bluuebunny/crossref_metadata_2025 huggingface dataset:
Elongation Factor 3, EF3, Associates with the Calcium Channel Cch1 and Targets Cch1 to the Plasma Membrane inCryptococcus neoformans
Authors: Liu Min , Gelli Angie
Published: May 2008

Ca2+-mediated signaling events in eukaryotic cells are initiated by Ca2+channels located in the plasma membranes and endomembranes. Cch1, a high-affinity Ca2+channel in the plasma membranes ofCryptococcus neoformansand other fungi, plays a role in many different cellular processes, but the mechanisms that regulate Cch1 are not well understood. A Ras recruitment two-hybrid screen was used to identify protein partners of Cch1 as a means of identifying possible mechanisms of channel regulation. Here, we show that Cch1 specifically associates with a cytoplasmic protein known as elongation factor 3 (EF3). The robust interaction between the cytosolic C terminus of the Cch1 protein and EF3 shown here was confirmed by demonstrating that Cch1 could coimmunoprecipitate with EF3 in yeast lysates. To examine the effects of EF3 on Cch1 behavior, we altered theEF3gene function by constructing aC. neoformansantisenseEF3repression strain. Our results show that the repression ofEF3led to the mislocalization of Cch1, suggesting a role for EF3 in targeting Cch1 to the plasma membrane ofC. neoformans. Consistent with this notion, the antisenseEF3repression strain displayed a growth defect under conditions of limited extracellular Ca2+. Collectively, these results suggest that EF3 and Cch1 are functionally coupled and that EF3 has a function apart from its role in the protein translation cycle.
Expression and Function of Sex Pheromones and Receptors in the Homothallic AscomyceteGibberella zeae
Authors: Lee Jungkwan , Leslie John F. , Bowden Robert L.
Published: May 2008

In heterothallic ascomycete fungi, idiomorphic alleles at theMATlocus control two sex pheromone-receptor pairs that function in the recognition and chemoattraction of strains with opposite mating types. In the ascomyceteGibberella zeae, theMATlocus is rearranged such that both alleles are adjacent on the same chromosome. Strains ofG. zeaeare self-fertile but can outcross facultatively. Our objective was to determine if pheromones retain a role in sexual reproduction in this homothallic fungus. Putative pheromone precursor genes (ppg1andppg2) and their corresponding pheromone receptor genes (pre2andpre1) were identified in the genomic sequence ofG. zeaeby sequence similarity and microsynteny with other ascomycetes.ppg1, a homolog of theSaccharomycesα-factor pheromone precursor gene, was expressed in germinating conidia and mature ascospores. Expression ofppg2, a homolog of thea-factor pheromone precursor gene, was not detected in any cells.pre2was expressed in all cells, butpre1was expressed weakly and only in mature ascospores.ppg1orpre2deletion mutations reduced fertility in self-fertilization tests by approximately 50%. Δppg1reduced male fertility and Δpre2reduced female fertility in outcrossing tests. In contrast, Δppg2and Δpre1had no discernible effects on sexual function. Δppg1/Δppg2and Δpre1/Δpre2double mutants had the same phenotype as the Δppg1and Δpre2single mutants. Thus, one of the putative pheromone-receptor pairs (ppg1/pre2) enhances, but is not essential for, selfing and outcrossing inG. zeaewhereas no functional role was found for the other pair (ppg2/pre1).
Modes of Overinitiation,dnaAGene Expression, and Inhibition of Cell Division in a Novel Cold-SensitivehdaMutant ofEscherichia coli
Authors: Fujimitsu Kazuyuki , Su'etsugu Masayuki , Yamaguchi Yoko , Mazda Kensaku , Fu Nisi , Kawakami Hironori , Katayama Tsutomu
Published: May 2008

The chromosomal replication cycle is strictly coordinated with cell cycle progression inEscherichia coli. ATP-DnaA initiates replication, leading to loading of the DNA polymerase III holoenzyme. The DNA-loaded form of the β clamp subunit of the polymerase binds the Hda protein, which promotes ATP-DnaA hydrolysis, yielding inactive ADP-DnaA. This regulation is required to repress overinitiation. In this study, we have isolated a novel cold-sensitivehdamutant, thehda-185mutant. Thehda-185mutant caused overinitiation of chromosomal replication at 25°C, which most likely led to blockage of replication fork progress. Consistently, the inhibition of colony formation at 25°C was suppressed by disruption of thediaAgene, an initiation stimulator. Disruption of theseqAgene, an initiation inhibitor, showed synthetic lethality withhda-185even at 42°C. The cellular ATP-DnaA level was increased in anhda-185-dependent manner. The cellular concentrations of DnaA protein anddnaAmRNA were comparable at 25°C to those in a wild-typehdastrain. We also found that multiple copies of the ribonucleotide reductase genes (nrdABornrdEF) ordnaBgene repressed overinitiation. The cellular levels of dATP and dCTP were elevated in cells bearing multiple copies ofnrdAB. The catalytic site within NrdA was required for multicopy suppression, suggesting the importance of an active form of NrdA or elevated levels of deoxyribonucleotides in inhibition of overinitiation in thehda-185cells. Cell division in thehda-185mutant was inhibited at 25°C in a LexA regulon-independent manner, suggesting that overinitiation in thehda-185mutant induced a unique division inhibition pathway.
Glycerol Metabolism and PrfA Activity inListeria monocytogenes
Authors: Joseph Biju , Mertins Sonja , Stoll Regina , Schär Jennifer , Umesha Kanasinakatte Rudrappa , Luo Qin , Müller-Altrock Stefanie , Goebel Werner
Published: May 2008

Listeria monocytogenesis able to efficiently utilize glycerol as a carbon source. In a defined minimal medium, the growth rate (during balanced growth) in the presence of glycerol is similar to that in the presence of glucose or cellobiose. Comparative transcriptome analyses ofL. monocytogenesshowed high-level transcriptional upregulation of the genes known to be involved in glycerol uptake and metabolism (glpFKandglpD) in the presence of glycerol (compared to that in the presence of glucose and/or cellobiose). Levels of expression of the genes encoding a second putative glycerol uptake facilitator (GlpF2) and a second putative glycerol kinase (GlpK2) were less enhanced under these conditions. GlpK1but not GlpK2was essential for glycerol catabolism inL. monocytogenesunder extracellular conditions, while the loss of GlpK1affected replication in Caco-2 cells less than did the loss of GlpK2and GlpD. Additional genes whose transcription levels were higher in the presence of glycerol than in the presence of glucose and cellobiose included those for two dihydroxyacetone (Dha) kinases and many genes that are under carbon catabolite repression control. Transcriptional downregulation in the presence of glycerol (compared to those in the presence glucose and cellobiose) was observed for several genes and operons that are positively regulated by glucose, including genes involved in glycolysis, N metabolism, and the biosynthesis of branched-chain amino acids. The highest level of transcriptional upregulation was observed for all PrfA-dependent genes during early and late logarithmic growth in glycerol. Under these conditions, a low level of HPr-Ser-P and a high level of HPr-His-P were present in the cells, suggesting that all enzyme IIA (EIIA) (or EIIB) components of the phosphotransferase system (PTS) permeases expressed will be phosphorylated. These and other data suggest that the phosphorylation state of PTS permeases correlates with PrfA activity.
Involvement of Nitrogen Regulation in
Bacillus subtilis degU
Expression
Authors: Yasumura Ayako , Abe Sadanobu , Tanaka Teruo
Published: May 2008

Bacillus subtilis
DegS-DegU belongs to a bacterial two-component system that controls many processes, including the production of exocellular proteases and competence development. It was found that when the glutamine synthetase gene
glnA
, which is involved in nitrogen regulation, was disrupted, the expression of the response regulator
degU
gene was increased. Deletion analysis and 5′-end mapping of the
degU
transcripts showed that the increase was caused by induction of a promoter (P2) located before the
degU
gene. Disruption of
tnrA
, a global regulator of nitrogen regulation, eliminated the P2 promoter induction by the
glnA
mutation. The fact that the P2 promoter is under nitrogen regulation was demonstrated by an increase in P2 expression with nitrogen-limited growth. It was also found by primer extension analysis that
degU
was transcribed by another promoter, P3, that is located downstream of P2. Efficient expression of P3 was dependent on phosphorylated DegU, as inactivation of the sensor kinase gene,
degS
, resulted in the loss of
degU
expression, although less efficient stimulation of
degU
expression was also observed with an enhanced level of DegU in a
degS
-deficient mutant. The promoter located upstream of the
degSU
operon, designated the P1 promoter here, was insensitive to
glnA
and
degU
mutations. These results suggest that
degU
expression is controlled by the three promoters under different growth conditions.
Transient Shielding of Intimin and the Type III Secretion System of Enterohemorrhagic and Enteropathogenic
Escherichia coli
by a Group 4 Capsule
Authors: Shifrin Yulia , Peleg Adi , Ilan Ophir , Nadler Chen , Kobi Simi , Baruch Kobi , Yerushalmi Gal , Berdichevsky Tatiana , Altuvia Shoshy , Elgrably-Weiss Maya , Abe Cecilia , Knutton Stuart , Sasakawa Chihiro , Ritchie Jennifer M. , Waldor Matthew K. , Rosenshine Ilan
Published: May 2008

Enterohemorrhagic and enteropathogenic
Escherichia coli
(EHEC and EPEC, respectively) strains represent a major global health problem. Their virulence is mediated by the concerted activity of an array of virulence factors including toxins, a type III protein secretion system (TTSS), pili, and others. We previously showed that EPEC O127 forms a group 4 capsule (G4C), and in this report we show that EHEC O157 also produces a G4C, whose assembly is dependent on the
etp
,
etk
, and
wzy
genes. We further show that at early time points postinfection, these G4Cs appear to mask surface structures including intimin and the TTSS. This masking inhibited the attachment of EPEC and EHEC to tissue-cultured epithelial cells, diminished their capacity to induce the formation of actin pedestals, and attenuated TTSS-mediated protein translocation into host cells. Importantly, we found that Ler, a positive regulator of intimin and TTSS genes, represses the expression of the capsule-related genes, including
etp
and
etk
. Thus, the expression of TTSS and G4C is conversely regulated and capsule production is diminished upon TTSS expression. Indeed, at later time points postinfection, the diminishing capsule no longer interferes with the activities of intimin and the TTSS. Notably, by using the rabbit infant model, we found that the EHEC G4C is required for efficient colonization of the rabbit large intestine. Taken together, our results suggest that temporal expression of the capsule, which is coordinated with that of the TTSS, is required for optimal EHEC colonization of the host intestine.
Direct Involvement of Type II Secretion System in Extracellular Translocation of
Shewanella oneidensis
Outer Membrane Cytochromes MtrC and OmcA
Authors: Shi Liang , Deng Shuang , Marshall Matthew J. , Wang Zheming , Kennedy David W. , Dohnalkova Alice C. , Mottaz Heather M. , Hill Eric A. , Gorby Yuri A. , Beliaev Alexander S. , Richardson David J. , Zachara John M. , Fredrickson James K.
Published: May 2008

MtrC and OmcA are cell surface-exposed lipoproteins important for reducing solid metal oxides. Deletions of type II secretion system (T2SS) genes reduced their extracellular release and their accessibility to the proteinase K treatment, demonstrating the direct involvement of T2SS in translocation of MtrC and OmcA to the bacterial cell surface.
Hydroquinone Dioxygenase from
Pseudomonas fluorescens
ACB: a Novel Member of the Family of Nonheme-Iron(II)-Dependent Dioxygenases
Authors: Moonen Mariëlle J. H. , Synowsky Silvia A. , van den Berg Willy A. M. , Westphal Adrie H. , Heck Albert J. R. , van den Heuvel Robert H. H. , Fraaije Marco W. , van Berkel Willem J. H.
Published: May 2008

Hydroquinone 1,2-dioxygenase (HQDO), an enzyme involved in the catabolism of 4-hydroxyacetophenone in
Pseudomonas fluorescens
ACB, was purified to apparent homogeneity. Ligandation with 4-hydroxybenzoate prevented the enzyme from irreversible inactivation. HQDO was activated by iron(II) ions and catalyzed the ring fission of a wide range of hydroquinones to the corresponding 4-hydroxymuconic semialdehydes. HQDO was inactivated by 2,2′-dipyridyl,
o
-phenanthroline, and hydrogen peroxide and inhibited by phenolic compounds. The inhibition with 4-hydroxybenzoate (
K

i

= 14 μM) was competitive with hydroquinone. Online size-exclusion chromatography-mass spectrometry revealed that HQDO is an α2β2 heterotetramer of 112.4 kDa, which is composed of an α-subunit of 17.8 kDa and a β-subunit of 38.3 kDa. Each β-subunit binds one molecule of 4-hydroxybenzoate and one iron(II) ion. N-terminal sequencing and peptide mapping and sequencing based on matrix-assisted laser desorption ionization—two-stage time of flight analysis established that the HQDO subunits are encoded by neighboring open reading frames (
hapC
and
hapD
) of a gene cluster, implicated to be involved in 4-hydroxyacetophenone degradation. HQDO is a novel member of the family of nonheme-iron(II)-dependent dioxygenases. The enzyme shows insignificant sequence identity with known dioxygenases.
Role of Cell Surface Signaling in Proteolysis of an Alternative Sigma Factor inPseudomonas aeruginosa
Authors: Spencer Matthew R. , Beare Paul A. , Lamont Iain L.
Published: May 2008

Alternative sigma factor proteins enable transcription of specific sets of genes in bacterial cells. Their activities can be controlled by posttranslational mechanisms including inhibition by antisigma proteins and proteolytic degradation. PvdS is an alternative sigma factor that is required for expression of genes involved in synthesis of a siderophore, pyoverdine, byPseudomonas aeruginosa. In the absence of pyoverdine, the activity of PvdS is inhibited by a membrane-spanning antisigma factor, FpvR. Inhibition is relieved by a cell surface signaling pathway. In this pathway, a combination of pyoverdine and a cell surface receptor protein, FpvA, suppresses the antisigma activity of FpvR, enabling transcription of PvdS-dependent genes. In this research, we investigated proteolytic degradation of PvdS in response to the signaling pathway. Proteolysis of PvdS was observed in strains ofP. aeruginosain which FpvR had anti-sigma factor activity due to the absence of pyoverdine or the FpvA receptor protein or overproduction of FpvR. Suppression of antisigma activity by addition of pyoverdine or through the absence of FpvR prevented detectable proteolysis of PvdS. The amounts of PvdS were less in bacteria in which proteolysis was observed, and reporter gene assays showed that this reduction was not due to decreased expression of PvdS. In wild-type bacteria, there was an average of 730 molecules of PvdS per cell in late exponential growth phase. Our results show that proteolysis and amounts of PvdS are affected by the antisigma factor FpvR and that this activity of FpvR is controlled by the cell surface signaling pathway.
Are Variable-Number Tandem Repeats Appropriate for GenotypingMycobacterium leprae?
Authors: Monot Marc , Honoré Nadine , Balière Charlotte , Ji Baohong , Sow Samba , Brennan Patrick J. , Cole Stewart T.
Published: May 2008

Comparative genomics analysis of the Tamil Nadu strain ofMycobacterium lepraehas uncovered several polymorphic sites with potential as epidemiological tools. In this study we compared the stability of two different markers of genomic biodiversity ofM. lepraein several biopsy samples isolated from the same leprosy patient. The first type comprises five different variable-number tandem repeats (VNTR), while the second is composed of three single nucleotide polymorphisms (SNP). Contrasting results were obtained, since no variation was seen in the SNP profiles ofM. lepraefrom 42 patients from 7 different locations in Mali whereas the VNTR profiles varied considerably. Furthermore, since variation in the VNTR pattern was seen not only between different isolates ofM. lepraebut also between biopsy samples from the same patient, these VNTR may be too dynamic for use as epidemiological markers for leprosy.
Practical Method for Detection and Identification of
Candida, Aspergillus
, and
Scedosporium
spp. by Use of Rolling-Circle Amplification
Authors: Zhou Xiaoyong , Kong Fanrong , Sorrell Tania C. , Wang Hui , Duan Yiqun , Chen Sharon C. A.
Published: May 2008

A sensitive rolling-circle amplification (RCA)-based method utilizing species-specific padlock probes targeted to the internal transcribed spacer 2 region of the fungal ribosomal DNA gene complex was developed. The assay was rapid (2 hours) and specific. Of 28 fungal isolates (16 of
Candida
, six of
Aspergillus
, and six of
Scedosporium
spp.), all were all identified correctly.
Primary Human Hepatocytes Are Susceptible to Infection by Hepatitis Delta Virus Assembled with Envelope Proteins of Woodchuck Hepatitis Virus
Authors: Gudima Severin , He Yiping , Chai Ning , Bruss Volker , Urban Stephan , Mason William , Taylor John
Published: May 2008

Hepatitis B virus (HBV) and hepatitis delta virus (HDV) share the HBV envelope proteins. When woodchucks chronically infected with woodchuck hepatitis virus (WHV) are superinfected with HDV, they produce HDV with a WHV envelope, wHDV. Several lines of evidence are provided that wHDV infects not only cultured primary woodchuck hepatocytes (PWH) but also primary human hepatocytes (PHH). Surprisingly, HBV-enveloped HDV (hHDV) and wHDV infected PHH with comparable efficiencies; however, hHDV did not infect PWH. The basis for these host range specificities was investigated using as inhibitors peptides bearing species-specific pre-S (where S is the small envelope protein) sequences. It was found that pre-S1 contributed to the ability of wHDV to infect both PHH and PWH. In addition, the inability of hHDV to infect PWH was not overcome using a chimeric form of hHDV containing WHV S protein, again supporting the essential role of pre-S1 in infection of target cells. One interpretation of these data is that host range specificity of HDV is determined entirely by pre-S1 and that the WHV and HBV pre-S1 proteins recognize different receptors on PHH.
Dimerization of the Papillomavirus E2 Protein Is Required for Efficient Mitotic Chromosome Association and Brd4 Binding
Authors: Cardenas-Mora Juan , Spindler Jonathan E. , Jang Moon Kyoo , McBride Alison A.
Published: May 2008

The E2 proteins of several papillomaviruses link the viral genome to mitotic chromosomes to ensure retention and the efficient partitioning of genomes into daughter cells following cell division. Bovine papillomavirus type 1 E2 binds to chromosomes in a complex with Brd4, a cellular bromodomain protein. Interaction with Brd4 is also important for E2-mediated transcriptional regulation. The transactivation domain of E2 is crucial for interaction with the Brd4 protein; proteins lacking or mutated in this domain do not interact with Brd4. However, we found that the C-terminal DNA binding/dimerization domain of E2 is also required for efficient binding to Brd4. Mutations that eliminated the DNA binding function of E2 had no effect on the ability of E2 to interact with Brd4, but an E2 protein with a mutation that disrupted C-terminal dimerization bound Brd4 with greatly reduced efficiency. Furthermore, E2 proteins in which the C-terminal domains were replaced with the dimeric DNA binding domain of EBNA-1 or Gal4 bound efficiently to the Brd4 protein, but the replacement of the E2 C-terminal domain with a monomeric red fluorescent protein did not rescue efficient Brd4 binding. Thus, E2 bound to Brd4 most efficiently as a dimer. To prove this finding further, the E2 DNA binding domain was replaced with an FKBP12-derived domain in which dimerization was regulated by a bivalent ligand. This fusion protein bound Brd4 efficiently only in the presence of the ligand, confirming that a dimer of E2 was required. Correspondingly, E2 proteins that could dimerize were able to bind to mitotic chromosomes much more efficiently than monomeric E2 polypeptides.
Vpx Is Critical for Reverse Transcription of the Human Immunodeficiency Virus Type 2 Genome in Macrophages
Authors: Fujita Mikako , Otsuka Masami , Miyoshi Masami , Khamsri Boonruang , Nomaguchi Masako , Adachi Akio
Published: May 2008

The abilities of wild-type and
vpx
-defective human immunodeficiency virus type 2 (HIV-2) clones to synthesize viral DNA in human monocyte-derived macrophages (MDMs) and lymphocytic cells were comparatively and quantitatively evaluated. While the
vpx
-defective mutant directed the synthesis of viral DNA comparably to the wild-type virus and normally in lymphocytic cells, no appreciable viral DNA was detected in MDMs infected with the mutant. To substantiate this finding and to determine whether there is some specific region(s) in Vpx crucial for viral DNA synthesis in MDMs, we generated a series of site-specific point mutants of
vpx
and examined their phenotypes. The resultant five mutants, with no infectivity for MDMs, showed, without exception, the same defect as the
vpx
-defective mutant. Our results here clearly demonstrated that the entire Vpx protein is critical for reverse transcription of the HIV-2 genome in human MDMs.
Dissecting prostate carcinogenesis throughETSgene rearrangement studies: implications for anticancer drug development
Authors: Attard G , Ang J E , Olmos D , de Bono J S
Published: May 2008

The discovery ofETSgene fusions as common events in prostate cancer represents a paradigmatic shift in the significance attributed to chromosomal translocations as a key mechanistic player in carcinogenesis. However, these chromosomal fusion events are poorly understood, as their functional significance and therapeutic potential remain unclear. Nonetheless, they have generally been used as novel molecular handles to sub-categorise the broad diversity of prostate cancers mainly via the use of fluorescence in-situ hybridisation-based “break-apart assays”. Thus, the potential roles of theseETSgene fusion events are being actively explored and are discussed in this review within the context of the existing scientific and clinical climates. Examples include their possible utilities as screening tools, markers for risk stratification and predictors of responses to therapies (in particular hormonal manipulation), biomarkers to guide early phase clinical trials, as well as therapeutic targets. Work is ongoing to address the many questions surrounding these pursuits in a very rapidly evolving area of research, and it is believed that an improved understanding of the biology underpinning these genetic events is vital in order to optimise their use in anticancer drug development.
Cystidial structure in two genera of the Russulales
Authors: McLaughlin David J. , Celio Gail J. , Padamsee Mahajabeen , Dentinger Bryn T.M.
Published: May 2008

As a part of a broader study to determine whether the subcellular structure of cystidia can provide synapomorphies for clades of Agaricomycetes, cystidia of Auriscalpium vulgare Gray and Russula emetica (Schaeff.) Pers. were examined ultrastructurally, after freeze substitution. Vesicles with tubular invaginations occurred in immature hymenial cystidia of both species, and microbodies were also present. Gloeohyphae of A. vulgare also contained these organelles. The tubular invaginations disappeared from the vesicles in maturing cystidia of A. vulgare and were replaced by electron-dense deposits. These patterns of cellular organization may be synapomorphic for the Russulales. The data will be incorporated into the “Assembling the Fungal Tree of Life” (AFTOL) Structural and Biochemical Database to facilitate the use of morphological characters in phylogenetic analyses.
Internal structure and conditions of permafrost mounds at Umiujaq in Nunavik, Canada, inferred from field investigation and electrical resistivity tomography
Authors: Fortier Richard , LeBlanc Anne-Marie , Allard Michel , Buteau Sylvie , Calmels Fabrice
Published: May 2008

A systematic approach was used for the interpretation of the electrical resistivity tomography carried out on two permafrost mounds at Umiujaq in Nunavik, Canada, to assess their internal structure and conditions. Prior information under the form of a geocryologic model of the permafrost mounds was integrated in the inversion of the pseudo-section of apparent electrical resistivity. The geocryologic model was developed from the synthesis of previous field investigations, including shallow and deep sampling, temperature and electrical resistivity logging, and cone penetration tests performed in the permafrost mounds. Values of electrical resistivity were ascribed to the different layers making of the geocryologic model to define a synthetic resistivity model of the permafrost mounds used as a reference model to constrain the inversion. The constrained resistivity model clearly show the presence of ice-rich cores in the permafrost mounds underscored by high resistivity values in excess of 30 000 Ωm, while the unfrozen zones surrounding the permafrost mounds are characterized by resistivity values lower than 1000 Ωm. The spatial distribution of unfrozen water and ice contents in the permafrost mounds were also assessed according to empirical relationships between the electrical resistivity and water contents. The ice content is highly variable and can be as high as 80% in the ice-rich cores, while the unfrozen water content varies between 2% and 5%. The integration of prior information in the inversion process leads to a more realistic constrained resistivity model showing sharp resistivity contrasts expected at the boundaries such as the permafrost table and base.
Genetic and environmental implications of reintroducing laboratory-raised unionid mussels to the wild
Authors: Hoftyzer Eileen , Ackerman Josef Daniel , Morris Todd J. , Mackie Gerald L.
Published: May 2008

The reintroduction of endangered species is a potentially useful conservation strategy, which in the case of freshwater unionid mussels, must be preceded by the successful laboratory rearing of juvenile mussels on their host fishes. However, an understanding of the genetic and environmental implications of reintroductions of artificially propagated mussels is required. Unfortunately, there is a dearth of information on these issues with respect to freshwater mussels. In general, regarding the genetic effects of reintroductions, small founder populations may lead to low heterozygosity (reduced genetic variability) in the reintroduced populations, which can make them more susceptible to extinction. Captive breeding programs may also alter the genetic composition of species through artificial selection, whether intentional or unintentional. Captive breeding may also affect an individual’s interactions with conspecifics or predators by altering behaviour. Genetic problems in reintroduced populations also have the potential to affect wild populations, particularly by reducing variability among populations of the same species and eliminating local adaptation. There is also the possibility that diseases, parasites, or exotic species may be spread when populations are relocated or augmented. Recommendations related to the minimization of these impacts are presented for freshwater mussels, with the recognition that many of the issues will require additional study.
A two-stage biomass random effects model for stock assessment without catches: What can be estimated using only biomass survey indices?
Authors: Trenkel Verena M.
Published: May 2008

A simple two-stage biomass random effects population dynamics model is presented for carrying out fish stock assessments based on survey indices using no commercial catch information. Recruitment and biomass growth are modelled as random effects, reducing the number of model parameters while maintaining model flexibility. No assumptions regarding natural mortality rates are required. The performance of the method was evaluated using simulated data with emphasis on identifying parameter redundancy, which showed that the variance of the biomass growth random effect might only be estimable if large (>0.2). The full and two nested models were fitted to European anchovy ( Engraulis encrasicolus ) in the Bay of Biscay using two survey series. The best-fitting model had fixed biomass growth and random recruitment following a lognormal distribution.
Influence of water chemistry and migratory distance on ability to distinguish progeny of sympatric resident and anadromous rainbow trout (Oncorhynchus mykiss)
Authors: Donohoe Christopher J. , Adams Peter B. , Royer Chantell F.
Published: May 2008

Otolith Sr:Ca ratios near primordia (Sr:CaCore) have been used to distinguish progeny of resident and anadromous Oncorhynchus mykiss and to estimate rates of exchange between the two forms; however, the influences of confounding variables on Sr:CaCore have not been quantified. We analyzed Sr:CaCore in juvenile O. mykiss produced at 13 California hatcheries that spawn primarily resident or anadromous broodstock. Mean Sr:CaCore of progeny of resident females increased with increasing Sr:Ca ratio of the stream (Sr:CaWater) in which the mother spawned (r2 = 0.71). Mean Sr:CaCore of progeny of anadromous females averaged 1.0 × 10–3 higher, also increased with Sr:CaWater, and decreased with increasing migratory difficulty (distance × elevation) of the mother (r2 = 0.96). Model results predict that discrimination of sympatric progeny is equally good among streams where Sr:CaWater is less than 5 mmol·mol–1, but limited at higher Sr:CaWater or when anadromous females return to freshwater 6 months or more before spawning (e.g., summer steelhead). The models also provide an alternative method of interpreting Sr:CaCore data that can improve discrimination between sympatric progeny. Analysis of adults from one stream and eight hatchery sites suggested that resident females made little or no contribution to populations of anadromous adults, but anadromous females contributed to populations of resident adults.
Response of littoral macroinvertebrate communities on rocks and sediments to lake residential development
Authors: De Sousa Simon , Pinel-Alloul Bernadette , Cattaneo Antonia
Published: May 2008

Previously pristine lakes of the Laurentian region of Quebec, Canada, have faced increasing residential development of their watershed since the 1970s. We tested whether littoral invertebrates respond to this perturbation, even though open-water nutrients and chlorophyll are not yet altered. We examined changes in biomass, size structure, and taxonomic composition of macroinvertebrates living on rocks and sediments in 13 lakes representing a gradient of lakeshore residential development and watershed clearing. Littoral invertebrates provided early indication of lake perturbation, but their response varied according to the substratum. On rocks, total invertebrate biomass increased along the perturbation gradient and size structure shifted towards large organisms. These changes were likely mediated by a concomitant increase in epilithon biomass, suggesting a bottom-up control. No significant change in total biomass and size structure was observed for invertebrates in sediments. In contrast, taxonomic composition changed with lake development in sediments, but not on rocks. Taxonomic shifts were likely related to changes in sediment heterogeneity due to a decline of woody litter and increased fine particle deposition. Oligochaetes were positively associated to perturbation, whereas mayflies were negatively associated; these taxa could be used as indicators. Sediments were a better sentinel substratum than rocks for biomonitoring the impact of lake residential development.
Discrimination of trait-based characteristics by trace element bioaccumulation in riverine fishes
Authors: Short Terry M. , Deweese Lawrence R. , Dubrovsky Neil M.
Published: May 2008

Relations between tissue trace element concentrations and species traits were examined for 45 fish species to determine the extent to which trait-based characteristics accounted for relative differences among species in trace element bioaccumulation. Percentages of fish species correctly classified by discriminant analysis according to traits predicted by tissue trace element concentrations ranged from 72% to 87%. Tissue concentrations of copper, mercury, selenium, and zinc appeared to have the greatest overall influence on differentiating species according to trait characteristics. Discrimination of trait characteristics did not appear to be strongly influenced by local sources of trace elements in the streambed sediment. Bioaccumulation was greatest for those species classified as primarily detritivores, having relatively large adult body size, considered nonmigratory with respect to reproductive strategy, occurring mostly in large or variable size streams and rivers, preferring depositional areas within the stream channel, and preferring benthic rather than open-water habitats. Our findings provide evidence of the strong relationship between bioaccumulation of environmental trace elements and trait-based factors that influence contaminant exposure.
Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus, through parental condition?
Authors: Friedland Kevin D. , Hare Jonathan A. , Wood Grayson B. , Col Laurel A. , Buckley Lawrence J. , Mountain David G. , Kane Joseph , Brodziak Jon , Lough R. Gregory , Pilskaln Cynthia H.
Published: May 2008

In 2003, the Georges Bank stock of haddock ( Melanogrammus aeglefinus ) experienced the largest recruitment event recorded during its assessed history. Several hypotheses have been advanced to explain recruitment variability in this much-scrutinized stock, including variability in the retention of eggs and larvae on Georges Bank, the timing of haddock spawning, and variability in the spring bloom, which influences larval growth and survival. Although these processes may contribute to the formation of successful year classes, none of the factors associated with these previous hypotheses provides an adequate explanation of the 2003 recruitment event. We analyzed data on the dynamics of the fall phytoplankton bloom the year prior to spawning and show it to be highly correlated with subsequent recruitment. We suggest that the fall bloom affects recruitment through enhanced condition of adults and by increasing the quantity and quality of their reproductive output, which in turn leads to a higher probability of survival of their offspring. Although synoptic data on the fall bloom are limited and our analyses are correlative, our purpose is to stimulate a rigorous test of this promising “parental condition hypothesis”.
The role of temperature in controlling diel activity in upstream migrant sea lampreys (Petromyzon marinus)
Authors: Binder Thomas R. , McDonald D. Gordon
Published: May 2008

This study used controlled laboratory conditions to directly assess the role of temperature in controlling diel activity in sexually immature, upstream migrant sea lampreys ( Petromyzon marinus ). Our results identified three separate temperature-induced changes to the normal nocturnal activity pattern of lampreys: (i) at low temperature (7 °C), lampreys became inactive; (ii) at high temperatures (≥20 °C), the normal nocturnal peak in activity was reduced and lampreys became active during the day; and (iii) rapid increases in temperature (7 or 8 °C over 4 h) stimulated transient daytime activity that subsided once temperature stabilized. In addition, we found evidence that temperature directly influences other aspects of sea lampreys behaviour, specifically light avoidance and rheotaxis. We propose that temperature-induced changes in diel activity represent adaptive behaviour, increasing the probability of lampreys reaching the spawning grounds within the narrow thermal range for successful embryonic development.
Analysis of mutations in thecreAgene involved in carbon catabolite repression inAspergillus nidulans
Authors: Shroff Robert A. , Lockington Robin A. , Kelly Joan M.
Published: May 2008

The molecular nature of a number of creA mutant alleles has been determined. Three alleles analysed are missense mutations in the DNA binding domain and predicted to reduce but not abolish binding. Of the other four alleles, two result from frameshifts: one has a nonsense mutation and the other has an inversion. All four alleles result in truncations of the protein after the zinc finger domain, such that the protein no longer contains at least the carboxy terminal 145 amino acids, so identifying a region required for repression. Transcriptional analysis of creA indicates that the transcript is autoregulated and analysis using 5′ rapid amplification of cDNA ends indicates that transcriptional start points exist in clusters over a region of 200 bp located up to 595 bp 5′ of the translational start point. The two major clusters have potential CREA-binding sites (SYGGRG) at appropriate positions to allow autoregulation. Autoregulation leads to the creA transcript being most abundant in carbon catabolite nonrepressing conditions, and this, together with the phenotypes of the mutant alleles, has led to the suggestion that CREA has effects under conditions generally not considered as carbon catabolite repressing, as well as in carbon catabolite repressing conditions.Key words: carbon catabolite repression, MIG1, CREA, zinc finger protein, transcriptional repressor.
A comparative study of the broth micro- and macro-dilution techniques for the determination of the in vitro susceptibility ofAspergillus fumigatus
Authors: Manavathu Elias K. , Alangaden George J. , Lerner Stephen A.
Published: May 2008

The effects of inoculum size, medium, temperature, and duration of growth on the in vitro susceptibility testing of Aspergillus fumigatus were investigated using broth micro- and macro-dilution techniques. The minimum inhibitory concentrations (MICs) of ketoconazole, miconazole, itraconazole, fluconazole, and amphotericin B were significantly influenced by the inoculum size, regardless of the techniques used. Two- to four-fold higher MIC values were obtained when the inoculum size was increased 100-fold. The use of peptone yeast extract glucose and RPMI 1640 media provided essentially identical MIC values at 30 and 35 °C after incubation for 48 h or longer. A comparison of broth micro- and macro-dilution techniques revealed that, under equivalent conditions, the latter with an inoculum size between 1 × 103and 1 × 104conidia (strain W73355)/mL consistently provided the lowest MICs of fluconazole (256 μg/mL), ketoconazole (8 μg/mL), miconazole (2 μg/mL), itraconazole (0.25 μg/mL), and amphotericin B (0.25 μg/mL). Using the broth macrodilution technique, we screened 24 clinical isolates of A. fumigatus obtained from the Detroit Medical Center in 1994. The MIC values of fluconazole, ketoconazole, miconazole, itraconazole and amphotericin B for all the isolates were 128–256, 8–16, 1–2, 0.25–0.5, and 0.25–1.0 μg/mL, respectively, indicating that none of the clinical isolates that we tested shows acquired resistance to the antifungals used.Key words: Aspergillus fumigatus, susceptibility test, antifungals, drug resistance, broth macrodilution.
Utilization ofD-leucine byHalobacterium halobiumVO107
Authors: Tanaka Mikiei , Yuasa Seiji , Mukohata Yasuo
Published: May 2008

Using the extreme halophile Halobacterium halobium VO107, the utilization of D-leucine was studied in comparison with that of L-leucine. The initial uptake of D-leucine into cells was found to be less efficient than that of L-leucine, but like L-leucine, the D-leucine uptake was inhibited by uncouplers and an ATPase inhibitor, suggesting that an energy-dependent process was involved in its uptake. Following uptake, D-leucine was isomerized to L-leucine for further metabolism by an enzyme(s) that was induced in the presence of D-leucine in medium.Key words: Halobacterium halobium, archaebacteria, D-amino acid utilization, isomerization.
The Canadian Softwood Lumber Industry: A Model
Authors: Manning Glenn H.
Published: May 2008

An econometric model of the Canadian softwood lumber industry was developed. It describes supply and demand conditions for the three main markets under the hypothesis that Canadian requirements are supplied as a residual of United States' demand for Canadian softwood lumber. The major determinants of softwood lumber supply and price in the United States are log prices and labor productivities. The United States' demand is determined by price and level of construction activity, whereas Canadian demand is influenced by the former's demand, construction wages, and growth of the economy as measured by the index of industrial production.
Microrelief, Water Level Fluctuations, and Diameter Growth in Wet-site Stands of Red and Black Spruce in New Brunswick
Authors: Groenewoud H. van
Published: May 2008

Soil water levels, rainfall, and tree diameter increments were measured during four successive growing seasons. Microrelief data and depth of the fluctuating water tables were incorporated into a measure of mean soil depth.Water table fluctuations were closely linked to rainfall. Deviations from the mean tree diameter growth were related to deviations from the mean depth of the water table. Maximum growth took place at the mean depth of the water table, with decreases in growth at higher or lower than average water levels.
Suggestions and Criteria for More Effective Regression Sampling. 2.
Authors: Demaerschalk Julien P. , Kozak Antal
Published: May 2008

Some suggestions are made and techniques are developed for more effective sampling for simple linear regression for situations in which little is known about the population or in which sampling for the independent variable is not feasible.
Effect of Storage on Germination of White-seedling Seeds in Douglas-fir
Authors: Sorensen Frank C.
Published: May 2008

During 6 years of storage, seeds with white-seedling embryos maintained their viability as well as did seeds with normal embryos.
Relationships among crown condition, growth, and stand nutrition in seven northern Vermont sugarbushes
Authors: Wilmot Timothy R. , Ellsworth David S. , Tyree Melvin T.
Published: May 2008

We compared growth with soil and foliar elemental composition in seven stands of sugar maple (Acersaccharum Marsh.) in northern Vermont characterized by high or low incidence of crown dieback over the period 1989–1992. In stands with low-quality crown conditions, such as elevated crown dieback, long-term basal area growth rates were approximately half of those in stands with higher crown quality. Average annual basal area growth was 17.5 cm2 for dominant trees in these stands during the period 1953–1992 compared with 32.3 cm2 for trees in higher quality stands. The occurrence of elevated crown dieback was apparently unrelated to stand characteristics such as stand age, basal area, stem density, elevation, or aspect among the stands sampled. Stands with elevated crown dieback were found on soils characterized by low pH ( <4.0), low base cation pools (particularly Ca and Mg), and higher Al in soil surface horizons than higher quality stands. Over 4 years, sugar maple stands with elevated crown dieback exhibited significantly lower (P < 0.01) foliar Ca concentrations and somewhat lower foliar N and Mg than higher quality stands, while soil and foliar K were similar in both dieback classes. Among survey plots sampled in 1989, soil pH and Ca were strongly correlated with foliar Ca and K (P < 0.001). Soil pH, soil Ca, and foliar Ca were also strongly correlated with the level of crown dieback among plots and stands (P < 0.0001). Our results indicate that podzolic soils in northern Vermont may present marginal conditions for sugar maple growth in terms of soil pH and soil Ca availability, but that P and K pools appear to be sufficient for growth. While a lack of historical data prevents identification of long-term trends in nutrient availability in these soils, factors promoting losses of base cations from acidic, base-cation-poor Podzols may also exacerbate foliar nutrient deficiencies and thus affect the crown condition of sugarbushes in northern Vermont.
Leaf optical properties in Liriodendrontulipifera and Pinusstrobus as influenced by increased atmospheric ozone and carbon dioxide
Authors: Carter Gregory A. , Rebbeck Joanne , Percy Kevin E.
Published: May 2008

Seedlings of Liriodendrontulipifera L. and PinusstrobusL. were grown in open-top chambers in the field to determine leaf optical responses to increased ozone (O3) or O3 and carbon dioxide (CO2). In both species, seedlings were exposed to charcoal-filtered air, air with 1.3 times ambient O3 concentrations (1.3×), or air with 1.3 times ambient O3 and 700 μL•L−1 CO2 (1.3× + CO2). Exposure to 1.3× increased reflectance in the 633–697 nm range in L. tulipifera. Also, 1.3× decreased transmittance within the 400–420 nm range, increased transmittance at 686–691 nm, and decreased absorptance at 655–695 nm. With 700 μL•L−1 CO2, O3 did not affect reflectance in L. tulipifera, but decreased transmittance and increased absorptance within the 400–421 nm range and increased transmittance and decreased absorptance in the 694–697 nm range. Under 1.3×, reflectance in P. strobus was not affected. However, 1.3× + CO2 increased pine reflectance in the 538–647, 650, and 691–716 nm ranges. Transmittances and absorptances were not determined for P. strobus. Reflectance in both species, and transmittance and absorptance in L. tulipifera, were most sensitive to O3 near 695 nm. Reflectance at 695 nm, but particularly the ratio of reflectance at 695 nm to reflectance at 760 nm, was related closely to ozone-induced decreases in leaf chlorophyll contents, particularly chlorophyll a (r = 0.82).
A DEDICATED TORSION BALANCE TO DETECT NEUTRINOS BY COHERENT SCATTERING ON HIGH DEBYE TEMPERATURE MONOCRYSTALS
Authors: CRUCERU I. , NICOLESCU G. , DULIU O. G.
Published: May 2008

The possibility of detecting neutrinos by coherent scattering on high Debye temperature monocrystals such as sapphire is presented and discussed. Preliminary estimations showed that 1 MeV neutrinos with a fluency density of 1012 cm-2 s-1 could interact with a force of about 10-6 dyn with a 100 g sapphire monocrystal. A torsion balance provided with 1 m length molybdenum wire and an optical autocollimator able to measure small rotation angles of about 0.1 arcsec could give positive results. The design of a high sensitivity torsion balance under construction provided with such a detector is presented and discussed.
DYNAMO EFFECTS IN MAGNETIZED IDEAL PLASMA COSMOLOGIES
Authors: KLEIDIS KOSTAS , KUIROUKIDIS APOSTOLOS , PAPADOPOULOS DEMETRIOS , VLAHOS LOUKAS
Published: May 2008

The excitation of cosmological perturbations in an anisotropic cosmological model and in the presence of a homogeneous magnetic field has been studied, using the ideal magnetohydrodynamic (MHD) equations. In this case, the system of partial differential equations which governs the evolution of the magnetized cosmological perturbations can be solved analytically. Our results verify that fast-magnetosonic modes propagating normal to the magnetic field, are excited. But, what is most important, is that, at late times, the magnetic-induction contrast(δB/B) grows, resulting in the enhancement of the ambient magnetic field. This process can be particularly favored by condensations, formed within the plasma fluid due to gravitational instabilities.