bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Late INa and Antiarrhythmic Drugs in EAD Formation and Termination in Purkinje Fibers
Authors: FEDIDA DAVID , ORTH PETER M.R. , HESKETH J. CHRISTIAN , EZRIN ALAN M.
Published: April 2006

Multiple components of cardiac Na current play a role in determining electrical excitation in the heart. Recently, the role of nonequilibrium components in controlling cardiac action potential plateau duration, and their importance in regulating the occurrence of afterdepolarizations and arrhythmias have garnered more attention. In particular, late Na current (late INa) has been shown to be important in LQT2 and LQT3 arrhythmias. Class III agents like dofetilide, clofilium, and sotalol, which can all cause a drug‐induced form of LQT2, significantly lengthen action potential duration at 50% and 90% repolarization in isolated rabbit Purkinje fibers, and can initiate the formation of early afterdepolarizations, and extra beats. These actions can lead to the development of a serious ventricular tachycardia, torsades de pointes, in animal models and patients. However, pretreatment with agents that block late INa, like lidocaine, mexiletine, and RSD1235, a novel mixed ion channel blocker for the rapid pharmacologic conversion of atrial fibrillation, significantly attenuates the prolonging effects of Class III agents or those induced by ATX‐II, a specific toxin that delays Na channel inactivation and amplifies late INa greatly, mimicking LQT3. The Na channel block caused by lidocaine and RSD1235 can be through the open or inactivated states of the channel, but both equivalently inhibit a late component of Na current (INa), recorded at 22°C using whole‐cell patch clamp of Nav1.5 expressed in HEK cells. These protective actions of lidocaine, mexiletine, and RSD1235 may result, at least in part, from their ability to inhibit late INa during action potential repolarization, and inhibition of the inward currents contributing to EAD and arrhythmia formation.
Metabolic Pathways for Ion Homeostasis and Persistent Na+ Current
Authors: HIRAOKA MASAYASU
Published: April 2006

ATP supply in heart cells is preserved by a number of different mechanisms to maintain a constant level of ATP concentration. ADP, phosphocreatine, inorganic phosphate, and cAMP‐activated kinases are effectively involved in ATP supply in abnormal conditions such as ischemia. Intracellular Na+ and Ca2+ concentrations in the heart cells are maintained at low levels through the operation of ion transport across the plasma membrane, such as Na+–K+ pumps, as well as Na+–Ca2+, and Na+–H+ exchangers. The activity of the latter two exchanger mechanisms depends on their expression levels and the concentration gradients of Na+ and Ca2+ across the membrane. These exchangers may interact, and both are strongly regulated by intracellular Na+, which is maintained by the Na+–K+ pump, utilizing ATP as an energy source. The mitochondria and the sarcoplasmic reticulum are the organelles responsible for intracellular Ca2+ stores and release sites for maintaining very low cytoplasmic concentration of Ca2+. Ischemia disrupts the delicate interactions of these transport mechanisms. This may cause intracellular Na+ and Ca2+ accumulation, which can cause decreased contractility and electrical instability. Further, a persistent (noninactivating) Na+ current may be enhanced during ischemia, and this can contribute to action potential prolongation, and the development of early afterdepolarizations. The Na+ influx via the persistent Na+ current may induce further Na+ and Ca2+ accumulation in the cells.
Feature‐Specific Penalized Latent Class Analysis for Genomic Data
Authors: Houseman E. Andrés , Coull Brent A. , Betensky Rebecca A.
Published: April 2006

SummaryGenomic data are often characterized by a moderate to large number of categorical variables observed for relatively few subjects. Some of the variables may be missing or noninformative. An example of such data is loss of heterozygosity (LOH), a dichotomous variable, observed on a moderate number of genetic markers. We first consider a latent class model where, conditional on unobserved membership in one ofkclasses, the variables are independent with probabilities determined by a regression model of low dimensionq. Using a family of penalties including the ridge and LASSO, we extend this model to address higher‐dimensional problems. Finally, we present an orthogonal map that transforms marker space to a space of “features” for which the constrained model has better predictive power. We demonstrate these methods on LOH data collected at 19 markers from 93 brain tumor patients. For this data set, the existing unpenalized latent class methodology does not produce estimates. Additionally, we show that posterior classes obtained from this method are associated with survival for these patients.
Joint Modeling of Survival and Longitudinal Data: Likelihood Approach Revisited
Authors: Hsieh Fushing , Tseng Yi‐Kuan , Wang Jane‐Ling
Published: April 2006

SummaryThe maximum likelihood approach to jointly model the survival time and its longitudinal covariates has been successful to model both processes in longitudinal studies. Random effects in the longitudinal process are often used to model the survival times through a proportional hazards model, and this invokes an EM algorithm to search for the maximum likelihood estimates (MLEs). Several intriguing issues are examined here, including the robustness of the MLEs against departure from the normal random effects assumption, and difficulties with the profile likelihood approach to provide reliable estimates for the standard error of the MLEs. We provide insights into the robustness property and suggest to overcome the difficulty of reliable estimates for the standard errors by using bootstrap procedures. Numerical studies and data analysis illustrate our points.
Bayesian Semiparametric Dynamic Frailty Models for Multiple Event Time Data
Authors: Pennell Michael L. , Dunson David B.
Published: April 2006

SummaryMany biomedical studies collect data on times of occurrence for a health event that can occur repeatedly, such as infection, hospitalization, recurrence of disease, or tumor onset. To analyze such data, it is necessary to account for within‐subject dependency in the multiple event times. Motivated by data from studies of palpable tumors, this article proposes a dynamic frailty model and Bayesian semiparametric approach to inference. The widely used shared frailty proportional hazards model is generalized to allow subject‐specific frailties to change dynamically with age while also accommodating nonproportional hazards. Parametric assumptions on the frailty distribution are avoided by using Dirichlet process priors for a shared frailty and for multiplicative innovations on this frailty. By centering the semiparametric model on a conditionally conjugate dynamic gamma model, we facilitate posterior computation and lack‐of‐fit assessments of the parametric model. Our proposed method is demonstrated using data from a cancer chemoprevention study.
Preparation of NiAl2O4/SiO2 and Co2+‐Doped NiAl2O4/SiO2 Nanocomposites by the Sol–Gel Route
Authors: Prakash I. , Muralidharan P. , Nallamuthu N. , Satyanarayana N. , Venkateswarlu M. , Carnahan David
Published: April 2006

NiAl2O4/SiO2 and Co2+‐doped NiAl2O4/SiO2 nanocomposite materials of compositions 5% NiO – 6% Al2O3– 89% SiO2 and 0.2% CoO – 4.8% NiO – 6% Al2O3– 89% SiO2, respectively, were prepared by a sol–gel process. NiAl2O4 and cobalt‐doped NiAl2O4 nanocrystals were grown in a SiO2 amorphous matrix at around 1073 K by heating the dried gels from 333 to 1173 K at the rate of 1 K/min. The formations of NiAl2O4 and cobalt‐doped NiAl2O4 nanocrystals in SiO2 amorphous matrix were confirmed through X‐ray powder diffraction, Fourier transform infrared spectroscopy, differential scanning calorimeter, transmission electron microscopy (TEM), and optical absorption spectroscopy techniques. The TEM images revealed the uniform distribution of NiAl2O4 and cobalt‐doped NiAl2O4 nanocrystals in the amorphous SiO2 matrix and the size was found to be ∼5–8 nm.
High‐Temperature Tensile Strength of Er2O3‐Doped ZrO2 Single Crystals
Authors: Pastor José Y. , LLorca Javier , Poza Pedro , Quispe José J. , De Arellano López A. R. , Martínez‐Fernández Julián , Sayir Ali , Orera Victor M.
Published: April 2006

The deformation and fracture mechanisms in tension were studied in single‐crystal Er2O3‐doped ZrO2 monofilaments processed by the laser‐heated floating zone method. Tensile tests were carried out between 25° and 1400°C at different loading rates and the dominant deformation and fracture mechanisms were determined from the shape of the stress–strain curves, the morphology of the fracture surfaces, and the evidence provided by monofilaments deformed at high temperature and broken at ambient temperature. The tensile strength presented a minimum at 600°–800°C and it was controlled by the slow growth of a crack from the surface. This mechanism was also dominant in some monofilaments tested at 1000°C and above, while others showed extensive plastic deformation before fracture at these temperatures. The strength of plastically deformed monofilaments was significantly higher than those which failed by slow crack growth due to the marked strain hardening capacity of this material.
A Soft‐Tissue Calcification: Differential Diagnosis and Pathogenesis
Authors: Goff Alaina K. , Reichard Ross
Published: April 2006

ABSTRACT: An autopsy of a 72‐year‐old white male revealed a 30.5 × 5.1 cm vertically aligned heterotopic ossification just deep to a 30.5 cm midline abdominal scar. The ossified mass was determined to be a heterotopic ossification or myostitis ossificans (MO) traumatica resulting from an abdominal surgical incision during life. While, MO traumatica is relatively common accounting for roughly 60–75% of patients with soft‐tissue ossification, heterotopic ossification of abdominal incisions are relatively rare and thus infrequently reported. This article details the manifestation of this relatively large heterotopic bone and provides a comprehensive review of the literature and pathogenesis of this unusual ossification. A review of the English literature from 1920 to the present produced only a handful of articles for a total of 185 reported cases. All had bone formed within vertical incisions, usually within 1 year of surgery, and 89% were males. Knowledge of this phenomenon and the variable size at presentation is useful to both the autopsy pathologist and the anthropologist in generating a diagnosis for abnormal calcifications.
Dietary Health Does Affect Histological Age Assessment: An Evaluation of the Stout and Paine (1992) Age Estimation Equation Using Secondary Osteons from the Rib*
Authors: Paine Robert R. , Brenton Barrett P.
Published: April 2006

ABSTRACT: An age at death estimation equation that uses rib histological variables presented by Stout and Paine was used to evaluate a skeletal population of individuals with a known age at death and cause of death from either malnutrition or the niacin deficiency disease pellagra. The sample was comprised of 26 autopsied black South Africans. Histological analysis of mounted thin sections involved the microscopic measurement of cortical area and a count of the number of intact and fragmentary secondary osteons for the entire cross‐section of the rib. Rib osteon population density values were then calculated for each case. It was found that this equation under‐aged individuals on average by 29.2 years. Overall, secondary osteon size and Haversian canals tended to be larger than expected, while cortical bone area was less when compared with a control population. The implications of these findings are critical given that many of the skeletal remains examined by forensic anthropologists come from marginalized backgrounds, including malnutrition. This research suggests that measurements based on healthy cases may not be useful in an analysis of individuals with poor diet and health. It is argued that new standards for histological age assessment methods need to be created that account for variation in the health status of individuals examined by forensic anthropologists.
Chemical Profiling of Heroin Recovered from the North Korean Merchant Vessel Pong Su
Authors: Collins Michael , Casale Ellen , Hibbert D. Brynn , Panicker Sini , Robertson James , Vujic Sasha
Published: April 2006

ABSTRACT: Heroin samples, seized from the North Korean merchant vessel Pong Su in Australian waters, were analyzed to determine geographic origin. Duplicate samples were analyzed by the National Measurement Institute's Australian Forensic Drug Laboratory and the United States Drug Enforcement Administration's Special Testing and Research Laboratory. Alkaloid ratios were determined by both liquid chromatography‐diode array detection (LC‐DAD) and capillary electrophoresis‐diode array detection (CE‐DAD) techniques. Acid/neutral manufacturing by‐products were determined by solvent extraction followed by gas chromatography‐mass spectrometry (GC‐MS). Solvents, trapped in the heroin particles during manufacture, were detected by both static headspace GC‐MS and purge and trap GC‐MS. The alkaloid ratios obtained were consistent with heroin of a Southeast Asian (SEA) origin and principal component analysis of the alkaloid results demonstrated the presence of at least four subgroupings within the seizure. The solvent analysis detected diethyl ether and ethyl acetate, solvents typically seen in SEA heroin. However, the acid/neutral analysis revealed compounds not normally seen in heroin of a SEA origin. Furthermore, sterol‐like molecules, always detected in the acid/neutral analysis of SEA heroin, were absent from the Pong Su samples. The Pong Su heroin, although similar to SEA heroin, has sufficient differences to classify it as having an unknown origin at the time of this writing.
A Forensic Case Study of a Naturally Mummified Brain from the Bushveld of South Africa
Authors: Eklektos Nikki , Dayal Manisha R. , Manger Paul R.
Published: April 2006

ABSTRACT: The present study reports our observations of a naturally mummified human brain found in the bushveld of South Africa. This case extends the geographic and climatic ranges in which mummified brains have been found, and it represents an additional case where no human activity has led to the mummification. The mummified brain was c. one fifth the size of a normal human brain, while the gyral and sulcal patterns of a typical human brain were clear. CT scanning of the brain revealed that subcortical structures, normally evident in this type of imaging, were not discernable, indicating a slow mummification process. Histological examination of the tissue revealed near complete degradation of the microanatomical structure, with only putative Nissl bodies remaining as identifiable neural microstructures. The specimen appears to have survived several veld fires, as well as a high annual rainfall, and a high relative humidity. It is thought that specific conditions amenable to brain mummification, but not other soft tissues, occurred in the skull of this specimen in the weeks postmortem.
Infrared Spectra of U.S. Automobile Original Finishes. VII. Extended Range FT‐IR and XRF Analyses of Inorganic Pigments In Situ—Nickel Titanate and Chrome Titanate
Authors: Suzuki Edward M. , McDermot Martin X.
Published: April 2006

ABSTRACT: The identification, analysis, and occurrence in U.S. automobile original finishes (1974–1989) of Nickel Titanate (yellow) and Chrome Titanate (yellow–orange) are described in this report. The titanate pigments are based on the rutile (titanium dioxide) structure and there are only minor differences between the infrared absorptions of rutile and the titanates. Titanate pigment absorptions in paint spectra can thus be easily mistaken for those of rutile. Each of the titanates, however, contains two elements in addition to titanium that can serve to distinguish them using elemental analyses. Fourier transform infrared (4000–220 cm−1) and X‐ray fluorescence instruments were used in combination for the in situ analysis of the titanates. In addition to titanium, nickel, and antimony, the three main detectable elements comprising Nickel Titanate, all of the commercial products of this pigment that were examined also contained impurities of zirconium, niobium, and usually lead. These elements were also detected in most of the monocoats in which Nickel Titanate was identified, as well as in the Chrome Titanate pigments, and the zirconium to niobium ratio was found to exhibit a wide variation. Nickel Titanate is a relatively common pigment that was identified in nearly three dozen U.S. automobile yellow nonmetallic monocoats (1974–1989), while Chrome Titanate appears to have been used in only a few yellow and orange nonmetallic monocoats. The use of the titanate pigments likely increased after this time period as they were replacements for lead chromate pigments (last used in a U.S. automobile original finish in the early 1990s), and are more amenable for use in basecoat/clearcoat finishes than in monocoats. Minor distortions of the infrared absorptions of rutile, anatase, and the titanates obtained using accessories with diamond windows were noted, and their origins are discussed.
Influence of Substrate Tissue Type on Larval Growth in Calliphora augur and Lucilia cuprina (Diptera: Calliphoridae)*
Authors: Day Donnah M. , Wallman James F.
Published: April 2006

ABSTRACT: The size of fly larvae is an important variable in the use of these insects to estimate postmortem interval. Furthermore, the nutritional intake of larvae is likely to vary subject to the part of a corpse on which they are feeding. A study was therefore conducted to investigate the effect of type of food substrate on larval growth in two species of forensically important Australian blowflies. After collection on sheep's liver in the laboratory, different groups of larvae of Lucilia cuprina (Wiedemann) and Calliphora augur (Fabricius) were grown on sheep's liver, meat, and brains, and their body lengths compared. Results indicated that the development of larvae fed sheep's liver was adversely affected compared with larvae fed meat and brain; they moulted later, reached maximum length more slowly and sometimes produced significantly smaller pupae. These findings, similar to those of another recent study, have obvious implications for postmortem interval determinations. Estimates may be considerably skewed if the site of collection of larvae at a death scene contains tissue types different to those used in reference experiments. We therefore recommend caution in forensic analyses that interpret crime scene data using developmental studies performed with a single type of larval food substrate.
Environmental Survey for Four Pathogenic Bacteria and Closely Related Species Using Phylogenetic and Functional Genes*
Authors: Kuske Cheryl R. , Barns Susan M. , Grow Christy C. , Merrill Lori , Dunbar John
Published: April 2006

ABSTRACT: Bacterial species with high DNA sequence similarity to pathogens could affect the specificity of assays designed to detect biological threat agents in environmental samples. The natural presence of four pathogenic bacteria, Bacillus anthracis, Clostridium perfringens, Francisella tularensis, and Yersinia pestis and their closely related species, was determined for a large collection of soil and aerosol samples. Polymerase chain reaction (PCR) and gene sequencing were used using group‐specific 16S rRNA primers to identify pathogens and related species, and pathogen‐specific virulence genes. Close relatives of B. anthracis (B. cereus group species) were detected in 37% of the soils and 25% of the aerosol samples. The B. anthracis protective antigen (pag) gene or a close homolog was detected in 16 of these samples. For the other three pathogen groups, the frequency of detection was much lower, and none of the samples were positive with both the phylogenetic and virulence gene primer sets.
ICT and agricultural productivity: evidence from cross‐country data
Authors: Lio Monchi , Liu Meng‐Chun
Published: April 2006

This article carries out agricultural production function estimations, based on data for the period 1995–2000 on 81 countries, to present empirical evidence on the relationship between the adoption of information and communication technology (ICT) and agricultural productivity. It is found that new ICT has a significantly positive impact on agricultural productivity. The evidence suggests that the adoption of modern industrial inputs in agricultural production relies on the information and communication infrastructure. However, the empirical evidence from this study also suggests that new ICT could be a factor for the divergence between countries in terms of overall agricultural productivity. Not only do we find that the ICT adoption levels of the richer countries are much higher than those of the poorer countries, but also that returns from ICT in agricultural production of the richer countries are about two times higher than those of the poorer countries. A plausible explanation for the poorer countries' relatively low productivity elasticity of ICT is the lack of important complementary factors, such as a substantial base of human capital.
It is where you are that matters: the spatial determinants of rural poverty in India
Authors: Palmer‐Jones Richard , Sen Kunal
Published: April 2006

The spatial patterns of poverty in India are of considerable importance in themselves and for development theory and practice. This article examines the determinants of rural poverty in India using spatial econometric methods. It finds that while agricultural growth is the key determinant of rural poverty declines, there is significant spatial dependence in the growth rates of agricultural output. Irrigation is the primary driver of agricultural growth, and spatial variations in irrigation development seem to be associated with agro‐ecological conditions which may be vastly different within Indian states, parts of which may be similar to those prevailing in geographically contiguous states. Poverty reduction strategies need to be designed in the light of spatial factors and using spatial methods.
Activation of p38 Mitogen‐Activated Protein Kinase Promotes Epidermal Growth Factor Receptor Internalization
Authors: Vergarajauregui Silvia , Miguel Anitza San , Puertollano Rosa
Published: April 2006

Endocytic trafficking plays an important role in the regulation of the epidermal growth factor receptor (EGFR). To address if cellular kinases regulate EGFR internalization, we used anisomycin, a potent activator of kinase cascades in mammalian cells, especially the stress‐activated mitogen‐activated protein (MAP) kinase subtypes. Here, we report that activation of p38 MAP kinase by anisomycin is sufficient to induce internalization of EGFR. Anisomycin and EGF employ different mechanisms to promote EGFR endocytosis as anisomycin‐induced internalization does not require tyrosine kinase activity or ubiquitination of the receptor. In addition, anisomycin treatment did not result in delivery and degradation of EGFR at lysosomes. Incubation with a specific inhibitor of p38, or depletion of endogenous p38 by small interfering RNAs, abolished anisomycin‐induced internalization of EGFR while having no effect on transferrin endocytosis, indicating that the effect of p38 activation on EGFR endocytosis is specific. Interestingly, inhibition of p38 activation also abolished endocytosis of EGFR induced by UV radiation. Our results reveal a novel role for p38 in the regulation of EGFR endocytosis and suggest that stimulation of EGFR internalization by p38 might represent a general mechanism to prevent generation of proliferative or anti‐apoptotic signals under stress conditions.
Did Swift measure gamma-ray burst prompt emission radii?
Authors: Lyutikov M.
Published: April 2006

The Swift X-Ray Telescope often observes a rapidly decaying X-ray emission stretching to as long as t ∼ 103 s after a conventional prompt phase. This component is most likely due to a prompt emission viewed at large observer angles θ > 1/Γ, where θ ∼ 0.1 is a typical viewing angle of the jet and Γ ⩾ 100 is the Lorentz factor of the flow during the prompt phase. This can be used to estimate the prompt emission radii, rem ⩾ 2t c/θ2 ∼ 6 × 1015 cm. These radii are much larger than is assumed within the framework of a fireball model. Such large emission radii can be reconciled with a fast variability, on time-scales as short as milliseconds, if the emission is beamed in the bulk outflow frame, e.g. because of a random relativistic motion of ‘fundamental emitters’. This may also offer a possible explanation for X-ray flares observed during early afterglows.
POSSIBLE CORRELATIONS BETWEEN CRUDE OIL CHEMICAL COMPOSITION AND RESERVOIR AGE
Authors: Polichtchouk Y. M. , Yashchenko I. G.
Published: April 2006

The sulphur, paraffin, resin and asphaltene contents of over 7,100 Cenozoic, Mesozoic and Palaeozoic oils were analysed and were tentatively correlated with reservoir rock age. The data came from 90 oil‐bearing basins worldwide. Oil compositions appear to show cyclical changes throughout the Phanerozoic, and these changes can be related to orogenic cycles and marine transgressions and regressions.
The effects of cattle grazing on plant‐pollinator communities in a fragmented Mediterranean landscape
Authors: Vulliamy Betsy , G. Potts Simon , G. Willmer P.
Published: April 2006

The main aims of this study were to assess grazing impacts on bee communities in fragmented mediterranean shrubland (phrygana) and woodland habitats that also experience frequent wildfires, and to explain the mechanisms by which these impacts occur. Fieldwork was carried out in 1999 and 2000 on Mount Carmel, in northern Israel, a known hot‐spot for bee diversity. Habitats with a range of post‐burn ages and varying intensities of cattle grazing were surveyed by transect recording, grazing levels, and the diversity and abundance of both flowers and bees were measured. The species richness of both bees and flowers were highest at moderate to high grazing intensities, and path‐analysis indicated that the effects of both grazing and fire on bee diversity were mediated mainly through changes in flower diversity, herb flowers being more important than shrubs. The abundance of bees increased with intensified grazing pressure even at the highest levels surveyed. Surprisingly though, changes in bee abundance at high grazing levels were not caused directly by changes in flower cover. The variation in bee abundance may have been due to higher numbers of solitary bees from the family Halictidae in grazed sites, where compacted ground (nesting resource) and composites (forage resource) were abundant. The effects of grazing on plants were clearest in the intermediate‐aged sites, where cattle inhibited the growth of some of the dominant shrubs, creating or maintaining more open patches where light‐demanding herbs could grow, thus allowing a diverse flora to develop. Overall, bee communities benefit from a relatively high level of grazing in phrygana. Although bee and flower diversity may decrease under very heavy grazing, the present levels of grazing on Mount Carmel appear to have only beneficial effects on the bee community.
Consumer diversity mediates invasion dynamics at multiple trophic levels
Authors: E. France Kristin , Emmett Duffy J.
Published: April 2006

Theory and recent experiments, mostly focused on plants, indicate that biodiversity can reduce invasion success, but diversity effects on mobile animal invasion have received little attention. We tested effects of mobile crustacean grazer diversity (species richness) on the establishment of invaders at multiple trophic levels in flow‐through seagrass mesocosms. On average, increasing diversity of resident grazers reduced population growth and biomass of experimentally introduced grazers. This increase in invasion resistance was concurrent with reductions in food and habitat availability and increases in resident density, paralleling previous results with plants. In many cases, mixtures of resident species resisted invasion better than did any single resident species, arguing that interactions among residents, rather than a sampling mechanism, explained diversity effects on invasion. Higher grazer diversity also generally reduced biomass of naturally recruiting invertebrates and algae and shifted epiphytic community dominance from algae to sessile invertebrates. Exploitation competition, then, appears to contribute to the diversity effect on invasion in both plant and animal systems. Our results further suggest that resident competitive advantage may also be at work in multi‐trophic level systems. Thus, negative effects of local diversity on invasion appear general, and trophically mediated processes can also strongly influence invader success and identity in multi‐trophic level systems.
Accumulation of local pathogens: a new hypothesis to explain exotic plant invasions
Authors: Eppinga Maarten B. , Rietkerk Max , Dekker Stefan C. , De Ruiter Peter C. , Van der Putten Wim H. , Van der Putten Wim H.
Published: April 2006

Recent studies have concluded that release from native soil pathogens may explain invasion of exotic plant species. However, release from soil enemies does not explain all plant invasions. The invasion of Ammophila arenaria (marram grass or European beach grass) in California provides an illustrative example for which the enemy release hypothesis has been refuted. To explore the possible role of plant–soil community interactions in this invasion, we developed a mathematical model. First, we analyzed the role of plant–soil community interactions in the succession of A. arenaria in its native range (north‐western Europe). Then, we used our model to explore for California how alternative plant–soil community interactions may generate the same effect as if A. arenaria were released from soil enemies. This analysis was carried out by construction of a ‘recovery plane’ that discriminates between plant competition and plant–soil community interactions. Our model shows that in California, the accumulation of local pathogens by A. arenaria could result in exclusion of native plant species. Moreover, this mechanism could trigger the rate and spatial pattern of invasive spread generally observed in nature. We propose that our ‘accumulation of local pathogens’ hypothesis could serve as an alternative explanation for the enemy release hypothesis to be considered in further experimental studies on invasive plant species.
Tmc1 is necessary for normal functional maturation and survival of inner and outer hair cells in the mouse cochlea
Authors: Marcotti Walter , Erven Alexandra , Johnson Stuart L. , Steel Karen P. , Kros Corné J.
Published: April 2006

The deafness (dn) and Beethoven (Bth) mutant mice are models for profound congenital deafness (DFNB7/B11) and progressive hearing loss (DFNA36), respectively, caused by recessive and dominant mutations of transmembrane cochlear‐expressed gene 1 (TMC1), which encodes a transmembrane protein of unknown function. In the mouse cochlea Tmc1 is expressed in both outer (OHCs) and inner (IHCs) hair cells from early stages of development. Immature hair cells of mutant mice seem normal in appearance and biophysical properties. From around P8 for OHCs and P12 for IHCs, mutants fail to acquire (dn/dn) or show reduced expression (Bth/Bth and, to a lesser extent Bth/+) of the K+ currents which contribute to their normal functional maturation (the BK‐type current IK,f in IHCs, and the delayed rectifier IK,n in both cell types). Moreover, the exocytotic machinery in mutant IHCs does not develop normally as judged by the persistence of immature features of the Ca2+ current and exocytosis into adulthood. Mutant mice exhibited progressive hair cell damage and loss. The compound action potential (CAP) thresholds of Bth/+ mice were raised and correlated with the degree of hair cell loss. Homozygous mutants (dn/dn and Bth/Bth) never showed CAP responses, even at ages where many hair cells were still present in the apex of the cochlea, suggesting their hair cells never function normally. We propose that Tmc1 is involved in trafficking of molecules to the plasma membrane or serves as an intracellular regulatory signal for differentiation of immature hair cells into fully functional auditory receptors.
Host Species Barriers to Influenza Virus Infections
Authors: Kuiken Thijs , Holmes Edward C. , McCauley John , Rimmelzwaan Guus F. , Williams Catherine S. , Grenfell Bryan T.
Published: April 2006

Most emerging infectious diseases in humans originate from animal reservoirs; to contain and eradicate these diseases we need to understand how and why some pathogens become capable of crossing host species barriers. Influenza virus illustrates the interaction of factors that limit the transmission and subsequent establishment of an infection in a novel host species. Influenza species barriers can be categorized into virus-host interactions occurring within individuals and host-host interactions, either within or between species, that affect transmission between individuals. Viral evolution can help surmount species barriers, principally by affecting virus-host interactions; however, evolving the capability for sustained transmission in a new host species represents a major adaptive challenge because the number of mutations required is often large.
Response to Comment on "Phylogenetic MCMC Algorithms Are Misleading on Mixtures of Trees"
Authors: Mossel Elchanan , Vigoda Eric
Published: April 2006

We presented a tree mixture in which Markov chain Monte Carlo (MCMC) methods have an exponentially slow convergence rate. We expect that many other mixture scenarios will show slow convergence. Ronquist
et al
. show that Metropolis-coupled MCMC (MC
3
) converges quickly on our mixture. However, they presented no theoretical or systematic experimental evidence determining the type of mixtures where MC
3
or other methods are efficient.
Nuclear Pores Form de Novo from Both Sides of the Nuclear Envelope
Authors: D'Angelo Maximiliano A. , Anderson Daniel J. , Richard Erin , Hetzer Martin W.
Published: April 2006

Nuclear pore complexes are multiprotein channels that span the double lipid bilayer of the nuclear envelope. How new pores are inserted into the intact nuclear envelope of proliferating and differentiating eukaryotic cells is unknown. We found that the Nup107-160 complex was incorporated into assembly sites in the nuclear envelope from both the nucleoplasmic and the cytoplasmic sides. Nuclear pore insertion required the generation of Ran guanosine triphosphate in the nuclear and cytoplasmic compartments. Newly formed nuclear pore complexes did not contain structural components of preexisting pores, suggesting that they can form de novo.
Stability via Asynchrony in
Drosophila
Metapopulations with Low Migration Rates
Authors: Dey Sutirth , Joshi Amitabh
Published: April 2006

Very few experimental studies have examined how migration rate affects metapopulation dynamics and stability. We studied the dynamics of replicate laboratory metapopulations of
Drosophila
under different migration rates. Low migration stabilized metapopulation dynamics, while promoting unstable subpopulation dynamics, by inducing asynchrony among neighboring subpopulations. High migration synchronized subpopulation dynamics, thereby destabilizing the metapopulations. Contrary to some theoretical predictions, increased migration did not affect average population size. Simulations based on a simple non–species-specific population growth model captured most features of the data, which suggests that our results are generalizable.
Drilling to Gabbro in Intact Ocean Crust
Authors: Wilson Douglas S. , Teagle Damon A. H. , Alt Jeffrey C. , Banerjee Neil R. , Umino Susumu , Miyashita Sumio , Acton Gary D. , Anma Ryo , Barr Samantha R. , Belghoul Akram , Carlut Julie , Christie David M. , Coggon Rosalind M. , Cooper Kari M. , Cordier Carole , Crispini Laura , Durand Sedelia Rodriguez , Einaudi Florence , Galli Laura , Gao Yongjun , Geldmacher Jörg , Gilbert Lisa A. , Hayman Nicholas W. , Herrero-Bervera Emilio , Hirano Nobuo , Holter Sara , Ingle Stephanie , Jiang Shijun , Kalberkamp Ulrich , Kerneklian Marcie , Koepke Jürgen , Laverne Christine , Vasquez Haroldo L. Lledo , Maclennan John , Morgan Sally , Neo Natsuki , Nichols Holly J. , Park Sung-Hyun , Reichow Marc K. , Sakuyama Tetsuya , Sano Takashi , Sandwell Rachel , Scheibner Birgit , Smith-Duque Chris E. , Swift Stephen A. , Tartarotti Paola , Tikku Anahita A. , Tominaga Masako , Veloso Eugenio A. , Yamasaki Toru , Yamazaki Shusaku , Ziegler Christa
Published: April 2006

Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.
Visualization of Cellulose Synthase Demonstrates Functional Association with Microtubules
Authors: Paredez Alexander R. , Somerville Christopher R. , Ehrhardt David W.
Published: April 2006

Expression of a functional yellow fluorescent protein fusion to cellulose synthase (CESA) in transgenic
Arabidopsis
plants allowed the process of cellulose deposition to be visualized in living cells. Spinning disk confocal microscopy revealed that CESA complexes in the plasma membrane moved at constant rates in linear tracks that were aligned and were coincident with cortical microtubules. Within each observed linear track, complex movement was bidirectional. Inhibition of microtubule polymerization changed the fine-scale distribution and pattern of moving CESA complexes in the membrane, indicating a relatively direct mechanism for guidance of cellulose deposition by the cytoskeleton.
Tennis injuries: occurrence, aetiology, and prevention
Authors: Pluim B M , Staal J B , Windler G E , Jayanthi N
Published: April 2006

A systematic search of published reports was carried out in three electronic databases from 1966 on to identify relevant articles relating to tennis injuries. There were 39 case reports, 49 laboratory studies, 28 descriptive epidemiological studies, and three analytical epidemiological studies. The principal findings of the review were: first, there is a great variation in the reported incidence of tennis injuries; second, most injuries occur in the lower extremities, followed by the upper extremities and then the trunk; third, there have been very few longitudinal cohort studies that investigated the association between risk factors and the occurrence of tennis injuries (odds ratios, risk ratios, hazard ratios); and fourth, there were no randomised controlled trials investigating injury prevention measures in tennis. More methodologically sound studies are needed for a better understanding of risk factors, in order to design useful strategies to prevent tennis injuries.
Leaving the professional tennis circuit: exploratory study of experiences and reactions from elite female athletes
Authors: Young J A , Pearce A J , Kane R , Pain M
Published: April 2006

In 2002, Tennis Australia commissioned a report into the experiences of elite female past players on leaving the professional tennis circuit. Australian players who were in the top 800 of the Women’s Tennis Association (WTA) end of year rankings and who had left the professional circuit within the previous 15 years were asked by mail to respond to a questionnaire. The questionnaire asked players to describe their feelings about leaving the tour during the time leading up to leaving the tour to two years after retirement. The main findings of the study suggested that those who planned to leave the tour found the transition process easy, whereas those who did not plan to leave the tour found the process difficult. Most players (66%) did not regret leaving the tour, and, although the remaining players responded that they regretted leaving, none attempted a comeback. Tennis Australia has implemented strategies to assist current players on the professional tour based on the results of this study.
Is tennis a predisposing factor for degenerative shoulder disease? A controlled study in former elite players
Authors: Maquirriain J , Ghisi J P , Amato S
Published: April 2006

Background:High demands imposed to the shoulder during tennis activity can decrease the efficiency of static and dynamic constraints. Subtle or frank instability of the glenohumeral joint may occur, and long term degenerative changes may be expected.

Objective:To determine and compare the prevalence of primary glenohumeral osteoarthritis in senior tennis players and matched controls.

Study design:Cross sectional controlled study.

Methods:18 asymptomatic senior tennis players were studied (17 male; mean (SD) age, 57.2 (8.8) years) with no history of shoulder surgery or major trauma. There were 18 matched controls. Radiographs were used to determine glenohumeral osteoarthritic changes: joint space narrowing, humeral and glenoid subchondral sclerosis, humeral and glenoid juxta-articular cysts, osteophytes, humeral and glenoid flattening, humeral posterior displacement and glenoid posterior erosion. Findings were classified as normal, minimal, moderate, or severe changes.

Results:33% of the players (95% confidence interval (CI), 13% to 59%) had osteoarthritic changes in their dominant shoulder (n = 6; five with minimal changes, one with moderate changes), and 11% of the controls (95% CI, 1% to 34%) had articular degeneration on their dominant side (n = 2; both minimal changes) (p = 0.04, Wilcoxon test). The osteoarthritic group was significantly older than the players without degenerative changes (p = 0.008).

Conclusions:The prevalence of glenohumeral osteoarthritis in the dominant shoulder was greater in former elite tennis players than in sedentary controls. Prolonged intensive tennis practice may be a predisposing factor for the development of mild degenerative articular changes in the dominant shoulder.
Tennis specific limitations in players with an ACL deficient knee: Table 1
Authors: Maquirriain J , Megey P J
Published: April 2006

Background:Complete rupture of the anterior cruciate ligament (ACL) causes significant alteration of knee joint kinematics. Untreated patients often develop joint instability, chronic articular degeneration, and knee dysfunction. Demands on the ACL produced by playing tennis have not been investigated.

Objective:To identify subjective sport-specific limitations in tennis players with isolated unilateral ACL deficiency.

Study design:Prospective case–control study.

Methods:16 players (mean (SD) age, 39.9 (2.3) years; 14 men) with a chronic unilateral ACL deficient knee and 16 healthy controls (38.25 (8.47) years; 14 men) were recruited. ACL deficiency was confirmed by clinical and magnetic resonance imaging. A Lysholm score was obtained in all patients, together with subjective evaluation of their current tennis performance compared with pre-injury levels, applying a 0–100% visual scale. Both groups completed a questionnaire on tennis specific abilities.

Results:Lysholm scores were: 85.6 (10.3) points in the study group and 100 (0) points in the control group (p<0.001,ttest for independent samples). Injured players evaluated their current tennis performance as 66.8 (15.2)% compared with 100% pre-injury level (p<0.005,ttest for dependent samples). Abilities affected in the ACL deficient group were landing after a smash stroke (p<0.001); stopping abruptly and changing (p<0.001); playing a three set singles match (p<0.05); and playing on a hard court surface (p<0.001, Kolmogorov-Smirnov test).

Conclusions:There are specific limitations associated with complete isolated ACL rupture, including subjective tennis performance impairment, limitations landing after a smash, stopping and changing step direction, difficulties playing a three set singles match, and playing on hard court surfaces.
Postero-medial elbow problems in the adult athlete
Authors: Eygendaal D , Safran M R
Published: April 2006

The ligamentous, osseous, musculotendinous, and neural structures at the postero-medial side of the elbow are at risk for various injuries in overhead athletes. The combination of valgus and extension overload during overhead activities results in tensile forces along the medial stabilising structures, with compression on the lateral compartment and shear stress posteriorly. The combination of tensile forces medially and shear forces posteriorly can result in ulnar collateral ligament (UCL) tears, flexor–pronator mass injuries, neuritis of the ulnar nerve, posterior impingement, and olecranon stress fractures. Most symptomatic conditions of the overhead athlete can be treated conservatively initially. In cases where conservative treatment is unsuccessful surgical intervention is indicated. Recent advances in arthroscopic surgical techniques and ligamentous reconstruction ensure that the prognosis for return to pre-injury level is good.
Placental restriction alters circulating thyroid hormone in the young lamb postnatally
Authors: De Blasio Miles J. , Gatford Kathryn L. , Robinson Jeffrey S. , Owens Julie A.
Published: April 2006

Intrauterine growth restriction (IUGR) is associated with accelerated growth and increased adiposity in early life due to unknown mechanisms, which could include increased thyroid hormone (TH) action. We hypothesized that placental restriction (PR) of fetal growth would increase circulating TH concentrations and alter their response to fasting, and that these would relate to growth and body composition in the young lamb. PR reduced size at birth, increased fractional growth rates (FGRs) of soft and skeletal tissues up to 30 days of age, and slowed the ontogenic decrease in plasma total T3and plasma total T3/T4. PR did not alter the abundance of plasma THs after short-term fasting. In general, plasma total T3and total T3/T4ratio correlated negatively, whereas plasma total T4correlated positively with size at birth. Absolute growth rates of weight and crown-rump length correlated positively with plasma total T3and total T4between days 15 and 35. Current FGRs for weight and metatarsal length correlated positively with plasma total T3between days 20 and 35. In conclusion, PR and small size at birth reduce plasma total T4and increase plasma total T3postnatally, whereas catch-up growth relates to increased abundance of the more bioactive forms of TH. Finally, greater soft tissue growth occurs in PR compared with control lambs at the same circulating TH concentrations. This suggests that PR and small size at birth may increase activation of T4to T3and sensitivity of soft tissues to TH, which may contribute to catch-up growth following IUGR.