bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence that SNF1‐related kinase and hexokinase are involved in separate sugar‐signalling pathways modulating post‐translational redox activation of ADP‐glucose pyrophosphorylase in potato tubers
Authors: Tiessen Axel , Prescha Katrin , Branscheid Anja , Palacios Natalia , McKibbin Rowan , Halford Nigel G. , Geigenberger Peter
Published: August 2003

We recently discovered that post‐translational redox modulation of ADP‐glucose pyrophosphorylase (AGPase) is a powerful new mechanism to adjust the rate of starch synthesis to the availability of sucrose in growing potato tubers. A strong correlation was observed between the endogenous levels of sucrose and the redox‐activation state of AGPase. To identify candidate components linking AGPase redox modulation to sugar supply, we used potato tuber discs as a model system. When the discs were cut from growing wild‐type potato tubers and incubated for 2 h in the absence of sugars, redox activation of AGPase decreased because of a decrease in internal sugar levels. The decrease in AGPase redox activation could be prevented when glucose or sucrose was supplied to the discs. Both sucrose uptake and redox activation of AGPase were increased when EDTA was used to prepare the tuber discs. However, EDTA treatment of discs had no effect on glucose uptake. Feeding of different glucose analogues revealed that the phosphorylation of hexoses by hexokinase is an essential component in the glucose‐dependent redox activation of AGPase. In contrast to this, feeding of the non‐metabolisable sucrose analogue, palatinose, leads to a similar activation as with sucrose, indicating that metabolism of sucrose is not necessary in the sucrose‐dependent AGPase activation. The influence of sucrose and glucose on redox activation of AGPase was also investigated in discs cut from tubers of antisense plants with reduced SNF1‐related protein kinase activity (SnRK1). Feeding of sucrose to tuber discs prevented AGPase redox inactivation in the wild type but not in SnRK1 antisense lines. However, feeding of glucose leads to a similar activation of AGPase in the wild type and in SnRK1 transformants. AGPase redox activation was also increased in transgenic tubers with ectopic overexpression of invertase, containing high levels of glucose and low sucrose levels. Expression of a bacterial glucokinase in the invertase‐expressing background led to a decrease in AGPase activation state and tuber starch content. These results show that both sucrose and glucose lead to post‐translational redox activation of AGPase, and that they do this by two different pathways involving SnRK1 and an endogenous hexokinase, respectively.
Two different thymidylate kinase gene homologues, including one that has catalytic activity, are encoded in the onion yellows phytoplasma genome
Authors: Miyata Shin-ichi , Oshima Kenro , Kakizawa Shigeyuki , Nishigawa Hisashi , Jung Hee-Young , Kuboyama Tsutomu , Ugaki Masashi , Namba Shigetou
Published: August 2003

Thymidylate kinase (TMK) catalyses the phosphorylation of dTMP to form dTDP in both thede novoand salvage pathways of dTTP synthesis in both prokaryotes and eukaryotes. Two homologues of bacterial thymidylate kinase genes were identified in a genomic library of the onion yellows (OY) phytoplasma, a plant pathogen that inhabits both plant phloem and the organs of insects. Southern blotting analysis suggested that the OY genome contained one copy of thetmk-bgene and multiple copies of thetmk-agene. Sequencing of PCR products generated by amplification oftmk-aenabled identification of three other copies oftmk-a, although the ORF in each of these was interrupted by point mutations. The proteins, TMK-a and TMK-b, encoded by the two intact genes contained conserved motifs for catalytic activity. Both proteins were overexpressed as fusion proteins with a polyhistidine tag inEscherichia coliand purified, and TMK-b was shown to have thymidylate kinase activity. This is believed to be the first report of the catalytic activity of a phytoplasmal protein, and the OY phytoplasma is the first bacterial species to be found to have two intact homologues oftmkin its genome.
Glucose uptake in germinating Aspergillus nidulans conidia: involvement of the creA and sorA genes
Authors: MacCabe Andrew P. , Miró Pilar , Ventura Luisa , Ramón Daniel
Published: August 2003

d-Glucose uptake in germinating wild-typeAspergillus nidulansconidia is an energy-requiring process mediated by at least two transport systems of differing affinities for glucose: a low-affinity system (Km∼1·4 mM) and a high-affinity system (Km∼16 μM). The low-affinity system is inducible by glucose; the high-affinity system is subject to glucose repression effected by the carbon catabolite repressor CreA and is absent insorA3mutant conidia, which exhibit resistance tol-sorbose toxicity. An intermediate-affinity system (Km∼400 μM) is present insorA3conidia germinating in derepressing conditions.creAderepressed mutants show enhanced sensitivity tol-sorbose. The high-affinity uptake system appears to be responsible for the uptake of this toxic sugar.
Yeast two-hybrid system survey of interactions between LEE-encoded proteins of enteropathogenic Escherichia coli
Authors: Creasey Elizabeth A. , Delahay Robin M. , Daniell Sarah J. , Frankel Gad
Published: August 2003

Many Gram-negative pathogens employ a specific secretion pathway, termed type III secretion, to deliver virulence effector proteins directly to the membranes and cytosol of host eukaryotic cells. Subsequent functions of many effector proteins delivered in this manner result in subversion of host-signalling pathways to facilitate bacterial entry, survival and dissemination to neighbouring cells and tissues. Whereas the secreted components of type III secretion systems (TTSSs) from different pathogens are structurally and functionally diverse, the structural components and the secretion apparatus itself are largely conserved. TTSSs are large macromolecular assemblies built through interactions between protein components of hundreds of individual subunits. The goal of this project was to screen, using the standard yeast two-hybrid system, pair-wise interactions between components of the enteropathogenicEscherichia coliTTSS. To this end 37 of the 41 genes encoded by the LEE pathogenicity island were cloned into both yeast two-hybrid system vectors and all possible permutations of interacting protein pairs were screened for. This paper reports the identification of 22 novel interactions, including interactions between inner-membrane structural TTSS proteins; between the type III secreted translocator protein EspD and structural TTSS proteins; between established and putative chaperones and their cognate secreted proteins; and between proteins of undefined function.
Layout modeling and construction procedure for the arrangement of exhibition spaces in a fair
Authors: Schneuwly P. , Widmer M.
Published: August 2003

This paper tackles a subset of layout problems that is not a subject of the scientific research to date: the arrangement of the exhibition spaces in a fair. A fair is a large‐scale exhibition for goods and services; for example a trade fair or a regional fair. The layout problem of fairs consists in finding an acceptable layout for both the exhibitors, the visitors, and the organizer of the fair. A model for representing the layout of fairs is presented: the adjacency model. Based on the adjacency model, a construction procedure is developed that leads to the generation of alternative layout solutions. Numerical results for the layout of a real fair are reported.
Who Wants to Reduce Greenhouse Gas Emissions?
Authors: O'Connor Robert E. , Bord Richard J. , Yarnal Brent , Wiefek Nancy
Published: August 2003

Objective. We examine cognitive, economic, and partisan heuristic theories of why some people express support for reducing greenhouse gas emissions. Methods. Data come from a mail survey of 623 residents of central Pennsylvania, a region in which mitigation costs exceed potential benefits from slowing the rate of global warming. Results. Ordinary least squares analysis shows that people who can accurately identify the causes of climate change and who expect bad consequences from climate change are likely to support both government anti‐fossil fuel initiatives and voluntary actions. Economic circumstances and anxieties are not important predictors, but the belief that environmental protection efforts do not threaten jobs for people like the respondent, limit personal freedoms, and hurt the economy is a strong predictor. Democrats are more likely than Republicans to support government efforts to reduce emissions. Conclusions. Cognitive explanations of support for reducing greenhouse gas emissions are more powerful than economic or partisan heuristic ones. People want to reduce emissions if they understand the causes of climate change, if they perceive substantial risks from climate change if average surface temperatures increase, and if they think climate change mitigation policies will not cost them their jobs.
The Politics of Market‐Based Environmental Regulation: Continuity and Change in Air Pollution Control Policy Conflict
Authors: Cook Brian J.
Published: August 2003

Objectives. To expand scholarly attention to a neglected area of environmental policy and politics, I attempt to test several empirical propositions drawn from the small body of existing research on the politics of market‐based environmental regulation. Methods. I analyze public comments on a recent U.S. Environmental Protection Agency regulatory action guiding states on the design of various market‐based air pollution control programs. I focus on the types of commenting organizations and the nature, extent, and foundations of their support or opposition to market‐based regulatory instruments. Results. I find more support for than opposition to the use of economic incentive programs in air pollution control. The support from business commenters is not surprising, but the level of support expressed by state regulators departs from previous research findings. Environmental groups are the principal dissenters. Overall, the findings suggest both change and continuity in the politics of air pollution control policymaking, with some possibility of a shift in the contours of the advocacy coalitions in the pollution control policy network. Conclusions. Market‐based environmental regulation is still an evolving phenomenon in American public policy. Further research on the politics of its development is in order, and the opportunities to pursue such research are substantial.
Organizing Across the Divide: Local Feminist Activism, Everyday Life, and the Election of Women to Public Office
Authors: Marshall Ann
Published: August 2003

Objectives. A disciplinary division of labor has discouraged research into the intersections between social movements and electoral participation. To address this gap, this study investigates the efforts of local women activists who organize around electing feminists to public office. Methods. Data was collected through participant observation and in–depth, unstructured interviews with 22 women active with a local chapter of the National Women's Political Caucus (NWPC). Results. The study found that local Caucus women (1) experience everyday life politics in connection with electoral activity, (2) organize through both their own formal structure and a vast informal community–based organizational network, and (3) influence electoral activity in a seemingly candidate–centered environment. Conclusions. Local Caucus activists play a critical albeit less visible role in organizing feminist electoral influence. These findings suggest the importance of research that transcends disciplinary boundaries to investigate the interactions between nonparty grassroots activism and electoral activity.
Policies, Procedures, and People: Sources of Support for Government?
Authors: Ulbig Stacey G.
Published: August 2003

Objective. Many have written about the public's low opinion of the federal government; however, the theoretical sources and consequences of political trust have been empirically elusive. Drawing on the procedural justice framework, this study investigates the structure and consequences of people's mistrust of the federal government. Methods. Using data from various years of the National Election Study (NES), this research investigates the relationship between policy, procedural, and personal concerns and support of government. Results. Judgments about policy outputs, the process by which these policies develop, and the people involved in this process are shown to be sources of governmental trust, and certain aspects of trust are shown to have important behavioral consequences. Conclusions. These findings help to explain the failure of previous research into the causes and consequences of political trust. The various policy and process judgments that the NES Index combines play important independent roles in explaining political trust itself and its relationship with political behaviors and other attitudes.
Religion, Race/Ethnicity, and Beliefs about Poverty
Authors: Hunt Matthew O.
Published: August 2003

Objective. Although an expanding literature on “stratification beliefs” has developed over the past three decades, research has neglected relationships between religion and beliefs about poverty and other inequalities. This study examines the relationship between religious affiliation and “individualistic,”“structuralist,” and “fatalistic” beliefs about the causes of poverty, and compares the beliefs of African Americans, Latinos, and whites. Methods. Survey data collected in 1993 from a sample of southern Californians are used to test whether several religious affiliations (Protestant, Catholic, Jew, “other religion,” and nonaffiliation) shape beliefs about poverty after controlling for race/ethnicity, SES, gender, and age. In addition, the question of whether African Americans, Latinos, and whites differ in the effects of key religious affiliations is examined. Results. Significant religious affiliation effects are found, net of sociodemographic controls. Protestants and Catholics are strongest on individualistic beliefs; Jews and followers of “other” religions are strongest on structuralist beliefs; Catholics and Jews are strongest on fatalistic beliefs. Finally, race/ethnic differences are found for the effects of key religious affiliations. Conclusion. The analyses demonstrate “religious factors” shaping beliefs about poverty, and reinforce the growing body of evidence that affiliations such as Protestant and Catholic have distinctive meanings and effects along race/ethnic lines in the United States.
Genotyping and Phenotyping of Beta2-Toxigenic
Clostridium perfringens
Fecal Isolates Associated with Gastrointestinal Diseases in Piglets
Authors: Waters Michael , Savoie Amanda , Garmory Helen S. , Bueschel Dawn , Popoff Michel R. , Songer J. Glenn , Titball Richard W. , McClane Bruce A. , Sarker Mahfuzur R.
Published: August 2003

Although
Clostridium perfringens
is recognized as an important cause of clostridial enteric diseases, only limited knowledge exists concerning the association of particular
C. perfringens
toxinotypes (type A to E) with gastrointestinal (GI) diseases in domestic animals. Some
C. perfringens
isolates also produce the newly discovered beta2-toxin (CPB2). Recent epidemiological studies suggested that
C. perfringens
isolates carrying the gene encoding CPB2 (
cpb2
) are strongly associated with clostridial GI diseases in domestic animals, including necrotic enteritis in piglets and typhlocolitis in horses. These putative relationships, obtained by PCR genotyping, were tested in the present study by further genotyping and phenotyping of 29
cpb2
-positive
C. perfringens
isolates from pigs with GI disease (pig GI disease isolates). PCR and restriction fragment length polymorphism analysis reconfirmed the presence of
cpb2
gene sequences in all the disease isolates included in the study. Furthermore, genotyping by pulsed-field gel electrophoresis analyses showed that the pig GI disease isolates included in this study all carry a plasmid
cpb2
gene, yet no clonal relationships were detected between the
cpb2
-positive pig GI disease isolates surveyed. Finally, CPB2-specific Western blotting demonstrated CPB2 expression by all of the
cpb2
-positive isolates surveyed. The CPB2 proteins made by five of these pig GI disease isolates were shown to have the same deduced amino acid sequences as the biologically active CPB2 protein made by the original type C isolate, CWC245. Collectively, our present results support a significant association between CPB2-positive
C. perfringens
isolates and diarrhea in piglets.
Identification of Swine Hepatitis E Virus (HEV) and Prevalence of Anti-HEV Antibodies in Swine and Human Populations in Korea
Authors: Choi In-Soo , Kwon Hyuk-Joon , Shin Na-Ri , Yoo Han Sang
Published: August 2003

The swine hepatitis E virus (HEV) is considered to be a new zoonotic agent due to its close genomic resemblance to the human HEV and its ability to infect nonhuman primates. Hepatitis caused by HEV infection has been a serious public health problem in developing countries. However, recent seroprevalence studies indicate that the HEV also circulates in industrialized countries. In this study, a nested reverse transcription (RT)-PCR was developed to detect a part of the swine HEV open reading frame 2. Three Korean isolates of swine HEV were identified in 128 swine sera (2.3% prevalence) by the nested RT-PCR method. They were isolated from 2- to 3-month old pigs showing an age-specific prevalence of the HEV viremia. A phylogenetic tree analysis with a number of swine and human HEV isolates indicated that all Korean isolates of the swine HEV belong to genotype III. They were closely related to the swine and human HEV isolates that were identified in the United States and Japan. In addition, they formed a distinct branch in genotype III, showing a 92.7 to 99.8% identity at their nucleotide sequences. The overall prevalence of anti-swine HEV antibodies in swine was 15%. Antibodies to the swine HEV were not detected in 1-month-old pigs. However, the anti-swine HEV antibodies appeared in pigs older than 1 month and also showed an age-specific prevalence. The antibody prevalence rates to the swine HEV were 6.0, 10.0, 36.0, and 25.0%, in 2-, 3-, 4-, and 5-to-7-month-old pigs, respectively. In addition, the seroprevalence in sows to the swine HEV was 8.8%. On the other hand, 18% of blood donors in Korea were found to be positive for anti-HEV antibodies. Overall, this study indicates that subclinical HEV infections may prevail in swine and human populations in Korea.
VIM-1 Metallo-β-Lactamase-Producing
Klebsiella pneumoniae
Strains in Greek Hospitals
Authors: Giakkoupi P. , Xanthaki A. , Kanelopoulou M. , Vlahaki A. , Miriagou V. , Kontou S. , Papafraggas E. , Malamou-Lada H. , Tzouvelekis L. S. , Legakis N. J. , Vatopoulos A. C.
Published: August 2003

Seventeen
Klebsiella pneumoniae
clinical isolates carrying the
bla
VIM-1
metallo-β-lactamase gene were collected in the intensive care units of three hospitals in Athens, Greece, in 2002. They exhibited various carbapenem resistance levels (Etest MICs of imipenem ranged from 4 to 32 μg/ml). All isolates gave positive results by the imipenem-EDTA synergy Etest. The isolates were classified into four main types by pulsed-field gel electrophoresis; the majority of the isolates (5 and 10 isolates) belonged to two types. The
bla
VIM-1
gene cassette was part of the variable region of a class 1 integron that also included
aac6
,
dhfrI
, and
aadA
. This structure was carried by transferable plasmids.
Comparison of Real-Time PCR, Conventional PCR, and Galactomannan Antigen Detection by Enzyme-Linked Immunosorbent Assay Using Bronchoalveolar Lavage Fluid Samples from Hematology Patients for Diagnosis of Invasive Pulmonary Aspergillosis
Authors: Sanguinetti Maurizio , Posteraro Brunella , Pagano Livio , Pagliari Gabriella , Fianchi Luana , Mele Luca , La Sorda Marilena , Franco Angelica , Fadda Giovanni
Published: August 2003

An iCycler iQ real-time PCR assay targeting 18S rRNA
Aspergillus
-specific sequences was developed for the diagnosis of invasive pulmonary aspergillosis (IPA). Positive findings were obtained for 18 of 20 (90%) bronchoalveolar lavage (BAL) fluid specimens from patients with probable or confirmed IPA and were obtained for none of the 24 BAL samples from patients with no clinical evidence of aspergillosis. These results were concordant with those of a nested PCR assay, which detected 90% of the patients with IPA, while galactomannan ELISA revealed positivity for 100% of these patients, suggesting that combined use of methods might improve the diagnosis of IPA.
Novel Nosocomial Infections by
Stenotrophomonas maltophilia
: First Reported Case from Lucknow, North India
Authors: Mukhopadhyay Chiranjoy , Bhargava Anudita , Ayyagari Archana
Published: August 2003

We describe a case of empyema with infected ascites caused by
Stenotrophomonas maltophilia
, which has rarely been reported as pathogenic. The source was determined to a disinfectant solution. The isolate was sensitive to a newer carbapenem-meropenem, and the patient was treated successfully. This case represents a novel dual presentation of a nosocomial infection by the isolate in question.
Increased yield of heterologous viral glycoprotein in the seeds of homozygous transgenic tobacco plants cultivated underground
Authors: Tackaberry Eilleen S , Prior Fiona , Bell Margaret , Tocchi Monika , Porter Suzanne , Mehic Jelica , Ganz Peter R , Sardana Ravinder , Altosaar Illimar , Dudani Anil
Published: August 2003

The use of transgenic plants in the production of recombinant proteins for human therapy, including subunit vaccines, is being investigated to evaluate the efficacy and safety of these emerging biopharmaceutical products. We have previously shown that synthesis of recombinant glycoprotein B (gB) of human cytomegalovirus can be targeted to seeds of transgenic tobacco when directed by the rice glutelin 3 promoter, with gB retaining critical features of immunological reactivity (E.S. Tackaberry et al. 1999. Vaccine, 17: 30203029). Here, we report development of second generation transgenic plant lines (T1) homozygous for the transgene. Twenty progeny plants from two lines (A23T1-2 and A24T1-3) were grown underground in an environmentally contained mine shaft. Based on yields of gB in their seeds, the A23T1-2 line was then selected for scale-up in the same facility. Analyses of mature seeds by ELISA showed that gB specific activity in A23T1-2 seeds was over 30-fold greater than the best T0plants from the same transformation series, representing 1.07% total seed protein. These data demonstrate stable inheritance, an absence of transgene inactivation, and enhanced levels of gB expression in a homozygous second generation plant line. They also provide evidence for the suitability of using this environmentally secure facility to grow transgenic plants producing therapeutic biopharmaceuticals.Key words: transgenic tobacco seeds, homozygous second generation, glycoprotein B, human cytomegalovirus, vaccine, underground mine.
Genome discrimination in progeny of interspecific hybrids between Brassica napus and Raphanus raphanistrum
Authors: Benabdelmouna A , Guéritaine G , Abirached-Darmency M , Darmency H
Published: August 2003

Genomic in situ hybridization (GISH) applied to the F1 interspecific hybrid between oilseed rape (Brassica napus, AACC, 2n = 38) and wild radish (Raphanus raphanistrum, RrRr, 2n = 18) showed the predicted 19 chromosomes from B. napus and 9 chromosomes from R. raphanistrum. The very low female fertility of these interspecific hybrids when backcrossed to R. raphanistrum led to only two descendants. Their chromosome number varied between 45 and 48. Both of these progenies showed only 9 chromosomes from R. raphanistrum and 3639 chromosomes from B. napus. These results indicate the efficiency and limits of GISH as a suitable tool to assess and interpret the behavior of chromosomes after such interspecific crosses. The unexpected chromosome combination is discussed.Key words: genomic in situ hybridization, interspecific hybrid, introgression, oilseed rape, wild radish.
Genetic variation of populations ofPinus oocarparevealed by resistance gene analog polymorphism (RGAP)
Authors: Díaz V , Ferrer E
Published: August 2003

Primers based on conserved motifs of plant resistance genes were used to generate multilocus molecular markers  referred to as resistance gene analog polymorphisms (RGAPs)  in Pinus oocarpa subsp. oocarpa. Ten populations from three regions of Nicaragua were analyzed with 53 RGAPs. The aim of this study was to determine the levels of within- and between-population diversity with this kind of marker, and to compare estimates with previously obtained results based on RAPD and AFLP. All populations showed high levels of diversity. GSTvalues and the analysis of molecular variance (AMOVA) revealed most variation to be within populations, although significant differences between populations and regions were also detected. This pattern of genetic diversity was similar to that obtained for RAPD and AFLP, which suggests that variation at RGAP loci as detected in this work is mostly influence by non-selective forces.Key words: resistance gene analogs, molecular markers, genetic diversity, population structure, Pinus oocarpa.
Analysis of genetic diversity in red clover (Trifolium pratenseL.) breeding populations as revealed by RAPD genetic markers
Authors: Ulloa Odeth , Ortega Fernando , Campos Hugo
Published: August 2003

Red clover is an important forage legume species for temperate regions and very little is known about the genetic organization of its breeding populations. We used random amplified polymorphic DNA (RAPD) genetic markers to address the genetic diversity and the distribution of variation in 20 breeding populations and cultivars from Chile, Argentina, Uruguay, and Switzerland. Genetic distances were calculated for all possible pairwise combinations. A high level of polymorphism was found and the proportion of polymorphic loci across populations was 74.2%. A population derived from a non-certified seedlot displayed a higher proportion of polymorphic loci than its respective certified seedlot. Gene diversity values and population genetics parameters suggest that the populations analyzed are diverse. An analysis of molecular variance (AMOVA) revealed that the largest proportion of variation (80.4%) resides at the within population level. RAPD markers are a useful tool for red clover breeding programs. A dendrogram based on genetic distances divided the breeding populations analyzed into three distinct groups. The amount and partition of diversity observed can be of value in identifying the populations that parents of synthetic cultivars are derived from and to exploit the variation available in the populations analyzed.Key words: red clover, AMOVA, plant breeding.
Hybridization and introgression of the genomes ofDrosophilanasutaandDrosophilaalbomicans: evolution of new karyotypes
Authors: Tanuja M T , Ramachandra N B , Ranganath H A
Published: August 2003

Drosophila nasuta (2n = 8) and Drosophila albomicans (2n = 6) are cross-fertile allopatric sibling chromosomal races of the nasuta subgroup of Drosophila. Hybrids of these races can be maintained for any number of generations. Some of the introgressed hybrid lineages of D. nasuta and D. albomicans, after passing through a transient phase of karyotypic polymorphism, ended up with a stable karyotype whose composition is different from those of the parental races. Such hybrid populations were called cytoraces, in which the chromosomes of D. nasuta and D. albomicans are represented in different combinations. The karyotypic composition of 16 such cytoraces have been presented and discussed with reference to evolutionary strategies such as balancing selection, directional selection, and sex-specific effect on different components of the evolving karyotypes.Key words: Drosophila, nasuta, albomicans, hybridization, cytoraces, karyotype, evolution.
Sequence analysis of the ribosomal DNA internal transcribed spacer region in some scallop species (Mollusca: Bivalvia: Pectinidae)
Authors: Insua Ana , López-Piñón María J , Freire Ruth , Méndez Josefina
Published: August 2003

The internal transcribed spacer (ITS) region of the ribosomal DNA from the European scallops Aequipecten opercularis, Mimachlamys varia, Hinnites distortus, and Pecten maximus was PCR amplified and sequenced. For each species, three or five clones were examined. The size ranged between 636 and 713 bp (ITS1, 209276 bp; 5.8S rRNA gene, 157 bp; ITS2, 270294 bp) and GC content ranged between 47 and 50% (ITS1, 4349%; 5.8S rRNA gene, 5657%; ITS2, 4449%). Variation within repeats was minimal; only clones from M. varia and P. maximus displayed a few variable sites in ITS2. Among scallops, including Chlamys farreri whose ITS sequence appears in databases, significant variation was observed in both ITS1 and ITS2. Phylogenetic analysis using ITS1, ITS2, or both spacer sequences always yielded trees with similar topology. Aequipecten opercularis and P. maximus grouped in one clade and the other three scallops (C. farreri, M. varia, and H. distortus) in another, where M. varia and H. distortus are the more closely related species. These results provide new insights into the evolutionary relationships of scallop species and corroborate the close evolutionary relationship between the tribes Aequipectinini and Pectinini previously deduced from 18S rDNA sequences.Key words: scallops, Pectinidae, ribosomal DNA, internal transcribed spacers, phylogeny.
Escape from X inactivation
Authors: Disteche C.M. , Filippova G.N. , Tsuchiya K.D.
Published: August 2003

Although the process of X inactivation in mammalian cells silences the majority of genes on the inactivated X chromosome, some genes escape this chromosome-wide silencing. Genes that escape X inactivation present a unique opportunity to study the process of silencing and the mechanisms that protect some genes from being turned off. In this review, we will discuss evolutionary aspects of escape from X inactivation, in relation to the divergence of the sex chromosomes. Molecular characteristics, expression, and epigenetic modifications of genes that escape will be presented, including their developmental regulation and the implications of chromatin domains along the X chromosome in modeling the escape process.
Overall DNA methylation and chromatin structure of normal and abnormal X chromosomes
Authors: Bernardino-Sgherri J. , Flagiello D. , Dutrillaux B.
Published: August 2003

DNA methylation patterns were studied at the chromosome level in normal and abnormal X chromosomes using an anti-5-methylcytosine antibody. In man, except for the late-replicating X of female cells, the labeled chromosome structures correspond to R- and T-bands and heterochromatin. Depending on the cell type, the species, and cell culture conditions, the late-replicating X in female cells appears to be more or less undermethylated. Under normal conditions, the only structures that remain methylated on the X chromosomes correspond to pseudoautosomal regions, which harbor active genes. Thus, active genes are usually hypomethylated but are located in methylated chromatin. Structural rearrangements of the X chromosome, such as t(X;X)(pter;pter), induce a Turner syndrome-like phenotype that is inconsistent with the resulting triple-X constitution. This suggests a position effect controlling gene inactivation. The derivative chromosomes are always late replicating, and their duplicated short arms, which harbor pseudoautosomal regions, replicate later than the normal late-replicating X chromosomes. The compaction or condensation of this segment is unusual, with a halo of chromatin surrounding a hypocondensed chromosome core. The chromosome core is hypomethylated, but the surrounding chromatin is slightly labeled. Thus, unusual DNA methylation and chromatin condensation are associated with the observed position effect. This strengthens the hypothesis that DNA methylation at the chromosome level is associated with both chromatin structure and gene expression.
Functional analysis of the highly conserved exon IV of Xist RNA
Authors: Caparros M.-L. , Alexiou M. , Webster Z. , Brockdorff N.
Published: August 2003

X inactivation is effected by a large cis-acting RNA molecule termed the X inactive specific transcript (Xist). Exon IV of Xist RNA is highly conserved at the primary sequence level and is predicted to form a stable stem-loop structure. These features suggest that it is important for Xist RNA function. We have used homologous recombination to delete exon IV of the mouse Xist gene. Surprisingly we found no detectable effects on X inactivation. Heterozygous female animals show normal random X inactivation and transcripts from the mutant allele were seen to localise in cis over the length of the inactive X chromosome. There was however a reduced steady state level of mutant relative to wild type Xist RNA. This effect was not attributable to decreased stability, suggesting that the deletion affects transcription or processing of Xist RNA.
Sex chromosome elimination, X chromosome inactivation and reactivation in the southern brown bandicoot Isoodon obesulus (Marsupialia: Peramelidae)
Authors: Johnston P.G. , Watson C.M. , Adams M. , Paull D.J.
Published: August 2003

Cytogenetic studies have shown that bandicoots (family Peramelidae) eliminate one X chromosome in females and the Y chromosome in males from some somatic tissues at different stages during development. The discovery of a polymorphism for X-linked phosphoglycerate kinase (PGK-1) in a population of Isoodon obesulus from Mount Gambier, South Australia, has allowed us to answer a number of long standing questions relating to the parental source of the eliminated X chromosome, X chromosome inactivation and reactivation in somatic and germ cells of female bandicoots. We have found no evidence of paternal PGK-1 allele expression in a wide range of somatic tissues and cell types from known female heterozygotes. We conclude that paternal X chromosome inactivation occurs in bandicoots as in other marsupial groups and that it is the paternally derived X chromosome that is eliminated from some cell types of females. The absence of PGK-1 paternal activity in somatic cells allowed us to examine the state of X chromosome activity in germ cells. Electrophoresis of germ cells from different aged pouch young heterozygotes showed only maternal allele expression in oogonia whereas an additional paternally derived band was observed in pre-dictyate oocytes. We conclude that reactivation of the inactive X chromosome occurs around the onset of meiosis in female bandicoots. As in other mammals, late replication is a common feature of the Y chromosome in male and the inactive X chromosome in female bandicoots. The basis of sex chromosome loss is still not known; however later timing of DNA synthesis is involved. Our finding that the paternally derived X chromosome is eliminated in females suggests that late DNA replication may provide the imprint for paternal X inactivation and the elimination of sex chromosomes in bandicoots.
Speculations on the role of natural antisense transcripts in mammalian X chromosome evolution
Authors: Kiyosawa H. , Abe K.
Published: August 2003

Recent comprehensive transcriptome analyses in mice have revealed tremendous numbers of natural antisense transcripts in a hitherto ignored category of genes in eukaryotes. We discuss the possible biological roles of these transcripts and their relationships with mammalian sex chromosome evolution. Of 60,770 full-length cDNA sequences, as many as 2,500 pairs of sense–antisense transcripts (SATs) with the potential to form RNA duplex via their complementary sequences have been identified. This high number of antisense transcripts indicates their generic roles in gene expression regulation. These SATs are almost evenly distributed along the chromosomes, with the exception of the X chromosome. The rate of occurrence of SATs on the X chromosome is one-third to one-half that on the autosomes, and this under-representation must be related to a property intrinsic to the X chromosome. Here we hypothesize that monoallelically expressed antisense RNA regulates its sense partner, but that this regulatory system cannot operate on the mammalian X chromosome, as the mammalian X chromosome is effectively in a hemizygous state in both sexes. Loss of such regulation may be involved in the evolution of the X chromosome itself.
Sex determination and sex chromosome evolution in the medaka, Oryzias latipes, and the platyfish, Xiphophorus maculatus
Authors: Volff J.-N. , Schartl M.
Published: August 2003

The first vertebrate master sex-determining gene different from Sry has been very recently discovered in a small aquarium fish, the medaka (Oryzias latipes). In this fish, the X and Y chromosomes apparently differ only by a 250-kb Y-specific region containing dmrt1bY (also called DMY and dmrt1Y), a male-specific copy of the autosomal gene dmrt1. Dmrt1 is a putative transcription factor probably involved in testis formation in different vertebrate lineages. Dmrt1bY is the only gene having escaped the drastic process of degeneration that devastated the small Y-specific region of the medaka. Mutations leading to truncation or lower expression of dmrt1bY result in XY male-to-female sex reversal. Hence, both genetic and functional evidences converge in making dmrt1bY an outstanding candidate for the function of a master sex-determining gene in fish. Nevertheless, dmrt1bY could not be detected in certain other Oryzias species or in more divergent fishes. Phylogenetic analysis revealed that the duplication of the autosomal dmrt1 that formed dmrt1bY is young in evolutionary terms. Hence, dmrt1bY is not the universal master sex-determining gene in fish. Because the classical fish models, such as zebrafish and pufferfish, are not very adequate to study the basis of genetic sex determination, alternative models, such as the platyfish (Xiphophorus maculatus), are re-emerging. In this fish, which is a well-suited laboratory organism, gene loci involved in pigmentation, melanoma formation, and sexual maturity have been mapped close to the master sex-determining gene. Interestingly, the platyfish can harbor three different sex chromosomes (W, X, and Y) in certain natural populations. Bacterial artificial chromosome contigs covering the sex-determining region of the platyfish are already available, and the positional cloning of the master sex-determining gene(s) should provide new insights into sex determination and sex chromosome evolution in fish and other vertebrates.
Comparative mapping of Z-orthologous genes in vertebrates: implications for the evolution of avian sex chromosomes
Authors: Nanda I. , Haaf T. , Schartl M. , Schmid M. , Burt D.W.
Published: August 2003

Sex chromosomes of birds and mammals are highly differentiated and share several cytological features. However, comparative gene mapping reveals extensive conserved synteny between the chicken Z sex chromosome and human chromosome 9 but not the human X sex chromosome, implying an independent origin of avian and mammalian sex chromosomes. To better understand the evolution of the avian Z chromosome we analysed the synteny of chicken Z-linked genes in zebrafish, which is the best-mapped teleost genome so far. Existing zebrafish maps do not support the existence of an ancestral Z linkage group in the zebrafish genome, whereas mammalian X-linked genes show at least some degree of synteny conservation. This is consistent with in situ hybridisation mapping data in the freshwater pufferfish, Tetraodon nigroviridis where mammalian X-linked genes show a much higher degree of conserved synteny than human chromosome 9 or the avian Z chromosome. Collectively, these data argue in favour of a more recent evolution of the avian Z chromosome, compared with the mammalian X.
Evidence that postnatal growth retardation in XO mice is due to haploinsufficiency for a non-PAR X gene
Authors: Burgoyne P.S. , Ojarikre O.A. , Turner J.M.A.
Published: August 2003

XO Turner women, irrespective of the parental source of the X chromosome, are of short stature, and this is now thought to be largely a consequence of haploinsufficiency for the pseudoautosomal region (PAR) gene SHOX. XpO mice (with a paternal X) are developmentally retarded in fetal life, are underweight at birth, and show reduced weight gain in the first few weeks after birth. XmO mice, on the other hand, are more developmentally advanced than their XX siblings in fetal life; their postnatal growth has not hitherto been assessed. Here we show that XmO mice are not underweight at birth, but they nevertheless show reduced weight gain postnatally. The fact that postnatal growth is affected in XpO and XmO mice, means that this must be due to X dosage deficiency. In order to see if haploinsufficiency for a PAR gene was responsible for this growth deficit (cf SHOX deficiency in Turner women), XmY*X females, in which the Y*X chromosome provides a second copy of the PAR, were compared with XX females. These XmY*X females were also growth-retarded relative to their XX sibs, suggesting that it may be haploinsufficiency for a non-dosage-compensated X gene or genes outside the PAR that is responsible for the postnatal growth deficit in XO mice. The X genes known to escape X inactivation in the mouse have closely similar Y homologues. XmYSry-negative females were therefore compared with XX females to see if the presence of the Sry-negative Y chromosome corrected the growth deficit; this proved to be the case. The postnatal growth deficit of XO mice is therefore probably due to haploinsufficiency for a non-dosage-compensated X gene that has a Y homologue that provides an equivalent function in the somatic tissues of males.
X-chromosomal localization of mammalian Y-linked genes in two XO species of the Ryukyu spiny rat
Authors: Arakawa Y. , Nishida-Umehara C. , Matsuda Y. , Sutou S. , Suzuki H.
Published: August 2003

Ryukyu spiny rats (genus Tokudaia), which are endemic to the central part of the Nansei Shoto archipelago in Japan, have unique karyotypes with odd numbers of chromosomes and no cytologically recognizable Y chromosome. The chromosome numbers of Tokudaia osimensis from Amamioshima and of Tokudaia sp. from Tokunoshima are 2n = 25 and 2n = 45, respectively, with a putative single X chromosome. The mouse X probe hybridized to the unpaired X chromosome, except for the distal part of the short arm in a female specimen of T. osimensis and in one male and one female of Tokudaia sp. Fluorescence in situ hybridization with the Tspy (testis-specific protein, Y-encoded) gene from both male and female cells of Tokudaia sp. by PCR localized Tspy to the distal part of the long arm of the X chromosome. Another Y-related gene, Zfy, from Tokudaia sp. was also localized to the same region in both species. Although the Sry gene is absent in this species, the present results suggest that the Y-chromosome segment carrying functional Y-linked genes, such as Tspy and Zfy, is translocated onto the distal part of the long arm of the X chromosome.
Chromosome banding in Amphibia
Authors: Schmid M. , Feichtinger W. , Steinlein C. , Haaf T. , Schartl M. , Visbal García R. , Manzanilla Pupo J. , Fernández Badillo A.
Published: August 2003

A 15-year cytogenetic survey on one population of the leaf litter frog Eleutherodactylus maussi in northern Venezuela confirmed the existence of multiple XXAA♂/XAAY♀ sex chromosomes which originated by a centric (Robertsonian) fusion between the original Y chromosome and an autosome. 95% of the male individuals in this population are carriers of this Y-autosome fusion. In male meiosis the XAAY sex chromosomes pair in the expected trivalent configuration. In the same population, 5% of the male animals still possess the original, free XY sex chromosomes. In a second population of E. maussi analyzed, all male specimens are characterized by these ancestral XY chromosomes which form normal bivalents in meiosis. E. maussi apparently represents the first vertebrate species discovered in which a derived Y-autosome fusion still coexists with the ancestral free XY sex chromosomes. The free XY sex chromosomes, as well as the multiple XAY sex chromosomes are still in a very primitive (homomorphic) stage of differentiation. With no banding technique applied it is possible to distinguish the Y from the X. DNA flow cytometric measurements show that the genome of E. maussi is among the largest in the anuran family Leptodactylidae. The present study also supplies further data on differential chromosome banding and fluorescence in situ hybridization experiments in this amphibian species.
Localization of A Novel Autosomal Recessive Non-Syndromic Hearing Impairment Locus (DFNB38) to 6q26-q27 in a Consanguineous Kindred from Pakistan
Authors: Ansar Muhammad , Ramzan Mohammad , Pham Thanh L. , Yan Kai , Jamal Syed Muhammad , Haque Sayedul , Ahmad Wasim , Leal Suzanne M.
Published: August 2003

For autosomal recessive nonsyndromic hearing impairment over 30 loci have been mapped and 19 genes have been identified. DFNB38, a novel locus for autosomal recessive nonsyndromic hearing impairment, was localized in a consanguineous Pakistani kindred to 6q26-q27. The affected family members present with profound prelingual sensorineural hearing impairment and use sign language for communications. Linkage was established to microsatellite markers located on chromosome 6q26-q27 (Multipoint lod score 3.6). The genetic region for DFNB38 spans 10.1 cM according to the Marshfield genetic map and is bounded by markers D6S980 and D6S1719. This genetic region corresponds to 3.4 MB on the sequence-based physical map.
Integrins as Unique Receptors for Vascular Control
Authors: Martinez-Lemus Luis A. , Wu Xin , Wilson Emily , Hill Michael A. , Davis George E. , Davis Michael J. , Meininger Gerald A.
Published: August 2003

Cells within the vascular wall connect their cytoskeleton to the extracellular matrix (ECM) through a family of cell surface receptors known as integrins. The ability of integrins to act as a link between the extracellular and intracellular environments allows transmission of inside-out and outside-in signals capable of modulating diverse vascular phenomena. In this review we summarize what is currently known about the involvement of integrins in the control of vascular tone, permeability and remodeling. We discuss the capacity of integrins to act as detectors of injury-generated molecules derived from ECM proteins, as well as the putative role of integrins as mechanosensors for shear and tension. Particular attention is given to the mechanisms responsible for linking integrins to the control of vascular tone, and we review the intracellular signaling pathways involved in effecting the vascular responses elicited by integrin activation. Finally, the involvement of integrins in vascular remodeling and vascular disease is analyzed. Considerable evidence strongly indicates that integrins are involved in both acute and chronic vascular control. Understanding the elements and the sequence of events linking integrins with vasoregulation is important for deciphering phenomena such as the pressure-dependent myogenic response, flow-dependent changes in vascular diameter, and vascular remodeling as they occur in physiological and pathological conditions. Further understanding of the role of integrins in vascular control holds promise as new avenues for prophylactic and therapeutic manipulation of vascular phenomena.