bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuronal nitric oxide synthase contributes to chronic stress‐induced depression by suppressing hippocampal neurogenesis
Authors: Zhou Qi‐Gang , Hu Yao , Hua Yao , Hu Mei , Luo Chun‐Xia , Han Xiao , Zhu Xin‐Jian , Wang Bin , Xu Jin‐Shu , Zhu Dong‐Ya
Published: September 2007

Increasing evidence suggests that depression may be associated with a lack of hippocampal neurogenesis. It is well established that neuronal nitric oxide synthase (nNOS)‐derived NO exerts a negative control on the hippocampal neurogenesis. Using genetic and pharmacological methods, we investigated the roles of nNOS in depression induced by chronic mild stress (CMS) in mice. Hippocampal nNOS over‐expression was first observed 4 days and remained elevated 21 and 56 days after exposure to CMS. The mice exposed to CMS exhibited behavioral changes typical of depression, and impaired neurogenesis in the hippocampus. The CMS‐induced behavioral despair and hippocampal neurogenesis impairment were prevented and reversed in the null mutant mice lacking nNOS gene (nNOS−/−) and in the mice receiving nNOS inhibitor. Disrupting hippocampal neurogenesis blocked the antidepressant effect of nNOS inhibition. Moreover, nNOS−/− mice exhibited antidepressant‐like properties. Our findings suggest that nNOS over‐expression in the hippocampus is essential for chronic stress‐induced depression and inhibiting nNOS signaling in brain may represent a novel approach for the treatment of depressive disorders.
Reduced neuronal nitric oxide synthase is involved in ischemia‐induced hippocampal neurogenesis by up‐regulating inducible nitric oxide synthase expression
Authors: Luo Chun Xia , Zhu Xin Jian , Zhou Qi Gang , Wang Bin , Wang Wei , Cai Hui Hui , Sun Yong Jun , Hu Mei , Jiang Jun , Hua Yao , Han Xiao , Zhu Dong Ya
Published: September 2007

Nitric oxide (NO), a free radical with signaling functions in the CNS, is implicated in some developmental processes, including neuronal survival, precursor proliferation, and differentiation. However, neuronal nitric oxide synthase (nNOS) ‐derived NO and inducible nitric oxide synthase (iNOS) ‐derived NO play opposite role in regulating neurogenesis in the dentate gyrus after cerebral ischemia. In this study, we show that focal cerebral ischemia reduced nNOS expression and enzymatic activity in the hippocampus. Ischemia‐induced cell proliferation in the dentate gyrus was augmented in the null mutant mice lacking nNOS gene (nNOS−/−) and in the rats receiving 7‐nitroindazole, a selective nNOS inhibitor, after stroke. Inhibition of nNOS ameliorated ischemic injury, up‐regulated iNOS expression, and enzymatic activity in the ischemic hippocampus. Inhibition of nNOS increased and iNOS inhibitor decreased cAMP response element‐binding protein phosphorylation in the ipsilateral hippocampus in the late stage of stroke. Moreover, the effects of 7‐nitroindazole on neurogenesis after ischemia disappeared in the null mutant mice lacking iNOS gene (iNOS−/−). These results suggest that reduced nNOS is involved in ischemia‐induced hippocampal neurogenesis by up‐regulating iNOS expression and cAMP response element‐binding protein phosphorylation.
Visible light induces matrix metalloproteinase‐9 expression in rat eye
Authors: Papp Andrea M. , Nyilas Rita , Szepesi Zsuzsanna , Lőrincz Magor L. , Takács Eszter , Ábrahám István , Szilágyi Nóra , Tóth Júlia , Medveczky Péter , Szilágyi László , Juhász Gábor , Juhász Gábor
Published: September 2007

Up‐regulation of matrix metalloproteinase‐9 (MMP‐9, gelatinase B) in the nervous system has been demonstrated when excitotoxicity‐induced tissue remodeling and neuronal death occurs. Induction of MMP‐9 by a natural stimulus has not been observed yet. Using RT‐PCR and gelatin‐zymography we demonstrated MMP‐9 induction at transcriptional and protein levels in different structures of the rat eye following over‐stimulation with white light. MMP‐9 elevation occurred in the retina without reduction in photoreceptor number or major anatomical reorganization. A transient decrease in electroretinogram b‐wave indicated the functional recovery. Retrobulbar injection of a broad‐spectrum MMP‐inhibitor GM6001, slowed the recovery rate of b‐wave amplitude. Even room‐light applied to dark‐adapted awake animals induced MMP‐9 increase in the retina, which suggests a role for MMP‐9 in physiological functional plasticity of the nervous system, such as light adaptation. This is the first demonstration of MMP‐9 induction by a sensory stimulus.
Neurexin Iβ and neuroligin are localized on opposite membranes in mature central synapses
Authors: Berninghausen Otto , Rahman M. Atiqur , Silva John‐Paul , Davletov Bazbek , Hopkins Colin , Ushkaryov Yuri A.
Published: September 2007

Synaptogenesis requires formation of trans‐synaptic complexes between neuronal cell‐adhesion receptors. Heterophilic receptor pairs, such as neurexin Iβ and neuroligin, can mediate distinct intracellular signals and form different cytoplasmic scaffolds in the pre‐ and post‐synaptic neuron, and may be particularly important for synaptogenesis. However, the functions of neurexin and neuroligin depend on their distribution in the synapse. Neuroligin has been experimentally assigned to the post‐synaptic membrane, while the localization of neurexin remains unclear. To study the subcellular distribution of neurexin Iβ and neuroligin in mature cerebrocortical synapses, we have developed a novel method for the physical separation of junctional membranes and their direct analysis by western blotting. Using urea and dithiothreitol, we disrupted trans‐synaptic protein links, without dissolving the lipid phase, and fractionated the pre‐ and post‐synaptic membranes. The purity of these fractions was validated by electron microscopy and western blotting using multiple synaptic markers. A quantitative analysis has confirmed that neuroligin is localized strictly in the post‐synaptic membrane. We have also demonstrated that neurexin Iβ is largely (96%) pre‐synaptic. Thus, neurexin Iβ and neuroligin normally form trans‐synaptic complexes and can transduce bidirectional signals.
Interrupting activator protein‐1 signaling in conscious rats can modify neuropeptide Y gene expression and feeding behavior of phenylpropanolamine
Authors: Hsieh Yih‐Shou , Yang Shun‐Fa , Chu Shu‐Chen , Kuo Dong‐Yih
Published: September 2007

The mechanism for phenylpropanolamine (PPA)‐induced anorexia has been attributed to its inhibitory action on hypothalamic neuropeptide Y (NPY), an orexigenic agent abundant in the brain. However, molecular mechanisms behind this effect are not well known. In this study, we investigated whether activator protein‐1 (AP‐1) signaling was involved. Rats were daily treated with PPA for 4 days. Changes in hypothalamic NPY, c‐fos, c‐jun, superoxide dismutase (SOD)‐1, and SOD‐2 mRNA contents were measured and compared. Results showed that c‐fos and c‐jun mRNA levels were increased following PPA treatment, which were relevant to a reduction in NPY mRNA level. To further determine if c‐fos/c‐jun genes were involved in PPA anorexia, infusions of antisense oligonucleotide into cerebroventricle were performed before daily PPA treatment in freely moving rats. Results showed that either c‐fos or c‐jun knock down could block PPA anorexia and restore NPY mRNA content to normal level. It is suggested that AP‐1 signaling may participate in the central regulation of PPA‐mediated appetite suppression via the modulation of NPY gene expression. Moreover, this modulation might be partly because of the neuroprotective effect of AP‐1 since SOD gene was activated during PPA treatment.
Digestive peptidases in Tenebrio molitor and possibility of use to treat celiac disease
Authors: ELPIDINA Elena N. , GOPTAR Irina A.
Published: September 2007

Digestion in Tenebrio molitor larvae occurs in the midgut, where there is a sharp pH gradient from 5.6 in the anterior midgut (AM) to 7.9 in the posterior midgut (PM). Accordingly, digestive enzymes are compartmentalized to the AM or PM. Enzymes in the AM are soluble and have acidic or neutral pH optima, while PM enzymes have alkaline pH optima. The main peptidases in the AM are cysteine endopeptidases presented by two to six subfractions of anionic proteins. The major activity belongs to cathepsin L, which has been purified and characterized. Serine post‐proline cleaving peptidase with pH optimum 5.3 was also found in the AM. Typical serine digestive endopeptidases, trypsin‐like and chymotrypsin‐like, are compartmentalized to the PM. Trypsin‐like activity is due to one cationic and three anionic proteinases. Chymotrypsin‐like activity consists of one cationic and four anionic proteinases, four with an extended binding site. The major cationic trypsin and chymotrypsin have been purified and thoroughly characterized. The predicted amino acid sequences are available for purified cathepsin L, trypsin and chymotrypsin. Additional sequences for putative digestive cathepsins L, trypsins and chymotrypsins are available, implying multigene families for these enzymes. Exopeptidases are found in the PM and are presented by a single membrane aminopeptidase N‐like peptidase and carboxypeptidase A, although multiple cDNAs for carboxypeptidase A were found in the AM, but not in the PM. The possibility of the use of two endopeptidases from the AM – cathepsin L and post‐proline cleaving peptidase – in the treatment of celiac disease is discussed.
Three new species of Arrhopalites (Collembola, Symphypleona, Arrhopalitidae) from Korea
Authors: PARK Kyung‐Hwa , KANG Jin‐Sun
Published: September 2007

Three new species of Arrhopalites in the Symphypleona from Korea are described and illustrated. This work also records new occurrence of Arrhopalites habei Yosii, 1956, with brief remarks. A key to the identification of the Korean species of Arrhopalites is provided.
First record of the family Cerylonidae (Coleoptera: Cucujoidea) in Korea
Authors: PARK Sun‐Jae , AHN Kee‐Jeong
Published: September 2007

The beetle family Cerylonidae, represented by Cautomus hystriculus Sharp, is identified for the first time in Korea. A habitus photo, redescription, diagnostic characters and illustrations of the species are provided.
Human tendon behaviour and adaptation,in vivo
Authors: Magnusson S. Peter , Narici Marco V. , Maganaris Constantinos N. , Kjaer Michael
Published: September 2007

Tendon properties contribute to the complex interaction of the central nervous system, muscle–tendon unit and bony structures to produce joint movement. Until recently limited information on human tendon behaviourin vivowas available; however, novel methodological advancements have enabled new insights to be gained in this area. The present review summarizes the progress made with respect to human tendon and aponeurosis functionin vivo, and how tendons adapt to ageing, loading and unloading conditions. During low tensile loading or with passive lengthening not only the muscle is elongated, but also the tendon undergoes significant length changes, which may have implications for reflex responses. During active loading, the length change of the tendon far exceeds that of the aponeurosis, indicating that the aponeurosis may more effectively transfer force onto the tendon, which lengthens and stores elastic energy subsequently released during unloading, in a spring‐like manner. In fact, data recently obtainedin vivoconfirm that,during walking, the human Achilles tendon provides elastic strain energy that can decrease the energy cost of locomotion. Also, new experimental evidence shows that, contrary to earlier beliefs, the metabolic activity in human tendon is remarkably high and this affords the tendon the ability to adapt to changing demands. With ageing and disuse there is a reduction in tendon stiffness, which can be mitigated with resistance exercises. Such adaptations seem advantageous for maintaining movement rapidity, reducing tendon stress and risk of injury, and possibly, for enabling muscles to operate closer to the optimum region of the length–tension relationship.
Regulation of skeletal muscle PPARδ mRNA expression in twins
Authors: Nilsson Emma , Poulsen Pernille , Sjögren Marketa , Ling Charlotte , Ridderstråle Martin , Groop Leif , Vaag Allan
Published: September 2007

Peroxisome proliferator‐activated receptors (PPARs) are nuclear receptors regulating the expression of genes involved in lipid and glucose metabolism in a complex and to some extent unknown manner. Our aim was to study the impact of different factors on PPARδ mRNA expression in human skeletal muscle on one side, and the impact of PPARδ mRNA expression on these factors, including glucose and lipid metabolism, aerobic capacity, fibre type composition and lipid profile, on the other side. PPARδ mRNA levels were quantified by real‐time PCR in muscle biopsies from 176 young and elderly monozygotic and dizygotic twins. Young twins had significantly increased PPARδ mRNA levels compared with elderly twins. A 2 h hyperinsulinaemic euglycaemic clamp had no significant effect on PPARδ mRNA levels. Biometric models were calculated for basal PPARδ mRNA expression to estimate the degree of genetic versus environmental influence. In both young and elderly twins there was a substantial genetic component influencing basal PPARδ mRNA levels. In a regression model, the muscle PPARδ mRNA expression was correlated to birth weight, central adiposity and age. The level of PPARδ mRNA was also positively correlated with markers for oxidative muscle fibres. However, in this apparently healthy study population, we found no correlations between PPARδ mRNA expression and aerobic capacity, lipid profile or glucose and lipid metabolism. In conclusion, we provide evidence that mRNA expression of PPARδ in human skeletal muscle is under genetic control but also influenced by factors such as age, birth weight and central adiposity.
Corticofugal modulation of the auditory thalamic reticular nucleus of the guinea pig
Authors: Xu Min , Liu Chun Hua , Xiong Ying , He Jufang
Published: September 2007

Neuronal responses to auditory stimuli and electrical stimulation were examined in 104 neurones in the auditory sector of thalamic reticular nucleus (TRN) and nine medial geniculate (MGB) neurones from anaesthetized guinea pigs. TRN neurones showed rhythmic spontaneous activities. TRN neurones changed firing pattern over time, from tonic to burst in a time interval of several seconds to tens of seconds. One‐third of the TRN neurones (25/76) responded to the acoustic stimulus in a slow oscillation mode, either producing a spike burst at one time and responded with nothing another time, or producing a spike burst at one time and a single spike at the other. Thirty‐two of 40 neurones received a corticofugal modulation effect. Nineteen of 32 neurones responded directly to electrical stimulation of the cortex with an oscillation of the same rhythm (7–14 Hz) as its auditory‐evoked oscillation. Six neurones changed their firing pattern from burst to tonic when the auditory cortex was activated. As the TRN applied inhibition to the MGB, the oscillatory nature of inhibition would affect the fidelity of MGB relays. Thus, it was unlikely that the MGB was in relay mode when the TRN was in a slow oscillation mode. These results hint at a possible mechanism for the modulation of states of vigilance through the corticofugal pathway via the TRN.
GABA transient sets the susceptibility of mIPSCs to modulation by benzodiazepine receptor agonists in rat hippocampal neurons
Authors: Mozrzymas Jerzy W. , Wójtowicz Tomasz , Piast Michał , Lebida Katarzyna , Wyrembek Paulina , Mercik Katarzyna
Published: September 2007

Benzodiazepines (BDZs) are known to increase the amplitude and duration of IPSCs. Moreover, at low [GABA], BDZs strongly enhance GABAergic currents suggesting the up‐regulation of agonist binding while their action on gating remains a matter of debate. In the present study we have examined the impact of flurazepam and zolpidem on mIPSCs by investigating their effects on GABAAR binding and gating and by considering dynamic conditions of synaptic receptor activation. Flurazepam and zolpidem enhanced the amplitude and prolonged decay of mIPSCs. Both compounds strongly enhanced responses to low [GABA] but, surprisingly, decreased the currents evoked by saturating or half‐saturating [GABA]. Analysis of current responses to ultrafast GABA applications indicated that these compounds enhanced binding and desensitization of GABAA receptors. Flurazepam and zolpidem markedly prolonged deactivation of responses to low [GABA] but had almost no effect on deactivation at saturating or half‐saturating [GABA]. Moreover, at low [GABA], flurazepam enhanced desensitization–deactivation coupling but zolpidem did not. Recordings of responses to half‐saturating [GABA] applications revealed that appropriate timing of agonist exposure was sufficient to reproduce either a decrease or enhancement of currents by flurazepam or zolpidem. Recordings of currents mediated by recombinant (‘synaptic’) α1β2γ2 receptors reproduced all major findings observed for neuronal GABAARs. We conclude that an extremely brief agonist transient renders IPSCs particularly sensitive to the up‐regulation of agonist binding by BDZs.
Alternative Approaches for the Derivation of Discontinuous Galerkin Methods for Nonlinear Mechanics
Authors: Noels L. , Radovitzky R.
Published: September 2007

Discontinuous Galerkin methods are commonly derived by seeking a weak statement of the governing differential equations via a weighted-average approach allowing for discontinuous fields at the element interfaces of the discretization. In order to ensure consistency and stability of the formulation, this approach requires the definition of a numerical flux and a stabilization term. Discontinuous Galerkin methods may also be formulated from a linear combination of the governing and compatibility equations weighted by suitable operators. A third approach based on a variational statement of a generalized energy functional has been proposed recently for finite elasticity. This alternative approach naturally leads to an expression of the numerical flux and the stabilization terms in the context of large deformation mechanics problems. This paper compares these three approaches and establishes the conditions under which identical formulations are obtained.
On the One-Parameter Lorentzian Spherical Motions and Euler-Savary Formula
Authors: Tosun M. , Gungor M. A. , Okur I.
Published: September 2007

In this paper, we have introduced one-parameter Lorentzian spherical motion. In addition to that, we have given the relations between the absolute, relative, and sliding velocities of these motions. Furthermore, the relations between fixed and moving pole curves in the Lorentzian spherical motions have also been obtained. At the end of this study, we have expressed the Euler-Savary formula for the one-parameter Lorentzian spherical motions.
A One-Dimensional Theory for the Analysis of Strip Surface Acoustic Waveguides
Authors: Chen Shi , Tang Tiantong , Wang Zhaohong
Published: September 2007

In this paper, an effective and new one-dimensional theory for the analysis of strip surface acoustic waveguides is presented. Compared with the known methods, a prominent advantage of this method proposed in this paper is that all the field variables can be calculated.
Stoneley Wave Generation in Joined Materials With and Without Thermal Relaxation Due to Thermal Mismatch
Authors: Brock L. M.
Published: September 2007

Two perfectly bonded, thermoelastic half-spaces differ only in their thermal parameters. Their governing equations include as special cases the Fourier heat conduction model and models with either one or two thermal relaxation times. An exact solution in transform space for the problem of line loads applied to the interface is obtained. Even though the elastic properties of the half-spaces are identical, a Stoneley function arises, and conditions for the existence of roots are more restrictive than for the isothermal case of two elastically dissimilar half-spaces. Moreover, roots may be either real or imaginary. An exact expression for the time transform of the Stoneley residue contribution to interface temperature change is derived. Asymptotic results for the inverse that, valid for either very short or very long times after load application, is obtained and show that, for long times, residue contributions for all three special cases obey Fourier heat conduction. Short-time results are sensitive to case differences. In particular, a time step load produces a propagating step in temperature for the Fourier and double-relaxation time models, but a propagating impulse for the single-relaxation time model.
Comment on "The Consensus Coding Sequences of Human Breast and Colorectal Cancers"
Authors: Forrest William F. , Cavet Guy
Published: September 2007

Sjöblomet al. (Research Articles, 13 October 2006, p. 268) used data from cancer genome resequencing to identify genes with elevated mutation rates. Their analysis used point probabilities when it should have usedPvalues for the hypotheses they intended to test. Reimplementing their analysis method with exactPvalues results in far fewer genes with mutation rates that achieve statistical significance.
Comment on "The Consensus Coding Sequences of Human Breast and Colorectal Cancers"
Authors: Getz Gad , Höfling Holger , Mesirov Jill P. , Golub Todd R. , Meyerson Matthew , Tibshirani Robert , Lander Eric S.
Published: September 2007

Sjöblomet al. (Research Article, 13 October 2006, p. 268) reported nearly 200 novel cancer genes said to have a 90% probability of being involved in colon or breast cancer. However, their analysis raises two statistical concerns. When these concerns are addressed, few genes with significantly elevated mutation rates remain. Although the biological methodology in Sjöblomet al. is sound, more samples are needed to achieve sufficient power.
Comment on "The Consensus Coding Sequences of Human Breast and Colorectal Cancers"
Authors: Rubin Alan F. , Green Phil
Published: September 2007

Sjöblom et al. (Research Article, 13 October 2006, p. 268) reported many new genes with an apparent significant excess of mutations in breast and colorectal cancer. Reanalysis of their data with more appropriate statistical methods and background mutation rate assumptions reveals that few if any of these genes have significantly elevated mutation rates.
Global Pattern Formation and Ethnic/Cultural Violence
Authors: Lim May , Metzler Richard , Bar-Yam Yaneer
Published: September 2007

We identify a process of global pattern formation that causes regions to differentiate by culture. Violence arises at boundaries between regions that are not sufficiently well defined. We model cultural differentiation as a separation of groups whose members prefer similar neighbors, with a characteristic group size at which violence occurs. Application of this model to the area of the former Yugoslavia and to India accurately predicts the locations of reported conflict. This model also points to imposed mixing or boundary clarification as mechanisms for promoting peace.
Complexity of Coupled Human and Natural Systems
Authors: Liu Jianguo , Dietz Thomas , Carpenter Stephen R. , Alberti Marina , Folke Carl , Moran Emilio , Pell Alice N. , Deadman Peter , Kratz Timothy , Lubchenco Jane , Ostrom Elinor , Ouyang Zhiyun , Provencher William , Redman Charles L. , Schneider Stephen H. , Taylor William W.
Published: September 2007

Integrated studies of coupled human and natural systems reveal new and complex patterns and processes not evident when studied by social or natural scientists separately. Synthesis of six case studies from around the world shows that couplings between human and natural systems vary across space, time, and organizational units. They also exhibit nonlinear dynamics with thresholds, reciprocal feedback loops, time lags, resilience, heterogeneity, and surprises. Furthermore, past couplings have legacy effects on present conditions and future possibilities.
Current-Induced Magnetization Switching with a Spin-Polarized Scanning Tunneling Microscope
Authors: Krause S. , Berbil-Bautista L. , Herzog G. , Bode M. , Wiesendanger R.
Published: September 2007

Switching the magnetization of a magnetic bit by injection of a spin-polarized current offers the possibility for the development of innovative high-density data storage technologies. We show how individual superparamagnetic iron nanoislands with typical sizes of 100 atoms can be addressed and locally switched using a magnetic scanning probe tip, thus demonstrating current-induced magnetization reversal across a vacuum barrier combined with the ultimate resolution of spin-polarized scanning tunneling microscopy. Our technique allows us to separate and quantify three fundamental contributions involved in magnetization switching (i.e., current-induced spin torque, heating the island by the tunneling current, and Oersted field effects), thereby providing an improved understanding of the switching mechanism.
Quantitative Imaging of Nitrogen Fixation by Individual Bacteria Within Animal Cells
Authors: Lechene Claude P. , Luyten Yvette , McMahon Gregory , Distel Daniel L.
Published: September 2007

Biological nitrogen fixation, the conversion of atmospheric nitrogen to ammonia for biosynthesis, is exclusively performed by a few bacteria and archaea. Despite the essential importance of biological nitrogen fixation, it has been impossible to quantify the incorporation of nitrogen by individual bacteria or to map the fate of fixed nitrogen in host cells. In this study, with multi-isotope imaging mass spectrometry we directly imaged and measured nitrogen fixation by individual bacteria within eukaryotic host cells and demonstrated that fixed nitrogen is used for host metabolism. This approach introduces a powerful way to study microbes and global nutrient cycles.
Production of Trout Offspring from Triploid Salmon Parents
Authors: Okutsu Tomoyuki , Shikina Shinya , Kanno Megumi , Takeuchi Yutaka , Yoshizaki Goro
Published: September 2007

Many salmonids have become at risk of extinction. For teleosts whose eggs cannot be cryopreserved, developing techniques other than egg cryopreservation to save genetic resources is imperative. In this study, spermatogonia from rainbow trout were intraperitoneally transplanted into newly hatched sterile triploid masu salmon. Transplanted trout spermatogonia underwent spermatogenesis and oogenesis in male and female recipients, respectively. At 2 years after transplantation, triploid salmon recipients only produced trout sperm and eggs. With use of these salmon as parents, we successfully produced only donor-derived trout offspring. Thus, by transplanting cryopreserved spermatogonia into sterile xenogeneic recipients, we can generate individuals of a threatened species.
Putting the Pieces Together
Authors: Love Alan C.
Published: September 2007

Fins into Limbs
. Evolution, Development, and Transformation.
By Brian K. Hall, Ed.
. University of Chicago Press, Chicago, 2007. 459 pp. $110, £69.50. ISBN 9780226313368. Paper, $45, £28.50. ISBN 9780226313375.

The contributors synthesize information from functional morphology, developmental biology, vertebrate paleontology, and evolutionary biology that provides our current understanding of this classic case of evolutionary transformation.
Early Archaean Microorganisms Preferred Elemental Sulfur, Not Sulfate
Authors: Philippot Pascal , Van Zuilen Mark , Lepot Kevin , Thomazo Christophe , Farquhar James , Van Kranendonk Martin J.
Published: September 2007

Microscopic sulfides with low
34
S/
32
S ratios in marine sulfate deposits from the 3490-million-yearold Dresser Formation, Australia, have been interpreted as evidence for the presence of early sulfate-reducing organisms on Earth. We show that these microscopic sulfides have a mass-independently fractionated sulfur isotopic anomaly (Δ
33
S) that differs from that of their host sulfate (barite). These microscopic sulfides could not have been produced by sulfate-reducing microbes, nor by abiologic processes that involve reduction of sulfate. Instead, we interpret the combined negative δ
34
S and positive Δ
33
S signature of these microscopic sulfides as evidence for the early existence of organisms that disproportionate elemental sulfur.
Functional Architecture and Evolution of Transcriptional Elements That Drive Gene Coexpression
Authors: Brown Christopher D. , Johnson David S. , Sidow Arend
Published: September 2007

Transcriptional coexpression of interacting gene products is required for complex molecular processes; however, the function and evolution of cis-regulatory elements that orchestrate coexpression remain largely unexplored. We mutagenized 19 regulatory elements that drive coexpression of
Ciona
muscle genes and obtained quantitative estimates of the cis-regulatory activity of the 77 motifs that comprise these elements. We found that individual motif activity ranges broadly within and among elements, and among different instantiations of the same motif type. The activity of orthologous motifs is strongly constrained, although motif arrangement, type, and activity vary greatly among the elements of different co-regulated genes. Thus, the syntactical rules governing this regulatory function are flexible but become highly constrained evolutionarily once they are established in a particular element.
FKF1 and GIGANTEA Complex Formation Is Required for Day-Length Measurement in
Arabidopsis
Authors: Sawa Mariko , Nusinow Dmitri A. , Kay Steve A. , Imaizumi Takato
Published: September 2007

Precise timing of
CONSTANS
(
CO
) gene expression is necessary for day-length discrimination for photoperiodic flowering. The FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1), and GIGANTEA (GI) proteins regulate
CO
transcription in
Arabidopsis
. We demonstrate that FKF1 and GI proteins form a complex in a blue-light–dependent manner. The timing of this interaction regulates the timing of daytime
CO
expression. FKF1 function is dependent on GI, which interacts with a
CO
repressor, CYCLING DOF FACTOR 1 (CDF1), and controls CDF1 stability. GI, FKF1, and CDF1 proteins associate with
CO
chromatin. Thus, the FKF1-GI complex forms on the
CO
promoter in late afternoon to regulate
CO
expression, providing a mechanistic view of how the coincidence of light with circadian timing regulates photoperiodic flowering.
Mutual Feedbacks Maintain Both Genetic and Species Diversity in a Plant Community
Authors: Lankau Richard A. , Strauss Sharon Y.
Published: September 2007

The forces that maintain genetic diversity among individuals and diversity among species are usually studied separately. Nevertheless, diversity at one of these levels may depend on the diversity at the other. We have combined observations of natural populations, quantitative genetics, and field experiments to show that genetic variation in the concentration of an allelopathic secondary compound in
Brassica nigra
is necessary for the coexistence of
B. nigra
and its competitor species. In addition, the diversity of competing species was required for the maintenance of genetic variation in the trait within
B. nigra
. Thus, conservation of species diversity may also necessitate maintenance of the processes that sustain the genetic diversity of each individual species.
A Summer Camp for Grown-Up Geeks
Authors: Bohannon John
Published: September 2007

"Summer camps" focused on science and technology themes have been sprouting everywhere in recent years. Science Contributing Correspondent John Bohannon provides an intimate look at what happens when grownups go back to camp.
Proficiency Analysis of Drug Susceptibility Testing by National-Level Tuberculosis Reference Laboratories from 1995 to 2003
Authors: Bai Gill-Han , Kim Sang-Jae , Chang Chulhun L.
Published: September 2007

A proficiency review of antituberculous drug susceptibility testing (DST) was undertaken by the regional tuberculosis reference laboratories of the Western Pacific Region of WHO to evaluate the performance of national reference laboratories (NRLs) and to ensure that the results from the participating laboratories are reliable and similar. A panel of 30
Mycobacterium tuberculosis
strains with various patterns of resistance to isoniazid, rifampin, ethambutol, and streptomycin was sent to the NRLs, and their DST results were analyzed by comparing them with the judicial results. The efficiency scores for each drug were 90 to 99% (mean, 95%) for isoniazid, 77 to 100% (mean, 94%) for rifampin, 82 to 97% (mean, 90%) for ethambutol, and 82 to 98% (mean, 89%) for streptomycin. Significant changes over time in the rates of accordance with the judicial results were observed for rifampin (
P
< 0.0001) and streptomycin (
P
= 0.0002), whereas no changes were observed for ethambutol (
P
= 0.0880). The efficiency score for isoniazid was consistently good throughout the nine rounds. As a whole, NRL02 showed the highest score (95%) in accordance rates for all drugs, while NRL03 (86%) and NRL04 (88%) ranked lowest. Continued proficiency testing with subsequent technical assistance improved the DST quality of participating laboratories, demonstrating the importance of the current WHO/IUATLD external quality assurance program for DST proficiency testing.
Lack of Repeat Transduction by Recombinant Adeno-Associated Virus Type 5/5 Vectors in the Mouse Airway
Authors: Sumner-Jones Stephanie G. , Gill Deborah R. , Hyde Stephen C.
Published: September 2007

While recombinant adeno-associated virus (rAAV) vectors promote long-term transgene expression in the lungs and other organs, the goal of correcting chronic inherited lung diseases such as cystic fibrosis with this type of viral gene transfer vector is limited by the requirement of achieving stable potent transgene expression, potentially requiring vector readministration. Here we evaluated the abilities of rAAV type 5/5 (rAAV5/5) vectors based on the genome and capsid of AAV5 to efficiently transduce the lungs and nasal epithelium of mice after repeated administration. Transduction efficiency as judged by reporter gene expression was markedly reduced on a second rAAV5/5 administration and effectively abolished on a third. Varying the period between administrations from 8 to 36 weeks did not allow efficient repeated administration. A rapid rise in anti-AAV5 antibodies was noted after rAAV5/5 vector administration that was sustained for the entire period of investigation (in some cases exceeding 9 months). Furthermore, this antibody response and subsequent failure to repeatedly administer the vector were not rescued by the in vivo expression of CTLA4Ig from an rAAV5/5 vector. These results suggest that without the development of an effective and clinically acceptable immunosuppression strategy, treatments for chronic diseases that require repeated administration of rAAV5/5 vectors will be unsuccessful.
Selection and Analysis of Mutations in an Encephalomyocarditis Virus Internal Ribosome Entry Site That Improve the Efficiency of a Bicistronic Flavivirus Construct
Authors: Orlinger Klaus K. , Kofler Regina M. , Heinz Franz X. , Hoenninger Verena M. , Mandl Christian W.
Published: September 2007

Flaviviruses have a positive-stranded RNA genome, which simultaneously serves as an mRNA for translation of the viral proteins. All of the structural and nonstructural proteins are translated from a cap-dependent cistron as a single polyprotein precursor. In an earlier study (K. K. Orlinger, V. M. Hoenninger, R. M. Kofler, and C. W. Mandl, J. Virol. 80:12197-12208, 2006), it was demonstrated that an artificial bicistronic flavivirus genome, TBEV-bc, in which the region coding for the viral surface glycoproteins prM and E from tick-borne encephalitis virus (TBEV) had been removed from its natural context and inserted into the 3′ noncoding region under the control of an internal ribosome entry site (IRES) from encephalomyocarditis virus (EMCV) produces viable, infectious virus when cells are transfected with this RNA. The rates of RNA replication and infectious particle formation were significantly lower with TBEV-bc, however, than with wild-type TBEV. In this study, we have identified two types of mutations, selected by passage in BHK-21 cells, that enhance the growth properties of TBEV-bc. The first type occurred in the E protein, and these most likely increase the affinity of the virus for heparan sulfate on the cell surface. The second type occurred in the inserted EMCV IRES, in the oligo(A) loop of the J-K stem-loop structure, a binding site for the eukaryotic translation initiation factor 4G. These included single-nucleotide substitutions as well as insertions of additional adenines in this loop. An A-to-C substitution in the oligo(A) loop decreased the efficiency of the IRES itself but nevertheless resulted in improved rates of virus particle formation and overall replication efficiency. These results demonstrate the need for proper balance in the competition for free template RNA between the viral RNA replication machinery and the cellular translation machinery at the two different start sites and also identify specific target sites for the improvement of bicistronic flavivirus expression vectors.
Highly Pathogenic Avian Influenza H5N1 Viruses Elicit an Attenuated Type I Interferon Response in Polarized Human Bronchial Epithelial Cells
Authors: Zeng Hui , Goldsmith Cynthia , Thawatsupha Pranee , Chittaganpitch Malinee , Waicharoen Sunthareeya , Zaki Sherif , Tumpey Terrence M. , Katz Jacqueline M.
Published: September 2007

The unparalleled spread of highly pathogenic avian influenza A (HPAI) H5N1 viruses has resulted in devastating outbreaks in domestic poultry and sporadic human infections with a high fatality rate. To better understand the mechanism(s) of H5N1 virus pathogenesis and host responses in humans, we utilized a polarized human bronchial epithelial cell model that expresses both avian alpha-2,3- and human alpha-2,6-linked sialic acid receptors on the apical surface and supports productive replication of both H5N1 and H3N2 viruses. Using this model, we compared the abilities of selected 2004 HPAI H5N1 viruses isolated from humans and a recent human H3N2 virus to trigger the type I interferon (IFN) response. H5N1 viruses elicited significantly less IFN regulatory factor 3 (IRF3) nuclear translocation, as well as delayed and reduced production of IFN-β compared with the H3N2 virus. Furthermore, phosphorylation of Stat2 and induction of IFN-stimulated genes (ISGs), such as MX1, ISG15, IRF7, and retinoic acid-inducible gene I, were substantially delayed and reduced in cells infected with H5N1 viruses. We also observed that the highly virulent H5N1 virus replicated more efficiently and induced a weaker IFN response than the H5N1 virus that exhibited low virulence in mammals in an earlier study. Our data suggest that the H5N1 viruses tested, especially the virus with the high-pathogenicity phenotype, possess greater capability to attenuate the type I IFN response than the human H3N2 virus. The attenuation of this critical host innate immune defense may contribute to the virulence of H5N1 viruses observed in humans.
Genetic Analysis of Murine Hepatitis Virus nsp4 in Virus Replication
Authors: Sparks Jennifer S. , Lu Xiaotao , Denison Mark R.
Published: September 2007

Coronavirus replicase polyproteins are translated from the genomic positive-strand RNA and are proteolytically processed by three viral proteases to yield 16 mature nonstructural proteins (nsp1 to nsp16). nsp4 contains four predicted transmembrane-spanning regions (TM1, -2, -3, and -4), demonstrates characteristics of an integral membrane protein, and is thought to be essential for the formation and function of viral replication complexes on cellular membranes. To determine the requirement of nsp4 for murine hepatitis virus (MHV) infection in culture, engineered deletions and mutations in TMs and intervening soluble regions were analyzed for effects on virus recovery, growth, RNA synthesis, protein expression, and intracellular membrane modifications. In-frame partial or complete deletions of nsp4; deletions of TM1, -2, and -3; and alanine substitutions of multiple conserved, clustered, charged residues in nsp4 resulted in viruses that were nonrecoverable, viruses highly impaired in growth and RNA synthesis, and viruses that were nearly wild type in replication. The results indicate that nsp4 is required for MHV replication and that while putative TM1, -2, and -3 and specific charged residues may be essential for productive virus infection, putative TM4 and the carboxy-terminal amino acids K
398
through T
492
of nsp4 are dispensable. Together, the experiments identify important residues and regions for studies of nsp4 topology, function, and interactions.
Mutational Analysis of the N-Terminal Domain of Moloney Murine Leukemia Virus Capsid Protein
Authors: Auerbach Marcy R. , Brown Kristy R. , Singh Ila R.
Published: September 2007

Retroviral capsid (CA) proteins contain a structurally conserved N-terminal domain (NTD) consisting of a β-hairpin and six to seven α-helices. To examine the role of this domain in Moloney murine leukemia virus (MoMLV) replication, we analyzed 18 insertional mutations in this region. All mutants were noninfectious. Based on the results of this analysis and our previous studies on additional mutations in this domain, we were able to divide the NTD of MoMLV CA into three functional regions. The first functional region included the region near the N terminus that forms the β-hairpin and was shown to control normal maturation of virions. The second region included the helix 4/5 loop and was essential for the formation of spherical cores. The third region encompassed most of the NTD except for the above loop. Mutants of this region assembled imperfect cores, as seen by detailed electron microscopy analyses, yet the resulting particles were efficiently released from cells. The mutants were defective at a stage immediately following entry of the core into cells. Despite possessing functional reverse transcriptase machinery, these mutant virions did not initiate reverse transcription in cells. This block could be due to structural defects in the assembling core or failure of an essential host protein to interact with the mutant CA protein, both of which may prevent correct disassembly upon entry of the virus into cells. Future studies are needed to understand the mechanism of these blocks and to target these regions pharmacologically to inhibit retroviral infection at additional stages.
The Role of NKG2D Signaling in Inhibition of Cytotoxic T-Lymphocyte Lysis by the Murine Cytomegalovirus Immunoevasinm152/gp40
Authors: Pinto Amelia K. , Jamieson Amanda M. , Raulet David H. , Hill Ann B.
Published: September 2007

Three proteins encoded by murine cytomegalovirus (MCMV)— gp34, encoded bym04(m04/gp34), gp48, encoded bym06(m06/gp48), and gp40, encoded bym152(m152/gp40)—act together to powerfully impact the ability of primed cytotoxic CD8 T lymphocytes (CTL) to kill virus-infected cells. Of these three, the impact ofm152/gp40 on CTL lysis appears greater than would be expected based on its impact on cell surface major histocompatibility complex (MHC) class I. In addition to MHC class I,m152/gp40 also downregulates the RAE-1 family of NKG2D ligands, which can provide costimulation for CD8 T cells. We hypothesized thatm152/gp40 may impact CTL lysis so profoundly because it inhibits both antigen presentation and NKG2D-mediated costimulation. We therefore tested the extent to whichm152/gp40's ability to inhibit CTL lysis of MCMV-infected cells could be accounted for by its inhibition of NKG2D signaling. As was predictable from the results reported in the literature, NKG2D ligands were not detected by NKG2D tetramer staining of cells infected with wild-type MCMV, whereas those infected with MCMV lackingm152/gp40 displayed measurable levels of the NKG2D ligand. To determine whether NKG2D signaling contributed to the ability of CTL to lyse these cells, we used a blocking anti-NKG2D antibody. Blocking NKG2D signaling did affect the killing of MCMV-infected cells for some epitopes. However, for all epitopes, the impact ofm152/gp40 on CTL lysis was much greater than the impact of inhibition of NKG2D signaling. We conclude that the downregulation of NKG2D ligands by MCMV makes only a small contribution to the impact ofm152/gp40 on CTL lysis and only for a small subset of CTL.
Fiber Shaft-Chimeric Adenovirus Vectors Lacking the KKTK Motif Efficiently Infect Liver Cells In Vivo
Authors: Di Paolo Nelson C. , Kalyuzhniy Oleksandr , Shayakhmetov Dmitry M.
Published: September 2007

The molecular mechanisms governing the infectivity of adenovirus (Ad) toward specific cell and tissue types in vivo remain poorly understood. The direct Ad binding to hepatic heparan sulfate proteoglycans via the KKTK motif within the fiber shaft domain was suggested to be the major mechanism of Ad liver cell infection in vivo. Here, we describe the generation and in vitro and in vivo infectivity studies of Ad5-based vectors possessing long Ad31- or Ad41-derived fiber shaft domains, which lack the KKTK motif. We found that all the critical early steps of Ad infection, including attachment to the cellular receptor, internalization, and virus genome transfer into the nucleus, occurred with similar levels of efficiency for fiber shaft-chimeric vectors and unmodified Ad5. Upon intravenous delivery into mice, fiber shaft-chimeric vectors accumulated in liver tissue, transduced liver cells, and induced the production of proinflammatory cytokines (tumor necrosis factor alpha and interleukin-6) and the chemokine monocyte chemoattractant protein 1 at levels indistinguishable from those observed for Ad5. Thus, our data provide evidence that the Ad5 fiber shaft amino acid sequence does not play any substantial role in determining adenovirus infectivity toward hepatic cells in vivo. The data obtained contribute to improving our understanding of the molecular mechanisms determining Ad infectivity and biodistribution in vivo and may aid in designing novel Ad-based vectors for gene therapy applications.
OPTICAL AND PHOTOCONDUCTION IN PbI2 POLYCRYSTALLINE DEPOSITED FROM SOLUTION
Authors: MOUSA ALI M.
Published: September 2007

A deposited layer of PbI 2 has been prepared by the solution technique. The yellow layers are made of hexagonal platelets parallel to the substrate plane. The photoconductive property has been investigated in the visible and near-IR bands using current measurements at different temperatures. The measurements show that an increase in the sample temperature leads to a remarkable decrease in photocurrent. The bandgap energy and type of optical transition were determined from transmission spectra, and an optical bandgap of Eg=2.32 eV for direct transition was estimated. Using the dependence of photoconductivity from temperature, a bandgap of Eg=2.32 eV was determined as well.