bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal design of experiments to estimate LDL transport parameters in arterial wall
Authors: Morris E. D. , Saidel G. M. , Chisolm G. M.
Published: December 2017

To quantify transport processes in atherosclerosis, the arterial wall is often exposed to labeled lipoproteins. In vivo experiments are desirable for estimation of transport parameters, but they are technically difficult. A dynamic mass transfer model has been developed to describe experimental transmural profiles of lipoprotein accumulation as a function of luminal permeability, diffusion, convection, and degradation. To avoid extraneous experiments and to assure successful parameter estimation, an optimal design of experiments is needed. For our purposes a design was considered optimal when it maximized the sensitivity of the model output to changes in parameter values as indicated by the determinant of the Hessian matrix of the objective function. A comparison was made between two designs: dual-time designs prescribing unequal circulation times for two distinguishable injections of labeled low-density lipoprotein (LDL) and dual-species designs requiring simultaneous circulation of LDL and tyramine-cellobiose-modified LDL. Circulation time was optimized for both designs. Although both were heavily dependent on the circulation times, dual-time designs required better preliminary knowledge of parameter values. Because labeled degradation products of the modified tracer become anchored in the arterial tissue, information about the degradation process is retained in the dual-species study. For this reason, dual-species designs were generally superior to dual-time designs.
Phosphocreatine pathway for energy transport: ADP diffusion and cardiomyopathy
Authors: Saks V. A. , Belikova Y. O. , Kuznetsov A. V. , Khuchua Z. A. , Branishte T. H. , Semenovsky M. L. , Naumov V. G.
Published: December 2017

Chemically skinned (by treatment with saponin, 40 μg/ml) isolated cardiomyocytes were used to study the intracellular diffusion of ADP and creatine (Cr). Stimulation of respiration was studied in these cardiomyocytes without intact sarcolemma and in isolated heart mitochondrial by addition of ADP and Cr in the presence of 0.2 mM ATP (via mitochondrial creatine kinase reaction: Cr + MgATP = MgADP + PCr). The Michaelis constant (Km) for Cr was similar in both cases, 5.67 ± 0.11 (SD) mM in skinned myocytes and 6.9 ± 0.2 mM in mitochondria, showing that there is no significant restriction to the diffusion of this substrate. However, the apparent Km for external ADP increased from 17.6 ± 1.0 μM for mitochondria to 250 ± 38 μM for skinned cardiomyocytes, showing decreased diffusivity of ADP as a result of binding to cellular structures. In the presence of 25 mM Cr, the Km for ADP for myocytes decreased to 35.6 ± 5.6 μM due to the coupling of the creatine kinase and oxidative phosphorylation reactions. Provision of substrate for the creatine kinase reaction amplified the weak ADP signal in the regulation of respiration. The activity of the mitochondrial creatine kinase was decreased by a factor of two in cardiomyopathic hamsters and human hearts and was associated with a twofold decrease in creatine-stimulated respiration. These data show a potentially key role of mitochondrial creatine kinase in the regulation of cellular respiration and the possible importance of changes in its activity for the functional disturbances of the cardiomyopathic heart.

cellular respiration; creatine kinase; oxidative phosphorylation
Role of endothelium-derived relaxing factor in cerebral circulation: large arteries vs. microcirculation
Authors: Faraci F. M.
Published: December 2017

This study examined the hypothesis that formation of endothelium-derived relaxing factor (EDRF) in the brain has a greater influence on basal tone in large arteries than arterioles. Diameters of the basilar artery and its branches and of arterioles on the cerebrum were measured through cranial windows in anesthetized rats. Under control conditions, topical application of NG-monomethyl-L-arginine (L-NMMA), which inhibits formation of EDRF or nitric oxide (NO) from L-arginine, produced concentration-related constriction that was dependent on initial vessel diameter. Large arteries [diameter = 275 +/- 10 microns (mean +/- SE)] constricted by 10.4 +/- 0.8% in response to 10(-5) M L-NMMA. In contrast, arterioles (62 +/- 6 microns) constricted by only 3.7 +/- 0.6% (P less than 0.01 vs. large arteries), regardless of brain region. U-46619 produced similar constriction of large arteries and arterioles, which indicates that reduced responses to L-NMMA in arterioles is not due to impaired constrictor capacity. Sodium nitroprusside produced similar dilatation of large arteries and arterioles, which suggests that activity of guanylate cyclase is not reduced in small vessels. Dilator responses of large arteries and arterioles to acetylcholine, but not nitroprusside, were inhibited by L-NMMA. Thus synthesis of EDRF from L-arginine influences basal tone of cerebral blood vessels, and the effect is greatest in large arteries. In contrast, the role of EDRF or NO in mediating responses to acetylcholine in the cerebral circulation is similar in large arteries and the microcirculation.
Contractile activity modulates myosin heavy chain-beta expression in neonatal rat heart cells
Authors: Samarel A. M. , Engelmann G. L.
Published: December 2017

To determine whether spontaneous contractile activity affected the expression of myosin heavy chain isoenzymes in cultured neonatal rat heart cells, ventricular myocytes were isolated from 2-day-old rat pups by collagenase digestion and cultured for 24-96 h in the presence and absence of verapamil (10 microM), KCl (50 mM), or dihydropyridine receptor antagonists that produced contractile arrest. Inhibition of spontaneous contractile activity was associated with significant reductions in total myosin heavy chain (MHC) content and synthetic rates. Electrophoretic analysis of MHC isoenzymes indicated that MHC-beta protein rapidly disappeared from arrested cells, whereas MHC-alpha isoenzyme levels were less affected. In association with these protein changes, mRNA transcript levels for MHC-beta were markedly reduced in quiescent cells, whereas mRNA transcript levels for several other contractile protein genes were relatively less affected. Inhibition of contractile activity and MHC-beta expression were reversible upon removal of the arresting agents. Furthermore, the decrease in MHC-beta mRNA levels in arrested myocytes could be prevented by direct activation of protein kinase C with phorbol 12-myristate 13-acetate (without restoration of contractile activity). Conversely, MHC-beta mRNA levels in beating cells were reduced by treatment with staurosporine (a selective protein kinase C inhibitor). Thus contractile arrest (produced by either L-channel blockade or membrane depolarization) inhibited the accumulation of MHC-beta in cultured neonatal rat heart cells via a pretranslational mechanism. These effects may occur in response to the modulation of signaling system(s) involving mechanical “stretch” transduced via protein kinase C.
Tumor necrosis factor-alpha primes pulmonary hemodynamic response to N-formyl-L-methionyl-L-leucyl-L-phenylalanine
Authors: Johnson A. , Hocking D. C. , Ferro T. J.
Published: December 2017

We tested the hypothesis that tumor necrosis factor-alpha (TNF-alpha) primes the hemodynamic response to the neutrophil agonist N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) in lungs isolated from guinea pigs. Lungs were isolated from animals 18 h after injection of TNF-alpha (3.20 x 10(5) U/kg ip). The infusion of FMLP (300 nM) into lungs isolated after the intraperitoneal administration of TNF-alpha resulted in increases in lung weight, lung (wet-dry)-to-dry weight ratio [(wet-dry)/dry wt], pulmonary capillary pressure, lung myeloperoxidase activity and perfusate thromboxane (Tx)B2 levels. Animals pretreated with the maximal possible amount of endotoxin in the TNF-alpha (1.7 pg endotoxin) did not respond to FMLP. WEB-2086 (37 microM), a platelet-activating factor (PAF) receptor antagonist, added to the perfusate attenuated the hemodynamic and TxA2 response to FMLP. Dazoxiben (0.5 mM), a TxA2 synthetase inhibitor, prevented the FMLP effect. Polyethylene glycol (PEG)-catalase (500 U/ml) added to the perfusate did not affect the FMLP response; however, PEG-catalase (10(5) U/kg) given intraperitoneally with the TNF-alpha decreased the synergism induced by TNF-alpha with FMLP. The data suggest that TNF-alpha primes the lung to the effects of FMLP by increasing the population of resident neutrophils in the lung and/or by in vivo oxidant generation. The pulmonary hemodynamic response and lung edema induced by FMLP are mediated by PAF and TxA2.
Response of canine internal carotid system to acetylcholine
Authors: Dieguez G. , Nava-Hernandez E. , Valle J. , Garcia-Villalon A. L. , Garcia J. L. , Monge L. , Gomez B.
Published: December 2017

The reactivity of the canine internal carotid system to acetylcholine (10(-8)-10(-4) M) was studied isometrically with 4-mm cylindrical segments from cervical and cavernous portions of the internal carotid artery and from the middle cerebral artery. Under control conditions, the cervical portion relaxed to every dose, the cavernous portion relaxed at low concentrations (10(-8)-10(-6) M) and contracted at higher concentrations (10(-5)-10(-4) M), whereas the middle cerebral artery contracted to every dose of acetylcholine. These responses were blocked by atropine (10(-6) M). Without endothelium, the cervical portion exhibited a lower relaxation, the cavernous portion contracted, and the middle cerebral artery was practically unresponsive to acetylcholine. These responses were also blocked by atropine. It suggests that the reactivity of the internal carotid system to acetylcholine 1) is endothelium dependent and 2) changes as it courses toward the brain, and this could be related to different embryological origin of the components of this arterial system.
Dietary sodium intake and left ventricular hypertrophy in normotensive rats
Authors: Yuan B. X. , Leenen F. H.
Published: December 2017

In three different normotensive rat strains, we evaluated the effects of a large range of dietary sodium (101, 342, and 1,370 mumol Na+/g) on cardiac structure in relation to age of the rats and to changes in central hemodynamics and cardiac sympathetic neuronal activity. In young, 4-wk-old Wistar-Kyoto rats (WKY) an increase in dietary sodium induced a dose-related increase in left ventricular (LV) weight (+10 and +24% after 4 wk of 342 or 1,370 mumol Na+/g diets, respectively). Young Wistar rats also developed LV hypertrophy (+14%) on a high sodium intake, but this was less than that seen in WKY. In more mature Wistar and WKY rats, the extent of this trophic response to high sodium intake diminished. In contrast to young Wistar and WKY rats, Dahl salt-resistant rats did not show a trophic response with initiation of high sodium intake at 4 wk of age. The cardiac trophic response to dietary sodium was not associated with changes in central hemodynamics (i.e., filling pressures, cardiac output, and blood pressure). Norepinephrine turnover rate of the left ventricle tended to decrease in response to high dietary sodium intake. We conclude that food sodium can significantly increase LV weight depending on the strain and age of the rats and that this trophic response occurs independent of cardiac volume or pressure overload.
Time-varying myocardial elastance of canine left ventricle
Authors: Takeda K. , Kadota R. , Yagi S.
Published: December 2017

A formula was derived from an active cross-bridge model for expressing the "time-varying myocardial elastance" of the left ventricular (LV) wall. To assess the validity of this model's predictions of the behavior of the intact left ventricle, eight healthy beagles were instrumented with ultrasonic crystals to measure LV diameter and a micromanometer for LV pressure measurement. During ejecting beats starting from short end-diastolic myocardial lengths, the predicted values for myocardial elastance and force closely approximated the measured values for the instantaneous external load-muscle length ratio and the external load, respectively. However, in cycles starting from long end-diastolic lengths, the predicted myocardial elastance and force values deviated from the actual values during the shortening phase of LV contraction. The differences between myocardial elastance and external load-muscle length ratio as well as those between force and external load during the shortening phase (shortening deactivation) appeared to result from an internal load in the shortening myocardium that was closely related to the product of instantaneous myocardial force and shortening velocity. Thus this model may provide reasonable approximations of myocardial elastance and force in the intact LV wall. In addition, time-varying myocardial elastance might reflect time-dependent changes in calcium activation.
Possible mechanisms underlying differences in force production between normal and cardiomyopathic hamster atria
Authors: Bobet J. , Howlett S. E. , Gordon T.
Published: December 2017

The rate of recovery of force after a long rest interval is lower than normal in left atria from 80- to 85-day-old cardiomyopathic (CM) golden Syrian hamsters. To determine whether this difference was due to a reduced amount of Ca2+ available for release with each beat, we manipulated the amount of Ca2+ entering excised atria using the Ca2+ agonist BAY K 8644 and the antagonist nifedipine. We also simulated altered Ca2+ influx in a recent model of cardiac excitation-contraction coupling (V. J. A. Schouten, J. K. Van Deen, P. de Tombe, and A. A. Verveen Biophys. J. 51: 13-26, 1987) by varying the parameter representing Ca2+ influx and observing the effect on the force it predicted. Steady-state force of normal and CM atria was recorded in response to 1-Hz stimulation and recovery of steady-state force was monitored after a 600-s rest interval. Ca2+ fluxes were manipulated by raising external Ca2+ or by the presence and absence of drug. The recovery of force after a 600-s rest interval was digitized and fitted with an exponential function, and the time constant and steady-state force to which the muscle recovered after the pause were compared. Inclusion of the Ca2+ agonist BAY K 8644 (0.25 or 2.0 microM) made the response of CM atria similar to that of normal, while inclusion of the Ca2+ antagonist nifedipine (0.8 microM) made the response of normal atria similar to that of the CM. Similarly, decreasing the simulated Ca2+ influx in the model produced all of the differences observed between normal and CM muscle.(ABSTRACT TRUNCATED AT 250 WORDS)
Leukocyte-induced vascular protein leakage in cat mesentery
Authors: Kubes P. , Grisham M. B. , Barrowman J. A. , Gaginella T. , Granger D. N.
Published: December 2017

The overall objective of this study was to determine whether leukocyte adherence and/or emigration is a prerequisite for the increased vascular protein leakage associated with acute inflammation. An in vivo preparation was used to monitor intestinal vascular protein leakage as well as polymorphonuclear leukocyte (PMN) adhesion and emigration in feline mesenteric microvessels exposed to platelet-activating factor (PAF) and leukotriene B4 (LTB4). Local intra-arterial infusion of PAF (4 ng/min) produced a fourfold increase in vascular protein leakage. A 50-fold higher concentration of LTB4 had no effect on vascular protein efflux. LTB4, however, did potentiate the PAF-induced vascular protein leakage. Both inflammatory mediators caused leukocytes to adhere to endothelial cells in postcapillary venules; however, leukocyte emigration was observed only in the presence of PAF. PAF-induced leukocyte adhesion and emigration and the increased vascular protein leakage were inhibited by a monoclonal antibody (MoAb IB4) directed against the common beta-subunit of the adhesive glycoprotein complex CD11/CD18. MoAb IB4 also prevented LTB4-induced leukocyte adhesion. Both PAF and LTB4 caused degranulation of cat PMNs in vitro, yet superoxide production was stimulated by PAF only. The data derived from these in vivo and in vitro studies indicate that leukocyte adhesion per se does not necessarily lead to increased vascular protein leakage and leukocyte emigration. Adhesion-dependent PMN functions such as emigration and superoxide production may play an important role in producing the alterations in vascular integrity observed in inflamed microvessels.
Vasopressin (V1) receptor characteristics in rat aortic smooth muscle cells
Authors: Gopalakrishnan V. , Xu Y. J. , Sulakhe P. V. , Triggle C. R. , McNeill J. R.
Published: December 2017

We report saturable, high-affinity, specific, reversible binding sites for both [3H]arginine vasopressin ([3H]AVP) and d(CH2)5Tyr(Me)-[3H]AVP, a V1-selective antagonist, in cultured smooth muscle cells obtained from rat aorta (RA) and rat mesenteric artery (RMA). Specific binding of [3H]AVP had the following characteristics in adherent monolayers of RA and RMA smooth muscle cells: dissociation constant (KD) = 1.42 and 1.23 nM and maximal binding capacity (Bmax) = 9,500 and 29,910 sites/cell, respectively. Lower KD and higher Bmax values were detected for 3H-labeled V1 antagonist binding to both types of cells. Complete dissociation of [3H]-AVP binding to RA cells occurred in a biphasic manner with two rate constants of dissociation, suggesting high- and low-affinity states of the binding site for the agonist interaction. Partial dissociation of the antagonist-specific binding occurred, and it was monophasic, suggesting interaction of the 3H-labeled V1 antagonist radioligand to the high-affinity binding state. Inhibition constant (Ki) values determined by competitive inhibition of [3H]AVP binding to RA cells by a series of AVP-related peptide analogues and antagonists were consistent with the saturation data. AVP in a concentration-dependent manner induced the accumulation of inositol phosphates [mean effective concentration (EC50) 1 nM] in the adherent RA cells. The free cytosolic Ca2+ level in the dispersed RA smooth muscle cells was increased by AVP (EC50 8.1 nM). Pretreatment with the V1 antagonist abolished these AVP-evoked responses. The data support the conclusion that the agonist binding occurs at a homogeneous population of V1-subtype receptors in the high-affinity (KD = approximately 1 nM) state and that these receptors are functionally coupled to phospholipase C.
Parathyroid hormone: an endogenous modulator of cardiac calcium channels
Authors: Rampe D. , Lacerda A. E. , Dage R. C. , Brown A. M.
Published: December 2017

We have tested the effects of the active 1-34 amino acid sequence of rat parathyroid hormone (PTH) on Ca2+ channel activity in neonatal rat ventricular cells. Rat PTH (30 pM to 10 nM) increased depolarization-induced Ca2+ influx into these cells, an effect that was abolished by 1 microM nifedipine. The 1-34 amino acid sequence of bovine PTH also stimulated Ca2+ influx in control cells but not in cells pretreated with cholera toxin. Rat PTH also elevated adenosine 3',5'-cyclic monophosphate accumulation in these ventricular myocytes. Whole cell voltage-clamp recordings confirmed a stimulatory effect of rat PTH on cardiac L-type Ca2+ channels. Cell-attached single channel recordings revealed an increase in the probability of channel opening as the primary mechanism for the enhancement of Ca2+ current. Taken together these results suggest an important role for PTH as an endogenous modulator of cardiac L-type Ca2+ channels.
Platelet inhibition by an L-arginine-derived substance released by IL-1 beta-treated vascular smooth muscle cells
Authors: Durante W. , Schini V. B. , Scott-Burden T. , Junquero D. C. , Kroll M. H. , Vanhoutte P. M. , Schafer A. I.
Published: December 2017

Experiments were performed to examine whether stimulation of cultured vascular smooth muscle cells by interleukin (IL)-1 beta would induce platelet inhibitory properties of these cells. Incubation of platelets with untreated rat aortic smooth muscle cells had no effect on thrombin-induced platelet aggregation. In contrast, incubation of platelets with IL-1 beta-pretreated smooth muscle cells or the perfusate from such cells resulted in the inhibition of thrombin-induced platelet aggregation. This effect was potentiated by superoxide dismutase and reversed by incubating the IL-1 beta-treated smooth muscle cells with NG-nitro-L-arginine (L-NNA) or by treating the platelets with methylene blue. Cytokine-treated smooth muscle cells inhibited thrombin-stimulated changes in platelet cytosolic ionized calcium, whereas untreated cells were without effect. Incubating platelets with IL-1 beta-treated smooth muscle cells resulted in a 10-fold increase in platelet guanosine 3',5'-cyclic monophosphate (cGMP) levels, whereas untreated smooth muscle cells had no effect. The elevation of platelet cGMP induced by the IL-1 beta-treated smooth muscle cells was prevented by exposing the cytokine-treated cells to L-NNA or by treating platelets with methylene blue. Treatment of smooth muscle cells with IL-1 beta also resulted in an eightfold increase in nitrite production, which was blocked when the cells were incubated with L-NNA. The addition of cycloheximide to smooth muscle cells during their incubation with IL-1 beta completely inhibited smooth muscle cell nitrite production, the effects of the smooth muscle cells on platelet cGMP levels, and platelet responses to thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)
Inhibitory effect of pindolol on hypoxic pulmonary vasoconstriction
Authors: Takashio T. , Yamashita H. , Onodera S.
Published: December 2017

The effects of a beta-agonist (isoproterenol) and beta-antagonists (propranolol and pindolol) on hypoxic pulmonary vasoconstriction (HPV) and on changes in some chemical mediators were examined in 28 isolated blood-perfused dog lung lobes. Hypoxic challenge (4 min) was repeated twice, and each drug was administered at a bolus dose of 0.2 mg between the hypoxic periods. The first hypoxia increased pulmonary vascular resistance (PVR) by 33% or more in all groups. Both isoproterenol and pindolol inhibited the second HPV completely, but propranolol did not influence HPV. During normoxia, isoproterenol and pindolol significantly decreased PVR by 17.5 and 6.7% (P less than 0.01), respectively, but propranolol had no effect on PVR. In the control and propranolol groups, plasma levels of adenosine 3',5'-cyclic monophosphate (cAMP) significantly decreased during hypoxia, but those of prostaglandin E2, 6-ketoprostaglandin F1 alpha, and thromboxane B2 did not change. cAMP increased from 17.0 +/- 4.0 to 76.7 +/- 15.6 pmol/ml in the isoproterenol group (P less than 0.01), and prostaglandin E2 increased from 87.0 +/- 13.6 to 1,015.4 +/- 309.7 pg/ml in the pindolol group (P less than 0.05). The results suggest that the mechanism of HPV inhibition is different between isoproterenol and pindolol.
Control of capillary hydraulic conductivity via membrane potential-dependent changes in Ca2+ influx
Authors: Zhang R. S. , Huxley V. H.
Published: December 2017

Capillary permeability has been shown to be sensitive to the levels of intracellular calcium. We examined the role of membrane potential in the regulation of capillary water permeability by a Ca2+ leak mechanism. Repeated measures of Lp were taken in situ on individually perfused mesenteric capillaries of cerebrally pithed frogs (Rana pipiens). A rise in extracellular potassium ([K+]o) to 24 mM induced a 45% decrease in Lp (n = 20), whereas lowering [K+]o to 0.24 mM elevated Lp by twofold (n = 9). To investigate whether these changes in Lp were due specifically to changes in membrane potential and consequent changes in the driving force for Ca2+ influx, we performed the following experiments: 1) [K+]o was elevated while the product of [K+]o and extracellular chloride concentration [Cl-]o was kept constant, 2) [K+]o was elevated under nominally Ca(2+)-free conditions, 3) K+ leak was induced by addition of 10 microM valinomycin, and 4) Na(+)-K+ pump was blocked by 10 microM ouabain. A constant [K+]o [Cl-]o product did not prevent high K+ from lowering Lp. Nominally Ca(2+)-free conditions abolished the effect of high K+. Valinomycin mimicked the response to low K+, and ouabain failed to change Lp. The data from this study conform to the hypothesis that membrane potential is an important regulator of capillary barrier properties via changes in Ca2+ influx through leak channels.
Is there a shortening-heat component in mammalian cardiac muscle contraction?
Authors: Holroyd S. M. , Gibbs C. L.
Published: December 2017

It has been suggested that there is a shortening-heat component that is an extra liberation of heat on shortening above that due to the external work, which contributes to the total energy expenditure of the beating heart. The presence of a shortening heat component was studied in isolated papillary muscles from the right ventricle of rabbits killed by cervical dislocation. At the onset of a contraction, muscles were shortened from various initial lengths through fixed distances at near maximum velocity before being allowed to develop force at the new length; the heat production accompanying such contractions was measured. The measured heat was compared with heat values predicted from previously established heat-stress curves obtained by using either preshortening or latency release methods. There was no shortening-related increment in heat output per contraction when comparison was made to a control heat-stress curve, obtained using the latency release method. An increase in heat production of 10% was observed with long shortening distances when comparison was made to a control heat-stress curve obtained by preshortening the muscles; however, this difference is most likely due to an underestimate of the magnitude of the activation heat component in these control heat-stress curves. An increase in isometric heat production due to maintained stretch per se was observed. The present data indicate that it is unlikely that there is a significant shortening heat component when cardiac muscle shortens. The absence of such a metabolic component may account for the rapid fall off in total enthalpy output in isotonic contractions at low to medium afterloads when compared with the skeletal muscle data.
H2 receptor-mediated responses of aortic endothelial cells to histamine
Authors: Hekimian G. , Cote S. , Van Sande J. , Boeynaems J. M.
Published: December 2017

It is well known that umbilical vein endothelial cells express H1 receptors that mediate the various responses of these cells to histamine, including accumulation of inositol phosphates, rise of cytosolic Ca2+, increased permeability to macromolecules, and release of prostacyclin. In bovine aortic endothelial cells, histamine did not increase the level of inositol phosphates nor the release of prostacyclin. In contrast, it increased the adenosine 3',5'-cyclic monophosphate (cAMP) content of these cells. That response was obtained in the 1 to 100 microM range of concentrations and reached a maximum within 2 min of histamine addition. It was mimicked by the H2-specific agonist dimaprit, inhibited by the H2 antagonist ranitidine, and insensitive to the H1 antagonist mepyramine. Histamine reduced the permeability to albumin of bovine aortic endothelial cell monolayers; this paradoxical effect is likely to be mediated by the rise in cAMP, which is known to enhance the barrier property of the endothelium. In conclusion, bovine aortic endothelial cells are responsive to histamine, and this response is mediated by H2 and not H1 receptors.
Myocardial oxygenation in the isolated working rabbit heart as a function of work
Authors: Heineman F. W. , Kupriyanov V. V. , Marshall R. , Fralix T. A. , Balaban R. S.
Published: December 2017

Myocardial O2 consumption (MVO2) was stimulated up to two-fold by either increasing afterload or beta-receptor stimulation in working normothermic isolated rabbit hearts while noninvasively monitoring the O2 delivery or phosphate compounds (total n = 48). Intracellular O2 delivery was estimated with the use of myocardial optical absorbance changes centered at 603.5 and 582 nm that correlate with cytochrome aa3 redox and myoglobin oxygenation states. Phosphate-containing metabolites (ATP, phosphocreatine, free ADP) were assessed using 31P nuclear magnetic resonance spectroscopy. Measurements were made both with intact autoregulation and after maximal vasodilation by 1 microM nitroprusside (NP). When afterload was used to increase MVO2, absorbance decreased at 603.5 nm and increased at 582 nm, consistent with a 10-15% increase in myocardial oxygenation, without an associated change in cardiac phosphate compounds. NP caused a further increase in myocardial oxygenation and venous PO2 consistent with an increase in the O2 supply-to-demand ratio. Increases in MVO2 due to beta-stimulation alone were not associated with changes in 603.5-nm absorbance or phosphate compounds, but in combination with NP were accompanied by increased oxygenation, venous PO2, and cardiac phosphocreatine. KCl arrest caused maximal increases in oxygenation and phosphocreatine. These findings suggest that neither cytochrome aa3 nor myoglobin in the isolated working rabbit heart is fully oxidized or oxygenated, respectively. Furthermore, the oxygenation state of the tissue varied both with afterload-induced changes in cardiac work and with changes in O2 supply/demand.
Myocardial depression produced by sustained tachycardia in rabbits
Authors: Freeman G. L. , Colston J. T.
Published: December 2017

Much recent attention has been focused on the tachycardia-induced heart failure model. We hypothesized that sustained tachycardia would lead to myocardial depression in rabbits, as it does in dogs and swine. We evaluated the passive and active length-tension relations and postrest contraction behavior in right ventricular papillary muscles from 22 New Zealand White rabbits, 11 controls, and 11 subjected to ventricular pacing at a rate of 400 beats/min for 29.4 +/- 10.6 days. Studies were performed in oxygenated buffer at 22 degrees C. Active tension was significantly reduced at muscle lengths of 0.95.Lmax and above; at Lmax it was 4.7 +/- 0.2 g/mm2 for the control group and 3.3 +/- 0.2 g/mm2 for the paced group (P less than 0.005). Both groups showed increased force development when the concentration of calcium in the buffer was increased. There were no differences between the groups in the passive length-tension relations. Of note, postrest contraction data showed that the second postrest beat was smaller for the paced animals for rest intervals up to 2 min, suggesting that beat-to-beat trans-sarcolemmal calcium handling may differ from normal in this model. We conclude that sustained tachycardia will lead to myocardial depression in rabbits; the extension of this model to a small animal species may offer new ways to explore its causative mechanisms.
Endothelin enhances delayed potassium current via phospholipase C in guinea pig ventricular myocytes
Authors: Habuchi Y. , Tanaka H. , Furukawa T. , Tsujimura Y. , Takahashi H. , Yoshimura M.
Published: December 2017

The effects of endothelin, a novel vasoconstrictive peptide, on the delayed rectifier K+ current (IK) were examined in single dialyzed cells from guinea pig ventricles. Either big endothelin or endothelin-1 enhanced IK at a dissociation constant of 2 nM with L-type Ca2+ current being unaffected. Under intracellular perfusion with pCa 7.6 solution, 3 nM big endothelin increased IK by 55 +/- 38.5%. Either pretreatment with 10 microM 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H 7) or a low Ca2+ [10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) and minus CaCl2] internal solution diminished the enhancement. Preceding stimulation of protein kinase C (PKC) by 10-20 nM 12-O-tetradecanoylphorbol-13-acetate also reduced the degree of enhancement. When Na+ was eliminated from the solutions, endothelin increased IK distinctively in cells internally dialyzed with a low Ca2+ solution. This enhancement was not abolished by either pretreatment with H 7 or by removal of Ca2+ from the external perfusate but by increasing the internal EGTA concentration to 40 mM. Preincubation with ryanodine or internal perfusion with heparin also reduced the IK enhancement under Na(+)-free conditions. Intracellular application of 200 microM guanosine 5'-O-(3-thiotriphosphate) effectively attenuated the effect of endothelin. It is concluded that endothelin enhances IK via phospholipase C-mediated PKC activation and intracellular Ca2+ mobilization. GTP-binding protein is involved in these reactions.
Role of oxygen radicals in canine myocardial metabolic derangement during regional ischemia
Authors: Ohmi H. , Ichihara K. , Abiko Y.
Published: December 2017

To clarify the role of oxygen radicals in the development of myocardial injury during ischemia, production of lipid peroxides mediated by oxygen radicals was determined in in vivo dogs subjected to regional ischemia and reperfusion. Myocardial injury was assessed by derangement in energy and carbohydrate metabolism caused by ischemia and reperfusion. The production of lipid peroxides mediated by oxygen radicals considerably increased not only during reperfusion after ischemia but also during ischemia. Removal of oxygen radicals by administration of radical scavengers [recombinant human superoxide dismutase + catalase or N-(2-mercaptopropionyl)glycine] completely prevented the increase in production of lipid peroxides during ischemia. However, the radical scavengers did not attenuate the myocardial energy and carbohydrate metabolic derangements caused by ischemia and reperfusion after ischemia. These results suggest that significant amounts of oxygen radicals are generated during ischemia as well as during reperfusion and that the oxygen radicals and subsequent lipid peroxidation are not major factors in development of myocardial injury during either ischemia or reperfusion after ischemia.
Protection from reperfusion injury by preconditioning hearts does not involve increased antioxidant defenses
Authors: Turrens J. F. , Thornton J. , Barnard M. L. , Snyder S. , Liu G. , Downey J. M.
Published: December 2017

Preconditioning the heart with 5 min of ischemia renders the heart very resistant to infarction from subsequent ischemia by an unknown mechanism. We investigated whether the protective effect of preconditioning might be related to an increase in rabbit heart antioxidant defenses. The antioxidant activities of catalase, glutathione peroxidase, Mn superoxide dismutase, Cu,Zn superoxide dismutase, glucose-6-phosphate dehydrogenase, glutathione reductase, and total glutathione were measured in ischemic and normal regions from both control and preconditioned rabbit hearts. All hearts experienced 30 min regional ischemia and 5 min reperfusion. None of the antioxidant enzymes changed in activity when comparing nonischemic and postischemic zones in either nonpreconditioned or preconditioned hearts. Total glutathione, however, was reduced in reperfused zones and showed better preservation in preconditioned hearts. To determine whether this preservation resulted from a higher value at the onset of reperfusion or slower washout during reperfusion, we analyzed a second group of nonreperfused hearts after 30 min ischemia. The hearts had normal glutathione content in both ischemic and nonischemic zones of either preconditioned or control hearts. The most likely explanation is that preconditioned hearts experienced less washout of glutathione simply because they were less injured. We therefore conclude that enhancement of antioxidant defenses is not the mechanism of preconditioning.
Modulation of bat wing venule contraction by transmural pressure changes
Authors: Davis M. J. , Shi X. , Sikes P. J.
Published: December 2017

We tested the hypothesis that the frequency and amplitude of spontaneous venular contractions in the bat wing could be modulated by changes in transmural pressure. In one series of experiments, venous pressure in the wing was elevated by pressurizing a box containing the body of the animal while the wing was exposed to atmospheric pressure. During this time, venular diameters were continuously recorded using intravital microscopic techniques while venular pressures were measured through servo-null micropipettes. In another series of experiments, single venular segments were dissected from the wing, cannulated, and pressurized in vitro. The results from both experimental protocols were qualitatively similar; alterations in venous pressure over a narrow range (+/- 5 cmH2O from control) produced substantial changes in contraction frequency and amplitude. The product of frequency and cross-sectional area was maximal over the venous pressure range between 10 and 15 cmH2O. Venules demonstrated a rate-sensitive component in their reaction to rapid pressure changes, because contraction bursts occurred immediately after positive pressure steps and quiescent periods often occurred after negative pressure steps. We conclude that venular vasomotion in the bat wing is modulated by intraluminal pressure and involves a bidirectional, rate-sensitive mechanism. In addition, comparisons with arteriolar vasomotion studies suggest that venules are more sensitive to luminal pressure changes than arterioles.
Cyclic nucleotide phosphodiesterases from frog atrial fibers: isolation and drug sensitivities
Authors: Lugnier C. , Gauthier C. , Le Bec A. , Soustre H.
Published: December 2017

The cyclic nucleotide phosphodiesterase (PDE) forms present in frog atrial fibers were isolated and characterized by their drug sensitivities. DEAE-sephacel chromatography of cytosolic PDE activity resolved three major PDE forms: peak A hydrolyzed both adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) and was activated by calcium-calmodulin (PDE I); peak B also hydrolyzed both cAMP and cGMP but was activated by 5 microM cGMP (PDE II); peak C specifically hydrolyzed cAMP (PDE IV). Rolipram specifically inhibited PDE IV (Ki = 1.1 microM), whereas dipyridamole potently inhibited both PDE II (Ki = 4.6 microM) and PDE IV (Ki = 0.8 microM). Atrial fiber PDE I was preferentially inhibited by zaprinast (Ki = 10 microM). 3-Isobutyl-1-methyl xanthine (IBMX) and theophylline inhibited nonspecifically all three different enzymes. The positive inotropic drug CI 930 only inhibited the different isolated atrial PDE forms at concentrations greater than 200 microM. However, under assay conditions for which PDE IV was specifically inhibited (presence of 100 microM rolipram), an IC50 of 17 microM for CI 930 was observed on the remaining 26% cAMP hydrolytic activity of peak C (which could represent a cGMP-inhibited PDE form: PDE III). The same PDE forms were also found in frog ventricle. The major difference between frog atrial fiber (and ventricular tissue) PDEs and mammalian cardiac PDEs is that the main cytosolic cAMP-specific hydrolytic activity in frog heart is due to PDE IV rather than PDE III. Rolipram, dipyridamole, and zaprinast might be useful tools to investigate the participation of cAMP in frog atrial contraction (unpublished observations).
Role of adenosine in platelet-mediated reduction in pulmonary vascular permeability
Authors: Paty P. S. , Sherman P. F. , Shepard J. M. , Malik A. B. , Kaplan J. E.
Published: December 2017

Previous studies have shown that platelets decrease 125I-labeled albumin permeability across confluent bovine pulmonary artery endothelial cell monolayers. In the current study, we addressed the role of platelets and platelet-derived adenosine (ADO) in vascular barrier function with cultured endothelial cells and isolated perfused lungs. Both 7 x 10(7) platelets/ml and conditioned media prepared from the same concentration of platelets reduced albumin permeability of endothelial monolayers by 37%. This activity was abolished by pretreatment of the platelets with adenosine deaminase (ADA). ADO (10(-7) M) added directly to the monolayer reduced permeability by 19%. Dipyridamole (10(-6) M), an inhibitor of facilitated ADO uptake, was used to evaluate the contribution of endothelial uptake of ADO in the platelet effect. Dipyridamole pretreatment of the endothelial monolayer did not alter the ability of platelets to decrease albumin permeability. Addition of either an A1- or A2-receptor-specific analogue of ADO to endothelial monolayers revealed that only the A1-analogue possessed permeability-decreasing activity. An isolated perfused guinea pig lung model was used to evaluate the effect of platelets on transvascular water flux as measured by the capillary filtration coefficient (Kf,c). Platelets (4.5 x 10(7) platelets/ml) added to the perfusate reduced Kf,c by 29%. Pretreatment of platelets with ADA abolished this response. The addition of ADO (10(-7) M) reduced Kf,c by 11%. Pulmonary vascular resistance was not changed by any intervention. Our results indicate that ADO is a component in platelet-mediated decreases both in albumin permeability across endothelial monolayers and of the capillary filtration coefficient in isolated perfused lungs.
Oxygen free radical-mediated selective endothelial dysfunction in isolated coronary artery
Authors: Todoki K. , Okabe E. , Kiyose T. , Sekishita T. , Ito H.
Published: December 2017

To understand the direct involvement of free radicals causing reduction in endothelium-dependent relaxation of isolated canine coronary ring preparations, this study was undertaken to examine the effect of free radicals generated from dihydroxy fumarate (DHF) plus Fe(3+)-ADP or from H2O2 plus FeSO4. The vasodilators (acetylcholine, bradykinin, A23187, and nitroglycerin) were given after DHF/Fe(3+)-ADP or H2O2/FeSO4 was removed from the organ chamber. The earlier DHF/Fe(3+)-ADP exposure produced an attenuation of the relaxation of the rings induced by acetylcholine, bradykinin, or A23187 but not of the relaxation induced by nitroglycerin. The observed effect of previous DHF/Fe(3+)-ADP exposure was significantly protected in the vessels isolated from the dogs treated with alpha-tocopherol. In the experiments for assessing the effect of various scavengers, 1O2 scavenger histidine or iron chelator deferoxamine effectively protected the attenuation induced by DHF/Fe(3+)-ADP exposure of the relaxation elicited by acetylcholine; superoxide dismutase (SOD), catalase, or dimethyl sulfoxide (DMSO) had no effect on this system. Furthermore, the relaxation elicited by acetylcholine, but not nitroglycerin, was significantly attenuated by the earlier exposure to .OH generated by Fenton's reagent (H2O2+FeSO4); the attenuation was significantly protected by DMSO. These results are consistent with the view that .OH, 1O2, and/or iron-dependent reactive species selectively damage endothelium-dependent relaxation as opposed to endothelium-independent relaxation in endothelium-intact coronary ring preparations. It is also postulated that lipid peroxidation may be responsible for this effect.
EDRF as a possible mediator of sepsis-induced arteriolar dilation in skeletal muscle
Authors: Lubbe A. S. , Garrison R. N. , Cryer H. M. , Alsip N. L. , Harris P. D.
Published: December 2017

Vascular endothelial cells influence microvessel diameters in vivo and in vitro and participate in host-defense mechanisms during sepsis. We examined whether small arteriole dilation in skeletal muscle during high cardiac output bacteremia (HOB) and low cardiac output live Escherichia coli sepsis (LOS) is mediated by an endothelium-derived relaxing factor (EDRF). Local chemical blockade of EDRF by hydroquinone (HQ) substantially blunted acetylcholine-induced dilation of small arterioles. HQ also prevented large arteriole (55-135 microns) constriction and small arteriole (6-22 microns) dilation in the cremaster muscle of rats during HOB. In LOS, small arteriole dilation was also prevented by HQ but only during the early period when blood pressure was unchanged from baseline. HQ did not alter large arteriole constriction during LOS. We conclude that small arteriole vasodilation in skeletal muscle is mediated at least in part by EDRF during bacteremia. Because EDRF cannot mediate large arteriole constriction and because HQ blunted large arteriole constriction during HOB, we now suspect that HQ also interferes at least in part with some large arteriole vasoconstrictor mechanism, possibly leukotrienes or an endothelium-derived constricting factor, which mediates large arteriole constriction during HOB. Our data also suggest that large arteriole constriction during LOS is partly mediated by factors that are unaffected by HQ. The endothelium appears to play an important role in the microcirculatory responses of skeletal muscle to live E. coli sepsis through more than one mechanism.
Role of intracellular thiols in release of EDRF from cultured endothelial cells
Authors: Hecker M. , Siegle I. , Macarthur H. , Sessa W. C. , Vane J. R.
Published: December 2017

The availability of intracellular reduced thiols, such as L-cysteine or glutathione (GSH), may be critically important for the biosynthesis of endothelium-derived relaxing factor (EDRF). We have, therefore, investigated the effects of various sulfhydryl (SH) reagents, such as 1-chloro-2,4-dinitrobenzene (CDNB), diamide, 2,2'-dithiodipyridine (DTDP), or N-ethyl-maleimide (NEM), on the release of EDRF from cultured endothelial cells. None of the SH reagents tested affected the flow-induced EDRF release, but DTDP and NEM inhibited the release of EDRF stimulated by ADP, ionomycin, or poly-L-lysine. In contrast, NG-nitro-L-arginine methyl ester, an inhibitor of EDRF biosynthesis, blocked both the flow- and agonist-induced release of EDRF. Although NEM substantially potentiated the flow-induced release of prostacyclin (PGI2), probably due to a blockade of the reacylation of arachidonic acid, it inhibited the stimulated release of PGI2, whereas diamide did not significantly affect either release. Like CDNB or diamide, NEM, but not DTDP, caused a significant decrease in endothelial GSH. In contrast, both NEM and DTDP, but not CDNB or diamide, inhibited the ADP-induced mobilization of intracellular calcium, suggesting that they act on specific target proteins involved in endothelial cell calcium homeostasis rather than intracellular free SH groups. Moreover, the selective inhibition by these two SH reagents of the stimulated release of EDRF implies that a fundamental regulatory difference exists between agonist- and flow-induced EDRF biosynthesis.
Animal species differences in erythrocyte aggregability
Authors: Ohta K. , Gotoh F. , Tomita M. , Tanahashi N. , Kobari M. , Shinohara T. , Terayama Y. , Mihara B. , Takeda H.
Published: December 2017

Species differences in erythrocyte aggregability were investigated employing our whole blood erythrocyte aggregometer. Blood was sampled from seven species, including humans and anesthetized (30 mg/kg pentobarbital) animals. The erythrocyte aggregation rates were the following (in s-1): cats, 0.213 +/- 0.027 (means +/- SD); dogs, 0.164 +/- 0.027; men, 0.112 +/- 0.025; rats, 0.111 +/- 0.005; domestic rabbits, 0.049 +/- 0.021; and mongolian gerbils, 0.034 +/- 0.015. Domestic fowls did not exhibit erythrocyte aggregograms like those seen in the other species. Statistical analysis revealed significant differences among the erythrocyte aggregation rates of the different species (multiple-comparisons with an overall significance level of 0.05) except between men and rats and between rabbits and gerbils. No single factor which is known to accelerate the erythrocyte aggregation rate (hematocrit, fibrinogen, etc.) was correlated with the erythrocyte aggregation rate except the globulin concentration in the blood. The failure to detect erythrocyte aggregation in domestic fowls was probably attributable to their erythrocyte shape. These results suggest that each species has its own proper tendency for erythrocyte aggregation. This factor must be taken into consideration when the blood circulation is discussed among different animal species.