bluuebunny/crossref_metadata_2025_split huggingface dataset:
Down‐regulation of epidermal growth factor receptor‐dependent signaling by Porphyromonas gingivalis lipopolysaccharide in life‐expanded human gingival fibroblasts
Authors: Quinchia‐Rios B. H. , Guerrero M. , Abozeid S. , Bainbridge B. , Darveau R. , Compton T. , Bertics P. J. 
Published: January 2008

Background and Objective:  Human gingival fibroblasts exhibit proliferative responses following epidermal growth factor exposure, which are thought to enhance periodontal regeneration in the absence of bacterial products such as lipopolysacharide. However, lipopolysaccharide challenge activates human gingival fibroblasts to release several inflammatory mediators that contribute to the immune response associated with periodontitis and attenuate wound repair. We tested the hypothesis that Porphyromonas gingivalis lipopolysaccharide‐activated signaling pathways down‐regulate epidermal growth factor receptor‐dependent events.Material and Methods:  To study lipopolysaccharide/epidermal growth factor interactions in human gingival fibroblasts, we introduced the catalytic subunit of human telomerase into human gingival fibroblasts, thereby generating a more long‐lived cellular model. These cells were characterized and evaluated for lipopolysaccharide/epidermal growth factor responsiveness and regulation of epidermal growth factor‐dependent pathways.Results:  Comparison of human telomerase‐transduced gingival fibroblasts with human gingival fibroblasts revealed that both cell lines exhibit a spindle‐like morphology and express similar levels of epidermal growth factor receptor, CD14 and Toll‐like receptors 2 and 4. Importantly, human telomerase‐transduced gingival fibroblasts proliferation rates are increased 5–9 fold over human gingival fibroblasts and exhibit a longer life span in culture. In addition, human telomerase‐transduced gingival fibroblasts and human gingival fibroblasts exhibit comparable profiles of mitogen‐activated protein kinase kinase (extracellular signal‐regulated kinase 1/2) activation upon epidermal growth factor or P. gingivalis lipopolysaccharide administration. Interestingly, treatment with P. gingivalis lipopolysaccharide leads to a down‐regulation of epidermal growth factor‐dependent extracellular signal‐regulated kinase 1/2, p38 and cyclic‐AMP response element binding protein phosphorylation in both cell types.Conclusion:  These studies demonstrate that human telomerase‐transduced gingival fibroblasts exhibit an extended life span and recapitulate human gingival fibroblasts biology. Moreover, this system has allowed for the first demonstration of lipopolysaccharide down‐regulation of epidermal growth factor activated pathways in human gingival fibroblasts and should facilitate the analysis of signaling events relevant to the pathogenesis and treatment of periodontitis.
The effects of RANTES/CCR5 promoter polymorphisms on HIV disease progression in HIV‐infected Koreans
Authors: Jang D. H. , Choi B.‐S. , Kim S. S. 
Published: January 2008

SummaryRecent studies have reported that two single nucleotide polymorphisms (SNPs) in the RANTES gene promoter region, –403G/A and –28C/G, are associated with a slower rate of decline in CD4+ T‐cell number, whereas genetic polymorphisms within the CCR5 promoter are linked to acceleration of AIDS progression. In this study, we investigated the distribution of SNPs in the RANTES and CCR5 promoters and the association between these SNPs and HIV‐1 disease progression in HIV‐infected Koreans. Twenty‐seven long‐term non‐progressors (LTNPs), 29 AIDS patients and 39 HIV‐uninfected persons were enrolled in this study. SNPs for the RANTES and CCR5 promoters were determined by polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP) and a direct sequencing method. In the analysis of RANTES promoter polymorphisms, the genotypic and allelic frequencies of the RANTES –28G mutation were significantly lower in HIV‐infected patients than in HIV‐uninfected persons (P = 0.005 and P = 0.001, respectively). The genotypic frequencies of RANTES –28G and –403A mutations did not differ significantly between LTNPs and AIDS patients. The frequencies of three CCR5 promoter polymorphisms, designated 59029 G/A, 59353T/C, and 59402G/A, did not differ significantly between HIV‐uninfected and HIV‐infected patients. However, the allelic frequency of CCR559353C was significantly higher in AIDS patients than in LTNPs (P = 0.003). These results suggest that RANTES‐28G and CCR5 59353C mutations might be associated with HIV infection or pathogenesis in the Korean population.
Diagnosing the site of gamma-ray burst prompt emission with spectral cut-off energy
Authors: Gupta Nayantara , Zhang Bing 
Published: January 2008

Abstract
The site and mechanism of gamma-ray burst (GRB) prompt emission is still unknown. Although internal shocks have been widely discussed as the emission site of GRBs, evidence supporting other emission sites, including the closer-in photosphere where the fireball becomes transparent and further-out radii near the fireball deceleration radius where magnetic dissipation may be important, have been also suggested recently. With the successful operation of the GLAST experiment, prompt high-energy emission spectra from many GRBs would be detected in the near future. We suggest that the cut-off energy of the prompt emission spectrum from a GRB depends on both the fireball bulk Lorentz factor and the unknown emission radius from the central engine. If the bulk Lorentz factor could be independently measured (e.g. from early afterglow observations), the observed spectral cut-off energy can be used to diagnose the emission site of gamma-rays. This would provide valuable information to understand the physical origin of GRB prompt emission.
Implications of very rapid TeV variability in blazars
Authors: Begelman Mitchell C. , Fabian Andrew C. , Rees Martin J. 
Published: January 2008

Abstract
We discuss the implications of rapid (few-minute) variability in the TeV flux of blazars, which has been observed recently with the HESS and MAGIC telescopes. The variability time-scales seen in PKS 2155−304 and Mrk 501 are much shorter than inferred light-crossing times at the black hole horizon, suggesting that the variability involves enhanced emission in a small region within an outflowing jet. The enhancement could be triggered by dissipation in part of the black hole magnetosphere at the base of the outflow, or else by instabilities in the jet itself. By considering the energetics of the observed flares, along with the requirement that TeV photons escape without producing pairs, we deduce that the bulk Lorentz factors in the jets must be ≳50. The distance of the emission region from the central black hole is less well-constrained. We discuss possible consequences for multi-wavelength observations.
Dielectronic recombination and stability of warm gas in active galactic nuclei
Authors: Chakravorty Susmita , Kembhavi Ajit K. , Elvis Martin , Ferland Gary , Badnell N. R. 
Published: January 2008

Abstract
Understanding the thermal equilibrium (stability) curve may offer insights into the nature of the warm absorbers often found in active galactic nuclei. Its shape is determined by factors such as the spectrum of the ionizing continuum and the chemical composition of the gas. We find that the stability curves obtained under the same set of the above-mentioned physical factors, but using recently derived dielectronic recombination rates, give significantly different results, especially in the regions corresponding to warm absorbers, leading to different physical predictions. Using the current rates we find a larger probability of having a thermally stable warm absorber at 105 K than previous predictions and also a greater possibility for its multiphase nature. The results obtained with the current dielectronic recombination rate coefficients are more reliable because the warm absorber models along the stability curve have computed coefficient values, whereas previous calculations relied on guessed averages for these because of a lack of available data.
An observation of a mutual event between two satellites of Uranus
Authors: Hidas M. G. , Christou A. A. , Brown T. M. 
Published: January 2008

Abstract
We present observations of the occultation of Umbriel by Oberon on 2007 May 4. We believe this is the first observed mutual event between satellites of Uranus. Fitting a simple geometric model to the light curve, we measure the mid-event time with a precision of 4 s. We assume previously measured values for the albedos of the two satellites, and measure the impact parameter to be 500 ± 80 km. These measurements are more precise than estimates based on current ephemerides for these satellites. Therefore observations of additional mutual events during the 2007–2008 Uranian equinox will provide improved estimates of their orbital and physical parameters.
Rural‐Urban Differences in Substance Use Among African‐American Adolescents
Authors: Gibbons Frederick X. , Reimer Rachel A. , Gerrard Meg , Yeh Hsiu‐Chen , Houlihan Amy E. , Cutrona Carolyn , Simons Ron , Brody Gene 
Published: January 2008

ABSTRACT:
Purpose: To examine substance use differences among African‐American adolescents living in rural and more urban areas in Iowa and Georgia and factors thought to be related to those differences. Specifically, negative affect and perceived availability were examined as mediators of the relation between community size and alcohol, tobacco, and drug use. Methods: In‐home interviews with the adolescents (Time 1: N = 897, Mean age = 10.5) assessed their use, perceived substance availability, and negative affect across 3 waves. Their parents’ use was also assessed. Census data were used to determine community size (rural ≤ 2,500; urban ≥ 2,500). Findings: Perceived substance availability and use were both higher among the more urban adolescents. As expected, negative affect was a primary antecedent to use at each wave. Structural Equation Modeling indicated that the relation between population and use was mediated by perceived availability of the substances. Additional multigroup analyses indicated that the relations between negative affect and use were significantly stronger among the urban adolescents at all waves. Conclusions: Results suggest that stress or negative affect is an important antecedent to use among African‐American adolescents, especially when it occurs at an early age, but living in rural areas may be a buffer for both problems, in part, because exposure to this type of risk is lower in these environments.
Research on Rural Residence and Access to Drug Abuse Services: Where Are We and Where Do We Go?
Authors: Borders Tyrone F. , Booth Brenda M. 
Published: January 2008

ABSTRACT:
Context: Illicit drug use is common in rural areas, but very little research has investigated rural populations' access to drug abuse services. Purpose: To describe the current state of the scientific literature on access to drug abuse services in rural areas and suggest directions for future research. Methods: We performed a literature review of published articles on rural drug abuse services and summarized the findings according to potential, realized, accommodating, and acceptable access. Relevant articles on rural access to medical, alcohol, and mental health care were selected to supplement the scarce literature specific to drug abuse. Findings: A limited body of work indicates that rural populations have lower availability and utilize needed drug abuse services less frequently than their urban counterparts. Even less is known about the accommodation and acceptability of drug abuse programs serving rural populations. Conclusions: Research that investigates the existence and determinants of problems with access to drug abuse services is greatly needed to enable policy makers, drug treatment managers, and practitioners to better meet the needs of their rural clientele. As this field of inquiry advances, methodologies for constructing drug abuse service areas and measuring consumers' evaluations must be developed.
Social biology of rodents
Authors: WOLFF Jerry O. 
Published: January 2008

AbstractHerein, I summarize some basic components of rodent social biology. The material in this paper is summarized and condensed from a recent book “Rodent Societies: An Ecological and Evolutionary Perspective” edited by J. O. Wolff and P. W. Sherman (2007). I describe the four basic spacing patterns and illustrate how female territoriality is a function of offspring defense and male mating tactics are a function of female defensibility. The vulnerability of young to infanticide shapes female spacing and mating behavior. Food does not appear to be a defensible resource for rodents, except for those species that larder hoard nonperishable items such as seeds. Philopatry and the formation of kin groups result in genetic sub‐structuring of the population, which in turn affects effective population size and genetic diversity. Dispersal is male biased and typically involves emigration from the maternal site to avoid female relatives and to seek unrelated mates. Scent marking is a major form of communication and is used in reproductive competition and to assess prospective mates, but it is also eavesdropped by predators to locate prey. Females do not appear to alter the sex ratio of litters in response to maternal condition but among arvicoline rodents daughters appear to be favored in spring and sons in autumn. Rodents are relatively monomorphic; however, females tend to be larger than males in the smallest species and smaller in the larger species. Predation risk results from an interaction among foraging time and vulnerability and in turn affects behavioral and life history characteristics.
Reproduction and population dynamics of Mastomys natalensis Smith, 1834 in an agricultural landscape in the Western Usambara Mountains, Tanzania
Authors: MAKUNDI Rhodes H. , MASSAWE Apia W. , MULUNGU Loth S. 
Published: January 2008

AbstractThe multimammate rat, Mastomys natalensis Smith 1834, is a dominant species in agro‐ecosystems in Sub‐Saharan Africa, but adapts quickly to changes in non‐agricultural landscape, particularly woodlands and forests. In this study we report on reproduction and population dynamics of M. natalensis in deforested high elevation localities in the Usambara Mountains, north‐east Tanzania. We conducted Capture‐Mark‐Recapture studies in 2002‐2004, and established that reproduction of M. natalensis takes place in the extended wet season between February and June, and the population density peaks in June‐August. Reproduction cease in July to January and population density drops from July onwards. Reproduction and population density fluctuations are linked to the duration and amount of rainfall. In years when rainfall was below average and the wet season was short, the population density was significantly lower (below 10 animals/ha and 60 animals/ha in 2003 and 2004 respectively, compared to >100 animals/ha in 2002 when rainfall was above the seasonal average) (Fdf 2,13= 9.092, p < 0.01 for in between years variations and Fdf 12,15= 5.389, p < 0.01 for effect of cumulative annual rainfall on population density). These densities were much lower than in the lowland savannah habitats in central and southwest Tanzania. A comparison between the farmland/fallow mosaic fields and agro–forestry areas showed higher population densities in the former, which have similarities to the preferred habitats in the lowland savannahs. The increasing abundance of M. natalensis in the Usambara could have some consequences: M. natalensis is major pest and is involved in the plague cycle in the western Usambara Mountains. Mastomys natalensis is also a strong competitor and the impact on endemic rodent species, e.g. Lophuromys flavopunctatus and Praomys delectorum is unknown.
Correlating rodent community structure with ecological integrity, Tussen‐die‐Riviere Nature Reserve, Free State province, South Africa
Authors: AVENANT Nico L. , CAVALLINI Paolo 
Published: January 2008

AbstractRodents form a vital component of Free State ecosystems and monitoring them may be a relatively quick and inexpensive method of indicating healthy or unhealthy ecosystem functioning. Using removal trapping, we have studied rodent seasonal abundance, species richness, Shannon diversity, and evenness of rodents in four habitats in the Tussen‐die‐Riviere Nature Reserve, inspected the most successful sampling method for these habitats, and report on their community structure and how it is related to an Ecological Index (≅ EI value of grassland). Both species richness and Shannon diversity increased significantly with EI value. The indicator species Mastomys coucha occurred at all plots, but contributed the largest proportion of the total captures (ca. 80%) at the plot with lowest EI value. Other results important for small mammal monitoring and collecting are that trap success and species richness was highest in autumn. This study also confirms that four days and nights continuous trapping is essential for the effective sampling of rodent communities in Free State grasslands. Our results partially support expectations that the number of specialist species increases with succession, M. coucha dominance acts as an indicator of habitat disturbance, rodent species richness conforms to Tilman's hump‐shaped curve model, and adds to a baseline of diversity indices in a variety of grassland habitats.
Pathogen evolution across the agro‐ecological interface: implications for disease management
Authors: Burdon Jeremy J. , Thrall Peter H. 
Published: January 2008

AbstractInfectious disease is a major causal factor in the demography of human, plant and animal populations. While it is generally accepted in medical, veterinary and agricultural contexts that variation in host resistance and pathogen virulence and aggressiveness is of central importance to understanding patterns of infection, there has been remarkably little effort to directly investigate causal links between population genetic structure and disease dynamics, and even less work on factors influencing host–pathogen coevolution. The lack of empirical evidence is particularly surprising, given the potential for such variation to not only affect disease dynamics and prevalence, but also when or where new diseases or pathotypes emerge. Increasingly, this lack of knowledge has led to calls for an integrated approach to disease management, incorporating both ecological and evolutionary processes. Here, we argue that plant pathogens occurring in agro‐ecosystems represent one clear example where the application of evolutionary principles to disease management would be of great benefit, as well as providing model systems for advancing our ability to generalize about the long‐term coevolutionary dynamics of host–pathogen systems. We suggest that this is particularly the case given that agro‐ecological host–pathogen interactions represent a diversity of situations ranging from those that only involve agricultural crops through to those that also include weedy crop relatives or even unrelated native plant communities. We begin by examining some of the criteria that are important in determining involvement in agricultural pathogen evolution by noncrop plants. Throughout we use empirical examples to illustrate the fact that different processes may dominate in different systems, and suggest that consideration of life history and spatial structure are central to understanding dynamics and direction of the interaction. We then discuss the implications that such interactions have for disease management in agro‐ecosystems and how we can influence those outcomes. Finally, we identify several major gaps where future research could increase our ability to utilize evolutionary principles in managing disease in agro‐ecosystems.
The great opportunity: Evolutionary applications to medicine and public health
Authors: Nesse Randolph M. , Stearns Stephen C. 
Published: January 2008

AbstractEvolutionary biology is an essential basic science for medicine, but few doctors and medical researchers are familiar with its most relevant principles. Most medical schools have geneticists who understand evolution, but few have even one evolutionary biologist to suggest other possible applications. The canyon between evolutionary biology and medicine is wide. The question is whether they offer each other enough to make bridge building worthwhile. What benefits could be expected if evolution were brought fully to bear on the problems of medicine? How would studying medical problems advance evolutionary research? Do doctors need to learn evolution, or is it valuable mainly for researchers? What practical steps will promote the application of evolutionary biology in the areas of medicine where it offers the most? To address these questions, we review current and potential applications of evolutionary biology to medicine and public health. Some evolutionary technologies, such as population genetics, serial transfer production of live vaccines, and phylogenetic analysis, have been widely applied. Other areas, such as infectious disease and aging research, illustrate the dramatic recent progress made possible by evolutionary insights. In still other areas, such as epidemiology, psychiatry, and understanding the regulation of bodily defenses, applying evolutionary principles remains an open opportunity. In addition to the utility of specific applications, an evolutionary perspective fundamentally challenges the prevalent but fundamentally incorrect metaphor of the body as a machine designed by an engineer. Bodies are vulnerable to disease – and remarkably resilient – precisely because they are not machines built from a plan. They are, instead, bundles of compromises shaped by natural selection in small increments to maximize reproduction, not health. Understanding the body as a product of natural selection, not design, offers new research questions and a framework for making medical education more coherent. We conclude with recommendations for actions that would better connect evolutionary biology and medicine in ways that will benefit public health. It is our hope that faculty and students will send this article to their undergraduate and medical school Deans, and that this will initiate discussions about the gap, the great opportunity, and action plans to bring the full power of evolutionary biology to bear on human health problems.
Evolutionary concepts in predicting and evaluating the impact of mass chemotherapy schistosomiasis control programmes on parasites and their hosts
Authors: Webster Joanne P. , Gower Charlotte M. , Norton Alice J. 
Published: January 2008

SummarySchistosomiasis is a parasitic disease of significant medical and veterinary importance in many regions of the world. Recent shifts in global health policy have led towards the implementation of mass chemotherapeutic control programmes at the national scale in previously ‘neglected’ countries such as those within sub‐Saharan Africa. Evolutionary theory has an important role to play in the design, application and interpretation of such programmes. Whilst celebrating the rapid success achieved to date by such programmes, in terms of reduced infection prevalence, intensity and associated human morbidity, evolutionary change in response to drug selection pressure may be predicted under certain circumstances, particularly in terms of the development of potential drug resistance, evolutionary changes in parasite virulence, transmission and host use, and/or competitive interactions with co‐infecting pathogens. Theoretical and empirical data gained to date serve to highlight the importance of careful monitoring and evaluation of parasites and their hosts whenever and wherever chemotherapy is applied and where parasite transmission remains.