bluuebunny/crossref_metadata_2025 huggingface dataset:
Examination of High-Loaded Nickel Catalysts by IR Spectroscopy: Effect of the Support and Pd on Surface Properties
Authors: Jirátová Květa , Morávková Lenka , Šnajdaufová Hana , Paukshtis Evgenii A.
Published: June 2004

Activation of the ammonia molecule and subsequent adsorption of the NH2 fragment on the surface of the NiO + Pd/TiO2 catalysts, in contrast to NiO + Pd/SiO2 catalysts, was demonstrated by IR spectroscopy. The decrease in the NiO + Pd/TiO2 catalyst acidity was manifested in the higher catalyst stability in reductive amination of diethylene glycol to morpholine.
Pollenvegetation relationships in Bay of Fundy salt marshes
Authors: Beecher C Beth , Chmura Gail L
Published: June 2004

We examined the distribution of vegetation and pollen in surface soils of three salt marshes on the outer Bay of Fundy to assess the value of pollen in paleoenvironmental reconstructions. We examined the relationship of pollen to vegetation using linear regression at two scales: vegetation zones dominated by graminoids and forb patches within these zones. Of the dominant graminoids, only pollen of Cyperaceae was a dependable indicator of source vegetation. In contrast, at least seven common forbs were significantly represented by their pollen at one or both scales. Because forbs are more abundant in northern marshes, increases in forb pollen abundance in buried sediments of southern marshes could signal colder climate regimes. Other studies have shown Plantago maritima L. and Ligusticum scoti cum L. to be associated with distinct ranges in elevation, and Triglochin maritima L. with soil anoxia. Thus, shifts in forb pollen abundance may indicate changes in tidal flooding frequency and sea levels.Key words: Potentilla anserina, Glaux maritima, Spergularia canadensis, wetland, palynology.
EFFECT OF Co–Ga PAIRED SUBSTITUTION ON SUPERCONDUCTIVITY IN YBa2Cu3O7-δ
Authors: DOGRA ANJANA , RAYAPROL S. , SHAH N. A. , KUBERKAR D. G.
Published: June 2004

The effect of Co–Ga paired substitution on the superconducting properties of YBa 2 Cu 3 O 7-δ (Y-123) has been investigated by X-ray diffraction, ac susceptibility, dc resistivity and oxygen content measurements. We report in this paper the results of our studies on the paired substitution of a magnetic and non-magnetic ion at Cu site in Y-123, while keeping the total dopant concentration fixed. The simultaneous substitution of Co and Ga at Cu site shows variation in the transition temperature (T c ), oxygen content and hole concentration as a function of change in the balance of magnetic (Co) and non-magnetic (Ga) concentration. Orthorhombicity (D), given as (b-a)/a, also varies as a function of increasing dopant concentration. The variation in T c due to Co–Ga substitution is discussed in the light of dopant valency and hole filling mechanism.
ORTHO AND PARA STATES OF INTERSTITIAL H2 IN SILICON AND GALLIUM ARSENIDE
Authors: LAVROV E. V.
Published: June 2004

A survey of recent Raman scattering studies on the interstitial hydrogen molecule ( H 2) in Si and GaAs is presented. It is shown that properties of H 2 strongly depend on the nuclear spin state I. In either material, para- H 2 (I=0) is unstable against irradiation with band gap light. In the case of Si, para- H 2 also preferentially disappears from the Raman spectra in the course of storage at room temperature in the dark. Possible explanations for this surprising behavior are discussed and compared with the latest infrared absorption studies.
DETERMINING WHETHER ${\mathsf V}({\bf A})$ HAS A MODEL COMPANION IS UNDECIDABLE
Authors: WILLARD ROSS
Published: June 2004

Using techniques pioneered by R. McKenzie, we prove that there is no algorithm which, given a finite algebra in a finite language, determines whether the variety (equational class) generated by the algebra has a model companion. In particular, there exists a finite algebra such that the variety it generates has no model companion; this answers a question of Burris and Werner from 1979.
Microarray analyses identify JAK2 tyrosine kinase as a key mediator of ligand-independent gene expression
Authors: Wallace Tiffany A. , VonDerLinden Dannielle , He Kai , Frank Stuart J. , Sayeski Peter P.
Published: June 2004

Mice lacking a functional Janus kinase 2 (JAK2) allele die embryonically, indicating the mandatory role of JAK2 in basic developmental cellular transcription. Currently, however, the downstream target genes of JAK2 are largely unknown. Here, in vitro conditions were created using a cell line lacking JAK2 expression. Microarray analysis was then used to identify genes that are differentially expressed as a result of the presence, or absence, of JAK2. The data identified 621 JAK2-dependent genes as having at least a twofold change in expression. Surprisingly, these genes did not require ligand-dependent activation of JAK2 but merely its expression in the cell. Thirty-one of these genes were found to have a greater than sevenfold change in expression levels, and a subset of these were further characterized. These genes represent a diverse cluster of ontological functions including transcription factors, signaling molecules, and cell surface receptors. The expression levels of these genes were validated by Northern blot and/or quantitative RT-PCR analysis in both the JAK2 null cells and cells expressing a JAK2-dominant negative allele. As such, this work demonstrates for the first time that, in addition to being a key mediator of ligand-activated gene transcription, JAK2 can perhaps also be viewed as a critical mediator of basal level gene expression.
cAMP-activated maxi-Cl− channels in native bovine pigmented ciliary epithelial cells
Authors: Do Chi-Wai , Peterson-Yantorno Kim , Mitchell Claire H. , Civan Mortimer M.
Published: June 2004

The eye’s aqueous humor is secreted by a bilayered ciliary epithelium comprising pigmented (PE) and nonpigmented (NPE) epithelial cell layers. Stromal Cl− enters the PE cells and crosses gap junctions to the NPE cells for release into the aqueous humor. Maxi-Cl− channels are expressed in PE cells, but their physiological significance is unclear. To address this question, excised patches and whole native bovine PE cells were patch clamped, and volume was monitored by calcein fluorescence. In symmetrical 130 mM NaCl, cAMP at the cytoplasmic surface of inside-out patches produced concentration-dependent activation of maxi-Cl− channels with a unitary conductance of 272 ± 2 pS ( n = 80). Voltage steps from 0 to ±80 mV, but not to ±40 mV, produced rapid channel inactivation consistent with the typical characteristics of maxi-Cl− channels. cAMP also activated the maxi-Cl− channels in outside-out patches. In both cases, maxi-Cl− channels were reversibly inhibited by SITS and 5-nitro-2-(phenylpropylamino)benzoate (NPPB). Decreasing cytoplasmic Cl− concentration reduced both open-channel probability and unitary conductance. Similarly, the membrane-permeant 8-bromo-cAMP stimulated outward and inward whole cell currents; the stimulation was larger at higher intracellular Cl− concentration. As with unitary currents, cAMP-triggered whole cell currents displayed inactivation at ±80 but not at ±40 mV. Moreover, cAMP triggered NPPB-sensitive shrinkage of PE cells. The results suggest that cAMP directly activates maxi-Cl− channels of native PE cells that contribute to Cl− release particularly from Cl−-loaded cells. These cAMP-activated channels provide a potential mechanism for reducing and modulating net aqueous humor secretion by facilitating Cl− reabsorption into the ciliary stroma.
Molecular analysis of fiber type-specific expression of murine myostatin promoter
Authors: Salerno Mônica Senna , Thomas Mark , Forbes Davanea , Watson Trevor , Kambadur Ravi , Sharma Mridula
Published: June 2004

Myostatin is a negative regulator of muscle growth, and absence of the functional myostatin protein leads to the heavy muscle phenotype in both mouse and cattle. Although the role of myostatin in controlling muscle mass is established, little is known of the mechanisms regulating the expression of the myostatin gene. In this study, we have characterized the murine myostatin promoter in vivo. Various constructs of the murine myostatin promoter were injected into the quadriceps muscle of mice, and the reporter luciferase activity was analyzed. The results indicate that of the seven E-boxes present in the 2.5-kb fragment of the murine myostatin promoter, the E5 E-box plays an important role in the regulation of promoter activity in vivo. Furthermore, the in vitro studies demonstrated that MyoD preferentially binds and upregulates the murine myostatin promoter activity. We also analyzed the activity of the bovine and murine promoters in murine skeletal muscle and showed that, despite displaying comparable levels of activity in murine myoblast cultures, bovine myostatin promoter activity is much weaker than murine myostatin promoter in mice. Finally, we demonstrate that in vivo, the 2.5-kb region of the murine myostatin promoter is sufficient to drive the activity of the reporter gene in a fiber type-specific manner.
Gene delivery of l-caldesmon protects cytoskeletal cell membrane integrity against adenovirus infection independently of myosin ATPase and actin assembly
Authors: Haxhinasto Kari , Kamath Anant , Blackwell Ken , Bodmer James , Van Heukelom Jon , English Anthony , Bai Er-Wei , Moy Alan B.
Published: June 2004

The cytoskeleton is critical to the viral life cycle. Agents like cytochalasin inhibit viral infections but cannot be used for antiviral therapy because of their toxicity. We report the efficacy, safety, and mechanisms by which gene delivery of human wild-type low-molecular-weight caldesmon (l-CaD) protects cell membrane integrity from adenovirus infection in a DF-1 cell line, an immortalized avian fibroblast that is null for l-CaD. Transfection with an adenovirus (Ad)-controlled construct mediated a dose-dependent decline in transcellular resistance. In accordance with a computational model of cytoskeletal membrane properties, Ad disturbed cell-cell and cell-matrix adhesion and membrane capacitance. Transfection with the Ad-l-CaD construct attenuated adenovirus-mediated loss in transcellular resistance. Quantitation of vinculin-stained plaques revealed an increase in total focal contact mass in monolayers transfected with the Ad-l-CaD construct. Expression of l-CaD protected transcellular resistance through primary effects on membrane capacitance and independently of actin solubility and effects on prestress, as measured by the decline in isometric tension in response to cytochalasin D. Expression of l-CaD exhibited less Trypan blue cell toxicity than cytochalasin, and, unlike cytochalasin, it did not interfere with wound closure or adversely effect transcellular resistance. These findings demonstrate the gene delivery of wild-type human l-CaD as a potentially efficacious and safe agent that inhibits some of the cytopathic effects of adenovirus.
A P2X7 receptor stimulates plasma membrane trafficking in the FRTL rat thyrocyte cell line
Authors: Kochukov M. Y. , Ritchie A. K.
Published: June 2004

Thyroid cells express a variety of P2Y and P2X purinergic receptor subtypes. G protein-coupled P2Y receptors influence a wide variety of thyrocyte-specific functions; however, functional P2X receptor-gated channels have not been observed. In this study, we used whole cell patch-clamp recording and fluorescence imaging of the plasma membrane marker FM1-43 to examine the effects of extracellular ATP on membrane permeability and trafficking in the Fisher rat thyroid cell line FRTL. We found a cation-selective current that was gated by ATP and 2′,3′- O-(4-benzoylbenzoyl)-ATP but not by UTP. The ATP-evoked currents were inhibited by pyridoxal phosphate 6-azophenyl-2′,4′-disulfonic acid, adenosine 5′-triphosphate-2′,3′-dialdehyde, 100 μM Zn2+, and 50 μM Cu2+. Fluorescence imaging revealed pronounced, temperature-sensitive stimulation of exocytosis and membrane internalization by ATP with the same pharmacological profile as observed for activation of current. The EC50 for ATP stimulation of internalization was 440 μM in saline containing 2 mM Ca2+ and 2 mM Mg2+, and 33 μM in low-Mg2+, nominally Ca2+-free saline. Overall, the results are most consistent with activation of a P2X7 receptor by ATP4−. However, low permeability to N-methyl-d-glucamine+ and the propidium cation YO-PRO-1 indicates absence of the cytolytic pore that often accompanies P2X7 receptor activation. ATP stimulation of internalization occurs in Na+-free, Ca2+-free, or low-Mg2+ saline and therefore does not depend on cation influx through the ATP-gated channel. We conclude that ATP activation of a P2X7 receptor stimulates membrane internalization in FRTL cells via a transduction pathway that does not depend on cation influx.
Force-induced focal adhesion translocation: effects of force amplitude and frequency
Authors: Mack P. J. , Kaazempur-Mofrad M. R. , Karcher H. , Lee R. T. , Kamm R. D.
Published: June 2004

Vascular endothelial cells rapidly transduce local mechanical forces into biological signals through numerous processes including the activation of focal adhesion sites. To examine the mechanosensing capabilities of these adhesion sites, focal adhesion translocation was monitored over the course of 5 min with GFP-paxillin while applying nN-level magnetic trap shear forces to the cell apex via integrin-linked magnetic beads. A nongraded steady-load threshold for mechanotransduction was established between 0.90 and 1.45 nN. Activation was greatest near the point of forcing (<7.5 μm), indicating that shear forces imposed on the apical cell membrane transmit nonuniformly to the basal cell surface and that focal adhesion sites may function as individual mechanosensors responding to local levels of force. Results from a continuum, viscoelastic finite element model of magnetocytometry that represented experimental focal adhesion attachments provided support for a nonuniform force transmission to basal surface focal adhesion sites. To further understand the role of force transmission on focal adhesion activation and dynamics, sinusoidally varying forces were applied at 0.1, 1.0, 10, and 50 Hz with a 1.45 nN offset and a 2.25 nN maximum. At 10 and 50 Hz, focal adhesion activation did not vary with spatial location, as observed for steady loading, whereas the response was minimized at 1.0 Hz. Furthermore, applying the tyrosine kinase inhibitors genistein and PP2, a specific Src family kinase inhibitor, showed tyrosine kinase signaling has a role in force-induced translocation. These results highlight the mutual importance of force transmission and biochemical signaling in focal adhesion mechanotransduction.
Three-compartment model: critical evaluation based on neutron activation analysis
Authors: Silva Analiza M. , Shen Wei , Wang ZiMian , Aloia John F. , Nelson Miriam E. , Heymsfield Steven B. , Sardinha Luis B. , Heshka Stanley
Published: June 2004

There is renewed interest in Siri's classic three-compartment (3C) body composition model, requiring body volume (BV) and total body water (TBW) estimates, because dual-energy X-ray absorptiometry (DEXA) and in vivo neutron activation (IVNA) systems cannot accommodate subjects with severe obesity. However, the 3C model assumption of a constant ratio (α) of mineral (M) to total body protein (TBPro) and related residual mass density (DRES) based on cadaver analyses might not be valid across groups differing in sex, race, age, and weight. The aim of this study was to derive new 3C model coefficients in vivo and to compare these estimates to those derived by Siri. Healthy adults ( n = 323) were evaluated with IVNA and DEXA and the measured components used to derive α and DRES. For all subjects combined, values of α and DRES(means ± SD, 0.351 ± 0.043; 1.565 ± 0.023 kg/l) were similar to Siri's proposed values of 0.35 and 1.565 kg/l, respectively. However, α and DRESvaried significantly as a function of sex, race, weight, and age. Expected errors in percent body fat arising by application of Siri's model were illustrated in a second group of 264 adults, including some whose size exceeded DEXA limits but whose BV and TBW had been measured by hydrodensitometry and2H2O dilution, respectively. Extrapolation of predictions by newly developed models to very high weights allows percent fat error estimation when Siri's model is applied in morbidly obese subjects. The present study results provide a critical evaluation of potential errors in the classic 3C model and present new formulas for use in selected populations.
Differential effect of sepsis on ability of leucine and IGF-I to stimulate muscle translation initiation
Authors: Lang Charles H. , Frost Robert A.
Published: June 2004

Polymicrobial sepsis impairs skeletal muscle protein synthesis, which results from impairment in translation initiation under basal conditions. The purpose of the present study was to test the hypothesis that sepsis also impairs the anabolic response to amino acids, specifically leucine (Leu). Sepsis was induced by cecal ligation and puncture, and 24 h later, Leu or saline (Sal) was orally administered to septic and time-matched nonseptic rats. The gastrocnemius was removed 20 min later for assessment of protein synthesis and signaling components important in peptide-chain initiation. Oral Leu increased muscle protein synthesis in nonseptic rats. Leu was unable to increase protein synthesis in muscle from septic rats, and synthetic rates remained below those observed in nonseptic + Sal rats. In nonseptic + Leu rats, phosphorylation of eukaryotic initiation factor (eIF)4E-binding protein 1 (4E-BP1) in muscle was markedly increased compared with values from time-matched Sal-treated nonseptic rats. This change was associated with redistribution of eIF4E from the inactive eIF4E·4E-BP1 to the active eIF4E·eIF4G complex. In septic rats, Leu-induced phosphorylation of 4E-BP1 and changes in eIF4E distribution were completely abrogated. Sepsis also antagonized the Leu-induced increase in phosphorylation of S6 kinase 1 and ribosomal protein S6. Sepsis attenuated Leu-induced phosphorylation of mammalian target of rapamycin and eIF4G. The ability of sepsis to inhibit anabolic effects of Leu could not be attributed to differences in plasma concentrations of insulin, insulin-like growth factor I, or Leu between groups. In contrast, the ability of exogenous insulin-like growth factor I to stimulate the same signaling components pertaining to translation initiation was not impaired by sepsis. Hence, sepsis produces a relatively specific Leu resistance in skeletal muscle that impairs the ability of this amino acid to stimulate translation initiation and protein synthesis.
Assessment of biomarkers of protein anabolism in skeletal muscle during the life span of the rat: sarcopenia despite elevated protein synthesis
Authors: Kimball Scot R. , O'Malley James P. , Anthony Joshua C. , Crozier Stephen J. , Jefferson Leonard S.
Published: June 2004

Loss of muscle strength is a principal factor in the development of physical frailty, a condition clinically associated with increased risk of bone fractures, impairments in the activities of daily living, and loss of independence in older humans. A primary determinant in the decline in muscle strength that occurs during aging is a loss of muscle mass, which could occur through a reduction in the rate of protein synthesis, an elevation in protein degradation, or a combination of both. In the present study, rates of protein synthesis and the relative expression and function of various biomarkers involved in the initiation of mRNA translation in skeletal muscle were examined at different times throughout the life span of the rat. It was found that between 1 and 6 mo of age, body weight increased fourfold. However, by 6 mo, gastrocnemius protein synthesis and RNA content per gram of muscle were lower than values observed in 1-mo-old rats. Moreover, the relative expression of two proteins involved in the binding of initiator methionyl-tRNA to the 40S ribosomal subunit, eukaryotic initiation factors (eIF)2 and eIF2B, as well as the 70-kDa ribosomal protein S6 kinase, S6K1, was lower at 6 mo compared with 1 mo of age. Muscle mass, protein synthesis, and the aforementioned biomarkers remained unchanged until ∼21 mo. Between 21 and 24 mo of age, muscle mass decreased precipitously. Surprisingly, during this period protein synthesis, relative RNA content, eIF2B activity, relative eIF2 expression, and S6K1 phosphorylation all increased. The results are consistent with a model wherein protein synthesis is enhanced during aging in a futile attempt to maintain muscle mass.
Rat liver sinusoidal endothelial cell phenotype is maintained by paracrine and autocrine regulation
Authors: DeLeve Laurie D. , Wang Xiangdong , Hu Liping , McCuskey Margaret K. , McCuskey Robert S.
Published: June 2004

The phenotypic features of liver sinusoidal endothelial cells (SEC), open fenestrae in sieve plates and lack of a basement membrane, are lost with capillarization. The current study examines localization of CD31 as a marker for the dedifferentiated, nonfenestrated SEC and examines regulation of SEC phenotype in vitro. CD31 localization in SEC was examined by confocal microscopy and immunogold-scanning electron microscopy. SEC cultured for 1 day express CD31 in the cytoplasm, whereas after 3 days, CD31 is also expressed on cell-cell junctions. Immunogold-scanning electron microscopy confirmed the absence of CD31 surface expression on fenestrated SEC 1 day after isolation and demonstrated the appearance of CD31 surface expression on SEC that had lost fenestration after 3 days in culture. SEC isolated from fibrotic liver do show increased expression of CD31 on the cell surface. Coculture with either hepatocytes or stellate cells prevents CD31 surface expression, and this effect does not require heterotypic contact. The paracrine effect of hepatocytes or stellate cells on SEC phenotype is abolished with anti-VEGF antibody and is reproduced by addition of VEGF to SEC cultured alone. VEGF stimulates SEC production of nitric oxide. NG-nitro-l-arginine methyl ester blocked the paracrine effect of hepatocytes or stellate cells on SEC phenotype and blocked the ability of VEGF to preserve the phenotype of SEC cultured alone. In conclusion, surface expression of CD31 is a marker of a dedifferentiated, nonfenestrated SEC. The VEGF-mediated paracrine effect of hepatocytes or stellate cells on maintenance of SEC phenotype requires autocrine production of nitric oxide by SEC.
Epithelial cell spreading induced by hepatocyte growth factor influences paxillin protein synthesis and posttranslational modification
Authors: Hopkins Ann M. , Bruewer Matthias , Brown G. Thomas , Pineda A’Drian A. , Ha Julie J. , Winfree L. Matthew , Walsh Shaun V. , Babbin Brian A. , Nusrat Asma
Published: June 2004

Superficial wounds in the gastrointestinal tract rapidly reseal by coordinated epithelial cell migration facilitated by cytokines such as hepatocyte growth factor (HGF)/scatter factor released in the wound vicinity. However, the mechanisms by which HGF promotes physiological and pathophysiologic epithelial migration are incompletely understood. Using in vitro models of polarized T84 and Caco-2 intestinal epithelia, we report that HGF promoted epithelial spreading and RhoA GTPase activation in a time-dependent manner. Inducible expression of enhanced green fluorescent protein-tagged dominant-negative RhoA significantly attenuated HGF-induced spreading. HGF expanded a zone of partially flattened cells behind the wound edge containing basal F-actin fibers aligned in the direction of spreading. Concomitantly, plaques positive for the focal adhesion protein paxillin were enhanced. HGF induced an increase in the translation of paxillin and, to a lesser extent, β1-integrin. This was independent of cell-matrix adhesion through β1-integrin. Subcellular fractionation revealed increased cosedimentation of paxillin with plasma membrane-containing fractions following HGF stimulation, without corresponding enhancements in paxillin coassociation with β1integrin or actin. Tyrosine phosphorylation of paxillin was reduced by HGF and was sensitive to the Src kinase inhibitor PP2. With these taken together, we propose that HGF upregulates a free cytosolic pool of paxillin that is unaffiliated with either the cytoskeleton or focal cell-matrix contacts. Thus early spreading responses to HGF may partly relate to increased paxillin availability for incorporation into, and turnover within, dynamic cytoskeletal/membrane complexes whose rapid and transient adhesion to the matrix drives migration.
Stimulation of small intestinal burst activity in the postprandial state differentially affects lipid and glucose absorption in healthy adult humans
Authors: Bryant L. K. , Fraser R. J. , Vozzo R. , Zacharakis B. , Matthews G. M. , Butler R.
Published: June 2004

Small intestinal motor activity is important for the optimal digestion and absorption of nutrients. These motor responses to feeding are frequently abnormal during critical illness, with the persistence of migrating bursts of contractions during enteral feeding. Whether this disturbance influences nutrient absorption is not known. In this study, the effects of small intestinal burst activity on lipid and glucose absorption were evaluated in 10 healthy human adults (6 males, 4 females, 19–47 yr). Upper gastrointestinal manometry was recorded for 6 h during and shortly after a 20-min intravenous infusion of either erythromycin (1 mg/kg), to stimulate burst activity, or saline (0.9%) in a double-blind randomized fashion. Simultaneously with the start of the intravenous infusion, 60 ml liquid feed mixed with 200 μl 13C-triolein and 2 g 3- O-methylglucose (3-OMG) was infused intraduodenally for 30 min. Absorption of lipid and glucose was assessed using the [13C]triolein breath test and plasma concentrations of 3-OMG, respectively. Infusion of erythromycin was followed by a more rapid onset of burst activity following commencement of the duodenal infusion compared with saline (30 ± 6.1 vs. 58 ± 10.7 min; P < 0.05). Erythromycin was associated with a slower recovery of 13CO2 ( P < 0.01). A positive correlation existed between the time to onset of burst activity and 13CO2 recovery ( P < 0.001). Erythromycin had no effect on 3-OMG absorption. In conclusion, stimulation of small intestinal burst activity reduces the rate of lipid absorption but not glucose absorption in healthy human adults.
Vasoconstriction in exercising skeletal muscles: a potential role for neuropeptide Y?
Authors: Buckwalter John B. , Hamann Jason J. , Kluess Heidi A. , Clifford Philip S.
Published: June 2004

There is evidence that neuropeptide Y (NPY) acts as a neurotransmitter in vascular smooth muscle and is released with norepinephrine from sympathetic nerves. We hypothesized that NPY Y1receptor stimulation would produce vasoconstriction in resting and exercising skeletal muscle. Nine mongrel dogs were instrumented chronically with flow probes on the external iliac arteries of both hindlimbs and a catheter in one femoral artery. The selective NPY Y1receptor agonist [Leu31,Pro34]NPY was infused as a bolus into the femoral artery catheter at rest and during mild, moderate, and heavy exercise. Intra-arterial infusions of [Leu31,Pro34]NPY elicited reductions ( P < 0.05) in vascular conductance of 38 ± 3, 25 ± 2, 17 ± 1, and 11 ± 1% at rest, 3 miles/h, 6 miles/h, and 6 miles/h and 10% grade, respectively. The agonist infusions did not affect ( P > 0.05) blood flow in the contralateral iliac artery. To examine whether nitric oxide (NO) is responsible for the attenuated vasoconstrictor response during exercise to NPY Y1receptor stimulation, the infusions were repeated after NO synthase blockade. These infusions yielded reductions ( P < 0.05) in vascular conductance of 47 ± 3, 23 ± 2, 19 ± 3, and 12 ± 2% at rest, 3 miles/h, 6 miles/h, and 6 miles/h and 10% grade, respectively. NPY Y1receptor responsiveness was attenuated ( P < 0.05) during exercise compared with rest. Blockade of NO production did not affect ( P > 0.05) the attenuation of NPY Y1receptor responsiveness during exercise. These data support the hypothesis that NPY Y1receptors can produce vasoconstriction in exercising skeletal muscle.
Moderate severity heart failure does not involve a downregulation of myocardial fatty acid oxidation
Authors: Chandler Margaret P. , Kerner Janos , Huang Hazel , Vazquez Edwin , Reszko Aneta , Martini Wenjun Z. , Hoppel Charles L. , Imai Makoto , Rastogi Sharad , Sabbah Hani N. , Stanley William C.
Published: June 2004

Recent human and animal studies have demonstrated that in severe end-stage heart failure (HF), the cardiac muscle switches to a more fetal metabolic phenotype, characterized by downregulation of free fatty acid (FFA) oxidation and an enhancement of glucose oxidation. The goal of this study was to examine myocardial substrate metabolism in a model of moderate coronary microembolization-induced HF. We hypothesized that during well-compensated HF, FFA oxidation would predominate as opposed to a more fetal metabolic phenotype of greater glucose oxidation. Cardiac substrate uptake and oxidation were measured in normal dogs ( n = 8) and in dogs with microembolization-induced HF ( n = 18, ejection fraction = 28%) by infusing three isotopic tracers ([9,10-3H]oleate, [U-14C]glucose, and [1-13C]lactate) in anesthetized open-chest animals. There were no differences in myocardial substrate metabolism between the two groups. The total activity of pyruvate dehydrogenase, the key enzyme regulating myocardial pyruvate oxidation (and hence glucose and lactate oxidation) was not affected by HF. We did not observe any difference in the activity of carnitine palmitoyl transferase I (CPT-I) and its sensitivity to inhibition by malonyl-CoA between groups; however, malonyl-CoA content was decreased by 22% with HF, suggesting less in vivo inhibition of CPT-I activity. The differences in malonyl-CoA content cannot be explained by changes in the Michaelis-Menten constant and maximal velocity for malonyl-CoA decarboxylase because neither were affected by HF. These results support the concept that there is no decrease in fatty acid oxidation during compensated HF and that the downregulation of fatty acid oxidation enzymes and the switch to carbohydrate oxidation observed in end-stage HF is only a late-stage phenomemon.
Upregulation of corin gene expression in hypertrophic cardiomyocytes and failing myocardium
Authors: Tran Katherine L. , Lu Xiangru , Lei Ming , Feng Qingping , Wu Qingyu
Published: June 2004

High levels of plasma atrial natriuretic peptides (ANP) are associated with pathological conditions such as congestive heart failure (CHF). Recently, we have identified a cardiac serine protease, corin, that is the pro-ANP convertase. In this study, we examined the regulation of corin gene expression in cultured hypertrophic cardiomyocytes and in the left ventricular (LV) myocardium of a rat model of heart failure. Quantitative RT-PCR analysis showed that both corin and ANP mRNA levels were significantly increased in phenylephrine (PE)-stimulated rat neonatal cardiomyocytes in culture. The increase in corin mRNA correlated closely with the increase in cell size and ANP mRNA expression in the PE-treated cells ( r = 0.95, P < 0.01; r = 0.92, P < 0.01, respectively). The PE-treated cardiomyocytes had an increased activity in converting recombinant human pro-ANP to biologically active ANP, as determined by a pro-ANP processing assay and a cell-based cGMP assay. In a rat model of heart failure induced by ligation of the left coronary artery, corin mRNA expression in the noninfarcted LV myocardium was significantly higher than that of control heart tissues from sham-operated animals, when examined by Northern blot analysis and RT-PCR at 8 wk. These results indicate that the corin gene is upregulated in hypertrophic cardiomyocytes and failing myocardium. Increased corin expression may contribute to elevation of ANP in the setting of cardiac hypertrophy and heart failure.
Hydrogen sulfide-induced relaxation of resistance mesenteric artery beds of rats
Authors: Cheng Youqin , Ndisang Joseph Fomusi , Tang Guanghua , Cao Kun , Wang Rui
Published: June 2004

Hydrogen sulfide (H2S) has been shown recently to function as an important gasotransmitter. The present study investigated the vascular effects of H2S, both exogenously applied and endogenously generated, on resistance mesenteric arteries of rats and the underlying mechanisms. Both H2S and NaHS evoked concentration-dependent relaxation of in vitro perfused rat mesenteric artery beds (MAB). The sensitivity of MAB to H2S (EC50, 25.2 ± 3.6 μM) was about fivefold higher than that of rat aortic tissues. Removal of endothelium or coapplication of charybdotoxin and apamin to endothelium-intact MAB significantly reduced the vasorelaxation effects of H2S. The H2S-induced relaxation of MAB was partially mediated by ATP-sensitive K+(KATP) channel activity in vascular smooth muscle cells. Pinacidil (EC50, 1.7 ± 0.1 μM, n = 6) mimicked, but glibenclamide (10 μM, n = 6) suppressed, the vasorelaxant effect of H2S. KATPchannel currents in isolated mesenteric artery smooth muscle cells were significantly augmented by H2S. l-Cysteine, a substrate of cystathionine-γ-lyase (CSE), at 1 mM increased endogenous H2S production by sixfold in rat mesenteric artery tissues and decreased contractility of MAB. dl-Propargylglycine (a blocker of CSE) at 10 μM abolished l-cysteine-dependent increase in H2S production and relaxation of MAB. Our results demonstrated a tissue-specific relaxant response of resistance arteries to H2S. The stimulation of KATPchannels in vascular smooth muscle cells and charybdotoxin/apamin-sensitive K+channels in vascular endothelium by H2S represents important cellular mechanisms for H2S effect on MAB. Our study also demonstrated that endogenous CSE can generate sufficient H2S from exogenous l-cysteine to cause vasodilation. Future studies are merited to investigate direct contribution of endogenous H2S to regulation of vascular tone.
The permissive role of endothelial NO in CO-induced cerebrovascular dilation
Authors: Barkoudah Ebrahim , Jaggar Jonathan H. , Leffler Charles W.
Published: June 2004

Carbon monoxide (CO) and nitric oxide (NO) are important paracrine messengers in the newborn cerebrovasculature that may act as comessengers. Here, we investigated the role of NO in CO-mediated dilations in the newborn cerebrovasculature. Arteriolar branches of the middle cerebral artery (100–200 μm) were isolated from 3- to 7-day-old piglets and cannulated at each end in a superfusion chamber, and intravascular pressure was elevated to 30 mmHg, which resulted in the development of myogenic tone. Endothelium removal abolished dilations of pressurized pial arterioles to bradykinin and to the CO-releasing molecule Mn2(CO)10 [dimanganese decacarbonyl (DMDC)] but not dilations to isoproterenol. With endothelium intact, Nω-nitro-l-arginine (l-NNA), 1 H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), or tetraethylammonium chloride (TEA+), inhibitors of NO synthase (NOS), guanylyl cyclase, and large-conductance Ca2+-activated K+ (KCa) channels, respectively, also blocked dilation induced by DMDC. After inhibition of NOS, a constant concentration of sodium nitroprusside (SNP), a NO donor that only dilated the vessel 6%, returned dilation to DMDC. The stable cGMP analog 8-bromo-cGMP also restored dilation to DMDC in endothelium-intact, l-NNA-treated, or endothelium-denuded arterioles, and this effect was blocked by TEA+. Similarly, in the continued presence of ODQ, 8-bromo-cGMP restored DMDC-induced dilations. These findings suggest that endothelium-derived NO stimulates guanylyl cyclase in vascular smooth muscle cells and, thereby, permits CO to cause dilation by activating KCa channels. Such a requirement for NO could explain the endothelium dependency of CO-induced dilation in piglet pial arterioles.
Prevention of diminished parasympathetic control of the heart in experimental heart failure
Authors: Bibevski Steve , Dunlap Mark E.
Published: June 2004

Decreased synaptic transmission in parasympathetic ganglia contributes to abnormal parasympathetic function in heart failure (HF). Because nicotinic ACh receptors (nAChR) mediate synaptic transmission at the ganglion and upregulate in response to chronic exposure to agonist in vitro, we tested the hypothesis that repeated exposures of ganglionic neurons to a nAChR agonist can prevent a loss of parasympathetic control in HF. Two sets of experiments were performed. In set 1, unpaced control dogs and dogs undergoing pacing-induced HF were treated with a repeated intravenous nicotinic agonist during the development of HF. Under conditions of sympathetic blockade, R-R responses to a bolus injection of 200 μg 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP; nicotinic agonist) were found to be increased five times over the untreated group after 6 wk. In experimental set 2, dogs treated with weekly DMPP injections and in HF were anesthetized and underwent electrical stimulation of the right vagus nerve, which showed sinus cycle length responses >10 times that of controls ( P < 0.05). Complete ganglionic blockade with hexamethonium abolished all responses, confirming that synaptic transmission was mediated entirely by nAChRs in both controls and HF. Despite decreased ganglionic function leading to reduced parasympathetic control of the heart in HF, repeated exposure with a nicotinic agonist during the development of HF results in not only preserved but also supranormal effects of parasympathetic stimulation on the sinus node.
Sphingosine kinase-1 mediates TNF-α-induced MCP-1 gene expression in endothelial cells: upregulation by oscillatory flow
Authors: Chen Xi-Lin , Grey Janice Y. , Thomas Suzanne , Qiu Fei-Hua , Medford Russell M. , Wasserman Martin A. , Kunsch Charles
Published: June 2004

Atherosclerosis is a focal inflammatory disease and preferentially occurs in areas of low fluid shear stress and oscillatory flow, whereas the risk of atherosclerosis is decreased in regions of high fluid shear stress and steady laminar flow. Sphingosine kinase-1 (SphK1) catalyzes the conversion of sphingosine to sphingosine-1 phosphate (S1P), a sphingolipid metabolite that plays important roles in angiogenesis, inflammation, and cell growth. In the present study, we demonstrated that exposure of human aortic endothelial cells to oscillatory flow (shear stress, ±5 dyn/cm2for 48 h) resulted in a marked increase in SphK1 mRNA levels compared with endothelial cells kept in static culture. In contrast, laminar flow (shear stress, 20 dyn/cm2for 48 h) decreased SphK1 mRNA levels. We further investigated the role of SphK1 in TNF-α-induced expression of inflammatory genes, such as monocyte chemoattractant protein-1 (MCP-1) and VCAM-1 by using small interfering RNA (siRNA) specifically for SphK1. Treatment of endothelial cells with SphK1 siRNA suppressed TNF-α-induced increase in MCP-1 mRNA levels, MCP-1 protein secretion, and activation of p38 MAPK. SphK1 siRNA also inhibited TNF-α-induced cell surface expression of VCAM-1, but not ICAM-1, protein. Exposure of endothelial cells to S1P led to an increase in MCP-1 protein secretion and MCP-1 mRNA levels and activation of NF-κB-mediated transcriptional activity. Treatment of endothelial cells with the p38 MAPK inhibitor SB-203580 suppressed S1P-induced MCP-1 protein secretion. These data suggest that SphK1 mediates TNF-α-induced MCP-1 gene expression through a p38 MAPK-dependent pathway and may participate in oscillatory flow-mediated proinflammatory signaling pathway in the vasculature.
Colloidal gold particles as a new in vivo marker of early acute lung injury
Authors: Heckel Kai , Kiefmann Rainer , Dörger Martina , Stoeckelhuber Mechthild , Goetz Alwin E.
Published: June 2004

Permeability of the endothelial barrier to large molecules plays a pivotal role in the manifestation of early acute lung injury. We present a novel and sensitive technique that brings microanatomical visualization and quantification of microvascular permeability in line. White New Zealand rabbits were anesthetized and ventilated mechanically. Rabbit serum albumin (RSA) was labeled with colloidal gold particles. We quantified macromolecular leakage of gold-labeled RSA and thickening of the gas exchange distance by electron microscopy, taking into account morphology of microvessels. The control group receiving a saline solution represented a normal gas exchange barrier without extravasation of gold-labeled albumin. Infusion of lipopolysaccharide (LPS) resulted in a significant displacement of gold-labeled albumin into pulmonary cells, the lung interstitium, and even the alveolar space. Correspondingly, intravital fluorescence microscopy and digital image analysis indicated thickening of width of alveolar septa. The findings were accompanied by a deterioration of alveolo-arterial oxygen difference, whereas wet/dry ratio and albumin concentration in the bronchoalveolar lavage fluid failed to detect that early stage of pulmonary edema. Inhibition of the nuclear enzyme poly(ADP-ribose) synthetase by 3-aminobenzamide prevented LPS-induced microvascular injury. To summarize: colloidal gold particles visualized by standard electron microscopy are a new and very sensitive in vivo marker of microvascular permeability in early acute lung injury. This technique enabling detailed microanatomical and quantitative pathophysiological characterization of edema formation can form the basis for evaluating novel treatment strategies against acute lung injury.
Mucins and their O-Glycans from human bronchial epithelial cell cultures
Authors: Holmén Jessica M. , Karlsson Niclas G. , Abdullah Lubna H. , Randell Scott H. , Sheehan John K. , Hansson Gunnar C. , Davis C. William
Published: June 2004

A longstanding question in obstructive airway disease is whether observed changes in mucin composition and/or posttranslational glycosylation are due to genetic or to environmental factors. We tested whether the mucins secreted by second-passage primary human bronchial epithelial cell cultures derived from noncystic fibrosis (CF) or CF patients have intrinsically different specific mucin compositions, and whether these mucins are glycosylated differently. Both CF and non-CF cultures produced MUC5B, predominantly, as judged by quantitative agarose gel Western blots with mucin-specific antibodies: MUC5B was present at ∼10-fold higher levels than MUC5AC, consistent with our previous mRNA studies (Bernacki SH, Nelson AL, Abdullah L, Sheehan JK, Harris A, William DC, and Randell SH. Am J Respir Cell Mol Biol 20: 595–604, 1999). O-linked oligosaccharides released from purified non-CF and CF mucins and studied by HPLC mass spectrometry had highly variable glycan structures, and there were no observable differences between the two groups. Hence, there were no differences in either the specific mucins or their O-glycans that correlated with the CF phenotype under the noninfected/noninflammatory conditions of cell culture. We conclude that the differences observed in the mucins sampled directly from patients are most likely due to environmental factors relating to infection and/or inflammation.
Do fever and anapyrexia exist? Analysis of set point-based definitions
Authors: Romanovsky Andrej A.
Published: June 2004

Fever and anapyrexia are the most studied thermoregulatory responses. They are defined as a body temperature (Tb) increase and decrease, respectively, occurring because of a shift in the set point (SP) and characterized by active defense of the new Tb. Although models of Tb control with a single SP (whether obvious or hidden) have been criticized, the SP-based definitions have remained unchallenged. In this article, the SP-based definitions of fever and anapyrexia were subjected to two tests. In test 1, they were compared with experimental data on changes in thresholds for activation of different thermoeffectors. Changes in thresholds were found compatible with an SP increase in some (but not all) cases of fever. In all cases of what is called anapyrexia, its mechanism (dissociation of thresholds of different effectors) was found incompatible with a decrease in a single SP. In test 2, experimental data on the dependence of Tb on ambient temperature (Ta) were analyzed. It was found that the febrile level of Tb is defended in some (but not all) cases. However, strong dependence on Ta was found in all cases of anapyrexia, which agrees with threshold dissociation but not with a decrease of the SP. It is concluded that fever (as defined) has only limited experimental support, whereas anapyrexia (as defined) does not exist. Two solutions are offered. A palliative is to accept that SP-based terms (anapyrexia, cryexia, regulated hypothermia, and such) are inadequate and should be abandoned. A radical solution is to transform all definitions based on comparing Tb with the SP into definitions based on balancing active and passive processes of Tb control.
Impact of periconceptional nutrition on maternal and fetal leptin and fetal adiposity in singleton and twin pregnancies
Authors: Edwards L. J. , McFarlane J. R. , Kauter K. G. , McMillen I. C.
Published: June 2004

It has been proposed that maternal nutrient restriction may alter the functional development of the adipocyte and the synthesis and secretion of the adipocyte-derived hormone, leptin, before birth. We have investigated the effects of restricted periconceptional undernutrition and/or restricted gestational nutrition on fetal plasma leptin concentrations and fetal adiposity in late gestation. There was no effect of either restricted periconceptional or gestational nutrition on maternal or fetal plasma leptin concentrations in singleton or twin pregnancies during late gestation. In ewes carrying twins, but not singletons, maternal plasma leptin concentrations in late gestation were directly related to the change in ewe weight that occurred during the 60 days before mating [maternal leptin = 0.9 (change in ewe weight) + 7.8; r = 0.6, P < 0.05]. In twin, but not singleton, pregnancies, there was also a significant relationship between maternal and fetal leptin concentrations (maternal leptin = 0.5 fetal leptin + 4.2, r = 0.63, P < 0.005). The relative mass of perirenal fat was also significantly increased in twin fetal sheep in the control-restricted group (6.0 ± 0.5) compared with the other nutritional groups (control-control: 4.1 ± 0.4; restricted-restricted: 4.4 ± 0.4; restricted-control: 4.3 ± 0.3). In conclusion, the impact of maternal undernutrition on maternal plasma leptin concentrations during late gestation is dependent on fetal number. Furthermore, we have found that there is an increased fetal adiposity in the twins of ewes that experienced restricted nutrition throughout gestation, and this may be important in the programming of postnatal adiposity.