bluuebunny/crossref_metadata_2025 huggingface dataset:
Assembly and Disassembly of the Capsid-Like External Scaffold of Immature Virions during Vaccinia Virus Morphogenesis
Authors: Bisht Himani , Weisberg Andrea S. , Szajner Patricia , Moss Bernard
Published: July 2009

Infectious poxvirus particles are unusual in that they are brick shaped and lack symmetry. Nevertheless, an external honeycomb lattice comprised of a capsid-like protein dictates the spherical shape and size of immature poxvirus particles. In the case of vaccinia virus, trimers of 63-kDa D13 polypeptides form the building blocks of the lattice. In the present study, we addressed two questions: how D13, which has no transmembrane domain, associates with the immature virion (IV) membrane to form the lattice structure and how this scaffold is removed during the subsequent stage of morphogenesis. Interaction of D13 with the A17 membrane protein was demonstrated by immunoaffinity purification and Western blot analysis. In addition, the results of immunogold electron microscopy indicated a close association of A17 and D13 in crescents, as well as in vesicular structures when crescent formation was prevented. Further studies indicated that binding of A17 to D13 was abrogated by truncation of the N-terminal segment of A17. The N-terminal region of A17 was also required for the formation of crescent and IV structures. Disassembly of the D13 scaffold correlated with the processing of A17 by the I7 protease. When I7 expression was repressed, D13 was retained on aberrant virus particles. Furthermore, the morphogenesis of IVs to mature virions was blocked by mutation of the N-terminal but not the C-terminal cleavage site on A17. Taken together, these data indicate that A17 and D13 interactions regulate the assembly and disassembly of the IV scaffold.
Mouse Adenovirus Type 1-Induced Breakdown of the Blood-Brain Barrier
Authors: Gralinski Lisa E. , Ashley Shanna L. , Dixon Shandee D. , Spindler Katherine R.
Published: July 2009

Infection with mouse adenovirus type 1 (MAV-1) results in fatal acute encephalomyelitis in susceptible mouse strains via infection of brain endothelial cells. Wild-type (wt) MAV-1 causes less brain inflammation than an early region 3 (E3) null virus in C57BL/6 mice. A mouse brain microvascular endothelial cell line infected with wt MAV-1 had higher expression of mRNAs for the proinflammatory chemokines CCL2 and CCL5 than mock- and E3 null virus-infected cells. Primary mouse brain endothelial cells infected with wt virus had elevated levels of CCL2 compared to mock- or E3 null virus-infected cells. Infection of C57BL/6 mice with wt MAV-1 or the E3 null virus caused a dose-dependent breakdown of the blood-brain barrier, primarily due to direct effects of virus infection rather than inflammation. The tight junction proteins claudin-5 and occludin showed reduced surface expression on primary mouse brain endothelial cells following infection with either wt MAV-1 or the E3 null virus. mRNAs and protein for claudin-5, occludin, and zona occludens 2 were also reduced in infected cells. MAV-1 infection caused a loss of transendothelial electrical resistance in primary mouse brain endothelial cells that was not dependent on E3 or on MAV-1-induced CCL2 expression. Taken together, these results demonstrate that MAV-1 infection caused breakdown of the blood-brain barrier accompanied by decreased surface expression of tight junction proteins. Furthermore, while the MAV-1-induced pathogenesis and inflammation were dependent on E3, MAV-1-induced breakdown of the blood-brain barrier and alteration of endothelial cell function were not dependent on E3 or CCL2.
Recruitment of the Transcriptional Coactivator HCF-1 to Viral Immediate-Early Promoters during Initiation of Reactivation from Latency of Herpes Simplex Virus Type 1
Authors: Whitlow Zackary W. , Kristie Thomas M.
Published: July 2009

The transcriptional coactivator host cell factor 1 (HCF-1) is critical for the expression of immediate-early (IE) genes of the alphaherpesviruses herpes simplex virus type 1 (HSV-1) and varicella-zoster virus. HCF-1 may also be involved in the reactivation of these viruses from latency as it is sequestered in the cytoplasm of sensory neurons but is rapidly relocalized to the nucleus upon stimulation that results in reactivation. Here, chromatin immunoprecipitation assays demonstrate that HCF-1 is recruited to IE promoters of viral genomes during the initiation of reactivation, correlating with RNA polymerase II occupancy and IE expression. The data support the model whereby HCF-1 plays a pivotal role in the reactivation of HSV-1 from latency.
Distinctive Effects of the Epstein-Barr Virus Family of Repeats on Viral Latent Gene Promoter Activity and B-Lymphocyte Transformation
Authors: Ali Ahmed K. M. , Saito Satoru , Shibata Sachiko , Takada Kenzo , Kanda Teru
Published: July 2009

The Epstein-Barr virus (EBV), a human B-lymphotropic gamma herpesvirus, contains multiple repetitive sequences within its genome. A group of repetitive sequences, known as the family of repeats (FR), contains multiple binding sites for the viral
trans
-acting protein EBNA-1. The FR sequences are important for viral genome maintenance and for the regulation of the promoter involved in viral latent gene expression. It has been reported that a palindromic sequence with a putative secondary structure exists at the 3′ end of the FR in the genome of the EBV B95-8 strain and that this palindromic sequence has been deleted from the FR of the commonly used EBV miniplasmids. For the first time, we cloned an EBV B95-8 DNA fragment containing the full-length FR, which enabled us to examine the functional difference between full-length and deleted FRs. The full-length FR, like the deleted FR, functioned as a transcriptional enhancer of the viral latent gene promoter, but that transactivation was significantly attenuated in the case of the full-length FR. No significant enhancement of replication was observed when the deleted FR was replaced with the full-length FR in an EBV miniplasmid. By contrast, when the same set of FR sequences were tested in the context of the complete EBV genome, the full-length FR resulted in more-efficient B-cell transformation than the deleted FR. We propose that the presence of the full-length FR contributes to the precise regulation of the viral latent promoter and increases the efficiency of B-cell transformation.
Viral Persistence and Chronic Immunopathology in the Adult Central Nervous System following Coxsackievirus Infection during the Neonatal Period
Authors: Feuer Ralph , Ruller Chelsea M. , An Naili , Tabor-Godwin Jenna M. , Rhoades Ross E. , Maciejewski Sonia , Pagarigan Robb R. , Cornell Christopher T. , Crocker Stephen J. , Kiosses William B. , Pham-Mitchell Ngan , Campbell Iain L. , Whitton J. Lindsay
Published: July 2009

Coxsackieviruses are significant human pathogens, and the neonatal central nervous system (CNS) is a major target for infection. Despite the extreme susceptibility of newborn infants to coxsackievirus infection and viral tropism for the CNS, few studies have been aimed at determining the long-term consequences of infection on the developing CNS. We previously described a neonatal mouse model of coxsackievirus B3 (CVB3) infection and determined that proliferating stem cells in the CNS were preferentially targeted. Here, we describe later stages of infection, the ensuing inflammatory response, and subsequent lesions which remain in the adult CNS of surviving animals. High levels of type I interferons and chemokines (in particular MCP-5, IP10, and RANTES) were upregulated following infection and remained at high levels up to day 10 postinfection (p.i). Chronic inflammation and lesions were observed in the hippocampus and cortex of surviving mice for up to 9 months p.i. CVB3 RNA was detected in the CNS up to 3 months p.i at high abundance (∼106genomes/mouse brain), and viral genomic material remained detectable in culture after two rounds of in vitro passage. These data suggest that CVB3 may persist in the CNS as a low-level, noncytolytic infection, causing ongoing inflammatory lesions. Thus, the effects of a relatively common infection during the neonatal period may be long lasting, and the prognosis for newborn infants recovering from acute infection should be reexplored.
Is cancer risk of radiation workers larger than expected?
Authors: Jacob P , Rühm W , Walsh L , Blettner M , Hammer G , Zeeb H
Published: July 2009

Occupational exposures to ionising radiation mainly occur at low-dose rates and may accumulate effective doses of up to several hundred milligray.

The objective of the present study is to evaluate the evidence of cancer risks from such low-dose-rate, moderate-dose (LDRMD) exposures.

Our literature search for primary epidemiological studies on cancer incidence and mortality risks from LDRMD exposures included publications from 2002 to 2007, and an update of the UK National Registry for Radiation Workers study. For each (LDRMD) study we calculated the risk for the same types of cancer among the atomic bomb survivors with the same gender proportion and matched quantities for dose, mean age attained and mean age at exposure. A combined estimator of the ratio of the excess relative risk per dose from the LDRMD study to the corresponding value for the atomic bomb survivors was 1.21 (90% CI 0.51 to 1.90).

The present analysis does not confirm that the cancer risk per dose for LDRMD exposures is lower than for the atomic bomb survivors. This result challenges the cancer risk values currently assumed for occupational exposures.
Environmental Factors Influencing the Distribution of Juvenile Groundfish in Nearshore Habitats of Southwest Nova Scotia
Authors: Horne John K. , Campana Steven E.
Published: July 2009

Eight nearshore (< 20 m) marine habitats were surveyed to estimate the relative abundance of juvenile groundfish and to assess the environmental variables influencing their distribution. Surveys were conducted as part of a depth-stratified, random sampling design; at each site a small otter trawl was towed for 15 min at eight stations in each of three depth strata. A suite of 13 environmental variables were measured in association with each tow. A total of 1908 fish from 13 different species were caught at 191 completed trawl stations. Standardized centered principal components analysis, orthogonally rotated factor analysis, and detrended correspondence analysis (DCA) were used to delineate aggregations in the abundance data. DCA coupled with stepwise multiple regression best resolved the species' distributions and dominant gradients in the environment. The first two DCA axes reflected estuarine to coastal gradients (68% of the variance) and significant environmental variables were plotted as vectors in the ordination diagram. An estuarine assemblage of species, characterized by winter flounder (Pseudopleuronectes americanus) and white hake (Urophycis tenuis), was associated with waters that were warmer, less saline, more turbid, and overlying a finer grained substrate, than a coastal assemblage of species which included cod (Gadus morhua) and rock gunnel (Pholis gunnellus). The biologically significant gradients corresponded to those which dominated variation in the physical environment.
Phosphorus–Limited Growth Dynamics of Lotic Periphytic Diatom Communities: Areal Biomass and Cellular Growth Rate Responses
Authors: Bothwell Max L.
Published: July 2009

Three long-term phosphate enrichment experiments were conducted at the Experimental Troughs Apparatus (EXTRA), South Thompson River British Columbia to determine the relationship between external orthophosphate (PO43−) concentration and peak areal biomass (PB) of periphytic diatom communities. Levels of PO43−which saturated PB were two orders of magnitude greater than those required to saturate specific growth rates in thin film periphyton communities of similar taxonomic composition. With PO43−additions between 0.1 to 1.0 μg P∙L−1, PB responded in a hyperbolic fashion, initially increasing rapidly, then showing signs of saturation PB continued to increase in a slow, linear manner above 1.0 μg P∙L−1. Maximum PB (PBmax) was calculated to occur at ca. 28 μg P∙L−1. At higher PO43−concentrations (> 30–50 μg P∙L−1) PB was no longer P limited. Below the saturation point, PB was approximated by a log–linear function of PO43−.
Managing Nonrandomly Varying Fisheries
Authors: Koslow J. Anthony
Published: July 2009

Theoretical studies indicate that constant effort or constant escapement harvest strategies are viable long-term management policies for fisheries influenced by random environmental variability. But the marine environment and fishery recruitment do not characteristically vary randomly: their time series tend to be autocorrelated. I examined the response of a model of an age-structured fish population to these harvest strategies, if recruitment is influenced by periodic variability. Variance in fish yield and the incidence of low stock size increased with both increasing amplitude and period length of environmental forcing. Sensitivity to environmental fluctuations increased sharply at periodicities between one and several times the generation length. Low-risk fisheries, which are subject to little nonrandom recruitment variability, may be satisfactorily managed by either management strategy, although constant effort harvesting provided greater stability to industry with little risk to the fish population. Neither strategy maintained stability in high-risk fisheries with high-amplitude, low-frequency recruitment variability, but a constant escapement policy minimized risk of stock collapse.
Lake Acidification Recovery can be Monitored using Chrysophycean Microfossils
Authors: Dixit Sushil S. , Dixit Aruna S. , Smol John P.
Published: July 2009

Chrysophyte scales in a sediment core from Swan Lake, Sudbury, Ontario were studied to examine their sensitivity for inference of recent lakewater pH change. The study indicates that, corresponding to an increase in metal mining and smelting activity in the Sudbury basin, lake acidification commenced in 1940. However, as a result of reductions in SO2 emissions in the early 1970's, the lake's pH has recovered from its chronic low pH of 4.0 in 1977 to its high of 5.6 in 1987. The chrysophyte-inferred pH recovery mirrors the increase in measured lakewater pH. The study identifies the potential of chrysophytes to document recent pH recovery in soft-water lakes containing undisturbed sediments. The approach offers promise for understanding the response in lakes of poorly buffered regions to decreased atmospheric loadings of SO2 and in establishing and implementing SO2 mitigation standards.
Bio-Socio-Economic Fishery Models: Labour Dynamics and Multi-Objective Management
Authors: Charles Anthony T.
Published: July 2009

Fishery systems involve complex interactions between resource stocks and the people involved in harvesting those stocks. While the population dynamics of fish stocks have received considerable attention in the ecological literature, the dynamics of human communities dependent on the fishery are equally important. Indeed the joint dynamics of the fish stocks and the fishermen must be taken into account in determining appropriate management policies. A bio-socio-economic modelling approach is developed here to incorporate these effects within a multi-objective optimization framework. Fishery labour dynamics are determined by the decisions of individual fishermen with net migration into and out of the fishery (and hence the fishing community) dependent on internal conditions such as per capita incomes and employment rates, as well as on the state of the external economy. The task of fishery management is then one of balancing multiple objectives – such as conservation, income generation, employment, and community stability – subject to fish and fishermen dynamics. Control theory and simulation methods are used to study the bio-socio-economic dynamics of the fishery system and the interactions of multiple management are also discussed.
Effect of Prey Density and Prey Size on Growth and Survival of Juvenile Walleye (Stizostedion vitreum vitreum)
Authors: Fox Michael G.
Published: July 2009

I investigated the influence of food availability on growth and survival of walleye (Stizostedion vitreum vitreum) fry stocked in six fertilized experimental ponds (density 40 fish∙m−3) and reared for 8 wk. Walleye fed largely on chironomid larvae and cyclopoid copepods in weeks 1 and 2, and chironomids thereafter. Prey choice and consumption were strongly influenced by chironomid biomass in the benthos, and to a lesser extent by zoo-plankton density. Weekly length increase of the populations and mean length in week 7 were significantly correlated with chironomid benthic biomass and mean prey length. Chironomid biomass and density of large zoo-plankton together explained 56% of the variation in the weekly population growth rate. Despite obvious food limitation in the second half of the experiment, pond survival rate was not significantly correlated with mean prey density, mean stomach fullness, or percentage of fish with empty stomachs. The results indicate that juvenile walleye growth can be regulated by the density and size of available prey. Prey availability apparently does not regulate short term juvenile walleye survival rates after the period around first feeding.
Factors Influencing Dispersion of Larval Black Flies (Diptera:Simuliidae): Effects of Current Velocity and Food Concentration
Authors: Ciborowski Jan J. H. , Craig Douglas A.
Published: July 2009

Positioning and feeding of Simulium vittatum larvae were studied on a ceramic tile in a flume at three current velocities and two food concentrations. Locomotory activity and drift decreased with increasing current but were independent of food. Using nearest neighbor analysis, we detected significant aggregation at 15 cm∙s−1 that resulted from accumulation of individuals at upstream boundaries. Larvae also aggregated at 43 cm∙s−1, but independently of tile margins. Dispersion was random at 24 cm∙s−1. Gross pattern formation results from individual responses to prevailing flow conditions independently of food concentration. Relative ingestion rates decreased with increasing food concentration, larval size, velocity, and incidence of parasitism. Individual larvae avoided locations directly upstream or downstream of a nearest neighbor at 15 and 24 cm∙s−1 when food concentration was low (0.5 mg∙L−1), but not at higher food levels (3.5 mg∙L−1). These trends were reversed at high velocity. Larvae immediately downstream of neighbors had reduced ingestion rates. Larvae selected positions lateral to others under low food conditions. These animals had greater ingestion rates than did individuals in other locations. Results are consistent with hypotheses of flow disruption and/or food preemption by upstream larvae and of mutually induced beneficial flow between laterally adjacent individuals. Positioning within aggregations reflects complex behavior among conspecifics that varies with the interaction of flow and food concentration.
Foraging Patterns of Nesting and Nonnesting Sunfish (Centrarchidae:Lepomis auritusandL.gibbosus)
Authors: Thorp James H. , Goldsmith Lawrence D. , Polgreen John A. , Mayer Lynn M.
Published: July 2009

We analyzed the gut contents of two species of Centrarchidae (the redbreast sunfish, Lepomis auritus and the pumpkinseed sunfish, L. gibbosus) and compared the diets of nesting and nonnesting individuals (position effect) at dawn and dusk (time effect). Although redbreast and pumpkinseed sunfish differ somewhat in anatomy and ecology, they had similar diets and foraging patterns in Calder Lake. Nesting behavior caused a slight to major reduction in the quantity and diversity of prey eaten. Sunfish, which ate prey from both the benthos and water surface, consumed a higher percentage of benthic prey at dawn in comparison to the proportion taken at dusk. Position influenced the percentage of benthic prey eaten at both times. We explore the possibility that a male nonnesting genotype ("cuckold'' sunfish) might be retained in a population of mostly-nesting sunfish (parentals) because of the former's greater foraging success.
Models of Tag Dynamics with Exchange between Available and Unavailable Populations
Authors: Hilborn Ray
Published: July 2009

Four models of the dynamics of an exploited population of fish are presented, and methods for the estimation of the parameters of each model from a mark recapture experiment are developed. The four models are (1) constant loss rate from the population, (2) constant natural mortality, with time varying fishing mortality proportional to fishing effort, (3) constant natural mortality, and time varying vulnerability to fishing gear, and (4) interchange between a vulnerable population and an invulnerable one, with natural mortality occurring in both populations, but fishing mortality occurring only in one. The parameter estimation methods are developed for a single release group recovered over discrete intervals. Each of these models is applied to tagging data on skipjack tuna (Euthynnus pelamis) in the western tropical Pacific.
Effects of Logging on Size and Age Composition of Juvenile Coho Salmon (Oncorhynchus kisutch) and Density of Presmolts in Southeast Alaska Streams
Authors: Thedinga John F. , Murphy Michael L. , Heifetz Jonathan , Koski K V. , Johnson Scott W.
Published: July 2009

Short-term effects of logging on age composition and size of juvenile coho salmon (Oncorhynchus kisutch) were studied in 18 streams in Southeast Alaska in 1982 and 1983; studies were in old-growth and clear-cut reaches with or without buffer strips. The number of fry (age 0) in summer and winter was proportionately higher in buffered and clear-cut reaches than in old-growth reaches, and all treatments averaged a 20% decrease in fry from summer to winter. Fry length and condition factor were greater for buffered and clear-cut reaches than for old-growth reaches, whereas parr (age 1 and older) size did not differ among treatments. Fry and parr were larger in the southern than in the northern regions and their length and weight were directly related to peripbyton biomass and benthos density. A higher percentage of large [Formula: see text] fry remained in buffered reaches than in clear-cut and old-growth reaches; therefore, the density of fry that were potentially large enough to become smolts the next spring (presmolts) was greater in buffered reaches. The larger fry in buffered and clear-cut reaches compared with old-growth reaches was probably due to earlier fry emergence that resulted from increased water temperature.
Differences in Morphology and Behavior between Juvenile Coho Salmon (Oncorhynchus kisutch) Rearing in a Lake and in its Tributary Stream
Authors: Swain Douglas P. , Holtby L. Blair
Published: July 2009

Juvenile coho salmon (Oncorhynchus kisutch) rear both in Mesachie Lake, B.C., and in its inlet stream. The duration and frequency of aggressive behavior were greater among stream-rearing than lake-rearing juveniles in mirror image stimulation and stream tank tests of agonistic behavior. Lateral displays made up a higher proportion of total behavior among the stream-rearing fish compared with the lake-rearing fish. Lake-type fish had more posteriorly placed pectoral fins, shallower bodies and smaller, less brightly colored dorsal and anal fins than did stream-type fish, even after 2 mo of laboratory rearing in a common environment. Diminished aggression, a shift in aggressive behavior away from lateral displays, a more streamlined shape, and reduced coloration, all appear to be adaptations to a schooling lifestyle in the open waters of the lake.
Predation on Fish Larvae and Eggs by the Hydromedusa Aequorea victoria at a Herring Spawning Ground in British Columbia
Authors: Purcell Jennifer E.
Published: July 2009

The importance of soft-bodied zooplankton as predators of fish eggs and larvae was examined during March–June, 1983 in Kulleet Bay, Vancouver Island, British Columbia. The diet of the jellyfish Aequorea victoria was evaluated by gut content analysis of individually collected specimens. Crustacean zooplankters were eaten in lesser proportion, and larvaceans, fish larvae, hydromedusae, and siphonophores were eaten in greater proportion than their presence in the environment. Numerous herring larvae (Clupea harengus pallasi) were consumed, as well as the larvae of fishes in several other families (primarily Pleuronectidae, Cottidae, Scorpaenidae, Stichaeidae, Pholidae, and Gadidae), and the pelagic eggs of flatfish (Family Pleuronectidae). When herring larvae hatched in mid-March, A. victoria medusae in the bay contained an average of 22 herring larvae each, comprising 48% of all ingested prey. The predation rates on herring and other fish larvae were calculated from the numbers of larvae in A. victoria, the digestion times, and the field densities of medusae and larvae. Accordingly, 4 newly-hatched herring larvae∙m−3∙d−1 (0.7%∙d−1) were consumed by A. victoria but few were eaten after April 5–6. Predation on other fish larvae was [Formula: see text] larvae∙m−3∙d−1 during April 5 to May 3, but was not detectable in samples collected during May 9 to June 7. Other soft-bodied predators (ctenophores, chaetognaths, siphonophores, and other hydromedusae) contained few fish larvae.
Mitochondrial DNA Polymorphism, Population Structure, and Life History Variation in American Shad (Alosa sapidissima)
Authors: Bentzen Paul , Brown Gregory C. , Leggett William C.
Published: July 2009

Restriction endonuclease analysis of mitochondrial DNA (mtDNA) variation was used to assess genetic differentiation and population structure in American shad (Alosa sapidissima) sampled from 14 rivers spanning the native range of the species (Florida to Quebec). Estimated mtDNA sequence divergences among 52 shad surveyed with 16 endonucleases were relatively low (mean 0.2%). The low level of mtDNA variation in shad may be a consequence of population bottlenecks that occurred during Pleistocene glacial maxima. A survey of 243 shad with four enzymes revealed several genotypes that were distributed across the range of the species. Three genotypes, a length variant and two single-enzyme genotypes, exhibited nonrandom, geographically clumped distributions. The distributions of shad mtDNA genotypes may have been influenced primarily by founder effects in the northern (glaciated) part of the range, and gene flow in the southern part of the range. The mtDNA data suggest that differences in the reproductive traits of northern and southern populations of shad, if genetically mediated, are likely to have evolved since the Pleistocene. The results of this study support theoretical predictions that mtDNA analysis is a highly sensitive means of examining population structures.
Assessment of Changes in Lake Water Chemistry in Sudbury Area Lakes since Preindustrial Times
Authors: Dixit Sushil S. , Dixit Aruna S. , Smol John P.
Published: July 2009

Surface (recent) and bottom (pre-1880s) sediment samples from each of 72 Sudbury area lakes were analyzed for diatom valves and chrysophyte scales, and using these microfossils, we inferred changes in lake water pH, [Al], [Ni], conductance, and [Ca]. The study shows that extensive acidification has occurred in presently acidic (pH < 6.0) Sudbury lakes. Inferred [Al] has also increased in these lakes. The region also contains a few naturally acidic lakes; however, even these lakes have acidified further since the bottom sediments were deposited. Lakes that have current measured pH between 6.0 and 7.0 have either declined or increased in inferred pH in the past, whereas all lakes that are presently alkaline (pH > 7.0) have become more alkaline. The increase in inferred [Ni] in most of the study lakes indicates that Ni inputs are mainly atmospheric. Our data suggest that, in general, ion concentrations have increased in Sudbury lakes. The extent of acidification or alkalification in Sudbury lakes was primarily a function of proximity of the lakes to the smelters, orientation of prevailing wind patterns, and differences in watershed geology.
Chemical Responses of Acidic Lakes in the Sudbury, Ontario, Area to Reduced Smelter Emissions, 1981–89
Authors: Keller W. , Pitblado J. Roger , Carbone J.
Published: July 2009

Monitoring of acidic lakes in the Sudbury, Ontario, area showed that general changes in water quality (increases in pH and acid-neutralizing capacity; decreases in concentrations of SO42−, Ca2+, Mg2+, Al, and Mn) have continued through the mid-1980's, following substantial reductions in sulphur emissions from area smelters in the late 1970's. By the late 1980's, these trends had levelled off, or even reversed in some lakes. No general, temporal trends were evident during the 1980's for concentrations of Cu, Ni, or Zn, metals directly associated with the smelter emissions. The widespread water quality improvements seen in lakes of the Sudbury area provide very strong support for the use of source controls to combat aquatic acidification. However, the fact that many Sudbury area lakes are still highly acidic and metal contaminated demonstrates that additional emission controls, which are being implemented, are essential in this region.
Phytoplankton of Sudbury Area Lakes (Ontario) and Relationships with Acidification Status
Authors: Nicholls K. H. , Nakamoto L. , Keller W.
Published: July 2009

Phytoplankton data from samples collected in July 1981 from 111 lakes in the Sudbury area were analyzed by canonical community ordination analysis and other techniques to reveal associations of taxa which were related to environmental gradients among the lakes. Phytoplankton data from a group of seven lakes sampled in the mid-1970's or early 1980's and in the mid-1980's were analyzed for evidence of temporal change. In both data sets, factors related to trophic status and acidification status were inferred to be important controlling variables. For example, desmid genera fell into two general groupings, one typical of clear-water, nutrient-poor, low-alkalinity lakes (e.g. species of Micrasterias, Bambusina, Euastrum, Spondylosium) and the other representing lakes higher in nutrients and alkalinity (e.g. species of Teilingia, Closterium, Xanthidium, Staurastrum). This latter group also included several chlorophytes (Ulothrix, Schroederia, Scenedesmus) and euglenoids (Euglena, Phacus). Well-defined relationships existed between lake alkalinity, pH, and total numbers of phytoplankton taxa. The smaller data set included lakes subjected to recent decreases in acid deposition and corresponding increases in pH over a 10-yr interval, and the increased numbers of phytoplankton taxa were indicative of recovery from earlier acidification.
Changes in Zooplankton during the Experimental Neutralization and Early Reacidification of Bowland Lake Near Sudbury, Ontario
Authors: Keller W. , Yan N. D. , Howell T. , Molot L. A. , Taylor W. D.
Published: July 2009

The zooplankton of Bowland Lake was sampled before and for 6 yr after neutralization of the lake from pH 4.9 to 6.9. Changes in community composition, including decreased abundance of the acidophilic rotifers Keratella taurocephala, Ploesoma lenticulare, and Gastropus stylifer and increased abundance of Keratella cochlearis, Polyarthra sp., and other species, occurred after neutralization. Two crustacean species not previously seen in Bowland Lake, Eubosmina tubicen and Epischura lacustris, became important in the zooplankton in the second and fourth years, respectively, after neutralization. Subsequently, increases in the abundances of K. taurocephala, G. stylifer, and P. lenticulare and decreases in the abundance of E. lacustris occurred during the early reacidification of the lake, when average pH declined to approximately 5.5. Temporal patterns in the total abundances of crustaceans, rotifers, and ciliates appeared linked to biological interactions, including predation by fish and larval Chaoborus, not directly to water quality changes.
Prediction of Lake Trout (Salvelinus namaycush) Presence in Low-Alkalinity Lakes near Sudbury, Ontario
Authors: Conlon Michael , Gunn John M. , Morris J. Robert
Published: July 2009

Surveys of 30 low-alkalinity lake trout (Salvelinus namaycush) lakes near Sudbury, Ontario, were conducted to assess factors that affect lake trout presence under acidification stress. At the time of the surveys the lakes varied widely in pH (4.5–6.9), concentrations of toxic metals (Al 12–300 μg∙L−1), and the status of lake trout populations (extinct–abundant). Fish community structure (species richness, species assemblages) reflected and was readily predicted from measured water quality variables. A PCA factor composed of pH, alkalinity, and conductivity was the variable that best predicted lake trout presence (correct discrimination (> 92%). The results of this study provide managers with easily obtainable predictors for monitoring lake trout status under changing levels of acidic deposition.
Amphibian Distribution with Respect to Pond Water Chemistry near Sudbury, Ontario
Authors: Glooschenko V. , Weller W. F. , Smith P. G. R. , Alvo R. , Archbold J. H. G.
Published: July 2009

Amphibians were present in 118 potential breeding sites 9–66 km northeast and southwest of Sudbury, Ontario. Detailed chemical analyses were done for 38 ponds, and 23 variables were subjected to principal components analysis to summarize the main gradients in pond chemistry. Discriminant analysis using scores of the first three principal components showed that the presence of Rana pipiens, R. clamitans and Hyla crucifer was positively related to buffering status (alkalinity, pH, and other correlated variables); the presence of H. crucifer was also negatively related to atmospheric deposition status (cadmium, nickel, other correlated metals, and sulphate). Discriminant analysis using the original water chemistry variables confirms these general patterns. Two species show relationships with buffering status variables: Rana sylvatica with conductivity and R. clamitans with alkalinity. Three species also show negative correlation with metal levels in pond water: Bufo americanus with nickel, R. clamitans with aluminum, and R. pipiens with zinc. Although most of the species expected do occur in the Sudbury area, the distributions of several species appear related to buffering status and metals present in their immediate environemnt. There were only two observations of Ambystoma maculatum, and low numbers of egg masses were noted for R. sylvatica.
NEUROMODULATION OF EPILEPTIC FOCI IN PATIENTS WITH NON-LESIONAL REFRACTORY MOTOR EPILEPSY
Authors: VELASCO ANA LUISA , VELASCO FRANCISCO , VELASCO MARCOS , MARÍA NÚÑEZ JOSÉ , TREJO DAVID , GARCÍA ISRAEL
Published: July 2009

We report two cases of chronic therapeutic stimulation of epileptic foci localized in motor areas. Case 1 is an adolescent with supplementary motor area seizures whose intracranial recordings showed a right SMA focus. Case 2 is a female teenager with primary motor seizures originating in the right motor cortex in the hand area as shown by her intracranial recordings and cortical mapping. Both had apparently normal MRI. Chronic stimulation of the epileptic focus decreased the number of seizures more than 90% the seizure number while preserving motor function. None of the patients had side effects. Neuromodulation is proposed as a safe, efficient surgical alternative for motor seizure control.
NON-INVASIVE COMPUTERIZED SYSTEM FOR AUTOMATICALLY INITIATING VAGUS NERVE STIMULATION FOLLOWING PATIENT-SPECIFIC DETECTION OF SEIZURES OR EPILEPTIFORM DISCHARGES
Authors: SHOEB ALI , PANG TRUDY , GUTTAG JOHN , SCHACHTER STEVEN
Published: July 2009

Objective: To demonstrate the feasibility of using a computerized system to detect the onset of a seizure and, in response, initiate Vagus nerve stimulation (VNS) in patients with medically refractory epilepsy. Methods: We designed and built a non-invasive, computerized system that automatically initiates VNS following the real-time detection of a pre-identified seizure or epileptiform discharge. The system detects these events through patient-specific analysis of the scalp electroencephalogram (EEG) and electrocardiogram (ECG) signals. Results: We evaluated the performance of the system on 5 patients (A-E). For patients A and B the computerized system initiated VNS in response to seizures; for patients C and D the system initiated VNS in response to epileptiform discharges; and for patient E neither seizures nor epileptiform discharges were observed during the evaluation period. During the 81 hour clinical test of the system on patient A, the computerized system detected 5/5 seizures and initiated VNS within 5 seconds of the appearance of ictal discharges in the EEG; VNS did not seem to alter the electrographic or behavioral characteristics of the seizures in this case. During the same testing session the computerized system initiated false stimulations at the rate of 1 false stimulus every 2.5 hours while the subject was at rest and not ambulating. During the 26 hour clinical test of the system on patient B, the computerized system detected 1/1 seizures and initiated VNS within 16 seconds of the appearance of ictal discharges; VNS did not alter the electrographic duration of the seizure but decreased anxiety and increased awareness during the post-seizure recovery phase. During the same testing session the computerized system did not declare any false detections. Significance: Initiating Vagus nerve stimulation soon after the onset of a seizure may abort or ameliorate seizure symptoms in some patients; unfortunately, a significant number of patients cannot initiate VNS by themselves following the start of a seizure. A system that automatically couples automated detection of seizure onset to initiation of VNS may be helpful for seizure treatment.
CONTROL OF SYNCHRONIZATION OF BRAIN DYNAMICS LEADS TO CONTROL OF EPILEPTIC SEIZURES IN RODENTS
Authors: GOOD LEVI B. , SABESAN SHIVKUMAR , MARSH STEVEN T. , TSAKALIS KOSTAS , TREIMAN DAVID , IASEMIDIS LEON
Published: July 2009

We have designed and implemented an automated, just-in-time stimulation, seizure control method using a seizure prediction method from nonlinear dynamics coupled with deep brain stimulation in the centromedial thalamic nuclei in epileptic rats. A comparison to periodic stimulation, with identical stimulation parameters, was also performed. The two schemes were compared in terms of their efficacy in control of seizures, as well as their effect on synchronization of brain dynamics. The automated just-in-time (JIT) stimulation showed reduction of seizure frequency and duration in 5 of the 6 rats, with significant reduction of seizure frequency (>50%) in 33% of the rats. This constituted a significant improvement over the efficacy of the periodic control scheme in the same animals. Actually, periodic stimulation showed an increase of seizure frequency in 50% of the rats, reduction of seizure frequency in 3 rats and significant reduction in 1 rat. Importantly, successful seizure control was highly correlated with desynchronization of brain dynamics. This study provides initial evidence for the use of closed-loop feedback control systems in epileptic seizures combining methods from seizure prediction and deep brain stimulation.
CALIBRATION OF NEUROTRANSMITTER RELEASE FROM NEURAL CELLS FOR THERAPEUTIC IMPLANTS
Authors: JEDLICKA SABRINA S. , DADARLAT MARIA , HASSELL TRAVIS , LIN YANZHU , YOUNG AARON , ZHANG MIN , IRAZOQUI PEDRO , RICKUS JENNA L.
Published: July 2009

In this work we quantified the in vitro calibration relationships between high frequency electrical stimulation and GABA and glutamate release in both mature retinoic acid differentiated P19 neurons and immortalized embryonic cortical cells engineered to express glutamic acid decarboxylase, GAD65. Extracellular glutamate and GABA was quantified by 2D gas chromatography and time of flight mass spectrometry after stimulation at varying amplitudes and frequencies. Amplitude sweeps resulted in a linear calibration for P19 neurons; the level of neurotransmitter varied over one order of magnitude from ~ 200 pg/neuron to ~ 1.2 ng/neuron for glutamate and ~ 1 ng/neuron to ~ 2 ng/neuron for GABA, depending on the stimulation amplitude. Frequency sweeps resulted in a peak release at 250 Hz for glutamate and 400 Hz for GABA in P19 cells. The GABA transporter inhibitor, nipecotic acid, increased extracellular GABA levels and decrease glutamate. In contrast the embryonic cortical cells had a strongly nonlinear dependency of release on stimulation amplitude, and a weak dependence on frequency. These cells had roughly equal extracellular glutamate and GABA levels after stimulation despite the expression of GAD65. In addition glutamate and GABA levels were insensitive to nipecotic acid. These results demonstrate an ability to calibrate and tune neurotransmitter release from neural cells using high frequency stimulation parameters.
DEEP BRAIN STIMULATION FOR THE TREATMENT OF EPILEPSY
Authors: HAMANI CLEMENT , ANDRADE DANIELLE , HODAIE MOJGAN , WENNBERG RICHARD , LOZANO ANDRES
Published: July 2009

During the last decade, deep brain stimulation (DBS) has been used to treat several neurologic disorders, including epilepsy. Promising results have been reported with stimulation in different brain regions. At present however, several issues remain unanswered. As an example, it is still unclear whether particular seizure types and syndromes should be treated with DBS in different targets or with different stimulation parameters. In addition, clinical, electrophysiological and anatomical features capable of predicting a good postoperative outcome are still unknown. We review the published literature on DBS, cortical and cerebellar stimulation for the treatment of epilepsy focusing predominantly on the rationale and clinical outcome in each target.
AVALANCHES OF BAK–SNEPPEN COEVOLUTION MODEL ON DIRECTED SCALE-FREE NETWORK
Authors: LEE KYOUNG EUN , LEE JAE WOO
Published: July 2009

We study the critical properties of the Bak–Sneppen coevolution model on scale-free networks by Monte Carlo method. We report the distribution of the avalanche size and fractal activity through the branching process. We observe that the critical fitness fc(N) depends on the number of the node such as fc(N) ~ 1/ log (N) for both the scale-free network and the directed scale-free network. Near the critical fitness many physical quantities show power-law behaviors. The probability distribution P(s) of the avalanche size at the critical fitness shows a power-law like P(s) ~ s-τ with τ = 1.53(5) regardless of the scale-free network and the directed scale free network. The probability distribution Pf(t) of the first return time also shows a power-law such as Pf(t) ~ t-τf. The critical exponents τf are equivalent for both the scale-free network and the directed scale-free network. We obtain the critical exponents as τf = 1.776(5) at the scalinge regime. The directionality of the network does not change the universality on the network.
FRACTAL DIMENSION AND LACUNARITY OF TRACTOGRAPHY IMAGES OF THE HUMAN BRAIN
Authors: KATSALOULIS P. , VERGANELAKIS D. A. , PROVATA A.
Published: July 2009

Tractography images produced by Magnetic Resonance Imaging scans have been used to calculate the topology of the neuron tracts in the human brain. This technique gives neuroanatomical details, limited by the system resolution properties. In the observed scales the images demonstrated the statistical self-similar structure of the neuron axons and its fractal dimensions were estimated using the classic Box Counting technique. To assess the degree of clustering in the neural tracts network, lacunarity was calculated using the Gliding Box method. The two-dimensional tractography images were taken from four subjects using various angles and different parts in the brain. The results demonstrated that the average estimated fractal dimension of tractography images is approximately Df = 1.60 with standard deviation 0.11 for healthy human-brain tissues, and it presents statistical self-similarity features similar to many other biological root-like structures.
ESTIMATE OF THE HAUSDORFF MEASURE OF THE SIERPINSKI TRIANGLE
Authors: MÓRA PÉTER
Published: July 2009

It is well-known that the Hausdorff dimension of the Sierpinski triangle Λ is s = log 3/ log 2. However, it is a long standing open problem to compute the s-dimensional Hausdorff measure of Λ denoted by [Formula: see text]. In the literature the best existing estimate is [Formula: see text] In this paper we improve significantly the lower bound. We also give an upper bound which is weaker than the one above but everybody can check it easily. Namely, we prove that [Formula: see text] holds.
CRITICAL PHENOMENON INDUCED BY NOISE IN THE BTW SANDPILE
Authors: CHEN LIUJUN , CHEN WEITING , DI ZENGRU , WANG DAHUI
Published: July 2009

The behavior of sandpile far from self-organized critical states (SOCS) is investigated in this paper. The results indicate that noise plays an important role in the critical phenomenon. The critical phenomena are detected in sandpile far from SOCS when external or internal noise is applied. In contrast to self-organized criticality, the exponent of avalanche distribution in sandpile far from SOCS increases with the distance of the sandpile from SOCS. At the same time, the exponent of avalanche distribution in a sandpile far from SOCS is consistent with some real systems such as earthquake.
GENERALIZED SECANT METHODS AND THEIR FRACTAL PATTERNS
Authors: LIU XIANG-DONG , ZHANG JIN-HAI , LI ZHI-JIE , ZHANG JUN-XING
Published: July 2009

In this paper, a class of generalized secant methods was investigated. The convergence of these methods was discussed, and their striking fractal patterns are generated to represent the chaotic behavior of these methods in the complex plane.
THE ASSOCIATIONS BETWEEN KNEE FLEXION, VERTICAL CENTER-OF-MASS EXCURSIONS AND LOWER-EXTREMITY MUSCLE WORK FOR END-STAGE KNEE OSTEOARTHRITIS
Authors: Mandeville David , Osternig Louis R. , Chou Li-Shan
Published: July 2009

Purpose: The purpose of this study was to assess the association of the knee flexion excursion to the vertical center-of-mass (COM) amplitude and to the lower-extremity muscle work during stance phase for subjects with knee osteoarthritis. Method: Twenty subjects scheduled for total knee replacement and 20 controls performed level walking during standard gait analysis. Dependent variables included stance-phase knee flexion excursion, vertical COM amplitude, and lower-extremity muscle work. Results: Compared to healthy control, subjects with knee osteoarthritis walked with significantly less stance-phase knee flexion and vertical COM excursion. Knee flexion excursion was found to have a strong positive correlation to vertical COM amplitude. The lower-extremity muscle work during single stance phase was found to have a moderate negative correlation to vertical COM amplitude. Conclusions: Osteoarthritis of the knee alters both the stance-phase knee flexion and vertical COM excursions. As these variables show a strong positive relation, efforts to restore stance-phase knee flexion based on the 3rd determinant of gait require a new justification.