bluuebunny/crossref_metadata_2025 huggingface dataset:
Daxx-Mediated Accumulation of Human Cytomegalovirus Tegument Protein pp71 at ND10 Facilitates Initiation of Viral Infection at These Nuclear Domains
Authors: Ishov Alexander M. , Vladimirova Olga V. , Maul Gerd G.
Published: July 2002

Human cytomegalovirus (HCMV) starts immediate-early transcription at nuclear domains 10 (ND10), forming a highly dynamic immediate transcript environment at this nuclear site. The reason for this spatial correlation remains enigmatic, and the mechanism for induction of transcription at ND10 is unknown. We investigated whether tegument-based transactivators are involved in the specific intranuclear location of HCMV. Here, we demonstrate that the HCMV transactivator tegument protein pp71 accumulates at ND10 before the production of immediate-early proteins. Intracellular trafficking of pp71 is facilitated through binding to a coiled-coil region of Daxx. The C-terminal domain of Daxx then interacts with SUMO-modified PML, resulting in the deposition of pp71 at ND10. In Daxx-deficient cells, pp71 does not accumulate at ND10, proving in vivo the necessity of Daxx for pp71 deposition. Also, HCMV forms immediate transcript environments at sites other than ND10 in Daxx-deficient cells, and so does the HCMV pp71 knockout mutant UL82
−/−
in normal cells. This result strongly suggests that pp71 and Daxx are essential for HCMV transcription at ND10. Lack of Daxx had the effect of reducing the infection rate. We conclude that the tegument transactivator pp71 facilitates viral genome deposition and transcription at ND10, possibly priming HCMV for more efficient productive infection.
Immunogenicity and Safety of Defective Vaccinia Virus Lister: Comparison with Modified Vaccinia Virus Ankara
Authors: Ober B. T. , Brühl P. , Schmidt M. , Wieser V. , Gritschenberger W. , Coulibaly S. , Savidis-Dacho H. , Gerencer M. , Falkner F. G.
Published: July 2002

Potent and safe vaccinia virus vectors inducing cell-mediated immunity are needed for clinical use. Replicating vaccinia viruses generally induce strong cell-mediated immunity; however, they may have severe adverse effects. As a vector for clinical use, we assessed the defective vaccinia virus system, in which deletion of an essential gene blocks viral replication, resulting in an infectious virus that does not multiply in the host. The vaccinia virus Lister/Elstree strain, used during worldwide smallpox eradication, was chosen as the parental virus. The immunogenicity and safety of the defective vaccinia virus Lister were evaluated without and with the inserted human p53 gene as a model and compared to parallel constructs based on modified vaccinia virus Ankara (MVA), the present “gold standard” of recombinant vaccinia viruses in clinical development. The defective viruses induced an efficient Th1-type immune response. Antibody and cytotoxic-T-cell responses were comparable to those induced by MVA. Safety of the defective Lister constructs could be demonstrated in vitro in cell culture as well as in vivo in immunodeficient SCID mice. Similar to MVA, the defective viruses were tolerated at doses four orders of magnitude higher than those of the wild-type Lister strain. While current nonreplicating vectors are produced mainly in primary chicken cells, defective vaccinia virus is produced in a permanent safety-tested cell line. Vaccines based on this system have the additional advantage of enhanced product safety. Therefore, a vector system was made which promises to be a valuable tool not only for immunotherapy for diseases such as cancer, human immunodeficiency virus infection, or malaria but also as a basis for a safer smallpox vaccine.
Friend Leukemia Virus Infection Enhances DNA Damage-Induced Apoptosis of Hematopoietic Cells, Causing Lethal Anemia in C3H Hosts
Authors: Kitagawa Masanobu , Yamaguchi Shuichi , Hasegawa Maki , Tanaka Kaoru , Sado Toshihiko , Hirokawa Katsuiku , Aizawa Shiro
Published: July 2002

Exposure of hematopoietic progenitors to gamma irradiation induces
p53
-dependent apoptosis. However, host responses to DNA damage are not uniform and can be modified by various factors. Here, we report that a split low-dose total-body irradiation (TBI) (1.5 Gy twice) to the host causes prominent apoptosis in bone marrow cells of Friend leukemia virus (FLV)-infected C3H mice but not in those of FLV-infected DBA mice. In C3H mice, the apoptosis occurs rapidly and progressively in erythroid cells, leading to lethal host anemia, although treatment with FLV alone or TBI alone induced minimal apoptosis in bone marrow cells. A marked accumulation of P53 protein was demonstrated in bone marrow cells from FLV-infected C3H mice 12 h after treatment with TBI. Although a similar accumulation of P53 was also observed in bone marrow cells from FLV-infected DBA mice treated with TBI, the amount appeared to be parallel to that of mice treated with TBI alone and was much lower than that of FLV- plus TBI-treated C3H mice. To determine the association of
p53
with the prominent enhancement of apoptosis in FLV- plus TBI-treated C3H mice,
p53
knockout mice of the C3H background (C3H

p53
−/−

) were infected with FLV and treated with TBI. As expected,
p53
knockout mice exhibited a very low frequency of apoptosis in the bone marrow after treatment with FLV plus TBI. Further, C3H

p53
−/−

→ C3H

p53
+/+

bone marrow chimeric mice treated with FLV plus TBI survived even longer than the chimeras treated with FLV alone. These findings indicate that infection with FLV strongly enhances radiation-induced apoptotic cell death of hematopoietic cells in host animals and that the apoptosis occurs through a
p53
-associated signaling pathway, although the response was not uniform in different host strains.
Avian Reoviruses Cause Apoptosis in Cultured Cells: Viral Uncoating, but Not Viral Gene Expression, Is Required for Apoptosis Induction
Authors: Labrada Lucía , Bodelón Gustavo , Viñuela Juan , Benavente Javier
Published: July 2002

The cytopathic effect evidenced by cells infected with avian reovirus S1133 suggests that this virus may induce apoptosis in primary cultures of chicken embryo fibroblasts. In this report we present evidence that avian reovirus infection of cultured cells causes activation of the intracellular apoptotic program and that this activation takes place during an early stage of the viral life cycle. The ability of avian reoviruses to induce apoptosis is not restricted to a particular virus strain or to a specific cell type, since different avian reovirus isolates were able to induce apoptosis in several avian and mammalian cell lines. Apoptosis was also provoked in ribavirin-treated avian reovirus-infected cells and in cells infected with UV-irradiated reovirions, indicating that viral mRNA synthesis and subsequent steps in viral replication are not needed for apoptosis induction in avian reovirus-infected cells and that the number of inoculated virus particles, not their infectivity, is the critical factor for apoptosis induction by avian reovirus. Our finding that apoptosis is no longer induced when intracellular viral uncoating is blocked indicates that intraendosomal virion disassembly is required for apoptosis induction and that attachment and uptake of parental reovirions are not sufficient to cause apoptosis. Taken together, our results suggest that apoptosis is triggered from within the infected cell by viral products generated after intraendosomal uncoating of parental reovirions.
Secondary Structure of the 3′ Terminus of Hepatitis C Virus Minus-Strand RNA
Authors: Schuster Catherine , Isel Catherine , Imbert Isabelle , Ehresmann Chantal , Marquet Roland , Kieny Marie Paule
Published: July 2002

The 3′-terminal ends of both the positive and negative strands of the hepatitis C virus (HCV) RNA, the latter being the replicative intermediate, are most likely the initiation sites for replication by the viral RNA-dependent RNA polymerase, NS5B. The structural features of the very conserved 3′ plus [(+)] strand untranslated region [3′ (+) UTR] are well established (K. J. Blight and C. M. Rice, J. Virol. 71:7345-7352, 1997). However, little information is available concerning the 3′ end of the minus [(−)] strand RNA. In the present work, we used chemical and enzymatic probing to investigate the conformation of that region, which is complementary to the 5′ (+) UTR and the first 74 nucleotides of the HCV polyprotein coding sequence. By combining our experimental data with computer predictions, we have derived a secondary-structure model of this region. In our model, the last 220 nucleotides, where initiation of the (+) strand RNA synthesis presumably takes place, fold into five stable stem-loops, forming domain I. Domain I is linked to an overall less stable structure, named domain II, containing the sequences complementary to the pseudoknot of the internal ribosomal entry site in the 5′ (+) UTR. Our results show that, even though the (−) strand 3′-terminal region has the antisense sequence of the 5′ (+) UTR, it does not fold into its mirror image. Interestingly, comparison of the replication initiation sites on both strands reveals common structural features that may play key functions in the replication process.
Mutations That Affect the Tropism of DA and GDVII Strains of Theiler's Virus In Vitro Influence Sialic Acid Binding and Pathogenicity
Authors: Jnaoui Karima , Minet Muriel , Michiels Thomas
Published: July 2002

Theiler's murine encephalomyelitis virus (TMEV) is a natural pathogen of the mouse. The different strains of TMEV are divided into two subgroups according to the pathology they provoke. The neurovirulent strains GDVII and FA induce an acute fatal encephalitis, while persistent strains, like DA and BeAn, cause a chronic demyelinating disease associated with viral persistence in the central nervous system. Different receptor usage was proposed to account for most of the phenotype difference between neurovirulent and persistent strains. Persistent but not neurovirulent strains were shown to bind sialic acid. We characterized DA and GDVII derivatives adapted to grow on CHO-K1 cells. Expression of glycosaminoglycans did not influence infection of CHO-K1 cells by parental and adapted viruses. Mutations resulting from adaptation of DA and GDVII to CHO-K1 cells notably mapped to the well-characterized VP1 CD and VP2 EF loops of the capsid. Adaptation of the DA virus to CHO-K1 cells correlated with decreased sialic acid usage for entry. In contrast, adaptation of the GDVII virus to CHO-K1 cells correlated with the appearance of a weak sialic acid usage for entry. The sialic acid binding capacity of the GDVII variant resulted from a single amino acid mutation (VP1-51, Asn→Ser) located out of the sialic acid binding region defined for virus DA. Mutations affecting tropism in vitro and sialic acid binding dramatically affected the persistence and neurovirulence of the viruses.
Molecular Architecture of Adenovirus DNA Polymerase and Location of the Protein Primer
Authors: Brenkman Arjan B. , Breure Elise C. , van der Vliet Peter C.
Published: July 2002

Adenovirus (Ad) DNA polymerase (pol) belongs to the distinct subclass of the polα family of DNA pols that employs the precursor terminal protein (pTP) as primer. Ad pol forms a stable heterodimer with this primer, and together, they bind specifically to the core origin in order to start replication. After initiation of Ad replication, the resulting pTP-trinucleotide intermediate jumps back and pTP starts to dissociate. Compared to free Ad pol, the pTP-pol complex shows reduced polymerase and exonuclease activities, but the reason for this is not understood. Furthermore, the interaction domains between these proteins have not been defined and the contribution of each protein to origin binding is unclear. To address these questions, we used oligonucleotides with a translocation block and show here that pTP binds at the entrance of the primer binding groove of Ad pol, thereby explaining the decreased synthetic activities of the pTP-pol complex and providing insight into how pTP primes Ad replication. Employing an exonuclease-deficient mutant polymerase, we further show that the polymerase and exonuclease active sites of Ad pol are spatially distinct and that the exonuclease activity of Ad pol is located at the N-terminal part of the protein. In addition, by probing the distances between both active sites and the surface of Ad pol, we show that Ad pol binds a DNA region of 14 to 15 nucleotides. Based on these results, a model for binding of the pTP-pol complex at the origin of replication is proposed.
Transcriptional Regulation of the Interleukin-6 Gene of Human Herpesvirus 8 (Kaposi's Sarcoma-Associated Herpesvirus)
Authors: Deng Hongyu , Song Moon Jung , Chu Julia T. , Sun Ren
Published: July 2002

Human herpesvirus 8 (HHV-8; Kaposi's sarcoma-associated herpesvirus is linked to Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), all of which are viewed as cytokine-driven malignancies. In particular, interleukin-6 (IL-6) has been found to promote the growth and proliferation of cells from KS and PEL. HHV-8 encodes a homologue of IL-6 (viral IL-6 [vIL-6]), which functions similarly to the cellular IL-6. Therefore, vIL-6 has been proposed to play an important role in tumor progression. Several groups have reported that vIL-6 is expressed from the HHV-8 genome at higher levels in PEL and MCD lesions than in KS lesions. However, it is not clear how vIL-6 expression is regulated. We characterized the transcription at the vIL-6 gene locus by Northern blot analysis and, in contrast to previous reports, we observed two distinct transcripts from induced PEL cell lines. This observation was confirmed by primer extension, as well as 5′ and 3′ rapid amplification of cDNA ends. Two transcription initiation sites and putative TATA boxes were mapped. A luciferase reporter system was used to show that each of the two putative TATA boxes contributed to vIL-6 promoter activity. Since virally encoded transcriptional activator Rta potently activates the viral lytic gene expression cascade, we examined the role of Rta in controlling vIL-6 gene expression and found that Rta activated the vIL-6 promoter. The Rta-responsive element was further mapped through a series of deletion constructs. Electrophoretic mobility shift assays demonstrated that Rta binds directly to the vIL-6 Rta-responsive element, and the core Rta-responsive element was mapped to a 26-bp region spanning from nucleotide 18315 to 18290 on the viral genome. We propose that the existence of two vIL-6 promoters offers opportunities for differential regulation of vIL-6 gene expression in different tissue types and may account for the variable vIL-6 levels observed in KS, PEL, and MCD.
Elevated Generation of Reactive Oxygen/Nitrogen Species in Hantavirus Cardiopulmonary Syndrome
Authors: Davis Ian C. , Zajac Allan J. , Nolte Kurt B. , Botten Jason , Hjelle Brian , Matalon Sadis
Published: July 2002

Hantavirus cardiopulmonary syndrome (HCPS) is a life-threatening respiratory disease characterized by profound pulmonary edema and myocardial depression. Most cases of HCPS in North America are caused by Sin Nombre virus (SNV), which is carried asymptomatically by deer mice (Peromyscus maniculatus). The underlying pathophysiology of HCPS is poorly understood. We hypothesized that pathogenic SNV infection results in increased generation of reactive oxygen/nitrogen species (RONS), which contribute to the morbidity and mortality of HCPS. Human disease following infection with SNV or Andes virus was associated with increased nitrotyrosine (NT) adduct formation in the lungs, heart, and plasma and increased expression of inducible nitric oxide synthase (iNOS) in the lungs compared to the results obtained for normal human volunteers. In contrast, NT formation was not increased in the lungs or cardiac tissue from SNV-infected deer mice, even at the time of peak viral antigen expression. In a murine (Mus musculus) model of HCPS (infection of NZB/BLNJ mice with lymphocytic choriomeningitis virus clone 13), HCPS-like disease was associated with elevated expression of iNOS in the lungs and NT formation in plasma, cardiac tissue, and the lungs. In this model, intraperitoneal injection of 1400W, a specific iNOS inhibitor, every 12 h during infection significantly improved survival without affecting intrapulmonary fluid accumulation or viral replication, suggesting that cardiac damage may instead be the cause of mortality. These data indicate that elevated production of RONS is a feature of pathogenic New World hantavirus infection and that pharmacologic blockade of iNOS activity may be of therapeutic benefit in HCPS cases, possibly by ameliorating the myocardial suppressant effects of RONS.
Direct Participation of Sam68, the 68-Kilodalton Src-Associated Protein in Mitosis, in the CRM1-Mediated Rev Nuclear Export Pathway
Authors: Li Jinliang , Liu Ying , Kim Byung Oh , He Johnny J.
Published: July 2002

Human immunodeficiency virus type 1 (HIV-1) replication requires efficient nuclear export of incompletely spliced and unspliced HIV-1 mRNA transcripts, which is achieved by Rev expression at an early stage of the viral life cycle. We have recently shown that expression of Sam68, the 68-kDa Src-associated protein in mitosis, is able to alleviate Rev function block in astrocytes by promoting Rev nuclear export. In the present study, we utilized an antisense RNA expression strategy to down-modulate constitutive Sam68 expression and examined its effect on Rev function, HIV-1 gene expression, and viral replication. These results showed that down-modulation of constitutive Sam68 expression markedly inhibited HIV-1 production in 293T cells and viral replication in T lymphocytes such as Jurkat and CEM cells, as well as human peripheral blood mononuclear cells (PBMCs). Rev-dependent in
trans
complementation and reporter gene assays further demonstrated that inhibition of HIV-1 gene expression by Sam68 down-modulation was due to impeded Rev activity. Moreover, digital fluorescence microscopic imaging revealed that down-modulation of Sam68 expression caused exclusive nuclear retention and colocalization of both Rev and CRM1. Taken together, these data suggest that adequate Sam68 expression is required for Rev function and, thereby, for HIV-1 gene expression and viral replication, and they support the notion that Sam68 is directly involved in the CRM1-mediated Rev nuclear export pathway.
Immunological Aspects of Recombinant Adeno-Associated Virus Delivery to the Mammalian Brain
Authors: Mastakov Mihail Y. , Baer Kristin , Symes C. Wymond , Leichtlein Claudia B. , Kotin Robert M. , During Matthew J.
Published: July 2002

Recombinant adeno-associated viruses (rAAV) are highly efficient vectors for gene delivery into the central nervous system (CNS). However, host inflammatory and immune responses may play a critical role in limiting the use of rAAV vectors for gene therapy and functional genomic studies in vivo. Here, we evaluated the effect of repeated injections of five rAAV vectors expressing different genetic sequences (coding or noncoding) in a range of combinations into the rat brain. Specifically, we wished to determine whether a specific immune or inflammatory response appeared in response to the vector and/or the transgene protein after repeated injections under conditions of mannitol coinjection. We show that readministration of the same rAAV to the CNS is possible if the interval between the first and second injection is more than 4 weeks. Furthermore, our data demonstrate that rAAV vectors carrying different genetic sequences can be administered at intervals of 2 weeks. Our data therefore suggest that the AAV capsid structure is altered by the vector genetic sequence, such that secondary structures of the single-stranded genome have an impact on the antigenicity of the virus. This study provides guidelines for more rational design of gene transfer studies in the rodent brain and, in addition, suggests the use of repeated administration of rAAV as a viable form of therapy for the treatment of chronic diseases.
Reinvestigation of Reaction of (2-Ethoxyvinyl)stannanes with Acetyl Bromide
Authors: Lébl Tomáš , Holeček Jaroslav , Dymák Marek , Steinborn Dirk
Published: July 2002

Four analogous (2-ethoxyvinyl)stannanes (E/Z)-Bu3SnC(R)=CHOEt (R = Bu, H) were prepared and characterised using 1H, 13C, 119Sn, 1H-13C HMQC, 1H-13C HMBC, and 1H-119Sn HMQC NMR spectroscopy. The course of their reactions with acetyl bromide was studied by NMR spectroscopy. Although tributyltin bromide, ethyl acetate and the coresponding alkyne were identified as reaction products, this present reinvestigation showed unambiguously that heterolytic fragementation reactions, as stated previously, did not take place. Acetyl bromide cleaves the Sn-C= bond yielding tributyltin bromide and vinyl ethers. Subsequent decomposition of vinyl ethers and impurities in the starting stannane is the source of ethyl acetate and the alkyne, respectively.
Synthesis and Conformation of 6-Amino-3,6-dideoxyhexono-1,6-lactams
Authors: Hamerníková Michaela , Havlíček Jaroslav , Votavová Hana , Kefurt Karel
Published: July 2002

Three isomeric 6-amino-3,6-dideoxyhexono-1,6-lactams of D-ribo (1a), L-lyxo (2a) and L-arabino (3a) configuration were synthesized via the corresponding 6-azido-3,6-dideoxyhexoses starting from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose. Conformation of lactams 1a, 2a and 3a and their tri-O-acetyl derivatives 1b, 2b and 3b was studied using NMR spectroscopy. CD spectra of the lactams 1a-3a, together with the D-xylo diastereoisomer 4a, were measured and interpreted according to semiempirical rules. NMR and CD measurements confirmed the chair conformation with an equatorial substituent on C-2 as prevailing for the all measured lactams.
Synthesis of 1-Amino-3-{2-[7-(6-deoxy-α/β-D-galactopyranos-6-yl)-1,7-dicarba-closo-dodecaboran(12)-1-yl]ethyl}cyclobutanecarboxylic Acid Hydrochloride
Authors: Kabalka George W. , Das Bhaskar C. , Das Sasmita , Li Guishing , Srivastava Rajiv , Natarajan Nisha , Khan Muhammad K.
Published: July 2002

1-Amino-3-{2-[7-(6-deoxy-α/β-D-galactopyranos-6-yl)-1,7-dicarba-closo-dodecaboran(12)-1-yl]ethyl}cyclobutanecarboxylic acid was synthesized as a potential new agent for boron neutron capture therapy. The key step in the synthesis is the alkylation of 3-{2-[1,7-dicarba-closo-dodecaboran(12)-1-yl]ethyl}cyclobutanone ethylene monothioketal with 1,2:3,4-di-O-isopropylidene-6-O-triflyl-α-D-galactopyranose which gave the precursor ketone that was then converted to the title amino acid via a Bücherer-Strecker synthesis followed by removal of isopropylidene groups in HCl. Preliminary toxicity data in A 435 cancer cells were obtained.
Survey of junior hospital doctors’ attitudes to cardiopulmonary resuscitation
Authors: Morgan R , Westmoreland C
Published: July 2002

Most cardiac arrest teams are made up of junior doctors. The stressful effect of cardiopulmonary resuscitation (CPR) on doctors has not previously been established. A questionnaire was sent to all 52 junior doctors who participated in the cardiac arrest team at a district general hospital. Forty one questionnaires were returned by 22 junior house officers, 12 senior house officers, and seven specialist registrars. The questionnaire was anonymous so non-responders could not be recontacted. Seventy three per cent found CPR stressful. The main reason for stress was the inappropriateness of CPR on the individual patient (12), poor outcome (13), no advanced life support (ALS) course (4), and the procedure itself (4). Fifty four per cent felt the number of inappropriate CPR had increased in the last six months with the main reason given (48%) being failure of senior staff to make “do not resuscitate” orders. Ninety seven per cent felt some CPRs were inappropriate; 70% felt a debriefing session should occur after CPR, while 88% reported not having one. Seventy six per cent felt competent at performing CPR, 22% felt incompetent of whom none had undergone ALS training. Fifty eight per cent found it difficult to discuss CPR with patients; 46% found it difficult to discuss CPR with relatives.

Most junior doctors feel stress from CPR. Adequate review by senior doctors with documentation of do not resuscitate orders where appropriate, after discussion with patients, might be beneficial. Adequate training, improving communication skills, and support for junior doctors in the cardiac arrest team need to be reviewed since improvement in these areas may reduce stress.
Regional differences in incidence of gastric and colonic cancer in the Maori of New Zealand
Authors: Thompson A G
Published: July 2002

Background

It is known that there are ethnic differences in cancer in New Zealand between Maori (the indigenous people) and non-Maori, however, until now no regional comparisons have been made.

Study design

A retrospective study of patients diagnosed at Whangarei Hospital, New Zealand between 1995 and 1997 with gastric or colonic cancer was combined with population data from the 1996 census for Whangarei District to calculate incidence figures. The incidence of cancer was compared to national rates.

Results

Between 1995 and 1997, 19 Maori and 24 non-Maori were diagnosed with gastric cancer, and 10 Maori and 125 non-Maori with colonic cancer. The age standardised rates (per 100 000) for Maori and non-Maori with gastric caner were 68.3 and 7.9 respectively. Gastric cancer is known to be increased in the Maori, but in Whangarei was significantly higher than the national Maori rates (20.5). There was no difference in the rate of colonic cancer in the Maori and non-Maori in Whangarei, again this differs from the national trends, in which the Maori are protected against cancer.

Conclusion

This study highlights that there is still much more to be learnt in understanding the aetiology of gastrointestinal cancers, to explain such strong regional differences.
Phalaris arundinacea seedling establishment: effects of canopy complexity in fen, mesocosm, and restoration experiments
Authors: Lindig-Cisneros Roberto , Zedler Joy B
Published: July 2002

Phalaris arundinacea L. (reed canary grass) is a major invader of wetlands in temperate North America; it creates monotypic stands and displaces native vegetation. In this study, the effect of plant canopies on the establishment of P. arundinacea from seed in a fen, fen-like mesocosms, and a fen restoration site was assessed. In Wingra Fen, canopies that were more resistant to P. arundinacea establishment had more species (eight or nine versus four to six species) and higher cover of Aster firmus. In mesocosms planted with Glyceria striata plus 1, 6, or 15 native species, all canopies closed rapidly and prevented P. arundinacea establishment from seed, regardless of the density of the matrix species or the number of added species. Only after gaps were created in the canopy was P. arundinacea able to establish seedlings; then, the 15-species treatment reduced establishment to 48% of that for single-species canopies. A similar experiment in the restoration site produced less cover of native plants, and P. arundinacea recruited more readily. Results suggest that, where conditions are favorable for native plant growth, even species-poor canopies can inhibit P. arundinacea establishment from seed, but when disturbances create gaps, species-rich canopies confer greater resistance to invasion.Key words: diversity, establishment, fen, invasion resistance, species richness, wetlands.
The effect of ectomycorrhizae on water relations in aspen (Populus tremuloides) and white spruce (Picea glauca) at low soil temperatures
Authors: Landhäusser Simon M , Muhsin Tawfik M , Zwiazek Janusz J
Published: July 2002

Low soil temperatures, common during the growing season in northern forests, have the potential to impede plant growth. In this study, water uptake, water relations, and growth characteristics were examined in aspen (Populus tremuloides) and white spruce (Picea glauca) seedlings that were inoculated with ectomycorrhizal fungi and grown at 20°C daytime air temperatures and low soil temperatures of 4°C and 8°C. Mycorrhizal associations had little effect on root and shoot biomass at both soil temperatures. Root hydraulic conductance (Kr) was higher in both mycorrhizal plant species compared to nonmycorrhizal plants, but there was no soil temperature effect on Kr in either species. Mycorrhizae also increased shoot water potential (Ψw) in Populus tremuloides but had no effect on Ψw in Picea glauca. The increases in Kr and Ψw were not reflected by changes in stomatal conductance (gs) and transpiration rates (E), suggesting that the reduction of water flow in seedlings exposed to low soil temperature was not likely the factor limiting gs in both plant species.Key words: boreal forest, root hydraulic conductance, root growth, stomatal conductance, water uptake.
Spectrophotometric assessment of leaf UV-B absorbing compounds and chemically determined total phenolic levels are strongly correlated
Authors: Levizou E , Manetas Y
Published: July 2002

Investigations concerning the two major ecological roles of phenolics use different methods to quantify these compounds (phenolics as antiherbivores, Folin-Ciocalteu chemical assay; phenolics as UV-B screening pigments, UV-B absorbance). Yet, comparisons of the corresponding results are not possible, since an empirical correlation between the two methods is lacking. In the present study, significant regressions between total phenolic levels (chemically determined with the Folin-Ciocalteu method) and leaf UV-B absorbing capacity (assessed from simple absorbance measurements of methanolic extracts at 300 nm) were found in all seven plant species tested, yet interspecies differences in regression equations were evident. Provided that a standard curve between UV-absorbance versus total phenolic levels is established for each test plant, the latter could be predicted from the former. The UV-absorbance method is preferable because it is time-saving, simpler, and less costly. Given the strong regression between the two variables, a comparison of the generalizations reached by the two lines of research using the corresponding methods for phenolic determination is attempted.Key words: UV-B absorbing capacity, phenolics, herbivory, Mediterranean plants.
Correlation chart of the Proterozoic assembly of the northeastern Canadian - Greenland Shield
Authors: Wardle Richard J , Gower C F , James Donald T , St-Onge Marc R , Scott David J , Garde Adam A , Culshaw Nicholas G , van Gool Jeroen AM , Connelly James N , Perreault Serge , Hall Jeremy
Published: July 2002

Chart 1: Correlation chart of the Proterozoic assembly of the northeastern Canadian  Greenland Shield, including a location map and reference list.
Augmented and reassessed U–Pb geochronological data from the Labradorian–Grenvillian front in the Smokey archipelago, eastern Labrador
Authors: Krogh Thomas E , Kamo Sandra , Gower Charles F , Owen J Victor
Published: July 2002

Four UPb dating sites straddling the Grenville front on the Labrador coast were investigated. Sites 1 and 2 exhibit complex intrusive, deformational, and metamorphic histories and were studied in detail, whereas two simpler outcrops (sites 3 and 4) were examined only at a reconnaissance level. At site 1, south of the Grenville front, a 1799+32 Ma granodioritic gneiss is intruded by two phases of mafic dykes, then by a 1647+75 Ma aplite and a ca. 16471500 Ma pegmatite, and lastly by the Michael gabbro. The pegmatite was metamorphosed at 1030 ± 10 Ma. Site 2 is on the Cut Throat Island thrust, which defines the Grenville front in the area. Early mylonitization occurred at 1790 ± 2 Ma, followed by 1730 ± 2 Ma pegmatite emplacement and then cooling at 1703 ± 15 Ma. A post-deformational melt pod gave a titanite age of 1662 ± 10 Ma. In the mylonitic host, based on positive correlation between Pb loss and degree of granularization in monazite, Grenvillian deformation was very short-lived. Sites 3 and 4 (north of the Cut Throat Island thrust), yielded 1709 ± 10 and 1726 ± 34 Ma ages, respectively. Lack of marked younger Pb loss demonstrates that these sites escaped both Labradorian and Grenvillian metamorphism. Emplacement, deformation, and (or) metamorphism occurred at 18001790 Ma, 17301700 Ma, 16601650 Ma, possibly at 1500 Ma, and at 10401030 Ma. The Cut Throat Island thrust was active during all events, but none was confined to it. The thrust marks the northern limit of Labradorian and Grenvillian orogenesis, but because similar pre-Labradorian history is preserved on both sides of the thrust, it is not a fundamental tectonic boundary after 1800 Ma. Nevertheless, because reactivation occurred during every geological orogenic event known in the region, it clearly represents a zone of persistent crustal weakness.
U–Pb geochronology of detrital zircons in metasedimentary rocks from southern Baffin Island: implications for the Paleoproterozoic tectonic evolution of Northeastern Laurentia
Authors: Scott David J , Stern Richard A , St-Onge Marc R , McMullen Sarah M
Published: July 2002

A geochronological investigation of metasedimentary rocks from southern Baffin Island using the Geological Survey of Canada SHRIMP II (sensitive high-resolution ion microprobe) has characterized the ages of detrital zircon populations to determine their provenance, bracket timing of deposition, and distinguish potentially distinct sequences of rocks. Four lithologically and structurally distinct metasedimentary packages have been identified; each appears to have been derived from a different source region. In the structurally lowest package, all analysed zircons are Archean, and > 90% have ages between 2.83 and 2.63 Ga; these rocks are interpreted as the northernmost exposures of the Paleoproterozoic Povungnituk Group of the Cape Smith Belt, northern Quebec, with detritus derived from the Superior craton. Occupying the intermediate structural levels, the most abundant supracrustal rocks on southern Baffin Island are siliciclastic and carbonate units of the Lake Harbour Group, and the Tasiuyak paragneiss. Five samples show a dominantly Paleoproterozoic signature (2.21.9 Ga), with only rare Archean zircons; the provenance of this detritus is uncertain. In the distinct package of feldspathic quartzite and pelite that stratigraphically overlies the Lake Harbour Group, all of the analysed detrital grains are Archean, ~80% are > 2.83 Ga, with a small proportion of the grains in excess of 3.0 Ga; all of this material is thought to be derived from the Archean craton exposed on the Hall Peninsula east of the study area. Finally, at the highest structural level, a sample associated with the Hall Peninsula orthogneisses contains zircons with prominent modes at 2.92, 2.82, and 2.77 Ga, consistent with derivation from the surrounding orthogneisses.
Geophysical correlations in the Ungava Bay area
Authors: Bourlon E , Mareschal J C , Roest W R , Telmat H
Published: July 2002

We used gravity and magnetic data to extend geological features across Ungava Bay and Hudson Strait, from northern Quebec and Labrador to Baffin Island. Tectonic domains identified on land were extended offshore by visual inspection of the potential fields. The boundaries identified on colour shaded relief maps were drawn on the original marine magnetic profiles to verify the robustness of the conclusions. Our interpretation in Ungava Bay remains speculative but gives some insight into the architecture of the northeastern Canadian Shield. Onshore, where trends are well marked, the magnetic fabric of the Superior Province reappears east of the New Quebec Orogen in the western core zone. Geochronology and geochemical data also suggest the affinity of the western core zone with the Superior Province. On the gravity map, the New Quebec Orogen appears to vanish offshore. A major trend in magnetic and gravity gradients can be followed offshore possibly as far north as Hudson Strait. It has been identified as the extension of the George River and Moonbase shear zones. The De Pas Batholith is associated with a linear trend west of this shear zone. To the east, several features appear distinctly in the magnetic map. A narrow northwest-trending anomaly can be followed from Quebec all the way to Baffin Island. On land, this feature marks the western limit of the Lake Harbour Group. Two wide north-trending bands that can be followed from the Torngat Orogen all the way to Baffin Island are interpreted as the extensions of the Lac Lomier Complex and Tasiuyak Domain.
Geochemistry and age of the Aillik Group and associated plutonic rocks, Makkovik Bay area, Labrador: implications for tectonic development of the Makkovik Province
Authors: Sinclair G S , Barr S M , Culshaw N G , Ketchum J W.F
Published: July 2002

The Aillik domain of the Makkovik Province is dominated by deformed and metamorphosed sedimentary and bimodal volcanic rocks of the redefined Aillik Group and abundant unfoliated late- to post-orogenic plutonic rocks. Mapping and petrological studies in the Makkovik Bay area of the Aillik domain showed that the upper part of the group, in addition to felsic volcanic rocks, also includes extensive areas of hypabyssal, foliated granitic rocks (Measles Point Granite). Although petrochemically similar to the spatially associated felsic volcanic rocks, a new UPb (zircon) age of 1929 Ma suggests that the Measles Point Granite may be about 70 million years older than the volcanic rocks of the Aillik Group, based on published UPb dates for the latter unit. The volcanic and granitic rocks show similar structural and metamorphic history, and both have characteristics of crust-derived A-type felsic rocks, although the granite shows less chemical variation than the felsic volcanic rocks. A within-plate setting is postulated, although the associated mafic metavolcanic rocks and amphibolite dykes show evidence of a volcanic-arc influence. Possible solutions of the paradox presented by the UPb ages imply that the Measles Point Granite either represents the juvenile basement to the Aillik Group or was derived from a basement with a large juvenile component. The setting for deposition of the Aillik Group that is consistent with current tectonic models for the Makkovik Province is a rifted arc built on a juvenile terrane accreted to Archean crust.
Age of volcanic rocks and syndepositional iron formations, Marquette Range Supergroup: implications for the tectonic setting of Paleoproterozoic iron formations of the Lake Superior region
Authors: Schneider D A , Bickford M E , Cannon W F , Schulz K J , Hamilton M A
Published: July 2002

A rhyolite in the Hemlock Formation, a mostly bimodal submarine volcanic deposit that is laterally correlative with the Negaunee Iron-formation, yields a sensitive high-resolution ion microprobe (SHRIMP) UPb zircon age of 1874 ± 9 Ma, but also contains inherited Archean zircons as old as 3.8 Ga. This precise age determination for the classic Paleoproterozoic stratigraphic sequence of northern Michigan, the Marquette Range Supergroup (MRS), necessitates modification of previous depositional and tectonic models. Our new data indicate that the Menominee Group, previously ascribed to continental rifting during early, pre-collision phases of the Penokean orogenic cycle, is coeval with arc-related volcanic rocks now preserved as accreted terranes immediately to the south and is more aptly interpreted as a foredeep deposit. We interpret these to be second-order basins created by oblique subduction of the continental margin rather than basins formed on a rifting margin. Along with a recently reported age for the Gunflint Formation in Ontario of 1878 ± 2 Ma, our data suggest that an extensive foredeep in the western Lake Superior region was the locus of iron-formation deposition during arc accretion from the south. Further, we interpret the lower MRS (Chocolay Group), a glaciogenic and shallow-marine succession that lies atop Archean basement, to be equivalent to the upper part of the Huronian Supergroup of Ontario and to represent the original continental rifting and passive-margin phase of the Penokean cycle. The upper MRS (Baraga Group) represents deeper marine basins, dominated by turbidites and lesser volcanic rocks, resulting from increased subsidence and continued collision. A stitching pluton, which cuts correlatives of the Hemlock Formation in a thrust sheet, yielded a UPb zircon age of 1833 ± 6 Ma, consistent with other post-tectonic plutons in Wisconsin and northern Michigan, indicating that Penokean convergence lasted no longer than ~40 million years.
Proterozoic evolution of the northeastern Canadian Shield: Lithoprobe Eastern Canadian Shield Onshore-Offshore Transect (ECSOOT), introduction and summary
Authors: Wardle R J , Hall J
Published: July 2002

The Lithoprobe Eastern Canadian Shield OnshoreOffshore Transect (ECSOOT) has focused on studies of the processes by which the northeastern Canadian (Laurentian) Shield evolved, firstly by the 1.91.8 Ga coalescence of Archean cratons and then by the addition of juvenile crust from the south in the period 1.90.9 Ga. The transect area is a microcosm of continental accretion and also offers a unique opportunity to link the geological evolution of the Canadian Shield with once-adjacent Greenland.
Crustacean zooplankton communities in lakes recovering from acidification
Authors: Keller W , Yan N D , Somers K M , Heneberry J H
Published: July 2002

Large reductions in sulphur emissions at the Sudbury, Ont., Canada, smelters in recent decades have resulted in decreased lake acidity, and biological improvements have followed. Lakes in the Sudbury area offer a very unique opportunity to develop our understanding of the processes regulating biological restructuring in aquatic ecosystems recovering from acidification. Here, we examine changes in crustacean zooplankton communities that have accompanied the chemical recovery of Whitepine and Sans Chambre lakes, near Sudbury, over the last two decades. In both these formerly acidic lakes, pH has increased to ~6.0, and some zooplankton community recovery has occurred. However, zooplankton communities have not completely recovered based on multivariate comparisons with the community composition of reference lakes. Although a number of acid-sensitive species have appeared, many did not persist, or did not achieve abundances typical of the reference lakes. This indicates that zooplankton community recovery will most likely depend on biotic and abiotic interactions within these lakes and not on factors affecting species dispersal. Both chemical and biological factors have large influences on biological recovery processes. Assessing biological recovery is very important since the restoration of healthy aquatic communities is a major objective of large-scale sulphur emission control programs.
Functional response of kokanee salmon (Oncorhynchus nerka) toDaphniaat different light levels
Authors: Koski Marci L , Johnson Brett M
Published: July 2002

In laboratory experiments, fingerling kokanee salmon (Oncorhynchus nerka, 38 g) were presented with varying densities of zooplankton prey (Daphnia spp.) ranging from 3 to 55 Daphnia·L1, under three light intensities (30, 15, and 0.1 lx). Kokanee exhibited a type I functional response at 0.1 lx (Daphnia consumption·min1= 1.74 prey·L1), a light level typical of moonlit epilimnetic conditions, but shifted to a type II functional response at higher light levels. Both 15 and 30 lx light levels occur during crepuscular periods when kokanee feeding is maximal in the wild, and consumption rates at these light levels were not significantly different (Daphnia consumption·min1= (163.6 prey·L1)(42.2 prey·L1)1). The shift from the type I to type II functional response may be attributed to a foraging mode switch and the incorporation of search time instead of random encounters with prey. Using these models to simulate feeding rates in a Colorado reservoir, attenuation of light intensity and prey density between the epilimnion and hypolimnion resulted in a 100-fold increase in predicted feeding duration. Functional responses that incorporate environmental characteristics like light are important components of foraging models that seek to understand fish consumption, growth, and behavior.
Throwing light on straddling stocks of Illex argentinus: assessing fishing intensity with satellite imagery
Authors: Waluda C M , Trathan P N , Elvidge C D , Hobson V R , Rodhouse P G
Published: July 2002

Marine fisheries provide around 20% of animal protein consumed by man worldwide, but ineffective management can lead to commercial extinction of exploited stocks. Fisheries that overlap nationally controlled and high seas waters cause particular problems, as few management data are available for the high seas. The Argentinean short-finned squid, Illex argentinus, exemplifies such a "straddling stock". Here we demonstrate that light emitted by fishing vessels to attract squid can be detected via remote-sensing. Unlike conventional fisheries data, which are restricted by political boundaries, satellite imagery can provide a synoptic view of fishing activity in both regulated and unregulated areas. By using known levels of fishing effort in Falkland Islands waters to calibrate the images, we are able to estimate effort levels on the high seas, providing a more comprehensive analysis of the overall impact of fishing on the stock. This innovative tool for quantifying fishing activity across management boundaries has wide-ranging applications to squid fisheries worldwide.
Glucosyltransferases acting on starch or sucrose for the synthesis of oligosaccharides
Authors: Plou Francisco J , Martín M Teresa , de Segura Aránzazu Gomez , Alcalde Miguel , Ballesteros Antonio
Published: July 2002

In this work we review the extraordinary biotechnological potential of two glycosyltransferases, cyclodextrin glucanotransferase and dextransucrase, especially their utility in the synthesis of oligosaccharides. Both enzymes are non-Leloir transferases that require neither co-factors nor activated substrates, as they directly employ the free energy of cleavage of starch and sucrose, respectively. Cyclodextrin glucanotransferase is able to produce cyclodextrins from starch. In the presence of appropriate acceptors (e.g., carbohydrates), this enzyme furnishes oligosaccharides containing α(1[Formula: see text]4) bonds. Thus, we have found that glucose, maltose, and sucrose readily serve as acceptors to form the corresponding [Glc-α(1[Formula: see text]4)]n- oligosaccharides, with the degree of polymerization being controlled by the starch:acceptor ratio. The ability of other sugars and related compounds to act as acceptors is also reviewed. Dextransucrase is a glycansucrase that synthesizes dextran using sucrose as glucosyl donor. The formation of dextrans can be quantitatively replaced with the formation of novel oligosaccharides by adding alternative carbohydrate acceptors to the reaction medium. With the dextransucrase from Leuconostoc mesenteroides B-1299, we have investigated the synthesis of gluco- oligosaccharides containing α(1[Formula: see text]2) bonds using methyl 1-O-α-D-glucopyranoside as the acceptor. These products constitute a class of nondigestible nutraceutical oligosaccharides with prebiotic properties relating to the stabilization and enhancement of gastrointestinal tract flora, and are being increasingly used by the food industry.Key words: glycansucrases, cyclodextrin glucanotransferase, cyclodextrin glucosyltransferase, dextransucrase, acceptor products, gluco-oligosaccharides, malto-oligosaccharides, coupling sugar, nutraceuticals, functional foods, prebiotics.