bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium in the mechanism of ammonia‐induced astrocyte swelling
Authors: Jayakumar Arumugam R. , Rama Rao Kakulavarapu V. , Tong Xiaoying Y. , Norenberg Michael D.
Published: April 2009

Brain edema, due largely to astrocyte swelling, is an important clinical problem in patients with acute liver failure. While mechanisms underlying astrocyte swelling in this condition are not fully understood, ammonia and associated oxidative/nitrosative stress appear to be involved. Mechanisms responsible for the increase in reactive oxygen/nitrogen species (RONS) and their role in ammonia‐induced astrocyte swelling, however, are poorly understood. Recent studies have demonstrated a transient increase in intracellular Ca2+in cultured astrocytes exposed to ammonia. As Ca2+is a known inducer of RONS, we investigated potential mechanisms by which Ca2+may be responsible for the production of RONS and cell swelling in cultured astrocytes after treatment with ammonia. Exposure of cultured astrocytes to ammonia (5 mM) increased the formation of free radicals, including nitric oxide, and such increase was significantly diminished by treatment with the Ca2+chelator 1,2‐bis‐(o‐aminophenoxy)‐ethane‐N,N,‐N′,N′‐tetraacetic acid tetraacetoxy‐methyl ester (BAPTA). We then examined the activity of Ca2+‐dependent enzymes that are known to generate RONS and found that ammonia significantly increased the activities of NADPH oxidase (NOX), constitutive nitric oxide synthase (cNOS), and phospholipase A2 (PLA2) and such increases in activity were significantly diminished by BAPTA. Pre‐treatment of cultures with 7‐nitroindazole, apocyanin, and quinacrine, respective inhibitors of cNOS, NOX, and PLA2, all significantly diminished RONS production. Additionally, treatment of cultures with BAPTA or with inhibitors of cNOS, NOX, and PLA2 reduced ammonia‐induced astrocyte swelling. These studies suggest that the ammonia‐induced rise in intracellular Ca2+activates free radical producing enzymes that ultimately contribute to the mechanism of astrocyte swelling.
Transglutaminases and neurodegeneration
Authors: Jeitner Thomas M. , Pinto John T. , Krasnikov Boris F. , Horswill Mark , Cooper Arthur J. L.
Published: April 2009

Transglutaminases (TGs) are Ca2+‐dependent enzymes that catalyze a variety of modifications of glutaminyl (Q) residues. In the brain, these modifications include the covalent attachment of a number of amine‐bearing compounds, including lysyl (K) residues and polyamines, which serve to either regulate enzyme activity or attach the TG substrates to biological matrices. Aberrant TG activity is thought to contribute to Alzheimer disease, Parkinson disease, Huntington disease, and supranuclear palsy. Strategies designed to interfere with TG activity have some benefit in animal models of Huntington and Parkinson diseases. The following review summarizes the involvement of TGs in neurodegenerative diseases and discusses the possible use of selective inhibitors as therapeutic agents in these diseases.
Contributions of Ca2+ and Zn2+ to spreading depression‐like events and neuronal injury
Authors: Dietz Robert M. , Weiss John H. , Shuttleworth C. William
Published: April 2009

The phenomenon of spreading depression (SD) involves waves of profound neuronal and glial depolarization that spread throughout brain tissue. Under many conditions, tissue recovers full function after SD has occurred, but SD‐like events are also associated with spread of injury following ischemia or trauma. Initial large cytosolic Ca2+ increases accompany all forms of SD, but persistently elevated Ca2+ loading is likely responsible for neuronal injury following SD in tissues where metabolic capacity is insufficient to restore ionic gradients. Ca2+ channels are also involved in the propagation of SD, but the channel subtypes and cation fluxes differ significantly when SD is triggered by different types of stimuli. Ca2+ influx via P/Q type channels is important for SD generated by localized application of high K+ solutions. In contrast, SD‐like events recorded in in vitro ischemia models are not usually prevented by Ca2+ removal, but under some conditions, Zn2+ influx via L‐type channels contributes to SD initiation. This review addresses different roles of Ca2+ in the initiation and consequences of SD, and discusses recent evidence that selective chelation of Zn2+ can be sufficient to prevent SD under circumstances that may have relevance for ischemic injury.
Kinetic validation of 6‐NBDG as a probe for the glucose transporter GLUT1 in astrocytes
Authors: Barros Luis Felipe , Bittner Carla X. , Loaiza Anitsi , Ruminot Iván , Larenas Valeria , Moldenhauer Hans , Oyarzún Carolina , Alvarez Mauro
Published: April 2009

In recent years, the use of fluorescent glucose analogs has allowed the study of rapid transport modulation in heterogeneous cell cultures and complex tissues. However, the kinetic behavior of these tracers is not conventional. For instance, the fluorescent glucose analog 6‐NBDG permeates the cell 50–100 times slower than glucose but the uptake of 6‐NBDG is almost insensitive to glucose, an observation that casts doubts as to the specificity of the uptake pathway. To investigate this apparent anomaly in cultured astrocytes, which are rich in the glucose transporter GLUT1, we first estimated the kinetic parameters of 6‐NBDG uptake, which were then incorporated into the kinetic model of GLUT1. The main outcome of the analysis was that 6‐NBDG binds to GLUT1 with 300 times higher affinity than glucose, which explains why its uptake is not efficiently displaced by glucose. The high binding affinity of 6‐NBDG also explains why cytochalasin B is less effective at inhibiting 6‐NBDG uptake than at inhibiting glucose uptake. We conclude that 6‐NBDG, used at low concentrations, permeates into astrocytes chiefly through GLUT1, and advise that the exofacial GLUT1 inhibitor 4,6‐ethylidine‐d‐glucose be used, instead of glucose, as the tool of choice to confirm the specificity of 6‐NBDG uptake.
Oxidative stress and mitochondrial dysfunction as determinants of ischemic neuronal death and survival
Authors: Niizuma Kuniyasu , Endo Hidenori , Chan Pak H.
Published: April 2009

Mitochondria are the powerhouse of the cell. Their primary physiological function is to generate adenosine triphosphate through oxidative phosphorylation via the electron transport chain. Reactive oxygen species generated from mitochondria have been implicated in acute brain injuries such as stroke and neurodegeneration. Recent studies have shown that mitochondrially‐formed oxidants are mediators of molecular signaling, which is implicated in the mitochondria‐dependent apoptotic pathway that involves pro‐ and antiapoptotic protein binding, the release of cytochrome c, and transcription‐independent p53 signaling, leading to neuronal death. Oxidative stress and the redox state of ischemic neurons are also implicated in the signaling pathway that involves phosphatidylinositol 3‐kinase/Akt and downstream signaling, which lead to neuronal survival. Genetically modified mice or rats that over‐express or are deficient in superoxide dismutase have provided strong evidence in support of the role of mitochondrial dysfunction and oxidative stress as determinants of neuronal death/survival after stroke and neurodegeneration.
Functional significance of brain glycogen in sustaining glutamatergic neurotransmission
Authors: Sickmann Helle M. , Walls Anne B. , Schousboe Arne , Bouman Stephan D. , Waagepetersen Helle S.
Published: April 2009

The involvement of brain glycogen in sustaining neuronal activity has previously been demonstrated. However, to what extent energy derived from glycogen is consumed by astrocytes themselves or is transferred to the neurons in the form of lactate for oxidative metabolism to proceed is at present unclear. The significance of glycogen in fueling glutamate uptake into astrocytes was specifically addressed in cultured astrocytes. Moreover, the objective was to elucidate whether glycogen derived energy is important for maintaining glutamatergic neurotransmission, induced by repetitive exposure to NMDA in co‐cultures of cerebellar neurons and astrocytes. In the astrocytes it was shown that uptake of the glutamate analogue d‐[3H]aspartate was impaired when glycogen degradation was inhibited irrespective of the presence of glucose, signifying that energy derived from glycogen degradation is important for the astrocytic compartment. By inhibiting glycogen degradation in co‐cultures it was evident that glycogen provides energy to sustain glutamatergic neurotransmission, i.e. release and uptake of glutamate. The relocation of glycogen derived lactate to the neuronal compartment was investigated by employing d‐lactate, a competitive substrate for the monocarboxylate transporters. Neurotransmitter release was affected by the presence of d‐lactate indicating that glycogen derived energy is important not only in the astrocytic but also in the neuronal compartment.
AMPK in the brain: its roles in energy balance and neuroprotection
Authors: Ronnett Gabriele V. , Ramamurthy Santosh , Kleman Amy M. , Landree Leslie E. , Aja Susan
Published: April 2009

Adenosine monophosphate‐activated protein kinase (AMPK) senses metabolic stress and integrates diverse physiological signals to restore energy balance. Multiple functions are indicated for AMPK in the CNS. While all neurons sense their own energy status, some integrate neuro‐humoral signals to assess organismal energy balance. A variety of disease states may involve AMPK, so determining the underlying mechanisms is important. We review the impact of altered AMPK activity under physiological (hunger, satiety) and pathophysiological (stroke) conditions, as well as therapeutic manipulations of AMPK that may improve energy balance.
The rate‐limiting step for glucose transport into the hypothalamus is across the blood–hypothalamus interface
Authors: Poitry‐Yamate Carol , Lei HongXia , Gruetter Rolf
Published: April 2009

Specialized glucosensing neurons are present in the hypothalamus, some of which neighbor the median eminence, where the blood–brain barrier has been reported leaky. A leaky blood–brain barrier implies high tissue glucose levels and obviates a role for endothelial glucose transporters in the control of hypothalamic glucose concentration, important in understanding the mechanisms of glucose sensing We therefore addressed the question of blood–brain barrier integrity at the hypothalamus for glucose transport by examining the brain tissue‐to‐plasma glucose ratio in the hypothalamus relative to other brain regions. We also examined glycogenolysis in hypothalamus because its occurrence is unlikely in the potential absence of a hypothalamus–blood interface. Across all regions the concentration of glucose was comparable at a given plasma glucose concentration and was a near linear function of plasma glucose. At steady‐state, hypothalamic glucose concentration was similar to the extracellular hypothalamic glucose concentration reported by others. Hypothalamic glycogen fell at a rate of ∼1.5 μmol/g/h and remained present in substantial amounts. We conclude for the hypothalamus, a putative primary site of brain glucose sensing that: the rate‐limiting step for glucose transport into brain cells is at the blood–hypothalamus interface, and that glycogenolysis is consistent with a substantial blood ‐to‐ intracellular glucose concentration gradient.
Redox dependence and compartmentation of [13C]pyruvate in the brain of deuterated rats bearing implanted C6 gliomas
Authors: Rodrigues Tiago B. , López‐Larrubia Pilar , Cerdán Sebastián
Published: April 2009

We investigated the redox dependence and compartmentation of the pyruvate pool in the brain of partially deuterated rats bearing C6 gliomas. Adult male Wistar rats implanted with C6 cells drunk 2H2O (50% v/v) or tap water for 9 days before they were infused with solutions containing [1‐13C]glucose and [2‐13C]pyruvate or [U‐13C3]lactate. Their brains were fixed with high‐power focused microwaves and biopsies prepared from the contralateral, ipsilateral, and tumor regions. 13C NMR analysis of the extracts allowed the determination of the relative amounts of [13C]lactate isotopomers derived from infused glucose or monocarboxylates. The relative amounts of [3‐13C]lactate derived from glucose to the [2‐13C] or [U‐13C3]lactate isotopomers derived from monocarboxylates decreased in the order contralateral > ipsilateral > tumor regions, revealing a progressive reduction in glycolysis for regions containing increasing endogenous lactate concentrations. Cortical astrocytes depicted similar reductions in glycolysis when incubated with [1,2‐13C2]glucose and increasing concentrations of [3‐13C]lactate. Deuterated animals bearing C6 tumors, infused with [1‐13C]glucose and [2‐13C]pyruvate, showed different deuterium enrichments in the methyl groups of cerebral [3‐13C] and [2‐13C]lactate, revealing a slow mixing of the [3‐13C] and [2‐13C]pyruvate precursors in the 2H exchange timescale of their methyl groups. Together, these evidences reveal the role of the redox state of the pyruvate pool derived from monocarboxylates in the modulation of cerebral glycolytic flux in vivo and in vitro.
Mitochondrial glutathione uptake: characterization in isolated brain mitochondria and astrocytes in culture
Authors: Wadey Alison L. , Muyderman Hakan , Kwek Perrin T. , Sims Neil R.
Published: April 2009

Glutathione in the mitochondria is an important determinant of cellular responses to oxidative stress. Mitochondrial glutathione is maintained by uptake from the cytosol, a process that has been little studied in brain cells. In the present study, measurements using isolated rat brain mitochondria showed a rapid uptake of [3H]‐glutathione that was strongly influenced by the mitochondrial glutathione content. [3H]‐glutathione incorporated into the mitochondria was not rapidly released. Uptake was inhibited by substrates and inhibitors for several known mitochondrial anion transporters. Citrate, isocitrate and benzene‐1,2,3‐tricarboxylate were particularly effective inhibitors, suggesting a possible role for a tricarboxylate carrier in the glutathione transport. The properties of uptake differed greatly from those reported previously for mitochondria from kidney and liver. In astrocytes in primary culture, diethylmaleate or hydrogen peroxide treatment resulted in depletion of cytosolic and mitochondrial glutathione. The pattern of restoration of glutathione content in the presence of glutathione precursors following treatment with diethylmaleate was consistent with uptake into mitochondria being controlled primarily by the glutathione gradient between the cytosol and mitochondria. However, following hydrogen peroxide treatment, recovery of glutathione in the mitochondria initially preceded comparable proportional restoration in the cytosol, suggesting the possibility of additional controls on glutathione uptake in some conditions.
The ketogenic diet has no effect on the expression of spike‐and‐wave discharges and nutrient transporters in genetic absence epilepsy rats from Strasbourg
Authors: Nehlig Astrid , Dufour Franck , Klinger Marianne , Willing Lisa B. , Simpson Ian A. , Vannucci Susan J.
Published: April 2009

The genetic absence epilepsy rat from Strasbourg is considered an isomorphic, predictive, and homologous model of typical childhood absence epilepsy. It is characterized by the expression of spike‐and‐wave discharges (SWDs) in the thalamus and cortex. The ketogenic diet (KD) is successfully used in humans and animals with various types of seizures, but was not effective in children with intractable atypical absence epilepsy. Here, we studied its potential impact on the occurrence of SWDs in genetic absence epilepsy rat from Strasbourg. Rats were fed the KD for 3 weeks during which they were regularly subjected to the electroencephalographic recording of SWDs. The KD did not influence the number and duration of SWDs despite a 15–22% decrease in plasma glucose levels and a large increase in β‐hydroxybutyrate levels. Likewise, the KD did not affect the level of expression of the blood–brain barrier glucose transporter GLUT1 or of the monocarboxylate transporters, MCT1 and MCT2. This report extends the observation in humans that the KD does not appear to show effectiveness in intractable atypical absence epilepsy to this model of typical childhood absence epilepsy which responds to specific antiepileptic drugs.
What learning in day‐old chickens can teach a neurochemist: focus on astrocyte metabolism
Authors: Hertz Leif , Gibbs Marie E.
Published: April 2009

The learning process sets in motion a prolonged, reproducible, and complicated pattern of brain activation, which provides information about biochemical reactions in activated brain. Study of this pattern during one‐trial aversive bead discrimination in day‐old chick is facilitated by precise timing of sequential metabolic events occurring between a 10‐s learning period, in which the chicks learn to associate a red bead with aversive taste, and memory consolidation, indicated by unwillingness to peck at untainted red beads while freely pecking at corresponding blue beads. Inhibition of learning by metabolic inhibitors and restoration of memory by specific substrates at specific times allow determination of specific metabolic events and their neuronal or astrocytic localization. Downstream metabolism of glycogen and of glucose to pyruvate/lactate is segregated into separate pools. Glucose metabolism via pyruvate dehydrogenation provides energy in both neurons and astrocytes and may include gap junction‐mediated lactate transport into astrocytes. A key role is played by glycogenolysis, stimulated by β2‐adrenergic and/or 5‐HT2‐receptor stimulation along with α2‐adrenergic stimulation of glycogen synthesis. The importance of glycogen reflects that it selectively supports de novo synthesis of transmitter glutamate by combined pyruvate dehydrogenation and carboxylation in astrocytes.
Neuronal glucose but not lactate utilization is positively correlated with NMDA‐induced neurotransmission and fluctuations in cytosolic Ca2+levels
Authors: Bak Lasse K. , Walls Anne B. , Schousboe Arne , Ring Avi , Sonnewald Ursula , Waagepetersen Helle S.
Published: April 2009

Although the brain utilizes glucose for energy production, individual brain cells may to some extent utilize substrates derived from glucose. Thus, it has been suggested that neurons consume extracellular lactate during synaptic activity. However, the precise role of lactate for fuelling neuronal activity is still poorly understood. Recently, we demonstrated that glucose metabolism is up‐regulated in cultured glutamatergic neurons during neurotransmission whereas that of lactate is not. Here, we show that utilization of glucose but not lactate correlates with NMDA‐induced neurotransmitter glutamate release in cultured cerebellar neurons from mice. Pulses of NMDA at 30, 100, and 300 μM, leading to a progressive increase in both cytosolic [Ca2+] and release of glutamate, increased uptake and metabolism of glucose but not that of lactate as evidenced by mass spectrometric measurement of13C incorporation into intracellular glutamate. In this manuscript, a cascade of events for the preferential neuronal utilization of glucose during neurotransmission is suggested and discussed in relation to our current understanding of neuronal energy metabolism.
Mild reduction in the activity of the α‐ketoglutarate dehydrogenase complex elevates GABA shunt and glycolysis
Authors: Shi Qingli , Risa Øystein , Sonnewald Ursula , Gibson Gary E.
Published: April 2009

Diminished energy metabolism and reduced activity of brain α‐ketoglutarate dehydrogenase complex (KGDHC) occur in a number of neurodegenerative diseases. The relation between diminished KGDHC activity and altered energy metabolism is unknown. The present study tested whether a reduction in the KGDHC activity would alter cellular metabolism by comparing metabolism of [U‐13C]glucose in a human embryonic kidney cell line (E2k100) to one in which the KGDHC activity was about 70% of control (E2k67). After a 2 h incubation of the cells with [U‐13C]glucose, the E2k67 cells showed a greater increase in 13C labeling of alanine compared with the E2k100 cells. This suggested an increase in glycolysis. Furthermore, an increase in labeled lactate after 12 h incubation supported the suggestion of an increased glycolysis in the E2k67 cells. Increased GABA shunt in the E2k67 cells was indicated by increased 13C labeling of GABA at both 2 and 12 h compared with the control cells. GABA concentration as determined by HPLC was also increased in the E2k67 cells compared with the control cells. However, the GABA shunt was not sufficient to normalize metabolism in the E2k67 cells compared with control at 2 or 12 h. However, by 24 h metabolism had normalized (i.e. labeling was similar in E2k67 and E2k100). Thus, the data are consistent with an enhanced glycolysis and GABA shunt in response to a mild reduction in KGDHC. Our findings indicate that a mild change in KGDHC activity can lead to large changes in metabolism. The changes may maintain normal energy metabolism but make the cells more vulnerable to perturbations such as occur with oxidants.
Synaptic and extrasynaptic GABA transporters as targets for anti‐epileptic drugs
Authors: Madsen Karsten K. , Clausen Rasmus P. , Larsson Orla M. , Krogsgaard‐Larsen Povl , Schousboe Arne , Steve White H.
Published: April 2009

Inhibition of the GABA transporter subtype GAT1 by the clinically available anti‐epileptic drug tiagabine has proven to be an effective strategy for the treatment of some patients with partial seizures. In 2005, the investigational drug EF1502 was described as possessing activity at both GAT1 and BGT‐1. When combined with the GAT1 selective inhibitor tiagabine, EF1502 was found to possess a synergistic anti‐convulsant action in the Frings audiogenic seizure‐susceptible mouse model of reflex epilepsy. This effect was subsequently attributed to inhibition of BGT‐1. In this study, the anti‐convulsant effect of the GAT2/3 inhibitor SNAP‐5114 was assessed in the Frings audiogenic seizure‐susceptible mouse alone, and in combination with tiagabine and EF1502. The results showed that SNAP‐5114 produced a synergistic anti‐convulsant effect in combination with EF1502 but not when used in combination with tiagabine. These findings support anatomical evidence that GAT2/3 are most likely located at the synapse in close proximity to GAT1; whereas BGT‐1 is located some distance away from the synapse and GAT1 and GAT2/3. Lastly, EF1502 and tiagabine were evaluated alone, and in combination, in the corneal kindled mouse model of partial epilepsy. The results of this evaluation provide further evidence in support of a role for BGT‐1 in the control of seizure activity. In addition, they suggest that the combined inhibition of GAT1 and BGT‐1 may afford some advantage over inhibiting either transporter alone.
Altered fatty acid metabolism and composition in cultured astrocytes under hyperammonemic conditions
Authors: Gottschalk Sven , Zwingmann Claudia
Published: April 2009

In vitro
1H‐ and 13C‐NMR spectroscopy was used to investigate the effect of ammonia on fatty acid synthesis and composition in cultured astrocytes. Cells were incubated 3 and 24 h with 5 mM ammonia in the presence or absence of the glutamine synthetase inhibitor methionine sulfoximine. An increase of de novo synthesized fatty acids and the glycerol subunit of lipids was observed after 3 h treatment with ammonia (35% and 40% over control, respectively), the initial time point examined. Both parameters further increased significantly to 85% and 60% over control after 24 h ammonia treatment. Three hours incubation with ammonia increased the synthesis of diacylglycerides, while formation of triacylglycerides was decreased (40% over and 15% under control, respectively). The degradation of fatty acids was not affected by ammonia treatment. Furthermore, ammonia caused alterations in the composition of fatty acids, e.g. increased mono‐ and decreased polyunsaturated fatty acids (85% over and 15% under control concentrations, respectively). The decrease of polyunsaturated fatty acids was even more pronounced in isolated astrocytic mitochondria (39% lower than controls). Our results suggest ammonia‐induced abnormalities in astrocytic membranes, which may be related to astrocytic mitochondrial dysfunction in hyperammonemic states. Most of the observed effects of ammonia on fatty acid synthesis and composition were ameliorated when glutamine synthetase was inhibited by methionine sulfoximine, supporting a pathological role of glutamine in ammonia toxicity. This study further emphasizes the importance of investigating the relative contribution of exogenous ammonia, effects of glutamine and of glutamine‐derived ammonia on astrocytes and astrocytic mitochondria.
The in vivo neuron‐to‐astrocyte lactate shuttle in human brain: evidence from modeling of measured lactate levels during visual stimulation
Authors: Mangia Silvia , Simpson Ian A. , Vannucci Susan J. , Carruthers Anthony
Published: April 2009

Functional magnetic resonance spectroscopy (fMRS) allows the non‐invasive measurement of metabolite concentrations in the human brain, including changes induced by variations in neurotransmission activity. However, the limited spatial and temporal resolution of fMRS does not allow specific measurements of metabolites in different cell types. Thus, the analysis of fMRS data in the context of compartmentalized metabolism requires the formulation and application of mathematical models. In the present study we utilized the mathematical model introduced by Simpson et al. (2007) to gain insights into compartmentalized metabolism in vivo from the fMRS data obtained in humans at ultra high magnetic field by Mangia et al. (2007a). This model simulates brain glucose and lactate levels in a theoretical cortical slice. Using experimentally determined concentrations and catalytic activities for the respective transporter proteins, we calculate inflow and export of glucose and lactate in endothelium, astrocytes, and neurons. We then vary neuronal and astrocytic glucose and lactate utilization capacities until close correspondence is observed between in vivo and simulated glucose and lactate levels. The results of the simulations indicate that, when literature values of glucose transport capacity are utilized, the fMRS data are consistent with export of lactate by neurons and import of lactate by astrocytes, a mechanism that can be referred to as a neuron‐to‐astrocyte lactate shuttle. A shuttle of lactate from astrocytes to neurons could be simulated, but this required the astrocytic glucose transport capacity to be increased by 12‐fold, and required that neurons not respond to activation with increased glycolysis, two conditions that are not supported by current literature.
Ciliary neurotrophic factor fused to a protein transduction domain retains full neuroprotective activity in the absence of cytokine‐like side effects
Authors: Rezende Alexandre C. , Peroni Daniele , Vieira Andrè S. , Rogerio Fabio , Talaisys Rafael L. , Costa Fabio T. M. , Langone Francesco , Skaper Stephen D. , Negro Alessandro
Published: April 2009

Ciliary neurotrophic factor (CNTF) is a multifunctional cytokine that can regulate the survival and differentiation of many types of developing and adult neurons. CNTF prevents the degeneration of motor neurons after axotomy and in mouse mutant progressive motor neuronopathy, which has encouraged trials of CNTF for human motor neuron disease. Given systemically, however, CNTF causes severe side effects, including cachexia and a marked immune response, which has limited its clinical application. The present work describes a novel approach for administering recombinant human CNTF (rhCNTF) while conserving neurotrophic activity and avoiding deleterious side effects. rhCNTF was fused to a protein transduction domain derived from the human immunodeficiency virus‐1 TAT (transactivator) protein. The resulting fusion protein (TAT‐CNTF) crosses the plasma membrane within minutes and displays a nuclear localization. TAT‐CNTF was equipotent to rhCNTF in supporting the survival of cultured chicken embryo dorsal root ganglion neurons. Local or subcutaneous administration of TAT‐CNTF, like rhCNTF rescued motor neurons from death in neonatal rats subjected to sciatic nerve transection. In contrast to subcutaneous rhCNTF, which caused a 20–30% decrease in body weight in neonatal rats between postnatal days 2 and 7 together with a considerable fat mobilization in brown adipose tissue, TAT‐CNTF lacked such side effects. Together, these results indicate that rhCNTF fused with the protein transduction domain/TAT retains neurotrophic activity in the absence of CNTFs cytokine‐like side effects and may be a promising candidate for the treatment of motor neuron and other neurodegenerative diseases.
Energy Absorption Characteristics of Dual Phase Steel Tubes Under Static and Dynamic Loading
Authors: Velmurugan R. , Muralikannan R. , Malhotra S. K. , Sudharsan V.
Published: April 2009

Abstract:  Thin walled tubes are used as energy absorbing elements in automobile applications. The circular tube proves to be a popular energy absorber because it provides a reasonably constant operating force which is the prime characteristics of the energy absorber. Square and rectangular tubes are widely used in automobile structures as these cross sections are suitable for welding with other components in the structure and hence highly preferred. Advanced high strength steels can be utilised to absorb crash energy and minimise intrusion in the occupant zone. In this work circular, square and rectangular tubes made up of dual phase steel are tested in static and dynamic conditions. All the tubes are subjected to same amount of input impact energy but the specific energy absorption is higher in circular steel tubes. The results are compared with those for annealed tubes of same cross section. The effect of impact velocity is also studied by keeping the impact mass constant and varying the drop height. The experimental results are compared with the theoretical results and good agreement is found.
Residual Lifetime Assessment of an Ancient Riveted Steel Road Bridge
Authors: de Jesus A. M. P. , Figueiredo M. A. V. , Ribeiro A. S. , de Castro P. M. S. T. , Fernandes A. A.
Published: April 2009

Abstract:  The present paper reports research work carried out to characterise the fatigue behaviour of the Portuguese Pinhão riveted road bridge, built in 1903 over the Douro river. The present traffic conditions are completely different from those foreseen by the bridge designer, rising new concerns, with respect to the bridge integrity, namely its fatigue behaviour. An experimental programme was performed using original material removed from the bridge. The chemical composition and microstructures of the removed materials were characterised. Also, the notch toughness, at room temperature, was evaluated using both notch impact and Crack Opening Displacement (COD) tests. Fatigue crack growth tests were also used to evaluate the fatigue crack growth behaviour. Finally, fatigue tests of riveted joints were conducted in order to define an appropriate S‐N curve. The experimental results were used to evaluate the residual fatigue strength of the bridge, adopting both S‐N and Fracture Mechanics approaches. The analysis revealed a good tolerance to fatigue cracking, even in the presence of small fatigue cracks, detected in the joints.
Integrated water management of the Brahmaputra basin: Perspectives and hope for regional development
Authors: Rahaman Muhammad Mizanur , Varis Olli
Published: April 2009

Water is strongly linked with the overall development framework of the Brahmaputra basin. However, the absence of integrated management of Brahmaputra water resources and lack of coordination among the riparian states constitutes an ongoing threat to future development plans within the basin. Brahmaputra's abundant hydropower potential can help give riparian countries a safer energy future that is the key driving force behind the prospect of potential cooperation. This paper analyses the current status of Brahmaputra water resources and identifies the perspectives of riparian countries regarding the development of the Brahmaputra basin. It also identifies the opportunities for cooperation and regional development through integrated water development and management of the Brahmaputra basin. It is essential to develop an integrated water resources management approach involving all riparians to foster regional development and overcome the prospect of severe water conflict along the Brahmaputra basin.
Critical review of Integrated Water Resources Management: Moving beyond polarised discourse
Authors: Saravanan V. S. , McDonald Geoffrey T. , Mollinga Peter P.
Published: April 2009

Integrated Water Resource Management (IWRM) emerged as a popular concept in the water sector in the 20th century. From a highly techno‐centric approach in the past, it has taken a new turn embracing Habermasian communicative rationality as a place‐based nexus for multiple actors to consensually and communicatively integrate decisions in a hydrological unit. The ‘how to integrate’ approach had remarkable appeal worldwide in promoting authentic participation of all stakeholders. However, critics argue that the domain of water resource management is a political process of contestation and negotiation; the emphasis is on complexities, contextuality, power dynamics and the importance of analysing real world situations. They demonstrate ‘how integration cannot be achieved’ given the power dynamics in social interactions. These apparently contradictory discourses draw on different theoretical paradigms and polarise the discourse on IWRM, without offering constructive alternatives. To this end, this paper offers an option to complement this polarised discourse by examining ‘how integration actually does take place’ in a strategic context thereby facilitating consensual decisions to integrate water management for a sustainable future.
Carbon monoxide produced by intrasinusoidally located haem‐oxygenase‐1 regulates the vascular tone in cirrhotic rat liver
Authors: Van Landeghem Lien , Laleman Wim , Vander Elst Ingrid , Zeegers Marcel , Van Pelt Jos , Cassiman David , Nevens Frederik
Published: April 2009

Background/Objective: Carbon monoxide (CO) produced by haem‐oxygenase isoforms (HO‐1 & HO‐2) is involved in the regulation of systemic vascular tone. We aimed to elucidate the vasoregulatory role of CO in the microcirculation in normal and thioacetamide cirrhotic rat livers.

Methods: Haem‐oxygenase expression was examined by Western blot. Total HO enzymatic activity was measured spectrophotometrically. Sensitivity of hepatic stellate cells (HSCs) to CO‐mediated relaxation was studied by a stress‐relaxed‐collagen‐lattice model. To define the relative role of CO, the CO‐releasing molecule CORM‐2, the HO‐inhibitor zinc protoporphyrin‐IX and the HO‐1 inducer hemin were added to an in situ liver perfusion set‐up. The topography of vasoactive CO production was evaluated by applying different CO‐ and nitric oxide‐trapping reagents in the liver perfusion set‐up and by immunohistochemistry.

Results: Western blot showed decreased expression of both HO isoenzymes (P<0.036 for HO‐1; P<0.001 for HO‐2) in cirrhotic vs normal rat livers, confirmed by the HO‐activity assay (P=0.004). HSCs relaxed on exposure to CORM‐2 (P=0.013). The increased intrahepatic vascular resistance (IHVR) of cirrhotic rats was attenuated by perfusion with CORM‐2 (P=0.016) and pretreatment with hemin (P<0.001). Inhibition of HO caused a dose‐related increase in IHVR in normal and cirrhotic liver. In normal liver, the haemodynamically relevant CO production occurred extrasinusoidally, while intrasinusoidally HO‐1 predominantly regulated the microcirculation in cirrhotic livers.

Conclusion: We demonstrate a role for CO and HO in the regulation of normal and cirrhotic microcirculation. These findings are of importance in the pathophysiology of portal hypertension and establish CO/HO as novel treatment targets.
Elevated concentrations of 15‐deoxy‐Δ12,14‐prostaglandin J2 in chronic liver disease propose therapeutic trials with peroxisome proliferator activated receptor γ‐inducing drugs
Authors: Gressner Olav A. , Gao Chunfang , Rehbein Katharina , Lahme Birgit , Siluschek Monika , Berg Thomas , Müller Tobias , Gressner Axel M.
Published: April 2009

Background/Aims: Current knowledge confers a crucial role to connective tissue growth factor (CTGF/CCN2) in hepatic fibrogenesis. Hepatocytes are likely to be the major cellular source of CTGF in the liver in which CTGF is sensitively upregulated by TGF‐β. Recently, we demonstrated that the methylxanthine derivate caffeine leads to an upregulation of peroxisome proliferator activated receptor γ (PPARγ) expression in hepatocytes, thus sensitizing these cells to the well‐known inhibitory effect of 15‐deoxy‐Δ12,14‐prostaglandin J2 (15‐d‐PGJ2) on CTGF expression. However, upregulation of the receptor alone is not sufficient per se; its physiological ligand 15‐d‐PGJ2 is required to exert an inhibitory effect on transforming growth factor‐β (TGF‐β) target genes such as CTGF.

Methods: This study compared serum concentrations of 15‐d‐PGJ2 in Caucasian patients with fibrotic liver diseases (n=289), Caucasian controls (n=136) and Caucasian non‐liver disease (NLD) sick (n=307), as well as of Chinese patients with hepatocellular carcinoma (HCC) (n=43) and Chinese healthy controls (n=63) in order to characterize their suitability for therapeutic approaches with PPARγ‐inducing (i.e. CTGF inhibitory) drugs such as caffeine.

Results: The presented data showed that Caucasian patients with ongoing hepatic fibrogenesis (mean 6.2±5.9 μg/L) displayed strikingly higher serum concentrations of 15‐d‐PGJ2 than healthy probands (mean 2.3±1.0) and Caucasian patients with NLD (mean 2.7±1.4 μg/L). Similar results were found in Chinese patients with fully developed HCC (mean 1.3±0.7 μg/L) compared with Chinese healthy controls (mean 0.4±0.2 μg/L).

Conclusions: In conclusion, our data thus proposed an increased suitability of these patient groups for therapeutic approaches with drugs inducing PPARγ expression, such as methylxanthine derivates.
Altered factor VII activating protease expression in murine hepatic fibrosis and its influence on hepatic stellate cells
Authors: Roderfeld Martin , Weiskirchen Ralf , Atanasova Srebrena , Gressner Axel M. , Preissner Klaus T. , Roeb Elke , Kanse Sandip M.
Published: April 2009

Background: Platelet‐derived growth factor‐BB (PDGF‐BB) is a profibrotic factor in liver fibrosis through its ability to stimulate hepatic stellate cells (HSC). The liver‐derived serine protease factor VII activating protease (FSAP) regulates the activities of PDGF‐BB in a cell‐specific manner.

Aims: Our aim was to determine the influence of FSAP on the activation of HSC and to analyse the regulation of FSAP in hepatic fibrogenesis.

Methods: The effect of FSAP on PDGF‐stimulated p42/p44 mitogen‐activated protein kinase (MAPK) activation in primary rat HSC was determined by Western blotting. Migration and proliferation of HSC was evaluated in Boyden chamber experiments and 3H‐thymidine incorporation assays respectively. Expression of FSAP was analysed in a CCl4 mouse model of liver fibrosis by Western blot, quantitative real‐time polymerase chain reaction and immunohistochemistry.

Results: FSAP inhibited PDGF‐BB‐stimulated p42/p44 MAPK phosphorylation, proliferation and migration of HSC. FSAP mRNA expression level was increased 3 h after CCl4 application and decreased after 18 h and, in established fibrosis, after chronic CCl4 administration. In parallel, there was a decrease in the circulating FSAP protein in chronic fibrosis. Concurrently, the homogenous hepatic expression pattern of FSAP was disturbed. Immunohistochemistry revealed a decrease of FSAP in hepatocytes in inflammatory and fibrotic lesions.

Conclusions: Our results demonstrate an inhibitory effect of FSAP on PDGF‐mediated activation of HSC. In addition, FSAP expression is transiently increased in acute‐phase reaction but decreased during chronic fibrogenesis, which in turn may influence PDGF‐BB availability and myofibroblast activity.
Predictive factors of advanced recurrence after curative resection of small hepatocellular carcinoma
Authors: Hosaka Tetsuya , Ikeda Kenji , Kobayashi Masahiro , Hirakawa Miharu , Kawamura Yusuke , Yatsuji Hiromi , Sezaki Hitomi , Akuta Norio , Suzuki Fumitaka , Suzuki Yoshiyuki , Saitoh Satoshi , Arase Yasuji , Kumada Hiromitsu
Published: April 2009

Background: The tumour recurrence rate after resection is still high even in patients with small hepatocellular carcinoma (HCC). The advanced patterns of recurrence occasionally occur after resection. In this study, we analysed the clinical and histological characteristics of small HCC and evaluated the predictive factors of advanced tumour recurrence.

Methods: One hundred and sixty‐five patients underwent resection of small HCC measuring 3 cm or less in greatest dimension. Patterns of tumour recurrences were classified into advanced recurrence and minor recurrence based on size, number, vascular invasion and extrahepatic metastasis of recurrent tumour. We created a simple index to closely evaluate the malignant potential of small HCC, named α‐foetoprotein–size ratio index (ASRI).

Results: Overall tumour recurrence was significantly associated with tumour multiplicity (P<0.001) and ASRI (P=0.001). Tumour multiplicity, ASRI and tumour differentiation were independent and significant predictive factors of advanced recurrences. The overall survival rates were lower in the advanced recurrence group than the minor recurrence or the no recurrence group.

Conclusions: Patients with advanced recurrences have a poor prognosis, although they have undergone curative resection of small HCC. On the other hand, patients with minor recurrences have a relatively good prognosis. ASRI was a useful index to predict advanced recurrence after curative resection of small HCC. The therapeutic management to prevent advanced recurrences is needed.
Atropine for prevention of cardiac dysrhythmias in patients with hepatocellular carcinoma undergoing percutaneous ethanol instillation: a randomized, placebo‐controlled, double‐blind trial
Authors: Arnulf Ferlitsch , Monika Schmid , Herwig Schmidinger , Monika Homoncik , Johannes Pleiner‐Duxneuner , Gregor Ulbrich , Alfred Gangl , Markus Peck‐Radosavljevic
Published: April 2009

Introduction:Percutaneous ethanol injection (PEI) is an established method in the treatment of hepatocellular carcinoma (HCC). During this procedure, severe cardiac bradyarrhythmias can occur. A preemptive injection of atropine is recommended by professional guidelines to prevent these dysrhythmias.

Methods:Patients scheduled for PEI were randomized 1:1 to receive 0.5 mg atropinehydrochloride or placebo in a double‐blind randomized placebo‐controlled trial. Patients were electrocardiogram monitored, which were then analysed by an experienced rhythmologist blinded to the treatment arm.

Results:Patients in 40 consecutive PEI sessions were included. During PEI, a significant reduction in the mean heart rate (>15%) was seen in 15% of patients in the placebo group (median, −37%; range, 15–41%) and in 25% of patients receiving atropine (median, −20%; range, 16–64%). There was no significant difference between both groups.

During PEI, two patients (10%) in the placebo group developed a sinuatrial block (SAB). Four patients in the atropine group (20%) developed arrhythmias: three patients SAB, one of them with escape rhythm and one AV‐bundle block. Blood ethanol levels post‐PEI, amount of instilled ethanol, tumour size and location were not different between patients with or without dysrhythmias.

Conclusion:In this randomized‐controlled trial, a preprocedure atropine injection did not prevent the occurrence of bradyarrhythmias. Prophylactic use of atropine might not be effective and therefore cannot be recommended as a routine procedure. Clinicaltrials.gov‐identifier: NCT00575523.
Characteristics and outcome of patients with dual hepatitis B and C‐associated hepatocellular carcinoma: are they different from patients with single virus infection?
Authors: Huo Teh‐Ia , Huang Yi‐Hsiang , Hsia Cheng‐Yuan , Su Chien‐Wei , Lin Han‐Chieh , Hsu Chia‐Yang , Lee Pui‐Ching , Lui Wing‐Yiu , Loong Che‐Chuan , Chiang Jen‐Huei , Chiou Yi‐You , Lee Shou‐Dong
Published: April 2009

Abstracts

Background: Patients with hepatocellular carcinoma (HCC) caused by dual hepatitis B and C virus (HBV, HCV) infection may constitute a distinct disease group that is different from patients with single virus infection. This study compared the clinical characteristics and outcomes of patients with HBV, HCV and dual virus infection.

Methods: A prospective database of 1215 HCC patients with chronic hepatitis B, C or dual virus infection was investigated.

Results: Patients with HCV infection (n=388) were significantly older (mean age, 69 years) than patients with dual virus (n=75, 65 years) and HBV (n=752; 60 years) infection (P<0.0001). The male‐to‐female ratios for the HBV, dual virus and HCV groups were 5.2, 3.4 and 1.3 respectively (P<0.0001). Patients in the HBV group more often had higher total tumour volume (mean, 409 cm3) than those in the dual virus group (244 cm3) and HCV (168 cm3) group (P<0.0001). No significant differences of the severity of liver cirrhosis, performance status, cancer staging and tumour cell differentiation were noted among the three groups. Patients in the HCV group had a significantly poor survival in comparison with the HBV group only in the subset of patients with small tumour volume (<50 cm3) in the Cox proportional hazards model (relative risk, 1.44; P=0.041).

Conclusions: Dual HBV and HCV virus infection does not accelerate the speed of HCC formation in patients with chronic hepatitis B, and appears to have a modified course of carcinogenesis pathway that is diverted away from the biological behaviour of HBV and HCV infection.
Factors associated with adherence to combination therapy of interferon and ribavirin for patients with chronic hepatitis C: importance of patient's motivation and physician's treatment experience
Authors: Tanioka Daisuke , Iwasaki Yoshiaki , Araki Yasuyuki , Osawa Toshiya , Ikeda Hiroshi , Ando Masaharu , Kobashi Haruhiko , Sakaguchi Kohsaku , Shiratori Yasushi , Yamamoto Kazuhide
Published: April 2009

Background/Aims: Adherence to combination therapy with interferon (IFN) or pegylated IFN plus ribavirin for chronic hepatitis C patients is important for a better virological response. However, the impact of the patient's treatment experience and treatment centre on adherence to combination therapy has not been fully analysed. In this prospective study, we analysed the factors that might have an effect on adherence to therapy in patients who had initial or retreatment IFN therapy.

Patients and methods: We consecutively enrolled 363 patients with chronic hepatitis C; 221 were IFN naïve and 142 were undergoing retreatment. The mean ages of the naïve and retreatment groups were 54.8 and 55.7 years respectively. IFN α‐2b was administered daily for 2 weeks, followed by three times per week for 22 weeks, while ribavirin was administered daily. We evaluated the tolerability and response to combination therapy and analysed its relevant factors.

Results: Of the 363 patients, 189 (52%) achieved 80% adherence. The multivariate logistic regression analysis revealed that retreatment, centre with more patients treated, patient age (<55 years), male, genotype 2 and dosage of IFN per weight (<0.13 million units/kg) were associated with achievement of 80% adherence to combination therapy. Accordingly, the achievement of 80% adherence was more frequent in the retreatment (62%) than that in the naïve group (46%) (P<0.01) and in centres with more patients treated (57%) than in those with less patients treated (46%) (P=0.03).

Conclusion: The present data suggest that the patient's motivation and the physician's treatment experience may be important for a better adherence to combination therapy for patients with chronic hepatitis C.