bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differences in Chicken Major Histocompatibility Complex (MHC) Class Iα Gene Expression between Marek's Disease‐Resistant and ‐Susceptible MHC Haplotypes
Authors: Dalgaard T. S. , Højsgaard S. , Skjødt K. , Juul‐Madsen H. R. 
Published: March 2003

AbstractThe expression of chicken major histocompatibility complex (MHC) class Iα genes was investigated in spleen cells from a panel of chickens with well‐defined MHC haplotypes, and two class Iα transcripts of 1.9 and 1.5 kb were detected in various amounts. In BW1, B130 and B21, the two transcripts were almost equally expressed. In B2, B6, B12 and B19, the ratio between the two transcripts was 4 : 1, with the 1.9 kb transcript having the strongest expression. In B14 and B15, the 1.5 kb transcript was undetectable and the 1.9 kb transcript appeared to be exclusively expressed. Thus, haplotypes considered to have an MHC‐determined resistance to Marek's disease (MD) had the highest relative amount of the 1.5 kb transcript, whereas haplotypes considered to be MD‐susceptible had the lowest.In order to address a possible correlation between MHC‐Iα transcriptional patterns and MD resistance, a larger animal material experimentally infected with MD virus (MDV) was examined. The expression of MHC class Iα genes was investigated in spleens as well as in other organs, 9 weeks post‐infection (p.i.), from animals of the two MD‐resistant haplotypes B21 and BW1 as well as from the MD‐susceptible haplotype B19. In the spleen cells of infected animals, the relative amount of the 1.5 kb transcript in the haplotypes BW1 and B21 was shown to be significantly higher than that in B19. Interestingly, in infected BW1 and B21 animals, the relative amount of the 1.5 kb transcript was also significantly higher than that in healthy MHC‐matched controls. In B19, no differences were detected between uninfected and infected animals.Furthermore, it was shown in BW1 and B21 that the two classical MHC‐Iα genes located in the MHC region were both able to produce both mRNA transcripts. Hybridization experiments, using specific probes upstream and downstream of the polyadenylation signals in the 3′ end of the MHC‐Iα genes, demonstrated that alternate use of these signals is probably involved in the production of the two mRNA transcripts.
Upper Ordovician facies in the Lac Saint‐Jean outlier, Québec (eastern Canada): palaeoenvironmental significance for Late Ordovician oceanography
Authors: LAVOIE  , ASSELIN  
Published: March 2003

Upper Ordovician (Caradocian) carbonates of eastern North America were deposited along the Iapetus continental margin and record a transition from warm‐ to cool‐water settings despite this margin having been within the southern hemisphere tropical belt. This event has been documented from Virginia (USA) to southern Québec (Canada) although, not previously from areas close to the palaeoequator.Field, petrographic and major element geochemistry data have been gathered from the poorly‐known Upper Ordovician carbonate succession outcropping in the Lac Saint‐Jean outlier in central Québec. The succession consists of a lower siliciclastic formation (Tremblay) overlain by three limestone formations (Simard, Shipshaw and Galets) and capped by shales (Pointe‐Bleue Shale). From macro‐ and microfaunal evidence, carbonate sedimentation occurred during the late Caradoc and is younger than the early‐ to mid‐Caradoc carbonate succession present farther south. Relative sea level fluctuations recorded in the sediments suggest an overall sea level rise briefly halted by a minor end‐Caradocian sea level fall.The lower limestone formation (Simard) consists of muddy sediments with algal‐coral‐stromatoporoid boundstones; green algae are abundant. This unit reflects low energy sedimentation on a shallow warm‐water carbonate ramp colonized by a diverse chlorozoan fauna. The upper limestone formation (Galets) is typified by coarse‐grained bioclastic sediments punctuated by numerous phosphate‐rich hardgrounds with evidence for high energy shallow marine conditions. Faunas were dominated by crinoids and bryozoans. This unit represents high energy sedimentation on a cool shallow water carbonate ramp colonized by a brynoderm faunal association. Between both units, a deeper marine (outer shelf) limestone formation (Shipshaw) was developed.In the Lac Saint‐Jean area, a transition from warm‐ to cool‐water carbonate ramps occurred in latest Caradoc times and is litho‐ and biofacies‐wise, similar to what is documented for lower Caradocian limestones present farther south. Upwelling of nutrient‐rich cool bottom oceanic waters was a probable cause for this transition.
Sedimentary organic matter in condensed sections from distal oxic environments: examples from the Mesozoic of SE France
Authors: BOMBARDIERE LUCA , GORIN GEORGES E. 
Published: March 2003

A detailed analysis of sedimentary organic matter (or palynofacies) was carried out on thermally immature to early mature Upper Jurassic and Hauterivian condensed intervals in deep‐sea carbonate–marl alternations outcropping in the Vocontian Basin (SE France). All the condensed sections studied are characterized by intense bioturbation and very low organic carbon content (< 0·25 wt.%), indicative of oxic depositional conditions.Oxic condensed sections display variable palynofacies signatures, which are best illustrated by: (1) the ratio of continental to marine constituents; (2) the ratio of opaque to translucent phytoclasts (i.e. woody debris) and (3) the preservation of palynomorphs (based on fluorescence intensity and morphological preservation state in transmitted light microscopy). Both of the ratios increase with the degree of palynomorph degradation, which shows that phytoclasts, especially the opaque ones, become relatively concentrated in the most degraded facies. These observations lead to the classification of oxic condensed sections into three organic facies types showing different degrees of preservation and palynofacies signatures. Type 1 organic facies display intense degradation and are characterized by high values of the ratio of continental to marine fraction. They record unfavourable depositional environments for preservation of organic matter. Type 2 organic facies are most common and are characterized by a decreasing value of the ratio of continental to marine fraction. Type 3 organic facies display the same trend of the ratio of continental to marine fraction as type 2, but the palynomorph assemblage is better preserved. Type 1 and type 3 organic facies are relatively rare.Recognizing these organic facies types is important when analysing the relationship between sedimentary organic matter and sequence stratigraphy, because it allows the use of the appropriate palynofacies parameters. In particular, the use of the ratio of continental to marine constituents, usually a very good indicator of regressive–transgressive trends, becomes questionable in highly degraded intervals. Moreover, distinguishing between well‐preserved or highly degraded palynofacies in condensed intervals provides valuable information on the oxicity of the depositional environment.
Quantitative models of sedimentary basin filling
Authors: Paola Chris 
Published: March 2003

SummaryQuantitative modelling of the filling of sedimentary basins was begun in earnest in the 1960s. Dozens of themes and variations have been proposed since then, and have yielded an abundance of idealized stratigraphic patterns as functions of both imposed changes and basin properties. Post‐plate‐tectonic modelling began with ‘rigid‐lid' models, which show the stratigraphic signature of subsidence variation. This work introduced the connection between stratigraphy and the rheology of the lithosphere. Rigid‐lid models are the simplest type of geometric model, in which the sediment surface is assigned prescribed geometries, usually corresponding to different depositional environments. These can reproduce many aspects of overall stratal geometry but are formally restricted to relatively long timescales, for which quasi‐steady surface topography can be assumed. So‐called dynamic models attempt to represent the morphodynamics of the sediment surface by abstracting and averaging short‐term transport processes. Most of the dynamic models proposed to date can be seen as special cases of a single general morpho‐dynamic equation.The most important result of the first wave of quantitative basin‐filling models is that even relatively simple models can produce reasonable stratal patterns. We now have a wide array of tools for exploring scenarios, searching for general behaviours and effects, and making initial quantitative predictions. We have also learned that basin response to external forcing as recorded in stratigraphy can be as sensitive to the characteristics of the basin as to the forcing.The main brake on the development of basin modelling is not computing power but lack of methods and data for testing the models we have already developed. Physical experiments, which are only just beginning, are one means of doing this. Experimental stratigraphy is a bridge to quantitative field tests, which will require collaboration among academic researchers from a wide range of areas, and between academia and industry, on projects of greater scale and degree of integration than we have seen so far. The advancement of quantitative sedimentary geology will also require significant changes in the way the subject is taught, at all levels.
Phylogenetics and evolution of the aphid genus Uroleucon based on mitochondrial and nuclear DNA sequences
Authors: Moran Nancy A. , Kaplan Matthew E. , Gelsey Michael J. , Murphy Troy G. , Scholes Edwin A. 
Published: March 2003

SummaryThe genus Uroleucon, and the related genus Macrosiphoniella, represent a large Tertiary radiation of aphids, with a total of about 300 species distributed throughout the world, primarily on host plant species in the family Asteraceae. A molecular phylogenetic study was conducted to identify major clades within Uroleucon and to address the cladistic validity of current subgeneric categories, the evolution of host plant associations, the age of origin, and intercontinental movements in this genus. The seventeen study species included members of the three major subgenera of Uroleucon, species from Europe and North America, one member of Macrosiphoniella, and two outgroups. Data consisted of DNA sequences for three mitochondrial regions and the nuclear gene EF1alpha, for a total of 4287 sites. Nodes supported strongly in both parsimony and maximum likelihood analyses suggest that: (1) Nearctic Uromelan are a monophyletic group branching near the base of the genus and not related to European Uromelan, (2) the New World subgenus Lambersius is possibly monophyletic but is not a tightly related group and is not closely related to other North American species, and (3) Nearctic members of subgenus Uroleucon are a closely related monophyletic group not allied with Nearctic Uromelan or Lambersius. Instead they represent a separate colonization by an Old World ancestor, as they are nested within a strongly supported clade containing European members of both subgenera Uroleucon and Uromelan. Neither of these subgenera is monophyletic. Molecular clock calculations, based on calibrations of mitochondrial divergences from other insects, suggest that Uroleucon + Macrosiphoniella is a relatively recent radiation, probably no more than 5–10 million years old. Although largely confined to Asteraceae, this clade did not radiate in parallel with its host plants. Rather, lateral movement between lineages of Asteraceae must have occurred repeatedly.
Phylogeny of carabid beetles as inferred from 18S ribosomal DNA (Coleoptera: Carabidae)
Authors: Maddison DaviD. R.. , And MichaeL. D. BakeR. , Ober KareN. A.. 
Published: March 2003

SummaryThe phylogeny of carabid tribes is examined with sequences of 18S ribosomal DNA from eighty‐four carabids representing forty‐seven tribes, and fifteen outgroup taxa. Parsimony, distance and maximum likelihood methods are used to infer the phylogeny. Although many clades established with morphological evidence are present in all analyses, many of the basal relationships in carabids vary from analysis to analysis. These deeper relationships are also sensitive to variation in the sequence alignment under different alignment conditions. There is moderate evidence against the monophyly of Migadopini + Amarotypini, Scaritini + Clivinini, Bembidiini and Brachinini. Psydrini are not monophyletic, and consist of three distinct lineages (Psydrus,Laccocenusand a group of austral psydrines, from the Southern Hemisphere consisting of all the subtribes excluding Psydrina). The austral psydrines are related to Harpalinae plus Brachinini. The placements of many lineages, includingGehringia,Apotomus,Omophron,PsydrusandCymbionotum, are unclear from these data. One unexpected placement, suggested with moderate support, isLoriceraas the sister group toAmarotypus. Trechitae plus Patrobini form a monophyletic group. Brachinini probably form the sister group to Harpalinae, with the latter containingPseudomorpha,MorionandCnemalobus. The most surprising, well supported result is the placement of four lineages (Cicindelinae, Rhysodinae, Paussinae and Scaritini) as near relatives of Harpalinae + Brachinini. Because these four lineages all have divergent 18S rDNA, and thus have long basal branches, parametric bootstrapping was conducted to determine if their association and placement could be the result of long branch attraction. Simulations on model trees indicate that, although their observed association might be due to long branch attraction, there was no evidence that their placement near Harpalinae could be so explained. These simulations also suggest that 18S rDNA might not be sufficient to infer basal carabid relationships.
Phylogenetic analysis of the New World Ptininae (Coleoptera: Bostrichoidea)
Authors: Philips T. Keith 
Published: March 2003

SummaryA phylogenetic analysis of the New World Ptininae (Anobiidae) was conducted with representatives of nine of ten New World genera, several Old World genera and seven more of the ten subfamilies of Anobiidae. One hundred and two characters (forty‐three multistate) from thirty‐four taxa were used. The single cladogram shows Ptininae as monophyletic and the sister group of the remaining Anobiidae, supporting their placement as subfamilies of a monophyletic Bostrichidae. Genus Niptus Boieldieu is polyphyletic supporting recognition of Pseudeurostus Heyden and the creation of a new genus to encompass the remaining New World species of Niptus. Flightlessness has evolved a minimum of three times within Ptininae and myrmecophily has probably evolved three times within just the New World taxa. The classifications of Ptininae and the remaining Anobiidae are examined and the evolution of feeding habits, myrmecophily and wing loss are discussed.
Chromosomes and identification of the sibling species Pterostichus nigrita (Paykull) and P. rhaeticus Heer (Coleoptera: Carabidae)
Authors: Angus R. B. , Brown R. E. , Bryant L. J. 
Published: March 2003

SummaryThe karyotypes of Pterostichus nigrita (Paykull) and P. rhaeticus Heer are described. Both species have eighteen pairs of autosomes, sex chromosomes which are XO (♂) and XX (♀), plus a variable number of totally heterochromatic B chromosomes. Males may be identified by the form of the inflated endophallus, but the shape of the right paramere is not a reliable character. Females may be identified by the form of the eighth abdominal sternite.
Phylogenetic studies of Meloidae (Coleoptera), with emphasis on the evolution of phoresy
Authors: Bologna Marco A. , Pinto John D. 
Published: March 2003

SummaryOne of the most recent classifications of Meloidae is based on the assumption that phoretic first‐instar larvae evolved twice in the family, once in Meloinae and again in Nemognathinae. Within Meloinae, this scheme places all presumed phoretic taxa in Meloini regardless of other characteristics. This paper challenges this classification with a cladistic analysis of all meloid genera whose first‐instar larvae were available for study. It concludes that phoresy evolved several times in Meloinae alone and that Meloini, when defined to include all phoretic genera, is polyphyletic. Cladistic support also is presented for four subfamilies of Meloidae and for several of the traditional tribes recognized in recent classifications.
Trans‐Tasman Platycoelostoma Morrison (Hemiptera: Coccoidea: Margarodidae) on endemic Cupressaceae, and the phylogenetic history of margarodids
Authors: Gullan P. J. , Sjaarda A. W. 
Published: March 2003

SummaryA new species of Platycoelostoma Morrison (Hemiptera: Coccoidea: Margarodidae) is described from the Tasmanian endemic conifer, Diselma archeri (Cupressaceae), growing in alpine heathland. Its sister species, P. compressa (Maskell), occurs in alpine and subalpine New Zealand on Libocedrus bidwilli (Cupressaceae). Vicariance dating provides a minimum age for Platycoelostoma of about 80 Ma. Cladistic analysis of morphological data from adult females and first‐instar nymphs suggests that Platycoelostoma is the sister genus of Callipappus Guérin‐Méneville and also is more closely related to members of subfamilies Margarodinae and Xylococcinae than to the New Zealand and South American genera of Coelostomidiinae, to which Platycoelostoma traditionally has been linked. The analysis also indicates that most traditional tribal groupings within Margarodidae are monophyletic, but that three (Coelostomidiinae, Margarodinae and Xylococcinae) of the five subfamilies in the widely used higher classification of Morrison may be either paraphyletic or polyphyletic as currently defined. Only Monophlebinae and Steingeliinae have adequate support from morphological characters. Relationships among subfamilies and many tribes are unresolved. These results lend some support to the classification previously proposed by Koteja, in which all margarodid subfamilies and a few tribes are elevated to the rank of family. Furthermore, the analysis suggests that Marchalini and Monophlebinae (in which all immature female instars have well developed appendages) are derived with respect to other margarodids and thus development via legless intermediate female instars (‘cyst’ form) may be plesiomorphic within margarodids. This hypothesis is weakly supported and requires corroboration from independent data. Platycoelostoma is transferred to tribe Callipappini, which is redefined, but the subfamily placement of this tribe must remain uncertain until the higher classification and rank of the various margarodid taxa can be re‐evaluated. A revised generic description of Platycoelostoma, based on the adult and intermediate female instars and the first instar of both species, and a key to separate the female instars of both species are provided. The first‐instar nymph, all female instars and the third‐instar male (the prepupa) of Platycoelostoma tasmanicum sp.n. are described and illustrated. Scanning electron micrographs depict the unusual cuticular features of the third‐instar female.
Oceanic circulation as an element in palaeogeographical reconstructions: the Arenig (early Ordovician) as an example
Authors: Christiansen J.L. , Stouge S. 
Published: March 2003

A new conceptual palaeo‐oceanographical model is outlined in this paper. The model differs from previous models by using shifts in Hadley circulation caused by orbital variations, and the rotation rate of the Earth, to locate the position of the planetary oceanic low‐and high‐pressure systems, around which the planetary ocean surface currents flow. Adapting the model to the Arenig (early Ordovician) the temperate low pressure zones were found to be located at 50° latitude and the subtropical high pressure zones at 25° latitude.Traditionally, most Palaeozoic palaeogeographical recon‐structions are reconstructed using palaeomagnetic data supplemented with data from climate‐sensitive lithofacies and palaeo‐biogeographical distributions. However, as a new approach in palaeogeographical reconstructions, the con‐ceptual palaeo‐oceanographical model is combined with palaeobiogeographical data for the Arenig series, comple‐menting the palaeomagnetic data, and resulting in a new, refined palaeogeographical reconstruction.
RNA binding characteristics of a 16 kDa glycine‐rich protein from maize
Authors: Ludevid M. Dolors , Freire Miguel Angel , Gómez Jordi , Burd Christopher G. , Albericio Fernando , Giralt Ernest , Dreyfuss Gideon , Pagès Montserrat 
Published: March 2003

SummaryWe have previously described a developmentally regulated mRNA in maize that accumulates in mature embryos and is involved in a variety of stress responses in the plant. The sequence of the encoded 16 kDa protein (MA 16) predicts that it is an RNA‐binding protein, since it possesses a ribonucleoprotein consensus sequence‐type RNA‐binding domain (CS‐RBD). To assess the predicted RNA binding property of the protein and as a starting point to characterize its function we have used ribohomopolymer‐binding assays. Here we show that the MA16‐encoded protein binds preferentially to uridine‐ and guanosine‐rich RNAs. In light of these results a likely role for this protein in RNA metabolism during late embryogenesis and in the stress response is discussed.
Members of the acetohydroxyacid synthase multigene family of Brassica napus have divergent patterns of expression
Authors: Ouellet Thérèse , Rutledge Robert G. , Miki Brian L. 
Published: March 2003

Summary Brassica species possess the most complex acetohydroxyacid synthase (AHAS) multigene family reported for plants. The AHAS genes code for an essential enzyme in branched‐chain amino acid biosynthesis. In the allotetraploid species, B. napus, four (AHAS1–4) of the five AHAS genes have been cloned and sequenced. The transcripts were examined by RNase protection assays using gene‐specific, antisense RNA probes. Only AHAS1, AHAS2 and AHAS3 were shown to be expressed in B. napus and one of the diploid progenitor species B. campestris or B. oleracea. AHAS1 and AHAS3 are highly conserved genes that presumably code for the essential AHAS housekeeping functions. They were expressed as low abundance mRNA in all somatic and reproductive tissues examined. AHAS2, which is structurally distinct from all other plant AHAS genes, was only expressed in mature ovules and extra‐embryonic tissues of immature seeds. This study provides direct evidence for multiple AHAS isoforms in plants and for an AHAS gene which is developmentally regulated in a tissue‐specific manner. The discovery raises questions concerning the functional significance of AHAS in seed development.