bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective activation method with A23187 and puromycin to produce haploid parthenogenones from freshly ovulated mouse oocytes
Authors: Nakasaka Hisayo , Yamano Shuji , Hinokio Kenji , Nakagawa Koji , Yoshizawa Midori , Aono Toshihiro
Published: July 2002

Freshly ovulated mouse oocytes exposed to 5 mM calcium ionophore A23187 for 5 min and controls (not exposed) were cultured in TYH medium with 10 μg/ml puromycin (the puromycin group) or 2 mM 6-dimethylaminopurine (DMAP; the DMAP group) for 4 h. Among the controls, few oocytes were activated even if they were treated with DMAP or puromycin. In the oocytes exposed to A23187, in contrast, the activation rate, i.e. the rate of oocytes showing at least one pronucleus (PN) after the treatment, was 46.2% (48/104) in the DMAP group and 90.0% (118/131) in the puromycin group. Activation rate in the puromycin group was significantly higher than in the DMAP and control groups (p < 0.0001, respectively). Furthermore, 82.4% (108/131) of the activated oocytes in the puromycin group showed one PN with extrusion of the second polar body (PB). In the puromycin group, the DNA content of the PN of parthenogenones with 1PN2PB was half that of a set of metaphase II chromosomes. Chromosomal analysis was possible in 14 parthenogenones with 1PN2PB in the puromycin group. The parthenogenones possessed a normal set (n = 20) of haploid chromosomes. The combination of A23187 and puromycin proved to be an effective method of producing haploid parthenogenones.
Time in biology with particular reference to humans
Authors: WATERHOUSE J.
Published: July 2002

Organisms possess an internal ‘body clock’ that measures the passage of the day, although they respond directly to the influences of the sun. The site of this clock, its properties, and its molecular and genetic mechanisms are now beginning to be discovered. In humans, the clock enables the processes required for daytime activities and nocturnal sleep to be separated; but the system can go wrong or cause difficulties, as in the blind, anybody after a time-zone transition or during night work
Making sense of time
Authors: MICHON JOHN A.
Published: July 2002

From the psychonomic point of view time is the conscious experiential product of the processes that enable the (human) organism to organize itself adaptively so that its behaviour stays tuned to the sequential contingencies afforded by its environment. This paper reviews some recent insights into the functioning of the timekeepers – clocks and regulators, organic and virtual – that make up the human ‘sense of time’.
Fuzzy network model for part-of-speech tagging under small

training data
Authors: KIM JAE-HOON , KIM GIL CHANG
Published: July 2002

Recently, most part-of-speech tagging approaches, such as

rule-based, probabilistic and neural network approaches, have shown

very promising results. In this paper, we are particularly interested

in probabilistic approaches, which usually require lots of training

data to get reliable probabilities. We alleviate such a restriction of

probabilistic approaches by introducing a fuzzy network model to

provide a method for estimating more reliable parameters of a model

under a small amount of training data. Experiments with the Brown

corpus show that the performance of the fuzzy network model is much

better than that of the hidden Markov model under a limited amount of

training data.
NL-OOPS: from natural language to object oriented requirements

using the natural language processing system LOLITA
Authors: MICH L.
Published: July 2002

This paper describes NL-OOPS, a CASE tool that supports

requirements analysis by generating object oriented models from

natural language requirements documents. The full natural language

analysis is obtained using as a core system the Natural Language

Processing System LOLITA. The object oriented analysis module

implements an algorithm for the extraction of the objects and their

associations for use in creating object models.
Robust grammatical analysis for spoken dialogue systems
Authors: VAN NOORD GERTJAN , BOUMA GOSSE , KOELING ROB , NEDERHOF MARK-JAN
Published: July 2002

We argue that grammatical analysis is a viable alternative to concept spotting for processing
spoken input in a practical spoken dialogue system. We discuss the structure of the grammar,
and a model for robust parsing which combines linguistic sources of information and statistical
sources of information. We discuss test results suggesting that grammatical processing allows
fast and accurate processing of spoken input.
“Expectation as etiology” versus “the
good old days”: Postconcussion syndrome symptom reporting
in athletes, headache sufferers, and depressed individuals
Authors: GUNSTAD JOHN , SUHR JULIE A.
Published: July 2002

The present study explored the explanatory power of
Mittenberg's “expectation as etiology”
theory for the persistence of postconcussion syndrome (PCS)
complaints. One hundred forty-one participants completed
a PCS symptom checklist under 2 conditions. Normal controls,
healthy athletes and depressed individuals reported current
symptoms and symptoms expected following a hypothetical
mild head injury. Head-injured athletes, chronic headache
sufferers, and a 2nd sample of normal controls reported
current symptoms and retrospective symptoms (prior to their
injury/illness or from some point in the past). Depressed
individuals reported more current symptoms than normal
controls and healthy athletes, demonstrating that “PCS”
symptoms are not specific to PCS. All groups expected more
symptoms following mild head injury than currently experienced,
supporting the idea that individuals expect negative consequences
following head injury. However, healthy athletes expected
fewer symptoms than normals or depressed individuals, possibly
due to preexisting expectations for speedy recovery. Both
head-injured athletes and headache sufferers reported more
current symptoms than the past, but not at a rate lower
than baseline of normal controls. Results suggest that
the “expectation as etiology” hypothesis may
be too specific, and that, following any negative event,
people may attribute all symptoms to that negative event
(the “good old days” hypothesis). (JINS,
2001, 7, 323–333.)
Neuroimaging: Clinical Applications
Authors: Risberg Jarl
Published: July 2002

Imaging of the structure and function of the human
brain has grown to an area with increasing impact on neuropsychological
research as well as on the routine clinical evaluation
of brain damaged patients. The scientific and popular literature
is now flooded by increasingly more spectacular pictures
of the brain. The images no longer only illustrate what
is well known from earlier research but they do also sometimes
provide information of importance for the further development
of neuropsychological theories. The two volumes edited
by Erin D. Bigler, Neuroimaging I and II,
offer a possibility for neuropsychologists and other interested
readers to get acquainted with the more recent developments
in measurement technology and applications in basic science
(Volume I) as well as in the clinic (Volume II). The authors
of the 24 chapters are generally outstanding researchers,
with impressive expertise within their fields of specialization.
Brain Repair: Bridging the Lab-Brain Barrier?
Authors: Gronwall Dorothy
Published: July 2002

This optimistic book about recovery of function
after brain injury or disease is written by three neuroscientists
specifically to counter the belief that brain injury is
permanent and that the brain cannot be repaired. They point
out that this belief leads to often inappropriate or no
treatment, which then makes it a self-fulfilling prophecy.
However there is an increasingly extensive body of evidence
from laboratories around the world that given the right
conditions and specific chemicals, for example, normal
function can be restored. This literature is highly specialized,
highly technical, and often apparently unrelated to human
recovery. It is also produced at a prodigious rate. According
to a 1989 survey, fact-based knowledge doubled every 18
months at that time, and it was predicted that by the year
2010 it will double every 4 weeks. It is not surprising,
therefore, that members of a health-professional team have
difficulty keeping up with the clinical rehabilitation
literature, and that they do not have the time or the energy
to read studies on laboratory animals or tissue studies
which are not seen as high priority or of relevance to
their work.
Three-dimensional neglect phenomena following right anterior
choroidal artery infarction
Authors: KORI ADRIANA , GELDMACHER DAVID S.
Published: July 2002

Neglect in the horizontal and vertical axes of
space has been observed after acute right anterior choroidal
artery (AChA) lesions. How spatial processing is affected
in the radial axis during the acute period following infarction
in this region is unknown. We report the case of a 69-year-old
man with acute left hemineglect and deficits in 3-dimensional
spatial processing following right AChA infarction. His
line bisections in 4 spatial conditions, oriented in the
3 primary axes of space, were compared with 6 control participants.
The patient's bisections were different from true
center and from control performance in all axes. His bisections
were to the right, below, and distal to the arithmetic
midpoint. This patient's bisection errors show a 3-dimensional
neglect pattern following right AChA infarction, supporting
the view that processing of all 3 spatial dimensions may
be simultaneously disturbed following unilateral right
hemisphere lesions. (JINS, 1999, 5, 567–571.)
The environmental Kuznets curve: an empirical analysis
Authors: COLE M.A. , RAYNER A.J. , BATES J.M.
Published: July 2002

This paper examines the relationship between per capita income and a wide range of environmental indicators using cross-country panel sets. The manner in which this has been done overcomes several of the weaknesses asscociated with the estimation of environmental Kuznets curves (EKCs). outlined by Stern et al. (1996). Results suggest that meaningful EKCs exist only for local air pollutants whilst indicators with a more global, or indirect, impact either increase monotonically with income or else have predicted turning points at high per capita income levels with large standard errors – unless they have been subjected to a multilateral policy initiative. Two other findings are also made: that concentration of local pollutants in urban areas peak at a lower per capita income level than total emissions per capita; and that transport-generated local air pollutants peak at a higher per capita income level than total emissions per capita. Given these findings, suggestions are made regarding the necessary future direction of environmental policy.
Demystifying the environmental Kuznets curve: turning a black box into a policy tool
Authors: PANAYOTOU THEODORE
Published: July 2002

The reduced-form approach to the income–environment relationship has been a useful first step towards answering the question of how economic growth affects the environment. However, without an explicit consideration of the underlying determinants of environmental quality, the scope for policy intervention is unduly circumscribed. In this paper a modest attempt is made to incorporate explicit policy considerations into the income–environment relationship and to explore its determinants as a step towards a better understanding of this relationship and its potential as a policy tool. The role of the rate of economic growth and population density is also explored. A main finding is that at least in the case of ambient SO2 levels, policies and institutions can significantly reduce environmental degradation at low income levels and speed up improvements at higher income levels, thereby flattening the EKC and reducing the environmental price of economic growth.
Is there a role for benefit-cost analysis in environmental, health, and safety regulation?
Authors: ARROW KENNETH J. , CROPPER MAUREEN L. , EADS GEORGE C. , HAHN ROBERT W. , LAVE LESTER B. , NOLL ROGER G. , PORTNEY PAUL R. , RUSSELL MILSON , SCHMALENSEE RICHARD , SMITH V. KERRY , STAVINS ROBERT N.
Published: July 2002

The growing impact of regulations on the economy has led both Congress and the Administration to search for new ways of reforming the regulatory process. Many of these initiatives call for greater reliance on the use of economic analysis in the development and evaluation of regulations. One specific approach being advocated is benefit-cost analysis, an economic tool for comparing the desirable and undesirable impacts of proposed policies.
Voices in the desert: an ontology of the electroacoustic community
Authors: RICHARD DOMINIQUE
Published: July 2002

When referring to the electroacoustic community, we often picture a set of select institutions whose members are engaged in the process of music making by electronic means. This mythic community is assumed to have a unity of purpose and a common set of be
liefs. However, considering the divergence of positions expressed in and around this ‘community’, we are tempted to dismiss the notion of any commonality. If we reframe our thinking and avoid transcendence to be ‘in a pure field of immanence’ (Deleuze 1988b: 7), we have the potential for a new definition of collegiality which may permit a community-in-becoming to emerge within electroacoustics.
Palatal Sound: a comprehensive model of vocal tract articulation*
Authors: EDGERTON MICHAEL EDWARD
Published: July 2002

Palatal Sound is a model of vocal tract articulation influenced by
physiologic and acoustic analysis of the voice. Specifically, the term
articulation refers to all movement within the vocal tract that results
in open, filter-like sonorities, as well as in turbulent to absolute
airflow modification. This model presents a complete mapping of place
within the vocal tract that features flexibility across different vocal
tract sizes and proportions. The principles behind this comprehensive
mapping of acoustic and physical sound production techniques should not
be foreign to those persons who create, combine, design, model or research
sound. Therefore, this model might suggest avenues of sound exploration
regardless of media or application. This text first presents a brief
overview of the current trends of oral modification using vowels, followed
by an introduction to and acoustic analyses of the comprehensive vocal
tract model as applied to open-like sonorities. This model is then expanded
through the presentation of other methods of open-like behaviours. Following
the discussion of open sonorities, turbulent-like behaviours are discussed
by first identifying the use of language-based fricatives and stops. After
this (re-)exposition, the comprehensive model is applied to turbulent
structures through examples and acoustic analyses. Finally, these turbulent
methods are completed by additional, complementary methods of vocal tract
turbulence. The intentions of this paper are: (i) to document this model
clearly, (ii) to identify differences between speech and song articulatory
behaviour and that of this comprehensive model with the aid of selected
acoustic analyses, (iii) to suggest that this model renders valuable
scientific information about the limits of vocal tract physiology, and
(iv) to propose the practical use of this model by composers and
performers.
Assessment Instruments for Asperger Syndrome
Authors: Howlin Patricia
Published: July 2002

This review describes the current situation with regard to diagnostic
instruments for Asperger syndrome. The paucity of such instruments, and
the lack of adequate standardisation data amongst the few that do exist,
represent a serious omission for both clinicians and researchers. The major
problem limiting the development of effective diagnostic or screening
instruments is the confusion inherent in ICD-10 and DSM-1V systems in
differentiating autism from Asperger syndrome. In the absence of clear and
clinically satisfactory diagnostic criteria, efforts to develop valid
assessment instruments may be attempting to put the horse before the
cart!
Structural Family Therapy
Authors: Vetere Arlene
Published: July 2002

Structural Family Therapy was developed by Salvador Minuchin and colleagues during the 1960s as part of the growing interest in systemic ways of conceptualising human distress and relationship dilemmas, and in working therapeutically with those natural systems and relationships, thought to give rise to distress. Structural family therapy is underpinned by a clearly articulated model of family functioning, and has been developed and used most consistently in services for children and families. A growing body of empirical evidence attests to the efficacy of structural family therapy. As an approach it was extensively critiqued during the 1980s by feminist writers and during the 1990s by those interested in the implications of a social constructionist position. Structural family therapy continues to evolve in response to challenges mounted from within and outwith the systemic field, and as part of integrative practice and multi-systemic approaches, with practitioners ever mindful of the need for regular feedback from family members themselves.
The Development of Play During Childhood: Forms and Possible Functions
Authors: Pellegrini Anthony D. , Smith Peter K.
Published: July 2002

In this review we consider the nature and possible developmental
functions
of three forms of play: pretend, social, and locomotor. Play is defined
in
terms of dispositional and contextual criteria. First, the frequency of

occurrence of each form of play across the period of childhood is
documented. Developmental function of play is conceptualised in terms of

immediate or deferred beneficial consequences. Four strategies for
examining developmental function are reviewed: arguments from design,
correlational analyses, experimental enrichment and deprivation, and cost-benefit analyses. Whereas most theories of play implicitly assume that

during childhood it occurs frequently and has benefits deferred until
adulthood, we suggest that some benefits of play are immediate.
THE ECONOMETRICS OF FINANCIAL MARKETS
Authors: Campbell John Y. , Lo Andrew W. , MacKinlay A. Craig , Whitelaw Robert F.
Published: July 2002

This book is an ambitious effort by three well-known and
well-respected scholars to fill an acknowledged void in the
literature—a text covering the burgeoning
field of empirical finance.
As the authors note in the preface, there are several excellent books
covering financial theory at a level suitable for a Ph.D. class or as
a reference for academics and practitioners, but there is little or
nothing similar that covers econometric methods and applications.
Perhaps the closest existing text is the recent addition to the Wiley
Series in Financial and Quantitative Analysis.
written by Cuthbertson
(1996). The major difference between the books is that Cuthbertson
focuses exclusively on asset pricing in the stock, bond, and foreign
exchange markets, whereas Campbell, Lo, and MacKinlay (henceforth CLM)
consider empirical applications throughout the field of finance,
including corporate finance, derivatives markets, and market
microstructure. The level of anticipation preceding publication
can be partly measured by the fact that at least three reviews
(including this one) have appeared since the book arrived. Moreover,
in their reviews, both Harvey (1998) and Tiso (1998) comment on the
need for such a text, a sentiment that has been echoed by numerous
finance academics.
Foliations Leaf Through Economics
Authors: Saari Donald G.
Published: July 2002

Foliations provide a general, convenient, geometric way
to catalogue information from topics as varied as sufficient
statistics, solutions of differential equations, indifference curves for
utility functions, distributed computing, and so forth. An introduction
to aspects of this area is provided.
The p120 catenin partner Kaiso is a DNA methylation-dependent transcriptional repressor
Authors: Prokhortchouk Anna , Hendrich Brian , Jørgensen Helle , Ruzov Alexei , Wilm Matthias , Georgiev Georgii , Bird Adrian , Prokhortchouk Egor
Published: July 2002

We describe a novel mammalian DNA binding activity that requires at least two symmetrically methylated CpG dinucleotides in its recognition sequence, preferably within the sequence 5′CGCG. A key component of the activity is Kaiso, a protein with POZ and zinc-finger domains that is known to associate with p120 catenin. We find that Kaiso behaves as a methylation-dependent transcriptional repressor in transient transfection assays. Kaiso is a constituent of one of two methyl–CpG binding complexes originally designated as MeCP1. The data suggest that zinc-finger motifs are responsible for DNA binding, and may therefore target repression to specific methylated regions of the genome. As Kaiso associates with p120 catenin, Kaiso may link events at the cell surface with DNA methylation-dependent gene silencing.
Involvement of small RNAs and role of the qde genes in the gene silencing pathway in Neurospora
Authors: Catalanotto Caterina , Azzalin Gianluca , Macino Giuseppe , Cogoni Carlo
Published: July 2002

Small RNA molecules have been found to be specifically associated with posttranscriptional gene silencing (PTGS) in both plants and animals. Here, we find that small sense and antisense RNAs are also involved in PTGS in Neurospora crassa. The accumulation of these RNA molecules depends on the presence of functional qde-1 and qde-3 genes previously shown to be essential for gene silencing, but does not depend on a functionalqde-2, indicating that this gene is involved in a downstream step of the gene silencing pathway. Supporting this idea, a purified QDE2 protein complex was found to contain small RNA molecules, suggesting that QDE2 could be part of a small RNA-directed ribonuclease complex involved in sequence-specific mRNA degradation.
Dmrt1, a gene related to worm and fly sexual regulators, is required for mammalian testis differentiation
Authors: Raymond Christopher S. , Murphy Mark W. , O'Sullivan M. Gerard , Bardwell Vivian J. , Zarkower David
Published: July 2002

The only molecular similarity in sex determination found so far among phyla is between the Drosophila doublesex (dsx) and Caenorhabditis elegans mab-3 genes. dsx andmab-3 contain a zinc finger-like DNA-binding motif called the DM domain, perform several related regulatory functions, and are at least partially interchangeable in vivo. A DM domain gene calledDmrt1 has been implicated in male gonad development in a variety of vertebrates, on the basis of embryonic expression and chromosomal location. Such evidence is highly suggestive of a conserved role(s) for Dmrt1 in vertebrate sexual development, but there has been no functional analysis of this gene in any species. Here we show that murine Dmrt1 is essential for postnatal testis differentiation, with mutant phenotypes similar to those caused by human chromosome 9p deletions that remove the gene. As in the case of 9p deletions, Dmrt1 is dispensable for ovary development in the mouse. Thus, as in invertebrates, a DM domain gene regulates vertebrate male development.
Phosphorylation of histone H3 correlates with transcriptionally active loci
Authors: Nowak Scott J. , Corces Victor G.
Published: July 2002

Posttranslational modifications of the N-terminal tails of the core histones within the nucleosome particle are thought to act as signals from the chromatin to the cell for various processes. The experiments presented here show that the acetylation of histones H3 and H4 in polytene chromosomes does not change during heat shock. In contrast, the global level of phosphorylated H3 decreased dramatically during a heat shock, with an observed increase in H3 phosphorylation at the heat shock loci. Additional experiments confirm that this change in phosphorylated H3 distribution is dependent on functional heat shock transcription factor activity. These experiments suggest that H3 phosphorylation has an important role in the induction of transcription during the heat shock response.
TEAD/TEF transcription factors utilize the activation domain of YAP65, a Src/Yes-associated protein localized in the cytoplasm
Authors: Vassilev Alex , Kaneko Kotaro J. , Shu Hongjun , Zhao Yingming , DePamphilis Melvin L.
Published: July 2002

Mammals express four highly conserved TEAD/TEF transcription factors that bind the same DNA sequence, but serve different functions during development. TEAD-2/TEF-4 protein purified from mouse cells was associated predominantly with a novel TEAD-binding domain at the amino terminus of YAP65, a powerful transcriptional coactivator. YAP65 interacted specifically with the carboxyl terminus of all four TEAD proteins. Both this interaction and sequence-specific DNA binding by TEAD were required for transcriptional activation in mouse cells. Expression of YAP in lymphocytic cells that normally do not support TEAD-dependent transcription (e.g., MPC11) resulted in up to 300-fold induction of TEAD activity. Conversely, TEAD overexpression squelched YAP activity. Therefore, the carboxy-terminal acidic activation domain in YAP is the transcriptional activation domain for TEAD transcription factors. However, whereas TEAD was concentrated in the nucleus, excess YAP65 accumulated in the cytoplasm as a complex with the cytoplasmic localization protein, 14-3-3. Because TEAD-dependent transcription was limited by YAP65, and YAP65 also binds Src/Yes protein tyrosine kinases, we propose that YAP65 regulates TEAD-dependent transcription in response to mitogenic signals.
GeneID in Drosophila
Authors: Parra Genís , Blanco Enrique , Guigó Roderic
Published: July 2002

GeneID is a program to predict genes in anonymous genomic sequences designed with a hierarchical structure. In the first step, splice sites, and start and stop codons are predicted and scored along the sequence using position weight matrices (PWMs). In the second step, exons are built from the sites. Exons are scored as the sum of the scores of the defining sites, plus the log-likelihood ratio of a Markov model for coding DNA. In the last step, from the set of predicted exons, the gene structure is assembled, maximizing the sum of the scores of the assembled exons. In this paper we describe the obtention of PWMs for sites, and the Markov model of coding DNA inDrosophila melanogaster. We also compare other models of coding DNA with the Markov model. Finally, we present and discuss the results obtained when GeneID is used to predict genes in the Adh region. These results show that the accuracy ofGeneID predictions compares currently with that of other existing tools but that GeneID is likely to be more efficient in terms of speed and memory usage. GeneID is available at http://www1.imim.es/∼eblanco/GeneId.
Identification of Novel Human Genes Evolutionarily Conserved inCaenorhabditis elegansby Comparative Proteomics
Authors: Lai Chun-Hung , Chou Chang-Yuan , Ch'ang Lan-Yang , Liu Chung-Shyan , Lin Wen-chang
Published: July 2002

Modern biomedical research greatly benefits from large-scale genome-sequencing projects ranging from studies of viruses, bacteria, and yeast to multicellular organisms, likeCaenorhabditis elegans. Comparative genomic studies offer a vast array of prospects for identification and functional annotation of human ortholog genes. We presented a novel comparative proteomic approach for assembling human gene contigs and assisting gene discovery. TheC. elegansproteome was used as an alignment template to assist in novel human gene identification from human EST nucleotide databases. Among the available 18,452C. elegansprotein sequences, our results indicate that at least 83% (15,344 sequences) ofC. elegansproteome has human homologous genes, with 7,954 records ofC. elegansproteins matching known human gene transcripts. Only 11% or less ofC. elegansproteome contains nematode-specific genes. We found that the remaining 7,390 sequences might lead to discoveries of novel human genes, and over 150 putative full-length human gene transcripts were assembled upon further database analyses.

[The sequence data described in this paper have been submitted to the GenBank data library under accession nos.AF132936–AF132973,AF151799–AF151909, andAF152097.]
The Basic Helix-Loop-Helix Protein Family: Comparative Genomics and Phylogenetic Analysis
Authors: Ledent Valérie , Vervoort Michel
Published: July 2002

The basic Helix-Loop-Helix (bHLH) proteins are transcription factors that play important roles during the development of various metazoans including fly, nematode, and vertebrates. They are also involved in human diseases, particularly in cancerogenesis. We made an extensive search for bHLH sequences in the completely sequenced genomes ofCaenorhabditis elegans and of Drosophila melanogaster. We found 35 and 56 different genes, respectively, which may represent the complete set of bHLH of these organisms. A phylogenetic analysis of these genes, together with a large number (>350) of bHLH from other sources, led us to define 44 orthologous families among which 36 include bHLH from animals only, and two have representatives in both yeasts and animals. In addition, we identified two bHLH motifs present only in yeast, and four that are present only in plants; however, the latter number is certainly an underestimate. Most animal families (35/38) comprise fly, nematode, and vertebrate genes, suggesting that their common ancestor, which lived in pre-Cambrian times (600 million years ago) already owned as many as 35 different bHLH genes.
Blockade of NMDA Receptors in the Amygdala Prevents Latent Inhibition of Fear-Conditioning
Authors: Schauz Cornelia , Koch Michael
Published: July 2002

The association between a conditioned stimulus (CS) and an unconditioned stimulus (US) in fear-conditioning depends onN-methyl-d-aspartate (NMDA) receptors in the basolateral amygdala complex (BLA). Latent inhibition (LI) is the retardation in learning due to nonreinforced presentation of the prospective CS before conditioning. Disruption of LI in rats is an animal model of schizophrenia, reflecting the deficits of schizophrenic patients in neglecting irrelevant information. We investigated whether the BLA is involved in LI of fear-potentiated startle. Infusions of the NMDA receptor antagonistd,l-2-amino-5-phosphonopentanoic acid (AP-5; 12.5 nmoles) into the BLA before preexposure of rats to the neutral stimulus prevent LI of fear-conditioning. We also demonstrated by the same method that a complex of thalamic nuclei, comprising the medial part of the medial geniculate nucleus, the posterior intralaminar nucleus, and the suprageniculate nucleus, is involved in fear-conditioning, but not in LI. This suggests that the presentation of an innocuous stimulus during preexposure leads to an NMDA receptor-dependent change of neurotransmission in the BLA, but not in the thalamus. Our data show that the BLA but not the thalamus regulates in LI of fear-potentiated startle. Furthermore, it supports the hypothesis that the inability of schizophrenic patients to ignore irrelevant stimuli may be caused by hypofunction of the glutamatergic transmission in the brain and suggests an involvement of the amygdala in the neuropathology of schizophrenia.
Effects of the Selective M1 Muscarinic Receptor Antagonist Dicyclomine on Emotional Memory
Authors: Fornari Raquel V. , Moreira Karin M. , Oliveira Maria Gabriela M.
Published: July 2002

The nonselective muscarinic antagonist scopolamine is known to impair the acquisition of some learning tasks such as inhibitory avoidance. There has been recent research into the effects of this drug in contextual fear conditioning and tone fear conditioning paradigms. The purpose of the present study was to assess the role of the selective M1 muscarinic antagonist dicyclomine in these paradigms and in the inhibitory avoidance test. Rats were administered different doses of dicyclomine or saline 30 min before acquisition training. The animals were tested 24 hr later, and it was observed that 16 mg/kg of dicyclomine impaired both contextual fear conditioning and inhibitory avoidance. However, dicyclomine (up to 64 mg/kg) did not affect tone fear conditioning. These results suggest that the selective M1 muscarinic antagonist dicyclomine differentially affects aversively motivated tasks known to be dependent on hippocampal integrity (such as contextual fear conditioning and inhibitory avoidance) but does not affect similar hippocampus-independent tasks.
Mice Lacking the ERK1 Isoform of MAP Kinase Are Unimpaired in Emotional Learning
Authors: Selcher Joel C. , Nekrasova Tanya , Paylor Richard , Landreth Gary E. , Sweatt J. David
Published: July 2002

The extracellular signal-regulated kinases (ERKs) are members of the mitogen-activated protein kinase (MAPK) superfamily of enzymes and have recently garnered considerable attention in the field of learning and memory. ERK activation has been shown to be required for the induction of long-term potentiation (LTP) in the rat hippocampus and for the formation of associative and spatial memories in both the rat and the mouse. However, the individual roles for the two isoforms of ERK have yet to be deciphered. To investigate the specific contribution of the ERK1 (p44) isoform of MAPK to mammalian learning, we performed a general behavioral and physiological characterization of mice lacking the ERK1 gene. The ERK1-null animals demonstrated significantly higher levels of activity in the open field test. However, we observed no other discernible deficits in the ERK1 knockout mice in our behavioral testing. Specifically, no differences were observed in the acquisition or retention (24 h and 2 wk after training) of either contextual or cue fear conditioning between the ERK1−/− and their wild-type littermate controls. In addition, no learning phenotype was observed in the passive avoidance test. When hippocampal slices were analyzed, we found no deficits in baseline synaptic transmission or in tetanus-induced LTP in hippocampal area CA1. We found no apparent compensatory changes in the expression of ERK2 (p42 MAPK). We conclude that hippocampus- and amygdala-dependent emotional learning does not depend critically on the activity of ERK1.
Contextual Modulation of Memory Consolidation
Authors: Gerber Bertram , Menzel Randolf
Published: July 2002

We investigate olfactory memory consolidation in honeybees. Three experiments are reported that include 1024 animals in 28 experimental groups. After one pairing of odorant and sucrose reward, retention is typically nonmonotonic with a minimum 3 min after conditioning. This corresponds to the “Kamin effect” in vertebrates; the postminimum rise in retention is usually interpreted as reflecting memory consolidation. First, we test for the generality of this effect across four different odorants. The postminimum rise in retention was reproducibly observed for 1-hexanol but not for 1-octanol, limonene, or geraniol. Second, we investigate whether previous learning about the training context modulates subsequent memory consolidation. On the day before training, a reward was applied either upon placement into the future training context for 1 min, halfway during exposure or just before removal from the context. In the latter group, the 3-min minimum in retention was eliminated; thus, in that group, forward pairings of context and reward (i.e., context exposure begins before reward is applied) lead to an associative context memory that can modulate subsequent olfactory memory consolidation. Third, we found no evidence for a modulation of olfactory memory consolidation by pre-exposure to the odorant.
Evidence for a Ustilago maydis Steroid 5α-Reductase by Functional Expression in Arabidopsis det2-1Mutants
Authors: Basse Christoph W. , Kerschbamer Christine , Brustmann Markus , Altmann Thomas , Kahmann Regine
Published: July 2002

We have identified a gene (udh1) in the basidiomycete Ustilago maydis that is induced during the parasitic interaction with its host plant maize (Zea mays). udh1 encodes a protein with high similarity to mammalian and plant 5α-steroid reductases. Udh1 differs from those of known 5α-steroid reductases by six additional domains, partially predicted to be membrane-spanning. A fusion protein of Udh1 and the green fluorescent protein provided evidence for endoplasmic reticulum localization in U. maydis. The function of the Udh1 protein was demonstrated by complementing Arabidopsisdet2-1 mutants, which display a dwarf phenotype due to a mutation in the 5α-steroid reductase encoding DET2gene. det2-1 mutant plants expressing either theudh1 or the DET2 gene controlled by the cauliflower mosaic virus 35S promoter differed from wild-type Columbia plants by accelerated stem growth, flower and seed development and a reduction in size and number of rosette leaves. The accelerated growth phenotype of udh1 transgenic plants was stably inherited and was favored under reduced light conditions. Truncation of the N-terminal 70 amino acids of the Udh1 protein abolished the ability to restore growth in det2-1 plants. Our results demonstrate the existence of a 5α-steroid reductase encoding gene in fungi and suggest a common ancestor between fungal, plant, and mammalian proteins.
Limits to Sulfur Accumulation in Transgenic Lupin Seeds Expressing a Foreign Sulfur-Rich Protein
Authors: Tabe Linda M. , Droux Michel
Published: July 2002

The low sulfur amino acid content of legume seeds restricts their nutritive value for animals. We have investigated the limitations to the accumulation of sulfur amino acids in the storage proteins of narrow leaf lupin (Lupinus angustifolius) seeds. Variation in sulfur supply to lupin plants affected the sulfur amino acid accumulation in the mature seed. However, when sulfur was in abundant supply, it accumulated to a large extent in oxidized form, rather than reduced form, in the seeds. At all but severely limiting sulfur supply, addition of a transgenic (Tg) sink for organic sulfur resulted in an increase in seed sulfur amino acid content. We hypothesize that demand, or sink strength for organic sulfur, which is itself responsive to environmental sulfur supply, was the first limit to the methionine (Met) and cysteine (Cys) content of wild-type lupin seed protein under most growing conditions. In Tg, soil-grown seeds expressing a foreign Met- and Cys-rich protein, decreased pools of free Met, free Cys, and glutathione indicated that the rate of synthesis of sulfur amino acids in the cotyledon had become limiting. Homeostatic mechanisms similar to those mediating the responses of plants to environmental sulfur stress resulted in an adjustment of endogenous protein composition in Tg seeds, even when grown at adequate sulfur supply. Uptake of sulfur by lupin cotyledons, as indicated by total seed sulfur at maturity, responded positively to increased sulfur supply, but not to increased demand in the Tg seeds.
Inhibition of Trehalase Activity Enhances Trehalose Accumulation in Transgenic Plants
Authors: Goddijn OJM. , Verwoerd T. C. , Voogd E. , Krutwagen RWHH. , de Graff PTHM. , Poels J. , van Dun K. , Ponstein A. S. , Damm B. , Pen J.
Published: July 2002

As a first step toward the exploitation of the disaccharide trehalose as a stress-protective and preservative agent in plants, we engineered trehalose biosynthesis in tobacco (Nicotiana tabacum) and potato (Solanum tuberosum) by introducing the otsA and otsB genes from Escherichia coli, which encode trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase, respectively. In leaves of transgenic tobacco plants, very low levels of trehalose accumulation were obtained (0.11 mg g-1 fresh weight), whereas in transgenic potato tubers, no trehalose accumulated at all. Plant trehalase activity was shown to affect the accumulation of trehalose in these plants. An increase in trehalose accumulation, up to 0.41 and 4.04 mg g-1 fresh weight in tobacco leaves and potato microtubers, respectively, was noted when the potent trehalase inhibitor validamycin A was added to in vitro plants and to hydroponically grown greenhouse plants. Stunted growth and the formation of lancet-shaped leaves by trehalose-accumulating tobacco plants suggest a negative effect of trehalose biosynthesis on N. tabacum development. It is surprising that experiments with wild-type plants cultured in the presence of validamycin A indicate that, despite current belief, the capacity to synthesize trehalose may not be restricted to primitive phyla of vascular plants and certain “resurrection plants,” but may exist throughout the angiosperms.
7-Dehydrobrefeldin A, a Naturally Occurring Brefeldin A Derivative, Inhibits Secretion and Causes a cis-to-trans Breakdown of Golgi Stacks in Plant Cells
Authors: Driouich A. , Jauneau A. , Staehelin L. A.
Published: July 2002

7-Dehydrobrefeldin A (7-oxo-BFA) is a brefeldin A (BFA) analog that, like BFA, is a potent phytotoxin of Alternaria carthami, a fungal pathogen of safflower (Carthamus tinctorius L.) plants. Both BFA and 7-oxo-BFA have been shown to be causal agents of the leaf spot disease of these plants. We have investigated the effects of 7-oxo-BFA on the secretion and the structure of the Golgi stacks of sycamore maple (Acer pseudoplatanus) suspension-cultured cells to determine whether 7-oxo-BFA affects these cells in the same manner as BFA. When applied at 10 [mu]g/mL for 1 h, 7-oxo-BFA inhibits secretion of proteins by approximately 80%, the same value obtained for BFA. However, electron micrographs of high-pressure frozen/freeze-substituted cells demonstrated that 7-oxo-BFA is a more potent disrupter of the Golgi stacks of sycamore maple cells than BFA. In cells treated for 1 h with 10 [mu]g/mL 7-oxo-BFA, very few Golgi stacks can be discerned. Most of those that are left consist of fewer than three cisternae, all of which stain like trans-Golgi cisternae. They are surrounded by clusters of large (150–300 nm in diameter), darkly staining vesicles that are embedded in a fine-filamentous, ribosome-excluding matrix. Similarly sized and stained vesicles are seen budding from the rims of the residual trans-Golgi cisternae. Both the large vesicles and the residual Golgi stack buds stain with anti-xyloglucan polysaccharide antibodies. Recovery of Golgi stacks after removal of 7-oxo-BFA from 1-h-treated cells takes 2 to 6 h, compared with 1 to 2 h for cells treated with BFA. In contrast to 7-oxo-BFA, the BFA breakdown product BFA acid had no effect either on secretion or on the secretory apparatus. This is the first report, to our knowledge, of a BFA analog inhibiting secretion in a eukaryotic cell system.
Proline Accumulation and Salt-Stress-Induced Gene Expression in a Salt-Hypersensitive Mutant of Arabidopsis
Authors: Liu J. , Zhu J. K.
Published: July 2002

The sos1 mutant of Arabidopsis thaliana is more than 20 times more sensitive to NaCl stress than wild-type Arabidopsis. Because proline (Pro) is generally thought to have an important role in plant salt tolerance, the sos1 mutant and the wild type were compared with respect to their capacity to accumulate Pro under NaCl stress, and sos1 mutant plants accumulated more Pro than the wild type. The P5CS gene, which catalyzes the rate-limiting step in Pro biosynthesis, is induced by salt stress to a higher level in sos1 than in the wild type. Although a defective high-affinity K uptake system in sos1 causes K deficiency and inhibits growth in NaCl-treated plants, this decrease is not a sufficient signal for Pro accumulation and P5CS gene expression. Not all salt-stress-induced genes have a higher level of expression in sos1. The expression levels of AtPLC and RD29A, which encode a phospholipase C homolog and a putative protective protein, respectively, are the same in sos1 as in the wild type. However, the expression of AtMYB, which encodes a putative transcriptional factor, is induced to a much higher level by salt stress in sos1. Thus, the SOS1 gene product serves as a negative regulator for the expression of P5CS and AtMYB, but has no effect on AtPLC and RD29A expression.
Gibberellins and Stem Growth in Arabidopsis thaliana (Effects of Photoperiod on Expression of the GA4 and GA5 Loci)
Authors: Xu Y. L. , Gage D. A. , Zeevaart JAD.
Published: July 2002

Arabidopsis thaliana (L.) Heynh. is a quantitative long-day (LD) rosette plant in which stem growth is mediated by gibberellins (GAs). Application of GAs to plants in short-day (SD) conditions resulted in rapid stem elongation and flower formation, with GA4 and GA9 being equally effective, and GA1 showing lower activity. The effects of photoperiod on the levels of endogenous GAs were measured by combined gas chromatography-mass spectrometry with selected ion monitoring. When plants were transferred from SD to LD conditions there was a slight decrease in the level of GA53 and an increase in the levels of C19-GAs, GA9, GA20, GA1, and GA8, indicating that GA 20-oxidase activity is stimulated in LD conditions. Expression of GA5, which encodes GA 20-oxidase, was highest in elongating stems and was correlated with the rate of stem elongation. By contrast, GA4, which encodes 3β-hydroxylase, showed low expression in stems and its expression was not correlated with the rate of stem elongation. We conclude that stem elongation in LD conditions is at least in part due to increased expression of GA5, whereas expression of GA4 is not under photoperiodic control.
Mapping the Functional Roles of Cap Cells in the Response of Arabidopsis Primary Roots to Gravity1
Authors: Blancaflor Elison B. , Fasano Jeremiah M. , Gilroy Simon
Published: July 2002

The cap is widely accepted to be the site of gravity sensing in roots because removal of the cap abolishes root curvature. Circumstantial evidence favors the columella cells as the gravisensory cells because amyloplasts (and often other cellular components) are polarized with respect to the gravity vector. However, there has been no functional confirmation of their role. To address this problem, we used laser ablation to remove defined cells in the cap of Arabidopsis primary roots and quantified the response of the roots to gravity using three parameters: time course of curvature, presentation time, and deviation from vertical growth. Ablation of the peripheral cap cells and tip cells did not alter root curvature. Ablation of the innermost columella cells caused the strongest inhibitory effect on root curvature without affecting growth rates. Many of these roots deviated significantly from vertical growth and had a presentation time 6-fold longer than the controls. Among the two inner columella stories, the central cells of story 2 contributed the most to root gravitropism. These cells also exhibited the largest amyloplast sedimentation velocities. Therefore, these results are consistent with the starch-statolith sedimentation hypothesis for gravity sensing.