bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mannose-Dependent Epitope for Neutralizing Antibody 2G12 on Human Immunodeficiency Virus Type 1 Glycoprotein gp120
Authors: Sanders Rogier W. , Venturi Miro , Schiffner Linnea , Kalyanaraman Roopa , Katinger Hermann , Lloyd Kenneth O. , Kwong Peter D. , Moore John P.
Published: July 2002

We have analyzed the unique epitope for the broadly neutralizing human monoclonal antibody (MAb) 2G12 on the gp120 surface glycoprotein of human immunodeficiency virus type 1 (HIV-1). Sequence analysis, focusing on the conservation of relevant residues across multiple HIV-1 isolates, refined the epitope that was defined previously by substitutional mutagenesis (A. Trkola, M. Purtscher, T. Muster, C. Ballaun, A. Buchacher, N. Sullivan, K. Srinivasan, J. Sodroski, J. P. Moore, and H. Katinger, J. Virol. 70:1100-1108, 1996). In a biochemical study, we digested recombinant gp120 with various glycosidase enzymes of known specificities and showed that the 2G12 epitope is lost when gp120 is treated with mannosidases. Computational analyses were used to position the epitope in the context of the virion-associated envelope glycoprotein complex, to determine the variability of the surrounding surface, and to calculate the surface accessibility of possible glycan- and polypeptide-epitope components. Together, these analyses suggest that the 2G12 epitope is centered on the high-mannose and/or hybrid glycans of residues 295, 332, and 392, with peripheral glycans from 386 and 448 on either flank. The epitope is mannose dependent and composed primarily of carbohydrate, with probably no direct involvement of the gp120 polypeptide surface. It resides on a face orthogonal to the CD4 binding face, on a surface proximal to, but distinct from, that implicated in coreceptor binding. Its conservation amidst an otherwise highly variable gp120 surface suggests a functional role for the 2G12 binding site, perhaps related to the mannose-dependent attachment of HIV-1 to DC-SIGN or related lectins that facilitate virus entry into susceptible target cells.
Modulating the Function of the Measles Virus RNA-Dependent RNA Polymerase by Insertion of Green Fluorescent Protein into the Open Reading Frame
Authors: Duprex W. Paul , Collins Fergal M. , Rima Bert K.
Published: July 2002

Measles virus
(MV) is the type species of the
Morbillivirus
genus and its RNA-dependent RNA polymerase complex is comprised of two viral polypeptides, the large (L) and the phospho- (P) proteins. Sequence alignments of morbillivirus L polymerases have demonstrated the existence of three well-conserved domains (D1, D2, and D3) which are linked by two variable hinges (H1 and H2). Epitope tags (c-Myc) were introduced into H1 and H2 to investigate the tolerance of the variable regions to insertions and to probe the flexibility of the proposed domain structures to spatial reorientation. Insertion into H1 abolished polymerase activity whereas introduction into H2 had no effect. The open reading frame of enhanced green fluorescent protein was also inserted into the H2 region of the MV L gene to extend these observations. This resulted in a recombinant protein that was both functional and autofluorescent, although the overall polymerase activity was reduced by over 40%. Two recombinant viruses which contained the chimeric L genes EdtagL(MMc-mycM) and EdtagL(MMEGFPM) were generated. Tagged L proteins were detectable, by indirect immunofluorescence in the case of EdtagL(MMc-mycM) and by autofluorescence in the case of EdtagL(MMEGFPM). We suggest that D3 enjoys a limited conformational independence from the other domains, indicating that the L polymerases of the
Mononegavirales
may function as multidomain proteins.
Viral Gene Expression Patterns in Human Herpesvirus 6B-Infected T Cells
Authors: Øster Bodil , Höllsberg Per
Published: July 2002

Herpesvirus gene expression is divided into immediate-early (IE) or α genes, early (E) or β genes, and late (L) or γ genes on the basis of temporal expression and dependency on other gene products. By using real-time PCR, we have investigated the expression of 35 human herpesvirus 6B (HHV-6B) genes in T cells infected by strain PL-1. Kinetic analysis and dependency on de novo protein synthesis and viral DNA polymerase activity suggest that the HHV-6B genes segregate into six separate kinetic groups. The genes expressed early (groups I and II) and late (groups V and VI) corresponded well with IE and L genes, whereas the intermediate groups III and IV contained E and L genes. Although HHV-6B has characteristics similar to those of other roseoloviruses in its overall gene regulation, we detected three B-variant-specific IE genes. Moreover, genes that were independent of de novo protein synthesis clustered in an area of the viral genome that has the lowest identity to the HHV-6A variant. The organization of IE genes in an area of the genome that differs from that of HHV-6A underscores the distinct differences between HHV-6B and HHV-6A and may provide a basis for further molecular and immunological analyses to elucidate their different biological behaviors.
Adding Genes to the RNA Genome of Vesicular Stomatitis Virus: Positional Effects on Stability of Expression
Authors: Wertz Gail W. , Moudy Robin , Ball L. Andrew
Published: July 2002

Gene expression of the nonsegmented negative strand (NNS) RNA viruses is controlled primarily at the level of transcription by the position of the genes relative to the single transcriptional promoter. We tested this principle by generating engineered variants of vesicular stomatitis virus in which an additional, identical, transcriptional unit was added to the genome at each of the viral gene junctions. Analysis of transcripts confirmed that the level of transcription was determined by the position of the gene relative to the promoter. However, the position at which a gene was inserted affected the replication potential of the viruses. Adding a gene between the first two genes, N and P, reduced replication by over an order of magnitude, whereas addition of a gene at the other gene junctions had no effect on replication levels. All genes downstream of the inserted gene had decreased levels of expression, since transcription of the extra gene introduced an additional transcriptional attenuation event. The added gene was stably maintained in the genome upon repeated passage in all cases. However, expression of the added gene was stable at only three of the four positions. In the case of insertion between the N and P genes, a virus population arose within two passages that had restored replication to wild-type levels. In this population, expression of the additional gene as a monocistronic mRNA was suppressed by mutations at the end of the upstream (N) gene that abolished transcriptional termination. Because transcription is obligatorily sequential, this prevented transcription of the inserted downstream gene as a monocistronic mRNA and resulted instead in polymerase reading through the gene junction to produce a bicistronic mRNA. This eliminated the additional attenuation step and restored expression of all downstream genes and viral replication to wild-type levels. These data show that transcriptional termination is a key element in control of gene expression of the negative strand RNA viruses and a means by which expression of individual genes may be regulated within the framework of a single transcriptional promoter. Further, these results are directly relevant to the use of NNS viruses as vectors and vaccine delivery agents, as they show that the level of expression of an added gene can be controlled by its insertion position but that not all positions of insertion yield stable expression of the added gene.
Subcellular Localization of the Bovine Leukemia Virus R3 and G4 Accessory Proteins
Authors: Lefèbvre Laurent , Ciminale Vincenzo , Vanderplasschen Alain , D'Agostino Donna , Burny Arsène , Willems Luc , Kettmann Richard
Published: July 2002

Bovine leukemia virus
(BLV) is a complex retrovirus that belongs to the
Deltaretrovirus
genus, which also includes
Human T-cell leukemia virus type 1
(HTLV-1). Both viruses contain an X region coding for at least four proteins: Tax and Rex, which are involved in transcriptional and posttranscriptional regulation, respectively, and the accessory proteins R3 and G4 (for BLV) and p12
I
, p13
II
, and p30
II
(for HTLV-1). The present study was aimed at characterizing the subcellular localization of BLV R3 and G4. The results of immunofluorescence experiments on transfected HeLa Tat cells demonstrated that R3 is located in the nucleus and in cellular membranes, as previously reported for HTLV-1 p12
I
. In contrast, G4, like p13
II
, is localized both in the nucleus and in mitochondria. In addition, we have shown that G4 harbors a mitochondrial targeting signal consisting of a hydrophobic region and an amphipathic α-helix. Thus, despite a lack of significant primary sequence homology, R3 and p12
I
and G4 and p13
II
exhibit similar targeting properties, suggesting possible overlap in their functional properties.
Handedness of the Herpes Simplex Virus Capsid and Procapsid
Authors: Cheng Naiqian , Trus Benes L. , Belnap David M. , Newcomb William W. , Brown Jay C. , Steven Alasdair C.
Published: July 2002

The capsid of herpes simplex virus has an icosahedral surface lattice with a nonskew triangulation number, T=16. Nevertheless, the proteins arrayed on this lattice necessarily have an intrinsic handedness. We have determined the handedness of both the herpes simplex virus type 1 capsid and its precursor procapsid by a cryoelectron microscopic tilting method.
1917 Avian Influenza Virus Sequences Suggest that the 1918 Pandemic Virus Did Not Acquire Its Hemagglutinin Directly from Birds
Authors: Fanning Thomas G. , Slemons Richard D. , Reid Ann H. , Janczewski Thomas A. , Dean James , Taubenberger Jeffery K.
Published: July 2002

Wild waterfowl captured between 1915 and 1919 were tested for influenza A virus RNA. One bird, captured in 1917, was infected with a virus of the same hemagglutinin (HA) subtype as that of the 1918 pandemic virus. The 1917 HA is more closely related to that of modern avian viruses than it is to that of the pandemic virus, suggesting (i) that there was little drift in avian sequences over the past 85 years and (ii) that the 1918 pandemic virus did not acquire its HA directly from a bird.
Effects of Varying Sequence Similarity on the Frequency of Repeat Deletion during Reverse Transcription of a Human Immunodeficiency Virus Type 1 Vector
Authors: An Wenfeng , Telesnitsky Alice
Published: July 2002

Genetic recombination contributes to human immunodeficiency virus type 1 (HIV-1) diversity, with homologous recombination being more frequent than nonhomologous recombination. In this study, HIV-1-based vectors were used to assay the effects of various extents of sequence divergence on the frequency of the recombination-related property of repeat deletion. Sequence variation, similar in degree to that which differentiates natural HIV-1 isolates, was introduced by synonymous substitutions into a gene segment. Repeated copies of this segment were then introduced into assay vectors. With the use of a phenotypic screen, the deletion frequency of identical repeats was compared to the frequencies of repeats that differed in sequence by various extents. During HIV-1 reverse transcription, the deletion frequency observed with repeats that differed by 5% was 65% of that observed with identical repeats. The deletion frequency decreased to 26% for repeats that differed by 9%, and when repeats differed by 18%, the deletion frequency was about 5% of the identical repeat value. Deletion frequencies fell to less than 0.3% of identical repeat values when genetic distances of 27% or more were examined. These data argue that genetic variation is not as inhibitory to HIV-1 repeat deletion as it is to the corresponding cellular process and suggest that, for sequences that differ by about 25% or more, HIV-1 recombination directed by sequence homology may be no more frequent than that which is homology independent.
Molecular and Enzymatic Characterization of the Porcine Endogenous Retrovirus Protease
Authors: Blusch Jürgen H. , Seelmeir Sigrid , von der Helm Klaus
Published: July 2002

The protease of the porcine endogenous retrovirus (PERV) subtypes A/B and C was recombinantly expressed in
Escherichia coli
as proteolytically active enzyme and characterized. The PERV Gag precursor was also recombinantly produced and used as the substrate in an in vitro enzyme assay in parallel with synthetic nonapeptide substrates designed according to cleavage site sequences identified in the PERV Gag precursor. The proteases of all PERV subtypes consist of 127 amino acid residues with an
M
r
of 14,000 as revealed by determining the protease N and C termini. The PERV proteases have a high specificity for PERV substrates and do not cleave human immunodeficiency virus (HIV)-specific substrates, nor are they inhibited by specific HIV protease inhibitors. Among the known retroviral proteases, the PERV proteases resemble most closely the protease of the murine leukemia retrovirus.
Identification of Two Additional Translation Products from the Matrix (M) Gene That Contribute to Vesicular Stomatitis Virus Cytopathology
Authors: Jayakar Himangi R. , Whitt Michael A.
Published: July 2002

The matrix (M) protein of vesicular stomatitis virus (VSV) is a multifunctional protein that is responsible for condensation of the ribonucleocapsid core during virus assembly and also plays a critical role in virus budding. The M protein is also responsible for most of the cytopathic effects (CPE) observed in infected cells. VSV CPE include inhibition of host gene expression, disablement of nucleocytoplasmic transport, and disruption of the host cytoskeleton, which results in rounding of infected cells. In this report, we show that the VSV M gene codes for two additional polypeptides, which we have named M2 and M3. These proteins are synthesized from downstream methionines in the same open reading frame as the M protein (which we refer to here as M1) and lack the first 32 (M2) or 50 (M3) amino acids of M1. Infection of cells with a recombinant virus that does not express M2 and M3 (M33,51A) resulted in a delay in cell rounding, but virus yield was not affected. Transient expression of M2 and M3 alone caused cell rounding similar to that with the full-length M1 protein, suggesting that the cell-rounding function of the M protein does not require the N-terminal 50 amino acids. To determine if M2 and M3 were sufficient for VSV-mediated CPE, both M2 and M3 were expressed from a separate cistron in a VSV mutant background that readily establishes persistent infections and that normally lacks CPE. Infection of cells with the recombinant virus that expressed M2 and M3 resulted in cell rounding indistinguishable from that with the wild-type recombinant virus. These results suggest that M2 and M3 are important for cell rounding and may play an important role in viral cytopathogenesis. To our knowledge, this is first report of the multiple coding capacities of a rhabdovirus matrix gene.
Alpha Interferon Inhibits Hepatitis C Virus Replication in Primary Human Hepatocytes Infected In Vitro
Authors: Castet Valérie , Fournier Chantal , Soulier Alexandre , Brillet Rozenn , Coste Joliette , Larrey Dominique , Dhumeaux Daniel , Maurel Patrick , Pawlotsky Jean-Michel
Published: July 2002

Chronic hepatitis C is a common cause of liver disease, the complications of which include cirrhosis and hepatocellular carcinoma. Treatment of chronic hepatitis C is based on the use of alpha interferon (IFN-α). Recently, indirect evidence based on mathematical modeling of hepatitis C virus (HCV) dynamics during human IFN-α therapy suggested that the major initial effect of IFN-α is to block HCV virion production or release. Here, we used primary cultures of healthy, uninfected human hepatocytes to show that: (i) healthy human hepatocytes can be infected in vitro and support HCV genome replication, (ii) hepatocyte treatment with IFN-α results in expression of IFN-α-induced genes, and (iii) IFN-α inhibits HCV replication in infected human hepatocytes. These results show that IFN-α acts primarily through its nonspecific antiviral effects and suggest that primary cultures of human hepatocytes may provide a good model to study intrinsic HCV resistance to IFN-α.
Cobalt Bis(1,2-dicarbollide) Ion with a Disulfur Bridge Between B(8) and B(8'). X-Ray Structure, Absolute Configuration of One Enantiomer, and Implications
Authors: Plešek Jaromír , Císařová Ivana , Bačkovský Jaroslav
Published: July 2002

The structure and absolute configuration of one enantiomer of the [3-Co-(1,2-C2B9H10)2-8,8'-μ-S2][NEt4] salt was established by X-ray diffraction. A spontaneous resolution took place during crystallization but attempts at resolution in solution via chiral HPLC and chiral capillary electrophoresis failed. The probable cause is discussed and successful resolution of less racemisable 8,8'-bridged metallacarboranes of this type is predicted. The criterion of resolvability ought to be the observation of two C-Hcarborane signals in 1H NMR of the respective compound with a symmetric bridge. The geometry of the disulfur-bridged title compound is discussed in terms of accessibility of the central ion to external moieties. The central ion is apparently screened from the environment by terminal hydrogens at the rim of the pentagonal ligand planes in any kind of commo-bis-icosahedral sandwich complexes.
Cosmic rays: are air crew at risk?
Authors: Lim M K
Published: July 2002

This article reviews the current knowledge about cosmic rays and their possible effects on health of air crew, discusses research directions necessary for establishing and measuring the risks, and highlights the need for physicians and air crew to be informed, despite the inconclusiveness of the evidence. A literature review of computerised medical and scientific databases was carried out. Recent reports highlighting increased incidence of cancer among airline pilots and cabin crew have renewed concerns about possible exposure to harmful levels of cosmic radiation at altitude. Such low energy ionising radiation has been shown to cause double stranded DNA deletions and induce genomic instability in human chromosomes. In the field of microelectronics, cosmic rays have been shown to cause “hard” and “soft” errors in computer microchips, in a dose-response fashion with increasing altitude. Pregnant cabin crew members are of special concern. Although the epidemiological evidence is still inconclusive, we know enough to warrant a cautionary stance. The European Union (EU) leads the way in legislation.
Cancer mortality among man-made graphite electrode manufacturing workers: results of a 38 year follow up
Authors: Mori I
Published: July 2002

Background and Aims:To examine the risk for cancer mortality among workers exposed to coal tar and coal tar pitch volatiles in a man-made graphite electrode factory. The risk for cancer mortality in this type of factory is still inconclusive, although coal tar and coal tar pitch are recognised as human carcinogens.

Methods:The study cohort consisted of 332 male employees who served more than five years in the period 1951–74. The cohort was traced until 1988. Analyses used standardised mortality ratios (SMRs) to compare cause specific mortality with that in the general and local population. Effect of smoking was estimated based on the information collected from the subgroup of the cohort. SMRs for leading causes of death were compared among different job titles, duration of employment, time since first employment, and observation subperiods. Exposure level for tar and benzo[a]pyrene (BaP) in the factory was also discussed, based on measurements done by other researchers in the past.

Results:During the study period, 52 deaths were identified (SMR 0.68), including 22 cancer deaths (SMR 1.01). The SMR for lung cancer was significantly increased in comparison with the general population (SMR 2.62). It was slightly decreased in comparison with the local population, but remained significant (SMR 2.35). Excess deaths were also observed for lymphatic and haematopoietic cancers (SMR 3.46). Smoking habits in the subgroup were similar to those in the general population; thus the increased SMR for lung cancer was unlikely to be explained by smoking.

Conclusion:Previous environmental measurements suggested that considerable exposure to tar and BaP had existed in the factory. The results suggest a possible risk for lung cancer among the cohort, but the limitations of the study, such as the small study population and insufficient information on exposure, indicate that further study is required.
Early diagnosis of colonic carcinoma: a haemorrhagic complication after the use of tissue plasminogen activator
Authors: Baker J W , Mitchell S J , Dixon A R
Published: July 2002

Haemorrhagic complications of thrombolytic therapy for myocardial infarction are common. A 68 year old man presented with a myocardial infarction and was started on tissue plasminogen activator. Soon after he experienced rectal bleeding and a barium enema showed a small carcinoma in the colon, which was treated surgically. It is important that gastrointestinal bleeding secondary to thrombolysis is always investigated for an underlying cause.
Hydroxycinnamic acid amide metabolism: physiology and biochemistry
Authors: Facchini Peter J , Hagel Jillian , Zulak Katherine G
Published: July 2002

Hydroxycinnamic acid amides (HCAAs) are a widely distributed group of plant secondary metabolites purported to function in several growth and developmental processes including floral induction, flower formation, sexual differentiation, tuberization, cell division, and cytomorphogenesis. Although most of these putative physiological roles for HCAAs remain controversial, the biosynthesis of amides and their subsequent polymerization in the plant cell wall are generally accepted as integral components of plant defense responses to pathogen challenge and wounding. Tyramine-derived HCAAs are commonly associated with the cell wall of tissues near pathogen-infected or wound healing regions. Moreover, feruloyltyramine and feruloyloctapamine are covalent cell wall constituents of both natural and wound periderms of potato (Solanum tuberosum) tubers, and are putative components of the aromatic domain of suberin. The deposition of HCAAs is thought to create a barrier against pathogens by reducing cell wall digestibility. HCAAs are formed by the condensation of hydroxycinnamoyl-CoA thioesters with phenylethylamines such as tyramine, or polyamines such as putrescine. The ultimate step in tyramine-derived HCAA biosynthesis is catalyzed by hydro xycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase (THT; E.C. 2.3.1.110). The enzyme has been isolated and purified from a variety of plants, and the corresponding cDNAs cloned from potato, tobacco (Nicotiana tabacum), and pepper (Capsicum annuum). THT exhibits homology with mammalian spermidine-spermine acetyl transferases and putative N-acetyltransferases from microorganisms. In this review, recent advances in our understanding of the physiology and biochemistry of HCAA biosynthesis in plants are discussed.Key words: hydroxycinnamic acid amides, hydroxycinnamoyl-CoA thioesters, metabolic engineering, phenylethylamines, plant cell wall, polyamines, secondary metabolism, tyramine.
A peculiar new fossil shrew (Lipotyphla, Soricidae) from the High Arctic of Canada
Authors: Hutchison J Howard , Harington C R
Published: July 2002

Arctisorex polaris, gen.n., sp.n., from the late Neogene of Ellesmere Island, Nunavut, is the most northerly record thus far of a shrew. The genus is represented by the posterior moiety of a dentary and last two molars. The well-developed M3 and the extreme distance between the articular condyles, separated by a narrow interarticular isthmus, agrees best with the neomyine shrews. The expansion and anterior inclination of the coronoid process, extreme elongation of the third molar that results in it being longer than the M2, and the M3 with a distinct entoconid valley, are unique among soricids. We suggest that Arctisorex may be the only shrew specialized for frugivory.
Evidence for reversal of basin polarity during carbonate ramp development in the Mesoproterozoic Borden Basin, Baffin Island
Authors: Sherman Anne G , James Noel P , Narbonne Guy M
Published: July 2002

Distribution of facies in the lower half of the Bylot Supergroup suggests overall westward deepening of the Mesoproterozoic Borden Basin. In marked contrast, the upper half of the succession records a reversal in the overall bathymetric trend, such that the eastern portion underwent relative deepening as the west experienced relative shallowing. Strata deposited during this reversal belong to the Victor Bay Formation, a ramp composed predominantly of limestone. Karsting of carbonate strata and development of an angular unconformity in the west contrast with back-stepping and drowning of the ramp in the east, followed by mantling by deep-water limestone, carbonaceous carbonate, and turbidites. Increased accommodation space during this time, via both tectonic subsidence and eustatic sea-level rise, led to a profusion of stromatolite pinnacle reefs and large biostromes. The reversal of basin polarity is best reconciled with development of a distal foreland basin superimposed on the Borden aulacogen. Crustal rethickening and uplift occurred along reactivated basement faults during an eastward-directed compressional event and could be related to thrusting of similar age and vergence in the Coppermine River Group of northwestern Canada.
Otolith sulfur isotope method to reconstruct salmon (Oncorhynchus tshawytscha) life history
Authors: Weber Peter K , Hutcheon Ian D , McKeegan Kevin D , Ingram B Lynn
Published: July 2002

We report a new ion microprobe method to reconstruct aspects of fish life history based on sulfur isotopes (34S/32S, expressed as δ34S). Selected hatchery raised and naturally spawned juvenile chinook salmon (Oncorhynchus tshawytscha) are shown to have a 12.96 ± 0.27 (mean ± 2 standard errors) difference in muscle δ34S values, corresponding to δ34S differences between the hatchery and freshwater diets. Isotopic microanalyses of otoliths demonstrate that this 13 difference is preserved in the otoliths. We interpret the otolith δ34S record to be a chronology of dietary δ34S, with approximately one-week temporal resolution, preserved in these banded calcium carbonate structures. Potential applications of this method include identifying hatchery raised fish and reconstructing nutrition sources, migration, and other aspects of fish life history.
Comparative growth and feeding in zebra and quagga mussels (Dreissena polymorphaandDreissena bugensis): implications for North American lakes
Authors: Baldwin Brad S , Mayer Marilyn S , Dayton Jeffrey , Pau Nancy , Mendilla Johanna , Sullivan Maura , Moore Aaron , Ma Aye , Mills Edward L
Published: July 2002

In laboratory experiments, quagga mussels (Dreissena bugensis) survived as well as zebra mussels (Dreissena polymorpha) and equaled or exceeded their growth rate (3 to 242% change in wet mass) when reared at 6 or 23°C and fed natural seston or Chlamydomonas at food levels ranging from 0.057.4 µg·L1chlorophyll a (chl a). Superior growth of quagga mussels was most pronounced at low food levels. We found no significant differences in per capita clearance rates (CR), functional responses, or feeding behavior between zebra and quagga mussels fed Chlamydomonas, Nannochloris, or mixed suspensions of Nannochloris and clay. Per capita CR ranged from 0.018 to 0.402 L·mussel1·h1for zebra mussels and from 0.010 to 0.407 L·mussel1·h1for quagga mussels. Because quagga mussels had more biomass per unit shell length, we found lower biomass-specific CR for quagga mussels. When fed natural seston, zebra and quagga mussels could selectively reject inorganic material and at the lowest seston level the assimilation efficiency of quagga mussels (81%) was significantly higher than that of zebra mussels (63%). Our experiments suggest that quagga mussels can survive, grow, and feed as well or better than zebra mussels in epilimnetic waters with either low or high productivity.
Formulation of particle pseudo-rapidity (rapidity) distribution in high-energy pp collision and e+e annihilation
Authors: Liu F -H
Published: July 2002

The pseudorapidity (rapidity) distributions of particles produced in high-energy collisions are analyzed using the revised thermalized cylinder model. The calculated results are compared and found to be in agreement with the experimental data of pp collision and e+e annihilation.

PACS Nos.: 13.85-t, 13.75-n, 13.85Hd, 13.65+i
Iterative solutions for relativistic dissipative cosmologies
Authors: Harko T , Mak M K
Published: July 2002

Iterative solutions of the gravitational field equations for a homogeneous flat FriedmannRobertsonWalker Universe filled with a causal bulk viscous fluid in the framework of the full IsraelStewartHiscock theory are presented. The general solution of the field equations are presented in a parametric form in the zeroth-, first-, second-, and mth-order approximation by the method of iteration. The time evolution of the scale factor, energy density, deceleration parameter, entropy, Kretschmann scalar, and bulk viscous pressure-thermodynamic pressure ratio for a Zeldovich fluid-filled space-time are discussed.

PACS Nos.: 98.80-k, 04.20Jb
The impact of the OSIRIS grating efficiency on radiance and trace-gas retrievals
Authors: McLinden C A , McConnell J C , Strong K , McDade I C , Gattinger R L , King R , Solheim B , Llewellyn E J , Evans W JF
Published: July 2002

The optical spectrograph and infrared imaging system (OSIRIS), launched in 2001, is a UVvisible diffraction-grating instrument designed to measure light scattered from the Earth's limb. Laboratory measurements of the OSIRIS diffraction-grating efficiency reveal a sensitivity to polarization including an anomalous structure of width 2030 nm introduced into light polarized in a direction perpendicular to the grooves of the grating. A vector radiative-transfer model was used to generate synthetic OSIRIS spectra in an effort to examine the effect of this on radiances and trace-gas retrievals. Radiances that included grating effects were found to deviate by nearly 10% from those that did not and also contained the anomalous structure. Performing differential optical absorption spectroscopy (DOAS) on these spectra revealed errors in ozone apparent column densities of up to 80 DU. The size of the error was controlled mainly by the difference in polarization between the two DOAS spectra. Two possible correction methods were investigated. The first was to remove the grating effects by applying a correction factor to the raw radiances calculated using the vector radiative-transfer model. The second was to include the efficiency coefficient spectra in the DOAS fit.

PACS Nos.: 42.68Mj, 98.55Qf
Retrieval of vertical concentration profiles from OSIRIS UVvisible limb spectra
Authors: Strong K , Joseph B M , Dosanjh R , McDade I C , McLinden C A , McConnell J C , Stegman J , Murtagh D P , Llewellyn E J
Published: July 2002

The OSIRIS instrument, launched on the Odin satellite in February 2001, includes an optical spectrograph that will record UVvisible spectra of sunlight scattered from the limb over a range of tangent heights. These spectra will be used to retrieve vertical profiles of ozone, NO2, OClO, BrO, NO3, O2, and aerosols, for the investigation of both stratospheric and mesospheric processes, particularly those related to ozone chemistry. In this work, the retrieval of vertical profiles of trace-gas concentrations from OSIRIS limb-radiance spectra is described. A forward model has been developed to simulate these spectra, and it consists of a single-scattering radiative-transfer model with partial spherical geometry, trace-gas absorption, Mie scattering by stratospheric aerosols, a Lambertian surface contribution, and OSIRIS instrument response and noise. Number-density profiles have been retrieved by using optimal estimation (OE) to combine an a priori profile with the information from sets of synthetic ``measurements''. For ozone, OE has been applied both to limb radiances at one or more discrete wavelengths and to effective-column abundances retrieved over a broad spectral range using differential optical absorption spectroscopy (DOAS). The results suggest that, between 15 and 35 km, ozone number densities can be retrieved to 10% accuracy or better on 1 and 2 km grids and to 5% on a 5 km grid. The combined DOAS-OE approach has also been used to retrieve NO2 number densities, yielding 13% accuracy or better for altitudes from 18 to 36 km on a 2 km grid. Differential optical absorption spectroscopy  optimal estimation retrievals of BrO and OClO reproduce the true profiles above 15 km in the noise-free case, but the quality of the retrievals is highly sensitive to noise on the simulated OSIRIS spectra because of the weak absorption of these two gases. The development of inversion methods for the retrieval of trace-gas concentrations from OSIRIS spectra is continuing, and a number of future improvements to the forward model and refinements of the retrieval algorithms are identified.

PACS Nos.: 42.68Mj, 94.10Dy
A vector radiative-transfer model for the Odin/OSIRIS project
Authors: McLinden C A , McConnell J C , Griffioen E , McElroy C T
Published: July 2002

A vector radiative-transfer code has been developed that is able to accurately and efficiently calculate radiance and polarization scattered from Earth's limb. A primary application of this code will be towards generating weighting functions, based on calculated limb radiances, for the retrieval of trace gases (O3, NO2, BrO, OClO, and O4) from the optical spectrograph and infrared imaging system (OSIRIS). OSIRIS is a UVvisible instrument on board the Odin satellite that measures limb-scattered light. This model solves the vector radiative-transfer equation using an iterative technique simultaneously in both plane-parallel and spherical-shell atmospheres. OSIRIS simulated limb radiance and polarization and OSIRIS weighting functions are presented along with a discussion of the numerical solution parameters, model intercomparisons and timings, and necessary model improvements. Overall agreement with other models was found to be very good and model speed is comparable to a fast finite-difference code. A set of OSIRIS reference atmospheres have been compiled for use with radiative-transfer models. Each of the 216 atmospheres (18 latitudes × 12 months) include profiles of air, pressure, temperature, ozone, NO2, BrO, and stratospheric aerosols.

PACS Nos.: 42.68-w, 94.10Gb
Studies for the Odin sub-millimetre radiometer: I. Radiative transfer and instrument simulation
Authors: Eriksson P , Merino F , Murtagh D , Baron P , Ricaud P , Noë J de la
Published: July 2002

The Odin satellite mission will include radiometric measurements of the Earth's atmosphere in a limb-sounding mode, using frequencies between 480 and 580 GHz, with the overall aim of retrieving vertical distributions of atmospheric constituents. The current paper, being one of a three-part series, addresses primarily the modelling of atmospheric radiative transfer and the effect of instrumental properties: the forward model. Such a model is required for the retrieval process and this presentation puts emphasis on refraction, sensor characteristics, systematic model errors, and some implementation aspects. Refraction must be considered below about 15 km and an efficient algorithm to include this effect is presented. Sensor parts treated are the antenna, the side-band filter, and the spectrometer. The forward model is also essential for determining the needed weighting functions. A semi-analytical expression for species-abundance weighting functions is derived. To form a common basis for the article series, a comprehensive formalism is reviewed and general issues, such as the separation between fixed and variable uncertainties, discussed. As a complement to the theoretical characterization, limited to linear situations, the possibility of using repeated simulations is also described.

PACS Nos.: 42.68A, 07.07D, 07.57K
Towards an unprotected self-activating glycosyl donor system: Bromobutyl glycosides
Authors: Davis Benjamin G , Wood Steven D , Maughan Michael AT
Published: July 2002

Bromobutyl mannopyranosides have been successfully used as both protected and unprotected glycosyl donors both with and without the use of an external activator.Key words: glycosylation, unprotected glycosyl donors, oligosaccharides.
Biocatalytic oxidation of 4-vinylphenol by Nocardia
Authors: Lee Kyung-Seon , Rosazza John PN
Published: July 2002

Nocardia species NRRL 5646 stereospecifically hydrates 4-vinylphenol (15) to S-1-(4'-hydroxyphenyl)ethanol (17), and further oxidizes 17 to 4'-hydroxyacetophenone (18). Labeled metabolites 17 and 18 obtained from incubations in D2O and H218O support initial enzymatic tautomerization of 15 to a reactive quinone methide (16), which adds water in the first reaction. Commitment to catalysis is high in the hydration reaction, while the alcohol dehydrogenation reaction appears to be reversible. The stereochemical features of water addition, alcohol oxidations, and ketone reductions with growing culture biocatalysis were established by chiral HPLC. Alcohol oxidations or ketone reductions in 12 000 × g supernatants preferentially require NADP+NADPH,H+ as co-factors. The alcohol dehydrogenase has broad substrate specificity, favoring the oxidation of primary alkanols and 4-hydroxybenzyl alcohols.Key words : 4-vinylphenol, Nocardia sp., enantiospecific hydration, 1-(4'-hydroxyphenyl)ethanol, 4'-hydroxyacetophenone
Metal substitution in thermolysin: Catalytic properties of tungstate thermolysin in sulfoxidation with H2O2
Authors: Bakker Martin , Rantwijk Fred van , Sheldon Roger A
Published: July 2002

The catalytic Zn2+ion was extracted from thermolysin, which had been covalently bound to Eupergit C. The apo-enzyme incorporated the oxometallate anions MoO42, SeO42, and WO42with partial restoration of the proteolytic activity. Tungstate thermolysin was moderately active in the sulfoxidation of thioanisole by hydrogen peroxide, whereas its activity towards phenylmercaptoacetophenone, which was designed to bind well in the active site of thermolysin, was much higher.
Hydroxynitrile lyase-catalyzed addition of HCN to 4-substituted cyclohexanones: stereoselective preparation of tetronic acids
Authors: Effenberger Franz , Roos Jürgen , Kobler Christoph , Bühler Holger
Published: July 2002

The addition of HCN to 4-alkylcyclohexanones 1 to give cyanohydrins 2 is strongly catalyzed by hydroxy-ni trile lyases (HNLs). With PaHNL, from bitter almond, trans-addition occurs almost exclusively, yielding trans-2. With MeHNL, from cassava, cis-addition is preferred to give cis-2. cis-Selectivity is nearly quantitative, especially for cyclohexanones with larger 4-substituents. Comparable results with respect to the stereoselectivity were observed in the HNL-catalyzed addition of HCN to 4-alkoxycyclohexanones 3ag. In contrast, the stereoselectivity in the HNL-catalyzed addition to 4-alkanoyloxycyclohexanones 3hk is very poor. The transformation of cis-4-propylcyclohexanone cyanohydrin (2c) into the corresponding cis-spirotetronic acid 7 occurs without any isomerization.Key words: enzyme, hydroxynitrile lyase, cyclohexanones, cyanohydrins, cis/trans-stereoselectivity.
Enzymatic hydrolysis of β-lactam antibiotics at low pH in a two-phase "aqueous solution - water-immiscible organic solvent" system
Authors: Chilov Ghermes G , vedas Vytas K
Published: July 2002

The application of the two-phase "aqueous solution  water-immiscible organic solvent" system is suggested not for effective biocatalytic synthesis, but for hydrolytic purposes. Enzymatic hydrolysis of benzylpenicillin and N-phenylacetamidodesacetoxycephalosporanic acid to corresponding antibiotic nuclei 6-aminopenicillanic and 7-aminodesacetoxycephalosporanic acids in a two-phase waterbutylacetate system at pH 34 is proposed as an alternative to the biocatalytic hydrolysis in an alkaline medium. An experimental study has been performed and a model has been developed, which describes the influence of pH, phase volume ratio, thermodynamic constants, and initial antibiotic concentration on the effectiveness of their hydrolysis in a two-phase "aqueous solution  water-immiscible organic solvent" system. The thermodynamic evaluation of penicillin G and 7-phenylacetamidodesacetoxycephalosporanic acid hydrolysis at low pH in a two-phase aqueous solution  water-immiscible organic solvent system has demonstrated high practical potential. The suggested approach allows for the exclusion of several technological steps during the transformation of natural β-lactam antibiotics to their semi-synthetic analogues: alkaline extraction of the biosynthetic antibiotic from butylacetate followed by its enzymatic hydrolysis at pH 7.58.0 and further acidification of the reaction mixture, which results in the precipitation of the antibiotic nucleus. Experimental observations also revealed a specific feature of this process: the kinetic supersaturation of the antibiotic nucleus slows down the attainment of the equilibrium, which should be taken into account when further developing this approach.Key words: enzymatic hydrolysis, β-lactam antibiotic nuclei, two-phase systems, supersaturation, penicillin acylase.
Effects of selective cuts on the mycorrhizae of regenerating Betula alleghaniensis and Acer saccharum seedlings in two Quebec mixed deciduous forests
Authors: DeBellis Tonia , Widden Paul , Messier Christian
Published: July 2002

The mycorrhizae of younger (2- to 3-year-old) and older (5- to 12-year-old) yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh.) seedlings and saplings were recorded from naturally regenerating plants in gaps created by selective cuts and compared with those of plants of comparable age growing in the undisturbed forest. The levels of ectomycorrhizal colonization and the diversity of ectomycorrhizal fungi (based on morphotyping) were recorded for yellow birch and the levels of colonization and the abundance of arbuscules, vesicles, and coils were reported for the vesiculararbuscular mycorrhizae of sugar maples. Selective cutting had no negative effect on the mycorrhizal community structure of yellow birch and sugar maple. This may be because of the quick regeneration of the mycorrhizal hosts coupled with the minor levels of soil disruption and relatively small gap size at the study sites. Greater colonization levels in the gaps versus uncut areas were observed in the 2- to 3-year-old maples but not in the 2- to 3-year-old birch seedlings. The types of ectomycorrhizal fungi colonizing the roots of birch seedlings from the gaps did not differ from those in the uncut forest areas.
NMR studies of CCK-8/CCK1complex support membrane-associated pathway for ligand-receptor interaction
Authors: Giragossian Craig , Pellegrini Maria , Mierke Dale F
Published: July 2002

The interaction of peptide ligands with their associated G-protein-coupled receptors has been examined by a number of different experimental approaches over the years. We have been developing an approach utilizing high-resolution NMR to determine the structural features of the peptide ligand, well-designed fragments of the receptor, and the ligandreceptor complexes formed upon titration of the peptide hormone. The results from these investigations provide evidence for a membrane-associated pathway for the initial interaction of peptide ligands with the receptor. Here, our results from the investigation of the interaction of CCK-8 with the CCK1receptor are described. Our spectroscopic results clearly show that both CCK-8 and the regions of CCK1with which it interacts are closely associated with the zwitterionic interface of the lipids utilized in our solution spectroscopic studies.Key words: G-protein-coupled receptors, NMR structural characterization, cholecystokinin, CCK-8, cholecystokinin receptor, subtype 1, CCK1, peptide hormones.
Biochemical and pharmacological activities of SSR 146977, a new potent nonpeptide tachykinin NK3 receptor antagonist
Authors: Emonds-Alt Xavier , Proietto Vincenzo , Steinberg Régis , Advenier Charles , Daoui Samira , Naline Emmanuel , Gueudet Christiane , Michaud Jean-Claude , Oury-Donat Florence , Poncelet Martine , Vilain Pol , Fur Gérard Le , Maffrand Jean-Pierre , Soubrié Philippe , Pascal Marc
Published: July 2002

SSR 146977 is a potent and selective antagonist of the tachykinin NK3 receptor. In Chinese hamster ovary cells expressing the human tachykinin NK3 receptor, SSR 146977 inhibited the binding of radioactive neurokinin B to NK3 receptors (Ki = 0.26 nM), senktide (10 nM) induced inositol monophosphate formation (IC50 = 7.813 nM), and intracellular calcium mobilization (IC50 = 10 nM). It antagonized [MePhe7]neurokinin B induced contractions of guinea pig ileum (pA2 = 9.07). Senktide (30 nM) induced firing rate increase of noradrenergic neurons in the guinea pig locus coeruleus and dopaminergic neurons in the guinea pig substantia nigra was also blocked by SSR 146977 (50 and 100 nM, respectively). In vivo, in the respiratory system, SSR 146977 inhibited bronchial hyperresponsiveness to acetylcholine, bronchial microvascular permeability hypersensitivity to histamine (doses of 0.11 mg/kg i.p.), and cough (doses of 0.031 mg/kg i.p.) provoked by citric acid in guinea pigs. In the central nervous system, SSR 146977 inhibited turning behaviour (ID50 = 0.2 mg/kg i.p. and 0.4 mg/kg p.o.) and prevented the decrease of locomotor activity (10 and 30 mg/kg i.p) mediated by the stimulation of NK3 receptors in gerbils. In guinea pigs, SSR 146977 antagonized senktide-induced acetylcholine release in the hippocampus (0.3 and 1 mg/kg i.p) and norepinephrine release in the prefrontal cortex (0.3 mg/kg i.p.). It also prevented haloperidol-induced increase of the number of spontaneously active dopamine A10 neurons (1 and 3 mg/kg i.p.).Key words: SSR 146977, tachykinin NK3 receptor, neurokinin B, antagonist.
Effects of elk group size on predation by wolves
Authors: Hebblewhite Mark , Pletscher Daniel H
Published: July 2002

Wolf-prey research has focused on single-prey systems in North America dominated by moose (Alces alces) or white-tailed deer (Odocoileus virginianus). Elk (Cervus elaphus) are social ungulates and the main prey item of wolves (Canis lupus) in Banff National Park (BNP), Alberta. Grouping behaviour may affect the functional response of predators by changing how predators encounter and kill prey. We studied wolf predation on elk in BNP during the winters of 19971998 and 19981999 and tested how elk group size affected the availability of and encounter rates with elk groups and attack success of wolves. Wolves encountered larger elk groups than expected based on availability, and killed more elk from large groups than expected based on numbers of encounters. Elk group size increased with elk density in BNP. Increased rates of encounter with and success of attacking large elk groups, and the positive group size  density relationship may be a mechanism for density-dependent predation. We developed a predation-risk model to test the prediction that grouping will benefit individual elk, given this predation regime. Elk appeared to adopt two different strategies to minimize predation risk: living in small herds that were rarely encountered by wolves or living in large herds that reduced their predation risk through dilution.