active renin and renin glycoform dynamics in the carotid artery
Authors: Katz S. A. , Opsahl J. A. , Forbis L. M. , Ayenew W.
Published: December 2017

Active renin and five major active renin glycoforms were measured in plasma and the carotid wall of anesthetized rabbits before and after 1.5- and 24-h bilateral nephrectomy (BNX). Before BNX, there was no difference in renin glycoform proportions between plasma and the carotid wall. Plasma renin concentration (PRC) fell by 67% after 1.5-h BNX due to preferential clearance of renin glycoforms I+II, but no significant change in renin concentration was seen in the carotid artery (or aorta). Twenty-four hours after BNX, PRC and carotid wall renin concentrations were reduced by 99.7 and 97.7%, respectively, while the proportion of renin glycoforms I+II in the carotid wall was significantly elevated. These data are consistent with the view that vascular renin is derived from plasma renin of renal origin. After BNX, renin disappearance from the carotid (and aortic wall) is slower than renin decay from plasma, and the less negatively charged active renin glycoforms I+II exit the carotid wall much more slowly than the more negatively charged glycoforms. After 24-h BNX, renin glycoforms I+II were still effluxing from the vascular wall and represented the only glycoforms present in the carotid wall.
Comparative effects of contraction and angiotensin II on growth of adult feline cardiocytes in primary culture
Authors: Wada H. , Zile M. R. , Ivester C. T. , Cooper G. , McDermott P. J.
Published: December 2017

The purposes of this study were 1) to determine whether angiotensin II causes growth of adult feline cardiocytes in long-term culture, 2) to compare the growth effects of angiotensin II with those resulting from electrically stimulated contraction, and 3) to determine whether the anabolic effects of contraction are exerted via the angiotensin type 1 receptor. Adult feline cardiocytes were cultured on laminin-coated trays in a serum-free medium. Cardiocytes were either electrically stimulated to contract (1 Hz, 5-ms pulse duration, alternating polarity) or were nonstimulated and quiescent. Quiescent cells were studied as controls and after treatment with angiotensin II (10(-8) M), losartan (10(-6) M; an angiotensin type 1-receptor antagonist), or angiotensin II plus losartan. Contracting cells were studied in the presence and absence of angiotensin II or losartan. In quiescent cardiocytes, angiotensin II treatment on day 7 significantly increased protein synthesis rates by 22% and protein content per cell by 17%. The effects of angiotensin II were completely blocked by losartan. Electrically stimulated contraction on days 4 and 7 in culture significantly increased protein synthesis rate by 18 and 38% and protein content per cell by 19 and 46%, respectively. Angiotensin II treatment did not further increase protein synthesis rate or protein content in contracting cardiocytes. Furthermore, losartan did not block the anabolic effects of contraction on protein synthesis rates or protein content. In conclusion, angiotensin II can exert a modest anabolic effect on adult feline cardiocytes in culture. In contracting feline cardiocytes, angiotensin II has no effect on growth. Growth caused by electrically stimulated contraction occurs more rapidly and is greater in magnitude than that caused by angiotensin II. Growth of contracting adult feline cardiocytes is not dependent on activation of the angiotensin receptor.
Openings of cardiac KATP channel by oxygen free radicals produced by xanthine oxidase reaction
Authors: Tokube K. , Kiyosue T. , Arita M.
Published: December 2017

We examined the effects of oxygen free radicals (OFRs) on action potentials and membrane currents of guinea pig ventricular myocytes. OFRs produced biphasic changes in the action potential duration, initial lengthening (30 s after exposure to OFRs) and subsequent shortening (within 5 min). In voltage-clamp experiments, OFRs suppressed the L-type calcium current, the delayed rectifier K+ current, and the inward rectifier K+ current. In addition, OFRs increased the time-independent outward current (I(term)) at potentials greater than -30 mV. The increases in I(term) reflected activation of the ATP-sensitive K+ (KATP) channels, as glibenclamide (1 microM) blocked this current. In inside-out patches, OFRs significantly increased the open probability of the channel at a relatively narrow range of ATP concentrations (0.2–2 mM), and this effect was enhanced in the presence of ADP (0.1 mM) and abolished in the presence of either free radical scavengers or gliben-clamide. These findings are compatible with the notion that OFRs activate KATP channels by modulating ATP binding sites of the KATP channels, without affecting ADP binding or glibenclamide binding sites.