bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Structural Characterization of [{(Et2O)Mg}6(NPh)4Br4]: A Magnesium–Imide Cage Species Derived from a Dimagnesylamine Solution
Authors: Hascall Tony , Olmstead Marilyn M. , Power Philip P.
Published: December 2003

Grignard compounds and amines were converted into “dimagnesylamines” RN‐(MgX)2 as long ago as 1903. Now for the first time a crystalline compound has been obtained from a PhN(MgBr)2 solution in ether and characterized by X‐ray structure analysis. The title compound has a Mg6N4 adamantanyl framework; each Mg2+ ion is solvated by an ether molecule, and the four Br− ions are located above the four hexagonal faces of the Mg6N4 cage.
Binary Encoding of Compound Libraries
Authors: Eckes Peter
Published: December 2003

The rapid identification of functional molecules that participate in specific supramolecular interactions is a major problem in the screening of compound libraries. The binary encoding developed by Still et al. allows the structure assignment of “active” compounds according to a simple encoding scheme, and is independent of the synthetic chemistry employed. The viability of this concept has already been demonstrated, but the advantages will first be fully realized with libraries of small organic molecules.
Active Surface Carbon—A Reactive Intermediate in the Production of Synthesis Gas from Methane and Carbon Dioxide
Authors: Mark Michael F. , Maier Wilhelm F.
Published: December 2003

Pulse chemisorption studies reveal that a subsequent reaction is part of the mechanism of the formation of synthesis gas from CH4 and CO2, known since 1928. In the first step CH4 is decomposed on a Rh/A12O3 catalyst into reactive surface carbon CS and H2; in the second step C8 reacts with CO2 to give CO, but it is still not clear whether this step is also catalyzed by Rh.
Detection and Imaging of Single Molecules by Optical Near‐Field Microscopy
Authors: Basché Thomas
Published: December 2003

Resolutions of λ/43 rather than λ/2 are achieved when surfaces are probed with optical near‐field microscopy. Single molecules can thus be examined under ambient conditions and with low light intensity, an important requirement for the study of biomolecules.
Human Oxalate—Really Just an End‐Product of Metabolism?
Authors: Albrecht Steffen , Brandl Herbert , Schönfels Christoph
Published: December 2003

Red and white blood cells contain oxalate at concentrations more than 100 times higher than extracellular levels. This surprising result was obtained by sensitive and specific chemoluminometric measurements for the determination of oxalate in human body fluids. It is not yet known whether oxalate has any useful physiological function in humans; it is excreted and the calcium salt crystallizes as gall and kidney stones.
Molecules and Ions with Heptacoordinated Central Atoms
Authors: Minkwitz Rolf
Published: December 2003

Not the energy‐minimum structures predicted by VSEPR theory, namely a capped octahedron with C2, or a capped prism with C3, symmetry, but a pentagonal‐bipyramidal structure with D5h symmetry, which, however, is highly fluxional, are observed for molecules and ions with a heptacoordinated central atom. These results were obtained from recent studies by Christe et al., Seppelt et al., and Cockcroft et al; the latter recently determined the structure of ReF7 by high‐resolution powder neutron diffraction.
The Photochemical Synthesis of Fine Chemicals with Sunlight
Authors: Esser Peter , Pohlmann Bettina , Scharf Hans‐Dieter
Published: December 2003

The light of the sun can be used directly for changing chemical structures photochemically. Any industrial application must conform to the limitations imposed by the spectral distribution of the photons from the sun, the interruptions to the radiation due to the day/night rhythm, and the weather. In this review, we describe the photochemical potential of the sun, give a fundamental treatment of the concept of photoreactors driven by sunlight (abbreviated to solar photoreactors), and give an account of the realization of this concept in the first pilot plant on the “Plataforma Solar de Almeria” in southern Spain and in other activities in this field. Based on experimental data from photochemical investigations on the pilot plant scale, possibilities, limitations, and the potential growth of solar photochemistry are described. Solar photochemistry, in our opinion, is a technique which could make a contribution to the chemistry of the future because of its photochemical synthesis potential, the avoidance of waste products, and the direct utilization of the sun, not only as a primary energy source, but also as a reaction partner.
The Kinetics of Heterogeneous Electron Transfer Reaction in Polar Solvents
Authors: Fawcett William Ronald , Opallo Marcin
Published: December 2003

Data for heterogeneous electron transfer reactions obtained in the last ten years have been examined within the context of contemporary theory. Special attention is focused on systems for which rate constants and activation parameters are available as functions of solvents and of temperataure. The role of reactant structure in deteriming the kinetic parameters is also considered. Double layer effects both at unmodified and modified electrodes are discussed in detail. Experimental techniques, especially those suited to measuring fast reactions, are also outlined.
Technetium Radiopharmaceuticals—Fundamentals, Synthesis, Structure, and Development
Authors: Schwochau Klaus
Published: December 2003

Technetium‐99m radiopharmaceuticals are increasingly finding application in nuclear medicine for scintigraphic and emission tomographic imaging, morphologic description and functional testing of organs. Over 80% of the radiopharmaceuticals currently clinically used are labeled with the short‐lived, metastable nuclide 99mTc, whose nuclear properties are almost optimal with regard to a low radiation exposure of the patient and an effective detection of the emitted γ quanta. 99mTcO can be easily prepared without the use of accelerator systems through generator columns. Most of the 99mTc radiopharmaceuticals are complexes which are synthesized by reduction of 99mTcO in the presence of suitable ligands. To achieve a high organ specificity, some understanding of the relationship between the structure of the diagnostic agent and its organ distribution is necessary. Structure analyses can be carried out on analogous compounds of the long‐lived nuclide technetium‐99g; these compounds are obtainable in weighable quantities. The development of new 99mTc radiopharmaceuticals is a challenge to coordination chemists. The syntheses, molecular structures, and applications of the most important 99mTc radiopharmaceuticals will be described in this review, and current directions and tendencies of the development will be shown.
Synthesis of the First Microporous Aluminum Phosphonate with Organic Groups Covalently Bonded to the Skeleton
Authors: Maeda Kazuyuki , Kiyozumi Yoshimichi , Mizukami Fujio
Published: December 2003

A hydrothermal procedure is used to prepare the molecular sieve Al2 (CH3PO3)3 (1). This compound has a new three‐dimensional framework, in which one six‐coordinate and two four‐coordinate Al centers are bound to the CH3PO3 units. The channel walls of the micropores of 1 are probably not lined with O atoms but with methyl groups.
The Key–Lock Theory and the Induced Fit Theory
Authors: Koshland Daniel E.
Published: December 2003

As a glove changes shape when a hand slips into it, so an enzyme changes its conformation on binding a ligand. This theory of induced fit extends the lock‐and‐key principle that Emil Fischer proposed exactly 100 years ago. The new theory proposed by D. E. Koshland, Jr. in 1958 allows one to explain regulation and cooperative effects, and adds some new specificity principles as well.
The First Unambiguous Characterization of a Neutral Phosphorus Ylide–Lithium Complex: Isolation, Structure, and Ab Initio Investigations of [(PhCH2)2NLi · CH2PPh3]2
Authors: Armstrong David R. , Davidson Matthew G. , Moncrieff David
Published: December 2003

A four‐membered ring of two lithium and two nitrogen atoms is in the central unit of the dimer in the title (1), a complex between an alkali metal and a neutral phosphorus ylide. Surprisingly, this is the first time that such a model complex for the generation of ylides from phosphonium salts and alkali metal bases has been characterized in the solid state. The structure in solution was also determined, and the complexation energies for this and other model complexes were estimated by ab initio calculations.
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Direct Spectroscopic Evidence for a Hitherto Elusive “Zwitterionic” Excited State
Authors: Gade Lutz H.
Published: December 2003

More than sixty years after the formulation of the four‐state model for two‐electron two‐orbital systems, Nocera et al. have now directly detected both zwitterionic excited states in the δ orbital manifold of the binuclear complex [Mo2(PMe3)4Cl4], which has a metal–metal quadruple bond. These results open up new perspectives for the multielectron photochemistry of the metal–metal quadruple bond.
Cobalt‐Containing Molecular Sieves as Catalysts for the Low Conversion Autoxidation of Pure Cyclohexane
Authors: Vanoppen Dominic L. , De Vos Dirk E. , Genet Michel J. , Rouxhet Paul G. , Jacobs Peter A.
Published: December 2003

Isolated and immobilized cobalt centers are the essential prerequisites for the heterognization of the industrially important catalysis of cyclohexane autoxidation. This study reveals inter alia a higher selectivity for the formation of cyclohexyl hydroperoxide and the suppression of cobalt deactivation when, instead of soluble cobalt salts, cobalt‐modified aluminophosphates with low cobalt loading are employed as catalysts.
DNA–Carbohydrate Recognition: Design and Synthesis of an Eight‐Base Sequence‐Selective DNA‐Binding Oligosaccharide
Authors: Nicolaou K. C. , Ajito Keiichi , Komatsu Hironori , Smith Brian M. , Li Tianhu , Egan Miles G. , Gomez‐Paloma Luigi
Published: December 2003

A decacyclic oligosaccharide was designed to dock into the minor groove of duplex DNA selectively at a TCCTXXAGGA sequence. Competition experiments with calicheamicin γ revealed that the oligosaccharide inhibits DNA cleavage and exhibits high DNA binding affinity.
Regio‐ and Stereoselective Syntheses with Organocopper Reagents
Authors: Krause Norbert , Gerold Andreas
Published: December 2003

Of all of the organometallic reagents currently used to form carbon–carbon bonds, organocopper reagents rank amongst the most important. Interest in these reagents centers not only on their regioselectivity, but also increasingly on their application in stereoselective transformations (principally Michael additions and SN2′ reactions); the use of suitable substrates or chirally modified cuprates can lead to highly diastereo‐ and enantioselective reactions. Simultaneously, extensions of methods for the preparation and application of these reagents (for example functionalized organocopper species and Lewis acid catalysis, respectively) have opened up new horizons for organocopper reagents. Mechanistically, the reactions are well‐documented and understood, but this aspect of the subject has not kept pace with the many rapid developments in preparative chemistry. Organocopper ragents have proved to be indispensable in the synthesis of complex natural products and pharmaceuticals, chiral auxiliaries, and molecules with interesting structural features. In this review we will discuss some of the more recent important developments in this area; the organization will follow the type of selectivity (regio‐, diastereo‐, and enantioselectivity).
The Fascination of Large Rings: Cyclic Metal Complexes of Polydendate Ligands
Authors: Plenio Herbert
Published: December 2003

Coupling reactions in the coordination spheres of metal ions are the most important steps in the synthesis of very large inorganic ring complexes. The majority of such compounds can be categorized as coordination complexes. In addition, there are also examples from organometallic chemistry, such as the ferrocene scoop wheel presented by F. H. Köhler et al. in this issue. Before a planned synthesis of these compounds can be achieved, principles that govern the formation of these unusually large macrocycles must be determined. Insights into these principles are given herein.
Acyclic Diyne Metathesis (ADIMET), an Efficient Route to Poly(phenylene)ethynylenes (PPEs) and Nonconjugated Polyalkynylenes of High Molecular Weight
Authors: Weiss Karin , Michel Armin , Auth Eva‐Maria , Bunz Uwe H. F. , Mangel Timo , Müllen Klaus
Published: December 2003

Conjugated and nonconjugated diynes can be readily converted to poly(phenylene)‐ethynylene derivatives and polyalkynylenes by acyclic diyne metathesis. The catalyst for these condensation reactions is [(tBuO)3 WCtBu], and they proceed with cleavage of volatile alkynes such as 2‐butyne and 3‐hexyne. The chain lengths of the polymers are controlled by reaction temperature and pressure.
Isolation of a Nonicosahedral Intermediate in the Isomerization of an Icosahedral Metallacarborane
Authors: Dunn Shirley , Rosair Georgina M. , Thomas Rhodri Ll. , Weller Andrew S. , Welch Alan J.
Published: December 2003

For corrigendum see DOI:10.1002/anie.199707821
Tetraethylammonium Trichloride: A Versatile Reagent for Chlorinations and Oxidations
Authors: Schlama Thierry , Gabriel Kiroubagaranne , Gouverneur Véronique , Mioskowski Charles
Published: December 2003

For corrigendum see DOI:10.1002/anie.199727111
Phanes with Three‐ and Four‐Membered Rings as Building Elements
Authors: Gleiter Rolf , Merger Martin
Published: December 2003

The systematic integration of the small 2π‐ and 4π‐electron systems cyclopropenylium ion, cyclopropenone, oxo‐cyclobutenylium ion, and cyclobutadiene into phane chemistry was initiated only a few years ago. [n2]Cyclopropenylophanes, [n2]cyclopropenonophanes, metal‐capped [n4]cyclobutadienosuperphanes, and other new families of double‐decker phane species became available from cycloalkydiynes through special methods of double [2+1]cycloaddition with carbenes and metal complex induced dimerization by double [2+2]cycloaddition. Phane‐specific structural features were elucidated by X‐ray structural analyses. Cyclic voltammetry and PE spectroscopy as well as MO calculations reealed considerable interactions between closely spaced π‐electron systems. Decapping cyclobutadienosuperphanes formally extended the synthetic principle to threefold [2+2]cycloadditions resulting in [n4]‐bridged tricyclo‐[4.2.0.03, 5]octa‐3,7‐dienes, which represent a new type of cage compounds. Moreover, completion to fourfold [2+2]addition was achieved with the photoinduced transformation of [34]bridged tricyclo[4.2.0.03, 5]octa‐3,7‐diene into propella[34]cubane.
Charge Transfer through the DNA Base Stack
Authors: Holmlin R. Erik , Dandliker Peter J. , Barton Jacqueline K.
Published: December 2003

Whether the DNA base pair stack might serve as a medium for efficient, long‐range charge transfer has been debated almost since the first proposal of the double‐helical structure of DNA. The consequences of long‐range radical migration through DNA are important with respect to understanding carcinogenesis and mutagenesis. Double‐helical DNA has in its core a stacked array of aromatic heterocyclic base pairs, and this molecular π stack represents a unique system in which to explore the chemistry of electron transfer. We designed a family of metal complexes which bind to DNA by intercalative stacking within the helix; these metallointercalators may be usefully applied in probing DNA‐mediated electron transfer. Here we describe a range of electron transfer reactions we carried out which are mediated by the DNA base paired stack. In some cases, DNA serves as a bridge, and spectroscopic analyses permit us to probe how the π stack couples DNA‐bound donors and acceptors. These studies point to the sensitivity of coupling to DNA intercalation. However, if the DNA π stack effectively bridges donors and acceptors, the base‐pair stack itself might serve not only as a conduit for electron transfer in DNA, but also in reactions initiated from a remote position. We carried out a series of reactions involving oxidative damage to DNA arising from the remotely positioned oxidant on the helix. The implications of long‐range charge migration through DNA to effect damage are substantial. As in other DNA‐mediated charge transfers, these reactions are highly dependent on DNA intercalation and the integrity of the intervening base‐pair stack, but not on molecular distance. Furthermore, a physiologically important DNA lesion, the thymine dimers, can be reversed in a reaction initiated by electron transfer. This repair reaction can also be promoted from a distance as a result of long‐range charge migration through the DNA base pair stack.
Comparative psychology is still alive but may be losing relevance
Authors: Denenberg Victor H.
Published: December 2003

Greenberg et al., in their perspective on the current state and fate of comparative psychology, present convincing data that the field is viable and that comparative psychologists are making important contributions to the research literature. The central feature of the field is its emphasis upon evolution. This is also its weakness since advances in genetic techniques permit researchers to create laboratory animals that have no counterpart in the natural world, and thus have no evolutionary history. These “unnatural” animals are widely used in behavioral, biological, and medical studies, but the findings cannot be interpreted within a comparative psychology framework. As the use of these preparations expand, the relevance of comparative psychology diminishes. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 44: 21–25, 2004.
Antioxidant effect of acetylsalicylic and salicylic acid in rat brain slices subjected to hypoxia
Authors: De La Cruz J.P. , Guerrero A. , González‐Correa J.A. , Arrebola M.M. , Sánchez de la Cuesta F.
Published: December 2003

Acetylsalicylic acid (ASA) reduces the incidence of ischemic stroke mainly through its antithrombotic action; however, it also has a direct neuroprotective effect. The present study was designed to evaluate the effect of ASA on oxidative stress and the activity of nitric oxide synthase (NOS) in an in vitro model of hypoxia in rat brain slices. Rat brain slices were perfused with nitrogen (hypoxia) for a maximum of 120 min, after which we measured lipid peroxidation, glutathione levels, glutathione‐related enzyme activities, and constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) activities. In brain tissue subjected to hypoxia, ASA reduced oxidative stress and iNOS activity (all increased by hypoxia), but only when used at higher concentrations. The effects of salicylic acid (SA) were similar but more intense than were those of ASA. After oral administration, the effect of SA was much greater than that of ASA, and the decrease in cell death with SA was seen much more clearly. In view of the greater effect of SA compared to ASA on changes in oxidative stress parameters in a model of hypoxia, and higher brain concentrations of SA when it is administered alone than when ASA is given (undetectable levels), we conclude that SA plays an important role in the cytoprotective effect in brain tissue after ASA administration. © 2003 Wiley‐Liss, Inc.
Axonal transport versus dendritic transport
Authors: Setou Mitsutoshi , Hayasaka Takahiro , Yao Ikuko
Published: December 2003

Neurons have polarized processes for information output and input, axons, and dendrites. This polarized architecture is essential for the neuronal function. An increasing number of molecular components that mediate neuronal polarity establishment have been characterized over the past few years. The vast majority of these molecules include proteins that act in scaffolding protein complexes to sustain the polarized anchoring of molecules. In addition, more signaling and cytoskeleton‐associated proteins have been proposed for establishment of polarity. It has become evident that dendritic and axonal transport of molecules depends on scaffolding/adaptor proteins that are recognized by molecular motors. Current and future research in the neuronal cell polarity will be focused on how different cargo molecules transmit their signals to the cytoskeleton and change its dynamic properties to affect the rate and direction of vesicular movement. In this review, we discuss recent evidence that scaffolding proteins can regulate motor motility and guidance by a mechanism of substrate‐cytoskeletal coupling and amino acid modifications during polarized transport. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 201–206, 2004
Yield line mechanism analysis of steel members and connections
Authors: Zhao Xiao‐Ling
Published: December 2003

Yield line mechanism analysis has been widely used to study steel members and connections that involve local collapse mechanisms. In the application of the yield line method, a fundamental requirement is to determine the reduced plastic moment capacity of an inclined yield line under axial force. This paper reviews various theories dealing with inclined yield lines. Comparisons between these theories are presented. The paper also summarizes some basic or simple yield line mechanisms that may be adopted directly to solve more complicated problems. The application of yield line mechanism analysis is included, covering steel plates, open‐section members, closed‐section members, void‐filled members, welded connections and bolted connections. It is shown that this method can be used to study post‐collapse behaviour, load‐carrying capacity, ductility, rotation capacity and energy absorption.
Role of internship in higher education in environmental sciences
Authors: Scholz, Roland W. , Steiner Regula , Hansmann Ralf
Published: December 2003

The benefits of a compulsory internship in environmental science education were investigated with respect to the three institutional goals of university education: (a) training for research, (b) professional education, and (c) general natural science education. A survey examined which student qualifications are improved by an internship complementary to traditional university education. The survey assessed 14 qualifications of students participating in a compulsory 15‐week internship in the 5‐year diploma program at the Swiss Federal Institute of Technology (ETH Zürich). Pre‐ and postinternship questionnaires of 478 students and 293 supervisors are included. Results indicated that internships enhance general abilities and key qualifications, such as communication skills, report writing, organization of work, information acquisition, and the ability to operate independently. This suggests that internships are of high value to professional education. However, internships also seem to promote salient qualifications of complex environmental problem solving which are relevant for the development of research capabilities in environmental sciences. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 41: 24–46, 2004
Ethnic identity and self‐esteem: examining the role of social context
Authors: Umaña‐Taylor Adriana J.
Published: December 2003

This study explored ethnic identity and self‐esteem among 1062 Mexican‐origin adolescents who were attending one of three schools, which varied in their ethnic composition (i.e., predominately Latino, predominately non‐Latino, and balanced Latino/non‐Latino). Significant relationships emerged between ethnic identity and self‐esteem among adolescents in all school settings. Furthermore, controlling for generation and maternal education, adolescents attending the predominately non‐Latino school reported significantly higher levels of ethnic identity than adolescents in the other schools. Consistent with ecological theory, these findings challenge researchers to design future studies in ways such that multiple layers of context and their influence on development can be examined.
Antisense suppression of the Arabidopsis PIF3 gene does not affect circadian rhythms but causes early flowering and increases FT expression
Authors: Oda Atsushi , Fujiwara Sumire , Kamada Hiroshi , Coupland George , Mizoguchi Tsuyoshi
Published: December 2003

Photoperiodic control of flowering is regulated by light and a circadian clock. Feedback regulation of the transcription of clock components is one of the most common and important mechanisms that control clock functions in animals, fungi, and plants. The Arabidopsis circadian clock is believed to involve two myb‐related proteins, LHY (late elongated hypocotyl) and CCA1 (circadian clock associated 1), which negatively regulate TOC1 (timing of cab expression 1) gene expression through direct binding to the TOC1 promoter. PIF3 (phytochrome‐interacting factor 3), a bHLH transcription factor binds promoter regions of the LHY and CCA1 genes, affecting the light induction of these genes, and interacts with TOC1 protein. Although the positive feedback regulation of clock components in plants has been predicted, and PIF3 has been assumed to be involved, the molecular nature of this process has not been elucidated. Here we demonstrate that the antisense suppression of the PIF3 gene causes higher levels of mRNA of floral activator genes CO (constans) and FT (flowering locus T) and results in early flowering under long days (LD). Neither the circadian rhythms of the clock‐controlled genes (CCGs) under constant conditions nor the diurnal rhythms of the CCGs under LD conditions are affected by the reduction in PIF3 gene expression. These results suggest that PIF3 may play an important role in the control of flowering through clock‐independent regulation of CO and FT gene expression in Arabidopsis.
Chronic hepatitis D: A vanishing disease? An Italian multicenter study
Authors: Gaeta Giovanni B. , Stroffolini Tommaso , Chiaramonte Maria , Ascione Tiziana , Stornaiuolo Gianfranca , Lobello Salvatore , Sagnelli Evangelista , Brunetto Maurizia R. , Rizzetto Mario
Published: December 2003

Hepatitis delta virus (HDV) was responsible for a high proportion of cases of acute and chronic liver disease in Southern Europe during the 1970s. Some data suggest that by the 1990s HDV circulation had substantially declined. We have assessed the prevalence of HDV infection and its clinical impact in 834 Italian hepatitis B surface antigen (HBsAg) carriers in 1997. Anti-HDV antibodies were sought in all consecutive chronic HBsAg carriers observed in 14 referral liver units throughout Italy. Risk factors for anti-HDV positivity were evaluated. Anti-HDV antibodies were found in 69 of 834 (8.3%) HBsAg-positive patients. Cohabitation with an anti-HDV-positive subject, intravenous drug addiction, residence in the South of the country, and the presence of cirrhosis were independently associated with the presence of anti-HDV antibodies. The overall prevalence of anti-HDV antibodies was lower than those observed in 2 multicenter surveys performed in 1987 and 1992 (23% and 14%, respectively). By 1997, the percentage of anti-HDV-positive subjects had sharply decreased in the 30 to 50 years age group, whereas it was almost unchanged in subjects over 50 years of age. The highest prevalence of anti-HDV antibodies (11.7%) was found in patients with cirrhosis. This prevalence was as high as 40% in the 1987 study. The circulation of HDV sharply decreased in Italy, by 1.5% per year, from 1987 to 1997. This decrease resulted mainly from the reduction in chronic HDV infections in the young, for whom high morbidity and mortality rates were recorded in the past. The results anticipate the almost complete control of HDV infection in the near future.
Shear stress modulates the vascular tone in perfused livers isolated from normal rats
Authors: Pastor Catherine M. , Hadengue Antoine
Published: December 2003

Fluid shear stress can be increased either by increasing the flow rate or perfusing increasing doses of norepinephrine (NE) at a constant flow rate. Concomitantly, increased fluid shear stress at the surface of endothelial cells releases nitric oxide (NO). To better understand the role of NO released by shear stress in regulating intrahepatic vascular resistances, we increased fluid shear stress either by changing the flow rate or by perfusing increasing doses of NE at a constant flow rate in perfused livers isolated from normal rats. When concentration-response curves to NE were studied at low, mild, and high flow rates, portal pressure increased during NE perfusion. The higher the flow rate, the lower the response to NE. NO synthase inhibition similarly increased the response to NE at each flow rate. Thus, NO was released by NE-induced increased shear stress, but other vasodilators are likely to be responsible for the flow-induced increased shear stress. In additional experiments, when flow rate was decreased while infusing increasing doses of NE to maintain the portal pressure constant, shear stress remained steady and NO was not released. Hepatic NO production in the different conditions of shear stress could not be detected. Our data are consistent with the fact that in the liver, NO released by shear stress decreases the vasoconstriction to NE and regulates the intrahepatic vascular resistances.
Transforming growth factor-β induces apoptosis in rat FaO hepatoma cells via cytochrome c Release and oligomerization of Apaf-1 to form a ˜700-kd apoptosome caspase-processing complex
Authors: Freathy Caroline , Brown David G. , Roberts Ruth A. , Cain Kelvin
Published: December 2003

In mammalian cells, non receptor-mediated apoptosis occurs via the cytochrome c-dependent assembly of a ˜700-kd apoptotic protease-activating factor 1 (Apaf-1)/caspase-9 containing apoptosome complex. This initiates the postmitochondrial-mediated effector caspase cascade. We now show that receptor mediated transforming growth factor β1(TGF-β1)-induced apoptosis in rat hepatoma cells is accompanied by processing and activation of caspases-2, -3, -7, and -8. Furthermore, we show that caspase activation is mediated via the release of cytochrome c and the oligomerization of Apaf-1 into an ˜700-kd apoptosome complex. Similarly, in vitroactivation of hepatoma cell lysates with 2′-deoxyadenosine 5′-triphosphate (dATP) results in the formation of the ˜700-kd apoptosome complex, which recruits and processes caspases-3 and -7. Z-VAD.FMK [benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethylketone], the pan-caspase inhibitor totally inhibits dATP-stimulated caspase activation but does not block the assembly of the large Apaf-1 containing apoptosome complex. However, the recruitment and subsequent processing of caspases-3 and -7 to the apoptosome is blocked. Similarly, in intact cells, although Z-VAD.FMK blocked TGF-β1-induced apoptosis, it did not prevent the oligomerization of Apaf-1 into the apoptosome. However, recruitment and processing of caspases-3 and -7 were prevented by Z-VAD.FMK. These data show that TGF-β1 induces apoptosis via release of cytochrome c and activation of the Apaf-1 apoptosome complex, which initiates the caspase cascade.
Computation in gene networks
Authors: Ben-Hur Asa , Siegelmann Hava T.
Published: December 2003

Genetic regulatory networks have the complex task of controlling all aspects of life. Using a model of gene expression by piecewise linear differential equations we show that this process can be considered as a process of computation. This is demonstrated by showing that this model can simulate memory bounded Turing machines. The simulation is robust with respect to perturbations of the system, an important property for both analog computers and biological systems. Robustness is achieved using a condition that ensures that the model equations, that are generally chaotic, follow a predictable dynamics.
Error function attack of chaos synchronization based encryption schemes
Authors: Wang Xingang , Zhan Meng , Lai C.-H. , Gang Hu
Published: December 2003

Different chaos synchronization based encryption schemes are reviewed and compared from the practical point of view. As an efficient cryptanalysis tool for chaos encryption, a proposal based on the error function attack is presented systematically and used to evaluate system security. We define a quantitative measure (quality factor) of the effective applicability of a chaos encryption scheme, which takes into account the security, the encryption speed, and the robustness against channel noise. A comparison is made of several encryption schemes and it is found that a scheme based on one-way coupled chaotic map lattices performs outstandingly well, as judged from quality factor.
Combined effect of volume and gravity on the three-dimensional flow instability in noncylindrical floating zones heated by an equatorial ring
Authors: Lappa Marcello
Published: December 2003

The present paper strongly extends a previous analysis dealing with the investigation of the three-dimensional Marangoni flow instability in cylindrical floating zones (straight liquid column of full-zone extent) of a low Prandtl liquid laterally heated by a ring positioned around the equatorial plane and under microgravity conditions. The new study gives insights into the combined influence of volume and gravitational effects. The deformation of the free melt–gas interface due to the gravity field is taken into account. Parallel supercalculus is used to reduce the otherwise prohibitive computational time. The prominent features of the three-dimensional field are largely dependent on geometrical parameters. The results (full zone) are heretofore unseen and show that the interplay between the upper half and lower half of the liquid domain is an essential factor for the correct description of the phenomena under investigation. They are contrasted with the case of the half zone for which a rich variety of interesting and worthy contributions is available in literature.
Male germ line stem cells: from cell biology to cell therapy
Authors: Lin David Pei-Cheng , Chang Ming-Yu , Chen Bo-Yie , Chang Han-Hsin
Published: December 2003

Research using stem cells has several applications in basic biology and clinical medicine. Recent advances in the establishment of male germ line stem cells provided researchers with the ability to identify, isolate, maintain, expand and differentiate the spermatogonia, the primitive male germ cells, as cell lines under in vitro conditions. The ability to culture and manipulate stem cell lines from male germ cells has gradually facilitated research into spermatogenesis and male infertility, to an extent beyond that facilitated by the use of somatic stem cells. After the introduction of exogenous genes, the spermatogonial cells can be transplanted into the seminiferous tubules of recipients, where the transplanted cells can contribute to the offspring. The present review concentrates on the origin, life cycle and establishment of stem cell lines from male germ cells, as well as the current status of transplantation techniques and the application of spermatogonial stem cell lines.
The Justification of Concepts in Carnap's Aufbau
Authors: Tsou Jonathan Y.
Published: December 2003

This paper concerns the recent debate on the nature and motivations of the epistemological project advanced in Rudolf Carnap's (1891–1970) Aufbau. Much of this debate has been initiated by Michael Friedman and Alan Richardson who argue (against the received view of the Aufbau as a foundationalist defense of empiricism) that Carnap's epistemological project is located in the tradition of neo-Kantian epistemology. On this revisionist reading of the Aufbau, Carnap's project is not motivated to address traditional empiricist problems regarding the justification of knowledge, but rather to show how objective knowledge is possible. A central aspect of the Aufbau that is neglected in the revisionists' analysis is the role of epistemic justification in Carnap's project. The aim of the present study is to argue that although the general epistemology in the Aufbau can be cast as neo-Kantian, Carnap's method of construction theory (or rational reconstruction) is formulated precisely as an empiricist method for the justification of conceptual knowledge. Construction theory radically redefines ‘empirical justification’ into a formal-conventional notion, and is part of Carnap's more general agenda of redefining epistemology as a purely formal discipline.
The Effects of the Plasminogen Pathway on Scar Tissue Formation
Authors: Samara Ghassan J. , Schaffner Adam D. , Eisenstat Jonathan , Nguyen Hoang‐Lan T.
Published: December 2003

Objectives/Hypothesis The authors sought to determine the role of the plasminogen pathway in wound healing. They hypothesized that decreased fibrin degradation may lead to increased collagen deposition. Presuming that the degree of histopathological abnormality correlates with the aesthetic appearance of the scar, we conducted a study that attempted to determine the histopathological appearance of scar tissue in mice with and without impaired function of the plasminogen pathway.

Study Design Mice with and without deficiencies in the plasminogen pathway underwent surgery. The role of the plasminogen pathway in wound healing was studied by analysis of scar tissue formation using the methods described.

Methods A 2‐cm incision was made on the dorsum of mice with and without specified genetic deficiencies in the plasminogen pathway. After the animals were killed, the tissue was harvested, fixed, and prepared using hematoxylin and eosin as well as trichrome stains. Histopathological analysis and scoring were performed by two separate investigators in a blinded manner. Student's t test was used to determine statistical significance between groups.

Results A statistically significant difference in collagen orientation was noted between mice with impaired plasminogen pathway function and the wild‐type (control) group (P = .0163). A statistical trend toward improved wound healing for plasminogen‐deficient mice was found for overall histomorphological score (P = .0706).

Conclusion The role of the plasminogen pathway in wound healing is one that should be noted and may lead to the development of new therapies that reduce scar tissue formation. Hence, the role of other thrombolytic and anti‐thrombolytic agents in wound healing should be further investigated to precisely identify agents that play the most significant role in scar tissue formation.
Comparison of Free Radicals and Antioxidant Enzymes in Chronic Otitis Media With and Without Tympanosclerosis
Authors: Karldağ Turgut , İlhan Nevin , Kaygusuz İrfan , Keleş Erol , Yalçn Şinasi
Published: December 2003

Objective/Hypothesis The pathogenesis of tympanosclerosis is unclear. The study was performed to investigate the role of nitric oxide, free oxygen radicals, and antioxidants in development of tympanosclerosis in patients with chronic otitis media.

Study Design A prospective study in patients with nasal polyps.

Methods Sixty‐five patients who underwent tympanoplasty or tympanoplasty together with mastoidectomy were included in the study. Preoperative venous blood samples were drawn, and serum sodium, potassium, calcium, alkaline phosphatase, inorganic phosphorus, parathormone, and calcitonin levels were measured. The patients who had tympanosclerotic plaques on tympanic membrane or middle ear mucosa or near the ossicular chain or mastoid bone were designated as group 1 (n = 34), and the remaining patients as group 2 (n = 31). Intraoperatively, specimens were obtained from the middle ear mucosa and tympanic membrane to measure nitric oxide and malondialdehyde levels. In addition, plasma malondialdehyde levels and erythrocyte superoxide dismutase and catalase activity were determined.

Results All patients had similar demographic features and serum electrolyte and hormone levels. Nitric oxide and malondialdehyde levels of the specimens obtained from the middle ear mucosa (P = .001) and tympanic membrane (P = .01) and, in parallel to this, the plasma malondialdehyde activity level were higher in group 1 than in group 2. Moreover, group 2 had significantly lower erythrocyte catalase activity levels (P = .001) compared with group 1, whereas such a significant difference was not present for superoxide dismutase activity levels (P > .05).

Conclusion The study results suggest that nitric oxide, free oxygen radicals, and catalase may have a role in the development of tympanosclerosis in patients with chronic otitis media.
Evaluation of the Inferior Turbinate in Patients With Deviated Nasal Septum by Using Computed Tomography
Authors: Egeli Erol , Demirci Levent , Yazýcý Burhan , Harputluoglu Ugur
Published: December 2003

Objectives/Hypothesis The objective was to measure the dimensions, composition, and possible structural and radiological changes of the compensatory hypertrophic inferior turbinate in patients with deviated nasal septum.

Study Design A prospective, nonrandomized clinical trial at a university medical center.

Methods Twenty‐three patients with deviated nasal septum and compensatory hypertrophy of the inferior turbinate in the contralateral nasal cavity were examined by computed tomography.

Results The dimensions of the compensatory hypertrophic inferior turbinate in patients with septal deviation were compared with normal control subjects. The difference in width of the medial and lateral mucosa and the conchal bone between the two groups was statistically significant (P < .05).

Conclusion The present study uncovers the dimensions and composition of the inferior turbinate with compensatory hypertrophy in patients with nasal septum deviation. The findings support the decision to excise the inferior turbinate bone at the time of septoplasty, because of the significant bony and mucosal expansion.
Smoking in Chronic Rhinosinusitis: A Predictor of Poor Long‐Term Outcome After Endoscopic Sinus Surgery
Authors: Briggs Russell D. , Wright Steven T. , Cordes Stephanie , Calhoun Karen H.
Published: December 2003

Objective This study was designed to determine whether smoking patients have poorer outcomes after endoscopic sinus surgery (ESS) based on a reliable validated rhinosinusitis‐specific quality‐of‐life outcomes test.

Study Design Retrospective chart and computed tomography (CT) review with telephone and letter questionnaire.

Methods Charts of 230 adult patients undergoing ESS for chronic rhinosinusitis between January 1995 and December 1998 were reviewed. Each participating patient completed a detailed questionnaire, including the Sino‐Nasal Outcome Test‐16 (SNOT‐16), at an average of 52 months after surgery. Preoperative CT scans were reviewed and the findings used to stage the patients' conditions. Multivariate analysis was used to assess these data.

Results Eighty‐two patients completed the questionnaire, with 26 who smoked at the time of surgery and continued to smoke at the time of answering the questionnaire (Smokers). Average SNOT‐16 score in Smokers was 27.5, versus 18.2 in those who did not smoke at the time of surgery (Non‐Smokers). There was a statistically significant correlation between elevated SNOT‐16 scores and smoking (P < .001) and antibiotic use within the past year (P < .001). There was an association between high SNOT‐16 scores and both prior smoking and passive smoke exposure that did not reach statistical significance (P = .055 and P = .267, respectively). CT staging scores and prior ESS were not statistically correlated with SNOT‐16 scores.

Conclusions Smoking is associated with statistically worse outcomes after ESS based on average SNOT‐16 scores. Although no investigator has proved that the effects of smoking on sinonasal health are reversible, we counsel smoking patients considering ESS about the desirability of smoking cessation (for this and many health reasons), and the possibility of a poorer postsurgery outcome should they continue smoking.
Recurrent Pleomorphic Adenoma of the Parotid Gland: A Prospective Histopathological and Immunohistochemical Study
Authors: Stennert Eberhard , Wittekindt Claus , Klussmann Jens Peter , Arnold Georg , Guntinas‐Lichius Orlando
Published: December 2003

Objectives/Hypothesis Histopathological characteristics and proliferation indices of recurrent pleomorphic adenoma were described in a series of 31 patients who were referred to the authors' clinic for revision surgery.

Study Design Prospective series of 31 patients.

Methods Serial sections of surgical specimen using the whole‐organ sectioning technique were carried out for light microscopic examination after total parotidectomy and periparotid fat resection. The nodules were examined with special reference to localization, amount, size, histological subtypes, capsular alterations, and the amount of nodule spilling. Expression of proliferation markers (Ki67/MIB‐1) according to the size and histological subtypes of the nodules was also investigated.

Results Most recurrences were multinodular, and the number of nodules was much higher than expected, ranging from 1 to 157. The myxoid subtype was predominant. Eighty percent of the patients exhibited widely distributed nodules also lying outside the scar. These nodules contained only a thin pseudocapsule and often lacked complete encapsulation. The majority of multinodular recurrences of parotid pleomorphic adenoma consisted of small nodules (less than 1 mm in diameter). Smaller nodules showed similar or higher levels of proliferative activity than larger nodules.

Conclusion The extended multifocal distribution of tumor recurrences after insufficient resection of pleomorphic adenoma (most often after enucleation) can explain a high incidence of further recurrences. Therefore, a total parotidectomy including removal of surrounding fat tissue seems to be appropriate for the initial treatment of recurrent pleomorphic adenoma.
The Methyltransferase from the LlaDII Restriction-Modification System Influences the Level of Expression of Its Own Gene
Authors: Christensen Lisa Lystbæk , Josephsen Jytte
Published: December 2003

The type II restriction-modification (R-M) system LlaDII isolated from
Lactococcus lactis
contains two tandemly arranged genes,
llaDIIR
and
llaDIIM
, encoding a restriction endonuclease (REase) and a methyltransferase (MTase), respectively. Interestingly, two LlaDII recognition sites are present in the
llaDIIM
promoter region, suggesting that they may influence the activity of the promoter through methylation status. In this study, separate promoters for
llaDIIR
and
llaDIIM
were identified, and the regulation of the two genes at the transcriptional level was investigated. DNA fragments containing the putative promoters were cloned in a promoter probe vector and tested for activity in the presence and absence of the active MTase. The level of expression of the MTase was 5- to 10-fold higher than the level of expression of the REase. The results also showed that the presence of M.LlaDII reduced the in vivo expression of the
llaDIIM
promoter (P

llaDIIM

) up to 1,000-fold, whereas the activity of the
llaDIIR
promoter (P

llaDIIR

) was not affected. Based on site-specific mutations it was shown that both of the LlaDII recognition sites within P

llaDIIM

are required to obtain complete repression of transcriptional activity. No regulation was found for
llaDIIR
, which appears to be constitutively expressed.