bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuropsychological test performance in Aruaco Indians: An exploratory study
Authors: ARDILA ALFREDO , MORENO SONIA
Published: July 2002

A sample of 20 right-handed Aruaco Indians (12 male,
8 female; age 8–30 years) from the Sierra Nevada
de Santa Marta (Colombia) participated in this study. A
brief neuropsychological test battery (visuoconstructive
and visuoperceptual abilities, memory, ideomotor praxis,
verbal fluency, spatial abilities, concept formation) was
individually administered. In addition, a handedness questionnaire
was included. In some neuropsychological tests performance
was virtually perfect (Recognition of Overlapped Figures
and Ideomotor Praxis Ability test), whereas performance
in other tests was impossible (e.g., Block Design using
a time limit). It was proposed that two types of variables
were significantly affecting performance: (1) educational
level; and (2) cultural relevance. Some tests appeared
significant and meaningful whereas others were meaningless
and even impossible to understand. The appropriateness
of current neuropsychological instruments for cross-cultural
assessment is discussed. (JINS, 2001, 7,
510–515.)
Behavioral, Biological, Genetic and Neuroanatomical Findings:
Revealing Multidisciplinary Perspectives on Complex
Disorders
Authors: Molfese V.J.
Published: July 2002

History, theories, methods and findings are characteristic
of all disciplines. Also characteristic is the tendency to keep
within a discipline much of what is known from discovery by
scholars in other fields. While unintentional for the most part,
the scant knowledge sharing across disciplines arises from deficits
or uncertainties in understanding the definitions of terms,
references to key constructs and features, variations in
methodologies, and in interpretations of findings. Yet, as the
chapters of this book reveal, much is known across several
disciplines that converge on many of the same developmental
disorders that are (and have been for decades) the focus of
considerable research activity. The extensive interest in the
study of developmental disorders exists both to understand their
natures and causes as well as to reveal differences and
similarities in development across normal and abnormal populations.
Emotional deficit as a neuropsychopathological disturbance
in HIV infection
Authors: BUNGENER CATHERINE , JOUVENT ROLAND
Published: July 2002

We have been very interested in the article of Castellon
et al. (2000) on the neuropsychiatric disturbances present in
HIV-infection, which reports results very congruent with those
published previously by our research group. Indeed, for many
years we have studied psychopathological perturbations (depression
and anxiety) as well as more specific emotional dimensions like
emotional deficit and loss of control in HIV positive patients.
Amnesic patients' impaired category exemplar production
priming
Authors: CERMAK LAIRD S. , WONG BONNIE M.
Published: July 2002

This study examined the effect of varying the number
of potential target words on amnesic patients' category
exemplar production performance. In Experiment 1, 4 words
from each of 6 categories were presented to amnesic patients
and normal control participants. This was followed by an
indirect task in which each participant produced the first
8 words that came to mind when presented with a category
cue. On this task the amnesic patients were impaired. This
outcome stands in sharp contrast to most other category
exemplar production tasks that have been reported. However,
these other paradigms tend to restrict participants'
processing during target item presentation while our procedure
allowed them to analyze the target words as they chose.
Our procedure may have allowed the control participant
more opportunity to “cluster” target words
from the same category during list presentation and this,
in turn, may have given them an advantage at the time of
category exemplar production. Therefore, in Experiment
2, only 1 word per category was presented in the target
list and only 2 words per category were requested during
category exemplar production. Surprisingly, the amnesic
patients still exhibited impaired performance. Therefore,
it was suggested that perhaps amnesic patients' known
inability to perform semantic levels of processing during
individual target word presentation may have resulted in
impaired priming for categorical features for these patients.
(JINS, 1998, 4, 576–583.)
To see better to the left when looking more to the right:
Effects of gaze direction and frames of spatial coordinates
in unilateral neglect
Authors: VUILLEUMIER PATRIK , VALENZA NATHALIE , MAYER EUGÈNE , PERRIG STEPHEN , LANDIS THEODOR
Published: July 2002

Unilateral spatial neglect entails a failure to
detect or respond to stimuli in the space opposite to a
brain lesion. However, the contralesional hemispace can
be determined by different frames of spatial coordinates,
such as eyes-, head-, body-, or environment-centered coordinates.
We observed 2 patients with a right hemisphere stroke whose
left spatial neglect was modulated by distinct coordinates
systems depending on the task. Four tasks were given in
different conditions of central gaze and either the eyes
or the head rotated 30° to the right or 30° to
the left. While the 2 patients had a retinotopic defect
in 1 visual field quadrant that remained the same irrespective
of gaze direction (upper or lower quadrant in 1 case each),
the other quadranopic field defect improved with eyes rotation
to the right but not with head rotation, suggesting a head-centered
spatiotopic deficit. Performance on line bisection was
influenced both by eyes and head rotation, as well as by
the position of the lines with respect to the trunk midline,
suggesting the involvement of both head-centered and body-centered
coordinates. Visual imagery and auditory extinction were
not modified by changing the eyes or head position. These
findings suggest that distinct spatial coordinates are
brought into play depending on the tasks demands. (JINS,
1999, 5, 75–82.)
Extensions and alternatives to climate change impact valuation: on the critique of IPCC Working Group III's impact estimates
Authors: FANKHAUSER SAMUEL , TOL RICHARD S.J. , PEARCE DAVID W.
Published: July 2002

The paper discusses valuation issues in the context of climate change impact estimation. Issues addressed are aggregation of damage costs over diverse regions (particularly equity-weighting), differentiation of per-unit values, willingness to pay versus willingness to accept compensation as a basis for valuation, and accountability for impacts. Numerical illustrations show that the damage cost estimates are quite sensitive to the assumptions made on these issues.
The economics of environments in transition
Authors: PANAYOTOU THEODORE
Published: July 2002

The sudden collapse of the centrally planned economies of Central and
Eastern Europe (CEE) and the former Soviet Union (FSU), has created
economic and environmental disequilibria of historically unprecedented
dimensions throughout the region, as well as a process of gradual transition
from plan to market. This historical ‘experiment’ provides a unique
opportunity to study economyÐenvironment interactions and the adjustment
process towards a new equilibrium, as well as the implications for
conventional and novel policy instruments under transitional conditions.
The changes that have taken place have been so many and so large that
they defy many of the tools of marginal analysis. Privatization, industrial
restructuring, market competition, price reform, and trade liberalization
among others have suddenly been introduced where none existed and
have so radically altered the fundamentals of these economies that they
could be considered as new economies rather than simply reformed
economies. However, underlying these radical changes, are many legacies
of the centrally planned economy that persist or change only gradually.
Furthermore, not all countries in CEE and the FSU have reformed their
economies at the same pace. The northern tier countries of CEE moved
faster than the southern tier and the latter faster than most FSU republics.
Analysis/synthesis comparison
Authors: WRIGHT MATTHEW , BEAUCHAMP JAMES , FITZ KELLY , RODET XAVIER , RÖBEL AXEL , SERRA XAVIER , WAKEFIELD GREGORY
Published: July 2002

We compared six sound analysis/synthesis systems used for computer music. Each system analysed the same collection

of twenty-seven varied input sounds, and output the results in Sound Description Interchange Format (SDIF). We

describe each system individually then compare the systems in terms of availability, the sound model(s) they use,

interpolation models, noise modelling, the mutability of various sound models, the parameters that must be set to

perform analysis, and characteristic artefacts. Although we have not directly compared the analysis results among the

different systems, our work has made such a comparison possible.
Model of Optimal Economic Growth with Endogenous Bias
Authors: Sato Ryuzo , Ramachandran Rama V. , Lian Cheng Ping
Published: July 2002

The objective of the paper is to develop a model of optimal endogenous technological
progress that will exhibit two properties sought in growth models: (1) The bias will
depend on the parameters of the model—particularly those affecting the cost of
inputs—instead of being constrained to be Harrod
neutral; (2) factor shares will be constant in
steady state. Using previously derived sufficient conditions, we show the
conditions under which such a model can be constructed.
Early emergence of structural constraints on code-mixing: evidence from French–English bilingual children
Authors: Paradis Johanne , Nicoladis Elena , Genesee Fred
Published: July 2002

Does young bilingual children's code-mixing obey the same structural constraints as bilingual adults' code-mixing? The present study addresses this question using code-mixing data from 15 French–English bilingual children filmed in conversation with both parents at six-month intervals from the age of 2;0 to 3;6. The children's code-mixed utterances were examined for violations of the principles set out in the Matrix-Language Frame model (e.g. Myers-Scotton, 1993, 1997). The results show that the children obeyed all the constraints set out in the Matrix Language Frame model the majority of the time. With respect to the Morpheme Order Principle and to the interaction of Congruence and Matrix Language Blocking, they demonstrated consistent adherence with only marginal violations from the outset. In contrast, the children produced comparatively more frequent violations of the System Morpheme Principle and showed increasing adherence to this principle over time. We discuss possible explanations for the contrast between the children's performance on the System Morpheme Principle and the other constraints, which include the unequal emergence of INFL in the acquisition of French and English.
Parasite resistance and genetic variation in the endangered Gila topminnow
Authors: Hedrick Philip W. , Kim Timothy J. , Parker Karen M.
Published: July 2002

In recent years, it has become apparent that introduced or novel pathogens or parasites may have a significant negative impact on endangered species. Here we examine experimentally the effect of an exotic fluke from guppies on the endangered Gila topminnow. Populations from different sources showed variable responses (although statistically non‐significant) to the fluke and, in particular, the most homozygous population had high fluke infections and high subsequent mortality. Homozygotes for a MHC (major histocompatibility complex) gene had lower (although statistically non‐significant) survival when infected with flukes than did heterozygotes. An inbred line from one of the populations had statistically significant lower survival and higher fluke infection than did a simultaneous outbred control. Overall, Gila topminnows appear quite susceptible to infection by the non‐native fluke compared to other related species. In addition, it was shown that Gila topminnows can be infected by casual contact with infected guppies. This is another example of the potential detrimental effects of a parasite on an endangered species, a threat that may constitute a particular problem for species with low genetic variation, either in general, for important MHC genes, or for populations with a past history of inbreeding.
Mitochondrial Mg2+ homeostasis is critical for group II intron splicing in vivo
Authors: Gregan Juraj , Kolisek Martin , Schweyen Rudolf J.
Published: July 2002

The product of the nuclear MRS2 gene, Mrs2p, is the only candidate splicing factor essential for all group II introns in mitochondria of the yeast Saccharomyces cerevisiae. It has been shown to be an integral protein of the inner mitochondrial membrane, structurally and functionally related to the bacterial CorA Mg2+ transporter. Here we show that mutant alleles of theMRS2 gene as well as overexpression of this gene both increase intramitochondrial Mg2+ concentrations and compensate for splicing defects of group II introns in mit− mutantsM1301 and B-loop. Yet, covariation of Mg2+concentrations and splicing is similarly seen when some other genes affecting mitochondrial Mg2+ concentrations are overexpressed in an mrs2Δ mutant, indicating that not the Mrs2 protein per se but certain Mg2+ concentrations are essential for group II intron splicing. This critical role of Mg2+ concentrations for splicing is further documented by our observation that pre-mRNAs, accumulated in mitochondria isolated from mutants, efficiently undergo splicing in organello when these mitochondria are incubated in the presence of 10 mM external Mg2+ (mit−M1301) and an ionophore (mrs2Δ). This finding of an exceptional sensitivity of group II intron splicing toward Mg2+ concentrations in vivo is unprecedented and raises the question of the role of Mg2+ in other RNA-catalyzed reactions in vivo. It explains finally why protein factors modulating Mg2+ homeostasis had been identified in genetic screens for bona fide RNA splicing factors.
Myc-enhanced expression of Cul1 promotes ubiquitin-dependent proteolysis and cell cycle progression
Authors: O'Hagan Rónán C. , Ohh Michael , David Gregory , de Alboran Ignacio Moreno , Alt Frederick W. , Kaelin William G. , DePinho Ronald A.
Published: July 2002

The c-Myc oncoprotein plays an important role in the growth and proliferation of normal and neoplastic cells. To execute these actions, c-Myc is thought to regulate functionally diverse sets of genes that directly govern cellular mass and progression through critical cell cycle transitions. Here, we provide several lines of evidence that c-Myc promotes ubiquitin-dependent proteolysis by directly activating expression of the Cul1 gene, encoding a critical component of the ubiquitin ligase SCFSKP2. The cell cycle inhibitor p27kip1 is a known target of the SCFSKP2 complex, and Myc-induced Cul1 expression matched well with the kinetics of declining p27kip1 protein. Enforced Cul1 expression or antisense neutralization of p27kip1 was capable of overcoming the slow-growth phenotype of c-Myc null primary mouse embryonic fibroblasts (MEFs). In reconstitution assays, the addition of in vitro translated Cul1 protein alone was able to restore p27kip1ubiquitination and degradation in lysates derived fromc-myc−/− MEFs or density-arrested human fibroblasts. These functional and biochemical data provide a direct link between c-Myc transcriptional regulation and ubiquitin-mediated proteolysis and together support the view that c-Myc promotes G1 exit in part via Cul1-dependent ubiquitination and degradation of the CDK inhibitor, p27kip1.
TGF-β inhibits p70 S6 kinase via protein phosphatase 2A to induce G1 arrest
Authors: Petritsch Claudia , Beug Hartmut , Balmain Allan , Oft Martin
Published: July 2002

On TGF-β binding, the TGF-β receptor directly phosphorylates and activates the transcription factors Smad2/3, leading to G1 arrest. Here, we present evidence for a second, parallel, TGF-β-dependent pathway for cell cycle arrest, achieved via inhibition of p70s6k. TGF-β induces association of its receptor with protein phosphatase-2A (PP2A)-Bα. Concomitantly, three PP2A-subunits, Bα, Aβ, and Cα, associate with p70s6k, leading to its dephosphorylation and inactivation. Although either pathway is sufficient to induce G1 arrest, abrogation of both, the inhibition of p70s6k, and transcription through Smad proteins is required for release of epithelial cells from TGF-β-induced G1 arrest. TGF-β thereby modulates the translational and posttranscriptional control of cell cycle progression.
Nrarp is a novel intracellular component of the Notch signaling pathway
Authors: Lamar Elise , Deblandre Gisèle , Wettstein Daniel , Gawantka Volker , Pollet Nicolas , Niehrs Christof , Kintner Chris
Published: July 2002

The Lin12/Notch receptors regulate cell fate during embryogenesis by activating the expression of downstream target genes. These receptors signal via their intracellular domain (ICD), which is released from the plasma membrane by proteolytic processing and associates in the nucleus with the CSL family of DNA-binding proteins to form a transcriptional activator. How the CSL/ICD complex activates transcription and how this complex is regulated during development remains poorly understood. Here we describe Nrarp as a new intracellular component of the Notch signaling pathway in Xenopus embryos. Nrarp is a member of the Delta–Notch synexpression group and encodes a small protein containing two ankyrin repeats. Nrarp expression is activated in Xenopus embryos by the CSL-dependent Notch pathway. Conversely, overexpression of Nrarp in embryos blocks Notch signaling and inhibits the activation of Notch target genes by ICD. We show that Nrarp forms a ternary complex with the ICD of XNotch1 and the CSL protein XSu(H) and that in embryos Nrarp promotes the loss of ICD. By down-regulating ICD levels, Nrarp could function as a negative feedback regulator of Notch signaling that attenuates ICD-mediated transcription.
Null Mutation of PCLN-1/Claudin-16 Results in Bovine Chronic Interstitial Nephritis
Authors: Hirano Takashi , Kobayashi Naohiko , Itoh Tomohito , Takasuga Akiko , Nakamaru Teruhiko , Hirotsune Shinji , Sugimoto Yoshikazu
Published: July 2002

Inherited chronic renal diseases are associated with failures in glomerular filtration and tubular resorption. Such failures invariably result from defects in selective filtration and absorption in surface renal epithelium. Recently, we described an autosomal recessive chronic interstitial nephritis with diffuse zonal fibrosis (CINF) in cattle. Bovine CINF, characterized by increased blood urea nitrogen, creatinine, and urinary proteins, leads to lethality before puberty, usually within the first 6 months or year of life. Here, we demonstrate that the first four exons of PCLN-1/Claudin-16(CL-16), which encodes a member of the claudin family of tight junction proteins, were deleted in CINF-affected cattle. CL-16was expressed preferentially in kidneys of normal cattle, but transcripts were totally absent in affected offspring. This observation suggests that the lack of CL-16 protein contributes to the dysfunction of paracellular renal transport systems.

[The CL-16cDNA sequence has been deposited at GenBank under accession no. AB030082.]
Inhibition of the Endothelial Isoform of Nitric Oxide Synthase Impairs Long-Term Memory Formation in the Chick
Authors: Rickard Nikki S. , Gibbs Marie E. , Ng Kim T.
Published: July 2002

Previous studies with general inhibitors of nitric oxide synthase have yielded variable and contradictory results with respect to their effects on memory. This may have been due to differential effects of blocking the various isoforms of this enzyme. We show that day-old chicks trained on a single-trial passive-avoidance task suffered significant memory loss from ∼40 min post-training following post-training intracranial administration of a potent inhibitor of eNOS. Administration of a specific nNOS or iNOS inhibitor at the same time had no effect on retention, although a role for either of these isoforms when administered at a different time after learning has yet to be fully investigated. The onset of memory loss following eNOS inhibition is the same as observed following general NOS inhibition, which suggests that amnestic effects observed in previous studies using nonspecific inhibitors may be attributable to blocking the function of eNOS. The findings indicate that eNOS may play a role in memory formation for this task, which is at least distinct from any role that may be played by nNOS.
Mechanically Stimulated TCH3 Gene Expression in Arabidopsis Involves Protein Phosphorylation and EIN6 Downstream of Calcium
Authors: Wright Andrew J. , Knight Heather , Knight Marc R.
Published: July 2002

Mechanical signals are important both as environmental and endogenous developmental cues in plants. Among the quickest measurable responses to mechanical stimulation (MS) in plants is the up-regulation of specific genes, including TCH3, in Arabidopsis. Little is known about the signaling events and components that link perception of mechanical signals to gene expression in plants. Calcium has been identified previously as being potentially involved, and a role for ethylene has also been suggested. Using the protein kinase inhibitor staurosporine, we determined that MS up-regulation ofTCH3 expression requires protein kinase activity in young Arabidopsis seedlings. Our data from studies on the Arabidopsisein6 mutant demonstrate that the EIN6 protein is also required, but that its role in mechanically induced TCH3expression appears to be independent of ethylene. Challenge of seedlings with protein phosphatase inhibitors calyculin A and okadaic acid stimulated TCH3 expression even in the absence of MS, implying protein phosphatase activity acting to negatively regulateTCH3 gene expression. This phosphatase activity acts either downstream or independently of EIN6. EIN6 and protein kinase activity, on the other hand, operate downstream of calcium to mediate mechanically stimulated TCH3 expression.
The Impact of Alteration of Polyunsaturated Fatty Acid Levels on C6-Aldehyde Formation of Arabidopsis thaliana Leaves
Authors: Zhuang H. , Hamilton-Kemp T. R. , Andersen R. A. , Hildebrand D. F.
Published: July 2002

C6-aldehydes are synthesized via lipoxygenase/hydroperoxide lyase action on polyunsaturated fatty acid (PUFA) substrates in plant leaves. The source pools and subcellular location of the processes are unknown. A close relationship is found between the composition of PUFA and the composition of C6-aldehydes. In the current study, this relationship was tested using the Arabidopsis PUFA mutant lines act1, fad2, fad3 fad5, fad6, and fad7. The results indicate that C6-aldehyde formation is influenced by the alteration of C18 PUFA levels. Mutants act1 and fad5, which are deficient in C16 unsaturated fatty acids, had wild-type levels of C6-aldehyde production. Mutants deficient in the chloroplast hexadecenoic acid/oleic acid desaturase (fad6) or hexadecadienoic acid/linoleic acid desaturase (fad7) had altered C6-aldehyde formation in a pattern similar to the changes in the PUFA. Mutations that impair phosphatidylcholine desaturase activity, such as fad2 and fad3, however, resulted in increased E-2-hexenal formation. The enzymes involved in C6-aldehyde production were partially characterized, including measurement of pH optima. The differences in C6-aldehyde formation among the fatty acid mutants of Arabidopsis appeared not to result from alteration of lipoxygenase/hydroperoxide lyase pathway enzymes. Investigation of the fatty acid composition in leaf phospholipids, glycolipids, and neutral lipids and analysis of the fatty acid composition of chloroplast and extrachloroplast lipids indicate that chloroplasts and glycolipids of chloroplasts may be the source or major source of C6-aldehyde formation in Arabidopsis leaves.
Immobilization of Flax Protoplasts in Agarose and Alginate Beads (Correlation between Ionically Bound Cell-Wall Proteins and Morphogenetic Response)
Authors: Roger D. , David A. , David H.
Published: July 2002

Linum usitatissimum protoplast-derived colonies that are cultured in auxin-supplemented medium and immobilized in Ca2+-alginate matrix form round colonies that develop into polarized, embryo-like structures. On the other hand, protoplast-derived colonies that are immobilized in agarose do not show an organized morphogenetic response, and unique, ionically bound cell-wall protein patterns match this response. Although only slight differences in neosynthesized or total constitutive polypeptides are observed, dramatic changes in ionically bound cell-wall proteins are seen. In protoplasts grown on Ca2+-alginate-solidified, auxin-containing medium. several basic polypeptides were strongly induced and were found tightly bound to the cell wall. In contrast, these basic proteins were found only weakly bound to the walls of protoplasts grown on agarose-solidified, auxin-containing medium or on Ca2+-alginate-solidified, auxin-free medium, in which they were released into the medium. Our results suggest that plant cells can perceive and respond to the adjacent extracellular matrix, since we show that the growth of flax cells on Ca2+-alginate in the presence of auxin-containing medium may promote the binding of specific proteins to the walls. This establishes a direct correlation of an embryo-like morphogenesis with ionically bound cell-wall basic proteins in flax protoplasts grown on Ca2+-alginate-solidified, auxin-containing medium.
Tomato Phosphate Transporter Genes Are Differentially Regulated in Plant Tissues by Phosphorus1
Authors: Liu Chunming , Muchhal Umesh S. , Uthappa Mukatira , Kononowicz Andrzej K. , Raghothama Kaschandra G.
Published: July 2002

Phosphorus is a major nutrient acquired by roots via high-affinity inorganic phosphate (Pi) transporters. In this paper, we describe the tissue-specific regulation of tomato (Lycopersicon esculentum L.) Pi-transporter genes by Pi. The encoded peptides of the LePT1 and LePT2genes belong to a family of 12 membrane-spanning domain proteins and show a high degree of sequence identity to known high-affinity Pi transporters. Both genes are highly expressed in roots, although there is some expression of LePT1 in leaves. Their expression is markedly induced by Pi starvation but not by starvation of nitrogen, potassium, or iron. The transcripts are primarily localized in root epidermis under Pi starvation. Accumulation of LePT1 message was also observed in palisade parenchyma cells of Pi-starved leaves. Our data suggest that the epidermally localized Pi transporters may play a significant role in acquiring the nutrient under natural conditions. Divided root-system studies support the hypothesis that signal(s) for the Pi-starvation response may arise internally because of the changes in cellular concentration of phosphorus.
Respiratory Elicitors from Rhizobium melilotiAffect Intact Alfalfa Roots1
Authors: Volpin Hanne , Phillips Donald A.
Published: July 2002

Molecules produced byRhizobium meliloti increase respiration of alfalfa (Medicago sativa L.) roots. Maximum respiratory increases, measured either as CO2 evolution or as O2 uptake, were elicited in roots of 3-d-old seedlings by 16 h of exposure to living or deadR. meliloti cells at densities of 107bacteria/mL. Excising roots after exposure to bacteria and separating them into root-tip- and root-hair-containing segments showed that respiratory increases occurred only in the root-hair region. In such assays, CO2 production by segments with root hairs increased by as much as 100% in the presence of bacteria. Two partially purified compounds from R. meliloti 1021 increased root respiration at very low, possibly picomolar, concentrations. One factor, peak B, resembled known pathogenic elicitors because it produced a rapid (15-min), transitory increase in respiration. A second factor, peak D, was quite different because root respiration increased slowly for 8 h and was maintained at the higher level. These molecules differ from lipo-chitin oligosaccharides active in root nodulation for the following reasons: (a) they do not curl alfalfa root hairs, (b) they are synthesized by bacteria in the absence of known plant inducer molecules, and (c) they are produced by a mutant R. meliloti that does not synthesize known lipo-chitin oligosaccharides. The peak-D compound(s) may benefit both symbionts by increasing CO2, which is required for growth of R. meliloti, and possibly by increasing the energy that is available in the plant to form root nodules.
Differential Expression of Two Novel Members of the Tomato Ethylene-Receptor Family
Authors: Tieman Denise M. , Klee Harry J.
Published: July 2002

The phytohormone ethylene regulates many aspects of plant growth, development, and environmental responses. Much of the developmental regulation of ethylene responses in tomato (Lycopersicon esculentum) occurs at the level of hormone sensitivity. In an effort to understand the regulation of ethylene responses, we isolated and characterized tomato genes with sequence similarity to the Arabidopsis ETR1 (ethyleneresponse 1) ethylene receptor. Previously, we isolated three genes that exhibit high similarity to ETR1 and to each other. Here we report the isolation of two additional genes,LeETR4 and LeETR5, that are only 42% and 40% identical to ETR1, respectively. Although the amino acids known to be involved in ethylene binding are conserved, LeETR5 lacks the histidine within the kinase domain that is predicted to be phosphorylated. This suggests that histidine kinase activity is not necessary for an ethylene response, because mutated forms of both LeETR4 and LeETR5 confer dominant ethylene insensitivity in transgenic Arabidopsis plants. Expression analysis indicates thatLeETR4 accounts for most of the putative ethylene-receptor mRNA present in reproductive tissues, but, likeLeETR5, it is less abundant in vegetative tissues. Taken together, ethylene perception in tomato is potentially quite complex, with at least five structurally divergent, putative receptor family members exhibiting significant variation in expression levels throughout development.
Molecular and Biochemical Characterization of the Involvement of Cyclin-Dependent Kinase A during the Early Development of Tomato Fruit
Authors: Joubès Jérôme , Phan Thi-Hai , Just Daniel , Rothan Christophe , Bergounioux Catherine , Raymond Philippe , Chevalier Christian
Published: July 2002

Following fruit set, the early development of tomato (Lycopersicon esculentum Mill.) fruit comprises two distinct phases: a cell division phase and a consecutive phase of cell expansion until the onset of ripening. In this study, we analyzed cytological and molecular changes characterizing these early phases of tomato fruit development. First we investigated the spatial and temporal regulation of the mitotic activity during fruit development. The DNA content of isolated nuclei from the different fruit tissues was determined by flow cytometry analysis. The results confirm the data of mitotic activity measurements and show that cell differentiation, leading to expanded cells, is characterized by endoreduplication. Second, we isolated two cDNAs, named Lyces;CDKA1 (accession no. Y17225) and Lyces;CDKA2 (accession no. Y17226), encoding tomato homologs of the cyclin-dependent kinase (CDK) p34cdc2. Tomato CDKA gene expression was followed at both the transcriptional and translational levels during fruit development. The transcripts for Lyces;CDKA1 and Lyces;CDKA2 and the corresponding CDKA proteins are predominantly accumulated during the phase of cell division between anthesis and 5 d post anthesis (DPA). In whole fruits, the maximum CDK activity was obtained between 5 and 10 DPA. The determination of the kinase activity using protein extracts from the different fruit tissues was in agreement with mitotic activity analysis. It showed the particular disappearance of the activity in the gel tissue as early as 15 DPA. The overall data of CDK activity measurements suggest a strong post-translational regulation of CDK at the temporal and spatial levels during early tomato fruit development.
A Possible Role for Pyrophosphate in the Coordination of Cytosolic and Plastidial Carbon Metabolism within the Potato Tuber
Authors: Farré Eva M. , Geigenberger Peter , Willmitzer Lothar , Trethewey Richard N.
Published: July 2002

The early stages of tuber development are characterized by cell division, high metabolic activity, and the predominance of invertase as the sucrose (Suc) cleaving activity. However, during the subsequent phase of starch accumulation the cleavage of Suc occurs primarily by the action of Suc synthase. The mechanism that is responsible for this switch in Suc cleaving activities is currently unknown. One striking difference between the invertase and Suc synthase mediated cleavage of Suc is the direct involvement of inorganic pyrophosphate (PPi) in the latter case. There is presently no convincing explanation of how the PPi required to support this process is generated in potato (Solanum tuberosum) tubers. The major site of PPi production in a maturing potato tubers is likely to be the reaction catalyzed by ADP-glucose pyrophosphorylase, the first committed step of starch biosynthesis in amyloplasts. We present data based on the analysis of the PPi levels in various transgenic plants altered in starch and Suc metabolism that support the hypothesis that PPi produced in the plastid is used to support cytosolic Suc breakdown and that PPi is an important coordinator of cytosolic and plastidial metabolism in potato tubers.
Antisense Inhibition of the Nr Gene Restores Normal Ripening to the Tomato Never-ripe Mutant, Consistent with the Ethylene Receptor- Inhibition Model
Authors: Hackett Rachel M. , Ho Chin-Wen , Lin Zhefeng , Foote Humphrey C.C. , Fray Rupert G. , Grierson Don
Published: July 2002

The hormone ethylene regulates many aspects of plant growth and development, including fruit ripening. In transgenic tomato (Lycopersicon esculentum) plants, antisense inhibition of ethylene biosynthetic genes results in inhibited or delayed ripening. The dominant tomato mutant, Never-ripe(Nr), is insensitive to ethylene and fruit fail to ripen. The Nr phenotype results from mutation of the ethylene receptor encoded by the NR gene, such that it can no longer bind the hormone. NR has homology to the Arabidopsis ethylene receptors. Studies on ethylene perception in Arabidopsis have demonstrated that receptors operate by a “receptor inhibition” mode of action, in which they actively repress ethylene responses in the absence of the hormone, and are inactive when bound to ethylene. In ripening tomato fruit, expression of NR is highly regulated, increasing in expression at the onset of ripening, coincident with increased ethylene production. This expression suggests a requirement for the NR gene product during the ripening process, and implies that ethylene signaling via the tomato NR receptor might not operate by receptor inhibition. We used antisense inhibition to investigate the role of NR in ripening tomato fruit and determine its mode of action. We demonstrate restoration of normal ripening in Nr fruit by inhibition of the mutantNr gene, indicating that this receptor is not required for normal ripening, and confirming receptor inhibition as the mode of action of the NR protein.
Regulation of a Wheat Actin-Depolymerizing Factor during Cold Acclimation
Authors: Ouellet François , Carpentier Éric , Cope M. Jamie T.V. , Monroy Antonio F. , Sarhan Fathey
Published: July 2002

We have previously shown that the wheat (Triticum aestivum) TaADF gene expression level is correlated with the plants capacity to tolerate freezing. Sequence analysis revealed that this gene encodes a protein homologous to members of the actin-depolymerizing factor (ADF)/cofilin family. We report here on the characterization of the recombinant TaADF protein. Assays for ADF activity showed that TaADF is capable of sequestering actin, preventing nucleotide exchange, and inducing actin depolymerization. In vitro phosphorylation studies showed that TaADF is a substrate for a wheat 52-kD kinase. The activity of this kinase is modulated by low temperature during the acclimation period. Western-blot analyses revealed that TaADF is expressed only in cold-acclimated Gramineae species and that the accumulation level is much higher in the freezing-tolerant wheat cultivars compared with the less tolerant ones. This accumulation was found to be regulated by a factor(s) encoded by a gene(s) located on chromosome 5A, the chromosome most often found to be associated with cold hardiness. The induction of an active ADF during cold acclimation and the correlation with an increased freezing tolerance suggest that the protein may be required for the cytoskeletal rearrangements that may occur upon low temperature exposure. These remodelings might be important for the enhancement of freezing tolerance.
Urea Is a Product of Ureidoglycolate Degradation in Chickpea. Purification and Characterization of the Ureidoglycolate Urea-Lyase
Authors: Muñoz Alfonso , Piedras Pedro , Aguilar Miguel , Pineda Manuel
Published: July 2002

A ureidoglycolate-degrading activity was analyzed in different organs of chickpea (Cicer arietinum). Activity was detected in all the tissues analyzed, but highest levels of specific activity were found in pods, from which it has been purified and characterized. This is the first ureidoglycolate-degrading activity that has been purified to homogeneity from any photosynthetic organism. Only one ureidoglycolate-degrading activity was found during the purification. The enzyme was purified 1,500-fold, and specific activity for the pure enzyme was 8.6 units mg−1, which corresponds with a turnover number of 1,600 min−1. The native enzyme has a molecular mass of 180 kD and consists of six identical or similar-sized subunits of 31 kD each. The enzyme exhibited hyperbolic, Michaelian kinetics for (−) ureidoglycolate withK  m values of 6 and 10 μm in the presence or absence of Mn2+, respectively. Optimum pH was between 7 and 8 and maximum activity was found at temperatures above 70°C, the enzyme being extremely stable and resistant to heat denaturation. The activity was inhibited by EDTA and enhanced by several bivalent cations, thus suggesting that the enzyme is a metalloprotein. This enzyme has been characterized as a ureidoglycolate urea-lyase (EC 4.3.2.3), which catalyzes the degradation of (−) ureidoglycolate to glyoxylate and urea. This is the first time that such an activity is detected in plant tissues. A possible function for this activity and its implications in the context of nitrogen mobilization in legume plants is also discussed.
Purification and Characterization of the Preprotein Translocase of the Outer Mitochondrial Membrane from Arabidopsis. Identification of Multiple Forms of TOM20
Authors: Werhahn Wolf , Niemeyer Astrid , Jänsch Lothar , Kruft Volker , Schmitz Udo K. , Braun Hans-Peter
Published: July 2002

The translocase of the outer mitochondrial membrane (TOM) complex is a preprotein translocase that mediates transport of nuclear-encoded mitochondrial proteins across the outer mitochondrial membrane. Here we report the purification of this protein complex from Arabidopsis. On blue-native gels the Arabidopsis TOM complex runs at 230 kD and can be dissected into subunits of 34, 23, 21, 8, 7, and 6 kD. The identity of four subunits could be determined by immunoblotting and/or direct protein sequencing. The 21- and the 23-kD subunits exhibit significant sequence homology to the TOM20 preprotein receptor from other organisms. Analysis by two-dimensional isoelectric focusing/Tricine sodium dodecyl sulfide-polyacrylamide gel electrophoresis revealed the presence of further forms for Arabidopsis TOM20. All TOM20 proteins comprise a large cytoplasmically exposed hydrophilic domain, which is degraded upon trypsination of intact mitochondria. Clones encoding four different forms of Arabidopsis TOM20 were identified and sequenced. The deduced amino acid sequences are rather conserved in the N-terminal half and in the very C-terminal part, but include a highly variable glycine-rich region close to the C terminus. Implications on the function of plant TOM complexes are discussed. Based on peptide and nucleic acid sequence data, the primary structure for Arabidopsis TOM40 is presented.
Flavonoid Accumulation Patterns of Transparent Testa Mutants of Arabidopsis
Authors: Peer Wendy Ann , Brown Dana E. , Tague Brian W. , Muday Gloria K. , Taiz Lincoln , Murphy Angus S.
Published: July 2002

Flavonoids have been implicated in the regulation of auxin movements in Arabidopsis. To understand when and where flavonoids may be acting to control auxin movement, the flavonoid accumulation pattern was examined in young seedlings and mature tissues of wild-type Arabidopsis. Using a variety of biochemical and visualization techniques, flavonoid accumulation in mature plants was localized in cauline leaves, pollen, stigmata, and floral primordia, and in the stems of young, actively growing inflorescences. In young Landsbergerecta seedlings, aglycone flavonols accumulated developmentally in three regions, the cotyledonary node, the hypocotyl-root transition zone, and the root tip. Aglycone flavonols accumulated at the hypocotyl-root transition zone in a developmental and tissue-specific manner with kaempferol in the epidermis and quercetin in the cortex. Quercetin localized subcellularly in the nuclear region, plasma membrane, and endomembrane system, whereas kaempferol localized in the nuclear region and plasma membrane. The flavonoid accumulation pattern was also examined in transparent testa mutants blocked at different steps in the flavonoid biosynthesis pathway. The transparent testa mutants were shown to have precursor accumulation patterns similar to those of end product flavonoids in wild-type Landsberg erecta, suggesting that synthesis and end product accumulation occur in the same cells.
Probing protein fine structures by wide angle solution X-ray scattering
Authors: Zhang R. , Thiyagarajan P. , Tiede D.M.
Published: July 2002

In this report we have investigated the use of wide angle scattering data not only to resolve overall size and shape of protein molecules in solution, but also to resolve details of fine structure. Methods have been developed for calculating protein solution scattering profiles based on atomic coordinates over a wide range of q with high accuracy in order to compare protein atomic models to wide angle scattering data. Calculations based upon these procedures show that X-ray scattering profiles for X-ray crystal and NMR solution structures for cytochrome c are significantly different, and that these differences can be resolved by high-precision wide angle X-ray scattering measurements. It is also shown that wide angle X-ray scattering profiles are rather sensitive to atomic fluctuations (Debye-Waller temperature factors), suggesting that wide angle scattering data may provide an opportunity for evaluation of protein dynamics.
Extended pseudo-Voigt function for approximating the Voigt profile
Authors: Ida T. , Ando M. , Toraya H.
Published: July 2002

The formula of the pseudo-Voigt function expressed by a weighted sum of Gaussian and Lorentzian functions is extended by adding two other types of peak functions in order to improve the accuracy when approximating the Voigt profile. The full width at half-maximum (FWHM) values and mixing parameters of the Gaussian, the Lorentzian and the other two component functions in the extended formula can be approximated by polynomials of a parameter ρ = ΓL/(ΓG+ ΓL), where ΓGand ΓLare the FWHM values of the deconvoluted Gaussian and Lorentzian functions, respectively. The maximum deviation of the extended pseudo-Voigt function from the Voigt profile is within 0.12% relative to the peak height when sixth-order polynomial expansions are used. The systematic errors of the integrated intensity ΓGand ΓL, estimated by fitting the extended formula to Voigt profiles, are typically less than 1/10 of the errors arising from the application of the original formula of the pseudo-Voigt approximation proposed by Thompsonet al.[J. Appl. Cryst.(1987),20, 79–83], while the time required for computation of the extended formula is only about 2.5 relative to the computation time required for the original formula.
High-pressure properties of TiP2O7, ZrP2O7and ZrV2O7
Authors: Carlson Stefan , Krogh Andersen Anne Marie
Published: July 2002

High-pressure synchrotron X-ray powder diffraction studies of TiP2O7, ZrP2O7and ZrV2O7have been performed. The ZrV2O7structure undergoes a reversible transition at 1.38–1.58 GPa from cubic α- to pseudo-tetragonal β-ZrV2O7that displays an orthorhombic 2 × 3 × 3 supercell. At pressures above 4 GPa, ZrV2O7becomes irreversibly X-ray amorphous. No such transformations are observed for TiP2O7and ZrP2O7, which compress smoothly up to the highest investigated pressures (40.3 and 20.5 GPa, respectively). These differences in high-pressure properties are discussed in terms of the negative thermal expansion of ZrV2O7. The bulk moduli at ambient pressure (B0) for TiP2O7, ZrP2O7, α-ZrV2O7and β-ZrV2O7were estimated to be 42 (3), 39 (1), 17.0 (7) and 20.8 (10) GPa, respectively.
Combined X-ray microbeam small-angle scattering and fibre diffraction experiments on single native cellulose fibres
Authors: Müller M. , Czihak C. , Burghammer M. , Riekel C.
Published: July 2002

The morphology of single native cellulose (flax) fibres was investigated by means of simultaneous small-angle scattering and fibre diffraction using an X-ray microbeam. The azimuthal broadenings both of the equatorial small-angle scattering streak and of Bragg reflections are found to be due to a misalignment of the crystalline cellulose microfibrils with respect to the fibre axis. Diffuse scattering on the layer lines and the equator of the fibre diffraction diagram indicates the presence of disordered cellulose between the cellulose microfibrils and of defects inside the crystallites.
Grain-size dependence of intergranular magnetic correlations in nanostructured metals
Authors: Löffler J.F. , Wagner W. , Kostorz G.
Published: July 2002

Magnetic small-angle neutron scattering experiments were performed on nanostructured Fe, Co and Ni samples of varying grain size, produced by inert-gas condensation. The experiments show that the spontaneous spatial magnetic correlations forming in zero-field extend over many individual grains. These correlations depend strongly on grain size. In Fe, they have a minimum at a grain size of around 35 nm and increase sharply for smaller grain sizes. The crossover occurs at grain sizes comparable with L
crit = πδ, where δ is the bulk domain-wall width. For grain sizes below L
crit, the results are explained on the basis of the random-anisotropy model, which takes into account that the magnetic alignment between the grains competes with the anisotropies of the individual grains. Above L
crit, where domain walls can form within one grain, the magnetization direction corresponds to the anisotropy direction varying from grain to grain, and the magnetic correlation length increases approximately linearly with grain size. Furthermore, the measurements on Fe, Co and Ni show that the spatial magnetic correlations measured by SANS are always larger than L
crit. This is in agreement with results of theoretical studies showing that nonuniform magnetization configurations can only exist in grains with sizes D > L
crit.