bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistent infection of Mongolian jirds with a non-pathogenic trypanosome,Trypanosoma (Herpetosoma) grosi
Authors: SATO H. , ISHITA K. , MATSUO K. , INABA T. , KAMIYA H. , ITO M.
Published: October 2003

Non-pathogenic trypanosomes of the subgenusHerpetosomaare normally host specific, and laboratory models includeTrypanosoma lewisiin rats andTrypanosoma musculiin mice. Two isolates ofTrypanosoma grosi, originating fromApodemus agrariusandApodemus peninsulae, grew well in Mongolian jirds,Meriones unguiculatus, after intraperitoneal inoculation of 2×105or a minimum 500 bloodstream forms. The course ofT. grosiinfection in jirds resembledT. musculiinfection in mice, rather thanT. lewisiinfection in rats. At week 2 to 3 p.i. trypanosomes disappeared from the bloodstream, and neither prednisolone treatment nor splenectomy prevented parasite elimination from the bloodstream. However, these treatments induced a marked increase in peak parasite counts. Regardless of prednisolone treatment or splenectomy, all jirds after day 21 p.i. became resistant to the reinfection. Although no trypanosomes were detected in the bloodstream of recovered jirds, dividing parasites persisted in the medullary capillaries of the kidney, likeT. musculiinfection in mice. We propose theT. grosiinfection in jirds as an additional laboratory model for the study of non-pathogenic trypanosomes.
What isBabesia microti?
Authors: GOETHERT H. K. , TELFORD S. R.
Published: October 2003

Babesia microti(Apicomplexa: Piroplasmida) has historically been considered a common parasite of Holarctic rodents. However, human babesiosis due to this species has generally been limited to the northeastern seaboard of the United States and Minnesota and Wisconsin. The absence of reports ofB. microtibabesiosis from sites where the agent is enzootic, such as in western Europe, remains unexplained. Previous work focusing on the 18S rDNA demonstrates little sequence diversity among samples from allopatric host populations across a wide geographical area. It may be that genetic diversity is underestimated due to sample size or the gene analysed. Accordingly, we collected blood or spleen samples from American or Eurasian animals with parasites that were morphologically consistent withB. microti, amplified the 18S rDNA andbeta-tubulin gene, and conducted phylogenetic analysis. Surprisingly, what was considered to be ‘B. microti’ by microscopy appears to be a diverse species complex. We identify 3 distinct clades within this complex, including parasites from non-rodent hosts. Rodent parasites comprise 2 clades, one representing zoonotic isolates, and the other apparently maintained in microtine rodents, and therefore their morphological detection within animals from a site does not necessarily imply a risk to public health.
Impact of parental onchocerciasis and intensity of transmission on development and persistence ofOnchocerca volvulusinfection in offspring: an 18 year follow-up study
Authors: KIRCH A. K. , DUERR H. P. , BOATIN B. , ALLEY W. S. , HOFFMANN W. H. , SCHULZ-KEY H. , SOBOSLAY P. T.
Published: October 2003

This study analysed the impact and the extent by which parentalOnchocerca volvulusinfection, intensity of transmission ofO. volvulusinfective 3rd-stage larvae (L3) and anthropometric factors may influence the acquisition, development and persistence ofO. volvulusinfection in offspring. A total of 15 290 individuals in 3939 families with 9640 children were surveyed for microfilariae ofO. volvulus, and prevalence and level ofO. volvulusinfection in children aged 0 to 20 years from infected and non-infected parents were followed longitudinally for 18 years. Children fromO. volvulus-infected mothers had not only a substantially higher risk to become infected; they also acquired infection earlier in life and developed higher infection levels. Multiple logistic regression analysis showed that maternalO. volvulusinfection and children's age are the predominant predictors for patentO. volvulusinfection, while the intensity of transmission, measured by the annual transmission potential (ATP) ofO. volvulusL3, was less decisive. Longitudinal follow up of children showed that during vector control activities by the Onchocerciasis Control Programme (OCP) and in low-level transmission areas, infection persisted at higher levels in children fromO. volvulus-positive mothers. In summary, the dominant risk factor for children to become infected is maternal onchocerciasis, and also age-associated factors will strongly impact on the development of patentO. volvulusinfection in offspring.
Interspecific interactions between Acanthocephala in the intestine of brown trout: are they more frequent in Ireland?
Authors: BYRNE C. J. , HOLLAND C. V. , KENNEDY C. R. , POOLE W. R.
Published: October 2003

The aim of this paper was to test the hypothesis that when the 2 species of AcanthocephalanPomphorhynchus laevisandAcanthocephalus clavulaare found concurrently within the intestine of brown trout under field conditions, they have the potential to interact negatively. Evidence has shown that Acanthocephala are more likely to exhibit negative interactions with their own and other species, under both field and experimental conditions. Furthermore, the likelihood of these interactions is increased in Ireland because of the absence of certain definitive hosts and the fact that concurrent infections by two or more species of Acanthocephala are more commonly observed in fish. Data collected from wild and stocked brown trout and from 2 lakes provided an opportunity to compare the 2 potentially interacting helminth species in their fundamental and realized niche and several pieces of convincing evidence are provided here to support the hypothesis. A significant negative association between the numbers of each species found in individual fish was reported and this was consistent for both wild and stocked trout. Furthermore, an analysis of the proportions of low, moderate and high intensity infections in single and concurrent infections revealed a significant reduction in increasing intensities in concurrent infections compared to single infections. Finally, strikingly different patterns of niche inhabitation were observed, particularly forP. laevisin the presence ofA. clavulain wild trout. Results from the niche width analysis also support the observations on average position in single and concurrent infections. The niche width ofP. laeviswhen it co-occurred withA. clavuladecreased markedly in high intensity infections compared to low intensity infections.
Interaction of the proteasome S5a/Rpn10 multiubiquitin-binding protein and the 8 kDa calcium-binding protein ofSchistosoma mansoni
Authors: RAM D. , ZIV E. , LANTNER F. , SCHECHTER I.
Published: October 2003

A distinct 8 kDa calcium-binding protein (CaBP) is preferentially expressed at the cercarial stage during the life-cycle of the schistosome. Available data indicate that this CaBP may be associated with tissue/organ remodelling (involving protein degradation and synthesis of new proteins) during transformation of the cercariae from free-living form in water to parasitic life in the vertebrate host. Many CaBP molecules (e.g. calmodulin) show Ca++-dependent interaction with target proteins and thus modulate their activity. Accordingly, the parasite 8 kDa CaBP was used as a probe to clone and identify putative target protein(s) directly by binding interaction. Screening of schistosome λgt11 expression library with radio-iodinated CaBP yielded several overlapping clones showing Ca++-dependent binding of the CaBP. Sequence analyses revealed that these clones encode the S5a/Rpn10 multiubiquitin-binding protein which is a component of the regulatory 19S subunit of the 26S proteasome. The schistosome molecule, designated SmS5a, is 420 amino acids long. The nearly full length molecule (Gln3–Ser420) as well as the amino terminal (N-S5a, Gln3–Gly200) and carboxyl-terminal (C-S5a, Asp225–Ser420) portions were synthesized in bacteria, purified, and antibodies to the parasite SmS5a were prepared. Interaction between SmS5a and the 8 kDa CaBP in a Ca++-dependent manner was found under various experimental conditions: CaBP-Sepharose bound soluble SmS5a, immobilized SmS5a bound soluble CaBP, and complex formation was found when both molecules were in solution. Furthermore, it was shown that the C-terminal portion of SmS5a, but not the N-terminal portion of the molecule, reacted with the CaBP. SmS5a synthesized in a cell-free system and Western blots revealed 2 species, conceivably corresponding to the naked molecule (~50 kDa) and the molecule subjected to post-translational modification (~70 kDa). The present studies suggest that proteasome activity may be modulated by calcium, and this modulation is mediated via CaBP molecule(s).
A multiplex PCR assay for the simultaneous detection and discrimination of the sevenEimeriaspecies that infect domestic fowl
Authors: FERNANDEZ S. , PAGOTTO A. H. , FURTADO M. M. , KATSUYAMA Â. M. , MADEIRA A. M. B. N. , GRUBER A.
Published: October 2003

This study reports the development of a novel multiplex PCR assay based on SCAR (Sequence-Characterised Amplified Region) markers for the simultaneous diagnosis of the 7Eimeriaspecies that infect domestic fowl. Primer pairs specific for each species were designed in order to generate a ladder of amplification products ranging from 200 to 811 bp. Sensitivity tests for each species were carried out, showing a detection threshold of 1–5 pg, which corresponds approximately to 2–8 sporulated oocysts. Distinct isolates of the 7Eimeriaspecies from different geographical sources were tested and successfully detected by the assay. All the species were amplified homogeneously, whether or not one of them was present in a high quantity, indicating that there was no cross-interference. The assay was also tested with different sources ofTaqDNA polymerase and thermocycler models, confirming the high reproducibility of the reaction. The economy of consumables and labour represented by a single-tube reaction greatly facilitates the molecular diagnosis of a large number of samples, making it appropriate for field epizootiological surveys. We propose the use of this multiplex PCR assay as a rapid and cost-effective diagnostic method for the detection and discrimination of the 7Eimeriaspecies that infect domestic fowl.
Clotrimazole, ketoconazole, and clodinafop-propargyl inhibit the in vitro growth of Babesia bigemina and Babesia bovis (Phylum Apicomplexa)
Authors: BORK S. , YOKOYAMA N. , MATSUO T. , CLAVERIA F. G. , FUJISAKI K. , IGARASHI I.
Published: October 2003

We evaluated the growth inhibitory efficacy of the imidazole derivatives, clotrimazole (CLT) and ketoconazole (KC), and the herbicide clodinafop-propargyl (CP), in in vitro cultures of Babesia bovis and B. bigemina. Clotrimazole was effective in a dose range of 15 to 60 μM (IC50: 11 and 23·5 μM), followed by KC (50 to 100 μM; IC50: 50 and 32 μM) and CP (500 μM; IC50: 265 and 390 μM). In transmission electron microscopy, extensive damage was observed in the cytoplasm of drug-treated parasites. Combinations of CLT/KC, CLT/CP and CLT/KC/CP acted synergistically in both parasites. In contrast, the combination of KC/CP was exclusively effective in B. bovis, but not in B. bigemina.
Lead concentrations in Hymenolepis diminuta adults and Taenia taeniaeformis larvae compared to their rat hosts (Rattus norvegicus) sampled from the city of Cairo, Egypt
Authors: SURES B. , SCHEIBLE T. , BASHTAR A. R. , TARASCHEWSKI H.
Published: October 2003

Concentrations of lead, determined by electrothermal atomic absorption spectrometry, were compared between the cestodes Hymenolepis diminuta and Taenia taeniaeformis and its host rat (Rattus norvegicus). Rats were sampled at 2 sites, which differed in respect to lead pollution as quantified from road dust, adjacent to the city of Cairo, Egypt. Comparing lead levels among host tissues and the parasites the significantly highest accumulation was found in H. diminuta, followed by rat kidney and larvae of T. taeniaeformis. Calculation of bioconcentration factors showed that H. diminuta contained 36-, 29-, 6- and 6-fold higher lead levels than intestinal wall, liver, kidney and larvae of T. taeniaeformis, at the more polluted site. At the less contaminated site lead bioconcentration factors for H. diminuta were found to be 87, 87 and 11 referred to intestine, liver and kidney of the host. Due to a high variability of the lead concentrations in H. diminuta it was not possible to indicate differences in metal pollution between both sampling sites. This variability may be influenced by different age structures of cestode infrapopulations. It is likely that younger worms contain lower metal levels than older worms due to a shorter exposure period. Thus, it is necessary to standardize the sampling of worms which should be used for indication purposes. Due to a lack of adequate sentinel species in terrestrial habitats more studies are required to validate and standardize the use of helminths as accumulation bioindicators in order to obtain mean values with low standard deviations. The host–parasite system rat–H. diminuta appears to be a useful and promising bioindication system at least for lead in urban ecosystems as rats as well as the tapeworm are globally distributed and easily accessible.
Molecular epidemiological survey on the vectors of Thelazia gulosa, Thelazia rhodesi and Thelazia skrjabini (Spirurida: Thelaziidae)
Authors: OTRANTO D. , TARSITANO E. , TRAVERSA D. , DE LUCA F. , GIANGASPERO A.
Published: October 2003

A Polymerase Chain Reaction (PCR)- based assay developed for the specific identification of Thelazia gulosa, Thelazia rhodesi and Thelazia skrjabini (Nematoda, Spirurida), which cause bovine ocular thelaziosis, was evaluated for its usefulness in detecting the intermediate hosts and in estimating the infection prevalence of vectors in field conditions throughout 5 years (from 1997 to 2001). A total of 5190 flies were captured and identified as Musca larvipara, Musca osiris, Musca autumnalis, Musca tempestiva or Musca domestica. Genomic DNA was extracted from pools constituted by heads, thoraces, abdomens and wings of 10 flies of each species, and 2076 samples were subjected to a PCR assay to specifically detect the ribosomal ITS-1 sequence of bovine Thelazia. Amplicons were sequenced and subjected to digestion with CpoI restriction enzyme. M. autumnalis, M. larvipara, M. osiris and M. domestica species were shown to be PCR positive. T. gulosa was specifically detected by PCR in M. autumnalis, M. larvipara, M. osiris and M. domestica, whereas T. rhodesi is in M. autumnalis and M. larvipara. Of 27 positive samples, 23 were positive for T. gulosa and 4 for T. rhodesi, with a mean prevalence of 2·86% in the whole fly population collected. The highest mean prevalence values of infection were detected in M. autumnalis (4·46%) and M. larvipara (3·21%), and the former species was confirmed to be the vector of T. gulosa and T. rhodesi. This study is the first report of M. osiris as a vector of T. gulosa and M. larvipara as a vector of T. gulosa and T. rhodesi under natural conditions. The occurrence of Thelazia in fly populations in the Apulia region of Italy (in the 5 grazing seasons considered) indicates that cattle thelaziosis is enzootic in southern Italy. This molecular assay should be a useful epidemiological tool for assessing the role of different species of flies as intermediate hosts of thelaziae.
Parasite infracommunity diversity in eels: a reflection of local component community diversity
Authors: NORTON J. , LEWIS J. W. , ROLLINSON D.
Published: October 2003

The intestinal macroparasite communities of freshwater eels (Anguilla anguilla) captured in the south of England from Windsor (River Thames) during August 2001, and Leckford (River Test) during late June/July 2000, are reported for the first time. Parasite component communities were among the most species rich and diverse recorded from European eels. A total of 13 intestinal macroparasite species were encountered during the study, 8 from each eel host population with 3 being common to both. Acanthocephalans, nematodes and cestodes were recovered from each host population. Eels from Windsor additionally harbouredNicolla gallica(Digenea), which was also the most prevalent and abundant macroparasite species in these hosts. Each component community followed a log normal rank abundance distribution and demonstrated reduced species dominance and increased species equitability compared with previous studies. As such, the study component communities were suitable for testing the hypothesis of low infracommunity diversity in European eel hosts. Specifically, this hypothesis predicts that the intestinal macroparasite infracommunities of European eels are species-poor, displaying low density and diversity with high dominance, irrespective of component community diversity, and that this may be more pronounced in UK host populations. This hypothesis was not upheld; study findings demonstrate that higher infracommunity diversity in eel hosts is possible, and suggest that infracommunity diversity in individual eel hosts may be a simple, stochastic reflection of component community diversity.
Toxicity of cadmium and zinc to the decaudised cercarial life-span of Diplostomum spathaceum (Trematoda: Diplostomidae)
Authors: MORLEY N. J. , CRANE M. , LEWIS J. W.
Published: October 2003

The toxicity of cadmium and zinc at concentrations ranging from 0·1 to 10 000 μg/l to the life-span of decaudised cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum was investigated. The effects of metal exposure at 3 temperatures (12, 20, and 25 °C) and 3 levels of water hardness (distilled water, soft water and hard water) were studied. In general, under most experimental conditions increasing metal concentrations reduced the life-span of decaudised cercariae. Increasing water hardness and decreasing water temperature caused an increase in the life-span of both control and metal exposed decaudised cercariae. However, at certain isolated metal concentrations, associated with a specific level of water hardness and temperature, increased survival above controls occurred. Differences in the relative toxicity of cadmium and zinc were dependent on the environmental conditions of exposure. The decaudised cercarial life-span under metal exposure was found to be generally independent of the overall cercarial survival and tail loss in most experimental conditions. Prolonged exposure to cadmium and zinc caused changes in the decaudised cercarial life-span when compared to individuals decaudised during the initial 24 h exposure period to those which were decaudised during the final 24 h period of cercarial survival. The validity of studying the decaudised cercarial life-span as an indicator of ‘fitness’ of larvae to migrate through the tissues of the target fish host, in terms of glycogen utilization, was assessed for those cercariae decaudised during the initial 24 h exposure period only. A limited reduction in the decaudised cercarial life-span during this period compared to controls was recorded, which may possibly indicate a reduced penetration ‘fitness’ of cercariae exposed to cadmium and zinc. The importance and relevance of these findings to parasite migration and establishment in the fish host are discussed.
Immunolocalization ofLeishmania (Viannia) braziliensismembrane antigens recognized by mAbs SST-2, SST-3, and SST-4
Authors: SILVEIRA T. G. V. , TAKAHASHI H. K. , STRAUS A. H.
Published: October 2003

The immunolocalization ofLeishmania (Viannia) braziliensisstage-specific antigens recognized by mAbs was analysed by transmission electron microscopy. The antigen recognized by mAb SST-2 was present at the surface of promastigotes, including the flagellum and flagellar pocket. The reactivity of SST-2 with isolates of different serodemes showed a pronounced microheterogeneity in terms of the number of reactive bands within the low molecular weight range from 24 to 33 kDa. The 180 kDa glycoprotein recognized by mAb SST-3 was present only in the flagellar membrane. SST-3 also recognized multiple discrete bands from 160 to 200 kDa, as observed in several serodemes. In contrast, mAb SST-4, which recognizes a 98 kDa antigen, showed weak labelling on the promastigote surface by transmission electron microscopy and indirect immunofluorescence. Based on Western blotting, indirect immunofluorescence, and solid-phase radio-immunoassay, the antigens recognized by mAbs SST-2, SST-3 and SST-4 were present in allL. (V.) braziliensisanalysed, from 7 different serodemes.
Host immune status affects maturation time in two nematode species – but not as predicted by a simple life-history model
Authors: GUINNEE M. A. , GEMMILL A. W. , CHAN B. H. K. , VINEY M. E. , READ A. F.
Published: October 2003

In theory, the age at which maturation occurs in parasitic nematodes is inversely related to pre-maturational mortality rate, and cross-species data on mammalian nematodes are consistent with this prediction. Immunity is a major source of parasite mortality and parasites stand to gain sizeable fitness benefits through short-term adjustments of maturation time in response to variation in immune-mediated mortality. The effects of thymus-dependent immune responses on maturation in the nematode parasites Strongyloides ratti and Nippostrongylus brasiliensis were investigated using congenitally thymus-deficient (nude) rats. As compared with worms in normal rats, reproductive maturity of parasites (presence of eggs in utero) in nude rats occurred later in S. ratti but earlier in N. brasiliensis. Immune-mediated differences in maturation time were not associated with differences in worm length. Thymus-dependent immunity had no effect on pre-maturational mortality. Results are discussed in relation to theoretical expectations and possible explanations for the observed patterns in parasite maturation.
Sex ratios in the rodent malaria parasite, Plasmodium chabaudi
Authors: REECE S. E. , DUNCAN A. B. , WEST S. A. , READ A. F.
Published: October 2003

The sex ratios of malaria and related Apicomplexan parasites play a major role in transmission success. Here, we address 2 fundamental issues in the sex ratios of the rodent malaria parasite, Plasmodium chabaudi. First we test the accuracy of empirical methods for estimating sex ratios in malaria parasites, and show that sex ratios made with standard thin smears may overestimate the proportion of female gametocytes. Secondly, we test whether the mortality rate differs between male and female gametocytes, as assumed by sex ratio theory. Conventional application of sex ratio theory to malaria parasites assumes that the primary sex ratio can be accurately determined from mature gametocytes circulating in the peripheral circulation. We stopped gametocyte production with chloroquine in order to study a cohort of gametocytes in vitro. The mortality rate was significantly higher for female gametocytes, with an average half-life of 8 h for female gametocytes and 16 h for male gametocytes.
Leishmania(Viannia)braziliensis-induced chronic granulomatous cutaneous lesions affecting the nasal mucosa in the rhesus monkey (Macaca mulatta) model
Authors: TEVA A. , PORROZZI R. , CUPOLILLO E. , PIRMEZ C. , OLIVEIRA-NETO M. P. , GRIMALDI G.
Published: October 2003

The present studies on infections withLeishmania(Viannia)braziliensisin rhesus macaques were made to characterize the evolution of different parasite strains and the immune responses they elicited in this experimental host. A standardized inoculum of promastigotes was injected intradermally either above the eyelid or on the forearm of each monkey. Sixteen infected monkeys developed longstanding infections which lasted until the end of the observation period (33 months). The time required for lesion development was very variable, not only for the isolates showing molecular differences but also for individual animals in groups infected with the same parasite strain. The inocula produced lesions of variable severity, ranging from localized cutaneous leishmaniasis (CL) with a tendency to spontaneous healing to non-healing disease. One infected animal developed persistent metastatic skin and mucosal lesions. Anti-Leishmaniaantibodies and parasite-specific T-cell responses were induced by the experimental infections. As the granulomatous inflammatory response found at the lesions inL. (V.)braziliensis-infectedM. mulattawas similar to that in patients with CL, this primate model could be useful for studying the pathophysiology and immunoregulatory events associated with disease evolution, as well as for the evaluation of new drugs or candidate vaccines.
Bottom friction and bed forms on the southern flank of Georges Bank
Authors: Werner Sandra R. , Beardsley Robert C. , Williams Albert J.
Published: October 2003

We present observational estimates of bottom stress, bottom roughness, and quadratic drag coefficient for the southern flank of Georges Bank, a shallow region dominated by strong semidiurnal tides. Our estimates are based on near‐bottom velocity measurements from two Benthic Acoustic Stress Sensor (BASS) tripod deployments at a depth of 76 m taken during winter (February–April 1995) and summer (July–August 1995). The dominant tidal constituent is the M2, which provides 76–89% of the total kinetic energy. Typical bottom friction velocities are 1.1–1.2 cm s−1 in the time mean, with standard deviations of 0.4–0.5 cm s−1. A representative drag coefficient is cD = 3.0 ± 0.1 × 10−3 at 1.2 m above the bottom. Our drag coefficient estimates at this and other elevations correspond to the apparent bottom roughness range z0 = 0.05–0.09 cm. Bottom photographs (taken February–June) show that from February until April the sea floor was covered by sand ripples 1–2 cm in height. These ripples were approximately aligned with the local isobath; their flanks were perpendicular to the major axis of the tidal ellipse. Ripples exhibited stationary behavior; that is, they did not migrate with the flow. Intermittent modification of the ripple pattern happened during times of strong wave‐current interaction, but along‐isobath ripples formed again after each wave event. Observations of bed forms affected by surface waves coincided with periods of wave‐enhanced bottom stress predicted by the Grant and Madsen [1979] combined wave‐current interaction model. Model results and bottom photographs indicate that sediments were kept in suspension only under extreme conditions, here the February 1995 storm. Sand ripples gradually eroded during late March and April until the sea floor was almost flat. Coinciding with slow ripple erosion, bioturbation levels increased. Our estimates of bottom stress do not exhibit seasonal changes, so that seasonal variation of bottom shear stress cannot explain the transition from a rippled to a nearly flat bottom. We conclude that biogenic modification of bottom sediment enhanced the critical shear stress for initiation of sediment movement, thereby prohibiting ripple formation in spring and summer.
A constitutive model for stress‐induced permeability and porosity evolution of Berea sandstone
Authors: Morris J. P. , Lomov I. N. , Glenn L. A.
Published: October 2003

Many applications in geophysics require good estimates of permeability evolution in response to deformation, pore collapse, dilatancy, and microfracturing. Simulations of the upper crust, oil well completion, and nuclear waste repositories depend upon reliable predictions of changes in rock permeability. For some applications, permeability can affect the strength of rock by influencing the pore pressure and effective stress. For example, the pore pressure during production from an oil bearing formation is controlled by the evolving permeability field. The rock strength, however, depends upon the effective stress which is influenced by the pore pressure. Accurate prediction of possible failure in such formations requires reliable estimates of permeability change. Ideally, such estimates could be obtained by directly simulating the changes in pore space connectivity at the microscale. In practice the system being studied is sufficiently large that constitutive models must be developed which address permeability evolution macroscopically. We develop a model for predicting porosity and permeability changes in Berea sandstone. The model has been kept as simple as possible in order to facilitate incorporation of the model into existing mechanics codes. For this reason we assume the existence of a separate material model capable of predicting the stress‐strain response of the rock. In addition, the model assumes that the original pores and pores created by microfracturing can be treated separately with respect to permeability and porosity evolution. Despite these simplifying assumptions, the model is able to reproduce most of the key features observed in previously reported triaxial experiments performed on Berea sandstone.
Simultaneous radar observations of the electrojet plasma irregularities at 18 and 54.95 MHz over Trivandrum, India
Authors: Tiwari Diwakar , Patra A. K. , Viswanathan K. S. , Jyoti N. , Devasia C. V. , Subbarao K. S. V. , Sridharan R.
Published: October 2003

Observations of equatorial electrojet (EEJ) plasma irregularities made using a newly established 18 MHz coherent backscatter radar at Trivandrum are presented. Also presented are the simultaneous observations of the electrojet plasma irregularities made using a collocated 54.95 MHz radar. These correspond to 8.3 m and 2.7 m scale irregularities, respectively. The statistics of spectral parameters observed at the two scale sizes are also presented and compared in detail. An interesting and new aspect of these observations is that the 8.3 m irregularities have significant anisotropy in the plane perpendicular to magnetic field in contrast to that reported for 3 m irregularities. While type‐1 and type‐2 spectra could be distinctly observed at 2.7 m, it is rather difficult to distinguish at 8.3 m. The type‐2 velocities for the two scale sizes are pretty close to each other below 102 km, but the velocities for 8.3 m are less than that of 2.7 m above. Type‐1 velocities are quite close to each other only at altitudes of the peak electrojet when clear type‐1 echoes are observed. Spectral widths are remarkably different at the two scale sizes. The ratio of spectral width corresponding to 2.7 m to that at 8.3 m is close to 1.4, quite similar to that reported earlier from Jicamarca. The observed difference in the velocities and spectral width at the two scale sizes are attributed to the effects of anomalous collision of electrons caused by the large‐scale turbulence present in the EEJ. The above observations are found to be consistent with the EEJ instability theories and related simulation works.
Long‐duration asynchronous ground motions in the Colfiorito plain, central Italy, observed on a two‐dimensional dense array
Authors: Di Giulio G. , Rovelli A. , Cara F. , Azzara R. M. , Marra F. , Basili R. , Caserta A.
Published: October 2003

In winter 1998 a small‐aperture (∼200 m), four‐station array was operating in the middle of the Colfiorito plain. Waveforms of seven small magnitude (2.1 < M < 3.7) local earthquakes are analyzed in this study. The peculiarity of the array seismograms is a ∼2‐min long duration of the horizontal ground motion. The predominant frequency in the plain is around 1 Hz. In this frequency band, earthquake‐induced ground shaking is synchronous for a few seconds during direct S waves; after this time window, wave trains show an increasingly chaotic behavior within the array. The energy variation of the horizontal ground shaking between the array and a nearby rock outcrop exceeds a factor of 500 at 1 Hz. In order to help understanding of observations and construct models for future numerical simulations, the buried structure of the Colfiorito plain has been investigated through seismic refraction profiles and geoelectric measurements. A three‐dimensional reconstruction of the basin structure reveals an extremely complex bedrock topography, which is probably a recurrent feature for intermontane basins in tectonically active regions. Apparent velocities and backazimuths in the frequency band 0.5–1.5 Hz indicate that a 180‐m deep depression NW of the array is responsible for the generation of edge‐diffracted surface (Love) waves. Their arrival to the array breaks the synchronism of vertically reverberating waves which predominate in the first seconds of the S‐wave window.
A new approach to assessing the burial depth of ground ice deposits and its application to proposed MER landing sites in Isidis Planitia
Authors: Helbert J. , Benkhoff J.
Published: October 2003

The recent results by the Gamma Ray Spectrometer instrument on Mars Odyssey [Boynton et al., 2002] indicate the possibility of ground ice deposits within a few meters of the surface even at low latitudes and midlatitudes. The stability of ground ice deposits at these latitudes is a puzzling question. To address this question, we have developed the Berlin Mars Near‐Surface Thermal model (BMST), a model for the thermal behavior of the Martian surface with a special focus on the volatile transport within the subsurface material. Using the BMST, we have performed a case study to derive limits on the burial depth of ground ice deposits stable over annual cycles at the MER landing sites in Isidis Planitia. We have studied the temperature gradient within the subsurface, assuming different structures and thermophysical properties for the surface and subsurface material. While the results derived here will have no immediate consequences for the MER mission because Isidis Planitia has been demoted to a backup landing site, the results show the potential and versatility of the model we have developed and give some results on the surface properties of Isidis Planitia.
Time‐lapse imaging of saline‐tracer transport in fractured rock using difference‐attenuation radar tomography
Authors: Day‐Lewis Frederick D. , Lane John W. , Harris Jerry M. , Gorelick Steven M.
Published: October 2003

Accurate characterization of fractured‐rock aquifer heterogeneity remains one of the most challenging and important problems in groundwater hydrology. We demonstrate a promising strategy to identify preferential flow paths in fractured rock using a combination of geophysical monitoring and conventional hydrogeologic tests. Cross‐well difference‐attenuation ground‐penetrating radar was used to monitor saline‐tracer migration in an experiment at the U.S. Geological Survey Fractured Rock Hydrology Research Site in Grafton County, New Hampshire. Radar data sets were collected every 10 min in three adjoining planes for 5 hours during each of 12 tracer tests. An innovative inversion method accounts for data acquisition times and temporal changes in attenuation during data collection. The inverse algorithm minimizes a combination of two functions. The first is the sum of weighted squared data residuals. Second is a measure of solution complexity based on an a priori space‐time covariance function, subject to constraints that limit radar‐attenuation changes to regions of the tomograms traversed by high difference‐attenuation ray paths. The time series of tomograms indicate relative tracer concentrations and tracer arrival times in the image planes; from these we infer the presence and location of a preferential flow path within a previously identified zone of transmissive fractures. These results provide new insights into solute channeling and the nature of aquifer heterogeneity at the site.
Pore network simulation of the dissolution of a single‐component wetting nonaqueous phase liquid
Authors: Zhao W. , Ioannidis M. A.
Published: October 2003

Soil wettability has been recently recognized as a factor that can dramatically influence the dissolution behavior of residual nonaqueous phase liquids (NAPL). A NAPL that wets the solid surface is trapped within the smaller pores and along the corners of pores invaded by water (the nonwetting phase). We present a two‐dimensional network simulator of wetting NAPL dissolution, inspired by observations of this process in transparent glass micromodels. The network model idealizes the pore space as a network of cubic pores connected by square tubes, following respective distributions. In accordance with micromodel observations, capillary equilibrium is assumed to exist between NAPL‐water interfaces along pore corners and within pores. Advection and diffusion of the organic dissolved in the aqueous phase, as well as dissolution mass transfer from residual NAPL, are explicitly accounted for in the model. Pores filled with NAPL are invaded at a rate which is controlled by mass transfer from dissolving thick NAPL films in pore corners and in order of increasing entry capillary pressure, resulting in quasi‐static drainage and fingering of the aqueous phase. Loss of NAPL continuity due to rupture of thick NAPL films and heterogeneity are found to affect profoundly the dissolution behavior, resulting in concentration tailing. The network simulator reproduces qualitatively the behavior observed in column experiments with oil‐wet media.
Asymmetric accretion along the slow‐spreading Mariana Ridge
Authors: Deschamps Anne , Fujiwara Toshiya
Published: October 2003

We report the results of several surface geophysical surveys of the central part of the Mariana Basin, western Pacific. Analysis of bathymetric and magnetic data along three distinct spreading segments indicates highly asymmetric spreading processes, the half‐spreading rate being two to three times more important on the western side of the basin than on its eastern side. Such an asymmetry is as strong at the centers of segments as at their ends, and does not systematically correlate with an asymmetric shape of the rift valley. A half‐graben shape of the rift valley is observed only at segment ends. At segments centers, a symmetric graben shape characterizes the valley. The asymmetric shape of the valley at segment ends probably reflects the localization of the tectonic strain due to changes in lithospheric rheology and thickness. Asymmetric spreading is likely accomplished through a different amount of deformation and magma emplacement on both sides of the spreading axis. It may result from the combined effects of (1) asymmetric rheologic, melting and stress conditions imposed by the influence of the pre‐existing volcanic arc and its melt sources on the eastern side of the basin, (2) the northwestward movement of the Philippine Sea Plate while the almost vertical Pacific slab in the Mariana subduction zone resists to this motion, (3) a roll‐back component at the Mariana subduction zone.
The snow/ice instability as a mechanism for rapid climate change: A Neoproterozoic Snowball Earth model example
Authors: Baum Steven K. , Crowley Thomas J.
Published: October 2003

Paleoclimate data increasingly suggest the likelihood of abrupt transitions due to instabilities in the climate system. Several previous studies offer support for the snow/ice instability mechanism as an explanation for some of these changes. However, most of these studies have either employed simple models or not closely examined the details of the transition. Herein we revisit this issue using a general circulation model (GCM) simulation for the late Precambrian, a time when glaciers may have reached the equator. Our results indicate that for CO2 concentrations near present levels the snow/ice instability occurs in one model year. The width of open water associated with the onset of instability agrees with theoretical calculations of the critical length scale predicted for this behavior. These results strengthen support for the existence of this phenomenon as a mechanism for rapid climate change.
Dynamics of global scale electron and proton precipitation induced by a solar wind pressure pulse
Authors: Meurant M. , Gérard J.‐C. , Hubert B. , Coumans V. , Blockx C. , Østgaard N. , Mende S. B.
Published: October 2003

On April 28 2001, simultaneous global images of electron and proton aurora were obtained by IMAGE‐FUV following a sudden increase of solar wind dynamic pressure. The local time and intensity distribution of both types of precipitation are examined and compared. It is found that the electron and the proton precipitation both start in the post noon sector and expand concurrently, but the expansion into the nightside starts sooner for the protons than for the electrons. The characteristic rise time in the onset sector is on the order of 6 minutes. A distinct dynamics and morphology of electron and proton precipitation is observed in the nightside sector. DMSP electron measurements in the afternoon sector indicate that the shock has a significant effect on the electron spectral characteristics. It is suggested that the various Alfven frequencies generated by the shock account for the two different speeds of propagation of the disturbance.
Growth of deformation bands into echelon and ladder geometries
Authors: Schultz Richard A. , Balasko Clara M.
Published: October 2003

We investigate the growth of cataclastic deformation bands in porous sandstone into Riedel, ladder, and “radiator rock” arrays. New field observations and mechanical modeling of DB growth using the distortional strain energy density criterion demonstrate that the physical control of these geometries is a contractional (mode‐II) stepover between two echelon bands. Propagation of bands under pre‐peak conditions, before Coulomb frictional sliding (faulting) begins, is not impeded by the echelon stepover geometry (as it is for brittle fractures under peak stress); continued in‐plane growth of echelon bands creates ladders from stepovers. Successive addition of stepovers/ladders along their shearing direction produces Riedel geometries, whereas addition normal to strike produces radiator rock (the damage zone) as a consequence of strain hardening of bands and linked stepovers. The new framework has implications for fluid flow in groundwater aquifers, hydrothermal and precious metals systems, and petroleum fields.
Jupiter's polar auroral emissions
Authors: Grodent D. , Clarke J. T. , Waite J. H. , Cowley S. W. H. , Gérard J.‐C. , Kim J.
Published: October 2003

This paper reports a study of Jupiter's polar auroral emissions observed in an extended series of FUV images. They were obtained on seven days, during winter 2000–2001, with the STIS camera on board the Hubble Space Telescope. The fixed pointing yielded highly accurate and consistent tracking of emisson features as Jupiter rotated, allowing the analysis of the auroral morphology and brightness on timescales ranging from seconds to days. In the Northern Hemisphere, the polar emissions, located poleward of the main oval, usually represent about 30% of the total auroral FUV emitted power. They show emission bursts lasting ∼100 s, while the main oval remains stable. The polar region may be divided into three regions apparently fixed in magnetic local time: the dawnside dark region, the poleward swirl region, and the duskside active region in which flares and arc‐like features are observed. Each of these UV emission regions can be identified with its infrared counterpart and probably relates to a different sector of the Dungey cycle or Vasyliunas cycle plasma flows.
Long‐term half‐hourly measurement of soil CO2 concentration and soil respiration in a temperate deciduous forest
Authors: Hirano Takashi , Kim Honghyun , Tanaka Yumiko
Published: October 2003

We conducted a field experiment in a cool‐temperate deciduous forest to investigate the dynamic behavior of soil CO2 and the vertical distribution of soil respiration. Soil CO2 concentration (C) was measured half‐hourly at four depths for 6 months in 2000 with infrared gas analyzers installed below ground. Using C profiles, soil surface CO2 efflux (F0), CO2 production rates of the topsoil (PA), and CO2 flux from the subsoil to topsoil (FCA) were evaluated half‐hourly by applying Fick's first law. Some remarkable short‐term and long‐term variations were found in C, F0, PA, FCA, and the contribution of topsoil respiration to total soil respiration (PA/F0), which include (1) rapid increase in C and decrease in F0 and PA due to rainwater infiltration, (2) diurnal variation in C coupled with that of the atmosphere, (3) diurnal variation in F0 and PA similar to that of topsoil temperature, (4) decrease in C, F0, and PA following soil drying in August, (5) linearly increasing FCA between late May and mid‐September, and (6) decrease in PA/F0 from around 0.9 during summer to 0.3 in November. The variation of PA was mainly controlled by soil temperature at −0.07 m between 7° and 17°C, although PA did not respond well to soil temperature above and below this temperature range. Above 17°C, PA increased linearly with soil moisture, and moisture variation accounted for the PA decrease in August. Neither temperature nor moisture explained the PA behavior below 7°C. Subsoil respiration (FCA) showed an exponential relationship with soil temperature at −1 m.
Cyclooxygenase‐2 and gastric carcinogenesis
Authors: SAUKKONEN KIRSI , RINTAHAKA JOHANNA , SIVULA ANNA , BUSKENS CHRISTIANNE J. , VAN REES BASTIAAN P. , RIO MARIE‐CHRISTINE , HAGLUND CAJ , VAN LANSCHOT J. JAN B. , OFFERHAUS G. JOHAN A. , RISTIMÄKI ARI
Published: October 2003

Epidemiological studies have shown that the use of nonsteroid anti‐inflammatory drugs (NSAIDs) is associated with reduced risk of gastric cancer. The best‐known target of NSAIDs is the cyclooxygenase (Cox) enzyme. Two Cox genes have been cloned, of which Cox‐2 has been connected with gastric carcinogenesis. Expression of Cox‐2 is elevated in gastric adenocarcinomas, which correlates with several clinicopathological parameters, including depth of invasion and lymph node metastasis. This suggests that Cox‐2–derived prostanoids promote aggressive behavior of adenocarcinomas of the stomach. Cox‐2 expression is especially prominent in intestinal‐type gastric carcinoma and it is already present in dysplastic precursor lesions of this disease, which suggests that Cox‐2 contributes to gastric carcinogenesis already at the preinvasive stage. Our most recent data show that Cox‐2 is expressed in gastric adenomas of trefoil factor 1 deficient mice. Treatment of these mice with a Cox‐2 selective inhibitor, celecoxib, reduced the size of the adenomas. Taken together these data support efforts to initiate clinical studies to investigate the effect of Cox‐2 inhibitors as chemotherapeutic agents and as adjuvant treatment modalities against gastric neoplasias.
Association of the φ nucleotide with codon bias, amino acid usage and expressivity: differences between Bacillus subtilis and Escherichia coli
Authors: FUGLSANG ANDERS
Published: October 2003

By measuring the non‐randomness in Shine‐Dalgarno regions it was recently shown that the compositional non‐randomness peaks approximately 10 nucleotides upstream of the start codons. This position, termed the φ position, was furthermore shown to be associated with certain characteristics of the gene/protein and start codon usage. This raises the question whether codon usage in general is associated with the φ position. In this study, the connection between the φ nucleotide and general codon usage, both gene‐wide and at the level of individual amino acids, was studied in Eschericia coli and Bacillus subtilis. E. coli but not B. subtilis shows a strong general association between the φ position and codon usage bias. In both species, the genes with higher expressivity show stronger conservation in the Shine‐Dalgarno region compared to the genes with lower expressivity.