bluuebunny/crossref_metadata_2025 huggingface dataset:
TransgenicLeishmaniaModel for Delta-Aminolevulinate-Inducible Monospecific Uroporphyria: Cytolytic Phototoxicity Initiated by Singlet Oxygen-Mediated Inactivation of Proteins and Its Ablation by Endosomal Mobilization of Cytosolic Uroporphyrin
Authors: Dutta Sujoy , Kolli Bala Krishna , Tang Aihua , Sassa Shigeru , Chang Kwang-Poo
Published: May 2008

Inherent deficiencies ofLeishmaniain heme biosynthesis were genetically complemented for delta-aminolevulinate-inducible biosynthesis and accumulation of light-excitable uroporphyrin. The phototoxic flagellar immobilization and cytolysis phenotypes and porphyrin mobilization noted previously were further analyzed biochemically and cytologically to delineate the mechanism of phototoxicity and detoxification in this monoporphyric model. Under optimal conditions of induction for approximately 3 days, cells remained viable but became increasingly uroporphyric, peaking at ≥90% of the population by approximately day 2; thereafter, a small population of less porphyric or aporphyric cells emerged. On exposure to light, the flagella of porphyric cells were immobilized in milliseconds, and singlet oxygen became detectable in their lysates. Both photosensitive phenotypes increased proportionally with the cellular uroporphyric levels and were susceptible to inhibition by azide, but not byd-mannitol. Brief irradiation of the uroporphyric cells produced no appreciable protein degradation but inactivated cytosolic neomycin phosphotransferase and significantly bleached cytosolic green fluorescent protein, which was azide reversible. These cells were irreparably photodamaged, as indicated by their subsequent loss of membrane permeability and viability. This is the first in situ demonstration that early inactivation of functional proteins by singlet oxygen initiates the cytolytic phototoxicity in uroporphyria. Detoxification appears to involve endocytic/exocytic mobilization of uroporphyrin from cytosol to “porphyrinosomes” for its eventual extracellular expulsion. This is proposed as the sole mechanism of detoxification, since it is attributable to the reversion of porphyric to aporphyric cells during uroporphyrinogenesis and repeated cycles of this event plus photolysis selected no resistant mutants, only aporphyric clones of the parental phenotypes. Further characterization of the transport system for uroporphyrin in this model is expected to benefit not only our understanding of the cellular mechanism for disposal of toxic soluble wastes but also potentially the effective management of human uroporphyria and the use of uroporphyricLeishmaniafor vaccine/drug delivery.
The Membrane-Bound Transcriptional Regulator CadC Is Activated by Proteolytic Cleavage in Response to Acid Stress
Authors: Lee Yong Heon , Kim Ji Hye , Bang Iel Soo , Park Yong Keun
Published: May 2008

Proteolytic processes often participate in signal transduction across bacterial membranes. In
Salmonella enterica
serovar Typhimurium, the transcriptional regulator CadC activates genes of lysine decarboxylase system in response to external acidification and exogenous lysine. However, the signaling mechanism of CadC activation remains unexplored. We report here that CadC is located on the inner membrane under normal growth conditions but rapidly cleaved under acid stress conditions, leading to the induction of target gene transcription. As full-length CadC is degraded, the N-terminal fragment containing the DNA-binding domain accumulates in the inner membrane. Moreover, we show that C-terminal truncations of CadC abolish its degradation, resulting in complete loss of activator function. Together, these observations suggest that site-specific proteolysis at the periplasmic domain of CadC generates a biologically active form of N-terminal DNA-binding domain to promote target gene activation.
The Evolution of Class 1 Integrons and the Rise of Antibiotic Resistance
Authors: Gillings Michael , Boucher Yan , Labbate Maurizio , Holmes Andrew , Krishnan Samyuktha , Holley Marita , Stokes H. W.
Published: May 2008

Class 1 integrons are central players in the worldwide problem of antibiotic resistance, because they can capture and express diverse resistance genes. In addition, they are often embedded in promiscuous plasmids and transposons, facilitating their lateral transfer into a wide range of pathogens. Understanding the origin of these elements is important for the practical control of antibiotic resistance and for exploring how lateral gene transfer can seriously impact on, and be impacted by, human activities. We now show that class 1 integrons can be found on the chromosomes of nonpathogenic soil and freshwaterBetaproteobacteria. Here they exhibit structural and sequence diversity, an absence of antibiotic resistance genes, and a phylogenetic signature of lateral transfer. Some examples are almost identical to the core of the class 1 integrons now found in pathogens, leading us to conclude that environmentalBetaproteobacteriawere the original source of these genetic elements. Because these elements appear to be readily mobilized, their lateral transfer into human commensals and pathogens was inevitable, especially given thatBetaproteobacteriacarrying class 1 integrons are common in natural environments that intersect with the human food chain. The strong selection pressure imposed by the human use of antimicrobial compounds then ensured their fixation and global spread into new species.
Contribution of Trimeric Autotransporter C-Terminal Domains of Oligomeric Coiled-Coil Adhesin (Oca) Family Members YadA, UspA1, EibA, and Hia to Translocation of the YadA Passenger Domain and Virulence ofYersinia enterocolitica
Authors: Ackermann Nikolaus , Tiller Maximilian , Anding Gisela , Roggenkamp Andreas , Heesemann Jürgen
Published: May 2008

The Oca family is a novel class of autotransporter-adhesins with highest structural similarity in their C-terminal transmembrane region, which supposedly builds a beta-barrel pore in the outer membrane (OM). The prototype of the Oca family is YadA, an adhesin ofYersinia enterocoliticaandYersinia pseudotuberculosis. YadA forms a homotrimeric lollipop-like structure on the bacterial surface. The C-terminal regions of three YadA monomers form a barrel in the OM and translocate the trimeric N-terminal passenger domain, consisting of stalk, neck, and head region to the exterior. To elucidate the structural and functional role of the C-terminal translocator domain (TLD) and to assess its promiscuous capability with respect to transport of related passenger domains, we constructed chimeric YadA proteins, which consist of the N-terminal YadA passenger domain and C-terminal TLDs of Oca family members UspA1 (Moraxella catarrhalis), EibA (Escherichia coli), and Hia (Haemophilus influenzae). These constructs were expressed inY. enterocoliticaand compared for OM localization, surface exposure, oligomerization, adhesion properties, serum resistance, and mouse virulence. We demonstrate that all chimeric YadA proteins translocated the YadA passenger domain across the OM.Y. enterocoliticastrains producing YadA chimeras or wild-type YadA showed comparable binding to collagen and epithelial cells. However, strains producing YadA chimeras were attenuated in serum resistance and mouse virulence. These results demonstrate for the first time that TLDs of Oca proteins of different origin are efficient translocators of the YadA passenger domain and that the cognate TLD of YadA is essential for bacterial survival in human serum and mouse virulence.
A Family of Insertion Sequences That Impacts Integrons by Specific Targeting of Gene Cassette Recombination Sites, the IS1111-attCGroup
Authors: Tetu Sasha G. , Holmes Andrew J.
Published: May 2008

Integrons facilitate the evolution of complex phenotypes by physical and transcriptional linkage of genes. They can be categorized as chromosomal integrons (CIs) or mobile resistance integrons (MRIs). The significance of MRIs for the problem of multiple antibiotic resistance is well established. CIs are more widespread, but their only demonstrated significance is as a reservoir of gene cassettes for MRIs. In characterizing CIs associated withPseudomonas, we discovered a subfamily of insertion sequences, termed the IS1111-attCgroup, that insert into the recombination sites of gene cassettes (attCsite) by site-specific recombination. IS1111-attCelements appear to have recently spread fromPseudomonasspecies to clinical class 1 integrons. Such elements are expected to significantly impact integrons. To explore this further, we examined CIs in 24 strains representing multiple levels of evolutionary divergence within the genusPseudomonas. Cassette arrays frequently had a degenerated “footprint” of an IS1111-attCgroup element at their terminus and in three cases were occupied by multiple functional IS1111-attCelements. WithinPseudomonasspp. the IS-integron interaction appears to follow an evolutionarily rapid cycle of infection, expansion, and extinction. The final outcome is extinction of the IS element and modification of the right-hand boundary of the integron. This system represents an unusual example of convergent evolution whereby heterologous families of site-specific recombinases of distinct genetic elements have adopted the same target site. The interactions described here represent a model for evolutionary processes that offer insights to a number of aspects of the biology of integrons and other mosaic genetic elements.
Symbiosis-Promoting and Deleterious Effects of NopT, a Novel Type 3 Effector of
Rhizobium
sp. Strain NGR234
Authors: Dai Wei-Jun , Zeng Yong , Xie Zhi-Ping , Staehelin Christian
Published: May 2008

Establishment of symbiosis between certain host plants and nitrogen-fixing bacteria (“rhizobia”) depends on type 3 effector proteins secreted via the bacterial type 3 secretion system (T3SS). Here, we report that the open reading frame y4zC of strain NGR234 encodes a novel rhizobial type 3 effector, termed NopT (for nodulation outer protein T). Analysis of secreted proteins from NGR234 and T3SS mutants revealed that NopT is secreted via the T3SS. NopT possessed autoproteolytic activity when expressed in
Escherichia coli
or human HEK 293T cells. The processed NopT exposed a glycine (G50) to the N terminus, which is predicted to be myristoylated in eukaryotic cells. NopT with a point mutation at position C93, H205, or D220 (catalytic triad) showed strongly reduced autoproteolytic activity, indicating that NopT is a functional protease of the YopT-AvrPphB effector family. When transiently expressed in tobacco plants, proteolytically active NopT elicited a rapid hypersensitive reaction.
Arabidopsis
plants transformed with
nopT
showed chlorotic and necrotic symptoms, indicating a cytotoxic effect. Inoculation experiments with mutant derivatives of NGR234 indicated that NopT affected nodulation either positively (
Phaseolus vulgaris
cv. Yudou No. 1;
Tephrosia vogelii
) or negatively (
Crotalaria juncea
). We suggest that NopT-related polymorphism may be involved in evolutionary adaptation of NGR234 to particular host legumes.
Biochemical and Mutational Analyses of AcuA, the Acetyltransferase Enzyme That Controls the Activity of the Acetyl Coenzyme A Synthetase (AcsA) in
Bacillus subtilis
Authors: Gardner Jeffrey G. , Escalante-Semerena Jorge C.
Published: May 2008

The
acuABC
genes of
Bacillus subtilis
comprise a putative posttranslational modification system. The AcuA protein is a member of the
G
cn5-related
N
-
a
cetyl
t
ransferase (GNAT) superfamily, the AcuC protein is a class I histone deacetylase, and the role of the AcuB protein is not known. AcuA controls the activity of acetyl coenzyme A synthetase (AcsA; EC 6.2.1.1) in this bacterium by acetylating residue Lys549. Here we report the kinetic analysis of wild-type and variant AcuA proteins. We contrived a genetic scheme for the identification of AcuA residues critical for activity. Changes at residues H177 and G187 completely inactivated AcuA and led to its rapid turnover. Changes at residues R42 and T169 were less severe. In vitro assay conditions were optimized, and an effective means of inactivating the enzyme was found. The basic kinetic parameters of wild-type and variant AcuA proteins were obtained and compared to those of eukaryotic GNATs. Insights into how the isolated mutations may exert their deleterious effect were investigated by using the crystal structure of an AcuA homolog.
Phage SPP1 Reversible Adsorption toBacillus subtilisCell Wall Teichoic Acids Accelerates Virus Recognition of Membrane Receptor YueB
Authors: Baptista Catarina , Santos Mário A. , São-José Carlos
Published: May 2008

Bacteriophage SPP1 targets the host cell membrane protein YueB to irreversibly adsorb and infectBacillus subtilis. Interestingly, SPP1 still binds to the surface ofyueBmutants, although in a completely reversible way. We evaluated here the relevance of a reversible step in SPP1 adsorption and identified the receptor(s) involved. We show that reversible adsorption is impaired inB. subtilismutants defective in the glucosylation pathway of teichoic acids or displaying a modified chemical composition of these polymers. The results indicate that glucosylated poly(glycerolphosphate) cell wall teichoic acid is the major target for SPP1 reversible binding. Interaction with this polymer is characterized by a fast adsorption rate showing low-temperature dependence, followed by a rapid establishment of an equilibrium state between adsorbed and free phages. This equilibrium is basically determined by the rate of phage dissociation, which exhibits a strong dependence on temperature compatible with an Arrhenius law. This allowed us to determine an activation energy of 22.6 kcal/mol for phage release. Finally, we show that SPP1 reversible interaction strongly accelerates irreversible binding to YueB. Our results support a model in which fast SPP1 adsorption to and desorption from teichoic acids allows SPP1 to scan the bacterial surface for rapid YueB recognition.
An OmpA Family Protein, a Target of the GinI/GinR Quorum-Sensing System in
Gluconacetobacter intermedius
, Controls Acetic Acid Fermentation
Authors: Iida Aya , Ohnishi Yasuo , Horinouchi Sueharu
Published: May 2008

Via
N
-acylhomoserine lactones, the GinI/GinR quorum-sensing system in
Gluconacetobacter intermedius
NCI1051, a gram-negative acetic acid bacterium, represses acetic acid and gluconic acid fermentation. Two-dimensional polyacrylamide gel electrophoretic analysis of protein profiles of strain NCI1051 and
ginI
and
ginR
mutants identified a protein that was produced in response to the GinI/GinR regulatory system. Cloning and nucleotide sequencing of the gene encoding this protein revealed that it encoded an OmpA family protein, named GmpA.
gmpA
was a member of the gene cluster containing three adjacent homologous genes,
gmpA
to
gmpC
, the organization of which appeared to be unique to vinegar producers, including “
Gluconacetobacter polyoxogenes
.” In addition, GmpA was unique among the OmpA family proteins in that its N-terminal membrane domain forming eight antiparallel transmembrane β-strands contained an extra sequence in one of the surface-exposed loops. Transcriptional analysis showed that only
gmpA
of the three adjacent
gmp
genes was activated by the GinI/GinR quorum-sensing system. However,
gmpA
was not controlled directly by GinR but was controlled by an 89-amino-acid protein, GinA, a target of this quorum-sensing system. A
gmpA
mutant grew more rapidly in the presence of 2% (vol/vol) ethanol and accumulated acetic acid and gluconic acid in greater final yields than strain NCI1051. Thus, GmpA plays a role in repressing oxidative fermentation, including acetic acid fermentation, which is unique to acetic acid bacteria and allows ATP synthesis via ethanol oxidation. Consistent with the involvement of
gmpA
in oxidative fermentation, its transcription was also enhanced by ethanol and acetic acid.
Functional Characterization and Localization of the TcpH Conjugation Protein fromClostridium perfringens
Authors: Teng Wee Lin , Bannam Trudi L. , Parsons Jennifer A. , Rood Julian I.
Published: May 2008

InClostridium perfringens, conjugative plasmids encode important virulence factors, such as toxins and resistance determinants. All of these plasmids carry a conjugation locus that consists of 11 genes:intPandtcpAtotcpJ. Three proteins, TcpA, a potential coupling protein, TcpF, a putative ATPase that is similar to ORF15 from Tn916, and TcpH, which contains VirB6-like domains, are essential for conjugation in the prototype conjugative plasmid pCW3. To analyze the functional domains of TcpH, a putative structural component of the mating-pair formation complex and deletion and site-directed mutants were constructed and analyzed. The results showed that the N-terminal 581 residues and the conserved242VQQPW246motif were required for conjugative transfer. Bacterial two-hybrid and biochemical studies showed that TcpH interacted with itself and with TcpC. An analysis of thetcpHmutants demonstrated that the region required for these interactions also was localized to the N-terminal 581 residues and that the function of the C-terminal region of TcpH was independent of protein-protein interactions. Finally, immunofluorescence studies showed that TcpH and TcpF were located at both cell poles of donorC. perfringenscells. The results provide evidence that TcpH is located in the cell membrane, where it oligomerizes and interacts with TcpC to form part of the mating-pair formation complex, which is located at the cell poles and is closely associated with TcpF.
The
c
-Type Cytochrome OmcA Localizes to the Outer Membrane upon Heterologous Expression in
Escherichia coli
Authors: Donald James W. , Hicks Matthew G. , Richardson David J. , Palmer Tracy
Published: May 2008

We have functionally produced the outer membrane cytochrome OmcA from
Shewanella oneidensis
in
Escherichia coli
. Substrate accessibility experiments indicate that OmcA is surface exposed in an
E. coli
B strain but not in a K-12 strain. We show that a functional type II secretion system is required for surface localization.
ATPase Activity of
Mycobacterium tuberculosis
SecA1 and SecA2 Proteins and Its Importance for SecA2 Function in Macrophages
Authors: Hou Jie M. , D'Lima Nadia G. , Rigel Nathan W. , Gibbons Henry S. , McCann Jessica R. , Braunstein Miriam , Teschke Carolyn M.
Published: May 2008

The Sec-dependent translocation pathway that involves the essential SecA protein and the membrane-bound SecYEG translocon is used to export many proteins across the cytoplasmic membrane. Recently, several pathogenic bacteria, including
Mycobacterium tuberculosis
, were shown to possess two SecA homologs, SecA1 and SecA2. SecA1 is essential for general protein export. SecA2 is specific for a subset of exported proteins and is important for
M. tuberculosis
virulence. The enzymatic activities of two SecA proteins from the same microorganism have not been defined for any bacteria. Here,
M. tuberculosis
SecA1 and SecA2 are shown to bind ATP with high affinity, though the affinity of SecA1 for ATP is weaker than that of SecA2 or
Escherichia coli
SecA. Amino acid substitution of arginine or alanine for the conserved lysine in the Walker A motif of SecA2 eliminated ATP binding. We used the SecA2(K115R) variant to show that ATP binding was necessary for the SecA2 function of promoting intracellular growth of
M. tuberculosis
in macrophages. These results are the first to show the importance of ATPase activity in the function of accessory SecA2 proteins.
Redox-State Dynamics of Ubiquinone-10 Imply Cooperative Regulation of Photosynthetic Membrane Expression in
Rhodospirillum rubrum
Authors: Grammel Hartmut , Ghosh Robin
Published: May 2008

It is now well established that, for photosynthetic bacteria, the aerobic-to-microaerophilic transition activates the membrane-bound sensor kinase RegB, which subsequently phosphorylates the transcriptional activator RegA, thereby inducing elevated levels of intracellular photosynthetic membranes. The mechanism of RegB activation—in particular, the role of ubiquinone-10—is controversial at present. One problem here is that very limited quantitative in vivo data for the response of the ubiquinone redox state to different cultivation conditions exist. Here, we utilize
Rhodospirillum rubrum
to study the correlation of the quinone redox state to the expression level of photosynthetic membranes and determine an effective response function directly. Our results show that changes in the photosynthetic membrane levels between 50 and 95% of that maximally attainable are associated with only a twofold change in the ubiquinol/ubiquinone ratio and are not necessarily proportional to the total levels of either quinone or [NAD
+
+ NADH]. There is no correlation between the redox potentials of the quinone and pyridine nucleotide pools. Hill function analysis of the photosynthetic membrane induction in response to the quinone redox state suggests that the induction process is highly cooperative. Our results are probably generally applicable to quinone redox regulation in bacteria.
Nitric Oxide Stress Induces Different Responses but Mediates Comparable Protein Thiol Protection inBacillus subtilisandStaphylococcus aureus
Authors: Hochgräfe Falko , Wolf Carmen , Fuchs Stephan , Liebeke Manuel , Lalk Michael , Engelmann Susanne , Hecker Michael
Published: May 2008

The nonpathogenicBacillus subtilisand the pathogenStaphylococcus aureusare gram-positive model organisms that have to cope with the radical nitric oxide (NO) generated by nitrite reductases of denitrifying bacteria and by the inducible NO synthases of immune cells of the host, respectively. The response of both microorganisms to NO was analyzed by using a two-dimensional gel approach. Metabolic labeling of the proteins revealed major changes in the synthesis pattern of cytosolic proteins after the addition of the NO donor MAHMA NONOate. WhereasB. subtilisinduced several oxidative stress-responsive regulons controlled by Fur, PerR, OhrR, and Spx, as well as the general stress response controlled by the alternative sigma factor SigB, the more resistantS. aureusshowed an increased synthesis rate of proteins involved in anaerobic metabolism. These data were confirmed by nuclear magnetic resonance analyses indicating that NO causes a drastically higher increase in the formation of lactate and butanediol inS. aureusthan inB. subtilis. Monitoring the intracellular protein thiol state, we observed no increase in reversible or irreversible protein thiol modifications after NO stress in either organism. Obviously, NO itself does not cause general protein thiol oxidations. In contrast, exposure of cells to NO prior to peroxide stress diminished the irreversible thiol oxidation caused by hydrogen peroxide.
A Cellulose Synthase-Like Protein Involved in Hyphal Tip Growth and Morphological Differentiation in
Streptomyces
Authors: Xu Hongbin , Chater Keith F. , Deng Zixin , Tao Meifeng
Published: May 2008

Cellulose synthase and cellulose synthase-like proteins, responsible for synthesizing β-glucan-containing polysaccharides, play a fundamental role in cellular architectures, such as plant cell and tissue morphogenesis, bacterial biofilm formation, and fruiting-body development. However, the roles of the proteins involved in the developmental process are not well understood. Here, we report that a cellulose synthase-like protein (CslA
Sc
) in
Streptomyces
has a function in hyphal tip growth and morphological differentiation. The

cslA
Sc

replacement mutant showed pleiotropic defects, including the severe delay of aerial-hyphal formation and altered cell wall morphology. Calcofluor white fluorescence analysis demonstrated that polysaccharide synthesis at hyphal tips was dependent on CslA
Sc
.

cslA
Sc

was constitutively transcribed, and an enhanced green fluorescent protein-CslA
Sc
fusion protein was mostly located at the hyphal tips. An extract enriched in morphogenetic chaplin proteins promoted formation of aerial hyphae by the mutant. Furthermore, a two-hybrid experiment indicated that the glycosyltransferase domain of CslA
Sc
interacted with the tropomyosin-like polarity-determining DivIVA protein, suggesting that the tip-located DivIVA governed tip recruitment of the CslA
Sc
membrane protein. These results imply that the cellulose synthase-like protein couples extracellular and cytoskeletal components functioning in tip growth and cell development.
Genes and Enzymes of Azetidine-2-Carboxylate Metabolism: Detoxification and Assimilation of an Antibiotic
Authors: Gross Carol , Felsheim Roderick , Wackett Lawrence P.
Published: May 2008

l
-(−)-Azetidine-2-carboxylate (AC) is a toxic, natural product analog of
l
-proline. This study revealed the genes and biochemical strategy employed by
Pseudomonas
sp. strain A2C to detoxify and assimilate AC as its sole nitrogen source. The gene region from
Pseudomona
s sp. strain A2C required for detoxification was cloned into
Escherichia coli
and sequenced. The 7.0-kb region contained eight identifiable genes. Four encoded putative transporters or permeases for γ-amino acids or drugs. Another gene encoded a homolog of 2-haloacid dehalogenase (HAD). The encoded protein, denoted
l
-azetidine-2-carboxylate hydrolase (AC hydrolase), was highly overexpressed by subcloning. The AC hydrolase was shown to catalyze azetidine ring opening with the production of 2-hydroxy-4-aminobutyrate. AC hydrolase was further demonstrated to be a new hydrolytic member of the HAD superfamily by showing loss of activity upon changing aspartate-12, the conserved active site nucleophile in this family, to an alanine residue. The presence of a gene encoding a potential export chaperone protein, CsaA, adjacent to the AC hydrolase gene suggested that AC hydrolase might be found inside the periplasm in the native
Pseudomonas
strain. Periplasmic and cytoplasmic cell fractions from
Pseudomonas
sp. strain A2C were prepared. A higher specific activity for AC hydrolysis was found in the periplasmic fraction. Protein mass spectrometry further identified AC hydrolase and known periplasmic marker proteins in the periplasmic fraction. A model was proposed in which AC is hydrolyzed in the periplasm and the product of that reaction is transported into and further metabolized in the cytoplasm.
Physical activity and breast cancer risk: impact of timing, type and dose of activity and population subgroup effects
Authors: Friedenreich C M , Cust A E
Published: May 2008

Objective:

To review (1) the epidemiological literature on physical activity and the risk of breast cancer, examining the effect of the different parameters of activity and effect modification within different population subgroups; and (2) the biological mechanisms whereby physical activity may influence the risk of breast cancer.

Methods:

A review of all published literature to September 2007 was conducted using online databases; 34 case-control and 28 cohort studies were included. The impact of the different parameters of physical activity on the association between activity and the risk of breast cancer was examined by considering the type of activity performed, the timing of activity over the life course and the intensity of activity. Effect modification of this association by menopausal status, body mass index (BMI), racial group, family history of breast cancer, hormone receptor status, energy intake and parity were also considered.

Results:

Evidence for a risk reduction associated with increased physical activity was found in 47 (76%) of 62 studies included in this review with an average risk decrease of 25–30%. A dose-response effect existed in 28 of 33 studies. Stronger decreases in risk were observed for recreational activity, lifetime or later life activity, vigorous activity, among postmenopausal women, women with normal BMI, non-white racial groups, those with hormone receptor negative tumours, women without a family history of breast cancer and parous women.

Conclusions:

The effect of physical activity on the risk of breast cancer is stronger in specific population subgroups and for certain parameters of activity that need to be further explored in future intervention trials.
The effects of the 5-HT2Cagonistm-chlorophenylpiperazine on elite athletes with unexplained underperformance syndrome (overtraining): Figure 1
Authors: Budgett R , Hiscock N , Arida R , Castell L M
Published: May 2008

A possible link between the neurotransmitter, 5-hydroxytryptamine (5-HT), plasma tryptophan, and branched chain amino acids concentration and exercise-induced fatigue is described by the central fatigue hypothesis. 5-HT receptors and neuroendocrine “challenge” tests, using prolactin release as an indirect measure of 5-HT activity were studied by recent investigations. In the present study, the original hypothesis about the role of amino acids in increasing brain 5-HT with a neuroendocrine challenge test on elite athletes diagnosed with unexplained, underperformance syndrome (UUPS) was combined. There was an apparent increased sensitivity of 5-HT receptors in athletes with UUPS compared with fit, well-trained controls, as measured via increased prolactin release following a bolus dose ofm-chlorophenylpiperazine , a 5-HT agonist. No changes were observed in plasma amino acid concentrations in either group. There is evidence that well-trained athletes have a reduced sensitivity of 5-HT receptors. The present study suggests that this adaptation may be lost in athletes with UUPS: this might explain some of their observed symptoms.
Why it is difficult to detect an illegally bowled cricket delivery with either the naked eye or usual two-dimensional video analysis
Authors: Aginsky K D , Noakes T D
Published: May 2008

Objective

In this study, the influence of various anatomical and biomechanical factors on the ability to detect the magnitude of elbow extension during the cricket bowling action, with either the naked eye or from conventional two-dimensional video footage was evaluated.

Design

Descriptive study

Setting

One male bowler who had a large ℌcarrying angleℍ was studied by means of a three-dimensional biomechanical analysis using the Vicon MX13 motion analysis system when bowling at match pace. Photographs were taken from various angles during the bowling delivery action to illustrate factors influencing the visual appearance of an illegal delivery.

Main outcome measures

The influence of extension of the elbow joint and the elbow's anatomically fixed position, known as the “carrying angle”, on the visual perception of an illegal (“thrown”) delivery were the main outcome measures.

Results

The elbow joint rotates about 90° as a result of humeral rotation during the movement of shoulder circumduction produced by the bowler's delivery action. This causes the plane in which the elbow joint moves to change throughout the delivery action. This movement will also vary between bowlers. The movement of elbow planar flexion/extension can be viewed only when the viewer's eyes are at exactly 90u to the plane of elbow joint movement. Thus, a cricket umpire wishing to detect elbow extension during the bowler's delivery action would need continuously to change his viewing position as the bowler's arm moved from the horizontal to the vertical position at ball release. We show that by viewing the action from only one position, the umpire will be confused by the illusion of a “throw” produced by a large “carrying angle” in some bowlers.

Conclusion

It is impossible for an umpire conclusively to cite a bowler for an illegal action based only on naked eye observation. To do this the umpire would need to be in at least three different positions throughout a single delivery. Similarly, video footage shot from at least three different angles during the bowler's delivery action would need to be viewed by the match referee. By viewing the delivery from only one position, the visual illusion of a “throw” will be created by the presence of a large “carrying angle”.
What factors are associated with physical activity in older people, assessed objectively by accelerometry?
Authors: Harris T J , Owen C G , Victor C R , Adams R , Cook D G
Published: May 2008

Objectives:

To assess physical activity (PA) levels measured objectively using accelerometers in community-dwelling older people and to examine the associations with health, disability, anthropometric measures and psychosocial factors.

Design:

Cross-sectional survey.

Setting:

Single general practice (primary care centre), United Kingdom.

Participants:

Random selection of 560 community-dwelling older people at least 65 years old, registered with the practice. 43% (238/560) participated.

Assessment of risk factors:

Participants completed a questionnaire assessing health, disability, psychosocial factors and PA levels; underwent anthropometric assessment; and wore an accelerometer (Actigraph) for 7 days.

Main outcome measures:

Average daily accelerometer step-counts and time spent in different PA levels. Associations between step-counts and other factors were examined using linear regression.

Results:

Average daily step-count was 6443 (95% CI 6032 to 6853). Men achieved 754 (84 to 1424) more steps daily than women. Step-count declined steadily with age. Independent predictors of average daily step-count were: age; general health; disability; diabetes; body mass index; exercise self-efficacy; and perceived exercise control. Activities associated independently with higher step-counts included number of long walks and dog-walking. Only 2.5% (6/238) of participants achieved the recommended 150 minutes weekly of at least moderate-intensity activity in ⩾10 minute bouts; 62% (147/238) achieved none.

Conclusions:

This is the first population-based sample of older people with objective PA and anthropometric measures. PA levels in older people are well below recommended levels, emphasising the need to increase PA in this age group, particularly in those who are overweight/obese or have diabetes. The independent effects of exercise self-efficacy and exercise control on PA levels highlight their role as potential mediators for intervention studies.
Six-minute walk test in children with chronic conditions
Authors: Hassan J , van der Net J , Helders P J M , Prakken B J , Takken T
Published: May 2008

Objectives

The 6-minute walk test (6MWT) is a frequently used indicator of functional exercise capacity. The goals of this study were to compare the 6-minute walk performance of three paediatric patient groups with that of healthy peers, to assess differences between published reference values and to investigate which anthropometric characteristics best predict 6-minute walk performance.

Methods

47 children with haemophilia (mean (SD) age 12.5 (2.9) years), 44 with juvenile idiopathic arthritis (JIA) (mean age 9.3 (2.2) years) and 22 with spina bifida (SB) (mean age 10.3 (3.1) years) were included. Subjects performed a 6MWT, and the distance walked (6MWD) was compared with published reference values.

Results

The haemophilia, JIA and SB patients achieved 90%–92%, 72%–75% and 60%–62% of predicted walking distances, respectively. There were significant associations between 6MWD and age, height and weight in the haemophilia group and 6MWD and height in the JIA group. None of the anthropometric variables was significantly related to 6MWD in the SB group. All anthropometric variables were strongly correlated with walking distance–body weight product (6Mwork) in all groups. Height explained 24% (haemophilia) and 11% (JIA) of the variance in 6MWD and 84% (haemophilia), 78% (JIA) and 73% (SB) of the variance in 6Mwork.

Conclusions

Walking distances of children with haemophilia, JIA and SB are significantly reduced compared with healthy references. Walking distance–body weight product seems to be a better outcome measure of the 6MWT compared with distance walked alone. Height is the best predictor of 6MWD and 6Mwork.
What Makes a Ru-Based Compound a Viable Lithium-Ion Insertion Material?
Authors: Johannes Michelle , Stux Arnold M. , Swider-Lyons Karen E.
Published: May 2008

We synthesize, measure and use first principles density functional theory (DFT) calculations to study two Ru-based metal oxides, layered Li2RuO3 and rutile RuO2, in terms of their electrochemical performance as potential battery cathode materials. Despite being composed of identical constituent elements, and having the same local structure, the two compounds have very different voltage profiles and conductivities that can be traced back to differences in their long range structures. We find that three basic factors contribute to the superior cathode properties of Li2RuO3 in comparison to RuO2: a lower Ru/O ratio that raises the oxidation state of Ru, more localized electron states due to quasi-two-dimensionality, and strong Ru-Ru bonding in the metal oxide plane that shifts the electronic energy levels. The principles extracted from the comparison of these two materials can be generalized and used to help guide the search for superior cathode compounds
Synchrotron Radiation Study of the M2MgSi2O7:Eu2+ Persistent Luminescence Materials
Authors: Holsa Jorma P. , Niittykoski Janne , Kirm Marco , Laamanen Taneli , Lastusaari Mika , Novak Pavel , Raud Juri
Published: May 2008

The synchrotron radiation luminescence and excitation spectra of the Eu2+ doped M2MgSi2O7 (M = Ca, Sr, Ba) materials were investigated at the SUPERLUMI station of HASYLAB at DESY, Germany. The measurement of the band gap (Eg) energy of all three host lattices using the excitation spectra of Eu2+ gave values around 7 eV. The measured band gap energies were very similar but slightly higher than those calculated with the DFT-methods. The effect of R3+ co-doping was studied at different temperatures between 10 K and room temperature. A significant increase in the band gap energy was observed with decreasing temperature. In contrast, no noteworthy change in this value was observed as a function of the R3+ co-doping ion.
Long Persistent White Light Emitting Diode
Authors: Jia Dongdong , Girardi Jenna , Greenland Kelly
Published: May 2008

Long persistent light emitting diode indicators for emergency indication were made by coat long persistent nanophosphors. During light down conversion when electrical power is available, photons were stored in the nanophosphors. When the electrical power is shut off, the persistent afterglow emission from the nanophosphor can extend the indication time for another 10 hours. White light is produced by using UV LED and green and blue nanophosphors.
Long Persistent Greenhouse Film
Authors: Jia Dongdong , Hunter David N. , Wilhelm Justin E.
Published: May 2008

Thin films for greenhouse application were prepared by doping with long persistent blue and red nanophosphors. Ultra violet and green light in the Sun spectrum were converted into blue and red light by using the nanophosphors. A more efficient blue and red light absorption by the chlorophyll in the plants can let the plants to grow faster. The blue and red light stored in the long persistent nanophosphors can also extend the growth time for the plants in the greenhouse which will increase productivity.
Initial Stage of the Delithiation of Li1.2-xMn0.4Fe0.4O2 Positive Electrode Material for Lithium-Ion Batteries Studied by Electron Energy-Loss Spectroscopy
Authors: Kikkawa Jun , Akita Tomoki , Tabuchi Mitsuharu , Shikano Masahiro , Tatsumi Kuniaki , Kohyama Masanori
Published: May 2008

We have investigated initial stage of the delithiation of Li1.2-xMn0.4Fe0.4O2 nanoparticles by means of transmission electron microscopy and electron energy-loss spectroscopy. It was found that depletion areas with diameters of less than 10 nm are preferentially formed at Fe-rich regions on the particle surfaces. Correlations between redox reactions of transition metal ions and formation of the depletion areas are discussed.
Electrochemical Performance of Nanostructured LiMn1.5Ni0.5O4 Spinel at Elevated Temperature
Authors: Marandian Hagh Nader , Amatucci Glenn G.
Published: May 2008

In order to identify the failure mechanism of LiMn1.5Ni0.5O4 (LMN) spinel at elevated temperature (60{degree sign}C), the effect of carbon black, Mn3+ content and charge/discharge state storage conditions were studied. It was identified that the main degradation mechanism at elevated temperature was the systematic impedance rise rather than intrinsic capacity loss. At this early stage we attribute most of this to the anodic decomposition of the electrolyte on the surface of the spinel. We introduce a surface conversion process to improve the elevated temperature performance of the spinel. The surface converted materials exhibited much lower impedance rise with improved capacity retention and rate capability at elevated temperature.
Evaluation of Rapid Charge Methodologies for Li-Ion Chemistry
Authors: Chin Keith B. , Ratnakumar B. V. , Smart M. C. , Smith Kiah A. , Narayanan Sekharipuram
Published: May 2008

Rapid charge comparison of pulse charge to conventional CC-CV charge was performed in this study using a three electrode Li-ion cell of 300 mAhr capacity and 18650 Li-ion cells of 2 Ahr initial capacity. Pulse current and pulse voltage charge up to 4.1 V were ineffective as a rapid charge technique. Beyond 4.1 V charge, 80% capacity gain was achieved with at T = 20oC. Lower temperature of 0oC results in 3 times capacity gain over CC-CV charge after 15 minutes. Cell polarization potential reached as high as 5.5V at 2.5C-rate, with anode potential as low as -0.6V vs Li reference electrode. Subsequent discharge indicated no lithium plating. Computed cell internal resistances and individual anode and cathode resistances during pulse charge suggest that charge rate capabilities are limited by the anode kinetics.
Electrochemical Thin Film Studies of Sn Metals for Rechargeable Lithium Batteries
Authors: Song Seungwan , Baek Seung-Won
Published: May 2008

Thin film electrodes of Sn in various film thckness of 58 -200 nm have been prepared on stainless steel with a pulsed laser deposition technique. The 58 nm thick film electrode showed a stable cycling at the limited voltage window of 0.1-1.0 V, delivering capacity ~265 mAh/g for 50 cycles. The superior performance, when compared to porous electrode of this metal, is due to the shorter lithium diffusion path and enhanced conductivity from the substrate. The SEI layer formed on Sn electrode after cycled at 0.1-1.0 V was characterized using FTIR spectroscopy; the layer is composed of a mixture of inorganics and organics. The continuous formation of the SEI layer contributes to a continuous irreversible capacity loss on the extended cycles.
Li-Ion Electrolytes Containing Ester Co-Solvents for Wide Operating Temperature Range
Authors: Smart M. C. , Ratnakumar B. V. , Whitcanack Larry D. , Smith Kiah A. , Santee Stuart , Gitzendanner Robert , Yevoli Vince
Published: May 2008

As part of our continuing efforts to develop advanced electrolytes to improve the performance of lithium-ion cells, especially at low temperatures, we have identified a number of electrolyte co-solvents that can be incorporated into multi-component electrolyte formulations for enhanced performance, especially at very low temperatures (down to -70oC). In the current work, we investigated a number of ester co-solvents, namely methyl propionate (MP), ethyl propionate (EP), methyl butyrate (MB), ethyl butyrate (EB), propyl butyrate (PB), and butyl butyrate (BB), in multi-component electrolytes of the following composition: 1.0 M LiPF6 in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + X (20:60:20 v/v %) [where X = ester co-solvent]. These electrolytes have been optimized to provide good low temperature performance (down to -60oC) while still offering reasonable high temperature resilience to produce the desired wide operating temperature systems (-60 to +60oC). This has primarily been achieved by fixing the EC-content at 20% and the ester co-solvent at 20%, in contrast to the previously developed systems.
Phase Behavior and Conductivity of Et4NTFSI-LiTFSI Mixtures - A Model System for Ionic Liquid Lithium Battery Electrolytes
Authors: Henderson Wesley A. , Passerini Stefano , De Long H. , Trulove Paul
Published: May 2008

The phase behavior and ionic conductivity of tetraethylammonium bis(trifluoromethanesulfonyl)imide (Et4NTFSI) salt mixtures with LiTFSI have been examined. Two new (1-x) Et4NTFSI-(x) LiTFSI (x = 0.50 and 0.67) mixed salt crystalline phases form. These mixtures serve as models for the previously studied N-alkyl-N-methylpyrrolidinium salt (1-x) PYR1RTFSI-(x) LiTFSI mixtures. New interesting variations in the ionic conductivity are observed which are attributed to the solid-solid phase transitions of the neat Et4NTFSI salt creating disordered plastic crystalline phases. Although Et4NTFSI melts at 102{degree sign}C and LiTFSI melts at 236{degree sign}C, the two salts form a eutectic with a melting temperature of 31-33{degree sign}C.
Solvent-free, PYR1ATFSI Ionic Liquids-based Ternary Polymer Electrolyte Systems. II. Battery Tests
Authors: Appetecchi Giovanni Battista , Kim Guk Tae , Montanino Maria , Alessandrini Fabrizio , Passerini Stefano
Published: May 2008

In this manuscript are reported the battery tests of ternary PEO electrolytes containing N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid. The results of the tests show that lithium-metal, solvent-free batteries based on these ternary electrolytes are able to deliver the full capacity in low-rate discharge C/50 rate at room temperature. Optimum performance, however, is obtained at slightly higher temperatures (40{degree sign}C). The performance of ionic liquid-containing polymer batteries at 40{degree sign}C are comparable to analogous ionic liquid-free Li/LiFePO4 systems at 90{degree sign}C. The P(EO)10LiTFSI + 0.96 PYR1n4TFSI batteries showed long cycle life and high coulombic efficiency.
PEO based Block Copolymer as Solid State Lithium Battery Electrolyte
Authors: Ghosh Ayan , Kofinas Peter
Published: May 2008

We report the use of a conductive electrolyte matrix containing a secondary source of lithium templated by the microphase separation of a block copolymer. The desired polymer matrix is synthesized by hydrolyzing a block copolymer of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA), to generate a lithium salt of acrylic acid in the minority block (PMAALi), resulting in a block copolymer with a random copolymer as its second block, PEO-b-(PMMA-ran-PMAALi). The electrolyte composition was optimized at (ethylene oxide : lithium bis(oxalato)borate = 3:1) and exhibited nearly an order of magnitude higher conductivity than PEO of similar molecular weight and salt composition.
Studying the Origin and Mechanism of Irreversible Capacity in Lithium-Ion Cells
Authors: Hardwick Laurence J. , Marcinek Marek , Kostecki Robert
Published: May 2008

The effect of surface structural damage on graphitic anodes, commonly observed in tested Li-ion cells, was investigated. Similar surface structural disorder in graphite was artificially induced in Mag-10 synthetic graphite anodes using argon-ion sputtering. Raman microscopy, scanning electron microscopy (SEM) and Brunauer Emmett Teller (BET) measurements confirmed that Ar-ion sputtered Mag-10 electrodes display similar degree of surface degradation as the anodes from tested Li-ion cells. Artificially modified Mag-10 anodes showed double the irreversible charge capacity during the first formation cycle, compared to fresh un-altered anodes. Impedance spectroscopy and Fourier transform infrared (FTIR) spectroscopy on surface modified graphite anodes indicated the formation of a thicker and slightly more resistive SEI layer. The structural disorder induced in the graphite during long-term cycling maybe responsible for the slow and continuous SEI layer reformation, and consequently, the loss of reversible capacity due to the shift of lithium inventory in cycled Li-ion cells.