bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Mechanisms by Which Human Immunodeficiency Virus Type 1 Integrase Stimulates the Early Steps of Reverse Transcription
Authors: Dobard Charles W. , Briones Marisa S. , Chow Samson A.
Published: July 2007

Reverse transcriptase (RT) and integrase (IN) are two essential enzymes that play a critical role in synthesis and integration of the retroviral cDNA, respectively. For human immunodeficiency virus type 1 (HIV-1), RT and IN physically interact and certain mutations and deletions of IN result in viruses defective in early steps of reverse transcription. However, the mechanism by which IN affects reverse transcription is not understood. We used a cell-free reverse transcription assay with different primers and compositions of deoxynucleoside triphosphates to differentially monitor the effect of IN on the initiation and elongation modes of reverse transcription. During the initiation mode, addition of IN stimulated RT-catalyzed reverse transcription by fourfold. The stimulation was specific to IN and could not be detected when the full-length IN was replaced with truncated IN derivatives. The IN-stimulated initiation was also restricted to the template-primer complex formed using tRNA
3
Lys
or short RNA oligonucleotides as the primer and not those formed using DNA oligonucleotides as the primer. Addition of IN also produced a threefold stimulation during the elongation mode, which was not primer dependent. The stimulation of both initiation and elongation by IN was retained in the presence of an RT trap. Furthermore, IN had no effect on steps at or before template-primer annealing, including packaging of viral genomic RNA and tRNA
3
Lys
. Taken together, our results showed that IN acts at early steps of reverse transcription by increasing the processivity of RT and suppressing the formation of the pause products.
Arterivirus Subgenomic mRNA Synthesis and Virion Biogenesis Depend on the Multifunctional nsp1 Autoprotease
Authors: Tijms Marieke A. , Nedialkova Danny D. , Zevenhoven-Dobbe Jessika C. , Gorbalenya Alexander E. , Snijder Eric J.
Published: July 2007

Many groups of plus-stranded RNA viruses produce additional, subgenomic mRNAs to regulate the expression of part of their genome. Arteriviruses and coronaviruses (order
Nidovirales
) are unique among plus-stranded RNA viruses for using a mechanism of discontinuous RNA synthesis to produce a nested set of 5′- and 3′-coterminal subgenomic mRNAs, which serve to express the viral structural protein genes. The discontinuous step presumably occurs during minus-strand synthesis and joins noncontiguous sequences copied from the 3′- and 5′-proximal domains of the genomic template. Nidovirus genome amplification (“replication”) and subgenomic mRNA synthesis (“transcription”) are driven by 13 to 16 nonstructural proteins (nsp's), generated by autocatalytic processing of two large “replicase” polyproteins. Previously, using a replicon system, the N-terminal nsp1 replicase subunit of the arterivirus equine arteritis virus (EAV) was found to be dispensable for replication but crucial for transcription. Using reverse genetics, we have now addressed the role of nsp1 against the background of the complete EAV life cycle. Mutagenesis revealed that nsp1 is in fact a multifunctional regulatory protein. Its papain-like autoprotease domain releases nsp1 from the replicase polyproteins, a cleavage essential for viral RNA synthesis. Several mutations in the putative N-terminal zinc finger domain of nsp1 selectively abolished transcription, while replication was either not affected or even increased. Other nsp1 mutations did not significantly affect either replication or transcription but still dramatically reduced the production of infectious progeny. Thus, nsp1 is involved in at least three consecutive key processes in the EAV life cycle: replicase polyprotein processing, transcription, and virion biogenesis.
ZEB1 and c-Jun Levels Contribute to the Establishment of Highly Lytic Epstein-Barr Virus Infection in Gastric AGS Cells
Authors: Feng Wen-hai , Kraus Richard J. , Dickerson Sarah J. , Lim Hui Jun , Jones Richard J. , Yu Xianming , Mertz Janet E. , Kenney Shannon C.
Published: July 2007

The induction of lytic infection has been proposed as a therapeutic strategy for treating Epstein-Barr virus (EBV)-positive malignancies. To succeed, efficient methods are needed for activating the EBV immediate-early (IE) promoters, Zp and Rp. Here we compared factors which regulate Zp and Rp in AGS gastric carcinoma cells that support a remarkably high level of persistently lytic EBV infection with HeLa cervical cells that permit only tightly latent infection. We found that the level of Zp activity assayed by transient transfection assays with reporter plasmids was high in AGS cells but low in HeLa cells. The level of Rp activity was low in both cell types. Mutational analysis indicated that sequences within Zp located between −70 and +27 relative to the transcription initiation site were sufficient to confer a high level of Zp activity in AGS cells. The Zp CRE motif was necessary for this constitutive activity, while the ZIA and ZIB MEF2D motifs were not. Consistent with these findings, immunoblot analysis indicated that phosphorylated c-Jun, which activates Zp through the CRE motif, was expressed at a much higher level in EBV-infected AGS cells than in EBV-infected HeLa cells. In contrast, ZEB1, which represses Zp via the ZV motif located near the transcription initiation site, was abundant in HeLa cells, while it was absent from AGS cells. Exogenous addition of ZEB1 led to the repression of Zp in AGS cells. We conclude that the unusually high Zp activity level in AGS cells is due to the high abundance of positively acting transcription factors such as c-Jun combined with the low abundance of negatively acting factors such as ZEB1.
Hepatitis C Virus Stabilizes Hypoxia-Inducible Factor 1α and Stimulates the Synthesis of Vascular Endothelial Growth Factor
Authors: Nasimuzzaman Md , Waris Gulam , Mikolon David , Stupack Dwayne G. , Siddiqui Aleem
Published: July 2007

Hepatitis C virus (HCV) infection is one of the major causes of chronic hepatitis, liver cirrhosis, which subsequently leads to hepatocellular carcinoma (HCC). The overexpression of the angiogenic factors has been demonstrated in HCC. In this study, we investigated the potential of HCV gene expression in inducing angiogenesis. Our results show that HCV infection leads to the stabilization of hypoxia-inducible factor 1α (HIF-1α). We further show that this stabilization was mediated via oxidative stress induced by HCV gene expression. The activation of NF-κB, STAT-3, PI3-K/AkT, and p42/44 mitogen-activated protein kinase was necessary for HIF-1α stabilization. HIF-1α induction in turn led to the stimulation of vascular endothelial growth factor. By using the chick chorioallantoic membrane assay, we show that HCV-infected cells released angiogenic cytokines, leading to neovascularization in vivo. These results indicate the potential of HCV gene expression in angiogenesis.
Analysis of Viral
cis
Elements Conferring Kaposi's Sarcoma-Associated Herpesvirus Episome Partitioning and Maintenance
Authors: Skalsky Rebecca L. , Hu Jianhong , Renne Rolf
Published: July 2007

Maintenance of Kaposi's sarcoma-associated herpesvirus (KSHV) episomes in latently infected cells is dependent on the latency-associated nuclear antigen (LANA). LANA binds to the viral terminal repeats (TR), leading to recruitment of cellular origin recognition complex proteins. Additionally, LANA tethers episomes to chromosomes via interactions with histones H2A and H2B (A. J. Barbera et al., Science
311
:856-861, 2006). Despite these molecular details, less is known about how episomes are established after de novo infection. To address this, we measured short-term retention rates of green fluorescent protein-expressing replicons in proliferating lymphoid cells. In the absence of antibiotic selection, LANA significantly reduced the loss rate of TR-containing replicons. Additionally, we found that LANA can support long-term stability of KSHV replicons for more than 2 months under nonselective conditions. Analysis of
cis
elements within TR that confer episome replication and partitioning revealed that these activities can occur independently, and furthermore, both events contribute to episome stability. We found that replication-deficient plasmids containing LANA binding sites (LBS1/2) exhibited measurable retention rates in the presence of LANA. To confirm these observations, we uncoupled KSHV replication and partitioning by constructing hybrid origins containing the Epstein-Barr virus (EBV) dyad symmetry for plasmid replication and KSHV LBS1/2. We demonstrate that multiple LBS1/2 function in a manner analogous to that of the EBV family of repeats by forming an array of LANA binding sites for partitioning of KSHV genomes. Our data suggest that the efficiency with which KSHV establishes latency is dependent on multiple LANA activities, which stabilize viral genomes early after de novo infection.
CD40-CD40 Ligand Interactions Promote Trafficking of CD8
+
T Cells into the Brain and Protection against West Nile Virus Encephalitis
Authors: Sitati Elizabeth , McCandless Erin E. , Klein Robyn S. , Diamond Michael S.
Published: July 2007

Recent studies have established a protective role for T cells during primary West Nile virus (WNV) infection. Binding of CD40 by CD40 ligand (CD40L) on activated CD4
+
T cells provides an important costimulatory signal for immunoglobulin class switching, antibody affinity maturation, and priming of CD8
+
T-cell responses. We examined here the function of CD40-dependent interactions in limiting primary WNV infection. Compared to congenic wild-type mice, CD40
−/−
mice uniformly succumbed to WNV infection. Although CD40
−/−
mice produced low levels of WNV-specific immunoglobulin M (IgM) and IgG, viral clearance from the spleen and serum was not altered, and CD8
+
T-cell priming in peripheral lymphoid tissues was normal. Unexpectedly, CD8
+
T-cell trafficking to the central nervous system (CNS) was markedly impaired in CD40
−/−
mice, and this correlated with elevated WNV titers in the CNS and death. In the brains of CD40
−/−
mice, T cells were retained in the perivascular space and did not migrate into the parenchyma, the predominant site of WNV infection. In contrast, in wild-type mice, T cells trafficked to the site of infection in neurons. Beside its role in maturation of antibody responses, our experiments suggest a novel function of CD40-CD40L interactions: to facilitate T-cell migration across the blood-brain barrier to control WNV infection.
PrP
c
Does Not Mediate Internalization of PrP
Sc
but Is Required at an Early Stage for De Novo Prion Infection of Rov Cells
Authors: Paquet Sophie , Daude Nathalie , Courageot Marie-Pierre , Chapuis Jérôme , Laude Hubert , Vilette Didier
Published: July 2007

We have studied the interactions of exogenous prions with an epithelial cell line inducibly expressing PrP
c
protein and permissive to infection by a sheep scrapie agent. We demonstrate that abnormal PrP (PrP
Sc
) and prion infectivity are efficiently internalized in Rov cells, whether or not PrP
c
is expressed. At odds with earlier studies implicating cellular heparan sulfates in PrP
Sc
internalization, we failed to find any involvement of such molecules in Rov cells, indicating that prions can enter target cells by several routes. We further show that PrP
Sc
taken up in the absence of PrP
c
was unable to promote efficient prion multiplication once PrP
c
expression was restored in the cells. This observation argues that interaction of PrP
Sc
with PrP
c
has to occur early, in a specific subcellular compartment(s), and is consistent with the view that the first prion multiplication events may occur at the cell surface.
CCR5 and CXCR3 Are Dispensable for Liver Infiltration, but CCR5 Protects against Virus-Induced T-Cell-Mediated Hepatic Steatosis
Authors: Holst P. J. , Orskov C. , Qvortrup K. , Christensen J. P. , Thomsen A. R.
Published: July 2007

CCR5 and CXCR3 are important molecules in regulating the migration of activated lymphocytes. Thus, the majority of tissue-infiltrating T cells found in the context of autoimmune conditions and viral infections express CCR5 and CXCR3, and the principal chemokine ligands are expressed within inflamed tissues. Accordingly, intervention studies have pointed to nonredundant roles of these receptors in models of allograft rejection, viral infection, and autoimmunity. In spite of this, considerable controversy exists, with many studies failing to support a role for CCR5 or CXCR3 in disease pathogenesis. One possible explanation is that different chemokine receptors may take over in the absence of any individual receptor, thus rendering individual receptors redundant. We have attempted to address this issue by analyzing CCR5−/−, CXCR3−/−, and CCR5/CXCR3−/−mice with regard to virus-induced liver inflammation, generation and recruitment of effector cells, virus control, and immunopathology. Our results indicate that CCR5 and CXCR3 are largely dispensable for tissue infiltration and virus control. In contrast, the T-cell response is accelerated in CCR5−/−and CCR5/CXCR3−/−mice and the absence of CCR5 is associated with the induction of CD8+T-cell-mediated immunopathology consisting of marked hepatic microvesicular steatosis.
Exposure to hardly soluble indium compounds in ITO production and recycling plants is a new risk for interstitial lung damage
Authors: Hamaguchi T , Omae K , Takebayashi T , Kikuchi Y , Yoshioka N , Nishiwaki Y , Tanaka A , Hirata M , Taguchi O , Chonan T
Published: July 2007

Objectives:

To identify the effects of indium on the lung and to assess exposure-effect and exposure-response relations between indium exposure and effects on the lungs.

Methods:

Ninety three male indium exposed and 93 male non-exposed workers from four ITO manufacturing or ITO recycling plants were analysed in a cross-sectional study. Indium in serum (In-S) was determined as a biological exposure index. Geometric means (GSD) of In-S were 8.25 ng/ml (4.55) in the exposed workers and 0.25 (2.64) in the non-exposed workers. The maximum concentration of In-S was 116.9 ng/ml. A questionnaire for respiratory symptoms and job histories, spirometry, high-resolution computerised tomography (HRCT) of the chest, serum KL-6, serum SP-A, serum SP-D and serum CRP were measured as the effect indices.

Results:

Spirometry, subjective symptoms and the prevalence of interstitial or emphysematous changes on lung HRCT showed no differences between exposed and non-exposed workers. Geometric means (GSD) of KL-6, SP-D and SP-A in the exposed workers were 495.4 U/ml (2.26), 85.2 ng/ml (2.02) and 39.6 ng/ml (1.57), and were significantly higher than those in the non-exposed workers. The prevalence (%) of the exposed and non-exposed workers exceeding the reference values were also significantly higher in KL-6 (41.9 vs 2.2), SP-D (39.8 vs 7.5), and SP-A (43.0 vs 24.7). Very sharp exposure-effect and exposure-response relations were discovered between In-S and KL-6 and between In-S and SP-D when the exposed workers were classified into seven groups by In-S.

Conclusions:

The study outcomes with regard to the basis of serum immunochemistry biomarkers and HRCT indicate that exposure to hardly soluble indium compound dust may represent a risk for interstitial lung damage.
Mortality from Alzheimer's, motor neuron and Parkinson's disease in relation to magnetic field exposure: findings from the study of UK electricity generation and transmission workers, 1973–2004
Authors: Sorahan T , Kheifets L
Published: July 2007

Background:

There are a number of reports linking magnetic field exposure to increased risks of Alzheimer's disease and motor neuron disease.

Methods:

The mortality experienced by a cohort of 83 997 employees of the former Central Electricity Generating Board of England and Wales was investigated for the period 1973–2004. All employees were employed for at least six months with some employment in the period 1973–82. Computerised work histories were available for 79 972 study subjects for the period 1971–93. Information on job and facility (location) were used to estimate exposures to magnetic fields. Two analytical approaches were used to evaluate risks, indirect standardisation (n = 83 997) and Poisson regression (n = 79 972).

Results:

Based on serial mortality rates for England and Wales, deaths from Alzheimer's disease and motor neuron disease were unexceptional. There was an excess of deaths from Parkinson's disease of borderline significance. No statistically significant trends were shown for risks of any of these diseases to increase with lifetime cumulative exposure to magnetic fields (RR per 10 μT-y: Alzheimer's disease 1.10 (95% CI 0.90 to 1.33); motor neuron disease 1.06 (95% CI 0.86 to 1.32); Parkinson's disease 0.88 (95% CI 0.74 to 1.05))

Conclusions:

There is no convincing evidence that UK electricity generation and transmission workers have suffered increased risks from neurodegenerative diseases as a consequence of exposure to magnetic fields.
Deformation of a soft estuarine deposit under a geotextile reinforced embankment
Authors: Kelln Curtis , Sharma Jitendra , Hughes David , Gallagher Gabriel
Published: July 2007

This paper presents a case history of a geotextile reinforced highway embankment constructed on a soft estuarine deposit installed with prefabricated vertical drains. The case history documents the geotechnical site characterization, embankment construction, and monitoring program. The loading response of the soft estuarine soil was monitored during construction using hydrostatic profile gauges, settlement plates, pneumatic piezometers, and slope inclinometers. Settlements of up to 1.3 m were measured under the 4 m high embankment. The deformation behaviour was interpreted qualitatively from the monitoring data using the general framework of elastic-plastic soil models. The effectiveness of the monitoring program is also briefly discussed. The paper provides performance details that make this case history useful to researchers studying the loading response of soft soils under a geotextile reinforced embankment.Key words: case history, embankment, soft clay, vertical drainage, reinforcement.
Effects of depth of water table and substrate temperature on root and top growth of Picea mariana and Larix lancina seedlings
Authors: Lieffers V. J. , Rothwell R. L.
Published: July 2007

Three thermally insulated tanks were divided in half and one side of each was cooled using a network of copper tubing, through which chilled ethylene glycol was pumped. Tanks were filled with peat and seedlings of black spruce (Piceamariana (Mill.) B.S.P.) and tamarack (Larixlaricina (Du Roi) K. Koch.) were transplanted to both ambient and cooled sides. Water table levels of the tanks were maintained at either 4, 10, or 25 cm below the substrate surface. Root biomass, length, and maximum depth, and shoot height, biomass, and branching for both species were lowest in the tank with water table at 4 cm below the surface. Oxygen diffusion rates were lowest and lenticel intumescences of black spruce roots most abundant in this treatment. With water table depth at 25 cm, the cooling treatment (9 °C at the 10 cm level) had a negative effect on root growth compared with the ambient treatment (18 °C at the 10 cm level). The reverse was true for the tank with water levels at 4 cm; the cooled side had greater root growth than the ambient side.
Biological factors influencing stem deterioration rates and salvage planning in balsam fir killed after defoliation by spruce budworm
Authors: Basham J. T.
Published: July 2007

Balsam fir (Abiesbalsamea (L.) Mill.) trees dead between 0 and 5 years were sampled in three widely separated areas that had distinctly different population levels of the secondary, stem-attacking, balsam fir bark beetle (Pityokteinessparsus (Lec.)). The percentage of stem volume affected by sap rot increased significantly with the number of years since tree death. The wood volume lost in debarking tests, simulating pulp mill conditions, averaged 23% in trees dead 4–5 years in the two areas with the most sap rot, and in individual trees, debarking losses were significantly correlated with the extent of sap rot. Sap rot developed most quickly where stems had the most bark beetle activity, whereas where the bark beetle population was very low, sap rot development was significantly slower. These results are consistent with those of many earlier studies and observations in which a close relationship has been noted between the extent of sap rot and the intensity of bark beetle attack in stands of budworm-killed balsam fir. Evidence is presented indicating that stem deterioration rates and beetle activity frequently change with time in specific regions during any one budworm outbreak. It is postulated that inoculum levels of Polyporusabietinus (Dicks ex Fr.), the fungus responsible for the sap rot, and population levels of the balsam fir bark beetle are similarly and greatly affected by earlier occurrences of balsam fir mortality in a region. The average density of bark holes, caused by bark beetle tunneling in recently killed trees, can be used as a nondestructive and quick indicator of the average rate of development and probable extent of stem sap rot in budworm-damaged balsam fir stands. This information can be useful in assessments of the economic feasibility of proposed salvage operations.
A comparison of competition measures for predicting growth of loblolly pine trees
Authors: Daniels Richard F. , Burkhart Harold E. , Clason Terry R.
Published: July 2007

Five families of competition indices were evaluated and compared on the basis of simple correlation with loblolly pine individual tree growth and multiple correlation with growth in the presence of other tree and stand attributes. The family of distance-independent indices included various relative size measures in the form of tree size to mean size ratios. Crown ratio was also included as a distance-independent measure. The four families of distance-dependent indices included various influence area overlap indices, distance-weighted size ratio indices, Spurr's point density, and Brown's point density or area potentially available (APA). All indices were significantly correlated with dbh and basal area growth. The relative size ratio indices, crown ratio, Spurr's point density, and several APA variations were judged best in simple correlations after accounting for tree size and stand density. The best distance-dependent indices had little if any advantage, either in simple or multiple correlation, over the best distance-independent indices. However, the point density index of Spurr and especially APA contributed significantly to growth prediction even in the presence of tree size, stand density, and the distance-independent size ratio and crown ratio indices. Further, APA had the highest partial correlation when all variables were included in this multiple correlation. It was concluded the APA would be a good index for growth prediction models when other tree and stand attributes are already known.
Mechanisms of intertree transmission of Ceratocystiswageneri in young Douglas-fir
Authors: Hessburg P. F. , Hansen E. M.
Published: July 2007

Root-feeding insects are known to vector black-stain root disease in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). Intertree spread through root grafts and limited growth through soil is demonstrated as well. In potted seedling experiments, contact between roots of inoculated and healthy seedlings was either allowed or prevented. Transmission occurred in both treatments but was significantly more frequent (P = 0.01) when intertree root contact was allowed. In the root-contact treatment, 67% of the receptor seedlings died as a result of successful transmission. In the noncontact treatment, 35% of the receptor seedlings died. Evidence points to wounds on fine roots as principal infection courts. Root graft transmission of C. wageneri was verified through field excavation and microscopic examination of 23 root grafts from three widely separated sites.
Effet des techniques de coupe sur la hauteur des cépées dans un taillis de chataignier (Castaneasativa Mill.)
Authors: Cabanettes Alain , Pages Loïc
Published: July 2007

The effects of both cutting tool and cutting height on the height of each stool's dominant shoot, 1 year after the cut were studied on a sweet chestnut coppice of west central France, traditionally managed with short rotations (between 6 and 10 years). Two tools (axe, chainsaw) and two heights (10 and 30 cm) were used in an experimental area of 0.5 ha divided into three blocks. One year after the cut, the height of the stool's dominant shoot was clearly correlated with morphological features of the stool, especially its mean diameter. The relation between these variables is affected by the environment (block effect) and, to a lesser extent, by the tool used for cutting: the chainsaw reduced the dominant shoot height. No effect of cutting height on this variable was observed.
On critical-height sampling
Authors: Deusen Paul C. Van , Meerschaert Walter J.
Published: July 2007

Critical-height sampling is shown to provide unbiased estimates of per-acre cubic volume if the sample trees are selected at stump height to determine if they are to be tallied. Selection at breast height implicitly assumes that the tree is a cylinder from breast height to stump height. It is also shown that unbiased estimates of merchantable volume can be obtained with critical-height sampling. The relationship between variances from critical-height sampling and the usual horizontal point procedure requiring volume estimates is shown to depend on tree spatial patterns. This is also true for growth estimates. A definite benefit of critical-height sampling is that no volume equation is needed.
Mating system and pollen contamination in a Douglas-fir clone bank
Authors: Fast Willi , Dancik Bruce P. , Bower Ralph C.
Published: July 2007

Pollen contamination and mating system of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) clone banks used as an interim seed orchard near Nanaimo, B.C., were estimated. Pollen contamination (m) from surrounding clone banks and natural stands ranged from 0.44 to 0.89. Overall contamination over 2 years was estimated to be 0.65. Pollen contamination varied significantly over 2 pollination years. Multilocus outcrossing rates (t) of four clone banks over 2 years ranged from 0.51 to 1.09, with an unweighted mean outcrossing estimate of 0.72. Outcrossing varied significantly among clone banks and pollination years. An excess of homozygotes suggests that these seed may be inbred. Although pollen contamination and inbreeding may be a problem in these clone banks, the seed may still be useful operationally.
Thinning and nitrogen fertilization effects on soil and tree water stress in a Douglas-fir stand
Authors: Brix H. , Mitchell A. K.
Published: July 2007

Soil and tree water potentials were studied over a 10-year period in a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand that was treated when 24 years old with different thinning and nitrogen fertilization regimes. Throughout the 10-year period, thinning increased the soil water potential during the dry summer periods (July–September) by as much as 1 MPa both with and without fertilization. Fertilization effect on soil water potential was slight and only apparent in the latter part of the study in spite of large increases in leaf area (50% after 7 years) possibly because of better stomatal control of water loss. Fertilization increased water use efficiency. The favorable soil water conditions produced by thinning led to improved shoot water potential only during predawn and early morning. Removal of understory in a thinned and fertilized plot did not affect soil or shoot water potential.
Croissance en hauteur comparée de marcottes et de plants à racines nues d'épinette noire, ainsi que de plants de pin gris
Authors: Doucet René , Boily Jocelyn
Published: July 2007

In 1985, two cutovers, 11 and 8 years old, that had been planted with bare-root stock of black spruce and jack pine were sampled for height growth of regeneration. Both planted stock and black spruce layers were sampled. Height growth was obtained for each year, going back to the year of planting or to the year of the cut. Annual height growth of transplants and layers of black spruce was similar. In one of the cutovers, height growth in 1985 was 28 cm for transplants and 30 cm for layers; in the other, height growth reached 39 and 36 cm, respectively. Jack pine, planted only in the second cutover, had a more rapid height development than black spruce and its current annual growth now stands at 43 cm.
Field performance of Douglas-fir seedlings after treatment with fungicides
Authors: Owston Peyton W. , Thies Walter G. , Fender William
Published: July 2007

Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings grown in containers with pasteurized or nonpasteurized potting mixture and treated with benomyl, captan, fenaminosulf, or ethazol, or left untreated were outplanted in the Cascade Range of western Oregon. The seedlings from all treatments appeared to have been in similar condition at time of planting, so neither nursery managers nor silviculturists would have suspected effects of the treatments to carry over to field performance. After 7 years, however, seedlings grown in pasteurized potting medium survived better than those grown in nonpasteurized medium. Furthermore, survival of benomyl-treated seedlings in pasteurized potting mixture was higher than survival of those grown in pasteurized mixture without any fungicide treatment and survival of ethazol-treated seedlings in unpasteurized mixture was lower than those in unpasteurized mixture without fungicide treatment. There was no evidence that the nursery treatments adversely affected seedling height or mycorrhizal development.
Calorific value variations in components of 10 Canadian tree species
Authors: Singh T. , Kostecky M. M.
Published: July 2007

Calorific values of six softwoods and four hardwoods were determined for components such as stump, main stem, treetop, branches, foliage, and bark. Tree components among groups (hardwoods and softwoods) and within species differed highly significantly (P < 0.01) in calorific values. The calorific means ranged from 19.122 to 21.099 MJ/kg for softwoods and 18.396 to 20.091 MJ/kg for hardwoods.
Rough handling, soil temperature, and root development in outplanted Sitka spruce and Douglas-fir
Authors: Tabbush Paul M.
Published: July 2007

Sealed bags containing forty 2-year-old Sitka spruce (Piceasitchensis (Bong.) Carr.) transplants were dropped 1–15 times from a height of 3 m onto a hard floor. A single drop reduced root growth potential of the plants as measured by a 10-day test, although after 18 days' growth the effect was no longer detectable. Dropping the bags 5 or 15 times severely decreased root growth potential even in the 18-day test. The 15-drop treatment significantly depressed 1-year survival of samples planted in the nursery. Sitka spruce and Douglas-fir (Pseudotsugamenziesii fMirb.) Franco.) transplants dropped 10 times, together with control plants, were placed in root observation boxes with an air temperature of 8 °C and a soil temperature of 4, 8, 12, or 16 °C. At 4 °C soil temperature, little or no root growth was observed in either species. At the higher temperatures the total numbers of new roots formed in 10 days and the number of new roots greater than 1 cm in length formed in 18 days were generally greater in Sitka spruce than Douglas-fir. In both species, root growth was sharply reduced by the mechanical shock treatment. Dropping the trees also depressed mycorrhizal development and resulted in a significant lowering of predawn water potential in Douglas-fir.
Radionuclides of cesium and strontium as indicators of tree growth rate and age: a negative result
Authors: Rundel P. W. , Wood R.
Published: July 2007

Recent suggestions have been made that the peak 1963 concentrations of 137Cs and 90Sr in the atmosphere, resulting from nuclear weapon tests, could be used as a marker to estimate growth rates and age in tropical forest trees where no rings are present. Neither wet- nor dry-ashed tissue samples of either radionuclide could be detected in analyses of large wood samples of Abiesmagnifica from the Sierra Nevada. These results suggest that if Abies woody tissues are typical, then sufficient concentrations of radionuclides of cesium and strontium to allow estimations of growth rates and ages will not be present in the trunks of tropical forest trees.
Bigleaf maple seedling establishment and early growth in Douglas-fir forests
Authors: Fried Jeremy S. , Tappeiner II John C. , Hibbs David E.
Published: July 2007

Survival, age and height distributions, and stocking of bigleaf maple (Acermacrophyllum Pursh) seedlings were studied in 1- to 250-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands in western Oregon to identify the stages in stand development in which bigleaf maple is most likely to establish successfully from seed. Maple seedling emergence averaged 30–40% where seeds were planted and protected from rodents but was typically <2% for unprotected seeds. Seedling survival after 2 years was highly dependent on canopy density, measured by percent sky. Average 1st-year survival of seedlings originating from planted, protected seeds was highest in clearcuts (1–2 years old, 36% survival, 56% sky) and pole-size stands (41–80 years old, 30% survival, 17% sky) with sparse understories and canopies. It was lowest in young stands with dense canopies (20–40 years old, 4% survival, 8% sky) and old stands (81–250 years old, 14% survival, 13% sky) with dense understories. Naturally regenerated populations of bigleaf maple seedlings, which occurred in aggregations (0.005–0.04 ha in area), were most abundant (up to 10 000/ha) in pole-size Douglas-fir stands. Although seedling size distributions within stands had a strongly inverse J shaped form, size distributions within aggregations appeared more normal (bell-shaped). Seedling age rarely exceeded 15 years. Seedlings grew slowly in the understory, often reaching only 25 cm in height after 8–10 years, and were intensively browsed by deer. Naturally regenerated seedlings were virtually absent from clearcuts, probably because of dense competing vegetation and lack of seed caused by poor dispersal and seed predation. The "window" for the most successful establishment of bigleaf maple seedlings appears to begin after canopy thinning and end before forbs and shrubs invade.
Magnesium deficiency symptoms associated with sugar maple dieback in a Lower Laurentians site in southeastern Quebec
Authors: Bernier B. , Brazeau M.
Published: July 2007

Observations made in 1987 on sugar maple (Acersaccharum Marsh.) dieback in the deciduous forest of the Lower Laurentians, northwest of Quebec City, revealed the occurrence of magnesium deficiency in various sites. Visual foliar symptoms observed on sugar maple in a severely declining stand growing on well-drained, stony, loamy-sand soil of granitic origin are briefly described and illustrated. Magnesium concentrations in the foliage of both trees and regeneration in early August averaged 0.06% (range 0.03–0.09%). Other tree or plant species present also exhibited conspicuous magnesium deficiency symptoms. The occurrence of magnesium deficiency in this and other sites of the deciduous forest in the Lower Laurentians contrasts with the general absence of this deficiency in a previously studied large section of forest in the Quebec Appalachians, where soils are derived from other rock formations.
An assessment of the structural method of deriving a black spruce site equation: Reply
Authors: Smith Victor G.
Published: July 2007

not available
A stand-level multispecies growth model for Appalachian hardwoods
Authors: Bowling Ernest H. , Burkhart Harold E. , Burk Thomas E. , Beck Donald E.
Published: July 2007

A stand-level growth and yield model was developed to predict future diameter at breast height (dbh) distributions of thinned stands of mixed Appalachian hardwoods. The model allows prediction by species group and dbh class. Stand attributes (basal area per unit area, trees per unit area, minimum stand dbh, and arithmetic mean dbh) were projected through time for the whole stand and for individual species groups. Future dbh distributions were obtained using the three-parameter Weibull probability density function and a variation of the parameter recovery method. The recovery method used employed the first two noncentral moments of dbh (arithmetic mean dbh and quadratic mean dbh2) to generate Weibull parameters. Future dbh distributions were generated for the whole stand and every species group but one; the diameter distribution for the remaining species group was obtained by subtraction.
Patterns of change of saturated sapwood permeability and sapwood conductance with stand development
Authors: Pothier David , Margolis Hank A. , Waring Richard H.
Published: July 2007

The saturated sapwood permeability (k) of jack pine (Pinusbanksiana Lamb.) from stands of different ages and site qualities was measured using a constant water flow apparatus. Saturated sapwood permeability at the base of the live crown (BLC) increased with age and reached a plateau just beyond 4 × 10−12 m2. The rate at which this plateau was reached, however, was dependent on site quality. Such age-related increases in k can partially explain how trees can maintain similar daytime leaf water potentials at different stages of stand development. Within age-classes 15 and 35, k at BLC was greater on the better-quality sites and was strongly correlated with both diameter and height growth. For age-class 120, k at BLC was not significantly different among sites. Saturated sapwood permeability at BLC could be predicted from age and site quality, using a negative exponential function (R2 = 0.66). The ability to predict changes in k with stand development has potential for improving leaf area estimates derived from sapwood area -leaf area correlations. Sapwood conductance from ground level to the upper third of the crown decreased with age for good-quality sites and increased with age for poor-quality sites. It corresponded to the pattern of average annual height growth over the last 5 years (R2 = 0.61). The number of annual rings contributing to the sapwood at a given age was independent of site quality. This suggests that the historical reconstruction of a tree's leaf area and growth efficiency is possible even after the formation of significant amounts of heartwood.
Early selection in tree breeding: principles for applying index selection and inferring input parameters
Authors: Burdon R. D.
Published: July 2007

Early selection is essential after the first generation of a tree-breeding programme. Two main issues that it raises are (i) the optimal age for selection for the next generation and (ii) how best to use early assessment data for the selection. Attention is given mainly to the latter issue. Early selection is considered as a special type of indirect selection that can embrace multiple traits. Where a sequence of early measurements has been made for single traits it is possible to treat the expressions of a trait at different dates as separate traits in a selection index. Constructing a least-squares selection index with this feature involves a number of questions. Outstanding among these is whether, and in what way, early measurements should be used as covariates for adjusting later ones. Such indices depend, however, on good estimates of phenotypic and genetic variance–covariance matrices. Potential aids for deriving and refining such matrices are reviewed, including the "Lambeth relationship" for age–age correlations and partial correlation analysis. However, analysis of the sensitivity of expected gains with respect to variations in assumed genetic parameters is strongly advocated before decisions are made on age of selection.
Moose browsing and allelopathic effects of Kalmiaangustifolia on balsam fir regeneration in central Newfoundland
Authors: Thompson I. D. , Mallik A. U.
Published: July 2007

We collected forest floor organic matter at two sites where exclosures had been established 12 years previously. The exclosures allowed examination of the effects of moose (Alcesalces) herbivory on the growth of balsam fir (Abiesbalsamea). The areas supported an understory with Kalmiaangustifolia, which has been shown to affect seedling growth of black spruce (Piceamariana). Balsam fir seedlings grown in the laboratory in soil from outside the exclosures showed a significant reduction in fresh weight of the primary root compared with plants grown in washed sand. Treatment soils also showed a previously known growth inhibition effect on roots of black spruce. Exclusion of moose browsing resulted in a higher density of balsam fir inside the exclosures, while Kalmia, which was not browsed, was more dense outside the exclosures. We postulate that moose browsing reduces the extent to which balsam fir shades Kalmia, and can result in a higher density of the latter species, with consequent inhibitory effects on regenerating coniferous species.
Estimating postfire survival of Douglas-fir in the Cascade Range
Authors: Peterson David L. , Arbaugh Michael J.
Published: July 2007

Factors related to survival of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) 2 years after spring wildfires were evaluated at four sites in the Cascade Range. A logistic regression model was developed to estimate postfire survival. Crown scorch and three variables related to bole damage were significant in the regression model, with differences in response among sites attributed to differences in size class. The regression model predicted postfire response of live trees more accurately than that of dead trees, based on estimates of survival probability. Crown scorch was the most significant predictor of tree response, although the importance of additional variables indicated that evaluating bole damage greatly improves postfire survival estimates.
EFFECT OF HYDROSTATIC PRESSURE ON THE BINDING ENERGIES OF EXCITONS IN QUANTUM WELLS
Authors: ZHAO G. J. , LIANG X. X. , BAN S. L.
Published: July 2007

The binding energies of excitons in finite barrier quantum wells under hydrostatic pressure are calculated by a variational method. The influences of hydrostatic pressure on the effective masses of the electron and hole, the dielectric constant, and the conduction band offset between the well and barriers are taken into account in the calculation. The numerical results for the GaAs/Al x Ga 1-x As and GaN/Al x Ga 1-x N quantum wells are given respectively. It is shown that the exciton binding energy increases linearly with the pressure and the pressure effect on arsenide quantum wells is more obvious than that on nitride ones. The exciton binding energies monotonically increase with increasing barrier height, which is related to the Al concentration of the barriers and the influence of the pressure.
A LIOUVILLE PROPERTY FOR GINZBURG–LANDAU SYSTEMS
Authors: FARINA ALBERTO
Published: July 2007

In this short paper, we consider solutions u ∈ C2(ℝN, ℝM) (with N,M ≥ 1) of the Ginzburg–Landau system Δu = u(|u|2 - 1). For N = 3 and M = 2, we prove that every solution satisfying ∫ℝ3 (|u|2 - 1)2 < +∞, is constant and of unit norm. We also give necessary and sufficient conditions, on the integers N and M, ensuring a Liouville property for finite potential energy solutions of the system under consideration.
Interaction between lysine 102 and aspartate 338 in the insect amino acid cotransporter KAAT1
Authors: Castagna M. , Soragna A. , Mari S. A. , Santacroce M. , Betté S. , Mandela P. G. , Rudnick G. , Peres A. , Sacchi V. F.
Published: July 2007

KAAT1 is a lepidopteran neutral amino acid transporter belonging to the NSS super family (SLC6), which has an unusual cation selectivity, being activated by K+ and Li+ in addition to Na+. We have previously demonstrated that Asp338 is essential for KAAT1 activation by K+ and for the coupling of amino acid and driver ion fluxes. By comparing sequences of NSS family members, site-directed mutagenesis, and expression in Xenopus laevis oocytes, we identified Lys102 as a residue likely to interact with Asp338. Compared with wild type, the single mutants K102V and D338E each showed altered leucine uptake and transport-associated currents in the presence of both Na+ and K+. However, in K102V/D338E double mutant, the K102V mutation reversed both the inhibition of Na+-dependent transport and the block in K+-dependent transport that characterize the D338E mutant. K+-dependent leucine currents were not observed in any mutants with D338E. In the presence of the oxidant Cu(II) (1,10-phenanthroline)3, we observed specific and reversible inhibition of K102C/D338C mutant, but not of the corresponding single cysteine mutants, suggesting that these residues are sufficiently close to form a disulfide bond. Thus both structural and functional evidence suggests that these two residues interact. Similar results have been obtained mutating the bacterial transporter homolog TnaT. Asp338 corresponds to Asn286, a residue located in the Na+ binding site in the recently solved crystal structure of the NSS transporter LeuTAa ( 41 ). Our results suggest that Lys102, interacting with Asp338, could contribute to the spatial organization of KAAT1 cation binding site and permeation pathway.
Characterization of CRF, AVT, and ACTH cDNA and pituitary-adrenal axis function in Japanese quail divergently selected for tonic immobility
Authors: Hazard D. , Couty M. , Guémené D.
Published: July 2007

Higher corticosterone (CORT) responses to acute stress have previously been reported in quail selected for short (STI) duration of tonic immobility (TI) than for long TI (LTI), although behavioral studies indicated that LTI quail were more fearful. To investigate adrenal and pituitary function in these quail lines and their possible involvement in the differences in hypothalamic-pituitary-adrenal (HPA) axis reactivity, we measured CORT responses to adrenocorticotropin (1-24 ACTH), corticotropin-releasing factor (CRF), and arginine vasotocin (AVT) after characterizing the nucleotide acid sequences of these peptides in quail. Although maximum adrenal responses, assessed by ACTH challenge, were higher in STI quail, adrenal sensitivity was comparable for the two genotypes. It is therefore unlikely that differences in HPA axis reactivity involved the adrenal level. AVT and ACTH induced comparable CORT responses in both genotypes, whereas those induced by CRF were much lower. AVT is thus more potent than CRF in quail, but the respective maximum pituitary capacity of both genotypes to secrete ACTH was similar, and it is doubtful that the AVT pathway is involved in the difference in HPA axis reactivity between genotypes. On the other hand, the higher CORT responses induced by CRF in STI quail suggest that CRF might be involved in the differences in HPA axis reactivity between LTI and STI genotypes.