bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered expression and in vivo lung function of protease-activated receptors during influenza A virus infection in mice
Authors: Lan Rommel S. , Stewart Geoffrey A. , Goldie Roy G. , Henry Peter J.
Published: January 2004

Protease-activated receptors (PARs) are widely distributed in human airways, and recent evidence indicates a role for PARs in the pathophysiology of inflammatory airway disease. To further investigate the role of PARs in airway disease, we determined the expression and function of PARs in a murine model of respiratory tract viral infection. PAR-1, PAR-2, PAR-3, and PAR-4 mRNA and protein were expressed in murine airways, and confocal microscopy revealed colocalization of PAR-2 and cyclooxygenase (COX)-2 immunostaining in basal tracheal epithelial cells. Elevated levels of PAR immunostaining, which was particularly striking for PAR-1 and PAR-2, were observed in the airways of influenza A/PR-8/34 virus-infected mice compared with sham-infected mice. Furthermore, increased PAR-1 and PAR-2 expression was associated with significant changes in in vivo lung function responses. PAR-1 agonist peptide potentiated methacholine-induced increases in airway resistance in anesthetized sham-infected mice (and in indomethacin-treated, virus-infected mice), but no such potentiation was observed in virus-infected mice. PAR-2 agonist peptide transiently inhibited methacholine-induced bronchoconstriction in sham-infected mice, and this effect was prolonged in virus-infected mice. These findings suggest that during viral infection, the upregulation of PARs in the airways is coupled to increased activation of COX and enhanced generation of bronchodilatory prostanoids.
Resistance of differentiated human airway epithelium to infection by rhinovirus
Authors: Lopez-Souza N. , Dolganov G. , Dubin R. , Sachs L. A. , Sassina L. , Sporer H. , Yagi S. , Schnurr D. , Boushey H. A. , Widdicombe J. H.
Published: January 2004

Virtually all in vitro studies of the effects of rhinovirus on human airway epithelium have used cells grown under conditions known to produce low levels of differentiation. The relevance of the results to native epithelium is questionable. Here we grew primary cultures of human tracheal or nasal epithelium under three conditions. One condition produced pseudostratified, mucociliary cells virtually indistinguishable from native epithelium. The other two conditions produced undifferentiated squamous cells lacking cilia. Cells were infected for 6 h with rhinovirus-16. After a 24-h incubation period, we determined levels of viral RNA in the cells, numbers of infectious viral particles released in the mucosal medium, expression of a variety of epithelial cytokines and other proteins, release of IL-6 and IL-8, and transepithelial electrical resistance and voltage. After infection, levels of viral RNA in the poorly differentiated cells were 30 or 130 times those in the differentiated. Furthermore, expression of mRNA for inflammatory cytokines, release of infectious particles, and release of IL-6 and IL-8 were closely correlated with the degree of viral infection. Thus well-differentiated cells are much more resistant to viral infection and its functional consequences than are poorly differentiated cells from the same source.
DNA microarray analysis of neonatal mouse lung connects regulation of KDR with dexamethasone-induced inhibition of alveolar formation
Authors: Clerch Linda Biadasz , Baras Alex S. , Massaro Gloria DeCarlo , Hoffman Eric P. , Massaro Donald
Published: January 2004

Treatment of newborn mice with dexamethasone (Dex) inhibits the subdivision of lung saccules to form alveoli; treatment with all- trans retinoic acid (RA) prevents this inhibition of septation. To better understand the early molecular signals responsible for the effects of Dex and RA, Affymetrix gene profiling was done on RNA isolated from 4-day-old mice after treatment with 1) diluent, 2) RA (1 mg/kg), 3) Dex (0.7 μg/pup), or 4) RA + Dex. Each sample was assayed in duplicate on U74Av2 GeneChips. Data were analyzed with Affymetrix suite 5.0, corrected for saturation, and evaluated with GeneSpring 5.1 software. Stringent filtering of data by the global error model and condition-to-condition comparisons was used to identify 46 genes demonstrating significantly different expression between the lungs of Dex- and RA + Dex-treated mice. A query of the gene ontology database revealed that the major biological processes affected by treatment with Dex and RA were cell growth/maintenance and cellular communication. On the basis of microarray data analysis, we hypothesize that Dex-induced inhibition of septation is associated with a block in angiogenesis due to downregulation of the kinase domain receptor (KDR), also known as VEGF receptor-2 and fetal liver kinase, and that the downregulation of KDR is prevented by treatment with RA.
Angiotensin II and the fibroproliferative response to acute lung injury
Authors: Marshall Richard P. , Gohlke Peter , Chambers Rachel C. , Howell David C. , Bottoms Steve E. , Unger Thomas , McAnulty Robin J. , Laurent Geoffrey J.
Published: January 2004

Angiotensin II (ANG II), generated by activation of local renin-angiotensin systems, is believed to play an important role in tissue repair and remodeling, in part via transforming growth factor-β (TGF-β). Angiotensin-converting enzyme (ACE) inhibitors have been shown to abrogate experimental lung injury via a number of potential mechanisms; however, the potentially fibroproliferative role for ANG II in the lung has not been characterized. We hypothesized that, after lung injury, ANG II would stimulate fibroblast procollagen synthesis and promote lung collagen deposition in rats. In vitro, ANG II was a potent inducer of procollagen production in human lung fibroblasts via activation of the type 1 receptor and, at least in part, via the autocrine action of TGF-β. After bleomycin-induced lung injury, an increase in lung ANG II concentration was observed by day 3 that preceded increases in lung collagen and was maintained until death at day 21. Administration of an ACE inhibitor (ramipril) reduced ACE activity, ANG II concentration, TGF-β expression, and collagen deposition. Losartan (an ANG II type 1 receptor antagonist) also attenuated the increase in TGF-β expression and lung collagen deposition. These observations suggest that ANG II, possibly generated locally within the lung, may play an important role in the fibrotic response to acute lung injury, at least in part via the action of TGF-β. ACE inhibitors and receptor antagonists, already widely used clinically, should be assessed as potential new therapies for fibrotic lung disease.
Latent adenoviral infection induces production of growth factors relevant to airway remodeling in COPD
Authors: Ogawa Emiko , Elliott W. Mark , Hughes Fiona , Eichholtz Thomas J. , Hogg James C. , Hayashi Shizu
Published: January 2004

Previous studies showed an association between latent adenoviral infection with expression of the adenoviral E1A gene and chronic obstructive pulmonary disease (COPD). The present study focuses on how the adenoviral E1A gene could alter expression of growth factors by human bronchial epithelial (HBE) cells. The data show that connective tissue growth factor (CTGF) and transforming growth factor (TGF)-β1 mRNA and protein expression were upregulated in E1A-positive HBE cells. Upregulation of CTGF in this in vitro model was independent of TGF-β secreted into the growth medium. Comparison of E1A-positive with E1A-negative HBE cells showed that both expressed cytokeratin but only E1A-positive cells expressed the mesenchymal markers vimentin and α-smooth muscle actin. We conclude that latent infection of epithelial cells by adenovirus E1A could contribute to airway remodeling in COPD by the viral E1A gene, inducing TGF-β1 and CTGF expression and shifting cells to a more mesenchymal phenotype.
Downregulation of ENaC activity and expression by TNF-α in alveolar epithelial cells
Authors: Dagenais André , Fréchette Rosalie , Yamagata Yuko , Yamagata Toshiyuki , Carmel Jean-François , Clermont Marie-Eve , Brochiero Emmanuelle , Massé Chantal , Berthiaume Yves
Published: January 2004

Sodium absorption by an amiloride-sensitive channel is the main driving force of lung liquid clearance at birth and lung edema clearance in adulthood. In this study, we tested whether tumor necrosis factor-α (TNF-α), a proinflammatory cytokine involved in several lung pathologies, could modulate sodium absorption in cultured alveolar epithelial cells. We found that TNF-α decreased the expression of the α-, β-, and γ-subunits of epithelial sodium channel (ENaC) mRNA to 36, 43, and 16% of the controls after 24-h treatment and reduced to 50% the amount of α-ENaC protein in these cells. There was no impact, however, on α1and β1Na+-K+-ATPase mRNA expression. Amiloride-sensitive current and ouabain-sensitive Rb+uptake were reduced, respectively, to 28 and 39% of the controls. A strong correlation was found at different TNF-α concentrations between the decrease of amiloride-sensitive current and α-ENaC mRNA expression. All these data show that TNF-α, a proinflammatory cytokine present during lung infection, has a profound influence on the capacity of alveolar epithelial cells to transport sodium.
Postnatal glucocorticoids induce α-ENaC formation and regulate glucocorticoid receptors in the preterm rabbit lung
Authors: Mustafa Shamimunisa B. , DiGeronimo Robert J. , Petershack Jean A. , Alcorn Joseph L. , Seidner Steven R.
Published: January 2004

At birth, lung fluid clearance is coupled to Na+transport through epithelial Na+channels (ENaC) in the distal lung epithelium. We evaluated the effect of postnatal glucocorticoids (GC) on lung α-ENaC expression in preterm 29-day gestational age (GA) fetal rabbits. Postnatal treatment of 29-day GA fetuses with 0.5 mg/kg of dexamethasone (Dex) iv resulted in a 2- and 22-fold increase in lung α-ENaC mRNA expression compared with saline-treated fetuses after 8 and 16 h, respectively. Lung α-ENaC protein levels in Dex-treated fetuses were also elevated compared with saline-treated counterparts. The extravascular lung water (EVLW)/dry lung tissue weight ratios of 29-day GA fetuses treated with either saline or Dex decreased over 24 h compared with that observed at birth; however, at 24 h, the EVLW/dry lung tissue weight ratios of saline- and Dex-treated fetuses were similar. Dex-induced α-ENaC mRNA and protein levels were attenuated by glucocorticoid receptor (GCR) antagonist RU-486 in fetal distal lung epithelial cells isolated from 29-day GA fetuses, indicating that GC-dependent augmentation of lung α-ENaC requires the presence of functional GCR. Lung GCR mRNA expression and protein levels were elevated in 29-day GA fetuses compared with fetuses at earlier GA. Exposure of 29-day GA fetuses to Dex for 16 h caused a 2.1-fold increase in lung GCR mRNA expression, but GCR protein levels were decreased in Dex-treated fetuses after 24 h. We conclude that postnatal treatment of preterm 29-day GA fetal rabbits with GC results in an elevation of lung α-ENaC accompanied by an autoregulation of pulmonary GCR.
Transient injury to rat lung mitochondrial DNA after exposure to hyperoxia and inhaled nitric oxide
Authors: Lightfoot Richard T. , Khov Steven , Ischiropoulos Harry
Published: January 2004

The effect of hyperoxia alone and in combination with inhaled nitric oxide (NO) on the integrity of lung mitochondrial DNA (mtDNA) in vivo was evaluated in Fischer 344 rats. PCR amplification of lung mtDNA using two sets of primers spanning 10.1 kb of the mtDNA revealed that inhalation of 20 ppm of NO in conjunction with hyperoxia (>95% O2) reduced the amplification of mtDNA templates by 10 ± 1% and 26 ± 3% after 24 h of exposure. The ability of mtDNA to amplify was not compromised in rats exposed to 80% O2, even in the presence of 20 ppm of inhaled NO. Surprisingly, exposure to >95% O2alone for either 24 or 48 h did not compromise the integrity of mtDNA templates compared with air-exposed controls, despite evidence of genomic DNA injury. Interestingly, inhaling NO alone for 48 h increased mtDNA amplification by 12 ± 2% to 21 ± 7%. Injury to the lung mtDNA after exposure to >95% O2plus 20 ppm of NO was transient as rats allowed to recover in room air after exposure displayed increased amplification, with levels exceeding controls by 20 ± 3% to 29 ± 4%. Increased amplification was not due to cellular proliferation or increased mitochondrial number. Moreover, the ratio of pulmonary mtDNA to genomic DNA remained the same between treatment groups. The results indicate that hyperoxia fails to induce significant injury to mtDNA, and whereas inhalation of NO with hyperoxia results in mtDNA damage, the lesions are rapidly repaired during recovery.
Differential roles for NF-κB in endotoxin and oxygen induction of interleukin-8 in the macrophage
Authors: D'Angio Carl T. , LoMonaco Michael B. , Johnston Carl J. , Reed Christina K. , Finkelstein Jacob N.
Published: January 2004

The alveolar macrophage is an important source of interleukin (IL)-8 during pulmonary injury. The IL-8 gene promoter sequence contains nuclear factor (NF)-κB, NF-IL6, and activator protein (AP)-1 binding sequences. These sites may have differing regulatory roles in hyperoxia-exposed macrophages than in those stimulated by bacterial lipopolysaccharide (LPS). U-937 and THP-1 macrophage-like cells were exposed to air-5% CO2or 95% O2-5% CO2, with or without 1.0 μg/ml of LPS, and transfected with an IL-8 promoter-reporter containing NF-κB, NF-IL6, or AP-1 mutations. Hyperoxia and LPS caused additive increases in IL-8 production by U-937 cells, whereas THP-1 cells responded only to LPS. An NF-κB mutation ablated baseline and O2- and LPS-stimulated reporter activity in both cell lines, whereas NF-IL6 mutations had little effect. An AP-1 mutation had an intermediate effect. LPS, but not hyperoxia, stimulated nuclear translocation of NF-κB in both cell lines. Pharmacological blockade of NF-κB nuclear translocation ablated LPS-, but not hyperoxia-, stimulated IL-8 production. Although an intact promoter NF-κB site is crucial to macrophage IL-8 production, only LPS-stimulated production appears to require additional nuclear translocation of NF-κB.
Role of IFN-γ and IL-2 in rat lung epithelial cell migration and apoptosis after oxidant injury
Authors: Lesur Olivier , Brisebois Marcel , Thibodeau Alexandre , Chagnon Frédéric , Lane Denis , Füllöp Tamas
Published: January 2004

In the present study, IFN-γ exposure to primary cultures of rat type II epithelial cells (TIIP) upregulated membrane expression of the common γ-chain of the IL-2 receptor (∼2.5- to 4-fold increase) and redistributed receptor affinity in TIIP, as assessed by Western blot, cell, and tissue histochemistry and Scatchard analysis. As for restitution processes of the lung epithelium, functionality of IL-2R on TIIP was conditional to IFN-γ exposure: 1) IFN-γ priming promoted a fivefold increase of IL-2-driven TIIP locomotion ( P < 0.05 vs. control at 100 U/ml) and 2) IFN-γ coincubation with IL-2 reduced bleomycin-induced TIIP apoptosis in vitro by 25% (caspase-3 activity) and by ∼70% (TdT-mediated dUTP nick end labeling/4′,6′-diamidino-2-phenylindole assay) as well as in vivo by ∼90% (caspase-3 activity; P < 0.05 vs. control). Sustained p42/44 extracellular signal-regulated kinase activity played a protective role in this process, whereas specific inhibition by PD-98059 (50 μM) significantly reversed bleomycin-induced TIIP apoptosis ( P < 0.05 vs. control). From these in vitro and in vivo data, it is proposed that combinations of IFN-γ and IL-2 can drive repair activity of TIIP by stimulating migration and preventing programmed cell death, both of which are speculated to be very fast restitution events after oxidant-induced acute lung injury.
Opposite effects of redox status on membrane potential, cytosolic calcium, and tone in pulmonary arteries and ductus arteriosus
Authors: Olschewski Andrea , Hong Zhigang , Peterson Douglas A. , Nelson Daniel P. , Porter Valerie A. , Weir E. Kenneth
Published: January 2004

At birth, associated with the rise in oxygen tension, the pulmonary arteries (PA) dilate and the ductus arteriosus (DA) constricts. Both PA and DA constrict with vasoconstrictors and dilate with vasodilators. They respond in a contrary manner only to changes in oxygen tension. We hypothesized that the effects of changes in oxygen are mediated by changes in redox status. Consequently, we tested whether a reducing agent, DTT, and an oxidizing agent, dithionitrobenzoic acid (DTNB), would have opposite effects on a major oxygen signaling pathway in the PA and DA smooth muscle cells (SMCs), the sequence of change in potassium current ( IK), membrane potential ( Em), cytosolic calcium, and vessel tone. Under normoxic conditions, DTT constricted adult and fetal resistance PA rings, whereas in DA rings DTT acted as a potent vasodilator. In normoxia, voltage-clamp measurements showed inhibition of IKby DTT in PASMCs and, in contrast, activation in DASMCs. Consequently, DTT depolarized fetal and adult PASMCs and hyperpolarized DASMCs. [Ca2+]iwas increased by DTT in fetal and adult PASMCs and decreased in DASMCs. Under hypoxic conditions, DTNB constricted DA rings and caused vasodilatation in fetal PA rings. DTNB inhibited IKand depolarized the cell membrane in DASMCs. In contrast, activation of IKand hyperpolarization was seen in PASMCs. Thus the same redox signal can elicit opposite effects on IK, Em, cytosolic calcium, and vascular tone in resistance PA and the DA. These observations support the concept that redox changes could signal the opposite effects of oxygen in the PA and DA.
TNF-α induces a decrease in eNOS promoter activity
Authors: Neumann Paul , Gertzberg Nancy , Johnson Arnold
Published: January 2004

We determined whether TNF-α induces a decrease in activity of the promoter for the endothelial nitric oxide synthase (eNOS) gene in pulmonary microvessel endothelial monolayers (PMEM). eNOS promoter activity was assessed in PMEM transfected with plasmids coding the wild-type (F1: -1600 nt from transcription start site) and truncated (F2: -1189, F4: -779, F5: -494, F6: -166) human eNOS promoters linked to a luciferase reporter. PMEM lysates were analyzed for the luciferase/galactosidase ratio (Luc/Gal) after incubation with TNF-α (50 ng/ml) for 0.5 or 4 h. TNF-α caused a decrease in the Luc/Gal ratio in the PMEM transfected with wild-type F1 and truncated F2, F4, and F5 plasmids but not with truncated F6 plasmid. Truncated-promoter analysis indicated the response elements-370CACCC,-231GATA, and-186CACCC may regulate the effect of TNF-α on the eNOS promoter. DNA-binding activity of32P-labeled oligonucleotide probes that span the GATA-binding site (-239-[-231GATA]--219) and the two different CACCC-binding regions (-379-[-370CACCC]--358and-196-[-186CACCC]--176) were assessed using EMSA. In response to TNF-α treatment for 4 h, nuclear protein binding to32P oligonucleotides was characterized as: 1) a significant increase in binding to-370CACCC, 2) a significant decrease in binding to-231GATA, and 3) no change in-186CACCC binding. EMSA supershift analysis indicated that the transcription factor protein GATA-4 bound to the-231GATA site, and Sp3 bound to the-370CACCC site. Our data indicate TNF causes a decrease in eNOS promoter activity that may be mediated by GATA-4 and Sp3.
Environmental oxygen tension affects phenotype in cultured bone marrow-derived macrophages
Authors: Pfau Jean C. , Schneider Jordan C. , Archer Amy J. , Sentissi Jami , Leyva Francisco J. , Cramton Jennifer
Published: January 2004

This study tested the hypothesis that the unique phenotype of alveolar macrophages (AM) is maintained through adaptation to the relatively high oxygen partial pressure (Po2) of the lung, through modification of redox-sensitive transcription factors. BALB/c mouse bone marrowderived macrophages (BMC) were differentiated under different Po2and compared functionally to AM and peritoneal macrophages (PM). BMC differentiated in normoxia (Po2140 Torr, BMChigh) were similar to AM in having low phagocytic and antigen presenting cell (APC) activities. However, BMC grown in low oxygen tension as found in other tissues (<40 Torr, BMClow) were better phagocytes and APCs, similar to PM. BMChighwere more oxidative intracellularly than BMClow, based on oxidation of dichlorofluorescein and higher glutathione disulfide/glutathione (GSH) ratios, despite having more GSH. Finally, lipopolysaccharide-induced nuclear factor-κB translocation, measured by laser scanning cytometry, was reduced in BMChighand AM, compared with BMClowand PM, respectively. These data suggest that regulation of the AM phenotype may occur, at least in part, via inhibition of NF-κB by the unique redox environment.
Surfactant protein A inhibits alveolar macrophage cytokine production by CD14-independent pathway
Authors: Alcorn John F. , Wright Jo Rae
Published: January 2004

The lung collectin surfactant protein A (SP-A) has both anti-inflammatory and prophagocytic activities. We and others previously showed that SP-A inhibits the macrophage production of tumor necrosis factor (TNF)-α stimulated by the gram-negative bacterial component LPS. We propose that SP-A decreases the production of proinflammatory cytokines by alveolar macrophages via a CD14-independent mechanism. SP-A inhibited LPS-simulated TNF-α production in rat and mouse macrophages in the presence and absence of serum (72% and 42% inhibition, respectively). In addition, SP-A inhibited LPS-induced mRNA levels for TNF-α, IL-1α, and IL-1β as well as NF-κB DNA binding activity. SP-A also diminished ultrapure LPS-stimulated TNF-α produced by wild-type and CD14-null mouse alveolar macrophages by 58% and 88%, respectively. Additionally, SP-A inhibited TNF-α stimulated by PMA in both wild-type and TLR4-mutant macrophages. These data suggest that SP-A inhibits inflammatory cytokine production in a CD14-independent manner and also by mechanisms independent of the LPS signaling pathway.
Bombesin-like peptide receptor gene expression, regulation, and function in fetal murine lung
Authors: Shan Lin , Emanuel Rodica L. , Dewald Denise , Torday John S. , Asokanathan Nithiananthan , Wada Keiji , Wada Etsuko , Sunday Mary E.
Published: January 2004

Bombesin-peptide (BLP) immunoreactivity occurs at high levels in fetal lung. Previous studies showed that bombesin promotes fetal lung development. To test the hypothesis that such effects are mediated by known mammalian bombesin receptors [gastrin-releasing peptide (GRP)/bombesin-preferring receptor (GRPR), neuromedin B (NMB) receptor (NMBR), and the orphan bombesin receptor subtype-3 (BRS-3)], we analyzed the ontogeny of GRPR, NMBR, and BRS-3 gene expression in mouse lung. We examined the regulation of these three genes by dexamethasone and bombesin, which modulate lung development. Using incorporation of [3H]thymidine and [3H]choline, we then assessed whether GRP, NMB, and Leu8-phyllolitorin modulate lung growth and maturation in fetal lung explants. GRPR gene expression was detected predominantly in utero, whereas NMBR and BRS-3 genes were expressed from embryonic days 13–16 and on multiple postnatal days. All three mRNAs are present in airway epithelium and mesenchymal cells but occur in different relative patterns. These genes were regulated differently. Dexamethasone and bombesin increased GRPR mRNA, bombesin downregulated NMBR, and neither agent affected BRS-3. GRP increased incorporation of [3H]thymidine and [3H]choline in explants, whereas NMB induced cell proliferation and Leu8-phyllolitorin yielded variable results. Cumulative data suggest the involvement of multiple BLP receptors, including novel molecules, and argue against simple functional redundancy within this gene family during lung development.
Regulation of MUC5AC mucin secretion and airway surface liquid metabolism by IL-1β in human bronchial epithelia
Authors: Gray Thomas , Coakley Ray , Hirsh Andrew , Thornton David , Kirkham S. , Koo Ja-Seok , Burch Lauranell , Boucher Richard , Nettesheim Paul
Published: January 2004

Mucociliary transport in the airways significantly depends on the liquid and mucin components of the airway surface liquid (ASL). The regulation of ASL water and mucin content during pathological conditions is not well understood. We hypothesized that airway epithelial mucin production and liquid transport are regulated in response to inflammatory stimuli and tested this hypothesis by investigating the effects of the pleiotropic, early-response cytokine, IL-1β, on cultured primary human bronchial epithelial and second-passage, normal human tracheo-bronchial epithelial (NHTBE) cell cultures. Fully differentiated NHTBE cultures secreted two major airway mucins, MUC5AC and MUC5B. IL-1β, in a dose- and time-dependent manner, increased the secretion of MUC5AC, but not MUC5B. MUC5AC mRNA levels were only transiently increased at 1 and 4 h after the start of IL-1β treatment and returned to control levels thereafter, even though MUC5AC mucin production remained elevated for at least 72 h. Synchronous with elevated MUC5AC secretion, ASL volume increased, its percentage of solid was reduced, and the pH/[[Formula: see text]] of the ASL was elevated. ASL volume changes reflected altered ion transport, including an upregulation of Cl-secretory currents (via CFTR and Ca2+-activated Cl-conductance) and an inhibition of epithelial sodium channel (ENaC)-mediated absorptive Na+currents. IL-1β increased CFTR mRNA levels without affecting those for ENaC subunits. The synchronous regulation of ASL mucin and liquid metabolism triggered by IL-1β may be an important defense mechanism of the airway epithelium to enhance mucociliary clearance during airway inflammation.
Effects of leptin administration on lactational infertility in food-restricted rats depend on milk delivery
Authors: Abizaid Alfonso , Kyriazis Diana , Woodside Barbara
Published: January 2004

Leptin administration has been shown to prevent the disruptive effects of acute food deprivation on reproductive function in cycling females and lactating females. We examined the ability of intracerebroventricular leptin administration to ameliorate the effects of food restriction for the first 2 wk postpartum on length of lactational infertility. Leptin administration did not reduce the effects of food restriction on reproductive function at either time period ( days 8-15 and 15-22 postpartum) or dose (1 and 10 μg/day) administered. Because of the sharp contrast between these results and the ability of leptin to offset the effects of acute food deprivation in lactating rats, the remaining studies investigated the possible causes of this difference. Both central and peripheral leptin administration eliminated food deprivation-induced prolongation of lactational infertility, suggesting that neither route of administration nor dose was a factor. However, we noticed that, whereas chronically food-restricted females continue to deliver milk to their young, acutely food-deprived females do not. To test the hypothesis that the continued energetic drain of milk production and delivery might prevent the ability of exogenous leptin administration to eliminate the effects of undernutrition, leptin was administered to food-restricted, lactating rats prevented from delivering milk. In this situation intracerebroventricular leptin treatment completely eliminated the effects of food restriction on lactational infertility, suggesting that leptin contributes to the maintenance of reproductive function via two pathways: direct binding in the central nervous system and through increasing the availability of oxidizable metabolic fuels.
Postnatal hypoxic-ischemic brain injury alters mechanisms mediating neuronal glucose transport
Authors: Zovein Ann , Flowers-Ziegler Judy , Thamotharan Shanthie , Shin Don , Sankar Raman , Nguyen Khoi , Gambhir Sanjiv , Devaskar Sherin U.
Published: January 2004

We examined the effect of hypoxic ischemia and hypoxia vs. normoxia on postnatal murine brain substrate transporter concentrations and function. We detected a transient increase in the neuronal brain glucose transporter isoform (GLUT-3) in response to hypoxic ischemia after 4 h of reoxygenation. This increase was associated with no change in GLUT-1 (blood-brain barrier/glial isoform), monocarboxylate transporter isoforms 1 and 2, synapsin I (neuronal marker), or Bax (proapoptotic protein) but with a modest increase in Bcl-2 (antiapoptotic mitochondrial protein) protein concentrations. At 24 h of reoxygenation, the increase in GLUT-3 disappeared but was associated with a decline in Bcl-2 protein concentrations and the Bcl2:Bax ratio, an increase in caspase-3 enzyme activity (apoptotic effector enzyme), and extensive DNA fragmentation, which persisted later in time (48 h) only in the hippocampus. Hypoxia alone in the absence of ischemia was associated with a transient but modest increase in GLUT-3 and synapsin I protein concentrations, which did not cause significant apoptosis and/or necrosis. Assessment of glucose transporter function by 2-deoxyglucose (2-DG) uptake using two distinct techniques, namely positron emission tomography (PET) and the modified Sokoloff method, revealed a discrepancy due to glucose uptake by extracranial Harderian glands that masked the accurate detection of intracranial brain glucose uptake by PET scanning. The modified Sokoloff method assessing 2-DG uptake revealed that the transient increase in GLUT-3 was critical in protecting against a decline in brain glucose uptake. We conclude that hypoxic-ischemic brain injury is associated with transient compensatory changes targeted at protecting glucose delivery to fuel cellular energy metabolism, which then may delay the processes of apoptosis and cell necrosis.
Rate and extent of compensatory changes in energy intake and expenditure in response to altered exercise and diet composition in humans
Authors: Stubbs R. J. , Hughes D. A , Johnstone A. M. , Whybrow S. , Horgan G. W. , King N. , Blundell J.
Published: January 2004

We assessed the effect of no exercise (Nex; control) and high exercise level (Hex; ∼4 MJ/day) and two dietary manipulations [a high-fat diet (HF; 50% of energy, 700 kJ/100 g) and low-fat diet (LF; 20% of energy, 300 kJ/100 g)] on compensatory changes in energy intake (EI) and energy expenditure (EE) over 7-day periods. Eight lean men were each studied four times in a 2 × 2 randomized design. EI was directly quantified by weight of food consumed. EE was assessed by heart rate (HR) monitoring. Body weight was measured daily. Mean daily EE was 17.6 and 11.5 MJ/day ( P < 0.001) on the pooled Hex and Nex treatments, respectively. EI was higher on HF diets (13.4 MJ/day pooled) compared with the LF diets (9.0 MJ/day). Regression analysis showed that these energy imbalances induced significant compensatory changes in EB over time of ∼0.3-0.4 MJ/day ( P < 0.05). These were due to changes in both EI and EE in the opposite direction to the perturbation in energy balance. These changes were significant, small but persistent, amounting to ∼0.2 and ∼0.35 MJ/day for EI and EE, respectively.
Heterogeneous patterns of pH regulation in glial cells in the dorsal and ventral medulla
Authors: Erlichman Joseph S. , Cook Aaron , Schwab Mary C. , Budd Thomas W. , Leiter J. C.
Published: January 2004

We examined pH regulation in two chemosensitive areas of the brain, the retrotrapezoid nucleus (RTN) and the nucleus tractus solitarius (NTS), to identify the proton transporters involved in regulation of intracellular pH (pHi) in medullary glia. Transverse brain slices from young rats [postnatal day 8 (P8) to P20] were loaded with the pH-sensitive probe 2′,7′-bis (2-carboxyethyl)-5,6-carboxyfluorescein after kainic acid treatment removed neurons. Cells were alkalinized when they were depolarized (extracellular K+ increased from 6.24 to 21.24 mM) in the RTN but not in the NTS. This alkaline shift was inhibited by 0.5 mM DIDS. Removal of [Formula: see text] or Na+ from the perfusate acidified the glial cells, but the acidification after Na+ removal was greater in the RTN than in the NTS. Treatment of the slice with 5-( N-ethyl- N-isopropyl)amiloride (100 μM) in saline containing [Formula: see text] acidified the cells in both nuclei, but the acidification was greater in the NTS. Restoration of extracellular Cl- after Cl- depletion during the control condition acidified the cells. Immunohistochemical studies of glial fibrillary acid protein demonstrated much denser staining in the RTN compared with the NTS. We conclude that there is evidence of [Formula: see text] cotransport and Na+/H+ exchange in glia in the RTN and NTS, but the distribution of glia and the distribution of these pH-regulatory functions are not identical in the NTS and RTN. The differential strength of glial pH regulatory function in the RTN and NTS may also alter CO2 chemosensory neuronal function at these two chemosensitive sites in the brain stem.
Mutual dependence of VIP/PACAP and CCK receptor signaling for a physiological role in duck exocrine pancreatic secretion
Authors: Xiao Rui , Cui Zong Jie
Published: January 2004

Unlike in rodents, CCK has not been established as a physiological regulator in avian exocrine pancreatic secretion. In the isolated duck pancreatic acini, 1 nM CCK was required for stimulation of amylase secretion, maximal effect being achieved at 10 nM; picomolar CCK was without effect. Vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase activating peptide (PACAP) receptor (VPAC) agonists PACAP-38 and PACAP-27 (10-12-10-7M) alone had no effect, but made picomolar CCK effective. VPAC agonist VIP 10-10-10-7M stimulated amylase secretion marginally, but made CCK 10-12-10-10M effective also. PACAP-27 and VIP both shifted the maximal CCK concentration from 10-8to 10-9M. This sensitizing effect was mimicked by forskolin. CCK dose dependently induced intracellular Ca2+concentration ([Ca2+]i) oscillations. PACAP-38 (1 nM), PACAP-27 (1 nM), VIP (10 nM), or forskolin (10 μM) alone did not stimulate [Ca2+]iincrease, neither did they modulate CCK (1 nM)-induced oscillations; but when they were added to cells simultaneously exposed to subthreshold CCK (10 pM), calcium spikes emerged. Amylase secretion induced by the simultaneous presence of 10 pM CCK and VPAC agonists was completely blocked by removing extracellular calcium, but the protein kinase C inhibitor staurosporine (1 μM) was without effect. CCK (10 nM)-induced secretion was inhibited by CCK1receptor antagonist FK480 (1 μM). Gastrin from 10-12to 10-6M did not stimulate amylase secretion nor did it (100 nM) induce [Ca2+]iincrease. The above data suggest that duck pancreatic acini possess both CCK1and VPAC receptors; simultaneous activation of both is required for each to play a physiological role.
Oral sucrose stimulation increases accumbens dopamine in the rat
Authors: Hajnal Andras , Smith Gerard P. , Norgren Ralph
Published: January 2004

Although taste can influence meal size and body weight, the neural substrate for these effects remains obscure. Dopamine, particularly in the nucleus accumbens, has been implicated in both natural and nonnatural rewards. To isolate the orosensory effects of taste from possible postingestive consequences, we investigated the quantitative relationship between sham feeding of sucrose and extracellular dopamine in the nucleus accumbens with microdialysis in rats. Sucrose intake linearly increased as a function of concentration (0.03 M, 18.07 ± 2.41 ml; 0.1 M, 30.92 ± 2.60 ml; 0.3 M, 43.28 ± 2.88 ml). Sham feeding also stimulated accumbens dopamine overflow as a function of sucrose solution concentration (0.03 M, 120.76 ± 2.6%; 0.1 M, 140.28 ± 7.8%; 0.3 M, 146.27 ± 5.05%). A second experiment used the same protocol but clamped the amount of sucrose ingested and revealed a similar, concentration-dependent dopamine activation in the nucleus accumbens. This is the first demonstration of a quantitative relationship between the concentration-dependent rewarding effect of orosensory stimulation by sucrose during eating and the overflow of dopamine in the nucleus accumbens. This finding provides new and strong support for accumbens dopamine in the rewarding effect of sucrose.
Agouti-related protein increases food hoarding more than food intake in Siberian hamsters
Authors: Day Diane E. , Bartness Timothy J.
Published: January 2004

Agouti-related protein (AgRP), an endogenous melanocortin 3/4 receptor antagonist, appears to play an important role in the control of food intake and energy balance because exogenous administration in rats and overexpression in mice result in hyperphagia and body mass gain. Furthermore, arcuate nucleus AgRP mRNA is increased with fasting in laboratory rats and mice and is decreased with refeeding. In Siberian hamsters, fasting also increases arcuate nucleus AgRP mRNA, but these animals increase food hoarding, rather than food intake with refeeding. Therefore, we tested whether exogenous AgRP increased food hoarding in this species. Hamsters were trained in a hoarding/foraging apparatus to run a programmed number of wheel revolutions to earn food pellets. Four doses of AgRP-(83-132) or vehicle were injected into the third ventricle at the beginning of the dark phase, and food hoarding, food intake, and foraging were measured at various time points subsequently. Overall, food hoarding was stimulated as much as 10 times more than food intake, and both responses occurred as early as 1 h after injection. Food hoarding was increased the greatest at the lowest dose (0.1 nmol), whereas food intake was increased the greatest at the second lowest dose (1 nmol). Food intake and especially food hoarding were increased up to seven days after the AgRP injections. Foraging was increased at all AgRP doses except the highest dose (100 nmol). These results suggest that AgRP triggers the search for food in this species, and once they find it, hoarding predominates over eating.
Effect of ribose supplementation on resynthesis of adenine nucleotides after intense intermittent training in humans
Authors: Hellsten Y. , Skadhauge L. , Bangsbo J.
Published: January 2004

The effect of oral ribose supplementation on the resynthesis of adenine nucleotides and performance after 1 wk of intense intermittent exercise was examined. Eight subjects performed a random double-blind crossover design. The subjects performed cycle training consisting of 15 × 10 s of all-out sprinting twice per day for 7 days. After training the subjects received either ribose (200 mg/kg body wt; Rib) or placebo (Pla) three times per day for 3 days. An exercise test was performed at 72 h after the last training session. Immediately after the last training session, muscle ATP was lowered ( P < 0.05) by 25 ± 2 and 22 ± 3% in Pla and Rib, respectively. In both Pla and Rib, muscle ATP levels at 5 and 24 h after the exercise were still lower ( P < 0.05) than pretraining. After 72 h, muscle ATP was similar ( P > 0.05) to pretraining in Rib (24.6 ± 0.6 vs. 26.2 ± 0.2 mmol/kg dry wt) but still lower ( P < 0.05) in Pla (21.1 ± 0.5 vs. 26.0 ± 0.2 mmol/kg dry wt) and higher ( P < 0.05) in Rib than in Pla. Plasma hypoxanthine levels after the test performed at 72 h were higher ( P < 0.05) in Rib compared with Pla. Mean and peak power outputs during the test performed at 72 h were similar ( P > 0.05) in Pla and Rib. The results support the hypothesis that the availability of ribose in the muscle is a limiting factor for the rate of resynthesis of ATP. Furthermore, the reduction in muscle ATP observed after intense training does not appear to be limiting for high-intensity exercise performance.
Effects of moderate exercise and oat β-glucan on innate immune function and susceptibility to respiratory infection
Authors: Davis J. M. , Murphy E. A. , Brown A. S. , Carmichael M. D. , Ghaffar A. , Mayer E. P.
Published: January 2004

Both moderate exercise and the soluble oat fiber β-glucan can increase immune function and decrease risk of infection, but no information exists on their possible combined effects. This study tested the effects of moderate exercise and oat β-glucan on respiratory infection, macrophage antiviral resistance, and natural killer (NK) cell cytotoxicity. Mice were assigned to four groups: exercise and water, exercise and oat β-glucan, control water, or control oat β-glucan. Oat β-glucan was fed in the drinking water for 10 days before intranasal inoculation of herpes simplex virus type 1 (HSV-1) or euthanasia. Exercise consisted of treadmill running (1 h/day) for 6 days. Macrophage resistance to HSV-1 was increased with both exercise and oat β-glucan, whereas NK cell cytotoxicity was only increased with exercise. Exercise was also associated with a 45 and 38% decrease in morbidity and mortality, respectively. Mortality was also decreased with oat β-glucan, but this effect did not reach statistical significance. No additive effects of exercise and oat β-glucan were found. These data confirm a positive effect of both moderate exercise and oat β-glucan on immune function, but only moderate exercise was associated with a significant reduction in the risk of upper respiratory tract infection in this model.
Influence of dietary NaCl on L-arginine transport in the renal medulla
Authors: Zewde Tewabech , Wu Feng , Mattson David L.
Published: January 2004

Previous work demonstrated that l-arginine, the substrate for nitric oxide (NO) synthase, is carried into inner medullary collecting duct (IMCD) cells via system y+, that the major system y+ gene product in IMCD is the cationic amino acid transporter 1 (CAT1), and that blockade of l-arginine uptake in the renal medulla decreases NO and leads to systemic hypertension. The present study determined the influence of dietary sodium intake on l-arginine uptake in IMCD, on CAT1 immunoreactive protein in the renal medulla, and on the hypertensive response to blockade of l-arginine uptake in the renal medulla. Transport studies in bulk-isolated IMCD demonstrated that l-arginine uptake by IMCD was significantly greater (663 ± 100 pmol·mg-1· min-1, n = 6) in rats exposed to a low-sodium diet (0.4% NaCl) compared with rats on a normal (1% NaCl, 519 ± 78 pmol·mg-1·min-1, n = 6) or high-sodium diet (4.0% NaCl, 302 ± 27 pmol·mg-1·min-1, n = 6). Immunoblotting experiments demonstrated that CAT1 immunoreactive protein was significantly decreased by ∼30% in rats maintained on a high-NaCl diet ( n = 5) compared with rats on a low-NaCl diet ( n = 5). In contrast to the l-arginine transport and immunoblotting data, in vivo blockade of l-arginine uptake led to hypertension of equal magnitude in rats maintained on a low- or high-NaCl diet. These results indicate that sodium loading leads to a decrease in immunoreactive CAT1 protein in the rat renal medulla, resulting in decreased l-arginine uptake capacity. The decrease in l-arginine uptake capacity, however, does not alter the blood pressure response to l-arginine uptake inhibition in the renal medulla.
LiCl-induced flavor avoidance compared between rats and mice using a nondeprivation protocol
Authors: Rowland Neil E. , Nasrallah Nicholas A. , Robertson Kimberly L.
Published: January 2004

The present studies examine some parameters involved in flavor avoidance learning, using LiCl to induce malaise, in a novel nondeprivation protocol that allows direct comparison between rats and mice. The procedure involves daily presentation of a gelatin dessert that contains carbohydrate (Polycose) and a distinctive food flavor. Regular chow is additionally available at all times. Both rats and mice showed robust intakes of these gels with little change of gram intake as concentration of Polycose was varied in the range 2-30%; at the highest concentration, the caloric yield was ∼7% of normal daily intake in both species. Rats that were injected on three occasions with LiCl (0.75 meq/kg) 1 h after consumption of a flavored gel formed a complete and sustained conditioned flavor avoidance (CFA). In a two-flavor discrimination protocol, in which a second flavor was followed by injections of saline, rats showed complete avoidance of the LiCl-paired flavor and partial avoidance of the saline-paired flavor. Mice injected on three occasions with LiCl (6 meq/kg) 1 h after intake of a flavored gel formed a partial CFA; a more complete CFA was formed when there was no delay between removal of the flavor and the injection. Using this no-delay protocol, mice, like rats, showed avoidance of a saline-paired flavor in a two-flavor discrimination protocol, and the CFA was strong when the dose of LiCl was reduced to that used in rats (0.75 meq/kg). In comparable protocols, mice thus are able to form complete CFAs using low doses of LiCl that are comparable to CFAs observed in rats, but the interval between flavor and sickness over which associative learning can occur may be shorter in mice.
Maturation of the homeothermic response of heart rate to altered ambient temperature in developing chick hatchlings (Gallus gallus domesticus)
Authors: Khandoker A. H. , Fukazawa K. , Dzialowski E. M. , Burggren W. W. , Tazawa H.
Published: January 2004

On the basis of evidence showing that instantaneous heart rate (IHR) of chick hatchlings responds to exposure to altered ambient temperature (Ta; Tazawa H, Moriya K, Tamura A, and Akiyama R. Comp Biochem Physiol A 131A: 797-803, 2002), we elucidate here the developmental timeline for the homeothermic response of HR in newly hatched chicks ( days 0-7) maintained at room temperature (∼24-27°C). Hatchlings were exposed to Ta of 25, 35, and 25°C for 1-h periods, respectively, and IHR was measured together with skin temperature (Ts) during this warming and cooling bout. Early 0-day-old (0 day) chicks responded to warming and cooling exposures with various changes in HR baseline. In newly hatched chicks (0-7 h old), HR baseline was elevated during warming (Δ126 beats/min, n = 13) and declined during cooling (-Δ94 beats/min). With progress of development on day 0, the elevation of HR baseline during warming decreased and advanced 0-day chicks tended to decrease HR baseline during warming rather than increase HR. The more developed 1- to 7-day-old chicks exhibited the expected homeothermic decrease in HR during warming. The diurnal variations of HR responses during warming and cooling on the first day of post-egg life indicate that pronounced development of thermoregulatory competence occurs during the day of hatching ( day 0). The response of IHR fluctuations to altered Ta was observed in the form of low- and high-frequency oscillations. High-frequency oscillations corresponding to respiratory sinus arrhythmia developed as the hatchlings aged. There was a significant increase in the number of chicks exhibiting both low- and high-frequency oscillations that depended on age and the development of thermoregulatory competence of hatchlings.