bluuebunny/crossref_metadata_2025 huggingface dataset:
Heredity of specific host-finding behaviour in Schistosoma mansoni miracidia
Authors: KALBE M. , HABERL B. , HERTEL J. , HAAS W.
Published: May 2004

Two strains of Schistosoma mansoni were used to investigate the hereditary basis of species-specific host recognition by analysing behavioural responses of miracidia to snail-conditioned water. An Egyptian strain of S. mansoni, capable of distinguishing its host snail Biomphalaria alexandrina from other snails was cycled repeatedly through Biomphalaria glabrata, the intermediate host of a Brazilian strain known to respond even to non-susceptible snails with high intensity. After 5 cycles in the non-natural host, miracidia of the Egyptian strain still retained their preference for the original host snail. In a second experiment, host-finding behaviour of hybrids between these two parasite strains was studied. In the F1 generation, hybrids of both parental combinations showed the same low degree of specificity as the pure-bred Brazilian strain. Approximately one quarter of F2 hybrids proved to be as discriminatory as the Egyptian strain, confirming dominant Mendelian inheritance of non-specificity in schistosome miracidial host-finding behaviour. Moreover, hybrids seem to have lost the ability to develop in B. alexandrina, possibly suggesting a link between host recognition and host compatibility. The heredity of this behavioural trait is of evolutionary and epidemiological significance, since a shift to low host-finding specificity might have been a prerequisite for S. mansoni to acquire new host snails after being introduced to South America by the slave trade.
Semantic matching
Authors: GIUNCHIGLIA FAUSTO , SHVAIKO PAVEL
Published: May 2004

We think of match as an operator that takes two graph-like structures (e.g. database schemas or ontologies) and produces a mapping between elements of the two graphs that correspond semantically to each other. The goal of this paper is to propose a new approach to matching, called semantic matching. As its name indicates, in semantic matching the key intuition is to exploit the model-theoretic information, which is codified in the nodes and the structure of graphs. The contributions of this paper are (i) a rational reconstruction of the major matching problems and their articulation in terms of the more generic problem of matching graphs, (ii) the identification of semantic matching as a new approach for performing generic matching and (iii) a proposal for implementing semantic matching by testing propositional satisfiability.
The Chinese Energy Security Debate
Authors: Downs Erica S.
Published: May 2004

China's shift to a net oil importer has generated much speculation outside China about how China's growing dependence on foreign oil will affect its international behaviour. This discussion is framed by two competing models of China's future approach to energy security: one that foresees deeper integration into global energy markets and another that predicts efforts to minimize reliance on these markets in potentially destabilizing ways. Less attention has been paid, however, to the parallel debate unfolding inside China over how to ensure the country's oil needs are met without undermining national security. This article introduces the main participants in the debate, how the debate relates to energy security decision-making, and some of the measures to enhance energy security under consideration. It concludes with a discussion of some of the factors that will shape China's emerging approach to energy security.
Between Separate Stoves and a Single Menu: Fiscal Decentralization in China
Authors: Tsui Kai-yuen , Wang Youqiang
Published: May 2004

A recent body of literature with the paradigm of market preserving federalism at its core contends that China is a de facto federalist state. With the autonomy and tax rights of local governments entrenched in the reform era, local governments have allegedly become decentralized engines of growth. Scrutinizing the underlying premises of the above paradigm, this article arrives at a picture of China's local governments as less autonomous and the system of vertical bureaucratic control as more potent than that painted by the above paradigm. Emerging from our findings is an alternative interpretation of China's central–local fiscal relations that may help us understand such recent phenomena as the proliferation of arbitrary charges.
Reformed Migration Control and New Targeted People: China's Hukou System in the 2000s
Authors: Wang Fei-Ling
Published: May 2004

This article outlines the latest reforms of China's hukou system in 1997–2002 and reports the system's functional changes and continuities. Today's hukou system still performs two leading functions: the widely discussed internal migration control with reformed mechanisms and the previously scarcely examined socio-political management of the targeted people (zhongdian renkou). An adapted and adjusted hukou system is expected to continue as a key component of China's institutional framework, playing a crucial role to determine socio-political stability, facilitate a rapid but uneven economic growth, and shape socio-economic stratification and spatial inequality in the PRC.
The Tiananmen Papers Revisited
Authors: Chan Alfred L. , Nathan Andrew J.
Published: May 2004

Authentic Chinese internal documents matter greatly as historical records that illuminate our understanding of Chinese politics. Yet careful scrutiny shows that the Chinese book version of the Tiananmen Papers is part fiction and part documentary history based on open and semi-open sources and document collections. The alleged transcripts of top-level meetings are basically stitched together ex post facto (even by the admission of the editors) and then presented as secret documents. Furthermore, the English translation is a heavily retouched version of the Chinese with differences in claims of authenticity, translation, citation and style. There is little evidence that any real secret documents are in the hands of the Chinese author, and even if they were, the two books under consideration are really secondary sources steps removed from the originals. The editors strongly vouch for the authenticity of these two books, but their efforts are inadequate and unconvincing.
Modernizing China's Military: Progress, Problems, and Prospects. By David Shambaugh. [Berkeley, CA, Los Angeles and London: University of California Press, 2003. xxviii+374 pp. £24.95; $34.95. ISBN 0-520-22507-4.]
Authors: Mulvenon James
Published: May 2004

The field of PLA studies is at a crossroads. Whereas specialists once pored over the few pages of a general political department Work Bulletin for hints of the inner workings of the military, experts now struggle with trying to drink from a fire hose of information. PLA publishing houses, cut off from subsidy and desperate to generate revenue, are flooding the market with military books of varying levels of authoritativeness, and the Internet is awash with the all-too-familiar flotsam and jetsam of truths, half-truths, and outright fiction. These new sources have overwhelmed a field with too few advanced linguists, and with only the most rudimentary tools and frameworks with which to process and assess this information.
Local Government and Politics in China. Challenges from Below. By Yang Zhong. [Armonk, NY: M. E. Sharpe, 2003. 229 pp. $25.95. ISBN: 0-7656-118-X.]
Authors: Christiansen Flemming
Published: May 2004

Yang Zhong's excellent book about Local Government and Politics in China gives a succinct and convincing account of the frameworks for local governance in the PRC today. The organization, functioning, powers and evolution of local government in China are notoriously difficult to grasp due to the many intersecting layers and lines of authority, the diversity of local conditions, and the shorthand language used by administrators to refer to local government. Although there is a growing literature on local government in contemporary China, we have, until now, lacked a comprehensive overview in English.

For almost a decade Yang Zhong has observed the behaviour of local government in a small number of places in China, and is thus able to base his account on actual practice. The style is refreshingly simple and easy to follow, the administrative jargon is well explained, and the structure of the presentation is lucid. The core aspects of local governance are covered, with a sound focus on counties, townships and towns, and a separate chapter dealing with village politics. Local authorities in cities are not covered; this omission is unfortunate, but understandable from the point of view of keeping the book within manageable limits.
The Dianszhizhai Pictorial: Shanghai Urban Life, 1884–1898. By Xiaoqing Ye. [Ann Arbor: University of Michigan Press, 2003. 249 pp. $50.00. ISBN 0-89264-162-2.]
Authors: Mittler Barbara
Published: May 2004

Finally, one is inclined to sigh, a scholarly study of the Shanghai illustrated magazine Dianshizhi huabao, one of the most significant pictorials in late-Qing China, founded by an Englishman, Ernest Major, who had successfully launched the Shanghai daily Shenbao a dozen years earlier. A handful of coffee table books hitherto featured illustrations from this pictorial, but there is no systematic study of its background and contents to date. This book is not that study either, but it presents a valuable mine of material. With its aim of reading the Dianshizhai huabao as a “source of Shanghai social history” (p. 2), it not only covers a wide range of material from the pictorial itself (laudably, it includes 137 illustrations), but also makes extensive use of the Shenbao, as well as contemporary memoirs and literary works.

The book consists of four parts, a short introduction and an afterword. Part one gives a brief history of the Dianshizhai, parts two and three deal with stories depicting Shanghai as a city between old and new and the source of a new urban culture, respectively. Part four turns to religious practices depicted in the Dianshizhai. No explanation is given for why these particular topics have been chosen. In the 1991 dissertation on which this book is based, an argument about urban popular culture had served to connect the several parts. This argument created coherence. It has been eschewed here.
The relationship between coronal place and vowel backness
Authors: Flemming Edward
Published: May 2004

This paper presents evidence that tongue-body position is always specified in the phonological representation of coronals, even where it is non-contrastive. Tongue-body position is needed to account for the typology of interactions between coronal consonants and adjacent vowels. For example, coronals only condition vowel fronting if they are produced with a front tongue body (usually anterior coronals), and only coronals produced with a back tongue body (usually retroflexes) condition vowel retraction. However, coronals do not have a fixed tongue-body position. Tongue-body position is affected by the position of the tongue tip/blade, because these articulators are physically connected, so each type of coronal has a preferred tongue-body position that facilitates the production of the coronal constriction. These preferences can be overridden, however, e.g. due to assimilation to a vowel. Optimality-theoretic feature co-occurrence constraints provide a good account of this type of dependency between articulators.
Bird responses to shade coffee production
Authors: Tejeda‐Cruz César , Sutherland William J.
Published: May 2004

It has been documented that certain types of shade coffee plantations have both biodiversity levels similar to natural forest and high concentrations of wintering migratory bird species. These findings have triggered a campaign to promote shade coffee as a means of protecting Neotropical migratory birds. Bird censuses conducted in the El Triunfo Biosphere reserve in southern Mexico have confirmed that shade coffee plantations may have bird diversity levels similar to, or higher than, natural forest. However, coffee and forest differed in species composition. Species with a high sensitivity to disturbance were significantly more diverse and abundant in primary ecosystems. Neotropical migratory birds, granivorous and omnivorous species were more abundant in disturbed habitats. Insectivorous bird species were less abundant only in shaded monoculture. Foraging generalists and species that prefer the upper foraging stratum were more abundant in disturbed habitats, while a decline in low and middle strata foragers was found there. Findings suggests that shade coffee may be beneficial for generalist species (including several migratory species), but poor for forest specialists. Although shade coffee plantations may play an important role in maintaining local biodiversity, and as buffer areas for forest patches, promotion of shade coffee may lead to the transformation of forest into shade coffee, with the consequent loss of forest species.
Is anti‐predator behaviour in Tasmanian eastern quolls (Dasyurus viverrinus) effective against introduced predators?
Authors: Jones Menna E. , Smith Georgina C. , Jones Susan M.
Published: May 2004

Exotic predators, particularly red foxes (Vulpes vulpes) and feral cats (Felis catus), have been implicated in the declines and extinctions of many Australian mammals and a recent incursion of foxes into Tasmania has therefore caused great concern. We tested the behavioural responses of eastern quolls (Dasyurus viverrinus) to acoustic cues of native (masked owl (Tyto novaehollandiae castanops) and Tasmanian devil (Sarcophilus laniarius)) and non‐native (fox and cat) predators and to non‐predators (cow (Bos taurus) and control noise). Juvenile quolls treated fox vocalisations like those of cows (as measured by an increase in movement), in contrast to their responses (a decrease in movement) to sympatric predators. Cats are probably a lesser threat to eastern quolls than native predators or foxes, their impact probably being greatest on the juveniles. Juvenile quolls, but not adults, showed similar responses to cat vocalisations as they did to owls and devils. Adult quolls responded differently from juveniles to owls and devils, by increasing vigilance. This is consistent with the smaller body size, inexperience and the presumed greater vulnerability of juveniles to predation. The lack of appropriate anti‐predator responses to foxes suggests that eastern quolls would be vulnerable to predation by foxes in Tasmania.
Detecting the vanishing populations of the highly endangered Darwin's fox, Pseudalopex fulvipes
Authors: Vilà Carles , Leonard Jennifer A. , Iriarte Agustín , O'Brien Stephen J. , Johnson Warren E. , Wayne Robert K.
Published: May 2004

Darwin's fox (Pseudalopex fulvipes) is known to survive only on Chiloé Island off the coast of southern Chile and in Nahuelbuta National Park, 600 km to the north in mainland Chile. The Valdivian coastal forest, in which the Darwin's fox lives, historically spanned from Nahuelbuta National Park southward past Chiloé Island on the mainland. Furthermore, the forest on Chiloé Island was connected to the mainland forest by a land bridge for much of the Pleistocene. Thus, the distribution of Valdivian forest suggests that the historic range of Darwin's fox may have been much larger. We searched the remnant pockets of coastal forest on mainland Chile using live traps, non‐invasive techniques and interviews to look for new populations of the critically endangered Darwin's fox. Although no Darwin's fox was captured, evidence of a new population near Punta Chanchán was found.
Non‐invasive genotyping of the endangered Apennine brown bear: a case study not to let one's hair down
Authors: Lorenzini Rita , Posillico Mario , Lovari Sandro , Petrella Annino
Published: May 2004

Individual identification was assessed for 30 brown bears (Ursus arctos) from the endangered Apennine population in central Italy, mostly through non‐invasive sampling. Shed hairs were used as a source of DNA to obtain single genotype profiling at 12 microsatellite loci. Average expected heterozygosity (0.438) and mean number of alleles per locus (2.2) showed that the level of genetic diversity was one of the lowest recorded for brown bear populations across their European and North American ranges. A large portion of the original genetic variation may have been lost through random genetic drift during the recent period of isolation. The level of genetic variability proved sufficient to identify the bears individually by using nine microsatellite loci. The probability that two animals shared by chance the same multilocus genotype was estimated to be 1 in 100. Despite the recent history of small population size, the average relatedness indicated that the majority of individuals are not first‐order relatives. Simulated paternity tests showed that a 12‐loci genotype may be necessary to assign paternity with an 80–95% confidence level. Lack of genetic diversity, as well as the maintenance of an adequately effective number, may seriously jeopardise the long‐term survival of this population. Furthermore, high mortality rates, poaching and encroachment by human activities represent immediate, urgent concerns. A population increase through enforced protection and habitat restoration is recommended. Presently, restocking with bears from other source populations should be discouraged to avoid genetic extinction. Non‐invasive sampling provided reliable population and individual genetic data. Microsatellite genotyping proved a valuable genetic tagging method and a feasible alternative to conventional field counts for the brown bear in central Italy.
The effects of inbreeding on mortality during a morbillivirus outbreak in the Mediterranean striped dolphin (Stenella coeruleoalba)
Authors: Valsecchi Elena , Amos William , Raga Juan Antonio , Podestà Michela , Sherwin William
Published: May 2004

Between 1990 and 1992, Mediterranean striped dolphins (Stenella coeruleoalba) suffered high mortality due to a morbillivirus epidemic. Ten highly variable microsatellite markers were used to assess the population structure of a sample of these stranded animals and to assess the genetic consequences of the epizootic on present stocks. We found little evidence of population structure within the Mediterranean, but distinct separation between this and the North Sea (Atlantic) population, the latter also showing greater genetic diversity. Using a genetic measure of inbreeding, we found that dolphins dying early in the outbreak were significantly more inbred than those dying later. Within 10 years of the end of the epidemic, the level of inbreeding among stranded dolphins had returned to its pre‐outbreak levels. However, on average all stranded animals showed elevated levels of inbreeding, suggesting that animals dying from disease may venture towards the shore more than those dying of old age. Our results imply an important role for inbreeding in the dynamics of disease spread and that, in marine mammal research, caution should be exercised when inferring demographic parameters from stranded specimens.
The ‘Checks and Balances’ Doctrine in Member States as a Rule of EC Law: The Cases of France and Germany
Authors: Georgopoulos Theodore
Published: May 2004

Abstract: Though the impact of EC law on the legal status of national powers has been fairly well examined, little attention has been paid to the overall evaluation of the relations developed between national authorities. The paper argues that the mutation of the Judiciary and the Executive role vis‐à‐vis the Legislature appears to be an application of an emerging doctrine in EC public law that conspicuously resembles the ‘Checks and Balances’ theory of American constitutionalism. The action of one public authority is—or must be—countered by the reaction of another for the benefit of EC law. Apart from identifying the features of this ‘principle’ in comparison to its equivalent American doctrine, the paper deals with the question of a possible coexistence of this new model of governance with the traditional one. The comparative perspective is necessary here. Whereas in Germany the constitutional model appears to cope with European demands, in France it seems largely opposed to such a dynamic conception of the separation of powers.
Strict Compliance versus Commercial Reality: The Practical Application of EC Public Procurement Law to the UK's Private Finance Initiative
Authors: Braun Peter
Published: May 2004

Abstract: The Private Finance Initiative (PFI) has been described as the largest cultural change for decades in the way the public sector operates in the United Kingdom. Most of these projects have to be delivered within the framework of public procurement law. This article investigates whether the divergence between the legal framework and the commercial requirements of PFI has resulted in the development of a ‘PFI procurement practice’. If so, it is aimed to examine the reasons for developing the practice and whether it deviated from procurement law. The results of the qualitative empirical study, on which the article is based, are not limited to PFI procurement, but have wider implications for EC procurement law and the general debate over whether it is suitable for modern procurement practice. The findings are also of interest to legal sociologists and European Union lawyers as they describe circumstances under which addressees of the law deviate from supra‐national rules.
Sisters in Arms: European Community Law and Sex Equality in the Armed Forces
Authors: Trybus Martin
Published: May 2004

Abstract: Recently the European Court of Justice has been shedding a new light on the limits of Community competence for defence. This article analyses the rulings in Sirdar, Kreil, and Dory with regards to two interrelated issues. First it discusses the effect of Community law on the equality of men and women in the armed forces of the Member States. Second, it deals with the impact of these decisions on the constitutional order of the European Union. The article argues that Community law has a considerable impact on defence‐related national law. Therefore the analysis ultimately contributes to a narrow aspect of the constitutional debate: the demarcation of competencies between the Member States and the Community in matters related to defence.>
Effects of increasing salinity and 15N-labelled urea levels on growth, N uptake, and water use efficiency of young tomato plants
Authors: Kütük C. , Çaycı G. , Heng L. K.
Published: May 2004

A greenhouse experiment was conducted to investigate the response of tomato plants (Lycopersicon lycopersicum L.) to salinity and to determine the interactive effects of salinity and nitrogen fertilisation on yield, nitrogen uptake, water use efficiency (WUE), and root-zone salinity during early plant growth. Furthermore, the effects of salinity and N fertilisation were evaluated by measurement of carbon isotope discrimination (Δ). Tomato plants were grown in pots filled with 8 kg (dry weight equivalent) of Krumbach sandy loam. Salinity treatments were imposed by irrigation water containing Na, Ca, and Mg salts and having electrical conductivity of 0, 3, 6, 9, and 12 dS/m at 25�C. 15N-labelled urea (10 atom % excess) was also applied at 0, 80, 160, and 240 mg N/kg soil. Increasing salinity reduced plant growth; fresh and dry weights of shoots and roots decreased significantly, except for the non-fertilised plants. The maximum growth reduction in shoots occurred due to salinity–N fertilisation relationships at 12 dS/m (59.4% reduction compared with 0 dS/m in 160 mg N/kg). Root growth was less affected than shoots. Vegetative growth and N content increased with increasing nitrogen treatment. However, salinity generally reduced N uptake by plants. Δ was negatively correlated with WUE at all salinity levels in young tomato plants. Similar correlations were also obtained between WUE and Δ at various N treatments; the result suggests that Δ is a useful tool for assessing stress conditions. Smaller Δ values were obtained when salinity or N level increased. Increasing N fertiliser increased WUE in plants, whereas increasing salinity increased WUE at 3 dS/m and decreased WUE to some extent at other salinity levels. Electrical conductivity of the root-zone increased due to increasing salinity and time, whereas pH decreased. It was concluded that the early stage of development was a salt sensitive period for tomato plants.
Corrigendum to: Dung decomposition in temperate dairy pastures. I. Changes in soil chemical properties
Authors: Aarons S. R. , Gourley C. J. P. , O'Connor C. R.
Published: May 2004

The effect of dung from cows grazing low and high input systems (2 cows/ha, 35 kg P/ha; 4 cows/ha, 140 kg P/ha) on soil chemical properties in temperate dairy pastures was investigated. Dung was used to create pads, and their effect on soil at 2 depths compared with control areas to which nothing was applied. Most dung had decomposed after 40 days in autumn, and was completely degraded by Day 60 in this temperate environment. Large quantities of the nutrients P, K, Ca, Na, Mg, and S were applied to the soil in these dung pads. The mechanism of movement of these nutrients from the pads into soil appeared to be based on their solubility in water. Phosphorus did not leach from the pads but was incorporated into the soil with the decomposing pad. Calcium, Mg, and S concentrations declined slowly in the decomposing pads. On the other hand, K and Na appeared to leach from the pads, as significant decreases in concentrations occurred during decomposition. Soil pH (1:20 soil:water) decreased under dung pads, although the effect did not last beyond 60 days and was linked to the observed increase in soil EC with depth. Extractable P and K increased considerably in soil under dung pads, but only in the upper 0–5 cm layer. Soil exchangeable aluminium and total organic P were not affected by the presence of dung pads. These results are discussed in relation to nutrient cycling in temperate Australian dairy pasture soils.
The liming effect of bauxite processing residue (red mud) on sandy soils
Authors: Snars K. E. , Gilkes R. J. , Wong M. T. F.
Published: May 2004

Bauxite residue (red mud) is produced in large amounts in alumina refineries as a waste product of the Bayer process. This material has the potential to be used as a soil liming agent due to its high pH and high acid neutralisation capacity. Soil incubation experiments compared red mud from several Australian and overseas refineries to estimate its liming effect relative to lime (CaCO3). Two acid (pH 4.3, 4.6) sandy soils were mixed with 8 rates of 17 red muds, 3 limes, and NaOH. Values of EC and pH were measured at 1, 4, and 16 weeks incubation. Each red mud produced a different buffering curve when added to soil, although the shapes of curves could be classified into 5 behavioural groups. The liming equivalent of red mud decreased with increasing target soil pH. For a target pH of 6 the lime equivalent of the red muds was 11–42% for soil 1 and 13–50% for soil 2. No single characteristic of red mud could be used to accurately predict the liming equivalent, as its liming effect is due to several, variable constituents (e.g. free caustic, sodalite, calcite). The pH reached for a certain rate of addition of red mud to soil can be estimated from a comparison of the buffering (titration) curves of both the soil and the red mud. In every case, CaCO3 had a much larger liming capacity than red mud and red mud may not be an economical alternative to lime except where other benefits are associated with its use (e.g. lower cost, decreased P leaching, reduced water repellence).
Field calibration of a capacitance soil water probe in heterogeneous fields
Authors: Geesing Dieter , Bachmaier Martin , Schmidhalter Urs
Published: May 2004

Soil water research requires methods to perform accurate measurements. A capacitance probe gauge has characteristics that seem to make it an attractive replacement for neutron scatter gauges to measure soil water content, but there is evidence that capacitance systems should be calibrated for individual soils. Laboratory calibrations and many field calibration methods are costly and time-consuming, and controlled conditions and disturbed soil samples do not always reflect field conditions, and thus, they are inadequate for practical use. The objectives of the present study were (i) to test a simple field calibration method for a recently developed capacitive sensor even under highly variable soil texture conditions, and (ii) to validate this approach under various soil moisture conditions. Soil samples were taken 0.5 m from the access tube of the sensor and a whole field calibration and several site-specific calibrations were developed using 10–142 observations per site under different soil water regimes. A regression of soil water content estimated by sensor reading on water content obtained by core sampling showed no significant difference in the slope and intercept of the 1:1 line when the field calibration was applied. However, the precision of the calibration was only considerably increased if the estimations were based on site-specific calibrations developed on at least 35 observations per site. The precision and accuracy of the calibration equations were not affected when data were obtained only under wet or dry soil conditions. The method presented in this paper is a speedy and cheap way to calibrate capacitance probe sensors.
Effects of carrot growing on volcanic ash soils in the Ohakune area, New Zealand
Authors: Basher L. R. , Ross C. W. , Dando J.
Published: May 2004

Effects of intensive carrot production on soils derived from young volcanic ash were determined at Ohakune, New Zealand. Erosion rates (derived from caesium-137) and key soil physical and chemical properties were determined in 3 fields with differing management history (6 and 16 years cropping) or topography (sloping and flat).Caesium-137 areal activity in cropped fields ranged from 90 to 2034 Bq/m2, compared with a reference value under long-term pasture of 602 Bq/m2. Mean areal activity was lower than the reference value in 2 sloping fields, but not in a flat field. Net erosion rates were low in both sloping fields (–16 and –5 t/ha.year), but within each field there was a wide range of erosion and deposition rates (–109 to +293 t/ha.year in Field 1 and –145 to +514 t/ha.year in Field 2). These very high rates imply total soil losses up to 238 mm and deposition up to 670 mm, consistent with observed elevation differences between the cropped fields and adjacent fields in long-term pasture and with topsoil depth variation from 145 to 1165 mm. Tillage erosion and deposition rates are high (up to c. 40 t/ha.year) but water erosion is the dominant mechanism of soil redistribution.Cropping has reduced organic matter and aggregate stability, increased bulk density in the lower part of the topsoil and subsoil, and increased aggregate size. Hydraulic conductivity was higher in the topsoil and lower in the subsoil under cropping than it was under pasture. However, it would not limit soil water movement as it was higher than typical rainfall intensities. Compacted wheel tracks were the primary control on runoff and erosion as they have low infiltration rates (4 mm/h) compared with carrot beds (853 mm/h).
Rescuing cystic fibrosis transmembrane conductance regulator (CFTR)-processing mutants by transcomplementation
Authors: Cormet-Boyaka Estelle , Jablonsky Michael , Naren Anjaparavanda P. , Jackson Patricia L. , Muccio Donald D. , Kirk Kevin L.
Published: May 2004

Most cases of cystic fibrosis (CF) are caused by mutations that block the biosynthetic maturation of the CF gene product, the CF transmembrane conductance regulator (CFTR) chloride channel. CFTR-processing mutants fail to escape the endoplasmic reticulum and are rapidly degraded. Current efforts to induce the maturation of CFTR mutants target components of the biosynthetic pathway (e.g., chaperones) rather than CFTR
per se
. Such methods are inherently nonspecific. Here we show that the most common CF-causing mutant (ΔF508-CFTR) can form mature, functional chloride channels that reach the cell surface when coexpressed with several other CFTR-processing mutants or with amino fragments of the wild-type CFTR protein. This transcomplementation effect required a specific match between the region flanking the disease-causing mutation and the complementing fragment; e.g., amino fragments complemented ΔF508-CFTR but not H1085R (a carboxy-processing mutant), whereas a carboxy fragment complemented H1085R but not ΔF508-CFTR. Transcomplementing fragments did not affect CFTR interactions with Hsc70, a chaperone previously implicated in CFTR biosynthesis. Instead, they may promote CFTR maturation by blocking nonproductive interactions between domains within the same or neighboring CFTR polypeptides that prevent normal processing. These findings indicate that it may be possible to develop CF therapies (e.g., mini-cDNA constructs for gene therapy) that are tailored to specific disease-causing mutants of CFTR.
Measurements of age-related changes of physiological processes that predict lifespan of
Caenorhabditis elegans
Authors: Huang Cheng , Xiong Chengjie , Kornfeld Kerry
Published: May 2004

Aging is characterized by progressive, degenerative changes in many tissues. To elucidate the relationships among degenerative changes in
Caenorhabditis elegans
, we developed methods to measure age-related changes quantitatively and analyzed correlations among these changes by using a longitudinal study. The age-related declines of pharyngeal pumping and body movement were positively correlated with each other and lifespan. These findings suggest that the declines of pharyngeal pumping and body movement cause a decline in survival probability or that a shared regulatory system mediates the declines in pharyngeal pumping, body movement, and survival probability. Furthermore, measurements of these processes can be used to predict lifespan and detect premature aging. The declines of physiological processes were measured in
daf-2
,
age-1
,
daf-16
,
eat-2
, and
clk-1
mutants that have altered lifespans. Each mutant strain displayed changes in one or more age-related declines, but the correlations among age-related changes were similar to WT. These measurements were used to generate a system of four stages that describes the aging process and is useful for the analysis of genetic and environmental effects on aging.
Stereocontrolled total synthesis of (+)-vincristine
Authors: Kuboyama Takeshi , Yokoshima Satoshi , Tokuyama Hidetoshi , Fukuyama Tohru
Published: May 2004

An efficient total synthesis of (+)-vincristine has been accomplished through a stereoselective coupling of demethylvindoline and the eleven-membered carbomethoxyverbanamine presursor. Demethylvindoline was prepared by oxidation of 17-hydroxy-11-methoxytabersonine, followed by regioselective acetylation with mixed anhydride method. Although an initial attempt of coupling by using demethylvindoline formamide was not successful and resulted in recovery of the starting compounds, the reaction using demethylvindoline took place smoothly to furnish the desired bisindole product with the correct stereochemistry at C18′. After formation of the piperidine ring by sequential removal of the protective groups and intramolecular nucleophilic cyclization, the total synthesis of vincristine was completed by formylation of N1.
Oligomeric catechins: An enabling synthetic strategy by orthogonal activation and C(8) protection
Authors: Ohmori Ken , Ushimaru Naoko , Suzuki Keisuke
Published: May 2004

Controlled formation of oligomeric catechins has become possible by an orthogonal synthetic strategy. Bromo-capping of the C(8) position of the flavan skeleton enabled the equimolar coupling of electrophilic and nucleophilic catechin derivatives, enabling an efficient synthetic strategy to complex catechin oligomers.
The ribosome as an entropy trap
Authors: Sievers Annette , Beringer Malte , Rodnina Marina V. , Wolfenden Richard
Published: May 2004

To determine the effectiveness of the ribosome as a catalyst, we compared the rate of uncatalyzed peptide bond formation, by the reaction of the ethylene glycol ester of
N
-formylglycine with Tris(hydroxymethyl)aminomethane, with the rate of peptidyl transfer by the ribosome. Activation parameters were also determined for both reactions, from the temperature dependence of their second-order rate constants. In contrast with most protein enzymes, the enthalpy of activation is slightly less favorable on the ribosome than in solution. The 2 × 10
7
-fold rate enhancement produced by the ribosome is achieved entirely by lowering the entropy of activation. These results are consistent with the view that the ribosome enhances the rate of peptide bond formation mainly by positioning the substrates and/or water exclusion within the active site, rather than by conventional chemical catalysis.
Early Occurrence of Spontaneous Tumors in CD-1 Mice and Sprague—Dawley Rats
Authors: Son Woo-Chan , Gopinath Chirukandath
Published: May 2004

It is sometimes difficult to assess the relevance of tumors that occur in treated animals in short-term studies. This report is intended to establish a general profile of tumor occurrence in young control CD-1 mice and Sprague—Dawley rats. Data from 20 rat and 20 mouse carcinogenicity studies conducted between 1990 and 2002 at Huntingdon Life Sciences, UK, were collected and evaluated. The route of administration was either dietary or oral gavage, and the analysis was confined to sporadic deaths (decedents) in control groups occurring during the first 50 weeks of study. In addition, tumor occurrence between 50—80 weeks were compared. In mice, the most common tumor was lymphoma, followed by bronchiolo-alveolar adenoma. In rats, the most common tumor was adenoma of the pituitary gland, followed by mammary fibroadenoma, and adenocarcinoma. When studies of up to 50 weeks, between 50 and 80 weeks, and at 2-year termination were compared, there was no great difference in tumor occurrence except in male rats, in which the most common tumor up to 50 weeks on study was lymphoma, whereas the most common tumor between 50—80 weeks and at 2 years was pituitary adenoma.
Activation of nonselective cation channels by physiological cholecystokinin concentrations in mouse pancreatic acinar cells.
Authors: Thorn P , Petersen O H
Published: May 2004

The activation of the nonselective cation channels in mouse pancreatic acinar cells has been assessed at low agonist concentrations using patch-clamp whole cell, cell-attached patch, and isolated inside-out patch recordings. Application of acetylcholine (ACh) (25-1,000 nM) and cholecystokinin (CCK) (2-10 pM) evoked oscillatory responses in both cation and chloride currents measured in whole cell experiments. In cell-attached patch experiments we demonstrate CCK and ACh evoked opening of single 25-pS cation channels in the basolateral membrane. Therefore, at least a component of the whole cell cation current is due to activation of cation channels in the basolateral acinar cell membrane. To further investigate the reported sensitivity of the cation channel to intracellular ATP and calcium we used excised inside-out patches. Micromolar Ca2+ concentrations were required for significant channel activation. Application of ATP and ADP to the intracellular surface of the patch blocked channel opening at concentrations between 0.2 and 4 mM. The nonmetabolizable ATP analogue, 5'-adenylylimidodiphosphate (AMP-PNP, 0.2-2 mM), also effectively blocked channel opening. The subsequent removal of ATP caused a transient increase in channel activity not seen with the removal of ADP or AMP-PNP. Patches isolated into solutions containing 2 mM ATP showed channel activation at micromolar Ca2+ concentrations. Our results show that ATP has two separate effects. The continuous presence of the nucleotide is required for operation of the cation channels and this action seems to depend on ATP hydrolysis. ATP can also close the channel and this effect can be demonstrated in excised inside-out patches when ATP is added to the bath after a period of exposure to an ATP-free solution. This action does not require ATP hydrolysis. Under physiological conditions hormonal stimulation can open the nonselective cation channels and this can be explained by the rise in the intracellular free Ca2+ concentration.
Effects of low myoplasmic Mg2+ on calcium binding by parvalbumin and calcium uptake by the sarcoplasmic reticulum in frog skeletal muscle.
Authors: Jacquemond V , Schneider M F
Published: May 2004

The effects of low intracellular free Mg2+ on the myoplasmic calcium removal properties of skeletal muscle were studied in voltage-clamped frog skeletal muscle fibers by analyzing the changes in intracellular calcium and magnesium due to membrane depolarization under various conditions of internal free [Mg2+]. Batches of fibers were internally equilibrated with cut end solutions containing two calcium indicators, antipyrylazo III (AP III) and fura-2, and different concentrations of free Mg2+ (25 microM-1 mM) obtained by adding appropriate total amounts of ATP and magnesium to the solutions. Changes in AP III absorbance were used to monitor [Ca2+] and [Mg2+] transients, whereas fura-2 fluorescence was mostly used to monitor resting [Ca2+]. Shortly after applying an internal solution containing less than 60 microM free Mg2+ to the cut ends of depolarized fibers most of the fibers exhibited spontaneous repetitive movements, suggesting that free internal Mg2+ might affect the activity of the sarcoplasmic reticulum (SR) calcium channels at rest. The spontaneous contractions generally subsided. In polarized fibers the maximal amplitude of the calcium transient elicited by a depolarizing pulse was about the same whatever the internal [Mg2+], but its decay after the end of the pulse slower in low [Mg2+]. In low [Mg2+] (less than 0.14 mM), the mean rate constant of decay obtained from fitting a single exponential plus a constant to the decay of the calcium transients was approximately 30% of its value in the control fibers (1 mM internal [Mg2+]). A model characterizing the main calcium removal properties of a frog skeletal muscle fiber, including the SR pump and the Ca-Mg sites on parvalbumin, was fitted to the decay of the calcium transients. Results of the fits show that in low internal [Mg2+] the slowing of the decay of the calcium transient can be well predicted by both a decreased rate of SR calcium uptake and an expected decreased resting magnesium occupancy of parvalbumin leading to a reduced contribution of parvalbumin to the overall rate of calcium removal. These results are thus consistent with the known properties of parvalbumin as a Ca-Mg buffer and furthermore suggest that in an intact portion of a muscle fiber, the activity of the SR calcium pump can be affected by the level of free Mg2+.
Calcium-dependent inactivation of the calcium current activated upon hyperpolarization of Paramecium tetraurelia.
Authors: Preston R R , Saimi Y , Kung C
Published: May 2004

The Ca2+ current activated upon hyperpolarization of Paramecium tetraurelia decays over a period of 150-200 ms during sustained steps under voltage clamp. At membrane potentials between -70 and approximately -100 mV, the time course of this inactivation is described by a single exponential function. Steps negative to approximately -100 mV elicit currents that decay biexponentially, however. Three lines of evidence suggest that this current's inactivation is a function of intracellular Ca2+ concentration rather than membrane potential: (a) Comparing currents with similar amplitudes but elicited at widely differing membrane potentials suggests that their time course of decay is a sole function of inward current magnitude. (b) The extent of current inactivation is correlated with the amount of Ca2+ entering the cell during hyperpolarization. (c) The onset and time course of recovery from inactivation can be hastened significantly by injecting cells with EGTA. We suggest that the decay of this current during hyperpolarization involves a Ca(2+)-dependent pathway.
Mutations in M2 alter the selectivity of the mouse nicotinic acetylcholine receptor for organic and alkali metal cations.
Authors: Cohen B N , Labarca C , Davidson N , Lester H A
Published: May 2004

We measured the permeability ratios (PX/PNa) of 3 wild-type, 1 hybrid, 2 subunit-deficient, and 22 mutant nicotinic receptors expressed in Xenopus oocytes for alkali metal and organic cations using shifts in the bi-ionic reversal potential of the macroscopic current. Mutations at three positions (2', 6', 10') in M2 affected ion selectivity. Mutations at position 2' (alpha Thr244, beta Gly255, gamma Thr253, delta Ser258) near the intracellular end of M2 changed the organic cation permeability ratios as much as twofold and reduced PCs/PNa and PK/PNa by 16-18%. Mutations at positions 6' and 10' increased the glycine ethyl ester/Na+ and glycine methyl ester/Na+ permeability ratios. Two subunit alterations also affected selectivity: omission of the delta subunit reduced PCs/PNa by 16%, and substitution of Xenopus delta for mouse delta increased Pguanidinium/PNa more than twofold and reduced PCs/PNa by 34% and PLi/PNa by 20%. The wild-type mouse receptor displayed a surprising interaction with the primary ammonium cations; relative permeability peaked at a chain length equal to four carbons. Analysis of the organic permeability ratios for the wild-type mouse receptor shows that (a) the diameter of the narrowest part of the pore is 8.4 A; (b) the mouse receptor departs significantly from size selectivity for monovalent organic cations; and (c) lowering the temperature reduces Pguanidinium/PNa by 38% and Pbutylammonium/PNa more than twofold. The results reinforce present views that positions -1' and 2' are the narrowest part of the pore and suggest that positions 6' and 10' align some permeant organic cations in the pore in an interaction similar to that with channel blocker, QX-222.
Divalent cation conduction in the ryanodine receptor channel of sheep cardiac muscle sarcoplasmic reticulum.
Authors: Tinker A , Williams A J
Published: May 2004

The conduction properties of the alkaline earth divalent cations were determined in the purified sheep cardiac sarcoplasmic reticulum ryanodine receptor channel after reconstitution into planar phospholipid bilayers. Under bi-ionic conditions there was little difference in permeability among Ba2+, Ca2+, Sr2+, and Mg2+. However, there was a significant difference between the divalent cations and K+, with the divalent cations between 5.8- and 6.7-fold more permeant. Single-channel conductances were determined under symmetrical ionic conditions with 210 mM Ba2+ and Sr2+ and from the single-channel current-voltage relationship under bi-ionic conditions with 210 mM divalent cations and 210 mM K+. Single-channel conductance ranged from 202 pS for Ba2+ to 89 pS for Mg2+ and fell in the sequence Ba2+ greater than Sr2+ greater than Ca2+ greater than Mg2+. Near-maximal single-channel conductance is observed at concentrations as low as 2 mM Ba2+. Single-channel conductance and current measurements in mixtures of Ba(2+)-Mg2+ and Ba(2+)-Ca2+ reveal no anomalous behavior as the mole fraction of the ions is varied. The Ca(2+)-K+ reversal potential determined under bi-ionic conditions was independent of the absolute value of the ion concentrations. The data are compatible with the ryanodine receptor channel acting as a high conductance channel displaying moderate discrimination between divalent and monovalent cations. The channel behaves as though ion translocation occurs in single file with at most one ion able to occupy the conduction pathway at a time.