bluuebunny/crossref_metadata_2025_split huggingface dataset:
HDQ, a Potent Inhibitor of Plasmodium falciparum Proliferation, Binds to the Quinone Reduction Site of the Cytochrome
bc
1
Complex
Authors: Vallières Cindy , Fisher Nicholas , Antoine Thomas , Al-Helal Mohammed , Stocks Paul , Berry Neil G. , Lawrenson Alexandre S. , Ward Stephen A. , O'Neill Paul M. , Biagini Giancarlo A. , Meunier Brigitte 
Published: May 2012

ABSTRACT

The mitochondrial
bc
1
complex is a multisubunit enzyme that catalyzes the transfer of electrons from ubiquinol to cytochrome
c
coupled to the vectorial translocation of protons across the inner mitochondrial membrane. The complex contains two distinct quinone-binding sites, the quinol oxidation site of the
bc
1
complex (Q
o
) and the quinone reduction site (Q
i
), located on opposite sides of the membrane within cytochrome
b
. Inhibitors of the Q
o
site such as atovaquone, active against the
bc
1
complex of
Plasmodium falciparum
, have been developed and formulated as antimalarial drugs. Unfortunately, single point mutations in the Q
o
site can rapidly render atovaquone ineffective. The development of drugs that could circumvent cross-resistance with atovaquone is needed. Here, we report on the mode of action of a potent inhibitor of
P. falciparum
proliferation, 1-hydroxy-2-dodecyl-4(1
H
)quinolone (HDQ). We show that the parasite
bc
1
complex—from both control and atovaquone-resistant strains—is inhibited by submicromolar concentrations of HDQ, indicating that the two drugs have different targets within the complex. The binding site of HDQ was then determined by using a yeast model. Introduction of point mutations into the Q
i
site, namely, G33A, H204Y, M221Q, and K228M, markedly decreased HDQ inhibition. In contrast, known inhibitor resistance mutations at the Q
o
site did not cause HDQ resistance. This study, using HDQ as a proof-of-principle inhibitor, indicates that the Q
i
site of the
bc
1
complex is a viable target for antimalarial drug development.
Decline and Rise of the Antimicrobial Susceptibility of Streptococcus pneumoniae Isolated from Middle Ear Fluid in Children: Influence of Changes in Circulating Serotypes
Authors: Pérez-Trallero Emilio , Marimón José M. , Alonso Marta , Ercibengoa María , García-Arenzana José M. 
Published: May 2012

ABSTRACT

Changes in the antimicrobial susceptibility of
Streptococcus pneumoniae
causing otitis media were studied in 916 isolates from children <5 years old between 1999 and 2010 in a region of northern Spain. The rate of antimicrobial resistance decreased between the period before the introduction of the heptavalent pneumococcal conjugate vaccine (from 1999 to 2001) and the period from 2005 to 2007. However, in 2008 to 2010, resistance rates increased again due to the spread of serotype 19A, especially the multidrug-resistant ST320 and ST276 clones.
Heme Protein and Hydroxyarginase Necessary for Biosynthesis of
d
-Cycloserine
Authors: Kumagai Takanori , Takagi Kisho , Koyama Yusuke , Matoba Yasuyuki , Oda Kosuke , Noda Masafumi , Sugiyama Masanori 
Published: May 2012

ABSTRACT

We have recently cloned a
d
-cycloserine (DCS) biosynthetic gene cluster that consists of 10 genes, designated
dcsA
∼
dcsJ
, from
Streptomyces lavendulae
ATCC 11924 (16). In the predicted pathway of hydroxyurea (HU) formation in DCS biosynthesis,
l
-arginine (L-Arg) must first be hydroxylated, prior to the hydrolysis of
N
ω
-hydroxy-
l
-arginine (NHA) by DcsB, an arginase homolog. The hydroxylation of L-Arg is known to be catalyzed by nitric oxide synthase (NOS). In this study, to verify the supply route of HU, we created a
dcsB
-disrupted mutant, Δ
dcsB
. While the mutant lost DCS productivity, its productivity was restored by complementation of
dcsB
, and also by the addition of HU but not NHA, suggesting that HU is supplied by DcsB. A NOS-encoding gene,
nos
, from
S. lavendulae
chromosome was cloned, to create a
nos
-disrupted mutant. However, the mutant maintained the DCS productivity, suggesting that NOS is not necessary for DCS biosynthesis. To clarify the identity of an enzyme necessary for NHA formation, a
dcsA
-disrupted mutant, designated Δ
dcsA
, was also created. The mutant lost DCS productivity, whereas the DCS productivity was restored by complementation of
dcsA
. The addition of NHA to the culture medium of Δ
dcsA
mutant was also effective to restore DCS production. These results indicate that the
dcsA
gene product, DcsA, is an enzyme essential to generate NHA as a precursor in the DCS biosynthetic pathway. Spectroscopic analyses of the recombinant DcsA revealed that it is a heme protein, supporting an idea that DcsA is an enzyme catalyzing hydroxylation.
Function of Cytochrome P450 Enzymes MycCI and MycG in Micromonospora griseorubida, a Producer of the Macrolide Antibiotic Mycinamicin
Authors: Anzai Yojiro , Tsukada Shu-ichi , Sakai Ayami , Masuda Ryohei , Harada Chie , Domeki Ayaka , Li Shengying , Kinoshita Kenji , Sherman David H. , Kato Fumio 
Published: May 2012

ABSTRACT

The cytochrome P450 enzymes MycCI and MycG are encoded within the mycinamicin biosynthetic gene cluster and are involved in the biosynthesis of mycinamicin II (a 16-membered macrolide antibiotic produced by
Micromonospora griseorubida
). Based on recent enzymatic studies, MycCI is characterized as the C-21 methyl hydroxylase of mycinamicin VIII, while MycG is designated multifunctional P450, which catalyzes hydroxylation and also epoxidation at C-14 and C-12/13 on the macrolactone ring of mycinamicin. Here, we confirm the functions of MycCI and MycG in
M. griseorubida
. Protomycinolide IV and mycinamicin VIII accumulated in the culture broth of the
mycCI
disruption mutant; moreover, the
mycCI
gene fragment complemented the production of mycinamicin I and mycinamicin II, which are produced as major mycinamicins by the wild strain
M. griseorubida
A11725. The
mycG
disruption mutant did not produce mycinamicin I and mycinamicin II; however, mycinamicin IV accumulated in the culture broth. The
mycG
gene was located immediately downstream of the self-resistance gene
myrB
. The
mycG
gene under the control of
mycGp
complemented the production of mycinamicin I and mycinamicin II. Furthermore, the amount of mycinamicin II produced by the strain complemented with the
mycG
gene under the control of
myrBp
was approximately 2-fold higher than that produced by the wild strain. In
M. griseorubida
, MycG recognized mycinamicin IV, mycinamicin V, and also mycinamicin III as the substrates. Moreover, it catalyzed hydroxylation and also epoxidation at C-14 and C-12/13 on these intermediates. However, C-14 on mycinamicin I was not hydroxylated.
Validation of the Rapid Fluorescent Focus Inhibition Test for Rabies Virus-Neutralizing Antibodies in Clinical Samples
Authors: Kostense Stefan , Moore Susan , Companjen Arjen , Bakker Alexander B. H. , Marissen Wilfred E. , von Eyben Rie , Weverling Gerrit Jan , Hanlon Cathleen , Goudsmit Jaap 
Published: May 2012

ABSTRACT
Monoclonal antibodies are successful biologics in treating a variety of diseases, including the prevention or treatment of viral infections. CL184 is a 1:1 combination of two human monoclonal IgG1 antibodies (CR57 and CR4098) against rabies virus, produced in the PER.C6 human cell line. The two antibodies are developed as replacements of human rabies immune globulin (HRIG) and equine rabies immune globulin (ERIG) in postexposure prophylaxis (PEP). The rapid fluorescent focus inhibition test (RFFIT) is a cell-based virus neutralization assay which is usually performed to determine the biological potency of a vaccine and to measure the levels of protection against rabies in humans and animals. In order to confirm the suitability of this assay as a pharmacodynamic assay, we conducted a validation using both HRIG- and CL184-spiked serum samples and sera from vaccinated donors. The validation results met all analytical acceptance criteria and showed that HRIG and CL184 serum concentrations can be compared. Stability experiments showed that serum samples were stable in various suboptimal conditions but that rabies virus should be handled swiftly once thawed. We concluded that the assay is suitable for the measurement of polyclonal and monoclonal rabies neutralizing antibodies in clinical serum samples.
Brucella abortus Invasion of Osteoblasts Inhibits Bone Formation
Authors: Scian Romina , Barrionuevo Paula , Fossati Carlos A. , Giambartolomei Guillermo H. , Delpino M. Victoria 
Published: May 2012

ABSTRACTOsteoarticular brucellosis is the most common presentation of the active disease in humans. Loss of bone is a serious complication of localized bacterial infection of bones or the adjacent tissue, and brucellosis proved not to be the exception. The skeleton is a dynamic organ system which is constantly remodeled. Osteoblasts are responsible for the deposition of bone matrix and are thought to facilitate the calcification and mineralization of the bone matrix, and their function could be altered under infectious conditions. In this article, we describe immune mechanisms wherebyBrucella abortusmay invade and replicate within osteoblasts, inducing apoptosis, inhibiting mineral and organic matrix deposition, and inducing upregulation of RANKL expression. Additionally, all of these mechanisms contributed in different ways to bone loss. These processes implicate the activation of signaling pathways (mitogen-activated protein kinases [MAPK] and caspases) involved in cytokine secretion, expression of activating molecules, and cell death of osteoblasts. In addition, considering the relevance of macrophages in intracellularBrucellasurvival and proinflammatory cytokine secretion in response to infection, we also investigated the role of these cells as modulators of osteoblast survival, differentiation, and function. We demonstrated that supernatants fromB. abortus-infected macrophages may also mediate osteoblast apoptosis and inhibit osteoblast function in a process that is dependent on the presence of tumor necrosis factor alpha (TNF-α). These results indicate thatB. abortusmay directly and indirectly harm osteoblast function, contributing to the bone and joint destruction observed in patients with osteoarticular complications of brucellosis.
Surfactant Protein D Facilitates Cryptococcus neoformans Infection
Authors: Geunes-Boyer Scarlett , Beers Michael F. , Perfect John R. , Heitman Joseph , Wright Jo Rae 
Published: May 2012

ABSTRACT

Concurrent with the global escalation of the AIDS pandemic, cryptococcal infections are increasing and are of significant medical importance. Furthermore,
Cryptococcus neoformans
has become a primary human pathogen, causing infection in seemingly healthy individuals. Although numerous studies have elucidated the virulence properties of
C. neoformans
, less is understood regarding lung host immune factors during early stages of fungal infection. Based on our previous studies documenting that pulmonary surfactant protein D (SP-D) protects
C. neoformans
cells against macrophage-mediated defense mechanisms
in vitro
(S. Geunes-Boyer et al., Infect. Immun. 77:2783–2794, 2009), we postulated that SP-D would facilitate fungal infection
in vivo
. To test this hypothesis, we examined the role of SP-D in response to
C. neoformans
using SP-D
−/−
mice. Here, we demonstrate that mice lacking SP-D were partially protected during
C. neoformans
infection; they displayed a longer mean time to death and decreased fungal burden at several time points postinfection than wild-type mice. This effect was reversed by the administration of exogenous SP-D. Furthermore, we show that SP-D bound to the surface of the yeast cells and protected the pathogenic microbes against macrophage-mediated defense mechanisms and hydrogen peroxide (H
2
O
2
)-induced oxidative stress
in vitro
and
in vivo
. These findings indicate that
C. neoformans
is capable of coopting host SP-D to increase host susceptibility to the yeast. This study establishes a new paradigm for the role played by SP-D during host responses to
C. neoformans
and consequently imparts insight into potential future preventive and/or treatment strategies for cryptococcosis.
NOD2 Signaling Contributes to Host Defense in the Lungs against Escherichia coli Infection
Authors: Theivanthiran Balamayooran , Batra Sanjay , Balamayooran Gayathriy , Cai Shanshan , Kobayashi Koichi , Flavell Richard A. , Jeyaseelan Samithamby 
Published: May 2012

ABSTRACT

Bacterial pneumonia remains a significant cause of mortality in the United States. The innate immune response is the first line of defense against invading bacteria. Neutrophil recruitment to the lungs is the first step in a multistep sequence leading to bacterial clearance. Ligand interaction with pattern-recognizing receptors (PRRs) leads to chemokine production, which drives neutrophils to the site of infection. Although we demonstrated that RIP2 is important for host defense in the lungs against
Escherichia coli
, the individual roles of NOD1 and NOD2 in pulmonary defense have not been addressed. Here, we explored the role of NOD2 in neutrophil-mediated host defense against an extracellular pathogen,
E. coli
. We found enhanced bacterial burden and reduced neutrophil and cytokine/chemokine levels in the lungs of NOD2
−/−
mice following
E. coli
infection. Furthermore, we observed reduced activation of NF-κB and mitogen-activated protein kinases (MAPKs) in the lungs of NOD2
−/−
mice upon
E. coli
challenge. Moreover, NOD2
−/−
neutrophils show impaired intracellular bacterial killing. Using NOD2/RIP2
−/−
mice, we observed bacterial burden and neutrophil accumulation in the lungs similar to those seen with NOD2
−/−
mice. In addition, bone marrow-derived macrophages obtained from NOD2/RIP2
−/−
mice demonstrate a reduction in activation of NF-κB and MAPKs similar to that seen with NOD2
−/−
mice in response to
E. coli
. These findings unveil a previously unrecognized role of the NOD2-RIP2 axis for host defense against extracellular Gram-negative bacteria. This pathway may represent a novel target for the treatment of lung infection/inflammation.
Fusobacterium nucleatum and Tannerella forsythia Induce Synergistic Alveolar Bone Loss in a Mouse Periodontitis Model
Authors: Settem Rajendra P. , El-Hassan Ahmed Taher , Honma Kiyonobu , Stafford Graham P. , Sharma Ashu 
Published: May 2012

ABSTRACT

Tannerella forsythia
is strongly associated with chronic periodontitis, an inflammatory disease of the tooth-supporting tissues, leading to tooth loss.
Fusobacterium nucleatum
, an opportunistic pathogen, is thought to promote dental plaque formation by serving as a bridge bacterium between early- and late-colonizing species of the oral cavity. Previous studies have shown that
F. nucleatum
species synergize with
T. forsythia
during biofilm formation and pathogenesis. In the present study, we showed that coinfection of
F. nucleatum
and
T. forsythia
is more potent than infection with either species alone in inducing NF-κB activity and proinflammatory cytokine secretion in monocytic cells and primary murine macrophages. Moreover, in a murine model of periodontitis, mixed infection with the two species induces synergistic alveolar bone loss, characterized by bone loss which is greater than the additive alveolar bone losses induced by each species alone. Further, in comparison to the single-species infection, mixed infection caused significantly increased inflammatory cell infiltration in the gingivae and osteoclastic activity in the jaw bones. These data show that
F. nucleatum
subspecies and
T. forsythia
synergistically stimulate the host immune response and induce alveolar bone loss in a murine experimental periodontitis model.
Nocardia brasiliensis Induces an Immunosuppressive Microenvironment That Favors Chronic Infection in BALB/c Mice
Authors: Rosas-Taraco Adrian G. , Perez-Liñan Amira R. , Bocanegra-Ibarias Paola , Perez-Rivera Luz I. , Salinas-Carmona Mario C. 
Published: May 2012

ABSTRACTNocardia brasiliensisis an intracellular microorganism and the most common etiologic agent of actinomycetoma in the Americas. Several intracellular pathogens induce an immunosuppressive microenvironment through increases in CD4+Foxp3+regulatory T cells (Treg), thus downregulating other T-cell subpopulations and assuring survival in the host. In this study, we determined whetherN. brasiliensismodulates T-lymphocyte responses and their related cytokine profiles in a murine experimental model. We also examined the relationship betweenN. brasiliensisimmunomodulation and pathogenesis and bacterial survival. In early infection, Th17/Tc17 cells were increased at day 3 (P< 0.05) in footpad tissue and spleen. Treg subpopulations peaked at days 7 and 15 (P< 0.01) in the footpad and spleen, respectively. Transforming growth factor β1 (TGF-β1) and interleuki-10 (IL-10) are cytokines known for their immunosuppressive effects. During early and chronic infections, these cytokines were elevated with increased TGF-β1 levels from days 3 to 30 (P< 0.01) and sustained IL-10 expression throughout infection compared to uninfected mice. IL-6 production was increased at day 3 (P< 0.01), whereas gamma interferon (IFN-γ), IL-17A, and IL-23 levels were highest at day 15 postinfection (P< 0.01) when a decrease in the bacterial load (>1 log) was also observed (P< 0.05). After these changes, at 30 to 60 days postinfection, IFN-γ production was decreased, whereas the expression of anti-inflammatory cytokines and the bacterial load again increased (P< 0.05). The increment in Treg cells and the related cytokine profile correlated with reduced inflammation at day 15 (P< 0.05) in the footpad. We conclude thatN. brasiliensismodulates the immune system to induce an immunosuppressive microenvironment that benefits its survival during the chronic stage of infection.
Vacciniumspecies of sectionHemimyrtillus: their value to cultivated blueberry and approaches to utilization1This article is part of a Special Issue entitled “A tribute to Sam Vander Kloet FLS: Pure and applied research from blueberries to heathland ecology”.
Authors: Ehlenfeldt M.K. , Ballington J.R. 
Published: May 2012

The primary gene pool of Vaccinium species used by breeders has traditionally been the North American Vaccinium species in section Cyanococcus. Blueberries in commercial production represent several Vaccinium species and ploidies. Moreover, significant use has been made of the secondary gene pool of Vaccinium, especially in the development of southern highbush cultivars. Section Hemimyrtillus represents species that are part of the tertiary gene pool of Vaccinium. Two species of section Hemimyrtillus, native to the Portuguese islands of Madeira (Vaccinium padifolium Smith) and the Azores (Vaccinium cylindraceum Smith), have features of notable value to conventional blueberry development such as upright structure, strong growth, abundant flowering and fruiting, good self-fertility, acceptable fruit quality, inflorescence structure suited to mechanical harvesting, and repeat flowering. Vaccinium cylindraceum is deciduous, whereas V. padifolium is evergreen. Vaccinium arctostaphylos L., a native of the Caucasus region, is closely allied to V. padifolium, hybridizes freely with it, and has many similar characters, but with the valuable addition of greater cold hardiness. Initial progress has been made at incorporating these species into forms compatible with Vaccinium corymbosum L. based blueberry cultivars, and further evaluations are being made of both parental material and the derived hybrids.
The use of partial extraction geochemistry for copper exploration in northern Chile
Authors: Kelley David L. , Hall Gwendy E. M. , Closs L. Graham , Hamilton Ian C. , McEwen Robert M. 
Published: May 2012

Future discoveries of copper resources in the richly endowed porphyry copper belts of northern Chile are likely to occur in areas covered by post-mineral sedimentary and volcanic rock. Most of northern Chile is within a region of interior drainage that has existed since at least mid-Tertiary time when many of the porphyry copper deposits were being uplifted, eroded and supergene enriched. This setting, combined with accumulation of metal-enriched material eroded from the tops of porphyry copper deposits, has produced regions with high geochemical background and geochemically complex post-mineral cover that includes alluvium, lake and playa sediments, evaporites, aeolian material, ignimbrites and volcanic ash. In addition, the climate changed from semi-arid to hyper-arid in mid-Miocene time, creating a surface environment that is saline and slightly alkaline.
The geochemical expression of the Chimborazo porphyry copper deposit in northern Chile was studied in detail using the following wet chemical extraction methods: 4-acid (HF-based), aqua regia, bulk cyanide leach, hot hydroxylamine hydrochloride, cold hydroxylamine hydrochloride, enzyme leach and de-ionized water. Limitations affecting several partial extraction methods include poor data quality, lack of pH control, re-adsorption, and the formation of colloids in the leachate. Experimentation with leach time and buffering capacity improved the robustness of some of the methods. Mechanical dispersion is the dominant secondary process in this region although chemical dispersion does occur laterally on a regional scale and vertically on a local scale. Vertical chemical dispersion is associated with dilatancy pumping of metalliferous groundwater along fractures. Supercedency, a process whereby the geochemical fingerprint of transported material is inherited from the underlying material, may have also played a role in the strong signature seen at Chimborazo.
Estimating water pollution risks arising from road and railway accidents
Authors: Lacey R.F. , Cole J.A. 
Published: May 2012

A method is presented for estimating the frequency of spillage of toxic liquids from road tanker accidents. The calculation requires information about the vehicular flow of tankers, their accident rate and the probability that an accident will result in a spill. The available sources of input data are discussed.
Railway goods traffic, either involving liquids transported in tanker wagons, or hazardous freight packed in individual containers as part wagon loads, is amenable to similar analysis but relevant input data are much more difficult to obtain.
For any type of spill, the estimation of frequency should be accompanied by surface and groundwater pathway analyses, to assess the consequential damage to the aquatic environment and any possible hazard to public water supplies.
This paper serves as an outline of a subject calling for more thorough study, for which improved databases, geared to the needs of risk assessment, would be strongly desired.