bluuebunny/crossref_metadata_2025 huggingface dataset:
Major Histocompatibility Complex Class I‐Restricted Presentation of Protein Antigens without Prior Intracellular Processing
Authors: Diegel M. L. , Chen F. , Laus R. , Graddis T. J. , Vidovic D.
Published: December 2004

Proteins in their native form are incapable of stimulating antigen (Ag)‐specific T cells, which can only recognize major histocompatibility complex (MHC)‐bound peptides that have been generated by intracellular processing within antigen‐presenting cells (APCs). Here, we show that APCs can trigger MHC class I‐restricted T‐cell responses after presenting proteins without conventional intracellular processing, provided the immunostimulatory MHC class I‐binding peptide sequence is incorporated at the carboxy‐terminal position. Such MHC‐bound proteins do not stimulate T cells directly, because the contact between MHC/peptide complex and its cognate ligand is sterically hindered by the amino‐terminal bulk of the protein. Removal of the latter via an extracellular Ag proteolysis by the T‐cell‐ and/or APC‐derived enzymes is required for effective T‐cell stimulation. Our data challenge the established concept that only small peptides can bind to the MHC class I molecules.
Threshold for particle entrainment into suspension
Authors: NiÑo Yarko , Lopez Fabian , Garcia Marcelo
Published: December 2004

ABSTRACT Laboratory observations regarding the limit conditions for particle entrainment into suspension are presented. A high‐speed video system was used to investigate conditions for the entrainment of sediment particles and glass beads lying over a smooth boundary as well as over a rough bed. The results extend experimental conditions of previous studies towards finer particle sizes. A criterion for the limit of entrainment into suspension is proposed which is a function of the ratio between the flow shear velocity and particle settling velocity. Observations indicate that particles totally immersed within the viscous sublayer can be entrained into suspension by the flow, which contradicts the conclusions of previous researchers. A theoretical analysis of the entrainment process within the viscous sublayer, based on force–balance considerations, is used to show that this phenomenon is related to turbulent flow events of high instantaneous values of the Reynolds stress, in agreement with previous observations. In the case of experiments with a rough bed, a hiding effect was observed, which tends to preclude the entrainment of particles finer than the roughness elements. This implies that, as the ratio between particle and roughness element sizes becomes smaller, progressively higher bed shear stresses are required to entrain particles into suspension. On the other hand, an overexposure effect was also observed, which indicates that a particle moving on a smooth bed is more prone to be entrained than the same particle moving on a bed formed by identical particles.
Characterization and correlation of Upper Jurassic (Oxfordian) bentonite deposits in the Paris Basin and the Subalpine Basin, France
Authors: Pellenard Pierre , Deconinck Jean‐Francois , Huff Warren D. , Thierry Jacques , Marchand Didier , Fortwengler Dominique , Trouiller Alain
Published: December 2004

Abstract Explosive volcanic activity is recorded in the Upper Jurassic of the Paris Basin and the Subalpine Basin of France by the identification of five bentonite horizons. These layers occur in Lower Oxfordian (cordatum ammonite zone) to Middle Oxfordian (plicatilis zone) clays and silty clays deposited in outer platform environments. In the Paris Basin, a thick bentonite (10–15 cm), identified in boreholes and in outcrop, is dominated by dioctahedral smectite (95%) with trace amounts of kaolinite, illite and chlorite. In contrast, five bentonites identified in the Subalpine Basin, where burial diagenesis and fluid circulation were more important, are composed of a mixture of kaolinite and regular or random illite/smectite mixed‐layer clays in variable proportions, indicating a K‐bentonite. In the Subalpine Basin, a 2–15 cm thick bentonite underlain by a layer affected by sulphate–carbonate mineralization can be correlated over 2000 km2. Euhedral zircon, apatite and biotite crystals have been identified in all the bentonites. The geochemical composition of the bentonites in both basins is characterized by high concentrations of Hf, Nb, Pb, Ta, Th, Ti, U, Y, Zr and low concentrations of Cr, Cs and Rb. Biostratigraphical and geochemical data suggest that the thick bentonite in the Paris Basin correlates with the thickest bentonite in the Subalpine Basin, located 400 km to the south. These horizons indicate that significant explosive volcanic events occurred during the Middle Oxfordian and provide potential long‐distance isochronous marker beds. Immobile element discrimination diagrams and rare‐earth element characteristics indicate that the original ash compositions of the thickest bentonites correspond to a trachyandesitic source from a within‐plate alkaline series that was probably related to North Atlantic rifting.
Morphology and internal structure of sand shoals and sandbanks off the Dorset coast, English Channel
Authors: Bastos Alex C. , Collins Michael , Kenyon Neil H.
Published: December 2004

The morphology and internal structure of sand shoals and sandbanks around a coastal headland (Portland Bill, southern UK) are described on the basis of sidescan sonar and high‐resolution seismic data sets. Morphological and architectural evidence, combined with the spatial distribution and nature of the bedrock surface, indicates that the evolution of these deposits, especially the sandbanks, may not only be hydrodynamically controlled but also morphologically controlled. The internal structure of the sand shoals reveals a simple pattern of clinoforms dipping in the same direction as their steeper profile. In contrast, the internal structure of the sandbanks reveals that their lower seismic units consist of a sedimentary core interpreted as the remains of a lowstand deposit or an early stage of the bank development under different prevailing hydrodynamic conditions. The present morphology of the sandbanks is represented by upper seismic units characterized by large‐scale sandwave foresets dipping at 6–8°. The nature and morphology of the bedrock surface may also influence the development of sandbanks in some cases. For example, to the west of Portland Bill, the morphology of the bedrock surface (basal reflector) restricts the development of the Portland Bank. This information may explain the asymmetric evolution of sandbanks around Portland Bill.
Migration and sedimentology of longshore sandwaves, Long Point, Lake Erie, Canada
Authors: Davidson‐Arnott Robin G. D. , Van Heyningen Anthony G.
Published: December 2004

This paper describes the formation, migration and sedimentology of sandwaves along the distal end of Long Point, a 40 km long spit in Lake Erie. Some seven to nine sandwaves occur in a zone over the last 14 km of the spit. They are characteristically 50–100 m wide at the downdrift end, range in length from 350 m to > 1500 m and migrate alongshore at rates that are typically 100–300 m year−1. Measurements over a 7‐year period show two forms of alongshore sandwave migration: (1) a migratory jump; and (2) downdrift accretion. The migratory jump is commonly 200–500 m year−1 and results from the onshore migration and welding of an inner nearshore bar to the downdrift end of the sandwave. This in turn leads to emergence of the bar over a distance of several hundred metres downdrift of the sandwave and isolation of the trough landward of the bar. Infilling of the trough abstracts large volumes of sediment from the local sediment transport system and may affect movement of the sandwave in the following year or movement of the next sandwave downdrift. Downdrift accretion commonly results in migration of 50–150 m year−1 and results from the refraction of waves around the distal end of the sandwave and episodic accretion of small swash bars. This mechanism occurs less frequently and appears to reflect a local condition of lower sediment abundance, often triggered by a large migratory jump in the previous year. The process of bar emergence and infilling produces a distinct suite of sedimentary structures associated with the infilling of the landward trough and building of the sandwave berm. The initial shoreline perturbation that generates the sandwave results from onshore migration and welding of inner nearshore bars, and the development and growth of the sandwaves is promoted by refraction of highly oblique waves.
Multiproxy approach to understanding the origin of Cretaceous pelagic limestone–marl alternations (DSDP site 391, Blake‐Bahama Basin)
Authors: Westphal Hildegard , Munnecke Axel , Pross Jörg , Herrle Jens Olaf
Published: December 2004

Limestone–marl alternations are usually directly interpreted to reflect cyclic palaeoenvironmental signals. However, uncertainty in such interpretations stems from the differential diagenesis that most limestone–marl alternations have undergone. Differential diagenesis results in markedly different alterations between limestones and marls and in the loss of comparability of many measurable parameters. For an unequivocal interpretation of the origin of rhythmic alternations, diagenetically robust parameters or parameters that clearly indicate the degree of diagenetic bias are required. The present study uses a multiproxy approach (independent biotic, sedimentary and geochemical parameters) in order to unravel the palaeoenvironmental signal recorded in Valanginian (Early Cretaceous) limestone–marl alternations from the Blake‐Bahama Basin (DSDP site 391). Using this approach, terrestrial and marine influences can be distinguished, changes in nutrient levels estimated and prediagenetic differences in the non‐carbonate fraction constrained. Surprisingly, no systematic variations in any of these parameters were observed between limestone and marl layers, implying that none of these was directly responsible for the formation of the rhythmic alternation. Hence, none of the current models of sedimentary formation of limestone–marl rhythmites is applicable here. Calcareous nannofossils are equally well preserved in limestone and marl layers, ruling out their dissolution in marl layers as a source of the calcite cement in the limestone beds. Sr values of 700–900 p.p.m. indicate that aragonite may have been present in the original, pelagic sediment. The assumption of fine‐grained sedimentary aragonite imported from nearby carbonate platforms as the source of the cement would explain a number of otherwise enigmatic features in these rhythmites, including the source of the calcite cement observed in the limestones, the equally good preservation of calcareous nannofossils in limestones and marls and the higher concentration of calcareous nannofossils in marl layers. The study demonstrates that examination of diagenetically inert parameters or parameters in which diagenetic effects can be filtered can yield unexpected results. Clearly, careful analysis of such parameters needs to be undertaken in order to make reliable palaeoenvironmental interpretations from rhythmite successions.
Depositional facies and stratal geometry of an Upper Carboniferous prograding and aggrading high‐relief carbonate platform (Cantabrian Mountains, N Spain)
Authors: Della Porta Giovanna , Kenter Jeroen A. M. , Bahamonde Juan R.
Published: December 2004

Seismic‐scale continuous exposures of an Upper Carboniferous (Bashkirian–Moscovian) carbonate platform (N Spain) provide detailed information about the lithofacies and stratal geometries (quantified with differential global positioning system measurements) of microbial boundstone‐dominated, steep prograding and aggrading platform margins. Progradational and aggradational platform‐to‐slope transects are characterized by distinct lithological features and stratal patterns that can be applied to the understanding of geometrically comparable, high‐relief depositional systems. The Bashkirian is characterized by rapid progradation at rates of 415–970 m My−1. Characteristic outer‐platform facies are high‐energy grainstones with coated intraclasts, ooids and pisoids, moderate‐energy algal‐skeletal grainstones to packstones and lower energy algal packstone and boundstone units. The Moscovian aggradational phase is characterized by aggradation rates of 108 m My−1. Coated‐grain shoals are less common, whereas crinoidal bars nucleated in well‐circulated settings below wave‐base. Boundstones form a belt (30–300 m wide) at the platform break and interfinger inwards with massive algal‐skeletal wackestones (mud‐rich banks). The progradational phase has divergent outer‐platform strata with basinward dips of 12° to 2°. Steep clinoforms with dips of 20–28° are 650–750 m in relief and possibly sigmoidal to concave in the lower part. The basinward‐dipping outer‐platform strata might be depositional for less than 6°, consistent with lithofacies deepening seaward. The basinward dip is attributed to the downward shift of upper‐slope boundstone, forced by late highstand and relative sea‐level fall, and to compaction‐induced differential subsidence during progradation. The aggradational phase is characterized by horizontally layered platform strata. Clinoforms steepen to 30–45° reaching heights of 850 m and are planar to concave. The evolution from progradation to aggradation, at the Bashkirian–Moscovian boundary, is attributed to increased foreland‐basin subsidence and decreased boundstone accumulation rates. Progradation was primarily controlled by boundstone growth rather than by highstand shedding from the platform top. Within the major phases, aggradational–progradational increments are produced by third‐ to fourth‐order relative sea‐level fluctuations.
Wing geometry in Triatoma infestans (Klug) and T. melanosoma Martinez, Olmedo & Carcavallo (Hemiptera: Reduviidae)
Authors: Gumiel M. , Catalá S. , Noireau F. , Rojas De Arias A. , García A. , Dujardin J. P.
Published: December 2004

Abstract. Geometric morphometrics is a novel approach to biological shape analysis, and its application to medical entomology is just beginning. Here, we use it to examine geographical and interspecific variation in the Triatoma infestans complex, vectors of Chagas disease in southern Latin America. Using six landmarks defining the membranous part of the hemelytra, we analysed the geographical patterns of variation in several populations of T. infestans, including the recently described ‘dark morph’ of T. infestans from hollow trees in the Bolivian Chaco. As a potential outgroup, T. melanosoma was added to the sample. A consistent geographical differentiation was observed, but no evidence was found in either sex to consider either the dark morph or T. melanosoma as a species distinct from T. infestans. Triatoma melanosoma is relegated to synonymy with T. infestans (syn.n.).
A new genus and species of bothriurid scorpion from the Brandberg Massif, Namibia, with a reanalysis of bothriurid phylogeny and a discussion of the phylogenetic position ofLisposomaLawrence
Authors: Prendini Lorenzo
Published: December 2004

Abstract.Brandbergia haringtoni, a new genus and species of bothriurid scorpion, is described from the Brandberg Massif, northwestern Namibia. A cladistic analysis, based on seventy‐four morphological characters scored for thirty‐one exemplar species representing all genera of Bothriuridae, and one genus from each of the six remaining families of Scorpionoidea, was conducted to test the phylogenetic placement of the new genus and whether it affects the internal relationships of Bothriuridae. The available data demonstrate, under a range of weighting regimes, that the new genus is the most basal bothriurid, and confirm the scheme of relationships among the remaining bothriurid genera that was recovered in a previous analysis: (Brandbergia(Lisposoma(Thestylus(Phoniocercus(Tehuankea(Cercophonius + Urophonius) (Bothriurus + Brachistosternus +Orobothriurus + Centromachetes(Timogenes + Vachonia))))))). On the basis of this evidence, Lourenço's recent proposal of family Lisposomidae forLisposomais rejected and Lisposomidae is synonymized with Bothriuridae. The implications of the phylogeny for understanding the biogeography of Bothriuridae are discussed.
A lacewing with the wanderlust: the European song species ‘Maltese’, Chrysoperla agilis, sp.n., of the carnea group of Chrysoperla (Neuroptera: Chrysopidae)
Authors: Henry Charles S. , Brooks Stephen J. , Duelli Peter , Johnson James B.
Published: December 2004

Abstract. A fifth European member of the Holarctic carnea sibling species group, Chrysoperla agilis, sp.n. is described. This species was initially recognized because of its unique song phenotype. Both sexes produce one type of song, characterized by a single very long volley averaging 4.5 s in duration and repeated every 9.5 s. The unit of exchange during heterosexual duets (the shortest repeated unit) is the single volley. The carrier frequency is upwardly, then downwardly, modulated during each volley. The maximum frequency is higher (around 110 Hz) than in other members of the carnea group. Each volley ends with an audible, percussive ‘rattle’. Song features vary only slightly over a large geographical range that extends from northern Iran westward to the Azores and northward to southern Switzerland. Discriminant function analysis confirms the uniqueness of the C. agilis song in comparison with nine other song species. Morphologically, the adult of C. agilis is very similar to C. carnea and C. pallida and is generally intermediate between them with respect to the size of the pretarsal basal dilation, the shape of the genital lip and chin, the colour and type of setae on the abdomen, and colour markings on the head and mouthparts. No single feature will distinguish C. agilis from either C. carnea or C. pallida, but a suite of physical attributes can be used with reasonable success. Larval morphology fails to distinguish clearly C. agilis from other song species. Ecologically, C. agilis shares an affinity for low vegetation with C. lucasina and C. carnea, and a preference for milder, Mediterranean climates with C. mediterranea. Adults undergo a colour change to pale yellowish brown during winter diapause, and eggs are laid singly rather than in groups. Based on its ecological characteristics, C. agilis may prove to be an effective agent of biological control in the agricultural fields of warmer, drier parts of southern Europe and the Middle East, where other members of the carnea group are less common or absent.
Morphological and molecular characterization of Anopheles (Anopheles) sacharovi Favre, a primary vector of malaria in the Middle East
Authors: Sedaghat Mohammad Mehdi , Linton Yvonne‐Marie , Nicolescu Gabriela , Smith Lisa , Koliopoulos George , Zounos Athanassios K. , Oshaghi Mohammad Ali , Vatandoost Hassan , Harbach Ralph E.
Published: December 2004

Abstract. Combined morphological and molecular studies were conducted on Anopheles (Anopheles) sacharovi Favre, an important malaria vector of the Palaearctic Maculipennis Complex. Specimens collected in Greece and Iran were identified on the basis of morphology and confirmed by correlation of their nuclear internal transcribed spacer 2 (ITS2) rDNA sequences with those available in GenBank. The progeny of females collected in Greece were used for detailed morphological study. The morphology of the adults, pupa, fourth‐instar larva and egg are described and distinguished from those of An. maculipennis, the nominotypical member of the Maculipennis Complex. In addition to sequence data for the nuclear ITS2 region, partial sequence data are provided for the mitochondrial cytochrome oxidase I gene. The taxonomy, systematics, bionomics and distribution of the species are reviewed. This work provides the first fully integrated assessment of An. sacharovi as a basis for comparative studies of the Maculipennis Complex.
Revision and phylogenetic analysis of the Central American endemic genus Phalangogonia Burmeister (Coleoptera: Scarabaeidae: Rutelinae: Anoplognathini)
Authors: Smith Andrew B. T. , Morón Miguel Angel
Published: December 2004

Abstract.  Phalangogonia Burmeister is revised and now includes eight species: P. dispar Ohaus, P. jamesonae, sp.n., P. lacordairei Bates, P. obesa Burmeister, P. parilis Bates, P. punctata Franz, P. ratcliffei, sp.n. and P. sperata Sharp. Phalangogonia debilidens Ohaus is placed in synonymy with P. sperata. Lectotypes are designated for the following nominal species: P. dispar Ohaus, P. lacordairei Bates, P. parilis Bates and P. championi Bates. Neotypes are designated for: P. obesa Burmeister, P. sperata Sharp, P. stipes Sharp and P. debilidens Ohaus. A cladistic analysis of the species of Phalangogonia was executed using thirty‐two morphological characters of adults.
Assessment of monophyly of species‐groups within Afrotropical Empidini (Diptera: Empididae: Empidinae), with a cladistic analysis of the Empis setitarsus‐group
Authors: Daugeron Christophe , Grootaert Patrick
Published: December 2004

Abstract.  The Afrotropical Empidini are reviewed from a phylogenetic point of view. Seven monophyletic groups are recognized within the tribe, namely Empis (Coptophlebia) bivittata, E. (C ) chrysocera, E. (C ) hyalea, E. (C ) namwamba, E. (C ) poecilosoma, E. (Disneyempis) and E. setitarsus. Their monophyly is assessed by comparison with the remaining Empidini. The E. setitarsus‐group is cladistically analysed to study the evolution of the length of vein M1 by optimization on the cladogram, and the status of subgenus Coptophlebia Bezzi is discussed. A key to the seven Afrotropical species‐groups of Empidini is provided, genus Rhamphomyia is no longer recognized for the Afrotropical Region, and four new species belonging to the E. setitarsus‐group, namely E. cinerarius sp.n., E. pseudosetitarsus sp.n., E. spinosa sp.n and E. spungaberaensis sp.n., are described and included in a key to all known species of this group.
Molecular systematics of Psocomorpha (Psocoptera)
Authors: Johnson Kevin P. , Mockford Edward L.
Published: December 2004

Abstract.  Previous classification of the insect order Psocoptera has relied on morphological characters. Psocoptera are generally divided into three suborders: Trogiomorpha, Troctomorpha, and Psocomorpha. Traditional classification divides the Psocomorpha into four infraorders (Homilopsocidea, Caeciliusetae, Psocetae and Epipsocetae), but a recent morphological cladistic study removed Archipsocidae from Homilopsocidea and Hemipsocidae from Psocetae. We investigated the phylogenetic relationships within the suborder Psocomorpha using DNA sequences from the nuclear 18S and mitochondrial 16S, 12S and cytochrome oxidase I genes. Phylogenetic analyses of these gene sequences supported monophyly for Psocomorpha. In addition, monophyly of the traditional subgroups Caeciliusetae and Psocetae was generally supported. Monophyly of Homilopsocidea was not supported, and Archipsocus is removed from this group. Although the molecular phylogeny is generally consistent with recent cladistic studies of morphological characters, we found no evidence that Hemipsocidae should be removed from Psocetae.
Late‐stage deformation in a collisional orogen (Western Alps): nappe refolding, back‐thrusting or normal faulting?
Authors: Bucher Stefan , Schmid Stefan M. , Bousquet Romain , Fügenschuh Bernhard
Published: December 2004

ABSTRACT Nappe refolding, back‐thrusting and normal faulting frequently cause severe late‐stage overprinting of the architecture of an orogen. A combined investigation of nappe stack polarity, kinematics of shearing and metamorphic gradients in the Western Alps develops criteria for distinguishing between these three modes of late‐stage deformation. This distinction is a prerequisite for any retro‐deformation necessary for understanding the main tectonic and metamorphic evolution of collisional orogens. In the case of the Western Alps overprint was by mega‐scale nappe refolding in the Oligocene. This implies exhumation of the HP‐rocks prior to postnappe folding, i.e. during nappe stacking and by foreland‐directed ascent within a subduction channel.
Motion on the Kaparelli fault (Greece) prior to the 1981 earthquake sequence determined from 36Cl cosmogenic dating
Authors: Benedetti L. , Finkel R. , King G. , Armijo R. , Papanastassiou D. , Ryerson F. J. , Flerit F. , Farber D. , Stavrakakis G.
Published: December 2004

ABSTRACT In February and March 1981, three successive destructive earthquakes occurred at the eastern end of the Gulf of Corinth. The third shock (March, 4, Ms ≈ 6.4) ruptured the Kaparelli fault. About 40 cm of a limestone fault scarp was exhumed by the earthquake. Each major prehistoric earthquake has added new surface to this cumulative scarp exposing fresh material to cosmic‐ray bombardment. Using 36Cl cosmic ray exposure dating we have obtained the continuous exposure history for this 4–5‐m‐high limestone surface at two sites about 50 m apart. The results suggest that the Kaparelli fault has ruptured three times prior to 1981 at 20 ± 3 ka, 14.5 ± 0.5 ka and 10.5 ± 0.5 ka with slip amplitudes between 0.6 m and 2.1 m. The Kaparelli fault appears to have been inactive for 10 thousand years prior to the 1981 event.
Excision of a transposable element from a viral vector introduced into maize plants by agroinfection
Authors: Shen Wen‐Hui , Hohn Barbara
Published: December 2004

The geminivirus maize streak virus (MSV) was used as a vector to introduce the maize transposable element Dissociation (Ds) and to study its excision in maize plants. MSV carrying Ds1 in its genome was introduced into maize plants by agroinfection. Excision of the Ds1 element from the MSV genome was detected only when functions from the transposable element Activator (Ac) were supplied in trans, either endogenously by the recipient maize plant or by co‐transformation with Agrobacterium carrying a genomic Ac clone. The excision of Ds1 could easily be visualized by the appearance of viral symptoms induced by the revertant virus. The junction sequences left on the MSV genome after excision revealed ‘footprints’ typical of transposition as described for maize. From these results, we conclude that transposition functions in our system and that the use of the MSV replicon provides a rapid and simple tool for the investigation of the excision of transposable elements in maize plants.
Growth and stomata development of Arabidopsis hypocotyls are controlled by gibberellins and modulated by ethylene and auxins
Authors: Saibo Nelson J. M. , Vriezen Wim H. , Beemster Gerrit T. S. , Van Der Straeten Dominique
Published: December 2004

The plant hormones gibberellin (GA), ethylene and auxin can promote hypocotyl elongation of Arabidopsis seedlings grown in the light on a low nutrient medium (LNM). In this study, we used hypocotyl elongation as a system to investigate interactions between GA and ethylene or auxin and analysed their influence on the development of stomata in the hypocotyl. When applied together, GA and ethylene or auxin exerted a synergistic effect on hypocotyl elongation. Stimulated cell elongation is the main cause of hypocotyl elongation. Furthermore, hypocotyls treated with GA plus either ethylene or auxin show an increased endoreduplication. In addition, a small but significant increase in cell number was observed in the cortical cell files of hypocotyls treated with ethylene and GA together. However, studies with transgenic seedlings expressing CycB1::uidA genes revealed that cell division in the hypocotyl occurs only in the epidermis and mainly to form stomata, a process strictly regulated by hormones. Stomata formation in the hypocotyl is induced by the treatment with either GA or ethylene. The effect of GA could be strongly enhanced by the simultaneous addition of ethylene or auxin to the growth medium. Gibberellin is the main signal inducing stomata formation in the hypocotyl. In addition, this signal regulates hypocotyl elongation and is modulated by ethylene and auxin. The implication of these three hormones in relation to cell division and stomata formation is discussed.
Double fertilization in maize: the two male gametes from a pollen grain have the ability to fuse with egg cells
Authors: Faure Jean‐Emmanuel , Rusche Maxine Losoff , Thomas Annie , Keim Paul , Dumas Christian , Mogensen H. Lloyd , Rougier Mireille , Chaboud Annie
Published: December 2004

In flowering plants, two male gametes from a single pollen grain fuse with two female gametes, the egg and central cells, to form the embryo and endosperm, respectively. The question then arises whether the two male gametes fuse randomly with the egg and central cells. We investigated this question using two nearly isogenic maize lines with supernumerary B chromosomes (TB10L18) or without (r‐tester). B chromosomes regularly undergo non‐disjunction at the second pollen mitosis, producing one sperm cell with zero B chromosomes and one with two. We first confirmed earlier studies showing an excess of transmission of the B chromosomes to the embryo rather than to the endosperm. We then tested the possibility of a directed fertilization. For TB10L18 pollen, we could demonstrate the existence of a size dimorphism between the two sperm cells, correlated to the content in B chromosomes, as detected by fluorescence in situ hybridization (FISH). However, no directed fusion of B chromosome containing sperm to egg cells could be detected when using in vitro fertilization. The absence of directed fusion in vitro could also be demonstrated for control lines. We conclude that both male gametes have the capacity to fuse with the egg cell in maize, although sexual reproduction results in a preferential transmission of supernumerary B chromosomes.
The role of PopCel1 and PopCel2 in poplar leaf growth and cellulose biosynthesis
Authors: Ohmiya Yasunori , Nakai Tomonori , Park Yong Woo , Aoyama Takashi , Oka Atsuhiro , Sakai Fukumi , Hayashi Takahisa
Published: December 2004

Poplar calli transcribed two cellulase (endo‐1,4‐β‐glucanase) genes, PopCel1 and PopCel2, whose mRNAs were differentially located in the growing leaves of poplar during cell wall synthesis. Histochemical and RT‐PCR analyses of promoter–GUS fusion gene activities in transgenic poplar demonstrated that PopCel1 promoter‐derived GUS activity was localized in the petiole and leaf veins, whereas PopCel2 was confined to mesophyll cells and disappeared from the tip during the development of leaves. Autoradiography of the leaf showed that the radioactivity of [14C]sucrose incorporated into cellulose corresponded to the combination of the sucrose‐induced tissue‐specific patterns of PopCel1 and PopCel2. Interestingly, 2,6‐dichlorobenzonitrile (DCB) not only inhibited the incorporation of the radioactivity into cellulose, but also repressed the induction of both cellulase genes. Suppression of cellulases by expression of PopCel1 antisense cDNA or co‐suppression of PopCel1 mRNA by overexpression of PopCel1 sense cDNA reduced leaf growth. Therefore, we came to the conclusion that PopCel1 and PopCel2 probably function to promote leaf growth in poplar by the endohydrolysis of 1,4‐β‐glucan.
Transport of cytokinins mediated by purine transporters of the PUP family expressed in phloem, hydathodes, and pollen of Arabidopsis
Authors: Bürkle Lukas , Cedzich Anna , Döpke Corinna , Stransky Harald , Okumoto Sakiko , Gillissen Bernd , Kühn Christina , Frommer Wolf B.
Published: December 2004

Nucleobases and derivatives like cytokinins and caffeine are translocated in the plant vascular system. Transport studies in cultured Arabidopsis cells indicate that adenine and cytokinin are transported by a common H+‐coupled high‐affinity purine transport system. Transport properties are similar to that of Arabidopsis purine transporters AtPUP1 and 2. When expressed in yeast, AtPUP1 and 2 mediate energy‐dependent high‐affinity adenine uptake, whereas AtPUP3 activity was not detectable. Similar to the results from cell cultures, purine permeases (PUP) mediated uptake of adenine can be inhibited by cytokinins, indicating that cytokinins are transport substrates. Direct measurements demonstrate that AtPUP1 is capable of mediating uptake of radiolabeled trans‐zeatin. Cytokinin uptake is strongly inhibited by adenine and isopentenyladenine but is poorly inhibited by 6‐chloropurine. A number of physiological cytokinins including trans‐ and cis‐zeatin are also efficient competitors for AtPUP2‐mediated adenine uptake, suggesting that AtPUP2 is also able to mediate cytokinin transport. Furthermore, AtPUP1 mediates transport of caffeine and ribosylated purine derivatives in yeast. Promoter–reporter gene studies point towards AtPUP1 expression in the epithem of hydathodes and the stigma surface of siliques, suggesting a role in retrieval of cytokinins from xylem sap to prevent loss during guttation. The AtPUP2 promoter drives GUS reporter gene activity in the phloem of Arabidopsis leaves, indicating a role in long‐distance transport of adenine and cytokinins. Promoter activity of AtPUP3 was only found in pollen. In summary, three closely related PUPs are differentially expressed in Arabidopsis and at least two PUPs have properties similar to the adenine and cytokinin transport system identified in Arabidopsis cell cultures.
Growth suppression, altered stomatal responses, and augmented induction of heat shock proteins in cytosolic ascorbate peroxidase (Apx1)‐deficient Arabidopsis plants
Authors: Pnueli Lilach , Liang Hongjian , Rozenberg Mira , Mittler Ron
Published: December 2004

The accumulation of hydrogen peroxide (H2O2) in plants is typically associated with biotic or abiotic stresses. However, H2O2 is continuously produced in cells during normal metabolism. Yet, little is known about how H2O2 accumulation will affect plant metabolism in the absence of pathogens or abiotic stress. Here, we report that a deficiency in the H2O2‐scavenging enzyme, cytosolic ascorbate peroxidase (APX1), results in the accumulation of H2O2 in Arabidopsis plants grown under optimal conditions. Knockout‐Apx1 plants were characterized by suppressed growth and development, altered stomatal responses, and augmented induction of heat shock proteins during light stress. The inactivation of Apx1 resulted in the induction of several transcripts encoding signal transduction proteins. These were not previously linked to H2O2 signaling during stress and may belong to a signal transduction pathway specifically involved in H2O2 sensing during normal metabolism. Surprisingly, the expression of transcripts encoding H2O2 scavenging enzymes, such as catalase or glutathione peroxidase, was not elevated in knockout‐Apx1 plants. The expression of catalase, two typical plant peroxidases, and several different heat shock proteins was however elevated in knockout‐Apx1 plants during light stress. Our results demonstrate that in planta accumulation of H2O2 can suppress plant growth and development, interfere with different physiological processes, and enhance the response of plants to abiotic stress conditions. Our findings also suggest that at least part of the induction of heat shock proteins during light stress in Arabidopsis is mediated by H2O2 that is scavenged by APX1.
The translation initiation factor eIF1A is an important determinant in the tolerance to NaCl stress in yeast and plants
Authors: Rausell Antonio , Kanhonou Rodolphe , Yenush Lynne , Serrano Ramon , Ros Roc
Published: December 2004

Protein synthesis is very sensitive to NaCl. However, the molecular targets responsible for this sensitivity have not been described. A cDNA library of the halotolerant plant sugar beet was functionally screened in a sodium‐sensitive yeast strain. We obtained a cDNA clone (BveIF1A) encoding the eukaryotic translation initiation factor eIF1A. BveIF1A was able to partially complement the yeast eIF1A‐deficient strain. Overexpression of the sugar beet eIF1A specifically increased the sodium and lithium salt tolerance of yeast. This phenotype was not accompanied by changes in sodium or potassium homeostasis. Under salt stress conditions, yeast cells expressing BveIF1A presented a higher rate of amino acid incorporation into proteins than control cells. In an in vitro protein synthesis system from wheat germ, the BveIF1A recombinant protein improved translation in the presence of NaCl. Finally, transgenic Arabidopsis plants expressing BveIF1A exhibited increased tolerance to NaCl. These results suggest that the translation initiation factor eIF1A is an important determinant of sodium tolerance in yeast and plants.
Theabi1‐1mutation blocks ABA signaling downstream of cADPR action
Authors: Wu Yan , Sanchez Juan Pablo , Lopez‐Molina Luis , Himmelbach Axel , Grill Erwin , Chua Nam‐Hai
Published: December 2004

Arabidopsis thaliana abscisic acid insensitive 1‐1(abi1‐1) is a dominant mutant that is insensitive to the inhibition of germination and growth by the plant hormone, abscisic acid (ABA). The mutation severely decreases the catalytic activity of the ABI1 type 2C protein phosphatase (PP2C). However, the site of action of theabi1‐1/ABI1 in the ABA signal transduction pathway has not yet been determined. Using single cell assays, we showed that microinjecting mutant abi1‐1 protein inhibited the activation ofRD29A‐GUSandKIN2‐GUSin response to ABA, cyclic ADP‐ribose (cADPR), and Ca2+. The inhibitory effect of the mutant protein, however, was reversed by co‐microinjection of an excess amount of the ABI1 protein. In transgenicArabidopsisplants, overexpression ofabi1‐1rendered the plants insensitive to ABA during germination, whereas overexpression of ABI1 did not have any apparent effect. Moreover, transgenic plants overexpressingabi1‐1were blocked in the induction of ABA‐responsive genes; however, overexpression of ABI1 did not affect gene expression. Taken together, our results demonstrate thatabi1‐1is likely to be a dominant negative mutation and ABI1 likely acts downstream of cADPR in the ABA‐signaling pathway. Our results on ABI1 overexpression inArabidopsisare not compatible with a negative regulatory role of this phosphatase in ABA responses.
Genome analysis at different ploidy levels allows cloning of the powdery mildew resistance gene Pm3b from hexaploid wheat
Authors: Yahiaoui Nabila , Srichumpa Payorm , Dudler Robert , Keller Beat
Published: December 2004

In wheat, race‐specific resistance to the fungal pathogen powdery mildew (Blumeria graminis f. sp. tritici) is controlled by the Pm genes. There are 10 alleles conferring resistance at the Pm3 locus (Pm3a to Pm3j) on chromosome 1AS of hexaploid bread wheat (Triticum aestivum L.). The genome of hexaploid wheat has a size of 1.6 × 1010 bp and contains more than 80% of repetitive sequences, making positional cloning difficult. Here, we demonstrate that the combined analysis of genomes from wheat species with different ploidy levels can be exploited for positional cloning in bread wheat. We have mapped the Pm3b gene in hexaploid wheat to a genetic interval of 0.97 centimorgan (cM). The diploid T. monococcum and the tetraploid T. turgidum ssp. durum provided models for the A genome of hexaploid wheat and allowed to establish a physical contig spanning the Pm3 locus. Although the haplotypes at the Pm3 locus differed markedly between the three species, a large resistance gene‐like family specific to wheat group 1 chromosomes was consistently found at the Pm3 locus. A candidate gene for Pm3b was identified using partial sequence conservation between resistant line Chul and T. monococcum cv. DV92. A susceptible Pm3b mutant, carrying a single‐base pair deletion in the coding region of the candidate gene was isolated. When tested in a single cell transformation assay, the Pm3b candidate gene conferred race‐specific resistance to powdery mildew. These results demonstrate that the candidate gene, a member of the coiled‐coil nucleotide binding site leucine‐rich repeat (NBS‐LRR) type of disease resistance genes, is the Pm3b gene.
Assessment of the incidence of substandard drugs in developing countries
Authors: Shakoor O. , Taylor R. B. , Behrens R. H.
Published: December 2004

In a number of developing countries there is reportedly a high incidence of the availability of substandard drugs. The majonty of these reports do not contain quantitative data to support these claims, nor do they describe the methodology employed for the quality assessment. Many assume counterfeiting as the reason for the poor quality and in some cases this is not justified. We collected 96 samples of chloroquine and selected antibacterials from Nigeria and Thailand in a controlled and methodical manner and analysed them using appropriately validated methods based on high‐performance liquid chromatography capable of detecting drug‐related impurities and quantifying active drug(s). The results indicate that 36.5% of the samples were substandard with respect to pharmacopoeial limits. Decomposition was the cause of poor quality in a number of the samples but overall, poor manufacturing appeared to be prevalent. The analyses generated little evidence to indicate fraudulent manufacturing. Treatment failure and drug‐resistance are possible consequences of the use of substandard drugs.
Malaria in Batavia in the 18th century
Authors: van den Brug P. H.
Published: December 2004

In 1733 an unknown deadly disease broke out in Batavia (now Jakarta), then the main seat of the Dutch East India Company (VOC) in Asia. Mortality among its personnel rose alarmingly and caused serious shortages of sailors, soldiers and craftsmen. Ever‐growing numbers of people had to be sent from the Netherlands to Batavia to make up for the high losses. In the end, military posts could no longer be filled, homeward‐bound vessels no longer be manned and precious cargo had to remain in Batavia. The unhealthiness of the town, ‘so deadly for the growth and prosperity of the colony [and] ruinous for the interests and finances of the Company’ (Nederburgh 1794), claimed more than 85000 victims among VOC personnel. The ‘unhealthiness of Batavia’ remained unexplained through the ages. In this paper reasons for its origin and aftermath are proposed.
Risk factors for urinary tract calculi in Trinidad
Authors: Anatol Trevor , Pereira Lexley Pinto , Simeon Donald , Sawh Lall
Published: December 2004

objective  To identify risk factors for urinary tract stones in Trinidad and Tobago.

methods  A consecutive series of patients presenting to institutions in Trinidad for the management of proven urinary tract calculi was interviewed by questionnaires designed to obtain data on age, gender, ethnicity, occupation, stone location, a family history of stone disease, a past history of certain medical diseases and a semiquantitative estimate of the magnesium intake in food, ‘over the counter’ drugs and drinking water. An equivalent number of patients attending the same institutions for follow‐up and verified from hospital records as having a previous radiological diagnosis of urinary tract stones, as well as a group of asymptomatic members of the community working in the same area, underwent the same interview. Chi‐square, anova and Kruskal–Wallis tests were used to examine differences between the groups. Multiple logistic regression analysis was used to determine persistence of the significance of these differences after controlling for confounding variables.

results  Data sufficient for analysis were obtained for 122 previous and 102 prospective patients and 102 controls. The mean age of the patients was 32 years. The ratio of males to females was 0.9–1.8:1 for the affected groups, but significantly more males than females had calculi in the lower urinary tract (19%vs. 6%; P = 0.004). More patients (30%) than controls (7%) gave a positive family history of urinary tract stone disease (P < 0.001). Affected persons had a lower dietary magnesium intake (P = 0.003), which accounted for a significantly lower total magnesium intake (P = 0.02). Logistic regression analysis of the variables studied indicated that independent predictors of the disease were a positive family history (P = 0.001), total magnesium intake (P = 0.001) and age (P < 0.001).

conclusion  A low magnesium intake and a positive family history are highly predictive of urinary tract calculi in this population.
The effect on haemoglobin of the use of iron cooking pots in rural Malawian households in an area with high malaria prevalence: a randomized trial
Authors: Geerligs Paul Prinsen , Brabin Bernard , Mkumbwa Albert , Broadhead Robin , Cuevas Luis E.
Published: December 2004

background  Innovative low‐cost sustainable strategies are required to reduce the high prevalence of iron‐deficiency anaemia in developing countries.

methods  We undertook a community‐based randomized controlled intervention trial to assess the effects of cooking in iron or aluminium cooking pots in Malawian households in an area with high malaria prevalence. Analysis was by intention to treat and consistency of use. The primary outcomes were change in haemoglobin and iron status.

findings  The study population comprised 164 participants eating from aluminium cooking pots and 158 from iron cooking pots. The mean haemoglobin change was significantly increased after 6 weeks in adults who consistently ate from an iron cooking pot (+3.6 g/l compared to −3.2 g/l, mean difference between groups 6.8 g/l, 95% CI +0.86, +12.74). In children, no significant haemoglobin change was observed in consistent pot users, although they showed a significant reduction in iron deficiency (iron 8.6 ZP/g and aluminium 10.8 ZP/g, mean difference 2.2 ZP/g, 95% CI +1.08, +3.32).

interpretation  Rural Malawian adults in a high malaria transmission area who consistently consume food prepared in iron cooking pots show a significant rise in haemoglobin after 6 weeks use. Children showed a reduction in iron deficiency, but no significant improvement in haemoglobin, possibly because of their high malaria parasite prevalence. Using iron cooking pots in developing countries could provide an innovative way to prevent iron deficiency and anaemia in malarious areas where regular iron supplementation is problematic.
Private practitioners and tuberculosis control in the Philippines: strangers when they meet?
Authors: Portero J. L. , Rubio M.
Published: December 2004

objective To investigate the knowledge, attitudes and perspectives of the Filipino private physicians (PPs) on tuberculosis (TB) control issues in the Philippines and their implications for future governmental public health policies.

design Cross‐sectional telephone survey from June to October 2001.

participants In each of the 78 provinces of the Philippines we randomly selected 10 PPs from the provincial capital city, five PPs from an urban centre with more than 50 000 population, and one PP from 15 rural villages with <50 000 population, making a total of 30 PPs per province. These data were complemented with information from focus group discussions with health workers and policy makers working in TB control, and through personal interviews with PPs.

results We interviewed 1355 (57.9%) of 2340 PPs identified. TB was diagnosed mainly through X‐ray (87.9%) and usually treated with inappropriate regimens of anti‐TB drugs (89.3%). The PPs did not follow‐up their TB patients, did not trace the defaulters (97.9%) and did not identify contacts (91.4%). Only 24.2% knew the National Tuberculosis Programme (NTP) policies in depth. They defined the NTP's weakest points as diagnosis through sputum microscopy (59.2%) and the management of smear negative patients (29.7%). Most PPs were willing to collaborate with the NTP (83.3%) provided they were paid (38.4%). More than a half (51.5%) objected to obligatory reporting of new TB cases. The PPs based their success in attracting TB patients to their offices on confidentiality (46.1%) and on the kind treatment and flexibility given (43.7%).

conclusions Diagnosis and treatment of TB patients is a daily issue for the PPs in the Philippines, although they did not follow usually the NTP guidelines. The majority of the PPs wished to collaborate with the NTP provided they were paid.