bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of the B Cell‐Attracting Chemokine CXCL13 in the Target Organ and Autoantibody Production in Ectopic Lymphoid Tissue in the Chronic Inflammatory Disease Sjögren's Syndrome
Authors: Salomonsson S. , Larsson P. , Tengnér P. , Mellquist E. , Hjelmström P. , Wahren‐Herlenius M.
Published: March 2003

Sjögren's syndrome is an autoimmune disease characterized by lymphocytic infiltrates resembling secondary lymphoid organs in salivary glands. In this study, we demonstrate the expression of the lymphoid tissue homing chemokine CXCL13 (BCA‐1/BLC), which has attracting properties for B cells and subsets of activated T cells, in salivary glands of patients with Sjögren's syndrome using immunohistochemistry and in situ hybridization. CXCL13 expression was primarily observed in epithelial cells in acini and ducts of inflamed glands while its receptor, CXCR5 (BLR‐1), was expressed on the infiltrating mononuclear cells. In addition, cells producing antibodies against one of the major autoantigens in Sjögren's syndrome, Ro 52, were identified at the periphery of the follicular infiltrates indicating that the ectopic lymphoid tissue is directly involved in the disease process. Identification of CXCL13 and CXCR5 in salivary glands suggests that the target organ plays an essential role in the inflammatory process by recruiting B and T cells. These results also provide a molecular mechanism by which lymphoid neogenesis and ectopic germinal centre formation might occur in the glands of these patients, which may be the key step in the development of the chronic inflammatory process in Sjögren's syndrome.
The Involvement of the Chemokine Receptor CXCR2 in Neutrophil Recruitment in LPS‐Induced Inflammation and in Mycobacterium avium Infection
Authors: Gonçalves A.‐S. , Appelberg R.
Published: March 2003

Knockout mice for CXC receptor 2 (CXCR2) chemokine receptor were used to study the recruitment of neutrophils during acute and chronic inflammatory responses. When treated with lipopolysaccharide (LPS), either intraperitoneally or intratracheally, these animals had a significant reduction in the neutrophil recruitment in the first 24–48 h as compared with control mice. During 15 days of intraperitoneal infection by Mycobacterium avium, the knockout mice showed significantly reduced numbers of neutrophils in the peritoneal cavity as compared with the control mice. In contrast, the recruitment of neutrophils to the lungs during an aerogenic M. avium infection was not affected by the CXCR2 mutation throughout the 60 days of the study. Finally, we could not find any impact of the mutation on the mycobacterial growth of the infected animals. These findings indicate that CXCR2 may be essentially involved in acute inflammatory responses where an early and rapid recruitment of neutrophils is observed.
Malaria Vaccine: Candidate Antigens, Mechanisms, Constraints and Prospects
Authors: CARVALHO L. J. M. , DANIEL‐RIBEIRO C. T. , GOTO H.
Published: March 2003

More than 30 years after the first report of successful vaccination against malaria using radiation‐attenuated sporozoites, an effective malaria vaccine is not yet available. However, field and experimental data indicate that it can be developed. An astonishing amount of data has accumulated concerning parasite biology, host–parasite interactions, immunity and escape mechanisms, targets and modulators of immune responses. Nevertheless, so far this knowledge has not been enough to make us understand how to properly manipulate the whole system to build an effective vaccine. In this article, we describe candidate antigens, mechanisms, targets and trials performed with potential malaria vaccines and discuss the approaches, in vivo and in vitro models, constraints and how technologies such as DNA vaccination, genomics/proteomics and reverse immunogenetics are providing exciting results and opening new doors to make malaria vaccine a reality.
Bacterially‐mediated authigenesis of clays in phosphate stromatolites
Authors: SÁNCHEZ‐NAVAS  , MARTÍN‐ALGARRA  , NIETO
Published: March 2003

Authigenic clays in close textural relation to carbonate fluorapatite within finely laminated phosphate stromatolites of Upper Jurassic age have been studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and analytical electron microscopy (AEM). Stromatolite laminae consist of hexagonal prisms of francolite (sizes ranging between 0·1 and 1 μm) that are surrounded by poorly crystalline smectite and amorphous Fe–Si–Al oxyhydroxides. Microanalyses show that smectite is Fe rich, with highly variable composition, particularly regarding Fe and Si contents. Smectite has significant beidellitic, montmorillonitic and non‐tronitic substitutions. Although the lack of fringe contrast in some areas adjacent to the smectite packets with 1·0–1·3 nm spacing is due to differences in orientation of layers, textural and analytical data clearly indicate the presence of Fe–Si–Al amorphous phases intimately intergrown with smectite. The occurrence of poorly crystalline smectite and associated amorphous phases within microbially precipitated stromatolite laminae, both as envelopes around, and as pore‐fillings between extremely small calcium phosphate crystals, demonstrates authigenic smectite growth from a precursor Fe–Si–Al amorphous material. This material is formed in close association with a phosphate‐rich precursor. The textural and structural relations, the preservation of chemical precursors of glauconite such as nontronitic montmorillonite, and the presence of Fe–Si–Al amorphous mineral phases, imply crystallization of the observed crystalline phases from synsedimentary (bacterially precipitated) amorphous precursors during early diagenesis in postoxic environments. Carbonate fluorapatite was the first phase to crystallize from the primary gel; smectite and associated amorphous Fe–Si–Al oxyhydroxides were the residual material of the crystallization process. The slow rate of transformation (at low temperatures) from Fe–Si–Al‐rich gels to smectite, explains the textural relations between the poorly crystalline phases and the phosphate crystals, as well as the preservation of amorphous substances in relation to clays. Authigenic smectite represents the first step in glauconitization.
Hydromagnesite replacement of biomineralized aragonite in a new location of Holocene stromatolites, Lake Walyungup, Western Australia
Authors: COSHELL L. , ROSEN M. R. , MCNAMARA K. J.
Published: March 2003

Holocene stromatolites are described from Lake Walyungup, a coastal hyposaline lake in south‐western Australia. At summer low water, this groundwater‐fed depression comprises two permanent shallow water bodies and an ephemeral southern pool, set within an areally extensive littoral zone of variably cemented carbonate crust. Up to 5 m of organic‐rich carbonate mud has been deposited within each of these basins in less than 7000 years. Stromatolites rim the water bodies with individual columns up to 2 m tall. Stromatolite‐capped tepee structures in subparallel alignment are widespread in the littoral crust, suggesting a linkage between stromatolite growth and zones of groundwater discharge. Lake Walyungup stromatolites, regardless of external morphology and setting, are coarsely laminated and have aragonitic mesoclot microfabrics. These microfabrics are similar to those from lithified portions of active thrombolitic microbialites from nearby Lake Clifton.

Hydromagnesite is a minor to subdominant phase (up to 47 wt%) of the carbonate mineral assemblage in Lake Walyungup. It occurs mainly in the littoral zone as a diagenetic replacement of precursor aragonite, particularly within the mesoclot fabric of stromatolites, but also in sediments (strandline and dune sand, crusts) derived mainly from erosion of stromatolites. In contrast with nonreplaced and impermeable inorganic aragonitic cements, stromatolite mesoclots are microper‐ meable. Micropermeability is inferred to facilitate hydromagnesite diagenesis. Dolomite is also present in minor amounts as a pore fill in stromatolites, and as a subdominant to dominant (up to 100 wt%) phase in thin, mudcracked micrite layers within the crust package. The layered dolomite may be precipitated directly from the lake water.

Major element abundance of the lake water is: Na+ > Mg2+ » K+ > Ca2+ for cations, and Cl− » SO42− ≈ HCO3− > CO32− for anions. Compared to other nearby coastal lakes, Lake Walyungup has a high pH (> 9·0), and an extremely high molar Mg/Ca ratio of > 90. Groundwater in the area has a Mg/Ca ratio generally less than 1. The unusual Mg/Ca ratio in Lake Walyungup is partially a result of in‐lake processes with additional minor contribution of Mg2+ sourced from basal marine sand because no Mg‐rich bedrock source has been found in the region.
Unusual intraclastic limestones in Lower Triassic carbonates and their bearing on the aftermath of the end‐Permian mass extinction
Authors: WIGNALL PAUL B. , TWITCHETT RICHARD J.
Published: March 2003

Flat pebble conglomerates were a common carbonate facies in Cambrian to Early Ordovician open marine settings, but they become extremely rare in these environments after this time. However, the Early Triassic witnessed an anachronistic reappearance of flat pebbles, together with other intraclast types, in a range of carbonate depositional settings. In south China, flat pebble conglomerates are encountered in storm‐dominated, platform carbonates to deep basinal settings, while prefossilized bivalve intraclasts and flat pebbles are common in mid‐ramp facies of northern Italy. The emplacement mechanisms of the intraclast‐bearing beds appear to have been diverse and to have included basinal turbidity flows and storm‐generated hyperconcentrated flows: true storm beds, deposited under combined flow conditions, are rare. The cause of the widespread early lithification implied by the Early Triassic intraclasts appears to have been twofold: suppression of bioturbation, allowing the preservation of thin beds, and rapid submarine lithification. Both features appear to be a response to the widespread development of benthic dysoxia/anoxia during and following the end‐Permian mass extinction. This event appears to have temporarily recreated the conditions that pertained in Cambro‐Ordovician shelf seas. Flat pebble conglomerates may, therefore, constitute a proxy indicator of stressed environmental conditions associated with global anoxic/dysoxic events.
Sedimentology of the debris‐flow‐dominated Warm Spring Canyon alluvial fan, Death Valley, California
Authors: Blair Terence C.
Published: March 2003

Facies analysis of widely distributed exposures of the 32·6 km2 and 8·1‐km‐long Warm Spring Canyon fan, central Death Valley, shows that it has been built principally by debris‐flow deposits. These deposits were derived from a mature Panamint Range catchment mostly underlain by Precambrian mudrock, quartzite and dolomite. Stacked, clast‐rich and matrix‐supported debris‐flow lobes of slightly bouldery, muddy, pebble–cobble gravel in beds 20–150 cm thick dominate the fan from apex to toe, accounting for 75–98% of most exposures. Interstratified with the debris flows are less abundant (2–25% of cuts), thinner (5–30 cm) and more discontinuous beds of clast‐supported and imbricated, pebble–cobble gravel deposited by overland flows and gully flows. This facies formed by the surficial fine‐fraction water winnowing of the debris flows primarily during recessional flood stage of the debris‐flow events. Two other facies associations make up a small part of the fan. The incised‐channel tract consists of a 250‐m‐wide clast‐supported ribbon of irregularly to thickly bedded, boulder, pebble, cobble gravel nested within debris‐flow deposits. This channel fill is oriented generally perpendicular to the Panamint range front. It formed by extensive erosion and winnowing of debris flows deposited within the incised channel, into which all water discharge from the catchment is funnelled. The limited presence of this facies only straddling the present incised channel indicates that this channel overall has maintained a consistent position on the fan except for slight lateral shifts, some caused by strike‐slip offset. Fault offset temporarily closed the upper incised channel, causing recessional debris‐flow mud to be ponded behind the dam. The other local facies assemblage consists of subrounded to rounded, moderately sorted pebble gravel in low‐angle cross‐beds that slope both basinwards and fanwards. This gravel was deposited in beachface, backshore and shoreface barrier‐spit environments that developed where Lake Manly impinged on the Warm Spring fan during late Pleistocene time. These deposits straddle headcuts into, and were derived from, erosion of the debris‐flow deposits. Wave energy sorted finer sediment from the shore zone, concentrated coarser sediment and rounded the coarse to very coarse pebble fraction by selective reworking.
Distinguishing base‐surge deposits and volcaniclastic fluviatile sediments: an ancient example from the Lower Devonian Snowy River Volcanics, south‐eastern Australia
Authors: Bull Stuart W. , Cas
Published: March 2003

A 500‐m‐long road cutting in the Lower Devonian Snowy River Volcanics (SRV), eastern Victoria, Australia, exposes phreatomagmatic units and volcaniclastic sediments. Based on bed geometry, sorting and sedimentary structures, it was possible to distinguish base‐surge deposits from ephemeral fluvial deposits in this relatively well‐exposed ancient succession. Where the base‐surge deposits infill irregular topography, bed sets mantle the pre‐existing surface but thicken into topographic lows. In contrast, where the fluvial deposits infill topographic depressions, beds onlap laterally against channel walls. In addition, curvi‐planar slide surfaces within the base‐surge deposits generated by inter‐eruptive slumping indicate rapid emplacement as a constructional tuff rampart (? maar). The base‐surge deposits are always poorly sorted and commonly contain accretionary lapilli, reflecting their deposition from turbulent, low‐particle‐concentration, steam‐rich pyroclastic currents. In contrast, the fluvial deposits are relatively well‐sorted, reflecting hydraulic sorting and winnowing during tractional transport and deposition. There are significant differences in the types of sedimentary structures present. (1) Bedding in the base‐surge deposits is entirely tabular, and beds can be traced laterally to the limits of the outcrop. In contrast, the fluvial deposits have abundant internal scour surfaces that result in beds/bedding intervals lensing out laterally over intervals of the order of 5–10 m. (2) Cross‐beds with relatively high‐angle foresets are restricted to the fluvial deposits. (3) Laterally persistent tabular beds that contain abundant, densely packed accretionary lapilli are restricted to the base‐surge deposits. In summary, although base‐surge deposits and ephemeral fluvial deposits can appear superficially similar, it is possible to apply facies models carefully to distinguish between them, even in ancient successions.
Composition and origin of clay minerals in Holocene sediments from the south‐eastern North Sea
Authors: Zuther Michael , Brockamp Olaf , Clauer Norbert
Published: March 2003

The distribution of clay minerals varies systematically in sediments from Holocene core material taken along a profile from the East Frisian coast to the Doggerbank. The proportion of illite increases with distance from the coast at the expense of kaolinite, whereas slight variations are seen in smectite and chlorite abundances. The chemical composition changes, and the K/Rb ratio and K‐Ar isotopic age of illite increase seawards. This trend results from progressive mixing processes of riverine detritus with Pleistocene fluvioglacial material reworked during the Holocene transgression. However, the clay fluvial flux only became dominant during the decreasing rate of sea‐level rise in the Late Holocene, especially near the shore. For example, modern sediments in tidal flats contain 75% of river‐borne Holocene‐supplied clay detritus, whereas this amount is only 10% in modern marine sediments at the Doggerbank.
Palaeoenvironmental records in Holocene Spanish tufas: a stable isotope approach in search of reliable climatic archives
Authors: Andrews Julian E. , Pedley Martyn , Dennis Paul F.
Published: March 2003

Tufa deposits are potential terrestrial archives of palaeoenvironmental and palaeoclimatic information. This study assesses the potential of stable isotopic archives from two closely juxtaposed Holocene tufa sites in SE Spain. The Ruidera site contains deep‐water lacustrine micrites and tufas, whereas the nearby Alcaraz site represents a shallow barrage tufa. Understanding site characteristics is critical to interpreting the stable isotopic variations. These Holocene lacustrine micrites have isotopic compositions consistent with modern European lake shore microbial carbonates, where the isotopic chemistry is strongly influenced by hydrological and residence time effects. All the lacustrine micrite δ13C values were influenced by microenvironmental microbial effects to some degree. Because of these effects, stable isotope data from lacustrine microbial micrites and tufas will not normally yield precise information on the isotopic composition of palaeoprecipitation, temperature or vegetation composition of an area. In contrast, Holocene tufas that formed in shallow, fast‐flowing riverine settings may contain valuable palaeoclimatic archives. The tufa deposits must be largely autochthonous, as at Alcaraz, where in situ reed stem encrustations are present. Records of relative change in air temperature and changes in the source of airmasses are potentially resolvable in the δ18O data. These interpretations can be verified by other independent climatic data where chronology is constrained. Variations in riverine tufa δ13C values probably record changes in local vegetation and/or soil respiration. Covariation between δ18O and δ13C values may be intrinsically linked to climatic factors such as aridity. Tentative palaeoclimatic interpretations for the middle Holocene at Alcaraz based on the isotope data suggest warming (or increasing influence of Mediterranean‐sourced precipitation) between approximately 5000–3000 radiocarbon years BP, accompanied by increased aridity. These interpretations are consistent with the sparse independent palaeoclimatic data and climate modelling results for the Holocene of SE Spain. This study supports the growing evidence that well‐chosen tufa sites could yield valuable palaeoclimatic information.
An ocean‐facing Aptian–Albian carbonate margin, Oman
Authors: Immenhauser A. , Van Der Kooij B. , Van Vliet A. , Schlager W. , Scott R. W.
Published: March 2003

A high‐energy Aptian–Albian platform margin in northern Oman fronted onto an open oceanic basin, making the area a valuable analogue for coeval guyot margins. Most similar aged carbonate margins described in the literature faced either intracratonic or minor oceanic basins. The studied margin is characterized by a stabilized outer rim, which, although it did not rise discernibly above the adjacent lagoonal deposits, flanked a steep upper slope (32–40°) basinwards with a relief of at least 30 m. Two main facies provided the rigidity of the outer margin:Lithocodiumboundstones that constituted up to 50% of the rock volume; and marine fibrous cements that occluded up to 35% of primary pore space. In contrast, coral–rudist patches and other shelly sessile benthos were distributed irregularly, and the rudist bioherms of the outer margin were often disrupted, with shells being transported and redeposited. The inner margin is characterized by wedge‐shaped storm layers that radiate from the platform top lagoonwards, where they interdigitate with carbonate sands and small rudist bioherms. Polygenetic discontinuity surfaces that bear evidence of both marine hardground and subaerial exposure stages are prominent features of the margin. Throughout the latest Aptian to Middle Albian, the platform succession recorded some 30 relative sea‐level falls, of which seven reached amplitudes of many tens of metres. These seven high‐amplitude falls in sea level are recorded across the entire south‐eastern portion of the Arabian craton and are probably of eustatic origin.
Isotopic constraints on growth conditions of multiphase calcite–pyrite–barite concretions in Carboniferous mudstones
Authors: Raiswell R. , Bottrell S. H. , Dean S. P. , Marshall J. D. , Carr A. , Hatfield D.
Published: March 2003

Carbonate concretions in the Lower Carboniferous Caton Shale Formation contain diagenetic pyrite, calcite and barite in the concretion matrix or in different generations of septarian fissures. Pyrite was formed by sulphate reduction throughout the sediment before concretionary growth, then continued to form mainly in the concretion centres. The septarian calcites show a continuous isotopic trend from δ13C=−28·7‰ PDB and δ18O=−1·6‰ PDB through to δ13C=−6·9‰ PDB and δ18O=−14·6‰ PDB. This trend arises from (1) a carbonate source initially from sulphate reduction, to which was added increasing contributions of methanogenic carbonate; and (2) burial/temperature effects or the addition of isotopically light oxygen from meteoric water. The concretionary matrix carbonates must have at least partially predated the earliest septarian cements, and thus used the same carbonate sources. Consequently, their isotopic composition (δ13C=−12·0 to −10·1‰ PDB and δ18O=−5·7 to −5·6‰ PDB) can only result from mixing a carbonate cement derived from sulphate reduction with cements containing increasing proportions of carbonate from methanogenesis and, directly or indirectly, also from skeletal carbonate. Concretionary growth was therefore pervasive, with cements being added progressively throughout the concretion body during growth. The concretions contain barite in the concretion matrix and in septarian fissures. Barite in the earlier matrix phase has an isotopic composition (δ34S=+24·8‰ CDT and δ18O=+16·4‰ SMOW), indicating formation from near‐surface, sulphate‐depleted porewaters. Barites in the later septarian phase have unusual isotopic compositions (δ34S=+6 to +11‰ CDT and δ18O=+8 to +11‰ SMOW), which require the late addition of isotopically light sulphate to the porewaters, either from anoxic sulphide oxidation (using ferric iron) or from sulphate dissolved in meteoric water. Carbon isotope and biomarker data indicate that oil trapped within septarian fissures was derived from the maturation of kerogen in the enclosing sediments.
Morphological variation and mating compatibility within the mealybugs Pseudococcus calceolariae and P. similans (Hemiptera: Pseudococcidae), and a new synonymy
Authors: Charles John G. , Froud Karyn J. , Henderson Rosa C.
Published: March 2003

A laboratory study of isolines of Pseudococcus calceolariae (Maskell) and P. similans (Lidgett) collected from Hawke's Bay and Auckland, two widely separated regions in the North Island of New Zealand, threw doubt on the validity of the defining characters of these species. For P. similans, the number and position of oral rim tubular ducts varied widely and sometimes fell outside the defined limits for the species, and characteristic ‘stout abdominal setae’ were lost in the F1 generation. The morphological characters that separate one species from the other were manipulated by changing the temperature at which the mealybugs developed, such that cohorts of F1 sisters reared in the laboratory contained phenotypes of both P. calceolariae and P. similans. No impediments were found to breeding among populations of P. calceolariae and P. similans from Hawke's Bay and Auckland. All combinations of crosses between virgin females and males produced viable progeny. Those reared at 16°C laid more eggs than those reared at 23°C. The data did not suggest the existence of cryptic or sibling species, and contrasted with experiments elsewhere which quite clearly showed species incompatibility of closely related mealybugs. Examination of 160 ‘wild’ specimens of P. calceolariae from New Zealand, Australia and California (U.S.A.) and P. similans from New Zealand and Australia showed a morphological continuum from one species to the other. It is concluded that P. calceolariae and P. similans merely represent the phenotypic extremes of one widely polymorphic species, with the morphological characters of individual adults determined by the microenvironment in which they developed. Pseudococcus calceolariae is thus the senior synonym of P. similans.
Phylogenetic revision of the Charis cleonus complex (Lepidoptera: Riodinidae)
Authors: HARVEY DONALD J. , HALL JASON P. W.
Published: March 2003

Abstract.  A revision of the Charis cleonus group of Neotropical riodinid butterflies is presented, including discussions on the taxonomy, biogeography and biology of its species, and illustrations of the adults and male and female genitalia (where known) of all taxa. We recognize twenty‐two species, including nineteen new species: C. ariquemes sp.n., C. brasilia sp.n., C. breves sp.n., C. cacaulandia sp.n., C. cuiaba sp.n., C. humaita sp.n., C. ipiranga sp.n., C. iquitos sp.n., C. ma sp.n., C. manicore sp.n., C. manu sp.n., C. matic sp.n., C. maues sp.n., C. negro sp.n., C. palcazu sp.n., C. rocana sp.n., C. santarem sp.n., C. tapajos sp.n and C. tefe sp.n. A cladistic analysis using thirty‐six characters of male and female genitalia and external facies generated a single most parsimonious cladogram highlighting the existence of two clades, the major and cleonus subgroups. As each species largely occupies a parapatric range, this cladogram provides the opportunity to reassess historical relationships among areas of endemism in the Amazon basin.
Evolution of the magmatic plumbing system at Mt Etna: new evidence from gravity and magnetic data
Authors: Rollin PJ. , Cassidy J. , Locke C.A. , Rymer H.
Published: March 2003

New gravity and aeromagnetic data from Mt Etna volcano are presented which provide evidence for and constraints on relatively dense, high magnetization bodies at shallow levels below the summit craters. These are modelled and interpreted in terms of dyke/sill complexes, which may be the sites of short‐term magma storage. A similar but larger body with high density and high magnetization is modelled below the southern wall of the Valle de Bove and may be the remnant of a prehistoric storage system. This body is close to the Valle del Bove, a major collapse feature, and may have influenced its geometry by buttressing and/or focusing zones of weakness.
The border of the East‐European Craton in south‐eastern Poland based on gravity and magnetic data
Authors: Grabowska T. , Bojdys G.
Published: March 2003

According to recent geological interpretations, the border of the East‐European Craton (EEC) in SE Poland is located in the NE foreland of the Holy Cross Mts. Results of gravity and magnetic anomaly interpretations presented herein confirm this. According to 3D and 2D gravity and magnetic modelling, the EEC borders the SW flank of the regional crystalline feature with increased magnetic and density properties, which occur in the SE part of the Teisseyre–Tornquist Zone (TTZ). This flank rests near a deep fracture delimiting the TTZ on SW. The feature is a cause of the regional magnetic gradient observed there. Two SE–NW belts of residual gravity anomalies (dislocations) are also identified in the magnetic gradient zone, cutting Mesozoic and Palaeozoic formations. Results of geophysical and geological investigations show the importance of this dislocation zone and confirm that it occurs in all crustal complexes and the upper mantle.
Karst in granitic rocks, South Cameroon: cave genesis and silica and taranakite speleothems
Authors: Willems L. , Compère Ph. , Hatert F. , Pouclet A. , Vicat J. P. , Ek C. , Boulvain F.
Published: March 2003

ABSTRACT A cave in granitic rocks was studied in Mezesse, South Cameroon. Coralloid speleothems, draperies and dissolution traces on the cave walls attest to its truly karstic nature. The speleothems consist of microlayers of opal and taranakite (K,NH4)Al3(PO4)3(OH).9H2O. They indicate a significant mobilization of silica, Al and K from granite during the formation of the cave. Identification of silicified bacteria in the speleothems layers suggests a possible role of these micro‐organisms in silica deposition. The presence of taranakite and of silicified organic remains within the speleothems lead to a better understanding of the genesis of the cave.
Particle size distributions of fault rocks and fault transpression: are they related?
Authors: Billi Andrea , Storti Fabrizio , Salvini Francesco
Published: March 2003

ABSTRACT Laboratory experiments on rock faulting show that processes of particle comminution in fault rocks are influenced by several parameters, including fault strike and normal stress across faults. In nature, normal stress across faults increases with increasing transpressional strike of faults. Accordingly, different structural fabrics and particle size distributions are expected for cataclastic rocks that have developed along faults with different transpressional orientations and comparable displacements within regional‐scale strike‐slip fault zones. Adjacent bands of cataclastic gouge and breccia were analysed from four small‐scale fault zones. All have comparable displacements and very similar protolith (i.e. shallow‐water limestone), structure, kinematics, size, and tectonic environment, but different transpressional strikes within the regional‐scale left‐lateral Mattinata strike‐slip fault, Italy. An inverse linear relationship is found between fault transpressional angles and fractal dimensions of particle size distributions from cataclastic rock samples.
Deep‐sea ostracods as indicators of palaeoceanographic changes: a case history from the middle–late Miocene of southern Italy (Central Mediterranean)
Authors: Dall'Antonia Barbara
Published: March 2003

ABSTRACT The middle–late Miocene palaeoceanography of the Central Mediterranean was investigated using bio‐chronostratigraphically constrained (estimated ages are based on plancktonic foraminifers) ostracod faunas from the Tremiti Islands and the Hyblean Plateau (southern Italy). Specifically, differences and similarities between the hydrographical evolution of the two study areas, inferred from the ostracod record, are herein used to provide new insights into the evolution of the Mediterranean deep‐water circulation. Ostracod assemblage compositions suggest a simultaneous progressive trend from deep thermospheric towards psychrospheric conditions in both the areas during the Langhian. However, this trend seems to have developed fully only in the Hyblean Plateau. Notably, the first sign of an oceanic deep water‐mass supply is shown by the almost synchronous entry of the upper psychrospheric genus Agrenocythere in the middle Langhian. The youngest reliable evidence of deep oceanic influences (common occurrence of Agrenocythere) in the Central Mediterranean comes from the Tremiti Islands and dates back to the earliest Serravallian. Similarities between the two study areas suggest large‐scale modifications in the Central Mediterranean deep basins. This hypothesis is discussed in the context of the global middle Miocene oceanographic scenario.
Identification and molecular mapping of a single Arabidopsis thaliana locus determining resistance to a phytopathogenic Pseudomonas syringae isolate
Authors: Debener Thomas , Lehnackers Hiltrud , Arnold Martin , Dangl Jeffery L
Published: March 2003

We present a model pathosystem to dissect genetically the disease resistance response of plants against phytopathogenic bacteria. The interaction between Pseudomonas syringae pathovar maculicola (Psm) and Arabidopsis thaliana displays phenotypic variaion which depends on the genotype of both partners. Compatible interactions are defined by sustained inplanta bacterial growth and are normally accompanied of their appearance. For compatible interactions, resistance is defined by limited in‐planta bacterial growth accompanied by a typical ‘hypersensitive response’ (HR). We show that at least parts of this system fit the paradigms of Flor’s ‘gene‐for‐gene’ hypothesis. We identify functionally a putative bacterial avirulence gene (avrRpm 1) from a Psm isolate which conditions the HR on A. thaliana ecotypes Oy‐0 abd Col‐ 0, but not Nd‐0. We also demonstrate that resistance to the Psm strain from which avrRpm1 was isolated segregates as a single trait in the crosses Col‐o x Nd‐0 and Nd‐0 x Oy‐0. Furthermore, we map this locus (RPM1) molecularly in the Col‐0 x Nd‐0 cross to a relatively small interval defined by two RFLP markers on A. thliana chromosome 3. Resistance in the second cross also maps to this locus and cosegregates with resistance to avrRpm1.
Molecular analyses of a barley multigene family homologous to the yeast protein kinase gene SNF1.
Authors: Halford NG , Vicente‐Carbajosa J , Sabelli PA , Shewry PR , Hannappel U , Kreis M
Published: March 2003

Genomic sequences homologous to the yeast gene SNF1 have been isolated from barley (Hordeum vulgare) cv. Sunbar. SNF1 encodes a protein serine/threonine kinase required for the derepression of a number of genes, including SUC2 (invertase) in response to glucose deprivation. Southern blotting showed the presence of a family of related genes in barley and full‐length sequences have been determined for two members of the family, one of which lacks an exon and is almost certainly non‐ functional. A partial sequence has been obtained for a third member of the family. The transcription start site of one of the genes has been determined by S1 nuclease protection. A transcript almost identical in sequence to the exons of one of the genes has been amplified from barley endosperm mRNA using the polymerase chain reaction. One of the full‐length genomic sequences contains nine introns and 10 exons and the number and position of the introns in the second full‐length sequence is identical except that it lacks exon 2. However, the length and sequence of the introns vary. Northern blot analyses indicated that related transcripts are present in aleurones, coleoptiles, endosperms, internodes, leaves, ovules, roots and root tips, with highest levels of expression in the aleurones and endosperms.
Efficient initiation of translation at non‐AUG triplets in plant cells.
Authors: Gordon K , Futterer J , Hohn T
Published: March 2003

The efficiency of translation initiation at triplets differing at one residue from AUG was tested by transient expression in protoplasts from two different plant species. All possible alternative codons were tested. Some triplets showed significant CAT activity, with CUG (30% of the AUG activity) being most active. Most others had between 5 and 15% of the activity obtained from AUG, whereas UUG and AUC yielded about 2% and the two composed only of purines, AAG and AGG, had no significant activity. Translation initiation from AUC, especially, responded to leader sequences outside the immediate context which did not affect translation initiation from AUG.
Metabolic regulation of rice α‐amylase and sucrose synthase genes in planta
Authors: Karrer Erik E. , Rodriguez Raymond L.
Published: March 2003

Isolated rice embryos were used to investigate the regulatory effects of endosperm extracts and pure sugars on the expression of α‐amylase gene RAmy3D and a sucrose synthase gene homologous to the maize isozyme Ss2. The high‐level expression of RAmy3D in the scutella of isolated embryos could be inhibited by a variety of sugars as well as endosperm extracts from germinated rice grains. Glucose, at a concentration of 250 mM, was most effective in repressing RAmy3D mRNA accumulation. Furthermore, this repression was reversible. Interestingly, RAmy3D repression was always accompanied by the induction of sucrose synthase gene expression. These results support a model in which the expression of α‐amylase and sucrose synthase genes in the rice scutellum are counter‐regulated by the influx of sugars from the endosperm.
A Brassica napus gene family which shows sequence similarity to ascorbate oxidase is expressed in developing pollen. Molecular characterization and analysis of promoter activity in transgenic tobacco plants
Authors: Albani Diego , Sardana Ravinder , Robert Laurian S. , Altosaar Illimar , Arnison Paul G. , Fabijanski Steven F.
Published: March 2003

The genomic clone named Bp 10 contains a member of a small pollen‐specific gene family of B. napus. The expression of the Bp 10 gene family is maximal in early binucleate microspores and declines considerably in mature trinucleate pollen. Homologues of the Bp 10 genes are expressed in the pollen of other plant species. The pollen‐specific expression of the gene contained in the genomic clone was confirmed in tobacco plants transformed with a chimeric Bp 10 promoter/GUS construct. A promoter fragment of 396 bp is sufficient to direct a strong and correct spatial and temporal expression in transgenic plants. The Bp 10 gene family codes for proteins of 62 kDa showing approximately 30% sequence identity to cucumber and pumpkin ascorbate oxidases (AAOs). However, the AAO active centres are not conserved in the Bp 10 products, suggesting an evolutionary relationship but a different enzymatic activity for these proteins. Expression of a recombinant Bp 10 protein in E. coli inhibits bacterial growth on minimal medium, suggesting the production of an enzymatically active polypeptide in bacteria. No AAO activity could be correlated with the expression of the recombinant protein. Moreover, substances affecting AAO activity do not appear to influence the inhibitory activity of the protein produced in bacteria. However, as indicated by the rescue of bacterial growth in the presence of sodium bicarbonate or gaseous CO2, the Bp 10 protein activity could be modulated by CO2 levels.
Characterization of the catalase antioxidant defense gene Cat1 of maize, and its developmentally regulated expression in transgenic tobacco
Authors: Guan Lingqiang , Scandalios John G.
Published: March 2003

A genomic clone containing the maize Cat1 gene has been isolated and its complete DNA sequence determined. The start of transcription has been mapped by primer extension. Six introns were identified in the Cat1 coding region. In order to determine the tissue‐specific expression pattern of the Cat1 gene, promoter‐reporter gene fusion constructs were made consisting of 2.5 kb and 0.8 kb of the 5′Cat1 sequence fused to the coding region of the β‐glucuronidase (GUS) gene. These fusion constructs were introduced into Nicotiana tabacum cv. Burley 21 and the expression of Cat1—GUS in various tissues was examined. In transgenic tobacco, the Cat1 promoter can drive GUS activity starts to accumulate at about 10 days after flowering, reaching a maximum at about 22 days after flowering, and decreases thereafter, but persists until after seed desiccation through early germination. Low levels of GUS activity can be detected in pollen. This corresponds to the Cat1 expression pattern observed in maize.
A procedure for mapping Arabidopsis mutations using co‐dominant ecotype‐specific PCR‐based markers
Authors: Konieczny Andrzej , Ausubel Frederick M.
Published: March 2003

A set of mapping markers have been designed for Arabidopsis thaliana that correspond to DNA fragments amplifed by the polymerase chain reaction (PCR). The ecotype of origin of these amplified fragments can be determined by cleavage with a restriction endo‐nuclease. Specifically, 18 sets of PCR primers were synthesized, each of which amplifies a single mapped DNA sequence from the Columbia and Landsberg erecta ecotypes. Also identifed was at least one restriction endonuclease for each of these PCR products that generates ecotype‐specific digestion patterns. Using these co‐dominant cleaved amplified polymorphic sequences (CAPS), an Arabidopsis gene can be unambiguously mapped to one of the 10 Arabidopsis chromosome arms in a single cross using a limited number of F2 progeny.
Molecular analysis of three maize 22 kDa auxin‐binding protein genes — transient promoter expression and regulatory regions
Authors: Schwob Etienne , Choi Soon‐Yong , Simmons Carl , Migliaccio Fernando , Ilag Lawrence , Hesse Thomas , Palme Klaus , Söll Dieter
Published: March 2003

The site I 22 kDa auxin‐binding proteins from maize are encoded by a small gene family comprising at least five members. Here the cloning and molecular analysis of the Zm‐ERabp1, Zm‐ERabp4, and Zm‐ERabp5 genes is presented. All three encode 22–23 kDa proteins displaying a transit peptide, a C‐terminal KDEL sequence, as well as glycosylation and auxin‐binding sites. The Zm‐ERabp4 and Zm‐ERabp5 genes are very similar. The Zm‐ERabp1 gene encodes a related protein, but its promoter, leader and signal peptide are very different. Northern analysis using gene‐specific oligonucleotide probes indicates that Zm‐ERabp4 is expressed in leaves and coleoptiles but weakly in roots, whereas Zm‐ERabp5 expression is barely detectable in these tissues. RNA‐PCR indicated that all three genes are none the less expressed in many tissues. Primer‐extension analysis revealed an unusually long (320 bases) Zm‐ERabp1 leader containing an 80 codon ORF which, if expressed, would encode a positively charged protein with some similarity to transcription factors. In a transient promoter—reporter gene expression system using maize leaf protoplasts the Zm‐ERabp1 promoter is more active than the Zm‐ERabp4 and Zm‐ERabp5 promoters. Promoter deletion analysis of Zm‐ERabp1 has identified a negative regulatory sequence in a region from −364 bp and −130 bp, deletion of which results in about twofold higher expression. This region contains both enhancer‐ and G‐box‐related sequences. Deletion of −129 bp to +64 bp, which contains the TATA box and transcription start, results in a large decrease in expression.
Pathogen, salicylic acid and developmental dependent expression of a β‐1,3‐glucanase/GUS gene fusion in transgenic tobacco plants
Authors: Hennig Jacek , Dewey Ralph E. , Cutt John R. , Klessig Daniel F.
Published: March 2003

The 5′ flanking region of a gene encoding an acidic β‐1,3‐glucanase from Nicotiana tabacum was isolated and characterized. A chimeric gene composed of 1759 bp of the promoter sequence from the PR‐2 gene was fused to the β‐glucuronidase (GUS) coding region and used to transform tobacco. Transcriptional activation of the PR‐2 promoter was investigated in response to inoculation with tobacco mosaic virus (TMV), after treatment of leaves with salicylic acid (SA), and in specific tissues during the normal development of healthy plants. In TMV‐inoculated transgenic plants, GUS activity was induced locally around necrotic viral lesions and systemically in uninoculated leaves. GUS activity was also induced by treatment of leaves with SA. The chimeric gene was expressed in floral organs of healthy plants and in newly germinated seedlings. Analyses of a series of 5′ deletions of the glucanase promoter indicated that the cis‐acting elements necessary for induction by all these signals are localized in the region between −321 bp and −607 bp upstream of the transcription start site.
Light‐ and sucrose‐dependent gene expression in photomixotrophic cell suspension cultures and protoplasts of rape (Brassica napus L.)
Authors: Harter Klaus , Talke‐Messerer Christiane , Barz Wolfgang , Schäfer Eberhard
Published: March 2003

Light‐dependent gene expression was analysed in photomixotrophic cell suspension cultures of rape (Brassica napus L.) growing in media containing either 2.0% or 0.6% sucrose. During growth in darkness phytochrome type I and NADPH‐protochlorophyllide oxidoreductase (Pchlide reductase) accumulated in both cell culture lines to a similar extent. Illumination with continuous white, blue or red light, but not with far‐red light, resulted in disappearance of both chromoproteins within 24 h in both cell cultures. Further analysis showed that the phytochrome system of rape cell cultures reacts in a similar way to that of re‐etiolated dicotyledonous plants, showing rapid Pfr destruction and rapid Pfr dark reversion. In contrast, the light‐dependent expression of genes encoding the major chlorophyll a‐ and b‐binding protein (CAB) and the re‐accumulation of chlorophyll were found to be strongly dependent on sucrose concentration in culture media. Whereas cells grown in darkness in medium containing 2.0% sucrose showed, after exposure to continuous white light, a very weak re‐induction of CAB mRNA, CAB protein and chlorophyll accumulation, the cells in medium containing 0.6% sucrose reacted very strongly. It was also possible to demonstrate that phytochrome (by high irradiance response, HIR, and by low fluence response, LF) and the blue/UV‐A receptor are involved in the light‐dependent gene expression of CAB. Similar to complete cells, protoplasts derived from the two different cell cultures showed an almost identical sucrose concentration‐dependent and light‐quality‐dependent regulation of CAB mRNA accumulation. As the dark‐grown photomixotrophic cells and protoplasts reflect some typical photoregulatory characteristics known from dark‐grown plants it is supposed that this system will be an excellent tool for studying biochemical and molecular biological aspects of light‐dependent signal transduction in cells of higher plants.
The role of of laccase in lignification
Authors: O'Malley David M. , Whetten Ross , Bao Wuli , Chen Chen‐Loung , Sederoff Ronald R.
Published: March 2003

The enzymatic mechanism of monolignol polymerization in lignin biosynthesis is not known, although it has been the subject of significant interest for more than 60 years. Peroxidase had been considered to be the exclusive plant enzyme involved in the oxidative polymerization of lignin precursors. Recently, laccase and laccase‐like oxidase activities have been associated with lignification. Laccase is bound to lignifying plant cell walls and can polymerize lignin precursors in vitro. Strong circumstantial evidence from different species implicates this enzyme in the polymerization of lignin precursors. Lignin has a complex structure and it has been difficult to analyze the heterogeneity of lignin by chemical and physical techniques. If lignin precursors are polymerized by enzymes that differ in their catalytic properties, then lignin heterogeneity could be produced by differential expression of multiple enzymes during plant development. When laccase genes are correctly identified, these ideas can be tested in genetic experiments where gain or loss of function can be predicted by the presence or absence of the functional gene.
Co‐assembly properties of higher plant microtubule‐associated proteins with purified brain and plant tubulins
Authors: Schellenbaum Paul , Vantard Marylin , Peter Christine , Fellous Arlette , Lambert Anne‐Marie
Published: March 2003

The knowledge of higher plant microtubule‐associated proteins (MAPs) remains limited to a few examples that illustrate essentially their binding properties to preformed microtubules as described in carrots. Using taxol‐stabilized microtubules a putative MAP‐enriched fraction has been isolated in maize cultured cell extracts, one of these polypeptides is immunologically related to neural tau. At present, these proteins are being characterized by co‐assembly assays that were not possible before. Similar experiments were done also in a heterologous system using brain tubulin. Three polypeptides out of seven that constituted the MAP fraction were found to co‐assemble specifically with tubulin subunits of both origins. Their apparent molecular weights are 67, 83 and 125 kDa. A two‐dimensional gel immunoblot of the 83 kDa polypeptide with tau antibodies revealed one major spot. Polypeptides were quantiated by scanning the gels. These results shed light on the present debate on higher plant MAPs and their potential activity in the regulation of microtubule assembly and function in the higher plant cell.