bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of a Bacteriophage on the Population Dynamics of Toxic Dinoflagellates by Lysis of Algicidal Bacteria
Authors: Cai Wenwei , Wang Hui , Tian Yun , Chen Feng , Zheng Tianling
Published: September 2011

A lytic phage (øZCW1) was isolated from an algicidal bacteriumPseudoalteromonassp. strain SP48 that specifically kills the toxic dinoflagellateAlexandrium tamarense. We demonstrated that øZCW1 could trigger the growth ofA. tamarenseby inhibiting the growth of algicidal bacterium SP48. In contrast, the growth ofA. tamarensewas suppressed when cocultured with either SP48 or the øZCW1-resistant mutant of SP48. This study provides the first evidence of the indirect impact of bacteriophage on bloom-forming microalgae via phage lysis of alga-killing bacteria.
Active Autotrophic Ammonia-Oxidizing Bacteria in Biofilm Enrichments from Simulated Creek Ecosystems at Two Ammonium Concentrations Respond to Temperature Manipulation
Authors: Avrahami Sharon , Jia Zhongjun , Neufeld Josh D. , Murrell J. Colin , Conrad Ralf , Küsel Kirsten
Published: September 2011

The first step of nitrification, the oxidation of ammonia to nitrite, is important for reducing eutrophication in freshwater environments when coupled with anammox (anaerobic ammonium oxidation) or denitrification. We analyzed active formerly biofilm-associated aerobic ammonia-oxidizing communities originating from Ammerbach (AS) and Leutra South (LS) stream water (683 ± 550 [mean ± standard deviation] and 16 ± 7 μM NH
4
+
, respectively) that were developed in a flow-channel experiment and incubated under three temperature regimens. By stable-isotope probing using
13
CO
2
, we found that members of the
Bacteria
and not
Archaea
were the functionally dominant autotrophic ammonia oxidizers at all temperatures under relatively high ammonium loads. The copy numbers of bacterial
amoA
genes in
13
C-labeled DNA were lower at 30°C than at 13°C in both stream enrichment cultures. However, the community composition of the ammonia-oxidizing bacteria (AOB) in the
13
C-labeled DNA responded differently to temperature manipulation at two ammonium concentrations. In LS enrichments incubated at the
in situ
temperature (13°C),
Nitrosomonas oligotropha
-like sequences were retrieved with sequences from
Nitrosospira
AmoA cluster 4, while the proportion of
Nitrosospira
sequences increased at higher temperatures. In AS enrichments incubated at 13°C and 20°C, AmoA cluster 4 sequences were dominant;
Nitrosomonas nitrosa
-like sequences dominated at 30°C. Biofilm-associated AOB communities were affected differentially by temperature at two relatively high ammonium concentrations, implicating them in a potential role in governing contaminated freshwater AOB distributions.
Fine-Scale Distribution Patterns of Synechococcus Ecological Diversity in Microbial Mats of Mushroom Spring, Yellowstone National Park
Authors: Becraft Eric D. , Cohan Frederick M. , Kühl Michael , Jensen Sheila I. , Ward David M.
Published: September 2011

Past analyses of sequence diversity in high-resolution protein-encoding genes have identified putative ecological species of unicellular cyanobacteria in the genus
Synechococcus
, which are specialized to 60°C but not 65°C in Mushroom Spring microbial mats. Because these studies were limited to only two habitats, we studied the distribution of
Synechococcus
sequence variants at 1°C intervals along the effluent flow channel and at 80-μm vertical-depth intervals throughout the upper photic layer of the microbial mat. Diversity at the
psaA
locus, which encodes a photosynthetic reaction center protein (PsaA), was sampled by PCR amplification, cloning, and sequencing methods at 60, 63, and 65°C sites. The evolutionary simulation programs Ecotype Simulation and AdaptML were used to identify putative ecologically distinct populations (ecotypes). Ecotype Simulation predicted a higher number of putative ecotypes in cases where habitat variation was limited, while AdaptML predicted a higher number of ecologically distinct phylogenetic clades in cases where habitat variation was high. Denaturing gradient gel electrophoresis was used to track the distribution of dominant sequence variants of ecotype populations relative to temperature variation and to O
2
, pH, and spectral irradiance variation, as measured using microsensors. Different distributions along effluent channel flow and vertical gradients, where temperature, light, and O
2
concentrations are known to vary, confirmed the ecological distinctness of putative ecotypes.
The Lcn972 Bacteriocin-Encoding Plasmid pBL1 Impairs Cellobiose Metabolism in Lactococcus lactis
Authors: Campelo Ana B. , Gaspar Paula , Roces Clara , Rodríguez Ana , Kok Jan , Kuipers Oscar P. , Neves Ana Rute , Martínez Beatriz
Published: September 2011

pBL1 is a
Lactococcus lactis
theta-replicating 10.9-kbp plasmid that encodes the synthetic machinery of the bacteriocin Lcn972. In this work, the transcriptomes of exponentially growing
L. lactis
strains with and without pBL1 were compared. A discrete response was observed, with a total of 10 genes showing significantly changed expression. Upregulation of the lactococcal oligopeptide uptake (
opp
) system was observed, which was likely linked to a higher nitrogen demand required for Lcn972 biosynthesis. Strikingly,
celB
, coding for the membrane porter IIC of the cellobiose phosphoenolpyruvate-dependent phosphotransferase system (PTS), and the upstream gene
llmg0186
were downregulated. Growth profiles for
L. lactis
strains MG1363, MG1363/pBL1, and MG1363 Δ
celB
grown in chemically defined medium (CDM) containing cellobiose confirmed slower growth of MG1363/pBL1 and MG1363 Δ
celB
, while no differences were observed with growth on glucose. The presence of pBL1 shifted the fermentation products toward a mixed acid profile and promoted substantial changes in intracellular pool sizes for glycolytic intermediates in cells growing on cellobiose as determined by high-pressure liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). Overall, these data support the genetic evidence of a constriction in cellobiose uptake. Notably, several cell wall precursors accumulated, while other UDP-activated sugar pools were lower, which could reflect rerouting of precursors toward the production of structural or storage polysaccharides. Moreover, cells growing slowly on cellobiose and those lacking
celB
were more tolerant to Lcn972 than cellobiose-adapted cells. Thus, downregulation of
celB
could help to build up a response against the antimicrobial activity of Lcn972, enhancing self-immunity of the producer cells.
Expression of Biomass-Degrading Enzymes Is a Major Event during Conidium Development in Trichoderma reesei
Authors: Metz Benjamin , Seidl-Seiboth Verena , Haarmann Thomas , Kopchinskiy Alexeij , Lorenz Patrick , Seiboth Bernhard , Kubicek Christian P.
Published: September 2011

The conidium plays a critical role in the life cycle of many filamentous fungi, being the primary means for survival under unfavorable conditions. To investigate the transcriptional changes taking place during the transition from growing hyphae to conidia in
Trichoderma reesei
, microarray experiments were performed. A total of 900 distinct genes were classified as differentially expressed, relative to their expression at time zero of conidiation, at least at one of the time points analyzed. The main functional categories (FunCat) overrepresented among the upregulated genes were those involving solute transport, metabolism, transcriptional regulation, secondary metabolite synthesis, lipases, proteases, and, particularly, cellulases and hemicellulases. Categories overrepresented among the downregulated genes were especially those associated with ribosomal and mitochondrial functions. The upregulation of cellulase and hemicellulase genes was dependent on the function of the positive transcriptional regulator XYR1, but XYR1 exerted no influence on conidiation itself. At least 20% of the significantly regulated genes were nonrandomly distributed within the
T. reesei
genome, suggesting an epigenetic component in the regulation of conidiation. The significant upregulation of cellulases and hemicellulases during this process, and thus cellulase and hemicellulase content in the spores of
T. reesei
, contributes to the hypothesis that the ability to hydrolyze plant biomass is a major trait of this fungus enabling it to break dormancy and reinitiate vegetative growth after a period of facing unfavorable conditions.
Protein Phosphatase Pph3 and Its Regulatory Subunit Psy2 Regulate Rad53 Dephosphorylation and Cell Morphogenesis during Recovery from DNA Damage in Candida albicans
Authors: Sun Ling Ling , Li Wan Jie , Wang Hai Tao , Chen Jie , Deng Ping , Wang Yue , Sang Jian Li
Published: September 2011

The ability of the pathogenic fungus
Candida albicans
to switch cellular morphologies is important for infection and virulence. Recent studies have revealed that
C. albicans
yeast cells can switch to filamentous growth under genotoxic stress in a manner dependent on the DNA replication/damage checkpoint. Here, we have investigated the functions of Pph3 (orf19.4378) and Psy2 (orf19.3685), whose orthologues in
Saccharomyces cerevisiae
mediate the dephosphorylation of the DNA damage checkpoint kinase Rad53 and the histone variant H2AX during recovery from DNA damage. Deleting
PPH3
or
PSY2
causes hypersensitivity to DNA-damaging agents, including cisplatin, methylmethane sulfonate (MMS), and UV light. In addition,
pph3
Δ and
psy2
Δ cells exhibit strong filamentous growth under genotoxic stress. Flow cytometry analysis shows that the mutant cells have lost the ability to adapt to genotoxic stress and remain arrested even after the stress is withdrawn. Furthermore, we show that Pph3 and Psy2 are required for the dephosphorylation of Rad53, but not H2AX, during DNA damage recovery. Taken together, these results show that
C. albicans
Pph3 and Psy2 have important roles in mediating genotoxin-induced filamentous growth and regulating Rad53 dephosphorylation.
RAS/Cyclic AMP and Transcription Factor Msn2 Regulate Mating and Mating-Type Switching in the Yeast Kluyveromyces lactis
Authors: Barsoum E. , Rajaei N. , Åström S. U.
Published: September 2011

In response to harsh environmental conditions, ascomycetes produce stress-resistant spores to promote survival. As sporulation requires a diploid DNA content, species with a haploid lifestyle, such as
Kluyveromyces lactis
, first induce mating in response to stress. In
K. lactis
, mating and mating-type switching are induced by the DNA-binding protein Mts1. Mts1 expression is known to be upregulated by nutrient limitation, but the mechanism is unknown. We show that a
ras2
mutation results in a hyperswitching phenotype. In contrast, strains lacking the phosphodiesterase Pde2 had lower switching rates compared to that of the wild type (WT). As Ras2 promotes cyclic AMP (cAMP) production and Pde2 degrades cAMP, these data suggest that low cAMP levels induce switching. Because the
MTS1
regulatory region contains several Msn2 binding sites and Msn2 is a transcription factor that is activated by low cAMP levels, we investigated if Msn2 regulates
MTS1
transcription. Consistently with this idea, an
msn2
mutant strain displayed lower switching rates than the WT strain. The transcription of
MTS1
is highly induced in the
ras2
mutant strain. In contrast, an
msn2 ras2
double mutant strain displays WT levels of the
MTS1
transcript, showing that Msn2 is a critical inducer of
MTS1
transcription. Strains lacking Msn2 and Pde2 also exhibit mating defects that can be complemented by the ectopic expression of Mts1. Finally, we show that
MTS1
is subjected to negative autoregulation, presumably adding robustness to the mating and switching responses. We suggest a model in which Ras2/cAMP/Msn2 mediates the stress-induced mating and mating-type switching responses in
K. lactis
.
Zap1 Control of Cell-Cell Signaling in Candida albicans Biofilms
Authors: Ganguly Shantanu , Bishop Andrew C. , Xu Wenjie , Ghosh Suman , Nickerson Kenneth W. , Lanni Frederick , Patton-Vogt Jana , Mitchell Aaron P.
Published: September 2011

Biofilms of
Candida albicans
include both yeast cells and hyphae. Prior studies indicated that a
zap1
Δ/Δ mutant, defective in zinc regulator Zap1, has increased accumulation of yeast cells in biofilms. This altered yeast-hypha balance may arise from internal regulatory alterations or from an effect on the production of diffusible quorum-sensing (QS) molecules. Here, we develop biosensor reporter strains that express yeast-specific
YWP1-RFP
or hypha-specific
HWP1-RFP
, along with a constitutive
TDH3-GFP
normalization standard. Seeding these biosensor strains into biofilms allows a biological activity assay of the surrounding biofilm milieu. A
zap1
Δ/Δ biofilm induces the yeast-specific
YWP1-RFP
reporter in a wild-type biosensor strain, as determined by both quantitative reverse transcription-PCR (qRT-PCR) gene expression measurements and confocal microscopy. Remediation of the
zap1
Δ/Δ zinc uptake defect through zinc transporter gene
ZRT2
overexpression reverses induction of the yeast-specific
YWP1-RFP
reporter. Gas chromatography-mass spectrometry (GC-MS) measurements of known organic QS molecules show that the
zap1
Δ/Δ mutant accumulates significantly less farnesol than wild-type or complemented strains and that
ZRT2
overexpression does not affect farnesol accumulation. Farnesol is a well-characterized inhibitor of hypha formation; hence, a reduction in farnesol levels in
zap1
Δ/Δ biofilms is unexpected. Our findings argue that a Zap1- and zinc-dependent signal affects the yeast-hypha balance and that it is operative in the low-farnesol environment of the
zap1
Δ/Δ biofilm. In addition, our results indicate that Zap1 is a positive regulator of farnesol accumulation.
Adjusting the Spokes of the Flagellar Motor with the DNA-Binding Protein H-NS
Authors: Paul Koushik , Carlquist William C. , Blair David F.
Published: September 2011

The H-NS protein of bacteria is a global regulator that stimulates transcription of flagellar genes and that also acts directly to modulate flagellar motor function. H-NS is known to bind FliG, a protein of the rotor that interacts with the stator and is directly involved in rotation of the motor. Here, we find that H-NS, well known for its ability to organize DNA, acts in the flagellar motor to organize protein subunits in the rotor. It binds to a middle domain of FliG that bridges the core parts of the rotor and parts nearer the edge that interact with the stator. In the absence of H-NS the organization of FliG subunits is disrupted, whereas overexpression of H-NS enhances FliG organization as monitored by targeted disulfide cross-linking, alters the disposition of a helix joining the middle and C-terminal domains of FliG, and enhances motor performance under conditions requiring a strengthened rotor-stator interface. The H-NS homolog StpA was also shown to bind FliG and to act similarly, though less effectively, in organizing FliG. The motility-enhancing effects of H-NS contrast with those of the recently characterized motility inhibitor YcgR. The present findings provide an integrated, structurally grounded framework for understanding the roughly opposing effects of these motility regulators.
Mutations in Genes
patA
and
patL
of Anabaena sp. Strain PCC 7120 Result in Similar Phenotypes, and the Proteins Encoded by Those Genes May Interact
Authors: Liu Jinjie , Wolk C. Peter
Published: September 2011

PatA resembles a response regulator protein with a defective DNA-binding domain, and PatL (All3305) is a pentapeptide repeat protein. A yeast two-hybrid library identified PatL as a protein with which PatA may interact. Heterocysts of
patA
and
patL Anabaena
sp. form nearly exclusively terminally in long filaments, further linking the genes.
The Opportunistic Pathogen Serratia marcescens Utilizes Type VI Secretion To Target Bacterial Competitors
Authors: Murdoch Sarah L. , Trunk Katharina , English Grant , Fritsch Maximilian J. , Pourkarimi Ehsan , Coulthurst Sarah J.
Published: September 2011

The type VI secretion system (T6SS) is the most recently described and least understood of the protein secretion systems of Gram-negative bacteria. It is widely distributed and has been implicated in the virulence of various pathogens, but its mechanism and exact mode of action remain to be defined. Additionally there have been several very recent reports that some T6SSs can target bacteria rather than eukaryotic cells.
Serratia marcescens
is an opportunistic enteric pathogen, a class of bacteria responsible for a significant proportion of hospital-acquired infections. We describe the identification of a functional T6SS in
S. marcescens
strain Db10, the first report of type VI secretion by an opportunist enteric bacterium. The T6SS of
S. marcescens
Db10 is active, with secretion of Hcp to the culture medium readily detected, and is expressed constitutively under normal growth conditions from a large transcriptional unit. Expression of the T6SS genes did not appear to be dependent on the integrity of the T6SS. The
S. marcescens
Db10 T6SS is not required for virulence in three nonmammalian virulence models. It does, however, exhibit dramatic antibacterial killing activity against several other bacterial species and is required for
S. marcescens
to persist in a mixed culture with another opportunist pathogen,
Enterobacter cloacae
. Importantly, this antibacterial killing activity is highly strain specific, with the
S. marcescens
Db10 T6SS being highly effective against another strain of
S. marcescens
with a very similar and active T6SS. We conclude that type VI secretion plays a crucial role in the competitiveness, and thus indirectly the virulence, of
S. marcescens
and other opportunistic bacterial pathogens.
Genetic Analysis of
SCO2997
, Encoding a TagF Homologue, Indicates a Role for Wall Teichoic Acids in Sporulation of Streptomyces coelicolor A3(2)
Authors: Kleinschnitz Eva-Maria , Latus Annette , Sigle Steffen , Maldener Iris , Wohlleben Wolfgang , Muth Günther
Published: September 2011

Streptomyces coelicolor
contains two gene clusters putatively involved in wall teichoic acid biosynthesis. Inactivation of the
tagF
homologue
SCO2997
or
SCO2584
, a component of the
Streptomyces
spore wall synthesizing complex, affected sporulation. The mutant phenotypes resembled those of
mre
mutants, suggesting a function of wall teichoic acids in the differentiation of
Streptomyces
.
Role of ArgP (IciA) in Lysine-Mediated Repression in Escherichia coli
Authors: Marbaniang Carmelita N. , Gowrishankar J.
Published: September 2011

Initially identified as an inhibitor of
oriC
-initiated DNA replication
in vitro
, the ArgP or IciA protein of
Escherichia coli
has subsequently been described as a nucleoid-associated protein and also as a transcriptional regulator of genes involved in DNA replication (
dnaA
and
nrdA
) and amino acid metabolism (
argO
,
dapB
, and
gdhA
[the last in
Klebsiella pneumoniae
]). ArgP mediates lysine (Lys) repression of
argO
,
dapB
, and
gdhA
in vivo
, for which two alternative mechanisms have been identified: at the
dapB
and
gdhA
regulatory regions, ArgP binding is reduced upon the addition of Lys, whereas at
argO
, RNA polymerase is trapped at the step of promoter clearance by Lys-bound ArgP. In this study, we have examined promoter-
lac
fusions in strains that were
argP
+
or Δ
argP
or that were carrying dominant
argP
mutations in order to identify several new genes that are ArgP-regulated
in vivo
, including
lysP
,
lysC
,
lysA
,
dapD
, and
asd
(in addition to
argO
,
dapB
, and
gdhA
). All were repressed upon Lys supplementation, and
in vitro
studies demonstrated that ArgP binds to the corresponding regulatory regions in a Lys-sensitive manner (with the exception of
argO
, whose binding to ArgP was Lys insensitive). Neither
dnaA
nor
nrdA
was ArgP regulated
in vivo
, although their regulatory regions exhibited low-affinity binding to ArgP. Our results suggest that ArgP is a transcriptional regulator for Lys repression of genes in
E. coli
but that it is noncanonical in that it also exhibits low-affinity binding, without apparent direct regulatory effect, to a number of additional sites in the genome.
How do centres begin the process to prevent contrast-induced acute kidney injury: a report from a new regional collaborative
Authors: Brown Jeremiah R , McCullough Peter A , Splaine Mark E , Davies Louise , Ross Cathy S , Dauerman Harold L , Robb John F , Boss Richard , Goldberg David J , Fedele Frank A , Kellett Mirle A , Phillips William J , Ver Lee Peter N , Nelson Eugene C , MacKenzie Todd A , O'Connor Gerald T , Sarnak Mark J , Malenka David J ,   for the Northern New England Cardiovascular Disease Study Group
Published: September 2011

Objectives

This study evaluates the variation in practice patterns associated with contrast-induced acute kidney injury (CI-AKI) and identifies clinical practices that have been associated with a reduction in CI-AKI.

Background

CI-AKI is recognised as a complication of invasive cardiovascular procedures and is associated with cardiovascular events, prolonged hospitalisation, end-stage renal disease, and all-cause mortality. Reducing the risk of CI-AKI is a patient safety objective set by the National Quality Forum.

Methods

This study prospectively collected quantitative and qualitative data from 10 centres, which participate in the Northern New England Cardiovascular Disease Study Group PCI Registry. Quantitative data were collected from the PCI Registry. Qualitative data were obtained through clinical team meetings to map care processes related to CI-AKI and focus groups to understand attitudes towards CI-AKI prophylaxis. Fixed and random effects modelling were conducted to test the differences across centres.

Results

Significant variation in rates of CI-AKI were found across 10 medical centres. Both fixed effects and mixed effects logistic regression demonstrated significant variability across centres, even after adjustment for baseline covariates (p<0.001 for both modelling approaches). Patterns were found in reported processes and clinical leadership that were attributable to centres with lower rates of CI-AKI. These included reducing nil by mouth (NPO) time to 4 h prior to case, and standardising volume administration protocols in combination with administering three to four high doses of N-acetylcysteine (1200 mg) for each patient.

Conclusions

These data suggest that clinical leadership and institution-focused efforts to standardise preventive practices can help reduce the incidence of CI-AKI.
The effects of bed height and time on the quality of chest compressions delivered during cardiopulmonary resuscitation: a randomised crossover simulation study
Authors: Lewinsohn A , Sherren P B , Wijayatilake D S
Published: September 2011

Introduction

The 2010 International Liaison Committee on Resuscitation gave a detailed update on best practice for cardiopulmonary resuscitation (CPR) with a discussion on appropriate patient and CPR provider position, based largely on expert opinion. The objective of this study was to ascertain robust evidence on the effect of bed height and fatigue on chest compression effectiveness.

Methods

A modified Laerdal manikin was connected to a Dragor ventilator (to measure intrathoracic pressures generated). The manikin was placed on a hospital trolley and CPR was performed by candidates at three different bed heights in a randomised order: (1) mid-thigh, (2) anterior superior iliac spine and (3) xiphisternum. Chest compressions were continuous and asynchronous with ventilation, and were allowed to continue for 30 s before recordings were taken. At the anterior superior iliac spine level, chest compressions were continued for 2 min, when further measurements were taken.

Results

101 subjects took part. The differences in intrathoracic pressures generated at different bed heights were compared using analysis of variance testing for multiple groups and were statistically significant for p<0.05. The authors also found that the effectiveness of CPR decreased 17% over a 2-minute period (p<0.05).

Conclusions

The most effective bed height position, allowing CPR providers to achieve the highest intrathoracic pressures during CPR, was one where the patient's chest was in line with the CPR provider's mid-thigh. The provider performing CPR should change every 2 min.
Plagued by kindness: contagious sympathy in Shakespearean drama
Authors: Langley Eric
Published: September 2011

This article considers Shakespeare's metaphors of transmission, contagion and infection in the light of period plague tracts, medical treatises and plague time literature. The author demonstrates how period conceptions of disease are predicated upon a notion of sympathetic transference and, consequently, how kindness, likeness and communication between characters in Shakespearean drama are complicated and fraught with period specific anxiety. This article situates Shakespearean literary texts within a precise historical and medical moment, considering how scientific conceptions contaminate dramatic text.
Solid-state nuclear magnetic resonance (NMR) spectroscopy reveals distinctive protein dynamics in closely related spider silks
Authors: Cloutier Isabelle , Leclerc Jérémie , Lefèvre Thierry , Auger Michèle
Published: September 2011

Structurally closely related spider silks, namely, major ampullate silk (MaS) reeled at 0.5 and 10 cm/s, minor ampullate silk (MiS), and cocoon silk have been investigated by solid-state nuclear magnetic resonance (NMR). These silks exhibit different mechanical properties that are not well explained with current structural data. NMR spectra confirm that the secondary structures of these silks are similar, but that differing relaxation dynamics exist at the alanine, glycine, and glutamine residue level. MaS reeled rapidly is made of more mobile proteins in both the β-sheet and amorphous regions, suggesting that reeling speed alters molecular rearrangement during spinning, with the chain packing being less organized in the fastpull fiber. Alanine and glycine relaxation dynamics increases as MaS < MiS < cocoon silk, showing that the whole fiber displays distinctive protein dynamics, chain packing, and intermolecular interactions. Besides molecular orientation, silk extensibility is related to a more mobile structural organization.
Pallid bat (Antrozous pallidus) foraging over native and vineyard habitats in British Columbia, Canada
Authors: Rambaldini D.A. , Brigham R.M.
Published: September 2011

Optimal foraging theory predicts organisms will forage in habitats providing the most profitable prey. Human alterations to ecosystems may affect predators’ foraging activity by changing landscape features, prey types, and prey availability. Assessing the selection of foraging habitats in a heterogeneous landscape can provide data to improve land management and conservation policies. In Canada, the pallid bat ( Antrozous pallidus (LeConte, 1856); Vespertilionidae) is listed as threatened partly because of loss or modification of shrub–steppe habitat. Our purpose was to determine if vineyards provide a suitable surrogate for foraging habitat relative to native habitat. We used pitfall traps to compare prey abundance in each habitat and analyzed faeces to assess diet composition. Over 24 nights, we surveyed both habitats for foraging bats. Bats foraged over vineyards, but we recorded significantly more foraging activity over native habitat. We collected over 2000 arthropods in pitfall traps and found significantly more in native habitat compared with vineyards. Species eaten by pallid bats were present in both habitats. Scarab beetles (Coleoptera: Scarabidae) and Jerusalem crickets (Orthopthera: Stenopelmatidae) represented the principal prey. The use of vineyards by pallid bats for foraging suggests that while they are adapting to a changing landscape, reduced prey abundance in vineyards may negatively affect them over the long term.
Stable isotopes reveal strategic allocation of resources during juvenile development in a cryptic and threatened seabird, the Marbled Murrelet (Brachyramphus marmoratus)
Authors: Janssen Michael H. , Arcese Peter , Kyser T. Kurt , Bertram Douglas F. , Norris D. Ryan
Published: September 2011

Identifying factors that influence growth throughout development is important for understanding the consequences of variation in resource quality on recruitment. Marbled Murrelets ( Brachyramphus marmoratus (J.F. Gmelin, 1789)) are threatened seabirds that are extremely cryptic in their nesting behaviour, which makes it challenging to understand how juveniles allocate resources during development. From a single capture at sea, we analyzed stable carbon isotopes in feathers and blood of juvenile murrelets to infer diet composition during both the pre- and the post-fledging periods. Consistent with the challenges juveniles face during their first year of life, we found that wing and bill growth were prioritized in the nest, whereas development of energy stores was delayed until after nest departure. We also found that diet quality after nest departure influenced bill size and body condition, two body components that continue to grow after independence. Our results provide evidence that murrelets strategically allocate resources according to their stage of development and that the availability of high-quality prey is likely to be important to juvenile development. These results identify a potential mechanism through which feeding conditions may influence reproduction of murrelets and demonstrate the utility of stable isotopes to examine the influence of diet quality on growth over multiple stages of development.
Evidence for altered circular smooth muscle cell function in lower esophageal sphincter ofW/Wvmutant mice
Authors: Bautista-Cruz Francisco , Paterson William G.
Published: September 2011

Nitrergic neurotransmission to gut smooth muscle is impaired in W/Wvmutant mice, which lack intramuscular interstitial cells of Cajal (ICC-IM). In addition, these mice have been reported to have smaller amplitude unitary potentials (UPs) and a more negative resting membrane potential (RMP) than control mice. These abnormalities have been attributed to absence of ICC-IM, but it remains possible that they are due to alterations at the level of the smooth muscle itself. Amphotericin-B-perforated patch-clamp recordings and Ca2+imaging (fura 2) were compared between freshly isolated single circular smooth muscle cells (CSM) from W/Wvmutant and control mice lower esophageal sphincter (LES). There was no significant difference in seal resistance, capacitance, or input resistance in response to applied electrotonic current pulses between CSM cells from W/Wvmutants and controls. Compared with control mice, RMP was more negative and UPs significantly smaller in CSM cells from mutant mice LES. Administration of caffeine induced an inward current in cells from both mutant and control mice, but the current density was significantly larger in cells from W/Wvmutants. Membrane potential hyperpolarization induced by sodium nitroprusside was larger in cells from control mice vs. W/Wvmutants. In addition, intracellular Ca2+transients induced by caffeine were significantly increased in cells from mutants. These findings indicate that LES CSM is abnormal in W/Wvmutant mice. Thus some physiological functions attributed to ICC-IM based on experiments in smooth muscle of ICC deficient mice may need to be reconsidered.
Variability in the muscle composition of rat esophagus and neural pathway of lower esophageal sphincter relaxation
Authors: Jiang Yanfen , Bhargava Valmik , Lal Harshal A. , Mittal Ravinder K.
Published: September 2011

Several studies from our laboratory show that axial stretch of the lower esophageal sphincter (LES) in an oral direction causes neurally mediated LES relaxation. Under physiological conditions, axial stretch of the LES is caused by longitudinal muscle contraction (LMC) of the esophagus. Because longitudinal muscle is composed of skeletal muscle in mice, vagal-induced LMC and LES relaxation are both blocked by pancuronium. We conducted studies in rats (thought to have skeletal muscle esophagus) to determine if vagus nerve-mediated LES relaxation is also blocked by pancuronium. LMC-mediated axial stretch on the LES was monitored using piezoelectric crystals. LES and esophageal pressures were monitored with a 2.5-Fr solid-state pressure transducer catheter. Following bilateral cervical vagotomy, the vagus nerve was stimulated electrically. LES, along with the esophagus, was harvested after in vivo experiments and immunostained for smooth muscle (smooth muscle α-actin) and skeletal muscle (fast myosin heavy chain). Vagus nerve-stimulated LES relaxation and esophageal LMC were reduced in a dose-dependent fashion and completely abolished by pancuronium (96 μg/kg) in six rats ( group 1). On the other hand, in seven rats, LES relaxation and LMC were only blocked completely by a combination of pancuronium ( group 2) and hexamethonium. Immunostaining revealed that the longitudinal muscle layer was composed of predominantly skeletal muscle in the group 1 rats. On the other hand, the longitudinal muscle layer of group 2 rats contained a significant amount of smooth muscle ( P < 0.05). Our study shows tight coupling between axial stretch on the LES and relaxation of the LES, which suggests a cause and effect relationship between the two. We propose that the vagus nerve fibers that cause LMC induce LES relaxation through the stretch-sensitive activation of inhibitory motor neurons.
Nitric oxide formation by lymphatic bulb and valves is a major regulatory component of lymphatic pumping
Authors: Bohlen H. Glenn , Gasheva Olga Yu. , Zawieja David C.
Published: September 2011

Microscopic lymphatics produce nitric oxide (NO) during contraction as flow shear activates the endothelial cells. The valve leaflets and bulbous valve housing contain a large amount of endothelial nitric oxide synthase (eNOS) due both to many endothelial cells and increased expression of eNOS. Direct NO measurements indicate the valve area has a 30–50% higher NO concentration ([NO]) than tubular regions although both regions generate equivalent relative increases in [NO] with each contraction. We hypothesize that 1) the greater eNOS and [NO] of the bulb region would have greater effects to lower pumping activity of the overall lymphatic than occurs in tubular regions and 2), the elevated [NO] in the bulb region may be because of high NO production in the valve leaflets that diffuses to the wall of the bulb. Measurement of [NO] with a micropipette inside the lymphatic bulb revealed the valve leaflets generate ∼50% larger [NO] than the bulb wall in the in vivo rat mesenteric lymphatics. The valves add NO to the lymph that quickly diffuses to the bulb wall. Bradykinin locally released iontophoretically from a micropipette on both bulbs and tubes increased the [NO] in a dose-dependent manner up to ∼50%, demonstrating agonist activation of the NO pathway. However, pumping output determined by contraction frequency and stroke volume decreased much more for the bulb than tubular areas in response to the bradykinin. In effect, NO generation by the bulb area and its valves limits the pumped flow of the total lymphatic by lowering frequency and stroke volume of individual contractions.
Endothelial growth factor therapy improves preeclampsia-like manifestations in a murine model induced by overexpression of sVEGFR-1
Authors: Mateus Julio , Bytautiene Egle , Lu Fangxian , Tamayo Esther H. , Betancourt Ancizar , Hankins Gary D. V. , Longo Monica , Saade George R.
Published: September 2011

This study examines the effects of VEGF-121 therapy in an animal model of preeclampsia induced by overexpression of soluble VEGF receptor 1 (sVEGFR-1). At day 8 of gestation, CD-1 mice were implanted with subcutaneous osmotic pumps containing either VEGF-121 or vehicle and fitted with telemetric blood pressure (BP) catheters for continuous BP monitoring ( days 8–18 of gestation). On day 9, the animals in the VEGF-121 group were randomly allocated for injection with adenovirus carrying sVEGFR-1 or the murine immunoglobulin G2α Fc fragment (mFc) as virus control (Adv-sVEGFR-1; Adv-mFc). Animals in the vehicle group were injected with Adv-sVEGFR-1. On day 18, mice were euthanized, placentas and pups weighted, carotid arteries isolated, and their responses studied in vitro using a wire myograph for isometric tension recording. In mice overexpressing sVEGFR-1, treatment with VEGF-121 significantly reduced BP from days 10 to 18 of gestation compared with that of vehicle. VEGF-sVEGFR-1 animals had significantly higher vasorelaxant response to sodium nitroprusside and significantly lower contractile response to the thromboxane agonist (U-46619) compared with that of the vehicle-sVEGFR-1 mice. Phenylephrine and acetylcholine responses did not significantly vary between the VEGF-sVEGFR-1 and the vehicle-sVEGFR-1 mice. Average pup weight was significantly lower in the vehicle-sVEGFR-1 group compared with the VEGF-sVEGFR-1 and VEGF-mFc groups. In conclusion, VEGF-121 therapy attenuates vascular dysfunction and diminishes intrauterine growth abnormality in an animal model of preeclampsia induced by overexpression of sVEGFR-1. Modulation of VEGF pathway turns into a promising therapeutic approach of preeclampsia.
The Rho kinase inhibitor Y-27632 increases erythrocyte deformability and low oxygen tension-induced ATP release
Authors: Thuet K. M. , Bowles E. A. , Ellsworth M. L. , Sprague R. S. , Stephenson A. H.
Published: September 2011

Low oxygen (O2) tension and mechanical deformation are stimuli for ATP release from erythrocytes. It has been shown previously that rabbit erythrocytes made less deformable with diamide, a thiol cross-linking agent, release less ATP in response to low O2 tension, suggesting a link between these two stimuli. In nonerythroid cells, activation of the Rho/Rho kinase signaling pathway has been reported to decrease cell deformability by altering Rho kinase-dependent cytoskeleton-protein interactions. We investigated the hypothesis that the Rho kinase inhibitor Y-27632 would increase erythrocyte deformability and thereby increase low O2 tension-induced ATP release from erythrocytes. Here we show that Y-27632 (1 μM) increases erythrocyte deformability (5%) and increases low O2 tension-induced ATP release (203%) from healthy human erythrocytes. In addition, we found that, when erythrocytes were made less deformable by incubation with diamide (100 μM), Y-27632 restored both deformability and low O2 tension-induced ATP release to levels similar to those measured in the absence of diamide. These findings suggest that the Rho kinase inhibitor Y-27632 is able to reverse the diamide-induced decrease in erythrocyte deformability and rescue low O2 tension-induced ATP release. These results further support a link between erythrocyte deformability and ATP release in response to low O2 tension.
Dehydroepiandrosterone inhibits the Src/STAT3 constitutive activation in pulmonary arterial hypertension
Authors: Paulin Roxane , Meloche Jolyane , Jacob Maria Helena , Bisserier Malik , Courboulin Audrey , Bonnet Sébastien
Published: September 2011

Pulmonary arterial hypertension (PAH) is an obstructive vasculopathy characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation and suppressed apoptosis. This phenotype is sustained by the activation of the Src/signal transducer and activator of transcription 3 (STAT3) axis, maintained by a positive feedback loop involving miR-204 and followed by an aberrant expression/activation of its downstream targets such as Pim1 and nuclear factor of activated T-cells (NFATc2). Dehydroepiandrosterone (DHEA) is a steroid hormone shown to reverse vascular remodeling in systemic vessels. Since STAT3 has been described as modulated by DHEA, we hypothesized that DHEA reverses human pulmonary hypertension by inhibiting Src/STAT3 constitutive activation. Using PASMCs isolated from patients with PAH ( n = 3), we demonstrated that DHEA decreases both Src and STAT3 activation (Western blot and nuclear translocation assay), resulting in a significant reduction of Pim1, NFATc2 expression/activation (quantitative RT-PCR and Western blot), as well as Survivin and upregulation of bone morphogenetic protein receptor 2 (BMPR2) and miR-204. Src/STAT3 axis inhibition by DHEA is associated with 1) mitochondrial membrane potential (tetramethylrhodamine methyl-ester perchlorate; n = 150; P < 0.05) depolarization increasing apoptosis by 25% (terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling; n = 150; P < 0.05); and 2) decreased intracellular Ca2+ concentration (fluo-3 AM; n = 150; P < 0.05) and proliferation by 30% (PCNA). Finally, in vivo similarly to STAT3 inhibition DHEA improves experimental PAH (monocrotaline rats) by decreasing mean PA pressure and right ventricle hypertrophy. These effects were associated with the inhibition of Src, STAT3, Pim1, NFATc2, and Survivin and the upregulation of BMPR2 and miR-204. We demonstrated that DHEA reverses pulmonary hypertension in part by inhibiting the Src/STAT3.
Nuclear GPCRs in cardiomyocytes: an insider's view of β-adrenergic receptor signaling
Authors: Vaniotis George , Allen Bruce G. , Hébert Terence E.
Published: September 2011

In recent years, we have come to appreciate the complexity of G protein-coupled receptor signaling in general and β-adrenergic receptor (β-AR) signaling in particular. Starting originally from three β-AR subtypes expressed in cardiomyocytes with relatively simple, linear signaling cascades, it is now clear that there are large receptor-based networks which provide a rich and diverse set of responses depending on their complement of signaling partners and the physiological state. More recently, it has become clear that subcellular localization of these signaling complexes also enriches the diversity of phenotypic outcomes. Here, we review our understanding of the signaling repertoire controlled by nuclear β-AR subtypes as well our understanding of the novel roles for G proteins themselves in the nucleus, with a special focus, where possible, on their effects in cardiomyocytes. Finally, we discuss the potential pathological implications of alterations in nuclear β-AR signaling.
High purity human-induced pluripotent stem cell-derived cardiomyocytes: electrophysiological properties of action potentials and ionic currents
Authors: Ma Junyi , Guo Liang , Fiene Steve J. , Anson Blake D. , Thomson James A. , Kamp Timothy J. , Kolaja Kyle L. , Swanson Bradley J. , January Craig T.
Published: September 2011

Human-induced pluripotent stem cells (hiPSCs) can differentiate into functional cardiomyocytes; however, the electrophysiological properties of hiPSC-derived cardiomyocytes have yet to be fully characterized. We performed detailed electrophysiological characterization of highly pure hiPSC-derived cardiomyocytes. Action potentials (APs) were recorded from spontaneously beating cardiomyocytes using a perforated patch method and had atrial-, nodal-, and ventricular-like properties. Ventricular-like APs were more common and had maximum diastolic potentials close to those of human cardiac myocytes, AP durations were within the range of the normal human electrocardiographic QT interval, and APs showed expected sensitivity to multiple drugs (tetrodotoxin, nifedipine, and E4031). Early afterdepolarizations (EADs) were induced with E4031 and were bradycardia dependent, and EAD peak voltage varied inversely with the EAD take-off potential. Gating properties of seven ionic currents were studied including sodium ( INa), L-type calcium ( ICa), hyperpolarization-activated pacemaker ( If), transient outward potassium ( Ito), inward rectifier potassium ( IK1), and the rapidly and slowly activating components of delayed rectifier potassium ( IKr and IKs, respectively) current. The high purity and large cell numbers also enabled automated patch-clamp analysis. We conclude that these hiPSC-derived cardiomyocytes have ionic currents and channel gating properties underlying their APs and EADs that are quantitatively similar to those reported for human cardiac myocytes. These hiPSC-derived cardiomyocytes have the added advantage that they can be used in high-throughput assays, and they have the potential to impact multiple areas of cardiovascular research and therapeutic applications.
Myocardial injury after ischemia-reperfusion in mice deficient in Akt2 is associated with increased cardiac macrophage density
Authors: Li Xue , Mikhalkova Deana , Gao Erhe , Zhang Jin , Myers Valerie , Zincarelli Carmen , Lei Yonghong , Song Jianliang , Koch Walter J. , Peppel Karsten , Cheung Joseph Y. , Feldman Arthur M. , Chan Tung O.
Published: September 2011

Akt2 protein kinase has been shown to promote cell migration and actin polymerization in several cell types, including macrophages. Because migrating macrophages constitute an important inflammatory response after myocardial ischemia, we determined cardiac macrophage expression after ischemia-reperfusion (I/R) injury and cryo-injury in mice lacking Akt2 (Akt2-KO). At 7 days post-I/R, Akt2-KO cardiac tissues showed an increase in immunohistochemical staining for macrophage markers (Galectin 3 and F4/80) compared with wild-type (WT) mice, indicating macrophage density was increased in the injured Akt2-KO myocardium. This change was time dependent because macrophage density was similar between WT and Akt2-KO myocardium at 3 days post-I/R, but by 7 and 14 days post-I/R, macrophage density was significantly increased in Akt2-KO myocardium. Concomitantly, infarct size was larger and cardiac function was reduced in Akt2-KO mice subjected to I/R. However, when cryo-infarction produced similar infarct sizes in the anterior wall in both WT and Akt2-KO mice, macrophage density remained higher in Akt2-KO mouse myocardium, suggesting Akt2 regulates myocardial macrophage density independent of infarct size. Consistently, bone marrow from Akt2-KO mice enhanced myocardial macrophage density in both C57/B6 WT and Akt2-KO recipient mice. Finally, reciprocal ex-vivo coculturing of macrophages and cardiac myocytes showed that activated Akt2-KO peritoneal macrophages had reduced mobility and adhesion when compared with WT littermate controls. Thus, although Akt-2 KO mice did not affect the initial inflammation response after injury and Akt2 deficiency has been shown to impair cell migration or motility in macrophages, our data suggested a novel mechanism in which increasing retention of Akt2-KO macrophages resulted in increasing cardiac Akt2-KO macrophage density in the myocardial space.
Mitochondrial DNA integrity may be a determinant of endothelial barrier properties in oxidant-challenged rat lungs
Authors: Chouteau Joshua M. , Obiako Boniface , Gorodnya Olena M. , Pastukh Viktor M. , Ruchko Mykhaylo V. , Wright Anthony J. , Wilson Glenn L. , Gillespie Mark N.
Published: September 2011

In cultured pulmonary artery endothelial cells and other cell types, overexpression of mt-targeted DNA repair enzymes protects against oxidant-induced mitochondrial DNA (mtDNA) damage and cell death. Whether mtDNA integrity governs functional properties of the endothelium in the intact pulmonary circulation is unknown. Accordingly, the present study used isolated, buffer-perfused rat lungs to determine whether fusion proteins targeting 8-oxoguanine DNA glycosylase 1 (Ogg1) or endonuclease III (Endo III) to mitochondria attenuated mtDNA damage and vascular barrier dysfunction evoked by glucose oxidase (GOX)-generated hydrogen peroxide. We found that both Endo III and Ogg1 fusion proteins accumulated in lung cell mitochondria within 30 min of addition to the perfusion medium. Both constructs prevented GOX-induced increases in the vascular filtration coefficient. Although GOX-induced nuclear DNA damage could not be detected, quantitative Southern blot analysis revealed substantial GOX-induced oxidative mtDNA damage that was prevented by pretreatment with both fusion proteins. The Ogg1 construct also reversed preexisting GOX-induced vascular barrier dysfunction and oxidative mtDNA damage. Collectively, these findings support the ideas that mtDNA is a sentinel molecule governing lung vascular barrier responses to oxidant stress in the intact lung and that the mtDNA repair pathway could be a target for pharmacological intervention in oxidant lung injury.