bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal stress analysis and homogenization for
catalytic combustor monoliths
Authors: KOLACZKOWSKI S. T. , LIN P. , MOVCHAN A. B. , SERKOV S. K. , SPENCE A.
Published: July 2002

We present a simple and rigorous mathematical model and efficient numerical algorithm for
the three-dimensional thermal stress analysis of composite structures used in high-temperature
catalytic combustors. Numerical experiments are carried out for three types of cell geometries.
A homogenization algorithm is implemented, and asymptotic formulae are derived for the
effective elastic moduli of the periodic structures.
The place of beta-adrenoreceptor-blocking drugs in the treatment of congestive heart failure in elderly people: review of current opinion
Authors: Woosnam L , Hasan M
Published: July 2002

The clinical syndrome of heart failure affects more than 1% of the population, and its prevalence increases steeply with advancing age, especially after 75, where it reaches approximately 10%. It is one of the commonest reasons for the admission of elderly people to hospital.

Despite recent advances in treatment of heart failure with angiotensin-converting enzyme (ACE) inhibitors, which were proven to provide survival benefit, the rates of morbidity and mortality from heart failure remain high, and new therapeutic strategie
s are needed.
The End of Yugoslavia
Authors: Drapac Vesna
Published: July 2002

Francine Friedman, The Bosnian Muslims: Denial of a Nation (Colorado: Westview Press, 1996), 288 pp., $35.00, ISBN 0-8133-2096-8. Eric D. Gordy, The Culture of Power in Serbia: Nationalism and the Destruction of Alternatives (University Park, PA: Pennsylvania State University Press, 1999), 230 pp., $17.95, ISBN 0-271-01958-1. Lorraine M. Lees, Keeping Tito Afloat: The United States, Yugoslavia, and the Cold War (University Park, PA: Pennsylvania State University Press, 1997), 246 pp., $40, ISBN 0-271-01629-9. Reneo Lukic and Allen Lynch, Europe from the Balkans to the Urals: The Disintegration of Yugoslavia and the Soviet Union (Oxford: Oxford University Press and Stockholm International Peace Research Institute Monographs, 1996), 436 pp., £35.00, ISBN 0-19-829200-7. Viktor Meier, Yugoslavia: A History of its Demise, trans. Sabrina Petra Ramet (London and New York: Routledge, 1999), 279 pp., £16.99, ISBN 0-415-18596-3. Aleksandar Pavkovic, The Fragmentation of Yugoslavia: Nationalism and War in the Balkans, 2nd edn (London and New York: Macmillan and St. Martin's Press, 2000), 243 pp., £42.50, ISBN 0-312-23084-2. Sabrina Petra Ramet, Balkan Babel: The Disintegration of Yugoslavia from the Death of Tito to Ethnic War, 2nd edn (Boulder, CO: Westview Press, 1996), 354 pp., $30.00, ISBN 0-8133-2559-5. Richard H. Ullman, ed., The World and Yugoslavia's Wars (New York: Council on Foreign Relations, 1996), 230 pp., $18.95, ISBN 0-87609-191-5. Susan L. Woodward, Balkan Tragedy: Chaos and Dissolution after the Cold War (Washington, DC: Brookings Institution, 1995), 536 pp., $16.95, ISBN 0-8157-9513-0.
‘A Situation of Delicacy and Danger’: Anglo-Soviet Relations, August 1939–March 1940
Authors: CARLEY MICHAEL JABARA
Published: July 2002

In September 1939, only a few weeks after the signature of the Nazi–Soviet non-aggression pact, the British government made perhaps its strongest effort since the Bolshevik revolution to achieve a rapproachement with the Soviet Union. This effort was interrupted and almost ruined by the Finno-Soviet ‘Winter War’, but the British initiative resumed after the war ended in March 1940. The Soviet government, though not the Soviet ambassador in London, Ivan M. Maiskii, was cool to British overtures, thus reversing the inter-war pattern where Moscow had often been the first to ask for better Anglo-Soviet relations. The publication of many Soviet diplomatic papers permits a comparison between Soviet and British accounts of important diplomatic meetings, a comparison which illustrates both British and Soviet foreign policy during the early months of the Second World War.
The physiology of ovarian oxytocin
Authors: Ivell Richard
Published: July 2002

The notion of an oxytocic principle residing within the ovary is not new. In as early as 1910, Ott and Scott showed that an extract of bovine corpus luteum could induce milk letdown and uterine contraction. However, it took a further 70 years before the identification of this principle with the nonapeptide hormone oxytocin (OT) was made at the peptide and mRNA levels. This was followed by the identification of the peptide in ovarian tissues and ovarian venous blood from a wide variety of species, including humans, monkeys, pigs and ruminants (reviewed in 7, 8). For the majority of non-ruminant species the levels of expression of the peptide and its specific mRNA are relatively low, implying that whatever function the ovarian hormone has in these species, it is most likely to be at the local, paracrine level. Ruminants are an exception. Cows and sheep both produce very high levels of OT and OT-mRNA – the latter attaining concentrations of approximately 1% of all transcripts – within the corpus luteum of the early oestrous cycle. In ruminants, evolution has culminated in a systemic link between ovarian OT production and OT receptors in the endometrium of the uterus, inducing there the production of prostaglandin-F2∞ (PGF2∞) which completes a positive feedback loop to the ovary by stimulating further OT release (reviewed in 10). It is important to note, however, that natural selection can only act on a preexisting system. In this case, it has developed a systemic endocrine pathway in ruminants from a local ovarian OT system present probably in all mammals. There is even evidence for OT-related peptides, such as mesotocin and vasotocin, within the ovaries of marsupials and chicken, though their function is not known.
Ethics and the Structures of Healthcare
Authors: EMANUEL LINDA L.
Published: July 2002

Suppose a “blue sky” meeting had been
called among chief medical officers, chief administrative
officers, and other leaders from a range of health-related
institutions in this country. The question posed for this
meeting was simple but unusual: Are the structures
of our organizations, systems, and institutions ethical?
Though it was a question reminiscent for a few of the focus
some time before on whether the conduct of individuals
in their organization was ethical, this question seemed
more demanding. Is it reasonable to consider structures
or arrangements as ethical or not; or in other words, is
ethics an applicable attribute of organizations?
And if it is reasonable to speak of an ethics of organizations,
by what method might one discern any kind of an answer?
And what of the informal connections that link different
organizations … how can they be evaluated?
CQ Sources/Bibliography
Authors: Anton Bette
Published: July 2002

These CQ Sources were compiled by Bette Anton.
Kate Christensen Speaks with Pat Matheny, a Recipient of
Lethal Medication under Oregon's Death with Dignity Act
Authors: CHRISTENSEN KATE
Published: July 2002

Oregon is the only state in the United States where
a physician may legally prescribe a lethal dose of barbiturate
for a patient intending suicide. The Oregon Death with
Dignity Act was passed by voters in 1994 and came into
effect after much legal wrangling in October of 1997. At
the same time, a cabinetmaker named Pat Matheny was struggling
with progressive weakness from amyotrophic lateral sclerosis,
or ALS. I met with Pat and his family for a lengthy interview
in October 1998 in Coos Bay, Oregon, for a television news
report on his decision to get a lethal prescription. Below
is an extract from that interview. On the day this introduction
was written, 10 March 1999, Pat took the prescribed lethal
overdose of barbiturates and died at home. His illness
was taking his voice, he could not move his hands or legs,
and breathing was becoming very difficult. His mother told
me he knew that was “the right time” for him.
Lagrangians of Hypergraphs
Authors: TALBOT J. M.
Published: July 2002

How large can the Lagrangian of an r-graph with m edges be? Frankl and Füredi [1]

conjectured that the r-graph of size m formed by taking the first m sets in the colex

ordering of N(r) has the largest Lagrangian of all r-graphs of size m.

We prove the first ‘interesting’ case of this conjecture, namely that the 3-graph with

(t3) edges and largest Lagrangian is [t](3).

We also prove that this conjecture is true for 3-graphs of several other sizes.

For general r-graphs we prove a weaker result: for t sufficiently large, the r-graph of

size (tr) supported on t + 1 vertices and with largest

Lagrangian, is [t](r).
Intersecting Chains in Finite Vector Spaces
Authors: CZABARKA ÉVA
Published: July 2002

We prove an Erdős–Ko–Rado-type theorem for
intersecting k-chains of subspaces of a finite
vector space. This is the q-generalization of earlier results of
Erdős, Seress and Székely for intersecting k-chains of subsets
of an underlying set. The proof hinges on the author's
proper generalization of the shift technique from extremal set theory to finite vector spaces,
which uses a linear map to define the generalized shift operation. The theorem is the
following.

For c = 0, 1, consider k-chains of subspaces of an
n-dimensional vector space over GF(q), such that the smallest
subspace in any chain has dimension at least c, and the
largest subspace in any chain has dimension at most n − c. The
largest number of such k-chains under the condition that any two share
at least one subspace as an element of the chain, is achieved by the
following constructions:

(1) fix a subspace of dimension c and take all k-chains containing it,

(2) fix a subspace of dimension n − c and take all
k-chains containing it.
The analysis of chromatin organisation allows selection of mouse antral oocytes competent for development to blastocyst
Authors: Zuccotti Maurizio , Ponce Rubén H. , Boiani Michele , Guizzardi Stefano , Govoni Paolo , Scandroglio Renato , Garagna Silvia , Redi Carlo Alberto
Published: July 2002

Mouse antral oocytes can be classified in two different types termed SN or NSN oocytes, depending on the presence or absence, respectively, of a ring of Hoechst 33342-positive chromatin surrounding the nucleolus. The aim of the present study was to test the developmental competence to blastocyst of the two types of oocytes. Here we show that following isolation, classification and culture of cumulus-free antral oocytes, 14.7% and 74.5% of NSN and SN oocytes, respectively, reached the metaphase II stage. When fertilised and further cultured none of the metaphase II NSN oocytes developed beyond the 2-cell stage whilst 47.4% of the metaphase II SN oocytes reached the 4-cell stage and 18.4% developed to blastocyst. The findings reported in this paper may contribute to improved procedures of female gamete selection for in vitro fertilisation of humans and farm animals. Furthermore, the selection of oocytes with better developmental potential may be of interest for studies on nuclear/cytoplasm interaction, particularly in nuclear-transfer experiments.
LacZ transgene expression as a cell marker to analyse rescue from the 2-cell block in mouse aggregation chimeras
Authors: Neganova Irina E. , Augustin Martin , Sekirina Galina G. , Jockusch Harald
Published: July 2002

Embryos from certain mouse strains are arrested at the 2-cell stage in cell culture (‘2-cell block’), whereas those from other strains develop to the blastocyst stage under the same conditions. It was previously shown that blocking embryos can be rescued in culture by aggregation with an excess of 2-cell stages of a non-blocking strain such as CBA × C57BL/6 F2. Here we have employed a LacZ transgene in a blocking strain (NMRI) to follow the fate of rescued blastomeres up to the blastocyst stage. We found that rescued blastomeres can participate in both inner cell mass and trophoblast formation, thus completely overcoming the 2-cell block.
SERVANTS AND HANDS: REPRESENTING THE WORKING CLASSES IN VICTORIAN FACTORY NOVELS
Authors: Elliott Dorice Williams
Published: July 2002

EARLY IN Frances Trollope’s 1839 novel The Life and Adventures of Michael Armstrong, the Factory Boy, the title character is introduced into the kitchen of Sir Matthew Dowling’s home. The assembled servants, rigidly organized into their own hierarchy of status and position, react with horror and derision at the very idea of a factory boy joining the household on any terms. The only way in which they can explain such a preposterous idea is to speculate that the boy is Sir Matthew’s illegitimate son; only by inventing a hidden genealogy can they imagine a place for a factory worker in the genteel British home (Figure 2).
The Japanese lexical transducer based on stem-suffix style forms
Authors: TATENO MASAKAZU , MASUICHI HIROSHI , UMEMOTO HIROSHI
Published: July 2002

A Lexical Transducer (LT) as defined by Karttunen, Kaplan, Zaenen
1992 is a
specialized finite state transducer (FST) that relates citation forms of
words and
their morphological categories to inflected surface forms. Using LTs is
advantageous
because the same structure and algorithms can be used for morphological
analysis
(stemming) and generation. Morphological processing (analysis and generation)
is
computationally faster, and the data for the process can be compacted more
tightly
than with other methods. The standard way to construct an LT consists of
three
steps: (1) constructing a simple finite state source lexicon
LA which defines all valid
canonical citation forms of the language; (2) describing morphological
alternations
by means of two-level rules, compiling the rules to FSTs, and intersecting
them to
form a single rule transducer RT; and (3) composing LA and RT.
Tactical generation in a free constituent order language
Authors: HAKKANI DILEK ZEYNEP , OFLAZER KEMAL
Published: July 2002

This paper describes tactical generation in Turkish, a
free constituent order language, in
which the order of the constituents may change according to the information
structure of
the sentences to be generated. In the absence of any information regarding
the information
structure of a sentence (i.e. topic, focus, background, etc.), the constituents
of the sentence
obey a default order, but the order is almost freely changeable, depending
on the constraints
of the text flow or discourse. We have used a recursively structured finite
state machine
(much like a Recursive Transition Network (RTN)) for handling the changes
in constituent
order, implemented as a right-linear grammar backbone. Our implementation
environment
is the GenKit system, developed at Carnegie Mellon University, Center for
Machine
Translation. Morphological realization has been implemented using an external
morphological
analysis/generation component which performs concrete morpheme selection
and handles
morphographemic processes.
COGNITIVE PERSONALITY STYLES IN OCD OUTPATIENTS COMPARED TO DEPRESSED OUTPATIENTS AND HEALTHY CONTROLS
Authors: Vogel Patrick A. , Stiles Tore C. , Nordahl Hans M.
Published: July 2002

The present study examined the dysfunctional attitudes and the personality styles of 40 psychiatric outpatients with obsessive-compulsive disorder (OCD) and compared them to 33 outpatients with major depressive disorder (MDD) and 41 healthy controls (HC). Scores on Beck's Depression Inventory (BDI), Dysfunctional Attitude Scale (DAS), and Sociotropy-Autonomy Scale (SAS) were obtained for the three groups. Based on previous research it was predicted that higher levels of sociotropy subscales S 1 (concern about disapproval), and S 2 (attachment/separation concerns) would be specifically related to the diagnosis of OCD after controlling for differences in demographic variables and other psychiatric diagnoses. These hypotheses were confirmed. Significantly lower scores on subscale A 3 (solitary pursuits) was also found specifically related to OCD diagnoses. Higher scores on DAS and lower scores on autonomy subscale A 1 (independent achievement) were found to be particularly related to MDD. Implications of these findings for a cognitive model of the development of OCD are discussed.
A Current Perspective on Cerebellar Research
Authors: Kashima Haruo
Published: July 2002

This is a reprint of one issue in the Cambridge
University Press journal Behavioral and Brain Sciences,
originally based on the symposium Controversies in
neuroscience IV: Motor learning and synaptic plasticity
in the cerebellum, held in Portland Oregon on August
24 to 26, 1993. These symposia were organized by the Robert
S. Dow Neurological Sciences Institute and supported by
NIH, NSF, and the Good Samaritan Foundation. The subjects
of the symposium were the role of the cerebellum in motor
learning and the connection between motor learning and
synaptic plasticity.
Authors Offer Counterpoints but Field Lacks Proof That Sociopolitical
Variables Cause Gender Differences in Cognition
Authors: McGlone Jeannette
Published: July 2002

Within the first pages, the authors focus their
scholarly energies on verbal, spatial, and mathematical
abilities because, we are told, researchers typically have
searched for individual differences within such test domains.
All four authors provide highly readable 30-page chapters,
each taking a variation on the same perspective, i.e.,
that whatever cognitive differences you thought had been
demonstrated between males and females should not be considered
biological because (1) cognitive abilities cannot be defined;
(2) narrative and meta-analytical reviews have serious
limitations as did the research designs of the original
studies, and (3) experience, training, expectations, attitudes,
preferences, power, status, and domination can influence
scores on tests. Knowing the premise in advance sets the
reader looking for tight logic and empirical support in
favor of the sociopolitical model. Over the past 20 years
we all have been subjected to media hype surrounding any
claim of biological explanations for sex differences in
cognition.
Stylistic randomness: about composing NTrope Suite
Authors: DUBNOV SHLOMO
Published: July 2002

This paper describes the ideas and methods that led to the writing of an
algorithmic composition NTrope Suite. This piece, for solo
recorders and voice, was generated by ‘mixing’ works by
different composers from different eras. The idea behind the work was to
examine random generation procedures that could maintain stylistic
properties typical to the reference works. The interesting property of
this method is that it implements a sort of ‘statistical
learning’, that optimally preserves the properties of the reference
pieces and also properly ‘generalises’ them so as to create a
new valid work. The musical result is very coherent, maintaining both
stylistic resemblance to the reference music and exhibiting some surprising
originality as well. Theoretically, the resulting piece is closest to the
reference works in terms of mutual entropy. The algorithm and its
theoretical significance are discussed in the paper.
Conservation genetics of the endangered Shenandoah salamander (Plethodon shenandoah, Plethodontidae)
Authors: Carpenter Daniel W. , Jung Robin E. , Sites Jack W.
Published: July 2002

The Shenandoah salamander (Plethodon shenandoah) is restricted to three isolated talus outcrops in Shenandoah National Park, VA, USA and has one of the smallest ranges of any tetrapod vertebrate. This species was listed as endangered under the US Endangered Species Act in 1989 over concern that direct competition with the red‐backed salamander (Plethodon cinereus), successional habitat changes, and human impacts may cause its decline and possible extinction. We address two issues herein: (1) whether extensive introgression (through long‐term hybridization) is present between the two species and threatens the survival of P. shenandoah, and (2) the level of population structure within P. shenandoah. We provide evidence from mtDNA haplotypes that shows no genetic differentiation among the three isolates of P. shenandoah, suggesting that their fragmentation is a geologically recent event, and/or that the isolates are still connected by occasional gene flow. There is also no evidence for extensive introgression of alleles in either direction between P. cinereus and P. shenandoah, which suggests that P. shenandoah may not be in danger of being genetically swamped out through hybridization with P. cinereus.
Microhabitat use by a translocated population of St Lucia whiptail lizards (Cnemidophorus vanzoi)
Authors: Dickinson Hannah C. , Fa John E. , Lenton Stuart M.
Published: July 2002

Microhabitat use studies of translocated species are crucial to assess their adaptation to the new environment. A total of 42 St Lucia whiptail lizards (Cnemidophorus vanzoi), an endemic to two islets (Maria Major, 10.2 ha and Maria Minor, 1.8 ha) off St Lucia in the Lesser Antilles, were translocated from Maria Major to Praslin Island (1.1 ha) in 1995. Three years after the release, we studied the abundance, density and distribution of the translocated lizard population in the prevailing five habitat types on the island. Habitats varied from more exposed open grasslands to tall, continuously canopied woodlands. Although lizards were distributed throughout the island, some habitats were used more than predicted with respect to availability. Habitat utilization showed a seasonal shift in distribution. Line transect sampling estimated a population of 145 ± 23 lizards on Praslin Island. There were significant seasonal differences in estimated lizard abundance indicating a change in activity during the dry season. Lizard density was significantly correlated with general habitat characteristics, rather than with any specific microhabitat variable measured. Factors affecting distribution (thermo‐regulation, food resources and competitive exclusion) are discussed and it is suggested that habitat use during the dry season may be best explained by thermal constraint. These results will help managers choose future translocation sites.
Conservation breeding for reintroductions: assessing survival in a captive flock of houbara bustards
Authors: van Heezik Yolanda , Ostrowski Stéphane
Published: July 2002

Conservation breeding for reintroduction is becoming a popular option for restoring threatened populations. Whereas post‐release results are widely reported in the conservation literature, little empirical information is presented on the captive populations that often make such releases possible, even though fecundity, fertility and survival rates can have an impact on the outcome and cost of wild population re‐establishment. We present results of survival analyses carried out on a captive population of houbara bustards to determine peak periods of mortality, and by identifying sources of variations in mortality to recognize the potential impact of management practices on productivity. There were two main mortality peaks: during incubation (53% survival of fertile eggs), and by 6 months post‐hatching (75% survival of hatchlings). Management‐related variables influencing survival of eggs and chicks included the year when laid, the cohort of females laying them, and possibly sex. Most post‐hatching deaths were due to trauma and infectious diseases. Trauma‐related deaths usually follow collisions with cages, and imply selection for the captive environment, an undesirable trend in populations maintained for reintroductions. Reducing losses during incubation would have the largest impact on production of birds for reintroduction, enabling the release of more birds, and reducing the overall costs of the project.
Earth-like worlds on eccentric orbits: excursions beyond the habitable zone
Authors: Williams Darren M. , Pollard David
Published: July 2002

Many of the recently discovered extrasolar giant planets move around their stars on highly eccentric orbits, and some with e [ges ] 0·7. Systems with planets within or near the habitable zone (HZ) will possibly harbour life on terrestrial-type moons if the seasonal temperature extremes resulting from the large orbital eccentricities of the planets are not too severe. Here we use a three-dimensional general-circulation climate model and a one-dimensional energy-balance model to examine the climates of either bound or isolated earths on extremely elliptical orbits near the HZ. While such worlds are susceptible to large variations in surface temperature, long-term climate stability depends primarily on the average stellar flux received over an entire orbit, not the length of the time spent within the HZ.
Functional comparison of the nematode Hox gene lin-39 in C. elegans and P. pacificus reveals evolutionary conservation of protein function despite divergence of primary sequences
Authors: Grandien Kaj , Sommer Ralf J.
Published: July 2002

Hox transcription factors have been implicated in playing a central role in the evolution of animal morphology. Many studies indicate the evolutionary importance of regulatory changes in Hox genes, but little is known about the role of functional changes in Hox proteins. In the nematodes Pristionchus pacificus and Caenorhabditis elegans, developmental processes can be compared at the cellular, genetic, and molecular levels and differences in gene function can be identified. The Hox gene lin-39 is involved in the regulation of nematode vulva development. Comparison of known lin-39mutations in P. pacificus and C. elegans revealed both conservation and changes of gene function. Here, we study evolutionary changes of lin-39 function using hybrid transgenes and site-directed mutagenesis in an in vivo assay using C. elegans lin-39 mutants. Our data show that despite the functional differences of LIN-39 between the two species, Ppa–LIN-39, when driven by Cel–lin-39 regulatory elements, can functionally replace Cel–lin-39. Furthermore, we show that the MAPK docking and phosphorylation motifs unique for Cel–LIN-39 are dispensable for Cel–lin-39 function. Therefore, the evolution of lin-39 function is driven by changes in regulatory elements rather than changes in the protein itself.
A conserved MYB transcription factor involved in phosphate starvation signaling both in vascular plants and in unicellular algae
Authors: Rubio Vicente , Linhares Francisco , Solano Roberto , Martín Ana C. , Iglesias Joaquín , Leyva Antonio , Paz-Ares Javier
Published: July 2002

Plants have evolved a number of adaptive responses to cope with growth in conditions of limited phosphate (Pi) supply involving biochemical, metabolic, and developmental changes. We prepared an EMS-mutagenized M2 population of an Arabidopsis thaliana transgenic line harboring a reporter gene specifically responsive to Pi starvation (AtIPS1∷GUS), and screened for mutants altered in Pi starvation regulation. One of the mutants,phr1 (phosphate starvation response 1), displayed reduced response of AtIPS1∷GUS to Pi starvation, and also had a broad range of Pi starvation responses impaired, including the responsiveness of various other Pi starvation-induced genes and metabolic responses, such as the increase in anthocyanin accumulation. PHR1 was positionally cloned and shown be related to the PHOSPHORUS STARVATION RESPONSE 1(PSR1) gene from Chlamydomonas reinhardtii. A GFP∷PHR1 protein fusion was localized in the nucleus independently of Pi status, as is the case for PSR1. PHR1 is expressed in Pi sufficient conditions and, in contrast to PSR1, is only weakly responsive to Pi starvation. PHR1, PSR1, and other members of the protein family share a MYB domain and a predicted coiled–coil (CC) domain, defining a subtype within the MYB superfamily, the MYB–CC family. Therefore, PHR1 was found to bind as a dimer to an imperfect palindromic sequence. PHR1-binding sequences are present in the promoter of Pi starvation-responsive structural genes, indicating that this protein acts downstream in the Pi starvation signaling pathway.
Translational misreading: a tRNA modification counteracts a +2 ribosomal frameshift
Authors: Brégeon Damien , Colot Vincent , Radman Miroslav , Taddei François
Published: July 2002

Errors during gene expression from DNA to proteins via transcription and translation may be deleterious for the functional maintenance of cells. In this paper, extensive genetic studies of the misreading of a GA repeat introduced into the lacZ gene of Escherichia coli indicate that in this bacteria, errors occur predominantly by a +2 translational frameshift, which is controlled by a tRNA modification involving the MnmE and GidA proteins. This ribosomal frameshift results from the coincidence of three events: (1) decreased codon–anticodon affinity at the P-site, which is caused by tRNA hypomodification in mnmE− andgidA− strains; (2) a repetitive mRNA sequence predisposing to slippage; and (3) increased translational pausing attributable to the presence of a rare codon at the A-site. Based on genetic analysis, we propose that GidA and MnmE act in the same pathway of tRNA modification, the absence of which is responsible for the +2 translational frameshift. The difference in the impact of the mutant gene on cell growth, however, indicates that GidA has at least one other function.
Role ofDIVARICATAin the control of dorsoventral asymmetry inAntirrhinumflowers
Authors: Galego Lisete , Almeida Jorge
Published: July 2002

Dorsoventral asymmetry of theAntirrhinumcorolla depends on expression of theCYCandDICHgenes in dorsal petals. One role of these genes is to inhibitDIVARICATA(DIV), a determinant of ventral identity. Therefore, incyc;dichdouble mutants ventral identity spreads all around the flower. We show thatDIVencodes a protein belonging to the MYB family of transcription factors. Early on in corolla development,DIVaffects specifically the growth of ventral and lateral petals but is transcribed in all petals. Analysis of a closely related gene suggests that the lack of effect on dorsal petals is not due to redundancy. More likely, therefore, DIV is regulated posttranscriptionally through a mechanism that depends onCYCandDICH. Later on,DIVaffects growth and cell types and is transcribed mostly in a single layer of cells of ventral and lateral petals. This late pattern may itself depend onDIVactivity because it fails to be established in a transcribed but inactivedivmutant and, conversely, spreads all around the flower incyc;dichdouble mutants.
Binding of c-Myc to chromatin mediates mitogen-induced acetylation of histone H4 and gene activation
Authors: Frank Scott R. , Schroeder Marianne , Fernandez Paula , Taubert Stefan , Amati Bruno
Published: July 2002

The Myc protein binds DNA and activates transcription by mechanisms that are still unclear. We used chromatin immunoprecipitation (ChIP) to evaluate Myc-dependent changes in histone acetylation at seven target loci. Upon serum stimulation of Rat1 fibroblasts, Myc associated with chromatin, histone H4 became locally hyperacetylated, and gene expression was induced. These responses were lost or severely impaired in Myc-deficient cells, but were restored by adenoviral delivery of Myc simultaneous with mitogenic stimulation. When targeted to chromatin in the absence of mitogens, Myc directly induced H4 acetylation. In addition, Myc recruited TRRAP to chromatin, consistent with a role for this cofactor in histone acetylation. Finally, unlike serum, Myc alone was very inefficient in inducing expression of most target genes. Myc therefore governs a step, most likely H4 acetylation, that is required but not sufficient for transcriptional activation. We propose that Myc acts as a permissive factor, allowing additional signals to activate target promoters.
Mutations that bypass tRNA binding activate the intrinsically defective kinase domain in GCN2
Authors: Qiu Hongfang , Hu Cuihua , Dong Jinsheng , Hinnebusch Alan G.
Published: July 2002

The protein kinase GCN2 is activated in amino acid-starved cells on binding of uncharged tRNA to a histidyl-tRNA synthetase (HisRS)-related domain. We isolated two point mutations in the protein kinase (PK) domain, R794G and F842L, that permit strong kinase activity in the absence of tRNA binding. These mutations also bypass the requirement for ribosome binding, dimerization, and association with the GCN1/GCN20 regulatory complex, suggesting that all of these functions facilitate tRNA binding to wild-type GCN2. While the isolated wild-type PK domain was completely inert, the mutant PK was highly active in vivo and in vitro. These results identify an inhibitory structure intrinsic to the PK domain that must be overcome on tRNA binding by interactions with a regulatory region, most likely the N terminus of the HisRS segment. As Arg 794 and Phe 842 are predicted to lie close to one another and to the active site, they may participate directly in misaligning active site residues. Autophosphorylation of the activation loop was stimulated byR794G and F842L, and the autophosphorylation sites remained critical for GCN2 function in the presence of these mutations. Our results imply a two-step activation mechanism involving distinct conformational changes in the PK domain.
Nature and Structure of Human Genes that Generate Retropseudogenes
Authors: Gonçalves Isabelle , Duret Laurent , Mouchiroud Dominique
Published: July 2002

The human genome is estimated to contain 23,000 to 33,000 retropseudogenes. To study the properties of genes giving rise to these retroelements, we compared the structure and expression of genes with or without known retropseudogenes. Four main features have emerged from the analysis of 181 genes associated to retropseudogenes: Reverse-transcribed genes are (1) widely expressed, (2) highly conserved, (3) short, and (4) GC-poor. The first two properties probably reflect the fact that genes giving rise to retropseudogenes have to be expressed in the germ-line. The two latter points suggest that reverse-transcription and transposition is more efficient for short GC-poor mRNAs. In addition, this analysis allowed us to reject previous hypotheses that widely expressed genes are GC rich. Rather, globally, genes with a wide tissue distribution are GC poor.
Large-Scale Statistical Analyses of Rice ESTs Reveal Correlated Patterns of Gene Expression
Authors: Ewing Rob M. , Kahla Alia Ben , Poirot Olivier , Lopez Fabrice , Audic Stéphane , Claverie Jean-Michel
Published: July 2002

Large, publicly available collections of expressed sequence tags (ESTs) have been generated from Arabidopsis thaliana and rice (Oryza sativa). A potential, but relatively unexplored application of this data is in the study of plant gene expression. Other EST data, mainly from human and mouse, have been successfully used to point out genes exhibiting tissue- or disease-specific expression, as well as for identification of alternative transcripts. In this report, we go a step further in showing that computer analyses of plant EST data can be used to generate evidence of correlated expression patterns of genes across various tissues. Furthermore, tissue types and organs can be classified with respect to one another on the basis of their global gene expression patterns. As in previous studies, expression profiles are first estimated from EST counts. By clustering gene expression profiles or whole cDNA library profiles, we show that genes with similar functions, or cDNA libraries expected to share patterns of gene expression, are grouped together. Promising uses of this technique include functional genomics, in which evidence of correlated expression might complement (or substitute for) those of sequence similarity in the annotation of anonymous genes and identification of surrogate markers. The analysis presented here combines the application of a correlation-based clustering method with a graphical color map allowing intuitive visualization of patterns within a large table of expression measurements.
Hippocampal Damage and Exploratory Preferences in Rats: Memory for Objects, Places, and Contexts
Authors: Mumby Dave G. , Gaskin Stephane , Glenn Melissa J. , Schramek Tania E. , Lehmann Hugo
Published: July 2002

Rats have a natural tendency to spend more time exploring novel objects than familiar objects, and this preference can be used as an index of object recognition. Rats also show an exploratory preference for objects in locations where they have not previously encountered objects (an index of place memory) and for familiar objects in contexts different from those in which the objects were originally encountered (an index of context memory). In this experiment, rats with cytotoxic lesions of the hippocampal formation were tested on all three versions of the novelty-preference paradigm, with a 5-min retention interval between the familiarization and test phases. Rats with sham lesions displayed a novelty preference on all three trial types, whereas the rats with hippocampal lesions displayed a novelty preference on Object trials but did not discriminate between the objects on Place trials or Context trials. The findings indicate that hippocampal damage impairs memory for contextual or spatial aspects of an experience, whereas memory for objects that were part of the same experience are left relatively intact.
Inhibitors of Serine/Threonine Phosphoprotein Phosphatases Alter Circadian Properties in Gonyaulax polyedra
Authors: Comolli J. , Taylor W. , Rehman J. , Hastings J. W.
Published: July 2002

Protein serine/threonine phosphatases were implicated in the regulation of circadian rhythmicity in the marine dinoflagellate Gonyaulax polyedra based on the effects of three inhibitors specific for protein phosphatases 1 and 2A (okadaic acid, calyculin A, and cantharidin). Chronic exposure to okadaic acid resulted in a significant period lenghtening, as measured by the bioluminescent glow rhythm, whereas cantharidin and calyculin A caused large phase delays but no persistent effect on period. Short pulses of the phosphatase inhibitors resulted in phase delays that were greatest near subjective dawn. Unlike 6-dimethylaminopurine, a protein kinase inhibitor, okadaic acid, calyculin A, and cantharidin did not block light-induced phase shifts. The inhibitors tested also increased radiolabeled phosphate incorporation into Gonyaulax proteins in vivo and blocked protein phosphatase 1 and 2A activities in Gonyaulax extracts. This study indicates that protein dephosphorylation catalyzed by protein serine/threonine phosphatases is necessary for proper functioning of the circadian system.
Tissue-Specific and Developmental Regulation of Cotton Gene FbL2A (Demonstration of Promoter Activity in Transgenic Plants)
Authors: Rinehart J. A. , Petersen M. W. , John M. E.
Published: July 2002

A gene (FbL2A) that is preferentially expressed in cotton (Gossypium barbadense L. cv Sea Island) fiber was isolated and characterized. Genomic and cDNA analyses suggest multiple FbL2A genes in cotton. The gene is developmentally regulated and is activated during late primary and early secondary wall synthesis stages. FbL2A encodes a polypeptide of 43.4 kD and a predicted isoelectric point of 5.97. The nucleotide-derived protein is highly hydrophilic except for a hydrophobic N terminus and has a compositional bias for glutamic acid (26.3 mol%) and lysine (18.9 mol%). Sixty-two percent of the putative protein is composed of repeat motifs. A 55-amino-acid peptide region is repeated four times in a concatenate fashion within the protein. The function of the protein in the fiber cells is not known. A 2.3-kb DNA fragment 5[prime] from the FbL2A gene is shown to direct expression of heterologous proteins in transgenic cotton in a fiber-specific and developmentally regulated fashion. The FbL2A promoter was used to express in transgenic cotton genes encoding acetoacetyl-coenzyme A reductase and polyhydroxyalkanoic acid synthase, which are involved in the synthesis of the thermoplastic polymer polyhydroxybutyric acid. Transgenic plants containing both enzymes produced polyhydroxybutyric acid in fiber. Thus, the FbL2A promoter is useful in genetic engineering schemes to modify cotton fiber.
Differential Effect of Purified Spruce Chitinases and β-1,3-Glucanases on the Activity of Elicitors from Ectomycorrhizal Fungi
Authors: Salzer P. , Hubner B. , Sirrenberg A. , Hager A.
Published: July 2002

Two chitinases (EC 3.2.1.14) and two β-1,3-glucanases (EC 3.2.1.39) were purified from the culture medium of spruce (Picea abies [L.] Karst.) cells to study their role in modifying elicitors, cell walls, growth, and hyphal morphology of ectomycorrhizal fungi. The 36-kD class I chitinase (isoelectric point [pl] 8.0) and the 28-kD chitinase (pl 8.7) decreased the activity of elicitor preparations from Hebeloma crustuliniforme (Bull. ex Fries.) Quel., Amanita muscaria (L.) Pers., and Suillus variegatus (Sw.: Fr.) O.K., as demonstrated by using the elicitor-induced extracellular alkalinization in spruce cells as a test system. In addition, chitinases released monomeric products from the walls of these ectomycorrhizal fungi. The β-1,3-glucanases (35 kD, pl 3.7 and 3.9), in contrast, had little influence on the activity of the fungal elicitors and released only from walls of A. muscaria some polymeric products. Furthermore, chitinases alone and in combination with β-1,3-glucanases had no effect on the growth and morphology of the hyphae. Thus, it is suggested that apoplastic chitinases in the root cortex destroy elicitors from the ectomycorrhizal fungi without damaging the fungus. By this mechanism the host plant could attenuate the elicitor signal and adjust its own defense reactions to a level allowing symbiotic interaction.
Actin Filaments of Guard Cells Are Reorganized in Response to Light and Abscisic Acid
Authors: Eun S. O. , Lee Y.
Published: July 2002

We recently showed that treatment with actin antagonists perturbed stomatal behavior in Commelina communis L. leaf epidermis and therefore suggested that dynamic changes in actin are necessary for signal responses in guard cells (M. Kim, P.K. Hepler, S.O. Eun, K.-S. Ha, Y. Lee [1995] Plant Physiol 109: 1077–1084). Here we show that actin filaments of guard cells, visualized by immunofluorescence microscopy, change their distribution in response to physiological stimuli. When stomata were open under white-light illumination, actin filaments were localized in the cortex of guard cells, arranged in a pattern that radiates from the stomatal pore. In marked contrast, for guard cells of stomata closed by darkness or by abscisic acid, the actin organization was characterized by short fragments randomly oriented and diffusely labeled along the pore site. Upon abscisic acid treatment, the radial pattern of actin arrays in the illuminated guard cells began to disintegrate within a few minutes and was completely disintegrated in the majority of labeled guard cells by 60 min. Unlike actin filaments, microtubules of guard cells retained an unaltered organization under all conditions tested. These results further support the involvement of actin filaments in signal transduction pathways of guard cells.
Purification of the Plasma Membrane Ca2+-ATPase from Radish Seedlings by Calmodulin-Agarose Affinity Chromatography1
Authors: Bonza Cristina , Carnelli Antonella , De Michelis Maria Ida , Rasi-Caldogno Franca
Published: July 2002

The Ca2+-ATPase of the plasma membrane (PM) of germinating radish (Raphanus sativus L.) seeds was purified by calmodulin (CaM)-affinity chromatography using a batch procedure. PM purified by aqueous two-phase partitioning was solubilized withn-dodecyl β-d-maltoside and applied to a CaM-agarose matrix. After various washings with decreasing Ca2+ concentrations, the Ca2+-ATPase was eluted with 5 mm ethylenediaminetetraacetate (EDTA). The EDTA-eluted fraction contained about 25% of the loaded Ca2+-ATPase activity, with a specific activity 70-fold higher than that of the starting PM fraction. The EDTA-eluted fraction was highly enriched in a 133-kD polypeptide, which was identified as the PM Ca2+-ATPase by 125I-CaM overlay and fluorescein-isothiocyanate labeling. The PM Ca2+-ATPase cross-reacted with an antiserum against a putative Ca2+-ATPase of the Arabidopsis thalianachloroplast envelope.
Biological Activity of Reducing-End-Derivatized Oligogalacturonides in Tobacco Tissue Cultures1
Authors: Spiro Mark D. , Ridley Brent L. , Eberhard Stefan , Kates Keith A. , Mathieu Yves , O'Neill Malcolm A. , Mohnen Debra , Guern Jean , Darvill Alan , Albersheim Peter
Published: July 2002

The biological activity of reducing-end-modified oligogalacturonides was quantified in four tobacco (Nicotiana tabacum) tissue culture bioassays. The derivatives used were oligogalacturonides with the C-1 of their reducing end (a) covalently linked to a biotin hydrazide, (b) covalently linked to tyramine, (c) chemically reduced to a primary alcohol, or (d) enzymatically oxidized to a carboxylic acid. These derivatives were tested for their ability to (a) alter morphogenesis of N. tabacum cv Samsun thin cell-layer explants, (b) elicit extracellular alkalinization by suspension-cultured cv Samsun cells, (c) elicit extracellular alkalinization by suspension-cultured N. tabacum cv Xanthi cells, and (d) elicit H2O2 accumulation in the cv Xanthi cells. In all four bioassays, each of the derivatives had reduced biological activity compared with the corresponding underivatized oligogalacturonides, demonstrating that the reducing end is a key element for the recognition of oligogalacturonides in these systems. However, the degree of reduction in biological activity depends on the tissue culture system used and on the nature of the specific reducing-end modification. These results suggest that oligogalacturonides are perceived differently in each tissue culture system.
Cyst(e)ine Is the Transport Metabolite of Assimilated Sulfur from Bundle-Sheath to Mesophyll Cells in Maize Leaves1
Authors: Burgener Marta , Suter Marianne , Jones Stephanie , Brunold Christian
Published: July 2002

The intercellular distribution of the enzymes and metabolites of assimilatory sulfate reduction and glutathione synthesis was analyzed in maize (Zea mays L. cv LG 9) leaves. Mesophyll cells and strands of bundle-sheath cells from second leaves of 11-d-old maize seedlings were obtained by two different mechanical-isolation methods. Cross-contamination of cell preparations was determined using ribulose bisphosphate carboxylase (EC 4.1.1.39) and nitrate reductase (EC 1.6.6.1) as marker enzymes for bundle-sheath and mesophyll cells, respectively. ATP sulfurylase (EC 2.7.7.4) and adenosine 5′-phosphosulfate sulfotransferase activities were detected almost exclusively in the bundle-sheath cells, whereas GSH synthetase (EC 6.3.2.3) and cyst(e)ine, γ-glutamylcysteine, and glutathione were located predominantly in the mesophyll cells. Feeding experiments using [35S]sulfate with intact leaves indicated that cyst(e)ine was the transport metabolite of reduced sulfur from bundle-sheath to mesophyll cells. This result was corroborated by tracer experiments, which showed that isolated bundle-sheath strands fed with [35S]sulfate secreted radioactive cyst(e)ine as the sole thiol into the resuspending medium. The results presented in this paper show that assimilatory sulfate reduction is restricted to the bundle-sheath cells, whereas the formation of glutathione takes place predominantly in the mesophyll cells, with cyst(e)ine functioning as a transport metabolite between the two cell types.
Osmotic Water Permeability of Isolated Protoplasts. Modifications during Development1
Authors: Ramahaleo Tiana , Morillon Raphaël , Alexandre Joël , Lassalles Jean-Paul
Published: July 2002

A transference chamber was developed to measure the osmotic water permeability coefficient (Pos) in protoplasts 40 to 120 μm in diameter. The protoplast was held by a micropipette and submitted to a steep osmotic gradient created in the transference chamber.Pos was derived from the changes in protoplast dimensions, as measured using a light microscope. Permeabilities were in the range 1 to 1000 μm s−1 for the various types of protoplasts tested. The precision forPos was ≤40%, and within this limit, no asymmetry in the water fluxes was observed. Measurements on protoplasts isolated from 2- to 5-d-old roots revealed a dramatic increase inPos during root development. A shift inPos from 10 to 500 μm s−1occurred within less than 48 h. This phenomenon was found in maize (Zea mays), wheat (Triticum aestivum), and rape (Brassica napus) roots. These results show that early developmental processes modify water-transport properties of the plasma membrane, and that the transference chamber is adapted to the study of water-transport mechanisms in native membranes.