bluuebunny/crossref_metadata_2025 huggingface dataset:
THRESHOLD VARIABLE SELECTION IN OPEN‐LOOP THRESHOLD AUTOREGRESSIVE MODELS
Authors: Chen Rong
Published: May 2008

Abstract.An open‐loop threshold autoregressive model is defined asThe main difficulty for building such a model is that the threshold variableZtis usually unknown. In practice, there may exist many possible candidates for the threshold variableZt. It is difficult and tedious, if not impossible, to search for the best among all the candidates using standard model selection procedures. In this paper, we introduce a digression concept and propose two simple algorithms to classify the observations without knowing the threshold variable. The classification is then used with several graphical procedures to search for the most suitable threshold variable. Simulated and real examples are included to illustrate the proposed procedures.
A NOTE ON TESTING FOR SEASONAL COINTEGRATION USING PRINCIPAL COMPONENTS IN THE FREQUENCY DOMAIN
Authors: Cubadda Gianluca
Published: May 2008

Abstract. This paper deals with testing for cointegration at any frequency with a focus on the bounds tests proposed by Joyeux (Tests for seasonal cointegration using principal components. J. Time Ser. Anal. 13 (1992), 109–18). It is shown that this class of tests has asymptotic size equal to one because the author does not take into account non‐contemporaneous cointegration at frequencies other than zero and π. The consequences of this size distortion with finite samples are investigated by a Monte Carlo experiment. Bounds tests for contemporaneous cointegration are also proposed. Finally, an empirical example of testing for seasonal cointegration in monthly time series is presented and discussed.
A CONDITIONAL LEAST SQUARES APPROACH TO BILINEAR TIME SERIES ESTIMATION
Authors: Grahn T.
Published: May 2008

Abstract.In this paper a conditional least squares (CLS) procedure for estimating bilinear time series models is introduced. This method is applied to a special superdiagonal bilinear model which includes the classical linear autoregressive moving‐average model as a particular case and it is proven that the limiting distribution of the CLS estimates is Gaussian and that the law of the iterated logarithm holds.
LINEAR INTERPOLATORS AND THE INVERSE CORRELATION FUNCTION OF NON‐STATIONARY TIME SERIES
Authors: Baragona Roberto , Battaglia Francesco
Published: May 2008

Abstract. The inverse correlation function of a stationary time series was introduced by Cleveland (The inverse autocorrelations of a time series and their applications. Technometrics 14 (1972), 277–93). In this paper inverse correlations are defined for non‐stationary time series {xt, integer t} such that yt= (1 —Bs)dxt is second‐order stationary. The linear interpolator and the inverse process of {xt} are also defined:their weights are shown to be time invariant and proportional to the inverse correlations. The interpolation method for the estimation of the inverse correlation function of a stationary time series is extended to the non‐stationary series {xt} and the asymptotic properties of the estimates are found to be similar to those in the stationary case.
ON THE STRENGTH OF DEPENDENCE OF A TIME SERIES GENERATED BY A CHAOTIC MAP
Authors: Hall Peter , Wolff Rodney C. L.
Published: May 2008

Abstract.A stochastic sequence generated by a chaotic map has extremely strong dependence in a structural sense, in that any data value may be represented exactly as a known deterministic function of any one of its antecedents. However, the range of dependence of the time series may be very short in a statistical sense ‐ in fact, all its lagged correlations could be zero. In the present paper we study the implications of this property for two of the statistical techniques which weak dependence is often invoked to justify ‐ asymptotic methods based on the central limit theorem, and the bootstrap. It is shown that in the case of the logistic map, the validity of these techniques depends critically on the value of the parameter governing the map. Very small alterations to the parameter value can produce dramatic changes in the strength of dependence, thereby altering the validity of even elementary statistical procedures based on asymptotic normality or resampling.
SIMULATION AND ESTIMATION OF LONG MEMORY CONTINUOUS TIME MODELS
Authors: Comte F.
Published: May 2008

Abstract. Some general properties of long memory continuous time processes are recalled or proved. Methods of simulation are studied. A comparison with the usual discrete time autoregressive fractionally integrated moving‐average filter is made and illustrations are provided. Then, two methods of estimation of the parameters of such a model from a discrete sample are studied, both theoretically and empirically, with Monte Carlo experiments.
ON THE ROBUSTNESS TO SMALL TRENDS OF ESTIMATION BASED ON THE SMOOTHED PERIODOGRAM
Authors: Heyde C. C. , Dai W.
Published: May 2008

Abstract. In this paper we are concerned with the robustness of inferences, carried out on a stationary process contaminated by a small trend, to this departure from stationarity. It is shown that a smoothed periodogram approach to model fining and parameter estimation is highly robust to the presence of a small trend if the underlying stationary process is short‐range dependent. If the underlying process is long‐range dependent the robustness properties are still good but now depend on the Hurst index of the process and deteriorate with increasing Hurst index.
SPECTRAL ANALYSIS OF A STATIONARY BIVARIATE POINT PROCESS WITH APPLICATIONS TO NEUROPHYSIOLOGICAL PROBLEMS
Authors: Rigas A. G.
Published: May 2008

Abstract. In this paper we discuss the spectral analysis of a stationary bivariate point process applied to the study of a complex physiological system. An estimate of the cross‐spectral density can be obtained by smoothing the modified cross‐periodogram statistic. The smoothed estimate is calculated by dividing the whole length of the data into a number of disjoint subrecords. Estimates of the coherence function and the cross‐intensity function follow directly from the estimate of the cross‐spectral density. It is shown that the asymptotic properties of the estimate of the cross‐intensity function can be improved by inserting a convergence factor in it. Examples of the estimates are illustrated by using two data sets from neurophysiological experiments and their importance is emphasized by examining the behaviour of the complex physiological system under study.
ON THE APPROXIMATION OF MOMENTS FOR CONTINUOUS TIME THRESHOLD ARMA PROCESSES
Authors: Stramer O.
Published: May 2008

Abstract. An approximating sequence of Markov processes with transitions at times 0, 1/n, 2/n,…, where n is large, was used in Brockwell and Hyndman (On continuous time threshold autoregression. Int. J. Forecasting 8 (1992), 157–73) and Brockwell (On continuous time threshold ARMA processes. J. Stat. Planning Inference 39 (1994). 291–304) to fit continuous time threshold autoregressive moving‐average (CTARMA) models with boundary width 2δ > 0 to both simulated and real data. In this paper we approximate CTARMA processes with δ= 0 by a new sequence of continuous processes and show that the distribution and conditional moments of these approximating processes converge to those of the process itself. This result provides us with a new method for estimating the conditional moments, which enables inference in such models. Some numerical examples illustrate the value of the latter approximation in comparison with the more direct representation of the proces obtained from the Cameron‐Martin‐Girsanov formula (see, for example, Brockwell (On continuous time threshold ARMA processes. J. Stat. Planning Inference 39 (1994). 291–304) and Brockwell and Stramer (On the approximation of continuous time threshold ARMA processes. Ann. Inst. Statist. Math., to appear (1995))).
LOCALLY ADAPTIVE LAG‐WINDOW SPECTRAL ESTIMATION
Authors: Bühlmann Peter
Published: May 2008

Abstract.We propose a procedure for the locally optimal window width in nonparametric spectral estimation, minimizing the asymptotic mean square error at a fixed frequencyΛof a lag‐window estimator. Our approach is based on an iterative plug‐in scheme. Besides the estimation of a spectral density at a fixed frequency, e.g. at frequencyΛ= 0, our procedure allows to perform nonparametric spectral estimation with variable window width which adapts to the smoothness of the true underlying density.
SOME PROPERTIES OF THE MAXIMUM LIKELIHOOD ESTIMATOR IN THE SIMULTANEOUS SWITCHING AUTOREGRESSIVE MODEL
Authors: Sato Seisho , Kunitomo Naoto
Published: May 2008

Abstract. The simultaneous switching autoregressive (SSAR) model proposed by Kunitomo and Sato (A non‐linearity in economic time series and disequilibrium econometric models. In Theory and Application of Mathematical Statistics (ed. A. Takemura). Tokyo:University of Tokyo Press (in Japanese), 1994; Asymmetry in economic time series and simultaneous switching autoregressive model. Struct. Change Econ. Dyn., forthcoming (1994).) is a Markovian non‐linear time series model. We investigate the finite sample as well as the asymptotic properties of the least squares estimator and the maximum likelihood (ML) estimator. Due to a specific simultaneity involved in the SSAR model, the least squares estimator is badly biased. However, the ML estimator under the assumption of Gaussian disturbances gives reasonable estimates.
THE EXACT ERROR IN ESTIMATING THE SPECTRAL DENSITY AT THE ORIGIN
Authors: Ng Serena , Perron Pierre
Published: May 2008

Abstract. This paper derives expressions for the exact bias and variance of a general class of spectral density estimators at the zero frequency, building on the work of Neave (The exact error in spectrum estimates. Ann. Math. Statist. 42 (1971), 961–75) who studied the case where the mean of the series is assumed known. These expressions are evaluated for 15 different windows and for a wide variety of stationary time series. The exact error of the estimators is found to depend on whether the sample mean has to be estimated, and some windows are noticeably inferior at certain values of the bandwidth. A response surface analysis reveals that the finite sample relationships between the bandwidth and the exact error are quite different from the ones suggested by asymptotic theory.
INITIALIZATION OF THE KALMAN FILTER WITH PARTIALLY DIFFUSE INITIAL CONDITIONS
Authors: Snyder Ralph D. , Saligari Grant R.
Published: May 2008

Abstract.The problem of computing estimates of the state vector when the Kalman filter is seeded with an arbitrarily large variance is considered. To date the response in the literature has been the development of a number of relatively complex hybrid filters, usually involving additional quantities and equations over and above the conventional filter. We show, however, that a certain square root covariance filter is capable of handling the complete range of variances (zero, positive and infinite) without modification to the filtering equations themselves and without additional computation loads. Instead of the more conventional Cholesky factorization, our filter employs an alternative matrix factorization procedure based on a unit lower triangular matrix and a diagonal matrix. This permits the use of a modified form of fast Givens transformations, central to the development of an efficient algorithm.
Impacts of Prime‐age Adult Mortality on Labour Supply: Evidence from Adolescents and Women in South Africa*
Authors: Yamauchi Futoshi , Buthelezi Thabani , Velia Myriam
Published: May 2008

This paper examines the impact of prime‐age adult mortality on the transition made by adolescents from school to the labour market and on female adult labour force participation decisions in South Africa. We find, first, that deaths of prime‐age adults significantly increase both male and female adolescents’ labour force participation as they stop their schooling. Secondly, the death of prime‐age adults in general also decreases school enrolment ex ante. Thirdly, female adults tend to join the labour force following the death of prime‐age adult males. These findings imply that prime‐age adult mortality increases labour supply and disrupts human capital formation.
Turning Unemployment into Self‐Employment: Effectiveness of Two Start‐Up Programmes*
Authors: Baumgartner Hans J. , Caliendo Marco
Published: May 2008

Turning unemployment into self‐employment has become a major focus of German active labour market policy (ALMP) in recent years. If effective, this would not only reduce Germany's persistently high unemployment rate, but also increase its notoriously low self‐employment rate. Empirical evidence on the effectiveness of such programmes is scarce. We evaluate the effectiveness of two start‐up programmes for the unemployed, where we include the probability of being employed, the probability of being unemployed and personal income as outcome variables. Our results show that at the end of the observation period, both programmes are effective. The considerable positive effects present a stark contrast to findings from evaluations of other German ALMP programmes in recent years. Hence, ALMP programmes aimed at moving the unemployed into self‐employment may prove to be among the most effective, both in Germany and elsewhere.
Seroprevalence of schistosomiasis in African patients infected with HIV
Authors: Smith C , Smith H , Seaton RA , Fox R
Published: May 2008

Background

Schistosomiasis is a highly prevalent parasitic infection causing significant morbidity and mortality in sub‐Saharan Africa. Infection is asymptomatic for many years. Long‐term complications such as portal hypertension and bladder cancer can be prevented by treatment with praziquantel.

Objectives

The aim of this study was to determine the prevalence of schistosomiasis in HIV‐infected African patients attending our department.

Methods

From March 2005, all patients of African origin attending our HIV clinics were tested for schistosomal antibodies using a peroxidase enzyme‐linked immunosorbent assay (ELISA). Stool and urine specimens from seropositive patients were examined for ova. All seropositive patients were offered treatment with praziquantel.

Results

Of 122 patients tested, 21 (17%) were ELISA positive for schistosomiasis. Ova were found in stools from four patients and on a cervical smear in one patient. There were no significant differences between infected and uninfected patients other than the presence of eosinophilia (48 vs. 6%; P<0.001), and 17 seropositive patients were treated with praziquantel.

Conclusions

The seroprevalence of schistosomiasis in HIV‐infected patients of African origin in the UK is high. We recommend that screening for schistosomiasis should be offered to these patients and those found to be positive treated with praziquantel.
University Patenting in Wales, Scotland and Northern Ireland: a Comparative Analysis
Authors: Beale Andrew , Blackaby David , Mainwaring Lynn
Published: May 2008

Using data on the patent portfolios of UK universities, the paper compares the levels of patenting activity (filings), success (grants) and quality (patents with commercial co‐assignees and patent citations) at Welsh, Scottish and Northern Irish institutions. Patent activity, per researcher, in Wales is on a par with that in Scotland and about twice the rate in Northern Ireland, but the numbers of researchers relative to population in Wales and Northern Ireland are around half of the number in Scotland. Patent quality indicators are less favourable to Wales, while both activity levels and conversion of applications into grants are poor in Northern Ireland. It is suggested that greater cross‐university collaboration in Wales and Northern Ireland would help improve performance.
Horizontal and Vertical Differentiation within Higher Education – Gender and Class Perspectives
Authors: Berggren Caroline
Published: May 2008

The study outline differences among classes and genders within higher education. Because of the expansion of places of study, higher education has lost some of its former selectivity. The matriculation of one full birth cohort into Swedish higher education was studied. The results showed that the enrolment of working‐ and intermediate‐class women had increased, while women from the upper‐middle class, also previously enrolled in higher education, had expanded their educational options becoming involved in prestigious and previously male‐dominated programmes.
Friendships and Social Interactions of School-Aged Children With Migraine
Authors: Vannatta K , Getzoff EA , Gilman DK , Noll RB , Gerhardt CA , Powers SW , Hershey AD
Published: May 2008

We set out to evaluate the friendships and social behaviour of school-aged children with migraine. Concern exists regarding the impact of paediatric migraine on daily activities and quality of life. We hypothesized that children with migraine would have fewer friends and be identified as more socially sensitive and isolated than comparison peers. Sixty-nine children with migraine participated in a school-based study of social functioning. A comparison sample without migraine included classmates matched for gender, race and age. Children with migraine had fewer friends at school; however, this effect was limited to those in elementary school. Behavioural difficulties were not found. Middle-school students with migraine were identified by peers as displaying higher levels of leadership and popularity than comparison peers. Concern may be warranted about the social functioning of pre-adolescent children with migraine; however, older children with migraine may function as well as or better than their peers.
Affiliate Stigma Among Caregivers of People with Intellectual Disability or Mental Illness
Authors: Mak Winnie W. S. , Cheung Rebecca Y. M.
Published: May 2008

Background Affiliate stigma refers to the extent of self‐stigmatization among associates of the targeted minorities. Given previous studies on caregiver stigma were mostly qualitative in nature, a conceptually based, unified, quantitative instrument to measure affiliate stigma is still lacking.

Materials and Methods Two hundred and ten caregivers of people with intellectual disability (CPID) and 108 caregivers of people with mental illness (CPMI) were recruited to validate the 22‐item Affiliate Stigma Scale with caregiving stress, subjective burden and positive perceptions.

Results Exploratory factor analysis suggested that the scale was unidimensional, with excellent internal consistencies for both CPID and CPMI. It showed good predictive validity on subjective burden, after the extent of caregiving involvement and caregiving stress were controlled for.

Conclusion Implications on psychoeducation and stigma reduction were discussed. The newly developed scale provided a quantitative instrument with which affiliate stigma can be compared across different conditions.
On the Origin of the Transthyretin Val30Met Familial Amyloid Polyneuropathy
Authors: Zaros C. , Genin E. , Hellman U. , Saporta M. A. , Languille L. , Wadington‐Cruz M. , Suhr O. , Misrahi M. , Planté‐Bordeneuve V.
Published: May 2008

Transthyretin (TTR) familial amyloid polyneuropathy is a severe autosomal dominant neuropathy of adulthood, frequently linked to the pathogenic Val30Met variant of the TTR gene. The condition was initially described in northern Portugal, which is the first focus of the disease. Other important clusters of families are found in Sweden, Japan and South America.

The origin of the Val30Met mutation and its distribution through the populations remains unclear. In the present work, we aimed at refining the history of the Val30Met mutation in patients affected with TTR amyloid neuropathy from Portugal, Sweden and Brazil. The decay of haplotype sharing was studied in 60 patients to estimate the age of the Most Recent Common Ancestor (MRCA) of mutation carriers in these populations. Our results showed a common haplotype in Portuguese and Brazilian patients and an age estimate of the MRCA of 750 and 650 years, respectively. In contrast, a different haplotype was found in the Swedish Val30Met patients with a corresponding age estimate for the MRCA, of 375 years.

This work strengthens the hypothesis of different founders in Portuguese and Swedish Val30Met carriers and suggested a Portuguese origin of the Brazilian mutation. The age estimates of the MRCA are in line with the current historical knowledge of these populations.
The impact of ethical concerns on family consumer decision‐making
Authors: Carey Lindsey , Shaw Deirdre , Shiu Edward
Published: May 2008

Ethical consumerism and family consumer decision‐making, including the influence of children in this area, are spheres of consumer behaviour in which a substantial amount of academic research has already been undertaken. However, the crossover of these two areas is as yet under‐researched, as well as the level of pester power parents are subjected to from children aged 3 and under. This paper uses qualitative methods to investigate the issues surrounding the ethical consumer decision‐making process with families who have children aged 3 years old or under. This research found that the motivation to pursue an ethical lifestyle varied across the sample, but the emergence of an ‘inheritance factor’, where parents are awakened to ethical issues because of the birth of their child, was prominent. Other issues that transpired from this research include the prominence of ethical trade‐offs in consumer decision‐making, ethical choices as normalizing behaviour and finally the presence of pester power in the ethical context. Ethical consumerism strongly emerged as an integral part of the parent's identity construction, especially for the mothers as they struggled to adapt to their new roles. Further research delving into the role ethical choices have on identity construction and the parental response to pester power would be a valuable addition to the overall context of this research.
Consumer product search and purchase behaviour using various retail channels: the role of perceived retail usefulness
Authors: Kim Jihyun , Lee Hyun‐Hwa
Published: May 2008

The purpose of this study was to examine the influences of consumers' perceptions of retail usefulness for product information search and their previous purchase satisfaction on their frequencies of product information search and product purchase behaviours for apparel products. These relationships were investigated in five retail settings – Internet shopping, catalogue shopping, television shopping, local retail shopping, and non‐local retail shopping. One hundred seventy‐six students in a US Midwestern university provided usable responses. The results of causal model analyses showed that the proposed model fits the data well for all five retail channels. Consumers who perceived a certain retail channel more useful for product information search searched for product information more frequently via that retail channel, and purchased products more often via that retail channel. Consumers who were more satisfied with apparel purchases from a retail channel purchased the products more frequently via that retail channel. Theoretical and managerial implications are discussed.
Environmental value chain management of laundry detergents in the use phase
Authors: Paloviita Ari , Järvi Pentti
Published: May 2008

Environmental value chain management is concerned with the environmental aspects of products and services along the whole value chain, from raw material and energy acquisition to waste management. The use phase in the value chain remains an understudied subject, despite considerable consumption‐related environmental impacts. The purpose of this paper is to analyse the use phase of laundry detergents in households. Our empirical data consist of interviews in the laundry rooms of 299 Finnish households. Consumers’ environmental awareness, use of dosage measuring devices and actual doses of laundry detergents are studied in the empirical part of the study. The results show that consumers do not perceive households as significant polluters, the measuring devices they use are diverse and the number of ‘heavy users’ is high in all detergent brands. It is concluded that in the consumption of laundry detergents, consumers do not perceive environmental issues as specific value criteria in relation to the use of laundry detergents. Manufacturers, marketers and other actors in the value chain of laundry detergents could contribute to alleviating the harmful environmental impacts of the use phase by more effective consumer education and better product design. For consumers, it might be beneficial to adopt eco‐efficiency thinking in their daily consumption.
Depletion of 14‐3‐3 zeta elicits endoplasmic reticulum stress and cell death, and increases vulnerability to kainate‐induced injury in mouse hippocampal cultures
Authors: Murphy Niamh , Bonner Helena P. , Ward Manus W. , Murphy Brona M. , Prehn Jochen H. M. , Henshall David C.
Published: May 2008

14‐3‐3 proteins are ubiquitous signalling molecules that regulate development and survival pathways in brain. Altered expression and cellular localization of 14‐3‐3 proteins has been implicated in neurodegenerative diseases and in neuronal death after acute neurological insults, including seizures. Presently, we examined expression and function of 14‐3‐3 isoforms in vitro using mouse organotypic hippocampal cultures. Treatment of cultures with the endoplasmic reticulum (ER) stressor tunicamycin caused an increase in levels of 14‐3‐3 zeta within the ER‐containing microsomal fraction, along with up‐regulation of Lys‐Asp‐Glu‐Leu‐containing proteins and calnexin, and the selective death of dentate granule cells. Depletion of 14‐3‐3 zeta levels using small interfering RNA induced both ER stress proteins and death of granule cells. Treatment of hippocampal cultures with the excitotoxin kainic acid increased levels of Lys‐Asp‐Glu‐Leu‐containing proteins and microsomal 14‐3‐3 zeta levels and caused cell death within the CA1, CA3 and dentate gyrus of the hippocampus. Kainic acid‐induced damage was significantly increased in each hippocampal subfield of cultures treated with small interfering RNA targeting 14‐3‐3 zeta. The present data indicate a role for 14‐3‐3 zeta in survival responses following ER stress and possibly protection against seizure injury to the hippocampus.
Kv 1.1 is associated with neuronal apoptosis and modulated by protein kinase C in the rat cerebellar granule cell
Authors: Hu Chang‐Long , Zeng Xi‐Min , Zhou Meng‐Hua , Shi Ying‐Tang , Cao Hong , Mei Yan‐Ai
Published: May 2008

Previously, we reported that apoptosis of cerebellar granular neurons induced by low‐K+ and serum‐free (LK‐S) was associated with an increase in the A‐type K+ channel current (IA), and an elevated expression of main α‐subunit of the IA channel, which is known as Kv4.2 and Kv4.3. Here, we show, as assessed by quantitative RT‐PCR and whole‐cell recording, that besides Kv4.2 and Kv4.3, Kv1.1 is very important for IA channel. The expression of Kv1.1 was elevated in the apoptotic neurons, while silencing Kv1.1 expression by siRNA reduced the IA amplitude of the apoptotic neuron, and increased neuron viability. Inhibiting Kv1.1 current by dendrotoxin‐K evoked a similar effect of reduction of IA amplitude and protection of neurons. Applying a protein kinase C (PKC) activator, phorbol ester acetate A (PMA) mimicked the LK‐S‐induced neuronal apoptotic effect, enhanced the IA amplitude and reduced the granule cell viability. The PKC inhibitor, bisindolylmaleimide I and Gö6976 protected the cell against apoptosis induced by LK‐S. After silencing the Kv1.1 gene, the effect of PMA on the residual K+ current was reduced significantly. Quantitative RT‐PCR and Western immunoblot techniques revealed that LK‐S treatment and PMA increased the level of the expression of Kv1.1, in contrast, bisindolylmaleimide I inhibited Kv1.1 expression. In addition, the activation of the PKC isoform was identified in apoptotic neurons. We thus conclude that in the rat cerebellar granule cell, the IA channel associated with apoptotic neurons is encoded mainly by the Kv1.1 gene, and that the PKC pathway promotes neuronal apoptosis by a brief modulation of the IA amplitude and a permanent increase in the levels of expression of the Kv1.1 α‐subunit.
Biochemical characterization of membrane‐associated septin from rat brain
Authors: Maimaitiyiming Maowulan , Kumanogoh Haruko , Nakamura Shun , Nagata Koh‐Ichi , Suzaki Toshinobu , Maekawa Shohei
Published: May 2008

Within the cell membrane there exist various microdomains (lipid rafts) in which specific lipids and proteins are assembled and these microdomains are recovered in the detergent‐resistant low‐density membrane fraction (DRM). Septin is a novel GTP‐binding, cytoskeletal protein having various isoforms that assemble into homo‐ and heterooligomers and filaments. As the localization of septin 3 in DRM was found through a proteomics analysis of brain‐derived DRM, the presence of other septin isoforms in DRM was studied. Western blotting analysis showed maturation‐dependent enrichment of several septin isoforms in DRM prepared from synaptic plasma membrane (SPM). These isoforms were solubilized with high MgCl2 solution and recovered as the precipitate after dialysis to low ionic solution. Three times cycling of the extraction‐dialysis process resulted in the partial purification of septin complex and electron microscopic observation of this fraction revealed rod‐like structures in which building units were observed. The presence of heterooligomers was shown with western blotting after the separation of the MgCl2 extract with blue‐native polyacrylamide gel electrophoresis. Immunoprecipitation assay using monoclonal anti‐septin11 antibody also showed the presence of heterooligomers. These results show that septin localizes in the membrane microdomains of the SPM in adult brain and may have important roles in the membrane dynamics of neurons.
Functions of human bitter taste receptors depend on N‐glycosylation
Authors: Reichling Claudia , Meyerhof Wolfgang , Behrens Maik
Published: May 2008

Human bitter taste receptors of the TAS2R gene family play a crucial role as warning sensors against the ingestion of toxic food compounds. Moreover, the genetically highly polymorphic hTAS2Rs recognize an enormous number of structurally diverse toxic and non‐toxic bitter substances, and hence, may substantially influence our individual eating habits. Heterologous expression in mammalian cells is a useful tool to investigate interactions between these receptors and their agonists. However, many bitter taste receptors are poorly expressed at the cell surface of heterologous cells requiring the addition of plasma membrane export promoting epitopes to the native receptor proteins. Currently, nothing is known about amino acid motifs or other receptor‐intrinsic features of TAS2Rs affecting plasma membrane association. In the present study, we analyzed the Asn‐linked glycosylation of hTAS2Rs at a consensus sequence in the second extracellular loop, which is conserved among all 25 hTAS2Rs. Non‐glycosylated receptors exhibit substantially lower cell surface localization and reduced association with the cellular chaperone calnexin. As the auxiliary factors receptor transporting proteins 3 and 4 are able to restore the function of non‐glycosylated hTAS2R16 partially, we conclude that glycosylation is important for receptor maturation but not for its function per se.
Metabolic syndrome and the role of dietary lifestyles in Alzheimer’s disease
Authors: Pasinetti Giulio Maria , Eberstein Jacqueline A.
Published: May 2008

Since Alzheimer’s disease (AD) has no cure or preventive treatment, an urgent need exists to find a means of preventing, delaying the onset, or reversing the course of the disease. Clinical and epidemiological evidence suggests that lifestyle factors, especially nutrition, may be crucial in controlling AD. Unhealthy lifestyle choices lead to an increasing incidence of obesity, dyslipidemia and hypertension – components of the metabolic syndrome. These disorders can also be linked to AD. Recent research supports the hypothesis that calorie intake, among other non‐genetic factors, can influence the risk of clinical dementia. In animal studies, high calorie intake in the form of saturated fat promoted AD‐type amyloidosis, while calorie restriction via reduced carbohydrate intake prevented it. Pending further study, it is prudent to recommend to those at risk for AD – e.g. with a family history or features of metabolic syndrome, such as obesity, insulin insensitivity, etc. – to avoid foods and beverages with added sugars; to eat whole, unrefined foods with natural fats, especially fish, nuts and seeds, olives and olive oil; and to minimize foods that disrupt insulin and blood sugar balance.
Role of AMPA receptor trafficking in NMDA receptor‐dependent synaptic plasticity in the rat lateral amygdala
Authors: Yu Shu Yan , Wu Dong Chuan , Liu Lidong , Ge Yuan , Wang Yu Tian
Published: May 2008

Stimulated exocytosis and endocytosis of post‐synaptic α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid subtype of glutamate receptors (AMPARs) have been proposed as primary mechanisms for the expression of hippocampal CA1 long‐term potentiation (LTP) and long‐term depression (LTD), respectively. LTP and LTD, the two most well characterized forms of synaptic plasticity, are thought to be important for learning and memory in behaving animals. Both LTP and LTD can also be induced in the lateral amygdala (LA), a critical structure involved in fear conditioning. However, the role of AMPAR trafficking in the expression of either LTP or LTD in this structure remains unclear. In this study, we show that NMDA receptor‐dependent LTP and LTD can be reliably induced at the synapses of the auditory thalamic inputs to the LA in brain slices. The expression of LTP was prevented by post‐synaptic blockade of vesicle‐mediated exocytosis with application of a light chain of Clostridium tetanus neurotoxin and was associated with increased cell‐surface AMPAR expression. In contrast, the expression of LTD was prevented by post‐synaptic application of a glutamate receptor 2‐derived interference peptide, which specifically blocks the stimulated clathrin‐dependent endocytosis of AMPARs, and was correlated with a reduction in plasma membrane‐surface expression of AMPARs. These results strongly suggest that regulated trafficking of post‐synaptic AMPARs is also involved in the expression of LTP and LTD in the LA.
Zebrafish as a new animal model for movement disorders
Authors: Flinn Laura , Bretaud Sandrine , Lo Christine , Ingham Phillip W. , Bandmann Oliver
Published: May 2008

The zebrafish, long recognized as a model organism for the analysis of basic developmental processes, is now also emerging as an alternative animal model for human diseases. This review will first provide an overview of the particular characteristics of zebrafish in general and their dopaminergic nervous system in particular. We will then summarize all work undertaken so far to establish zebrafish as a new animal model for movement disorders and will finally emphasize its particular strength – amenability to high throughput in vivo drug screening.
Regulation of DYT1 gene expression by the Ets family of transcription factors
Authors: Armata Ioanna A. , Ananthanarayanan Meenakshisundaram , Balasubramaniyan Natarajan , Shashidharan Pullanipally
Published: May 2008

The DYT1 gene encodes for torsinA, a protein with widespread tissue distribution, involved in early onset dystonia (EOD). Numerous studies have focused on torsinA function but no information is available on its transcriptional regulation. We cloned mouse and human 5′‐upstream DYT1 DNA fragments, exhibiting high transcriptional activity, as well as tissue specificity. We identified a proximal minimal DYT1 promoter within −141 bp for mouse and −191 bp for human with respect to the ATG codon. Primer extension analysis indicated multiple transcription start sites. In silico analysis of approximately 500 bp 5′‐upstream DYT1 fragment demonstrated lack of a classical TATA or CAAT box and the presence of a highly conserved direct repeat of two Ets binding cores within −86 bp to −77 bp and −78 bp to −69 bp of the mouse and human DYT1 gene, respectively. A single or a two base nucleotide alteration within the downstream Ets core resulted in approximately 90% (mouse) or 45–60% (human) drop in activity. Interestingly, a 3‐bp distance increase between the two Ets cores dramatically decreased transcriptional activity which was partially restored when the distance was increased up to 10 bp. Ets‐like dominant negatives confirmed the Ets factors as DYT1 transcriptional activators.
Telomeres and race: what can we learn about human biology from health differentials?
Authors: Kaufman Jay S. , Cooper Richard S.
Published: May 2008

The advent of molecular technology that can be applied across large population samples has added – rather than reduced – complexity in the analysis of the intertwined effects of social history and heritable factors on health outcomes. The report by Hunt et al. in this issue of Aging Cell provides an example of the promises and dilemmas associated with this increased complexity.
Leukocyte telomeres are longer in African Americans than in whites: the National Heart, Lung, and Blood Institute Family Heart Study and the Bogalusa Heart Study
Authors: Hunt Steven C. , Chen Wei , Gardner Jeffrey P. , Kimura Masayuki , Srinivasan Sathanur R. , Eckfeldt John H. , Berenson Gerald S. , Aviv Abraham
Published: May 2008

Leukocyte telomere length (LTL) is ostensibly a bio‐indicator of human aging. Here we report that African Americans have longer LTL than whites. We studied cross‐sectionally 2453 individuals from the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study (age = 30–93 years) and the Bogalusa Heart Study (age = 19–37 years), comprising 1742 whites and 711 African Americans. We measured LTL by Southern blots of the terminal restriction fragments length. In 234 participants, telomere repeats were also measured by quantitative polymerase chain reaction (qPCR). Adjusted for age and body mass index (BMI), the respective leukocyte telomere lengths (mean ± SEM) were considerably longer in African Americans than in whites both in the Family Heart Study (7.004 ± 0.033 kb vs. 6.735 ± 0.024 kb, p < 0.0001) and the Bogalusa Heart Study (7.923 ± 0.063 kb vs. 7.296 ± 0.039 kb, p < 0.0001). We confirmed the racial effect on LTL by qPCR (3.038 ± 0.565 T/S units for African Americans vs. 2.714 ± 0.487 T/S units for whites, p < 0.001). Cross‐sectionally, sex‐ and BMI‐adjusted LTL became shorter with age (range 19–93 years) at a steeper slope in African Americans than in whites (0.029 kb year−1 vs. 0.020 kb year−1, respectively, p = 0.0001). We suggest that racial difference in LTL arises from a host of interacting biological factors, including replication rates of hematopoietic stem cells.
How Many Nurses per Patient? Measurements of Nurse Staffing in Health Services Research
Authors: Spetz Joanne , Donaldson Nancy , Aydin Carolyn , Brown Diane S.
Published: May 2008

Objective. To compare alternative measures of nurse staffing and assess the relative strengths and limitations of each measure.

Data Sources/Study Setting. Primary and secondary data from 2000 and 2002 on hospital nurse staffing from the American Hospital Association, California Office of Statewide Health Planning and Development, California Nursing Outcomes Coalition, and the California Workforce Initiative Survey.

Study Design. Hospital‐level and unit‐level data were compared using summary statistics, t‐tests, and correlations.

Data Collection/Extraction Methods. Data sources were matched for each hospital. When possible, hospital units or types of units were matched within each hospital. Productive nursing hours and direct patient care hours were converted to full‐time equivalent employment and to nurse‐to‐patient ratios to compare nurse staffing as measured by different surveys.

Principal Findings. The greatest differences in staffing measurement arise when unit‐level data are compared with hospital‐level aggregated data reported in large administrative databases. There is greater dispersion in the data obtained from publicly available, administrative data sources than in unit‐level data; however, the unit‐level data sources are limited to a select set of hospitals and are not available to many researchers.

Conclusions. Unit‐level data collection may be more precise. Differences between databases may account for differences in research findings.
Edgeworth Price Cycles and Focal Prices: Computational Dynamic Markov Equilibria
Authors: Noel Michael D.
Published: May 2008

Motivated by the apparent discovery of Edgeworth Cycles in many retail gasoline markets, this article extends the theory of Edgeworth Cycles along several key dimensions, including models of fluctuating marginal costs, differentiation, capacity constraints and triopoly. A computational approach to search for Markov perfect equilibria is taken. Edgeworth Cycles are found in equilibrium in many situations, and the shape of the cycles are found to carry information about underlying competitive intensity. Cycles in triopoly exhibit interesting coordination problems such as delayed starts and false starts.
Patents, Research Exemption, and the Incentive for Sequential Innovation
Authors: Moschini GianCarlo , Yerokhin Oleg
Published: May 2008

We develop a quality ladder model to study the R&D incentive impacts of intellectual property rights with a “research exemption” or “experimental use” provision. The innovation process is sequential and cumulative and takes place alongside production in an infinite‐horizon setting. We solve the model under two distinct intellectual property regimes, characterize the properties of the relevant Markov perfect equilibria, and investigate the profit and welfare effects of the research exemption. We find that firms, ex ante, always prefer full patent protection. The welfare ranking of the two intellectual property regimes, on the other hand, depends on the relative magnitudes of the costs of initial innovation and improvements.
A probable case of hepatitis B virus transfusion transmission revealed after a 13‐month‐long window period
Authors: Wendel Silvano , Levi José E. , Biagini Silvana , Candotti Daniel , Allain Jean‐Pierre
Published: May 2008

BACKGROUND: Transfusion‐transmitted hepatitis B virus (HBV) infection in recipients with drug‐related immunodeficiency is rarely described in endemic areas. Hepatitis B surface antigen (HBsAg)–negative infectious donor blood can be identified by sensitive nucleic acid testing (NAT). Two immunodeficient patients who received blood components from a single seronegative blood donor subsequently found to contain HBV DNA are described.

MATERIALS AND METHODS: Multiple samples from the implicated donor and the two recipients were tested for HBV serologic and molecular markers. HBV genome fragments were amplified, sequenced, and phylogenetically analyzed.

RESULTS: The implicated donation had low‐level HBV DNA due to the donor being in the window period before the donor's seroconversion. Recipient 1 had been vaccinated to HBV and carried anti‐HBs but remained negative for all other HBV markers until she developed acute hepatitis B (viral load 2.7 × 108 IU/mL and alanine aminotransferase [ALT] level 1744 IU/L) 13 months after transfusion of red cells. Identical HBV sequences from both donor and recipient provided evidence of transfusion‐related infection. Recipient 2, who received platelets from the same donation while receiving major chemotherapy, remained uninfected.

CONCLUSIONS: In unusual circumstances, HBV incubation time can be considerably prolonged. Both active and passive neutralizing antibodies to HBV likely delayed, but did not prevent, acute infection when the immune system was impaired. HBV NAT may have interdicted the infectious unit, although the donation viral load could not be quantified and odds of detection calculated.
Expression of human telomerase reverse transcriptase in bone marrow CD34+ cells from patients with β‐thalassemia major
Authors: Li Xihong , Qu Yi , Mao Meng , Yu Fan , Li Qiang , Hua Yimin , Mu Dezhi
Published: May 2008

BACKGROUND: Normal stem cells usually express a low level of telomerase activity that serves to stabilize the chromosomes during cell division and helps prevent cell senescence. Human telomerase reverse transcriptase (hTERT) is a rate‐limiting enzyme that dictates the activity of human telomerase and thus decides the life span of cells. The expression of hTERT and its roles in β‐thalassemia major are unclear, however.

STUDY DESIGN AND METHODS: hTERT mRNA expression in bone marrow (BM) CD34+ cells from 25 children with β‐thalassemia major and 15 control subjects was investigated using real‐time reverse transcription polymerase chain reaction (RT‐PCR) analysis. The serum erythropoietin (sEPO) and hemoglobin (Hb) levels in peripheral blood were also determined. The relationship between hTERT and sEPO as well as Hb was then examined.

RESULTS: It was found that hTERT mRNA expression was significantly up regulated in BM CD34+ cells from patients with β‐thalassemia major. Furthermore, a significantly positive correlation was found between hTERT mRNA and sEPO (r = 0.771, p < 0.001). A significantly inverse correlation, however, was found between hTERT mRNA and Hb concentration (r = −0.929, p < 0.001).

CONCLUSION: Our findings suggest that severe anemia with low Hb concentration might up regulate hTERT expression of BM CD34+ cells and sEPO levels in patients with β‐thalassemia major.
Dynamic Prevention in Short‐Term Insurance Contracts
Authors: Martin Boyer M. , Gobert Karine
Published: May 2008

Abstract

This article looks at the dynamic properties of insurance contracts when insurers have a better technology at preventing catastrophic losses than the insured. When the prevention technology is irreversible and its benefits last for all future periods although its cost is borne in the period in which it is made, a hold‐up problem occurs because the insured can change insurer after his initial insurer has invested in prevention. Investment in prevention is then delayed compared to the first best outcome. When the audit cost must be incurred by the insured when he wants to change insurer, the incumbent insurer has an informational advantage so that he can keep his client over the entire investment horizon, even though long‐term contracts are not possible. This does not avoid the delay in investment, however.
A Study of the Interaction of Insurance and Financial Markets: Efficiency and Full Insurance Coverage
Authors: Penalva Zuasti Jose S.
Published: May 2008

Abstract

The first contribution of this article is to provide a framework, a model together with a corresponding equilibrium notion, suitable for the study of the interaction between insurance and dynamic financial markets. Our central result is that in equilibrium risk‐averse agents purchase full insurance coverage, despite unfair insurance prices. We identify three conditions that explain this result: (1) insurance contracts are priced competitively, (2) financial prices include a risk premium only for undiversifiable risk, and (3) financial markets are effectively complete. An implication is that in this model disasters can be insured by fully assessable stock insurance companies.
When Is a Coinsurance‐Type Insurance Policy Inferior or Even Giffen?
Authors: Hau Arthur
Published: May 2008

Abstract

This article derives the necessary and sufficient conditions for a coinsurance‐type insurance policy covering a particular risk to be inferior and to be Giffen. Mossin's decreasing absolute risk aversion assumption for insurance to be inferior is avoided. The result generalizes Hoy and Robson and Briys, Dionne, and Eeckhoudt's results to the case with a continuum of states and relaxes their assumption of constant relative risk aversion. It is shown that knowledge about the distribution of risk can be used to relax assumptions on an utility function for a coinsurance‐type insurance policy to be inferior and to be Giffen.