bluuebunny/crossref_metadata_2025 huggingface dataset:
Sorption of naphthalene derivatives on to soils from a long‐term field experiment: a particle size fractionation and extraction study
Authors: Novoszad M. , Gerzabek M. H. , Lischka H. , Haberhauer G. , Jakusch M.
Published: March 2006

The present work investigates the impact of site management on the retention of organic compounds in soil in a long‐term field experiment and focuses on the role of particle size fractions. Specifically, we studied the influence of long‐term farming practices on the soil’s ability to adsorb five hydrophobic organic compounds (HOCs), specifically naphthalene derivatives (naphthalene, 1‐naphthol, 1‐naphthylamine, 1‐hydroxy‐2‐naphthoic acid, 1,4‐naphthoquinone). We examined the sorption on soil and its particle‐size fractions with varying amounts and origins of organic matter in soil amended with farmyard manure and mineral fertilizers over more than 40 years. The soil organic matter had no significant impact on the sorption behaviour of the HOCs. Adsorption on the clay and silt fraction provided a deeper insight into the mechanisms and indicates a strong affinity with adsorption sites of the mineral phase. Naphthalene derivatives with hydrogen atoms in their functional groups adsorbed more strongly than other compounds on to soils containing smaller amounts of organic carbon. Desorption experiments with five organic extractants showed partitioning models for HOCs between extractant and soil surface. Only in experiments with the most polar extractant, formamide, did we observe an influence of the compound’s functional groups on the desorption mechanisms. Column experiments with a HPLC‐system and on‐line UV‐detection proved to be a satisfactory alternative to batch experiments. This approach should enable investigations of adsorption with larger numbers of compounds and soils at the same time.
Comparing the direct and community‐mediated effects of disturbance on plant population dynamics: flooding, herbivory and Mimulus guttatus
Authors: ELDERD BRET D. , DOAK DAN F.
Published: March 2006

Competition, trophic interactions and abiotic disturbances play important roles in governing plant population dynamics, yet few studies have addressed their relative contributions or interacting effects.

We used Life Table Response Experiment (LTRE) analysis, coupled with stochastic analyses, to examine how a major abiotic disturbance, flooding, influences the fitness and population growth of a common riparian plant, Mimulus guttatus, and how this effect compares and interacts with that exerted by herbivory.

We also extended LTRE analysis to include nested factors, which enabled us to examine differences across experimental sites. These spatial contributions to changes in population growth rate, λ, were compared and contrasted with those derived for year and experimental treatments.

Flooding had direct positive impacts on population growth, while protection from herbivory benefited plants in both flooded and non‐flooded areas. Spatial variation in plant performance was also substantial, with greater variation across experimental sites than temporal variation across years.

Our stochastic analysis revealed that the impact of herbivores on population growth was much greater when the environment fluctuated between years with and without flooding than in more constant environments.

Both flooding and herbivory exerted the majority of their impacts on plant performance via changes in adult summer survival. For flooded sites, this was surprising, given the small difference in summer survival between control and herbivore‐exclusion treatments, and results from the high sensitivity of population growth to adult survival.

The importance of herbivory in flooded sites would have not been discerned had we not considered how adult survival interacts with other stages of the M. guttatus life cycle. Thus, in order to increase ecological understanding associated with shifts in community dynamics, experimental results should be placed in a life‐history context.

Within disturbance‐driven systems, the direct abiotic effects of factors such as flooding play a critical role in determining population dynamics. However, the biotic interactions that change as a consequence of disturbance can have equal and lasting impacts on population growth.
DNA polymerase X fromDeinococcus radioduranspossesses a structure‐modulated 3′→5′ exonuclease activity involved in radioresistance
Authors: Blasius Melanie , Shevelev Igor , Jolivet Edmond , Sommer Suzanne , Hübscher Ulrich
Published: March 2006

Recently a family X DNA polymerase (PolXDr) was identified in the radioresistant bacteriumDeinococcus radiodurans. Knockout cells show a delay in double‐strand break repair (DSBR) and an increased sensitivity to γ‐irradiation. Here we show that PolXDrpossesses 3′→5′ exonuclease activity that stops cutting close to a loop. PolXDrconsists of a DNA polymerase X domain (PolXc) and a Polymerase and Histidinol Phosphatase (PHP) domain. Deletion of the PHP domain abolishes only the structure‐modulated but not the canonical 3′→5′ exonuclease activity. Thus, the exonuclease resides in the PolXc domain, but the structure‐specificity requires additionally the PHP domain. Mutation of two conserved glycines in the PolXc domain leads to a specific loss of the structure‐modulated exonuclease activity but not the exonuclease activity in general. The PHP domain itself does not show any activity. PolXDris the first family X DNA polymerase that harbours an exonuclease activity. The wild‐type protein, the glycine mutant and the two domains were expressed separately in ΔpolXDrcells. The wild‐type protein could restore the radiation resistance, whereas intriguingly the mutant proteins showed a significant negative effect on survival of γ‐irradiated cells. Taken together ourin vivoresults suggest that both PolXDrdomains play important roles in DSBR inD. radiodurans.
A bacterium that has three pathways to regulate membrane lipid fluidity
Authors: Cronan John E.
Published: March 2006

Well‐studied bacteria such as Bacillus subtilis and Escherichia coli each have only a single pathway for synthesis of the unsaturated fatty acids required to make functional membrane lipids. In marked contrast, unsaturated fatty acid synthesis in Pseudomonas aeruginosa proceeds by three distinct pathways.
Analysis of the requirements for pilus biogenesis at the outer membrane usher and the function of the usher C‐terminus
Authors: Shu Kin So Stephane , Thanassi David G.
Published: March 2006

Uropathogenic strains of Escherichia coli assemble type 1 and P pili to colonize the bladder and kidney respectively. These pili are prototype structures assembled by the chaperone/usher secretion pathway. In this pathway, a periplasmic chaperone works together with an outer membrane (OM) usher to control the folding of pilus subunits, their assembly into a pilus fibre and secretion of the fibre to the cell surface. The usher serves as the assembly and secretion platform in the OM. The usher has distinct functional domains, with the N‐terminus providing the initial targeting site for chaperone–subunit complexes and the C‐terminus required for subsequent stages of pilus biogenesis. In this study, we investigated the molecular interactions occurring at the usher during pilus biogenesis and the function of the usher C‐terminus. We provide genetic and biochemical evidence that the usher functions as a complex in the OM and that interaction of the pilus adhesin with the usher is critical to prime the usher for pilus biogenesis. Analysis of C‐terminal truncation and substitution mutants of the P pilus usher PapC demonstrated that the C‐terminus is required for proper binding of chaperone–subunit complexes to the usher and plays an important role in assembly of complete pili.
Comparative immunology of human and animal models of hookworm infection
Authors: FUJIWARA R. T. , GEIGER S. M. , BETHONY J. , MENDEZ S.
Published: March 2006

Hookworm infection is a major cause of disease burden for animals and humans. Over the past years, the use of animal models in hookworm infections has been driven by the search of new anthelminthic therapies and, especially, vaccine development. These studies also contributed to the advance of knowledge on immunity to hookworms, offering new insights to understand the nature of this parasitic infection. In this article, we will summarize the essential features of the immune response in the two major animal models of hookworm infections (dog and hamster) and then consider its implication for the human immune response.
In vitroinvestigation of ceruminolytic activity of various otic cleansers for veterinary use
Authors: Sánchez‐Leal J. , Mayós I. , Homedes J. , Ferrer L.
Published: March 2006

Knowledge of the ceruminolytic activity of commercially available ear cleansing products assists the practitioner to choose the best available product for specific clinical situations. The aim of this study was to quantify and compare the ceruminolytic activity of commercially available canine ear cleansers. For this purpose, the ceruminolytic activity of 13 ear cleansers was evaluated using a standardized synthetic cerumen (SSC) that mimics the composition and texture of canine cerumen. The test products were incubated with mild agitation for 20 min with 500 mg of SSC previously compacted at the bottom of a test tube. Ceruminolytic activity was then assessed by quantifying the SSC removed by decantation. This procedure was repeated five consecutive times on each tube simulating repeated applications in the canine ear canal. Good repeatability among replicates was found in this assay, allowing direct comparisons between products. The final percentage of SSC elimination ranged from none (similar to water), between 8 and 39% for three products and up to 90% for one product (P < 0.001). It is concluded that, in the experimental conditions used in this study, only 1/13 products had significant ceruminolytic activity.
A trade‐off between sexual signalling and immune function in a natural population of the drumming wolf spider Hygrolycosa rubrofasciata
Authors: AHTIAINEN J. J. , ALATALO R. V. , KORTET R. , RANTALA M. J.
Published: March 2006

The field of ecological immunology is ultimately seeking to address the question ‘Why is there variation in immune function?’ Here, we provide experimental evidence that costs of ubiquitous sexual signals are a significant source of variation in immune function. In the mating season, males of the wolf spider Hygrolycosa rubrofasciata drum against dry leaves while wandering around the habitat searching for receptive females. According to a previous study, the male metabolic rate during the drumming increases 22‐fold compared to the resting metabolic rate. In the present study, we examined whether investment in costly courtship drumming decreases male immune function in a wild population of H. rubrofasciata. We induced males to increase their drumming rate by introducing females in proximity. As estimates of male immune function, we used lytic activity and encapsulation rate. Lytic activity estimates the concentration of antimicrobial peptides in haemolymph, which have been shown to play an important role in defence against bacteria, viruses and fungi. Encapsulation is an important defence mechanism against nematodes and insect parasitoids, but it also plays a role in defence against viruses. Our results show that males with nonarbitrarily increased investment in drumming rate had considerably lower lytic activities than control males. Also, there was a tendency for males with nonarbitrarily increased investment in drumming rate to have lower encapsulation rates than control males. This study provides experimental evidence for the first time, to our knowledge, that there are direct immunological costs of sexual signalling in natural populations. Therefore, immunological costs of sexual signals may provide significant phenotypic variation to parasite‐mediated sexual selection.
Restricted gene flow between two social forms in the ant Formica truncorum
Authors: GYLLENSTRAND N. , SEPPÄ P. , PAMILO P.
Published: March 2006

We studied genetic differentiation between two social forms (M‐type: single queen, independent nest founding; P‐type: multiple queens, dependent nest founding, building of colonial networks) of the ant Formica truncorum in a locality where the social types characterize two sympatric populations. The genetic results indicate restricted gene flow between the social forms. Female gene flow between the forms appears to be absent as they did not share mitochondrial haplotypes. Significant nuclear differentiation and the distribution of private alleles suggest that male gene flow between the forms is weak. However, the assignment analysis indicates some gene flow with P males mating with M females. The results have potentially important implications concerning social evolution within the forms but they need to be confirmed in other localities before they can be generalized. The colonies in the M‐type population have earlier been shown to produce split sex ratios, depending on the mating frequency of the queens. The inferred gene flow from the P to the M type means that the split sex ratio is partly suboptimal, possibly because the P populations are not long‐lived enough to influence the behavioural decisions in the M colonies.
Male sterility at extreme temperatures: a significant but neglected phenomenon for understanding Drosophila climatic adaptations
Authors: DAVID J. R. , ARARIPE L. O. , CHAKIR M. , LEGOUT H. , LEMOS B. , PÉTAVY G. , ROHMER C. , JOLY D. , MORETEAU B.
Published: March 2006

The thermal range for viability is quite variable among Drosophila species and it has long been known that these variations are correlated with geographic distribution: temperate species are on average more cold tolerant but more heat sensitive than tropical species. At both ends of their viability range, sterile males have been observed in all species investigated so far. This symmetrical phenomenon restricts the temperature limits within which permanent cultures can be kept in the laboratory. Thermal heat sterility thresholds are very variable across species from 23 °C in heat sensitive species up to 31 °C in heat tolerant species. In Drosophila melanogaster, genetic variations are observed among geographic populations. Tropical populations are more tolerant to heat induced sterility and recover more rapidly than temperate ones. A genetic analysis revealed that about 50% of the difference observed between natural populations was due to the Y chromosome. Natural populations have not reached a selection limit, however: thermal tolerance was still increased by keeping strains at a high temperature, close to the sterility threshold. On the low temperature side, a symmetrical reverse phenomenon seems to exist: temperate populations are more tolerant to cold than tropical ones. Compared to Mammals, drosophilids exhibit two major differences: first, male sterility occurs not only at high temperature, but also at a low temperature; second, sterility thresholds are not evolutionarily constrained, but highly variable. Altogether, significant and sometimes major genetic variations have been observed between species, between geographic races of the same species, and even between strains kept in the laboratory under different thermal regimes. In each case, it is easily argued that the observed variations correspond to adaptations to climatic conditions, and that male sterility is a significant component of fitness and a target of natural selection.
Effects of artificial foods on the blood chemistry of the Australian magpie
Authors: ISHIGAME G. , BAXTER G. S. , LISLE A. T.
Published: March 2006

Abstract  Bird feeding on residential property is a popular activity throughout Western countries. Advocates insist the practice is beneficial, while opponents maintain that it can result in a wide range of negative outcomes including malnutrition. The biological effects of ‘backyard feeding’ were studied in Australian magpies Gymnorhina tibicen during the non‐breeding season in 1999 in the Greater Brisbane and the Lockyer Valley regions, south‐east Queensland, Australia. Six magpie populations were selected and 70 birds were individually tagged for identification. The birds were provided with processed foods, 20–40 g per bird daily. To monitor the effects of the food, blood chemistry and body mass (BM) were used as indices. Significant effects were observed in BM and plasma cholesterol (PC), showing strong sensitivity to food provisioning. Significant effects on PC and uric acid were found only when birds were fed dog sausage. Results suggest that blood PC levels in magpies are readily influenced by, probably, the lipids present in food, and that the type of food can affect blood PC levels. These effects may occur widely among fed magpies if the influence that we demonstrated at plasma level can be generalized. Following the free‐ranging study, six magpies were captured and subjected to a 6‐day captive experiment to determine whether the selected foods had the potential to alter the birds’ blood chemistry. It was found that all of the foods, when provided ad libitum, influence at least two of the three blood parameters (PC and non‐esterified fatty acids). Due to its popularity, wildlife feeding will continue. To make wildlife‐feeding activities truly sustainable, there is a need for further studies. This study clearly demonstrated that the physiology of wild magpies can be affected by ‘backyard feeding’.
Advancing urban ecological studies: Frameworks, concepts, and results from the Baltimore Ecosystem Study
Authors: PICKETT S. T. A. , CADENASSO M. L.
Published: March 2006

Abstract  Urban ecological studies have had a long history, but they have not been a component of mainstream ecology until recently. The growing interest of ecologists in urban systems provides an opportunity to articulate integrative frameworks, and identify research tools and approaches that can help achieve a broader ecological understanding of urban systems. Based on our experience in the Baltimore Ecosystem Study (BES), Long‐term Ecological Research project, located in metropolitan Baltimore, Maryland, USA, we identify several frameworks that may be useful in comparative urban studies, and may be worthy of consideration in other integrative urban ecosystem studies: (i) spatial patch dynamics of biophysical and social factors; (ii) the watershed as an integrative tool; and (iii) the human ecosystem framework. These frameworks build on empirical research investigating urban biota, nutrient and energy budgets, ecological footprints of cities, as well as biotic classifications aimed at urban planning. These frameworks bring together perspectives, measurements, and models from biophysical and social sciences. We illustrate their application in the BES, which is designed to investigate (i) the structure and change of the urban ecosystem; (ii) the fluxes of matter, energy, capital, and population in the metropolis; and (iii) how ecological information affects the quality of the local and regional environments. Exemplary results concerning urban stream nutrient flux, the ability of riparian zones to process nitrate pollution, and the lags in the relationships between vegetation structure and socio‐economic factors in specific neighbourhoods are presented. The current advances in urban ecological studies have profited greatly from the variety of integrative frameworks and tools that have been tested and applied in urban areas over the last decade. The field is poised to make significant progress as a result of ongoing conceptual and empirical consolidation.
Range expansion due to urbanization: Increased food resources attract Grey‐headed Flying‐foxes (Pteropus poliocephalus) to Melbourne
Authors: WILLIAMS NICHOLAS S. G. , MCDONNELL MARK J. , PHELAN GEMMA K. , KEIM LAUREN D. , VAN DER REE RODNEY
Published: March 2006

Abstract  Urbanization profoundly alters the biota of areas that become cities and towns. Many species are introduced by humans while indigenous species often decline. Although these changes are well known, the long‐term ecological effects of new species and their interactions are seldom considered and rarely documented. This study examines changes in diversity and temporal availability of the food resources of Pteropus poliocephalus (Grey‐headed Flying‐fox) in the Melbourne region using a variety of historical and current data sources. Our results indicate that urbanization has influenced the distribution, abundance and ecology of P. poliocephalus through a dramatic increase in the quantity and temporal availability of food resources. Prior to European settlement, only 13 species recorded in the range‐wide diet of P. poliocephalus grew in the Melbourne area. Compilations of street‐tree databases indicate that an additional 87 species have been planted on Melbourne’s streets and that there are at least 315 500 trees that are able to provide food for P. poliocephalus. Phenology records indicate that street trees have lengthened the temporal availability of food for P. poliocephalus. A period of natural food scarcity between May and August has been ameliorated by street trees which have provided nectar and a previously absent fruit resource. These changes are likely to be a major factor contributing to the recent range expansion of P. poliocephalus and the establishment of a permanent camp in Melbourne.
Serum testosterone levels using the radioimmunoassay method in healthy Japanese male volunteers
Authors: SATO YOSHIKAZU , TANDA HITOSHI , KATO SHUJI , ONISHI SHIGEKI , NAKAJIMA HISAO , NANBU AKIHITO , NITTA TOSHIKAZU , KOROKU MIKIO , AKAGASHI KEIGO , HANZAWA TATSUO , SHINOZAKI TADATOSHI , TERAO NAOAKI , FUJISAKI NOBUTA , KUWABARA MORIMASA , NIIMURA KENJI
Published: March 2006

Aim:  The objective of the present study was to measure serum free and total testosterone values using the radioimmunoassay (RIA) method in healthy Japanese male volunteers with no current diseases.

Methods:  Two hundred and fifty‐one healthy men who had no medical illness and received no current medical treatment were selected from 405 male volunteers. Free and total testosterone were measured in blood samples using the RIA method.

Results:  Free but not total testosterone significantly decreased with age. Mean free testosterone values from morning blood samples for each age decade from the 20s to the 70s were 17.0, 14.6, 12.5, 10.6, 8.9 and 8.5 pg/mL, respectively. Mean total testosterone values from morning blood samples for each age decade from the 20s to the 70s were 4.7, 4.2, 4.4, 4.2, 4.2, 4.0 and 4.0 ng/mL, respectively. The rates of healthy volunteers that fell within the standard reference ranges for free and total testosterone were 97% and 97%, respectively. However, 19% of the total testosterone values were considered to indicate hypogonadism according to the International Society for the Study of the Aging Male (ISSAM) criteria (<3.17 ng/mL).

Conclusions:  Our data corresponded to the standard reference ranges of Japanese men but not the ISSAM criteria. It may be more appropriate to establish a standard reference range for serum testosterone for individual countries. (Reprod Med Biol 2006; 5: 37–41)
Factors Influencing Voluntary Corporate Disclosure by Kenyan Companies
Authors: Barako Dulacha G. , Hancock Phil , Izan H. Y.
Published: March 2006

There has been considerable research in respect of voluntary disclosure by companies and factors that may explain such disclosure. However, most of the research has been centred in developed countries. This study extends the previous literature by examining voluntary disclosure in a developing country, namely Kenya. Over the last decade, the Kenyan Government has initiated several far‐reaching reforms at the Nairobi Stock Exchange (NSE) in order to mobilise domestic savings and attract foreign capital investment. These measures include privatisation of state corporations through the stock exchange and allowing foreign investors to own shares in the listed companies. This study provides a longitudinal examination of voluntary disclosure practices in the annual reports of listed companies in Kenya from 1992 to 2001. The study investigates the extent to which corporate governance attributes, ownership structure and company characteristics influence voluntary disclosure practices.

Our results suggest that the extent of voluntary disclosure is influenced by a firm's corporate governance attributes, ownership structure and company characteristics. The presence of an audit committee is a significant factor associated with the level of voluntary disclosure, and the proportion of non‐executive directors on the board is found to be significantly negatively associated with the extent of voluntary disclosure. The study also finds that the levels of institutional and foreign ownership have a significantly positive impact on voluntary disclosure. Large companies and companies with high debt voluntarily disclose more information. In contrast, board leadership structure, liquidity, profitability and type of external audit firm do not have a significant influence on the level of voluntary disclosure by companies in Kenya.
Disaster risk, climate change and international development: scope for, and challenges to, integration
Authors: Schipper Lisa , Pelling Mark
Published: March 2006

Reducing losses to weather‐related disasters, meeting the Millennium Development Goals and wider human development objectives, and implementing a successful response to climate change are aims that can only be accomplished if they are undertaken in an integrated manner. Currently, policy responses to address each of these independently may be redundant or, at worst, conflicting. We believe that this conflict can be attributed primarily to a lack of interaction and institutional overlap among the three communities of practice. Differences in language, method and political relevance may also contribute to the intellectual divide. Thus, this paper seeks to review the theoretical and policy linkages among disaster risk reduction, climate change and development. It finds that not only does action within one realm affect capacity for action in the others, but also that there is much that can be learnt and shared between realms in order to ensure a move towards a path of integrated and more sustainable development.
Financing climate change adaptation
Authors: Bouwer Laurens M. , Aerts Jeroen C.J.H.
Published: March 2006

This paper examines the topic of financing adaptation in future climate change policies. A major question is whether adaptation in developing countries should be financed under the 1992 United Nations Framework Convention on Climate Change (UNFCCC), or whether funding should come from other sources. We present an overview of financial resources and propose the employment of a two‐track approach: one track that attempts to secure climate change adaptation funding under the UNFCCC; and a second track that improves mainstreaming of climate risk management in development efforts. Developed countries would need to demonstrate much greater commitment to the funding of adaptation measures if the UNFCCC were to cover a substantial part of the costs. The mainstreaming of climate change adaptation could follow a risk management path, particularly in relation to disaster risk reduction. ‘Climate‐proofing’ of development projects that currently do not consider climate and weather risks could improve their sustainability.
On Parametric Bootstrap Methods for Small Area Prediction
Authors: Hall Peter , Maiti Tapabrata
Published: March 2006

The particularly wide range of applications of small area prediction, e.g. in policy making decisions, has meant that this topic has received substantial attention in recent years. The problems of estimating mean-squared predictive error, of correcting that estimator for bias and of constructing prediction intervals have been addressed by various workers, although existing methodology is still restricted to a narrow range of models. To overcome this difficulty we develop new, bootstrap-based methods, which are applicable in very general settings, for constructing bias-corrected estimators of mean-squared error and for computing prediction regions. Unlike existing techniques, which are based largely on Taylor expansions, our bias-corrected mean-squared error estimators do not require analytical calculation. They also have the property that they are non-negative. Our prediction intervals have a high degree of coverage accuracy, O(n−3), where n is the number of areas, if double-bootstrap methods are employed. The techniques do not depend on the form of the small area estimator and are applicable to general two-level, small area models, where the variables at either level can be discrete or continuous and, in particular, can be non-normal. Most importantly, the new methods are simple and easy to apply.
Researching human resource development: emergence of a critical approach to HRD enquiry
Authors: Valentin Claire
Published: March 2006

This paper argues that mainstream research in management and human resource development (HRD) is dominated by a positivist paradigm. In a theoretical discussion and review of literature on management, human resource management, HRD and organization studies, it explores critical perspectives in research, which draw on postmodernism and critical theory. It examines how they have contributed to the emergence of a critical HRD and discusses the features of a critical HRD research.
Genetic Variations and Haplotype Structures of theABCB1Gene in a Japanese Population: An Expanded Haplotype Block Covering the Distal Promoter Region, and Associated Ethnic Differences
Authors: Sai K. , Itoda M. , Saito Y. , Kurose K. , Katori N. , Kaniwa N. , Komamura K. , Kotake T. , Morishita H. , Tomoike H. , Kamakura S. , Kitakaze M. , Tamura T. , Yamamoto N. , Kunitoh H. , Yamada Y. , Ohe Y. , Shimada Y. , Shirao K. , Minami H. , Ohtsu A. , Yoshida T. , Saijo N. , Kamatani N. , Ozawa S. , Sawada J.
Published: March 2006

As functionalABCB1haplotypes were recently reported in the promoter region of the gene, we resequenced theABCB1distal promoter region, along with other regions (the enhancer and proximal promoter regions, and all 28 exons), in a total of 533 Japanese subjects. Linkage disequilibrium (LD) analysis based on 92 genetic variations revealed 4 LD blocks with the same make up as previously described (Blocks −1, 1, 2 and 3), except that Block 1 was expanded to include the distal promoter region, and that a new linkage between polymorphisms −1789G>A in the distal promoter region and IVS5 + 123A>G in intron 5 was identified. We re‐assigned Block 1 haplotypes, and added novel haplotypes to the other 3 blocks. The reported promoter haplotypes were further classified into several types according to tagging variations within Block 1 coding or intronic regions. Our current data reconfirm the haplotype profiles of the other three blocks, add more detailed information on functionally‐important haplotypes in Block 1 and 2 in the Japanese population, and identified differences in haplotype profiles between ethnic groups. Our updated analysis ofABCB1haplotype blocks will assist pharmacogenetic and disease‐association studies carried out using Asian subjects.
Spatio‐temporal dynamics of the egg‐laying‐inducing peptides during an egg‐laying cycle: a semiquantitative matrix‐assisted laser desorption/ionization mass spectrometry approach
Authors: Jiménez C. R. , Ter Maat A. , Pieneman A. , Burlingame A. L. , Smit A. B. , Li K. W.
Published: March 2006

The activity‐dependent release of peptides from the neuro‐endocrine caudodorsal cell (CDC) system of the freshwater snail Lymnaea stagnalis regulates egg laying and related behaviors. In this study, we optimized a mass spectrometry‐based approach to study the spatio‐temporal dynamics of peptides that are largely derived from the CDC hormone precursor during an egg‐laying cycle and a CDC discharge in vitro. Semi‐quantitative peptide mass profiling using matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) indicated a massive depletion of peptides from the neurohemal area in the cerebral commissure (COM) during egg laying and the existence of a reserve pool of peptides in the CDC somata that were transported to the COM to restore peptide levels. The depletion of CDC peptides from the COM was correlated to their release during an induced electrical discharge in vitro. Moreover, MALDI‐MS of the releasate revealed extensive truncation of the carboxyl terminal peptide. Finally, two novel peptides of 1788 and 5895 Da, not encoded by the CDC hormone precursor, also exhibited temporal quantitative changes similar to those of CDC peptides. Sequencing of the peptide of 1788 Da by tandem mass spectrometry yielded the novel sequence HF(FH)FYGPYDVFQRDVamide. Together, this implicates a more complex set of CDC peptides for the regulation of egg laying than previously anticipated.
Mossy fibre contact triggers the targeting of Kv4.2 potassium channels to dendrites and synapses in developing cerebellar granule neurons
Authors: Shibasaki Koji , Nakahira Kensuke , Trimmer James S. , Shibata Riichi , Akita Masumi , Watanabe Shu‐Ichi , Ikenaka Kazuhiro
Published: March 2006

Compartmentalization of neuronal function is achieved by highly localized clustering of ion channels in discrete subcellular membrane domains. Voltage‐gated potassium (Kv) channels exhibit highly variable cellular and subcellular patterns of expression. Here, we describe novel activity‐dependent synaptic targeting of Kv4.2, a dendritic Kv channel, in cerebellar granule cells (GCs). In vivo, Kv4.2 channels are highly expressed in cerebellar glomeruli, specializations of GC dendrites that form synapses with mossy fibres. In contrast, in cultured GCs, Kv4.2 was found localized, not to dendrites but to cell bodies. To investigate the role of synaptic contacts, we developed a co‐culture system with cells from pontine grey nucleus, the origin of mossy fibres. In these co‐cultures, synaptic structures formed, and Kv4.2 was now targeted to these synaptic sites in a manner dependent on synaptic activity. Activation of NMDA‐ and/or AMPA‐type glutamate receptors was necessary for the targeting of Kv4.2 in co‐cultures, and activation of these receptor systems in GC monocultures induced dendritic targeting of Kv4.2 in the absence of synapse formation. These results indicate that the proper targeting of Kv4.2 channels is dynamically regulated by synaptic activity. This activity‐dependent regulation of Kv4.2 localization provides a crucial yet dynamic link between synaptic activity and dendritic excitability.
Possible involvement of pyruvate kinase in acquisition of tolerance to hypoxic stress in glial cells
Authors: Shimizu Takahiro , Uehara Takashi , Nomura Yasuyuki
Published: March 2006

Neurons are highly vulnerable to ischemic/hypoxic stress, while glial cells show tolerance to such stress. However, the mechanisms for tolerance acquisition in glial cells have yet to be established. We attempted to isolate and identify a stress protein that is upregulated in response to hypoxia in human astrocytoma CCF‐STTG1 cells. In particular, pyruvate kinase (PK) was upregulated by hypoxia in CCF‐STTG1 cells. Hypoxia‐inducible factor 1 (HIF‐1), the primary transcription factor that is responsible for multiple gene activation under hypoxia, plays a critical role in PK expression during hypoxic challenge. To determine whether newly synthesized PK is involved in tolerance to hypoxic stress, we established the PK‐overexpressing neuronal cells. Overexpression of the wild‐type, but not the kinase‐negative mutant, resulted in attenuation of the loss of cell viability and the typical apoptotic features by hypoxia or oxidative stress in SK‐N‐MC cells. These findings suggest that upregulation of PK may result in acquisition of tolerance against hypoxic stress, and that the antioxidant effect may be involved in the protective effect of PK.
Cerebral ischemia and the unfolded protein response
Authors: DeGracia Donald J. , Montie Heather L.
Published: March 2006

We review studies of endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) following cerebral ischemia and reperfusion (I/R). The UPR is a cell stress program activated when misfolded proteins accumulate in the ER lumen. UPR activation causes: (i) a PERK‐mediated phosphorylation of eIF2α, inhibiting protein synthesis to prevent further accumulation of unfolded proteins in the ER and (ii) upregulation of genes coding for ER‐resident enzymes and chaperones and others, via eIF2α(p), and ATF6 and IRE1 activation. UPR‐induced transcription increases capacity of the ER to process misfolded proteins. If ER stress and the UPR are prolonged, apoptosis ensues. Multiple forms of ER stress have been observed following brain I/R. The UPR following brain I/R is not isomorphic between in vivo I/R models and in vitro cell culture systems with pharmacological UPR induction. Although PERK and IRE1 are activated in the initial hours of reperfusion, total PERK decreases, ATF6 is not activated, and there is delayed appearance of UPR‐induced mRNAs. Thus, multiple damage mechanisms associated with brain I/R alter UPR expression and contribute to a pro‐apoptotic phenotype in neurons. Insights resulting from these studies will be important for the development of therapies to halt neuronal death following brain I/R.
Characterization of an allosteric citalopram‐binding site at the serotonin transporter
Authors: Chen Fenghua , Larsen Mads Breum , Neubauer Henrik Amtoft , Sánchez Connie , Plenge Per , Wiborg Ove
Published: March 2006

The serotonin transporter (SERT), which belongs to a family of sodium/chloride‐dependent transporters, is the major pharmacological target in the treatment of several clinical disorders, including depression and anxiety. In the present study we show that the dissociation rate, of [3H]S‐citalopram from human SERT, is retarded by the presence of serotonin, as well as by several antidepressants, when present in the dissociation buffer. Dissociation of [3H]S‐citalopram from SERT is most potently inhibited by S‐citalopram followed by R‐citalopram, sertraline, serotonin and paroxetine. EC50 values for S‐ and R‐citalopram are 3.6 ± 0.4 µm and 19.4 ± 2.3 µm, respectively. Fluoxetine, venlafaxine and duloxetine have no significant effect on the dissociation of [3H]S‐citalopram. Allosteric modulation of dissociation is independent of temperature, or the presence of Na+ in the dissociation buffer. Dissociation of [3H]S‐citalopram from a complex with the SERT double‐mutant, N208Q/N217Q, which has been suggested to be unable to self‐assemble into oligomeric complexes, is retarded to an extent similar to that found with the wild‐type, raising the possibility that the allosteric mechanism is mediated within a single subunit. A species‐scanning mutagenesis study comparing human and bovine SERT revealed that Met180, Tyr495 and Ser513 are important residues in mediating the allosteric effect, as well as contributing to high‐affinity binding at the primary site.
Androgen‐induced neurite outgrowth is mediated by neuritin in motor neurones
Authors: Marron T. U. , Guerini V. , Rusmini P. , Sau D. , Brevini T. A. L. , Martini L. , Poletti A.
Published: March 2006

In the brain, the spinal cord motor neurones express the highest levels of the androgen receptor (AR). Experimental data have suggested that neurite outgrowth in these neurones may be regulated by testosterone or its derivative 5α‐dihydrotestosterone (DHT), formed by the 5α‐reductase type 2 enzyme. In this study we have produced and characterized a model of immortalized motor neuronal cells expressing the mouse AR (mAR) [neuroblastoma‐spinal cord (NSC) 34/mAR] and analysed the role of androgens in motor neurones. Androgens either activated or repressed several genes; one has been identified as the mouse neuritin, a protein responsible for neurite elongation. Real‐time PCR analysis has shown that the neuritin gene is expressed in the basal condition in immortalized motor neurones and is selectively up‐regulated by androgens in NSC34/mAR cells; the DHT effect is counteracted by the anti‐androgen Casodex. Moreover, DHT induced neurite outgrowth in NSC34/mAR, while testosterone was less effective and its action was counteracted by the 5α‐reductase type 2 enzyme inhibitor finasteride. Finally, the androgenic effect on neurite outgrowth was abolished by silencing neuritin with siRNA. Therefore, the trophic effects of androgens in motor neurones may be explained by the androgenic regulation of neuritin, a protein linked to neurone development, elongation and regeneration.
Preferentially impaired neurotransmitter release sites not their discreteness compromise the validity of microdialysis zero‐net‐flux method
Authors: Chen Kevin C.
Published: March 2006

Intracerebral microdialysis is a popular technique for studying neurochemistry and neural circuits in various brain regions. Recent studies called into question the validity of the microdialysis zero‐net‐flux (ZNF) method by suggesting that this method significantly underestimates the basal level of extracellular dopamine as a result of the discreteness of dopamine release sites as well as the preferential damage to dopamine release over uptake. To identify which factor is most important in undermining the microdialysis ZNF measurements and the extent of underestimation, two mathematical models were developed to explore the influences of the discrete nature and the probe‐induced impairment in the neurotransmitter release. The two models differ in their characterizations of the transmitter release as spatially discrete and homogeneous, respectively. Simulations using physiologically reasonable parameters for striatal dopamine systems indicate that the preferential release site damage surrounding the implanted probe is the most important determinant to the underestimation of the microdialysis ZNF concentration. Under normal physiological conditions, the discreteness of neurotransmitter release sites is of minor importance, except when neuronal degeneration occurs. It is concluded that homogeneous models can adequately describe microdialysis operating processes as long as the corresponding tissue damage parameters in such models are appropriately incorporated.
Structural membrane alterations in Alzheimer brains found to be associated with regional disease development; increased density of gangliosides GM1 and GM2 and loss of cholesterol in detergent‐resistant membrane domains
Authors: Molander‐Melin Marie , Blennow Kaj , Bogdanovic Nenad , Dellheden Birgitta , Månsson Jan‐Eric , Fredman Pam
Published: March 2006

The formation of neurotoxic beta‐amyloid fibrils in Alzheimer's disease (AD) is suggested to involve membrane rafts and to be promoted, in vitro, by enriched concentrations of gangliosides, particularly GM1, and the cholesterol therein. In our study, the presence of rafts and their content of the major membrane lipids and gangliosides in the temporal cortex, reflecting late stages of AD pathology, and the frontal cortex, presenting earlier stages, has been investigated. Whole tissue and isolated detergent‐resistant membrane fractions (DRMs) were analysed from 10 AD and 10 age‐matched control autopsy brains. DRMs from the frontal cortex of AD brains contained a significantly higher concentration (µmol/µmol glycerophospholipids), of ganglioside GM1 (22.3 ± 4.6 compared to 10.3 ± 6.4, p < 0.001) and GM2 (2.5 ± 1.0 compared to 0.55 ± 0.3, p < 0.001). Similar increases of these gangliosides were also seen in DRMs from the temporal cortex of AD brains, which, in addition, comprised significantly lower proportions of DRMs. Moreover, these remaining rafts were depleted in cholesterol (from 1.5 ± 0.2 to 0.6 ± 0.3 µmol/µmol glycerophospholipids, p < 0.001). In summary, we found an increased proportion of GM1 and GM2 in DRMs, and accelerating plaque formation at an early stage, which may gradually lead to membrane raft disruptions and thereby affect cellular functions associated with the presence of such membrane domains.
Hypoxia‐inducible factor and nuclear factor kappa‐B activation in blood–brain barrier endothelium under hypoxic/reoxygenation stress
Authors: Witt Ken A. , Mark Karen S. , Huber Jason , Davis Thomas P.
Published: March 2006

This investigation focuses on transcription factor involvement in blood–brain barrier (BBB) endothelial cell‐induced alterations under conditions of hypoxia and post‐hypoxia/reoxygenation (H/R), using establishedin vivo/ex vivoandin vitroBBB models. Protein/DNA array analyses revealed a correlation in key transcription factor activation during hypoxia and H/R, including NFκB and hypoxia‐inducible factor (HIF)1. Electrophoretic mobility shift assays confirmed NFκB and HIF1 binding activityex vivoandin vitro, under conditions of hypoxia and H/R. Hypoxia‐ and H/R‐treated BBB endothelium showed increased HIF1α protein expression in both cytoplasmic and nuclear fractions, inex vivoandin vitromodels. Co‐immunoprecipitation of HIF1α and HIF1β was shown in the nuclear fraction under conditions of hypoxia and H/R in both models. Hypoxia‐ and H/R‐treated BBB endothelium showed increased expression of NFκB‐p65 protein in both cytoplasmic and nuclear fractions. Co‐immunoprecipitation of NFκB‐p65 with NFκB‐p50 was shown in the nuclear fraction under conditions of hypoxia and H/R in theex vivomodel, and after H/R in thein vitromodel. These data offer novel avenues in which to alter and/or investigate BBB activity across model systems and to further our understanding of upstream regulators during hypoxia and H/R.
Regulation of the preprotachykinin‐I gene promoter through a protein kinase A‐dependent, cyclic AMP response element‐binding protein‐independent mechanism
Authors: Calin‐Jageman Irina E. , Wang Jun , Bannon Michael J.
Published: March 2006

Preprotachykinin‐I (PPT) gene expression is regulated by a number of stimuli that signal through cyclic AMP (cAMP)‐mediated pathways. In the present study, forskolin, an adenylyl cyclase stimulator, significantly increased PPT mRNA levels in PPT‐expressing RINm5F cells, an effect paralleled by an increase in PPT promoter‐luciferase reporter construct activity. The forskolin‐induced stimulation of PPT transcription was protein kinase A dependent (PKA), as shown by blockade with the PKA inhibitor N‐[2‐(p‐bromocinnamylamino) ethyl]‐5‐isoquinolinesulfonamide. We found that the activation protein 1/cAMP response element (AP1/CRE) site centered at − 196 relative to the transcription start site was important for basal and forskolin‐induced PPT promoter activity. Because of the involvement of PKA and the similarity of the AP1/CRE element to consensus CRE sequences, we investigated the role of CRE‐binding protein (CREB) in the regulation of the PPT promoter. Surprisingly, overexpression of a dominant‐negative CREB (i.e. CREB‐A) did not affect basal or forskolin‐induced PPT promoter activity. Furthermore, binding of CREB to the PPT promoter AP1/CRE site was not demonstrable in electrophoretic mobility shift assays. Rather, our experiments suggested that c‐Jun is a member of the complex that binds to this site. We conclude that, at least in RINm5F cells, cAMP‐mediated up‐regulation of PPT gene expression does not involve CREB or CREB‐related transcription factor recruitment to the AP1/CRE site.