bluuebunny/crossref_metadata_2025_split huggingface dataset:
Consequences of low mobility in spatially and temporally heterogeneous ecosystems
Authors: MATLACK GLENN R. , MONDE JOHN 
Published: December 2004

Summary

Spatially explicit landscape models have revealed the importance of spatial arrangement of habitat patches in the behaviour of mobile organisms. Such models fail to account for creation and destruction of habitat, which may interrupt the movement of slowly migrating species such as forest herbs.
To explore the interaction of habitat turnover and population migration, we present a dynamic landscape model inhabited by a dispersing species. The landscape is represented as a square lattice in which individual cells may be either habitat or non‐habitat, and a hypothetical species may spread among habitat cells. Rate of species spread, habitat frequency and habitat clearance and regeneration are allowed to vary.
In static landscapes, the fraction of the landscape occupied by the species is limited by connectivity among habitat patches and rate of population migration. Slow species often cannot reach all available habitat despite the presence of continuous paths to it.
In dynamic landscapes, slow‐moving species show reduced map‐scale frequency and high risk of extinction due to the cumulative effects of habitat patch destruction and the failure to colonize newly created habitat. Such species decline cannot be predicted based on static descriptions of habitat connectivity or migration rate.
Fast‐moving species may be reduced in dynamic landscapes by the cumulative effect of numerous local isolation events. Fast‐moving species may also experience a modest range expansion in low‐connectivity landscapes due to the cumulative effects of short‐lived patch adjacency.
These results suggest a novel mechanism that could account for species impoverishment in fragmented landscapes. They emphasize the importance of maintaining habitat connectivity on a time‐scale that accommodates slow‐migrating species such as forest herbs.
Herbivory influences tree lines
Authors: CAIRNS DAVID M. , MOEN JON 
Published: December 2004

Summary

Transitions between major vegetation types, such as the tree line, are useful systems for monitoring the response of vegetation to climate change. Tree lines have, however, shown equivocal responses to such change.
Tree lines are considered to be primarily thermally controlled, although recent work has highlighted the importance of biotic factors. Dispersal limitation and the invasibility of the tundra matrix have been implicated and here we propose herbivory as an additional control at some tree lines.
We propose a conceptual model in which differing relative impacts of foliage consumption, availability of establishment sites, trampling, dispersal and seed predation can lead to very different tree‐line responses.
The presence of large numbers of small trees above the current tree line at a site in northern Sweden that experiences limited reindeer (Rangifer tarandus) herbivory suggests range expansion. Other locations in the same region with higher reindeer populations have considerably fewer small trees, suggesting that range expansion is occurring much more slowly, if at all.
The use of tree lines as indicators of climate change is confounded by the activity of herbivores, which may either strengthen or nullify the impacts of a changed climate. Similar arguments are likely to be applicable to other ecotones.
Volunteers in Marine Conservation Monitoring: a Study of the Distribution of Seahorses Carried Out in Collaboration with Recreational Scuba Divers
Authors: GOFFREDO STEFANO , PICCINETTI CORRADO , ZACCANTI FRANCESCO 
Published: December 2004

Abstract:
Seahorses ( Hippocampus) live in tropical and temperate waters. Habitat degradation and fishery overexploitation have led to drastic population declines on a global scale. Population monitoring is therefore essential to determine current status and manage conservation. In this first study in Italian waters on the geographic and ecological distribution of the two Mediterranean species, Hippocampus hippocampus and Hippocampus ramulosus, recreational scuba divers were recruited and trained to report sightings. A specially formulated questionnaire was produced and distributed to scuba diving schools and centers. In the 3‐year study, 2536 divers spent 6077 diving hours gathering data and completed 8827 questionnaires. Eight percent of the questionnaires showed seahorse sightings, for a total of 3061 sighted specimens, 68% of which referred to Hippocampus ramulosus. The two species had overlapping geographic distributions. Seahorse abundance varied, with the northern Adriatic Sea showing greatest abundance, followed by the central‐southern Tyrrhenian Sea. Seahorses were rare in the Ligurian and northern Tyrrhenian seas. Preferred habitats were shallow areas with either sandy bottoms or Posidonia oceanica (L.) Delile meadows. Seahorse distribution may be correlated with the degree of degradation of P. oceanica meadows. Resource users (the divers) were willing to take part in biological monitoring and contributed in scientific terms by collecting considerable amounts of data over short time periods and in economic terms by decreasing costs. The greatest limitation with volunteers was the difficulty in obtaining a uniformly distributed sample across time and space. We conclude that recreational divers and other resource users can play an active part in monitoring the marine environment and that the Mediterranean Hippocampus Mission may be used as a model for biodiversity monitoring.
Catastrophic Decline in Mollusc Diversity in Eastern Tasmania and Its Concurrence with Shellfish Fisheries
Authors: EDGAR G.J. , SAMSON C.R. 
Published: December 2004

Abstract:
We used historical patterns of deposition of mollusc shells to infer changes to inshore benthic assemblages in the southeastern Tasmanian region over the past 120 years. We identified and counted shells in slices embedded within 1m long 210Pb‐dated sediment cores were collected at 13 sites in water depths of 8–16 m. Declines in mollusc species richness and shell production occurred during the past century at all sites studied, with a mean decline per 5‐cm sediment slice from 21 species in 1890 to 7 species in 1990 and in shell abundance from 150 to 30 individuals over the same period. The time course of decline notably corresponded with the history of the scallop dredge fishery, presumably either because scallop dredging caused general declines in populations of mollusc species or because other factors caused a catastrophic regional decline in molluscs that included scallops. As a consequence, the fishery was forced to close. Of major concern is that losses had not previously been recognized but extended throughout the 100‐km coastal span of the study. Given that fishing and other anthropogenic impacts, as well as a lack of observational data, are virtually ubiquitous for the coastal zone, major recent losses in mollusc biodiversity may be globally widespread but have gone unnoticed.
Changes in Forest Use Value through Ecological Succession and Their Implications for Land Management in the Peruvian Amazon
Authors: GAVIN MICHAEL C. 
Published: December 2004

Abstract:
Research on local use values of forests across an ecological succession informs land‐use decisions and conservation planning. I evaluated use values of three age classes of secondary forest: fallow fields (<5 years old, $8.20/ha/year), young secondary forest (5–20 years old, $20.60/ha/year), and old secondary forest (>20 years old, $6.80/ha/year). I quantified daily forest product use and calculated use values in dollars per hectare per year for three communities in the northern Peruvian Amazon. I made three comparisons between forest types: number of useful species, value based on different use categories, and overall use values. Old secondary forest had the greatest number of total species present and species collected. Wood, food, and medicine were the three most valuable use categories. The value different families extracted from local forests varied enormously, but median forest values were lower for all forest types than potential gains from agricultural land use (e.g., coffee $167/ha/year). Values of different‐aged stands on privately owned lands in two communities did not differ significantly, whereas in the third community, young secondary forest had a significantly greater value than other forest types. Old secondary forests were the most valuable source of wood products, and wood was the only use category in which there was any difference in the value of products extracted from different‐aged forest stands. The value of all three forest types on open‐access (nonprivate) lands was minimal (mean in each forest type, $0/ha/year). Local people can utilize the valuation results to develop land‐use strategies that balance forest product use, agricultural productivity, and biodiversity conservation.
Response of Savanna Fire Regimes to Changing Fire‐Management Policies in a Large African National Park
Authors: VAN WILGEN B.W. , GOVENDER N. , BIGGS H.C. , NTSALA D. , FUNDA X.N. 
Published: December 2004

Abstract:
Approaches to fire management in the savanna ecosystems of the 2‐million ha Kruger National Park, South Africa, have changed several times over the past six decades. These approaches have included regular and flexible prescribed burning on fixed areas and a policy that sought to establish a lightning‐dominated fire regime. We sought to establish whether changes in management induced the desired variability in fire regimes over a large area. We used a spatial database of information on all fires in the park between 1957 and 2002 to determine elements of the fire regime associated with each management policy. The area that burned in any given year was independent of the management approach and was strongly related to rainfall (and therefore grass fuels) in the preceding 2 years. On the other hand, management did affect the spatial heterogeneity of fires and their seasonal distribution. Heterogeneity was higher at all scales during the era of prescribed burning, compared with the lightning‐fire interval. The lightning‐fire interval also resulted in a greater proportion (72% vs. 38%) of the area burning in the dry season. Mean fire‐return intervals varied between 5.6 and 7.3 years, and variability in fire‐return intervals was strongly influenced by the sequencing of annual rainfall rather than by management. The attempt at creating a lightning‐dominated fire regime failed because most fires were ignited by humans, and the policy has been replaced by a more pragmatic approach that combines flexible prescribed burning with lightning‐ignited fires.
Linkage of Conservation Activity to Trends in the U.S. Economy
Authors: PERGAMS OLIVER R. W. , CZECH BRIAN , HANEY J. CHRISTOPHER , NYBERG DENNIS 
Published: December 2004

Abstract:
As an economy grows, natural capital such as timber, soil, and water is reallocated to the human economy. This conflict between economic growth and biodiversity conservation creates a conundrum for conservation biologists because traditional forms of conservation action require money. We hypothesize that conservation spending in the United States is highly correlated with income and wealth, and we tested whether selected proxies for U.S. conservation activity could be predicted by U.S. economic indicators over time scales of 7–71 years. Stock market indexes (Dow Jones Industrial Average, Standard & Poor's 500 Index), gross domestic product (GDP), and personal income (PI) explained as much as 99% of annual variation in total revenue (including contributions) to four large nongovernmental organizations (NGOs), the World Wildlife Fund, Sierra Club, Environmental Defense, The Nature Conservancy. These broad economic indicators also explained as much as 96% of the annual number of university conservation programs, 83% of membership in professional conservation organizations (Natural Areas Association, Society for Conservation Biology), 93% of national park visitation, and 99+% of national park acreage. In most analyses, the income variables GDP and PI explained more variation in conservation activity than did either of the stock‐market wealth variables. After long‐term growth was removed from the time series, changes in revenues to the four NGOs combined were significantly correlated with GDP but not PI over the short term. Short‐term variation in park acreage was significantly correlated with GDP and PI but lagged both by 3 years. Using linear models based on GDP, we predicted increases of 2.3% in 2003 cumulative NGO revenues and 1.0% in 2006 acreage owned by the National Park Service. The conservation activity parameters we measured may exhibit positive trends even in the face of declining biodiversity, but biodiversity conservation will ultimately require the cessation of economic growth. The challenge to the conservation biology community is to retain a significant presence during and after the cessation of growth.
Understanding the Causes of Disease in European Freshwater Crayfish
Authors: EDGERTON BRETT F. , HENTTONEN PAULA , JUSSILA JAPO , MANNONEN ARI , PAASONEN PIETARI , TAUGBØL TROND , EDSMAN LENNART , SOUTY‐GROSSET CATHERINE 
Published: December 2004

Abstract:
Native European freshwater crayfish (Astacida, Decapoda) are under severe pressure from habitat alteration, the introduction of nonindigenous species, and epizootic disease. Crayfish plague, an acute disease of freshwater crayfish caused by the fungus‐like agent Aphanomyces astaci, was introduced into Europe in the mid‐nineteenth century and is responsible for ongoing widespread epizootic mortality in native European populations. We reviewed recent developments and current practices in the field of crayfish pathology. The severity of crayfish plague has resulted in an overemphasis on it. Diagnostic methods for detecting fungi and fungal‐like agents, and sometimes culturing them, are frequently the sole techniques used to investigate disease outbreaks in European freshwater crayfish. Consequently, the causes of a significant proportion of outbreaks are undetermined. Pathogen groups well known for causing disease in other crustaceans, such as viruses and rickettsia‐like organisms, are poorly understood or unknown in European freshwater crayfish. Moreover, the pathogenic significance of some long‐known pathogens of European freshwater crayfish remains obscure. For effective management of this culturally significant and threatened resource, there is an urgent need for researchers, diagnosticians, and resource managers to address the issue of disease in European freshwater crayfish from a broader perspective than has been applied previously.
Evidence for a Role of the Regulator of G-Protein Signaling Protein CPRGS-1 in Gα Subunit CPG-1-Mediated Regulation of Fungal Virulence, Conidiation, and Hydrophobin Synthesis in the Chestnut Blight Fungus
Cryphonectria parasitica
Authors: Segers Gerrit C. , Regier Jerome C. , Nuss Donald. L. 
Published: December 2004

ABSTRACT

We previously reported that the chestnut blight fungus
Cryphonectria parasitica
expresses at least three G-protein α subunits and that Gα subunit CPG-1 is essential for regulated growth, pigmentation, sporulation, and virulence. We now report the cloning and characterization of a
C. parasitica
regulator of G-protein signaling (RGS) protein, CPRGS-1. The phylogenetic relationship of CPRGS-1 to orthologs from other fungi was inferred and found to be generally concordant with species relationships based on 18S ribosomal sequences and on morphology. However, Hemiascomycotine RGS branch lengths in particular were longer than for their 18S sequence counterparts, which correlates with functional diversification in the signaling pathway. Deletion of
cprgs-1
resulted in reduced growth, sparse aerial mycelium, and loss of pigmentation, sporulation, and virulence. Disruption of
cprgs-1
was also accompanied by a severe posttranscriptional reduction in accumulation of CPG-1 and Gβ subunit CPGB-1 and severely reduced expression of the hydrophobin-encoding gene cryparin. The changes in phenotype, cryparin expression, and CPGB-1 accumulation resulting from
cprgs-1
gene deletion were also observed in a strain containing a mutationally activated copy of CPG-1 but not in strains containing constitutively activated mutant alleles of the other two identified Gα subunits, CPG-2 and CPG-3. Furthermore,
cprgs-1
transcript levels were increased in the activated CPG-1 strain but were unaltered in activated CPG-2 and CPG-3 strains. The results strongly suggest that CPRGS-1 is involved in regulation of Gα subunit CPG-1-mediated signaling and establish a role for a RGS protein in the modulation of virulence, conidiation, and hydrophobin synthesis in a plant pathogenic fungus.
RGD-modified liposomes targeted to activated platelets as a potential vascular drug delivery system
Authors: Gupta Anirban , Huang Guofeng , Lestini Brian , Sagnella Sharon , Kottke-Marchant Kandice , Marchant Roger 
Published: December 2004

SummaryLocal drug delivery has become an important treatment modality for the prevention of thrombotic events following coronary angioplasty. In this study, we investigate the ability of liposomes bearing surface conjugated linear Arg-Gly-Asp (RGD) peptide (GSSSGRGD SPA) moieties to target and bind activated platelets, and the effect of such RGD-modified liposomes on platelet activation and aggregation. The binding of RGD-liposomes to human platelets was assessed by fluorescence microscopy,phase contrast microscopy and flow cytometry. The effect of RGDmodified liposomes on platelet activation and aggregation was investigated in vitro, with and without platelet agonists. RGD-liposomes were found to bind activated platelets at levels significantly greater than the control RGE-liposomes.The RGD-liposomes did not exhibit any statistically significant effect on platelet activation or aggregation.The results demonstrate the ability of the RGD-modified liposomes to target and bind activated platelets without causing significant platelet aggregation and suggests a feasible way for the development of a platelet-targeted anti-thrombogenic drug delivery system. Furthermore, the approach can be extended to the development of liposomes for other vascular targets, for application in drug delivery or gene therapy.
Health worker (internal customer) satisfaction and motivation in the public sector in Ghana
Authors: Agyepong Irene Akua , Anafi Patricia , Asiamah Ebenezer , Ansah Evelyn K. , Ashon Daniel A. , Narh‐Dometey Christiana 
Published: December 2004

AbstractThis paper describes factors affecting health worker motivation and satisfaction in the public sector in Ghana. The data are from a survey of public sector health care providers carried out in January 2002 and repeated in August 2003 using an interviewer administered structured questionnaire. It is part of a continuous quality improvement (CQI) effort in the health sector in the Greater Accra region of Ghana. Workplace obstacles identified that caused dissatisfaction and de‐motivated staff in order of the most frequently mentioned were low salaries such that obtaining basic necessities of daily living becomes a problem; lack of essential equipment, tools and supplies to work with; delayed promotions; difficulties and inconveniences with transportation to work; staff shortages; housing, additional duty allowances and in‐service (continuous) training. Others included children's education, vehicles to work with such as ambulances and pickups, staff transfer procedures, staff pre‐service education inadequate for job requirements, and the effect of the job on family and other social factors. There were some differences in the percentages of staff selecting a given workplace obstacle between the purely rural districts, the highly urbanized Accra metropolis and the districts that were a mixture of urbanized and rural. It is unlikely that the Ghana Health Service can provide high quality of care to its end users (external customers) if workplace obstacles that de‐motivate staff (internal customers) and negatively influence their performance are not properly recognized and addressed as a complex of inter‐related problems producing a common result—dissatisfied poorly motivated staff and resulting poor quality services. Copyright © 2004 John Wiley & Sons, Ltd.
A validated liquid chromatographic/tandem mass spectrometric method for the determination of phencyclidine in microliter samples of rat serum
Authors: Hendrickson Howard P. , Whaley E. Cathrine , Owens S. Michael 
Published: December 2004

AbstractA liquid chromatographic/tandem mass spectrometric method is described for the determination of phencyclidine (PCP) in small volumes of rat serum (e.g. 50 µl). Samples were extracted using a mixed‐mode strong cation‐exchange column and then separated isocratically using a narrow‐bore (2.1 mm i.d.) 3 µm Hypersil phenyl column and a mobile phase consisting of an ammonium formate buffer (pH 2.7) with 60% (v/v) methanol. Detection was accomplished using positive ion electrospray ionization in the multiple reaction monitoring mode. Mass spectra were obtained and peaks were observed at an m/z (% abundance) of 244 (100), 159 (25), and 86 (89). Tandem mass spectra were also obtained from the m/z 244 precursor ion with peaks observed at m/z 159 (100), 86 (96), and 91 (11). Optimum serum PCP sensitivity and precision were obtained at a transition of m/z 244 → 159. Matrix‐associated ion suppression did not significantly affect the accuracy (100–112%) or precision (CV ≤8%) of the assay. The lower limit of quantitation was 1 ng ml−1 in 50 µl of serum. The method was used to study the serum pharmacokinetics of PCP in rats after an intravenous bolus dose of PCP. Copyright © 2004 John Wiley & Sons, Ltd.
Novel Biodegradable Polymers as Gene Carriers
Authors: Yang Yuan , Jia Wenxiang , Qi Xin , Yang Chun , Liu Li , Zhang Zairong , Ma Juhui , Zhou Shaobing , Li Xiaohong 
Published: December 2004

AbstractSummary: This study investigated two new biodegradable polymers as gene controlled‐released coatings for gene transfer. Poly(ethylene glycol)‐co‐poly(D,L‐lactic acid) (PELA) and poly(ethylene glycol)‐co‐poly(lactic acid)‐co‐poly(glycolic acid) random copolymer (PELGA) were synthesized and used as microspheres matrices with encapsulated plasmid pCH110. The plasmid loading efficiency, cytotoxicity, transfection efficiency and in vitro degradation and release profiles of microsphere complexes were evaluated in details. The biodegradable polymers showed high DNA loading efficiency and low cytotoxicity as gene controlled‐released coatings, and the poly(ethylene glycol) (PEG) contents of polymer matrices influenced the diameter, loading efficiency and transfection efficiency of plasmid DNA within the microspheres. The average diameters of PELA and PELGA microspheres were between 0.5 and 1.5 μm, and the plasmid loading efficiency was 62 and 73% for PELA and PELGA microspheres with 10% PEG content, respectively. In vitro testing showed a gradual release profile of DNA from polymeric matrices. The polymers/DNA microspheres had high transfection efficiency and early gene expression and maintenance of gene expression level for up to 96 h, although transfection efficiency were slightly lower than that of liposome in the initial 24 h. The biodegradable polymeric materials possess potential superiority as gene carriers.Percent release of DNA from PELA and PELGA microspheres with 10% PEG content in vitro.magnified imagePercent release of DNA from PELA and PELGA microspheres with 10% PEG content in vitro.