bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical and Virological Characteristics of Hepatitis B Virus Subgenotypes Ba, C1, and C2 in China
Authors: Wang Zhanhui , Tanaka Yasuhito , Huang Yuehua , Kurbanov Fuat , Chen Jinjun , Zeng Guobing , Zhou Bin , Mizokami Masashi , Hou Jinlin
Published: March 2007

Hepatitis B virus (HBV) subgenotypes Ba, C1 (Cs), and C2 (Ce) are the most prevalent HBV variants in China. To investigate the virological characteristics of these subgenotypes and their clinical implications, we enrolled a cohort of 211 patients in the Guangdong Province of China, including 132 with chronic hepatitis B virus infection (CH), 32 with liver cirrhosis (LC), and 47 with hepatocellular carcinoma (HCC) according to clinical examination, liver function test, and ultrasonograph results. Overall, HBV Ba was found in 51.2% (108/211), HBV C1 in 33.6% (71/211), and HBV C2 in 15.2% (32/211) of the cases. The distribution of HBV genotype C was greater among patients in the LC and HCC groups than among patients in the CH group, while the distribution of HBV genotype B was greater among the CH patients than among the LC and HCC patients. No significant differences in clinical features were found among patients with HBV Ba, C1, and C2. Virologically, HBV C1 had the strongest association with the A1762T G1764A double mutation, while the mutation at position 1896 resulting in A (1896A) was uncommon. In contrast, HBV Ba had the highest frequency of 1896A but the lowest of A1762T G1764A, and HBV C2 had intermediate frequencies of these mutations. Mutations of 1653T and 1753V were specifically associated with HBV C2 and C1, respectively. Multivariate analyses showed that the 1653T, 1753V, and A1762T G1764A mutations and patient age significantly increased the risk of HCC development. In conclusion, HBV Ba, C1, and C2 have different mutation patterns in the enhancer II/core promoter/precore region. Therefore, genotyping and detecting the 1653T and 1753V mutations, in addition to the A1762T G1764A double mutation, might have important clinical implications as predictive risk factors for hepatocarcinogenesis.
Infectivity Determinants of the Hepatitis B Virus Pre-S Domain Are Confined to the N-Terminal 75 Amino Acid Residues
Authors: Blanchet Matthieu , Sureau Camille
Published: March 2007

The N-terminal pre-S domain of the large hepatitis B virus (HBV) envelope protein plays a pivotal role at the initial step of the viral entry pathway. In the present study, the entire pre-S domain was mapped for infectivity determinants, following a reverse-genetics approach and using in vitro infection assays with hepatitis delta virus (HDV) or HBV particles. The results demonstrate that lesions created within the N-terminal 75 amino acids of the pre-S region abrogate infectivity, whereas mutations between amino acids 76 and 113, overlapping the matrix domain, had no effect. In contrast to the results of a recent study (L. Stoeckl, A. Funk, A. Kopitzki, B. Brandenburg, S. Oess, H. Will, H. Sirma, and E. Hildt, Proc. Natl. Acad. Sci. 103:6730-6734, 2006), the deletion of a cell membrane translocation motif (TLM) located between amino acids 148 and 161 at the C terminus of pre-S2 did not interfere with the infectivity of the resulting HDV or HBV mutants. Furthermore, a series of large deletions overlapping the pre-S2 domain were compatible with infectivity, although the efficiency of infection was reduced when the deletions extended to the pre-S1 domain. Overall, the results demonstrate that the activity of the pre-S domain at viral entry solely depends on the integrity of its first 75 amino acids and thus excludes any function of the matrix domain or TLM.
Identification of Hendra Virus G Glycoprotein Residues That Are Critical for Receptor Binding
Authors: Bishop Kimberly A. , Stantchev Tzanko S. , Hickey Andrew C. , Khetawat Dimple , Bossart Katharine N. , Krasnoperov Valery , Gill Parkash , Feng Yan Ru , Wang Lemin , Eaton Bryan T. , Wang Lin-Fa , Broder Christopher C.
Published: March 2007

Hendra virus (HeV) is an emerging paramyxovirus capable of infecting and causing disease in a variety of mammalian species, including humans. The virus infects its host cells through the coordinated functions of its fusion (F) and attachment (G) glycoproteins, the latter of which is responsible for binding the virus receptors ephrinB2 and ephrinB3. In order to identify the receptor binding site, a panel of G glycoprotein constructs containing mutations was generated using an alanine-scanning mutagenesis strategy. Based on a predicted G structure, charged amino acids residing in regions that could be homologous to those in the measles virus H attachment glycoprotein known to be involved in its protein receptor interaction were targeted. Using a coprecipitation-based assay, seven single-amino-acid substitutions in HeV G were identified as having significantly impaired binding to both the ephrinB2 and ephrinB3 viral receptors: D257A, D260A, G439A, K443A, G449A, K465A, and D468A. The impairment of receptor interaction conferred a concomitant diminution in their abilities to promote membrane fusion when coexpressed with F. The G glycoprotein mutants were also recognized by three or more conformation-dependent monoclonal antibodies of a panel of five, were expressed on the cell surface, and retained their abilities to bind and coprecipitate F. Interestingly, some of these mutant G glycoproteins coprecipitated with F more efficiently than wild-type G. Taken together, these data provide strong biochemical and functional evidence that some of these residues could be part of a conformation-dependent, discontinuous, and overlapping ephrinB2 and -B3 binding domain within the HeV G glycoprotein.
Downregulation of an Astrocyte-Derived Inflammatory Protein, S100B, Reduces Vascular Inflammatory Responses in Brains Persistently Infected with Borna Disease Virus
Authors: Ohtaki Naohiro , Kamitani Wataru , Watanabe Yohei , Hayashi Yohei , Yanai Hideyuki , Ikuta Kazuyoshi , Tomonaga Keizo
Published: March 2007

Borna disease virus (BDV) is a neurotropic virus that causes a persistent infection in the central nervous system (CNS) of many vertebrate species. Although a severe reactive gliosis is observed in experimentally BDV-infected rat brains, little is known about the glial reactions contributing to the viral persistence and immune modulation in the CNS. In this regard, we examined the expression of an astrocyte-derived factor, S100B, in the brains of Lewis rats persistently infected with BDV. S100B is a Ca
2+
-binding protein produced mainly by astrocytes. A prominent role of this protein appears to be the promotion of vascular inflammatory responses through interaction with the receptor for advanced glycation end products (RAGE). Here we show that the expression of S100B is significantly reduced in BDV-infected brains despite severe astrocytosis with increased glial fibrillary acidic protein immunoreactivity. Interestingly, no upregulation of the expression of S100B, or RAGE, was observed in the persistently infected brains even when incited with several inflammatory stimuli, including lipopolysaccharide. In addition, expression of the vascular cell adhesion molecule 1 (VCAM-1), as well as the infiltration of encephalitogenic T cells, was significantly reduced in persistently infected brains in which an experimental autoimmune encephalomyelitis was induced by immunization with myelin-basic protein. Furthermore, we demonstrated that the continuous activation of S100B in the brain may be necessary for the progression of vascular immune responses in neonatally infected rat brains. Our results suggested that BDV infection may impair astrocyte functions via a downregulation of S100B expression, leading to the maintenance of a persistent infection.
Hepatitis C Virus (HCV)-Specific CD8+Cells Produce Transforming Growth Factor β That Can Suppress HCV-Specific T-Cell Responses
Authors: Alatrakchi Nadia , Graham Camilla S. , van der Vliet Hans J. J. , Sherman Kenneth E. , Exley Mark A. , Koziel Margaret James
Published: March 2007

Hepatitis C virus (HCV)-specific T-cell responses are rarely detected in peripheral blood, especially in the presence of human immunodeficiency virus (HIV) coinfection. Based on recent evidence that T-regulatory cells may be increased in chronic HCV, we hypothesized that functional blockade of regulatory cells could raise HCV-specific responses and might be differentially regulated in the setting of HIV coinfection. Three groups of subjects were studied: HCV monoinfected, HCV-HIV coinfected, and healthy controls. Frequencies of peripheral T cells specific for peptides derived from HCV core, HIV type 1 p24, and recall antigens were analyzed by gamma interferon (IFN-γ) enzyme-linked immunospot assay. HCV-specific T-cell responses were very weak in groups with HCV and HCV-HIV infections. Addition of blocking antibodies against transforming growth factor β1 (TGF-β1), -2, and -3 and interleukin-10 specifically increased the HCV-specific T-cell responses in both infected groups; however, this increase was attenuated in the group with HCV-HIV coinfection compared to HCV infection alone. No increase in recall antigen- or HIV-specific responses was observed. Flow cytometric sorter analysis demonstrated that regulatory-associated cytokines were produced by HCV-specific CD3+CD8+CD25−cells. Enhancement of the IFN-γ effect was observed for both CD4 and CD8 T cells and was mediated primarily by TGF-β1, -2, and -3 neutralization. In conclusion, blockade of TGF-β secretion could enhance peripheral HCV-specific T-cell responses even in the presence of HIV coinfection.
Inhibition of Transcription of the Beta Interferon Gene by the Human Herpesvirus 6 Immediate-Early 1 Protein
Authors: Jaworska Joanna , Gravel Annie , Fink Karin , Grandvaux Nathalie , Flamand Louis
Published: March 2007

Human herpesviruses (HHV) are stealth pathogens possessing several decoy or immune system evasion mechanisms favoring their persistence within the infected host. Of these viruses, HHV-6 is among the most successful human parasites, establishing lifelong infections in nearly 100% of individuals around the world. To better understand this host-pathogen relationship, we determined whether HHV-6 could interfere with the development of the innate antiviral response by affecting interferon (IFN) biosynthesis. Using inducible cell lines and transient transfection assays, we have identified the immediate-early 1 (IE1) protein as a potent inhibitor of IFN-β gene expression. IE1 proteins from both HHV-6 variants were capable of suppressing IFN-β gene induction. IE1 prevents IFN-β gene expression triggered by Sendai virus infection, double-stranded RNA (dsRNA) and dsDNA transfection, or the ectopic expression of IFN-β gene activators such as retinoic inducible gene I protein, mitochondrial antiviral signaling protein, TBK-1, IκB kinase ε (IKKε), and IFN regulatory factor 3 (IRF3). While the stability of IFN-β mRNA is not affected, IE1-expressing cells have reduced levels of dimerized IRF3 and nucleus-translocated IRF3 in response to activation by TBK-1 or IKKε. Using nuclear extracts and gel shift experiments, we could demonstrate that in the presence of IE1, IRF3 does not bind efficiently to the IFN-β promoter sequence. Overall, these results indicate that the IE1 protein of HHV-6, one of the first viral proteins synthesized upon viral entry, is a potent suppressor of IFN-β gene induction and likely contributes to favor the establishment of and successful infection of cells with this virus.
Functional Effects of Coxsackievirus and Adenovirus Receptor Glycosylation on Homophilic Adhesion and Adenoviral Infection
Authors: Excoffon Katherine J. D. Ashbourne , Gansemer Nicholas , Traver Geri , Zabner Joseph
Published: March 2007

The coxsackievirus and adenovirus receptor (CAR) is both a viral receptor and homophilic adhesion protein. The extracellular portion of CAR consists of two immunoglobulin (Ig)-like domains, each with a consensus sequence for N-glycosylation. We used chemical, genetic, and biochemical studies to show that both sites are glycosylated and contribute to the function of CAR. Although the glycosylation of CAR does not alter cell surface levels or junctional localization, it affects both adhesion and adenovirus infection in unique ways. CAR-mediated adhesion appears to require at least one site of glycosylation since cells expressing CAR without glycosylation do not cluster with each other. In contrast, glycosylation of the Ig-like domain proximal to the membrane is key to the cooperative behavior of adenovirus binding and infection. Contrary to the hypothesis that cooperativity improves viral infection, our data show that although glycosylation of the D2 domain is required for adenovirus cooperative binding, it has a negative consequence upon infection. This is the first report dissecting the adhesion and receptor activities of CAR, revealing that factors other than the binding interface play a significant role in the function of CAR. These data have important implications for both cancers with altered glycosylation states and cancer treatments using oncolytic adenovirus.
Admitting ageing error when fitting growth curves: an example using the von Bertalanffy growth function with random effects
Authors: Cope Jason M , Punt André E
Published: March 2007

A way to explicitly incorporate ageing error into the estimation of von Bertalanffy growth function (VBGF) parameters using a random effects (RE) modeling framework is presented. This RE framework also accounts for the effects of selectivity on growth curve estimation by characterizing the distribution of true ages derived from multiple age reads using either an exponential or gamma distribution. Simulation testing across four life histories is used to compare the RE approach with standard nonlinear (SNL) approaches that use the primary, average, or median ages in growth estimation. Sensitivity tests compare the effects of assumed length and ageing error, selectivity, and recruitment variability on the estimation of growth curve parameters. Results support the use of the RE method using a gamma distribution over the SNL methods because RE method estimates of VBGF growth parameters were more precise across life histories and sensitivity trials. This general approach can be applied and expanded to other growth models. Applications demonstrate that the results from RE methods may differ in biologically important ways to those obtained from SNL approaches.
Natural mortality, growth parameters, and environmental temperature in fishes revisited
Authors: Griffiths David , Harrod Chris
Published: March 2007

Pauly (1980. J. Cons. Int. Explor. Mer, 39: 175–192) showed that natural mortality rates in fish could be predicted from body growth parameters and environmental temperature but found no evidence for ecological or taxonomic influences. Using an updated database and techniques that avoid some of the earlier analytical problems, we confirm Pauly's conclusion that mortality is correlated with growth and temperature. A path model supports the role of ecological effects on mortality. A phylogenetic effect is also apparent: perciform fishes occupy warmer environments than other species, but in the predator-rich reef habitat they suffer much lower mortality rates. Species that are cryptic or hide in burrows or have morphological defences against predators show the lowest mortality rates.
Effects of hypoxia on scope-for-activity and power capacity of lake trout (Salvelinus namaycush)
Authors: Evans David O
Published: March 2007

This study develops a quantitative model of the combined effects of temperature and ambient dissolved oxygen on metabolic scope-for-activity and power capacity of juvenile lake trout (Salvelinus namaycush). The model provides a framework for evaluating the effects of hypoxia on the capacity of lake trout to perform critical daily life support activities. Maximum power output for sustained swimming of yearling lake trout occurred at 12–20 °C and a dissolved oxygen concentration of >7 mg·L–1. At 4–8 °C, temperatures typical of the hypolimnetic summer habitat of juvenile lake trout, maximum power capacity was reduced by 33%, 67%, and 100% at ambient dissolved oxygen concentrations of 7, 5, and 3 mg·L–1, respectively. Analysis of power outputs, growth impairment, and recruitment success indicated that attainment of 3/4 power capacity would accommodate most daily life support activities of juvenile lake trout. At 4–14 °C, the threshold dissolved oxygen concentration for attainment of 3/4 scope-for-activity varied from 7.5 to 6.6 mg·L–1, respectively, with a mean and standard deviation of 7.04 ± 0.33 mg·L–1. A dissolved oxygen criterion of 7 mg·L–1is recommended for protection of the hypolimnetic habitat of juvenile lake trout.
Juvenile coho salmon (Oncorhynchus kisutch) responses to salmon carcasses and in-stream wood manipulations during winter and spring
Authors: Giannico Guillermo R , Hinch Scott G
Published: March 2007

We investigated the growth rate, winter survival, presmolt size, and emigration timing of juvenile coho salmon (Oncorhynchus kisutch) in response to salmon carcasses and in-stream wood. Experimental trials were conducted during two consecutive years and pre-winter fish size and densities differed between years. Sixteen pens with emigration traps were built in a side-channel of the Mamquam River, British Columbia. Pens were randomly assigned salmon carcasses, in-stream wood, both carcasses and in-stream wood, or neither (control). Our first trial was conducted between December 1996 and August 1997 and the second between December 1997 and August 1998. Initial rearing densities and average individual body mass were 3.1 fish·m–2 and 2.4 g, respectively, in the first trial and were 1.6 fish·m–2 and 6.6 g, respectively, in the second trial. Results were influenced by both fish initial size and density. During the first trial (smaller-sized fish at high densities), salmon carcasses increased fish growth rates and presmolt size. Winter survival did not increase in response to any treatment; however, a pre-winter size-related survival pattern was observed during the first trial. During the second trial, (larger-sized fish at low densities), no treatment influenced fish growth rates or presmolt size but all treatments augmented fish survival.
Multiple determinants of welfare in farmed fish: stocking density, disturbance, and aggression in Atlantic salmon (Salmo salar)
Authors: Adams C E , Turnbull J F , Bell A , Bron J E , Huntingford F A
Published: March 2007

Adult Atlantic salmon (Salmo salar) were held in seawater tanks at stocking densities of 15, 25, and 35 kg·m–3(with five replicates). After 51 days, four measures of welfare (body condition, fin condition, plasma glucose, and cortisol) were collected and combined by principal components analysis into an integrated welfare score for each fish. Fish with high and low welfare scores were found in all conditions, but overall welfare was best at the intermediate density, supporting the view that low densities as well as high densities can compromise welfare in salmon. The effect of stocking density interacted with the stronger effect of disturbance, creating a complex pattern of variation in welfare among the experimental tanks. Counter-intuitively, welfare scores were higher in tanks with a high level of disturbance, while welfare scores were strikingly low at the lowest density. Aggression in all tanks was low, but rose after feeding, when aggression was negatively related to both disturbance and stocking density. These data highlight the complex determinants of welfare in fish in production systems and, taken together, suggest that negative effects of husbandry practice and density on welfare in Atlantic salmon might be mediated by their influence on social interactions.
Many-body calculation of helium 1D–3D term intervals for 1snd (n = 12 ∼ 20) high Rydberg states
Authors: He Liming , Cao Wei
Published: March 2007

With many-body perturbation theory, 1D–3D term intervals of helium 1snd (n = 12 ∼ 20) configurations are calculated. Based on two different models, Rayleigh-Schrodinger perturbation expansion terms consisting of bound states only, and those of continua are evaluated, respectively. As for bound states, zeroth-order wave functions are strictly generated from self-iteration solutions of the Hartree equation and residues of infinite expansion series are dealt with by the integral processing method, while a simplified hydrogen potential is adopted to get the continua. Using Rayleigh–Schrodinger expansions, we evaluate exchange energy up to third-order terms. It is found that level splittings are mainly attributed to summations over bound states. The fine-structure level splittings yielded here are found to agree quite well with experimental results.PACS Nos.: 31.15.Md, 32.10Fn, 02.60Ed
Probabilistic remote preparation of a three-atom Greenberger–Horne–Zeilinger class state via cavity quantum electrodynamics
Authors: Xu Xiao -B , Liu Jin -Ming
Published: March 2007

We present two schemes for remotely preparing a three-atom Greenberger–Horne–Zeilinger class state via entanglement swapping in cavity quantum electrodynamics. We show that each of our schemes can be achieved probabilistically by means of separate atomic measurements with the choice of an appropriate atom-cavity field interaction time.PACS Nos.: 03.67–a, 03.67.Lx, 42.50.Dv
Silviculture that sustains: the nexus between silviculture, frequent prescribed fire, and conservation of biodiversity in longleaf pine forests of the southeastern United States
Authors: Mitchell R J , Hiers J K , O'Brien J J , Jack S B , Engstrom R T
Published: March 2007

The longleaf pine (Pinus palustris Mill.) forest ecosystems of the US southeastern Coastal Plain, among the most biologically diverse ecosystems in North America, originally covered over 24 × 106 ha but now occupy less than 5% of their original extent. The key factor for sustaining their high levels of diversity is the frequent application of prescribed fire uninterrupted in time and space. Pine fuels, critical to application of fire and regulated by canopy distribution, provide the nexus between silviculture and fire management in this system. Typical silvicultural approaches for this type were, in large part, developed to maximize the establishment and growth of regeneration as well as growth and yield of timber, with much less regard to how those practices might influence the ability to sustain prescribed burning regimes or the associated biodiversity. However, many landholdings in the region now include conservation of biodiversity as a primary objective with sustained timber yield as an important but secondary goal. This review synthesizes the literature related to controls of biodiversity for longleaf pine ecosystems, and silvicultural approaches are compared in their ability to sustain natural disturbance such as fire and how closely they mimic the variation, patterns, and processes of natural disturbance regimes while allowing for regeneration.
Capturing expert knowledge for ecosystem mapping using Bayesian networks
Authors: Walton Adrian , Meidinger Del
Published: March 2007

Large-scale ecosystem maps are essential tools for managers of forest-related activities. In British Columbia, the prevailing approach for ecosystem mapping has been to use an expert system that captures expert knowledge in the form of a belief matrix. In this project, a Bayesian network rather than a belief matrix was used in an attempt to overcome some of the drawbacks of the belief-matrix approach. A Bayesian-network knowledge base was created for each of the following three biogeoclimatic variants: montane very wet maritime coastal western hemlock (CWHvm2), submontane very wet maritime coastal western hemlock (CWHvm1), and central very wet hypermaritime coastal western hemlock (CWHvh2), and applied to a study area encompassing Prince Rupert. A map of ecosystems by grouping site series was produced using each of the knowledge bases. Accuracy assessments performed on each of the maps of grouped site series revealed that the maps poorly predicted the spatial distribution of uncommon and very wet site-series groups. For example, overall map accuracy for the CWHvm2, CWHvm1, and CWHvh2 variants was 47.8%, 50.3%, and 33.3%, respectively. The results of the map-accuracy assessment, however, were consistent with those resulting from a belief-matrix approach conducted in an earlier study. We feel that Bayesian network knowledge bases are easier to develop, interpret, and update than belief matrices.
Developing breeding objectives for radiata pine structural wood production. II. Sensitivity analyses
Authors: Ivković Milo , Wu Harry X , McRae Tony A , Matheson Colin A
Published: March 2007

In a companion paper we describe a bioeconomic model of a production system for radiata pine (Pinus radiata D. Don) structural timber and estimated economic weights for four breeding-objective traits: mean annual increment, stem sweep, average branch size, and modulus of elasticity. In this paper we show estimation errors and the sensitivity of the economic weights to the input parameters of the production-system model. We also illustrate the linearity and independence of the economic weights and the sensitivity of selection indices to variation in economic weights and genetic parameters. Estimated standard errors of economic weights were generally low. Among the production-system parameters studied, discount rate and roundwood and sawn-timber prices had the largest impact on the estimates of economic weights. The relationship between the change in values of breeding-objective traits and the corresponding change in profit was nonlinear. The profit change due to change in one objective trait was not independent of the values of the other traits. The most important factors affecting the sensitivity of the selection index were the phenotypic variances of early selection traits such as tree diameter and wood basic density and the economic weights of mean annual increment and modulus of elasticity.
Poisson mixture models for regression analysisof stand-level mortality
Authors: Affleck David LR
Published: March 2007

Periodic stand-level mortality data from permanent plots tend to be highly variable, skewed, and frequently contain many zero observations. Such data have commonly been modeled using nonlinear mortality functions fitted by least squares, and more recently by a two stage approach incorporating a logistic regression step. This study describes a set of nonlinear regression models that structure stochastic variation about a mortality function according to basic probability distributions appropriate for non-negative count data, including the Poisson, negative binomial (NB), and generalized Poisson (GP). Also considered are zero-inflated and hurdle modifications of these basic models. The models are developed and fit to mortality data from a loblolly pine (Pinus taeda L.) spacing trial with a conspicuous mode at 0. The sample data exhibit more variability than can be accommodated by a Poisson or modified Poisson model; the NB and GP models incorporate the extra-Poisson dispersion and offer an improved fit. A hurdle NB model best describes this sample, but, like the zero-inflated models and two-stage approach, modifies the interpretation of the mean structure and raises the question of overfitting. Considering both data-model agreement and the biological relevance of these models' components, the analysis suggests that the NB model offers a more compelling and credible inferential basis for fitting stand-level mortality functions.
Linking juvenile white spruce density, dispersion, stocking, and mortality to future yield
Authors: Feng Zhili , Stadt Kenneth J , Lieffers Victor J
Published: March 2007

We examined methods of linking density, dispersion, and stocking information from juvenile regeneration surveys with mortality estimates to predict future yield of white spruce (Picea glauca (Moench) Voss) in boreal mixedwoods. The study focused on data from 709 stands (7–150 years) and defined a stocked plot (10 m2) as having one or more acceptable trees. In juvenile surveys, ingress of natural spruce overwhelmed the regular planting pattern, creating clumped dispersion patterns, as indicated by the Morisita index. A function was developed to describe the relationship between stocking, density, and dispersion. In mature, permanent sample plots, only 30%–40% stocking of 10 m2 plots (700 stems·ha–1) was needed to achieve full yields. Mortality rates for planted spruce varied from 0.1% to 0.8% per year for juvenile stands and from 1.7% to 3.3% per year for mature stands. For rotation-length predictions in Alberta, 0.7% per year is likely a mean mortality loss. These findings were combined to generate stocking versus time curves at a range of mortality rates. The tallest spruce measured in each juvenile survey plot had the same mortality rate regardless of absolute size, and spruce mortality was reduced when associated with aspen. These findings call into question minimum height requirements and free-to-grow criteria in regeneration standards.
Oxidative protein damage is associated with poor grip strength among older women living in the community
Authors: Howard Caitlin , Ferrucci Luigi , Sun Kai , Fried Linda P. , Walston Jeremy , Varadhan Ravi , Guralnik Jack M. , Semba Richard D.
Published: March 2007

Grip strength, an indicator of muscle strength, has been shown to be a predictor of poor outcomes among older adults. Protein carbonylation, an indicator of oxidative damage to proteins, leads to cellular dysfunction and a decline in tissue function. Oxidative stress has been implicated in the pathogenesis of sarcopenia. The objective was to determine whether serum protein carbonyl concentrations are associated with grip strength in older women living in the community. A cross-sectional study was conducted in 672 women, aged 65 and older, from the Women's Health and Aging Study (WHAS) I, the one-third most disabled women residing in the community in Baltimore, MD. Protein carbonyl and grip strength were measured in each patient. In a multivariate analysis adjusting for age, race, body mass index, and Mini-Mental Status Examination score, protein carbonyls (nmol/mg) were associated with grip strength (β = −6.77, P < 0.01). The statistical association was unchanged after the analysis adjusted for hypertension, congestive heart failure, and depression. Ordered logistic regression models adjusted for the above factors showed that protein carbonyls are associated with increased odds of being in the lower quartiles of grip strength (odds ratio 8.74, 95% confidence interval 1.06–71.89, P = 0.043). These results suggest oxidative protein damage is independently associated with low grip strength among older women living in the community. Increased oxidative stress may be contributing to loss of muscle strength in older adults.
Visual Scene Processing in Familiar and Unfamiliar Environments
Authors: Epstein Russell A. , Higgins J. Stephen , Jablonski Karen , Feiler Alana M.
Published: March 2007

Humans and animals use information obtained from the local visual scene to orient themselves in the wider world. Although neural systems involved in scene perception have been identified, the extent to which processing in these systems is affected by previous experience is unclear. We addressed this issue by scanning subjects with functional magnetic resonance imaging (fMRI) while they viewed photographs of familiar and unfamiliar locations. Scene-selective regions in parahippocampal cortex (the parahippocampal place area, or PPA), retrosplenial cortex (RSC), and the transverse occipital sulcus (TOS) responded more strongly to images of familiar locations than to images of unfamiliar locations with the strongest effects (>50% increase) in RSC. Examination of fMRI repetition suppression (RS) effects indicated that images of familiar and unfamiliar locations were processed with the same degree of viewpoint specificity; however, increased viewpoint invariance was observed as individual scenes became more familiar over the course of a scan session. Surprisingly, these within-scan-session viewpoint-invariant RS effects were only observed when scenes were repeated across different trials but not when scenes were repeated within a trial, suggesting that within- and between-trial RS effects may index different aspects of visual scene processing. The sensitivity to environmental familiarity observed in the PPA, RSC, and TOS supports earlier claims that these regions mediate the extraction of navigationally relevant spatial information from visual scenes. As locations become familiar, the neural representations of these locations become enriched, but the viewpoint invariance of these representations does not change.
Magnitude and Ethanol Sensitivity of Tonic GABAAReceptor-Mediated Inhibition in Dentate Gyrus Changes From Adolescence to Adulthood
Authors: Fleming Rebekah L. , Wilson Wilkie A. , Swartzwelder H. Scott
Published: March 2007

Ethanol consumption by adolescents is a public health problem of striking importance. Educational and clinical efforts to address this problem have been aided by recent neurobehavioral studies indicating that ethanol disrupts memory and memory-related brain functions more powerfully in adolescent animals than in adults. Still, the mechanisms underlying this developmental sensitivity remain unclear. GABAAreceptor (GABAAR)-mediated neurotransmission in the hippocampal formation, particularly that which is driven by extrasynaptic GABAARs, is enhanced by pharmacologically relevant concentrations of ethanol, and may be, in part, responsible for the modulation of memory and memory-related circuit plasticity. Using hippocampal slices from adolescent and adult rats, we have shown that tonic current mediated by extrasynaptic GABAARs is larger in dentate gyrus granule cells from adult animals than in those from adolescents and that 30 mM ethanol enhances inhibitory tonic current more in cells from adolescent rats than in those from adults. It is possible that more powerful promotion of tonic GABAAR-mediated inhibition by ethanol in the dentate gyrus of adolescent rats, compared with adults, contributes to the developmental differences that have previously been observed with respect to ethanol-induced memory impairment and reduction of synaptic plasticity.
Voltage-Dependent Calcium Channel CaV1.3 Subunits Regulate the Light Peak of the Electroretinogram
Authors: Wu Jiang , Marmorstein Alan D. , Striessnig Jörg , Peachey Neal S.
Published: March 2007

In response to light, the mouse retinal pigment epithelium (RPE) generates a series of slow changes in potential that are referred to as the c-wave, fast oscillation (FO), and light peak (LP) of the electroretinogram (ERG). The LP is generated by a depolarization of the basolateral RPE plasma membrane by the activation of a calcium-sensitive chloride conductance. We have previously shown that the LP is reduced in both mice and rats by nimodipine, which blocks voltage-dependent calcium channels (VDCCs) and is abnormal in lethargic mice, carrying a null mutation in the calcium channel β4 subunit. To define the α1 subunit involved in this process, we examined mice lacking CaV1.3. In comparison with wild-type (WT) control littermates, LPs were reduced in CaV1.3−/− mice. This pattern matched closely with that previously noted in lethargic mice, confirming a role for VDCCs in regulating the signaling pathway that culminates in LP generation. These abnormalities do not reflect a defect in rod photoreceptor activity, which provides the input to the RPE to generate the c-wave, FO, and LP, because ERG a-waves were comparable in WT and CaV1.3−/− littermates. Our results identify CaV1.3 as the principal pore-forming subunit of VDCCs involved in stimulating the ERG LP.
Differential Activity-Dependent Development of Corticospinal Control of Movement and Final Limb Position During Visually Guided Locomotion
Authors: Friel K. M. , Drew T. , Martin J. H.
Published: March 2007

Although we understand that activity- and use-dependent processes are important in determining corticospinal axon terminal development in the spinal cord, little is known about the role of these processes in development of skilled control of limb movements. In the present study we determined the effects of unilateral motor cortex activity blockade produced by muscimol infusion during the corticospinal axon terminal refinement period, between postnatal weeks 5–7, on visually guided locomotion. We examined stepping and forepaw placement on the rungs of a horizontal ladder and gait modifications as animals stepped over obstacles during treadmill walking. When cats traversed the horizontal ladder, the limb contralateral to inactivation was placed significantly farther forward on the rungs than the ipsilateral limb, indicating defective endpoint control. Similarly, when animals stepped over obstacles on a treadmill, the contralateral limb was placed farther in front of the obstacle, but only when it was the first (i.e., leading) limb to step over the obstacle, not when it was the second (i.e., trailing) limb. This is also indicative of an endpoint control deficit. In contrast, neither during ladder walking, nor when stepping over obstacles on the treadmill, was there any consistent evidence for a major impairment in limb trajectory. These results point to distinct and possibility independent corticospinal mechanisms for movement trajectory control and endpoint control. Although corticospinal activity during early postnatal development is needed to refine circuits for accurate endpoint control, this activity-dependent refinement is not needed for movement trajectory control.
Drug Therapy of High-Risk Lipid Abnormalities in Children and Adolescents
Authors: McCrindle Brian W. , Urbina Elaine M. , Dennison Barbara A. , Jacobson Marc S. , Steinberger Julia , Rocchini Albert P. , Hayman Laura L. , Daniels Stephen R.
Published: March 2007

Despite compliance with lifestyle recommendations, some children and adolescents with high-risk hyperlipidemia will require lipid-lowering drug therapy, particularly those with familial hypercholesterolemia. The purpose of this statement is to examine new evidence on the association of lipid abnormalities with early atherosclerosis, discuss challenges with previous guidelines, and highlight results of clinical trials with statin therapy in children and adolescents with familial hypercholesterolemia or severe hypercholesterolemia. Recommendations are provided to guide decision-making with regard to patient selection, initiation, monitoring, and maintenance of drug therapy.
Persistent Patterns of International Commerce
Authors: Ward Michael D. , Hoff Peter D.
Published: March 2007

The authors examine a standard gravity model of international commerce augmented to include political as well as institutional influences on bilateral trade. Using annual data from 1980-2001, they estimate regression coefficients and residual dependencies using a hierarchy of models in each year. Rather than gauge the generalizability of these patterns via traditional measures of statistical significance such as p-values, this article develops and employs a strategy to evaluate the out-of-sample predictive strength of various models. The analysis of recent international commerce shows that in addition to a typical gravity-model specification, political and institutional variables are important. The article also demonstrates that the often-reported link between international conflict and bilateral trade is elusive, and that inclusion of conflict in a trade model can sometimes lead to reduced out-of-sample predictive performance. Further, this article illustrates that there are substantial, persistent residual exporter- and importer-specific effects, and that ignoring such patterns in relational trade data results in an incomplete picture of international commerce, even in the context of a well-established framework such as the gravity model.
Learning in Small Manufacturing Firms
Authors: Ekanem Ignatius , Smallbone David
Published: March 2007

This article is concerned with investment decision-making processes in small manufacturing enterprises.The study, on which the article is based, used `insider accounts' as an innovative, qualitative methodology, involving in-depth, semi-structured interviews and direct observation, conducted longitudinally in eight case study companies. It is a research method which includes detailed accounts from the actors themselves, incorporating their actual motives and behaviour. Data from two case study firms is presented in the article to demonstrate different types of learning behaviour.The findings suggest that conceptualizing investment decision-making processes in small firms within the context of organizational learning holds promise as an explanatory framework for investment behaviour in small firms.
Advising the Small Business Client
Authors: Dyer Linda M. , Ross Christopher A.
Published: March 2007

The context of the professional business advisor is explored, with specific focus on the culture, com m unication preferences and learning styles they prefer.The advisor's rational and analytic world-view is contrasted with the inform al and idiosyncratic world of the typical sm all business owner. Interviews with ten professional advisors suggest that there is som e truth to the assum ption that advisors and owners have disparate world-views. Advisors do recognize this disparity, but recognition of the problem is only the first step. Even advisors who are m otivated to improve the advice relationship by im m ersing them selves in the world of the sm all business owner can expect to face challenges because of the dynam ic nature of the advisory relationship and of the firm 's development.
Market Orientation and Planning Flexibility in SMEs
Authors: Alpkan Lütfihak , Yilmaz Cengiz , Kaya Nihat
Published: March 2007

The study examines the joint effects of market orientation (an internal, cultural factor) and planning flexibility (an internal, process factor) on business performance in small and medium-sized firms. In addition, the conceptual model incorporates market dynamism (an external factor) as a moderator on business performance. A number of hypothesized relationships are tested with a sample of small and medium-sized manufacturing firms in Turkey.The results suggest that while, in general, both market orientation and planning flexibility positively influence firm performance, contrary to the author's hypothesis, planning flexibility exerts a negative effect on performance in highly dynamic markets.Theoretical and managerial implications of these and other findings are discussed.
Expansion Through Multiple Unit Franchising
Authors: Weaven Scott , Frazer Lorelle
Published: March 2007

In this article we explore strategic reasons justifying the recent emergence of multiple unit franchising arrangements within Australia from the perspective of the franchisor. Extending resource constraints, efficiency and agency rationales explaining organizational choice, the present study suggests that franchisors encourage franchisee subsystem development as it affords strategic, operational and performance advantages. Dimensions including agency cost minimization, system-wide uniformity, franchise system brand value, reward strategies, and subsystem unit (geographical) proximity and intra-system competition, were found to be important. Less important elements included ownership redirection, system adaptability, local market innovation and franchisee opportunism motives. Given the exploratory nature of this research, in-depth interviews with 23 franchisors were used to collect data.The preliminary research evidence has important implications for franchising theorists and practitioners and, in addition, provides a platform on which future research can be developed to further understand multiple unit franchising arrangements.
Function of Posterior Cruciate Ligament Bundles during in Vivo Knee Flexion
Authors: Papannagari Ramprasad , DeFrate Louis E. , Nha Kyung W. , Moses Jeremy M. , Moussa Mohamed , Gill Thomas J. , Guoan Li
Published: March 2007

Background

The biomechanical functions of the anterolateral and posteromedial bundles of the posterior cruciate ligament over the range of flexion of the knee joint remain unclear.

Hypothesis

The posterior cruciate ligament bundles have minimal length at low flexion angles and maximal length at high flexion angles.

Study Design

Descriptive laboratory study.

Methods

Seven knees from normal, healthy subjects were scanned with magnetic resonance, and 3-dimensional models of the femur, tibia, and posterior cruciate ligament attachment sites were created. The lines connecting the centroids of the corresponding bundle attachment sites on the femur and tibia represented the anterolateral and posteromedial bundles of the posterior cruciate ligament. Each knee was imaged during weightbearing flexion (from 0° to maximal flexion) using a dual-orthogonal fluoroscopic system. The length, elevation, deviation, and twist of the posterior cruciate ligament bundles were measured as a function of flexion.

Results

The lengths of the anterolateral and posteromedial bundles increased with flexion from 0° to 120° and decreased beyond 120° of flexion. The posteromedial bundle had a lower elevation angle than the anterolateral bundle beyond 60° of flexion. The anterolateral bundle had a larger deviation angle than the posteromedial bundle beyond 75° of flexion. The femoral attachment of the posterior cruciate ligament twisted externally with increasing flexion and reached a maximum of 86.4° ± 14.7° at 135° of flexion (P < .05).

Conclusion

These data suggest that there is no reciprocal function of the bundles with flexion, which is contrary to previous findings. The orientation of the anterolateral and posteromedial bundles suggests that at high flexion, the anterolateral bundle might play an important role in constraining the mediolateral translation, whereas the posteromedial bundle might play an important role in constraining the anteroposterior translation of the tibia.

Clinical Relevance

These data provide a better understanding of the biomechanical function of the posterior cruciate ligament bundles and may help to improve the design of the 2-bundle reconstruction techniques of the ruptured posterior cruciate ligament.
Clinical and laboratory features of neuromyelitis optica with oligoclonal IgG bands
Authors: Nakamura M. , Nakashima I. , Sato S. , Miyazawa I. , Fujihara K. , Itoyama Y.
Published: March 2007

Of 23 neuromyelitis optica (NMO) cases, we found two cases with oligoclonal IgG bands (OBs). Both patients were positive for NMO-IgG. Their common features were long disease duration and co-existing autoimmune diseases (myasthenia gravis and sicca syndrome). Although OBs are mostly negative in NMO, which distinguishes it from multiple sclerosis (MS), they can be positive by long-standing autoimmunity, which may not be directly related to NMO. Multiple Sclerosis 2007; 13: 332-335. http://msj.sagepub.com
Down's syndrome and neuromyelitis optica (Devic's disease). An autopsy-proven case
Authors: Cabrera-Gómez J.A. , Galarraga-Inza J. , Coro-Antich R.M. , Real-González Y. , Cristofol-Corominas M. , Gómez H. , Romero-Garcia K. , Gil-Gil M.X. , Gonzalez-Quevedo A.
Published: March 2007

Neuromyelitis optica (NMO) has been attributed to different underlying pathological events. The aim of this paper is to present the first case report of a patient with Down's syndrome (DS) who died of a fulminant NMO. A 29-year-old woman with DS developed acute transverse myelitis, with complete visual loss and swollen optic discs. Two days later, she developed quadriplegia, respiratory arrest and died. The anatomical study demonstrated typical findings of DS in the brain without demyelinating lesions. A severe destruction of medulla and cervical cord with a very high degree of demyelination of the optic nerves was typical of monophasic NMO (Devic's disease). Most of the cases of NMO in Cuba are of the relapsing form, but this case report is the first one with monophasic NMO and DS with a very aggressive course. The link of the pathogenetic relationship between DS and NMO remains unclear; it may well be coincidence but the fact that the patient died very shortly after the onset suggests, at least on clinical grounds, that the presence of DS could have accelerated the fatal evolution of NMO. Multiple Sclerosis 2007; 13: 433-436. http://msj.sagepub.com