bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthetic Strands of Neonatal Mouse Cardiac Myocytes
Authors: Thomas Stuart P. , Bircher-Lehmann Lilly , Thomas Suma A. , Zhuang Jianping , Saffitz Jeffrey E. , Kléber André G.
Published: June 2012

Abstract
—The aim of the present study was to morphologically and electrically characterize synthetic strands of mouse ventricular myocytes. Linear strands of mouse ventricular myocytes with widths of 34.7±4.4 μm (W
1
), 57.9±2.5 μm (W
2
), and 86.4±3.6 μm (W
3
) and a length of 10 mm were produced on glass coverslips with a photolithographic technique. Action potentials (APs) were measured from individual cells within the strands with cell-attached microelectrodes. Impulse propagation and AP upstrokes were measured with multisite optical mapping (RH237). Immunostaining was performed to assess cell-cell connections and myofibril arrangement with polyclonal antisera against connexin43 and N-cadherins and monoclonal antibodies against cardiac myosin. Light microscopy and myosin staining showed dense growth of well-developed elongated myocytes with lengths of 34.2±4.2 μm (W
1
), 36.9±5.8 μm (W
2
), and 43.7±6.9 μm (W
3
), and length/width ratios of 3.9±0.2. Gap junctions were distributed around the cell borders (3 to 4 junctions/μm
2
cell area). Each cell was connected by gap junctions to 6.5±1.1 neighboring cells. AP duration shortened with time in culture (action potential duration at 50% repolarization: day 4, 103±34 ms; day 8, 16±3 ms;
P
<0.01). Minimum diastolic potential and AP amplitude were 71±5 and 97.2±7.6 mV, respectively. Conduction velocity and the maximum dV/dt of the AP upstroke were 43.9±13.6 cm/s and 196±67 V/s, respectively. Thus, neonatal ventricular mouse myocytes can be grown in continuous synthetic strands. Gap junction distribution is similar to the neonatal pattern observed in the hearts of larger mammals. Conduction velocity is in the range observed in adult mice and in the higher range for mammalian species probably due to the higher dV/dt
max
. This technique will permit the study of propagation, AP, and structure-function relations at cellular resolution in genetically modified mice.
Dystrophin Associates With Caveolae of Rat Cardiac Myocytes
Authors: Doyle Donald D. , Goings Gwen , Upshaw-Earley Judy , Ambler S. Kelly , Mondul Alison , Palfrey H. Clive , Page Ernest
Published: June 2012

Abstract
—The possibility of an interaction between the cytoskeletal protein dystrophin and cell surface caveolae in the mammalian myocardium was investigated by several techniques. Caveolin (cav)-3–enriched, detergent-insoluble membranes isolated from purified ventricular sarcolemma by density-gradient fractionation were found to contain dystrophin and dystroglycan. Further purification of cav-3–containing membranes by immunoprecipitation using anti–cav-3–coated magnetic beads yielded dystrophin but not always dystroglycan. Electron microscopic analysis of precipitated material revealed caveola-sized vesicular profiles that could be double-labeled with anti-dystrophin and anti–cav-3 antibodies. In contrast, immunoprecipitation of membranes with anti-dystrophin–coated beads yielded both cav-3 and dystroglycan. Electron microscopic analysis of this material showed heterogeneous membrane profiles, some of which could be decorated with anti–cav-3 antibodies. To confirm that dystrophin and cav-3 were closely associated in cardiac myocytes, we verified that dystrophin was also present in immunoprecipitated cav-3–containing membranes from detergent extracts, as well as in sonicated extracts of purified ventricular myocytes. Confocal immunofluorescence microscopy of ventricular and atrial cardiac myocytes showed that the cellular distributions of cav-3 and dystrophin partially overlapped. Immuno–electron micrographs of thin sections of rat atrial myocytes revealed a fraction of dystrophin molecules that are in apparently close apposition to caveolae. These results suggest that a subpopulation of dystrophin molecules interacts with cardiac myocyte caveolae in vivo and that some of the dystrophin is engaged in linking cav-3 with the dystroglycan complex.
Selective Downregulation of VEGF-A
165
, VEGF-R
1
, and Decreased Capillary Density in Patients With Dilative but Not Ischemic Cardiomyopathy
Authors: Abraham Dietmar , Hofbauer Reinhold , Schäfer Romana , Blumer Roland , Paulus Patrick , Miksovsky Aurelia , Traxler Hannes , Kocher Alfred , Aharinejad Seyedhossein
Published: June 2012

Abstract
—Cardiomyopathy (CM) comprises a heterogeneous group of diseases, including ischemic (ICM) and dilative (DCM) forms. The pathogenesis of primary DCM is not clearly understood. Recent studies in mice show that vascular endothelial growth factor (VEGF) is involved in ICM. Whether VEGF plays a role in human CM is unknown. We examined the mRNA and protein expression of VEGF and its receptors in hearts of patients with end-stage DCM and ICM and in healthy individuals using real-time polymerase chain reaction and Western blotting. Number of capillaries, area of myocytes, and collagen were calculated in cardiac biopsies using transmission electron microscopy. In DCM, except for VEGF-C, mRNA transcript levels of VEGF-A
165
, VEGF-A
189
, and VEGF-B and the protein level of VEGF-A and VEGF-R
1
were downregulated compared with controls (
P
<0.05). However, in ICM, mRNA transcript levels of VEGF isoforms and protein levels of VEGF-C were upregulated. The vascular density was decreased in DCM but increased in ICM compared with controls (
P
<0.05). Muscular hypertrophy was not different for ICM and DCM, although DCM had more collagen (
P
<0.05). Blunted VEGF-A and VEGF-R
1
protein expression and downregulated mRNA of the predominant isoform of VEGF-A, VEGF-A
165
, to our knowledge shown here for the first time, provide evidence that the VEGF-A defect in DCM is located upstream. Whether downregulation of certain VEGF isoforms in DCM is a cause or consequence of this disorder remains unclear, although upregulated VEGF levels in ICM are most likely the result of ischemia.
Myocardial Mechanics and Collagen Structure in the Osteogenesis Imperfecta Murine (
oim
)
Authors: Weis Sara M. , Emery Jeffrey L. , Becker K. David , McBride Daniel J. , Omens Jeffrey H. , McCulloch Andrew D.
Published: June 2012

Abstract
—Because the amount and structure of type I collagen are thought to affect the mechanics of ventricular myocardium, we investigated myocardial collagen structure and passive mechanical function in the osteogenesis imperfecta murine (
oim
) model of pro-α2(I) collagen deficiency, previously shown to have less collagen and impaired biomechanics in tendon and bone. Compared with wild-type littermates, homozygous
oim
hearts exhibited 35% lower collagen area fraction (
P
<0.05), 38% lower collagen fiber number density (
P
<0.05), and 42% smaller collagen fiber diameter (
P
<0.05). Compared with wild-type,
oim
left ventricular (LV) collagen concentration was 45% lower (
P
<0.0001) and nonreducible pyridinoline cross-link concentration was 22% higher (
P
<0.03). Mean LV volume during passive inflation from 0 to 30 mm Hg in isolated hearts was 1.4-fold larger for
oim
than wild-type (
P
=NS). Uniaxial stress-strain relations in resting right ventricular papillary muscles exhibited 60% greater strains (
P
<0.01), 90% higher compliance (
P
=0.05), and 64% higher nonlinearity (
P
<0.05) in
oim
. Mean opening angle, after relief of residual stresses in resting LV myocardium, was 121±9 degrees in
oim
compared with 45±4 degrees in wild-type (
P
<0.0001). Mean myofiber angle in
oim
was 23±8 degrees greater than wild-type (
P
<0.02). Decreased myocardial collagen diameter and amount in
oim
is associated with significantly decreased fiber and chamber stiffness despite modestly increased collagen cross-linking. Altered myofiber angles and residual stress may be beneficial adaptations to these mechanical alterations to maintain uniformity of transmural fiber strain. In addition to supporting and organizing myocytes, myocardial collagen contributes directly to ventricular stiffness at high and low loads and can influence stress-free state and myofiber architecture.
β
2
-Adrenergic and Several Other G Protein–Coupled Receptors in Human Atrial Membranes Activate Both G
s
and G
i
Authors: Kilts Jason D. , Gerhardt Mark A. , Richardson Mark D. , Sreeram Gautam , Mackensen G. Burkhard , Grocott Hilary P. , White William D. , Davis R. Duane , Newman Mark F. , Reves Joseph G. , Schwinn Debra A. , Kwatra Madan M.
Published: June 2012

Abstract
—Cardiac G protein–coupled receptors that couple to Gα
s
and stimulate cAMP formation (eg, β-adrenergic, histamine, serotonin, and glucagon receptors) play a key role in cardiac inotropy. Recent studies in rodent cardiac myocytes and transfected cells have revealed that one of these receptors, the β
2
-adrenergic receptor (AR), also couples to the inhibitory G protein Gα
i
(activation of which inhibits cAMP formation). If β
2
ARs could be shown to couple to Gα
i
in the human heart, it would have important ramifications, because levels of Gα
i
increase with age and in failing human heart. Therefore, we investigated whether β
2
ARs in the human heart activate Gα
i
. By photoaffinity labeling human atrial membranes with [
32
P]azidoanilido-GTP, followed by immunoprecipitation with antibodies specific for Gα
i
, we found that Gα
i
is activated by stimulation of β
2
ARs but not of β
1
ARs. In addition, we found that other Gα
s
-coupled receptors also couple to Gα
i
, including histamine, serotonin, and glucagon. When coupling of these receptors to Gα
i
is disrupted by pertussis toxin, their ability to stimulate adenylyl cyclase is enhanced. These data provide the first evidence that β
2
AR and many other Gα
s
-coupled receptors in human atrium also couple to Gα
i
and that abolishing the coupling of these receptors to Gα
i
increases the receptor-mediated adenylyl cyclase activity.
Gene Transfer of Calcitonin Gene–Related Peptide Prevents Vasoconstriction After Subarachnoid Hemorrhage
Authors: Toyoda Kazunori , Faraci Frank M. , Watanabe Yoshimasa , Ueda Toshihiro , Andresen Jon J. , Chu Yi , Otake Shoichiro , Heistad Donald D.
Published: June 2012

Abstract
—We sought to determine whether adenovirus-mediated gene transfer in vivo of calcitonin gene–related peptide (CGRP), a potent vasodilator, ameliorates cerebral vasoconstriction after experimental subarachnoid hemorrhage (SAH). Arterial blood was injected into the cisterna magna of rabbits to mimic SAH 5 days after injection of AdRSVCGRP (8×10
8
pfu), AdRSVβgal (control virus), or vehicle. After injection of AdRSVCGRP, there was a 400-fold increase in CGRP in cerebrospinal fluid. Contraction of the basilar artery to serotonin in vitro was greater in rabbits after SAH than after injection of artificial cerebrospinal fluid (
P
<0.001). Contraction to serotonin was less in rabbits with SAH after AdRSVCGRP than after AdRSVβgal or vehicle (
P
<0.02). Basal diameter of the basilar artery before SAH (measured with digital subtraction angiogram) was 13% greater in rabbits treated with AdRSVCGRP than in rabbits treated with vehicle or AdRSVβgal (
P
<0.005). In rabbits treated with vehicle or AdRSVβgal, arterial diameter after SAH was 25±3% smaller than before SAH (
P
<0.0005). In rabbits treated with AdRSVCGRP, arterial diameter was similar before and after SAH and was reduced by 19±3% (
P
<0.01) after intracisternal injection of CGRP-(8-37) (0.5 nmol/kg), a CGRP
1
receptor antagonist. To determine whether gene transfer of CGRP after SAH may prevent cerebral vasoconstriction, we constructed a virus with a cytomegalovirus (CMV) promoter, which results in rapid expression of the transgene product. Treatment of rabbits with AdCMVCGRP after experimental SAH prevented constriction of the basilar artery 2 days after SAH. Thus, gene transfer of CGRP prevents cerebral vasoconstriction in vivo after experimental SAH.
Phenotypic Alteration of Vascular Smooth Muscle Cells Precedes Elastolysis in a Mouse Model of Marfan Syndrome
Authors: Bunton Tracie E. , Biery Nancy Jensen , Myers Loretha , Gayraud Barbara , Ramirez Francesco , Dietz Harry C.
Published: June 2012

Abstract
—Marfan syndrome is associated with early death due to aortic aneurysm. The condition is caused by mutations in the gene (FBN1) encoding fibrillin-1, a major constituent of extracellular microfibrils. Prior observations suggested that a deficiency of microfibrils causes failure of elastic fiber assembly during late fetal development. Mice homozygous for a targeted hypomorphic allele (mgR) of Fbn1 revealed a predictable sequence of abnormalities in the vessel wall including elastic fiber calcification, excessive deposition of matrix elements, elastolysis, and intimal hyperplasia. Here we describe previously unrecognized concordant findings in elastic vessels from patients with Marfan syndrome. Furthermore, ultrastructural analysis of mgR mice revealed cellular events that initiate destructive changes. The first detectable abnormality was an unusually smooth surface of elastic laminae, manifesting the loss of cell attachments that are normally mediated by fibrillin-1. Adjacent cells adopted alteration in their expression profile accompanied by morphological changes but retained expression of vascular smooth muscle cell markers. The abnormal synthetic repertoire of these morphologically abnormal smooth muscle cells in early vascular lesions included elastin, among other matrix elements, and matrix metalloproteinase 9, a known mediator of elastolysis. Ultimately, cell processes associated with zones of elastic fiber thinning and fragmentation. These data suggest that the loss of cell attachments signals a nonproductive program to synthesize and remodel an elastic matrix. This refined understanding of the pathogenesis of vascular disease in Marfan syndrome will facilitate the development of therapeutic strategies.
Overexpression of FK506-Binding Protein FKBP12.6 in Cardiomyocytes Reduces Ryanodine Receptor–Mediated Ca
2+
Leak From the Sarcoplasmic Reticulum and Increases Contractility
Authors: Prestle Jürgen , Janssen Paul M.L. , Janssen Anita P. , Zeitz Oliver , Lehnart Stephan E. , Bruce Lorraine , Smith Godfrey L. , Hasenfuss Gerd
Published: June 2012

Abstract
—The FK506-binding protein FKBP12.6 is tightly associated with the cardiac sarcoplasmic reticulum (SR) Ca
2+
-release channel (ryanodine receptor type 2 [RyR2]), but the physiological function of FKBP12.6 is unclear. We used adenovirus (Ad)-mediated gene transfer to overexpress FKBP12.6 in adult rabbit cardiomyocytes. Western immunoblot and reverse transcriptase–polymerase chain reaction analysis revealed specific overexpression of FKBP12.6, with unchanged expression of endogenous FKBP12. FKBP12.6-transfected myocytes displayed a significantly higher (21%) fractional shortening (FS) at 48 hours after transfection compared with Ad-GFP–infected control cells (4.8±0.2% FS versus 4±0.2% FS, respectively; n=79 each;
P
=0.001). SR-Ca
2+
uptake rates were monitored in β-escin–permeabilized myocytes using Fura-2. Ad-FKBP12.6–infected cells showed a statistically significant higher rate of Ca
2+
uptake of 0.8±0.09 nmol/s
−
1
/10
6
cells (n=8,
P
<0.05) compared with 0.52±0.1 nmol/s
−
1
/10
6
cells in sham-infected cells (n=8) at a [Ca
2+
] of 1 μmol/L. In the presence of 5 μmol/L ruthenium red to block Ca
2+
efflux via RyR2, SR-Ca
2+
uptake rates were not significantly different between groups. From these measurements, we calculate that SR-Ca
2+
leak through RyR2 is reduced by 53% in FKBP12.6-overexpressing cells. Caffeine-induced contractures were significantly larger in Ad-FKBP12.6–infected myocytes compared with Ad-GFP–infected control cells, indicating a higher SR-Ca
2+
load. Taken together, these data suggest that FKBP12.6 stabilizes the closed conformation state of RyR2. This may reduce diastolic SR-Ca
2+
leak and consequently increase SR-Ca
2+
release and myocyte shortening.
Decreased Expression of Voltage- and Ca
2+
-Activated K
+
Channels in Coronary Smooth Muscle During Aging
Authors: Marijic Jure , Li QingXia , Song Min , Nishimaru Kazuhide , Stefani Enrico , Toro Ligia
Published: June 2012

Abstract
—Aging is the main risk factor for coronary artery disease. One characteristic of aging coronary arteries is their enhanced contractile responses to endothelial vasoconstricting factors, which increase the risk of coronary vasospasm in older people. Because large-conductance voltage- and Ca
2+
-activated K
+
channels (MaxiK) are key regulators of vascular tone, we explored the possibility that this class of channels is diminished with increasing age. Using site-directed antibodies recognizing the pore-forming α subunit and electrophysiological methods, we demonstrate that the number of MaxiK channels is dramatically diminished in aged coronary arteries from old F344 rats. Channel density was reduced from 52±9 channels/pF (3 months old) to 18±5 channels/pF (25 to 30 months old), which represents a 65% reduction in the older population. Pixel intensity of Western blots was also diminished by ≈50%. Moreover, the age-related decrease in the channel protein expression was also evident in humans, which showed ≈80% reduction in 61- to 70-year-old subjects compared with 3- to 18-year-old youngsters and ≈45% reduction compared with 19- to 56-year-old adults. In agreement with a reduction of MaxiK channel numbers in aging coronary arteries, old coronary arteries from F344 rats contract less effectively (≈70% reduction) than young coronary arteries when exposed to the MaxiK channel blocker iberiotoxin. The contraction studies indicate that under physiological conditions, MaxiK channels are tonically active, serving as a hyperpolarizing force that opposes contraction. Thus, reduced expression of MaxiK channels in aged coronary arteries would lead to a decreased vasodilating capacity and increased risk of coronary spasm and myocardial ischemia in older people.
Functional Alterations of the
Nppa
Promoter Are Linked to Cardiac Ventricular Hypertrophy in WKY/WKHA Rat Crosses
Authors: Deschepper Christian F. , Masciotra Sandro , Zahabi Ahmad , Boutin-Ganache Isabelle , Picard Sylvie , Reudelhuber Timothy L.
Published: June 2012

Abstract
—Cardiac left ventricular hypertrophy (LVH) is commonly associated with hypertension, but its variance is determined for more than 50% by blood pressure–independent genetic factors. Because it constitutes one of the most important risk factors for cardiovascular mortality, we have performed a genome-wide scan of the F2 progeny of crosses between inbred WKY and WKHA rats to detect quantitative trait loci (QTL) linked to cardiac mass. In addition to left ventricular mass (LVM), we also measured left ventricle (LV) concentration of atrial natriuretic factor (ANF), because we have previously established that there was a genetic link between these 2 traits in the same animal cross. We found 2 contiguous QTL on chromosome 5 that were linked to either LVM (logarithm of odds [LOD]=3.5) or log
n
(LV ANF) (LOD=12). The 1-LOD support intervals of both QTL shared a region overlapping the locus of natriuretic peptide precursor A (
Nppa
) (ie, the ANF-coding gene). We found by sequencing 2 single nucleotide polymorphisms (SNPs) within the first 650 bp of the
Nppa
minimal promoters of the genes from both strains. One of these SNPs increased the transcriptional activity of the
Nppa
minimal promoter in transfected neonatal cardiomyocytes in keeping with the higher LV concentration of ANF observed in WKY versus WKHA rats. Taken together with the previous reports showing that ANF may protect cardiomyocytes against hypertrophy, our genetic data single out
Nppa
as a strong candidate gene for the determination of LVM.
Mechanisms Underlying Endothelial Dysfunction in Diabetes Mellitus
Authors: Hink Ulrich , Li Huige , Mollnau Hanke , Oelze Mathias , Matheis Edi , Hartmann Mark , Skatchkov Mikhail , Thaiss Friedrich , Stahl Rolf A. K. , Warnholtz Ascan , Meinertz Thomas , Griendling Kathy , Harrison David G. , Forstermann Ulrich , Munzel Thomas
Published: June 2012

Abstract
—Incubation of endothelial cells in vitro with high concentrations of glucose activates protein kinase C (PKC) and increases nitric oxide synthase (NOS III) gene expression as well as superoxide production. The underlying mechanisms remain unknown. To address this issue in an in vivo model, diabetes was induced with streptozotocin in rats. Streptozotocin treatment led to endothelial dysfunction and increased vascular superoxide production, as assessed by lucigenin- and coelenterazine-derived chemiluminescence. The bioavailability of vascular nitric oxide (as measured by electron spin resonance) was reduced in diabetic aortas, although expression of endothelial NOS III (mRNA and protein) was markedly increased. NOS inhibition with
N
G
-nitro-L-arginine increased superoxide levels in control vessels but reduced them in diabetic vessels, identifying NOS as a superoxide source. Similarly, we found an activation of the NADPH oxidase and a 7-fold increase in gp91

phox

mRNA in diabetic vessels. In vitro PKC inhibition with chelerythrine reduced vascular superoxide in diabetic vessels, whereas it had no effect on superoxide levels in normal vessels. In vivo PKC inhibition with
N
-benzoyl-staurosporine did not affect glucose levels in diabetic rats but prevented NOS III gene upregulation and NOS-mediated superoxide production, thereby restoring vascular nitric oxide bioavailability and endothelial function. The reduction of superoxide in vitro by chelerythrine and the normalization of NOS III gene expression and reduction of superoxide in vivo by
N
-benzoyl-staurosporine point to a decisive role of PKC in mediating these phenomena and suggest a therapeutic potential of PKC inhibitors in the prevention or treatment of vascular complications of diabetes mellitus. The full text of this article is available at http://www.circresaha.org.
Vasoactive Potential of the B
1
Bradykinin Receptor in Normotension and Hypertension
Authors: Duka Irena , Kintsurashvili Ekaterina , Gavras Irene , Johns Conrado , Bresnahan Margaret , Gavras Haralambos
Published: June 2012

Abstract
—The B
1
type receptor of bradykinin (Bk B
1
R) is believed to be physiologically inert but highly inducible by inflammatory mediators and tissue damage. To explore the potential participation of the Bk B
1
R in blood pressure (BP) regulation, we studied mice with deleted Bk B
2
R gene with induced experimental hypertension, either salt-dependent (subtotal nephrectomy with 0.5% NaCl as drinking water) or renin/angiotensin-dependent (renovascular 2-kidney–1-clip). Compared with the wild-type controls, the B
2
R gene knockout mice had a higher baseline BP (109.7±1.1 versus 101.1±1.3 mm Hg,
P
=0.002), developed salt-induced hypertension faster (in 19.3±2.3 versus 27.7±2.4 days,
P
=0.024), and had a more severe end point BP (148±3.7 versus 133±3.1 mm Hg,
P
<0.05). On the contrary, renovascular hypertension developed to the same extent (149.7±4.3 versus 148±3.6 mm Hg) and in the same time frame (14±2.2 versus 14±2.1 days). A bolus infusion of a selective B
1
R antagonist at baseline produced a significant hypertensive response (by 11.4±2 mm Hg) in the knockout mice only. Injection of graded doses of a selective B
1
R agonist produced a dose-dependent hypotensive response in the knockout mice only. Assessment of tissue expression of B
1
R and B
2
R genes by reverse transcription–polymerase chain reaction techniques revealed significantly higher B
1
R mRNA levels in the B
2
R knockout mice at all times (normotensive baseline and hypertensive end points). At the hypertensive end points, there was always an increase in B
1
R gene expression over the baseline values. This increase was significant in cardiac and renal tissues in all hypertensive wild-type mice but only in the clipped kidney of the renovascular knockout mice. The B
2
R gene expression in the wild-type mice remained unaffected by experimental manipulations. These results confirm the known vasodilatory and natriuretic function of the Bk B
2
R; they also indicate that in its absence, the B
1
R can become upregulated and assume some of the hemodynamic properties of the B
2
R. Furthermore, they indicate that experimental manipulations to produce hypertension also induce upregulation of the B
1
R, but not the B
2
R, in cardiac and renal tissues.
Nitric Oxide Dependency of Arterial Pressure–Induced Changes in Renal Interstitial Hydrostatic Pressure in Dogs
Authors: Majid Dewan S. A. , Said Karim E. , Omoro Sophia A. , Navar L. Gabriel
Published: June 2012

Abstract
—A direct relationship between renal arterial pressure (RAP) and renal interstitial hydrostatic pressure (RIHP) has been shown under conditions of efficient renal blood flow autoregulation. Experiments were performed in six anesthetized dogs to evaluate whether these RIHP responses to changes in RAP were modified during nitric oxide (NO) inhibition with nitro-
l
-arginine (NLA) or after administration of NO donor agents. A microtip catheter transducer was placed underneath the renal capsule to measure RIHP. Stepwise reductions in RAP (140 to 80 mm Hg) during control conditions resulted in decreases in RIHP from its basal value of 4.7±1.1 mm Hg with a slope of 0.04±0.026 mm Hg · mm Hg
−
1
along with decreases in urinary nitrate/nitrite excretion rate (U
NOx
V). Renal cortical and medullary blood flows, measured by laser-Doppler flowmetry, exhibited high autoregulatory efficiency over this RAP range. The changes in RIHP during alterations in RAP were positively correlated (
r
=0.743;
P
<0.001) with the changes in U
NOx
V but not with cortical or medullary blood flow. NLA infusion decreased RIHP to 1.9±0.5 mm Hg and also reduced U
NOx
V from 1.8±0.2 to 0.9±0.01 nmol · min
−
1
· g
−
1
. Infusion of NO donors restored RIHP (4.3±0.9 mm Hg) and U
NOx
V (1.5±0.2 nmol · min
−
1
· g
−
1
). During NLA infusion, the RIHP responses to reductions in RAP were markedly attenuated and were not restored even during constant-rate infusion of NO donors. The results suggest that changes in RIHP in response to alterations in RAP are associated with changes in intrarenal NO, suggesting a direct effect of NO to regulate RIHP.
Modulation of Ca
2+
Signaling by Microtubule Disruption in Rat Ventricular Myocytes and Its Dependence on the Ruptured Patch-Clamp Configuration
Authors: Calaghan S. C. , Le Guennec J.-Y. , White E.
Published: June 2012

Abstract
—In the absence of hypertrophic proliferation of microtubules, microtubule disruption by colchicine does not modulate contraction of adult cardiac myocytes. However, Gomez et al (
Circ Res.
2000;86:30–36) recently reported that disruption of microtubules by colchicine in ruptured patch-clamped myocytes increased
I
Ca,L
density and [Ca
2+
]
i
transient amplitude and depressed the response of these parameters to the β-adrenoceptor agonist isoproterenol. These effects were ascribed to stimulation of adenylyl cyclase by increased intracellular free tubulin. In the present study, we show that in intact rat ventricular myocytes, 2 to 4 hours of exposure to 10 μmol/L colchicine had no effect on shortening or [Ca
2+
]
i
transient amplitude or on the amplitude of
I
Ca,L
in perforated patch-clamped cells, under basal conditions and after stimulation with 1 μmol/L isoproterenol. However, in ruptured patch-clamped myocytes, basal
I
Ca,L
was 2-fold higher after treatment with colchicine compared with vehicle and, in contrast to vehicle-treated cells,
I
Ca,L
did not increase in response to isoproterenol. Cell width decreased during ruptured patch-clamp experiments in colchicine-treated but not vehicle-treated myocytes. We conclude that in cells with intact sarcolemma, colchicine does not modulate Ca
2+
signaling or the response to β stimulation. However, the combination of microtubule disruption by colchicine and the ruptured patch configuration activates
I
Ca,L
and attenuates the response to β stimulation. We propose that these effects may be due to loss of free tubulin by intracellular dialysis or to increased sensitivity to mechanical stimulation as a result of microtubule disruption. These findings have important implications for cardiomyopathies associated with decreased free tubulin or a diminished microtubular network. The full text of this article is available at http://www.circresaha.org.
Fibrillar Collagen Specifically Regulates Human Vascular Smooth Muscle Cell Genes Involved in Cellular Responses and the Pericellular Matrix Environment
Authors: Ichii Takuya , Koyama Hidenori , Tanaka Shinji , Kim Shokei , Shioi Atsushi , Okuno Yasuhisa , Raines Elaine W. , Iwao Hiroshi , Otani Shuzo , Nishizawa Yoshiki
Published: June 2012

Abstract
—Proliferation and α
v
β
3
integrin–dependent migration of vascular smooth muscle cells are suppressed on polymerized type I collagen. To identify genes specifically regulated in human smooth muscle cells by polymerized collagen, we used the suppressive subtraction hybridization technique. Compared with smooth muscle cells cultured on monomer collagen, polymerized collagen suppresses the following: (1) a number of other extracellular matrix proteins, including fibronectin, thrombospondin-1, tenascin-C, and cysteine-rich protein 61; (2) actin binding proteins including α-actinin; (3) signaling molecules; (4) protein synthesis–associated proteins; and (5) genes with unknown functions. Some of the identified genes, including cysteine-rich protein 61, show unique kinetics of mRNA regulation by monomer or polymerized collagen distinct from growth factors, suggesting extracellular matrix–specific gene modulation. Moreover, in vivo balloon catheter–mediated injury to the rat carotid artery induces many of the genes that are suppressed by polymerized collagen. Protein levels of thrombospondin-1 and fibronectin are also suppressed by polymerized collagen. Thrombospondin-1–mediated smooth muscle cell migration on vitronectin is significantly inhibited after culture on polymerized collagen for 24 hours, which is associated with decreased α-actinin accumulation at focal adhesions. Thus, polymerized type I collagen dynamically regulates gene expression, pericellular accumulation of extracellular matrix molecules, and the response to a given matrix molecule.
Functional Roles of Cardiac and Vascular ATP-Sensitive Potassium Channels Clarified by Kir6.2-Knockout Mice
Authors: Suzuki Masashi , Li Ronald A. , Miki Takashi , Uemura Hiroko , Sakamoto Naoya , Ohmoto-Sekine Yuki , Tamagawa Masaji , Ogura Takehiko , Seino Susumu , Marbán Eduardo , Nakaya Haruaki
Published: June 2012

Abstract
—ATP-sensitive potassium (K
ATP
) channels were discovered in ventricular cells, but their roles in the heart remain mysterious. K
ATP
channels have also been found in numerous other tissues, including vascular smooth muscle. Two pore-forming subunits, Kir6.1 and Kir6.2, contribute to the diversity of K
ATP
channels. To determine which subunits are operative in the cardiovascular system and their functional roles, we characterized the effects of pharmacological K
+
channel openers (KCOs, ie, pinacidil, P-1075, and diazoxide) in Kir6.2-deficient mice. Sarcolemmal K
ATP
channels could be recorded electrophysiologically in ventricular cells from Kir6.2
+/+
(wild-type [WT]) but not from Kir6.2
−/−
(knockout [KO]) mice. In WT ventricular cells, pinacidil induced an outward current and action potential shortening, effects that were blocked by glibenclamide, a K
ATP
channel blocker. KO ventricular cells exhibited no response to KCOs, but gene transfer of Kir6.2 into neonatal ventricular cells rescued the electrophysiological response to P-1075. In terms of contractile function, pinacidil decreased force generation in WT but not KO hearts. Pinacidil and diazoxide produced concentration-dependent relaxation in both WT and KO aortas precontracted with norepinephrine. In addition, pinacidil induced a glibenclamide-sensitive current of similar magnitude in WT and KO aortic smooth muscle cells and comparable levels of hypotension in anesthetized WT and KO mice. In both WT and KO aortas, only Kir6.1 mRNA was expressed. These findings indicate that the Kir6.2 subunit mediates the depression of cardiac excitability and contractility induced by KCOs; in contrast, Kir6.2 plays no discernible role in the arterial tree.
Weekly Dosing With the Platelet-Derived Growth Factor Receptor Tyrosine Kinase Inhibitor SU9518 Significantly Inhibits Arterial Stenosis
Authors: Yamasaki Yasundo , Miyoshi Kazuhisa , Oda Nobuyuki , Watanabe Motomu , Miyake Hidekazu , Chan Julie , Wang Xueyan , Sun Li , Tang Cho , McMahon Gerald , Lipson Kenneth E.
Published: June 2012

Abstract
—The platelet-derived growth factor (PDGF) ligands and their receptors have been implicated as critical regulators of the formation of arterial lesions after tissue injury. SU9518 (3[5-{5-bromo-2-oxo-1,2-dihydroindol-3-ylidenemethyl}-2,4-dimethyl-1
H
-pyrrol-3-yl]propionic acid) is a novel synthetic indolinone that potently and selectively inhibits the cellular PDGF receptor kinase and PDGF receptor–induced cell proliferation. Inhibition of PDGF receptor phosphorylation in cell-based assays occurs within 5 minutes after drug exposure and persists for >6 hours after drug removal. The pharmacokinetics indicate plasma levels that exceeded the effective concentration required to inhibit the PDGF receptor in cells for up to 8 hours or 7 days after a single oral or subcutaneous administration, respectively. In the rat balloon arterial injury–induced stenosis model, once-daily oral or once-weekly subcutaneous administration of SU9518 reduced intimal thickening of the carotid artery (ratio of neointimal to medial area, 1.94±0.38 versus 1.03±0.29 [
P
<0.01] 2.21±0.32 versus 1.34±0.45 [
P
<0.01], respectively). These studies provide the rationale to evaluate PDGF receptor tyrosine kinase inhibitors, including inhibitors related to the indolinone, SU9518, for the treatment of arterial restenosis.
Effect of Intra-arterial Insulin on Tissue Cholesterol and Fatty Acids in Alloxan-Diabetic Dogs
Authors: CRUZ ANATOLIO B. , AMATUZIO DONALD S. , GRANDE FRANCISCO , HAY LYLE J.
Published: June 2012

Insulin and saline were injected into the right and left femoral arteries respectively of 19 alloxan-diabetes-mellitus dogs for 1 to 28 weeks. A significant increase of artery tissue cholesterol and total fatty acids was found on comparing the insulin-administered right leg with the saline-administered left leg. Similarly, a significant increase of total fatty acids in muscle was found on comparing the right with the left leg of the alloxan-diabetes mellitus dogs. No significant differences were observed in the normal animals when the insulin-injected side was compared with the noninjected.
Factors Affecting the Determination of Uterine Blood Flow in Vivo
Authors: HUCKABEE WILLIAM E. , BAERON DONALD H.
Published: June 2012

When 4-aminoantipyrine (4AA) was injected into pregnant goats, the time curves of blood concentration could be determined easily and accurately when the injection was carried out over about seven minutes' time. The arterial-and uterine venous-blood concentration curves came together after 15 minutes, and afterward the arteriovenous difference remained negligible. The blood concentration of 4AA gave an accurate estimate of concentrations in the tissue water of the uterus, placenta, and fetus after disappearance of the arteriovenous difference. At the time interval of 15 to 20 minutes, 4AA concentrations in amniotic and allantoic fluids were so low that they could be regarded as negligible. There fore, when 4AA was used as the diffusing substance, the major factors affecting the determination of uterine blood flow by diffusion-equilibration methods were favorable for an estimate of the rate of blood flow per unit weight of metabolically active tissue.
Effects of Magnesium-Deficient Diet Upon Puppies
Authors: VITALE JOSEPH J. , HELLERSTEIN EARL E. , NAKAMURA MOTOOMI , LOWN BERNARD
Published: June 2012

Diet-induced magnesium deficiency in male puppies resulted in lowered weight gain, hy perirritability, and convulsions. The histopathological changes consisted of calcification of the elastica and media of the aorta, of coronary and other peripheral arteries, and of the inner portion of the myocardium. Fibrous, virtually fat-free, plaques were seen in the coronary arteries. Magnesium deficiency had no effect on serum cholesterol, sodium, calcium, ortotal protein. Slight lowering of serum magnesium lacked statistical significance. There was a significant decrease in the serum-potassium concentration of these magnesium-deficient dogs. Electrocardiographic changes were noted.
Harmonic Analysis of Aortic Pressure Pulses in the Dog
Authors: FARROW ROBERT L. , STACY RALPH W.
Published: June 2012

Aortic pulse waves were recorded in dogs at the junctions of the left renal artery and the inferior mescntcric artery with the aorta, under normal conditions, after administration of norepincphriue and acetylcholine, and after manual blocking of the femoral arteries. These pulses (343) were subjected to Fourier analysis, and apparent phase velocities and foot-of-the-wave velocities were calculated. The results strongly indicate the presence of reflected waves, and it is shown that foot-of-the- wave velocities provide erroneous information. The arterial system is such that in the arteries per se, the reflected wave is a discrete and definable quantity; its origin can be shown to be an apparent site of reflection located in the peripheral one-third of the thighs of the dog.
Dicumarol Therapy and Platelet Turnover
Authors: MURPHY E. A. , MUSTARD J. F.
Published: June 2012

Platelet survival and turnover were studied by the use of diisopropyl fluorophosphate, which contains phosphorus as P
32
(DFP
32
)in atherosclerotic male subjects. Twenty-nine were given dicumarol in doses sufficient to diminish platelet function in vitro and 31 were used as controls. Platelet survival was prolonged and platelet turnover was decreased by dieumarol therapy. Of the coagulation tests, the platelet adhesive index showed the best correlation with platelet turnover. These findings indicate that platelet function in vitro and in vivo is diminished by adequate dicumarol therapy. Evidence is presented that the survival of the platelet, at least in the atherosclerotic subject, is largely determined by factors external to the platelet, among which the activity of the coagulation mechanism is important.
On the Antigenic Identity of Human Serum Beta and Alpha-2 Lipoproteins, and Their Identification in the Aortic Intima
Authors: TRACY RICHARD E. , MERCHANT EDMUND B. , KAO. VINCENT C.
Published: June 2012

By the use of immunoelectrophoresis, it was demonstrated that ultracentrifugally isolated, very-low-density (alpha-2) lipoproteins migrate faster toward the anode in electro-phoresis and diffuse more slowly in agar than do low-density (beta) lipoproteins. However, these two lipoprotein fractions were found to be antigenically indistinguishable with this technique. Extracts of the intima of aortas were shown to contain material with all the physical properties consistent with those of the low-density (beta) lipoproteins. Further-more, this was the only serum protein which was consistently found in high concentration in washed aortas. Beta lipoprotein was frequently found in plaque-free intimae. The impression was obtained that this lipoprotein was present in greater concentration in early atheromatous plaques than in plaque-free intimae, and that it was much more concentrated in the intimae of severely sclerotic aortas than in those of moderately or uninvolved aortas. However, it has not been demonstrated in the gruel from far-advanced plaques.
Interrelation Between Central and Peripheral Mechanisms Regulating Blood Pressure
Authors: WILSON MICHAEL F. , CLARKE NEVILLE P. , SMITH ORVILLE A. , RUSHMER ROBERT F.
Published: June 2012

Electrical stimulation of selected discrete sites in the diencephalon induced a profound and coordinated response consisting of increased respiratory activity, limb movements, and cardiovascular adjustments. The effects on the cardiovascular system were similar to those of exercise, although the increases in aortic pressure, left ventricular pressure, and heart rate were greater. Massive splanchnicnerve discharge occurred immediately when the diencephalon was stimulated, but splanchilic activity abruptly fell below control levels with cessation of the stimulus. The increase in respiratory activity and the organized running movements seen during stimu lation apparently did miot contribute to the pressor and cardioaccelerator responses.

There appeared to be no marked difference between control and diencephalic-stimulation experiments in the ease with which in duced pressure pulsations in the partially isolated carotid sinus caused bradycardia and blood-pressure depression. It may be that the influences of the diencephalon and carotid- sinus reflex upon blood pressures are inde pendent and sum algebraically.

Experiments in which effects of epinephrine on splanchnic-nerve activity and systemic arterial pressure were measured before and during dieneephalic stimulation did not support the concept that catecholamines have an important role in normal pressor responses.
Mesenteric Circulation in Hemorrhagic Shock
Authors: FRIEDMAN JULIUS J.
Published: June 2012

The effect of hemorrhage and of reinfusion on the mesenteric circulation of dogs was determined. During the control period, the average mesenteric vascular resistance was 0.6 P.R.U., and the average mesenteric plasma volume was 100 ml. Hemorrhagc produced an early reduction in mesenteric plasma volume, averaging 50 per cent, without any accompanying change in mesenteric vascular resistance. As the hemorrhagie period progressed, mesenteric vascular resistance rose to a level 120 per cent above control coincidental with the autoinfusion of blood from the hemorrhagc reservoir. With the elevation in mesenteric vascular resistance, mesenteric plasma volume displayed a slight additional decline. Reinfusion produced only a slight and transient recovery of mesenteric vascular resistance and plasma volume. A comparison of mesenteric vascular resistance changes with those of mesenteric plasma volume indicates that no uniform relationship exists. Similar dissociation was seen between mesenteric plasma volume and portal venous pressure. No evidence of pooling of blood in the mesenteric circulation during the induction and development of normovolemic hemorrhagie shock was observed.
Effects of Exercise and Anemia on Coronary Arteries of Small Animals as Revealed by the Corrosion-Cast Technique
Authors: TEPPERMAN JAY , PEARLMAN DAVID
Published: June 2012

Vinyl acetate corrosion casts were prepared of the coronary arterial trees of chronically exercised rats and of suitable control animals. In four experiments, there was a statistically significant increase in the mean coronary-cast weight of the exercised animals over that of controls. In two experiments, the coronary- cast/heart-weight ratios were significantly increased.

In three-week-old ducklings rendered anemic by an iron-deficient diet, corrosion casts of the coronary vessels showed marked increases in cast weight, increase in size of homologous vessels, and generally more luxuriant arborization of the tree. No differences were found when coronary casts of thyroxin-injected or of pentaerythritol tetranitrate-injected rats were compared with those of control animals. Right-to-left-side coronary anastomoses were demonstrated in 75 per cent of guinea-pig hearts studied by the corrosion-cast technique. In five experiments, retrograde filling of a ligated anterior descending branch of the left coronary artery was demonstrated when the vinyl acetate solution was injected into the aorta.
Stretch Reflexes from the Main Pulmonary Artery to the Systemic Circulation
Authors: LEWIN RICHARD J. , CROSS CECIL E. , RIEBEN P. ANDRE , SALISBURY PETER F.
Published: June 2012

In open-chest dogs, the greater and lesser circulations were perfused by a system of pumps and oxygenator. All blood was drained from the right heart and from the left atrium. in most experiments, there was no dissection around the pulmonary hila, the aorta, or the pulmonary artery. A 30-ml. balloon (Foley catheter) was inserted into the pulmonary artery through a stab wound in the wall of the right ventricle. Pressures were recorded in the pulmonary-artery balloon and in a femoral artery. In other experiments, the main pulmonary artery was distended with blood at known pressures after hydraulic isolation with ligatures and snares.

When the main pulmonary artery was distended proximal to its bifurcation, constriction of the systemic arteries occurred. This phenomenon was abolished by local anesthesia of the wall of the main pulmonary artery, by interrupting conduction in the vagi, by a sympatholytic drug, and by reflex systemic hypotension elicited by multiple small pulmonary emboli. The pressor reflex from the pulmonary artery to the systemic circulation was not influenced by changes of pulmonary blood flow or by inflation of other balloons in various chambers of the heart. Limitations inherent in the experimental procedure did not permit us to assign physiological significance to the phenomenon.
Some Theoretical Aspects of Quantification of Mitral Valve Regurgitation by the Indicator-Dilution Method
Authors: POLISSAR MILTON J. , RAPAPORT ELLIOT
Published: June 2012

A theoretical analysis of indicator-dilution curves produced by a pulsatile, two-chamber mathematical model simulating a normal in vivo heart and one with atrioventricular valve regurgitation is presented. A set of difference equations is developed expressing the concentrations within the chambers at the end of each cycle in terms of the number of cycles or beats. It is shown theoretically that the downstroke slope of the dilution curve is insensitive to the extent of regurgitation. Solution of the difference equations for the parameters of the heart governing the curve (chamber volumes, forward output, and regurgitant flow), when the dilution curve is sampled from the chamber in which the injection is made, is achieved through a system of four equations in four unknowns. Sampling of the concentration curve from the chamber which does not receive the injection produces a theoretical curve giving three equations in four unknowns and results in an indeterminate solution. As a consequence, quantification of atrioventricular valve regurgitation through analysis of a single distal indicator-dilution curve following proximal injection cannot be accomplished.
Cardiovascular Interaction of Nicotine, Ergonovine, and Hypercholesterolemia in the Rabbit
Authors: WENZEL DUANE G. , TURNER JAMES A. , JORDAN SCOTT W. , SINGH JASBIR
Published: June 2012

Rabbits were treated with nicotine and a hypercholesterolemic diet for 24 weeks. At the initiation of the experiment and at four-week intervals thereafter, the following functions were measured: peripheral circulation through the use of the thermal circulation index (TCI), systolic blood pressure, and coagulation time. After 24 weeks, the heart and vessels of the hind legs were examined for pathological changes. Throughout the course of the experiment, the peripheral circulation was depressed, the systolic pressure elevated, and the coagulation rate speeded. Peripheral pathological changes were minimal and areas of cardiac necrosis observed in a similar previous study were absent. In order to determine the cause of this apparent discrepancy, a second group of rabbits was then similarly treated except that ergonovine was added to the regimen. The 24-week histological examination this time revealed cardiac necrosis in all animals receiving the combined nicotine-cholesterol-ergonovine treatment. This effect had not been obtained with any single member or pair of components of the treatment. Possible explanations for the observed interaction are presented.