bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple PV1 dimers reside in the same stomatal or fenestral diaphragm
Authors: Stan Radu V.
Published: March 2004

Several of the endothelium-specific structures that have been involved in microvascular permeability [such as caveolae, transendothelial channels (TECs), vesiculovacuolar organelles (VVOs), and fenestrae] can be provided with either a stomatal or fenestral diaphragm. In the case of fenestrae, the diaphragm has the presumed function of creating a permselective barrier for solutes from blood plasma and interstitium. PV1 is an endothelium-specific integral membrane glycoprotein that is associated with both the stomatal diaphragms of caveolae, TECs, and VVOs as well as the diaphragms of endothelial fenestrae. The intimate structure of these diaphragms has been shown to consist of a meshwork formed by radial fibrils. We have recently shown that PV1 is a key structural element of both types of diaphragms, with its expression being sufficient to form de novo stomatal and fenestral diaphragms in both endothelial and nonendothelial cell types in culture. We have further tested the role of PV1 in the structure of the diaphragms and demonstrate here that multiple PV1 homodimers reside in close proximity within the same diaphragm. Our data bring further support to the paradigm by which PV1 dimers would form the fibrils of the diaphragms with a function in the microvascular permeability.
α,β-Methylene ATP enhances P2Y4 contraction of rabbit basilar artery
Authors: Miyagi Yasushi , Zhang John H.
Published: March 2004

Interactions between different selective P2 receptor agonists have been used as tools to identify different P2 receptor subtypes. In the present study, we examined the P2 receptor subtypes and the mechanisms of potentiation of UTP contraction (P2Y contraction) by α,β-methylene ATP [(2-carboxypiperazin-4-yl)propyl-1-phosphanoic acid (CPP), a P2X agonist] using isometric tension in the denuded rabbit basilar artery. We made the following observations: 1) a predominant P2X receptor contraction was observed in the rabbit ear artery by the rank order of CPP » 2-methylthioATP > ATP > UTP; 2) functional P2Y receptors were observed in the rabbit basilar artery by the rank order of UTP » ATP = CPP = 2-methylthioATP; 3) CPP potentiated UTP-, ATP-, and ATPγS-induced contractions, possibly by activation of P2Y4 receptors because ATPγS does not activate P2Y6 receptors; and 4) ectonucleotidase did not play a predominant role in the potentiative effect of CPP because Evans blue, Ca2+-free medium, or divalent cation Ni2+ did not affect the effect of CPP. Evans blue potentiated the contraction by UTP but not by ATP or ATPγS. We conclude that CPP enhanced P2Y4-mediated contraction in the rabbit basilar artery, and the influence by ectonucleotidases on CPP-potentiation remains unclear.
Profiling substrate fluxes in the isolated working mouse heart using13C-labeled substrates: focusing on the origin and fate of pyruvate and citrate carbons
Authors: Khairallah Maya , Labarthe François , Bouchard Bertrand , Danialou Gawiyou , Petrof Basil J. , Des Rosiers Christine
Published: March 2004

The availability of genetically modified mice requires the development of methods to assess heart function and metabolism in the intact beating organ. With the use of radioactive substrates and ex vivo perfusion of the mouse heart in the working mode, previous studies have documented glucose and fatty acid oxidation pathways. This study was aimed at characterizing the metabolism of other potentially important exogenous carbohydrate sources, namely, lactate and pyruvate. This was achieved by using13C-labeling methods. The mouse heart perfusion setup and buffer composition were optimized to reproduce conditions close to the in vivo milieu in terms of workload, cardiac functions, and substrate-hormone supply to the heart (11 mM glucose, 0.8 nM insulin, 50 μM carnitine, 1.5 mM lactate, 0.2 mM pyruvate, 5 nM epinephrine, 0.7 mM oleate, and 3% albumin). The use of three differentially13C-labeled carbohydrates and a13C-labeled long-chain fatty acid allowed the quantitative assessment of the metabolic origin and fate of tissue pyruvate as well as the relative contribution of substrates feeding acetyl-CoA (pyruvate and fatty acids) and oxaloacetate (pyruvate) for mitochondrial citrate synthesis. Beyond concurring with the notion that the mouse heart preferentially uses fatty acids for energy production (63.5 ± 3.9%) and regulates its fuel selection according to the Randle cycle, our study reports for the first time in the mouse heart the following findings. First, exogenous lactate is the major carbohydrate contributing to pyruvate formation (42.0 ± 2.3%). Second, lactate and pyruvate are constantly being taken up and released by the heart, supporting the concept of compartmentation of lactate and glucose metabolism. Finally, mitochondrial anaplerotic pyruvate carboxylation and citrate efflux represent 4.9 ± 1.8 and 0.8 ± 0.1%, respectively, of the citric acid cycle flux and are modulated by substrate supply. The described13C-labeling strategy combined with an experimental setup that enables continuous monitoring of physiological parameters offers a unique model to clarify the link between metabolic alterations, cardiac dysfunction, and disease development.
Low angiogenic potency induced by the implantation of ex vivo expanded CD117+stem cells
Authors: Li Tao-Sheng , Hayashi Masanori , Liu Ze-Lin , Ito Hiroshi , Mikamo Akihito , Furutani Akira , Matsuzaki Masunori , Hamano Kimikazu
Published: March 2004

Ex vivo expansion of stem cells might be a feasible method of resolving the problem of limited cell supply in cell-based therapy. The implantation of expanded CD34+endothelial progenitor cells has the capacity to induce angiogenesis. In this study, we tried to induce angiogenesis by implanting expanded CD117+stem cells derived from mouse bone marrow. After 2 wk of culture with the addition of several growth factors, the CD117+stem cells expanded ∼20-fold and had an endothelial phenotype with high expression of CD34 and vascular endothelial-cadherin. However, >70% of these ex vivo expanded cells had a senescent phenotype by β-galactosidase staining, and their survival and incorporation were poor after implantation into the ischemic limbs of mice. Compared with the PBS injection only, the microvessel density and the percentage of limb blood flow were significantly higher after the implantation of 2 × 105freshly collected CD117+cells ( P < 0.01) but not after the implantation of 2 × 105expanded CD117+cells ( P > 0.05). These data indicate that ex vivo expansion of CD117+stem cells has low potency for inducing therapeutic angiogenesis, which might be related to the cellular senescence during ex vivo expansion.
Differential regulation of activator protein-1 and heat shock factor-1 in myocardial ischemia and reperfusion injury: role of poly(ADP-ribose) polymerase-1
Authors: Zingarelli Basilia , Hake Paul W. , O'Connor Michael , Denenberg Alvin , Wong Hector R. , Kong Sue , Aronow Bruce J.
Published: March 2004

Poly(ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme activated in response to DNA strand breaks, has been implicated in cell dysfunction in myocardial reperfusion injury. PARP-1 has also been shown to participate in transcription and regulation of gene expression. In this study, we investigated the role of PARP-1 on the signal transduction pathway of activator protein-1 (AP-1) and heat shock factor-1 (HSF-1) in myocardial reperfusion injury. Mice genetically deficient of PARP-1 (PARP-1–/–mice) exhibited a significant reduction of myocardial damage after occlusion and reperfusion of the left anterior descending branch of the coronary artery compared with their wild-type littermates. This cardioprotection was associated with a reduction of the phosphorylative activity of JNK and, subsequently, reduction of the DNA binding of the signal transduction factor AP-1. On the contrary, in PARP-1–/–mice, DNA binding of HSF-1 was enhanced and was associated with a significant increase of the cardioprotective heat shock protein (HSP)70 compared with wild-type mice. Microarray analysis revealed that expression of several AP-1-dependent genes of proinflammatory mediators and HSPs was altered in PARP-1–/–mice. The data indicate that PARP-1 may exert a pathological role in reperfusion injury by functioning as an enhancing factor of AP-1 activation and as a repressing factor of HSF-1 activation and HSP70 expression.
HMG-CoA reductase inhibitor attenuates platelet adhesion in intestinal venules of hypercholesterolemic mice
Authors: Tailor Anitaben , Lefer David J. , Granger D. Neil
Published: March 2004

Whereas the anti-inflammatory properties of statins have been extensively studied, less attention has been devoted to the antithrombogenic effects of these drugs. We evaluated the effect of short-term (18 h) treatment with pravastatin (1 mg/kg) on hypercholesterolemia-induced platelet-endothelial (P/E) cell adhesion in intestinal venules. Mice were placed on either a normal diet (ND) or cholesterol-enriched diet (HCD) for 2 wk. Wild-type mice fed a HCD exhibited significantly elevated blood serum cholesterol levels, which were unaltered by pravastatin treatment. ND or HCD platelets were isolated, fluorescently labeled, and administered to either ND or HCD recipients. Intravital videomicroscopy was used to quantify transient (saltation) and firm adhesion of platelets. HCD mice receiving platelets from either ND or HCD mice exhibited increased P/E cell interactions compared with ND mice receiving platelets from ND or HCD mice. P/E adhesion was dramatically reduced when platelets from donor mice, recipient mice, or both were treated with pravastatin. The protective effect of pravastatin in hypercholesterolemia-induced P/E cell adhesion was abolished in NG-nitro-l-arginine methyl ester-treated mice. These results indicate that 1) hypercholesterolemia-induced P/E cell adhesion is mediated by changes in the vascular wall rather than circulating platelets; 2) pravastatin treatment inhibits the prothrombogenic effects of hypercholesterolemia via an action on both endothelial cells and platelets; and 3) the protective effect of pravastatin is nitric oxide dependent.
Effects of phospholemman downregulation on contractility and [Ca2+]itransients in adult rat cardiac myocytes
Authors: Mirza M. Ayoub , Zhang Xue-Qian , Ahlers Belinda A. , Qureshi Anwer , Carl Lois L. , Song Jianliang , Tucker Amy L. , Mounsey J. Paul , Moorman J. Randall , Rothblum Lawrence I. , Zhang Thomas S. , Cheung Joseph Y.
Published: March 2004

Phospholemman (PLM) expression was increased in rat hearts after myocardial infarction (MI). Overexpression of PLM in normal adult rat cardiac myocytes altered contractile function and cytosolic Ca2+concentration ([Ca2+]i) homeostasis in a manner similar to that observed in post-MI myocytes. In this study, we tested whether PLM downregulation in normal adult rat myocytes resulted in contractility and [Ca2+]itransient changes opposite to those observed in post-MI myocytes. Compared with control myocytes infected with adenovirus (Adv) expressing green fluorescent protein (GFP) alone, myocytes infected with Adv expressing both GFP and rat antisense PLM (rASPLM) had 23% less PLM protein ( P < 0.012) at 3 days, but no differences were found in sarcoplasmic reticulum (SR) Ca2+-ATPase, Na+/Ca2+exchanger (NCX1), Na+-K+-ATPase, and calsequestrin levels. SR Ca2+uptake and whole cell capacitance were not affected by rASPLM treatment. Relaxation from caffeine-induced contracture was faster, and NCX1 current amplitudes were higher in rASPLM myocytes, indicating that PLM downregulation enhanced NCX1 activity. In native rat cardiac myocytes, coimmunoprecipitation experiments indicated an association of PLM with NCX1. At 0.6 mM [Ca2+]o, rASPLM myocytes had significantly ( P < 0.003) lower contraction and [Ca2+]itransient amplitudes than control GFP myocytes. At 5 mM [Ca2+]o, both contraction and [Ca2+]itransient amplitudes were higher in rASPLM myocytes. This pattern of contractile and [Ca2+]itransient behavior in rASPLM myocytes was opposite to that observed in post-MI rat myocytes. We conclude that downregulation of PLM in normal rat cardiac myocytes enhanced NCX1 function and affected [Ca2+]itransient and contraction amplitudes. We suggest that PLM downregulation offers a potential therapeutic strategy for ameliorating contractile abnormalities in MI myocytes.
Interpreting cardiac muscle force-length dynamics using a novel functional model
Authors: Campbell Kenneth B. , Chandra Murali , Kirkpatrick Robert D. , Slinker Bryan K. , Hunter William C.
Published: March 2004

To describe the dynamics of constantly activated cardiac muscle, we propose that length affects force via both recruitment and distortion of myosin cross bridges. This hypothesis was quantitatively tested for descriptive and explanative validity. Skinned cardiac muscle fibers from animals expressing primarily α-myosin heavy chain (MHC) (mouse, rat) or β-MHC (rabbit, ferret) were activated with solutions from pCa 6.1 to 4.3. Activated fibers were subjected to small-amplitude length perturbations [Δ L( t)] rich in frequency content between 0.1 and 40 Hz. In descriptive validation tests, the model was fit to the ensuing force response [ΔF( t)] in the time domain. In fits to 118 records, the model successfully accounted for most of the measured variation in ΔF( t) ( R2 range, 0.997–0.736; median, 0.981). When some residual variations in ΔF( t) were not accounted for by the model (as at low activation), there was very little coherence (<0.5) between these residual force variations and the applied Δ L( t) input function, indicating that something other than Δ L( t) was causing the measured variation in ΔF( t). With one exception, model parameters were estimated with standard errors on the order of 1% or less. Thus parameters of the recruitment component of the model could be uniquely separated from parameters of the distortion component of the model and parameters estimated from any given fiber could be considered unique to that fiber. In explanative validation tests, we found that recruitment and distortion parameters were positively correlated with independent assessments of the physiological entity they were assumed to represent. The recruitment distortion model was judged to be valid from both descriptive and explanative perspectives and is, therefore, a useful construct for describing and explaining dynamic force-length relationships in constantly activated cardiac muscle.
Protein kinase C plays an essential role in sildenafil-induced cardioprotection in rabbits
Authors: Das Anindita , Ockaili Ramzi , Salloum Fadi , Kukreja Rakesh C.
Published: March 2004

Sildenafil citrate (Viagra) is the most widely used pharmacological drug for treating erectile dysfunction in men. It has potent cardioprotective effects against ischemia-reperfusion injury via nitric oxide and opening of mitochondrial ATP-sensitive K+ channels. We further investigated the role of protein kinase C (PKC)-dependent signaling pathway in sildenafil-induced cardioprotection. Rabbits were treated (orally) with sildenafil citrate (1.4 mg/kg) 30 min before index ischemia for 30 min and reperfusion for 3 h. The PKC inhibitor chelerythrine (5 mg/kg iv) was given 5 min before sildenafil. Infarct size (% of risk area) reduced from 33.65 ± 2.17 in the vehicle (saline) group to 15.07 ± 0.63 in sildenafil-treated groups, a 45% reduction compared with vehicle (mean ± SE, P < 0.05). Chelerythrine abolished sildenafil-induced protection, as demonstrated by increase in infarct size to 31.14 ± 2.4 ( P < 0.05). Chelerythrine alone had an infarct size of 33.5 ± 2.5, which was not significantly different compared with DMSO-treated group (36.8 ± 1.7, P > 0.05). Western blot analysis demonstrated translocation of PKC-α, -θ, and -δ isoforms from cytosol to membrane after treatment with sildenafil. However, no change in the PKC-β and -ϵ isoforms was observed. These data provide direct evidence of an essential role of PKC, and potentially PKC-α, -θ, and -δ, in sildenafil-induced cardioprotection in the rabbit heart.
Nicorandil induces late preconditioning against myocardial infarction in conscious rabbits
Authors: Tang Xian-Liang , Xuan Yu-Ting , Zhu Yanqing , Shirk Gregg , Bolli Roberto
Published: March 2004

Nicorandil has been shown to induce an infarct-limiting effect similar to that induced by the early phase of ischemic preconditioning (PC). The goals of this study were to determine whether nicorandil induces a delayed cardioprotection that is analogous to the late phase of ischemic PC and, if so, whether nicorandil-induced late PC is associated with upregulation of cardioprotective proteins. Chronically instrumented, conscious rabbits received vehicle (intravenous normal saline; control group, n = 10), nicorandil (100 μg/kg bolus + 30 μg·kg–1·min–1 iv for 60 min; nicorandil group, n = 10), or ischemic PC (6 cycles of 4-min coronary occlusion/4-min reperfusion; PC group, n = 8). Twenty-four hours later, rabbits underwent a 30-min coronary occlusion, followed by 3 days of reperfusion. Myocardial infarct size was significantly reduced in rabbits pretreated with nicorandil (27.5 ± 5.3% of the risk region) or with ischemia (30.3 ± 4.2%) versus controls (59.1 ± 4.7%, P < 0.05 vs. both). Furthermore, the expression of cyclooxygenase-2 (COX-2) and Bcl-2 was significantly elevated (+38% and +126%, respectively; P < 0.05) in myocardium of rabbits given nicorandil 24 h earlier versus controls. We conclude that nicorandil induces delayed cardioprotection against myocardial infarction similar to that afforded by the late phase of ischemic PC, possibly by upregulating COX-2 and Bcl-2.
Coupling of angiotensin II AT1receptors to neuronal NHE activity and carrier-mediated norepinephrine release in myocardial ischemia
Authors: Reid Alicia C. , Mackins Christina J. , Seyedi Nahid , Levi Roberto , Silver Randi B.
Published: March 2004

In ischemia, cardiac sympathetic nerve endings (cSNE) release excessive amounts of norepinephrine (NE) via the nonexocytotic Na+-dependent NE transporter (NET). NET, normally responsible for NE reuptake into cSNE, reverses in myocardial ischemia, releasing pathological amounts of NE. This carrier-mediated NE release can be triggered by elevated intracellular Na+levels in the axoplasm. The fact that ischemia activates the intracellular pH regulatory Na+/H+exchanger (NHE) in cSNE is pivotal in increasing intraneuronal Na+and thus activating carrier-mediated NE release. Angiotensin (ANG) II levels are also significantly elevated in the ischemic heart. However, the effects of ANG II on cSNE, which express the ANG II receptor, AT1R, are poorly understood. We hypothesized that ANG II-induced AT1R activation in cSNE may be positively coupled to NHE activity and thereby facilitate the pathological release of NE associated with myocardial ischemia. We tested this hypothesis in a cSNE model, human neuroblastoma cells stably transfected with rat recombinant AT1Areceptor (SH-SY5Y-AT1A). SH-SY5Y-AT1Aconstitutively expresses amiloride-sensitive NHE and the NET. NHE activity was assayed in BCECF-loaded SH-SY5Y-AT1Aas the rate of the Na+-dependent alkalinization in response to an acute acidosis. ANG II activation of AT1R markedly increased NHE activity in SH-SY5Y-AT1Avia a Ca2+-dependent pathway and promoted carrier-mediated NE release. In addition, in guinea pig cSNE expressing native AT1R, ANG II elicited carrier-mediated NE release. In SH-SY5Y-AT1Aand cSNE, amiloride inhibited the ANG II-mediated release of NE. Our results provide a link between AT1R and NHE in cSNE, which can exacerbate carrier-mediated NE release during protracted myocardial ischemia.
Aging attenuates vascular and metabolic plasticity but does not limit improvement in muscle Vo2 max
Authors: Lawrenson L. , Hoff J. , Richardson R. S.
Published: March 2004

The interactions between exercise, vascular and metabolic plasticity, and aging have provided insight into the prevention and restoration of declining whole body and small muscle mass exercise performance known to occur with age. Metabolic and vascular adaptations to normoxic knee-extensor exercise training (1 h 3 times a week for 8 wk) were compared between six sedentary young (20 ± 1 yr) and six sedentary old (67 ± 2 yr) subjects. Arterial and venous blood samples, in conjunction with a thermodilution technique facilitated the measurement of quadriceps muscle blood flow and hematologic variables during incremental knee-extensor exercise. Pretraining, young and old subjects attained a similar maximal work rate (WRmax) (young = 27 ± 3, old = 24 ± 4 W) and similar maximal quadriceps O2 consumption (muscle V̇o2 max) (young = 0.52 ± 0.03, old = 0.42 ± 0.05 l/min), which increased equally in both groups posttraining (WRmax, young = 38 ± 1, old = 36 ± 4 W, Muscle V̇o2 max, young = 0.71 ± 0.1, old = 0.63 ± 0.1 l/min). Before training, muscle blood flow was ∼500 ml lower in the old compared with the young throughout incremental knee-extensor exercise. After 8 wk of knee-extensor exercise training, the young reduced muscle blood flow ∼700 ml/min, elevated arteriovenous O2 difference ∼1.3 ml/dl, and increased leg vascular resistance ∼17 mmHg·ml–1·min–1, whereas the old subjects revealed no training-induced changes in these variables. Together, these findings indicate that after 8 wk of small muscle mass exercise training, young and old subjects of equal initial metabolic capacity have a similar ability to increase quadriceps muscle WRmax and muscle V̇o2 max, despite an attenuated vascular and/or metabolic adaptation to submaximal exercise in the old.
Effects of left ventricular contractility and coronary vascular resistance on coronary dynamics
Authors: Sun Yi-Hui , Anderson Todd J. , Parker Kim H. , Tyberg John V.
Published: March 2004

Wave-intensity analysis, which separates upstream from downstream events and defines their interaction, has been used to study the effects of changes in left ventricular (LV) contractility ( Emax) and left circumflex coronary artery resistance ( RLCx) on the coronary systolic flow impediment (CSFI). In 10 anesthetized, open-chest dogs, we measured coronary, aortic, and LV pressures, coronary velocity (Flowire), and flow. Emax was increased by paired pacing and RLCx was modulated by intracoronary infusions of vasodilators (adenosine and nitroglycerin) and a vasoconstrictor (phenylephrine). When both Emax and RLCx were varied, CSFI and the energy of the backward-going compression wave ( IW–) were greatest at the highest levels of Emax and the lowest levels of RLCx. IW– was proportional to the CSFI. We conclude that contractility and coronary resistance change CSFI by modulating the backward-going compression wave.
Red blood cell velocity and oxygen tension measurement in cerebral microvessels by double-wavelength photoexcitation
Authors: Tsukada Kosuke , Sekizuka Eiichi , Oshio Chikara , Tsujioka Katsuhiko , Minamitani Haruyuki
Published: March 2004

Because the regulation of microcirculation in the cerebral cortex cannot be analyzed without measuring the blood flow dynamics and oxygen concentration in cerebral microvessels, we developed a fluorescence and phosphorescence system for estimating red blood cell velocity and oxygen tension in cerebral microcirculation noninvasively and continuously with high spatial resolution. Using red blood cells labeled with fluorescent isothiocyanate to visualize red cell distribution and using the oxygen quenching of Pd-meso-tetra-(4-carboxyphenyl)-porphyrin phosphorescence to measure oxygen tension enabled simultaneous measurement of blood velocity and oxygen tension. We examined how the measurement accuracy was affected by the spatial resolution and by the excitation laser light passing through the targeted microvessel and exciting the oxygen probe dye in the tissue beneath it. Focusing the excitation light into the microvessel stabilized the phosphorescence lifetime at each spatial resolution; moreover, it greatly reduced phosphorescence from the brain tissue. Animal experiments involving acute hemorrhagic shock demonstrated the feasibility of our system by showing that the changes in venular velocity and oxygen tension are synchronized to the change in mean arterial pressure. Our system measures the red cell velocity and oxygen concentration in the cerebral microcirculation by using the differences in luminescence and wavelength between fluorescence and phosphorescence, making it possible to easily acquire information about cerebral microcirculatory distribution and oxygen tension simultaneously.
Limiting mechanisms of force production after repetitive dynamic contractions in human triceps surae
Authors: Klass M. , Guissard N. , Duchateau J.
Published: March 2004

The influence of repetitive dynamic fatiguing contractions on the neuromuscular characteristics of the human triceps surae was investigated in 10 subjects. The load was 50% of the torque produced during a maximal voluntary contraction, and the exercise ended when the ankle range of motion declined to 50% of control. The maximal torque of the triceps surae and the electromyographic (EMG) activities of the soleus and medial gastrocnemius were studied in response to voluntary and electrically induced contractions before and after the fatiguing task and after 5 min of recovery. Reflex activities were also tested by recording the Hoffmann reflex (H reflex) and tendon reflex (T reflex) in the soleus muscle. The results indicated that whereas the maximal voluntary contraction torque, tested in isometric conditions, was reduced to a greater extent ( P < 0.05) at 20° of plantar flexion (-33%) compared with the neutral position (-23%) of the ankle joint, the EMG activity of both muscles was not significantly reduced after fatigue. Muscle activation, tested by the interpolated-twitch method or the ratio of the voluntary EMG to the amplitude of the muscle action potential (M-wave), as well as the neuromuscular transmission and sarcolemmal excitation, tested by the M-wave amplitude, did not change significantly after the fatiguing exercise. Although the H and T reflexes declined slightly (10-13%; P < 0.05) after fatigue, these adjustments did not appear to have a direct deleterious effect on muscle activation. In contrast, alterations in the mechanical twitch time course and postactivation potentiation indicated that intracellular Ca2+-controlled excitation-contraction coupling processes most likely played a major role in the force decrease after dynamic fatiguing contractions performed for short duration.
Calcium and TRP Channels in Pulmonary Vascular Smooth Muscle Cell Proliferation
Authors: Landsberg Judd W. , Yuan Jason X.-J.
Published: March 2004

Ca2+ is a major trigger for pulmonary vasoconstriction and a stimulus for pulmonary vascular smooth muscle cell proliferation. The transient receptor potential cation channels participate in regulating intracellular Ca2+ and thus vascular contractility and cell proliferation. Upregulation of genes encoding these channels is involved in the development of pulmonary hypertension.
Unorthodox Sites and Modes of Aldosterone Action
Authors: Oberleithner Hans
Published: March 2004

Aldosterone controls electrolyte balance by acting on the renal epithelium. However, there is strong evidence that vascular endothelium is another target for mineralocorticoids. Endothelial cells gain sensitivity to diuretics when exposed to aldosterone. Atomic force microscopy detects such phenomena. It is speculated that endothelium and kidney join forces in the regulation of body fluids.
Comparative Physiology of Lung Complexity: Implications for Gas Exchange
Authors: Powell Frank L. , Hopkins Susan R.
Published: March 2004

Lungs evolved to increase diffusing capacity by compartmentalizing and reducing the size of individual gas exchange units. This increased the potential for gas exchange limitations from ventilation-perfusion heterogeneity. However, comparative studies on reptiles, birds, and mammals show that heterogeneity is independent of lung complexity.
Molecular Mechanisms of Epithelial Polarity: About Shapes, Forces, and Orientation Problems
Authors: Kroschewski Ruth
Published: March 2004

In a variety of organs, epithelial cells assemble into networks of cysts and tubules. Such structures can be reproduced in vitro. Here the importance of plasma membrane compartmentalization and forces that drive morphogenetic events during cystogenesis are discussed.
Central Pathways Controlling Brown Adipose Tissue Thermogenesis
Authors: Morrison Shaun F.
Published: March 2004

Heat production in brown adipose tissue contributes to cold defense, to stress-induced increases in body temperature, and to energy balance. Elucidating the functional organization of the central network controlling the sympathetic outflow to brown adipose tissue could provide a framework for understanding how dysregulation of thermogenesis contributes to hyperthermia and to obesity.
A Nonconventional Look at Ionic Fluxes in the Skin: Lessons From Genetically Modified Mice
Authors: Guitard Marjorie , Leyvraz Celine , Hummler Edith
Published: March 2004

The mammalian, highly amiloride-sensitive epithelial sodium channel (ENaC) is member of the degenerin/ENaC superfamily of ion channels known to be implicated in sodium homeostasis, mechanosensation, and mechanoperception. A novel role for ENaC implicated in differentiation processes in skin reshapes our current view of this ancient transmembrane channel protein.
Electrophysiological Insights into the Mechanism of Ion-Coupled Cotransporters
Authors: Peres Antonio , Giovannardi Stefano , Bossi Elena , Fesce Riccardo
Published: March 2004

Most ion-coupled cotransporters display, in the absence of organic substrate, transient currents resembling the gating currents of voltage-dependent ion channels. Detailed comparison of these currents in different ionic and temperature conditions with the corresponding steady-state currents when translocation of the substrate occurs reveals new insights into the mechanisms of the process.
Rat model of familial combined hyperlipidemia as a result of comparative mapping
Authors: Ueno Takahiro , Tremblay Johanne , Kunes Jaroslav , Zicha Josef , Dobesova Zdenka , Pausova Zdenka , Deng Alan Y. , Sun Yu-Lin , Jacob Howard J. , Hamet Pavel
Published: March 2004

Total genome scan was carried out in 266 F2intercrosses from the Prague hypertriglyceridemic (HTG) rat that shares several clinical characteristics with human metabolic syndrome. Two loci for plasma triglycerides (TG) were localized on chromosome 2 (Chr 2) (LOD 4.4, 3.2). The first locus overlapped with the rat syntenic region of the human locus for the metabolic syndrome and for small, dense LDL, while the second overlapped with the syntenic region of another locus for small, dense LDL in humans by the comparative mapping approach. Loci for TG on rat Chr 13 (LOD 3.3) and Chr 1 (LOD 2.7) overlapped with the syntenic region of loci for human familial combined hyperlipidemia (FCHL) in Finnish and Dutch populations, respectively. The concordances of loci for TG localized in this study with previously reported loci for FCHL and its related phenotypes are underlying the generalized importance of these loci in dyslipidemia. These data suggest the close relationship between dyslipidemia in HTG rats and human FCHL, establishing a novel animal model for exploration of pathophysiology and therapy based on genomic determinants.
Novel QTLs for HDL levels identified in mice by controlling forApoa2allelic effects: confirmation of a chromosome 6 locus in a congenic strain
Authors: Welch Carrie L. , Bretschger Sara , Wen Ping-Zi , Mehrabian Margarete , Latib Nashat , Fruchart-Najib Jamila , Fruchart Jean Charles , Myrick Christy , Lusis Aldons J.
Published: March 2004

Atherosclerosis is a complex disease resulting from the interaction of multiple genes, including those causing dyslipidemia. Relatively few of the causative genes have been identified. Previously, we identified Apoa2 as a major determinant of high-density lipoprotein cholesterol (HDL-C) levels in the mouse model. To identify additional HDL-C level quantitative trait loci (QTLs), while controlling for the effect of the Apoa2 locus, we performed linkage analysis in 179 standard diet-fed F2mice derived from strains BALB/cJ and B6.C- H25c(a congenic strain carrying the BALB/c Apoa2 allele). Three significant QTLs and one suggestive locus were identified. A female-specific locus mapping to chromosome 6 (Chr 6) also exhibited effects on plasma non-HDL-C, apolipoprotein AII (apoAII), apoB, and apoE levels. A Chr 6 QTL was independently isolated in a related congenic strain (C57BL/6J vs. B6.NODc6: P = 0.003 and P = 0.0001 for HDL-C and non-HDL-C levels, respectively). These data are consistent with polygenic inheritance of HDL-C levels in the mouse model and provide candidate loci for HDL-C and non-HDL-C level determination in humans.
Proinflammatory phenotype of coronary arteries promotes endothelial apoptosis in aging
Authors: Csiszar Anna , Ungvari Zoltan , Koller Akos , Edwards John G. , Kaley Gabor
Published: March 2004

Previously we demonstrated that aging in coronary arteries is associated with proinflammatory phenotypic changes and decreased NO bioavailability, which, we hypothesized, promotes vascular disease by enhancing endothelial apoptosis. To test this hypothesis we characterized proapoptotic alterations in the phenotype of coronary arteries of aged (26 mo old) and young (3 mo old) F344 rats. DNA fragmentation analysis and TUNEL assay showed that in aged vessels there was an approximately fivefold increase in the number of apoptotic endothelial cells. In aged coronary arteries there was an increased expression of TNFα, TNFβ, and caspase 9 (microarray, real-time PCR), as well as increased caspase 9 and caspase 3 activity, whereas expression of TNFR1, TNFα-converting enzyme (TACE), Bcl-2, Bcl-X(L), Bid, Bax, caspase 8, and caspase 3 were unchanged. In vessel culture (18 h) incubation of aged coronary arteries with a TNF blocking antibody or the NO donor S-nitroso-penicillamine (SNAP) decreased apoptotic cell death. Incubation of young arteries with exogenous TNFα increased caspase 9 activity and elicited endothelial apoptosis, which was attenuated by SNAP. Inhibition of NO synthesis in cultured young coronary arteries also induced apoptotic cell death and potentiated the apoptotic effect of TNFα. Thus we propose that age-related upregulation of TNFα and caspase 9 and decreased bioavailability of NO promote endothelial apoptosis in coronary arteries that may lead to impaired endothelial function and ischemic heart disease in the elderly.
Quantitative trait loci that determine lipoprotein cholesterol levels in an intercross of 129S1/SvImJ and CAST/Ei inbred mice
Authors: Lyons Malcolm A. , Wittenburg Henning , Li Renhua , Walsh Kenneth A. , Korstanje Ron , Churchill Gary A. , Carey Martin C. , Paigen Beverly
Published: March 2004

To identify genetic determinants of lipoprotein levels, we are performing quantitative trait locus (QTL) analysis on a series of mouse intercrosses in a “daisy chain” experimental design, to increase the power of detecting QTL and to identify common variants that should segregate in multiple intercrosses. In this study, we intercrossed strains CAST/Ei and 129S1/SvImJ, determined HDL, total, and non-HDL cholesterol levels, and performed QTL mapping using Pseudomarker software. For HDL cholesterol, we identified two significant QTL on chromosome (Chr) 1 ( Hdlq5, 82 cM, 60–100 cM) and Chr 4 ( Hdlq10, 20 cM, 10–30 cM). For total cholesterol, we identified three significant QTL on Chr 1 ( Chol7, 74 cM, 65–80 cM), Chr 4 ( Chol8, 12 cM, 0–30 cM), and Chr 17 ( Chol9, 54 cM, 20–60 cM). For non-HDL cholesterol, we identified significant QTL on Chr 8 ( Nhdlq1, 34 cM, 20–60 cM) and Chr X ( Nhdlq2, 6 cM, 0–18 cM). Hdlq10 was the only QTL detected in two intercrosses involving strain CAST/Ei. Hdlq5, Hdlq10, Nhdlq1, and two suggestive QTL at D7Mit246 and D15Mit115 coincided with orthologous human lipoprotein QTL. Our analysis furthers the knowledge of the genetic control of lipoprotein levels and points to the importance of Hdlq10, which was detected repeatedly in multiple studies.
Regional variations in ABC transporter expression along the mouse intestinal tract
Authors: Mutch David M. , Anderle Pascale , Fiaux Muriel , Mansourian Robert , Vidal Karine , Wahli Walter , Williamson Gary , Roberts Matthew-Alan
Published: March 2004

The ATP-binding cassette (ABC) family of proteins comprise a group of membrane transporters involved in the transport of a wide variety of compounds, such as xenobiotics, vitamins, lipids, amino acids, and carbohydrates. Determining their regional expression patterns along the intestinal tract will further characterize their transport functions in the gut. The mRNA expression levels of murine ABC transporters in the duodenum, jejunum, ileum, and colon were examined using the Affymetrix MuU74v2 GeneChip set. Eight ABC transporters (Abcb2, Abcb3, Abcb9, Abcc3, Abcc6, Abcd1, Abcg5, and Abcg8) displayed significant differential gene expression along the intestinal tract, as determined by two statistical models (a global error assessment model and a classic ANOVA, both with a P < 0.01). Concordance with semiquantitative real-time PCR was high. Analyzing the promoters of the differentially expressed ABC transporters did not identify common transcriptional motifs between family members or with other genes; however, the expression profile for Abcb9 was highly correlated with fibulin-1, and both genes share a common complex promoter model involving the NFκB, zinc binding protein factor (ZBPF), GC-box factors SP1/GC (SP1F), and early growth response factor (EGRF) transcription binding motifs. The cellular location of another of the differentially expressed ABC transporters, Abcc3, was examined by immunohistochemistry. Staining revealed that the protein is consistently expressed in the basolateral compartment of enterocytes along the anterior-posterior axis of the intestine. Furthermore, the intensity of the staining pattern is concordant with the expression profile. This agrees with previous findings in which the mRNA, protein, and transport function of Abcc3 were increased in the rat distal intestine. These data reveal regional differences in gene expression profiles along the intestinal tract and demonstrate that a complete understanding of intestinal ABC transporter function can only be achieved by examining the physiologically distinct regions of the gut.
Large-scale gene discovery in human airway epithelia reveals novel transcripts
Authors: Scheetz Todd E. , Zabner Joseph , Welsh Michael J. , Coco Justin , Eyestone Mari , de Fatima Bonaldo Maria , Kucaba Tamara , Casavant Thomas L. , Soares M. Bento , McCray Paul B.
Published: March 2004

The airway epithelium represents an important barrier between the host and the environment. It is a first site of contact with pathogens, particulates, and other stimuli, and has evolved the means to dynamically respond to these challenges. In an effort to define the transcript profile of airway epithelia, we created and sequenced cDNA libraries from cystic fibrosis (CF) and non-CF epithelia and from human lung tissue. Sequencing of these libraries produced ∼53,000 3′-expressed sequence tags (3′-ESTs). From these, a nonredundant UniGene set of more than 19,000 sequences was generated. Despite the relatively small contribution of airway epithelia to the total mass of the lung, focused gene discovery in this tissue yielded novel results. The ESTs included several thousand transcripts (6,416) not previously identified from cDNA sequences as expressed in the lung. Among the abundant transcripts were several genes involved in host defense. Most importantly, the set also included 879 3′-ESTs that appear to be novel sequences not previously represented in the National Center for Biotechnology Information UniGene collection. This UniGene set should be useful for studies of pulmonary diseases involving the airway epithelium including cystic fibrosis, respiratory infections and asthma. It also provides a reagent for large-scale expression profiling.
Overexpression of membrane-associated fatty acid binding protein (FABPpm) in vivo increases fatty acid sarcolemmal transport and metabolism
Authors: Clarke David C. , Miskovic Dragana , Han Xiao-Xia , Calles-Escandon Jorge , Glatz Jan F. C. , Luiken Joost J. F. P. , Heikkila John J. , Bonen Arend
Published: March 2004

Fatty acid translocase (FAT/CD36) is a key fatty acid transporter in skeletal muscle. However, the effects on fatty acid transport by another putative fatty acid transporter, plasma membrane-associated fatty acid binding protein (FABPpm), have not been determined in mammalian tissue. We examined the functional effects of overexpressing FABPpm on the rates of 1) palmitate transport across the sarcolemma and 2) palmitate metabolism in skeletal muscle. One muscle (soleus) was transfected with pTracer containing FABPpm cDNA. The contralateral muscle served as control. After injecting the FABPpm cDNA, muscles were electroporated. FABPpm overexpression was directly related to the quantity of DNA administered. Electrotransfection (200 μg/muscle) rapidly induced FABPpm protein overexpression ( day 1, +92%, P < 0.05), which was further increased during the next few days ( days 3–7; range +142% to +160%, P < 0.05). Sarcolemmal FABPpm was comparably increased ( day 7, +173%, P < 0.05). Neither FAT/CD36 expression nor sarcolemmal FAT/CD36 content was altered. FABPpm overexpression increased the rates of palmitate transport (+79%, P < 0.05). Rates of palmitate incorporation into phospholipids were also increased +36%, as were the rates of palmitate oxidation (+20%). Rates of palmitate incorporation into triacylglycerol depots were not altered. These studies demonstrate that in mammalian tissue FABPpm overexpression increased the rates of palmitate transport across the sarcolemma, an effect that is independent of any changes in FAT/CD36. However, since the overexpression of plasmalemmal FABPpm (+173%) exceeded the effects on the rates of palmitate transport and metabolism, it appears that the overexpression of FABPpm alone is not sufficient to induce completely parallel increments in palmitate transport and metabolism. This suggests that other mechanisms are required to realize the full potential offered by FABPpm overexpression.
Differential expression of the closely linked KISS1, REN, and FLJ10761 genes in transgenic mice
Authors: Nistala Ravi , Zhang Xiaoji , Sigmund Curt D.
Published: March 2004

We previously reported the development and characterization of transgenic mice containing a large 160-kb P1 artificial chromosome (PAC) encompassing the renin (REN) locus from human chromosome 1. Here we demonstrate that PAC160 not only encodes REN, but also complete copies of the next upstream (KISS1) and downstream ( FLJ10761 ) gene along human chromosome 1. Incomplete copies of the second upstream (PEPP3) and downstream (SOX13) genes are also present. The gene order PEPP3-KISS1-REN-FLJ10761-SOX13 is conserved in mice containing either one or two copies of the REN locus. Despite the close localization of KISS1, REN, and FLJ10761 , they each exhibit distinct, yet overlapping tissue-specific expression profiles in humans. The tissue-specific expression patterns of REN and FLJ10761 were retained in transgenic mice containing PAC160. Expression of REN and FLJ10761 were also proportional to copy number. Expression of KISS1 in PAC160 mice showed both similarities and differences to humans. These data suggest that expression of gene blocks encoded on large genomic clones are retained when the clones are used to generate transgenic mice. Genomic elements which act to insulate genes from their neighbors are also apparently retained.
Review of radiation-induced bystander effects
Authors: Snyder Andrew R
Published: March 2004

It is now apparent that the target for the biological effects of ionizing radiation (IR) is not solely the irradiated cell(s), but also includes the surrounding cells/tissue as well. Radiation-induced bystander effects (BSEs) are defined by the presence of the biological effects of radiation in cells that were not themselves in the field of irradiation. Decreased plating efficiency, increased sister chromatid exchanges, oncogenic transformation, among other endpoints have been used to describe the BSE. Two primary means have been established for the transmission of the bystander signal; one is mediated by gap-junction intracellular communication, and the other is initiated through the secretion of factors from irradiated cells. While the basis for these phenomena have been established in cell culture systems, there is also evidence for their presence in vivo. This in vivo effect may contribute to increased tumor cell killing, and may also play a role in the abscopal effects of radiation, where radiation responses are seen in areas separated from the irradiated tissue. Although the precise molecular components and mechanisms remain unknown, their discovery will shed new light on the role of the BSEs in radiation risk assessment, and clinical radiotherapy in the clinic.
Classical radiation biology dogma, bystander effects and paradigm shifts
Authors: Waldren Charles A
Published: March 2004

A classical dogma of radiation biology asserts that all effects of radiation on cells are due to it's direct, immediate actions. But evidence accumulated over the last 50 years shows that radiation also has, indirect ‘non-target’ actions including ‘bystander’ effects in which effects of radiation on cells or media are transported to cells or tissues that were not ‘hit’ by the radiation, leading to changes in their function. This important but heretical recognition of radiation actions has been referred to, probably incorrectly, as a ‘paradigm shift.’ What these signals are and how they induce changes is not well understood. Also not clear is how, or if, bystander effects might affect risk estimates for exposure to low doses of radiation. These issues are reviewed and explored in this series of papers.
Fotemustine Compared With Dacarbazine in Patients With Disseminated Malignant Melanoma: A Phase III Study
Authors: Avril M.F. , Aamdal S. , Grob J.J. , Hauschild A. , Mohr P. , Bonerandi J.J. , Weichenthal M. , Neuber K. , Bieber T. , Gilde K. , Guillem Porta V. , Fra J. , Bonneterre J. , Saïag P. , Kamanabrou D. , Pehamberger H. , Sufliarsky J. , Gonzalez Larriba J.L. , Scherrer A. , Menu Y.
Published: March 2004

Purpose

To compare fotemustine and dacarbazine (DTIC) in terms of overall response rate (ORR) as primary end-point and overall survival, duration of responses, time to progression, time to occurrence of brain metastases (BM), and to assess safety and quality of life in patients with disseminated cutaneous melanoma.

Patients and Methods

Patients received either intravenous fotemustine 100 mg/m2 weekly for 3 weeks or DTIC 250 mg/m2/d for 5 consecutive days every 4 weeks (two cycles). Nonprogressive patients received a maintenance treatment every 4 weeks (fotemustine 100 mg/m2 or DTIC 250 mg/m2 for 5 days).

Results

Two hundred twenty-nine patients were randomly assigned to fotemustine or DTIC arms. The best ORR was higher in the fotemustine arm than in the DTIC arm in the intent-to-treat population (n = 229; 15.2% v 6.8%; P = .043) and in full analysis set (n = 221) (15.5% v 7.2%; P = .053). Similar median durations of responses (5.8 months with fotemustine v 6.9 months with DTIC) and time to progression (1.8 v 1.9 months, respectively) were observed. In patients without BM at inclusion, the median time to BM was 22.7 months with fotemustine versus 7.2 months with DTIC (P = .059). Median survival was 7.3 months with fotemustine versus 5.6 months with DTIC (P = .067). The main toxicity was grade 3 to 4 neutropenia (51% with fotemustine v 5% with DTIC) and thrombocytopenia (43% v 6%, respectively). No significant difference was noted for quality of life between arms.

Conclusion

ORR was higher in the fotemustine arm compared to the DTIC arm in first-line treatment of disseminated melanoma. A trend in favor of fotemustine in terms of overall survival and time to BM was evidenced.