bluuebunny/crossref_metadata_2025 huggingface dataset:
Virulence of
Leucobacter chromiireducens
subsp.
solipictus
to
Caenorhabditis elegans
: Characterization of a Novel Host-Pathogen Interaction
Authors: Muir Rachel E. , Tan Man-Wah
Published: May 2008

We describe the pathogenic interaction between a newly described gram-positive bacterium,
Leucobacter chromiireducens
subsp.
solipictus
strain TAN 31504, and the nematode
Caenorhabditis elegans
. TAN 31504 pathogenesis on
C. elegans
is exerted primarily through infection of the adult nematode uterus. TAN 31504 enters the uterus through the external vulval opening, and the ensuing uterine infection is strongly correlated with a significant reduction in host life span. Young worms can feed and develop on TAN 31504, but not preferably over the standard food source.
C. elegans
worms reared on TAN 31504 as the sole food source develop into thin adults with little intestinal fat stores, produce few progeny, and subsequently cannot persist on the pathogenic food source. Within 12 h of exposure, adult worms challenged with TAN 31504 alter the expression of a number of
C. elegans
innate immunity-related genes, including
nlp-29
, which encodes a neuropeptide-like protein.
C. elegans
worms exposed briefly to TAN 31504 develop lethal uterine infections analogous to worms exposed continuously to pathogen, suggesting that mere contact with the pathogen is sufficient for the host to become infected. TAN 31504 produces a robust biofilm, and this behavior is speculated to play a role in the virulence exerted on the nematode host. The interaction between TAN 31504 and
C. elegans
provides a convenient opportunity to study bacterial virulence on nematode tissues other than the intestine and may allow for the discovery of host innate immunity elicited specifically in response to vulva-uterus infection.
The Explosive-Degrading Cytochrome P450 System Is Highly Conserved among Strains of
Rhodococcus
spp
Authors: Seth-Smith Helena M. B. , Edwards James , Rosser Susan J. , Rathbone Deborah A. , Bruce Neil C.
Published: May 2008

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a widely used explosive and a serious environmental pollutant. Nineteen strains of
Rhodococcus
spp. capable of utilizing RDX as the sole nitrogen source have been isolated. The cytochrome P450 system XplA-XplB, which is responsible for RDX breakdown, is present in 18 of these strains.
Highly Efficient Method for Introducing Successive Multiple Scarless Gene Deletions and Markerless Gene Insertions into the
Yersinia pestis
Chromosome
Authors: Sun Wei , Wang Shifeng , Curtiss Roy
Published: May 2008

An efficient two-step recombination method for markerless gene deletion and insertion that can be used for repetitive genetic modification in
Yersinia pestis
was developed. The method combines λ Red recombination and counterselective screening (
sacB
gene) and can be used for genetic modification of
Y. pestis
to construct live attenuated vaccines.
Genotypic Diversity, Antimicrobial Resistance, and Virulence Factors of Human Isolates and Probiotic Cultures Constituting Two Intraspecific Groups of
Enterococcus faecium
Isolates
Authors: Vankerckhoven Vanessa , Huys Geert , Vancanneyt Marc , Snauwaert Cindy , Swings Jean , Klare Ingo , Witte Wolfgang , Van Autgaerden Tim , Chapelle Sabine , Lammens Christine , Goossens Herman
Published: May 2008

The intraspecific relationships among a collection of
Enterococcus faecium
isolates comprising probiotic cultures and human clinical isolates were investigated through the combined use of two high-resolution DNA-fingerprinting techniques. In addition, the incidences of antimicrobial resistance and virulence traits were investigated. A total of 128
E. faecium
isolates from human clinical or nonclinical sources or used as probiotic cultures were subjected to fluorescent amplified fragment length polymorphism (FAFLP) fingerprinting and pulsed-field gel electrophoresis (PFGE) analysis of SmaI macrorestriction patterns. Susceptibilities to 16 antimicrobial agents were tested using broth microdilution, and the presence of the corresponding resistance genes was investigated using PCR. Multiplex PCR was used to detect the presence of the enterococcal virulence genes
asa1
,
gelE
,
cylA
,
esp
, and
hyl
. The results of the study showed that two intraspecific genomic groups (I and II) were obtained in FAFLP analysis. PFGE analysis demonstrated high variability within these two groups but also indicated that some probiotic cultures were indistinguishable and that a number of clinical isolates may be reisolations of commercial probiotic cultures. Compared to group II, which contained the majority of the probiotic isolates and fewer human clinical isolates, higher phenotypic and genotypic resistance frequencies were observed in group I. Two probiotic isolates were phenotypically resistant to erythromycin, one of which contained an
erm
(B) gene that was not transferable to enterococcal recipients. None of the probiotic
E. faecium
isolates demonstrated the presence of the tested virulence genes. The previously reported observation that
E. faecium
consists of two intraspecific genomic groups was further substantiated by FAFLP fingerprinting of 128 isolates. In combination with antimicrobial resistance and virulence testing, this grouping might represent an additional criterion in assessing the safety of new potential probiotic
E. faecium
isolates.
Novel Bacterial Surface Display Systems Based on Outer Membrane Anchoring Elements from the Marine Bacterium
Vibrio anguillarum
Authors: Yang Zhao , Liu Qin , Wang Qiyao , Zhang Yuanxing
Published: May 2008

Surface display of heterologous peptides and proteins such as receptors, antigens, and enzymes on live bacterial cells is of considerable value for various biotechnological and industrial applications. In this study, a series of novel cell surface display systems were examined by using
Vibrio anguillarum
outer membrane protein and outer membrane lipoprotein as anchoring motifs. These display systems consist of (i) the signal sequence and first 11 N-terminal amino acids of
V. anguillarum
outer membrane lipoprotein Wza, or the signal sequence and first 9 N-terminal amino acids of the mature major
Escherichia coli
lipoprotein Lpp, and (ii) transmembrane domains of
V. anguillarum
outer membrane proteins Omporf1, OmpU, or Omp26La. In order to assay the translocation efficiency of constructed display systems in bacteria, green fluorescent protein (GFP) was inserted to the systems and the results of GFP surface localization confirmed that four of the six surface display systems could successfully display GFP on the
E. coli
surface. For assaying its potential application in live bacteria carrier vaccines, an excellent display system Wza-Omporf1 was fused with the major capsid protein (MCP) of large yellow croaker iridovirus and introduced into attenuated
V. anguillarum
strain MVAV6203, and subsequent analysis of MCP surface localization proved that the novel display system Wza-Omporf1 could function as a strong tool in
V. anguillarum
carrier vaccine development.
Characterization of Nitrifying, Denitrifying, and Overall Bacterial Communities in Permeable Marine Sediments of the Northeastern Gulf of Mexico
Authors: Mills Heath J. , Hunter Evan , Humphrys Mike , Kerkhof Lee , McGuinness Lora , Huettel Markus , Kostka Joel E.
Published: May 2008

Sandy or permeable sediment deposits cover the majority of the shallow ocean seafloor, and yet the associated bacterial communities remain poorly described. The objective of this study was to expand the characterization of bacterial community diversity in permeable sediment impacted by advective pore water exchange and to assess effects of spatial, temporal, hydrodynamic, and geochemical gradients. Terminal restriction fragment length polymorphism (TRFLP) was used to analyze nearly 100 sediment samples collected from two northeastern Gulf of Mexico subtidal sites that primarily differed in their hydrodynamic conditions. Communities were described across multiple taxonomic levels using universal bacterial small subunit (SSU) rRNA targets (RNA- and DNA-based) and functional markers for nitrification (
amoA
) and denitrification (
nosZ
). Clonal analysis of SSU rRNA targets identified several taxa not previously detected in sandy sediments (i.e.,
Acidobacteria
,
Actinobacteria
,
Chloroflexi
,
Cyanobacteria
, and
Firmicutes
). Sequence diversity was high among the overall bacterial and denitrifying communities, with members of the
Alphaproteobacteria
predominant in both. Diversity of bacterial nitrifiers (
amoA
) remained comparatively low and did not covary with the other gene targets. TRFLP fingerprinting revealed changes in sequence diversity from the family to species level across sediment depth and study site. The high diversity of facultative denitrifiers was consistent with the high permeability, deeper oxygen penetration, and high rates of aerobic respiration determined in these sediments. The high relative abundance of
Gammaproteobacteria
in RNA clone libraries suggests that this group may be poised to respond to short-term periodic pulses of growth substrates, and this observation warrants further investigation.
Partially Functional Outer-Arm Dynein in a Novel
Chlamydomonas
Mutant Expressing a Truncated γ Heavy Chain
Authors: Liu Zhongmei , Takazaki Hiroko , Nakazawa Yuki , Sakato Miho , Yagi Toshiki , Yasunaga Takuo , King Stephen M. , Kamiya Ritsu
Published: May 2008

The outer dynein arm of
Chlamydomonas
flagella contains three heavy chains (α, β, and γ), each of which exhibits motor activity. How they assemble and cooperate is of considerable interest. Here we report the isolation of a novel mutant,
oda2
-
t
, whose γ heavy chain is truncated at about 30% of the sequence. While the previously isolated γ chain mutant
oda2
lacks the entire outer arm,
oda2
-
t
retains outer arms that contain α and β heavy chains, suggesting that the N-terminal sequence (corresponding to the tail region) is necessary and sufficient for stable outer-arm assembly. Thin-section electron microscopy and image analysis localize the γ heavy chain to a basal region of the outer-arm image in the axonemal cross section. The motility of
oda2
-
t
is lower than that of the wild type and
oda11
(lacking the α heavy chain) but higher than that of
oda2
and
oda4
-
s7
(lacking the motor domain of the β heavy chain). Thus, the outer-arm dynein lacking the γ heavy-chain motor domain is partially functional. The availability of mutants lacking individual heavy chains should greatly facilitate studies on the structure and function of the outer-arm dynein.
A Gain-of-Function Mutation in the Transcription Factor Upc2p Causes Upregulation of Ergosterol Biosynthesis Genes and Increased Fluconazole Resistance in a Clinical
Candida albicans
Isolate
Authors: Dunkel Nico , Liu Teresa T. , Barker Katherine S. , Homayouni Ramin , Morschhäuser Joachim , Rogers P. David
Published: May 2008

In the pathogenic yeast
Candida albicans
, the zinc cluster transcription factor Upc2p has been shown to regulate the expression of
ERG11
and other genes involved in ergosterol biosynthesis upon exposure to azole antifungals.
ERG11
encodes lanosterol demethylase, the target enzyme of this antifungal class. Overexpression of
UPC2
reduces azole susceptibility, whereas its disruption results in hypersusceptibility to azoles and reduced accumulation of exogenous sterols. Overexpression of
ERG11
leads to the increased production of lanosterol demethylase, which contributes to azole resistance in clinical isolates of
C. albicans
, but the mechanism for this has yet to be determined. Using genome-wide gene expression profiling, we found
UPC2
and other genes involved in ergosterol biosynthesis to be coordinately upregulated with
ERG11
in a fluconazole-resistant clinical isolate compared with a matched susceptible isolate from the same patient. Sequence analysis of the
UPC2
alleles of these isolates revealed that the resistant isolate contained a single-nucleotide substitution in one
UPC2
allele that resulted in a G648D exchange in the encoded protein. Introduction of the mutated allele into a drug-susceptible strain resulted in constitutive upregulation of
ERG11
and increased resistance to fluconazole. By comparing the gene expression profiles of the fluconazole-resistant isolate and of strains carrying wild-type and mutated
UPC2
alleles, we identified target genes that are controlled by Upc2p. Here we show for the first time that a gain-of-function mutation in
UPC2
leads to the increased expression of
ERG11
and imparts resistance to fluconazole in clinical isolates of
C. albicans
.
Combined Deletion of Four
Francisella novicida
Acid Phosphatases Attenuates Virulence and Macrophage Vacuolar Escape
Authors: Mohapatra Nrusingh P. , Soni Shilpa , Reilly Thomas J. , Liu Jirong , Klose Karl E. , Gunn John S.
Published: May 2008

Francisella tularensis
is a facultative intracellular pathogen and the etiologic agent of tularemia. It is capable of escape from macrophage phagosomes and replicates in the host cell cytosol. Bacterial acid phosphatases are thought to play a major role in the virulence and intracellular survival of a number of intracellular pathogens. The goal of this study was to delete the four primary acid phosphatases (Acps) from
Francisella novicida
and examine the interactions of mutant strains with macrophages, as well as the virulence of these strains in mice. We constructed
F. novicida
mutants with various combinations of
acp
deletions and showed that loss of the four Acps (AcpA, AcpB, AcpC, and histidine acid phosphatase [Hap]) in an
F. novicida
strain (ΔABCH) resulted in a 90% reduction in acid phosphatase activity. The ΔABCH mutant was defective for survival/growth within human and murine macrophage cell lines and was unable to escape from phagosome vacuoles. With accumulation of Acp deletions, a progressive loss of virulence in the mouse model was observed. The ΔABCH strain was dramatically attenuated and was an effective single-dose vaccine against homologous challenge. Furthermore, both
acpA
and
hap
were induced when the bacteria were within host macrophages. Thus, the
Francisella
acid phosphatases cumulatively play an important role in intracellular trafficking and virulence.
Vibrio cholerae
RND Family Efflux Systems Are Required for Antimicrobial Resistance, Optimal Virulence Factor Production, and Colonization of the Infant Mouse Small Intestine
Authors: Bina Xiaowen R. , Provenzano Daniele , Nguyen Nathalie , Bina James E.
Published: May 2008

Vibrio cholerae
is a gram-negative human intestinal pathogen that causes the diarrheal disease cholera. Humans acquire cholera by ingesting
V. cholerae
-contaminated food or water. Upon ingestion,
V. cholerae
encounters several barriers to colonization, including bile acid toxicity and antimicrobial products of the innate immune system. In many gram-negative bacteria, resistance to the antimicrobial effects of these products is mediated by RND (resistance-nodulation-division) family efflux systems. In this study we tested the hypothesis that the
V. cholerae
RND efflux systems are required for antimicrobial resistance and virulence. The six
V. cholerae
genes encoding RND efflux pumps were deleted from the genome of the O1 El Tor strain N16961, resulting in the generation of 14 independent RND deletion mutants, including one RND-null strain. Determination of the antimicrobial susceptibilities of the mutants revealed that the RND efflux systems were responsible for resistance to multiple antimicrobial compounds, including bile acids, antimicrobial peptides, and antibiotics. VexB (VC0164) was found to be the RND efflux pump primarily responsible for the resistance of
V. cholerae
to multiple antimicrobial compounds in vitro. In contrast, VexD (VC1757) and VexK (VC1673) encoded efflux pumps with detergent-specific substrate specificities that were redundant with VexB. A strain lacking VexB, VexD, and VexK was attenuated in the infant mouse model, and its virulence factor production was unaffected. In contrast, a
V. cholerae
RND-null strain produced significantly less cholera toxin and fewer toxin-coregulated pili than the wild type and was unable to colonize the infant mouse. The decreased virulence factor production in the RND-null strain was linked to reduced transcription of
tcpP
and
toxT
. Our findings show that the
V. cholerae
RND efflux systems are required for antimicrobial resistance, optimal virulence factor production, and colonization of the infant mouse.
Characterization of Two β-1,3-Glucosyltransferases fromEscherichia coliSerotypes O56 and O152
Authors: Brockhausen Inka , Hu Bo , Liu Bin , Lau Kenneth , Szarek Walter A. , Wang Lei , Feng Lu
Published: May 2008

The O antigens of outer membrane-bound lipopolysaccharides (LPS) in gram-negative bacteria are oligosaccharides consisting of repeating units with various structures and antigenicities. The O56 and O152 antigens ofEscherichia coliboth contain a Glc-β1-3-GlcNAc linkage within the repeating unit. We have cloned and identified the genes (wfaPin O56 andwfgDin O152) within the two O-antigen gene clusters that encode glucosyltransferases involved in the synthesis of this linkage. A synthetic substrate analog of the natural acceptor substrate undecaprenol-pyrophosphate-lipid [GlcNAc-α-PO3-PO3-(CH2)11-O-phenyl] was used as an acceptor and UDP-Glc as a donor substrate to demonstrate that bothwfgDandwfaPencode glucosyltransferases. Enzyme products from both glucosyltransferases were isolated by high-pressure liquid chromatography and analyzed by nuclear magnetic resonance. The spectra showed the expected Glc-β1-3-GlcNAc linkage in the products, confirming that both WfaP and WfgD are forms of UDP-Glc: GlcNAc-pyrophosphate-lipid β-1,3-glucosyltransferases. Both WfaP and WfgD have a DxD sequence, which is proposed to interact with phosphate groups of the nucleotide donor through the coordination of a metal cation, and a short hydrophobic sequence at the C terminus that may help to associate the enzymes with the inner membrane. We showed that the enzymes have similar properties and substrate recognition. They both require a divalent cation (Mn2+or Mg2+) for activity, are deactivated by detergents, have a broad pH optimum, and require the pyrophosphate-sugar linkage in the acceptor substrate for full activity. Substrates lacking phosphate or pyrophosphate linked to GlcNAc were inactive. The length of the aliphatic chain of acceptor substrates also contributes to the activity.
Transcription of theehxEnterohemolysin Gene Is Positively Regulated by GrlA, a Global Regulator Encoded within the Locus of Enterocyte Effacement in EnterohemorrhagicEscherichia coli
Authors: Saitoh Takehito , Iyoda Sunao , Yamamoto Shouji , Lu Yan , Shimuta Ken , Ohnishi Makoto , Terajima Jun , Watanabe Haruo
Published: May 2008

The pathogenicity island termed locus of enterocyte effacement (LEE) encodes a type 3 protein secretion system, whose function is required for full virulence of enterohemorrhagicEscherichia coli(EHEC). GrlR and GrlA are LEE-encoded negative and positive regulators, respectively, for controlling transcription of thelergene, which encodes a central activator of LEE gene expression. We previously reported that the GrlR-GrlA regulatory system controls not only the LEE genes but also flagellar gene expression in EHEC (S. Iyoda et al., J. Bacteriol.188:5682-5692, 2006). In order to further explore virulence-related genes under the control of the GrlR-GrlA regulatory system, we characterized agrlR-deleted EHEC O157 strain, which was found to have high and low levels of expression of LEE and flagellar genes, respectively. We report here that thegrlRdeletion significantly induced enterohemolysin (Ehx) activity of EHEC O157 on plates containing defibrinated sheep erythrocytes. Ehx levels were not induced in thegrlR grlAdouble mutant strain but increased markedly by overexpression of GrlA even in thelermutant, indicating that GrlA is responsible for this regulation. Ehx of the EHEC O157 Sakai strain is encoded by theehxCABDgenes, which are carried on the large plasmid pO157. The expression ofehxCfused with FLAG tag or a promoterlesslacZgene on pO157 was significantly induced under conditions in which GrlA was overproduced. These results together suggest that GrlA acts as a positive regulator for theehxtranscription in EHEC.
The
Burkholderia mallei
BmaR3-BmaI3 Quorum-Sensing System Produces and Responds to
N
-3-Hydroxy-Octanoyl Homoserine Lactone
Authors: Duerkop Breck A. , Herman Jake P. , Ulrich Ricky L. , Churchill Mair E. A. , Greenberg E. Peter
Published: May 2008

Burkholderia mallei
has two acyl-homoserine lactone (acyl-HSL) signal generator-receptor pairs and two additional signal receptors, all of which contribute to virulence. We show that
B. mallei
produces
N
-3-hydroxy-octanoyl HSL (3OHC
8
-HSL) but a
bmaI3
mutant does not. Recombinant
Escherichia coli
expressing BmaI3 produces hydroxylated acyl-HSLs, with 3OHC
8
-HSL being the most abundant compound. In recombinant
E. coli
, BmaR3 responds to 3OHC
8
-HSL but not to other acyl-HSLs. These data indicate that the signal for BmaR3-BmaI3 quorum sensing is 3OHC
8
-HSL.
Roles of Coenzyme F
420
-Reducing Hydrogenases and Hydrogen- and F
420
-Dependent Methylenetetrahydromethanopterin Dehydrogenases in Reduction of F
420
and Production of Hydrogen during Methanogenesis
Authors: Hendrickson Erik L. , Leigh John A.
Published: May 2008

Reduced coenzyme F
420
(F
420
H
2
) is an essential intermediate in methanogenesis from CO
2
. During methanogenesis from H
2
and CO
2
, F
420
H
2
is provided by the action of F
420
-reducing hydrogenases. However, an alternative pathway has been proposed, where H
2
-dependent methylenetetrahydromethanopterin dehydrogenase (Hmd) and F
420
H
2
-dependent methylenetetrahydromethanopterin dehydrogenase (Mtd) together reduce F
420
with H
2
. Here we report the construction of mutants of
Methanococcus maripaludis
that are defective in each putative pathway. Their analysis demonstrates that either pathway supports growth on H
2
and CO
2
. Furthermore, we show that during growth on formate instead of H
2
, where F
420
H
2
is a direct product of formate oxidation, H
2
production occurs. H
2
presumably arises from the oxidation of F
420
H
2
, and the analysis of the mutants during growth on formate suggests that this too can occur by either pathway. We designate the alternative pathway for the interconversion of H
2
and F
420
H
2
the Hmd-Mtd cycle.
Population Heterogeneity inCorynebacterium glutamicumATCC 13032 Caused by Prophage CGP3
Authors: Frunzke Julia , Bramkamp Marc , Schweitzer Jens-Eric , Bott Michael
Published: May 2008

The genome ofCorynebacterium glutamicumtype strain ATCC 13032 (accession number BX927147) contains three prophages, CGP1, CGP2, and CGP3. We recently observed that many genes within the CGP3 prophage region have increased mRNA levels in adtxRdeletion mutant that lacks the master regulator of iron homeostasis (J. Wennerhold and M. Bott, J. Bacteriol.188:2907-2918, 2006). Here, we provide evidence that this effect is due to the increased induction of the prophage CGP3 in thedtxRmutant, possibly triggered by DNA damage caused by elevated intracellular iron concentrations. Upon induction, the CGP3 prophage region is excised from the genome and forms a circular double-stranded DNA molecule. Using quantitative real-time PCR, an average copy number of about 0.1 per chromosome was determined for circular CGP3 DNA in wild-typeC. glutamicum. This copy number increased about 15-fold in thedtxRmutant. In order to visualize the CGP3 DNA within single cells, a derivative of the wild type was constructed that contained an array oftetoperators integrated within the CGP3 region and a plasmid-encoded YFP-TetR fusion protein. As expected, one to two fluorescent foci that represented the chromosomally integrated CGP3 prophage were detected in the majority of cells. However, in a small fraction (2 to 4%) of the population, 4 to 10 CGP3 DNA molecules could be observed in a single cell. Interestingly, the presence of many CGP3 copies in a cell often was accompanied by an efflux of chromosomal DNA, indicating the lysis of the corresponding cell. However, evidence for the formation of functional infective CGP3 phage particles could not be obtained.
Effects of cycle strategy and fibre composition on muscle glycogen depletion pattern and subsequent running economy
Authors: Suriano R , Edge J , Bishop D
Published: May 2008

Purpose

In this study, the effects of variable and constant-intensity cycling on muscle glycogen depletion patterns and subsequent running economy was examined. 60 minutes of cycling at a constant power (CON) or variable intensity (VAR) followed by a treadmill run to determine running economy was completed by nine male triathletes (Vo2max = 67.7 (4.9 ml) kg−min−1). During CON, there was greater glycogen depletion in the type I fibres compared with type II (0.08 (0.04) vs 0.02 (0.01) optical density (OD) units; p<0.05), while during VAR, there was greater glycogen depletion in the type II fibres compared with type I (0.06 (0.03) vs 0.03 (0.02) OD; p<0.05). The variation in muscle glycogen depletion patterns was not associated with the detriment in running economy, which was not significantly different between conditions (52.1 vs 52.8 ml kg−1min−1). There was a strong correlation between total muscle glycogen depletion and the change in running Vo2(r = 0.73, p<0.05) when the data from both trials were combined. There was also a negative correlation between type I fibre percentage and glycogen depletion within type II fibres during CON (r = −0.85, p<0.05). The results demonstrate that the decrease in running economy, subsequent to 60 minutes of cycling, is not affected by the cycling strategy employed. While different glycogen depletion patterns in the type I and II fibres were observed between conditions, total glycogen depletion may be more important to subsequent running economy. The percentage of type I fibres was associated with the glycogen depletion pattern during constant load, but not variable-intensity exercise.
Independent and inverse association of healthcare utilisation with physical activity in older adults with multiple chronic conditions
Authors: Liu-Ambrose T Y L , Ashe M C , Marra C ,   the Physical Activity and Chronic Conditions Research Team
Published: May 2008

Objective

In this study, whether physical activity is independently associated with direct healthcare costs in community-dwelling older adults with multiple chronic conditions was examined.

Design

Cross-sectional analysis

Setting

Research laboratory

Participants

299 community-dwelling men and women volunteers aged 65 years and older with chronic conditions.

Intervention

None.

Main outcome measures

Primary dependent variable was direct healthcare costs incurred in the previous 3 months. Participants completed the Health Resource Utilisation (HRU) questionnaire. To estimate HRU, direct costs in the previous 3 months were calculated using the three-party payer perspective of the British Columbia Ministry of Health, deemed representative of the Canadian healthcare system costs. For medications, the Retail Pharmacy Dispensed prescription cost tables were used. Primary independent variables were (1) self-report current level of physical activity as assessed by the Physical Activity Scale for Individuals with Physical Disabilities (PASIPD) and (2) general balance and mobility as assessed by the National Institute on Aging Balance Scale.

Results

The mean number of chronic conditions per participant was six. Current level of physical activity was independently and inversely associated with HRU. Age, sex, number of chronic conditions, global cognitive function, body mass index, and general balance and mobility together accounted for 24.3% of the total variance. Adding the PASIPD score resulted in an R2 change of 3.3% and significantly improved the model. The total variance accounted by the final model was 27.6%.

Conclusions

Physical activity promotion may reduce healthcare costs in older adults with chronic conditions.
Seston Dynamics in Southern Appalachian Streams: Effects of Clear-cutting
Authors: Gurtz Martin E. , Webster Jackson R. , Wallace J. Bruce
Published: May 2008

Suspended particulate matter (seston) was studied from July 1977 to July 1978 in two second-order streams in the southern Appalachian Mountains. In the first stream, which drains an undisturbed hardwood forest watershed, seston concentrations fluctuated with season (lowest during winter high flows) and with storm flows. Most organic and inorganic particles were smaller than 105 μm diameter. The second stream drains a watershed (formerly a hardwood forest) that was clear-cut in early 1977. Increased levels of both organic and inorganic seston were found in the latter stream, especially beginning 1 yr after clear-cutting (2 yr after construction of logging roads). Particles larger than 234 μm in diameter accounted for most of the increases in inorganic seston. These increases were probably due to sediments deposited in the stream bed during road building and transported downstream during periods of peak flow. Increased levels of organic seston were probably related to breakdown of debris that entered the stream during logging and reduced retention by leaf packs. We hypothesize that eventual recovery of the stream will be limited by the rate of recovery of the surrounding terrestrial ecosystem.Key words: seston, sediment, detritus, stream, clear-cut, roads
Effects of Tubificid Worms on Denitrification and Nitrification in Stream Sediment
Authors: Chatarpaul Lakeram , Robinson John B. , Kaushik Narinder K.
Published: May 2008

Labeled nitrate-N in the form of K15NO3 was used to determine the effects of the tubificid oligochaetes, Tubifex tubifex and Limnodrilus hoffmeisteri, on the N transformation processes in stream sediment contained in laboratory columns. Denitrification and nitrification occurred simultaneously and were enhanced significantly in the presence of the worms. The denitrification rate over 48 d at 15 °C in the sediment that contained the worms was 90 mg N/m2∙d−1; the simultaneous rate of nitrification was 69 mg N/m2∙d−1. The corresponding rates for denitrification and nitrification in sediment without worms were 50 mg N/m2∙d−1 and 29 mg N/m2∙d−1. The rate of CO2 evolution from sediment containing worms and overlain with nitrate-N solution was about 21% greater than that of sediment with worms overlain with distilled water. It was concluded from experiments using chloride as tracer that denitrification could be enhanced by the worms at least in part as a result of accelerated movement of nitrate-N into the sediment. However, when a column of glass beads was used as substrate for worms, and with no organic matter present, the concentration of nitrate in an overlying solution declined at an appreciable rate. This suggested that denitrification occurred in or on the worms, a possibility supported by the observation that denitrifying bacteria could be isolated from both the exterior and the gut contents of the worms.Key words: tubificid worms, stream nutrient cycling, denitrification, nitrogen cycling
Distribution and Biological Availability of Reactive High Molecular Weight Phosphorus in Natural Waters in New Zealand
Authors: White E. , Payne G.
Published: May 2008

Eutrophic lakes and many streams on the central volcanic plateau of the North Island, New Zealand, contain dissolved chemically reactive phosphorus which is not orthophosphate. Sephadex gel (G25-150) chromatograms reveal that one reactive component is of high molecular weight (MW > 5000) while a second component elutes in the same way as phosphate-phosphorus (PO4-P). The reactive high molecular weight phosphorus (RHMW-P) in streams generally forms only a small proportion of the dissolved reactive phosphorus (DRP). In some eutrophic lakes the proportion of RHMW-P in the DRP is high (70–80%). Each lake may have a characteristic distribution of the two forms of reactive phosphorus. In summer where DRP concentrations are low (<2 mg∙m−3) in lake surface waters, PO4-P seems to dominate over RHMW-P which is consistent with long 32PO4 turnover times which are found in many of the central volcanic plateau lakes. Algal growth responses to phosphorus uptake were similar for PO4-P and RHMW-P, but not all of the RHMW-P was taken up by Chlorella in bioassays. The proportion of the RHMW-P taken up by Chlorella was different for each lake examined, posing problems in relating DRP concentrations to algal growth responses in lakes.Key words: reactive phosphorus, phosphate-phosphorus, algae, Chlorella, growth, bioassay, freshwater analysis, molybdenum blue method, Sephadex gel chromatography
Estimating Parameters in a Flexible Growth Equation, the Richards Fonction
Authors: Ebert Thomas A.
Published: May 2008

Two methods are presented for estimating parameters in the Richards function, a generalized growth equation. Both methods use typical mark–recapture data: initial and final size separated by a time interval. Three examples are presented. Data on the sea urchin, Diadema setosum, is best fit with Method I and tree seedling (Acer pseudoplatanus) data by Method II. Cisco (Coregonus artedii) growth is described about equally well by either method. The two methods could be applied to population growth in numbers as well as individual growth in size.Key words: Richards function, Brody–Bertalanffy, logistic, growth
Carbon-13/Carbon-12 Variation in Subalpine Lake Aquatic Insects: Food Source Implications
Authors: Rau Greg H.
Published: May 2008

Relative 13C concentrations were found to be significantly different among the three primary organic carbon sources for aquatic insect production within Findley Lake, Washington, USA. These three carbon sources were conifer tree detritus (mean δ18C = −27.3 per mil), periphyton (−34.6 per mil), and plankton (−45.9 per mil). Correspondingly, the δ18C of the adults of assumed autochthonous carbon feeders, Paraleptophlebia sp. (Ephemeroptera: Leptophlebiidae) and Chaoborus trivittatus (Diptera: Chaoboridae), well approximated the δ13C of periphyton and plankton, respectively. The remainder of the adult insect emergence, mostly Limnelphilidae and Chironomidae, exhibited δ13C values intermediate between the terrestrial and periphyton carbon. Approximately 38% of the 51 kg C of insect biomass annually emerging from this lake was conservatively estimated to originate from terrestrial plant sources.Key words: carbon-13, carbon pathways, lake, aquatic insects, feeding ecology, insect emergence, terrestrial detritus
Behavioral Stock-Isolating Mechanisms in Great Lakes Fishes with Special Reference to Homing and Site Imprinting
Authors: Horrall Ross M.
Published: May 2008

A moderately high degree of reproductive isolation is necessary for the formation and maintenance of discrete stocks of fish. This reproductive isolation can be developed through spawning site imprinting and homing—behavioral mechanisms that are apparently very common in fish. During some part of their early life history, the fish become imprinted to, or conditioned to, environmental characteristics of the spawning site and/or to the pheromonal characteristics of their stock. At sexual maturity, they show an orientation-homing behavior back to the natal area where spawning then occurs reinitiating the cycle. Over time, stock-specific adaptations are made to the local environment which can involve changes in the morphological, physiological, or behavioral characteristics of the fish. Research on salmonids has provided the best evidence for site imprinting and natal homing in fish. Tagging and transplantation experiments with these species have been especially important sources of information. In coho salmon (Oncorhynchus kisutch), olfactory homing and olfactory site imprinting have been demonstrated by artificial imprinting techniques; it was found that the critical period for imprinting occurred during smoltification at an age of 15 or 16 mo. Most species do not undergo smolting, and imprinting occurs at a very early stage in the life history. It is hypothesized that the information which is imprinted about the natal site may be obtained from one or more of the following: odors in the water flowing over the site; odors originating from the site itself; and stock-specific pheromones emitted directly from the fish or from their waste products. Differences in characteristics of homing and imprinting in relation to the formation and maintenance of stocks are discussed for several Great Lake species including coho salmon, pink salmon (O. gorbuscha), lake trout (Salvelinus namaycush), white bass (Morone chrysops), and walleye (Stizostedion vitreum vitreum). Inferences are made about how these characteristics relate to the rehabilitation of fish stocks in the Great Lakes and their tributaries.Key words: stock-isolating mechanisms, Great Lakes fish, homing, site imprinting
The Stock Concept and the Uncoupling of Organismal and Molecular Evolution
Authors: Clayton James W.
Published: May 2008

Evidence in support of the view that molecular evolution proceeds at a steady rate is presented in a brief review. This view of the steady rate of evolution of structural proteins, known as the molecular clock hypothesis, is shown to apply to the kinds of proteins that are commonly examined for variation by means of electrophoretic and immunological techniques in investigations of the stock structure of populations. The review is extended, with examples from the ichthyological literature, to show that the pace of organismal evolution is quite erratic in comparison to the pace of molecular evolution. A resolution of the apparent paradox regarding the uncoupling of the course of molecular and organismal evolution is offered based on the published suggestion of Allan C. Wilson and colleagues that the molecular divergence of any pair of populations should be seen as representing a time scale for the divergence. On this basis, disparities between divergences estimated from molecular and organismal data may be interpreted as reflections of the erratic pace of organismal evolution. Finally, it is suggested that the biological significance of distinctions between populations is to be seen in the summation of the organismal and molecular data.Key words: stock concept, organismal, molecular, evolution
The Stock Concept from the Viewpoint of Population Genetics
Authors: Altukhov Yu. P.
Published: May 2008

Results are presented of a comparative study of the spatial and temporal structure of fish species from the standpoint of biochemical population genetics. Local fish stocks within historically established natural boundaries are considered as genetically stable population systems, in contrast to the elementary populations, which are variable structural components of such systems. The general principle in maintaining a rational fish industry is formulated on the basis of an approach to the population system as a whole, to distribute the appropriate efforts among all components of its structure.Key words: biochemical population genetics, stock concept of fish, optimal fishing industry
Stock Characteristics and Catches of Atlantic Salmon (Salmo salar) in Quebec, and Newfoundland and Labrador in Relation to Environmental Variables
Authors: Power G.
Published: May 2008

More than 500 stocks of anadromous Atlantic salmon (Salmo salar) in a natural vigorous state are estimated to exist in Newfoundland and the Quebec–Labrador peninsula. They represent the end result of 6000–13 000 years of natural selection for local conditions and have been subject to relatively little manipulation. Stock characteristics correlating with environmental variables include an inverse relation between smolt age and mean temperature, and smolt age and growing season, and a positive relation between the length of sea life and river discharge. Variations in precipitation and temperature across the area result in different patterns of river discharge. Winter discharge is critically low in the north and salmon are restricted to larger rivers; low summer discharge on the east coast of Newfoundland and in southern Quebec may limit parr territory and hamper adult upstream migration. Because upstream migrations are delayed in years of low rainfall, causing salmon to remain longer in the area of commercial fisheries, salmon catches are generally higher in years of low rain than in wet years. The negative correlation occurs again in the catches of salmon 1, 2, and 7 years after years of low rainfall, but the reasons for this are obscure. Sea and river temperatures confine migration to a very short interval in Ungava and affect life cycles and maturation patterns. Most males spend over 12 mo in freshwater before spawning. Constraints are relaxed further south until high summer temperatures cause selection for early and late running stocks. There is a need for more systematic compilation of salmon stock data particularly over long enough periods to evaluate the effects of climatic variables and management strategies.Key words: Atlantic salmon, stock characteristics, precipitation and catches, temperature, migration
Management Implications for Different Genetic Stocks of Largemouth Bass (Micropterus salmoides) in the United States
Authors: Philipp David P. , Childers William F. , Whitt Gregory S.
Published: May 2008

Genetic differences exist among 90 largemouth bass (Micropterus salmoides) populations from different geographic regions of the United States. Genetic variation at 28 loci was determined through the use of vertical starch gel electrophoretic analyses. Allelic polymorphism was observed at 16 of these loci. Marked differences in allele frequencies at six of these loci exist among the populations. Distinct north–south clinal distributions of the alleles at the MDH-B, SOD-A, IDH-B, and AAT-B loci suggest a possible involvement of the associated enzymes in the thermal tolerance/preference limits for this species.We conclude that one or more of these enzymes may be directly involved in temperature tolerance/preference or indirectly associated with temperature-related effects. In either instance, selection (if occurring) may be acting upon the enzyme locus or genes closely linked to it. Through a combination of ecological and genetic principles, it is becoming increasingly feasible to select or construct specific populations of marine or freshwater fish optimally suited for specific environments. Fisheries management programs would benefit from the application of these principles. Multidisciplinary approaches of this nature are essential to maximize the successful conservation and management of our natural resources.Key words: largemouth bass, allele, loci, polymorphism, selection, population
Survey of the Genetic Variation Among Eastern Lake Superior Lake Trout (Salvelinus namaycush)
Authors: Dehring Terrence R. , Brown Anne F. , Daugherty Charles H. , Phelps Stevan R.
Published: May 2008

Patterns of genetic variation among lake trout (Salvelinus namaycush) of eastern Lake Superior were examined using starch gel electrophoresis. We used 484 individuals sampled from three areas, representing three morphological types (leans, humpers, and siscowets). Of 50 loci examined, 44 were monomorphic in all groups sampled. Genetic variation occurs at six loci AAT-1,2, MDH-3,4, ME-1, and SOD-1. The average heterozygosity found (H = 0.015) is low relative to other salmonid species. A significant amount of heterogeneity exists among the 10 lake trout samples. These differences are due to variation within as well as between morphological types. The significance and management implications of these data are discussed.Key words: genetic variation, lake trout, Salvelinus namaycush, Lake Superior
Life History, Morphology, and Electrophoretic Characteristics of Five Allopatric Stocks of Lake Whitefish (Coregonus clupeaformis) in the Great Lakes Region
Authors: Ihssen P. E. , Evans D. O. , Christie W. J. , Reckahn J. A. , DesJardine R. L.
Published: May 2008

Ecological, morphological, and electrophoretic variation among five allopatric Ontario lake whitefish (Coregonus clupeaformis) stocks was studied. The stocks differ in terms of diet, growth rate, movement patterns, fecundity, and egg and larval size. Morphologically, the five stocks were also different for characters such as number of gill rakers, number of pyloric ceca, and in size, adjusted for fork length, of the tail, dorsal fin, and the eye. Discriminant functions, derived from body measurements and meristic counts, classified specimens accurately into their lakes of origin. Highly significant allele frequency differences were found at 6 of the 32 electrophoretic loci examined. Standard genetic distances, derived from electrophoretic allele frequency differences, corresponded roughly to the order in which these stocks became isolated following retreat of the last continental glaciation. The genetic distance of the Opeongo stock from the other stocks is about one order of magnitude larger than the genetic distances among the other stocks. The Opeongo stock is also somewhat unusual ecologically, having different egg size and fecundity characteristics compared with the other stocks and being a member of a sympatric dwarf/normal pair. Dendrograms, derived from the Mahanalobis distances for the meristic variation and the Nei genetic distances for the electrophoretic variation, showed similar branching patterns, but the branching patterns for the morphometric versus the biochemical variation were different. A significant part of the morphometric variation among the stocks was related to differences in growth rates of the stocks, most body measurements being negatively correlated with growth rate. The Mahanalobis distances for the meristic variation (including pyloric ceca counts) were correlated with the standard genetic distances from the electrophoretic data. The ecological, morphological, and biochemical variation among the stocks, in relation to local adaptation, is discussed.Key words: lake whitefish, stock concept, genotype, phenotype, ecology, morphology, meristics, multivariate analysis, electrophoresis, growth, diet, fecundity
Allelic Variability in Species and Stocks of Lake Superior Ciscoes (Coregoninae)
Authors: Todd Thomas N.
Published: May 2008

Starch gel electrophoresis was used as a means of recognizing species and stocks in Lake Superior Coregonus. Allelic variability at isocitrate dehydrogenase and glycerol-3-phosphate dehydrogenase loci was recorded for samples of lake herring (Coregonus artedii), bloater (C. hoyi), kiyi (C. kiyi), and shortjaw cisco (C. zenithicus) from five Lake Superior localities. The observed frequencies of genotypes within each subsample did not differ significantly from those expected on the basis of random mating, and suggested that each subsample represented either a random sample from a larger randomly mating population or an independent and isolated subpopulation within which mating was random. Significant contingency χ2 values for comparisons between both localities and species suggested that more than one randomly mating population occurred among the Lake Superior ciscoes, but did not reveal how many such populations there were. In contrast to the genetic results of this study, morphology seems to be a better descriptor of cisco stocks, and identification of cisco stocks and species will still have to be based on morphological criteria until more data are forthcoming. Where several species are sympatric, management should strive to preserve the least abundant. Failure to do so could result in the extinction or depletion of the rarer forms.Key words: Coregonus, electrophoresis, genetic heterogeneity, speciation, Great Lakes