bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxo-iron clusters in a bacterial iron-trafficking protein: new roles for a conserved motif
Authors: ZHU Haizhong , ALEXEEV Dmitriy , HUNTER Dominic J. B. , CAMPOPIANO Dominic J. , SADLER Peter J.
Published: November 2003

We report a set of three 1.8–1.9 Å resolution X-ray crystal structures of Neisseria gonorrhoeae Fbp (ferric-ion binding protein): (i) open-cleft apo-Fbp containing bound phosphate, (ii) open-cleft mono-Fe Fbp capped by nitrilotriacetate, and (iii) open-cleft trinuclear oxo-iron Fbp, the first structure of an iron-cluster adduct of a transferrin. The nine independent molecules in the unit cells provide ‘snapshots’ of the versatile dynamic structural roles of the conserved dityrosyl iron-binding motif (Tyr195-Tyr196) which control the capture and, possibly, processing of iron. These findings have implications for understanding bacterial iron acquisition and dissimilation, and organic/mineral interfaces.
On the Concept of Territorial Competitiveness: Sound or Misleading?
Authors: Camagni Roberto
Published: November 2003

In a globalising economy, territories and not just firms increasingly find themselves in competition with each other. In fact, unlike countries, cities and regions compete, in single currency areas, on the basis of an absolute advantage principle and not a comparative advantage principle. This means that no efficient, automatic mechanism—like currency devaluation or prompt flexibility of wages and prices—exists to grant each territory some role in the international division of labour, whatever its relative performance. The competitiveness of territories thus emerges as a central issue, in order to secure employment stability, benefits from external integration, continuing growth of local well-being and wealth. The arguments put forward by Paul Krugman, defining the concept of competitiveness, are wrong and misleading, and cannot be accepted in a territorial—regional and urban-context.
Conceptualising the Contemporary Role of Housing in the Transition to Adult Life in England
Authors: Ford Janet , Rugg Julie , Burrows Roger
Published: November 2003

This paper uses both survey and qualitative panel data collected from five different case-study areas in England in order to offer a conceptualisation of the contemporary role that housing is playing in the transition to adult life. The data suggest that the types of housing pathway that young people follow are a function of differences in the combination and intensity of three main factors: the ability of young people to plan for and control their entry to independent living; the extent and form of constraints that characterise their access to housing; and the degree of family support available to them. Based around these three dimensions (each of which is a continuum), the following ideal typical pathways can be identified: a chaotic pathway, an unplanned pathway, a constrained pathway, a planned (non-student) pathway and a student pathway.
Who Built Irvine? Private Planning and the Federal Government
Authors: Forsyth Ann
Published: November 2003

The Irvine Ranch in Southern California is the largest privately master-planned 'new community' or satellite new town ever to be built in the US. The development was led by the private sector but government played an important role. This paper traces how the federal government shaped the Irvine development through a range of policies and programmes from defence to habitat protection. In turn, the developers of Irvine were cast in a role of co-ordinating parts of government. This analysis highlights some of the problems likely to be faced as governments promote similarly phased, co-ordinated and mixed-use proposals under the rubric of smart growth or sustainable development.
Density Gradients in Canadian Metropolitan Regions, 1971-96: Differential Patterns of Central Area and Suburban Growth and Change
Authors: Bunting T. , Filion P. , Priston H.
Published: November 2003

This paper demonstrates that over the 25-year period, 1971-96, the majority of Canadian cities have undergone transition towards an increasingly decentralised urban form. The trends, however, are quite diverse, pointing to fundamental differences in the respective importance of growth in central and outer parts of the metropolitan area. On the whole, the relatively high densities observed in Canadian central cities, in comparison with US ones, appear to reflect residual centralisation rather than continued growth in metropolitan regions' innermost parts. Only Vancouver, and to a lesser extent Toronto and Victoria, exhibit indisputable evidence of post-1971 central-area growth. The predominant trend has been towards suburban-style, low-density expansion, albeit with considerable intercity variation regarding changes in central-area and suburban density. Findings presented here point to previously unidentified trends towards recentralisation in a few CMAs and, in about half of the surveyed metropolitan areas, densification of suburban tracts.
The Changing Spatial Concentration of Income and Poverty among Suburbs of Large US Metropolitan Areas
Authors: Madden Janice Fanning
Published: November 2003

After developing a longitudinal data-base of civil divisions within 27 large metropolitan areas (MSAs) from the 1970-1990 US censuses, this study examines changes in the spatial concentration of income and poverty within these MSAs. A series of cross-sectional analyses of geographical and social determinants of poverty rates and median household income are used to analyse whether the determinants are changing over time. Large, older central cities in the north-east and mid-west have experienced increasing poverty and decreases in income relative to their own history and relative to their own suburbs. There is some evidence of economic decline in the inner suburbs of these central cities relative to other suburbs, but not relative to the central cities. The geographical shifts in MSA population among suburbs by income between 1970 and 1990 are analysed relative to initial social characteristics of civil divisions. The study concludes that the filtering of older residential buildings to, and the lower marginal preference for land of, lower-income groups contributes to the rising poverty rates and decreases in median household income for all central cities and for the inner suburbs of the north-eastern and mid-western MSAs. The study finds little evidence that either 'white flight' or the non-poor's avoidance of taxes to support the poor are important factors in the shifts of population among suburbs.
The Evolution of Spanish Urban Structure during the Twentieth Century
Authors: Lanaspa Luis , Pueyo Fernando , Sanz Fernando
Published: November 2003

In this paper, an analysis is made of the evolution of Spanish urban structure during the period 1900-99. It is postulated that the size distribution of the cities follows a Pareto distribution, which is estimated on a yearly basis. At the same time, the hypothesis is adopted that the intradistribution dynamics can be modelled by means of a Markov chain. In this way, are deduced the so-called transition matrix and its associated vector or ergodic probabilities. This methodology allows two main results to be obtained. First, this evolution has not been homogeneous ; there has been a divergent pattern of growth during the period 1900-70; and a convergent pattern for the period 1970-99. Secondly, the intradistribution movements in the Spanish urban hierarchy have been very significant during the course of the 20th century. In addition, the existence of spatial correlation has also been detected for those cities that have either entered or exited from the sample of the 100 largest cities during the course of the century.
Social Behaviour as a Basis for Modelling the Urban Housing Market: A Review
Authors: Meen David , Meen Geoffrey
Published: November 2003

This paper considers how empirical models of urban housing markets might be constructed as a basis for policy analysis. It is suggested that this is fundamentally more difficult than national or regional models, because of particular characteristics of urban markets-notably, the importance of social interactions, non-linearity and segregation. However, recent advances in the modelling of social interactions point to a possible way forward. The paper begins by reviewing some aspects of this literature and shows how the models generate non-linearities consistent with recent work on thresholds in local housing markets. Simple cellular automata are also used to demonstrate this point and how segregation may arise. A review follows of work on discrete choice models, which include social interactions within their structure. Bringing all the tools together, it is suggested that there is now the potential to construct urban housing models, although a great deal of theoretical and empirical work remains to be done.
Taxing Residential Housing Capital
Authors: Englund Peter
Published: November 2003

This paper discusses the main aspects of the taxation of housing drawing on general principles of optimal taxation. It focuses on the role of the property tax in achieving neutrality between rental and owner-occupied housing. Assuming that landlords are taxed according to a neutral profits tax, it follows that the property tax should be based on the rate of interest. The paper discusses how the tax rate could be adjusted to account for the lack of effective taxation of capital gains, the double taxation of dividends and the differences in the cost of labour between rental and owner-occupied housing. In most OECD countries, the combined effect of the different housing taxes amounts to a tax subsidy to owner-occupied housing. It is demonstrated how this subsidy has been reduced in Sweden—as in many other countries—in the past decade as a result of tax reforms and a lower rate of inflation. The subsidy has effects on consumption patterns, saving, capital accumulation, the distribution of welfare across generations and the allocation of risks. The paper provides a brief overview of the literature, trying to quantify some of these effects. Finally, a number of problems are noted in the practical application of a property tax.
House Price Dynamics and Market Fundamentals: The Parisian Housing Market
Authors: Meese Richard , Wallace Nancy
Published: November 2003

The paper compares two methods to evaluate the effect of market fundamentals on housing price dynamics. The first method follows the traditional two-step procedures found in the literature in which one first estimates a house price index and then uses the estimated index in subsequent structural modelling. The second method applies a Kalman filter strategy that allows for the simultaneous estimation of the parameters of a dynamic hedonic price model, the price index and the parameters of a structural model for housing prices. Very similar empirical results are found for the two estimation strategies suggesting that the small efficiency gains of the simultaneous estimator may be outweighed by the relative ease of implementing the traditional methods. Using transaction-level data for dwellings in Paris over the period 1986-92, the paper finds evidence consistent with the hypothesis that economic fundamentals constrain movements in Parisian dwelling prices over longer-term horizons. Both procedures for estimating an error correction model of housing prices based on supply and demand fundamentals lead to the same conclusions, suggesting that the speed of adjustment in the Paris dwelling market was about 30 per cent per month over the period.
Appraisal Smoothing and Price Discovery in Real Estate Markets
Authors: Geltner David , MacGregor Bryan D. , Schwann Gregory M.
Published: November 2003

This paper reviews the literature on price determination in the private and public real estate markets. In particular, it discusses the processes of appraisal smoothing in the private market and of price discovery between the public and the private markets. In real estate markets, the absence of good quality information on price, whether because of lack of trades or confidentiality, has led to the widespread use of appraisals for market tracking and as the basis for performance measurement. Appraisers have to make an optimum assessment of value, based on fundamental variables and market information, including transactions and a market-wide appraisal index. However, transaction prices are a noisy signal and it is the appraiser's role to extract the signal from the noise in an efficient manner. This involves a process of optimal combination of past and current information and leads to appraisal smoothing. Price discovery is the process by which the opinions of market participants about the value of an asset are combined together into a single statistic—its market price. A development of this basic concept is where two markets have a common component of value and the relevant price information is discovered first in one market and then transmitted to the second market. The process of price discovery is considered between the public and private real estate markets.
International Direct Real Estate Investment: A Review of the Literature
Authors: Sirmans C.F. , Worzala Elaine
Published: November 2003

This paper provides a critical review of research on international direct real estate investment issues. To date, no review article has explored the various findings of studies completed on the benefits of international real estate diversification. In the past 10 years, the quantity and variety of work have increased dramatically. The paper is organised by how investing in a real estate asset is analysed: in a mixed-asset portfolio context or a real-estate-only portfolio context. A fourth section focuses on research that has explored currency risk, one of the prevailing risks associated with international investing. The last section provides conclusions about the research and offers ideas for future research in this growing area of real estate investment.
Investing in International Real Estate Stocks: A Review of the Literature
Authors: Worzala Elaine , Sirmans C.F.
Published: November 2003

This paper summarises the various findings of studies completed on the benefits of international diversification using real estate stocks. With the increased availability of data and analytical tools, the quantity and variety of work over the past decade have increased dramatically in this area. The first two sections of the paper chronologically review the studies, focusing on how the diversification benefits are analysed: in a mixed-asset portfolio context or a real-estate-only portfolio context. The third section highlights work that uses alternative analyses to the traditional mean-variance framework to examine the international real estate stock as an investment alternative. Almost all of the studies reach the same conclusion: diversification gains are possible but are often reduced if currency risk is included in the analysis.
Occupier Requirements in Commercial Real Estate Markets
Authors: Lizieri C.M.
Published: November 2003

Changes in the business environment associated with globalisation, innovation in information and communications technologies and the drive towards more flexible production systems should be reflected in changes in occupational requirements for property. Although much research assumes that property, as a derived demand, will simply be supplied in response to changed demand, in practice, the institutional structure of the market can act as a constraint on the provision of appropriate space. Empirical research into new working practices and their impact on the property portfolio suggest that change is muted and gradual. In part, this reflects resistance to the adoption of working practices; in part, it reflects the inertia of a traditional model of property procurement. However, there is growing evidence of innovation in the nature of provision and more active and strategic management of the property resource. Research in this area, as in many other areas of real estate, is hampered by lack of reliable and accessible data. However, it is also damaged by a lack of attention to theory and methodology, with too much emphasis on anecdote, assertion and unsound empiricism. A more rigorous approach to research is needed if the dynamics of corporate real estate are to be fully understood.
The International and Historical Dimensions of Romani Migration in Central and Eastern Europe
Authors: Crowe David M.
Published: November 2003

This article analyses how migration has affected the Roma in Central and Eastern Europe (CEE) since they entered both regions in the Middle Ages. It explores the importance of migration in the culture and history of the Roma and looks at how forced migration has harmed the Roma and helped build some of the negative stereotypes and prejudices that have haunted them until today.
Usuli, Akhbari, Shaykhi, Babi: The Tribulations of a Qazvin Family
Authors: Momen Moojan
Published: November 2003

The Last Half of the Eighteenth Century and the First Half of the Nineteenth century saw Twelver Shiᶜi Islam, especially in Iran, undergoing a number of upheavals as a result of conflicts between different schools of thought. These upheavals were primarily ideological but they also led to conflict, fighting and even deaths. This period began in the political turmoil following the collapse of the Safavid Empire. The Akhbari school of Twelver Shiᶜism had been in the ascendant during the latter half of the Safavid era, but the period following the overthrow of the Safavids saw the defeat of the Akhbari school and the triumph of the Usuli school at the hands of Aqa Muhammad Baqir Bihbihani, known as Vahid Bihbihani (d. ca. 1207/1792) in the shrine cities of Iraq, the main centre of Twelver scholarship. The Usuli school enabled the ulama to give legal opinions (fatwās) and hence intervene in social areas from which the more restrained Akhbari school would refrain.
The Global Impact of the Internet: Widening the Economic Gap Between Wealthy and Poor Nations?
Authors: Lucas Henry , Sylla Richard
Published: November 2003

Does the Internet have the potential to accelerate development in poor nations? Or is it an innovation that will widen the gap between wealthy and poor countries? This paper places the Internet in a framework of major innovations in modern economic history that have contributed to increased global economic inequality. To study whether the Internet has the potential to do the same, we investigate the determinants of Internet diffusion and explore differences between developed and developing nations. Our findings indicate that developing countries are being left behind as the transformation to the 'new economy' takes place in wealthier countries. If this trend continues, it may have dire consequences for world economic inequality and political stability, as did great innovations of earlier eras. We consider policies that might accelerate the development of information technology in poorer countries so these nations can benefit from the technological revolution occurring in wealthier countries. We also discuss why it might be in the interest of the developed countries to pursue such policies.
Extending the Knowledge-based View: An Examination of Intellectual Property Strategies in Australian Biotechnology Firms
Authors: Clarke Jayne , Turner Paul
Published: November 2003

Knowledge management (KM) approaches have developed traditionally from the knowledge-based view (KBV), a derivative of the resource-based view (RBV). Drawing on the relational and industry structure views, this paper presents a framework for analysing knowledge management practices in the biotechnology industry. These firms exhibit sophisticated and strategic KM practices and deploy a range of strategies in leveraging competitive advantage through their intellectual property practices. The paper demonstrates that the current KBV needs to be modified and extended to reflect current KM practice within Australian biotechnology firms through examining their use and management of intellectual property.
Knut Wicksell and Gustav Cassel on the Cumulative Process and the Price-Stabilizing Policy Rule
Authors: Humphrey Thomas M.
Published: November 2003

In economics as in anthropology, old artifacts spur continuing debates. A case in point is Knut Wicksell's 1898 analysis of the cumulative process of price inflation in pure credit, cashless economies. Some economists view Wicksell's model as a milestone in the evolution of quantity-theoretic monetary analysis inasmuch as it constitutes the seminal rigorous explanation of how loan-created stocks of bank money translate interest rate differentials into price level changes. Others, however, dispute this point and instead argue that money plays no role in determining price level changes in Wicksell's model.
Fatty acid profile in skeletal muscle of the rat in response to acute (2.5 hours) and prolonged (6 weeks) ethanol‐dosage
Authors: ADACHI JUNKO , KUDO RISA , NUSHIDA HIDEYUKI , UENO YASUHIRO , KOLL MICHAEL , PREEDY VICTOR
Published: November 2003

We tested the hypothesis that phospholipids are altered in skeletal muscles of rats exposed to ethanol for either acute (2.5 hours) or prolonged (6 weeks) periods. In acute studies, rats were dosed with saline (0.15 mmol/l; controls) or ethanol (75 mmol/kg body weight; treated). There were four groups: (A) saline (control); (B) cyanamide (an aldehyde dehydrogenase inhibitor); (C) ethanol; and (D) cyanamide+ethanol. In prolonged studies, two groups of rats were fed liquid diets containing 35% of total dietary energy as either glucose [group (E)] or ethanol [group (F)]. At the end of the treatments, membrane phospholipids were measured in soleus (Type I fibre‐predominant) and plantaris (Type II fibre‐predominant) muscle. In acute studies, ethanol alone [(A) vs. (C)] and cyanamide+ethanol [(A) vs. (D)] significantly increased 18:2 in plantaris (p <0.05), whereas in soleus none of the treatments had any effect on the phospholipids. In prolonged studies [(E) vs. (F)], there were decreases in 16:0 (p <0.05) and 18:1 (p <0.01) and increases in 18:2 (p<0.001) in plantaris. In soleus, decreases in 18:1 (p<0.05) and increases in 18:2 (p <0.01) occurred. In conclusion, alterations in the proportions of 16:0, 18:1 and 18:2 provide evidence of an altered membrane domain which may contribute to the pathogenesis of alcohol‐induced muscle disease. Changes due to prolonged exposure are more profound than those in acute exposure and the preferential effects in Type II plantaris may reflect the greater susceptibility of this muscle to alcohol.
Nutritional intake of hazardous drinkers and dependent alcoholics in the UK
Authors: MANARI ADRIANA , PREEDY VICTOR , PETERS TIMOTHY
Published: November 2003

There are no recent assessments of nutritional intake in alcohol misusers in the United Kingdom. The purpose of this study was to measure nutritional intake in alcoholics attending an Alcohol Misuse outpatient clinic in an inner city general hospital in the United Kingdom and relating this to various measures of alcohol dependence. All patients (n =30; 27 male, 3 female) consumed at least 100 g ethanol per day (mean 162 g/day) for at least 5 years and completed questionnaires on socio‐demographics, alcohol dependency and psychosocial problems and had assays of biochemical and haematological indices. The data were analysed first with respect to the entire patient population and then according to the degree of alcohol dependency (mild, moderate or severe). The results showed that with respect to the entire patient group, one‐third were below normal body weights, but one‐quarter was overweight. The total energy intake (kJ/day) including alcohol was apparently adequate with respect to recommended levels in most patients. On average, approx. 60% of energy intake came from alcohol. The whole patient population had a low intake of one or more macro‐ and micro‐nutrient compared to the dietary reference requirements. All patients had intakes of vitamin E and folate below UK recommended standards, while 85–95% of patients had low intakes of selenium and Vitamin D. Between 50 and 85% of all patents had intakes below UK recommended standards in calcium and zinc and Vitamins A, B 1, B 2, B 6 and C. There were significant correlations between calorie intake (when alcohol was excluded) and vitamins B 1, B 2, B 6 and C, and Ca, Mg, Fe and Zn intake. There were no correlations between alcohol intake with any of the nutritional and anthropometric variables or between the three subgroups with respect to daily energy, micro‐ and macro‐nutrient intakes. In conclusion, malnutrition was common in this patient group: all subjects had intakes below UK recommended standards in one or more micro‐ or macro‐nutrient. However, there was no difference in the degree of malnutrition between the harmful drinkers (mild dependency) and heavily dependent subgroups.
Mutation in neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes blocks ethanol action
Authors: BORGHESE CECILIA , WANG LINGNA , BLECK VIRGINIA , HARRIS R ADRON
Published: November 2003

Amino acids (AAs) in the extracellular portion of the transmembrane domain of several inhibitory ligand‐gated ion channels participate in an alcohol binding site. To extend these studies to neuronal nicotinic acetylcholine receptors (nAChRs), we focused on an AA (L262) located in the same region of the second transmembrane domain of the α2 subunit of neuronal nAChRs. Single‐point mutation of α2L262 was carried out, the resulting α2 subunits co‐expressed with wild‐type β4 subunits in Xenopus laevis oocytes, and studied using two‐electrode voltage clamp. Ethanol enhancement of ACh responses was diminished [α2(L262F)β4] or abolished [α2(L262G)β4, α2(L262S)β4 and α2(L262A)β4]. Mutation of the homologous AA in β4 [β4(L258A)] did not modify the ethanol modulation and the mutation in α2 was dominant, because ethanol did not enhance ACh responses in α2(L262A)β4(L258A) nAChRs. n‐Alcohols (ethanol through octanol) were applied to α2(L262A)β4 nAChRs. As described previously for other nAChRs, short‐chain alcohols enhanced, intermediate‐chain alcohols had no effect and long‐chain alcohols inhibited ACh responses in the wild‐type receptor. For α2(L262A)β4 nAChRs the alcohol enhancing effect was absent, and the alcohol inhibitory action was increased. Although this suggests removal of an alcohol enhancing site through mutagenesis, we cannot rule out the enhancement of action at an alcohol inhibitory site.
Changes in G‐protein activity mediated through the stimulation of dopamine and GABA B receptors in the mesolimbic dopaminergic system of morphine‐sensitized mice
Authors: NARITA MINORU , SHIBASAKI MASAHIRO , MIZUO KEISUKE , SUZUKI TSUTOMU
Published: November 2003

The behavioural sensitization has been recognized as the increased behavioural response and the undesirable long‐lasting changes in brain functions after repeated administration of abuse drugs. We examined whether behavioural sensitization to hyperlocomotion induced by intermittent morphine treatment could result from any changes in dopamine and GABA B receptor functions to activate G‐proteins in the brain rewarding system in mice. Intermittent morphine treatment results in the upregulation of dopamine receptor‐regulated G‐protein activation in the mouse limbic forebrain, whereas this treatment causes the downregulation of GABA B receptor function to activate G‐protein in the mouse lower midbrain. In behavioural experiments, intermittent administration of morphine in combination with either a dopamine receptor antagonist haloperidol or a GABA B receptor agonist baclofen abolished the development of sensitization to morphine‐induced hyperlocomotion. The present data provide evidence that these G‐protein activation changes may lead to behavioural sensitization to morphine‐induced hyperlocomotion in mice.
A pilot study to assess the impact of naltrexone implant on accidental opiate overdose in ‘high‐risk’ adolescent heroin users
Authors: HULSE GARY , TAIT ROBERT J.
Published: November 2003

Morbidity and mortality rates for regular heroin users are much greater than those observed in the general population. In ‘high‐risk’ heroin users implantable naltrexone has been used under Commonwealth Therapeutic Goods Administration Compassionate guidelines in Western Australia since August 2000. This pilot study compared the frequency of accidental opiate overdose and other morbidity resulting in hospital presentations in eight ‘high‐risk’ dependent heroin using adolescents pre‐ and post‐naltrexone implant treatment. We reviewed the hospital medical records retrospectively for the participants across the four public hospitals in Perth. The review period was September 1999‐October 2002. The eight adolescents (aged 15–19 years) initially underwent naltrexone implant treatment between September 2000 and September 2001. The data indicated a dramatic reduction in opiate overdose post‐implantable naltrexone treatment, with a smaller reduction in opiate overdose during oral naltrexone treatment compared to the pre‐oral/implant period. Implant treatment in the high‐risk heroin user may provide an important prophylaxis against mortality associated with accidental opiate overdose. These encouraging findings now require validation using a larger cohort over an extended period.
Writing with voice: an investigation of the use of a voice recognition system as a writing aid for a man with aphasia
Authors: Bruce Carolyn , Edmundson Anne , Coleman Michael
Published: November 2003

Background: People with aphasia may experience difficulties that prevent them from demonstrating in writing what they know and can produce orally. Voice recognition systems that allow the user to speak into a microphone and see their words appear on a computer screen have the potential to assist written communication.

Aim: This study investigated whether a man with fluent aphasia could learn to use Dragon NaturallySpeaking® to write.

Methods & Procedures: A single case study of a man with acquired writing difficulties is reported. A detailed account is provided of the stages involved in teaching him to use the software. The therapy tasks carried out to develop his functional use of the system are then described. Outcomes included the percentage of words accurately recognized by the system over time, the quantitative and qualitative changes in written texts produced with and without the use of the speech‐recognition system, and the functional benefits the man described.

Outcomes & Results: The treatment programme was successful and resulted in a marked improvement in the subject's written work. It also had effects in the functional life domain as the subject could use writing for communication purposes.

Conclusions: The results suggest that the technology might benefit others with acquired writing difficulties.
Growth Factor‐Dependent Proliferation of the Pancreatic β‐cell Line βTC‐tet: An Assay for β‐cell Mitogenic Factors
Authors: Milo-Landesman Dalit , Efrat Shimon
Published: November 2003

The ability to expand normal pancreatic islet
β cells in culture would significantly advance
the prospects of cell therapy for diabetes. A
number of growth factors can stimulate limited
islet cell replication, however other factors may
exist which are more effective β‐cell‐specific
mitogens. The search for novel β‐cell growth
factors has been hampered by the lack of a β‐cell‐specific proliferation assay. We developed a
simple and sensitive assay for β‐cell growth factors
based on a conditionally‐transformed
mouse β‐cell line (βTC‐tet). These cells express
the SV40 T antigen (Tag) oncoprotein under
control of the tetracycline (Tc) operon regulatory
system. In the presence of Tc, Tag expression
is tightly shut off and the cells undergo
complete growth arrest. Here we show that the
growth‐arrested cells can proliferate in
response to growth factors in the absence of Tag. Using this assay, a number of growth factors
previously shown to be mitogenic to a
mixed islet cell population were found to
induce proliferation of pure β cells. We conclude
that growth‐arrested βTC‐tet cells can be
employed in a survey of factors from various
sources for identifying novel factors with β‐cell
mitogenic activity.
Protein Tyrosine Phosphatase 1B is Impaired in Skeletal Muscle of Diabetic Psammomys Obesus
Authors: Ikeda Yukio , Ziv Ehud , Shafrir Eleazar , Mosthaf-Seedorf Luitgard
Published: November 2003

Protein tyrosine phosphatases (PTPases) have been suggested
to modulate the insulin receptor signal transduction pathways.We
studied PTPases in Psammomys obesus, an animal model of nutritionally
induced insulin resistance. No changes in the protein
expression level of src homology PTPase 2 (SHP‐2) (muscle, liver)
or leukocyte antigen receptor (LAR) (liver) were detected. In contrast,
the expression level of PTPase 1B (PTP 1B) in the skeletal
muscle, but not in liver, was increased by 83% in the diabetic animals,
compared with a diabetes‐resistant line. However, PTP 1B–
specific activity (activity/protein) significantly decreased (50% to
56%) in skeletal muscle of diabetic animals, compared with both
the diabetes‐resistant line and diabetes‐prone animals. In addition,
PTP 1B activity was inversely correlated to serum glucose level
(r = –.434, P < .02). These findings suggest that PTP 1B, though
overexpressed, is not involved in the susceptibility to insulin resistance
in Psammomys obesus and is secondarily attenuated by
hyperglycemia or other factors in the diabetic milieu.
Differential Indicators of Diabetes‐Induced Oxidative Stress in New Zealand White Rabbits: Role of Dietary Vitamin E Supplementation
Authors: Davis Randall L. , Lavine Christy L. , Arredondo Melissa A. , McMahon Patrick , Tenner, Thomas E.
Published: November 2003

Determination of reliable bioindicators of diabetes‐induced oxidative
stress and the role of dietary vitamin E supplementation
were investigated. Blood (plasma) chemistries, lipid peroxidation
(LPO), and antioxidant enzyme activities were measured over
12 weeks in New Zealand White rabbits (control, diabetic, and diabetic +
vitamin E). Cholesterol and triglyceride levels did not correlate
with diabetic state. PlasmaLPOwas influenced by diabetes and
positively correlated with glucose concentration only, not cholesterol
or triglycerides. Liver glutathione peroxidase (GPX) activity
negatively correlated with glucose and triglyceride levels. Plasma
and erythrocyte GPX activities positively correlated with glucose,
cholesterol, and triglyceride concentrations. Liver superoxide dismutase
activity positively correlated with glucose and cholesterol
concentration. Vitamin E reduced plasma LPO, but did not affect
the diabetic state. Thus, plasmaLPOwas the most reliable indicator
of diabetes‐induced oxidative stress. Antioxidant enzyme activities
and types of reactive oxygen species generated were tissue dependent.
Diabetes‐induced oxidative stress is diminished by vitamin E
supplementation.
Endothelin‐1–Mediated Alteration of Metallothionein and Trace Metals in the Liver and Kidneys of Chronically Diabetic Rats
Authors: Cai Lu , Chen Shali , Evans Terry , Cherian M. George , Chakrabarti Subrata
Published: November 2003

In the present study, the role of endothelin‐1 (ET‐1) on alterations
of hepatic and renal metallothionein (MT) and trace metals
(Zn, Cu, and Fe) were investigated in streptozotocin (STZ)‐
induced diabetic rats. Diabetic rats, age‐ and sex‐matched controls,
as well as control and diabetic animals on a dual ETA/ETB receptor
blocker, bosentan, were investigated after 6 months of follow‐up.
MT was measured by cadmium‐heme assay. Metals were measured
by atomic absorption spectrometer. ET‐1 mRNA was analyzed by
reverse transcriptase–polymerase chain reaction (RT‐PCR) technique.
Hepatic and renal ET‐1 mRNA was increased in diabetic
rats as compared to control rats, along with an increase in both
hepatic and renal MT proteins. The increased hepatic MT protein
level was associated with decreases in hepatic Cu and Fe, whereas
increased renal MT was associated with increases in renal Cu and
Fe accumulation. Zn levels were unaltered in both organs in diabetic
rats. Bosentan treatment partially prevented the increase in
MT levels in both liver and kidney, along with reduced serum creatinine
and increased urinary creatinine levels. Further bosentan
treatment corrected the increased Cu and Fe levels in the kidney in
diabetic rats, but reduced hepatic Cu and Fe levels. No significant
effects of bosentan treatment on nondiabetic rats were observed.
The data suggest that the possible effects of ET antagonism in diabetes
may be mediated via changes in MT and trace metals.
Renal AT1 Receptor Protein Expression During the Early Stage of Diabetes Mellitus
Authors: Harrison-Bernard Lisa M. , Imig John D. , Carmines Pamela K.
Published: November 2003

Experiments were performed to evaluate the
hypothesis that the early stage of Type 1 diabetes
mellitus (DM) increases renal angiotensin
II (AngII) concentration and angiotensin type 1
(AT1) receptor protein levels. Nineteen or twenty
days after vehicle (Sham rats) or streptozotocin
(STZ rats) treatment, plasma [AngII] was
higher in STZ rats (152±23 fmol/ml) than in
Sham rats (101±7 fmol/ml); however, kidney
[AngII] did not differ between groups. AT1
receptor protein expression was greater in STZ
kidneys than in Sham kidneys. This increase
was restricted to the cortex, where AT1 protein
levels were elevated by 77±26% (42 kDa) and
101±16% (58 kDa) in STZ kidneys.
Immunohistochemistry revealed this effect to
be most evident in distal nephron segments
including the connecting tubule/cortical collecting
duct. Increased renal cortical AT1 receptor
protein and circulating AngII levels are consistent
with an exaggerated AngII‐dependent
influence on renal function during the early
stage of DM in the rat.
The Independence of Signaling Pathways Mediating Increased Expression of Plasminogen Activator Inhibitor Type 1 in HepG2 Cells Exposed to Free Fatty Acids or Triglycerides
Authors: Chen Yabing , Schneider David J.
Published: November 2003

We have shown that both free fatty acids (FFA)
and triglycerides (TG) increase expression of
plasminogen activator inhibitor type 1 (PAI‐1)
in vivo and in vitro. To determine signaling
mechanisms responsible, HepG2 cells were
exposed to FFA, emulsified TG, or the combination.
The combination of FFA and TG
increased PAI‐1 to a greater extent than either
agent alone (fold induction: 0.45mM FFA
1.7±0.2, 1000mg/dl TG 1.9±0.1, both 2.3±0.2,
n=10, p<0.05 for comparison of combination
with either alone). Cells transfected with PAI‐1
5′ flanking region containing the 4G or 5G
polymorphism displayed similar activity in
response to FFA, but modestly greater activity
with the 4G polymorphism in response to TG
(fold induction: 5G‐1.28±0.14 and 4G‐
1.46±0.13, n=6, p<0.05 for comparison).
Deletion analyses demonstrated that FFA and
TG induce PAI‐1 expression through distinct
regions of the promoter. Inhibition of protein
kinase C inhibited the response to FFA but not
TG. Accordingly, increased FFA and TG contribute
to increased PAI‐ I through independent
mechanisms.
C‐Peptide Prevents Hippocampal Apoptosis in Type 1 Diabetes
Authors: Li Zhen-guo , Zhang Weixian , Sima Anders A. F.
Published: November 2003

To explore mechanisms underlying central nervous system
(CNS) complications in diabetes, we examined hippocampal neuronal
apoptosis and loss, and the effect of C‐peptide replacement
in type 1 diabetic BB/W rats. Apoptosis was demonstrated after
8 months of diabetes, by DNA fragmentation, increased number of
apoptotic cells, and an elevated ratio of Bax/Bcl‐xL, accompanied
by reduced neuronal density in the hippocampus. No apoptotic activity
was detected and neuronal density was unchanged in 2‐month
diabetic hippocampus, whereas insulin‐like growth factor (IGF) activities
were impaired. In type 1 diabetic BB/W rats replaced with
C‐peptide, no TdT‐mediated dUTP nick‐end labeling (TUNEL)‐
positive cells were shown and DNA laddering was not evident in
hippocampus at either 2 or 8 months. C‐peptide administration prevented
the preceding perturbation of IGF expression and reduced
the elevated ratio of Bax/Bcl‐xL. Our data suggest that type 1 diabetes
causes a duration‐dependent programmed cell death of the
hippocampus, which is partially prevented by C‐peptide.
Effect of Acipimox on Plasma Lipids and Glucose/Insulin in Pregnant Rats
Authors: Sánchez-Vera I. , Bonet B. , Viana M. , Herrera E. , Indart A.
Published: November 2003

To determine how a reduction in maternal hypertriglyceridemia
during late pregnancy may affect glucose/insulin relationships,
pregnant and virgin rats were orally treated with acipimox, a potent
antilipolytic agent. In 20‐day pregnant rats receiving 80 mg of acipimox,
plasma triglycerides (TG), free fatty acids (FFA), and glycerol
decreased more than in virgin rats shortly after the drug (up to
7 hours), when compared with animals treated with distilled water,
whereas plasma glucose level was unaffected by the treatment in
either group of rats. When acipimox was given every 12 hours from
day 17 to day 20 of pregnancy, plasma TG, FFA, and glycerol levels
progressively increased, whereas they either decreased or did not
change in virgin rats receiving the same treatment, with no effect in
plasma glucose levels in either group. Fetal body weight was lower
than in controls in 20‐day pregnant rats that received acipimox for
3 days. On day 20 of pregnancy, 3 hours after receiving acipimox
or distilled water, rats received a 2 g glucose/kg oral load and it was
found that the change in plasma glucose was similar in both groups,
whereas the increase in plasma insulin was greater in pregnant rats
treated with acipimox. However, no difference was found in either
variable after the oral glucose load in virgin rats receiving acipimox
or distilled water. No differences in plasma glucose levels were
found after intravenous (IV) administration of insulin in pregnant
rats treated or not treated with acipimox. In conclusion, present
results show that administration of acipimox during the last days
of gestation inhibited lipolysis and decreased fetal weight. Over a
short period of time, in pregnant rats, reductions of plasma FFA
and TG after acipimox treatment improved the glucose‐induced
insulin release, but did not seem to have any effect in peripheral
insulin resistance.
Crystal structure of a β-catenin/Axin complex suggests a mechanism for the β-catenin destruction complex
Authors: Xing Yi , Clements Wilson K. , Kimelman David , Xu Wenqing
Published: November 2003

The “β-catenin destruction complex” is central to canonical Wnt/β-catenin signaling. The scaffolding protein Axin and the tumor suppressor adenomatous polyposis coli protein (APC) are critical components of this complex, required for rapid β-catenin turnover. We determined the crystal structure of a complex between β-catenin and the β-catenin-binding domain of Axin (Axin-CBD). The Axin-CBD forms a helix that occupies the groove formed by the third and fourth armadillo repeats of β-catenin and thus precludes the simultaneous binding of other β-catenin partners in this region. Our biochemical studies demonstrate that, when phosphorylated, the 20-amino acid repeat region of APC competes with Axin for binding to β-catenin. We propose that a key function of APC in the β-catenin destruction complex is to remove phosphorylated β-catenin product from the active site.
Functional and Phylogenetic Analyses of a Conserved Regulatory Program in the Phloem of Minor Veins
Authors: Ayre Brian G. , Blair Jaime E. , Turgeon Robert
Published: November 2003

The minor-vein phloem of mature leaves is developmentally and physiologically distinct from the phloem in the rest of the vascular system. Phloem loading of transport sugars occurs in the minor veins, and consistent with this, galactinol synthase is expressed in the minor veins of melon (Cucumis melo) as part of the symplastic-loading mechanism that operates in this species. A galactinol synthase promoter from melon drives gene expression in the minor-vein companion cells of both transgenic tobacco (Nicotiana tabacum) and Arabidopsis. Neither of these plants use galactinol in the phloem-loading process, implying that the promoter responds to a minor-vein-specific regulatory cascade that is highly conserved across a broad range of eudicotyledons. Detailed analysis of this promoter by truncation and mutagenesis identified three closely coupled sequences that unambiguously modulate tissue specificity. These sequences cooperate in a combinatorial fashion: two promote expression throughout the vascular system of the plant, whereas the third functions to repress expression in the larger bundles. In a complementary approach, phylogenetic footprinting was used to obtain single-nucleotide resolution of conserved sites in orthologous promoters from diverse members of the Cucurbitaceae. This comparative analysis confirmed the importance of the closely coupled sites but also revealed other highly conserved sequences that may modulate promoter strength or contribute to expression patterns outside of the phloem. The conservation of this regulatory design among species that phloem load by different mechanisms supports a model for organismal development in which tissues and cell types are controlled by relatively ancient and conserved paradigms but expression of genes influencing final form and function are relatively plastic.
SAGE Analysis of Transcriptome Responses in Arabidopsis Roots Exposed to 2,4,6-Trinitrotoluene
Authors: Ekman Drew R. , Lorenz W. Walter , Przybyla Alan E. , Wolfe N. Lee , Dean Jeffrey F.D.
Published: November 2003

Serial analysis of gene expression was used to profile transcript levels in Arabidopsis roots and assess their responses to 2,4,6-trinitrotoluene (TNT) exposure. SAGE libraries representing control and TNT-exposed seedling root transcripts were constructed, and each was sequenced to a depth of roughly 32,000 tags. More than 19,000 unique tags were identified overall. The second most highly induced tag (27-fold increase) represented a glutathione S-transferase. Cytochrome P450 enzymes, as well as an ABC transporter and a probable nitroreductase, were highly induced by TNT exposure. Analyses also revealed an oxidative stress response upon TNT exposure. Although some increases were anticipated in light of current models for xenobiotic metabolism in plants, evidence for unsuspected conjugation pathways was also noted. Identifying transcriptome-level responses to TNT exposure will better define the metabolic pathways plants use to detoxify this xenobiotic compound, which should help improve phytoremediation strategies directed at TNT and other nitroaromatic compounds.
PRT1 of Arabidopsis Is a Ubiquitin Protein Ligase of the Plant N-End Rule Pathway with Specificity for Aromatic Amino-Terminal Residues
Authors: Stary Susanne , Yin Xiao-jun , Potuschak Thomas , Schlögelhofer Peter , Nizhynska Victoria , Bachmair Andreas
Published: November 2003

The gene PRT1 of Arabidopsis, encoding a 45-kD protein with two RING finger domains, is essential for the degradation of F-dihydrofolate reductase, a model substrate of the N-end rule pathway of protein degradation. We have determined the function of PRT1 by expression in yeast (Saccharomyces cerevisiae). PRT1 can act as a ubiquitin protein ligase in the heterologous host. The identified substrates of PRT1 have an aromatic residue at their amino-terminus, indicating that PRT1 mediates degradation of N-end rule substrates with aromatic termini but not of those with aliphatic or basic amino-termini. Expression of model substrates in mutant and wild-type plants confirmed this substrate specificity. A ligase activity exclusively devoted to aromatic amino-termini of the N-end rule pathway is apparently unique to plants. The results presented also imply that other known substrates of the plant N-end rule pathway are ubiquitylated by one or more different ubiquitin protein ligases.