bluuebunny/crossref_metadata_2025 huggingface dataset:
Spontaneous revisitation during visual exploration as a link among strategic behavior, learning, and the hippocampus
Authors: Voss Joel L. , Warren David E. , Gonsalves Brian D. , Federmeier Kara D. , Tranel Dan , Cohen Neal J.
Published: July 2011

Effective exploratory behaviors involve continuous updating of sensory sampling to optimize the efficacy of information gathering. Despite some work on this issue in animals, little information exists regarding the cognitive or neural mechanisms for this sort of behavioral optimization in humans. Here we examined a visual exploration phenomenon that occurred when human subjects studying an array of objects spontaneously looked “backward” in their scanning paths to view recently seen objects again. This “spontaneous revisitation” of recently viewed objects was associated with enhanced hippocampal activity and superior subsequent memory performance in healthy participants, but occurred only rarely in amnesic patients with severe damage to the hippocampus. These findings demonstrate the necessity of the hippocampus not just in the aspects of long-term memory with which it has been associated previously, but also in the short-term adaptive control of behavior. Functional neuroimaging showed hippocampal engagement occurring in conjunction with frontocerebellar circuits, thereby revealing some of the larger brain circuitry essential for the strategic deployment of information-seeking behaviors that optimize learning.
Serine protease autotransporters fromShigella flexneriand pathogenicEscherichia colitarget a broad range of leukocyte glycoproteins
Authors: Ruiz-Perez Fernando , Wahid Rezwanul , Faherty Christina S. , Kolappaswamy Krishnan , Rodriguez Liliana , Santiago Araceli , Murphy Ebony , Cross Alan , Sztein Marcelo B. , Nataro James P.
Published: July 2011

The serine protease autotransporters of Enterobacteriaceae (SPATEs) are secreted by pathogenic Gram-negative bacteria through the autotransporter pathway. We previously classified SPATE proteins into two classes: cytotoxic (class 1) and noncytotoxic (class 2). Here, we show that Pic, a class 2 SPATE protein produced byShigella flexneri2a, uropathogenic and enteroaggregativeEscherichia colistrains, targets a broad range of human leukocyte adhesion proteins. Substrate specificity was restricted to glycoproteins rich in O-linked glycans, including CD43, CD44, CD45, CD93, CD162 (PSGL-1; P-selectin glycoprotein ligand 1), and the surface-attached chemokine fractalkine, all implicated in leukocyte trafficking, migration, and inflammation. N-terminal sequencing of proteolytic products revealed Pic (protease involved in colonization) cleavage sites to occur before Thr or Ser residues. The purified carbohydrate sLewis-X implied in inflammation and malignancy inhibited cleavage of PSGL-1 by Pic. Exposure of human leukocytes to purified Pic resulted in polymorphonuclear cell activation, but impaired chemotaxis and transmigration; Pic-treated T cells underwent programmed cell death. We also show that the Pic-related protease Tsh/Hbp, implicated in extraintestinal infections, exhibited a spectrum of substrates similar to those cleaved by Pic. In the guinea pig keratoconjunctivitis model, aShigella picmutant induced greater inflammation than its parent strain. We suggest that the class-2 SPATEs represent unique immune-modulating bacterial virulence factors.
Composition and fate of gas and oil released to the water column during the
Deepwater Horizon
oil spill
Authors: Reddy Christopher M. , Arey J. Samuel , Seewald Jeffrey S. , Sylva Sean P. , Lemkau Karin L. , Nelson Robert K. , Carmichael Catherine A. , McIntyre Cameron P. , Fenwick Judith , Ventura G. Todd , Van Mooy Benjamin A. S. , Camilli Richard
Published: July 2011

Quantitative information regarding the endmember composition of the gas and oil that flowed from the Macondo well during the
Deepwater Horizon
oil spill is essential for determining the oil flow rate, total oil volume released, and trajectories and fates of hydrocarbon components in the marine environment. Using isobaric gas-tight samplers, we collected discrete samples directly above the Macondo well on June 21, 2010, and analyzed the gas and oil. We found that the fluids flowing from the Macondo well had a gas-to-oil ratio of 1,600 standard cubic feet per petroleum barrel. Based on the measured endmember gas-to-oil ratio and the Federally estimated net liquid oil release of 4.1 million barrels, the total amount of C
1
-C
5
hydrocarbons released to the water column was 1.7 × 10
11
 g. The endmember gas and oil compositions then enabled us to study the fractionation of petroleum hydrocarbons in discrete water samples collected in June 2010 within a southwest trending hydrocarbon-enriched plume of neutrally buoyant water at a water depth of 1,100 m. The most abundant petroleum hydrocarbons larger than C
1
-C
5
were benzene, toluene, ethylbenzene, and total xylenes at concentrations up to 78 μg L
-1
. Comparison of the endmember gas and oil composition with the composition of water column samples showed that the plume was preferentially enriched with water-soluble components, indicating that aqueous dissolution played a major role in plume formation, whereas the fates of relatively insoluble petroleum components were initially controlled by other processes.
Activity of abundant and rare bacteria in a coastal ocean
Authors: Campbell Barbara J. , Yu Liying , Heidelberg John F. , Kirchman David L.
Published: July 2011

The surface layer of the oceans and other aquatic environments contains many bacteria that range in activity, from dormant cells to those with high rates of metabolism. However, little experimental evidence exists about the activity of specific bacterial taxa, especially rare ones. Here we explore the relationship between abundance and activity by documenting changes in abundance over time and by examining the ratio of 16S rRNA to rRNA genes (rDNA) of individual bacterial taxa. The V1–V2 region of 16S rRNA and rDNA was analyzed by tag pyrosequencing in a 3-y study of surface waters off the Delaware coast. Over half of the bacterial taxa actively cycled between abundant and rare, whereas about 12% always remained rare and potentially inactive. There was a significant correlation between the relative abundance of 16S rRNA and the relative abundance of 16S rDNA for most individual taxa. However, 16S rRNA:rDNA ratios were significantly higher in about 20% of the taxa when they were rare than when abundant. Relationships between 16S rRNA and rDNA frequencies were confirmed for five taxa by quantitative PCR. Our findings suggest that though abundance follows activity in the majority of the taxa, a significant portion of the rare community is active, with growth rates that decrease as abundance increases.
Stimulus-specific suppression preserves information in auditory short-term memory
Authors: Linke Annika C. , Vicente-Grabovetsky Alejandro , Cusack Rhodri
Published: July 2011

Philosophers and scientists have puzzled for millennia over how perceptual information is stored in short-term memory. Some have suggested that early sensory representations are involved, but their precise role has remained unclear. The current study asks whether auditory cortex shows sustained frequency-specific activation while sounds are maintained in short-term memory using high-resolution functional MRI (fMRI). Investigating short-term memory representations within regions of human auditory cortex with fMRI has been difficult because of their small size and high anatomical variability between subjects. However, we overcame these constraints by using multivoxel pattern analysis. It clearly revealed frequency-specific activity during the encoding phase of a change detection task, and the degree of this frequency-specific activation was positively related to performance in the task. Although the sounds had to be maintained in memory, activity in auditory cortex was significantly suppressed. Strikingly, patterns of activity in this maintenance period correlated negatively with the patterns evoked by the same frequencies during encoding. Furthermore, individuals who used a rehearsal strategy to remember the sounds showed reduced frequency-specific suppression during the maintenance period. Although negative activations are often disregarded in fMRI research, our findings imply that decreases in blood oxygenation level-dependent response carry important stimulus-specific information and can be related to cognitive processes. We hypothesize that, during auditory change detection, frequency-specific suppression protects short-term memory representations from being overwritten by inhibiting the encoding of interfering sounds.
Structural basis for complement factor I control and its disease-associated sequence polymorphisms
Authors: Roversi Pietro , Johnson Steven , Caesar Joseph J. E. , McLean Florence , Leath Kirstin J. , Tsiftsoglou Stefanos A. , Morgan B. Paul , Harris Claire L. , Sim Robert B. , Lea Susan M.
Published: July 2011

The complement system is a key component of innate and adaptive immune responses. Complement regulation is critical for prevention and control of disease. We have determined the crystal structure of the complement regulatory enzyme human factor I (fI). FI is in a proteolytically inactive form, demonstrating that it circulates in a zymogen-like state despite being fully processed to the mature sequence. Mapping of functional data from mutants of fI onto the structure suggests that this inactive form is maintained by the noncatalytic heavy-chain allosterically modulating activity of the light chain. Once the ternary complex of fI, a cofactor and a substrate is formed, the allosteric inhibition is released, and fI is oriented for cleavage. In addition to explaining how circulating fI is limited to cleaving only C3b/C4b, our model explains the molecular basis of disease-associated polymorphisms in fI and its cofactors.
Sec16B is involved in the endoplasmic reticulum export of the peroxisomal membrane biogenesis factor peroxin 16 (Pex16) in mammalian cells
Authors: Yonekawa Shusuke , Furuno Akiko , Baba Takashi , Fujiki Yukio , Ogasawara Yuta , Yamamoto Akitsugu , Tagaya Mitsuo , Tani Katsuko
Published: July 2011

Sec16 plays a key role in the formation of coat protein II vesicles, which mediate protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus. Mammals have two Sec16 isoforms: Sec16A, which is a longer primary ortholog of yeast Sec16, and Sec16B, which is a shorter distant ortholog. Previous studies have shown that Sec16B, as well as Sec16A, defines ER exit sites, where coat protein II vesicles are formed in mammalian cells. Here, we reveal an unexpected role of Sec16B in the biogenesis of mammalian peroxisomes. When overexpressed, Sec16B was targeted to the entire ER, whereas Sec16A was mostly cytosolic. Concomitant with the overexpression of Sec16B, peroxisomal membrane biogenesis factors peroxin 3 (Pex3) and Pex16 were redistributed from peroxisomes to Sec16B-positive ER membranes. Knockdown of Sec16B but not Sec16A by RNAi affected the morphology of peroxisomes, inhibited the transport of Pex16 from the ER to peroxisomes, and suppressed expression of Pex3. These phenotypes were significantly reversed by the expression of RNAi-resistant Sec16B. Together, our results support the view that peroxisomes are formed, at least partly, from the ER and identify a factor responsible for this process.
Motivating voter turnout by invoking the self
Authors: Bryan Christopher J. , Walton Gregory M. , Rogers Todd , Dweck Carol S.
Published: July 2011

Three randomized experiments found that subtle linguistic cues have the power to increase voting and related behavior. The phrasing of survey items was varied to frame voting either as the enactment of a personal identity (e.g., “being a voter”) or as simply a behavior (e.g., “voting”). As predicted, the personal-identity phrasing significantly increased interest in registering to vote (experiment 1) and, in two statewide elections in the United States, voter turnout as assessed by official state records (experiments 2 and 3). These results provide evidence that people are continually managing their self-concepts, seeking to assume or affirm valued personal identities. The results further demonstrate how this process can be channeled to motivate important socially relevant behavior.
Streamlined platform for short hairpin RNA interference and transgenesis in cultured mammalian cells
Authors: Khandelia Piyush , Yap Karen , Makeyev Eugene V.
Published: July 2011

Sequence-specific gene silencing by short hairpin (sh) RNAs has recently emerged as an indispensable tool for understanding gene function and a promising avenue for drug discovery. However, a wider biomedical use of this approach is hindered by the lack of straightforward methods for achieving uniform expression of shRNAs in mammalian cell cultures. Here we report a high-efficiency and low-background (HILO) recombination-mediated cassette exchange (RMCE) technology that yields virtually homogeneous cell pools containing doxycycline-inducible shRNA elements in a matter of days and with minimal efforts. To ensure immediate utility of this approach for a wider research community, we modified 11 commonly used human (A549, HT1080, HEK293T, HeLa, HeLa-S3, and U2OS) and mouse (CAD, L929, N2a, NIH 3T3, and P19) cell lines to be compatible with the HILO-RMCE process. Because of its technical simplicity and cost efficiency, the technology will be advantageous for both low- and high-throughput shRNA experiments. We also provide evidence that HILO-RMCE will facilitate a wider range of molecular and cell biology applications by allowing one to rapidly engineer cell populations expressing essentially any transgene of interest.
Functional analysis of environmental DNA-derived type II polyketide synthases reveals structurally diverse secondary metabolites
Authors: Feng Zhiyang , Kallifidas Dimitris , Brady Sean F.
Published: July 2011

A single gram of soil is predicted to contain thousands of unique bacterial species. The majority of these species remain recalcitrant to standard culture methods, prohibiting their use as sources of unique bioactive small molecules. The cloning and analysis of DNA extracted directly from environmental samples (environmental DNA, eDNA) provides a means of exploring the biosynthetic capacity of natural bacterial populations. Environmental DNA libraries contain large reservoirs of bacterial genetic diversity from which new secondary metabolite gene clusters can be systematically recovered and studied. The identification and heterologous expression of type II polyketide synthase-containing eDNA clones is reported here. Functional analysis of three soil DNA-derived polyketide synthase systems in
Streptomyces albus
revealed diverse metabolites belonging to well-known, rare, and previously uncharacterized structural families. The first of these systems is predicted to encode the production of the known antibiotic landomycin E. The second was found to encode the production of a metabolite with a previously uncharacterized pentacyclic ring system. The third was found to encode the production of unique KB-3346-5 derivatives, which show activity against methicillin-resistant
Staphylococcus aureus
and vancomycin-resistant
Enterococcus faecalis
. These results, together with those of other small-molecule-directed metagenomic studies, suggest that culture-independent approaches are capable of accessing biosynthetic diversity that has not yet been extensively explored using culture-based methods. The large-scale functional screening of eDNA clones should be a productive strategy for generating structurally previously uncharacterized chemical entities for use in future drug development efforts.
Processive phosphorylation of ERK MAP kinase in mammalian cells
Authors: Aoki Kazuhiro , Yamada Masashi , Kunida Katsuyuki , Yasuda Shuhei , Matsuda Michiyuki
Published: July 2011

The mitogen-activated protein (MAP) kinase pathway is comprised of a three-tiered kinase cascade. The distributive kinetic mechanism of two-site MAP kinase phosphorylation inherently generates a nonlinear switch-like response. However, a linear graded response of MAP kinase has also been observed in mammalian cells, and its molecular mechanism remains unclear. To dissect these input-output behaviors, we quantitatively measured the kinetic parameters involved in the MEK (MAPK/ERK kinase)-ERK MAP kinase signaling module in HeLa cells. Using a numerical analysis based on experimentally determined parameters, we predicted
in silico
and validated in vivo that ERK is processively phosphorylated in HeLa cells. Finally, we identified molecular crowding as a critical factor that converts distributive phosphorylation into processive phosphorylation. We proposed the term
quasi-processive phosphorylation
to describe this mode of ERK phosphorylation that is operated under the physiological condition of molecular crowding. The generality of this phenomenon may provide a new paradigm for a diverse set of biochemical reactions including multiple posttranslational modifications.
Vasopressin-independent targeting of aquaporin-2 by selective E-prostanoid receptor agonists alleviates nephrogenic diabetes insipidus
Authors: Olesen Emma T. B. , Rützler Michael R. , Moeller Hanne B. , Praetorius Helle A. , Fenton Robert A.
Published: July 2011

In the kidney, the actions of vasopressin on its type-2 receptor (V2R) induce increased water reabsorption alongside polyphosphorylation and membrane targeting of the water channel aquaporin-2 (AQP2). Loss-of-function mutations in the V2R cause X-linked nephrogenic diabetes insipidus. Treatment of this condition would require bypassing the V2R to increase AQP2 membrane targeting, but currently no specific pharmacological therapy is available. The present study examined specific E-prostanoid receptors for this purpose. In vitro, prostaglandin E2 (PGE2) and selective agonists for the E-prostanoid receptors EP2 (butaprost) or EP4 (CAY10580) all increased trafficking and ser-264 phosphorylation of AQP2 in Madin-Darby canine kidney cells. Only PGE2 and butaprost increased cAMP and ser-269 phosphorylation of AQP2. Ex vivo, PGE2, butaprost, or CAY10580 increased AQP2 phosphorylation in isolated cortical tubules, whereas PGE2 and butaprost selectively increased AQP2 membrane accumulation in kidney slices. In vivo, a V2R antagonist caused a severe urinary concentrating defect in rats, which was greatly alleviated by treatment with butaprost. In conclusion, EP2 and EP4 agonists increase AQP2 phosphorylation and trafficking, likely through different signaling pathways. Furthermore, EP2 selective agonists can partially compensate for a nonfunctional V2R, providing a rationale for new treatment strategies for hereditary nephrogenic diabetes insipidus.
Crystal structure of the human astrovirus capsid spike
Authors: Dong Jinhui , Dong Liping , Méndez Ernesto , Tao Yizhi
Published: July 2011

Astroviruses are single-stranded, plus-sense RNA viruses that infect both mammals and birds, causing gastroenteritis and other extraintestinal diseases. Clinical studies have established astroviruses as the second leading cause of viral diarrhea in young children. Here we report the crystal structure of the human astrovirus dimeric surface spike determined to 1.8-Å resolution. The overall structure of each spike/projection domain has a unique three-layered β-sandwiches fold, with a core, six-stranded β-barrel structure that is also found in the hepatitis E virus capsid protrusions, suggesting a closer phylogenetic relationship between these two viruses than previously acknowledged. Based on a hepatitis E virus capsid model, we performed homology modeling and produced a complete,
T
 = 3 astrovirus capsid model with features remarkably similar to those observed in a cryoelectron microscopy reconstruction image of a human astrovirus. Mapping conserved residues onto the astrovirus projection domain revealed a putative receptor binding site with amino acid compositions characteristic for polysaccharide recognition. Our results will have an important impact on future characterization of astrovirus structure and function, and will likely have practical applications in the development of vaccines and antivirals.
High-resolution, noninvasive longitudinal live imaging of immune responses
Authors: Abdulreda Midhat H. , Faleo Gaetano , Molano Ruth Damaris , Lopez-Cabezas Maite , Molina Judith , Tan Yaohong , Echeverria Oscar A. Ron , Zahr-Akrawi Elsie , Rodriguez-Diaz Rayner , Edlund Patrick K. , Leibiger Ingo , Bayer Allison L. , Perez Victor , Ricordi Camillo , Caicedo Alejandro , Pileggi Antonello , Berggren Per-Olof
Published: July 2011

Intravital imaging emerged as an indispensible tool in biological research, and a variety of imaging techniques have been developed to noninvasively monitor tissues in vivo. However, most of the current techniques lack the resolution to study events at the single-cell level. Although intravital multiphoton microscopy has addressed this limitation, the need for repeated noninvasive access to the same tissue in longitudinal in vivo studies remains largely unmet. We now report on a previously unexplored approach to study immune responses after transplantation of pancreatic islets into the anterior chamber of the mouse eye. This approach enabled (i) longitudinal, noninvasive imaging of transplanted tissues in vivo; (ii) in vivo cytolabeling to assess cellular phenotype and viability in situ; (iii) local intervention by topical application or intraocular injection; and (iv) real-time tracking of infiltrating immune cells in the target tissue.
Association of selected persistent organic pollutants in the placenta with the risk of neural tube defects
Authors: Ren Aiguo , Qiu Xinghua , Jin Lei , Ma Jin , Li Zhiwen , Zhang Le , Zhu Huiping , Finnell Richard H. , Zhu Tong
Published: July 2011

Persistent organic pollutants (POPs) have been associated with a wide range of adverse health effects. Our case–control study was performed to explore the association between placental levels of selected POPs and risks for neural tube defects (NTDs) in a Chinese population with a high prevalence of NTDs. Cases included 80 fetuses or newborns with NTDs, whereas the controls were 50 healthy, nonmalformed newborn infants. Placental concentrations of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers were analyzed by gas chromatography–mass spectrometry. The medians of PAHs, o,p′-isomers of dichlorodiphenyltrichloroethane (DDT) and metabolites, α- and γ-hexachlorocyclohexane (HCH), and α-endosulfan were significantly higher in case placentas than in controls. PAH concentrations above the median were associated with a 4.52-fold [95% confidence interval (CI), 2.10–9.74) increased risk for any NTDs, and 5.84- (95% CI, 2.28–14.96) and 3.71-fold (95% CI, 1.57–8.79) increased risks for anencephaly and spina bifida, respectively. A dose–response relationship was observed between PAH levels and the risk of NTDs, with odds ratios for the second, third, and fourth quartiles, compared with the first, of 1.77- (95% CI, 0.66–4.76), 3.83- (95% CI, 1.37–10.75), and 11.67-fold (95% CI, 3.28–41.49), respectively. A dose–response relationship was observed for anencephaly and spina bifida subtypes. Similar results were observed for o,p′-DDT and metabolites, α-HCH, γ-HCH, and α-endosulfan, whereas no dose–response relationship was observed for the last two pollutants. Elevated placental concentrations of PAHs, o,p′-DDT and metabolites, and α-HCH were associated with increased risks of NTDs in this population
.
Noncanonical NF-κB regulates inducible costimulator (ICOS) ligand expression and T follicular helper cell development
Authors: Hu Hongbo , Wu Xuefeng , Jin Wei , Chang Mikyoung , Cheng Xuhong , Sun Shao-Cong
Published: July 2011

Follicular helper T (Tfh) cells have a central role in mediating humoral immune responses. Generation of Tfh cells depends on both T-cell intrinsic factors and the supporting function of B cells, but the underlying molecular mechanisms are incompletely understood. Here we show that NF-κB–inducing kinase (NIK), a central component of the noncanonical NF-κB signaling pathway, is required for Tfh cell development. Unlike other known Tfh regulators, NIK acts by controlling the supporting function of B cells. NIK and its upstream BAFF receptor regulate B-cell expression of inducible costimulator ligand (ICOSL), a molecule required for Tfh cell generation. Consistently, injection of a recombinant ICOSL protein into
NIK
-deficient mice largely rescues their defect in Tfh cell development. We provide biochemical and genetic evidence indicating that the ICOSL gene is a specific target of the noncanonical NF-κB. Our findings suggest that the noncanonical NF-κB pathway regulates the development of Tfh cells by mediating ICOSL gene expression in B cells.
Large-scale opening of utrophin’s tandem calponin homology (CH) domains upon actin binding by an induced-fit mechanism
Authors: Lin Ava Y. , Prochniewicz Ewa , James Zachary M. , Svensson Bengt , Thomas David D.
Published: July 2011

We have used site-directed spin labeling and pulsed electron paramagnetic resonance to resolve a controversy concerning the structure of the utrophin–actin complex, with implications for the pathophysiology of muscular dystrophy. Utrophin is a homolog of dystrophin, the defective protein in Duchenne and Becker muscular dystrophies, and therapeutic utrophin derivatives are currently being developed. Both proteins have a pair of N-terminal calponin homology (CH) domains that are important for actin binding. Although there is a crystal structure of the utrophin actin-binding domain, electron microscopy of the actin-bound complexes has produced two very different structural models, in which the CH domains are in open or closed conformations. We engineered a pair of labeling sites in the CH domains of utrophin and used dipolar electron–electron resonance to determine the distribution of interdomain distances with high resolution. We found that the two domains are flexibly connected in solution, indicating a dynamic equilibrium between two distinct open structures. Upon actin binding, the two domains become dramatically separated and ordered, indicating a transition to a single open and extended conformation. There is no trace of this open conformation of utrophin in the absence of actin, providing strong support for an induced-fit model of actin binding.
Synthetic analogues of [Fe
4
S
4
(Cys)
3
(His)] in hydrogenases and [Fe
4
S
4
(Cys)
4
] in HiPIP derived from all-ferric [Fe
4
S
4
{N(SiMe
3
)
2
}
4
]
Authors: Ohki Yasuhiro , Tanifuji Kazuki , Yamada Norihiro , Imada Motosuke , Tajima Tomoyuki , Tatsumi Kazuyuki
Published: July 2011

The all-ferric [Fe
4
S
4
]
4+
cluster [Fe
4
S
4
{N(SiMe
3
)
2
}
4
]
1
and its one-electron reduced form [
1
]
-
serve as convenient precursors for the synthesis of 3∶1-site differentiated [Fe
4
S
4
] clusters and high-potential iron-sulfur protein (HiPIP) model clusters. The reaction of
1
with four equivalents (equiv) of the bulky thiol HSDmp (Dmp = 2,6-(mesityl)
2
C
6
H
3
, mesityl = 2,4,6-Me
3
C
6
H
2
) followed by treatment with tetrahydrofuran (THF) resulted in the isolation of [Fe
4
S
4
(SDmp)
3
(THF)
3
]
2
. Cluster
2
contains an octahedral iron atom with three THF ligands, and its Fe(S)
3
(O)
3
coordination environment is relevant to that in the active site of substrate-bound aconitase. An analogous reaction of [
1
]
-
with four equiv of HSDmp gave [Fe
4
S
4
(SDmp)
4
]
-
3
, which models the oxidized form of HiPIP. The THF ligands in
2
can be replaced by tetramethyl-imidazole (Me
4
Im) to give [Fe
4
S
4
(SDmp)
3
(Me
4
Im)]
4
modeling the [Fe
4
S
4
(Cys)
3
(His)] cluster in hydrogenases, and its one-electron reduced form [
4
]
-
was synthesized from the reaction of
3
with Me
4
Im. The reversible redox couple between
3
and [
3
]
-
was observed at
E
1/2
 = -820 mV vs. Ag/Ag
+
, and the corresponding reversible couple for
4
and [
4
]
-
is positively shifted by +440 mV. The cyclic voltammogram of
3
also exhibited a reversible oxidation couple, which indicates generation of the all-ferric [Fe
4
S
4
]
4+
cluster, [Fe
4
S
4
(SDmp)
4
].
The naïve airway hyperresponsiveness of the A/J mouse is
Kit
-mediated
Authors: Cozzi Emily , Ackerman Kate G. , Lundequist Anders , Drazen Jeffrey M. , Boyce Joshua A. , Beier David R.
Published: July 2011

There is a wide variation among humans and mice in airway hyperresponsiveness (AHR) in the absence of allergen sensitization, i.e., naïve AHR. Because mast cell (MC) activation is thought to mediate AHR in atopic asthmatic subjects, we asked whether MCs mediate naïve AHR in A/J mice. We generated an A/J congenic strain lacking c-Kit by introgression of the
Wv
mutation, which resulted in the elimination of MCs and the abrogation of naïve AHR. Imatinib, which disrupts
Kit
signaling, also abrogated AHR in A/J mice. Remarkably, introduction of the
Vga9 Mitf
mutation into the A/J background resulted in the ablation of MCs but did not ameliorate AHR. These results indicate that c-Kit is required for development of AHR in an MC-independent fashion.
Sidestream tobacco smoke is a male germ cell mutagen
Authors: Marchetti Francesco , Rowan-Carroll Andrea , Williams Andrew , Polyzos Aris , Berndt-Weis M. Lynn , Yauk Carole L.
Published: July 2011

Active cigarette smoking increases oxidative damage, DNA adducts, DNA strand breaks, chromosomal aberrations, and heritable mutations in sperm. However, little is known regarding the effects of second-hand smoke on the male germ line. We show here that short-term exposure to mainstream tobacco smoke or sidestream tobacco smoke (STS), the main component of second-hand smoke, induces mutations at an expanded simple tandem repeat locus (
Ms6-hm
) in mouse sperm. We further show that the response to STS is not linear and that, for both mainstream tobacco smoke and STS, doses that induced significant increases in expanded simple tandem repeat mutations in sperm did not increase the frequencies of micronucleated reticulocytes and erythrocytes in the bone marrow and blood of exposed mice. These data show that passive exposure to cigarette smoke can cause tandem repeat mutations in sperm under conditions that may not induce genetic damage in somatic cells. Although the relationship between noncoding tandem repeat instability and mutations in functional regions of the genome is unclear, our data suggest that paternal exposure to second-hand smoke may have reproductive consequences that go beyond the passive smoker.
Pink1 regulates the oxidative phosphorylation machinery via mitochondrial fission
Authors: Liu Wencheng , Acín-Peréz Rebeca , Geghman Kindiya D. , Manfredi Giovanni , Lu Bingwei , Li Chenjian
Published: July 2011

Mutations in PTEN-induced kinase 1 (PINK1), a mitochondrial Ser/Thr kinase, cause an autosomal recessive form of Parkinson's disease (PD), PARK6. To investigate the mechanism of PINK1 pathogenesis, we used the
Drosophila Pink1 knockout (KO)
model. In mitochondria isolated from
Pink1-KO
flies, mitochondrial respiration driven by the electron transport chain (ETC) is significantly reduced. This reduction is the result of a decrease in ETC complex I and IV enzymatic activity. As a consequence,
Pink1-KO
flies also display a reduced mitochondrial ATP synthesis. Because mitochondrial dynamics is important for mitochondrial function and
Pink1-KO
flies have defects in mitochondrial fission, we explored whether fission machinery deficits underlie the bioenergetic defect in
Pink1-KO
flies. We found that the bioenergetic defects in the
Pink1-KO
can be ameliorated by expression of
Drp1
, a key molecule in mitochondrial fission. Further investigation of the ETC complex integrity in
wild type, Pink1-KO, PInk1-KO/Drp1 transgenic, or Drp1 transgenic
flies indicates that the reduced ETC complex activity is likely derived from a defect in the ETC complex assembly, which can be partially rescued by increasing mitochondrial fission. Taken together, these results suggest a unique pathogenic mechanism of PINK1 PD: The loss of PINK1 impairs mitochondrial fission, which causes defective assembly of the ETC complexes, leading to abnormal bioenergetics.
Clustered patterns of species origins of nature-derived drugs and clues for future bioprospecting
Authors: Zhu Feng , Qin Chu , Tao Lin , Liu Xin , Shi Zhe , Ma Xiaohua , Jia Jia , Tan Ying , Cui Cheng , Lin Jinshun , Tan Chunyan , Jiang Yuyang , Chen Yuzong
Published: July 2011

Many drugs are nature derived. Low drug productivity has renewed interest in natural products as drug-discovery sources. Nature-derived drugs are composed of dozens of molecular scaffolds generated by specific secondary-metabolite gene clusters in selected species. It can be hypothesized that drug-like structures probably are distributed in selective groups of species. We compared the species origins of 939 approved and 369 clinical-trial drugs with those of 119 preclinical drugs and 19,721 bioactive natural products. In contrast to the scattered distribution of bioactive natural products, these drugs are clustered into 144 of the 6,763 known species families in nature, with 80% of the approved drugs and 67% of the clinical-trial drugs concentrated in 17 and 30 drug-prolific families, respectively. Four lines of evidence from historical drug data, 13,548 marine natural products, 767 medicinal plants, and 19,721 bioactive natural products suggest that drugs are derived mostly from preexisting drug-productive families. Drug-productive clusters expand slowly by conventional technologies. The lack of drugs outside drug-productive families is not necessarily the result of under-exploration or late exploration by conventional technologies. New technologies that explore cryptic gene clusters, pathways, interspecies crosstalk, and high-throughput fermentation enable the discovery of novel natural products. The potential impact of these technologies on drug productivity and on the distribution patterns of drug-productive families is yet to be revealed.
An inspector speaks: the Annual Report of Her Majesty's Chief Inspector of Schools
Authors: Maw Janet
Published: July 2011

In the United Kingdom one of the most important ways in which accountability relations in schools and between schools and outside bodies have been changed is through the introduction of a new inspection system. OFSTED inspection has largely replaced HMI and local authority inspection. In relation to this, the author examines three key inspection documents: the 1995 and 1996‐7 Chief Inspector's Annual Reports and the final Annual Report issued by HMI in 1992. She suggests that these documents are ideological constructions and therefore have to be read as such.
The school‐to‐work movement in the United States: policies, problems and possibilities
Authors: Wraga William G.
Published: July 2011

The school‐to‐work movement is best understood as part of a broader educational reform initiative aimed at providing workers with the necessary skills to place the US in a position of international economic competitiveness. The school‐to‐work movement grew out of the educational reforms of the 1980s and 1990s and is defined largely by the School‐to‐Work Opportunities Act of 1994. The reforms of this period also influenced a paradigm shift in vocational education in the US. Although key premises of the school‐to‐work movement are invalid and the reforms have failed to build upon past efforts, the rediscovery of progressive vocational education practices holds promise for the improvement of public schooling in the US. The comprehensive high school is considered the setting logistically conducive for school‐to‐work activities.
Curriculum costs
Authors: Deets Jennifer
Published: July 2011

A. W. Foshay has written a series of essays on what he calls the ‘curriculum matrix’. In them, he considers the interactions of unlikely elements such as aesthetics and history, and transcendence and mathematics. Thus far he has not explicitly attended to practice, one of the three dimensions of the model. Therefore, this article represents a first attempt at testing the model from the point of view of practice. In the process of exploring the practical element of cost, it becomes evident that the richness and depth of too easily disregarded terms, such as cost, must be reconsidered in order to enable sound curriculum decisions to be made in classrooms, school districts and national committees.
Issues in multicultural education
Authors: Wilhelm Ronald W.
Published: July 2011

This article examines issues that are central to the multicultural curriculum in the United States of America. It focuses on contributions to the journal Multicultural Education, and analyses them in terms of: culture, critical theory, transformative multicultural education, white privilege and racism, anti‐bias curricula, voice or cultural and historical perspectives, cultural pluralism and instructional practice.
The (mis)use of SATs to examine gender and achievement at Key Stage 2
Authors: Fielding Shaun , Daniels Harry , Creese Angela , Hey Valerie , Leonard Diana
Published: July 2011

This article discusses some of the issues raised in the early stages of an Economic and Social Research Council (ESRC) study.1 The first phase of the project involved an analysis of end of Key Stage 2 (children aged 10–11) Standard Assessment Test (SAT) data within a Midlands and a London local education authority (LEA(M) and LEA(L) respectively). The LEAs were identified according to the quality and accessibility of the data and their socio‐economic and socio‐cultural diversity. The analysis was used as an instrument for selecting schools in each LEA that displayed specific but con‐ sistent patterns of high, low and average achievement which were cross cut by large differences between boys' and girls' achievement in all three SAT subjects (English, maths and science). On one level, this article discusses the difficulties we encountered in identifying schools with consistent patterns of gendered achievement as well as signposting the ‘political’ significance of these difficulties for present and future edu‐ cation policies. On another level, it is a vehicle for the development of the theoretical lenses of learner identity and post‐Vygotskian analysis that have shaped our under‐ standing of gendered achievement which we use to ‘speak’ to and influence the development of the test procedures highlighted in this article.
Quantitative and case‐based insights into issues of gender and school‐based achievement: beyond simplistic explanations
Authors: Kutnick Peter
Published: July 2011

This article reports findings from a large‐scale research study exploring female attainment and male underachievement in a representative sample of students and case‐ studies from the Caribbean island of Barbados. The article shows that simplistic gender‐based (matrilineal and male marginal) explanations are not adequate explanations for school attainment. The representative survey of 2255 primary and secondary school children used both simple and complex comparisons between children. Dependent on statistical approach, females can be shown to attain at higher levels than males or that ‘gendered’ explanations disguise more important factors including type of school attended, pre‐school attendance, with whom the student lives and occupation of mother and father. Two small case‐studies are included to further describe how cultures of top and bottom performing secondary schools may affect attainment, especially as the top performing school was co‐educational with no sex differences in curriculum attainment and the bottom performing school was female only. These attainment effects occur through school personnel, attitudes to students and the learning process, and student involvement.
Can we tell the difference and does it matter? Differences in achievement between girls and boys in Australian senior secondary education
Authors: Matters Gabrielle , Allen Reg , Gray Ken , Pitman John
Published: July 2011

The nature and interpretation of differences between the achievements of females and males in senior secondary school studies in Australia, and the implications for policy and practice of these perceived differences, are showing signs of change. The ways in which these issues are discussed publicly across Australia are reviewed and then matched against indications that have emerged from data in one state (Queensland) and from other, published studies. This analysis suggests that there are important notions of gendered achievement that may not be receiving due consideration by those who formulate policy or analyse practice.
ICT in subject teaching: an opportunity for curriculum renewal?
Authors: Bonnett Michael , Mcfarlane Angela , Williams Jacquetta
Published: July 2011

At a time of unprecedented levels of investment in ICT in UK schools this article reflects on curriculum issues raised by a recent piece of research into the potential of multimedia authoring to enhance children's learning in the context of a drugs education programme with Year 6 children. It is argued that, given proper supporting structures, ICT of this highly interactive kind has the potential to develop qualities of evaluation, independence and responsibility in children's learning and understanding. Its use can also challenge the existing culture of the classroom and stimulate teachers to devise teaching strategies which celebrate a reassertion of liberal educational values which have implications for the role of the teacher in interpreting the curriculum, teacher‐pupil interaction and modes of assessment.
Community, culture and identity: geography, the National Curriculum and Wales
Authors: Daugherty Richard , Jones Sian
Published: July 2011

The 1988 Education Reform Act legislated for a National Curriculum not for one nation but for two, Wales and England. This article reviews the way in which attempts to develop a distinctive curriculum in Wales for one subject, geography, were thwarted by the dominance among key policy‐makers in England of views about the study of place which were unsympathetic to the idea of the school curriculum being a vehicle for the development of a sense of community and national identity. Drawing on evidence from a survey of secondary school geography teachers in Wales, it considers the extent to which the teaching of geography is seen by teachers as a means of achieving such educational goals.
HJURP is a CENP-A chromatin assembly factor sufficient to form a functional de novo kinetochore
Authors: Barnhart Meghan C. , Kuich P. Henning J. L. , Stellfox Madison E. , Ward Jared A. , Bassett Emily A. , Black Ben E. , Foltz Daniel R.
Published: July 2011

Centromeres of higher eukaryotes are epigenetically marked by the centromere-specific CENP-A nucleosome. New CENP-A recruitment requires the CENP-A histone chaperone HJURP. In this paper, we show that a LacI (Lac repressor) fusion of HJURP drove the stable recruitment of CENP-A to a LacO (Lac operon) array at a noncentromeric locus. Ectopically targeted CENP-A chromatin at the LacO array was sufficient to direct the assembly of a functional centromere as indicated by the recruitment of the constitutive centromere-associated network proteins, the microtubule-binding protein NDC80, and the formation of stable kinetochore–microtubule attachments. An amino-terminal fragment of HJURP was able to assemble CENP-A nucleosomes in vitro, demonstrating that HJURP is a chromatin assembly factor. Furthermore, HJURP recruitment to endogenous centromeres required the Mis18 complex. Together, these data suggest that the role of the Mis18 complex in CENP-A deposition is to recruit HJURP and that the CENP-A nucleosome assembly activity of HJURP is responsible for centromeric chromatin assembly to maintain the epigenetic mark.
Competitive binding of Rab21 and p120RasGAP to integrins regulates receptor traffic and migration
Authors: Mai Anja , Veltel Stefan , Pellinen Teijo , Padzik Artur , Coffey Eleanor , Marjomäki Varpu , Ivaska Johanna
Published: July 2011

Integrin trafficking from and to the plasma membrane controls many aspects of cell behavior including cell motility, invasion, and cytokinesis. Recruitment of integrin cargo to the endocytic machinery is regulated by the small GTPase Rab21, but the detailed molecular mechanisms underlying integrin cargo recruitment are yet unknown. Here we identify an important role for p120RasGAP (RASA1) in the recycling of endocytosed α/β1-integrin heterodimers to the plasma membrane. Silencing of p120RasGAP attenuated integrin recycling and augmented cell motility. Mechanistically, p120RasGAP interacted with the cytoplasmic domain of integrin α-subunits via its GAP domain and competed with Rab21 for binding to endocytosed integrins. This in turn facilitated exit of the integrin from Rab21- and EEA1-positive endosomes to drive recycling. Our results assign an unexpected role for p120RasGAP in the regulation of integrin traffic in cancer cells and reveal a new concept of competitive binding of Rab GTPases and GAP proteins to receptors as a regulatory mechanism in trafficking.
APC/CCdh1-dependent proteolysis of USP1 regulates the response to UV-mediated DNA damage
Authors: Cotto-Rios Xiomaris M. , Jones Mathew J.K. , Busino Luca , Pagano Michele , Huang Tony T.
Published: July 2011

Targeted protein destruction of critical cellular regulators during the G1 phase of the cell cycle is achieved by anaphase-promoting complex/cyclosomeCdh1 (APC/CCdh1), a multisubunit E3 ubiquitin ligase. Cells lacking Cdh1 have been shown to accumulate deoxyribonucleic acid (DNA) damage, suggesting that it may play a previously unrecognized role in maintaining genomic stability. The ubiquitin-specific protease 1 (USP1) is a known critical regulator of DNA repair and genomic stability. In this paper, we report that USP1 was degraded in G1 via APC/CCdh1. USP1 levels were kept low in G1 to provide a permissive condition for inducing proliferating cell nuclear antigen (PCNA) monoubiquitination in response to ultraviolet (UV) damage before DNA replication. Importantly, expression of a USP1 mutant that cannot be degraded via APC/CCdh1 inhibited PCNA monoubiquitination during G1, likely compromising the recruitment of trans-lesion synthesis polymerase to UV repair sites. Thus, we propose a role for APC/CCdh1 in modulating the status of PCNA monoubiquitination and UV DNA repair before S phase entry.
Tumor necrosis factor restricts hematopoietic stem cell activity in mice: involvement of two distinct receptors
Authors: Pronk Cornelis J.H. , Veiby Ole Petter , Bryder David , Jacobsen Sten Eirik W.
Published: July 2011

Whereas maintenance of hematopoietic stem cells (HSCs) is a requisite for life, uncontrolled expansion of HSCs might enhance the propensity for leukemic transformation. Accordingly, HSC numbers are tightly regulated. The identification of physical cellular HSC niches has underscored the importance of extrinsic regulators of HSC homeostasis. However, whereas extrinsic positive regulators of HSCs have been identified, opposing extrinsic repressors of HSC expansion in vivo have yet to be described. Like many other acute and chronic inflammatory diseases, bone marrow (BM) failure syndromes are associated with tumor necrosis factor-α (TNF) overexpression. However, the in vivo relevance of TNF in the regulation of HSCs has remained unclear. Of considerable relevance for normal hematopoiesis and in particular BM failure syndromes, we herein demonstrate that TNF is a cell-extrinsic and potent endogenous suppressor of normal HSC activity in vivo in mice. These effects of TNF involve two distinct TNF receptors.