bluuebunny/crossref_metadata_2025 huggingface dataset:
Feeding activates protein synthesis in mouse pancreas at the translational level without increase in mRNA
Authors: Sans Maria Dolors , Lee Sae-Hong , D'Alecy Louis G. , Williams John A.
Published: May 2004

To determine the mechanism of meal-regulated synthesis of pancreatic digestive enzymes, we studied the effect of fasting and refeeding on pancreatic protein synthesis, relative mRNA levels of digestive enzymes, and activation of the translational machinery. With the use of the flooding dose technique with l-[3H]phenylalanine, morning protein synthesis in the pancreas of Institute for Cancer Research mice fed ad libitum was 7.9 ± 0.3 nmol phenylalanine·10 min−1·mg protein−1. Prior fasting for 18 h reduced total protein synthesis to 70 ± 1.4% of this value. Refeeding for 2 h, during which the mice consumed 29% of their daily food intake, increased protein synthesis to 117.3 ± 4.9% of the control level. Pancreatic mRNA levels of amylase, lipases, trypsins, chymotrypsin, elastases, as well as those for several housekeeping genes tested were not significantly changed after refeeding compared with fasted mice. By contrast, the major translational control pathway involving Akt, mTOR, and S6K was strongly regulated by fasting and refeeding. Fasting for 18 h decreased phosphorylation of ribosomal protein S6 to almost undetectable levels, and refeeding highly increased it. The most highly phosphorylated form of the eIF4E binding protein (4E-BP1) made up the 14.6% of total 4E-BP1 in normally fed animals, was only 2.8% after fasting, and was increased to 21.4% after refeeding. This was correlated with an increase in the formation of the eIF4E-eIF4G complex after refeeding. By contrast, feeding did not affect eIF2B activity. Thus food intake stimulates pancreatic protein synthesis and translational effectors without increasing digestive enzyme mRNA levels.
Comparison of Ca2+release and uptake characteristics of the sarcoplasmic reticulum in isolated horse and rabbit cardiomyocytes
Authors: Loughrey C. M. , Smith G. L. , MacEachern K. E.
Published: May 2004

Both the cardiac action potential duration (APD) (0.6–1 s) and resting heart rate (30–40 beats/min) in the horse are significantly different from humans and smaller mammals, including the rabbit. This would be anticipated to have consequences for excitation-contraction (EC) coupling and require adaptation of the individual processes involved. The sarcoplasmic reticulum (SR) is one of the main components involved in EC coupling. This study examines and compares the activity of this organelle in the horse with that of the rabbit. In particular, the study focuses on SR Ca2+release via the Ca2+release channel/ryanodine receptor (RyR2) and Ca2+uptake via the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) pump. Isolated cardiomyocytes from both horse and rabbit hearts were permeabilized, bathed in a mock intracellular solution, and exposed to a specified [Ca2+]. Rabbit cardiomyocytes exposed to 260 nM [Ca2+] produced spontaneous Ca2+release and propagated Ca2+waves. Horse cells failed to produce Ca2+waves; instead, only local release in the form of Ca2+sparks was evident. However, at 550 nM [Ca2+], Ca2+waves were produced in both species. Ca2+waves were four times less frequent yet ∼1.5 times greater in amplitude in the horse compared with the rabbit. Ca2+wave velocity was comparable between the species. The reason for this disparity in Ca2+wave characteristics is unknown. Separate measurements of oxalate-supported Ca2+uptake into the SR suggest that both horse and rabbit cardiomyocytes have comparable levels SERCA activity. The possible reasons for the observed differences in SR Ca2+release between the horse and rabbit are discussed.
Regional blood volume and peripheral blood flow in postural tachycardia syndrome
Authors: Stewart Julian M. , Montgomery Leslie D.
Published: May 2004

Variants of postural tachycardia syndrome (POTS) are associated with increased [“high-flow” POTS (HFP)], decreased [“low-flow” POTS (LFP)], and normal [“normal-flow” POTS (NFP)] blood flow measured in the lower extremities while subjects were in the supine position. We propose that postural tachycardia is related to thoracic hypovolemia during orthostasis but that the patterns of peripheral blood flow relate to different mechanisms for thoracic hypovolemia. We studied 37 POTS patients aged 14–21 yr: 14 LFP, 15 NFP, and 8 HFP patients and 12 healthy control subjects. Peripheral blood flow was measured in the supine position by venous occlusion strain-gauge plethysmography of the forearm and calf to subgroup patients. Using indocyanine green techniques, we showed decreased cardiac index (CI) and increased total peripheral resistance (TPR) in LFP, increased CI and decreased TPR in HFP, and unchanged CI and TPR in NFP while subjects were supine compared with control subjects. Blood volume tended to be decreased in LFP compared with control subjects. We used impedance plethysmography to assess regional blood volume redistribution during upright tilt. Thoracic blood volume decreased, whereas splanchnic, pelvic, and leg blood volumes increased, for all subjects during orthostasis but were markedly lower than control for all POTS groups. Splanchnic volume was increased in NFP and LFP. Pelvic blood volume was increased in HFP only. Calf volume was increased above control in HFP and LFP. The results support the hypothesis of (at least) three pathophysiologic variants of POTS distinguished by peripheral blood flow related to characteristic changes in regional circulations. The data demonstrate enhanced thoracic hypovolemia during upright tilt and confirm that POTS is related to inadequate cardiac venous return during orthostasis.
Radicicol activates heat shock protein expression and cardioprotection in neonatal rat cardiomyocytes
Authors: Griffin Tina M. , Valdez Tina V. , Mestril Ruben
Published: May 2004

Heat shock proteins (HSPs) constitute an endogenous cellular defense mechanism against environmental stresses. In the past few years, studies have shown that overexpression of HSPs can protect cardiac myocytes against ischemia-reperfusion injury. In an attempt to increase the HSPs in cardiac tissue, we used the compound radicicol that activates HSP expression by binding to the HSP 90 kDa (HSP90). HSP90 is the main component of the cytosolic molecular chaperone complex, which has been implicated in the regulation of the heat shock factor 1 (HSF1). HSF1 is responsible for the transcriptional activation of the heat shock genes. In the present study, we show that radicicol induces HSP expression in neonatal rat cardiomyocytes, and this increase in HSPs confers cardioprotection to these cardiomyocytes. We also show that radicicol induction of the HSP and cardioprotection is dependent on the inhibition of HSP90 in cardiomyocytes. These results indicate that modulation of the active HSP90 protein level plays an important role in cardioprotection. Therefore, compounds, such as radicicol and its possible derivatives that inhibit the function of HSP90 in the cell may represent potentially useful cardioprotective agents.
8-Bromo-cAMP decreases the Ca2+sensitivity of airway smooth muscle contraction through a mechanism distinct from inhibition of Rho-kinase
Authors: Endou Katsuaki , Iizuka Kunihiko , Yoshii Akihiro , Tsukagoshi Hideo , Ishizuka Tamotsu , Dobashi Kunio , Nakazawa Tsugio , Mori Masatomo
Published: May 2004

To clarify whether cyclic AMP (cAMP)/cAMP-dependent protein kinase (PKA) activation and Rho-kinase inhibition share a common mechanism to decrease the Ca2+sensitivity of airway smooth muscle contraction, we examined the effects of 8-bromoadenosine 3′,5′-cyclic monophosphate (8-BrcAMP), a stable cAMP analog, and (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexane carboxamide dihydrochloride, monohydrate (Y-27632), a Rho-kinase inhibitor, on carbachol (CCh)-, guanosine 5′- O-(3-thiotriphosphate) (GTPγS)-, 4β-phorbol 12,13-dibutyrate (PDBu)-, and leukotriene D4(LTD4)-induced Ca2+sensitization in α-toxin-permeabilized rabbit tracheal and human bronchial smooth muscle. In rabbit trachea, CCh-induced smooth muscle contraction was inhibited by 8-BrcAMP and Y-27632 to a similar extent. However, GTPγS-induced smooth muscle contraction was resistant to 8-BrcAMP. In the presence of a saturating concentration of Y-27632, PDBu-induced smooth muscle contraction was completely reversed by 8-BrcAMP. Conversely, PDBu-induced smooth muscle contraction was resistant to Y-27632. In the presence of a saturating concentration of 8-BrcAMP, GTPγS-induced Ca2+sensitization was also reversed by Y-27632. The 8-BrcAMP had no effect on the ATP-triggered contraction of tracheal smooth muscle that had been treated with calyculin A in rigor solutions. The 8-BrcAMP and Y-27632 additively accelerated the relaxation rate of PDBu- and GTPγS-treated smooth muscle under myosin light chain kinase-inhibited conditions. In human bronchus, LTD4-induced smooth muscle contraction was inhibited by both 8-BrcAMP and Y-27632. We conclude that cAMP/PKA-induced Ca2+desensitization contains at least two mechanisms: 1) inhibition of the muscarinic receptor signaling upstream from Rho activation and 2) cAMP/PKA's preferential reversal of PKC-mediated Ca2+sensitization in airway smooth muscle.
Hypoxic control of the development of the surfactant system in the chicken: evidence for physiological heterokairy
Authors: Blacker Helen A. , Orgeig Sandra , Daniels Christopher B.
Published: May 2004

The surfactant system, a complex mixture of lipids and proteins, controls surface tension in the lung and is crucial for the first breath at birth, and thereafter. Heterokairy is defined as plasticity of a developmental process within an individual. Here, we provide experimental evidence for the concept of heterokairy, as hypoxia induces a change in the onset and rate of development of surfactant, probably via endogenous glucocorticoids, to produce individuals capable of surviving early hatching. Chicken eggs were incubated under normoxic (21% O2) conditions throughout or under hypoxic (17% O2) conditions from day 10 of incubation. Embryos were sampled at days 16, 18, and 20 and also 24 h after hatching. In a second experiment, dexamethasone (Dex), tri-iodothyronine (T3), or a combination (Dex + T3) was administered 24 and 48 h before each time point. Both hypoxia and Dex accelerated maturation of the surfactant lipids by increasing total phospholipid (PL), disaturated phospholipid (DSP), and cholesterol (Chol) in lavage at days 16 and 18. Maturation of surfactant lipid composition was accelerated, with day 16 %DSP/PL, Chol/DSP, and Chol/PL resembling the ratios of day 20 control animals. The effect of Dex + T3was similar to that of Dex alone. Hypoxia increased plasma corticosterone levels at day 16, while plasma T3levels were not affected. Hence, exposure to hypoxia during critical developmental windows accelerates surfactant maturation, probably by increasing corticosterone production. This internal modulation of the developmental response to an external stimulus is a demonstration of physiological heterokairy.
Comparison of effects of exercise and diuretic on left ventricular geometry, mass, and insulin resistance in older hypertensive adults
Authors: Rinder Morton R. , Spina Robert J. , Peterson Linda R. , Koenig Christopher J. , Florence Christa R. , Ehsani Ali A.
Published: May 2004

To compare the effects of exercise training and hydrochlorothiazide on left ventricular (LV) geometry and mass, blood pressure (BP), and hyperinsulinemia in older hypertensive adults, we studied 28 patients randomized either to a group (age 66.4 ± 1.3 yr; n = 16) that exercised or to a group (age 65.3 ± 1.2 yr; n = 12) that received hydrochlorothiazide for 6 mo. Endurance exercise training induced a 15% increase in peak aerobic power. The reduction in systolic BP was twofold greater with thiazide than with exercise (26.6 ± 12.2 vs. 11.5 ± 10.9 mmHg). Exercise and thiazide reduced LV wall thickness, LV mass index (14% in each group), and the LV wall thickness-to-radius ratio ( h/ r) similarly (exercise: before 0.48 ± 0.2, after 0.42 ± 0.01; thiazide: before 0.47 ± 0.04, after 0.40 ± 0.04; P = 0.017). The reductions in systolic BP and h/ r were correlated in the exercise group ( r = 0.70, P = 0.005) but not in the thiazide group. Exercise training reduced glucose-stimulated hyperinsulinemia (before: 13.65 ± 2.6 vs. 9.84 ± 1.5 mU·ml−1·min; P = 0.04) and insulin resistance. Thiazide did not affect plasma insulin levels. The results suggest that although exercise is less effective in reducing systolic BP than thiazide, it can induce regression of LV hypertrophy similar in magnitude to thiazide. Unlike hydrochlorothiazide, exercise training can improve insulin resistance and aerobic capacity in older hypertensive people.
Chronic in ovo hypoxia decreases pulmonary arterial contractile reactivity and induces biventricular cardiac enlargement in the chicken embryo
Authors: Villamor Eduardo , Kessels Carolina G. A. , Ruijtenbeek Karin , van Suylen Robert J. , Belik Jaques , De Mey Jo G. R. , Blanco Carlos E.
Published: May 2004

Although chronic prenatal hypoxia is considered a major cause of persistent pulmonary hypertension of the newborn, experimental studies have failed to consistently find pulmonary hypertensive changes after chronic intrauterine hypoxia. We hypothesized that chronic prenatal hypoxia induces changes in the pulmonary vasculature of the chicken embryo. We analyzed pulmonary arterial reactivity and structure and heart morphology of chicken embryos maintained from days 6 to 19 of the 21-day incubation period under normoxic (21% O2) or hypoxic (15% O2) conditions. Hypoxia increased mortality (0.46 vs. 0.14; P < 0.01) and reduced the body mass of the surviving 19-day embryos (22.4 ± 0.5 vs. 26.6 ± 0.7 g; P < 0.01). A decrease in the response of the pulmonary artery to KCl was observed in the 19-day hypoxic embryos. The contractile responses to endothelin-1, the thromboxane A2mimetic U-46619, norepinephrine, and electrical-field stimulation were also reduced in a proportion similar to that observed for KCl-induced contractions. In contrast, no hypoxia-induced decrease of response to vasoconstrictors was observed in externally pipped 21-day embryos (incubated under normoxia for the last 2 days). Relaxations induced by ACh, sodium nitroprusside, or forskolin were unaffected by chronic hypoxia in the pulmonary artery, but femoral artery segments of 19-day hypoxic embryos were significantly less sensitive to ACh than arteries of control embryos [pD2(= −log EC50): 6.51 ± 0.1 vs. 7.05 ± 0.1, P < 0.01]. Pulmonary vessel density, percent wall area, and periarterial sympathetic nerve density were not different between control and hypoxic embryos. In contrast, hypoxic hearts showed an increase in right and left ventricular wall area and thickness. We conclude that, in the chicken embryo, chronic moderate hypoxia during incubation transiently reduced pulmonary arterial contractile reactivity, impaired endothelium-dependent relaxation of femoral but not pulmonary arteries, and induced biventricular cardiac hypertrophy.
NHE3 Na+/H+exchanger supports proximal tubular protein reabsorption in vivo
Authors: Gekle Michael , Völker Katharina , Mildenberger Sigrid , Freudinger Ruth , Shull Gary E. , Wiemann Martin
Published: May 2004

Proximal tubular receptor-mediated endocytosis (RME) of filtered proteins prevents proteinuria. Pharmacological and genetic studies in cultured opossum kidney cells have shown that the apical Na+/H+exchanger isoform 3 (NHE3) supports RME by interference with endosomal pH homeostasis and endocytic fusion events. However, it is not known whether NHE3 also supports proximal tubular RME in vivo. We analyzed proximal tubular protein reabsorption by microinfusion experiments in rats and investigated renal protein excretion in NHE3 knockout (Nhe3 −/−) mice. Inhibition of NHE3 by EIPA or S-3226 reduced the fractional reabsorption of [14C]cytochrome c by ∼50% during early proximal microinfusion. During early distal microinfusion, no protein reabsorption could be detected. Urinary protein excretion of Nhe3 −/− or heterozygous mutant mice was significantly higher compared with wild-type mice. SDS-PAGE analysis of urinary proteins revealed that Nhe3 −/− animals excreted proteins the size of albumin or smaller. Thus a reduction in NHE3 activity or abundance causes tubular proteinuria. These data show that NHE3 supports proximal tubular RME of filtered proteins in vivo.
Stimulation of renin release by prostaglandin E2is mediated by EP2and EP4receptors in mouse kidneys
Authors: Schweda Frank , Klar Jürgen , Narumiya Shuh , Nüsing Rolf M. , Kurtz Armin
Published: May 2004

PGE2is a potent stimulator of renin release. So far, the contribution of each of the four PGE2receptor subtypes (EP1–EP4) in the regulation of renin release has not been characterized. Therefore, we investigated the effects PGE2on renin secretion rates (RSR) from isolated, perfused kidneys of EP1−/−, EP2−/−, EP3−/−, EP4−/−, and wild-type mice. PGE2concentration dependently stimulated RSR from kidneys of all four knockout strains with a threshold concentration of 1 nM in EP1−/−, EP2−/−, EP3−/−, and wild-type mice, whereas the threshold concentration was shifted to 10 nM in EP4−/− mice. Moreover, the maximum stimulation of RSR by PGE2at 1 μM was significantly reduced in EP4−/− (12.8-fold of control) and EP2−/− (15.9-fold) compared with wild-type (20.7-fold), EP1−/− (23.8-fold), and EP3−/− (20.1-fold). In contrast, stimulation of RSR by either the loop diuretic bumetanide or the β-adrenoceptor agonist isoproterenol was similar in all strains. PGE2exerted a dual effect on renal vascular tone, inducing vasodilatation at low concentrations (1 nmol/) and vasoconstriction at higher concentrations (100 nmol/) in kidneys of wild-type mice. In kidneys of EP2−/− as well as EP4−/− mice, vasodilatation at low PGE2concentrations was prevented, whereas vasoconstriction at higher concentrations was augmented. In contrast, the vasodilatatory component was pronounced in kidneys of EP1and EP3knockout mice, whereas in both genotypes the vasoconstriction at higher PGE2concentrations was markedly blunted. Our data provide evidence that PGE2stimulates renin release via activation of EP2and EP4receptors, whereas EP1and EP3receptors appear to be without functional relevance in juxtaglomerular cells. In contrast, all four receptor subtypes are involved in the control of renal vascular tone, EP1and EP3receptors increasing, and EP2as well as EP4receptors, decreasing it.
Inhibition of apoptosis by Zn2+in renal tubular cells following ATP depletion
Authors: Wei Qingqing , Wang Jinzhao , Wang Mong-Heng , Yu Fushin , Dong Zheng
Published: May 2004

Apoptosis has been implicated in ischemic renal injury. Thus one strategy of renal protection is to antagonize apoptosis. However, apoptosis inhibitory approaches remain to be fully explored. Zn2+has long been implicated in apoptosis inhibition; but systematic analysis of the inhibitory effects of Zn2+is lacking. Moreover, whether Zn2+blocks renal cell apoptosis following ischemia is unknown. Here, we demonstrate that Zn2+is a potent apoptosis inhibitor in an in vitro model of renal cell ischemia. ATP depletion induced apoptosis in cultured renal tubular cells, which was accompanied by caspase activation. Zn2+at 10 μM inhibited both apoptosis and caspase activation, whereas Co2+was without effect. In ATP-depleted cells, Zn2+partially prevented Bax activation and cytochrome c release from mitochondria. In isolated cell cytosol, Zn2+blocked cytochrome c-stimulated caspase activation at low-micromolar concentrations. In addition, Zn2+could directly antagonize the enzymatic activity of purified recombinant caspases. We conclude that Zn2+is a potent inhibitor of apoptosis in renal tubular cells following ATP depletion. Zn2+blocks apoptosis at multiple steps including Bax activation, cytochrome c release, apoptosome function, and caspase activation.
Annexin A2 heterotetramer: role in tight junction assembly
Authors: Lee David B. N. , Jamgotchian Nora , Allen Suni G. , Kan Frederick W. K. , Hale Irene L.
Published: May 2004

The tight junction has been characterized as a domain of focal fusions of the exoplasmic leaflets of the lipid bilayers from adjacent epithelial cells. Approximating membranes to within fusion distance is a thermodynamically unfavorable process and requires the participation of membrane-bridging or -fusion proteins. No known tight junction protein exhibits such activities. Annexin A2 (A2), in particular its heterotetramer (A2t), is known to form junctions between lipid bilayer structures through molecular bridging of their external leaflets. We demonstrate abundant A2 expression in Madin-Darby canine kidney II monolayers by two-dimensional gel electrophoresis. Confocal immunofluorescence microscopic analysis suggests the bulk of A2 is located along the apical and lateral plasma membrane in its tetrameric configuration, consisting of two A2 and two p11 (an 11-kDa calmodulin-related protein, S100A10) subunits. Immunocytochemistry and ultrastructural immunogold labeling demonstrate colocalization of the A2 subunit with bona fide tight junction proteins, zonula occludens-1, occludin, and claudin-1, at cell-cell contacts. The extracellular addition of a synthetic peptide, targeted to disrupt the binding between A2 and p11, completely aborts tight junction assembly in calcium chelation studies. We propose A2t as a member of a new class of tight junction proteins responsible for the long-observed convergence of adjacent exoplasmic lipid leaflets in tight junction assembly.
Endothelin stimulates endothelial nitric oxide synthase expression in the thick ascending limb
Authors: Herrera Marcela , Garvin Jeffrey L.
Published: May 2004

Endothelin-1 (ET-1) acutely inhibits NaCl reabsorption by the thick ascending limb (THAL) by activating the ETBreceptor, stimulating endothelial nitric oxide synthase (eNOS), and releasing nitric oxide (NO). In nonrenal tissue, chronic exposure to ET-1 stimulates eNOS expression via the ETBreceptor and activation of phosphatidylinositol 3-kinase (PI3K). We hypothesized that ET-1 increases eNOS expression in the THAL by binding to ETBreceptors and stimulating PI3K. In primary cultures of medullary THALs treated for 24 h, eNOS expression increased by 36 ± 18% with 0.01 nM ET-1, 123 ± 30% with 0.1 nM ( P < 0.05; n = 5), and 71 ± 30% with 1 nM, whereas 10 nM had no effect. BQ-788, a selective ETBreceptor antagonist, completely blocked stimulation of eNOS expression caused by 0.1 nM ET-1 (12 ± 25 vs. 120 ± 40% for ET-1 alone; P < 0.05; n = 5). BQ-123, a selective ETAreceptor antagonist, did not affect the increase in eNOS caused by 0.1 nM ET-1. Sarafotoxin c (S6c; 0.1 μM), a selective ETBreceptor agonist, increased eNOS expression by 77 ± 30% ( P < 0.05; n = 6). Wortmannin (0.01 μM), a PI3K inhibitor, completely blocked the stimulatory effect of 0.1 μM S6c (77 ± 30 vs. −28 ± 9%; P < 0.05; n = 6). To test whether the increase in eNOS expression heightens activity, we measured NO release in response to simultaneous treatment with l-arginine, ionomycin, and clonidine using a NO-sensitive electrode. NO release by control cells was 337 ± 61 and 690 ± 126 pA in ET-1-treated cells ( P < 0.05; n = 5). Taken together, these data suggest that ET-1 stimulates THAL eNOS, activating ETBreceptors and PI3K and thereby increasing NO production.
Daily short-period gravitation can prevent functional and structural changes in arteries of simulated microgravity rats
Authors: Sun Biao , Zhang Li-Fan , Gao Fang , Ma Xiao-Wu , Zhang Miao-Li , Liu Jian , Zhang Le-Ning , Ma Jin
Published: May 2004

This study was designed to clarify whether simulated microgravity-induced differential adaptational changes in cerebral and hindlimb arteries could be prevented by daily short-period restoration of the normal distribution of transmural pressure across arterial vasculature by either dorsoventral or footward gravitational loading. Tail suspension (Sus) for 28 days was used to simulate cardiovascular deconditioning due to microgravity. Daily standing (STD) for 1, 2, or 4 h, or +45° head-up tilt (HUT) for 2 or 4 h was used to provide short-period dorsoventral or footward gravitational loading as countermeasure. Functional studies showed that Sus alone induced an enhancement and depression in vasoconstrictor responsiveness of basilar and femoral arterial rings, respectively, as previously reported. These differential functional alterations can be prevented by either of the two kinds of daily gravitational loading treatments. Surprisingly, daily STD for as short as 1 h was sufficient to prevent the differential functional changes that might occur due to Sus alone. In morphological studies, the effectiveness of daily 4-h HUT or 1-h STD in preventing the differential remodeling changes in the structure of basilar and anterior tibial arteries induced by Sus alone was examined by histomorphometry. The results showed that both the hypertrophic and atrophic changes that might occur, respectively, in cerebral and hindlimb arteries due to Sus alone were prevented not only by daily HUT for 4 h but also by daily STD even for 1 h. These data indicate that daily gravitational loading by STD for as short as 1 h is sufficient to prevent differential adaptational changes in function and structure of vessels in different anatomic regions induced by a medium-term simulated microgravity.
Hypoxia-responsive growth factors upregulate periostin and osteopontin expression via distinct signaling pathways in rat pulmonary arterial smooth muscle cells
Authors: Li Peng , Oparil Suzanne , Feng Wenguang , Chen Yiu-Fai
Published: May 2004

This study tested the hypothesis that expression of the novel adhesion molecule periostin (PN) and osteopontin (OPN) is increased in lung and in isolated pulmonary arterial smooth muscle cells (PASMCs) in response to the stress of hypoxia and explored the signaling pathways involved. Adult male rats were exposed to 10% O2 for 2 wk, and growth-arrested rat PASMCs were incubated under 1% O2 for 24 h. Hypoxia increased PN and OPN mRNA expression in rat lung. In PASMCs, hypoxia increased PN but not OPN expression. The hypoxia-responsive growth factors fibroblast growth factor-1 (FGF-1) and angiotensin II (ANG II) caused dose- and time-dependent increases in PN and OPN expression in PASMCs. FGF-1-induced PN expression was blocked by the FGF-1 receptor antagonist PD-166866 and by inhibitors of phosphatidylinositol 3-kinase (PI3K) (LY-294002, wortmannin), p70S6K (rapamycin), MEK1/2 (U-0126, PD-98059), and p38MAPK (SB-203580) but not of JNK (SP-600125). ANG II-induced PN expression was blocked by the AT1-receptor antagonist losartan and by inhibitors of PI3K and MEK1/2. In contrast, FGF-1-induced OPN expression was blocked by inhibitors of JNK or MEK1/2 but not of PI3K, p70S6K, or p38MAPK. Activation of p70S6K and p38MAPK by anisomycin robustly stimulated PN but not OPN expression. This study is the first to demonstrate that growth factor-induced expression of PN in PASMCs is mediated through PI3K/p70S6K, Ras/MEK1/2, and Ras/p38MAPK signaling pathways, whereas the expression of OPN is mediated through Ras/MEK1/2 and Ras/JNK signaling pathways. These differences in signaling suggest that PN and OPN may play different roles in pulmonary vascular remodeling under pathophysiological conditions.
Kinematics in Newly Walking Toddlers Does Not Depend Upon Postural Stability
Authors: Ivanenko Yuri P. , Dominici Nadia , Cappellini Germana , Lacquaniti Francesco
Published: May 2004

When a toddler starts to walk without support, gait kinematics and electromyographic (EMG) activity differ from those of older children and the body displays considerable oscillations due to poor equilibrium. Postural instability clearly affects motor patterns in adults, but does instability explain why toddlers walk with a different gait? Here we addressed this question by comparing kinematics and EMGs in toddlers performing their first independent steps with or without hand or trunk support. Hand support significantly improved postural stability and some general gait parameters, reducing percent of falls, step width, lateral hip deviations and trunk oscillations. However, the kinematic and EMG patterns were unaffected by increased postural stability. In particular, the co-variance of the angular motion of the lower limb segments, the pattern of bilateral coordination of the vertical movement of the two hip joints, high variability of the foot path, the elliptic or single peak trajectory of the foot in the swing phase, and characteristic EMG bursts at foot contact remained idiosyncratic of toddler locomotion. Instead the toddler pattern shared fundamental features with adult stepping in place, suggesting that toddlers implement a mixed locomotor strategy, combining forward progression with elements of stepping in place. Furthermore, gait kinematics remained basically unchanged until the occurrence of the first unsupported steps and rapidly matured thereafter. We conclude that idiosyncratic features in newly walking toddlers do not simply result from undeveloped balance control but may represent an innate kinematic template of stepping.
Neural Correlates of the Automatic and Goal-Driven Biases in Orienting Spatial Attention
Authors: Fecteau Jillian H. , Bell Andrew H. , Munoz Douglas P.
Published: May 2004

How do stimuli in the environment interact with the goals of observers? We addressed this question by showing that the relevance of an abruptly appearing visual object (cue) changes how observers orient attention toward a subsequent object (target) and how this target is represented in the activity of neurons in the superior colliculus. Initially after the appearance of the cue, attention is driven to its locus. This capture of attention is followed by a second bias in orienting attention, where observers preferentially orient to new locations in the visual scene—an effect called inhibition of return. In the superior colliculus, these two automatic biases in orienting attention were associated with changes in neural activity linked to the appearance of the target—relatively stronger activity linked to the capture of attention and weaker activity linked to inhibition of return. This behavioral pattern changes when the cue predicts the upcoming location of the target—the benefit associated with the capture of attention is enhanced and inhibition of return is reduced. These goal-driven changes in behavior were associated with an increase in pretarget- and target-related activity. Taken together, the goals of observers modify stimulus-driven changes in neural activity with both signals represented in the salience maps of the superior colliculi.
Cycle Period of a Network Oscillator Is Independent of Membrane Potential and Spiking Activity in Individual Central Pattern Generator Neurons
Authors: Katz Paul S. , Sakurai Akira , Clemens Stefan , Davis Deron
Published: May 2004

Rhythmic motor patterns are thought to arise through the cellular properties and synaptic interactions of neurons in central pattern generator (CPG) circuits. Yet, when examining the CPG underlying the rhythmic escape response of the opisthobranch mollusc, Tritonia diomedea, we found that the cycle period of the fictive swim motor pattern recorded from the isolated nervous system was not altered by changing the resting membrane potential or the level of spiking activity of any of the 3 known CPG cell types: ventral swim interneuron-B (VSI-B), the dorsal swim interneurons (DSIs), and cerebral neuron 2 (C2). Furthermore, tonic firing in one or more DSIs or C2 evoked rhythmic bursting that did not differ from the cycle period of the motor pattern evoked by nerve stimulation, regardless of the firing frequency. In contrast, the CPG produced a large range of cycle periods as a function of temperature. The temperature sensitivity of the fictive motor pattern produced by the isolated nervous system was similar to the temperature sensitivity of the swimming behavior produced by the intact animal. Thus, although the CPG is capable of producing a wide range of cycle periods under the influence of temperature, the membrane potentials and spiking activity of the identified CPG neurons do not determine the periodicity of the motor pattern. This suggests that the timing of activity in this network oscillator may be determined by a mechanism that is independent of the membrane potentials and spike rate of its constituent neurons.
Cutaneous Inputs Can Activate the Ipsilateral Primary Motor Cortex During Bimanual Sensory-Driven Movements in Humans
Authors: Shibuya Satoshi , Ohki Yukari
Published: May 2004

Using transcranial magnetic stimulation (TMS), we examined whether sensory input from a finger affects activity of the ipsilateral primary motor cortex (M1) when human subjects hold a virtual object bimanually and whether this ipsilateral activation varies under different contexts. Subjects used both index fingers to hold two plates, which were subjected to unpredictable pulling loads from torque motors. Loads were delivered in a random sequence to either plate or concurrently to both, although the latter occurred most frequently. Finger forces vertical to the plates and surface electromyographs from the first dorsal interosseous muscles were recorded bilaterally during the task. TMS was sometimes applied over the finger area of the left M1 at variable times relative to load onset to examine cortical excitability. Strength of TMS was set around the active motor threshold of the right finger muscle while subjects waited for loading to the handheld plates. When one plate was singly loaded, the M1 contralateral to the loaded finger was activated, causing automatic force increases in the finger. In addition, the ipsilateral M1 was activated during such loading, associated with transient force increases in the contralateral nonloaded finger. Activations in the ipsilateral M1 were also observed during concurrent loading, when activations were stronger than those following single loading of the contralateral plate. Ipsilateral activations weakened when concurrent loading was less frequent. These results suggest interactions between bilateral sensorimotor cortices during bimanual coordinated movements, with strength varying by context.
Discharge Rate of Substantia Nigra Pars Reticulata Neurons Is Reduced In Non-Parkinsonian Monkeys With Apomorphine-Induced Orofacial Dyskinesia
Authors: Nevet Alon , Morris Genela , Saban Guy , Fainstein Nina , Bergman Hagai
Published: May 2004

Involuntary movements (dyskinesia) are a common symptom of dopamine-replacement therapy in parkinsonian patients, neuroleptic drug treatment of mental patients, and tic disorders. Levodopa-induced dyskinesia has been shown to be associated with substantial reduction of firing rate in the internal part of the globus pallidus. This study characterizes the changes that occur in the activity of the substantia nigra pars reticulata (SNr) of non-parkinsonian (normal) monkeys with apomorphine (APO)-induced orofacial dyskinesia. We conducted extracellular recordings of SNr neurons of two monkeys before and after induction of orofacial dyskinesia by systemic administration of APO. Involuntary orofacial movements appeared a few minutes after the injections and lasted 20–40 min. Almost all recorded neurons changed their firing rate after APO injection (96%), and most declined (70%). The mean amplitude of decreases was also larger than that of increases (40 vs. 21% of the control rate). Changes in firing pattern were not significant on average. Pairs of SNr neurons were uncorrelated before APO injection, similar to the normal pallidum. However, unlike the increased correlations in the pallidum that accompany parkinsonism, orofacilal dyskinesia in non-parkinsonian monkeys was not associated with changes in correlation between SNr neurons. We conclude that normal monkeys treated with APO can model orofacial dyskinesia and tic disorders that are a consequence of dopaminergic over-activity. These symptoms appear to be more related to reduced firing rate of SNr neurons and thus to disinhibition of their targets, than to changes in pattern and synchronization.
Biphasic Response to Nitric Oxide of Spinal Trigeminal Neurons With Meningeal Input in Rat–Possible Implications for the Pathophysiology of Headaches
Authors: Koulchitsky Stansilav , Fischer Michael J.M. , De Col Roberto , Schlechtweg Philipp M. , Messlinger Karl
Published: May 2004

Nitric oxide (NO) is suggested to play a causative role in the pathogenesis of primary headaches. Infusion of NO donors can trigger headache attacks, and products of NO metabolism are found to be increased in the cranial circulation in patients suffering from such headaches. To examine if NO is involved in mediating and maintaining spinal trigeminal neuronal activity, an animal model of meningeal nociception was used. In barbiturate-anesthetized rats, a cranial window was made to expose the parietal dura mater. An access to the medullary brain stem allowed extracellular action potentials to be recorded from neurons in the spinal trigeminal nucleus that received afferent input from the exposed dura. Slow intravenous infusion of the NO donor, sodium nitroprusside (SNP, 50 μg/kg), transiently increased spontaneous activity in a subset of neurons and, with a latency of 50 min, caused a progressive increase in impulse activity across the entire sample of neurons. A similar pattern of delayed activation was seen after topical application of the same dose of SNP onto the exposed medulla. Slow injection of the nonspecific inhibitor of NO synthase, Nω-nitro-l-arginine methyl ester (20 mg/kg), reduced the spontaneous activity in all neurons within 15 min. The results suggest that NO can induce delayed, slowly developing activation of central trigeminal neurons and that endogenous release of NO may contribute to the ongoing activity of these neurons. The delayed changes in neuronal activity may include gene expression of pro-nociceptive mediators. These mechanisms may be relevant for the pathogenesis of chronic headaches.
Dynamics and Reproducibility of a Moderately Complex Sensory-Motor Response in the Medicinal Leech
Authors: Garcia-Perez Elizabeth , Zoccolan Davide , Pinato Giulietta , Torre Vincent
Published: May 2004

Local bending, a motor response caused by mechanical stimulation of the leech skin, has been shown to be remarkably reproducible, in its initial phase, despite the highly variable firing of motoneurons sustaining it. In this work, the reproducibility of local bending was further analyzed by monitoring it over a longer period of time and by using more intact preparations, in which muscle activation in an entire body segment was studied. Our experiments showed that local bending is a moderately complex motor response, composed of a sequence of four different phases, which were consistently identified in all leeches. During each phase, longitudinal and circular muscles in specific areas of the body segment acted synergistically, being co-activated or co-inhibited depending on their position relative to the stimulation site. Onset and duration of the first phase were reproducible across different trials and different animals as a result of the massive co-activation of excitatory motoneurons sustaining it. The other phases were produced by the inhibition of excitatory and activation of inhibitory motoneurons, and also by the intrinsic relaxation dynamics of leech muscles. As a consequence, their duration and relative timing was variable across different preparations, whereas their order of appearance was conserved. These results suggest that, during local bending, the leech neuromuscular system 1) operates a reduction of its available degrees of freedom, by simultaneously recruiting groups of otherwise antagonistic muscles and large populations of motoneurons; and 2) ensures reliability and effectiveness of this escape reflex, by guaranteeing the reproducibility of its crucial initial phase.
Role of Tissue Factor in Hemostasis, Thrombosis, and Vascular Development
Authors: Mackman Nigel
Published: May 2004

Tissue factor (TF) is best known as the primary cellular initiator of blood coagulation. After vessel injury, the TF:FVIIa complex activates the coagulation protease cascade, which leads to fibrin deposition and activation of platelets. TF deficiency causes embryonic lethality in the mouse and there have been no reports of TF deficiency in humans. These results indicate that TF is essential for life, most likely because of its central role in hemostasis. In addition, aberrant TF expression within the vasculature initiates life-threatening thrombosis in various diseases, such as sepsis, atherosclerosis, and cancer. Finally, recent studies have revealed a nonhemostatic role of TF in the generation of coagulation proteases and subsequent activation of protease activated receptors (PARs) on vascular cells. This TF-dependent signaling contributes to a variety of biological processes, including inflammation, angiogenesis, metastasis, and cell migration. This review focuses on the roles of TF in hemostasis, thrombosis, and vascular development.
Susceptibility to Early Atherosclerosis in Male Mice Is Mediated by Estrogen Receptor α
Authors: Villablanca Amparo , Lubahn Dennis , Shelby Lauren , Lloyd Kent , Barthold Stephen
Published: May 2004

Objective—

Vascular tissues express 2 types of estrogen receptors (ERs): ERα and ERβ. Their role in early atherosclerosis remains poorly understood, particularly in males. We developed and characterized an atherosclerosis model in ERα knockout male mice to investigate directly its role in atheroma.

Methods and Results—

Cholesterol-fed ERα knockout and wild-type mice developed early atheroma characterized by fatty streaks and foam cells. ERα wild-type mice developed 3.8-fold greater lesion area, more advanced lesions, more extensive lesion distribution, twice the number of lesions, and at a 2.2-fold faster rate than ERα knockout mice. Lesion development and atheroma susceptibility in ERα wild-type and knockout mice were independent of serum cholesterol, triglycerides, high-density lipoproteins, 17β-estradiol, and testosterone levels. In contrast, castration eliminated the predilection of ERα wild-type mice for atheroma, suggesting that testosterone mediates ERα-dependent atheroma formation in males.

Conclusions—

This study is the first to report that the ERα mediates susceptibility to early atherosclerosis in male mice by a testosterone-dependent pathway, suggesting that local production of estrogen from testosterone in the vessel wall may promote atheroma formation in ERα males. Our findings may have implications for selective targeting of ERα in atherosclerotic disease.
Delayed Enhancement and T2-Weighted Cardiovascular Magnetic Resonance Imaging Differentiate Acute From Chronic Myocardial Infarction
Authors: Abdel-Aty Hassan , Zagrosek Anja , Schulz-Menger Jeanette , Taylor Andrew J. , Messroghli Daniel , Kumar Andreas , Gross Michael , Dietz Rainer , Friedrich Matthias G.
Published: May 2004

Background—

Delayed enhancement (DE) cardiovascular magnetic resonance (CMR) detects acute and chronic myocardial infarction (MI) by visualizing contrast media accumulation in infarcted segments. T2-weighted CMR depicts infarct-related myocardial edema as a marker of acute but not chronic myocardial injury. We investigated the clinical utility of an approach combining both techniques to differentiate acute from chronic MI.

Methods and Results—

Seventy-three MI patients were studied in 2 groups. Group A consisted of 15 acute MI patients who were studied twice, on day 1 and 3 months after MI. In group B, 58 patients with acute or chronic MI underwent 1 CMR scan. T2-weighted and DE images of matched slices were acquired on a 1.5-T system. In group A, quantitative segmental and region of interest-based analyses were performed to observe signal changes between the acute and chronic phases. In group B, T2-weighted and DE images were examined visually by 2 blinded observers for the presence or absence of hyperintense areas in corresponding segments. For infarct localization, coronary angiography and/or ECG changes served as the reference standard. In group A, the contrast-to-noise ratio on T2-weighted images dropped in the infarcted segments from 2.7±1.1 on day 1 to 0.1±1.2 after 3 months (
P
<0.0001). There was no significant change in contrast-to-noise ratio in DE images (1.9±1.5 versus 1.3±1.0;
P
=NS). The qualitative assessment of T2-weighted and DE images in group B yielded a specificity of 96% to differentiate acute from chronic lesions.

Conclusions—

An imaging approach combining DE and T2-weighted CMR accurately differentiates acute from chronic MI.
Aldosterone Administration to Mice Stimulates Macrophage NADPH Oxidase and Increases Atherosclerosis Development
Authors: Keidar Shlomo , Kaplan Marielle , Pavlotzky Elsa , Coleman Raymond , Hayek Tony , Hamoud Shadi , Aviram Michael
Published: May 2004

Background—

The renin-angiotensin-aldosterone system is involved in the pathogenesis of atherosclerosis, partially because of its pro-oxidative properties. We questioned the effect and mechanisms of action of administration of aldosterone to apolipoprotein E–deficient (E
0
) mice on their macrophages and aorta oxidative status and the ability of pharmacological agents to block this effect.

Methods and Results—

Aldosterone (0.2 to 6 μg · mouse
−1
· d
−1
) was administered to E
0
mice alone or in combination with eplerenone (200 mg · kg
−1
· d
−1
), ramipril (5 mg · kg
−1
· d
−1
), or losartan (25 mg · kg
−1
· d
−1
). Mouse aortic atherosclerotic lesion area and macrophage and aortic oxidative status were evaluated. Aldosterone administration enhanced the mouse atherosclerotic lesion area by 32%. Mouse peritoneal macrophages and aortic segments from aldosterone-treated mice exhibited increased superoxide anion formation by up to 155% and 69%, respectively, and this effect was probably mediated by NADPH oxidase activation, because increased translocation of its cytosolic component p47
phox
to the macrophage plasma membrane was observed. THP-1 macrophages incubated in vitro with aldosterone (10 μmol/L) exhibited a higher capacity to release superoxide ions by 110% and increased ability to oxidize LDL by 74% compared with control cells. Aldosterone administration enhanced mouse peritoneal macrophage ACE activity and mRNA expression by 2.3-fold and 2.4-fold, respectively. Only cotreatment of eplerenone with ramipril or losartan completely blocked the oxidative effects of aldosterone.

Conclusions—

Aldosterone administration to E
0
mice increased macrophage oxidative stress and atherosclerotic lesion development. Blocking of the mineralocorticoid receptor and inhibition of tissue ACE and/or the angiotensin receptor-1 reduced aldosterone deleterious pro-oxidative and proatherogenic effects.
Scintigraphic Imaging of Matrix Metalloproteinase Activity in the Arterial Wall In Vivo
Authors: Schäfers Michael , Riemann Burkhard , Kopka Klaus , Breyholz Hans-Jörg , Wagner Stefan , Schäfers Klaus P. , Law Marilyn P. , Schober Otmar , Levkau Bodo
Published: May 2004

Background—

Matrix metalloproteinases (MMPs) are enzymes involved in the proteolytic degradation of extracellular matrix. They play an important role in several disease processes, such as inflammation, cancer, and atherosclerosis.

Methods and Results—

In this study, we have used the broad-spectrum MMP inhibitor CGS 27023A to develop the radioligand [
123
I]I-HO-CGS 27023A for in vivo imaging of MMP activity. Using this radioligand, we were able to specifically image MMP activity by scintigraphy in vivo in the MMP-rich vascular lesions that develop after carotid artery ligation and cholesterol-rich diet in apolipoprotein E-deficient mice. These results were confirmed by gamma counting of lesional tissue (counts per minute per milligram).

Conclusions—

Imaging of MMP activity in vivo is feasible using radiolabeled MMP inhibitors. Additional studies are needed to test the potential of this approach as a novel noninvasive clinical diagnostic tool for the management of human MMP-related diseases.