bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthetic curcuminoids modulate the arachidonic acid metabolism of human platelet 12-lipoxygenase and reduce sprout formation of human endothelial cells
Authors: Jankun Jerzy , Aleem Ansari M. , Malgorzewicz Sylvia , Szkudlarek Maria , Zavodszky Maria I. , DeWitt David L. , Feig Michael , Selman Steven H. , Skrzypczak-Jankun Ewa
Published: May 2006

Platelet 12-lipoxygenase (P-12-LOX) is overexpressed in different types of cancers, including prostate cancer, and the level of expression is correlated with the grade of this cancer. Arachidonic acid is metabolized by 12-LOX to 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], and this biologically active metabolite is involved in prostate cancer progression by modulating cell proliferation in multiple cancer-related pathways inducing angiogenesis and metastasis. Thus, inhibition of P-12-LOX can reduce these two processes. Several lipoxygenase inhibitors are known, including plant and mammalian lipoxygenases, but only a few of them are known inhibitors of P-12-LOX. Curcumin is one of these lipoxygenase inhibitors. Using a homology model of the three-dimensional structure of human P-12-LOX, we did computational docking of synthetic curcuminoids (curcumin derivatives) to identify inhibitors superior to curcumin. Docking of the known inhibitors curcumin and NDGA to P-12-LOX was used to optimize the docking protocol for the system in study. Over 75% of the compounds of interest were successfully docked into the active site of P-12-LOX, many of them sharing similar binding modes. Curcuminoids that did not dock into the active site did not inhibit P-12-LOX. From a set of the curcuminoids that were successfully docked and selected for testing, two were found to inhibit human lipoxygenase better than curcumin. False-positive curcuminoids showed high LogP (theoretical) values, indicating poor water solubility, a possible reason for lack of inhibitory activity or/and nonrealistic binding. Additionally, the curcuminoids inhibiting P-12-LOX were tested for their ability to reduce sprout formation of endothelial cells (in vitro model of angiogenesis). We found that only curcuminoids inhibiting human P-12-LOX and the known inhibitor NDGA reduced sprout formation. Only limited inhibition of sprout formation at ∼IC50 concentrations has been seen. At IC50, a substantial amount of 12-HETE can be produced by lipoxygenase, providing a stimulus for angiogenic sprouting of endothelial cells. Increasing the concentration of lipoxygenase inhibitors above IC50, thus decreasing the concentration of 12(S)-HETE produced, greatly reduced sprout formation for all inhibitors tested. This universal event for all tested lipoxygenase inhibitors suggests that the inhibition of sprout formation was most likely due to the inhibition of human P-12-LOX but not other cancer-related pathways. [Mol Cancer Ther 2006;5(5):1371–82]
Multiple signaling pathways must be targeted to overcome drug resistance in cell lines derived from melanoma metastases
Authors: Smalley Keiran S.M. , Haass Nikolas K. , Brafford Patricia A. , Lioni Mercedes , Flaherty Keith T. , Herlyn Meenhard
Published: May 2006

Although >66% of melanomas harbor activating mutations in BRAF and exhibit constitutive activity in the mitogen-activated protein kinase/extracellular signal–regulated kinase kinase (MEK)/extracellular signal–regulated kinase signaling pathway, it is unclear how effective MEK inhibition will be as a sole therapeutic strategy for melanoma. We investigated the anticancer activity of MEK inhibition in a panel of cell lines derived from radial growth phase (WM35) and vertical growth phase (WM793) of primary melanomas and metastatic melanomas (1205Lu, 451Lu, WM164, and C8161) in a three-dimensional spheroid model and found that the metastatic lines were completely resistant to MEK inhibition (U0126 and PD98059) but the earlier stage cell lines were not. Similarly, these same metastatic melanoma lines were also resistant to inhibitors of the phosphatidylinositol 3-kinase/Akt pathway (LY294002 and wortmannin). Under adherent culture conditions, the MEK inhibitors blocked growth through the induction of cell cycle arrest and up-regulation of p27, but this was readily reversible following inhibitor washout. However, when the phosphatidylinositol 3-kinase and MEK inhibitors were combined, the growth and invasion of the metastatic melanoma three-dimensional spheroids were blocked. Taken together, these results suggest that the most aggressive melanomas are resistant to strategies targeting one signaling pathway and that multiple signaling pathways may need to be targeted for maximal therapeutic efficacy. It is further suggested that BRAF mutational status is not predictive of response to MEK inhibition under three-dimensional culture conditions. [Mol Cancer Ther 2006;5(5):1136–44]
Antisecretory Drugs for Diarrheal Disease
Authors: Farthing Michael J.G.
Published: May 2006

Acute diarrhea is a major cause of morbidity and mortality worldwide. Infants and pre-school children are the most vulnerable in whom there are 2–3 million deaths each year as a result of the associated dehydration and acidosis. Although oral rehydration therapy has reduced mortality during the past 30 years ago, the search for agents that will directly inhibit intestinal secretory mechanisms and thereby reduce faecal losses in patients with high-volume watery diarrhea has continued for more than 20 years. A variety of potential targets for antisecretory agents have been explored which include loci within the enterocyte (the chloride channel, calcium-calmodulin) and other sites such as enteric nerves and endogenous mediators (such as 5-HT, prostaglandins). Although the potential of calcium-calmodulin inhibition has as yet not been realised, preliminary studies suggest that there are chloride channel blockers under development that will find a place in the management of secretory diarrheas. Recent work has highlighted the importance of neurohumoral mechanisms in the pathogenesis of acute diarrhea. Potentiation of the effects of endogenous enkephalin activity by enkephalinase inhibition has already produced a safe, effective anti-secretory drug, racecadotril. Speculative early work indicates that there may be a role for antagonists of 5-HT, substance P, and VIP receptors. There now seems to be a real possibility that antisecretory therapy will become more widely available in the future.
Drugs Acting on Serotonin Receptors for the Treatment of Functional GI Disorders
Authors: Tonini Marcello , Pace Fabio
Published: May 2006

In the gut, serotonin (5-hydroxytryptamine: 5-HT) exerts a variety of effects on intrinsic enteric neurons, extrinsic afferents, enterocytes and smooth muscle cells, which are related to the expression of multiple 5-HT receptor types and subtypes regulating motility, vascular tone, secretion and perception. Agonists and antagonists at 5-HT receptors have gained access to the market for the two major variants of the irritable bowel syndrome (IBS), a functional disorder characterized by abdominal pain associated with diarrhea and/or constipation in the absence of any organic abnormality. Indeed, the 5-HT3 receptor antagonist alosetron is available in the US market for the treatment of women with severe, diarrhea-predominant IBS (D-IBS) refractory to conventional therapy, whereas tegaserod, a partial 5-HT4 receptor agonist, has been approved by the FDA and other regulatory agencies for the treatment of women with constipation-predominant IBS (C-IBS) or functional constipation. This review is mainly intended to discuss the role of non-neuronal (paracrine) and neuronal 5-HT in the pathophysiology of functional gastrointestinal disorders (FGIDs), such as IBS and functional dyspepsia, and the mechanisms through which drugs acting on 5-HT receptors regulate visceral motility, perception and secretion in these two conditions.
CCK1 Antagonists: Are They Ready for Clinical Use?
Authors: Peter Shajan A.S. , D’Amato Massimo , Beglinger Christoph
Published: May 2006

Cholecystokinin (CCK) is a peptide hormone which is found both in the gastrointestinal tract throughout the human small intestine and nerves in the myenteric plexus of the enteric nervous system and in the central nervous system. This dual location constitutes the anatomical basis for this in functions as a hormone and a neurotransmitter implicated in the regulation of both systems. CCK regulates not only motor functions in the gastrointestinal tract like lower oesophageal sphincter relaxation, gastric secretion and emptying, gall bladder contractility and bile secretion into the duodenum, intestinal and colonic motility, but also sensory functions and plays a role in the regulation of food intake. These effects are mediated through selective receptors CCK1 and CCK2. Over the last few years, research has focused on understanding the role of CCK, its receptors with antagonists at the biological, pharmacological, clinical and therapeutic level. As far as the CCK1 antagonists is concerned, important inroads have been made in the potential role of these antagonists in the treatment of GERD, IBS and pancreatitis. They have also shown encouraging results in sphincter of Oddi dysfunction and some gastrointestinal cancers. This review focuses on the recent ad vances of the biological role of CCK and their CCK1 antagonists: their current basic and clinical status in gastroenterology, with particular emphasis on the potential therapeutic role of the CCK1 antagonists and future research directions.
Tachykinin Receptors as Drug Targets for Motility Disorders
Authors: Hoogerwerf Willemijntje A. , Sarna Sushil K.
Published: May 2006

The tachykinins and their receptors are strategically distributed within the gut wall, spinal cord, and central nervous system to be potential targets of therapeutic agents for gastrointestinal motility disorders. However, the development of effective tachykinin receptor agonists or antagonists to treat these disorders has had very limited success so far. This is, in part, due to the complex and multilevel of regulation of gastrointestinal motility function and the challenges faced in targeting the specific type of gut contraction to normalize function in disease state.
Living Drugs for Gastrointestinal Diseases: The Case for Probiotics
Authors: Marteau Philippe
Published: May 2006

Nonpathogenic micro-organisms may contain or produce molecules of potential therapeutic interest. This led to the concept of using ingested living micro-organisms to produce and transport these molecules to targets in the proximal or distal intestine. Several characteristics of this pharmacological approach are very original: potential for in vivo production of active molecules, for targeting immune cells, for presenting immunogenic molecules in a microbial context, for duodenal delivery using bile sensitivity. Probiotics have been studied for some decades and more recently worm eggs have also received some interest. This paper summarizes facts (especially results of randomized controlled trials and pharmacokinetic studies), and ideas about the use of probiotics to treat or prevent gastrointestinal diseases. The safety of this approach (exceptional cases of infections have been observed), and the potential for using new agents or genetically modified micro-organisms (ongoing trials in humans with Crohn’s disease) are also discussed.
Established and Emerging Therapies for the Treatment of Viral Hepatitis
Authors: Forton Daniel , Karayiannis Peter
Published: May 2006

Patients who are chronically infected with either hepatitis B or C viruses run the risk of developing cirrhosis and hepatocellular carcinoma in later life. Antiviral treatment offers the only means of interrupting this progression. To date, recombinant interferon alpha and the nucleos(t)ide analogues lamivudine and adefovir dipivoxil are the only licensed drugs for the treatment of chronic hepatitis B, whilst recombinant or pegylated interferons in combination with ribavirin are the ones used for chronic hepatitis C virus infections. The efficacy of these treatments, reasons for treatment failure, drug resistance and future options are discussed in the present review.
Emerging Therapies for Liver Fibrosis
Authors: Fowell Andrew J. , Iredale John P.
Published: May 2006

Liver fibrosis occurs as a result of a wide range of injurious processes and in its end-stage results in cirrhosis. This gross disruption of liver architecture is associated with impaired hepatic function, portal hypertension and significant resultant morbidity and mortality. Indeed, liver fibrosis and cirrhosis represent a major worldwide healthcare burden. Recent progress in liver transplantation, the management of portal hypertension and the treatment of chronic viral hepatitis have had an important impact. However, these approaches are not without their limitations – in particular, issues regarding organ availability for transplantation – and serve to highlight the urgent requirement to influence pharmacologically the underlying fibrotic process in many patients. Liver fibrosis has been shown to be a bidirectional process and increasing data from laboratory and clinical studies reveal that even advanced fibrosis and cirrhosis are potentially reversible. Exploration of the molecular mechanisms underlying this bi-directionality will lead to char acterisation of the essential attributes of an antifibrotic therapy. In this review, these mechanisms are highlighted and the growing number of emerging antifibrotic agents discussed.
Rifaximin-Based Regimens for Eradication of Helicobacter pylori: A Pilot Study
Authors: Gasbarrini Antonio , Lauritano Ernesto Cristiano , Nista Enrico Celestino , Candelli Marcello , Gabrielli Maurizio , Santoro Michele , Zocco Maria Assunta , Cazzato Alessia , Finizio Rosalba , Ojetti Veronica , Cammarota Giovanni , Gasbarrini Giovanni
Published: May 2006

Background: Triple therapy is the treatment of choice for Helicobacter pylori-infected patients with an eradication rate ranging from 70 to 85%. Poor compliance and antibiotic resistance are the main causes of treatment failure. The aim of the present study was to assess the efficacy of rifaximin, a poorly absorbed antibiotic, for H. pylori eradication. Methods: We enrolled 48 consecutive H. pylori-positive patients affected. They were randomized to receive two 7-day rifaximin-based triple therapies: rifaximin tablets 400 mg t.i.d., esomeprazole 40 mg o.d. and clarithromycin 500 mg b.i.d. (CRE) or levofloxacin 500 mg o.d. (LRE). H. pylori eradication was assessed using a 13C-urea breath test 4 weeks after the end of therapy. Treatment compliance and the incidence of side effects were also evaluated. Results: No dropouts were observed. The eradication rate both on intention-to-treat and per-protocol analysis did not show significant differences between groups: 58% (14/24 patients) in group 1 and 42% (10/24 patients) in group 2 (p = 0.24, OR 1.96, 95% CI 0.62–6.18). No significant differences in patients’ compliance and incidence of side effects were found between groups. Conclusions: Rifaximin-based therapy showed optimal compliance but a limited eradication rate compared to standard first-line treatment. Further investigations are needed to evaluate different dosages and combinations.
Diarrea intratable causada por anomalías congénitas de los enterocitos
Authors: Philips Alan D.
Published: May 2006

Fundamento: La diarrea intratable de la lactancia representa un problema grave que conlleva un grado elevado de morbilidad y mortalidad. Estos casos requieren una asistencia dedicada tanto por parte de los padres como del personal médico, dado que no se dispone de remedios fáciles. La escasez de pacientes indica que para progresar en el conocimiento de estos trastornos son necesarios esfuerzos internacionales concertados para combinar recursos y pacientes. Son indispensables revisiones regulares de publicaciones pertinentes para propagar los avances y airear hipótesis y criterios diagnósticos. Métodos: Ésta es una revisión de la literatura actual y preliminar sobre las anomalías congénitas de los enterocitos. Resultados: Es posible establecer diagnósticos separados dentro de este síndrome, y los criterios diagnósticos están empezando a ser aceptados. Se está informando de casos a nivel mundial y las diferencias en los cursos clínicos están empezando a evidenciarse, con mejoría de la gravedad en algunos casos. No obstante, persiste un nivel elevado de morbilidad y mortalidad. Conclusiones: Cabe recorrer todavía un largo trecho hasta poder determinar la base subyacente de los trastornos. No obstante, la esperanza de determinar la base genética de las enfermedades está empezando a ser una realidad a medida que se realicen análisis genéticos moleculares. Esto es prioritario si tenemos en cuenta la posibilidad de que proporcione criterios diagnósticos más evidentes, aclarare las relaciones de la enfermedad y suministre una información muy necesaria sobre la patogénesis.
Infliximab Therapy Improves the Bone Metabolism in Fistulizing Crohn’s Disease
Authors: Miheller Pal , Müzes Gyorgyi , Zagoni Tamas , Toth Miklos , Racz Karoly , Tulassay Zsolt
Published: May 2006

Background: Tumor necrosis factor-α (TNF-α) plays a pivotal role in the pathogenesis of inflammatory bowel diseases and bone resorption as well. Limited data exist about the effect of anti-TNF-α infliximab on bone metabolism in inflammatory-type Crohn’s disease (CD). Aim: Our aim was to evaluate the effect of infliximab treatment on rapid changes of bone metabolism in fistulizing CD patients. Methods: 27 patients with fistulizing CD were treated with three series of infliximab. Serum osteocalcin (OC) and β-CrossLaps (bCL) were measured before administration of each infliximab infusion. 54 patients with inactive CD were controls. Results: In treated patients, there were significant differences in bCL concentrations on days 0 and 14 (p < 0.01) and days 0 and 42 (p < 0.05). OC levels increased significantly between day 0 and 42 (p < 0.05). The values of bCL and OC of control groups differed from serum levels in active patients before the treatment, but not on day 42. Bone markers improved significantly in responder patients, but not in non-responders. Conclusion: The beneficial effect of infliximab to the bone metabolism is more expressive in patients whose fistulizing disease improves with this therapy. Our results suggest that TNF-α has an important role in the alteration of bone metabolism in fistulizing CD patients.
Biochemical and Structural Analysis of the Bacillus subtilis ABC Transporter OpuA and Its Isolated Subunits
Authors: Horn Carsten , Jenewein Stefan , Sohn-Bösser Linda , Bremer Erhard , Schmitt Lutz
Published: May 2006

Adaptation of microorganisms to changing osmotic conditions is a prerequisite for survival and cellular vitality for most microorganisms. In the Gram-positive soil bacterium Bacillus subtilis, five transport systems catalyze the uptake of compatible solutes across the plasma membrane that allow the growth of B. subtilis over a wide range of osmotic conditions. Focus of this review is the osmoprotectant uptake A (OpuA) transporter, a member of the family of substrate-binding protein (SBP)-dependent ATP-binding cassette (ABC) transporters that mediates the uptake of the compatible solutes glycine betaine and proline betaine. OpuA is composed of three subunits: a nucleotide-binding domain (OpuAA) located in the cytosol, a transmembrane domain (OpuAB), and a SBP (OpuAC), which binds glycine betaine and proline betaine with high specificity and targets it to OpuAB for ATP-dependent translocation across the plasma membrane. After a brief introduction in the field of bacterial osmoadaptation, we will summarize our recent findings about the biochemical and structural analysis of the components of the OpuA systems. Our studies covered both the isolated subunits of the OpuA transporter and initial investigations of the whole transporter in vitro.
Energy-Converting [NiFe] Hydrogenases: More than Just H2 Activation
Authors: Hedderich Reiner , Forzi Lucia
Published: May 2006

The well-characterized [NiFe] hydrogenases have a key function in the H2 metabolism of various microorganisms. A subfamily of the [NiFe] hydrogenases with unique properties has recently been identified. The six conserved subunits that build the core of these membrane-bound hydrogenases share sequence similarity with subunits that form the catalytic core of energy-conserving NADH:quinone oxidoreductases (complex I). The physiological role of some of these hydrogenases is to catalyze the reduction of H+ with electrons derived from reduced ferredoxins or polyferredoxins. This exergonic reaction is coupled to energy conservation by means of electron-transport phosphorylation. Other members of this hydrogenase subfamily mainly function in providing the cell with reduced ferredoxin using H2 as electron donor in a reaction driven by reverse electron transport. These hydrogenases have therefore been designated as energy-converting [NiFe] hydrogenases.
Prokaryotic Kdp-ATPase: Recent Insights into the Structure and Function of KdpB
Authors: Haupt Melina , Bramkamp Marc , Coles Murray , Kessler Horst , Altendorf Karlheinz
Published: May 2006

P-type ATPases are amongst the most abundant enzymes that are responsible for active transport of ions across biological membranes. Within the last 5 years a detailed picture of the structure and function of these transport ATPases has emerged. Here, we report on the recent progress in elucidating the molecular mechanism of a unique, prokaryotic member of P-type ATPases, the Kdp-ATPase. The review focuses on the catalytic parts of the central subunit, KdpB. The structure of the nucleotide-binding domain was solved by NMR spectroscopy at high resolution and a model of the nucleotide-binding mode was presented. The nucleotide turned out to be ‘clipped’ into the binding pocket by a π-π interaction to F377 on one side and a cation-π interaction to K395 on the other. The 395KGXXD/E motif and thus the nucleotide-binding mode seems to be conserved in all P-type ATPases, except the heavy metal-transporting (class IB) ATPases. Hence, it can be concluded that KdpB is currently misgrouped as class IA. Mutational studies on two highly conserved residues (D583 and K586) in the transmembrane helix 5 of KdpB revealed that they are indispensable in coupling ATP hydrolysis to ion translocation. Based on these results, two possible pathways for the reaction cycle are discussed.
Structure and Function of the Betaine Uptake System BetP of Corynebacterium glutamicum: Strategies to Sense Osmotic and Chill Stress
Authors: Morbach Susanne , Krämer Reinhard
Published: May 2006

The soil bacterium Corynebacterium glutamicum has to cope with frequent fluctuations of the external osmolarity and temperature. The consequences of hyperosmotic and chill stress seem to differ, either causing dehydration of the cytoplasm or leading to impairment of cellular functions due to low temperature. Nevertheless, a particular type of regulatory response, namely the accumulation of so-called compatible solutes, is induced under both conditions. Compatible solutes are known to stabilize the native conformation of enzymes, which may be affected by osmotic and chill stress. BetP is a high-affinity uptake carrier for the compatible solute glycine betaine in C. glutamicum. BetP includes, besides its catalytic function, the ability to sense hyperosmotic conditions and chill stress. As a consequence, the carrier is activated in dependence of the extent of these types of stress. The signal input related to these changes of the environmental conditions is based on at least two different mechanisms. In case of hyperosmotic stress, BetP responds to the internal potassium concentration as a measure for hypertonicity, whereas chill stress is detected by an independent signal, most probably changes of the physical state of the membrane.
Biogenesis of the Bacterial Respiratory CuA, Cu-S Enzyme Nitrous Oxide Reductase
Authors: Zumft Walter G.
Published: May 2006

Nitrous oxide reductase (NosZ, EC 1.7.99.6) is the terminal oxidoreductase of a respiratory electron transfer chain that transforms nitrous oxide to dinitrogen. The enzyme carries six Cu atoms. Two are arranged in the mixed-valent binuclear CuA site, and four make up the µ4-sulfide-bridged Cu cluster, CuZ. The biogenesis of a catalytically active NosZ requires auxiliary functions for metal center assembly in the periplasm. Both Tat and Sec pathways share the task to transport the various Nos proteins to their functional sites. Biogenesis of NosZ requires an ABC transporter complex and the periplasmic Cu chaperone NosL. Sustaining whole-cell NosZ function depends on the periplasmic, FAD-containing protein NosX, and the membrane-bound iron-sulfur flavoprotein NosR. Most components with a biogenetic function are now amenable to structural studies.
Bioenergetics of Archaea: ATP Synthesis under Harsh Environmental Conditions
Authors: Müller V. , Lemker T. , Lingl A. , Weidner C. , Coskun Ü. , Grüber G.
Published: May 2006

Archaea are a heterogenous group of microorganisms that often thrive under harsh environmental conditions such as high temperatures, extreme pHs and high salinity. As other living cells, they use chemiosmotic mechanisms along with substrate level phosphorylation to conserve energy in form of ATP. Because some archaea are rooted close to the origin in the tree of life, these unusual mechanisms are considered to have developed very early in the history of life and, therefore, may represent first energy-conserving mechanisms. A key component in cellular bioenergetics is the ATP synthase. The enzyme from archaea represents a new class of ATPases, the A1A₀ ATP synthases. They are composed of two domains that function as a pair of rotary motors connected by a central and peripheral stalk(s). The structure of the chemically-driven motor (A1) was solved by small-angle X-ray scattering in solution, and the structure of the first A1A₀ ATP synthases was obtained recently by single particle analyses. These studies revealed novel structural features such as a second peripheral stalk and a collar-like structure. In addition, the membrane-embedded electrically-driven motor (A₀) is very different in archaea with sometimes novel, exceptional subunit composition and coupling stoichiometries that may reflect the differences in energy-conserving mechanisms as well as adaptation to temperatures at or above 100°C.
Structure Determination of Secondary Transport Proteins by Electron Crystallography: Two-Dimensional Crystallization of the Betaine Uptake System BetP
Authors: Tsai Ching-Ju , Ziegler Christine
Published: May 2006

Structure determination at high resolution is still a challenge for membrane proteins in general, but in particular for secondary transporters due to their highly dynamic nature. X-ray structures of ten secondary transporters have recently been determined, but a thorough understanding of transport mechanisms necessitates structures at different functional states. Electron cryo-microscopy of two-dimensional (2D) crystals offers an alternative to obtain structural information at intermediate resolution. Electron crystallography is a sophisticated way to study proteins in a natural membrane environment and to track conformational changes in situ. Furthermore, basic interactions between protein and lipids can be investigated. Projection and 3-dimensional maps of six secondary transporters from different families have been determined by electron crystallography of 2D crystals at a resolution of 8 Å and better. In this review, we give an overview about the principles of 2D crystallization, in particular of secondary transporters, and summarize the important steps successfully applied to establish and improve the 2D crystallization of the high-affinity glycine betaine uptake system from Corynebacterium glutamicum, BetP.
A Possible Role for Iron-Sulfur Cluster N2 in Proton Translocation by the NADH:Ubiquinone Oxidoreductase (Complex I)
Authors: Flemming Dirk , Stolpe Stefan , Schneider Daniel , Hellwig Petra , Friedrich Thorsten
Published: May 2006

The proton-pumping NADH:ubiquinone oxidoreductase, the respiratory complex I, couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. The enzyme mechanism is still unknown due to the lack of a high-resolution structure and its complicated composition. The complex from Escherichia coli is made up of 13 subunits called NuoA through NuoN and contains one FMN and nine iron-sulfur (Fe/S) clusters as redox groups. The pH dependence of the midpoint redox potential of the Fe/S cluster named N2 and its spin-spin interaction with ubiquinone radicals made it an ideal candidate for a key component in redox-driven proton translocation. During the past years we have assigned the subunit localization of cluster N2 to subunit NuoB by site-directed mutagenesis and predicted its ligation by molecular simulation. Redox-induced FT-IR spectroscopy has shown that its redox reaction is accompanied by the protonation and deprotonation of individual amino acid residues. These residues have been identified by site-directed mutagenesis. The enzyme catalytic activity depends on the presence of cluster N2 and is coupled with major conformational changes. From these data a model for redox-induced conformation-driven proton translocation has been derived.
Key Bacterial Multi-Centered Metal Enzymes Involved in Nitrate and Sulfate Respiration
Authors: Fritz G. , Einsle O. , Rudolf M. , Schiffer A. , Kroneck P.M.H.
Published: May 2006

Many essential life processes, such as photosynthesis, respiration, nitrogen fixation, depend on transition metal ions and their ability to catalyze multi-electron redox and hydrolytic transformations. Here we review some recent structural studies on three multi-site metal enzymes involved in respiratory processes which represent important branches within the global cycles of nitrogen and sulfur: (i) the multi-heme enzyme cytochrome c nitrite reductase, (ii) the FAD, FeS-enzyme adenosine-5′-phosphosulfate reductase, and (iii) the siroheme, FeS-enzyme sulfite reductase. Structural information comes from X-ray crystallography and spectroscopical techniques, in special cases catalytically competent intermediates could be trapped and characterized by X-ray crystallography.
Apoptosis: Future Targets for Neuroprotective Strategies
Authors: Ferrer Isidro
Published: May 2006

Focal permanent or transient cerebral artery occlusion produces massive cell death in the central core of the infarction, whereas in the peripheral zone (penumbra) nerve cells are subjected to various determining survival and death signals. Cell death in the core of the infarction and in the adult brain is usually considered a passive phenomenon, although events largely depend on the partial or complete disruption of crucial metabolic pathways. Cell death in the penumbra is currently considered an active process largely dependent on the activation of cell death programs leading to apoptosis. Yet cell death in the penumbra includes apoptosis, necrosis, intermediate and other forms of cell death. A rather simplistic view implies poor prospects regarding cell survival in the core of the infarction and therapeutic expectations in the control of cell death and cell survival in the penumbra. However, the capacity for neuroprotection depends on multiple factors, primarily the use of the appropriate agent, at the appropriate time and during the appropriate interval. Understanding the mechanisms commanding cell death and survival area is as important as delimiting the therapeutic time window and the facility of a drug to effectively impact on specific targets. Moreover, the detrimental effects of homeostasis and the activation of multiple pathways with opposing signals following ischemic stroke indicate that better outcome probably does not depend on a single compound but on several drugs acting in combination at the optimal time in a particular patient.
Vascular Protection in Brain Ischemia
Authors: Rodríguez-Yáñez Manuel , Castellanos Mar , Blanco Miguel , Mosquera Esther , Castillo José
Published: May 2006

Vascular damage occurring after cerebral ischemia may lead to a worse outcome in patients with ischemic stroke, as it facilitates edema formation and hemorrhagic transformation. There are several phases in the development of vascular injury (acute, subacute and chronic) and different mediators act in each one. Therapeutic options to avoid vascular injury must be focused on acting in each phase. However, even though experimental studies have demonstrated the benefit of therapeutic interventions both in the acute and chronic phases of cerebral ischemia, only the chronic phase offers a therapeutic window sufficiently wide enough to provide vascular protection in clinical practice. Several drugs including erythropoietin and HMG-CoA reductase inhibitors (statins), antihypertensive (angiotensin modulators), antibiotics (minocycline) and antihyperglycemic drugs (thiazolidinediones) have been proved to provide vascular protection in patients with ischemic stroke. Anti-inflammatory, antioxidant, and antiapoptotic actions are responsible for the vascular protective effect related to these drugs.
The Ischemic Penumbra: A New Opportunity for Neuroprotection
Authors: Fisher Marc
Published: May 2006

The development of acute stroke therapies has yielded only limited success and many failures in multiple clinical trials. The target of acute stroke therapy is that portion of the ischemic region that is still potentially salvageable, i.e. the ischemic penumbra. Neuroprotective drugs have the potential to prevent a portion of the ischemic penumbra from evolving into infracted tissue and designing trials that target neuroprotective drugs at patients with persistent penumbra should enhance the likelihood of a positive outcome. Currently, diffusion and perfusion MRI has the potential to approximate the location and persistence of the ischemic penumbra and can be used in clinical trials to select appropriate patients for inclusion and to evaluate a meaningful treatment effect. Perfusion CT may also have similar capabilities. Use of these imaging modalities in clinical trials and ultimately in clinical practice will likely help in the development and utilization of novel neuroprotective drugs.
Deterioration in Acute Ischemic Stroke as the Target for Neuroprotection
Authors: Serena Joaquín , Rodríguez-Yáñez Manuel , Castellanos Mar
Published: May 2006

The prevention and treatment of progressing stroke should be one of the main therapeutic targets of neuroprotective therapies. Despite the high prevalence of progressing stroke in acute stroke (25–35%) and its importance as a predictor of poor outcome, no treatment capable of preventing early neurological deterioration (END) or of reducing its impact has yet been developed. It is essential that our understanding of END’s underlying mechanisms be improved as it is currently not possible to predict its occurrence accurately. Published studies to date have been unable to identify a clinical profile which reliably predicts those patients likely to suffer neurological deterioration in the very early acute phase of ischemic stroke. In the following pages, we will discuss the present situation with regard to neurological worsening in general, paying special attention to END given the prognostic and therapeutic implications of this common condition. Factors associated with neurological deterioration and the potential mechanisms, particularly excitotoxic theory, are discussed.
Neuroprotection in Malignant MCA Infarction
Authors: Delgado Pilar , Sahuquillo Juan , Poca M. Antonia , Álvarez-Sabin José
Published: May 2006

Massive unilateral hemispheric infarction often develops progressive postischemic edema that leads to a malignant course of stroke with mortality of up to 80% with conventional medical therapies. Hypothermia and decompressive hemicraniectomy have shown neuroprotective effects in several animal models of focal transient and permanent MCA occlusion by reducing infarct size and improving neurological outcome. Our aim in this paper was to review the possible mechanisms of both therapies as well as the optimal time window and duration of application of each treatment in animal model and in human malignant MCA infarction reported in the literature.
Neuroprotection in Vascular Dementia
Authors: Martínez-Vila Eduardo , Murie-Fernández Manuel , Gállego Pérez-Larraya Jaime , Irimia Pablo
Published: May 2006

Vascular dementia (VaD) is the second most common form of dementia after Alzheimer’s disease (AD), and one of the major causes of mental and physical disability in developed countries. As such, the identification and implementation of strategies which prevent the development of the condition or enable improvements in patients with VaD are healthcare objectives of the first order. VaD is now regarded as a combined group of clinical-pathological entities rather than one disease, that is, multiple pathogenic mechanisms and lesion types underlie a cognitive impairment of vascular origin. The clinical diagnosis of VaD is complex and difficult because of the heterogeneous nature of its clinical presentation and progression and the low sensitivity of existing clinical criteria. Moreover, there is growing evidence of the epidemiological significance of mixed forms of dementia, and that ischemic processes may precipitate and exacerbate cognitive impairment in AD. Numerous compounds have been proposed as potentially useful in the treatment of patients with VaD, comprising vasodilatative, antithrombotic, hemorrheological, nootropic, antiserotoninergic and, most recently, antiglutamatergic and cholinergic approaches. In spite of some initially favorable reports based on the use of memantine, donepezil and galantamine, there is as yet no conclusive evidence of a definitive treatment for VaD. Unsatisfactory results from VaD drug trials may be attributed in part to the diversity of the patients included (underlying pathogenic mechanisms, number, type, and location of vascular lesions), and to methodological limitations in the design of the trials (outcome measures, end-points, size, follow-up period). The treatment of modifiable vascular risk factors – hypertension, diabetes mellitus, hypercholesterolemia and heart disease – is an important strategy for the reduction of the risk of dementia, and is likely to slow the progress of cognitive decline.
Other Neuroprotective Therapies on Trial in Acute Stroke
Authors: Ferro José M. , Dávalos Antoni
Published: May 2006

New neuroprotective agents on trial may potentially offer benefit to stroke patients without the associated hemorrhagic risk of thrombolytic therapy. Clinical investigation of these drugs has been designed to obtain the highest probability of success, or concentrates on the salvageable ischemic brain and use infarct growth on MRI as a surrogate end-point. Nine substances in 10 trials are currently being tested in three therapeutical strategies in patients with acute ischemic stroke. These strategies focus on: (1) the optimal management of serum glucose with the infusion of glucose, insulin and potassium to induce and maintain euglycemia; (2) the modulation of the inflammatory response with recombinant human interferon-β1a, and (3) interfering with the ischemic cascade using magnesium, albumin, the metal iron chelator DP-b99, the AMPA receptor antagonist zonampanel, the serotonin agonists repinotan and piclozotan, the free radical scavenger cerovive, and the membrane modulator citicoline. Future directions should develop neuroprotective compounds that are safe and well tolerated, are effective in a broad range of patients and can be used with or without rt-PA.
Bone Mass Increase in Puberty: What Makes It Happen?
Authors: Schoenau Eckhard
Published: May 2006

It is now thought that the critical property of bone is strength rather than weight, and that control of bone strength is mainly exercised through the effect of the mechanical loads brought to bear on bone. Muscle contraction places the greatest physiological load on bone, and so the strength of bone must be adapted to muscle strength (the functional muscle-bone unit). The Utah paradigm of skeletal physiology [J Hum Biol 1998;10:599–605] provides a model of bone development that describes how bone structure is regulated by local mechanical effects that can be adjusted by the effects of hormones. The DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) study analysed the interaction between the muscle and bone systems in males and females before and during puberty. This study found that differences between the genders in bone adaptation during puberty are at least partly driven by the influence of oestrogen in females. Testosterone seems to have no direct relevant effect on bone during puberty, but may be implicated in the greater amount of muscle mass achieved in boys compared with girls.
A Five-Week Exercise Program Can Reduce Falls and Improve Obstacle Avoidance in the Elderly
Authors: Weerdesteyn Vivian , Rijken Hennie , Geurts Alexander C.H. , Smits-Engelsman Bouwien C.M. , Mulder Theo , Duysens Jacques
Published: May 2006

Background: Falls in the elderly are a major health problem. Although exercise programs have been shown to reduce the risk of falls, the optimal exercise components, as well as the working mechanisms that underlie the effectiveness of these programs, have not yet been established. Objective: To test whether the Nijmegen Falls Prevention Program was effective in reducing falls and improving standing balance, balance confidence, and obstacle avoidance performance in community-dwelling elderly people. Methods: A total of 113 elderly with a history of falls participated in this study (exercise group, n = 79; control group, n = 28; dropouts before randomization, n = 6). Exercise sessions were held twice weekly for 5 weeks. Pre- and post-intervention fall monitoring and quantitative motor control assessments were performed. The outcome measures were the number of falls, standing balance and obstacle avoidance performance, and balance confidence scores. Results: The number of falls in the exercise group decreased by 46% (incidence rate ratio (IRR) 0.54, 95% confidence interval (CI) 0.36–0.79) compared to the number of falls during the baseline period and by 46% (IRR 0.54, 95% CI 0.34–0.86) compared to the control group. Obstacle avoidance success rates improved significantly more in the exercise group (on average 12%) compared to the control group (on average 6%). Quiet stance and weight-shifting measures did not show significant effects of exercise. The exercise group also had a 6% increase of balance confidence scores. Conclusion: The Nijmegen Falls Prevention Program was effective in reducing the incidence of falls in otherwise healthy elderly. There was no evidence of improved control of posture as a mechanism underlying this result. In contrast, an obstacle avoidance task indicated that subjects improved their performance. Laboratory obstacle avoidance tests may therefore be better instruments to evaluate future fall prevention studies than posturographic balance assessments.
Food Habits and Intake of Nutrients in Elderly Patients with Parkinson’s Disease
Authors: Lorefält B. , Ganowiak W. , Wissing U. , Granérus A.-K. , Unosson M.
Published: May 2006

Background: Weight loss is reported frequently in patients with Parkinson´s disease also early during the disease. Objective: To investigate food habits and nutrient intake in elderly Parkinson´s disease patients compared with matched controls, as well as to compare PD patients with and without weight loss. Methods: Twenty-six elderly free-living patients with PD, and 26 sex- and age-matched healthy controls, were assessed twice with one year interval between. All food consumed was recorded over 3 consecutive days. Food habits were assessed with the Food Based Concept for Classification of Eating Episodes and intakes of energy and nutrients were calculated. PD symptoms, olfaction, swallowing function, daily activities and serum concentration of different nutri ents were investigated. Results: After 1 year, the PD patients decreased their intakes of daily high quality snacks from 0.5 ± 0.7 to 0.3 ± 0.3 (p < 0.05) and their prepared complete meals from 0.8 ± 0.3 to 0.6 ± 0.3 (p < 0.05), while their daily number of prepared incomplete meals increased from 0.2 ± 0.2 to 0.3 ± 0.3 (p < 0.01). PD patients with weight loss increased their daily intakes of fat by 12 ± 34 g and their energy intake per kg body weight increased by 21 ± 31 kJ (p < 0.05), respectively, and this was higher than in those without weight loss (p < 0.01). PD patients required more help with buying and cooking food compared with the controls. Conclusions: PD patients’ food habits changed so that they consumed a lower number of prepared complete meals. PD patients with weight loss had a higher intake of fat and energy than those without weight loss, although this was obviously not sufficient to prevent weight loss. Impaired absorption of fat in PD should be discussed.
Outcome of Older Critically lIl Patients: A Matched Cohort Study
Authors: Rodríguez-Regañón Inmaculada , Colomer Isabel , Frutos-Vivar Fernando , Manzarbeitia Jorge , Rodríguez-Mañas Leocadio , Esteban Andrés
Published: May 2006

Background: Admission of older patients to intensive care units is a controversial issue. Objective: To estimate age-associated mortality of critically ill patients. Methods: A prospective matched cohort study in the Medical-Surgical Intensive Care Unit of a tertiary hospital was conducted. We included 100 consecutive patients older than 70 years admitted to the intensive care unit (cases) and 100 patients younger than 70 years (controls). The matching criterion was the severity of illness at admission to the intensive care unit as estimated by the simplified acute physiological score (SAPS II) without including age in its calculation. Results: Mortality in the intensive care unit was higher, but not statistically significant, in the older group: 26% vs. 19% (p = 0.23). Patients older than 70 years had a longer duration of mechanical ventilation (median 7 vs. 3 days) and longer stay in the intensive care unit (median 8 vs. 5 days). There were no differences in organ dysfunctions, except for a higher incidence of respiratory failure in the older group (p < 0.001). The use of invasive procedures was similar in both groups. There were more orders for the withholding/withdrawal of treatment in patients older than 70 years (9 vs. 3%, p = 0.07). Conclusion: In our study, age was not related with a significant higher mortality. In the older patients included in our study the survival was greater than 70% with a similar resource utilization except for a longer stay in the intensive care unit.