bluuebunny/crossref_metadata_2025 huggingface dataset:
Body surface mapping of ectopic left ventricular activation. QRS spectrum in patients with prior myocardial infarction.
Authors: SippensGroenewegen A , Spekhorst H , van Hemel N M , Kingma J H , Hauer R N , Janse M J , Dunning A J
Published: June 2012

To improve electrocardiographic localization of the site of origin of ectopic left ventricular (LV) impulse formation in the heart with prior myocardial infarction, 62-lead body surface QRS integral maps were studied during LV pacing at a total of 221 endocardial sites in 14 patients with previous anterior (AMI), inferior (IMI), lateral (LMI), or anterior and inferior (AMI/IMI) myocardial infarction. The anatomic location of each pacing site was computed using digitized biplane fluoroscopic images and plotted on standardized LV endocardial polar projections. A data base of characteristic AMI and IMI mean QRS integral maps was developed after visually selecting subgroups with nearly identical QRS integral morphology from the ectopic activation sequences produced at 110 sites in eight patients with AMI and at 66 sites in four patients with IMI. Intrasubgroup pattern uniformity and intersubgroup pattern variability were statistically verified. The endocardial pacing site locations belonging to each AMI and IMI subgroup were depicted as segments on the respective LV polar projections. In patients with AMI, a total of 18 typical mean QRS integral patterns were obtained, whereas 22 different mean total QRS integral patterns showing more substantial intersubgroup variation were acquired in patients with IMI. Posterolateral regions exhibited a relatively low electrocardiographic sensitivity (six AMI and five IMI patterns) as compared with anteroseptal regions (12 AMI and 17 IMI patterns). Total QRS integral patterns obtained at 24 sites in one patient with LMI were largely compatible with the IMI mean total QRS integral patterns, whereas the majority of total QRS integral patterns acquired at 21 sites in one patient with AMI/IMI corresponded with the AMI mean total QRS integral patterns. The results show that total body surface QRS integral maps generated during LV pacing in patients with prior myocardial infarction cluster by pattern and that each QRS integral pattern is related to a circumscribed endocardial segment of ectopic impulse formation. The relation between a given QRS integral pattern and the position and size of the corresponding paced segment is dependent on infarct location. The present infarct-specific data base of characteristic total body surface QRS integral patterns provides a clinical tool to obtain detailed electrocardiographic localization of ventricular arrhythmias in patients with previous myocardial infarction.
Accumulation and assembly of myosin in hypertrophic cardiomyopathy with the 403 Arg to Gln beta-myosin heavy chain mutation.
Authors: Vybiral T , Deitiker P R , Roberts R , Epstein H F
Published: June 2012

The sarcomeric proteins and organization of cardiac myofibrils appeared intact in multiple unrelated patients with hypertrophic cardiomyopathy. In two subjects demonstrating the missense mutation at position 403 (Arg to Gln) in the beta-myosin heavy chain gene, total myosin and immunoreactive beta-myosin heavy chain levels were similar to those found in other patients with hypertrophic cardiomyopathy and various disease control subjects. No alteration in expression of the cardiac alpha-myosin heavy chain gene was observed. These results are consistent with the examined myosin heavy chain mutation, permitting proper accumulation and assembly of myosin while primarily impairing contractile function. The characteristic myocyte disarray would appear likely to be a secondary consequence of the mutations.
Regulation of muscle transcription by the MyoD family. The heart of the matter.
Authors: Olson E N
Published: June 2012

The two striated muscle cell types, skeletal and cardiac muscle, express overlapping sets of muscle-specific genes. Activation of muscle-specific transcription in skeletal muscle is controlled by the MyoD family of regulatory factors, which are expressed exclusively in skeletal muscle. Members of the MyoD family share homology within a basic helix-loop-helix (HLH) motif that mediates DNA binding and dimerization and form heterodimers with widely expressed HLH proteins, referred to as E proteins. Although many of the genes that are regulated by members of the MyoD family are also expressed in cardiac muscle, known members of the MyoD family have never been detected in cardiac muscle, suggesting that cardiac myocytes either express unique cell type-specific HLH proteins or rely on a distinct regulatory strategy for activation of cardiac muscle transcription. This review will summarize current knowledge of the mechanisms through which the MyoD family activates skeletal muscle transcription and will consider potential mechanisms that may regulate gene expression in the heart.
Effects of intense antecedent sympathetic stimulation on sympathetic neurotransmission in the heart.
Authors: Yang T , Levy M N
Published: June 2012

We studied the effects of intense sympathetic stimulation on the chronotropic responses of the heart to subsequent test stimulations of the cardiac autonomic nerves in dogs anesthetized with alpha-chloralose. Such intense sympathetic stimulations (which we refer to as "release stimulations") are known to release neuropeptide Y as well as norepinephrine. The changes in cardiac cycle length evoked by vagal and sympathetic test stimulations were progressively more attenuated as we increased the frequency and duration of the antecedent sympathetic release stimulations. We found that 2.5 minutes after a maximal release stimulation (30 Hz for 5 minutes), the mean +/- SEM chronotropic responses to the vagal and sympathetic test stimulations were diminished to 36.5 +/- 1.6% and 54.7 +/- 1.3% respectively, of the prestimulation responses. The mean times for the chronotropic responses to the vagal and sympathetic test stimulations to recover to their control values were 52.0 +/- 1.3 and 63.2 +/- 2.9 minutes, respectively. This enduring effect suggests the action of a neuropeptide, such as neuropeptide Y. Phentolamine potentiated the inhibitory effects of the sympathetic release stimulations. The chronotropic responses to isoproterenol infusions were not affected appreciably by antecedent sympathetic release stimulation. We conclude, therefore, that the inhibitory effects of antecedent sympathetic release stimulation on cardiac sympathetic neurotransmission are mediated prejunctionally, probably via an inhibition of the neuronal release of norepinephrine by neuropeptide Y.
Selective A2-adenosine receptor agonists do not alter action potential duration, twitch shortening, or cAMP accumulation in guinea pig, rat, or rabbit isolated ventricular myocytes.
Authors: Shryock J , Song Y , Wang D , Baker S P , Olsson R A , Belardinelli L
Published: June 2012

In this study, the hypothesis that mammalian ventricular myocytes possess A2-adenosine receptors was tested. Electrophysiological, contractile, and cAMP responses to the selective A2-adenosine receptor agonists 2-[2-(4-methylphenyl)ethoxy]adenosine (WRC-0090) and 2-(2-cyclohexylethoxy)adenosine (WRC-0013) and the nonselective adenosine receptor agonist 5'-(N-ethylcarboxamido)adenosine (NECA) were measured using ventricular myocytes isolated from guinea pig, rabbit, and rat hearts. Pertussis toxin pretreatment and/or the selective A1-adenosine receptor antagonists 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) and (+/-)N6-endonorbornan-2-yl-9-methyladenine (N-0861) were used to prevent activation of A1-adenosine receptors in these cells. Action potential duration at 50% repolarization was not altered by WRC-0090, NECA, or WRC-0013 with or without 0.1 microM DPCPX or pertussis toxin pretreatment, and WRC-0090 and NECA failed to prolong the action potential duration of myocytes exposed to 0.1 or 1 microM forskolin. WRC-0090 alone or with 0.1 microM DPCPX did not increase the amplitude of shortening of pertussis toxin-treated or untreated myocytes, and WRC-0090 or NECA did not significantly increase cAMP accumulation. In contrast to these results with myocytes, in the smooth muscle cell line DDT1MF-2 the effect of both selective A2-agonists on cAMP accumulation was biphasic: low concentrations (< or = 0.3 microM) increased but higher concentrations decreased accumulation of cAMP. The decreased cAMP accumulation seen at higher agonist concentrations was completely abolished by either 0.1 microM DPCPX or pretreatment of cells with pertussis toxin. In summary, the results of the present study do not provide evidence for A2-adenosine receptors on mammalian ventricular cardiomyocytes but confirm reports of the coexistence of both A1 and A2 subtypes of adenosine receptors on DDT1MF-2 cells.
Cationic amphiphiles prevent calcium leak induced by ATP depletion in myocardial cells.
Authors: Clague J R , Post J A , Langer G A
Published: June 2012

Excessive calcium influx is important in the irreversible injury of cardiac myocytes and other cell types. The mechanism is unknown, but possibilities include L-type channels, Na(+)-Ca2+ exchange, sarcolemmal (SL) defects, and calcium leak channels. In this study, metabolic inhibition was used to induce ATP depletion and augmented calcium influx in cultured cardiac myocytes. Inhibition of the L-type calcium channel and Na(+)-Ca2+ exchanger had no significant effect on the calcium leak. There was no significant lactate dehydrogenase release, indicating that the leak did not occur through major SL defects. No alterations in the asymmetric distribution of SL phospholipids were demonstrated. Phospholipid rearrangements were therefore not responsible. The leak was unaffected by 0.5 mM cadmium and 1 microM nifedipine but was augmented by 50 microM nifedipine, characteristics in common with calcium leak channels. Insertion of the cationic amphiphiles dodecyltrimethylammonium bromide or polymyxin B sulfate into the SL had a profound inhibitory effect on the calcium leak. The anionic amphiphile sodium dodecyl sulfate had the opposite effect, and the neutral amphiphile lauryl acetate had no effect. These results suggest that an alteration in the SL surface charge affects calcium leak. It is proposed that the augmented calcium influx occurs via calcium leak channels and that these can be modulated by charged amphiphiles.
Novel cation-selective mechanosensitive ion channel in the atrial cell membrane.
Authors: Kim D
Published: June 2012

Stretch of atrial muscle causes the release of atrial natriuretic peptide, but no stretch-sensitive membrane sensors have been clearly identified so far. The existence of an ion channel that could mediate stretch-induced Ca2+ influx and subsequent release of the peptide was examined in rat atrial cells. In this report, the discovery of a novel atrial ion channel whose opening probability is extremely sensitive to either positive or negative pressure (half-maximal activation pressure, approximately 1.5 mm Hg) is described. Activation of the current by pressure applied to the pipette was observed both at the whole-cell and single-channel levels. The channel was permeable to cations including Ca2+. The channels were clustered with six to nine channels in each cluster, and several channels tended to open simultaneously in response to a graded increase in pressure for the inwardly passing current. Hypotonic swelling also activated these channels. These results show that mechanosensitive nonselective cation channels exist in atrial cells and suggest that they could be involved in beat-to-beat regulation of the atrial contraction as well as the stretch-induced expression of proto-oncogenes and secretion of atrial natriuretic peptide via increased Ca2+ entry.
Induction of vascular smooth muscle cell expression of plasminogen activator inhibitor-1 by thrombin.
Authors: Noda-Heiny H , Fujii S , Sobel B E
Published: June 2012

Local accumulation of plasminogen activator inhibitor-1 (PAI-1) in response to thrombosis has been implicated not only in inhibition of fibrinolysis but also in the pathogenesis of vascular disease. To determine whether thrombin, known to be released from thrombi, can induce expression of PAI-1 in vascular smooth muscle, bovine aortic smooth muscle cells were exposed to highly purified bovine thrombin. Thrombin, in the absence of serum, induced production of PAI-1 by bovine aortic smooth muscle cells in a dose-dependent manner. PAI-1 activity in the conditioned media reached a maximum with 12 nM thrombin. Metabolic labeling with [35S]methionine demonstrated that the elaborated PAI-1 was newly synthesized and that it comprised both a cleaved inactive 42-kd form and an uncleaved active 46-kd form. The increase of PAI-1 activity in the media paralleled the thrombin-induced increase in the concentration of the 46-kd form. Preincubation of thrombin with hirudin, a specific inhibitor of thrombin, or with D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone, an inhibitor of the active site of thrombin, prevented the induction of PAI-1 synthesis. The stimulatory effect of thrombin on PAI-1 synthesis was also evident at the level of expression of mRNA, with steady-state PAI-1 mRNA levels increasing by 100% in 4-8 hours. When the bovine aortic smooth muscle cells were exposed to transforming growth factor-beta 1, an agonist shown previously to increase PAI-1 synthesis in diverse cell types, synergy with thrombin was evident.(ABSTRACT TRUNCATED AT 250 WORDS)
Altered calcium sensitivity of isometric tension in myocyte-sized preparations of porcine postischemic stunned myocardium.
Authors: Hofmann P A , Miller W P , Moss R L
Published: June 2012

Postischemic ventricular myocardial dysfunction, termed stunning, is characterized by a persistent but ultimately reversible depression of contractile function. The present study was undertaken to investigate the possibilities that reduced contractile force in stunning is due to a decrease in maximal tension-generating capability or to a decrease in the Ca2+ sensitivity of the myofilaments. The experiments combine an in vivo open-chest porcine heart model of stunning (n = 5) with in vitro measures of myocyte myofilament calcium sensitivity from these same hearts. Regional myocardial function in the left anterior descending coronary artery (LAD) perfusion bed of porcine hearts was measured with transmural ultrasonic crystals. The protocol was 45 minutes of low-flow LAD ischemia at 40% of control flow, followed by 30 minutes of postischemic reperfusion at control aerobic flow. Percent systolic wall thickening decreased to 8 +/- 5% of control during ischemia (p < 0.05) and returned to 38 +/- 8% of control in the postischemic stunned state (p < 0.05). Serial endocardial biopsies were obtained from the preischemic and postischemic myocardium in the LAD perfusion bed and from the aerobically perfused myocardium in the circumflex bed. The biopsies were mechanically disrupted, and myocyte-sized preparations of permeabilized myocardium were attached to a force transducer and a length-changing device to allow for direct measurement of steady-state tension-pCa (i.e., -log[Ca2+]) relations. The pCa for half-maximal activation of tension, i.e., pCa50, in LAD myocardium decreased from 5.88 +/- 0.05 before ischemia to 5.69 +/- 0.03 after ischemia (p < 0.05); however, maximal Ca(2+)-activated tension and the slope of the tension-pCa relation were unaffected by the ischemic episode.(ABSTRACT TRUNCATED AT 250 WORDS)
XeCl laser-induced fluorescence of atherosclerotic arteries. Spectral similarities between lipid-rich lesions and peroxidized lipoproteins.
Authors: Oraevsky A A , Jacques S L , Pettit G H , Sauerbrey R A , Tittel F K , Nguy J H , Henry P D
Published: June 2012

Autofluorescence spectroscopy of arterial surfaces provides information about the distribution and composition of atherosclerotic plaques. The aim of the study was to determine whether accumulation of peroxidized lipoproteins in arterial walls, a process postulated to play a role in initiating atherosclerotic changes, can be demonstrated by fluorescence spectroscopy. XeCl excimer laser (308 nm)-induced fluorescence of human aortas containing early lipid-rich noncollagenous lesions exhibited marked red shifts and broadening of the fluorescence spectra compared with spectra from nonatherosclerotic aortas. Similar profiles were observed in spectra obtained from oxidatively modified low density lipoprotein but not native low density lipoprotein. In hypercholesterolemic rabbits with early foam cell lesions, spectral shifts resembled those of oxidized beta-very low density lipoprotein, the major lipoprotein accumulating in arteries of rabbits fed cholesterol. XeCl laser-fluorescence spectroscopy of arterial surfaces may be useful for the identification of arteries accumulating modified lipoproteins (oxidized low density lipoprotein), a chemical change indicative of atherosclerosis in its early and probably reversible stages.
Abdominal coarctation increases insulin-like growth factor I mRNA levels in rat aorta.
Authors: Fath K A , Alexander R W , Delafontaine P
Published: June 2012

We have previously demonstrated specific insulin-like growth factor I (IGF I) mRNA transcripts in cultured endothelial and vascular smooth muscle cells and postulated an important role for IGF I in blood vessel growth responses. The purpose of this study was to characterize IGF I gene expression in a model of aortic coarctation hypertension in the rat. This high-renin model of hypertension is associated with hyperplastic vascular responses. Northern analysis of rat aorta demonstrated four specific IGF I mRNA transcripts sized 7.6, 4.6, 1.8, and 0.9-1.2 kb. Quantitation of aortic IGF I mRNA levels by solution hybridization/RNase protection assay demonstrated induction of IGF I transcripts in the hypertensive aorta; levels more than doubled at 7 days and were still significantly elevated 21 days after coarctation. In situ hybridization analysis indicated that IGF I transcripts were localized primarily to adventitial surfaces in normotensive aorta, with minimal signal detected over vascular cells. In hypertensive aortas, there was an increase in IGF I transcripts primarily over vascular smooth muscle cells. Thus, vascular IGF I gene expression is induced in this model of high-renin hypertension. IGF I may play an important role in autocrine/paracrine-mediated vessel wall remodeling in hypertension.
Alteration of reactivity of native arteries induced by venous graft placement.
Authors: Bjorling D E , Saban R , Tengowski M W , Gruel S M , Rao V K
Published: June 2012

Occlusion of aortocoronary venous grafts can be due to thrombosis, atherosclerosis, or vasospasm. Investigations have focused on properties of the graft itself, and little is known about the vascular reactivity and function of the native arteries proximal and distal to the vein graft, although spasm of the native artery distal to the graft site has been observed in patients. We hypothesized that the function of the endothelium of the native arteries may be altered after surgery. Autogenous venous grafts were placed in femoral arteries of rabbits to study the reactivity of the native arteries after grafting. Four weeks after graft implantation, the vein graft, ipsilateral vein, and native artery proximal and distal to the graft were removed for in vitro studies. Morphological evaluation by scanning electron microscopy and fluorescence microscopy after labeling with acetylated low density lipoprotein labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate indicated the presence of an intact, metabolically active endothelial layer. There was no alteration in the contractile responses to phenylephrine of the arteries, vein grafts, or veins. Precontracted vein grafts, veins, and arterial segments proximal to the grafts relaxed when exposed to endothelium-dependent vasodilators (acetylcholine, arachidonic acid, and substance P), but the native arteries distal to the grafts did not. In bioassay cascade experiments, the distal artery did not release any measurable relaxing factor when exposed to acetylcholine. We conclude that the endothelium of the distal artery did not function normally. The extent and reversibility of altered endothelial function remain to be determined. This observation may help to explain the occurrence of myocardial infarction after aortocoronary bypass grafting in some patients.
Selective inhibition of endothelium-dependent vasodilator capacity by Escherichia coli endotoxemia.
Authors: Parker J L , Adams H R
Published: June 2012

Increased release of endothelium-derived relaxing factor/nitric oxide has been proposed as the final common pathway for vasodilator responses to gram-negative lipopolysaccharide (endotoxin). To test this hypothesis, we examined endothelium-dependent and endothelium-independent vasodilator agents in vascular smooth muscle isolated from guinea pigs 16 hours after injection of saline (control group) or induction of Escherichia coli endotoxemia; aortic rings (approximately 1 mm in diameter) were studied with standard isometric tension techniques. Endotoxemia resulted in a significant loss of vasodilator responses to the endothelium-dependent receptor agonists acetylcholine (10(-10)-10(-5) M) and ADP (10(-8)-10(-5) M). In contrast, endotoxemia did not affect vasodilator responses to either the endothelium-dependent receptor agonist substance P (10(-11)-10(-7) M), the endothelium-dependent and receptor-independent agonist A23187 (10(-9)-10(-6) M), or the endothelium-independent agonist nitroprusside (10(-10)-10(-4) M). The nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) inhibited the vasodilator response to acetylcholine more in vessels from lipopolysaccharide-injected than control guinea pigs. Unexpectedly, L-NAME converted the endothelium-dependent vasodilator action of ADP to an endothelium-dependent vasoconstrictor response that was blocked individually by the cyclooxygenase inhibitor indomethacin, the thromboxane synthase inhibitor dazoxiben, and the thromboxane A2 receptor antagonist SQ29548. We conclude that in vivo endotoxemia inhibits the constitutive isoform of nitric oxide synthase in endothelial cells by selectively disrupting receptor-coupled activation mechanisms shared by acetylcholine and ADP. Furthermore, since L-NAME unmasks a thromboxane A2-mediated vasoconstrictor action of the endogenous purinoceptor agonist ADP, drugs that inhibit nitric oxide synthase could exacerbate sepsis-induced vasoconstriction and ischemia by synergizing with lipopolysaccharide-induced inhibition of endothelial nitric oxide synthase.
Hypoxia enhances isoproterenol-induced increase in heart interstitial adenosine, depressing beta-adrenergic contractile responses.
Authors: Fenton R A , Dobson J G
Published: June 2012

Endogenous interstitial adenosine may protect the hypoxic heart by attenuating beta-adrenergic-induced contractile and metabolic responses, thereby reducing energy utilization. Constant-flow perfused rat hearts were used to study: 1) the effect of hypoxia on isoproterenol (ISO)-induced increase in interstitial adenosine, as estimated with epicardial surface transudates, and 2) the role of endogenous adenosine in hypoxic depression of ISO-induced contractile responses. ISO (1 nM for 10 minutes) in the normoxic heart increased transudate adenosine 114% from a pre-ISO normoxic value of 343 pmol/ml. ISO administered to the hypoxic heart increased transudate adenosine 357% from a pre-ISO hypoxic value of 797 pmol/ml. The absolute magnitude of the ISO-induced increase in transudate adenosine was 625% greater during hypoxia than during normoxia. This was associated with a reduction in the ISO-induced contractile response during hypoxia. In other experiments, with normoxia ISO (10 nM for 10 seconds) increased developed left ventricular pressure by 140 mm Hg, and the maximum rates of left ventricular pressure development and relaxation by 5,860 and 2,771 mm Hg/sec, respectively, above control values of 90 mm Hg, 2,250 mm Hg/sec, and 1,875 mm Hg/sec. Hypoxia reduced the three ISO-induced contractile responses by 50%, 56%, and 36%. However, 1,3-dipropyl-8-cyclopentylxanthine (5 x 10(-7) M), an adenosine A1-receptor antagonist, added to the hypoxic hearts resulted in only a 31%, 39%, and 9% reduction in the ISO-induced responses in developed left ventricular pressure and the maximum rates of left ventricular pressure development and relaxation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Regulation of Ca2+ transport by platelet-derived growth factor-BB in rat vascular smooth muscle cells.
Authors: Cirillo M , Quinn S J , Romero J R , Canessa M L
Published: June 2012

The present study investigates the effects of platelet-derived growth factor (PDGF) isoform BB (PDGF-BB) on cytosolic Ca2+ concentration ([Ca2+]i), Ca2+ transport, and Ca2+ pools in rat vascular smooth muscle (VSM) cells. VSM cells from thoracic aorta of Milan normotensive rats were enzymatically dispersed, cultured in 10% serum medium, and made quiescent by 72 hours in 0.3% serum medium. [Ca2+]i, Ca2+ influx, Ca2+ efflux, and exchangeable cell Ca2+ pool were evaluated by ratiometric fluorescent and radioisotope techniques. Ca2+ transport showed time-dependent changes during stimulation with PDGF-BB. The initial early responses to this peptide were transient rise in [Ca2+]i, a 30% decrease in Ca2+ influx, and a 3.6-fold increase in the rate constant for active Ca2+ efflux. Stimulation of Ca2+ efflux and inhibition of Ca2+ influx were associated with a substantial 30% reduction in the cell Ca2+ pool. This initial stimulation of Ca2+ efflux is concomitant with Ca2+ mobilization into the cytosol and is due to activation of Na(+)-independent Ca2+ efflux via the Ca2+ pump. After a 10-minute stimulation, Ca2+ influx returned to the basal value, whereas Ca2+ efflux remained 2.2-fold above control values, leading to a decline in [Ca2+]i below basal levels and a further decrease in the cell Ca2+ pool. Nearly half of this late Ca2+ efflux appears to be driven by Na(+)-Ca2+ exchange, as evidenced by its external Na+ dependence. After a 120-minute stimulation with PDGF-BB, nifedipine-sensitive Ca2+ influx is increased 37% above basal levels, and Ca2+ efflux remains elevated. During prolonged stimulation by PDGF-BB, both Ca2+ influx and efflux are stimulated, resulting in a new intracellular Ca2+ homeostasis marked by the recovery of the cell Ca2+ pool but a lowered [Ca2+]i. These final events coincide with the initiation of cell proliferation in VSM cells by PDGF-BB.
Natural course of endothelium-dependent and -independent responses in autogenous femoral veins grafted into the arterial circulation of the dog.
Authors: Ishii T , Okadome K , Komori K , Odashiro T , Sugimachi K
Published: June 2012

We examined the natural course of endothelium-dependent and -independent responses in reversed autogenous vein grafts during regeneration and tissue repair processes after vein grafting in dogs. Vein grafts implanted in the canine femoral artery were removed, cut into rings, and suspended in organ chambers for isometric tension recording at 3 days and 1, 2, 4, and 6 weeks after implantation. Endothelial cells were denuded from some rings. Control veins were taken from nonsurgically treated femoral veins. Acetylcholine caused endothelium-dependent relaxations in the control veins, whereas in the vein grafts there was no evidence of endothelium-dependent relaxations to acetylcholine 3 days after the operation. Acetylcholine caused endothelium-independent contractions throughout the study. The endothelium-dependent responses to ADP and calcium ionophore A23187 were constantly maintained. Three days after the operation, the amplitude of norepinephrine-induced contractions of the vein grafts was impaired, and at 1 week the amplitude was recovered, although it was significantly smaller than the amplitude of contractions of the control veins at any postoperative period. Endothelium-independent relaxations to sodium nitroprusside were maintained throughout the study. Thus, there was a selective loss of acetylcholine-mediated relaxation in vein grafts in the early postoperative stage, a time when the intima is not thickened. These altered responses in vein grafts in the early postoperative period may have a role in graft failure.
In vivo gene transfer and expression in normal uninjured blood vessels using replication-deficient recombinant adenovirus vectors.
Authors: Lemarchand P , Jones M , Yamada I , Crystal R G
Published: June 2012

Replication-deficient recombinant adenovirus vectors do not require target cell replication for transfer and expression of exogenous genes and thus may be useful for in vivo gene therapy in the endothelium. To evaluate the feasibility of adenovirus-mediated gene transfer in vivo in normal intact blood vessels, adenovirus vectors containing the Escherichia coli lacZ gene or a human alpha 1-antitrypsin (alpha 1AT) cDNA were injected in vivo into the lumen of an occluded vessel segment of sheep jugular vein and/or carotid artery. After 15 minutes of incubation, circulation was restored; the vessels were harvested 1-28 days later and evaluated for gene transfer and expression. Three days after in vivo exposure to the lacZ adenovirus vector, the endothelium of jugular veins and carotid arteries expressed beta-galactosidase. Exposure of jugular veins and carotid arteries in vivo to the alpha 1AT adenovirus vector resulted in the expression of alpha 1AT mRNA transcripts detected by Northern analysis and in the synthesis and secretion of alpha 1AT detected by ex vivo [35S]methionine labeling. Expression with the adenovirus vectors was efficient and easily detectable 1-14 days after injection, with maximum expression at 7 days. Expression was no longer evident at 28 days. Thus, adenovirus vectors are capable of transferring exogenous genes to the endothelium of normal arteries and veins with expression for at least 2 weeks, suggesting that these vectors have the potential for a variety of cardiovascular experimental and clinical applications.
Identification of functional PGH2/TxA2 receptors on human endothelial cells.
Authors: Kent K C , Collins L J , Schwerin F T , Raychowdhury M K , Ware J A
Published: June 2012

Although functional receptors for thromboxane A2 and prostaglandin H2 (TxA2/PGH2) have been identified in platelets and vascular smooth muscle cells, receptor-mediated events in human endothelial cells stimulated by these endoperoxides have not been shown. Using cultured endothelial cells harvested from human umbilical or saphenous veins, we measured the effect of the TxA2 mimetic U46619 on mobilization of cytoplasmic calcium ([Ca2+]i), as well as release of prostacyclin and expression of the proto-oncogene c-fos, intracellular events that have been linked to [Ca2+]i rise in stimulated endothelial cells. Addition of U46619 to confluent fura 2-loaded endothelial cells caused a concentration-dependent rise in intracellular [Ca2+]i, with agonist concentrations of 300 nM producing a maximal [Ca2+]i rise. This [Ca2+]i rise was a uniform response observed in all individual endothelial cells throughout the monolayer, as shown by microspectrofluorimetric visualization. Similar effects were seen with a structurally dissimilar endoperoxide analogue, I-BOP, and with the naturally occurring endoperoxide PGH2. The initial [Ca2+]i rise was not reduced when extracellular [Ca2+]i was chelated with EGTA, but a later "plateau" phase was eliminated. An antagonist of the receptor for TxA2/PGH2 (SQ29548) strongly inhibited [Ca2+]i mobilization. Stimulation of endothelial cells with U46619 also transiently increased expression of the proto-oncogene c-fos, as determined by RNA hybridization, and induced a fivefold increase in prostacyclin release. Thus, endoperoxides can stimulate human venous endothelial cells by means of TxA2/PGH2 receptors, whose occupancy can activate intracellular events associated with functional changes.
Regulation of insulin-like growth factor I receptors on vascular smooth muscle cells by growth factors and phorbol esters.
Authors: Ververis J J , Ku L , Delafontaine P
Published: June 2012

Insulin-like growth factor I (IGF I) is an important mitogen for vascular smooth muscle cells. To characterize regulation of vascular IGF I receptors, we performed radioligand displacement experiments using rat aortic smooth muscle cells (RASMs). Serum deprivation for 48 hours caused a 40% decrease in IGF I receptor number. Exposure of quiescent RASMs to platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), or angiotensin II (Ang II) caused a 1.5-2.0-fold increase in IGF I receptors per cell. After FGF exposure, there was a marked increase in the mitogenic response to IGF I. IGF I downregulated its receptors in the presence of platelet-poor plasma. Stimulation of protein kinase C (PKC) by exposure of quiescent RASMs to phorbol 12-myristate 13-acetate caused a biphasic response in IGF I binding; there was a 42% decrease in receptor number at 45 minutes and a 238% increase at 24 hours. To determine the role of PKC in growth factor-induced regulation of IGF I receptors, we downregulated PKC by exposing RASMs to phorbol 12,13-dibutyrate (PDBu) for 48 hours. PDGF- and FGF- but not Ang II-mediated upregulation of IGF I receptors was completely inhibited in PDBu-treated cells. Thus, acute PKC activation by phorbol esters inhibits IGF I binding, whereas chronic PKC activation increases IGF I binding. PDGF and FGF but not Ang II regulate vascular IGF I receptors through a PKC-dependent pathway. These data provide new insights into the regulation of vascular smooth muscle cell IGF I receptors in vitro and are of potential importance in characterizing vascular proliferative responses in vivo.
Dual effect of thrombin on voltage-dependent Ca2+ channels of portal vein smooth muscle cells.
Authors: Baron A , Loirand G , Pacaud P , Mironneau C , Mironneau J
Published: June 2012

Thrombin induces a number of physiological responses in several types of cells. To determine the action of thrombin in the vein, the electrophysiological and mechanical effects of thrombin were studied in rat portal vein smooth muscle cells. Ca2+ channel currents were recorded using the whole-cell patch-clamp technique. Thrombin had both inhibitory and stimulatory effects on the Ca2+ channel current. The inhibitory effect was reversed on washout of thrombin, whereas the stimulatory effect was maintained after thrombin was removed. Thrombin (1 unit/ml) produced a reversible decrease of 27.3 +/- 3.3% (n = 12) in the current amplitude and a sustained increase of 71.2 +/- 12.9% (n = 20). The thrombin-induced inhibition of Ca2+ channel current was blocked by the thrombin inhibitor hirudin and by the protease inhibitor leupeptin. The stimulatory effect of thrombin was inhibited by hirudin, by intracellular application of guanosine 5'-O-(beta-thio)diphosphate, and by antiphophatidylinositide antibodies but not by pertussis toxin. The thrombin-induced enhancement of the Ca2+ channel current amplitude was not observed when the current was previously stimulated by phorbol 12,13-dibutyrate. This suggests that the inhibitory effect of thrombin was related to its proteolytic activity and that the stimulatory effect involved activation of a pertussis toxin-insensitive GTP-binding protein, phosphatidylinositide hydrolysis, and protein kinase C activation. Both thrombin effects occurred in the same concentration range (0.001-10 units/ml). The thrombin-induced contraction of portal vein strips was completely inhibited by isradipine, and thrombin did not produce an increase in cytosolic [Ca2+], measured by indo-1 fluorescence in cells clamped at -50 mV, sufficient to activate Ca(2+)-dependent chloride current.(ABSTRACT TRUNCATED AT 250 WORDS)
Developmentally regulated herpesvirus plaque formation in arterial smooth muscle cells.
Authors: Kaner R J , Medina J , Nicholson A C , Ursea R , Schwartz S M , Hajjar D P
Published: June 2012

Previous studies of age-related susceptibility to viral infection have focused largely on the effects of aging on the immune response. Little attention has been given to age-related changes in the infectivity of target cells. We show here a fourfold greater plating efficiency of herpes simplex virus type 1 (HSV-1) for cultured vascular smooth muscle cells derived from adult rats compared with cells from genetically identical pup rats. The difference in plating efficiency appeared to be due to differences in initial attachment of the virion to the cell surface. There were no differences in the rate of viral entry or the efficiency of viral replication at high multiplicities of infection and no resistant "subpopulation" of pup cells. The pup cells did not release a soluble inhibitor of infection. Infection in both cell types was inhibited similarly by basic fibroblast growth factor (bFGF). Although adult cells exhibited a more vigorous mitogenic response to bFGF than did pup cells, binding studies did not demonstrate significant differences in the binding of bFGF to the cell surface, suggesting that differential expression of high-affinity FGF receptors could not be correlated with the difference in infectivity. We speculate that differences in the distribution of heparan sulfate in the cell surface, which serves as the initial attachment site for HSV-1, may explain the observed differences in plating efficiency. Since age is a risk factor for the development of atherosclerosis, these results have potential implications for susceptibility of the vasculature to herpesviral infections as a function of the development of the vessel wall.
Cellular mechanisms of endotoxin-induced myocardial depression in rabbits.
Authors: Hung J , Lew W Y
Published: June 2012

We investigated the mechanisms by which endotoxic shock induces intrinsic myocardial depression by studying cardiac myocytes isolated from 10 anesthetized instrumented rabbits given 172 +/- 42 (mean +/- SD) micrograms/kg IV endotoxin. Left ventricular (LV) depression developed 4 +/- 1 hours after endotoxin administration, with a 15 +/- 4% increase in LV internal end-systolic diameter, measured with sonomicrometers at a matched LV end-systolic pressure of 65 +/- 10 mm Hg. Normal LV pressure, arterial PO2, and pH were maintained to minimize confounding effects of ischemia, hypoxia, and acidosis. Cardiac myocytes from endotoxin-exposed rabbits had less unloaded cell shortening and lower peak rates of cell shortening (-dL/dt) and lengthening (+dL/dt) at [Ca2+] levels ranging from 0.5 to 16 mM when compared with myocytes isolated from normal rabbits or rabbits undergoing an identical protocol but without exposure to endotoxin. At 2 mM [Ca2+], cell shortening was depressed by approximately 25% because of a decrease in action potential duration (207 +/- 70 versus 375 +/- 64 milliseconds). In contrast, there was only mild impairment of sarcoplasmic reticulum (SR) function. When myocytes were restimulated after rest periods of 4 to 480 seconds, the decrement in cell shortening (rest decay), peak -dL/dt and peak +dL/dt, and the recovery from rest decay were similar in myocytes from endotoxin-treated and normal rabbits. There was a greater decrement in cell shortening in the second beat of postrest recovery in myocytes from endotoxin-treated rabbits than in normal myocytes. This was partly due to a 12% decrement in action potential duration with rest decay, which did not occur in normal myocytes. The SR Ca2+ content assessed by contractures in 10 mM caffeine was similar in the two groups. We conclude that endotoxic shock produces a LV depression in vivo that persists in isolated myocytes studied in vitro. This intrinsic myocardial depression is largely related to endotoxin-mediated sarcolemmal alterations, which shorten action potential duration, and is not due to alterations in SR function.
Tumor necrosis factor downregulates an endothelial nitric oxide synthase mRNA by shortening its half-life.
Authors: Yoshizumi M , Perrella M A , Burnett J C , Lee M E
Published: June 2012

Nitric oxide (NO), which accounts for the biological properties of endothelium-derived relaxing factor, is generated by NO synthase (NOS). The vascular endothelium contains two types of NOS: one is constitutively expressed (cNOS), and the other is inducible. Endothelium-mediated vasorelaxation is impaired in atherosclerotic vessels. To determine whether tumor necrosis factor (TNF)-alpha, which is commonly found in atherosclerotic lesions, has an effect on NOS message, we measured cNOS mRNA levels in TNF-treated human umbilical vein endothelial cells (HUVECs) by RNA blot analysis with a cNOS cDNA probe. TNF-alpha markedly reduced cNOS mRNA levels in HUVECs in a dose- and time-dependent manner. In response to 3 ng/mL TNF-alpha, cNOS mRNA levels began to decrease at 4 hours and diminished to only 5% of control levels at 24 hours. As little as 0.1 ng/mL TNF-alpha reduced cNOS mRNA levels by 50%. This reduction in cNOS message in response to TNF-alpha depended on protein synthesis as it was blocked by cycloheximide. In nuclear runoff experiments, TNF-alpha did not change the rate of cNOS gene transcription. cNOS mRNA is very stable under basal conditions, with a half-life of 48 hours; however, treatment with TNF-alpha shortened this half-life to 3 hours. TNF-alpha thus appears to decrease cNOS mRNA levels by increasing the rate of mRNA degradation. TNF-induced reductions in cNOS mRNA levels may have an important effect on impaired endothelium-mediated vasorelaxation in atherosclerosis.
Multiple connexins colocalize in canine ventricular myocyte gap junctions.
Authors: Kanter H L , Laing J G , Beyer E C , Green K G , Saffitz J E
Published: June 2012

We have recently shown that adult canine ventricular myocytes express three distinct gap junction channel proteins, connexin40 (Cx40), connexin43 (Cx43), and connexin45 (Cx45). These proteins have unique cytoplasmic domains that likely confer connexin-specific physiological properties. To determine whether the three distinct channel proteins are distributed in identical or different populations of gap junctions, we performed double-label immunofluorescence on disaggregated canine ventricular myocytes incubated simultaneously with a mouse monoclonal anti-Cx43 and affinity-purified polyclonal rabbit antibodies against Cx40 or Cx45. Analysis of double-labeled cardiac myocytes using laser scanning confocal microscopy revealed virtually identical patterns of immunoreactivity for both the Cx43/Cx40 and Cx43/Cx45 pairs. Double-label immunoelectron microscopy confirmed that ultrastructurally identified cardiac myocyte gap junctions contain multiple channel proteins. Thus, three channel proteins colocalize in canine cardiac myocyte gap junctions. The presence of multiple functionally distinct connexins suggests complex possibilities regarding the composition of individual channels and the regulation of intercellular coupling.
Glibenclamide, a putative ATP-sensitive K+ channel blocker, inhibits coronary autoregulation in anesthetized dogs.
Authors: Narishige T , Egashira K , Akatsuka Y , Katsuda Y , Numaguchi K , Sakata M , Takeshita A
Published: June 2012

We tested the hypothesis that ATP-sensitive K+ channels are involved in the mechanism mediating coronary autoregulation in open-chest dogs. We perfused the left anterior descending coronary artery with arterial blood from an extracorporeal circuit and measured steady-state coronary blood flow (CBF) with stepwise changes in coronary perfusion pressure (CPP) between 50 and 150 mm Hg during an intracoronary infusion of vehicle or glibenclamide (a putative blocker of ATP-sensitive K+ channels). CBF was relatively stable over CPP between 50 and 110 mm Hg during vehicle infusion, indicating the presence of autoregulation at the CPP range. During glibenclamide infusion (10 micrograms.min-1 x kg-1), CBF progressively decreased with reduction in CPP below 110 mm Hg, whereas the CPP-CBF relation at CPP above 110 mm Hg was not altered by glibenclamide. The autoregulation index [1-(delta F/F)/(delta P/P), where F indicates CBF and P indicates CPP] was greater than 0 over the CPP range between 50 and 100 mm Hg during vehicle infusion and was less than 0 during glibenclamide infusion. Glibenclamide did not alter systemic arterial pressure, heart rate, left ventricular pressure, and changes in regional myocardial oxygen consumption associated with changes in CPP. In the absence of glibenclamide, the CPP-CBF relation was reproducible in the repeated studies for time control. These results suggest that ATP-sensitive K+ channels play an important role in mediating coronary autoregulation at the lower range of CPP in the blood-perfused dog heart.
Effects of graded muscle contractions on spinal cord substance P release, arterial blood pressure, and heart rate.
Authors: Wilson L B , Fuchs I E , Mitchell J H
Published: June 2012

The release of substance P (SP)-like immunoreactivity (SP-LI) in the dorsal horn of the spinal cord and the cardiovascular changes to both high-tension (HT) and low-tension (LT) contractions were determined using alpha-chloralose-anesthetized cats. Over a 10-minute period, seven contractions (HT or LT) were induced. Each contraction was 20 seconds in duration and was followed by an 80-second quiescent period. The tension-time index (TTI) for the HT contractions was 2751 +/- 348 kg.s (mean +/- SD), which was greater than the TTI of 813 +/- 167 kg.s for the LT contractions. The HT contractions caused a greater release of SP-LI than the LT contractions: SP-LI increased from 0.18 +/- 0.02 to 0.32 +/- 0.03 fmol/100 microL and from 0.18 +/- 0.02 to 0.25 +/- 0.04 fmol/100 microL for the two types of contractions, respectively. Concomitant with this greater SP-LI release, HT contractions caused larger increases in mean arterial pressure (34 +/- 16 versus 11 +/- 4 mm Hg) and heart rate (18 +/- 7 versus 8 +/- 4 beats per minute) than did the LT contractions. These changes in SP-LI, mean arterial pressure, and heart rate were virtually abolished when the contractions were repeated after sectioning the L-5-S-2 dorsal and ventral roots or when the electrical stimulation of the ventral roots was repeated after muscle paralysis with gallamine triethiodide. These results demonstrate that contraction-evoked SP-LI release in the dorsal horn is related to the developed tension. Furthermore, these data provide additional support for the hypothesis that the release of SP from the central terminations of muscle afferents plays a role in mediating the cardiovascular responses to static contraction of skeletal muscle.