bluuebunny/crossref_metadata_2025 huggingface dataset:
Anti-
Pseudomonas
Activity of Frog Skin Antimicrobial Peptides in a
Caenorhabditis elegans
Infection Model: a Plausible Mode of Action
In Vitro
and
In Vivo
Authors: Uccelletti Daniela , Zanni Elena , Marcellini Ludovica , Palleschi Claudio , Barra Donatella , Mangoni Maria Luisa
Published: July 2010

The emergence of multidrug-resistant (MDR) microorganisms makes it increasingly difficult to treat infections. These infections include those associated with
Pseudomonas aeruginosa
, which are hard to eradicate, especially in patients with a compromised immune system. Naturally occurring membrane-active cationic antimicrobial peptides (CAMPs) serve as attractive candidates for the development of new therapeutic agents. Amphibian skin is one of the richest sources for such peptides, but only a few studies on their
in vivo
activities and modes of action have been reported. We investigated (i) the activity and mechanism underlying the killing of short CAMPs from frog skin (e.g., temporins and esculentin fragments) on an MDR clinical isolate of
P. aeruginosa
and (ii) their
in vivo
antibacterial activities and modes of action, using the minihost model of
Caenorhabditis elegans
. Our data revealed that
in vivo
, both temporin-1Tb and esculentin(1-18) were highly active in promoting the survival of
Pseudomonas
-infected nematodes, although temporin-1Tb did not show significant activity
in vitro
under the experimental conditions used. Importantly, esculentin(1-18) permeated the membrane of
Pseudomonas
cells within the infected nematode. To the best of our knowledge, this is the first report showing the ability of a CAMP to permeate the microbial membrane within a living organism. Besides shedding light on a plausible mode of action of frog skin CAMPs
in vivo
, our data suggest that temporins and esculentins would be attractive molecules as templates for the development of new therapeutics against life-threatening infections.
Inhibition of Antibiotic-Resistant
Staphylococcus aureus
by the Broad-Spectrum Dihydrofolate Reductase Inhibitor RAB1
Authors: Bourne C. R. , Barrow E. W. , Bunce R. A. , Bourne P. C. , Berlin K. D. , Barrow W. W.
Published: July 2010

The bacterial burden on human health is quickly outweighing available therapeutics. Our long-term goal is the development of antimicrobials with the potential for broad-spectrum activity. We previously reported phthalazine-based inhibitors of dihydrofolate reductase (DHFR) with potent activity against
Bacillus anthracis
, a major component of Project BioShield. The most active molecule, named RAB1, performs well
in vitro
and, in a cocrystal structure, was found deep within the active site of
B. anthracis
DHFR. We have now examined the activity of RAB1 against a panel of bacteria relevant to human health and found broad-spectrum applicability, particularly with regard to Gram-positive organisms. RAB1 was most effective against
Staphylococcus aureus
, including methicillin- and vancomycin-resistant (MRSA/VRSA) strains. We have determined the cocrystal structure of the wild-type and trimethoprim-resistant (Phe 98 Tyr) DHFR enzyme from
S. aureus
with RAB1, and we found that rotational freedom of the acryloyl linker region allows the phthalazine moiety to occupy two conformations. This freedom in placement also allows either enantiomer of RAB1 to bind to
S. aureus
, in contrast to the specificity of
B. anthracis
for the
S
-enantiomer. Additionally, one of the conformations of RAB1 defines a unique surface cavity that increases the strength of interaction with
S. aureus
. These observations provide insights into the binding capacity of
S. aureus
DHFR and highlight atypical features critical for future exploitation in drug development.
Liposomal Amphotericin B and Echinocandins as Monotherapy or Sequential or Concomitant Therapy in Murine Disseminated and Pulmonary
Aspergillus fumigatus
Infections
Authors: Olson Jon A. , George Ancy , Constable David , Smith Peter , Proffitt Richard T. , Adler-Moore Jill P.
Published: July 2010

Monotherapy and combination therapy were compared using optimal doses of liposomal amphotericin B, micafungin, or caspofungin in
Aspergillus fumigatus
pulmonary and disseminated infections. Mice were challenged intravenously (2.8 × 10
4
to 5.7 × 10
4
conidia) or intranasally (5.8 × 10
7
conidia) with
A. fumigatus
. Drugs (5, 10, or 15 mg/kg of body weight) were given for 3 or 6 days as single, concomitant, or sequential therapy (i.e., days 1 to 3 and then days 4 to 6). Mice were monitored for survival, and tissues were assayed for fungal burden and drug concentrations. Treatments starting 24 h postchallenge significantly prolonged survival in disseminated aspergillosis (
P
< 0.002), but only liposomal amphotericin B treatments or treatments beginning with liposomal amphotericin B increased survival to 100% in the pulmonary aspergillosis model. Fungi in kidneys and spleens (disseminated) and lungs (pulmonary) were significantly decreased (
P
≤ 0.04) by liposomal amphotericin B, liposomal amphotericin B plus echinocandin, or liposomal amphotericin B prior to echinocandin. In the disseminated infection, liposomal amphotericin B and micafungin (10 or 15 mg/kg) had similar kidney drug levels, while in the spleen, 5 and 15 mg/kg liposomal amphotericin B gave higher drug levels than micafungin (
P
< 0.02). In the pulmonary infection, drug levels in lungs and spleen with 5-mg/kg dosing were significantly higher with liposomal amphotericin B than with caspofungin (
P
≤ 0.002). In summary, treatment of
A. fumigatus
infections with liposomal amphotericin B plus echinocandin or liposomal amphotericin B prior to echinocandin was as effective as liposomal amphotericin B alone, and a greater decrease in the fungal burden with liposomal amphotericin B supports using liposomal amphotericin B prior to echinocandin.
The BceABRS Four-Component System Regulates the Bacitracin-Induced Cell Envelope Stress Response in
Streptococcus mutans
Authors: Ouyang Jing , Tian Xiao-Lin , Versey Jennifer , Wishart Alexander , Li Yung-Hua
Published: July 2010

Streptococcus mutans
is known to be resistant to bacitracin, a cyclic polypeptide antibiotic produced by certain species of the genus
Bacillus
. This property is often exploited in the isolation of
S. mutans
strains from highly heterogeneous oral microflora. A genetic locus consisting of a four-gene operon,
bceABRS
(formerly
mbrABCD
), the component genes of which are homologous to
Bacillus subtilis bceRS-bceAB
(encoding a two-component system and an ABC transporter), is required for bacitracin resistance in
S. mutans
. Here we describe the identification of a DNA binding site for the BceR response regulator and its transcriptional control of the
bceABRS
operon in response to the presence of bacitracin. We provide evidence indicating that phosphorylated BceR binds directly to a conserved invert repeat located between bp −120 and −78 of the
bceABRS
promoter region and positively regulates expression of the
bceABRS
operon. We also demonstrate that sensing of bacitracin by the BceS histidine kinase requires the presence of an intact BceAB transporter, since deletion of either
bceA
or
bceB
abolishes BceRS-mediated bacitracin sensing. The results suggest that the BceAB transporter acts as a cosensor, together with the BceRS two-component system, for bacitracin perception in
S. mutans
. By searching the
S. mutans
genome databases, we have identified three additional genes that share the consensus BceR binding motif at their promoter regions. Our initial work has confirmed that expression of these genes is directly controlled by BceRS, indicating that the
bceABRS
operon, along with the three additional genes, forms the BceRS regulon in
S. mutans
. Taking these findings together, we conclude that BceABRS comprises a four-component system that plays an important role in stimulus sensing, signal transduction, the gene regulatory network, and substrate transport for the cell envelope stress response in
S. mutans
.
Medical and Legal Implications of Testing for Sexually Transmitted Infections in Children
Authors: Hammerschlag Margaret R. , Guillén Christina D.
Published: July 2010

Testing for sexually transmitted infections (STIs) in children presents a number of problems for the practitioner that are not usually faced when testing adults for the same infections. The identification of an STI in a child can have, in addition to medical implications, serious legal implications. The presence of an STI is often used to support the presence or allegations of sexual abuse, and conversely, the identification of an STI in a child will prompt an investigation of possible abuse. The purpose of this paper is to review the epidemiology of child sexual abuse, including the epidemiology of major STIs including
N
eisseria gonorrhoeae
,
C
hlamydia trachomatis
, syphilis, herpes simplex virus (HSV),
Trichomonas vaginalis
, and human papillomavirus, and the current recommendations for diagnostic testing in this population.
Validation of Laboratory-Developed Molecular Assays for Infectious Diseases
Authors: Burd Eileen M.
Published: July 2010

Molecular technology has changed the way that clinical laboratories diagnose and manage many infectious diseases. Excellent sensitivity, specificity, and speed have made molecular assays an attractive alternative to culture or enzyme immunoassay methods. Many molecular assays are commercially available and FDA approved. Others, especially those that test for less common analytes, are often laboratory developed. Laboratories also often modify FDA-approved assays to include different extraction systems or additional specimen types. The Clinical Laboratory Improvement Amendments (CLIA) federal regulatory standards require clinical laboratories to establish and document their own performance specifications for laboratory-developed tests to ensure accurate and precise results prior to implementation of the test. The performance characteristics that must be established include accuracy, precision, reportable range, reference interval, analytical sensitivity, and analytical specificity. Clinical laboratories are challenged to understand the requirements and determine the types of experiments and analyses necessary to meet the requirements. A variety of protocols and guidelines are available in various texts and documents. Many of the guidelines are general and more appropriate for assays in chemistry sections of the laboratory but are applied in principle to molecular assays. This review presents information that laboratories may consider in their efforts to meet regulatory requirements.
Causes of Outbreaks Associated with Drinking Water in the United States from 1971 to 2006
Authors: Craun Gunther F. , Brunkard Joan M. , Yoder Jonathan S. , Roberts Virginia A. , Carpenter Joe , Wade Tim , Calderon Rebecca L. , Roberts Jacquelin M. , Beach Michael J. , Roy Sharon L.
Published: July 2010

Since 1971, the CDC, EPA, and Council of State and Territorial Epidemiologists (CSTE) have maintained the collaborative national Waterborne Disease and Outbreak Surveillance System (WBDOSS) to document waterborne disease outbreaks (WBDOs) reported by local, state, and territorial health departments. WBDOs were recently reclassified to better characterize water system deficiencies and risk factors; data were analyzed for trends in outbreak occurrence, etiologies, and deficiencies during 1971 to 2006. A total of 833 WBDOs, 577,991 cases of illness, and 106 deaths were reported during 1971 to 2006. Trends of public health significance include (i) a decrease in the number of reported outbreaks over time and in the annual proportion of outbreaks reported in public water systems, (ii) an increase in the annual proportion of outbreaks reported in individual water systems and in the proportion of outbreaks associated with premise plumbing deficiencies in public water systems, (iii) no change in the annual proportion of outbreaks associated with distribution system deficiencies or the use of untreated and improperly treated groundwater in public water systems, and (iv) the increasing importance of
Legionella
since its inclusion in WBDOSS in 2001. Data from WBDOSS have helped inform public health and regulatory responses. Additional resources for waterborne disease surveillance and outbreak detection are essential to improve our ability to monitor, detect, and prevent waterborne disease in the United States.
Mechanisms of Action and Clinical Application of Macrolides as Immunomodulatory Medications
Authors: Kanoh Soichiro , Rubin Bruce K.
Published: July 2010

Macrolides have diverse biological activities and an ability to modulate inflammation and immunity in eukaryotes without affecting homeostatic immunity. These properties have led to their long-term use in treating neutrophil-dominated inflammation in diffuse panbronchiolitis, bronchiectasis, rhinosinusitis, and cystic fibrosis. These immunomodulatory activities appear to be polymodal, but evidence suggests that many of these effects are due to inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and nuclear factor kappa B (NF-κB) activation. Macrolides accumulate within cells, suggesting that they may associate with receptors or carriers responsible for the regulation of cell cycle and immunity. A concern is that long-term use of macrolides increases the emergence of antimicrobial resistance. Nonantimicrobial macrolides are now in development as potential immunomodulatory therapies.
The Changing Epidemiology of
Clostridium difficile
Infections
Authors: Freeman J. , Bauer M. P. , Baines S. D. , Corver J. , Fawley W. N. , Goorhuis B. , Kuijper E. J. , Wilcox M. H.
Published: July 2010

The epidemiology of
Clostridium difficile
infection (CDI) has changed dramatically during this millennium. Infection rates have increased markedly in most countries with detailed surveillance data. There have been clear changes in the clinical presentation, response to treatment, and outcome of CDI. These changes have been driven to a major degree by the emergence and epidemic spread of a novel strain, known as PCR ribotype 027 (sometimes referred to as BI/NAP1/027). We review the evidence for the changing epidemiology, clinical virulence and outcome of treatment of CDI, and the similarities and differences between data from various countries and continents. Community-acquired CDI has also emerged, although the evidence for this as a distinct new entity is less clear. There are new data on the etiology of and potential risk factors for CDI; controversial issues include specific antimicrobial agents, gastric acid suppressants, potential animal and food sources of
C. difficile
, and the effect of the use of alcohol-based hand hygiene agents.
Acanthamoeba culbertsoni
Elicits Soluble Factors That Exert Anti-Microglial Cell Activity
Authors: Harrison Jenica L. , Ferreira Gabriela A. , Raborn Erinn S. , Lafrenaye Audrey D. , Marciano-Cabral Francine , Cabral Guy A.
Published: July 2010

Acanthamoeba culbertsoni
is an opportunistic pathogen that causes granulomatous amoebic encephalitis (GAE), a chronic and often fatal disease of the central nervous system (CNS). A hallmark of GAE is the formation of granulomas around the amoebae. These cellular aggregates consist of microglia, macrophages, lymphocytes, and neutrophils, which produce a myriad of proinflammatory soluble factors. In the present study, it is demonstrated that
A. culbertsoni
secretes serine peptidases that degrade chemokines and cytokines produced by a mouse microglial cell line (BV-2 cells). Furthermore, soluble factors present in cocultures of
A. culbertsoni
and BV-2 cells, as well as in cocultures of
A. culbertsoni
and primary neonatal rat cerebral cortex microglia, induced apoptosis of these macrophage-like cells. Collectively, the results indicate that
A. culbertsoni
can apply a multiplicity of cell contact-independent modes to target macrophage-like cells that exert antiamoeba activities in the CNS.
Accumulation ofPlasmodium berghei-Infected Red Blood Cells in the Brain Is Crucial for the Development of Cerebral Malaria in Mice
Authors: Baptista Fernanda G. , Pamplona Ana , Pena Ana C. , Mota Maria M. , Pied Sylviane , Vigário Ana M.
Published: July 2010

Cerebral malaria is the most severe complication of human infection withPlasmodium falciparum. It was shown thatPlasmodium bergheiANKA-induced cerebral malaria was prevented in 100% of mice depleted of CD8+T cells 1 day prior to the development of neurological signs. However, the importance of parasites in the brains of these mice was never clearly investigated. Moreover, the relevance of this model to human cerebral malaria has been questioned many times, especially concerning the relative importance of leukocytes versus parasitized erythrocytes sequestered in the brain. Here, we show that mice protected from cerebral malaria by CD8+T-cell depletion have significantly fewer parasites in the brain. Treatment of infected mice with an antimalarial drug 15 to 20 h prior to the estimated time of death also protected mice from cerebral malaria without altering the number of CD8+T cells in the brain. These mice subsequently developed cerebral malaria with parasitized red blood cells in the brain. Our results clearly demonstrated that sequestration of CD8+T cells in the brain is not sufficient for the development of cerebral malaria in C57BL/6 mice but that the concomitant presence of parasitized red blood cells is crucial for the onset of pathology. Importantly, these results also demonstrated that the experimental cerebral malaria model shares many features with human pathology and might be a relevant model to study its pathogenesis.
Conidia but Not Yeast Cells of the Fungal PathogenHistoplasma capsulatumTrigger a Type I Interferon Innate Immune Response in Murine Macrophages
Authors: Inglis Diane O. , Berkes Charlotte A. , Hocking Murray Davina R. , Sil Anita
Published: July 2010

Histoplasma capsulatumis the most common cause of fungal respiratory infections and can lead to progressive disseminated infections, particularly in immunocompromised patients. Infection occurs upon inhalation of the aerosolized spores, known as conidia. Once inside the host, conidia are phagocytosed by alveolar macrophages. The conidia subsequently germinate and produce a budding yeast-like form that colonizes host macrophages and can disseminate throughout host organs and tissues. Even though conidia are the predominant infectious particle forH. capsulatumand are the first cell type encountered by the host during infection, very little is known at a molecular level about conidia or about their interaction with cells of the host immune system. We examined the interaction between conidia and host cells in a murine bone-marrow-derived macrophage model of infection. We used whole-genome expression profiling and quantitative reverse transcription-PCR (qRT-PCR) to monitor the macrophage signaling pathways that are modulated during infection with conidia. Our analysis revealed that type I interferon (IFN)-responsive genes and the beta type I IFN (IFN-β) were induced in macrophages during infection withH. capsulatumconidia but notH. capsulatumyeast cells. Further analysis revealed that the type I IFN signature induced in macrophages in response to conidia is independent of Toll-like receptor (TLR) signaling and the cytosolic RNA sensor MAVS but is dependent on the transcription factor interferon regulatory factor 3 (IRF3). Interestingly,H. capsulatumgrowth was restricted in mice lacking the type I IFN receptor, indicating that an intact host type I IFN response is required for full virulence ofH. capsulatumin mice.
Delineation and Analysis of Chromosomal Regions Specifying
Yersinia pestis
Authors: Derbise Anne , Chenal-Francisque Viviane , Huon Christèle , Fayolle Corinne , Demeure Christian E. , Chane-Woon-Ming Béatrice , Médigue Claudine , Hinnebusch B. Joseph , Carniel Elisabeth
Published: July 2010

Yersinia pestis
, the causative agent of plague, has recently diverged from the less virulent enteropathogen
Yersinia pseudotuberculosis
. Its emergence has been characterized by massive genetic loss and inactivation and limited gene acquisition. The acquired genes include two plasmids, a filamentous phage, and a few chromosomal loci. The aim of this study was to characterize the chromosomal regions acquired by
Y. pestis
. Following
in silico
comparative analysis and PCR screening of 98 strains of
Y. pseudotuberculosis
and
Y. pestis
, we found that eight chromosomal loci (six regions [R1
pe
to R6
pe
] and two coding sequences [CDS1
pe
and CDS2
pe
]) specified
Y. pestis
. Signatures of integration by site specific or homologous recombination were identified for most of them. These acquisitions and the loss of ancestral DNA sequences were concentrated in a chromosomal region opposite to the origin of replication. The specific regions were acquired very early during
Y. pestis
evolution and were retained during its microevolution, suggesting that they might bring some selective advantages. Only one region (R3
pe
), predicted to carry a lambdoid prophage, is most likely no longer functional because of mutations. With the exception of R1
pe
and R2
pe
, which have the potential to encode a restriction/modification and a sugar transport system, respectively, no functions could be predicted for the other
Y. pestis
-specific loci. To determine the role of the eight chromosomal loci in the physiology and pathogenicity of the plague bacillus, each of them was individually deleted from the bacterial chromosome. None of the deletants exhibited defects during growth
in vitro
. Using the
Xenopsylla cheopis
flea model, all deletants retained the capacity to produce a stable and persistent infection and to block fleas. Similarly, none of the deletants caused any acute flea toxicity. In the mouse model of infection, all deletants were fully virulent upon subcutaneous or aerosol infections. Therefore, our results suggest that acquisition of new chromosomal materials has not been of major importance in the dramatic change of life cycle that has accompanied the emergence of
Y. pestis
.
Comparative Proteomic Analysis of Extracellular Proteins of
Clostridium perfringens
Type A and Type C Strains
Authors: Sengupta Nabonita , Alam Syed Imteyaz , Kumar Bhoj , Kumar Ravi Bhushan , Gautam Vandana , Kumar Subodh , Singh Lokendra
Published: July 2010

Clostridium perfringens
is a medically important clostridial pathogen and an etiological agent causing several diseases in humans and animals.
C. perfringens
and its toxins have been listed as potential biological and toxin warfare (BTW) agents; thus, efforts to develop strategies for detection and protection are warranted. Forty-eight extracellular proteins of
C. perfringens
type A and type C strains have been identified here using a 2-dimensional gel electrophoresis-mass spectrometry (2-DE-MS) technique. The SagA protein, the DnaK-type molecular chaperone hsp70, endo-beta-
N
-acetylglucosaminidase, and hypothetical protein CPF_0656 were among the most abundant proteins secreted by
C. perfringens
ATCC 13124. The antigenic component of the exoproteome of this strain has also been identified. Most of the extracellular proteins were predicted to be involved in carbohydrate transport and metabolism (16%) or cell envelope biogenesis or to be outer surface protein constituents (13%). More than 50% of the proteins were predictably secreted by either classical or nonclassical pathways. LipoP and TMHMM indicated that nine proteins were extracytoplasmic but cell associated. Immunization with recombinant ornithine carbamoyltransferase (cOTC) clearly resulted in protection against a direct challenge with
C. perfringens
organisms. A significant rise in IgG titers in response to recombinant cOTC was observed in mice, and IgG2a titers predominated over IgG1 titers (IgG2a/IgG1 ratio, 2). The proliferation of spleen lymphocytes in cOTC-immunized animals suggested a cellular immune response. There were significant increases in the levels of gamma interferon (IFN-γ) and interleukin 2 (IL-2), suggesting a Th1 type immune response.
SalmonellaVaccine Vectors Displaying Delayed Antigen SynthesisInVivoTo Enhance Immunogenicity
Authors: Wang Shifeng , Li Yuhua , Scarpellini Giorgio , Kong Wei , Shi HuoYing , Baek Chang-Ho , Gunn Bronwyn , Wanda Soo-Young , Roland Kenneth L. , Zhang Xin , Senechal-Willis Patti , Curtiss Roy
Published: July 2010

We have developed a regulated delayed antigen synthesis (RDAS) system for use in recombinant attenuatedSalmonellavaccine (RASV) strains to enhance immune responses by reducing the adverse effects of high-level antigen synthesis. This system includes a chromosomal repressor gene,lacI, expressed from the arabinose-regulatedaraCPBADpromoter. LacI serves to regulate expression from a plasmid promoter, Ptrc, that directs antigen synthesis. In the presence of arabinose LacI is produced, which binds to Ptrc, blocking antigen synthesis.In vivo, an arabinose-poor environment, the concentration of LacI decreases with each cell division, allowing increased antigen synthesis. To optimize the system and for comparison, we altered thelacIribosome-binding site, start codon, and/or codon content to construct RDAS strains χ9095, χ9959, and χ9241, synthesizing from low to high levels of LacI, respectively, and non-RDAS strain χ9555 as a control. We evaluated this system with two test antigens, the green fluorescent protein for initialin vitroassessment and theStreptococcus pneumoniaePspA protein for validation of our system in mice. All RASV strains expressing PspA generated high antilipopolysaccharide antibody titers, indicating that expression oflacIdid not interfere with the capacity to induce an immune response. Strain χ9241 induced significantly higher anti-PspA IgG and IgA antibody titers than strain χ9555, which expressed PspA constitutively. Anti-PspA antibody titers were inversely correlated to the level of LacI synthesis. Strain χ9241 also induced significantly greater protective efficacy against challenge with virulentS. pneumoniae. These results suggest that regulated delayed antigen synthesis is useful for improving immunogenicity of RASV strains.
Development and Validation of an
In Vivo Candida albicans
Biofilm Denture Model
Authors: Nett Jeniel E. , Marchillo Karen , Spiegel Carol A. , Andes David R.
Published: July 2010

The most common form of oral candidiasis, denture-associated stomatitis, involves biofilm growth on an oral prosthetic surface. Cells in this unique environment are equipped to withstand host defenses and survive antifungal therapy. Studies of the biofilm process on dentures have primarily been limited to
in vitro
models. We developed a rodent acrylic denture model and characterized the
Candida albicans
and mixed oral bacterial flora biofilm formation, architecture, and drug resistance
in vivo
, using time course quantitative culture experiments, confocal microscopy, scanning electron microscopy, and antifungal susceptibility assays. We also examined the utility of the model for measurement of
C. albicans
gene expression and tested the impact of a specific gene product (Bcr1p) on biofilm formation. Finally, we assessed the mucosal host response to the denture biofilm and found the mucosal histopathology to be consistent with that of acute human denture stomatitis, demonstrating fungal invasion and neutrophil infiltration. This current oral denture model mimics human denture stomatitis and should be useful for testing the impact of gene disruption on biofilm formation, studying the impact of anti-infectives, examining the biology of mixed
Candida
-oral bacterial flora biofilm infections, and characterizing the host immunologic response to this disease process.
Wall-rock structure at the present contact surfaces between repeatedly deformed thrust sheets, Grenville Orogen of central Ontario, Canada
Authors: Schwerdtner Walfried M. , Lu Sheng J. , Yang Jack F.
Published: July 2010

In the Central Gneiss Belt of the Grenville Orogen (Ontario), ca. 1020 Ma, extensional shearing, disharmonic buckle folding, and seismic faulting at middle to upper crustal levels affected the geological structure of pre-1040 Ma, ductile-thrust sheets. Because much of the repeated in situ deformation was mechanically discontinuous, the present contacts between thrust sheets may not coincide at all localities with the original thrust surfaces. We focused special attention on the basal contact of the Parry Sound domain, whose synformal structure may have resulted from gravitational subsidence of its dense rocks immediately after ductile thrusting. East of Wahwashkesh Lake, a transverse gradient of total strain is absent on horizontal scales of 100–1000 m in lithologically uniform granite gneiss comprising the uppermost western footwall of the northern Parry Sound domain. This contrasts with the steep transverse-strain gradients documented by others, on the same scale, in the wall rocks of Phanerozoic ductile thrusts. We hypothesize that ductile or brittle extension faulting may have removed a 10–20 km long sole-thrust segment at the western flank of the northern Parry Sound domain, together with severely strained rocks of the original uppermost footwall, from the level of the current erosion surface. Within the Parry Sound domain, by contrast, most if not all of the original footwall of the 1160 Ma Mill Lake thrust seems to be preserved at the presently exposed contact surface between the allochthonous basal and interior Parry Sound assemblages.
Palaeocope ostracods from the Silurian Wenlock Series of Arctic Canada
Authors: Miller C. Giles , Williams Mark , Siveter David J.
Published: July 2010

Silurian Wenlock Series deposits of the Cape Phillips Formation on Baillie-Hamilton Island and Cornwallis Island, Arctic Canada, have yielded a silicified ostracod assemblage that spans the late Sheinwoodian and Homerian stages. Sixteen palaeocope ostracod species are recorded, including the new species Beyrichia ( Beyrichia ) marssae , Gabrielsella ? copelandi , and Platybolbina ( Abruptobolbina ) adraini . The ostracod faunas can be linked into local trilobite, microvertebrate, and graptolite zonal schemes, and a few of the ostracod species offer potential for local and perhaps wider biostratigraphical correlation. The ostracods are mostly known only from the Cape Phillips Formation, but also include two taxa found in the Wenlock Series of the Avalanche Lake area, Northwest Territories, Canada. Other ostracod species suggest links with Silurian successions in northern Canada and the Baltic. Low-diversity ostracod faunas characterize the level of a marked positive carbon isotope excursion and coeval mid-Homerian regression at the level of the regional Pristiograptus dubius – Gothograptus nassa graptolite Biozone. Comparison with the pattern of distribution of coeval ostracod faunas elsewhere in Canada suggests that diversity changes in the Cape Phillips Formation ostracod faunas are controlled by local palaeoenvironmental factors perhaps linked to global sea-level change.
Description of a new specimen of Ianthasaurus hardestiorum (Eupelycosauria: Edaphosauridae) and a re-evaluation of edaphosaurid phylogeny
Authors: Mazierski David M. , Reisz Robert R.
Published: July 2010

Ianthasaurus hardestiorum , a basal edaphosaurid from the Upper Pennsylvanian of Garnett, Kansas, has been described on the basis of two incomplete, juvenile specimens and a series of disarticulated vertebral elements. New skeletal material of this poorly known species includes previously unknown cranial elements, increasing our knowledge of the anatomy and variation in this taxon. The complete ossification of the neural arches and the overall larger size of the vertebrae relative to those previously described indicate that they were part of an adult individual, and marginal tooth morphology resembles more closely that seen in the genus Edaphosaurus . Phylogenetic analysis of edaphosaurid synapsids confirms the hypothesis that Ianthasaurus is a sister-taxon of all other members of the clade. However, the incomplete fossil record of other putative edaphosaurids, such as Lupeosaurus and Glaucosaurus , makes full resolution of their phylogenetic interrelationships difficult to assess.
Consistent patterns of maturity and density-dependent growth among populations of walleye (Sander vitreus): application of the growing degree-day metric
Authors: Venturelli Paul A. , Lester Nigel P. , Marshall Terry R. , Shuter Brian J.
Published: July 2010

Growing degree-days (GDD, °C·days) are an index of ambient thermal energy that relates directly to an ectotherm’s cumulative metabolism but is rarely used to describe growth and development in fish. We applied GDD to length and maturity data from 416 populations of walleye ( Sander vitreus ) from Ontario and Quebec, Canada (mean annual GDD = 1200 to 2300 °C·days). On average, males matured after they had experienced 6900 °C·days and reached 350 mm total length (L) (n = 77 populations), and females matured after 10 000 °C·days and at 450 mm L (n = 70). Across 143 populations, GDD accounted for up to 96% of the variation in the length of immature walleye but also revealed a twofold difference in growth rate that was indicative of variation in food availability. When applied to data from eight populations in which walleye abundances have changed dramatically over time, GDD revealed a 1.3-fold increase in immature growth rate when abundance was low compared with when it was high. Our results both demonstrate the explanatory power of GDD with respect to fish growth and maturity and inform the development of regional management strategies for walleye.
Abundance and distribution of Antarctic krill (Euphausia superba) nearshore of Cape Shirreff, Livingston Island, Antarctica, during six austral summers between 2000 and 2007
Authors: Warren Joseph D. , Demer David A.
Published: July 2010

Abundance and distribution of Antarctic krill ( Euphausia superba ) in the nearshore waters north of Livingston Island, Antarctica, were characterized from six small-boat surveys conducted in late January or early February from 2000 to 2007. The first three surveys (2000, 2002, 2004) were conducted using a 120 kHz split-beam echosounder to measure water column acoustic backscatter. The last three surveys (2005–2007) were conducted using 38 kHz and 200 kHz single-beam echosounders. A portion of the acoustic backscatter was attributed to Antarctic krill based on the results of net tows, underwater video observations, and a multiple-frequency acoustic classification algorithm. The annual mean krill biomass density in the survey area ranged from 11 to 84 g·m–2. Results are compared with the western Scotia Sea area of the US Antarctic Marine Living Resources (AMLR) program’s acoustic surveys of krill biomass density for the same years. Nearshore krill biomass densities were significantly larger (t test, p < 0.05), more stable, and the coefficients of variation were smaller than the much larger AMLR surveys. Increased competition between seals, penguins, and humans for the nearshore krill resource, especially during the austral summer months, could impact the recruitment success of these land-based krill predators. Implications of nearshore krill biomass on small-scale management units are discussed.
Contemporary and historical patterns of connectivity among populations of an inland river fish species inferred from genetics and otolith chemistry
Authors: Woods Ryan J. , Macdonald Jed I. , Crook David A. , Schmidt Daniel J. , Hughes Jane M.
Published: July 2010

Patterns of dispersal in riverine populations of Australian smelt ( Retropinna semoni ) were examined using otolith chemistry (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) and genetic markers (allozymes, mtDNA, microsatellite DNA). During a period of prolonged low flows, young-of-year smelt were collected from 13 streams within three catchments of the southern Murray–Darling Basin, Australia. Spatial differences in otolith core and edge chemical signatures and high levels of genetic assignment to sampling locations were observed, suggesting that most recruits were retained in natal areas after spawning. Following a subsequent period of hydrological connection, the same cohort was sampled as 1-year-olds. Maximum likelihood estimation using otolith core chemistry data from these fish suggested that retention in natal areas was highly variable between years and a similar, though less pronounced, pattern was evident in genetic assignments. Partitioning of genetic variation among catchments was not significant (FCT < 0.004) and probably reflects disequilibrium between migration and genetic drift due to an historical population expansion (~270 000 years ago). Taken together, otolith chemistry and genetic analyses suggest that contemporary dispersal of smelt within these catchments is relatively restricted and may be mediated by changes in hydrological connectivity.
Long-term functional group recovery of lotic macroinvertebrates from logging disturbance
Authors: Ely Damon T. , Wallace J. Bruce
Published: July 2010

Clear-cut logging rapidly affects stream macroinvertebrates through substantial alteration of terrestrial–aquatic resource linkages; however, lesser known are the long-term influences of forest succession on benthic macroinvertebrate assemblages, which play key roles in stream ecosystem function. We compared secondary production and standing crops of detritus in two mountain headwater streams within Coweeta Hydrologic Laboratory, North Carolina, USA, as part of a long-term, paired-watershed investigation of macroinvertebrate recovery from whole-catchment logging. Mean annual habitat-weighted abundance and biomass in the disturbed stream (catchment entirely logged 26 years prior) did not differ from that of the reference stream, and secondary production was only 0.8 g ash-free dry mass (AFDM)·m–2·year–1 greater in the disturbed stream (disturbed, 10.1; reference, 9.3). Taxonomic composition, shredder–scraper ratios, and North Carolina biotic index scores were more similar between streams than in previous years. However, mean annual standing crops of benthic organic matter (BOM) were much lower in the disturbed stream (167 g AFDM·m–2) than in the reference stream (339 g AFDM·m–2), and the disturbed stream supported greater macroinvertebrate biomass per unit BOM. We suggest that despite similarities in macroinvertebrate structure and function, past logging activity continues to influence consumer–resource relationships in the disturbed stream through enhanced resource quality.
Estimating bioenergetics model parameters for fish with incomplete recapture histories
Authors: Thompson Bradley E. , Hayes Daniel B.
Published: July 2010

Traditional methods for modeling growth of free-ranging fish are often limited by missing recapture observations that prevent individual growth estimates for a given time interval. Our purpose is to present a method for modeling growth rates of juvenile steelhead ( Oncorhynchus mykiss ) that addresses this limitation. Age-1 juvenile steelhead were individually marked with passive integrated transponder (PIT) tags, released in a Michigan, USA, watershed, and sampled monthly (May–November) with barge electrofishing. Individual growth was modeled using daily water temperature and observed fish sizes as inputs and by determining the proportion of maximum consumption parameter (P) for the bioenergetics equation that provided a minimum residual squared error. Results demonstrate that individual steelhead growth can be accurately modeled using water temperature and a temporally specific P shared by all individuals. Advantages of using this method to model fish growth include the ability to bridge data gaps where observations are lacking in individual length histories, rigorously test for differences in P across time periods, and estimate variability of P among fish within a given stream reach.
Effects of temperature and elemental concentration on the chemical composition of juvenile yellow perch (Perca flavescens) otoliths
Authors: Collingsworth Paris D. , Van Tassell Jason J. , Olesik John W. , Marschall Elizabeth A.
Published: July 2010

Otolith microchemistry studies assume that a relationship exists between the concentration of trace elements in the environment and otolith chemical composition. Although this assumption has been tested using marine and estuarine fish in controlled laboratory experiments, the relationships among temperature, ambient elemental concentration, and otolith chemical composition for freshwater species is not well documented. Here, juvenile yellow perch ( Perca flavescens ) were reared under different concentrations of four elements (Ba, Mg, Mn, and Sr) crossed with three temperatures (10 °C, 15 °C, and 20 °C) to determine the interactive influence of ambient elemental concentrations and temperature on otolith chemical composition. Sr:Ca and Ba:Ca were significantly related to ambient elemental concentrations, but Mg:Ca and Mn:Ca were not. Although the relative influence of temperature was less than that of ambient elemental concentrations, Sr:Ca, Ba:Ca, and Mn:Ca were all influenced by either water temperature or the interaction between temperature and elemental concentration, but the direction of the temperature effect differed for each element. Patterns in our partition coefficients are consistent with the idea that uptake of strontium facilitates uptake of barium. Overall, yellow perch otolith element composition was influenced primarily by ambient Sr and Ba concentrations, but temperature could potentially confound the results of otolith microchemistry studies.
A multispecies age-structured assessment model for the Gulf of Alaska
Authors: Van Kirk Kray F. , Quinn Terrance J. , Collie Jeremy S.
Published: July 2010

Predation is the largest source of mortality for marine fish and may be an important process in regulating population size. Recent population models have attempted to quantify predation separately from other sources of natural mortality. Building upon such work, a multispecies age-structured assessment model (MSASA) for the Gulf of Alaska was developed, which included arrowtooth flounder ( Atheresthes stomias ), Pacific cod ( Gadus macrocephalus ), and walleye pollock ( Theragra chalcogramma ). Predation mortality was a flexible function of predator and prey abundances that was fitted to stomach-content data. A proof of concept illustration is presented here, assessing model outputs against a set of single-species models. The MSASA model was able to successfully estimate predation between species and integrate it into total mortality. Significant predation occurred on younger pollock and flounder. Results indicate a significant change in predation over time on pollock as a function of increased arrowtooth flounder abundance. Estimating mortality and other parameters for three species simultaneously is complex, and the advantage of greater biological realism of MSASA comes at the expense of greater uncertainty in parameter estimation.
Population structure of lake trout (Salvelinus namaycush) in a large glacial-fed lake inferred from microsatellite DNA and morphological analysis
Authors: Northrup Sara , Connor Mark , Taylor Eric B.
Published: July 2010

Understanding the structure of intraspecific genetic and morphological diversity within and across habitats is a fundamental aspect of biodiversity research with conservation value. Atlin Lake is the largest lake in British Columbia, Canada, and contains relatively pristine populations of lake trout ( Salvelinus namaycush ) that are key components of the lake’s fish community and local fisheries. Lake trout from Atlin Lake were examined for genetic and phenotypic variation using eight microsatellite DNA loci, body form, and colouration. Genetic assays were also conducted on lake trout from the adjoining Tagish Lake and from 17 other localities to provide spatial context for the variation within Atlin Lake. The genetic data suggested that there were three genetic subpopulations within the Atlin–Tagish lake system. Morphological analysis identified two morphological groups of lake trout within Atlin Lake. Genetic and morphological groupings in Atlin Lake were not associated with each other. A mixed-stock analysis of samples collected from Atlin Lake commercial and recreational fisheries suggested that all genetic subpopulations contributed to the fishery and that there was some contribution from fish originating from within Tagish Lake.
Wintertime ocean conditions synchronize rockfish growth and seabird reproduction in the central California Current ecosystem
Authors: Black Bryan A. , Schroeder Isaac D. , Sydeman William J. , Bograd Steven J. , Lawson Peter W.
Published: July 2010

Chronologies developed from annual growth-increment widths of splitnose rockfish ( Sebastes pinniger ) and yelloweye rockfish ( Sebastes ruberrimus ) otoliths were compared with time series of lay date and fledgling success for the common murre ( Uria aalge ) and Cassin’s auklet ( Ptychoramphus aleuticus ) in the north-central California Current. All time series were exactly dated and spanned 1972 through 1994. In a principal components analysis, the leading principal component (PC1bio) accounted for 64% of the variance in the data set. By entering the upwelling index, the Northern Oscillation index, sea surface temperatures, and the multivariate ENSO (El Niño Southern Oscillation) index into principal components analysis, a time series of environmental variability PC1env was developed for each month of the year. Over the interval 1972 through 1994, PC1bio most strongly correlated with PC1env for February and, to a lesser extent, January and March. Moreover, when each of the six biological time series was related to the 12 PC1env through stepwise multiple regression, February was always the most significant (p < 0.01). The same was true if upwelling index was substituted for PC1env. As upper-trophic predators, rockfish and seabirds independently corroborate that wintertime ocean conditions are critical for productivity in the California Current ecosystem.
Experimental modelling of debris flow behaviour using a geotechnical centrifuge
Authors: Bowman Elisabeth T. , Laue Jan , Imre Bernd , Springman Sarah M.
Published: July 2010

Physical modelling of debris flows has been carried out in the geotechnical drum centrifuge at ETH Zürich. A new apparatus to model debris flows in the centrifuge is described. The apparatus permits the final reach of a typical debris flow to be modelled within the centrifuge, with unconsolidated material flowing down a slope to deposit as a fan around the drum. Experiments are described for both fixed base conditions and erodible bases. Tests to examine the verification (modelling) of models show that debris flow behaviour is governed mainly by friction and consolidation processes, although some resolution is required between flow behaviour downslope and flow arrest during runout. The results are compared with bulk parameters determined for field-scale debris flows. It is found that some important flow mechanisms, such as contact-dominated behaviour and high pore pressures, are developed that are closer to those developed at field-scale than tests conducted at 1g. Velocity profiles for erodible beds are compared with a semi-empirical expression derived for experimental debris flows at 1g. Normalized velocity profiles are found to be in agreement; however, absolute velocities differ from those predicted. Scaling, the limitations of the apparatus, and potential for future work are discussed.