bluuebunny/crossref_metadata_2025 huggingface dataset:
AUTOMATED DATA FUSION AND SITUATION ASSESSMENT IN SPACE SYSTEMS
Authors: HANSON MARK L. , GONSALVES PAUL G. , TSE JESSICA , GREY RACHEL
Published: April 2004

Space systems are an important part of everyday life. They provide global positioning data, communications, and Earth science data such as weather information. All space systems require satellite operators to ensure high performance and continuous operations in the presence of off-nominal conditions due to space weather and onboard anomalies. Similar to other high-stress, time critical operations (e.g., piloting an aircraft or operating a nuclear power plant), situation awareness is a crucial factor in operator performance during these conditions. Because situation awareness is largely acquired by monitoring large numbers of parameters, it is difficult to rapidly and accurately fuse the data to develop an accurate assessment. To aid operators in this task, we have developed a prototype Multi-Agent Satellite System for Information Fusion (MASSIF) for automated data fusion and situation awareness. This system is based on human cognitive decision-making models and integrates a fuzzy logic system for semantic data processing, Bayesian belief networks for multi-source data fusion and situation assessment, and rule-bases for automatic network construction. This paper describes initial simulation-based results to establish feasibility and baseline performance. We describe knowledge engineering efforts, belief network construction, and operator-interfaces for automated data fusion and situation awareness for a hypothetical geosynchronous satellite.
Acidic duodenal pH alters gene expression in the cystic fibrosis mouse pancreas
Authors: Kaur Simran , Norkina Oxana , Ziemer Donna , Samuelson Linda C. , De Lisle Robert C.
Published: April 2004

The duodenum is abnormally acidic in cystic fibrosis (CF) due to decreased bicarbonate ion secretion that is dependent on the CF gene product CFTR. In the CFTR null mouse, the acidic duodenum results in increased signaling from the intestine to the exocrine pancreas in an attempt to stimulate pancreatic bicarbonate ion secretion. Excess stimulation is proposed to add to the stress/inflammation of the pancreas in CF. DNA microarray analysis of the CF mouse revealed altered pancreatic gene expression characteristic of stress/inflammation. When the duodenal pH was corrected genetically (crossing CFTR null with gastrin null mice) or pharmacologically (use of the proton pump inhibitor omeprazole), expression levels of genes measured by quantitative RT-PCR were significantly normalized. It is concluded that the acidic duodenal pH in CF contributes to the stress on the exocrine pancreas and that normalizing duodenal pH reduces this stress.
Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro
Authors: Tuo Bi-Guang , Chow Jimmy Y. C. , Barrett Kim E. , Isenberg Jon I.
Published: April 2004

PKC has been shown to regulate epithelial Cl-secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Iscin a concentration-dependent manner (from 10-8to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.
Impact of leukocytes and platelets in mediating hepatocyte apoptosis in a rat model of systemic endotoxemia
Authors: Eipel C. , Bordel R. , Nickels R. M. , Menger M. D. , Vollmar B.
Published: April 2004

Apoptotic hepatocytes have been demonstrated to represent an important signal for transmigration of leukocytes sequestered in sinusoids during endotoxemia in vivo. Beside leukocytes, platelets and their adhesion to endothelial cells and leukocytes have been implicated in inflammatory liver injury. Using in vivo multifluorescence microscopy, we examined the possibility that hepatocellular apoptosis causes both leukocytes and platelets to colocalize within the sinusoidal microvasculature of endotoxemic livers. We further addressed the issue whether cellular colocalization with apoptotic hepatocytes is cause or consequence of apoptosis. Intraperitoneal exposure of rats with LPS (5 mg/kg) induced liver injury after 6 and 16 h, as given by nutritive perfusion failure (20 ± 2 and 21 ± 2%), intrahepatic leukocyte (60 ± 10 and 121 ± 48 cells/mm2), and platelet (12 ± 4 and 34 ± 4 cells/mm2) accumulation as well as parenchymal cell apoptosis (4 ± 1 and 11 ± 2 cells/mm2) and caspase cleavage (4.7 ± 2.4- and 7.0 ± 3.0-fold increase; P < 0.05 vs. saline-exposed controls). Higher doses of LPS (10 mg/kg ip) further increased intrahepatic leukocyte and platelet accumulation but not the extent of parenchymal apoptosis. Detailed spatial analysis revealed colocalization of leukocytes (range 12–24%) but barely of platelets (<6%) with apoptotic hepatocytes in all endotoxemic groups studied. It is of interest, however, that platelets were found at increasing rates in colocalization with leukocytes at 6 and 16 h after LPS exposure (5 mg/kg LPS: 7 ± 3 and 25 ± 6%; 10 mg/kg LPS: 11 ± 4 and 14 ± 1%). Platelet-leukocyte events significantly correlated with the extent of caspase cleavage as an indicator of tissue apoptosis ( P < 0.05; r = 0.82). Blockade of apoptosis by a pan-caspase inhibitor caused a significant reduction of leukocyte adherence and platelet-leukocyte colocalization on LPS exposure. On the other hand, leukocytopenic animals revealed reduced hepatocyte apoptosis, although values still exceeded those of controls, and in leuko- and thrombocytopenic animals, hepatocyte apoptosis was found reduced to control values. Taken together, LPS-associated hepatocyte apoptosis seems to be initiated by circulating blood cells that become adherent within the liver but might also contribute to further sustain the inflammatory cell-cell response.
Inhibition of acid secretion by the nonsteroidal anti-inflammatory drugs diclofenac and piroxicam in isolated gastric glands: analysis of a multifocal mechanism
Authors: Salvatella María , Rossi Irma , Del Valle Juan C. , Gutiérrez Yolanda , Pereda Carmen , Samper Begoña , Felíu Juan E.
Published: April 2004

In nonstimulated rabbit gastric glands, acetylsalicylic acid (10–500 μM) and indomethacin (3–300 μM) did not significantly modify the basal rate of acid secretion, whereas diclofenac and piroxicam (10–1,000 μM each) caused a marked and dose-dependent inhibitory effect (EC50= 138 and 280 μM, respectively). In gastric glands stimulated by histamine (100 μM), diclofenac also reduced the rate of acid formation in a dose-dependent manner. In contrast, acetylsalicylic acid, indomethacin, and piroxicam exerted a biphasic effect; thus low concentrations (3–100 μM) of these three agents significantly increased the rate of histamine-stimulated acid secretion (10–20% over the corresponding control value) by a cAMP-independent mechanism, whereas higher concentrations reduced the rate of acid formation. With respect to underlying biochemical mechanisms that could mediate inhibitory effects of NSAIDs on gastric acid formation, it was observed that both diclofenac and piroxicam, but not acetylsalicylic acid or indomethacin, decreased the glandular content of ATP, inhibited hydrolytic activity of gastric gland microsomal H+-K+-ATPase, and reduced the rate of H+-K+-ATPase-dependent proton transport across microsomal membranes in a dose-dependent manner. Furthermore, diclofenac and piroxicam also significantly increased passive permeability of microsomal membranes to protons. In conclusion, our work shows that diclofenac and piroxicam cause a significant reduction in the rate of basal and histamine-stimulated acid formation in isolated rabbit gastric glands at concentrations that can be attained in the gastric lumen of patients treated with these drugs. Mechanisms involved in these inhibitory effects appear to be multifocal and include different steps of stimulus-secretion coupling.
Inhibition of lipopolysaccharide-stimulated TNF-α promoter activity byS-adenosylmethionine and 5′-methylthioadenosine
Authors: Veal Nary , Hsieh Chih-Lin , Xiong Shigang , Mato Jose M. , Lu Shelly , Tsukamoto Hidekazu
Published: April 2004

S-adenosylmethionine (SAM) is the principal biological methyl donor and precursor for polyamines. SAM is known to be hepatoprotective in many liver disease models in which TNF-α is implicated. The present study investigated whether and how SAM inhibited LPS-stimulated TNF-α expression in Kupffer cells (hepatic macrophages). SAM downregulated TNF-α expression in LPS-stimulated Kupffer cells at the transcriptional level as suggested by a transfection experiment with a TNF-α promoter-reporter gene. This inhibition was not mediated through decreased NF-κB binding to four putative κB binding elements located within the promoter. The inhibited promoter activity was neither prevented by overexpression of p65 and/or its coactivator p300 nor enhanced by overexpression of coactivator-associated arginine methyltransferase-1, an enzyme that methylates p300 and inhibits a p65-p300 interaction. SAM did not lead to DNA methylation at the most common CpG target sites in the TNF-α promoter. Moreover, 5′-methylthioadenosine (MTA), which is derived from SAM but does not serve as a methyl donor, recapitulated SAM's effect with more potency. These data demonstrate that SAM inhibits TNF-α expression at the level downstream of NF-κB binding and at the level of the promoter activity via mechanisms that do not appear to involve the limited availability of p65 or p300. Furthermore, our study is the first to demonstrate a potent inhibitory effect on NF-κB promoter activity and TNF-α expression by a SAM's metabolite, MTA.
Putative intestine-specific enhancers located in 5′ sequence of theCDX1gene regulateCDX1expression in the intestine
Authors: Rankin Erinn B. , Xu Wei , Silberg Debra G. , Suh EunRan
Published: April 2004

CDX1 is a homeobox transcription factor that plays a critical role in intestinal epithelial cell growth and differentiation. CDX1 gene expression is tightly regulated in a temporal and cell-type specific manner. However, very little is known about the regulatory mechanisms that direct CDX1 gene expression in the intestine. To elucidate these mechanisms, we employed a series of transgenic mouse studies using the 5′ flanking sequences of the human CDX1 gene. Transgenic mice containing nucleotides between -5667 and +68 relative to the transcription start site of the CDX1 gene demonstrated ectopic expression of the transgene in the brain and gastric smooth muscle. However, transgenic expression of the nucleotides -15601 to +68 of the CDX1 gene was restricted to the intestinal epithelium, which was identical to endogenous CDX1 gene expression. Taken together, the upstream sequences between -15601 and -5667 contain regulatory elements that direct transgene expression specifically to the intestinal epithelium. Furthermore, DNase I hypersensitivity assays revealed two active chromatin regions in the CDX1 gene (hypertensive sites 1 and 2) located at approximately -5.8 and -6.8 kb upstream of the CDX1 gene, respectively, which may function as potential intestine-specific enhancers.
Effect of hyperglycemia on triggering of transient lower esophageal sphincter relaxations
Authors: Zhang Qing , Horowitz Michael , Rigda Rachael , Rayner Christopher , Worynski Andrew , Holloway Richard H.
Published: April 2004

Acute changes in blood glucose concentration have major effects on gastrointestinal motor function. Patients with diabetes mellitus have an increased prevalence of gastroesophageal reflux. Transient lower esophageal sphincter (LES) relaxation (TLESR) is the most common sphincter mechanism underlying reflux. The aim of this study was to investigate the effect of acute hyperglycemia on triggering TLESRs evoked by gastric distension in healthy volunteers. TLESRs were stimulated by pressure-controlled and volume-controlled (500 ml) gastric distension using an electronic barostat and performed on separate days. On each day, esophageal manometry was performed in the sitting position during gastric distension for 1 h under euglycemia (5 mM), and either marked hyperglycemia (15 mM) or physiological hyperglycemia (8 mM) in randomized order was maintained by a glucose clamp. Marked hyperglycemia doubled the rate of TLESRs in response to both pressure-controlled [5 (3–10.5, median or interquartile range) to 10 (9.5–14.5) per hour, P < 0.02] and volume-controlled [4 (2.5–7.5) to 10.5 (7–12.5) per hour, P < 0.02] gastric distension but had no effect on basal LES pressure. Physiological hyperglycemia had no effect on the triggering of TLESRs or basal LES pressure. In healthy human subjects, marked hyperglycemia increases the rate of TLESRs. Increase in the rate of TLESRs is independent of proximal gastric wall tension. Mechanisms underlying the effect remain to be determined. Hyperglycemia may be an important factor contributing to the increased esophageal acid exposure in patients with diabetes mellitus.
Lack of biliary lipid excretion in the little skate,Raja erinacea, indicates the absence of functional Mdr2, Abcg5, and Abcg8 transporters
Authors: Elferink Ronald P. J. Oude , Ottenhoff Roelof , Fricker Gert , Seward David J. , Ballatori Nazzareno , Boyer James
Published: April 2004

The ABC transporters bile salt export pump (BSEP; encoded by the ABCB11 gene), MDR3 P-glycoprotein ( ABCB4), and sterolin 1 and 2 ( ABCG5 and ABCG8) are crucial for the excretion of bile salt, phospholipid, and cholesterol, respectively, into the bile of mammals. The current paradigm is that phospholipid excretion mainly serves to protect membranes of the biliary tree against bile salt micelles. Bile salt composition and cytotoxicity, however, differ greatly between species. We investigated whether biliary phospholipid and cholesterol excretion occurs in a primitive species, the little skate, which almost exclusively excretes the sulphated bile alcohol scymnolsulphate. We observed no phospholipid and very little cholesterol excretion into bile of these animals. Conversely, when scymnolsulphate was added to the perfusate of isolated mouse liver perfusions, it was very well capable of driving biliary phospholipid and cholesterol excretion. Furthermore, in an erythrocyte cytolysis assay, scymnolsulphate was found to be at least as cytotoxic as taurocholate. These results demonstrate that the little skate does not have a system for the excretion of phospholipid and cholesterol and that both the MDR3 and the two half-transporter genes, ABCG5 and ABCG8, have evolved relatively late in evolution to mediate biliary lipid excretion. Little skate plasma membranes may be protected against bile salt micelles mainly by their high sphingomyelin content.
Treatment of EFA deficiency with dietary triglycerides or phospholipids in a murine model of extrahepatic cholestasis
Authors: Werner Anniek , Havinga Rick , Kuipers Folkert , Verkade Henkjan J.
Published: April 2004

Essential fatty acid (EFA) deficiency during cholestasis is mainly due to malabsorption of dietary EFA ( 23 ). Theoretically, dietary phospholipids (PL) may have a higher bioavailability than dietary triglycerides (TG) during cholestasis. We developed murine models for EFA deficiency (EFAD) with and without extrahepatic cholestasis and compared the efficacy of oral supplementation of EFA as PL or as TG. EFAD was induced in mice by feeding a high-fat EFAD diet. After 3 wk on this diet, bile duct ligation was performed in a subgroup of mice to establish extrahepatic cholestasis. Cholestatic and noncholestatic EFAD mice continued on the EFAD diet (controls) or were supplemented for 3 wk with EFA-rich TG or EFA-rich PL. Fatty acid composition was determined in plasma, erythrocytes, liver, and brain. After 4 wk of EFAD diet, induction of EFAD was confirmed by a sixfold increased triene-to-tetraene ratio (T/T ratio) in erythrocytes of noncholestatic and cholestatic mice ( P < 0.001). EFA-rich TG and EFA-rich PL were equally effective in preventing further increase of the erythrocyte T/T ratio, which was observed in cholestatic and noncholestatic nonsupplemented mice (12- and 16-fold the initial value, respectively). In cholestatic mice, EFA-rich PL was superior to EFA-rich TG in decreasing T/T ratios of liver TG and PL (each P < 0.05) and in increasing brain PL concentrations of the long-chain polyunsaturated fatty acids (LCPUFA) docosahexaenoic acid and arachidonic acid (each P < 0.05). We conclude that oral EFA supplementation in the form of PL is more effective than in the form of TG in increasing LCPUFA concentrations in liver and brain of cholestatic EFAD mice.
Inflammation and Cancer III. Somatostatin and the innate immune system
Authors: Zavros Yana , Kao John Y. , Merchant Juanita L.
Published: April 2004

In the stomach, somatostatin is secreted from D cells and is a potent inhibitor of gastrin-induced acid secretion. During bacterial infection, somatostatin expression and release are suppressed. As a result, gastric infection often induces hypergastrinemia that, in turn, stimulates gastric acid secretion, the stomach's most important antimicrobial agent. There are an abundance of data showing that inflammatory cytokines regulate somatostatin in immune and neural cells. However, it was not until recently that the immunoregulation of gastric somatostatin was studied in vivo. This theme article discusses the role of somatostatin as an immunoregulatory peptide during gastritis.
Influence of cytokines and growth factors in ANG II-mediated collagen upregulation by fibroblasts in rats: role of myocytes
Authors: Sarkar Sagartirtha , Vellaichamy Elangovan , Young David , Sen Subha
Published: April 2004

Abnormal stiffness and altered cardiac function arising from abnormal collagen deposition occur in hypertrophy and heart failure. ANG II has been shown to play a role in this process. To evaluate the mechanism, we developed an in vitro model by subjecting fibroblasts to ANG II treatment in the presence or absence of myocytes in coculture ( 25 ). Employing this model, we demonstrated that ANG II-induced collagen gene transcription in cardiac fibroblasts was potentiated by myocyte-derived factors. In attempting to identify mechanisms of collagen upregulation and to define the role of myocytes, we found that interleukin (IL)-6, tumor necrosis factor (TNF)-α, and the transforming growth factor (TGF)-β superfamily were also involved in collagen upregulation. Collagen transcripts were increased after fibroblasts were treated with IL-6 (20–50 ng/ml) and TNF-α (0.1–0.5 ng/ml). In this study, we show that cardiomyocytes induce secretion of active TGF-β in the presence of ANG II and that a paracrine action of TGF-β subsequently induces different cytokines (IL-6) in fibroblasts, thereby promoting collagen synthesis. The cross-talk between myocytes and fibroblasts and involvement of these cytokines in the upregulation of collagen transcript levels are novel findings that may explain their possible roles in the upregulation of collagen.
Lipopolysaccharide induces expression of fibronectin α5β1-integrin receptors in human monocytic cells in a protein kinase C-dependent fashion
Authors: Roman Jesse , Ritzenthaler Jeffrey D. , Boles Bonnie , Lois Manuel , Roser-Page Susanne
Published: April 2004

LPS is an outer-membrane glycolipid component of gram-negative bacteria known for its fervent ability to activate monocytic cells and for its potent proinflammatory capabilities. In addition, LPS triggers the release of cytokines and chemokines as well as cell-cell adhesion molecules. We postulate that LPS may also affect the expression of matrix-binding integrin receptors, thereby modulating cell-adhesive functions in monocytic cells. To test this hypothesis, we investigated the effects of LPS on the expression of the integrin α5β1, a fibronectin receptor, in a human monocytic cell line (U937) as well as in isolated human peripheral blood mononuclear cells (PBMCs). We found that LPS increased the expression of α5β1receptors and enhanced the adherence of U937 cells and PBMCs to fibronectin-coated surfaces; this was blocked by anti-α5β1antibodies. LPS increased α5-subunit mRNA accumulation in a dose- and time-dependent manner. The induction by LPS occurred, at least in part, at the level of gene transcription as indicated by experiments using α5intact and deletion promoter constructs. LPS-induced α5gene transcription was associated with rapid induction of conventional PKC-α protein and activity, was blocked by PKC inhibitors, and was mimicked by lipid A. Finally, we found that an anti-CD14 antibody was able to inhibit the LPS response. Overall, the data suggest that LPS stimulates α5gene transcription via CD14 and PKC-dependent signals to enhance the expression of functional α5β1receptors in monocytic cells. This process may help stimulate monocytic cell activation and facilitate their migration into fibronectin-containing tissues during infection.
Relationship between renal sympathetic nerve activity and renal blood flow during natural behavior in rats
Authors: Yoshimoto Misa , Sakagami Tamaki , Nagura Satsuki , Miki Kenju
Published: April 2004

The purpose of the present study was to determine the relationship between renal sympathetic nerve activity (RSNA) and renal blood flow (RBF) during normal daily activity in conscious, chronically instrumented Wistar rats ( n = 8). The animal's behavior was classified as rapid eye movement (REM) sleep, non-REM (NREM) sleep, quiet awake, moving, and grooming states. On average RSNA was lowest during REM sleep, which was decreased by 39.0 ± 3.2% ( P < 0.05) relative to NREM sleep, and rose linearly with an increase in activity level in the order of quiet awake (by 10.9 ± 1.8%, P < 0.05), moving (by 29.4 ± 2.9%, P < 0.05), and grooming (by 65.3 ± 3.9%, P < 0.05) relative to NREM sleep. By contrast, RBF was highest during REM sleep, which was increased by 4.8 ± 0.7% ( P < 0.05) relative to NREM sleep and decreased significantly ( P < 0.05) by 5.5 ± 0.6 and 6.6 ± 0.5% during moving and grooming states, respectively, relative to NREM sleep. There was a significant ( P < 0.05) inverse linear relationship between the percent changes in RSNA and RBF and between those in RSNA and renal vascular conductance. Furthermore, renal denervation ( n = 8) abolished the changes in RBF induced by different natural behavioral activities. These results suggest that the changes in RSNA induced by natural behavioral activities had a significant influence on RBF.
Hypothermia and hypoxia inhibit the Hering-Breüer reflex in the marsupial newborn
Authors: MacFarlane P. M. , Frappell P. B.
Published: April 2004

The effects of lowering body temperature (Tb) on metabolic rate, ventilation, and the strength of the Hering-Breüer expiratory promoting reflex (HB reflex; determined from an inhibitory ratio calculated from volumetric measurements of the respiratory rhythm) were examined in 18-day-old ectothermic pouch young of the tammar wallaby during normoxia or hypoxia (10% O2). Hypoxia and hypothermia, either singularly or combined, depressed metabolic rate. At all Tb, the hypoxic hyperventilation was associated with a significant hyperpnea. At pouch Tb(36.5°C) during normoxia, inflation of the lungs with -5 or -10 cmH2O extrathoracic pressure induced a significant HB reflex. Exposure to cold reduced the strength of the reflex, almost abolishing it at 28°C. For Tbabove 28°C, the reflex in hypoxia was always less than the corresponding normoxic value. Taken in context with the changes in metabolic state that occurred, these data in the ectothermic marsupial newborn suggest that the decline in the HB reflex during moderate hypothermia is the result of a direct effect of Tbon vagal mechanisms rather than a temperature-driven decline in metabolic rate that should have acted to strengthen the HB reflex. Therefore, it seems that inputs inhibitory to breathing are more negatively affected during cold than those inputs that are excitatory.
Metabolic and mitogenic effects of IGF-I and insulin on muscle cells of rainbow trout
Authors: Castillo Juan , Codina Marta , Martínez María Laura , Navarro Isabel , Gutiérrez Joaquim
Published: April 2004

The relative function of IGF-I and insulin on fish muscle metabolism and growth has been investigated by the isolation and culture at different stages (myoblasts at day 1, myocytes at day 4, and myotubes at day 10) of rainbow trout muscle cells. This in vitro model avoids interactions with endogenous peptides, which could interfere with the muscle response. In these cells, the effects of IGF-I and insulin on cell proliferation, 2-deoxyglucose (2-DG), and l-alanine uptake at different development stages, and the use of inhibitors were studied and quantified. Insulin (10-1,000 nM) and IGF-I (10-100 nM) stimulated 2-DG uptake in trout myocytes at day 4 in a similar manner (maximum of 124% for insulin and of 142% for IGF-I), and this stimulation increased when cells differentiated to myotubes (maximum for IGF-I of 193%). When incubating the cells with PD-98059 and especially cytochalasin B, a reduction in 2-DG uptake was observed, suggesting that glucose transport takes place through specific facilitative transporters. IGF-I (1-100 nM) stimulated the l-alanine uptake in myocytes at day 4 (maximum of 239%), reaching higher values of stimulation than insulin (100-1,000 nM) (maximum of 160%). This stimulation decreased when cells developed to myotubes at day 10 (118% for IGF-I and 114% for insulin). IGF-I (0.125-25 nM) had a significant effect on myoblast proliferation, measured by thymidine incorporation (maximum of 170%), and required the presence of 2-5% fetal serum (FBS) to promote thymidine uptake. On the other hand, insulin was totally ineffective in stimulating thymidine uptake. We conclude that IGF-I is more effective than insulin in stimulating glucose and alanine uptake in rainbow trout myosatellite cells and that the degree of stimulation changes when cells differentiate to myotubes. IGF-I stimulates cell proliferation in this model of muscle in vitro and insulin does not. These results indicate the important role of IGF-I on growth and metabolism of fish muscle.
Exogenous liposomal IGF-I cDNA gene transfer leads to endogenous cellular and physiological responses in an acute wound
Authors: Jeschke Marc G. , Schubert Thomas , Klein Dagmar
Published: April 2004

The purpose of the present study was to examine whether exogenous liposomal cDNA gene transfer is recognized by the cell and causes endogenous cellular and physiological responses. When administered as a protein, IGF-I is known to cause adverse side effects due to lack of cellular responses. Therefore, we used IGF-I cDNA as a vector to study cellular and physiological effects after liposomal administration to wounded skin. Sprague-Dawley rats were given a scald burn to inflict an acute wound and were divided into two groups to receive weekly subcutaneous injections of liposomes plus the Lac-Z gene (0.2 μg vehicle) or liposomes plus the IGF-I cDNA (2.2 μg) and Lac Z gene (0.22 μg). Transfection was confirmed by histochemical assays for β-galactosidase. Planimetry, immunological assays, and histological and immunohistochemical techniques were used to determine molecular mechanisms after gene transfer, protein expression, and dermal and epidermal regeneration. IGF-I cDNA transfer increased IGF-I protein expression and caused concomitant cellular responses by increasing IGF binding protein (IGFBP)-3 and decreasing IGFBP-1. IGF-I cDNA gene transfer increased keratinocyte growth factor expression and exerted promitogenic antiapoptotic effects on basal keratinocytes, thus improving epidermal regeneration. IGF-I cDNA improved dermal regeneration by an increased collagen deposition and morphology. IGF-I cDNA increased VEGF concentrations and thus neovascularization. Exogenous-administered IGF-I cDNA is recognized by the cell and leads to similar intracellular responses as the endogenous gene. Liposomal IGF-I gene transfer further leads to improved dermal and epidermal regeneration by interacting with other growth factors.
Novel phase-shifting effects of GABAA receptor activation in the suprachiasmatic nucleus of a diurnal rodent
Authors: Novak C. M. , Albers H. E.
Published: April 2004

The vast majority of neurons in the suprachiasmatic nucleus (SCN), the primary circadian pacemaker in mammals, contain the inhibitory neurotransmitter GABA. Most studies investigating the role of GABA in the SCN have been performed using nocturnal rodents. Activation of GABAA receptors by microinjection of muscimol into the SCN phase advances the circadian activity rhythm of nocturnal rodents, but only during the subjective day. Nonphotic stimuli that reset the circadian pacemaker of nocturnal rodents also produce phase advances during the subjective day. The role of GABA in the SCN of diurnal animals and how it may differ from nocturnal animals is not known. In the studies described here, the GABAA agonist muscimol was microinjected directly into the SCN region of diurnal unstriped Nile grass rats ( Arvicanthis niloticus) at various times in their circadian cycle. The results demonstrate that GABAA receptor activation produces large phase delays during the subjective day in grass rats. Treatment with TTX did not affect the ability of muscimol to induce phase delays, suggesting that muscimol acts directly on pacemaker cells within the SCN. These data suggest that the circadian pacemakers of nocturnal and diurnal animals respond to the most abundant neurochemical signal found in SCN neurons in opposite ways. These findings are the first to demonstrate a fundamental difference in the functioning of circadian pacemaker cells in diurnal and nocturnal animals.
Optimal Impedance Control for Task Achievement in the Presence of Signal-Dependent Noise
Authors: Osu Rieko , Kamimura Naoki , Iwasaki Hiroshi , Nakano Eri , Harris Chris M. , Wada Yasuhiro , Kawato Mitsuo
Published: April 2004

There is an infinity of impedance parameter values, and thus different co-contraction levels, that can produce similar movement kinematics from which the CNS must select one. Although signal-dependent noise (SDN) predicts larger motor-command variability during higher co-contraction, the relationship between impedance and task performance is not theoretically obvious and thus was examined here. Subjects made goal-directed, single-joint elbow movements to either move naturally to different target sizes or voluntarily co-contract at different levels. Stiffness was estimated as the weighted summation of rectified EMG signals through the index of muscle co-contraction around the joint (IMCJ) proposed previously. When subjects made movements to targets of different sizes, IMCJ increased with the accuracy requirements, leading to reduced endpoint deviations. Therefore without the need for great accuracy, subjects accepted worse performance with lower co-contraction. When subjects were asked to increase co-contraction, the variability of EMG and torque both increased, suggesting that noise in the neuromotor command increased with muscle activation. In contrast, the final positional error was smallest for the highest IMCJ level. Although co-contraction increases the motor-command noise, the effect of this noise on the task performance is reduced. Subjects were able to regulate their impedance and control endpoint variance as the task requirements changed, and they did not voluntarily select the high impedance that generated the minimum endpoint error. These data contradict predictions of the SDN-based theory, which postulates minimization of only endpoint variance and thus require its revision.
A Functional Connection Between Inferior Frontal Gyrus and Orofacial Motor Cortex in Human
Authors: Greenlee Jeremy D. W. , Oya Hiroyuki , Kawasaki Hiroto , Volkov Igor O. , Kaufman Olaf P. , Kovach Christopher , Howard Matthew A. , Brugge John F.
Published: April 2004

The inferior frontal gyrus (IFG) of humans is known to play a critical role in speech production. The IFG is a highly convoluted and cytoarchitectonically diverse structure, classically forming 3 subgyri. It is reasonable to speculate that during speaking the IFG, or some portion of it, influences by corticocortical connections the orofacial representational area of primary motor cortex. To test the hypothesis that such corticocortical connections exist, electrical-stimulation tract tracing experiments were performed intraoperatively on 14 human subjects undergoing surgical treatment of medically intractable epilepsy. Bipolar electrical stimulation was applied to sites on the IFG, while the resulting evoked potentials were recorded from orofacial motor cortex, using a multichannel recording array. Stimulation of the IFG evoked polyphasic waveforms on motor cortex of both language-dominant and -nondominant hemispheres. The evoked waveforms had consistent features across subjects. The responses were seen in discrete regions on precentral cortex. Stimulation of motor cortex also evoked responses on portions of IFG. The data provide evidence for a functional connection between the human IFG and orofacial motor cortex.
Milk Ejection Burst-Like Electrical Activity Evoked in Supraoptic Oxytocin Neurons in Slices From Lactating Rats
Authors: Wang Yu-Feng , Hatton Glenn I.
Published: April 2004

To examine the mechanisms underlying milk-ejection bursts of oxytocin (OT) neurons during suckling, both in vivo and in vitro studies were performed on supraoptic OT neurons from lactating rats. The bursts were first recorded extracellularly in anesthetized rats. Burst-related electrical parameters were essentially the same as previous reports except for a trend toward transient decreases in basal firing rates immediately preceding the burst. From putative OT neurons in slices with extracellular recordings, bursts that closely mimicked the in vivo bursts were elicited by phenylephrine, an α1-adrenoceptor agonist, in a low-Ca2+ medium. Moreover, in whole cell patch-clamp recordings, the in vitro bursts were recorded from immunocytochemically identified OT neurons. After a transient decrease in the basal firing rate, the in vitro bursts started with a sudden increase in the firing rate, quickly reaching a peak level, then gradually decaying, and ended with a postburst inhibition. A brief depolarization of the membrane potential and an increase in membrane conductance appeared after the onset of the burst. Spikes during a burst were characterized by a significant increase in the duration and decrease in the amplitude around the peak rate firing. These bursts were significantly different from short-lasting burst firing of vasopressin neurons in membrane potential changes, time to reach peak firing rate, spike amplitude and duration during peak rate firing. Our extensive analysis of these results suggests that the in vitro burst is a useful model for further study of mechanisms underlying milk-ejection bursts of OT neurons in vivo.
Representation of an Abstract Perceptual Decision in Macaque Superior Colliculus
Authors: Horwitz Gregory D. , Batista Aaron P. , Newsome William T.
Published: April 2004

We recorded from neurons in the intermediate and deep layers of the superior colliculus (SC) while monkeys performed a novel direction discrimination task. In contrast to the task we used previously, the new version required the monkey to dissociate perceptual judgments from preparation to execute specific operant saccades. The monkey discriminated between 2 opposed directions of motion in a random-dot motion stimulus and was required to maintain the decision in memory throughout a delay period before the target of the required operant saccade was revealed. We hypothesized that perceptual decisions made in this paradigm would be represented in an “abstract” or “categorical” form within the brain, probably in the frontal cortex, and that decision-related neural activity would be eliminated from spatially organized preoculomotor structures such as the SC. To our surprise, however, a small population of neurons in the intermediate and deep layers of the SC fired in a choice-specific manner early in the trial well before the monkey could plan the operant saccade. Furthermore, the representation of the decision during the delay period appeared to be spatial: the active region in the SC map corresponded to the region of space toward which the perceptually discriminated stimulus motion flowed. Electrical microstimulation experiments suggested that these decision-related SC signals were not merely related to covert saccade planning. We conclude that monkeys may employ, in part, a spatially referenced mnemonic strategy for representing perceptual decisions, even when an abstract, categorical representation might appear more likely a priori.
Nonlinear Encoding of Tactile Patterns in the Barrel Cortex
Authors: Webber Roxanna M. , Stanley Garrett B.
Published: April 2004

Cells in the rodent barrel cortex respond to vibrissa deflection with a brief excitatory component and a longer suppressive component. The response to a given deflection is thus scaled because of suppression induced by a preceding deflection, causing the neuronal response to be linked to the temporal properties of the peripheral stimulus. A paired-deflection stimulus was used to characterize the postexcitatory suppression and a 3-deflection stimulus was used to investigate the nonlinear response to patterns of whisker deflections in barbiturate-anesthetized Sprague–Dawley rats. The postexcitatory suppression was not dependent on a sensory-evoked action potential to the first deflection, implying that it is likely a subthreshold property of the network. The suppression induced by a deflection served to suppress both the excitatory and suppressive components of a subsequent neuronal response, thus effectively disinhibiting it. Two different response properties were observed in the recorded cells. Approximately 65% responded to a vibrissa deflection with an excitatory component followed by a suppressive component and 35% responded with excitation, suppression, and a subsequent rebound in excitation. Based on these observations of postexcitatory dynamics, a prediction method was used to estimate neuronal responses to more complex stimulus trains. Using the 2nd-order representation obtained from the paired-deflection stimulus, responses to general periodic deflection patterns were well predicted. A higher cutoff frequency was predicted for rebound cells compared with cells not exhibiting rebound excitation, consistent with experimental observations. The method also predicted the response of neurons to a random aperiodic deflection pattern. Therefore the temporal structure of cortical dynamics after a single deflection dictates the response to complex temporal patterns, which are more representative of stimuli encountered under natural conditions.
Characterization of Wide Dynamic Range Neurons in the Deep Dorsal Horn of the Spinal Cord in Preprotachykinin-A Null Mice In Vivo
Authors: Martin William J. , Cao YuQing , Basbaum Allan I.
Published: April 2004

We previously reported that mice with a deletion of the preprotachykinin-A ( pptA) gene, from which substance P (SP) and neurokinin A (NKA) are derived, exhibit reduced behavioral responses to intense stimuli, but that behavioral hypersensitivity after injury is unaltered. To understand the contribution of SP and NKA to nociceptive transmission in the spinal cord, we recorded single-unit activity from wide dynamic range neurons in the lamina V region of the lumbar dorsal horn of urethane-anesthetized wild-type and ppt-A null mutant (–/–) mice. We found that intensity coding to thermal stimuli was largely preserved in the ppt-A –/– mice. Neither the peak stimulus-evoked firing nor the neuronal activity during the initial phase (0–4 s) of the 41–49°C thermal stimuli differed between the genotypes. However, electrophysiological responses during the late phase of the stimulus (5–10 s) and poststimulus (11–25 s) were significantly reduced in ppt-A –/– mice. To activate C-fibers and to sensitize the dorsal horn neurons we applied mustard oil (MO) topically to the hindpaw. We found that neither total MO-evoked activity nor sensitization to subsequent stimuli differed between the wild-type and ppt-A –/– mice. However, the time course of the sensitization and the magnitude of the poststimulus discharges were reduced in ppt-A –/– mice. We conclude that SP and/or NKA are not required for intensity coding or sensitization of nociresponsive neurons in the spinal cord, but that these peptides prolong thermal stimulus-evoked responses. Thus whereas behavioral hypersensitivity after injury is preserved in ppt-A –/– mice, our results suggest that the magnitude and duration of these behavioral responses would be reduced in the absence of SP and/or NKA.
Spastic Long-Lasting Reflexes in the Awake Rat After Sacral Spinal Cord Injury
Authors: Bennett D. J. , Sanelli L. , Cooke C. L. , Harvey P. J. , Gorassini M. A.
Published: April 2004

Following chronic sacral spinal cord transection in rats the affected tail muscles exhibit marked spasticity, with characteristic long-lasting tail spasms evoked by mild stimulation. The purpose of the present paper was to characterize the long-lasting reflex seen in tail muscles in response to electrical stimulation of the tail nerves in the awake spastic rat, including its development with time and relation to spasticity. Before and after sacral spinal transection, surface electrodes were placed on the tail for electrical stimulation of the caudal nerve trunk (mixed nerve) and for recording EMG from segmental tail muscles. In normal and acute spinal rats caudal nerve trunk stimulation evoked little or no EMG reflex. By 2 wk after injury, the same stimulation evoked long-lasting reflexes that were 1) very low threshold, 2) evoked from rest without prior EMG activity, 3) of polysynaptic latency with >6 ms central delay, 4) about 2 s long, and 5) enhanced by repeated stimulation (windup). These reflexes produced powerful whole tail contractions (spasms) and developed gradually over the weeks after the injury (≤52 wk tested), in close parallel to the development of spasticity. Pure low-threshold cutaneous stimulation, from electrical stimulation of the tip of the tail, also evoked long-lasting spastic reflexes, not seen in acute spinal or normal rats. In acute spinal rats a strong C-fiber stimulation of the tip of the tail (20 × T) could evoke a weak EMG response lasting about 1 s. Interestingly, when this C-fiber stimulation was used as a conditioning stimulation to depolarize the motoneuron pool in acute spinal rats, a subsequent low-threshold stimulation of the caudal nerve trunk evoked a 300–500 ms long reflex, similar to the onset of the long-lasting reflex in chronic spinal rats. A similar conditioned reflex was not seen in normal rats. Thus there is an unusually long low-threshold polysynaptic input to the motoneurons (pEPSP) that is normally inhibited by descending control. This pEPSP is released from inhibition immediately after injury but does not produce a long-lasting reflex because of a lack of motoneuron excitability. With chronic injury the motoneuron excitability is increased markedly, and the pEPSP then triggers sustained motoneuron discharges associated with long-lasting reflexes and muscle spasms.
EMG Responses to an Unexpected Load in Fast Movements Are Delayed With an Increase in the Expected Movement Time
Authors: Shapiro Mark B. , Gottlieb Gerald L. , Corcos Daniel M.
Published: April 2004

When moving an object, the motor system estimates the dynamic properties of the object and then controls the movement using a combination of predictive feedforward control and proprioceptive feedback. In this study, we examined how the feedforward and proprioceptive feedback processes depend on the expected movement task. Subjects made fast elbow flexion movements from an initial position to a target. The experimental protocol included movements made over a short and a long distance against an expected light or heavy inertial load. In each task in a few randomly chosen trials, a motor applied an unexpected viscous load that produced a velocity error, defined as the difference between the expected and unexpected velocities, and electromyographic (EMG) responses. The EMG responses appeared not earlier than 170–250 ms from the agonist EMG onset. Our main finding is that the onset of the EMG responses was correlated with the expected time of peak velocity, which increased for longer distances and larger loads. An analysis of the latency of the EMG responses with respect to the velocity error suggested that the EMG responses were due to segmental reflexes. We conclude that segmental reflex gains are centrally modulated with the time course dependent on the expected movement task. According to this view, the control of fast point-to-point movement is feedforward from the agonist EMG onset until the expected time of peak velocity after which the segmental reflex feedback is briefly facilitated.
Combined Unilateral Lesions of the Amygdala and Orbital Prefrontal Cortex Impair Affective Processing in Rhesus Monkeys
Authors: Izquierdo Alicia , Murray Elisabeth A.
Published: April 2004

The amygdala and orbital prefrontal cortex (PFo) interact as part of a system for affective processing. To assess whether there is a hemispheric functional specialization for the processing of emotion or reward or both in nonhuman primates, rhesus monkeys ( Macaca mulatta) with combined lesions of the amygdala and PFo in one hemisphere, either left or right, were compared with unoperated controls on a battery of tasks that tax affective processing, including two tasks that tax reward processing and two that assess emotional reactions. Although the two operated groups did not differ from each other, monkeys with unilateral lesions, left and right, showed altered reward-processing abilities as evidenced by attenuated reinforcer devaluation effects and an impairment in object reversal learning relative to controls. In addition, both operated groups showed blunted emotional reactions to a rubber snake. By contrast, monkeys with unilateral lesions did not differ from controls in their responses to an unfamiliar human (human “intruder”). Although the results provide no support for a hemispheric specialization of function, they yield the novel finding that unilateral lesions of the amygdala-orbitofrontal cortical circuit in monkeys are sufficient to significantly disrupt affective processing.