bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics and Origin of Rock Varnish from the Hyperarid Coastal Deserts of Northern Peru
Authors: Jones Charles E.
Published: December 2004

The characteristics of a new type of rock varnish from the hyperarid coastal deserts of northern Peru, combined with laboratory experiments on associated soil materials, provide new insights into the formation of rock varnish. The Peruvian varnish consists of an Fe-rich, Mn-poor component covering up to 95% of a varnished surface and a Fe-rich, Mn-rich component found only in pits and along cracks and ridges. The alkaline soils plus the catalytic Fe oxyhydroxides that coat much of the varnish surfaces make the Peruvian situation ideal for physicochemical precipitation of Mn. However, the low Mn content of the dominant Fe-rich, Mn-poor component suggests that such precipitation is minor. This, plus the presence of abundant bacteria in the Mn-rich varnish and the recorded presence of Mn-precipitating bacteria in varnish elsewhere, suggests that bacteria are almost solely responsible for Mn-precipitation in rock varnish. A set of experiments involving Peruvian soil samples in contact with water-CO2solutions indicates that natural fogs or dews release Mn but not Fe when they come in contact with eolian materials on rock surfaces. This mechanism may efficiently provide Mn to bacteria on varnishing surfaces. The lack of Fe in solution suggests that a large but unknown proportion of Fe in varnish may be in the form of insoluble Fe oxyhydroxides sorbed onto the clay minerals that form the bulk of rock varnish. The results of this study do not substantively change R. I. Dorn's paleoenvironmental interpretations of varnish Mn:Fe ratios, but they do suggest areas for further inquiry.
Late-Glacial to Holocene Changes in Winds, Upwelling, and Seasonal Production of the Northern California Current System
Authors: Sancetta Constance , Lyle Michell , Heusser Linda , Zahn Rainer , Bradbury J.Platt
Published: December 2004

A core 120 km off the coast of southern Oregon was examined for changes in lithology, diatoms, and pollen over the past 30,000 yr. Primary production during the late Pleistocene was about half that of the Holocene. Evidence from diatoms and pollen indicates that summer upwelling was much weaker, implying an absence of strong northerly winds. Early Pliocene diatoms found throughout the late Pleistocene section were probably derived from diatomites east of the Cascades and provide evidence for strong easterly winds over a dry continental interior. The findings verify predictions of a climate model based on glacial maximum conditions. There is no compelling evidence for a climatic reversal corresponding to the European Younger Dryas chron. During the early Holocene (9000−7000 yr B.P.) there may have been years when winds were insufficiently strong to support upwelling, so that warm stratified waters lay closer to the coast.
Capped acyclic permutants of the circular protein kalata B1
Authors: Simonsen Shane M. , Daly Norelle L. , Craik David J.
Published: December 2004

The cyclotides are a family of head‐to‐tail cyclized peptides that display exceptionally high stability and a range of biological activities. Acyclic permutants that contain a break in the circular backbone have been reported to be devoid of the haemolytic activity of the prototypic cyclotide kalata B1, but the potential role of the charges at the introduced termini in this loss of membraneolytic activity has not been fully determined. In this study, acyclic permutants of kalata B1 with capped N‐ and C‐termini were synthesized and found to adopt a native fold. These variants were observed to cause no measurable lysis of erythrocytes, strengthening the connection between backbone cyclization and haemolytic activity.
Structure–activity relationships of aminoglycoside‐arginine conjugates that bind HIV‐1 RNAs as determined by fluorescence and NMR spectroscopy
Authors: Lapidot Aviva , Vijayabaskar Veerappan , Litovchick Alexander , Yu Jingua , James Thomas L.
Published: December 2004

We present here a new set of aminoglycoside‐arginine conjugates (AACs) that are either site‐specific or per‐arginine conjugates of paromomycin, neamine, and neomycin B as well as their structure–activity relationships. Their binding constants (K
D) for TAR and RRE RNAs, measured by fluorescence anisotropy, revealed dependence on the number and location of arginines in the different aminoglycoside conjugates. The binding affinity of the per‐arginine aminoglycosides to TAR is higher than to RRE, and hexa‐arginine neomycin B is the most potent binder (K
D=5 and 23 nM, respectively). The 2D TOCSY NMR spectrum of the TAR monoarginine‐neomycin complex reveals binding at the bulge region of TAR.
A genome‐wide screen identifies Yos9p as essential for ER‐associated degradation of glycoproteins
Authors: Buschhorn Bettina A. , Kostova Zlatka , Medicherla Balasubrahmanyam , Wolf Dieter H.
Published: December 2004

We undertook a growth‐based screen exploiting the degradation of CTL*, a chimeric membrane‐bound ERAD substrate derived from soluble lumenal CPY*. We screened the Saccharomyces cerevisiae genomic deletion library containing ∼5000 viable strains for mutants defective in endoplasmic reticulum (ER) protein quality control and degradation (ERAD). Among the new gene products we identified Yos9p, an ER‐localized protein previously involved in the processing of GPI anchored proteins. We show that deficiency in Yos9p affects the degradation only of glycosylated ERAD substrates. Degradation of non‐glycosylated substrates is not affected in cells lacking Yos9p. We propose that Yos9p is a lectin or lectin‐like protein involved in the quality control of N‐glycosylated proteins. It may act sequentially or in concert with the ERAD lectin Htm1p/Mnl1p (EDEM) to prevent secretion of malfolded glycosylated proteins and deliver them to the cytosolic ubiquitin‐proteasome machinery for elimination.
Effect of IGF‐1 on the balance between autophagy of dysfunctional mitochondria and apoptosis
Authors: Gu Yiping , Wang Chunjie , Cohen Amos
Published: December 2004

Mutations in mitochondrial DNA (mtDNA) cause excessive production of mitochondrial reactive oxygen species (ROS) and shorten animal life span. We examined the mechanisms responsible for removal of mitochondria with deleterious mtDNA mutations by autophagy. Incubation of primary cells and cell lines in the absence of serum promotes autophagy of mitochondria with deleterious mtDNA mutations but spares their normal counterparts. The effect of serum withdrawal on the autophagy of dysfunctional mitochondria is prevented by the addition of IGF‐1. As a result of the elimination of mitochondria with deleterious mutations, excessive ROS production, characteristic of dysfunctional mitochondria, is greatly reduced. Mitochondrial autophagy shares a common mechanism with mitochondrial‐induced cell apoptosis, including mitochondrial transition pore formation and increased ROS production.
The intravenous anesthetic propofol inhibits hypoxia‐inducible factor 1 activity in an oxygen tension‐dependent manner
Authors: Takabuchi Satoshi , Hirota Kiichi , Nishi Kenichiro , Oda Seiko , Oda Tomoyuki , Shingu Koh , Takabayashi Arimichi , Adachi Takehiko , Semenza Gregg L. , Fukuda Kazuhiko
Published: December 2004

Hypoxia elicits a wide range of responses that occur at different organizational levels in the body. Hypoxia is not only a signal for energy conservation and metabolic change, but triggers expression of a select set of genes. The transcription factor hypoxia‐inducible factor 1 (HIF‐1) is now appreciated to be a master factor of the gene induction. Although knowledge on molecular mechanisms of HIF‐1 activation in response to hypoxia is accumulating, the molecular mechanism of maintenance of HIF‐1 activity under normoxic conditions remains to be elucidated. We demonstrate that the intravenous anesthetic propofol reversibly inhibits HIF‐1 activity and the gene expression mediated by HIF‐1 by blocking the synthesis of the HIF‐1α subunit under 20% or 5% O2 conditions, but not under 1% O2 conditions.
Vitamin D3 inhibits fatty acid synthase expression by stimulating the expression of long‐chain fatty‐acid‐CoA ligase 3 in prostate cancer cells
Authors: Qiao Shengjun , Tuohimaa Pentti
Published: December 2004

FAS and FACL3 are enzymes of fatty acid metabolism. In our previous studies, we found that FAS and FACL3 genes were vitamin D3‐regulated and involved in the antiproliferative effect of 1α,25(OH)2D3 in the human prostate cancer LNCaP cells. Here, we elucidated the mechanism behind the downregulation of FAS expression by vitamin D3. Triacsin C, an inhibitor of FACL3 activity, completely abolished the downregulation of FAS expression by vitamin D3, whereas an inhibitor of FAS activity, cerulenin, had no significant effect on the upregulation of FACL3 expression by vitamin D3 in LNCaP cells. In human prostate cancer PC3 cells, in which FACL3 expression is not regulated by vitamin D3, no regulation of FAS expression was seen. This suggests that the downregulation of FAS expression by vitamin D3 is mediated by vitamin D3 upregulation of FACL3 expression. Myristic acid, one of the substrates preferential for FACL3, enhanced the repression of FAS expression by vitamin D3. The action of myristic acid was abrogated by inhibition of FACL3 activity, suggesting that the enhancement in the downregulation of FAS expression by vitamin D3 is due to the formation of myristoyl‐CoA. The data suggest that vitamin D3‐repression of FAS mRNA expression is the consequence of feedback inhibition of FAS expression by long chain fatty acyl‐CoAs, which are formed by FACL3 during its upregulation by vitamin D3 in human prostate cancer LNCaP cells.
Editorial
Authors: BEAUDOIN MARTIN , LEVY MIKE
Published: December 2004

This special issue of ReCALL is composed of 17 articles selected from presentations made at the
WorldCALL 2003 conference, held May 7–10 2003 in Banff, Canada. Against all odds, during the heat of the war on terrorism,
in the middle of the SARS crisis, approximately 250 people gathered in a breathtakingly beautiful town in the Rocky Mountains to
discuss the latest advances in the field of Computer Assisted Language Learning (CALL). Registrants came to Banff for four
spring days from fifty countries to take part in 158 lectures and poster sessions. The conference was steered by an international
committee composed of members from twelve countries and organized by researchers
from the Faculté Saint-Jean (Edmonton, Alberta),
the University of Alberta (Edmonton, Alberta), and the University of Calgary (Calgary, Alberta). The programme committee
was established at the University of Victoria (Victoria, British Columbia). The specificity of WorldCALL conferences is
that they are truly international, taking place in various parts of the world and attracting specialists from all parts of the
planet. One of the unique contributions of this conference is that participants from underserved regions of the world are
particularly encouraged to share their experience in CALL. In this respect, the conference was very successful. This was
made possible by awarding eleven scholarships to participants from selected countries. WorldCALL 2003 was particular
in one respect: being held in Canada and organized by French and English speakers, the organizers decided to provide a bilingual
environment where presentations could be made in either of Canada's official languages. This is reflected in the selected papers
by the fact that some of the articles are in French.
Corrective feedback and learner uptake in CALL
Authors: HEIFT TRUDE
Published: December 2004

This paper describes a study in which we investigated the effects of corrective feedback on learner uptake
in CALL. Learner uptake is here defined as learner responses to corrective feedback in which, in case of an error, students
attempt to correct their mistake(s). 177 students from three Canadian universities participated in the study during the Spring
semester 2003. The study considered three feedback types: Meta-linguistic, Meta-linguistic + Highlighting, and Repetition +
Highlighting. Study results indicate that feedback that provides an explanation of the error and also highlights the error in the
student input (Meta-linguistic + Highlighting) is most effective at eliciting learner uptake. The study also considered two learner
variables, gender and language proficiency. Our data suggest that none of the two learner characteristics has a significant
impact on student responses to corrective feedback.
Évaluation et multimédia dans l’apprentissage
d’une L2
Authors: LAURIER MICHEL
Published: December 2004

In the first part of this paper different areas where technology may be used for second language assessment
are described. First, item banking operations, which are generally based on Item Response Theory but not necessarily restricted
to dichotomously scored items, facilitate assessment task organization and require technological support. Second, technology may
help to design more authentic assessment tasks or may be needed in some direct testing situations. Third, the assessment
environment may be more adapted and more stimulating when technology is used to give the student more control. The second part
of the paper presents different functions of assessment. The monitoring function (often called formative assessment) aims at
adapting the classroom activities to students and to provide continuous feedback. Technology may be used to train the teachers
in monitoring techniques, to organize data or to produce diagnostic information; electronic portfolios or quizzes that are built
in some educational software may also be used for monitoring. The placement function is probably the one in which the application
of computer adaptive testing procedures (e.g. French CAPT) is the most appropriate. Automatic scoring devices may also be used
for placement purposes. Finally the certification function requires more valid and more reliable tools. Technology may be
used to enhance the testing situation (to make it more authentic) or to facilitate data processing during the construction of a
test. Almond et al. (2002) propose a four component model (Selection, Presentation, Scoring and Response) for
designing assessment systems. Each component must be planned taking into account the assessment function.
Electronic texts or learning through textbooks: An experimental study
Authors: CARTES-ENRIQUEZ NINETTE , SOLAR RODRIGUEZ M. I. , QUINTANA LETELIER R.
Published: December 2004

This is an experimental study in the area of Didactics applied to the learning of English
as a foreign language and complemented by CALL. The main objective of this work is to know the degree of incidence existing
between two groups of students: one, based on conference-style classes where students, guided by the teacher, have to search for
information about a topic in the computer lab and present it in front of the class and, in the other, where students are taught
by the teacher according to a printed text. The experimental design consisted of a pre-test/post-test plus the application of
different techniques to develop the different linguistic and cognitive strategies, between these tests. The methodology used by
the Experimental Group forced learners to generate their own knowledge, so they had to apply the information and work by
themselves in Workshops; and the Control Group participated in the classroom according to the communicative approach, guided
by the teacher in the traditional class. Statistics were applied to the scores obtained between both tests, and the scores
obtained weekly in the different competences contributed to knowing whether there were significant differences between
both groups.
Episodic slow slip events accompanied by non‐volcanic tremors in southwest Japan subduction zone
Authors: Obara Kazushige , Hirose Hitoshi , Yamamizu Fumio , Kasahara Keiji
Published: December 2004

Episodic slow slip events have been recognized by means of tilt changes in the western Shikoku area, southwest Japan. The crustal tilt deformation was observed repeatedly with a recurrence interval of approximately six months coincident with the occurrences of major non‐volcanic deep tremor activities in this area. Observed tilt changes can be explained by slow slip events occurring around the source area of tremors. In each episode, the source of the slow slip event and tremor migrate simultaneously. The spatial and temporal coincidence of tremors and slow slip events indicates that they both may be coupling phenomena reflecting the stress accumulation process at the subducting plate.
Evidence of vertical transport of carbon monoxide from Measurements of Pollution in the Troposphere (MOPITT)
Authors: Kar Jayanta , Bremer Holger , Drummond James R. , Rochon Yves J. , Jones Dylan B. A. , Nichitiu Florian , Zou Jason , Liu Jane , Gille John C. , Edwards David P. , Deeter Merritt N. , Francis Gene , Ziskin Dan , Warner Juying
Published: December 2004

Vertical profiles of carbon monoxide (CO) mixing ratio retrieved from MOPITT measurements have been analyzed. We find that variations in the vertical structure of CO can be detected in the MOPITT data. The Asian summer monsoon plume in CO is observed for the first time as a strong enhancement of CO in the upper troposphere (UT) over India and southern China indicating the effect of deep convective transport. Similarly, zonal mean height latitude cross‐sections for the months of September–December, 2002 indicate deep convective transport of CO from biomass burning in the southern tropics. These findings show that MOPITT CO can provide valuable information on vertical transport phenomena in the troposphere.
Laboratory measurements of limiting freak waves on currents
Authors: Wu Chin H. , Yao Aifeng
Published: December 2004

The results of laboratory measurements on limiting freak waves in the presence of currents are reported. Both dispersive spatial‐temporal focusing and wave‐current interaction are used to generate freak waves in a partial random wave field in the presence of currents. Wave group structure, for example, spectral slope and frequency bandwidth, is found to be critical to the formation and the geometric properties of freak waves. A nondimensional spectral bandwidth is shown to well represent wave group structure and proves to be a good indicator in determining limiting freak wave characteristics. The role of a co‐existing current in the freak wave formation is recognized. Experimental results confirm that a random wave field does not prevent freak wave formation due to dispersive focusing. Strong opposing currents inducing partial wave blocking significantly elevate the limiting steepness and asymmetry of freak waves. At the location where a freak wave occurs, the Fourier spectrum exhibits local energy transfer to high‐frequency waves. The Hilbert‐Huang spectrum, a time‐frequency‐amplitude spectrum, depicts both the temporal and spectral evolution of freak waves. A strong correlation between the magnitude of interwave instantaneous frequency modulation and the freak wave nonlinearity (steepness) is observed. The experimental results provide an explanation to address the occurrence and characteristic of freak waves in consideration of the onset of wave breaking.
Accelerated telomere shortening in response to life stress
Authors: Epel Elissa S. , Blackburn Elizabeth H. , Lin Jue , Dhabhar Firdaus S. , Adler Nancy E. , Morrow Jason D. , Cawthon Richard M.
Published: December 2004

Numerous studies demonstrate links between chronic stress and indices of poor health, including risk factors for cardiovascular disease and poorer immune function. Nevertheless, the exact mechanisms of how stress gets “under the skin” remain elusive. We investigated the hypothesis that stress impacts health by modulating the rate of cellular aging. Here we provide evidence that psychological stress— both perceived stress and chronicity of stress—is significantly associated with higher oxidative stress, lower telomerase activity, and shorter telomere length, which are known determinants of cell senescence and longevity, in peripheral blood mononuclear cells from healthy premenopausal women. Women with the highest levels of perceived stress have telomeres shorter on average by the equivalent of at least one decade of additional aging compared to low stress women. These findings have implications for understanding how, at the cellular level, stress may promote earlier onset of age-related diseases.
Protein chemical shifts arising from α-helices and β-sheets depend on solvent exposure
Authors: Avbelj Franc , Kocjan Darko , Baldwin Robert L.
Published: December 2004

The NMR chemical shifts of certain atomic nuclei in proteins (
1
H
α
,
13
C
α
, and
13
C
β
) depend sensitively on whether or not the amino acid residue is part of a secondary structure (α-helix, β-sheet), and if so, whether it is helix or sheet. The physical origin of the different chemical shifts of atomic nuclei in α-helices versus β-sheets is a problem of long standing. We report that the chemical shift contributions arising from secondary structure (secondary structure shifts) depend strongly on the extent of exposure to solvent. This behavior is observed for
1
H
α
,
13
C
α
, and
13
C
β
(sheet), but not for
13
C
β
(helix), whose secondary structure shifts are small. When random coil values are subtracted from the chemical shifts of all
1
H
α
nuclei (Pro residues excluded) and the residual chemical shifts are summed to plot the mean values against solvent exposure, the results give a funnel-shaped curve that approaches a small value at full-solvent exposure. When chemical shifts are plotted instead against
E
local
, the electrostatic contribution to conformational energy produced by local dipole–dipole interactions, a well characterized dependence of
1
H
α
chemical shifts on
E
local
is found. The slope of this plot varies with both the type of amino acid and the extent of solvent exposure. These results indicate that secondary structure shifts are produced chiefly by the electric field of the protein, which is screened by water dipoles at residues in contact with solvent.
Multiple spatially distinct types of facultative heterochromatin on the human inactive X chromosome
Authors: Chadwick Brian P. , Willard Huntington F.
Published: December 2004

Heterochromatin is defined classically by condensation throughout the cell cycle, replication in late S phase and gene inactivity. Facultative heterochromatin is of particular interest, because its formation is developmentally regulated as a result of cellular differentiation. The most extensive example of facultative heterochromatin is the mammalian inactive X chromosome (Xi). A variety of histone variants and covalent histone modifications have been implicated in defining the organization of the Xi heterochromatic state, and the features of Xi heterochromatin have been widely interpreted as reflecting a redundant system of gene silencing. However, here we demonstrate that the human Xi is packaged into at least two nonoverlapping heterochromatin types, each characterized by specific Xi features: one defined by the presence of Xi-specific transcript RNA, the histone variant macroH2A, and histone H3 trimethylated at lysine 27 and the other defined by H3 trimethylated at lysine 9, heterochromatin protein 1, and histone H4 trimethylated at lysine 20. Furthermore, regions of the Xi packaged in different heterochromatin types are characterized by different patterns of replication in late S phase. The arrangement of facultative heterochromatin into spatially and temporally distinct domains has implications for both the establishment and maintenance of the Xi and adds a previously unsuspected degree of epigenetic complexity.
Evolution of xylem lignification and hydrogel transport regulation
Authors: Boyce C. Kevin , Zwieniecki Maciej A. , Cody George D. , Jacobsen Chris , Wirick Sue , Knoll Andrew H. , Holbrook N. Michele
Published: December 2004

In vascular plants, the polysaccharide-based walls of water-conducting cells are strengthened by impregnation with the polyphenolic polymer lignin. The fine-scale patterning of lignin deposition in water-conducting cells is shown here to vary phylogenetically across vascular plants. The extent to which water transport in xylem cells can be modified in response to changes in the ionic content of xylem sap also is shown to vary in correlation with variation in lignification patterns, consistent with the proposed mechanism for hydraulic response through size change of middle-lamella pectins. This covariation suggests that the fine-scale distribution of hydrophilic polysaccharides and hydrophobic lignin can affect hydraulic as well as mechanical properties, and that the evolutionary diversification of vascular cells thus reflects biochemical as well as morphological innovations evolved to fulfill opposing cell functions of transport and structural support.
IκB kinase β phosphorylates Dok1 serines in response to TNF, IL-1, or γ radiation
Authors: Lee Sanghoon , Andrieu Charlotte , Saltel Frédéric , Destaing Olivier , Auclair Jessie , Pouchkine Véronique , Michelon Jocelyne , Salaun Bruno , Kobayashi Ryuji , Jurdic Pierre , Kieff Elliott D. , Sylla Bakary S.
Published: December 2004

Dok1 is an abundant Ras-GTPase-activating protein-associated tyrosine kinase substrate that negatively regulates cell growth and promotes migration. We now find that IκB kinase β (IKKβ) associated with and phosphorylated Dok1 in human epithelial cells and B lymphocytes. IKKβ phosphorylation of Dok1 depended on Dok1 S439, S443, S446, and S450. Recombinant IKKβ also phosphorylated Dok1 or Dok1 amino acids 430–481in vitro. TNF-α, IL-1, γ radiation, or IKKβ overexpression phosphorylated Dok1 S443, S446, and S450in vivo, as detected with Dok1 phospho-S site-specific antisera. Moreover, Dok1 with S439, S443, S446, and S450mutated to A was not phosphorylated by IKKβin vivo. Surprisingly, mutant Dok1 A439, A443, A446, and A450differed from wild-type Dok1 in not inhibiting platelet-derived growth factor-induced extracellular signal-regulated kinase 1/2 phosphorylation or cell growth. Mutant Dok1 A439, A443, A446, and A450also did not promote cell motility, whereas wild-type Dok1 promoted cell motility, and Dok1 E439, E443, E446, and E450further enhanced cell motility. These data indicate that IKKβ phosphorylates Dok1 S439S443and S446S450after TNF-α, IL-1, or γ-radiation and implicate the critical Dok1 serines in Dok1 effects after tyrosine kinase activation.
Transcriptional Networks and Cellular Senescence in Human Mammary Fibroblasts
Authors: Hardy K. , Mansfield L. , Mackay A. , Benvenuti S. , Ismail S. , Arora P. , O'Hare M. J. , Jat P. S.
Published: December 2004

Senescence, the molecular program that limits the finite proliferative potential of a cell, acts as an important barrier to protect the body from cancer. Techniques for measuring transcriptome changes and for modulating their expression suggest that it may be possible to dissect the transcriptional networks underlying complex cellular processes. HMF3A cells are conditionally immortalized human mammary fibroblasts that can be induced to undergo coordinated senescence. Here, we used these cells in conjunction with microarrays, RNA interference, and in silico promoter analysis to promote the dissection of the transcriptional networks responsible for regulating cellular senescence. We first identified changes in the transcriptome when HMF3A cells undergo senescence and then compared them with those observed upon replicative senescence in primary human mammary fibroblasts. In addition to DUSP1 and known p53 and E2F targets, a number of genes such as PHLDA1, NR4A3, and a novel splice variant of STAC were implicated in senescence. Their role in senescence was then analyzed by RNA silencing followed by microarray analysis. In silico promoter analysis of all differential genes predicted that nuclear factor-κB and C/EBP transcription factors are activated upon senescence, and we confirmed this by electrophoretic mobility shift assay. The results suggest a putative signaling network for cellular senescence.
An Internal Motor Kinesin Is Associated with the Golgi Apparatus and Plays a Role in Trichome Morphogenesis inArabidopsis
Authors: Lu Ling , Lee Yuh-Ru Julie , Pan Ruiqin , Maloof Julin N. , Liu Bo
Published: December 2004

Members of the kinesin superfamily are microtubule-based motor proteins that transport molecules/organelles along microtubules. We have identified similar internal motor kinesins, Kinesin-13A, from the cotton Gossypium hirsutum and Arabidopsis thaliana. Their motor domains share high degree of similarity with those of internal motor kinesins of animals and protists in the MCAK/Kinesin13 subfamily. However, no significant sequence similarities were detected in sequences outside the motor domain. In Arabidopsis plants carrying the T-DNA knockout kinesin-13a-1 and kinesin-13a-2 mutations at the Kinesin-13A locus, >70% leaf trichomes had four branches, whereas wild-type trichomes had three. Immunofluorescent results showed that AtKinesin-13A and GhKinesin-13A localized to entire Golgi stacks. In both wild-type and kinesin-13a mutant cells, the Golgi stacks were frequently associated with microtubules and with actin microfilaments. Aggregation/clustering of Golgi stacks was often observed in the kinesin-13a mutant trichomes and other epidermal cells. This suggested that the distribution of the Golgi apparatus in cell cortex might require microtubules and Kinesin-13A, and the organization of Golgi stacks could play a regulatory role in trichome morphogenesis. Our results also indicate that plant kinesins in the MCAK/Kinesin-13 subfamily have evolved to take on different tasks than their animal counterparts.
Constitutively Active G Protein-coupled Receptor Mutants BlockDictyosteliumDevelopment
Authors: Zhang Minghang , Goswami Mousumi , Hereld Dale
Published: December 2004

cAR1, a G protein-coupled receptor (GPCR) for cAMP, is required for the multicellular development of Dictyostelium. The activation of multiple pathways by cAR1 is transient because of poorly defined adaptation mechanisms. To investigate this, we used a genetic screen for impaired development to isolate four dominant-negative cAR1 mutants, designated DN1-4. The mutant receptors inhibit multiple cAR1-mediated responses known to undergo adaptation. Reduced in vitro adenylyl cyclase activation by GTPγS suggests that they cause constitutive adaptation of this and perhaps other pathways. In addition, the DN mutants are constitutively phosphorylated, which normally requires cAMP binding and possess cAMP affinities that are ∼100-fold higher than that of wild-type cAR1. Two independent activating mutations, L100H and I104N, were identified. These residues occupy adjacent positions near the cytoplasmic end of the receptor's third transmembrane helix and correspond to the (E/D)RY motif of numerous mammalian GPCRs, which is believed to regulate their activation. Taken together, these findings suggest that the DN mutants are constitutively activated and block development by turning on natural adaptation mechanisms.
Laminin-5 Induces Osteogenic Gene Expression in Human Mesenchymal Stem Cells through an ERK-dependent Pathway
Authors: Klees Robert F. , Salasznyk Roman M. , Kingsley Karl , Williams William A. , Boskey Adele , Plopper George E.
Published: December 2004

The laminin family of proteins is critical for managing a variety of cellular activities including migration, adhesion, and differentiation. In bone, the roles of laminins in controlling osteogenic differentiation of human mesenchymal stem cells (hMSC) are unknown. We report here that laminin-5 is found in bone and expressed by hMSC. hMSC isolated from bone synthesize laminin-5 and adhere to exogenous laminin-5 through α3β1 integrin. Adhesion to laminin-5 activates extracellular signal-related kinase (ERK) within 30 min and leads to phosphorylation of the osteogenic transcription factor Runx2/CBFA-1 within 8 d. Cells plated on laminin-5 for 16 d express increased levels of osteogenic marker genes, and those plated for 21 d deposit a mineralized matrix, indicative of osteogenic differentiation. Addition of the ERK inhibitor PD98059 mitigates these effects. We conclude that contact with laminin-5 is sufficient to activate ERK and to stimulate osteogenic differentiation in hMSC.
Synthetic Genetic Array Analysis of the PtdIns 4-kinase Pik1p Identifies Components in a Golgi-specific Ypt31/rab-GTPase Signaling Pathway
Authors: Sciorra Vicki A. , Audhya Anjon , Parsons Ainslie B. , Segev Nava , Boone Charles , Emr Scott D.
Published: December 2004

Phosphorylated derivatives of phosphatidylinositol are essential regulators of both endocytic and exocytic trafficking in eukaryotic cells. In Saccharomyces cerevisiae, the phosphatidylinositol 4-kinase, Pik1p generates a distinct pool of PtdIns(4)P that is required for normal Golgi structure and secretory function. Here, we utilize a synthetic genetic array analysis of a conditional pik1 mutant to identify candidate components of the Pik1p/PtdIns(4)P signaling pathway at the Golgi. Our data suggest a mechanistic involvement for Pik1p with a specific subset of Golgi-associated proteins, including the Ypt31p rab-GTPase and the TRAPPII protein complex, to regulate protein trafficking through the secretory pathway. We further demonstrate that TRAPPII specifically functions in a Ypt31p-dependent pathway and identify Gyp2p as the first biologically relevant GTPase activating protein for Ypt31p. We propose that multiple stage-specific signals, which may include Pik1p/PtdIns(4)P, TRAPPII and Gyp2p, impinge upon Ypt31 signaling to regulate Golgi secretory function.
Shingles Immunity and Health Functioning in the Elderly: Tai Chi Chih as a Behavioral Treatment
Authors: Irwin Michael , Pike Jennifer , Oxman Michael
Published: December 2004

Both the incidence and severity of herpes zoster (HZ) or shingles increase markedly with increasing age in association with a decline in varicella zoster virus (VZV)‐specific immunity. Considerable evidence shows that behavioral stressors, prevalent in older adults, correlate with impairments of cellular immunity. Moreover, the presence of depressive symptoms in older adults is associated with declines in VZV‐responder cell frequency (VZV‐RCF), an immunological marker of shingles risk. In this review, we discuss recent findings that administration of a relaxation response‐based intervention, tai chi chih (TCC), results in improvements in health functioning and immunity to VZV in older adults as compared with a control group. TCC is a slow moving meditation consisting of 20 separate standardized movements which can be readily used in elderly and medically compromised individuals. TCC offers standardized training and practice schedules, lending an important advantage over prior relaxation response‐based therapies. Focus on older adults at increased risk for HZ and assay of VZV‐specific immunity have implications for understanding the impact of behavioral factors and a behavioral intervention on a clinically relevant end‐point and on the response of the immune system to infectious pathogens.
The AMP-activated protein kinase AAK-2 links energy levels and insulin-like signals to lifespan in C. elegans
Authors: Apfeld Javier , O'Connor Greg , McDonagh Tom , DiStefano Peter S. , Curtis Rory
Published: December 2004

Although limiting energy availability extends lifespan in many organisms, it is not understood how lifespan is coupled to energy levels. We find that the AMP:ATP ratio, a measure of energy levels, increases with age in Caenorhabditis elegans and can be used to predict life expectancy. The C. elegans AMP-activated protein kinase α subunit AAK-2 is activated by AMP and functions to extend lifespan. In addition, either an environmental stressor that increases the AMP:ATP ratio or mutations that lower insulin-like signaling extend lifespan in an aak-2-dependent manner. Thus, AAK-2 is a sensor that couples lifespan to information about energy levels and insulin-like signals.
The Drosha-DGCR8 complex in primary microRNA processing
Authors: Han Jinju , Lee Yoontae , Yeom Kyu-Hyun , Kim Young-Kook , Jin Hua , Kim V. Narry
Published: December 2004

RNase III proteins play key roles in microRNA (miRNA) biogenesis. The nuclear RNase III Drosha cleaves primary miRNAs (pri-miRNAs) to release hairpin-shaped pre-miRNAs that are subsequently cut by the cytoplasmic RNase III Dicer to generate mature miRNAs. While Dicer (class III) and other simple RNase III proteins (class I) have been studied intensively, the class II enzyme Drosha remains to be characterized. Here we dissected the action mechanism of human Drosha by generating mutants and by characterizing its new interacting partner, DGCR8. The basic action mechanism of Drosha was found to be similar to that of human Dicer; the RNase III domains A and B form an intramolecular dimer and cleave the 3′ and 5′ strands of the stem, respectively. Human Drosha fractionates at ∼650 kDa, indicating that Drosha functions as a large complex. In this complex, Drosha interacts with DGCR8, which contains two double-stranded RNA (dsRNA)-binding domains. By RNAi and biochemical reconstitution, we show that DGCR8 may be an essential component of the pri-miRNA processing complex, along with Drosha. Based on these results, we propose a model for the action mechanism of class II RNase III proteins.
Hippocampal sharp wave bursts coincide with neocortical “up-state” transitions
Authors: Battaglia Francesco P. , Sutherland Gary R. , McNaughton Bruce L.
Published: December 2004

The sleeping neocortex shows nested oscillatory activity in different frequency ranges, characterized by fluctuations between “up-states” and “down-states.” High-density neuronal ensemble recordings in rats now reveal the interaction between synchronized activity in the hippocampus and neocortex: Electroencephalographic sharp waves in the hippocampus were more probable during down-states than during up-states, and tended to coincide with transitions from down-states to up-states. The form of cortical activity fluctuations and their interactions with sharp waves depend on sleep depth: In deeper sleep stages, characterized by strong neocortical oscillation in the delta range or slower (∼0.8-4 Hz), sharp-wave-triggered peri-event time histograms (PETH) are consistent with a longer duration for down-states than for up-states. In lighter sleep, the sharp-wave-triggered PETH suggested longer up-states than down-states. These results highlight the interplay in the hippocampal/neocortical loop: Decreased neocortical input during down-states may be a factor in generation of sharp waves. In turn, sharp waves may facilitate down-to-up transitions. This interplay may reflect joint memory trace reactivation in the hippocampus and in the neocortex, possibly contributing to consolidation of long-term memory: Off-line reactivation of recent neural activity patterns in the hippocampus occurs during 50-100-msec electroencephalographic sharp waves, corresponding to pyramidal-cell population bursts. The neocortical up-states starting in correspondence with sharp waves may be influenced by the reactivated information carried by the hippocampal sharp wave.
Sleep-dependent learning and motor-skill complexity
Authors: Kuriyama Kenichi , Stickgold Robert , Walker Matthew P.
Published: December 2004

Learning of a procedural motor-skill task is known to progress through a
series of unique memory stages. Performance initially improves during
training, and continues to improve, without further rehearsal, across
subsequent periods of sleep. Here, we investigate how this delayed
sleep-dependent learning is affected when the task characteristics are varied
across several degrees of difficulty, and whether this improvement
differentially enhances individual transitions of the motor-sequence pattern
being learned. We report that subjects show similar overnight improvements in
speed whether learning a five-element unimanual sequence (17.7% improvement),
a nine-element unimanual sequence (20.2%), or a five-element bimanual sequence
(17.5%), but show markedly increased overnight improvement (28.9%) with a
nine-element bimanual sequence. In addition, individual transitions within the
motor-sequence pattern that appeared most difficult at the end of training
showed a significant 17.8% increase in speed overnight, whereas those
transitions that were performed most rapidly at the end of training showed
only a non-significant 1.4% improvement. Together, these findings suggest that
the sleep-dependent learning process selectively provides maximum benefit to
motor-skill procedures that proved to be most difficult prior to sleep.
Evolution of the vertebrate jaw: comparative embryology and molecular developmental biology reveal the factors behind evolutionary novelty
Authors: Kuratani Shigeru
Published: December 2004

It is generally believed that the jaw arose through the simple transformation of an ancestral rostral gill arch. The gnathostome jaw differentiates fromHox‐free crest cells in the mandibular arch, and this is also apparent in the lamprey. The basicHoxcode, including theHox‐free default state in the mandibular arch, may have been present in the common ancestor, and jaw patterning appears to have been secondarily constructed in the gnathostomes. The distribution of the cephalic neural crest cells is similar in the early pharyngula of gnathostomes and lampreys, but different cell subsets form the oral apparatus in each group through epithelial–mesenchymal interactions: and this heterotopy is likely to have been an important evolutionary change that permitted jaw differentiation. This theory implies that the premandibular crest cells differentiate into the upper lip, or the dorsal subdivision of the oral apparatus in the lamprey, whereas the equivalent cell population forms the trabecula of the skull base in gnathostomes. Because the gnathostome oral apparatus is derived exclusively from the mandibular arch, the concepts ‘oral’ and ‘mandibular’ must be dissociated. The ‘lamprey trabecula’ develops from mandibular mesoderm, and is not homologous with the gnathostome trabecula, which develops from premandibular crest cells. Thus the jaw evolved as an evolutionary novelty through tissue rearrangements and topographical changes in tissue interactions.
Gender‐specific distribution of glycosaminoglycans during cartilage mineralization of human thyroid cartilage
Authors: Claassen Horst , Werner Jochen
Published: December 2004

The role of glycosaminoglycans (GAG) in the process of cartilage mineralization, especially in the hypertrophic zone of growth plates, is not yet fully understood. Human thyroid cartilage can serve as a model to observe matrix changes associated with cartilage mineralization because the processes follow a distinct route, progress very slowly and show sexual differences. Histochemical staining for low sulphated GAG (chondroitin‐4‐ and ‐6‐sulphates) was decreased in the interterritorial matrix of thyroid cartilage starting at the beginning of the fifth decade, but not in the pericellular or territorial matrix of chondrocytes. Because cartilage mineralization progressed in the interterritorial matrix it seems likely that a decreasing content of chondroitin‐4‐ and ‐6‐sulphates is involved in the mineralization process. This hypothesis is supported by the observation that immunostaining for chondroitin‐4‐ and ‐6‐sulphates was weaker in mineralized cartilage areas than in unmineralized areas, whereas there was no difference in staining for keratan sulphate. In all life decades, female thyroid cartilages contained more chondrocytes with a territorial rim of chondroitin‐4‐ and ‐6‐sulphates probably preventing cartilage mineralization compared with age‐matched male specimens. Taken together, the characteristic distribution pattern of chondroitin‐4‐ and ‐6‐sulphates being more concentrated in female than in male thyroid cartilages provided evidence that these macromolecules decrease in cartilage mineralization.
Cytomorphology of notochordal and chondrocytic cells from the nucleus pulposus: a species comparison
Authors: Hunter Christopher J. , Matyas John R. , Duncan Neil A.
Published: December 2004

The nuclei pulposi of the intervertebral discs (IVDs) contain a mixed population of cell types at various stages of maturation. This tissue is formed either by or with the help of cells from the embryonic notochord, which appear to be replaced during development by a population of chondrocyte‐like cells of uncertain origin. However, this transition occurs at widely varying times, depending upon the species – or even breed – of the animal being examined. There is considerable debate among spine researchers as to whether the presence of these residual notochordal cells has a significant impact upon IVD degeneration models, and thus which models may best represent the human condition. The present study examines several different species commonly used in lumbar spine investigations to explore the variability of notochordal cells in the IVD.
LOCALISATION AND CONCENTRATION OF ORGANIC FARMING IN THE 1990s – THE DANISH CASE
Authors: FREDERIKSEN PIA , LANGER VIBEKE
Published: December 2004

This paper explores the localisation of organic farms in Denmark for the three years 1994, 1997 and 2001, on a county and parish level. Spatial concentration is found in counties with a high share of milk producers, but also in the counties, which contain the two largest urban centres. General regional specialisation of the agricultural sector in Denmark contributes to the explanation of concentration patterns of organic conversion, but other factors such as a regional favourable policy climate and support also appear to play a role. Major variations in concentration within regions are found, suggesting that local factors play an important role for the explanation of spatial patterns of organic conversion and diffusion.
West Nile virus blood transfusion‐related infection despite nucleic acid testing
Authors: Macedo de Oliveira Alexandre , Beecham Brady D. , Montgomery Susan P. , Lanciotti Robert S. , Linnen Jeffrey M. , Giachetti Cristina , Pietrelli Larry A. , Stramer Susan L. , Safranek Thomas J.
Published: December 2004

BACKGROUND:  A case of West Nile virus (WNV) encephalitis associated with transfusion of blood that did not react when tested for WNV by minipool (MP) nucleic acid testing (NAT) is described. A Nebraska man developed clinical encephalitis 13 days after surgery and transfusion of 26 blood components. Antibody testing confirmed WNV infection. An investigation was initiated to determine the source of this infection.

STUDY DESIGN AND METHODS:  The patient's family members were interviewed to identify risk factors for WNV infection. Residual samples were retested for WNV RNA using transcription‐mediated amplification (TMA) assay and two polymerase chain reaction (PCR) assays. Blood donors’ follow‐up serum samples were collected. All samples were tested for WNV‐specific immunoglobulin M antibodies.

RESULTS:  The patient's family denied recent mosquito exposure. The 20 blood components collected after July 2003 did not react when tested for WNV in a six‐member MP‐NAT at the time of donation. Retrospective individual testing identified one sample as WNV‐reactive by the TMA assay and one of the PCR assays. Seroconversion was demonstrated in the donor associated with this sample.

CONCLUSION:  WNV RNA detection by individual donation NAT demonstrates viremic blood escaping MP‐NAT and supports transfusion‐related WNV transmission. MP‐NAT may not detect all WNV‐infected blood donors, allowing WNV transmission to continue at low levels. WNV NAT assays might vary in sensitivity and pooling donations could further impact test performance.

Understanding MP NAT limitations can improve strategies to maintain safety of the blood supply in the United States.