bluuebunny/crossref_metadata_2025 huggingface dataset:
IGFBP-3 activates TGF-β receptors and directly inhibits growth in human intestinal smooth muscle cells
Authors: Kuemmerle John F. , Murthy Karnam S. , Bowers Jennifer G.
Published: June 2004

We have shown that human intestinal smooth muscle cells produce IGF-I and IGF binding protein-3 (IGFBP-3). Endogenous IGF-I acts in autocrine fashion to stimulate growth of these cells. IGFBP-3 inhibits the binding of IGF-I to its receptor and thereby inhibits IGF-I-stimulated growth. In several carcinoma cell lines and some normal cells, IGFBP-3 regulates growth independently of IGF-I. Two mechanisms for this effect have been identified: IGFBP-3 can directly activate transforming growth factor-β (TGF-β) receptors or it can undergo direct nuclear translocation. The aim of the present study was to determine whether IGFBP-3 acts independently of IGF-I and to characterize the mechanisms mediating this effect in human intestinal smooth muscle cells. The direct effects of IGFBP-3 were determined in the presence of an IGF-I receptor antagonist to eliminate its IGF-I-dependent effects. Affinity labeling of TGF-β receptors (TGF-βRI, TGF-βRII, and TGF-βRV) with125I-labeled TGF-β1 showed that IGFBP-3 displaced binding to TGF-βRII and TGF-βRV in a concentration-dependent fashion. IGFBP-3 stimulated TGF-βRII-dependent serine phosphorylation (activation) of both TGF-βRI and of its primary substrate, Smad2(Ser465/467). IGFBP-3 also caused IGF-I-independent inhibition of basal [3H]thymidine incorporation. The effects of IGFBP-3 on Smad2 phosphorylation and on smooth muscle cell proliferation were independent of TGF-β1 and were abolished by transfection of Smad2 siRNA. Immunoneutralization of IGFBP-3 increased basal [3H]thymidine incorporation, implying that endogenous IGFBP-3 inhibits proliferation. We conclude that endogenous IGFBP-3 directly inhibits proliferation of human intestinal smooth muscle cells by activation of TGF-βRI and Smad2, an effect that is independent of its effect on IGF-I-stimulated growth.
Global gene expression profiles reveal an increase in mRNA levels of collagens, MMPs, and TIMPs in late radiation enteritis
Authors: Strup-Perrot Carine , Mathé Denis , Linard Christine , Violot Dominique , Milliat Fabien , François Agnès , Bourhis Jean , Vozenin-Brotons Marie-Catherine
Published: June 2004

Radiation enteritis, a common complication of radiation therapy for abdominal and pelvic cancers, is characterized by severe transmural fibrosis associated with mesenchymal cell activation, tissue disorganization, and deposition of fibrillar collagen. To investigate the mechanisms involved in this pathological accumulation of extracellular matrix, we studied gene expression of matrix components along with that of genes involved in matrix remodeling, matrix metalloproteinases (MMPs), and tissue inhibitors of metalloproteinases (TIMPs). Hybrid selection on high-density cDNA array, real-time RT-PCR, gelatin zymography and imunohistochemistry were used to characterize the mRNA expression profile, activity, and tissue location of extracellular matrix-related genes in radiation enteritis compared with healthy ileum. cDNA array analysis revealed a strong induction of genes coding for collagens I, III, IV, VI, and VIII, SPARC, and tenascin-C, extracellular-matrix degrading enzymes (MMP-1, -2, -3, -14, -18+19), and metalloproteinase inhibitors (TIMP-1, -2, plasminogen activator inhibitor-1) in radiation enteritis. This increase was correlated with the degree of infiltration of the mucosa by inflammatory cells, and the presence of differentiated mesenchymal cells in the submucosa and muscularis propria. Despite the fact that expression of collagens, MMPs, and TIMPs simultaneously increase, quantification of net collagen deposition shows an overall accumulation of collagen. Our results indicate that late radiation enteritis tissues are subjected to active process of fibrogenesis as well as fibrolysis, with a balance toward fibrogenesis. This demonstrates that established fibrotic tissue is not scarred fixed tissue but is subjected to a dynamic remodeling process.
Neuronal activity and CRF receptor gene transcription in the brains of rats with colitis
Authors: Porcher Christophe , Sinniger Valérie , Juhem Aurélie , Mouchet Patrick , Bonaz Bruno
Published: June 2004

We aimed to characterize neuronal and corticotropin-releasing factor (CRF) pathways at the acute phase of a model of colitis in rats. Male rats received an intracolonic injection of either vehicle (controls) or trinitrobenzenesulfonic acid (TNBS) and were killed 1, 2, 3, 4, 6, 12, or 24 h later. Coronal frozen sections of the brain were cut and mRNAs encoding the rat c- fos, CRF1receptor, and CRF2α,βreceptors were assayed by in situ hybridization histochemistry. Localization of these transcripts within CRF-immunoreactive (CRF-ir) neurons of the paraventricular nucleus (PVN) of the hypothalamus was also determined. Intracolonic TNBS induced c- fos mRNA expression in brain nuclei involved in the autonomic, behavioral, and neuroendocrine response to a stimulus (PVN, amygdala, locus coeruleus, parabrachial nucleus, nucleus of the solitary tract) and in circumventricular organs (lamina terminalis, subfornical organ, area postrema). CRF pathways, particularly in the PVN, were activated in this model as represented by a robust signal of c- fos and CRF1receptor transcripts in the PVN and numerous CRF-ir neurons expressed c- fos or CRF1receptor transcripts in the PVN of TNBS-treated animals. No expression of CRF2receptor transcripts was observed in the PVN, either in basal conditions or after TNBS. These neuroanatomical data argue for an involvement of CRF pathways, through CRF1receptor, within the PVN in TNBS-induced colitis.
Complex regulation of the lactase-phlorizin hydrolase promoter by GATA-4
Authors: van Wering Herbert M. , Bosse Tjalling , Musters Anna , de Jong Evelien , de Jong Naomi , Hogen Esch Caroline E. , Boudreau Francois , Swain Gary P. , Dowling Lauren N. , Montgomery Robert K. , Grand Richard J. , Krasinski Stephen D.
Published: June 2004

Lactase-phlorizin hydrolase (LPH), a marker of intestinal differentiation, is expressed in absorptive enterocytes on small intestinal villi in a tightly regulated pattern along the proximal-distal axis. The LPH promoter contains binding sites that mediate activation by members of the GATA-4, -5, and -6 subfamily, but little is known about their individual contribution to LPH regulation in vivo. Here, we show that GATA-4 is the principal GATA factor from adult mouse intestinal epithelial cells that binds to the mouse LPH promoter, and its expression is highly correlated with that of LPH mRNA in jejunum and ileum. GATA-4 cooperates with hepatocyte nuclear factor (HNF)-1α to synergistically activate the LPH promoter by a mechanism identical to that previously characterized for GATA-5/HNF-1α, requiring physical association between GATA-4 and HNF-1α and intact HNF-1 binding sites on the LPH promoter. GATA-4 also activates the LPH promoter independently of HNF-1α, in contrast to GATA-5, which is unable to activate the LPH promoter in the absence of HNF-1α. GATA-4-specific activation requires intact GATA binding sites on the LPH promoter and was mapped by domain-swapping experiments to the zinc finger and basic regions. However, the difference in the capacity between GATA-4 and GATA-5 to activate the LPH promoter was not due to a difference in affinity for binding to GATA binding sites on the LPH promoter. These data indicate that GATA-4 is a key regulator of LPH gene expression that may function through an evolutionarily conserved mechanism involving cooperativity with an HNF-1α and/or a GATA-specific pathway independent of HNF-1α.
Increased abdominal-to-peripheral fat distribution contributes to altered autonomic-circulatory control with human aging
Authors: Christou Demetra D. , Parker Jones Pamela , Pimentel Annemarie E. , Seals Douglas R.
Published: June 2004

Autonomic nervous system (ANS) control of the circulation is altered with aging in adult humans. Similar changes are observed in obesity, particularly abdominal obesity. To determine whether age-associated differences in ANS-circulatory function can be partially explained by increased body fatness, we examined ANS function and three expressions of adiposity (total body fat, abdominal body fat, and abdominal-to-peripheral body fat distribution; dual-energy X-ray absorptiometry) in 43 healthy men: 27 young (25 ± 1 yr) and 16 older (65 ± 1). ANS functions assessed included 1) autonomic support of arterial blood pressure (BP; radial artery catheter), i.e., the reduction in BP during versus before acute ganglionic blockade (GB; intravenous trimethaphan); 2) baroreflex buffering, i.e., the increase in systolic BP with continuous incremental and bolus infusions of phenylephrine during versus before GB; 3) cardiovagal baroreflex sensitivity (Oxford technique); and 4) heart rate variability (time- and frequency-domain analyses). Covarying for abdominal-to-peripheral fat distribution reduced or abolished age-related differences in ANS support of BP, cardiovagal baroreflex sensitivity, and heart rate variability but did not affect age-related differences in baroreflex buffering. Covarying for abdominal and total fat had small selective or no effects on age-associated differences in autonomic-circulatory control. Abdominal-to-peripheral fat distribution explains a significant portion of the variance in a number of autonomic-circulatory functions attributable to aging. Therefore, the development of this fat pattern may contribute to several changes in ANS-cardiovascular function observed with aging. These results may help explain how changes in body fat distribution with advancing age are linked to impairments in circulatory control.
Cigarette smoke extract inhibits angiogenesis of pulmonary artery endothelial cells: the role of calpain
Authors: Su Yunchao , Cao Wengang , Han Zhaosheng , Block Edward R.
Published: June 2004

Angiogenesis is an integral part of both the pulmonary inflammatory response to chronic exposure to cigarette smoke and the lung tissue remodeling associated with cigarette smoke-induced chronic obstructive pulmonary disease (COPD). To investigate the role of angiogenesis in the pathogenesis of COPD, we evaluated the effect of cigarette smoke extract (CSE) on angiogenesis of pulmonary artery endothelial cells (PAEC). Incubation of PAEC with 2.5–10% CSE resulted in a dose-dependent inhibition of endothelial monolayer wound repair. CSE also caused inhibition of tube formation on Matrigel, migration in a Boyden chamber, and proliferation of PAEC. Because calpain, a family of calcium-dependent intracellular proteases, mediates cytoskeletal signaling in endothelial motility, we explored the role of calpain in the CSE-induced inhibition of endothelial angiogenesis. Incubation of CSE resulted in a dose-dependent decrease in calpain activity. Calpain inhibitor-1, a specific inhibitor of calpain, potentiates inhibitory effect of CSE on the endothelial monolayer wound repair, tube formation, cell migration, and cell proliferation. Transfection of PAEC with antisense oligodeoxyribonucleotides of calpastatin, the major endogenous calpain inhibitor, prevented CSE-induced increase in calpastatin protein content and CSE-induced decreases in calpain activity. It also prevented CSE-induced decreases in monolayer wound repair, tube formation, and migration. These results suggest that CSE attenuates angiogenesis of PAEC and the mechanism involves inhibition of calpain. Impaired angiogenesis may impede the repair process in the lungs of cigarette smokers and contribute to the altered structural remodeling observed in the lungs of patients with cigarette smoke-related COPD.
Proteomics: current techniques and potential applications to lung disease
Authors: Hirsch Jan , Hansen Kirk C. , Burlingame Alma L. , Matthay Michael A.
Published: June 2004

Proteomics aims to study the whole protein content of a biological sample in one set of experiments. Such an approach has the potential value to acquire an understanding of the complex responses of an organism to a stimulus. The large vascular and air space surface area of the lung expose it to a multitude of stimuli that can trigger a variety of responses by many different cell types. This complexity makes the lung a promising, but also challenging, target for proteomics. Important steps made in the last decade have increased the potential value of the results of proteomics studies for the clinical scientist. Advances in protein separation and staining techniques have improved protein identification to include the least abundant proteins. The evolution in mass spectrometry has led to the identification of a large part of the proteins of interest rather than just describing changes in patterns of protein spots. Protein profiling techniques allow the rapid comparison of complex samples and the direct investigation of tissue specimens. In addition, proteomics has been complemented by the analysis of posttranslational modifications and techniques for the quantitative comparison of different proteomes. These methodologies have made the application of proteomics on the study of specific diseases or biological processes under clinically relevant conditions possible. The quantity of data that is acquired with these new techniques places new challenges on data processing and analysis. This article provides a brief review of the most promising proteomics methods and some of their applications to pulmonary research.
Adrenomedullin in the rostral ventrolateral medulla increases arterial pressure and heart rate: roles of glutamate and nitric oxide
Authors: Xu Yong , Krukoff Teresa L.
Published: June 2004

This study was done to investigate the effects of microinjections of adrenomedullin (ADM), a vasoactive neuropeptide, in the rostral ventrolateral medulla (RVLM) on mean arterial pressure (MAP) and heart rate (HR) in urethane-anesthetized rats, and to assess the potential roles of glutamate and nitric oxide (NO) in these effects. Unilateral injections of ADM (0.01 or 0.1 pmol) into the RVLM significantly increased MAP and HR in a dose-dependent manner, whereas ADM at 0.001 pmol was ineffective. Microinjections of ADM (0.01 pmol) outside the RVLM had no effects on MAP or HR. Coinjections of a putative ADM receptor antagonist, ADM22–52 (0.01 pmol), abolished the increases in MAP and HR evoked by ADM (0.01 pmol). The vasopressor effects of ADM (0.01 pmol) in the RVLM were abolished by coinjections of either dizocilpine hydrogen maleate (a selective NMDA glutamate receptor antagonist, 500 pmol) or 6-cyano-7-nitroquinoxaline-2,3-dione (a selective non-NMDA glutamate receptor antagonist, 50 pmol). The ADM-induced vasopressor effects were also abolished by coadministration of either 7-nitroindazole sodium salt (a selective neuronal NO synthase inhibitor, 0.05 pmol) or methylene blue (a soluble guanylyl cyclase inhibitor, 100 pmol). These results suggest that ADM in the RVLM stimulates increases in MAP and HR through ADM receptor-mediated mechanisms. These effects are mediated by glutamate via both NMDA and non-NMDA receptors. NO, derived from neuronal NO synthase, also contributes to the ADM-induced vasopressor effects via a soluble guanylyl cyclase-associated signaling pathway.
Influence of gestational age and fetal iron status on IRP activity and iron transporter protein expression in third-trimester human placenta
Authors: Bradley Jenni , Leibold Elizabeth A. , Harris Z. Leah , Wobken Jane D. , Clarke Stephen , Zumbrennen Kimberly B. , Eisenstein Richard S. , Georgieff Michael K.
Published: June 2004

Placental iron transport during the last trimester of pregnancy determines the iron endowment of the neonate. Iron transport is a function of the major iron transport proteins: transferrin receptor-1 (TfR-1) and ferroportin-1 (FPN-1). The mRNAs for TfR-1 and, potentially, FPN-1 are posttranscriptionally regulated by iron regulatory protein (IRP)-1 and IRP-2. We assessed the effect of gestational age and fetal iron status on IRP-1- and IRP-2-binding activity and on the localization and protein expression of TfR-1 and FPN-1 protein at 24–40 wk of gestation in 21 placentas obtained from iron-sufficient nonanemic mothers. Gestational age had no effect on cord serum ferritin concentration, IRP-2 RNA-binding activity, transporter protein location, and TfR-1 or FPN-1 protein expression. IRP-1 activity remained constant until full term, when it decreased ( P = 0.01). Placental ferritin ( r = 0.76, P < 0.001) and FPN-1 ( r = 0.44, P < 0.05) expression increased with gestational age. Fetal iron status, as indexed by cord serum ferritin concentration, was inversely related to placental IRP-1 ( r = −0.66, P < 0.001) and IRP-2 ( r = −0.42, P = 0.05) activities. Placental ferritin protein expression correlated better with IRP-1 ( r = −0.45, P = 0.04) than with IRP-2 ( r = −0.35, P = 0.10) activity. Placental TfR-1 and FPN-1 protein expression was independent of fetal or placental iron status and IRP activities. Iron status had no effect on transport protein localization. We conclude that, toward the end of the third trimester of iron-sufficient human pregnancy, the placenta accumulates ferritin and potentially increases placental-fetal iron delivery through increased FPN-1 expression. IRP-1 may have a more dominant role than IRP-2 activity in regulating ferritin expression.
Effect of fasting on the V̇o2-fhrelationship in king penguins,Aptenodytes patagonicus
Authors: Fahlman A. , Handrich Y. , Woakes A. J. , Bost C.-A. , Holder R. , Duchamp C. , Butler P. J.
Published: June 2004

King penguins ( Aptenodytes patagonicus) may fast for up to 30 days during their breeding period. As such extended fasting may affect the relationship between the rate of O2consumption (V̇o2) and heart rate ( fH), five male king penguins were exercised at various speeds on repeated occasions during a fasting period of 24–31 days. In addition, V̇o2and fHwere measured in the same animals during rest in cold air and water (4°C). V̇o2and fHat rest and V̇o2during exercise decreased with fasting. There was a significant relation between V̇o2and fH( r2= 0.56) that was improved by including speed, body mass ( Mb), number of days fasting ( t), and a cross term between fHand t ( r2= 0.92). It was concluded that there was a significant change in the V̇o2- fHrelationship with fasting during exercise. As t is measurable in the field and was shown to be significant and, therefore, a practical covariate, a regression equation for use when birds are ashore was obtained by removing speed and Mb. When this equation was used, predicted V̇o2was in good agreement with the observed data, with an overall error of 3.0%. There was no change in the V̇o2- fHrelationship in penguins at rest in water.
Inhibition of bicarbonate reabsorption in the rat proximal tubule by activation of luminal P2Y1receptors
Authors: Bailey Matthew A.
Published: June 2004

The present study used a stationary microperfusion technique to investigate in vivo the effect of P2Y1receptor activation on bicarbonate reabsorption in the rat proximal tubule. Proximal tubules were perfused with a bicarbonate Ringer solution before flow was stopped by means of an oil block. The recovery of lumen pH from the initial value (pH 8.0) to stationary values (pH ∼6.7) was recorded by a H+-sensitive microelectrode inserted downstream of the perfusion pipette and oil block. The stationary pH value and the t of pH recovery were used to calculate bicarbonate reabsorption ( JHCO3). Both EIPA and bafilomycin A1 caused significant reductions in proximal tubule JHCO3, consistent with the established contributions of Na/H exchange and H+-ATPase to proximal tubule HCO3reabsorption. The nucleotides ADP and, to a lesser extent, ATP reduced JHCO3but AMP and UTP were without effect. 2MeSADP, a highly selective agonist of the P2Y1receptor, reduced JHCO3in a dose-dependent manner. MRS-2179, a P2Y1receptor-specific antagonist, abolished the effect of 2MeSADP, whereas theophylline, an antagonist of adenosine (P1) receptors, did not. The inhibitory action of 2MeSADP was blocked by inhibition of protein kinase C and reduced by inhibition of protein kinase A. The effects of EIPA and 2MeSADP were not additive. The data provide functional evidence for P2Y1receptors in the apical membrane of the rat proximal tubule: receptor activation impairs acidification in this nephron segment.
Minocycline inhibits apoptosis and inflammation in a rat model of ischemic renal injury
Authors: Kelly K. J. , Sutton T. A. , Weathered N. , Ray N. , Caldwell E. J. , Plotkin Z. , Dagher P. C.
Published: June 2004

Tetracyclines exhibit significant anti-inflammatory properties in a variety of rheumatologic and dermatologic conditions. They have also been shown to inhibit apoptosis in certain neurodegenerative disorders. Because ischemic renal injury is characterized by both apoptosis and inflammation, we investigated the therapeutic potential of tetracyclines in a rat model of renal ischemia-reperfusion. Male Sprague-Dawley rats underwent bilateral renal artery clamp for 30 min followed by reperfusion and received either minocycline or saline for 36 h before ischemia. Minocycline reduced tubular cell apoptosis 24 h after ischemia as determined by terminal transferase-mediated dUTP nick end-labeling staining and nuclear morphology. It also decreased cytochrome c release into the cytoplasm and reduced upregulation of p53 and Bax after ischemia. The minocycline-treated group showed a significant reduction in tubular injury and cast formation. In addition, minocycline reduced the number of infiltrating leukocytes, decreased leukocyte chemotaxis both in vitro and ex vivo, and downregulated the expression of ICAM-1. Serum creatinine 24-h postischemia was significantly reduced in the minocycline-treated group. We conclude that minocycline has potent antiapoptotic and anti-inflammatory properties and protects renal function in this model of ischemia-reperfusion. Tetracyclines are among the safest and best-studied antibiotics. They are thus attractive candidates for the therapy of human ischemic acute renal failure.
Uncoupling of vasopressin signaling in collecting ducts from rats with CBL-induced liver cirrhosis
Authors: Brønd Lone , Hadrup Niels , Salling Nanna , Torp Malene , Græbe Martin , Christensen Sten , Nielsen Søren , Jonassen Thomas E. N.
Published: June 2004

Vasopressin (AVP) stimulates collecting duct water reabsorption through cAMP-mediated membrane targeting and increased expression of the aquaporin-2 (AQP2) water channel. Rats with liver cirrhosis induced by common bile duct ligation (CBL) show decreased protein expression of AQP2 despite increased plasma concentrations of AVP. The present study was conducted to investigate possible mechanisms behind this uncoupling of AVP signaling. The rats were examined 4 wk after CBL or sham operation. The CBL rats had increased plasma AVP concentrations (CBL: 3.2 ± 0.2 vs. sham: 1.4 ± 0.4 pg/ml, P < 0.05) and reduced AQP2 (0.62 ± 0.11) and phosphorylated AQP2 (0.50 ± 0.06) protein expression compared with sham-operated rats. However, examination of subcellular AQP2 localization by immunohistochemistry showed unchanged plasma membrane targeting in CBL rats, indicating a sustained ability of AQP2 short-term regulation. In a separate series of animals, thirsting was found to normalize AQP2 expression, indicating that AVP uncoupling in CBL rats is a physiological compensatory mechanism aimed at avoiding dilutional hyponatremia. Studies on microdissected collecting ducts from CBL rats showed decreased cAMP accumulation in response to AVP stimulation. The presence of the nonspecific phosphodiesterase inhibitor IBMX normalized the cAMP accumulation, indicating that cAMP-phosphodiesterase activity is increased in CBL rats. However, in contrast to this, Western blotting showed a decreased expression of several phosphodiesterase splice variants. We conclude that CBL rats develop an escape from AVP to prevent the formation of dilutional hyponatremia in response to increased plasma AVP concentrations. The mechanism behind AVP escape seems to involve decreased collecting duct sensitivity to AVP as a result of increased cAMP-phosphodiesterase activity.
Coagulation in the mesangial area promotes ECM accumulation through factor V expression in MsPGN in rats
Authors: Liu Ning , Makino Toshiaki , Nogaki Fumiaki , Kusano Hitoshi , Suyama Katsuo , Muso Eri , Honda Gisho , Kita Toru , Ono Takahiko
Published: June 2004

It is well known that tissue factor starts the extrinsic coagulation pathway, which activates factor X to Xa, and factor V is a membrane-bound potent cofactor for the terminating stage of prothrombin activation by factor Xa. In a previous in vitro study, factor V was induced in cultured mesangial cells by inflammatory stimulation and increased expression of factor V promoted fibrin generation on the cultured mesangial cell surface. We report that extracellular matrix (ECM) accumulation is increased in association with coagulation in the mesangial area through factor V expression in mesangioproliferative glomerulonephritis (MsPGN). Wistar rats were intravenously injected with rabbit anti-rat thymocyte serum accompanied with or without simultaneous injection of rabbit anti-factor V antibody. Time course study in immunohistochemistry revealed that factor V expression was prominent on day 3 and fibrin-related antigen (FRA) deposition, then ECM accumulation, followed from day 3 to day 8. Massive fibronectin depositions and transforming growth factor (TGF)-β expression were also noted in glomeruli from the disease control group, markedly higher than those in the normal group, and these depositions and expressions were significantly decreased in the anti-factor V neutralizing antibody-injected group. Northern blot analysis revealed that factor V mRNA expression was prominent on day 3 and was weak on day 8. Double-labeling experiments revealed the frequent colocalization of α-smooth muscle actin with factor V, FRA, and fibronectin in the same mesangial areas of glomeruli. TGF-β, connective tissue growth factor (CTGF), collagen type IV, and fibronectin mRNA were upregulated in the disease control group, and anti-factor V-neutralizing antibody injection suppressed these mRNA expressions in glomeruli. The present results suggest that ECM components accumulation may progress in accordance with coagulation in the mesangial area through mesangial factor V expression and upregulated expression of TGF-β and CTGF in MsPGN.
Influence of the interleukin-6 −174 G/C gene polymorphism on exercise training-induced changes in glucose tolerance indexes
Authors: McKenzie Jennifer A. , Weiss Edward P. , Ghiu Ioana A. , Kulaputana Onanong , Phares Dana A. , Ferrell Robert E. , Hagberg James M.
Published: June 2004

A polymorphism in the IL-6 gene, a G-to-C substitution 176 bp upstream of the ATG translation initiation site, has been associated with diabetes prevalence and insulin resistance. Interventions including exercise training are frequently used to modify cardiovascular disease risk factors. Consequently, this project examined associations between the IL-6 −174 genotype and oral glucose tolerance test outcomes in 50- to 75-yr-old sedentary men and postmenopausal women before and after aerobic exercise training. Among the 87 individuals who started the study, 56 were retested after 6 mo of aerobic exercise training. Subject characteristics at baseline did not differ between the IL-6 genotype groups with the exception of fasting glucose, which was higher ( P = 0.02, covariates age, gender, and ethnicity) in the CC genotype group. The training-induced change in glucose area under the curve during the oral glucose tolerance test varied between the IL-6 −174 genotype groups ( P = 0.05, covariates age, gender, ethnicity, baseline glucose area under the curve, and percent body fat change) with a significant decrease occurring only in the GG genotype group. Insulin outcomes did not differ among the groups at baseline or after training. Training-induced changes in weight, percent body fat, maximal oxygen consumption, fasting glucose, and an insulin sensitivity index also changed similarly among the genotype groups. In conclusion, fasting glucose and the extent to which glucose tolerance changes with exercise training may be influenced by the IL-6 −174 gene polymorphism.
Reperfusion injury in skeletal muscle is reduced in inducible nitric oxide synthase knockout mice
Authors: Qi Wen-Ning , Chen Long-En , Zhang Li , Eu Jerry P. , Seaber Anthony V. , Urbaniak James R.
Published: June 2004

Inducible nitric oxide synthase (iNOS) participates in many pathological events, and selective inhibition of iNOS has been shown to reduce ischemia-reperfusion (I/R) injury in different tissues. To further confirm its role in this injury process, I/R injury was observed in denervated cremaster muscles of iNOS-deficient (iNOS−/−) and wild-type mice. After 3-h ischemia and 90-min reperfusion, blood flow in reperfused muscle was 80 ± 8.5% (mean ± SE) of baseline at 10-min reperfusion and completely returned to the preischemia baseline after 20 min in iNOS−/− mice. In contrast, blood flow was 32 ± 7.4% at 10 min and increased to 60 ± 20% of the baseline level at 90 min in wild-type mice ( P < 0.001 vs. iNOS−/− mice at all time points). The increased muscle blood flow in iNOS−/− mice was associated with significantly less vasospasm in all three sizes of arterial vessel size categories. The weight ratio to the contralateral muscle not subjected to I/R was greater in wild-type mice (173 ± 11%) than in iNOS−/− mice (117 ± 3%; P < 0.01). Inflammation and neutrophil extravasation were also more severe in wild-type mice. Western blot analysis demonstrated an absence of iNOS protein band in iNOS−/− mice and upregulation of iNOS protein expression in wild-type mice. Our results confirm the importance of iNOS in I/R injury. Upregulated iNOS exacerbates I/R injury and appears to be a therapeutic target in protection of tissues against this type of injury.
Hypoxic reduction in cellular glutathione levels requires mitochondrial reactive oxygen species
Authors: Mansfield Kyle D. , Simon M. Celeste , Keith Brian
Published: June 2004

When exposed to hypoxia (1.5% O2), several cell types have been shown to increase production of reactive O2species derived from the mitochondrial electron transport chain (mtROS). The general physiological consequences of hypoxic mtROS production are not completely understood, although several groups have demonstrated that mtROS promote the stabilization and activity of hypoxia inducible factor-1α (HIF-1α) transcription factor, alter cardiac myocyte contractility, and modulate Na+-K+-ATPase activity. To investigate the effects of hypoxia-induced mtROS on general cellular oxidative metabolism, we measured the levels of glutathione, a major cellular antioxidant, in response to hypoxic treatment. Our data indicate that HEK293 and Hep3B cells exposed to 1.5% O2exhibit a time-dependent decrease in cellular glutathione stores and concomitant inhibition of glutathione biosynthesis, which correlates to impaired transport of the substrate cystine. Using a combination of ROS scavengers, mitochondrial electron transport inhibitors, and mitochondrial DNA-deficient ρ0cells, we demonstrate that this decrease in cellular glutathione levels is mediated by hypoxia-induced mtROS. Intriguingly, this effect is also inhibited by cyclohexamide but is not dependent on HIF-mediated transcription. Overall, these data suggest a novel HIF-independent role for mitochondrial ROS in regulating glutathione synthesis, and hence cellular oxidative homeostasis, during hypoxic exposure.
Origin of Orientation-Dependent Asymmetries in Vestibulo-Ocular Reflexes Evoked by Caloric Stimulation
Authors: Peterka Robert J. , Gianna-Poulin Claire C. , Zupan Lionel H. , Merfeld Daniel M.
Published: June 2004

A caloric stimulus evokes primarily a horizontal vestibulo-ocular reflex (VOR) when subjects are in a supine or prone orientation with the horizontal semicircular canal plane oriented vertically. In both monkeys and humans, the magnitude of VOR eye movements is greater in the supine than in the prone orientation, indicating that some factor or factors, other than the conventionally accepted convective stimulation of the horizontal canals, contributes to the generation of the VOR. We used long-duration caloric irrigations and mathematical models of canal-otolith interactions to investigate factors contributing to the prone/supine asymmetry. Binaural caloric irrigations were applied for 7.5 or 9.5 min with subjects in a null orientation with horizontal canals in the earth-horizontal plane (control trial), or with the subject's pitch orientation periodically changing between null, supine, and prone positions with each orientation held for 30 s (caloric step trial). The control trial responses identified a small response attributable to a direct thermal effect on vestibular afferent activity that accounted for only 15% of the observed prone/supine asymmetry. We show that the gravito-inertial force resolution hypothesis for sensory integration of canal and otolith information predicts that the central processing of canal and otolith information produces an internal estimate of motion that includes both a rotational motion component and a linear acceleration component. These components evoke a horizontal angular VOR and linear VOR, which combine additively in the supine orientation, but subtract in the prone orientation, thus accounting for the majority of the observed prone/supine asymmetry.
Brain State–Dependency of Coherent Oscillatory Activity in the Cerebral Cortex and Basal Ganglia of the Rat
Authors: Magill Peter J. , Sharott Andrew , Bolam J. Paul , Brown Peter
Published: June 2004

The nature of the coupling between neuronal assemblies in the cerebral cortex and basal ganglia (BG) is poorly understood. We tested the hypothesis that coherent population activity is dependent on brain state, frequency range, and/or BG nucleus using data from simultaneous recordings of electrocorticogram (ECoG) and BG local field potentials (LFPs) in anesthetized rats. The coherence between ECoG and LFPs simultaneously recorded from subthalamic nucleus (STN), globus pallidus (GP), and substantia nigra pars reticulata (SNr) was largely confined to slow- (∼1 Hz) and spindle- (7–12 Hz) frequency oscillations during slow-wave activity (SWA). In contrast, during cortical activation, coherence was mostly restricted to high-frequency oscillations (15–60 Hz). The coherence between ECoG and LFPs also depended on BG recording site. Partial coherence analyses showed that, during SWA, STN and SNr shared the same temporal coupling with cortex, thereby forming a single functional axis. Cortex was also tightly, but independently, correlated with GP in a separate functional axis. During activation, STN, GP, and, to a lesser extent, SNr shared the same coherence with cortex as part of one functional axis. In addition, GP formed a second, independently coherent loop with cortex. These data suggest that coherent oscillatory activity is present at the level of LFPs recorded in cortico-basal ganglia circuits, and that synchronized population activity is dynamically organized according to brain state, frequency, and nucleus. These attributes further suggest that synchronized activity should be considered as one of a number of candidate mechanisms underlying the functional organization of these brain circuits.
Dexterous Finger Movements in Primate Without Monosynaptic Corticomotoneuronal Excitation
Authors: Sasaki Shigeto , Isa Tadashi , Pettersson Lars-Gunnar , Alstermark Bror , Naito Kimisato , Yoshimura Kazuya , Seki Kazuhiko , Ohki Yukari
Published: June 2004

It is generally accepted that the precision grip and independent finger movements (IFMs) in monkey and man are controlled by the direct (monosynaptic) corticomotoneuronal (CM) pathway. This view is based on previous observations that pyramidotomy causes near permanent deficits of IFMs. However, in addition to the direct CM pathway, pyramidotomy interrupts several corticofugal connections to the brain stem and upper cervical segments. Indirect (oligosynaptic) CM pathways, which are phylogenetically older, have been considered to be of little or no importance in prehension. In three adult macaque monkeys, complete transection of the direct CM pathway was made in C4/C5, which is rostral to the forelimb segments (C6–Th1). Electrophysiological recordings revealed lack of the direct lateral corticospinal tract (LCST) volley, monosynaptic extracellular field potentials in the motor nuclei, and monosynaptic CM excitation. However, a disynaptic volley, disynaptic field potentials and disynaptic CM excitation mediated via C3–C4 propriospinal neurons remained after the lesion. Thus the lesion interrupted the monosynaptic CM pathway and oligosynaptic LCST pathways mediated by interneurons in the forelimb segments. Precision grip and IFMs were observed already after 1–28 days postoperatively. Weakness in force and deficits in preshaping remained for an observation period of 3 mo. Indirect CM pathways may be important for neuro-rehabilitation.
Brief Trains of Action Potentials Enhance Pyramidal Neuron Excitability Via Endocannabinoid-Mediated Suppression of Inhibition
Authors: Fortin Dale A. , Trettel Joseph , Levine Eric S.
Published: June 2004

Depolarization-induced suppression of inhibition (DSI) is a form of retrograde signaling at GABAergic synapses that is initiated by the calcium- and depolarization-dependent release of endocannabinoids from postsynaptic neurons. In the neocortex, pyramidal neurons (PNs) appear to use DSI as a mechanism for regulating somatic inhibition from a subpopulation of GABAergic inputs that express the type 1 cannabinoid receptor. Although postsynaptic control of afferent inhibition may directly influence the integrative properties of neocortical PNs, little is known about the patterns of activity that evoke endocannabinoid release and the impact such disinhibition may have on the excitability of PNs. Here we provide the first systematic survey of action potential (AP)-induced DSI in the neocortex. The magnitude and time course of DSI was directly related to the number and frequency of postsynaptic APs with significant suppression induced by a 20-Hz train containing as few as three APs. This AP-induced DSI was mediated by endocannabinoids as it was prevented by the cannabinoid receptor antagonist AM251 and potentiated by the endocannabinoid transport inhibitor AM404. We also explored the effects of endocannabinoid-mediated DSI on PN excitability. We found that single AP trains markedly increased PN responsiveness to excitatory synaptic inputs and promoted AP discharge by suppressing GABAergic inhibition. The time course of this effect paralleled DSI expression and was completely blocked by AM251. Taken together, our data suggest a role for endocannabinoids in regulating the output of cortical PNs.
Functional Connectivity Between the Red Nucleus and the Hippocampus Supports the Role of Hippocampal Formation in Sensorimotor Integration
Authors: Dypvik Audny T. , Bland Brian H.
Published: June 2004

Experiments were carried out in urethane-anesthetized rats to evaluate the hypothesis that the red nucleus has functional connections with the hippocampal formation. Depth profiles of electrical stimulation in experiment 1 confirmed that stimulation administered to the red nucleus elicited theta field activity in the hippocampal formation with a linear relationship between stimulus intensity and theta frequency. Experiment 2 showed that microinfusion of local anesthetic procaine hydrochloride into the medial septum resulted in a reversible blockade of theta field activity elicited by electrical stimulation of the red nucleus. In experiment 3, the discharge activity of red nucleus cells was recorded during the field conditions of hippocampal synchrony (theta) and hippocampal asynchrony [large amplitude irregular activity (LIA)]. Analysis revealed that 26/46 (56%) of red nucleus cells were theta-related, whereas the remaining 20 (44%) were nonrelated. The majority of theta-related cells were classified as tonic theta-on. A brief increase above the basal discharge rate of tonic theta-on red nucleus cells during LIA predicted the transition from LIA to theta with 400- to 500-ms latency. Furthermore, higher frequency transitional discharges predicted higher theta frequencies, whereas higher discharge rates during theta predicted shifts to higher theta frequencies. The results supported the conclusion that the red nucleus, traditionally associated with motor functions, is functionally connected with the neural circuitry involved in the generation of theta band oscillation and synchrony in the hippocampal formation, in agreement with the predictions of the sensorimotor integration model of hippocampal function.
Blockade of Glycine Transporter-1 (GLYT-1) Potentiates NMDA Receptor-Mediated Synaptic Transmission in Hypoglossal Motorneurons
Authors: Lim Rebecca , Hoang Priscilla , Berger Albert J.
Published: June 2004

NMDA receptor (NMDAR)-mediated spontaneous miniature excitatory postsynaptic currents (mEPSCs) are potentiated by exogenously applied glycine. In this study, we have investigated the effect of blocking glycine uptake on NMDAR-mediated responses from hypoglossal motorneurons (HMs) of rats. We have used N[3-(4′-fluorophenyl)-3-(4′-phenylphenoxy)-propyl]sarcosine (NFPS; 500 nM), an antagonist of glycine transporter-1 (GLYT1), to study the effect of blocking endogenous glycine uptake on NMDAR-mediated synaptic transmission. We show that the charge transfer of NMDAR-mediated mEPSCs was enhanced after NFPS application in neonate (P2-4) and juvenile rats (P8-11), but this enhancement was statistically significant only in the former group. Spontaneous and evoked EPSCs showed a significant increase in NMDAR-mediated charge transfer in both neonates and juveniles. The greater increase observed in spontaneous EPSCs may be due to increased release of glycine from glycinergic terminals in the absence of tetrodotoxin (TTX). Brief application of NMDA onto HMs showed that extrasynaptic NMDARs may be potentiated by NFPS only in the presence of extracellularly applied glycine. Immunohistochemistry of GLYT1 and -2 shows labeling throughout the hypoglossal nucleus. GLYT1 labeling is diffuse and becomes more intense and uniform during development consistent with its glial localization. In contrast, GLYT2 labeling is intense throughout the nucleus and increases in intensity with age. Our results demonstrate the glycine binding site of the NMDAR is not saturated in the brain stem slice during the first 2 wk of development. We suggest that modulation of glycine concentration by GLYT1 is an important mechanism to regulate NMDAR-mediated synaptic transmission.
Direction-Dependent Phasing of Locomotor Muscle Activity Is Altered Post-Stroke
Authors: Schindler-Ivens Sheila , Brown David A. , Brooke John D.
Published: June 2004

A major contributor to impaired locomotion post-stroke is abnormal phasing of muscle activity. While inappropriate paretic muscle phasing adapts to changing body orientation, load, and speed, it remains unclear whether paretic muscle phasing adapts to reversal of locomotor direction. We examined muscle phasing in backward pedaling, a task that requires shifts in biarticular but not uniarticular muscle phasing relative to forward pedaling. We hypothesized that if paretic and neurologically intact muscle phasing adapt similarly, then paretic biarticular but not paretic uniarticular muscles would shift phasing in backward pedaling. Paretic and neurologically intact individuals pedaled forward and backward while recording electromyograms (EMGs) from vastus medialis (VM), soleus (SOL), rectus femoris (RF), semimembranosus (SM), and biceps femoris (BF). Changes in muscle phasing were assessed by comparing the probability of muscle activity in forward and backward pedaling throughout 18 pedaling cycles. Paretic uniarticular muscles (VM and SOL) showed phase-advanced activity in backward versus forward pedaling, whereas the corresponding neurologically intact muscles showed little to no phasing change. Paretic biarticular muscles were less likely than neurologically intact biarticular muscles to display phasing changes in backward pedaling. Paretic RF displayed no phase change during backward pedaling, and paretic BF displayed no consistent adaptation to backward pedaling. Paretic SM was the only muscle to display backward/forward phase changes that were similar to the neurologically intact group. We conclude that paretic uniarticular muscles are more susceptible and paretic biarticular muscles are less susceptible to direction-dependent phase shifts, consistent with altered sensory integration and impaired cortical control of locomotion.
Synthesis and crystallochemistry of Na4CrNi(PO4)3
Authors: Manoun B. , El Jazouli A. , Krimi S. , Lachgar A.
Published: June 2004

Na4CrNi(PO4)3 orthophosphate powder was prepared from acid solutions of NiO, Na2CO3 and aqueous solutions of Cr(NO3)3.9H2O, and (NH4)2HPO4 at a final temperature of 750 °C. The hexagonal unit cell parameters were determined to be ah≈8.789 Å and ch≈21.481 Å in space group R3¯c. These parameters were compared to those of Na4AA′(PO4)3 (AA′=CrMg, CrCo, TiNa, ZrNa). The linear variations of these parameters versus the mean A cation radius (rAA′) are consistent with the atomic distribution found for the structure of Na4NiCr(PO4)3. The ah and ch parameters are functions of the An+ ion size.
Crystal structure of Ca1−xSrxZr4(PO4)6 (0≤x≤1)
Authors: Fischer Werner , Singheiser Lorenz , Basu Debabrata , Dasgupta Amit
Published: June 2004

The crystal structure of several compounds of Ca1−xSrxZr4(PO4)6 ceramics has been investigated by X-ray powder diffraction at room temperature. All compounds form a solid solution with a unique unit cell. While the lattice parameter a of the hexagonal unit cell decreases of about 0.9% with increasing Sr content only slightly, it considerably elongates in c direction (2.8%). No structural transformation has been observed by high-temperature X-ray diffraction up to 1000 °C.
Application of the Rietveld method to quantitative analysis of impurities in synthetic diamond powder
Authors: Rashmi  , Singh Nahar , Sarkar A. K.
Published: June 2004

Synthetic diamonds are an important class of industrial material. During synthesis impurities may get introduced into diamond. Identification and quantification of impurities is important as they affect the properties and suitability of the diamonds for their application. Impurities in an industrial synthetic diamond powder sample were analyzed by X-ray diffraction (XRD) and also by chemical methods. X-ray diffraction pattern showed diamond as the major phase and α-iron as a minor phase. Quantitative analysis of crystalline phases was done by performing Rietveld refinement of the XRD profile. Chemical analysis showed the presence of several other impurities as well, though in small amounts. It was considered that the impurities other than iron were in amorphous form and an estimate of the amorphous content was made on this basis. Relative phase composition of diamond and iron as estimated by XRD were corrected for the amorphous content to obtain absolute phase composition.
Effect of Cr doping on the structure of (Pr0.55Ca0.45)(Mn1−yCry)O3: A Rietveld refinement study
Authors: Martinelli A. , Ferretti M. , Castellano C.
Published: June 2004

(Pr0.55Ca0.45)(Mn1−yCry)O3 (with y=0.00, 0.03, and 0.06) have been prepared by means of a solid state reaction from stoichiometric powder mixtures of binary oxides. X-ray powder diffraction analysis reveals the formation of the perovskite-type compound for the whole considered compositions; no evidence for secondary phases may be detected. The structural refinements have been carried out using X-ray powder diffraction data applying the Rietveld method; the lattice parameters of the orthorhombic cell faintly change with composition. On the contrary the tilting of the octahedra results are strongly dependent on the concentration of Cr in the 4b site. Bond valence sum method has been applied in order to evaluate the possible presence of lattice-induced strains and the amount of Mn4+. Structural data are also reported.