bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Starvation-Induced Chlorosis inSynechococcus PCC 7942. Low-Level Photosynthesis As a Mechanism of Long-Term Survival
Authors: Sauer Jörg , Schreiber Ulrich , Schmid Roland , Völker Uwe , Forchhammer Karl
Published: July 2002

Cells of the non-diazotrophic cyanobacteriumSynechococcus sp. strain PCC 7942 acclimate to nitrogen deprivation by differentiating into non-pigmented resting cells, which are able to survive prolonged periods of starvation. In this study, the physiological properties of the long-term nitrogen-starved cells are investigated in an attempt to elucidate the mechanisms of maintenance of viability. Preservation of energetic homeostasis is based on a low level of residual photosynthesis; activities of photosystem II and photosystem I were approximately 0.1% of activities of vegetatively growing cells. The low levels of photosystem I activity were measured by a novel colorimetric assay developed from the activity staining of ferredoxin:NADP+ oxidoreductase. Photosystem II reaction centers, as determined by chlorophyll fluorescence measurements, exhibited normal properties, although the efficiency of light harvesting was significantly reduced compared with that of control cells. Long-term chlorotic cells carried out protein synthesis at a very low, but detectable level, as revealed by in vivo [35S]methionine labeling and two-dimensional gel electrophoresis. In conjunction with the very low levels of total cellular protein contents, this implies a continuous protein turnover during chlorosis. Synthesis of components of the photosynthetic apparatus could be detected, whereas factors of the translational machinery were stringently down-regulated. Beyond the massive loss of protein during acclimation to nitrogen deprivation, two proteins that were identified as SomA and SomB accumulated due to an induced expression following nitrogen reduction.
An Insight into Cell Elasticity and Load-Bearing Ability. Measurement and Theory
Authors: Wei Chunfang , Lintilhac Philip M. , Tanguay Jason J.
Published: July 2002

We have studied the elasticity and load bearing ability of plant tissue at the cellular level, using onion (Allium cepa) epidermal cells. The Young's modulus and Poisson's ratio of the cells were obtained by loading a tensile force on onion epidermal peels of different turgor pressures, and measuring the elongation and the lateral contraction of the peels. The Young's moduli and the Poisson's ratios ranged from 3.5 to 8.0 MPa and 0.18 to 0.30, respectively. To determine the effects of cell elasticity and turgor pressure on the cell's ability to bear load, we loaded a small glass ball onto a cell and measured the projected contact area between the ball and the cell. Unlike previous studies, we considered the cell as a whole entity, and utilized the Boussinesq's solution to derive the relevant equations that related the elastic parameters and cell deformation. For cells with a turgor pressure ≥ 0.34 MPa, the predicted contact area agreed well with the measured area. The equations could also predict cell turgor pressure with a deviation from the measured value of 0.01 MPa. This study gives strong support to ball tonometry, a new method of measuring cell turgor pressure.
The influence of N‐heterocyclics on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions
Authors: Muralidharan S. , Venkatakrishna Iyer S.
Published: July 2002

The influence of N‐heterocyclics, viz. imidazole (IA), benzimidazole (BIA) and 2‐methyl imidazole (MIA) on the corrosion and hydrogen permeation through mild steel in 1 N H2SO4 and in 1N HC1 has been studied using weight loss and various corrosion monitoring techniques. Imidazole and benzimidazole inhibit the corrosion of mild steel in both the acidic solutions, but methyl imidazole accelerates the corrosion. They behave as cathodic inhibitors by influencing the cathodic polarization reaction. Except methyl imidazole, the other two compounds reduce the hydrogen permeation current in both the acids. The adsorption of these compounds on the mild steel surface from both the acids obeys Temkin’s adsorption isotherm. Trends in the increase of charge transfer resistance and decrease of capacitance values also show the adsorption of inhibitors on the metal surface.
International initiatives in authority control
Authors: Danskin Alan
Published: July 2002

The requirement for and development of the Anglo‐American Authority File (AAAF) is described. The mechanics of its production and updating are indicated and its role within British Library cataloguing practice examined. Further developments of the file are discussed and developments through IFLA towards international exchange of authority data are described, indicating both opportunities and difficulties. The EC‐funded project AUTHOR is outlined and, finally, the British Library’s work with the Library of Congress and American Library Association on extending LCSH to works of fiction is described.
Learning to “think global and act local”: experiences from the small business sector
Authors: Fletcher Denise
Published: July 2002

Examines how entrepreneurs learn from the experience of conducting international business and how they “draw upon” that knowledge when “thinking globally” and enacting international strategies. The findings draw attention to the values, visions and key learning issues that are continually being reproduced as entrepreneurs respond to international opportunities, find partners and build cross‐border networks. International entrepreneuring, it is argued, is about learning from different cross border exchanges and converting that experience into organisational practices that build strategic capability in international markets. Such a perspective also has important implications for the education and training of small business entrepreneurs and managers as they think about and enact their international strategies.
Preparation for negotiation
Authors: Fells Ray
Published: July 2002

Examines the task of preparing for negotiation, making the distinction between preparation for handling the issue and giving consideration to the process itself. Data from 28 negotiation simulations suggest that negotiators will tend to take a position‐based approach on the issue, but at the same time will try and establish orderly if not co‐operative forms of interaction. Suggests some practical implications, the principal one being that more attention could usefully be given to behavioural aspects of the process rather than concentrating on issue‐based strategies when preparing for a negotiation.
Effects of perceived power of supervisor on subordinate work attitudes
Authors: Elangovan A.R. , Lin Xie Jia
Published: July 2002

This study examined the relationships between perceptions of supervisor power and subordinate work attitudes. Results showed that perceived legitimate power and coercive power of the supervisor were major predictors of subordinate stress, while perceived legitimate power and reward power were important predictors of employee motivation. Further, perceived coercive, reward and legitimate powers were all significant predictors of subordinate commitment. Also, perceived coercive power was negatively associated with subordinate satisfaction, while expert and referent powers were positively related to satisfaction. Implications for future research and practising managers are discussed.
Women and men politicians: are some of the best leaders dissatisfied?
Authors: Tucker Mary L. , McCarthy Anne M. , Colleen Jones M.
Published: July 2002

Today’s political arena calls for strong leadership. As technology facilitates information sharing, constituents are becoming more vocal in governmental affairs. Legislators are now expected to be transformational leaders who envision the future needs of constituents and are capable of negotiating, mediating, and championing these causes in an effective and credible manner. Using transformational leadership theory, this article examines the perceived leadership styles among state‐level legislators in the United States as well as the relationship between leadership style and perceptions of extra effort, effectiveness, and satisfaction. Leaders in this study described their style as transformational and perceived high extra effort from their followers. Yet, compared to women, male politicians had more positive perceptions of effectiveness and satisfaction with their leadership style. This substantiates research that women in male‐dominated careers report less self‐confidence. Future research might verify this study’s contradictory findings that female politicians, with transformational styles, are not satisfied with their leadership.
Automatic vision for dimensional measurement
Authors: Schmald Reimund
Published: July 2002

A new off‐line measuring technique using standard video and PC technology has been described. The image of the object to be qualified or measured is illuminated, digitalized by a video camera and transferred into a computer which is performing the data evaluation. This task can be according to customers’ internal specifications, or according to international standards like IEC, AEIC or ASTM, respectively. Discusses three examples from the cable and wire industry: the fully automatic measurement of cable insulation, woven wire cloth and felting needles. The main advantages of this automized measuring procedure are its speed, repeatability and its high reliability.
Testing Belbin’s team role theory of effective groups
Authors: Prichard Jane S. , Stanton Neville A.
Published: July 2002

Belbin’s Team‐Role Theory is extensively used as a counselling and team development tool by organisations and management consultancies in the UK. However, there is little empirical support for his work, largely because there has been scant research. This study sought to redress this situation by testing Belbin’s proposal that teams in which a wide range of team‐roles are represented perform better than those where there is an imbalance of roles because certain roles are over‐represented. The task performance of six teams of four individuals identified as shapers by the Team‐Role Self‐Perception Inventory (Belbin, 1981), was compared with that of six mixed teams of four individuals; one co‐ordinator, one plant, one completer finisher, and one team worker. It was found that consistent with Belbin’s proposal the “mixed” teams performed better than teams consisting of shapers alone. Some possible explanations and implications of the findings are discussed.
Building scholarly online multimedia collections and services
Authors: Chrisfield Ted , Cosgrove Richard , Stinson John
Published: July 2002

This paper outlines the evolution of an approach to building multimedia database applications for research and learning in an Australian university. This has involved an ongoing collaboration between the library, as database developer, together with research scholars and course managers, as application directors and discipline consultants. The paper provides details of three particular projects, the Australian Zooarchaeology image database, the fourteenth century music database and Audio Visual online. Each application has used the technological infrastructure provided by the library to develop unique and successful approaches to research and learning. All, in different ways, take advantage of the many new multimedia capabilities of the WWW and suggest that such an approach could be developed into a working model for building sustainable quality multimedia Web resources for research and learning.
Layerwise adaptive topology optimization of laminate structures
Authors: Hansel W. , Becker W.
Published: July 2002

Presents a simple heuristic optimization algorithm to determine weight‐minimal laminate structures. The algorithm is based on an inverted form of growth strategy, where material is removed in areas with low stresses. In the presented algorithm the removal of material is performed in a layerwise manner in areas with low stress or in areas where the layer orientation angle differs significantly from the principal stress direction. In order to get a production‐adapted structure, the layer orientation angles of the available individual plies are not modified and the material is removed only locally in the respective plies. Contrary to a more formal mathematical optimization no sensitivity analyses are needed by the procedure outlined so far and this keeps the corresponding numerical effort reasonably low. The structural analyses have been performed by the Finite Element Program ANSYS and the outlined heuristic algorithm has been implemented by ANSYS‐macros. Several examples of rectangular laminate plates show the effectiveness of the present algorithm.
An exploration of the emotional impact of tele‐working via computer‐mediated communication
Authors: Mann Sandi , Varey Richard , Button Wendy
Published: July 2002

The practice of tele‐ or home‐working, has been adopted by an increasing number of companies and workers in response to the changing economic and social needs that characterise the world of work today. Working from home brings new challenges as well as benefits, and a variety of studies have examined the impact of tele‐working in terms of such benefits and costs. Few studies, however, have focused on the emotional impact that working away from the office may have on workers as they cope with new technologies, reduced support, increased social isolation and other changes. This neglect of the feelings of workers reflects a somewhat wider neglect in the arena of emotion at work in general. The present study aims to redress this balance through a qualitative pilot study that examines the changing emotions that tele‐workers experience. The implications of the study for tele‐workers and managers are outlined.
Towards a redefinition of strategic HRD
Authors: McCracken Martin , Wallace Mary
Published: July 2002

Reviews the literature on strategic human resource development (SHRD) and explores the concept specifically in the context of the work of Garavan (1991), which highlighted nine key characteristics of SHRD. Garavan’s seminal paper is used as a starting point from which to examine the development of the concept of SHRD. By examining and reviewing the literature, the nine characteristics are redefined and enhanced, thus moving towards a new model and definition of SHRD. Concludes by defining SHRD as the creation of a learning culture, within which a range of training, development and learning strategies both respond to corporate strategy and also help to shape and influence it. It is the reciprocal, mutually enhancing, nature of the relationship between HRD and corporate strategy which lies at the heart of SHRD and at the heart of the development of a learning culture.
A macro model of training and development: validation
Authors: Al‐Khayyat Ridha M. , Elgamal Mahmoud A.
Published: July 2002

Addresses the theoretical foundation of training and development, and attempts to develop and test empirically a macro model of training and development based on a systems approach. Emphasizes the importance of management’s perception of training and development and organizations’ gains and return on investment. The results provide support for the proposed macro model. The macro model makes it possible to trace the determinants of outcome indicators along both the input and process variables. Each of the output indicators are related to a unique set of inputs and process indicators. Infers that organizations need to focus on the set of input and process indicators that relate to the output indicators most desired. Supports the classification of the study indicators (i.e. input, process, output). The factor analysis produced a clear factor loading, each set of indicators loaded clearly on one factor.
Training and development in the Irish context: responding to the competitiveness agenda?
Authors: Heraty Noreen , Morley Michael
Published: July 2002

Recent years have witnessed considerable efforts to improve the national system of training and development in Ireland. Much of this renewed effort has been instigated by heightened international competition, technological advancements leading to the emergence of skill gaps in certain industries, and renewed pressure to provide increased incentives for organisational level training. The combined effect has been the dilution of the essentially voluntarist nature of the State’s role in training and development towards a more interventionist approach. This paper is divided into four key sections. The first section provides an overview of Ireland in terms of her labour market, educational and vocational infrastructure. In section two, we describe the evolution of the national system of training and development in Ireland and provide a basic “map” of Ireland’s training framework. Section three reviews current practices and trends in training and development at the organisational level using both national statistics on the incidences of training, and data collected by the Cranet‐E Survey on International Human Resource Management (1995). Finally, section four discusses a range of critical challenges facing Ireland as we approach the new millennium.
A hybrid technique for electromagnetic torque and force analysis of electric machines
Authors: Low T.S. , Bi C. , Liu Z.J.
Published: July 2002

In electric machines, the electromagnetic torques and forces are developed as a result of the interaction of the magnetic fields. These forces can be computed from the results of field analysis, using numerical or analytical methods. Describes a hybrid technique, which is suitable for the calculation and analysis of electromagnetic torques and forces. This method exploits the advantages of numerical and analytical methods for field analysis, and thus provides a more efficient and effective tool for torque/force computation, in comparison with traditional methods. The computational examples presented show that the method is particularly useful for accurate prediction of the electromagnetic torque and unbalanced magnetic pull in electric machines.
Management education in Hong Kong: needs and challenges
Authors: Hau‐Siu Chow Irene
Published: July 2002

Examines Hong Kong′s current requirements in terms of management
training and development against the various challenges to be met in
providing for those needs. Much of the available training material is
produced by Western theorists and practitioners and aimed at Western
consumers. The problems involved in transferring such material to the
Hong Kong context far exceed those of language and translation.
Considerable cultural gaps have to be narrowed, not only in adapting the
training material to ensure its relevance, but also in matters of style
of delivery, in order to meet the training needs of today′s Chinese
students of management.
Completing the triangle: Taylorism and the paradigms
Authors: Fleischman Richard K.
Published: July 2002

Taylorism and scientific management, as significant components of productive relations in the USA during the early twentieth century, have been examined by accounting historians representing the major paradigms that hold sway in contemporary historiography – the Foucauldian, the Marxist (labour process), and the economic rationalist (Neoclassical). The great bulk of this work has assumed that the major tenets of scientific management, such as time study, incentive wage schemes, standard costing, and variance analysis, were in common usage during the first two decades of the current century. This paper intends to set the record straight by demonstrating that theory was running far ahead of practice in that the number of actual adoptions of the new methods were not concomitant with the prevalence of scientific management literature. Subsequently, the paper will endeavour to show how the three major paradigms combine to enhance our understanding of Taylorism. Much of what Taylor wrote can be interpreted within a Foucauldian framework; the negative reaction of organised labour was much in the Marxist tradition; and, finally, the lack of applications in practice reflected economically rational action on the part of entrepreneurs (thereby completing the triangle).
Environmentally friendly dyeing of synthetic fibres and textile accessories
Authors: Knittel Dierk , Schollmeyer Eckhard
Published: July 2002

Provides a survey about a new process for dyeing synthetic fibres and fabrics. The use of disperse dyes in supercritical carbon dioxide as a dyeing medium completely avoids water pollution and the need for drying. Presents laboratory results showing excellent levelness and fastnesses on the dyeing of polyethylene terephthalate and on polyamides. Describes the state of technical development.
A mixed approach to finite element analysis of hyperbolic heat conduction problems
Authors: Manzari Mehrdad T. , Manzari Majid T.
Published: July 2002

Using a non‐Fourier heat conduction (NFHC) hypothesis, the governing equations of thermal wave propagation are established. The resulting differential equations are transformed to integral forms using the Galerkin weighted residual method and then are discretized by a finite element technique. The proposed finite element formulation is verified by comparing the results of analytical and numerical solutions to a number of selected 1‐D problems. A couple of 2‐D sample problems are solved and the responses of the system to various input signals are studied. The proposed mixed approach shows superiority to the conventional finite element solution of hyperbolic heat conduction equation, because of the simultaneous determination of heat fluxes and temperature at each nodal point. The mixed approach is also shown to be capable of capturing the sudden temperature jump due to heat pulses.
Dimensions of biological terrorism: to what must we mitigate and respond?
Authors: Fischer Henry W.
Published: July 2002

The emergence of biological weapons of mass destruction as likely terrorist means of reigning terror on domestic urban populations is outlined. The dimensions of such a possible future catastrophe are described. The lack of preparedness to mitigate and respond to such an event is noted and it is argued that the disaster research literature should be consulted as a guide to help develop effective mitigation and response plans.
Internet marketing practices
Authors: Heinen Joseph
Published: July 2002

This project explores some of the ways that companies are ‐ or will be ‐ using the Internet to improve the marketing of their commercial businesses. It focuses upon practical lessons that marketing professionals can use to match and customize the resources of their form to the needs of their customers. In particular, it shows how marketing professionals can begin to use the tools of the Internet ‐ web sites, e‐mail, newsgroup, and search engines ‐ to move closer to their customers and add value to their products.
A top‐down methodology for building corporate Web applications
Authors: Artz John M.
Published: July 2002

Explains that a corporate Web application is a corporate information system that uses World Wide Web technology to provide easy access to a wide variety of corporate information resources for internal and external users on a wide variety of platforms in geographically distributed locations. Corporate Web applications go beyond corporate web pages in that they serve a specific set of business objectives beyond providing a presence on the World Wide Web. As with all types of information systems, there are two approaches to Web application development: top‐down and evolutionary. Evolutionary development is exploratory and appropriate for learning about the technology and the application domain. However, evolutionary development leads to complex applications that are difficult to use and difficult to maintain. Top‐down development organizes the complexity of these applications and produces applications that can: meet business objectives; be developed by a programming team; and be maintained by people other than the developers. Provides a methodology for top‐down development of corporate Web applications.
Cyberspace pornography: problems with enforcement
Authors: Saunders Thomas Daphyne
Published: July 2002

Considers that, in addition to all the positive attributes of the Internet, negatives are bound to emerge. Negative influences include the ability of children to access information that is not suitable for their age and the absence of laws or legal legislation to limit this access to the material. Laws are in existence prohibiting young people under the age of 18 years from accessing sexually explicit or sexually deviant materials. The problem with the Internet is the fact that there is no sanction limiting people from posting material of this kind. Warns that as an increasing number of children get online, solutions to these controversial issues must be discussed openly.
Organizational culture, TQM, and business process reengineering
Authors: Gore Edward W.
Published: July 2002

This study explores organizational culture by examining the relationship between total quality management (TQM) and culture, and specifically three elements of a culture related to quality improvement: customer focus, employee involvement, and continuous improvement. Process reengineering is used as an alternative management initiative. A survey of 220 mid‐level professionals in 123 organizations was conducted to determine the extent to which there is a relation between the presence of these cultural elements, and the presence of TQM reengineering. The success of process improvement through either TQM or reengineering is used as a vehicle for examining the importance of these cultural elements. The importance of organizational culture and the implications for managers are discussed.
Second virial coefficients as a measure of protein–osmolyte interactions
Authors: Weatherly Gresham T. , Pielak Gary J.
Published: July 2002

The cytoplasm contains high concentrations of cosolutes. These cosolutes include macromolecules and small organic molecules called osmolytes. However, most biophysical studies of proteins are conducted in dilute solutions. Two broad classes of models have been used to describe the interaction between osmolytes and proteins. One class focuses on excluded volume effects, while the other focuses on binding between the protein and the osmolyte. To better understand protein–smolyte interactions, we have conducted sedimentation equilibrium analytical ultracentrifugation experiments using ferricytochrome c as a model protein. From these experiments, we determined the second virial coefficients for a series of osmolytes. We have interpreted the second virial coefficient as a measure of both excluded volume and protein–osmolyte binding. We conclude that simple models are not sufficient to understand the interactions between osmolytes and proteins.
The energetic cost of induced fit catalysis: Crystal structures of trypsinogen mutants with enhanced activity and inhibitor affinity
Authors: Pasternak Annette , White Andre , Jeffery Constance J. , Medina Nivia , Cahoon Marguerite , Ringe Dagmar , Hedstrom Lizbeth
Published: July 2002

The contribution of induced fit to enzyme specificity has been much debated, although with little experimental data. Here we probe the effect of induced fit on enzyme specificity using the trypsin(ogen) system. BPTI is known to induce trypsinogen to assume a trypsinlike conformation. Correlations are observed between BPTI affinity and the values of kcat/Km for the hydrolysis of two substrates by eight trypsin(ogen) variants. The slope of both correlations is −1.8. The crystal structures of the BPTI complexes of four variant trypsinogens were also solved. Three of these enzymes, K15A, ΔI16V17/D194N, and ΔI16V17/Q156K trypsinogen, are 10‐ to 100‐fold more active than trypsinogen. The fourth variant, ΔI16V17 trypsinogen, is the lone outlier in the correlations; its activity is lower than expected based on its affinity for BPTI. The S1 site and oxyanion hole, formed by segments 184A–194 and 216–223, are trypsinlike in all of the enzymes. These structural and kinetic data confirm that BPTI induces an active conformation in the trypsin(ogen) variants. Thus, changes in BPTI affinity monitor changes in the energetic cost of inducing a trypsinlike conformation. Although the S1 site and oxyanion hole are similar in all four variants, the N‐terminal and autolysis loop (residues 142–152) segments have different interactions for each variant. These results indicate that zymogen activity is controled by a simple conformational equilibrium between active and inactive conformations, and that the autolysis loop and N‐terminal segments control this equilibrium. Together, these data illustrate that induced fit does not generally contribute to enzyme specificity.
Dopa decarboxylase exhibits low pH half‐transaminase and high pH oxidative deaminase activities toward serotonin (5‐hydroxytryptamine)
Authors: Bertoldi Mariarita , Voltattorni Carla Borri
Published: July 2002

Dopa decarboxylase (DDC) catalyzes not only the decarboxylation of l‐aromatic amino acids but also side reactions including half‐transamination of d‐aromatic amino acids and oxidative deamination of aromatic amines. The latter reaction produces, in equivalent amounts, an aromatic aldehyde or ketone (depending on the nature of the substrate), and ammonia, accompanied by O2 consumption in a 1 : 2 molar ratio with respect to the products. The kinetic mechanism and the pH dependence of the kinetic parameters have been determined in order to obtain information on the chemical mechanism for this reaction toward 5‐hydroxytryptamine (5‐HT). The initial velocity studies indicate that 5‐HT and O2 bind to the enzyme sequentially, and that d‐Dopa is a competitive inhibitor versus 5‐HT and a noncompetitive inhibitor versus O2. The results are consistent with a mechanism in which 5‐HT binds to DDC before O2. The pH dependency of log V for the oxidative deaminase reaction shows that the enzyme possesses a single ionizing group with a pK value of ∼7.8 that must be unprotonated for catalysis. In addition to an ionizing residue with a pK value of 7.9 similar to that found in the V profile, the (V/K)5‐HT profile exhibits a pK value of 9.8, identical to that of free substrate. This pK was therefore tentatively assigned to the α‐amino group of 5‐HT. No titrable ionizing residue was detected in the (V/K)O2 profile, in the pH range examined. Surprisingly, at pH values lower than 7, where oxidative deamination does not occur to a significant extent, a half‐transamination of 5‐HT takes place. The rate constant of pyridoxamine 5′‐phosphate formation increases below a single pK of ∼6.7. This value mirrors the spectrophotometric pKspec of the shift 420–384 nm of the external aldimine between DDC and 5‐HT. Nevertheless, the analysis of the reaction of DDC with 5‐HT under anaerobic conditions indicates that only half‐transamination occurs with a pH‐independent rate constant over the pH range 6–8.5. A model accounting for these data is proposed that provides alternative pathways leading to oxidative deamination or half‐transamination.
Biochemical and X‐ray crystallographic studies on shikimate kinase: The important structural role of the P‐loop lysine
Authors: Krell Tino , Maclean John , Boam Deborah J. , Cooper Alan , Resmini Marina , Brocklehurst Keith , Kelly Sharon M. , Price Nicholas C. , Lapthorn Adrian J. , Coggins John R.
Published: July 2002

Shikimate kinase, despite low sequence identity, has been shown to be structurally a member of the nucleoside monophosphate (NMP) kinase family, which includes adenylate kinase. In this paper we have explored the roles of residues in the P‐loop of shikimate kinase, which forms the binding site for nucleotides and is one of the most conserved structural features in proteins. In common with many members of the P‐loop family, shikimate kinase contains a cysteine residue 2 amino acids upstream of the essential lysine residue; the side chains of these residues are shown to form an ion pair. The C13S mutant of shikimate kinase was found to be enzymatically active, whereas the K15M mutant was inactive. However, the latter mutant had both increased thermostability and affinity for ATP when compared to the wild‐type enzyme. The structure of the K15M mutant protein has been determined at 1.8 Å, and shows that the organization of the P‐loop and flanking regions is heavily disturbed. This indicates that, besides its role in catalysis, the P‐loop lysine also has an important structural role. The structure of the K15M mutant also reveals that the formation of an additional arginine/aspartate ion pair is the most likely reason for its increased thermostability. From studies of ligand binding it appears that, like adenylate kinase, shikimate kinase binds substrates randomly and in a synergistic fashion, indicating that the two enzymes have similar catalytic mechanisms.
Modulation of human corticomotor excitability by somatosensory input
Authors: Kaelin‐Lang Alain , Luft Andreas R. , Sawaki Lumy , Burstein Aaron H. , Sohn Young H. , Cohen Leonardo G.
Published: July 2002

In humans, somatosensory stimulation results in increased corticomotoneuronal excitability to the stimulated body parts. The purpose of this study was to investigate the underlying mechanisms. We recorded motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) from abductor pollicis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) muscles. MEP amplitudes, recruitment curves (RC), intracortical inhibition (ICI), intracortical facilitation (ICF), resting (rMT) and active motor thresholds (aMT) were recorded before and after a 2‐h period of ulnar nerve electrical stimulation at the wrist. Somatosensory input was monitored by recording somatosensory evoked potentials. To differentiate excitability changes at cortical vs. subcortical sites, we recorded supramaximal peripheral M‐responses and MEPs to brainstem electrical stimulation (BES). In order to investigate the involvement of GABAergic mechanisms, we studied the influence of lorazepam (LZ) (a GABAA receptor agonist) relative to that of dextromethorphan (DM) (an NMDA receptor antagonist) and placebo in a double‐blind design. We found that somatosensory stimulation increased MEP amplitudes to TMS only in the ADM, confirming a previous report. This effect was blocked by LZ but not by either DM or placebo and lasted between 8 and 20 min in the absence of (i) changes in MEPs elicited by BES, (ii) amplitudes of early somatosensory‐evoked potentials or (iii) M‐responses. We conclude that somatosensory stimulation elicited a focal increase in corticomotoneuronal excitability that outlasts the stimulation period and probably occurs at cortical sites. The antagonistic effect of LZ supports the hypothesis of GABAergic involvement as an operating mechanism.
Phasic and tonic attenuation of EPSPs by inward rectifier K+ channels in rat hippocampal pyramidal cells
Authors: Takigawa Tomoko , Alzheimer Christian
Published: July 2002

We made whole‐cell recordings from CA1 pyramidal cells of hippocampal slices in combination with brief dendritic glutamate pulses to study the role of constitutive inwardly rectifying K+ channels (IRK, Kir2.0) and G‐protein‐activated inwardly rectifying K+ channels (GIRK, Kir3.0) in the processing of excitatory inputs. Phasic activation of GIRK channels by baclofen (20 μm) produced a reversible reduction of glutamate‐evoked postsynaptic potentials (GPSPs), our equivalent of EPSPs, by about one‐third. Conversely, tertiapin (30 nm), a selective inhibitor of GIRK channels, and Ba2+ (200 μm), a non‐selective blocker of inwardly rectifying K+ channels, enhanced GPSPs and, in voltage‐clamp experiments, reduced the underlying K+ conductances, indicating a functionally significant background GIRK conductance, in addition to constitutive IRK channel activity. When examined after suppression of endogenous adenosinergic inhibition, using either adenosine deaminase or the selective A1 receptor antagonist, 1,3‐dipropyl‐8‐cyclopentylxanthine, tertiapin failed to influence either the GPSPs or the inwardly rectifying K+ conductance. Voltage‐clamp recordings from acutely isolated CA1 pyramidal cells not exposed to ambient adenosine exhibited no response to tertiapin, whereas Ba2+ was still capable of reducing hyperpolarizing inward rectification. Our data indicate that in hippocampal pyramidal cells, two components of the inwardly rectifying K+ conductance can be identified, which together exert a tonic modulation of excitatory synaptic input: one arises from constitutive putative IRK channels, the other is mediated by the background activity of GIRK channels that results from the tonic activation of A1 receptors by ambient adenosine.
Haemodynamic changes during neck pressure and suction in seated and supine positions
Authors: Ogoh S. , Fadel P. J. , Monteiro F. , Wasmund W. L. , Raven P. B.
Published: July 2002

We sought to quantify the contribution of cardiac output (Q) and total vascular conductance (TVC) to carotid baroreflex‐mediated changes in mean arterial pressure (MAP) in the upright seated and supine positions. Acute changes in carotid sinus transmural pressure were evoked using brief 5 s pulses of neck pressure and neck suction (NP/NS) via a simplified paired neck chamber that was developed to enable beat‐to‐beat measurements of stroke volume using pulse‐doppler ultrasound. Percentage contributions of Q and TVC were achieved by calculating the predicted change in MAP during carotid baroreflex stimulation if only the individual changes in Q or TVC occurred and all other parameters remained at control values. All NP and NS stimuli from +40 to −80 Torr (+5.33 to −10.67 kPa) induced significant changes in Q and TVC in both the upright seated and supine positions (P < 0.001). Cardiopulmonary baroreceptor loading with the supine position appeared to cause a greater reliance on carotid baroreflex‐mediated changes in Q. Nevertheless, in both the seated and supine positions the changes in MAP were primarily mediated by alterations in TVC (percentage contribution of TVC at the time‐of‐peak MAP, seated 95 ± 13, supine 76 ± 17 %). These data indicate that alterations in vasomotor activity are the primary means by which the carotid baroreflex regulates blood pressure during acute changes in carotid sinus transmural pressure.
Development of membrane conductance improves coincidence detection in the nucleus laminaris of the chicken
Authors: Kuba Hiroshi , Koyano Konomi , Ohmori Harunori
Published: July 2002

Coincidence detection at the nucleus laminaris (NL) of a chicken was improved between embryos (embryonic days (E) 16 and 17) and chicks (post‐hatch days (P) 2–7) in slice preparations. Electrical stimuli were applied bilaterally to the projection fibres to the NL at various intervals. The response window corresponding to the temporal separation of electrical stimuli that resulted in half‐maximal firing probability was adopted as the measure of coincidence detection, and was narrower in chicks (1.4 ms) than in embryos (3.9 ms). Between these two ages, the membrane time constant of NL neurons was reduced from 18.4 to 3.2 ms and the membrane conductance was increased 5‐fold, while no difference was measured in the input capacitance. Evoked EPSCs decayed slightly faster in chicks, while the size and the time course of miniature EPSCs were unchanged. Action potentials had lower thresholds and larger after‐hyperpolarization in chicks than in embryos. Dendrotoxin‐I depolarized cells and increased their input resistance significantly at both ages, eliminated the after‐hyperpolarization, and delayed the decay phase of action potentials, indicative of the expression of low‐threshold K+ channels. Cs+ hyperpolarized the cells, increased the input resistance and eliminated sags during hyperpolarization at both ages, while the hyperpolarization sag was affected by neither Ba2+ nor TEA. These data indicate the expression of hyperpolarization‐activated cation channels. Between these two ages, the maximum conductance of low‐threshold K+ channels increased 4‐fold to about 16 nS, and hyperpolarization‐activated channels increased 6‐fold to about 10 nS. Improvement of coincidence detection correlated with the acceleration of the EPSP time course as a result of the increase of these conductances.
Charge movement and transcription regulation of L‐type calcium channel α1S in skeletal muscle cells
Authors: Zheng Zhenlin , Wang Zhong‐Min , Delbono Osvaldo
Published: July 2002

Several factors, such as Ca2+, trophic factors and ageing, regulate dihydropyridine‐sensitive receptor (DHPR) α1 subunit expression. However, basic mechanisms of DHP α1S expression are unknown. To better understand the regulatory elements that control transcription, the 1.2 kb 5′‐flanking region fragment immediately upstream of the mouse L‐type Ca2+ channel or DHPR α1S gene was isolated and sequenced. Luciferase reporter constructs driven by different promoter regions of mouse DHPR α1S gene were used for transient transfection assays in muscle C2C12 cells. In these preparations we found that three regions corresponding to CREB, GATA‐2 and SOX‐5 consensus sequence within the 5′‐flanking region of the DHPR α1S gene are important for DHPR α1S gene transcription. Antisense oligonucleotides against CREB, GATA‐2 and SOX‐5 significantly reduced charge movement in C2C12 cells. Charge movement was recorded in the whole‐cell configuration of the patch clamp technique. Results from cells transfected with antisense (AS) and sense (S) oligonucleotides and nontransfected cells were compared. Charge movement experiments were fitted to a Boltzmann equation. Maximum charge movement (Qmax) (nC μF−1, mean ±s.e.m.) for S‐ and AS‐CREB was 70.3 ± 2.9 and 52.8 ± 3.3, respectively (P < 0.05). The same parameter for S‐ and AS‐GATA‐2 was 71.3 ± 3.9 and 48.2 ± 2.3, respectively (P < 0.05) and for S‐ and AS‐SOX‐5 was 70.4 ± 4.2 and 45.1 ± 3.2, respectively (P < 0.05). Values recorded in cells transfected with sense S‐CREB, S‐GATA‐2 and S‐SOX‐5 oligonucleotides were not significantly different from those recorded in nontransfected cells. This study demonstrates that the transcription factors CREB, GATA‐2 and SOX‐5 play a significant role in the expression of the skeletal muscle DHPR or L‐type Ca2+ channel α1S.
Is autonomic support of arterial blood pressure related to habitual exercise status in healthy men?
Authors: Jones Pamela Parker , Shapiro Linda F. , Keisling Gretchen A. , Quaife Robert A. , Seals Douglas R.
Published: July 2002

We determined if the tonic autonomic nervous system (ANS) contribution to arterial blood pressure (BP) maintenance in humans is related to habitual endurance exercise status. Twenty‐three healthy young (age 18–31 years) males, 11 endurance exercise‐trained and 12 untrained, were studied. Maximal oxygen consumption was higher (P < 0.001) and resting heart rate and body fatness were lower (P < 0.05) in the exercise‐trained men. Plasma noradrenaline concentrations and BP decreased from baseline levels in response to ganglionic blockade (intravenous trimethaphan) in both groups (all P < 0.001). The absolute (ΔmmHg: systolic =−35 ± 2 vs. −32 ± 4; diastolic =−13 ± 2 vs. −10 ± 2; mean =−21 ± 2 vs. −17 ± 3) and relative (Δ%: systolic =−35 ± 2 vs. −31 ± 3; diastolic =−26 ± 3 vs. −20 ± 3; mean =−31 ± 2 vs. −26 ± 3) decreases in BP were not significantly different between the endurance‐trained and untrained men. There were no significant group differences in the heart rate, stroke volume, cardiac output or systemic vascular resistance (conductance) responses to trimethaphan. Systemic vascular α‐adrenergic sensitivity (slope of the increase in mean BP with incremental phenylephrine infusion during ganglionic blockade) also did not differ in the two groups (endurance‐trained: 3.2 ± 0.5; untrained: 3.2 ± 0.7 mmHg (ng phenylephrine)−1 (ml plasma)−1). In the pooled sample, the decrease in mean BP during trimethaphan was related to baseline and changes in plasma noradrenaline concentrations (r= 0.58–0.65, P < 0.001) and α‐adrenergic sensitivity (r= 0.49, P < 0.02). Our results suggest that the endurance exercise‐trained state is not obviously associated with altered ANS support of BP in healthy young men. Basal sympathetic nervous system (SNS) activity and α‐adrenergic vascular sensitivity are significant physiological correlates of ANS support of BP in this population.
Direct Simulation of Droplet Flow With Mass Transfer at Interface
Authors: Sato T. , Jung R.-T. , Abe S.
Published: July 2002

A direct simulation code has been developed to solve two-phase flow with mass transfer at the interface. The position of the interface is determined by solving a transport equation of the maker density function, one of front-capturing methods. The present method performs the dissolution of mass of a dispersed phase into a continuous phase as a notable feature. Moreover, transfer of the dissolved mass is solved in the continuous phase. At the interface, mass diffusion flux is calculated both for the boundary condition of mass transfer and for the shrinkage of a droplet. For the validation of the present method, three case studies are successfully demonstrated: rise of single droplet, dissolution from a rigid sphere, and dissolution from a rising droplet. [S0098-2202(00)01303-1]
Dynamics of Human Coronary Arterial Motion and Its Potential Role in Coronary Atherogenesis
Authors: Ding Zhaohua , Friedman Morton H.
Published: July 2002

Mechanical forces have been widely recognized to play an important role in the pathogenesis of atherosclerosis. Since coronary arterial motion modulates both vessel wall mechanics and fluid dynamics, it is hypothesized that certain motion patterns might be atherogenic by generating adverse wall mechanical forces or fluid dynamic environments. To characterize the dynamics of coronary arterial motion and explore its implications in atherogenesis, a system was developed to track the motion of coronary arteries in vivo, and employed to quantify the dynamics of four right coronary arteries (RCA) and eight left anterior descending (LAD) coronary arteries. The analysis shows that: (a) The motion parameters vary among individuals, with coefficients of variation ranging from 0.25 to 0.59 for axially and temporally averaged values of the parameters; (b) the motion parameters of individual vessels vary widely along the vessel axis, with coefficients of variation as high as 2.28; (c) the LAD exhibits a greater axial variability in torsion, a measure of curve “helicity,” than the RCA; (d) in comparison with the RCA, the LAD experiences less displacement p=0.009, but higher torsion p=0.03. These results suggest that: (i) the variability of certain motion parameters, particularly those that exhibit large axial variations, might be related to variations in susceptibility to atherosclerosis among different individuals and vascular regions; and (ii) differences in motion parameters between the RCA and LAD might relate to differences in their susceptibility to atherosclerosis. [S0148-0731(00)00405-2]
Dynamic Formulations and Energy Analysis of Rotating Flexible-Shaft/Multi-Flexible-Disk System With Eddy-Current Brake
Authors: Fung Rong-Fong , Hsu Shih-Ming
Published: July 2002

In this paper, the rotating flexible-Timoshenko-shaft/flexible-disk coupling system is formulated by introducing the kinetic and strain energies, and the virtual work done by the eddy-current brake system into Hamilton’s principle. The attachment of disk to shaft becomes flexible for Timoshenko-beam theory and rigid for Euler-beam theory. It is found that the eddy-current brake system can be used to decrease speed and suppress flexible and shear vibrations simultaneously. From the dynamic formulations and energy analysis, some important discussions are made. Numerical results are provided to validate the theoretical analysis. [S0739-3717(00)01504-X]