bluuebunny/crossref_metadata_2025 huggingface dataset:
The FecI Extracytoplasmic-Function Sigma Factor of
Escherichia coli
Interacts with the β′ Subunit of RNA Polymerase
Authors: Mahren Susanne , Braun Volkmar
Published: March 2003

Transcription of the ferric citrate transport system of
Escherichia coli
K-12 is mediated by the extracytoplasmic-function (ECF) sigma factor FecI, which is activated by ferric citrate in the growth medium. By using a bacterial two-hybrid system, it was shown in vivo that FecI binds to the β′ subunit of RNA polymerase. The inactive mutant protein FecI(K155E) displayed reduced binding to β′, and small deletions along the entire FecI protein led to total impairment of β′ binding. In vitro, FecI was retained on Ni
2+
-nitrilotriacetic acid agarose loaded with a His-tagged β′
1-313
fragment and coeluted with β′
1-313
. Binding of FecI to β′ and β′
1-313
was enhanced by FecR
1-85
, which represents the cytoplasmic portion of the FecR protein that transmits the inducing signal across the cytoplasmic membrane. Interaction of FecR with FecI was demonstrated by showing that isolated FecR inhibited degradation of FecI by trypsin. This is the first demonstration of binding of an ECF sigma factor of the FecI type to the β′ subunit of RNA polymerase and of binding being enhanced by the protein that activates the ECF sigma factor.
The
Escherichia coli mazEF
Suicide Module Mediates Thymineless Death
Authors: Sat Boaz , Reches Myriam , Engelberg-Kulka Hanna
Published: March 2003

In 1954, Cohen and Barner discovered that a thymine auxotrophic (
thyA
) mutant of
Escherichia coli
undergoes cell death in response to thymine starvation. This phenomenon, called thymineless death (TLD), has also been found in many other organisms, including prokaryotes and eukaryotes. Though TLD has been studied intensively, its molecular mechanism has not yet been explained. Previously we reported on the
E. coli mazEF
system, a regulatable chromosomal suicide module that can be triggered by various stress conditions. MazF is a stable toxin, and MazE is an unstable antitoxin. Here, we show that cell death that is mediated by the
mazEF
module can also be activated by thymine starvation. We found that TLD depends on
E. coli mazEF
and that under thymine starvation, the activity of the
mazEF
promoter P
2
is significantly reduced. Our results, which describe thymine starvation as a trigger for a built-in death program, have implications for programmed cell death in both prokaryotes and eukaryotes.
Identification of a Novel Membrane-Associated Gene Product That Suppresses Toxicity of a TrfA Peptide from Plasmid RK2 and Its Relationship to the DnaA Host Initiation Protein
Authors: Kim Peter D. , Banack Trevor , Lerman Daniel M. , Tracy Jeremiah C. , Camara Johanna Eltz , Crooke Elliot , Oliver Don , Firshein William
Published: March 2003

The toxicity of a peptide derived from the amino-terminal portion of 33-kDa TrfA, one of the initiation proteins encoded by the broad-host-range plasmid RK2, was suppressed by a host protein related to DnaA, the initiation protein ofEscherichia coli. The newly identified 28.4-kDa protein, termed a DnaA paralog (Dp) because it is similar to a region of DnaA but likely has a different function in initiation of plasmid RK2 replication, interacts physically with the 33-kDa TrfA initiation protein, including the initiation-active monomeric form. The Dp has a cellular distribution similar to that of the 33-kDa TrfA initiation protein, being found primarily in the inner membrane fraction, with lesser amounts detected in the outer membrane fraction and almost none in the soluble fraction ofE. coli. Maintenance and inner membrane-associated replication of plasmid RK2 were enhanced in a Dp knockout strain and inhibited in strains containing extra copies of the Dp gene or in membrane extracts to which a tagged form of Dp was added. Recently, the Dp was independently shown to help prevent overinitiation inE. coliand was termed Hda (S. Kato and T. Katayama, EMBO J.20:4253-4262, 2001).
tmRNA in
Caulobacter crescentus
Is Cell Cycle Regulated by Temporally Controlled Transcription and RNA Degradation
Authors: Keiler Kenneth C. , Shapiro Lucy
Published: March 2003

SsrA, or tmRNA, is a small RNA found in all bacteria that intervenes in selected translation reactions to target the nascent polypeptide for rapid proteolysis. We have found that the abundance of SsrA RNA in
Caulobacter crescentus
is regulated with respect to the cell cycle. SsrA RNA abundance increases in late G
1
phase, peaks during the G
1
-S transition, and declines in early S phase, in keeping with the reported role for SsrA in the timing of DNA replication initiation. Cell cycle regulation of SsrA RNA is accomplished by a combination of temporally controlled transcription and regulated RNA degradation. Transcription from the
ssrA
promoter peaks late in G
1
, just before the peak in SsrA RNA abundance. SsrA RNA is stable in G
1
-phase cells and late S-phase cells but is degraded with a half-life of 4 to 5 min at the onset of S phase. This degradation is surprising, since SsrA RNA is both highly structured and highly abundant. This is the first observation of a structural RNA that is cell cycle regulated.
Novel Genomic Rearrangement That Affects Expression of theStreptococcus pyogenesStreptolysin O (slo) Gene
Authors: Savic Dragutin J. , Ferretti Joseph J.
Published: March 2003

A RecA-independent chromosomal rearrangement in the upstream region of the streptolysin O (slo) gene ofStreptococcus pyogeneswhich affectssloexpression was identified. PCR analysis was used to demonstrate that this kind of rearrangement was found in several strains of different lineages. Chromosomal loci involved in the recombination were found to be 746 kb apart on the 1.85-Mb-long chromosome. The primary structure of the splicing region, the reproducibility of the rearrangement, and the fact that reconstructed recombinant molecules fused toermandlacZreporter genes affected their expression indicate that this event is not accidental but may play a role in the expression of theslogene. In addition, the product of the recombining DNAs, including the splicing site, does not follow any example of a known recombination mechanism. The implications of this rearrangement forsloexpression are discussed.
Leucine-Responsive Regulatory Protein-Mediated Repression of
clp
(Encoding CS31A) Expression by
l
-Leucine and
l
-Alanine in
Escherichia coli
Authors: Crost Cécile , Garrivier Annie , Harel Josée , Martin Christine
Published: March 2003

CS31A produced by septicemic and diarrheic
Escherichia coli
belongs to the Pap-regulatory family of adhesive factors, which are under methylation-dependent transcriptional regulation. Common features of operons encoding members of this family include two conserved GATC sites in the upstream regulatory region, and transcriptional regulators homologue to the PapB and PapI proteins. Methylation protection of GATC sites was previously shown to be dependent on the leucine-responsive regulatory protein (Lrp). Lrp and ClpB, the PapB equivalent, repressed
clp
basal transcription. A PapI homologue (AfaF) was required together with Lrp to establish the phase variation control, which gave rise to phase-ON cells that expressed CS31A and phase-OFF cells that did not express CS31A. In phase-OFF cells, the GATC
dist
site was methylated and the GATC
prox
site was protected from methylation, whereas in phase-ON cells, the inverse situation was found. Unlike Pap fimbriae, CS31A synthesis was dramatically reduced in media containing
l
-alanine or
l
-leucine.
l
-Alanine prevented the OFF-to-ON switch, locking
clp
expression in the OFF phase, whereas
l
-leucine repressed transcription without obvious effect on the switch frequency of phase variation. In phase-variable cells, leucine and alanine promoted methylation of GATC
dist
and methylation protection of GATC
prox
, increasing the methylation pattern characteristic of repressed cells. Furthermore, alanine prevented the AfaF-dependent methylation protection of GATC
dist
and thus the appearance of phase-ON cells. In addition, analysis of
clp
expression in a Lrp-negative background indicated that alanine and leucine also repressed
clp
transcription by a methylation-independent mechanism.
Operon Structure and Regulation of the
nos
Gene Region of
Pseudomonas stutzeri
, Encoding an ABC-Type ATPase for Maturation of Nitrous Oxide Reductase
Authors: Honisch Ulrike , Zumft Walter G.
Published: March 2003

The synthesis of a functional nitrous oxide reductase requires an assembly apparatus for the insertion of the prosthetic copper. Part of the system is encoded by maturation genes located in
Pseudomonas stutzeri
immediately downstream of the structural gene for the enzyme. We have studied the transcriptional organization and regulation of this region and found a
nosDFYL tatE
operon structure. In addition to a putative ABC transporter, consisting of NosD, NosF, and NosY, the operon encodes a Cu chaperone, NosL, and a component of the Tat translocon, TatE. The
nosD
operon was activated in response to anaerobiosis and nitrate denitrification. The membrane-bound regulator NosR was required for operon expression; in addition, DnrD, a regulator of the Crp-Fnr family, enhanced expression under anaerobic conditions. This establishes a likely signal transduction sequence of NO → DnrD →
nosR
/NosR →
nosD
operon. DnrD-dependent expression was also observed for the
nnrS
operon (located immediately downstream of the
nosD
operon), which encodes a putative heme-Cu protein (NnrS) and a member of the short-chain dehydrogenase family (ORF247). The NosF protein, encoded within the
nosD
operon, exhibits sequence similarity to ABC-type ATPases. It was fused to the
Escherichia coli
maltose-binding protein and overexpressed in soluble form. The fusion protein was purified and shown to have ATPase activity. NosF is the first maturation factor for which a catalytic function has been demonstrated in vitro.
Identification of the Immunodominant Protein and Other Proteins of theBacillus anthracisExosporium
Authors: Steichen Christopher , Chen Ping , Kearney John F. , Turnbough, Charles L.
Published: March 2003

Spores ofBacillus anthracis, the causative agent of anthrax, are enclosed by a prominent loose-fitting, balloon-like layer called the exosporium. Although the exosporium serves as the source of surface antigens and a primary permeability barrier of the spore, its molecular structure and function are not well characterized. In this study, we identified five major proteins in purifiedB. anthracis(Sterne strain) exosporia. One protein was the recently identified collagen-like glycoprotein BclA, which appears to be a structural component of the exosporium hair-like nap. Using a large panel of unique antispore monoclonal antibodies, we demonstrated that BclA is the immunodominant antigen on theB. anthracisspore surface. We also showed that the BclA protein and not a carbohydrate constituent directs the dominant immune response. In addition, the length of the central (GXX)nrepeat region of BclA appears to be strain specific. Two other unique proteins, BxpA and BxpB, were identified. BxpA is unusually rich in Gln and Pro residues and contains several different tandem repeats, which also exhibit strain-specific variation. In addition, BxpA was found to be cleaved approximately in half. BxpB appears to be glycosylated or associated with glycosylated material and is encoded by a gene that (along withbclA) may be part of an exosporium genomic island. The other two proteins identified were alanine racemase and superoxide dismutase, both of which were reported to be associated with the surface of otherBacillusspores. Possible functions of the newly identified proteins are discussed.
Additional Targets of theBacillus subtilisGlobal Regulator CodY Identified by Chromatin Immunoprecipitation and Genome-Wide Transcript Analysis
Authors: Molle Virginie , Nakaura Yoshiko , Shivers Robert P. , Yamaguchi Hirotake , Losick Richard , Fujita Yasutaro , Sonenshein Abraham L.
Published: March 2003

Additional targets of CodY, a GTP-activated repressor of early stationary-phase genes inBacillus subtilis, were identified by combining chromatin immunoprecipitation, DNA microarray hybridization, and gel mobility shift assays. The direct targets of CodY newly identified by this approach included regulatory genes for sporulation, genes that are likely to encode transporters for amino acids and sugars, and the genes for biosynthesis of branched-chain amino acids.
Design of Antisense RNA Constructs for Downregulation of the Acetone Formation Pathway of
Clostridium acetobutylicum
Authors: Tummala Seshu B. , Welker Neil E. , Papoutsakis Eleftherios T.
Published: March 2003

We investigated the effect of antisense RNA (asRNA) structural properties on the downregulation efficacy of enzymes in the acetone-formation pathway (acetoacetate decarboxylase [AADC] and coenzyme A-transferase [CoAT]) of
Clostridium acetobutylicum
strain ATCC 824. First, we generated three strains,
C. acetobutylicum
ATCC 824 (pADC38AS), 824(pADC68AS), and 824(pADC100AS), which contain plasmids that produce asRNAs of various lengths against the AADC (
adc
) transcript. Western analysis showed that all three strains exhibit low levels of AADC compared to the plasmid control [ATCC 824(pSOS95del)]. By using computational algorithms, the three different asRNAs directed toward AADC, along with previously reported clostridial asRNAs, were examined for structural features (free nucleotides and components). When the normalized metrics of these structural features were plotted against percent downregulation, only the component/nucleotide ratio correlated well with in vivo asRNA effectiveness. Despite the significant downregulation of AADC in these strains, there were no concomitant effects on acetone formation. These findings suggest that AADC does not limit acetone formation and, thus, we targeted next the CoAT. Using the component/nucleotide ratio as a selection parameter, we developed three strains [ATCC 824 (pCTFA2AS), 824(pCTFB1AS), and 824(pCOAT11AS)] which express asRNAs to downregulate either or both of the CoAT subunits. Compared to the plasmid control strain, these strains produced substantially low levels of acetone and butanol and Western blot analyses showed significantly low levels of both CoAT subunits. These results show that CoAT is the rate-limiting enzyme in acetone formation and strengthen the hypothesis that the component/nucleotide ratio is a predictive indicator of asRNA effectiveness.
Mutational Analysis of the Residue at Position 48 in the
Salmonella enterica
Serovar Typhimurium PhoQ Sensor Kinase
Authors: Sanowar Sarah , Martel Alexandre , Moual Hervé Le
Published: March 2003

The PhoP/PhoQ two-component regulatory system of
Salmonella enterica
serovar Typhimurium plays an essential role in controlling virulence by mediating the adaptation to Mg
2+
depletion. The
pho
-
24
allele of
phoQ
harbors a single amino acid substitution (T48I) in the periplasmic domain of the PhoQ histidine kinase sensor. This mutation has been shown to increase net phosphorylation of the PhoP response regulator. We analyzed the effect on signaling by PhoP/PhoQ of various amino acid substitutions at this position (PhoQ-T48X [X = A, S, V, I, or L]). Mutations T48V, T48I, and T48L were found to affect signaling by PhoP/PhoQ both in vivo and in vitro. Mutations PhoQ-T48V and PhoQ-T48I increased both the expression of the
mgtA
::
lacZ
transcriptional fusion and the net phosphorylation of PhoP, conferring to cells a PhoP constitutively active phenotype. In contrast, mutation PhoQ-T48L barely responded to changes in the concentration of external Mg
2+
, in vivo and in vitro, conferring to cells a PhoP constitutively inactive phenotype. By analyzing in vitro the individual catalytic activities of the PhoQ-T48X sensors, we found that the PhoP constitutively active phenotype observed for the PhoQ-T48V and PhoQ-T48I proteins is solely due to decreased phosphatase activity. In contrast, the PhoP constitutively inactive phenotype observed for the PhoQ-T48L mutant resulted from both decreased autokinase activity and increased phosphatase activity. Our data are consistent with a model in which the residue at position 48 of PhoQ contributes to a conformational switch between kinase- and phosphatase-dominant states.
High Levels of Intracellular Cysteine Promote Oxidative DNA Damage by Driving the Fenton Reaction
Authors: Park Sunny , Imlay James A.
Published: March 2003

Escherichia coli
is generally resistant to H
2
O
2
, with >75% of cells surviving a 3-min challenge with 2.5 mM H
2
O
2
. However, when cells were cultured with poor sulfur sources and then exposed to cystine, they transiently exhibited a greatly increased susceptibility to H
2
O
2
, with <1% surviving the challenge. Cell death was due to an unusually rapid rate of DNA damage, as indicated by their filamentation, a high rate of mutation among the survivors, and DNA lesions by a direct assay. Cell-permeable iron chelators eliminated sensitivity, indicating that intracellular free iron mediated the conversion of H
2
O
2
into a hydroxyl radical, the direct effector of DNA damage. The cystine treatment caused a temporary loss of cysteine homeostasis, with intracellular pools increasing about eightfold. In vitro analysis demonstrated that cysteine reduces ferric iron with exceptional speed. This action permits free iron to redox cycle rapidly in the presence of H
2
O
2
, thereby augmenting the rate at which hydroxyl radicals are formed. During routine growth, cells maintain small cysteine pools, and cysteine is not a major contributor to DNA damage. Thus, the homeostatic control of cysteine levels is important in conferring resistance to oxidants. More generally, this study provides a new example of a situation in which the vulnerability of cells to oxidative DNA damage is strongly affected by their physiological state.
Molecular Analysis of the Multiple GroEL Proteins of Chlamydiae
Authors: Karunakaran Karuna P. , Noguchi Yasuyuki , Read Timothy D. , Cherkasov Artem , Kwee Jeffrey , Shen Caixia , Nelson Colleen C. , Brunham Robert C.
Published: March 2003

Genome sequencing revealed that all six chlamydiae genomes contain three
groEL
-like genes (
groEL1
,
groEL2
, and
groEL3
). Phylogenetic analysis of
groEL1
,
groEL2
, and
groEL3
indicates that these genes are likely to have been present in chlamydiae since the beginning of the lineage. Comparison of deduced amino acid sequences of the three
groEL
genes with those of other organisms showed high homology only for
groEL1
, although comparison of critical amino acid residues that are required for polypeptide binding of the
Escherichia coli
chaperonin GroEL revealed substantial conservation in all three chlamydial GroELs. This was further supported by three-dimensional structural predictions. All three genes are expressed constitutively throughout the developmental cycle of
Chlamydia trachomatis
, although
groEL1
is expressed at much higher levels than are
groEL2
and
groEL3
. Transcription of
groEL1
, but not
groEL2
and
groEL3
, was elevated when HeLa cells infected with
C. trachomatis
were subjected to heat shock. Western blot analysis with polyclonal antibodies raised against recombinant GroEL1, GroEL2, and GroEL3 demonstrated the presence of the three proteins in
C. trachomatis
elementary bodies, with GroEL1 being present in the largest amount. Only
C. trachomatis groEL1
and
groES
together complemented a temperature-sensitive
E. coli groEL
mutant. Complementation did not occur with
groEL2
or
groEL3
alone or together with
groES
. The role for each of the three GroELs in the chlamydial developmental cycle and in disease pathogenesis requires further study.
Mass Distribution and Spatial Organization of the Linear Bacterial Motor ofSpiroplasma citriR8A2
Authors: Trachtenberg Shlomo , Andrews S. Brian , Leapman Richard D.
Published: March 2003

In the simple, helical, wall-less bacterial genusSpiroplasma, chemotaxis and motility are effected by a linear, contractile motor arranged as a flat cytoskeletal ribbon attached to the inner side of the membrane along the shortest helical line. With scanning transmission electron microscopy and diffraction analysis, we determined the hierarchical and spatial organization of the cytoskeleton ofSpiroplasma citriR8A2. The structural unit appears to be a fibril, ∼5 nm wide, composed of dimers of a 59-kDa protein; each ribbon is assembled from seven fibril pairs. The functional unit of the intact ribbon is a pair of aligned fibrils, along which pairs of dimers form tetrameric ring-like repeats. On average, isolated and purified ribbons contain 14 fibrils or seven well-aligned fibril pairs, which are the same structures observed in the intact cell. Scanning transmission electron microscopy mass analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified cytoskeletons indicate that the 59-kDa protein is the only constituent of the ribbons.
Identification and Biosynthesis of Cyclic Enterobacterial Common Antigen in
Escherichia coli
Authors: Erbel Paul J. A. , Barr Kathleen , Gao Ninguo , Gerwig Gerrit J. , Rick Paul D. , Gardner Kevin H.
Published: March 2003

Phosphoglyceride-linked enterobacterial common antigen (ECA
PG
) is a cell surface glycolipid that is synthesized by all gram-negative enteric bacteria. The carbohydrate portion of ECA
PG
consists of linear heteropolysaccharide chains comprised of the trisaccharide repeat unit Fuc4NAc-ManNAcA-GlcNAc, where Fuc4NAc is 4-acetamido-4,6-dideoxy-
d
-galactose, ManNAcA is
N
-acetyl-
d
-mannosaminuronic acid, and GlcNAc is
N
-acetyl-
d
-glucosamine. The potential reducing terminal GlcNAc residue of each polysaccharide chain is linked via phosphodiester linkage to a phosphoglyceride aglycone. We demonstrate here the occurrence of a water-soluble cyclic form of enterobacterial common antigen, ECA
CYC
, purified from
Escherichia coli
strains B and K-12 with solution nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and additional biochemical methods. The ECA
CYC
molecules lacked an aglycone and contained four trisaccharide repeat units that were nonstoichiometrically substituted with up to four O-acetyl groups. ECA
CYC
was not detected in mutant strains that possessed null mutations in the
wecA
,
wecF
, and
wecG
genes of the
wec
gene cluster. These observations corroborate the structural data obtained by NMR and ESI-MS analyses and show for the first time that the trisaccharide repeat units of ECA
CYC
and ECA
PG
are assembled by a common biosynthetic pathway.
Gene Expression Profile of
Campylobacter jejuni
in Response to Growth Temperature Variation
Authors: Stintzi Alain
Published: March 2003

The foodborne pathogen
Campylobacter jejuni
is the primary causative agent of gastroenteritis in humans. In the present study a whole genome microarray of
C. jejuni
was constructed and validated. These DNA microarrays were used to measure changes in transcription levels over time, as
C. jejuni
cells responded to a temperature increase from 37 to 42°C. Approximately 20% of the
C. jejuni
genes were significantly up- or downregulated over a 50-min period after the temperature increase. The global change in
C. jejuni
transcriptome was found to be essentially transient, with only a small subset of genes still differentially expressed after 50 min. A substantial number of genes with a downregulated coexpression pattern were found to encode for ribosomal proteins. This suggests a short growth arrest upon temperature stress, allowing the bacteria to reshuffle their energy toward survival and adaptation to the new growth temperature. Genes encoding chaperones, chaperonins, and heat shock proteins displayed the most dramatic and rapid upregulation immediately after the temperature change. Interestingly, genes encoding proteins involved in membrane structure modification were differentially expressed, either up- or downregulated, suggesting a different protein membrane makeup at the two different growth temperatures. Overall, these data provide new insights into the primary response of
C. jejuni
to surmount a sudden temperature upshift, allowing the bacterium to survive and adapt its transcriptome to a new steady state.
Definition of the
Escherichia coli
MC4100 Genome by Use of a DNA Array
Authors: Peters Joseph E. , Thate Timothy E. , Craig Nancy L.
Published: March 2003

We have used an
Escherichia coli
K-12 whole-genome array based on the DNA sequence of strain MG1655 as a tool to identify deletions in another
E. coli
K-12 strain, MC4100, by probing the array with labeled chromosomal DNA. Despite the continued widespread use of MC4100 as an experimental system, the specific genetic relationship of this strain to the sequenced K-12 derivative MG1655 has not been resolved. MC4100 was found to contain four deletions, ranging from 1 to 97 kb in size. The exact nature of three of the deletions was previously unresolved, and the fourth deletion was altogether unknown.
Plasmid R16 ArdA Protein Preferentially Targets Restriction Activity of the Type I Restriction-Modification System
Eco
KI
Authors: Thomas Angela T. , Brammar William J. , Wilkins Brian M.
Published: March 2003

The ArdA antirestriction protein of the IncB plasmid R16 selectively inhibited the restriction activity of
Eco
KI, leaving significant levels of modification activity under conditions in which restriction was almost completely prevented. The results are consistent with the hypothesis that ArdA functions in bacterial conjugation to allow an unmodified plasmid to evade restriction in the recipient bacterium and yet acquire cognate modification.
Identification of an Unknown Promoter,
OUTIIp
, within the IS
10
R Element
Authors: Martínez-García Esteban , Navarro-Lloréns Juana María , Tormo Antonio
Published: March 2003

A novel promoter in IS
10
R (
OUTIIp
) has been found in one of its ends in an inverted position relative to promoter pOUT.
OUTIIp
shows characteristics similar to those of
rpoS
-dependent promoters such as a gearbox expression pattern. It is under catabolite repression and positively regulated by ppGpp or conditioned media. This opens new challenges in IS
10
R transposition.
Genetic control over survival in Pacific salmon (Oncorhynchus spp.): experimental evidence between and within populations of New Zealand chinook salmon (O. tshawytscha)
Authors: Unwin Martin J , Kinnison Michael T , Boustead Nelson C , Quinn Thomas P
Published: March 2003

The ability to survive to adulthood and return to natal sites is a fundamental characteristic of anadromous salmonids, and low survival is likely to have prevented establishment of new populations within and outside their native range. We hypothesised that there is family-level genetic variation in traits contributing to survival and that populations evolve to maximise survival in response to prevailing local conditions. To test these predictions, we compared postrelease survival for chinook salmon families from two populations established in New Zealand in the 1900s. Both populations, Glenariffe Stream and Hakataramea River, had similar survival when released after translocation to a drainage familiar to neither population. However, Glenariffe families had higher survival than Hakataramea families when both populations were released from Glenariffe Stream, indicating a survival advantage for the local fish. In addition, there were significant correlations between survival rates for paternal half-sib families of Glenariffe fish and between survival rates for families released from the two locations. Family-specific survival was positively correlated with weight at release, but there were underlying genetic correlations unexplained by size. Taken together, these results suggest considerable genetic influence over survival and return of salmon and that population-specific adaptation can occur within 30 generations of establishment.
Assessment of net change of productive capacity of fish habitats: the role of uncertainty and complexity in decision making
Authors: Minns Charles K , Moore James E
Published: March 2003

Canada's fish habitat management is guided by the principle of "no net loss of the productive capacity of fish habitat" (NNL). Many development proposals are assessed using habitat information alone, rather than fish data. Because fishhabitat linkages are often obscured by uncertainty, uncertainty must be factored into NNL assessments. Using a quantitative framework for assessing NNL and lake habitats as a context, the implications of uncertainty for decision making are examined. The overall behaviour of a net change equation given uncertainty is explored using Monte Carlo simulation. Case studies from Great Lakes development projects are examined using interval analysis. The results indicate that uncertainty, even when large, can be incorporated into assessments. This has important implications for the habitat management based on NNL. First, schemas to specify relative levels of uncertainty using simple habitat classifications can support robust decision making. Second, attaining NNL requires greater emphasis on minimizing habitat loss and creating new areas to compensate for losses elsewhere and less on detailing small incremental changes in modified habitats where the fish response is difficult to demonstrate. Third, the moderate to high levels of uncertainty in fishhabitat linkages require that created compensation is at least twice the losses to reasonably ensure NNL.
Chemosterilization of male sea lampreys (Petromyzon marinus) does not affect sex pheromone release
Authors: Siefkes Michael J , Bergstedt Roger A , Twohey Michael B , Li Weiming
Published: March 2003

Release of males sterilized by injection with bisazir is an important experimental technique in management of sea lamprey (Petromyzon marinus), an invasive, nuisance species in the Laurentian Great Lakes. Sea lampreys are semelparous and sterilization can theoretically eliminate a male's reproductive capacity and, if the ability to obtain mates is not affected, waste the sex products of females spawning with him. It has been demonstrated that spermiating males release a sex pheromone that attracts ovulating females. We demonstrated that sterilized, spermiating males also released the pheromone and attracted ovulating females. In a two-choice maze, ovulating females increased searching behavior and spent more time in the side of the maze containing chemical stimuli from sterilized, spermiating males. This attraction response was also observed in spawning stream experiments. Also, electro-olfactograms showed that female olfactory organs were equally sensitive to chemical stimuli from sterilized and nonsterilized, spermiating males. Finally, fast atom bombardment mass spectrometry showed that extracts from water conditioned with sterilized and nonsterilized, spermiating males contained the same pheromonal molecule at similar levels. We concluded that injection of bisazir did not affect the efficacy of sex pheromone in sterilized males.
Chemical potential and concentration fluctuation in some aqueous alkane-mono-ols at 25oC
Authors: Hu Jianhua , Haynes Charles A , Wu Amy HY , Cheung Candy MW , Chen Mark M , Yee Eric GM , Ichioka Takehiko , Nishikawa Keiko , Westh Peter , Koga Yoshikata
Published: March 2003

Vapour pressures of binary aqueous solutions of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-hexanol were measured at 25.00oC in small compositional increments over the entire compositional range. Without resorting to any fitting function, the partial pressures were calculated numerically by methods based on the GibbsDuhem relation. When the system had an azeotrope, near which the numerical methods caused large errors, a graphical readjustment was applied such that the concentration fluctuation, SXX(0) = RT(1  xAL)/([Formula: see text]µ EAL/[Formula: see text]xAL), connected smoothly across the azeotrope. Values of SXX(0) from scattering experiments were also used as a guide for the readjustment procedure. Hence, we report here chemical potential data free from any model or any fitting function.Key Words: aqueous mono-ols, partial pressures by the Boissonnas method, concentration fluctuations.
Excess partial molar entropy of alkane-mono-ols in aqueous solutions at 25°C
Authors: Koga Yoshikata , Westh Peter , Nishikawa Keiko
Published: March 2003

In the preceding paper, we reported the values of model-free chemical potentials for aqueous methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-hexanol at 25°C over the entire compositional region. Using alcohol excess partial molar enthalpies, HEAL, determined earlier in this laboratory (Can. J. Chem. 74, 713 (1996)), we have calculated excess partial molar entropies for the alcohols, SEAL, where AL stands for an alcohol. We then calculated, numerically, the entropic interaction, SEALAL = N([Formula: see text]SEAL/[Formula: see text]nAL)p,T,nW, where nAL is the amount of AL, nW is the amount of H2O, and N is the total amount of solution. SEALAL signifies the effect of addition of AL upon the entropic situation of existing AL in solution. Using these quantities, the mixing schemes in aqueous alcohols have been studied. The earlier conclusions, which used HEAL and HEALAL alone, are confirmed. Furthermore, the order of the relative hydrophobic nature of alcohols is established from the behaviour of SEALAL and of HEALAL as methanol < ethanol < 2-propanol < 1-propanol. Key Words: aqueous alcohols, excess partial molar entropies, entropic interaction mixing schemes, hydrophobicity ranking.
A new method for the preparation of peroxymonophosphoric acid
Authors: Zhu Tian , Chang Hou-min , Kadla John F
Published: March 2003

A new method for the preparation of peroxymonophosphoric acid (H3PO5) has been developed. It utilizes a biphasic solution to moderate the vigorous reaction between phosphorous pentoxide (P2O5) and hydrogen peroxide (H2O2). P2O5 is suspended in carbon tetrachloride (CCl4), and concentrated H2O2 is slowly added while being vigorously stirred at low temperature. Careful control of the reaction temperature through the slow addition of H2O2 is critical. Using typical preparation conditions (P2O5:H2O2 = 0.5:1, H2O2 70 wt %, 2°C, 120180 min), ~70% of the H2O2 is effectively converted to H3PO5. Increasing the concentration of H2O2, as well as the mole ratio of P2O5:H2O2, leads to an even higher % conversion of H2O2 to H3PO5. The addition of glacial acetic acid to the P2O5:H2O2 suspension at the end of the 120180 min reaction (P2O5:H2O2:CH3COOH = 0.5:1:0.3) leads to the formation of peracetic acid in addition to H3PO5, and to an overall increase in the conversion ratio of total peroxy acids based on H2O2 (>95%).Key words: peroxymonophosphoric acid, synthesis, stability, conversion ratio.
Electrocatalytic oxidation and flow amperometric detection of hydrazine on a dinuclear ruthenium phthalocyanine-modified electrode
Authors: Ebadi Mehrdad
Published: March 2003

Electrocatalytic oxidation of hydrazine on a dinuclear ruthenium phthalocyanine ((RuPc)2) modified electrode was studied using cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques. At pH = 13, a four-electron oxidation of hydrazine to N2 was observed. A suitable mechanism was proposed by analyzing the rate equation and the Tafel slope. The flow injection analysis was performed to characterize the (RuPc)2-modified electrode as an amperometric sensor for the detection of hydrazine. The electrode displays an excellent accuracy and precision in phosphate solution at pH 12 and 13. The linearity range was from 30 nM to 1 mM with a correlation coefficient of 0.9998.Key words: ruthenium phthalocyanine, electrocatalysis, surface-modified electrode, hydrazine, amperometric sensor.
XANES of chromium in sludges used as soil ameliorants
Authors: Martin R R , Naftel S J , Sham T K , Hart B , Powell M A
Published: March 2003

Samples of sewage sludges proposed for use as soil ameliorants in an Indo-Canadian project were tested for chromium content. Standard aqua regia extractions found one sludge to have excessive amounts of Cr. X-ray absorption near-edge structure (XANES) spectroscopy, however, indicated that the Cr was present in the relatively benign Cr(III) oxidation state in all the sludge samples.Key words: soil, chromium, synchrotron, XANES.
ADAPTIVE AND MONOTONE SPLINE ESTIMATION OF THE CROSS-SECTIONAL TERM STRUCTURE
Authors: RAMPONI ALESSANDRO
Published: March 2003

A number of numerical methods based on a piecewise polynomial approximation have been proposed for the estimation of the term structure of interest rates. Some drawbacks have been pointed out, such as a possible non monotonic estimated discount function and a highly fluctuating spot and forward rates. In order to overcome these kind of problems, we study the feasibility of an adaptive regression spline technique which use a monotone basis together with two alternative knot location procedures: a deterministic greedy algorithm and its randomized version in a simulated annealing framework. The features of the proposed method are tested on a set of data.
A CONTINUOUS-TIME REEXAMINATION OF DOLLAR-COST AVERAGING
Authors: MILEVSKY MOSHE A. , POSNER STEVEN E.
Published: March 2003

The widespread practice of dollar-cost averaging (DCA) amongst the investing public, has puzzled most financial economists, ever since Constantinides [2] demonstrated the dynamic inefficiency of this strategy under very general conditions. This enduring phenomena has forced researchers, such as Statman [12], to suggest behavioral explanations for DCA's popularity, predicated on the prospect theory of Kahneman and Tversky [4].

In this paper we reexamine the payoff structure of DCA via continuous-time financial mathematics and then ask the question: Is it possible to reconcile the theory and practice of dollar-cost averaging?

To answer this question, we take a slightly different approach to the issue by using the tools of stochastic calculus and Brownian bridges. We demonstrate that engaging in a dollar-cost averaging strategy is akin to purchasing a zero strike arithmetic Asian option on the underlying security. In other words, people who engage in dollar-cost averaging are implicitly purchasing a path-dependent contingent claim. We then prove that the expected return from this exotic option — i.e. the DCA strategy — conditional on knowing the final value of the security will uniformly exceed the return from the underlying security for all sufficiently large volatilities.

This leads us to argue that investors may be dollar-cost averaging because they have "target prices" for the underlying asset price. The strategy of dollar-cost averaging would then exceed the returns from lump-sum investing, based on their subjective conditional expectation. In fact, the more volatile the underlying security, the greater is the benefit to dollar-cost averaging — conditional on knowing the final value — which is consistent with common practice.
Mechanisms of Alternative Pre-Messenger RNA Splicing
Authors: Black Douglas L.
Published: March 2003

▪ Abstract  Alternative pre-mRNA splicing is a central mode of genetic regulation in higher eukaryotes. Variability in splicing patterns is a major source of protein diversity from the genome. In this review, I describe what is currently known of the molecular mechanisms that control changes in splice site choice. I start with the best-characterized systems from the Drosophila sex determination pathway, and then describe the regulators of other systems about whose mechanisms there is some data. How these regulators are combined into complex systems of tissue-specific splicing is discussed. In conclusion, very recent studies are presented that point to new directions for understanding alternative splicing and its mechanisms.
MOLECULAR APPROACHES TO SPINAL CORD REPAIR
Authors: David Samuel , Lacroix Steve
Published: March 2003

▪ Abstract  Axon growth inhibitors associated with myelin and the glial scar contribute to the failure of axon regeneration in the injured adult mammalian central nervous system (CNS). A number of these inhibitors, their receptors, and signaling pathways have been identified. These inhibitors can now be neutralized by a variety of approaches that point to the possibility of developing new therapeutic strategies to stimulate regeneration after spinal cord injury.
TROPHIC AND CYTOPROTECTIVE NUTRITION FOR INTESTINAL ADAPTATION, MUCOSAL REPAIR, AND BARRIER FUNCTION
Authors: Ziegler Thomas R. , Evans Mary E. , Fernández-Estívariz Concepción , Jones Dean P.
Published: March 2003

▪ Abstract  Intestinal epithelial cell turnover (proliferation, migration, differentiation, and apoptosis) and gut barrier functions are dynamic processes that are markedly affected by nutritional status, the route of feeding, and the adequacy of specific nutrients in the diet. Emerging studies are defining potential therapeutic roles for specific nutrients and diet-derived compounds (including arginine, glutamate, glutamine, glutathione, glycine, vitamin A, zinc, and specific lipids) in gut mucosal turnover, repair, adaptation after massive bowel resection, and barrier function. The role and regulation of endogenous bowel flora in generating short-chain fatty acids from diet-derived fiber and other diet-derived compounds and the effects of these agents on gut function are increasingly being elucidated. Results of these investigations should define new nutritional methods for trophic and cytoprotective effects on the intestine in conditions such as inflammatory bowel disease, malnutrition, and short bowel syndrome.
GUGULIPID: A Natural Cholesterol-Lowering Agent
Authors: Urizar Nancy L. , Moore David D.
Published: March 2003

▪ Abstract  The resin of the Commiphora mukul tree has been used in Ayurvedic medicine for more than 2000 years to treat a variety of ailments. Studies in both animal models and humans have shown that this resin, termed gum guggul, can decrease elevated lipid levels. The stereoisomers E- and Z-guggulsterone have been identified as the active agents in this resin. Recent studies have shown that these compounds are antagonist ligands for the bile acid receptor farnesoid X receptor (FXR), which is an important regulator of cholesterol homeostasis. It is likely that this effect accounts for the hypolipidemic activity of these phytosteroids.
THE INTERRUPTION OF MYTH: A NANCIAN READING OF BLANCHOT AND AL-BAYATI
Authors: Salama Mohammad Ramadan
Published: March 2003

Jean-Luc Nancy's provocative second chapter of The Inoperative Community, "Myth Interrupted," sets to redefine the relationship between myth and literature. This paper puts Nancy's new perspective to test through juxtaposing Abd al-Wahhab al-Bayati's myth of Orpheus with Maurice Blanchot's. The assumption is that when literature stages myth and presents it from various perspectives, it does so not to invoke or allegorize its content through the letter, but rather to interrupt it. This new discovery of the "untraceability" of myth leaves us with a different perspective of literature as that language which cuts across myth and exposes its limit and as a language that inhabits myth only to interrupt it. Blanchot's interest in Orpheus, as it is articulated in his novel/story Thomas l'obscur (the 1950 New Version) and in his chapter on "Orpheus's Gaze" in The Space of Literature, and al-Bayati's reference to Orpheus in his poetic collections He Who Comes and Does Not Come, Death in Life, and Writing on the Mud thematize this playful staging of the myth of Orpheus. Both seem to follow a different path with the same myth. Blanchot disregards the ending of the Orpheus story, and al-Bayati disregards the gaze. However, it is not just selection, but modification that is at work here: both shape their chosen materials in conformity to a specific need. The logic that binds the two writers together in relation to myth and literature expresses itself not only in the choice of the same myth, but they also have in common the shared debt to this classical material and more importantly in their (re)definition of this material. The point of departure between the two of them in their treatment (reinterpretation) of Orpheus is that Blanchot is looking at the effect of death on writing, while al-Bayati is exploring the effect of writing on death.
Human cytomegalovirus protein pp65 mediates accumulation of HLA-DR in lysosomes and destruction of the HLA-DR α-chain
Authors: Odeberg Jenny , Plachter Bodo , Brandén Lars , Söderberg-Nauclér Cecilia
Published: March 2003

Human cytomegalovirus (HCMV) has developed multiple strategies to escape immune recognition. Here, we demonstrate that HCMV down-regulates HLA-DR expression in infected interferon γ (IFN-γ)–stimulated fibroblasts at 1 day after infection. Decreased HLA-DR expression was not observed on cells infected with an HCMV strain lacking the pp65 gene (RVAD65), but was observed on cells transfected with the pp65 gene. HLA-DR expression accumulated in vacuoles near the nucleus in HCMV-infected, but not in uninfected or RVAD65-infected cells. In addition, the HLA-DR α-chain, but not the β-chain or HLA-DM, was degraded in HCMV-infected but not in RVAD65-infected cells. Thus, the HCMV protein pp65 mediates decreased expression of HLA-DR, by mediating an accumulation of HLA class II molecules in lysosomes that results in degradation of the HLA-DR α-chain.
A subset of t(11;14) lymphoma with mantle cell features displays mutated IgVH genes and includes patients with good prognosis, nonnodal disease
Authors: Orchard Jenny , Garand Richard , Davis Zadie , Babbage Gavin , Sahota Surinder , Matutes Estella , Catovsky Daniel , Thomas Peter W. , Avet-Loiseau Hervé , Oscier David
Published: March 2003

We analyzed lymphocyte morphology, histology, immunophenotype, immunoglobulin heavy chain (IgVH) gene mutations, and clinical course in 80 unselected patients presenting with circulating t(11;14) lymphocytes. Of the 80 patients, 43 had peripheral lymphadenopathy (nodal group), and histology confirmed mantle cell lymphoma (MCL) in all. There were 37 patients with no lymphadenopathy (nonnodal group); 13 of 37 had histology, all showing MCL. IgVH genes were unmutated in 28 (90%) of 31 nodal and 15 (44%) of 34 nonnodal cases (P = .0001); CD38 was positive in 32 (94%) of 34 nodal and 16 (48%) of 33 nonnodal cases (P < .001); 41 (95%) of 43 nodal patients required immediate treatment compared with 18 (49%) of 37 nonnodal patients who had indolent disease (P < .0001). Median survival (95% confidence interval) was 30 months (10-50) in the nodal group and 79 months (22-136) in the nonnodal group (P = .005). Mutation status did not statistically affect survival, but of 6 long-term survivors (> 90 months) all were nonnodal and 5 of 5 had mutated IgVH genes. Lymphocyte morphology was heterogeneous in both groups: typical MCL in 56 cases (34 nodal, 22 nonnodal), blastoid MCL in 8 cases (3 nodal, 5 nonnodal), and small-cell MCL in 16 cases (6 nodal, 10 nonnodal, P = .12). Matutes immunophenotyping score was 1 in 65 cases and 2 in 15 (8 nodal, 7 nonnodal). We find no evidence against a diagnosis of MCL in the nonnodal group and suggest that mutated IgVH genes may help identify patients with indolent disease.