bluuebunny/crossref_metadata_2025 huggingface dataset:
Aggressive behaviour and physiological responses to pheromones are strongly impaired in mice deficient for the olfactory G‐protein γ‐subunit Gγ8
Authors: Montani Giorgia , Tonelli Simone , Sanghez Valentina , Ferrari Pier Francesco , Palanza Paola , Zimmer Andreas , Tirindelli Roberto
Published: July 2013

Key points

Pheromones are intraspecies chemical signals that take part in the sexual recognition and choice of appropriate mating partners.

In the vomeronasal organ (VNO), pheromone responses are probably triggered by two distinct neuronal populations, respectively expressing the heterotrimeric G‐proteins Gαi2β2γ2 and Gαoβ2γ8 that, in turn, coexpress with two pheromone receptor families, V1R and V2R.

We demonstrate that the olfactory‐specific G‐protein γ8 subunit (Gγ8) plays an important role in pheromone‐dependent socio‐sexual recognition.

Deficient mice for Gγ8 show a marked reduction in the pheromone‐mediated aggressive behaviour in both females and males that corresponds with a failure to activate V2R targets in the brain. These effects occur in combination with a consistent loss of vomeronasal neurons.

Thus, Gγ8 is essential for maintenance of the neuronal population of the VNO and for correct transduction of the pheromonal signal.

Abstract  Heterotrimeric G‐proteins are critical players in the transduction mechanisms underlying odorant and pheromonal signalling. In the vomeronasal organ (VNO) of the adult mouse, two different G‐protein complexes have been identified. Gαoβ2γ8 is preferentially expressed in the basal neurons and coexpresses with type‐2 vomeronasal pheromone receptors (V2Rs) whereas Gαi2β2γ2 is found in the apical neurons and coexpresses with type‐1 vomeronasal pheromone receptors (V1Rs). V2R‐expressing neurons project to the posterior accessory olfactory bulb (AOB) whereas neurons expressing V1Rs send their axon to the anterior AOB. Gγ8 is also expressed in developing olfactory neurons where this protein is probably associated with Go. Here, we generated mice with a targeted deletion of the Gγ8 gene and investigated the behavioural effects and the physiological consequences of this mutation. Gγ8−/− mice show a normal development of the main olfactory epithelium; moreover, they do not display major deficits in odour perception. In contrast, the VNO undergoes a slow but remarkable loss of basal neurons starting from the fourth postnatal week, with a 40% reduction of cells at 2 months and 70% at 1 year. This loss is associated with a reduced early‐gene expression in the posterior AOB of mice stimulated with pheromones. More interestingly, the Gγ8 deletion specifically leads to a reduced pheromone‐mediated aggressiveness in both males and females, all other socio‐sexual behaviours remaining unaltered. This study defines a specific role for Gγ8 in maintenance of the neuronal population of the VNO and in the mechanisms of pheromonal signalling that involve the aggressive behaviour towards conspecifics.
TRPV3: time to decipher a poorly understood family member!
Authors: Nilius Bernd , Bíró Tamás , Owsianik Grzegorz
Published: July 2013

The vanilloid transient receptor potential channel TRPV3 differs in several aspects from other members of the TRPV subfamily. This Ca2+‐, ATP‐ and calmodulin‐regulated channel constitutes a target for many natural compounds and has a unique expression pattern as the most prominent and important TRP channel in keratinocytes of the skin. Although TRPV3 is considered as a thermosensitive channel, its function as a thermosensor in the skin is challenged. Nevertheless, it plays important roles in other skin functions such as cutaneous sensations, hair development and barrier function. More recently, mutations in TRPV3 were linked with a rare genodermatosis known as the Olmsted syndrome. This review gives an overview on properties of TRPV3 and its functions in the skin and skin diseases.
Cardiac calcium signalling pathologies associated with defective calmodulin regulation of type 2 ryanodine receptor
Authors: Arnáiz‐Cot Juan José , Damon Brooke James , Zhang Xiao‐Hua , Cleemann Lars , Yamaguchi Naohiro , Meissner Gerhard , Morad Martin
Published: July 2013

Abstract  Cardiac ryanodine receptor (RyR2) is a homotetramer of 560 kDa polypeptides regulated by calmodulin (CaM), which decreases its open probability at diastolic and systolic Ca2+ concentrations. Point mutations in the CaM‐binding domain of RyR2 (W3587A/L3591D/F3603A, RyR2ADA) in mice result in severe cardiac hypertrophy, poor left ventricle contraction and death by postnatal day 16, suggesting that CaM inhibition of RyR2 is required for normal cardiac function. Here, we report on Ca2+ signalling properties of enzymatically isolated, Fluo‐4 dialysed whole cell clamped cardiac myocytes from 10–15‐day‐old wild‐type (WT) and homozygous Ryr2ADA/ADA mice. Spontaneously occurring Ca2+ spark frequency, measured at −80 mV, was 14‐fold lower in mutant compared to WT myocytes. ICa, though significantly smaller in mutant myocytes, triggered Ca2+ transients that were of comparable size to those of WT myocytes, but with slower activation and decay kinetics. Caffeine‐triggered Ca2+ transients were about three times larger in mutant myocytes, generating three‐ to four‐fold bigger Na+‐Ca2+ exchanger NCX currents (INCX). Mutant myocytes often exhibited Ca2+ transients of variable size and duration that were accompanied by similarly alternating and slowly activating INCX. The data suggest that RyR2ADA mutation produces significant reduction in ICa density and ICa‐triggered Ca2+ release gain, longer but infrequently occurring Ca2+ sparks, larger sarcoplasmic reticulum Ca2+ loads, and spontaneous Ca2+ releases accompanied by activation of large and potentially arrhythmogenic inward INCX.
Length dependence of striated muscle force generation is controlled by phosphorylation of cTnI at serines 23/24
Authors: Hanft Laurin M. , Biesiadecki Brandon J. , McDonald Kerry S.
Published: July 2013

Key points

An important mechanism in beat‐to‐beat optimization of heart performance is matching ventricular output with end‐diastolic volume, which is known as the Frank–Starling Relationship.

The cellular basis for this regulation involves myofilament length–tension relationships.

We previously showed two populations of length–tension relationships in mammalian left ventricular cardiac myocytes, one steep like fast‐twitch skeletal muscle fibres and the other shallow like slow‐twitch skeletal muscle fibres, and cardiac myocytes with shallow length–tension relationships shift to steep relationships by protein kinase A‐induced myofilament phosphorylation.

The current study investigated the molecular and amino acid residue mechanisms that control length–tension relationships.

The single muscle cell experiments demonstrated that cardiac troponin I phosphorylation at serines 23/24 control length–tension relationships in striated muscle.

This study provides: (i) a mechanism to explain a length dependence of force generation in striated muscle; and (ii) an important target to potentially treat heart disease associated with compromised Frank–Starling relationships.

Abstract  According to the Frank–Starling relationship, greater end‐diastolic volume increases ventricular output. The Frank–Starling relationship is based, in part, on the length–tension relationship in cardiac myocytes. Recently, we identified a dichotomy in the steepness of length–tension relationships in mammalian cardiac myocytes that was dependent upon protein kinase A (PKA)‐induced myofibrillar phosphorylation. Because PKA has multiple myofibrillar substrates including titin, myosin‐binding protein‐C and cardiac troponin I (cTnI), we sought to define if phosphorylation of one of these molecules could control length–tension relationships. We focused on cTnI as troponin can be exchanged in permeabilized striated muscle cell preparations, and tested the hypothesis that phosphorylation of cTnI modulates length dependence of force generation. For these experiments, we exchanged unphosphorylated recombinant cTn into either a rat cardiac myocyte preparation or a skinned slow‐twitch skeletal muscle fibre. In all cases unphosphorylated cTn yielded a shallow length–tension relationship, which was shifted to a steep relationship after PKA treatment. Furthermore, exchange with cTn having cTnI serines 23/24 mutated to aspartic acids to mimic phosphorylation always shifted a shallow length–tension relationship to a steep relationship. Overall, these results indicate that phosphorylation of cTnI serines 23/24 is a key regulator of length dependence of force generation in striated muscle.
A Set-Point Control for a Two-link Underactuated Robot With a Flexible Elbow Joint
Authors: Xin Xin , Liu Yannian
Published: July 2013

This paper concerns a set-point control problem for a two-link underactuated robot moving in the vertical plane with a single actuator at the first joint and a spring between the two links (flexible elbow joint). First, we present two new properties of such a flexible robot about the linear controllability at the upright equilibrium point (UEP, where two links are in the upright position) and about its equilibrium configuration. Second, we show that for the robot with a certain range of spring constant, the proportional derivative (PD) control on the angle of the first joint can globally stabilize the robot at the UEP. Third, for the robot not satisfying the above range of spring constant, we study how to extend the energy-based control approach, which aims to control the total mechanical energy and the angle and angular velocity of the first joint of the robot, to design a swing-up controller. We provide a necessary and sufficient condition for avoiding the singularity in the controller, and we analyze the motion of the robot under the presented controller by studying the convergence of the total mechanical energy and clarifying the structure and stability of the closed-loop equilibrium points. We present the results of numerical investigation, which support our theoretical conclusions.
Blockade of Glioma Proliferation Through Allosteric Inhibition of JAK2
Authors: He Kunyan , Qi Qi , Chan Chi-Bun , Xiao Ge , Liu Xia , Tucker-Burden Carol , Wang Liya , Mao Hui , Lu Xiang , McDonald Frank E. , Luo Hongbo , Fan Qi-Wen , Weiss William A. , Sun Shi-Yong , Brat Daniel J. , Ye Keqiang
Published: July 2013

An allosteric inhibitor of the kinase JAK2 impedes the growth of aggressive glioblastoma.
Presenilins and Calcium Signaling—Systems Biology to the Rescue
Authors: Bezprozvanny Ilya
Published: July 2013

New results support function of presenilins as endoplasmic reticulum calcium leak channels.
Science Signaling
Podcast: 9 July 2013
Authors: Ye Keqiang , VanHook Annalisa M.
Published: July 2013

A small-molecule inhibitor of the kinase JAK2 blocks proliferation of glioblastoma cells.
RGM Proteins
Authors: Ray L. Bryan
Published: July 2013

A complex of a guidance molecule and its receptor reveals how signals cross the membrane.
Enhancer-Targeted Immunosuppression
Authors: Ferrarelli Leslie K.
Published: July 2013

The Rev-Erb nuclear receptor family represses gene transcription in macrophages indirectly by inhibiting the transcription of enhancer-derived RNAs.
Autonomous Cycling in a Shared Cytoplasm
Authors: VanHook Annalisa M.
Published: July 2013

Localization of cyclin transcripts enables nuclei sharing a common cytoplasm to divide autonomously.
Delivering a Mixed Message
Authors: Gough Nancy R.
Published: July 2013

Blood vessel endothelial cells deliver messages triggering both quiescence and proliferation of tumor cells.
Relative Fecal Abundance of Extended-Spectrum-β-Lactamase-Producing Escherichia coli Strains and Their Occurrence in Urinary Tract Infections in Women
Authors: Ruppé Etienne , Lixandru Brandusa , Cojocaru Radu , Büke Çağrı , Paramythiotou Elisabeth , Angebault Cécile , Visseaux Claire , Djuikoue Ingrid , Erdem Esra , Burduniuc Olga , El Mniai Assiya , Marcel Candice , Perrier Marion , Kesteman Thomas , Clermont Olivier , Denamur Erick , Armand-Lefèvre Laurence , Andremont Antoine
Published: July 2013

Extended-spectrum-beta-lactamase (ESBL)-producing
Escherichia coli
(ESBL
E. coli
) strains are of major concern because few antibiotics remain active against these bacteria. We investigated the association between the fecal relative abundance (RA) of ESBL-producing
E. coli
(ESBL-RA) and the occurrence of ESBL
E. coli
urinary tract infections (UTIs). The first stool samples passed after suspicion of UTI from 310 women with subsequently confirmed
E. coli
UTIs were sampled and tested for ESBL-RA by culture on selective agar. Predictive values of ESBL-RA for ESBL
E. coli
UTI were analyzed for women who were not exposed to antibiotics when the stool was passed. ESBL
E. coli
isolates were characterized for ESBL type, phylogroup, relatedness, and virulence factors. The prevalence of ESBL
E. coli
fecal carriage was 20.3%, with ESBL
E. coli
UTIs being present in 12.3% of the women. The mean ESBL-RA (95% confidence interval [CI]) was 13-fold higher in women exposed to antibiotics at the time of sampling than in those not exposed (14.3% [range, 5.6% to 36.9%] versus 1.1% [range, 0.32% to 3.6%], respectively;
P
< 0.001) and 18-fold higher in women with ESBL
E. coli
UTI than in those with another
E. coli
UTI (10.0% [range, 0.54% to 100%] versus 0.56% [range, 0.15% to 2.1%[, respectively;
P
< 0.05). An ESBL-RA of <0.1% was 100% predictive of a non-ESBL
E. coli
UTI. ESBL type, phylogroup, relatedness, and virulence factors were not found to be associated with ESBL-RA. In conclusion, ESBL-RA was linked to the occurrence of ESBL
E. coli
UTI in women who were not exposed to antibiotics and who had the same clone of
E. coli
in urine samples and fecal samples. Especially, a low ESBL-RA appeared to be associated with a low risk of ESBL
E. coli
infection.
Efficacy of Ceftaroline Fosamil against Penicillin-Sensitive and -Resistant Streptococcus pneumoniae in an Experimental Rabbit Meningitis Model
Authors: Cottagnoud P. , Cottagnoud M. , Acosta F. , Stucki A.
Published: July 2013

Ceftaroline is a new cephalosporin with bactericidal activity against resistant Gram-positive organisms, including methicillin-resistant
Staphylococcus aureus
(MRSA) and penicillin-resistant
Streptococcus pneumoniae
, as well as common Gram-negative organisms. This study tested the prodrug, ceftaroline fosamil, against a penicillin-sensitive and a penicillin-resistant strain of
S. pneumoniae
in an experimental rabbit meningitis model. The penetration of ceftaroline into inflamed meninges was approximately 14%. Ceftaroline fosamil was slightly superior to ceftriaxone against the penicillin-sensitive strain and significantly superior to the combination of ceftriaxone and vancomycin against the penicillin-resistant strain.
Antimicrobial Activity of the Pleuromutilin Antibiotic BC-3781 against Bacterial Pathogens Isolated in the SENTRY Antimicrobial Surveillance Program in 2010
Authors: Paukner Susanne , Sader Helio S. , Ivezic-Schoenfeld Zrinka , Jones Ronald N.
Published: July 2013

BC-3781 is a novel semisynthetic pleuromutilin antibiotic inhibiting bacterial protein synthesis. BC-3781 has completed a phase 2 clinical trial in acute bacterial skin and skin structure infections (ABSSSI). Its antibacterial spectrum additionally covers the predominant pathogens causing community-acquired bacterial pneumonia (CABP). In this study, the antibacterial activity of BC-3781 was evaluated against a contemporary collection of 10,035 bacterial isolates predominately causing ABSSSI and CABP, among other infections, collected within the SENTRY Antimicrobial Surveillance Program worldwide in 2010. BC-3781 exhibited potent activity against organisms commonly isolated from ABSSSI such as
Staphylococcus aureus
(MIC
50/90
, 0.12/0.12 μg/ml; 99.8% inhibited at ≤0.5 μg/ml), beta-hemolytic streptococci (MIC
50/90
, 0.03/0.03 μg/ml; 99.3% inhibited at ≤0.5 μg/ml), and coagulase-negative staphylococci (CoNS; MIC
50/90
, 0.06/0.12 μg/ml; 97.8% inhibited at ≤1 μg/ml). BC-3781 displayed similar MIC distributions among methicillin-susceptible (MSSA) and methicillin-resistant (MRSA)
S. aureus
strains. BC-3781 was also active against
Enterococcus faecium
, with 76.3% of vancomycin-susceptible and 97.0% of vancomycin-resistant isolates being inhibited at BC-3781 concentrations of ≤1 μg/ml. Beta-hemolytic and viridans group streptococci were highly susceptible to BC-3781, with 99.3% and 96.7% of isolates inhibited at ≤0.5 μg/ml, respectively. Further, activity of BC-3781 against
Streptococcus pneumoniae
(MIC
50/90
, 0.12/0.25 μg/ml),
Haemophilus influenzae
(MIC
50/90
, 1/2 μg/ml), and
Moraxella catarrhalis
(MIC
50/90
, 0.12/0.25 μg/ml) was not negatively influenced by β-lactamase production or resistance to other antimicrobial classes tested. In all, BC-3781 displayed a very potent antibacterial profile including the most prevalent bacterial pathogens causing ABSSSI and CABP, thus warranting further clinical development of this antibiotic in these and possibly other indications.
The Perfidious Effect of Topical Placebo: Calibration of Staphylococcus aureus Ventilator-Associated Pneumonia Incidence within Selective Digestive Decontamination Studies versus the Broader Evidence Base
Authors: Hurley James C.
Published: July 2013

Among various methods for preventing ventilator-associated pneumonia (VAP), the evidence base for selective digestive decontamination (SDD) appears most compelling. However, the extent of
Staphylococcus aureus
emergence with SDD use remains uncertain. Groups from 37 observational studies and component (control and intervention) groups from 58 studies of SDD and other methods of VAP prevention were sourced exclusively from 10 systematic reviews.
S. aureus
as a proportion of VAP isolates (
S. aureus
isolate proportion [
S. aureus
IP]) among component groups was calibrated versus that among observational groups (the benchmark). The influence of topical placebo used for blinding purposes and other group-level factors was estimated using generalized estimating equation methods (GEE). The mean
S. aureus
IP is 22% (95% confidence interval [CI], 19 to 25) for 37 observational groups versus 32% (24 to 41) and 20% (15 to 25) for 22 control groups from the SDD evidence base which did versus did not receive topical placebo, respectively. In GEE models including all 148 observational and component groups, membership of a control (
P
= 0.03) or intervention (
P
< 0.001) group of an SDD study that used topical placebo was associated with higher
S. aureus
IP, whereas, in contrast, membership of these groups was without effect on
Pseudomonas aeruginosa
. Topical placebo is implicated as a vehicle for selective cross-infection with
S. aureus
within the specific context of the SDD evidence base. This effect of topical placebo is perfidious; it could contribute to the higher VAP incidence and inflate the apparent “effectiveness” of SDD. The SDD evidence base requires reappraisal.
Impact of Fluoroquinolone Resistance on Bactericidal and Sterilizing Activity of a Moxifloxacin-Containing Regimen in Murine Tuberculosis
Authors: Fillion Aurélie , Aubry Alexandra , Brossier Florence , Chauffour Aurélie , Jarlier Vincent , Veziris Nicolas
Published: July 2013

It has been shown previously that fluoroquinolone resistance (defined by resistance to at least 2 mg/liter ofloxacin) has a different impact on moxifloxacin monotherapy depending on the mutation in the sole fluoroquinolone target in
Mycobacterium tuberculosis
, i.e., DNA gyrase. Since tuberculosis treatment relies on multidrug therapy, we wished to determine the impact of fluoroquinolone resistance on the bactericidal and sterilizing activity of a second-line antituberculous regimen containing moxifloxacin. A total of 280 mice were inoculated with the wild-type
Mycobacterium tuberculosis
H37Rv strain or one of 3 isogenic fluoroquinolone-resistant mutant strains with increasing moxifloxacin resistance (the GyrB D500N, GyrA A90V, and GyrA D94G strains) and then treated for 6 months with a second-line regimen containing moxifloxacin, pyrazinamide, and ethionamide supplemented with amikacin during the first 2 months. Mice were sacrificed during treatment for measurement of bactericidal activity and 3 months after treatment completion for measurement of relapse rates (sterilizing activity). The CFU counts decreased faster in mice inoculated with the wild type than in mice inoculated with the mutant strains. The relapse rate after treatment completion was different among mice inoculated with mutant strains in relation to the drug resistance level: wild type, 0%; GyrB D500N strain, 33%; GyrA A90V strain, 50%; and GyrA D94G strain, 86%. The relapse rate observed with the GyrB D500N strain was the only one not statistically different from that observed with the wild-type strain. We demonstrated that the impact on sterilizing activity of the most active second-line drug regimen containing moxifloxacin depends on the MIC of moxifloxacin. We suggest that the precise level of moxifloxacin resistance be determined for all strains resistant to 2 mg/liter ofloxacin.
Correlations of Antibiotic Use and Carbapenem Resistance in Enterobacteriaceae
Authors: McLaughlin Milena , Advincula M. Renee , Malczynski Michael , Qi Chao , Bolon Maureen , Scheetz Marc H.
Published: July 2013

Epidemiological studies have shown a link between carbapenem use and resistance; however, the clinical relationship between antibiotic consumption and the epidemiology of carbapenem-intermediate or -resistant
Enterobacteriaceae
(CIRE) remains unclear. This study sought to analyze temporal antibiotic consumption trends for relationships with incident CIRE. In total, 310,892 days of therapy and 55 deduplicated CIRE were analyzed. When conservative corrections were applied for multiple comparisons, carbapenem class use and piperacillin-tazobactam use retained significant positive and negative relationships with the incidence of CIRE, respectively.
Membrane Perturbation Action Mode and Structure-Activity Relationships of Protonectin, a Novel Antimicrobial Peptide from the Venom of the Neotropical Social Wasp Agelaia pallipes pallipes
Authors: Wang Kairong , Dang Wen , Yan Jiexi , Chen Ru , Liu Xin , Yan Wenjin , Zhang Bangzhi , Xie Junqiu , Zhang Jindao , Wang Rui
Published: July 2013

With the extensive use of antibiotics, multidrug-resistant bacteria emerge frequently. New antimicrobial agents with novel modes of action are urgently needed. It is now widely accepted that antimicrobial peptides (AMPs) could be promising alternatives to conventional antibiotics. In this study, we aimed to study the antimicrobial activity and mechanism of action of protonectin, a cationic peptide from the venom of the neotropical social wasp
Agelaia pallipes pallipes
. We demonstrated that protonectin exhibits potent antimicrobial activity against a spectrum of bacteria, including multidrug-resistant strains. To further understand this mechanism, the structural features of protonectin and its analogs were studied by circular dichroism (CD). The CD spectra demonstrated that protonectin and its natural analog polybia-CP formed a typical α-helical conformation in the membrane-mimicking environment, while its proline-substituted analog had much lower or even no α-helix conformation. Molecular dynamics simulations indicated that the α-helical conformation in the membrane is required for the exhibition of antibacterial activity. In conclusion, protonectin exhibits potent antimicrobial activity by disruption of the integrity of the bacterial membrane, and its α-helical confirmation in the membrane is essential for this action.
Biochemical Characterization of IMP-30, a Metallo-β-Lactamase with Enhanced Activity toward Ceftazidime
Authors: Pegg Kevin M. , Liu Eleanor M. , LaCuran Alecander E. , Oelschlaeger Peter
Published: July 2013

IMP-type enzymes constitute a clinically important family of metallo-β-lactamases that has grown dramatically in the past decade to its current 45 known members. Here, we report the biochemical characterization of IMP-30 in comparison to IMP-1, from which it deviates by a single E59K mutation. Kinetics, MIC assays, docking, and molecular dynamics simulations support a scenario in which Lys59 interacts with the ceftazidime R
1
group, resulting in increased water access and enhanced turnover and MIC of ceftazidime.
Plasmodium Dipeptidyl Aminopeptidases as Malaria Transmission-Blocking Drug Targets
Authors: Tanaka Takeshi Q , Deu Edgar , Molina-Cruz Alvaro , Ashburne Michael J. , Ali Omar , Suri Amreena , Kortagere Sandhya , Bogyo Matthew , Williamson Kim C.
Published: July 2013

The
Plasmodium falciparum
and
P. berghei
genomes each contain three dipeptidyl aminopeptidase (
dpap
) homologs.
dpap1
and -3 are critical for asexual growth, but the role of
dpap2
, the gametocyte-specific homolog, has not been tested. If DPAPs are essential for transmission as well as asexual growth, then a DPAP inhibitor could be used for treatment and to block transmission. To directly analyze the role of DPAP2, a
dpap2
-minus
P. berghei
(
Pbdpap2
Δ) line was generated. The
Pbdpap2
Δ parasites grew normally, differentiated into gametocytes, and generated sporozoites that were infectious to mice when fed to a mosquito. However,
Pbdpap1
transcription was >2-fold upregulated in the
Pbdpap2
Δ clonal lines, possibly compensating for the loss of
Pbdpap2
. The role of DPAP1 and -3 in the
dpap2
Δ parasites was then evaluated using a DPAP inhibitor, ML4118S. When ML4118S was added to the
Pbdpap2
Δ parasites just before a mosquito membrane feed, mosquito infectivity was not affected. To assess longer exposures to ML4118S and further evaluate the role of DPAPs during gametocyte development in a parasite that causes human malaria, the
dpap2
deletion was repeated in
P. falciparum
. Viable
P. falciparum dpap2
(
Pfdpap2
)-minus parasites were obtained that produced morphologically normal gametocytes. Both wild-type and
Pfdpap2
-negative parasites were sensitive to ML4118S, indicating that, unlike many antimalarials, ML4118S has activity against parasites at both the asexual and sexual stages and that DPAP1 and -3 may be targets for a dual-stage drug that can treat patients and block malaria transmission.
T4-Like Phage Bp7, a Potential Antimicrobial Agent for Controlling Drug-Resistant Escherichia coli in Chickens
Authors: Zhang Can , Li Wenli , Liu Wenhua , Zou Ling , Yan Chen , Lu Kai , Ren Huiying
Published: July 2013

Chicken-pathogenicEscherichia coliis severely endangering the poultry industry in China and worldwide, and antibiotic therapy is facing an increasing problem of antibiotic resistance. Bacteriophages can kill bacteria with no known activity in human or animal cells, making them an attractive alternative to antibiotics. In this study, we present the characteristics of a novel virulent bacteriophage, Bp7, specifically infecting pathogenic multidrug-resistantE. coli. Phage Bp7 was isolated from chicken feces. Bp7 belongs to the familyMyoviridae, possessing an elongated icosahedral head and contractile sheathed tail. It has a 168-kb double-stranded DNA genome. For larger yields, its optimal multiplicity of infection (MOI) to infectE. coliwas about 0.001. The latent period was 10 to 15 min, and the burst size was 90 PFU/infected cell. It was stable both at pH 5.0 to 10.0 and at 40°C or 50°C for at least 1 h. Bp7 could infect 46% of pathogenic clinicalE. colistrains. Bp7 harbored 791 open reading frames (ORFs) and 263 possible genes. Among the 263 genes, 199 possessed amino acid sequence identities with ORFs of phage T4, 62 had identities with other T4-like phages, and only one lacked any database match. The genome of Bp7 manifested obvious division and rearrangement compared to phages T4, JS98, and IME08. Bp7 is a new member of the “T4-like” genus, familyMyoviridae. Its wide host range, strong cell-killing activity, and high stability to pH make it an alternative to antimicrobials for controlling drug-resistantE. coliin chickens.
prfA
-Like Transcription Factor Gene
lmo0753
Contributes to
l
-Rhamnose Utilization in Listeria monocytogenes Strains Associated with Human Food-Borne Infections
Authors: Salazar Joelle K. , Wu Zhuchun , McMullen P. David , Luo Qin , Freitag Nancy E. , Tortorello Mary Lou , Hu Shencai , Zhang Wei
Published: July 2013

Listeria monocytogenes
is a food-borne bacterial pathogen and the causative agent of human and animal listeriosis. Among the three major genetic lineages of
L. monocytogenes
(i.e., LI, LII, and LIII), LI and LII are predominantly associated with food-borne listeriosis outbreaks, whereas LIII is rarely implicated in human infections. In a previous study, we identified a Crp/Fnr family transcription factor gene,
lmo0753
, that was highly specific to outbreak-associated LI and LII but absent from LIII. Lmo0753 shares two conserved functional domains, including a DNA binding domain, with the well-characterized master virulence regulator PrfA in
L. monocytogenes
. In this study, we constructed
lmo0753
deletion and complementation mutants in two fully sequenced
L. monocytogenes
LII strains, 10403S and EGDe, and compared the flagellar motility, phospholipase C production, hemolysis, and intracellular growth of the mutants and their respective wild types. Our results suggested that
lmo0753
plays a role in hemolytic activity in both EGDe and 10403S. More interestingly, we found that deletion of
lmo0753
led to the loss of
l
-rhamnose utilization in EGDe, but not in 10403S. RNA-seq analysis of EGDe Δ
0753
incubated in phenol red medium containing
l
-rhamnose as the sole carbon source revealed that 126 (4.5%) and 546 (19.5%) out of 2,798 genes in the EGDe genome were up- and downregulated more than 2-fold, respectively, compared to the wild-type strain. Genes related to biotin biosynthesis, general stress response, and rhamnose metabolism were shown to be differentially regulated. Findings from this study collectively suggested varied functional roles of
lmo0753
in different LII
L. monocytogenes
strain backgrounds associated with human listeriosis outbreaks.
Bacillus subtilis Strain Engineered for Treatment of Soil-Transmitted Helminth Diseases
Authors: Hu Yan , Miller Melanie M. , Derman Alan I. , Ellis Brian L. , Monnerat Rose Gomes , Pogliano Joe , Aroian Raffi V.
Published: July 2013

Soil-transmitted helminths (hookworms, whipworms, and large roundworms) are agents of intestinal roundworm diseases of poverty that infect upwards of 2 billion people worldwide. A great challenge in treating these diseases is the development of anthelmintic therapeutics that are inexpensive, can be produced in great quantity, and are capable of delivery under varied and adverse environmental conditions. A potential solution to this challenge is the use of live bacteria that are acceptable for human consumption, e.g.,
Bacillus subtilis
, and that can be engineered with therapeutic properties. In this study, we expressed the
Bacillus thuringiensis
anthelmintic protein Cry5B in a bacterial strain that has been used as a model for live bacterial therapy,
Bacillus subtilis
PY79. PY79 transformed with a Cry5B expression plasmid (PY79-Cry5B) is able to express Cry5B from the endogenous
B. thuringiensis cry5B
promoter. During sporulation of PY79-Cry5B, Cry5B is packaged as a crystal. Furthermore, Cry5B produced in PY79 is bioactive, with a 50% lethal concentration (LC
50
) of 4.3 μg/ml against the roundworm
Caenorhabditis elegans
. PY79-Cry5B was a significantly effective therapeutic in experimental
Ancylostoma ceylanicum
hookworm infections of hamsters. A single 10-mg/kg (0.071 μmol/kg of body weight) dose of Cry5B administered as a Cry5B-PY79 spore crystal lysate achieved a 93% reduction in hookworm burdens, which is superior on a molar level to reductions seen with clinically used anthelmintics. Given that a bacterial strain such as this one can be produced cheaply in massive quantities, our results demonstrate that the engineering and delivery of live bacterial strains have great potential to treat a significant contributor to poverty worldwide, namely, hookworm disease and other soil-transmitted helminthiasis.
Conserved Regions of Gonococcal TbpB Are Critical for Surface Exposure and Transferrin Iron Utilization
Authors: Ostberg Karen L. , DeRocco Amanda J. , Mistry Shreni D. , Dickinson Mary Kathryne , Cornelissen Cynthia Nau
Published: July 2013

The transferrin-binding proteins TbpA and TbpB enable
Neisseria gonorrhoeae
to obtain iron from human transferrin. The lipoprotein TbpB facilitates, but is not strictly required for, TbpA-mediated iron acquisition. The goal of the current study was to determine the contribution of two conserved regions within TbpB to the function of this protein. Using site-directed mutagenesis, the first mutation we constructed replaced the lipobox (LSAC) of TbpB with a signal I peptidase cleavage site (LAAA), while the second mutation deleted a conserved stretch of glycine residues immediately downstream of the lipobox. We then evaluated the resulting mutants for effects on TbpB expression, surface exposure, and transferrin iron utilization. Western blot analysis and palmitate labeling indicated that the lipobox, but not the glycine-rich motif, is required for lipidation of TbpB and tethering to the outer membrane. TbpB was released into the supernatant by the mutant that produces TbpB LSAC. Neither mutation disrupted the transport of TbpB across the bacterial cell envelope. When these mutant TbpB proteins were produced in a strain expressing a form of TbpA that requires TbpB for iron acquisition, growth on transferrin was either abrogated or dramatically diminished. We conclude that surface tethering of TbpB is required for optimal performance of the transferrin iron acquisition system, while the presence of the polyglycine stretch near the amino terminus of TbpB contributes significantly to transferrin iron transport function. Overall, these results provide important insights into the functional roles of two conserved motifs of TbpB, enhancing our understanding of this critical iron uptake system.
Modeling Klebsiella pneumoniae Pathogenesis by Infection of the Wax Moth Galleria mellonella
Authors: Insua José Luis , Llobet Enrique , Moranta David , Pérez-Gutiérrez Camino , Tomás Anna , Garmendia Junkal , Bengoechea José A.
Published: July 2013

The implementation of infection models that approximate human disease is essential for understanding pathogenesis at the molecular level and for testing new therapies before they are entered into clinical stages. Insects are increasingly being used as surrogate hosts because they share, with mammals, essential aspects of the innate immune response to infections. We examined whether the larva of the wax mothGalleria mellonellacould be used as a host model to conceptually approximateKlebsiella pneumoniae-triggered pneumonia. We report that theG. mellonellamodel is capable of distinguishing between pathogenic and nonpathogenicKlebsiellastrains. Moreover,K. pneumoniaeinfection ofG. mellonellamodels some of the known features ofKlebsiella-induced pneumonia, i.e., cell death associated with bacterial replication, avoidance of phagocytosis by phagocytes, and the attenuation of host defense responses, chiefly the production of antimicrobial factors. Similar to the case for the mouse pneumonia model, activation of innate responses improvedG. mellonellasurvival against subsequentKlebsiellachallenge. Virulence factors necessary in the mouse pneumonia model were also implicated in theGalleriamodel. We found that mutants lacking capsule polysaccharide, lipid A decorations, or the outer membrane proteins OmpA and OmpK36 were attenuated inGalleria. All mutants activatedG. mellonelladefensive responses. TheGalleriamodel also allowed us to monitorKlebsiellagene expression. The expression levels ofcpsand the loci implicated in lipid A remodeling peaked during the first hours postinfection, in a PhoPQ- and PmrAB-governed process. Taken together, these results support the utility ofG. mellonellaas a surrogate host for assessing infections withK. pneumoniae.
H-NS Is a Negative Regulator of the Two Hemolysin/Cytotoxin Gene Clusters in Vibrio anguillarum
Authors: Mou Xiangyu , Spinard Edward J. , Driscoll Maureen V. , Zhao Wenjing , Nelson David R.
Published: July 2013

Hemolysins produced by
Vibrio anguillarum
have been implicated in the development of hemorrhagic septicemia during vibriosis, a fatal fish disease. Previously, two hemolysin gene clusters responsible for the hemolysis and cytotoxicity of
V. anguillarum
were identified: the
vah1-plp
gene cluster and the
rtxACHBDE
gene cluster. In this study, we identified the
hns
gene, which encodes the H-NS protein and acts as a negative regulator of both gene clusters. The
V. anguillarum
H-NS protein shares strong homology with other bacterial H-NS proteins. An
hns
mutant exhibited increased hemolytic activity and cytotoxicity compared to the wild-type strain. Complementation of the
hns
mutation restored hemolytic activity and cytotoxicity levels to nearly wild-type levels. Furthermore, expression of
rtxA
,
rtxH
,
rtxB
,
vah1
, and
plp
increased in the
hns
mutant and decreased in the
hns
-complemented mutant strain compared to expression in the wild-type strain. Additionally, experiments using DNase I showed that purified recombinant H-NS protected multiple sites in the promoter regions of both gene clusters. The
hns
mutant also exhibited significantly attenuated virulence against rainbow trout. Complementation of the
hns
mutation restored virulence to wild-type levels, suggesting that H-NS regulates many genes that affect fitness and virulence. Previously, we showed that HlyU is a positive regulator of expression for both gene clusters. In this study, we demonstrate that upregulation by
hlyU
is
hns
dependent, suggesting that H-NS acts to repress or silence both gene clusters and HlyU acts to relieve that repression or silencing.
Immunization with Apical Membrane Antigen 1 Confers Sterile Infection-Blocking Immunity against Plasmodium Sporozoite Challenge in a Rodent Model
Authors: Schussek Sophie , Trieu Angela , Apte Simon H. , Sidney John , Sette Alessandro , Doolan Denise L.
Published: July 2013

Apical membrane antigen 1 (AMA-1) is a leading blood-stage malaria vaccine candidate. Consistent with a key role in erythrocytic invasion, AMA-1-specific antibodies have been implicated in AMA-1-induced protective immunity. AMA-1 is also expressed in sporozoites and in mature liver schizonts where it may be a target of protective cell-mediated immunity. Here, we demonstrate for the first time that immunization with AMA-1 can induce sterile infection-blocking immunity againstPlasmodiumsporozoite challenge in 80% of immunized mice. Significantly higher levels of gamma interferon (IFN-γ)/interleukin-2 (IL-2)/tumor necrosis factor (TNF) multifunctional T cells were noted in immunized mice than in control mice. We also report the first identification of minimal CD8+and CD4+T cell epitopes onPlasmodium yoeliiAMA-1. These data establish AMA-1 as a target of both preerythrocytic- and erythrocytic-stage protective immune responses and validate vaccine approaches designed to induce both cellular and humoral immunity.
Sequestration and Scavenging of Iron in Infection
Authors: Parrow Nermi L. , Fleming Robert E. , Minnick Michael F.
Published: July 2013

The proliferative capability of many invasive pathogens is limited by the bioavailability of iron. Pathogens have thus developed strategies to obtain iron from their host organisms. In turn, host defense strategies have evolved to sequester iron from invasive pathogens. This review explores the mechanisms employed by bacterial pathogens to gain access to host iron sources, the role of iron in bacterial virulence, and iron-related genes required for the establishment or maintenance of infection. Host defenses to limit iron availability for bacterial growth during the acute-phase response and the consequences of iron overload conditions on susceptibility to bacterial infection are also examined. The evidence summarized herein demonstrates the importance of iron bioavailability in influencing the risk of infection and the ability of the host to clear the pathogen.
LL-37 Opsonizes and Inhibits Biofilm Formation of Aggregatibacter actinomycetemcomitans at Subbactericidal Concentrations
Authors: Sol Asaf , Ginesin Ofir , Chaushu Stella , Karra Laila , Coppenhagen-Glazer Shunit , Ginsburg Isaac , Bachrach Gilad
Published: July 2013

Host defense peptides are immediate responders of the innate immunity that express antimicrobial, immunoregulatory, and wound-healing activities. Neutrophils are a major source for oral host defense peptides, and phagocytosis by neutrophils is a major mechanism for bacterial clearance in the gingival tissue. Dysfunction of or reduction in the numbers of neutrophils or deficiency in the LL-37 host defense peptide was each previously linked with proliferation of oral
Aggregatibacter actinomycetemcomitans
which resulted in an aggressive periodontal disease. Surprisingly,
A. actinomycetemcomitans
shows resistance to high concentrations of LL-37. In this study, we demonstrated that submicrocidal concentrations of LL-37 inhibit biofilm formation by
A. actinomycetemcomitans
and act as opsonins and agglutinins that greatly enhance its clearance by neutrophils and macrophages. Improved uptake of
A. actinomycetemcomitans
by neutrophils was mediated by their opsonization with LL-37. Enhanced phagocytosis and killing of
A. actinomycetemcomitans
by murine macrophage-like RAW 264.7 cells were dependent on their preagglutination by LL-37. Although
A. actinomycetemcomitans
is resistant to the bactericidal effect of LL-37, our results offer a rationale for the epidemiological association between LL-37 deficiency and the expansion of oral
A. actinomycetemcomitans
and indicate a possible therapeutic use of cationic peptides for host defense.
Interwoven Biology of the Tsetse Holobiont
Authors: Snyder Anna K. , Rio Rita V. M.
Published: July 2013

Microbial symbionts can be instrumental to the evolutionary success of their hosts. Here, we discuss medically significant tsetse flies (Diptera: Glossinidae), a group comprised of over 30 species, and their use as a valuable model system to study the evolution of the holobiont (i.e., the host and associated microbes). We first describe the tsetse microbiota, which, despite its simplicity, harbors a diverse range of associations. The maternally transmitted microbes consistently include two
Gammaproteobacteria
, the obligate mutualists
Wigglesworthia
spp. and the commensal
Sodalis glossinidius
, along with the parasitic
Alphaproteobacteria Wolbachia
. These associations differ in their establishment times, making them unique and distinct from previously characterized symbioses, where multiple microbial partners have associated with their host for a significant portion of its evolution. We then expand into discussing the functional roles and intracommunity dynamics within this holobiont, which enhances our understanding of tsetse biology to encompass the vital functions and interactions of the microbial community. Potential disturbances influencing the tsetse microbiome, including salivary gland hypertrophy virus and trypanosome infections, are highlighted. While previous studies have described evolutionary consequences of host association for symbionts, the initial steps facilitating their incorporation into a holobiont and integration of partner biology have only begun to be explored. Research on the tsetse holobiont will contribute to the understanding of how microbial metabolic integration and interdependency initially may develop within hosts, elucidating mechanisms driving adaptations leading to cooperation and coresidence within the microbial community. Lastly, increased knowledge of the tsetse holobiont may also contribute to generating novel African trypanosomiasis disease control strategies.
Dam removal
Authors: Wildman Laura
Published: July 2013

In the northeastern United States, we have been removing dams for almost as long as we have been building them, yet many communities involved in current decisions to repair, replace, or remove a dam are not aware of this. This paper highlights some of the stories that have been recorded regarding the history of decision points for dams, including the colorful history of the Billerica Dam in Massachusetts, which has been removed and rebuilt numerous times and is now under consideration for removal for at least the sixth time in its 300 yr history.

By understanding that dam removal is just one of the potential dam safety decisions that needs to be analyzed over the life cycle of a dam, and that dams are man-made structures with finite life spans, we can deconstruct the notion of dam removal as a radical concept. Dam removal is just one of many dam safety options that may be discussed over the course of a dam’s history. It is most commonly implemented when a dam no longer serves any economic purpose that justifies the expense of maintaining the dam structure.

In the past, dams have been removed for many of the same reasons that we remove dams today; however, the procedures currently required to remove a dam are far more complex and highly regulated. This has led to increased documentation of dam removal efforts and now allows us to compare and categorize dam removal projects, such that the lessons learned from these projects can be incorporated into a more informed decision-making process in the future.
Sediment management at small dam removal sites
Authors: MacBroom James G. , Schiff Roy
Published: July 2013

The removal of obsolete and unsafe dams for safety, environmental, or economic purposes frequently involves the exploration of sediments trapped within the impoundment and the subsequent assessment of sediment management needs and techniques. Sediment management planning requires a thorough understanding of the watershed’s surficial geology, topography, land cover, land use, and hydrology. The behavior of sediments is influenced by their age, consolidation, and stratigraphy. All watersheds have a history that helps forecast sediment loads, quality, gradation, and stratigraphy. Impounded sediment deposits may include coarse deltas and foreset slopes, fine or coarse bottom deposits, cohesive or organic matter, and wedge deposits immediately behind the dam. Some watersheds have anthropogenic pollutants from agricultural activities, mining, industries, or urban runoff.

The volume and rate of sediment release during and after small dam removal can be limited by active management plans to reduce potential downstream impacts. Management strategies include natural erosion, phased breaches and drawdowns, natural revegetation of sediment surfaces, pre-excavation of an upstream channel, hazardous waste removal or containment, flow bypass plans, and sediment dredging.