bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model to account for the consequences of host nutrition on the outcome of gastrointestinal parasitism in sheep: model evaluation
Authors: VAGENAS D. , BISHOP S. C. , KYRIAZAKIS I. 
Published: April 2007

SUMMARYThis paper describes sensitivity analyses and expectations obtained from a mathematical model developed to account for the effects of host nutrition on the consequences of gastrointestinal parasitism in sheep. The scenarios explored included different levels of parasitic challenge at different planes of nutrition, for hosts differing only in their characteristics for growth. The model was able to predict the consequences of host nutrition on the outcome of parasitism, in terms of worm burden, number of eggs excreted per gram faeces and animal performance. The model outputs predict that conclusions on the ability of hosts of different characteristics for growth to cope with parasitism (i.e. resistance) depend on the plane of nutrition. Furthermore, differences in the growth rate of sheep, on their own, are not sufficient to account for differences in the observed resistance of animals. The model forms the basis for evaluating the consequences of differing management strategies and environments, such as breeding for certain traits associated with resistance and nutritional strategies, on the consequences of gastrointestinal parasitism on sheep.
Poorer results of mice with latent toxoplasmosis in learning tests: impaired learning processes or the novelty discrimination mechanism?
Authors: HODKOVA H. , KODYM P. , FLEGR J. 
Published: April 2007

SUMMARYThe heteroxenous protozoan parasite Toxoplasma gondii is transmitted from the intermediate host (any warm-blooded animal) to the definitive host (members of the felidae) by carnivory. The infected intermediate hosts develop several specific behavioural changes that are usually considered products of manipulative activity of the parasite aimed to increase the probability of its transmission to the definitive host. Among other changes, the infected rodents were shown to have impaired learning capability. All previous studies were done 2–6 weeks after the infection. Therefore, it was difficult to resolve whether the observed impairment of learning processes was a result of acute or latent toxoplasmosis, i.e. whether it was a side-effect of the disease or a product of manipulation activity. Here we studied the learning capability of Toxoplasma-infected mice in the static rod test and 8-arm radial maze test and their spontaneous activity in the wheel running test 10 weeks after the infection. The infected mice achieved worse scores in the learning tests but showed higher spontaneous activity in the wheel running test. However, a detailed study of the obtained results as well as of the data reported by other authors suggested that the differences between infected and control mice were a result of impaired ability to recognize novel stimuli rather than of impaired learning capacity in animals with latent toxoplasmosis.
Antioxidant gene expression and function inin vitro-developingSchistosoma mansonimother sporocysts: possible role in self-protection
Authors: VERMEIRE J. J. , YOSHINO T. P. 
Published: April 2007

SUMMARYThe ability of the larval forms ofSchistosoma mansonito invade and parasitize their molluscan host,Biomphalaria glabrata, is determined by a multitude of factors. In this study we sought to elucidate the possible mechanisms by which the invading larvae are able to counteract the potentially harmful oxidative environment presented by the host upon initial miracidial infection. This was attempted by examining the gene expression profile of parasite antioxidant enzymes of the linked glutathione-(GSH) thioredoxin (Trx) redox pathway during early intramolluscan larval development. Three such enzymes, the peroxiredoxins (Prx1, Prx2 and Prx3) were examined as to their activity and sites of expression withinS. mansonimiracidia andin vitro-cultured mother sporocysts. Results of these studies demonstrated that the H2O2-reducing enzymes Prx1 and 2 are upregulated during early mother sporocyst development compared to miracidia. Immunolocalization studies further indicated that Prx1 and Prx2 proteins are expressed within the apical papillae of miracidia and tegumental syncytium of sporocysts, and are released with parasite excretory-secretory proteins (ESP) duringin vitrolarval transformation. Removal of Prx1 and Prx2 from larval ESP by immunoabsorption significantly reduced the ability of ESP to breakdown exogenous H2O2, thereby directly linking ESP Prx proteins with H2O2-scavenging activity. Moreover, exposure of live sporocysts to exogenous H2O2stimulated an upregulation of Prx1 and 2 gene expression suggesting the involvement of H2O2–responsive elements in regulating larval Prx gene expression. These data provide evidence that Prx1 and Prx2 may function in the protection ofS. mansonisporocysts during the early stages of infection.
Local climate aridity influences the distribution of thelastomatoid nematodes of the Australian giant burrowing cockroach
Authors: JEX A. R. , SCHNEIDER M. A. , ROSE H. A. , CRIBB T. H. 
Published: April 2007

SUMMARYIn this study, we examined the effects of local climate aridity on the richness and composition of the thelastomatoid (Nematoda: Oxyurida) guild parasitizing the Australian giant burrowing cockroach,Macropanesthia rhinoceros(Blattodea: Geoscapheinae). In total, 9 thelastomatoid species parasitized this cockroach in north-eastern Australia (Queensland). Local observed richness ranged from 3 species (in Cooktown, Magnetic Island, Maiden Springs and Whitsunday Island) to 7 species (in Rochford Scrub). The lowest richness occurred in both relatively wet and dry climates, and the highest richness was in moderate climates. Three species,Cordonicola gibsoni,Leidynemella fusiformisandTravassosinema jaidenae, were found at all 13 collection sites. One species,Geoscaphenema megaovum, was found exclusively in dry to moderate climates. The remaining species,Blattophila sphaerolaima,Coronostoma australiae,Desmicola ornata,Hammerschmidtiella hochiandJaidenema rhinoceratum, were found in moderate climates only. We hypothesize that the egg is the stage in the thelastomatoid life-cycle most vulnerable to the effects of adverse climate and that the geographical distribution for each species is, in part, bound by environments that are too dry, resulting in egg desiccation, and by environments that are too wet, resulting in decreased oxygen uptake across the egg-shell and in osmotic lysing.
Density dependence of feeding success in haematophagous ectoparasites
Authors: KRASNOV B. R. , HOVHANYAN A. , KHOKHLOVA I. S. , DEGEN A. A. 
Published: April 2007

SUMMARYWe studied the effect of density on feeding success of 2 fleas, Xenopsylla conformis and Xenopsylla ramesis, when exploiting rodents Meriones crassus and Gerbillus dasyurus. We tested 2 alternative hypotheses: (i) that intraspecific interference competition occurs and, thus, feeding success of a flea decreases with an increase in density and (ii) that facilitation via suppression of a host defence system occurs and thus, feeding success of a flea increases with an increase in density. The mean size of a bloodmeal and the proportion of highly engorged individuals in X. conformis feeding on both hosts were affected by density. When on G. dasyurus, both the size of a bloodmeal and the proportion of highly engorged individuals were lower at low (5–15 fleas per host) than at high (25–50 fleas per host) densities. The opposite was true when this flea fed on M. crassus. The mean bloodmeal size and proportions of highly engorged X. ramesis parasitizing either host were not affected by flea density. This study showed that the density dependence of feeding success of a flea (a) varied both between fleas and within-fleas between hosts and (b) indicated either intraspecific competition or facilitation via the host in a particular flea-host association.
Autonomously clearing obstacles using the biological flexor reflex in a quadrupedal robot
Authors: Xiuli Zhang , Haojun Zheng 
Published: April 2007

SUMMARYThis paper suggests one possible mechanism for the biological flexor reflex by emulating a cat's behavior with its robotic counterpart, making it capable of walking around and clearing obstacles autonomously in various environments. A central pattern generator and a hip-to-knee mapping function are employed to realize basic rhythmic motion for a quadrupedal robot. When an input from a contact sensor on the robot's toe is detected, a patterned motion generated by the flexor reflex emerges depending on the location of the bumping phase, and replaces the ongoing rhythmic motion of that leg, causing it to be raised high enough to clear the obstacle. By restricting this reflex to within one cycle time of the walk and only to the bumping leg, rhythm and stability of motion are ensured. Numerical simulations and experimental implementation on a physical quadrupedal robot demonstrate the effectiveness of the proposed method.
Efficient LEO Dynamic Orbit Determination with Triple Differenced GPS Carrier Phases
Authors: Bae Tae-Suk , Grejner-Brzezinska Dorota , Hyoun Kwon Jay 
Published: April 2007

The dynamic precise orbit determination of a Low Earth Orbit satellite using triple differenced GPS phases is presented in this study. The atmospheric drag parameters are estimated to compensate the incomplete atmosphere model for better precision of the orbit solution. In addition, the empirical force parameters, especially once- and twice-per-revolution components, along with the new IERS Conventions and models to compute the perturbing forces are introduced to absorb the remaining unmodelled forces. The optimal arc length for the parameterization and the data processing strategy are also tested and analyzed for the best orbit solutions. The triple differencing technique enables fast and efficient orbit estimation, because no ambiguity resolution and cycle slip detection are required. With the triple differenced ion-free GPS phase observables, the orbit and the velocity solutions for 24 hours of CHAMP are calculated; they compare with the published Rapid Science Orbit with the accuracy of 8 cm and 0·12 mm/s in 3D RMS for the orbit and the velocity, respectively, and are statistically consistent with the RSO when it is not better than 4 cm in terms of an absolute accuracy. The approach presented here provides an efficient and simple, but robust, alternative approach, while the solution's accuracy is still comparable to the double-difference results.
Analyses of the 1957 (Asian) influenza pandemic in the United Kingdom and the impact of school closures
Authors: VYNNYCKY E. , EDMUNDS W. J. 
Published: April 2007

SUMMARYMany countries plan to close schools during a future influenza pandemic, although the potential impact is poorly understood. We apply a model of the transmission dynamics of pandemic influenza to consultation, serological and clinical data from the United Kingdom from the 1957 (Asian) influenza pandemic, to estimate the basic reproduction number (R0), the proportion of infected individuals who experience clinical symptoms and the impact of school/nursery closures. The R0 for Asian influenza was about 1·8 and 60–65% of infected individuals were estimated to have experienced clinical symptoms. During a future pandemic, closure of schools/nurseries could reduce the epidemic size only by a very small amount (<10%) if R0 is high (e.g. 2·5 or 3·5), and modest reductions, e.g. 22% might be possible if it is low (1·8) and schools are closed early, depending on assumptions about contact patterns. Further data on contact patterns and their dependence on school closures are needed.
Prevalence and determinants of high-risk human papillomavirus (HPV) infection and cervical cytological abnormalities in imprisoned women
Authors: GONZÁLEZ C. , CANALS J. , ORTIZ M. , MUÑOZ L. , TORRES M. , GARCÍA-SAIZ A. , DEL AMO J. 
Published: April 2007

SUMMARYThe aim of the study was to estimate the prevalence and risk factors associated with infection by high-risk human papillomavirus (HR-HPV) in cervix and squamous intra-epithelial lesions (SIL) in imprisoned women. This was done by a cross-sectional study of imprisoned women attending the gynaecological clinic in Foncalent prison in Alicante, Spain. The study period was from May 2003 to December 2005. HR-HPV infection was determined through Digene HPV Test, Hybrid Capture II (HC-II). HPV typing was determined by multiplex nested PCR assay combining degenerate E6/E7 consensus primers. Multiple logistic regression modelling was used for the analysis of associations between variables where some were considered possible confounders after checking for interactions. A total of 219 women were studied. HR-HPV prevalence was 27·4% and prevalence of SIL was 13·3%. HIV prevalence was 18%, higher in Spaniards than in migrant women (24·6%vs. 14·3%,P<0·05). In multivariate analyses, risk factors for HPV infection were younger age (Pfor trend=0·001) and tobacco use (OR 2·62, 95% CI 1·01–6·73). HPV infection (OR 4·8, 95% CI 1·7–13·8) and HIV infection were associated with SIL (OR 4·8, 95% CI 1·6–14·1). The commonest HPV types were HPV16 (29·4%), HPV18 (17·6%), HPV39 (17·6%) and HPV68 (17·6%). The prevalence of both HR-HPV infection and SIL in imprisoned women found in this study is high. Determinants for each of the outcomes studied were different. HPV infection is the most important determinant for SIL. A strong effect of HIV co-infection on the prevalence of SIL has been detected. Our findings reinforce the need to support gynaecological clinics in the prison setting.
Use of sensitivity analysis to assess the effects on anti-hepatitis A virus antibodies of access to household water supply
Authors: CABRAL M. D. B. , LUIZ R. R. 
Published: April 2007

SUMMARYThe objective of this study was to assess the impact of a possible unmeasured confounding variable in a previously published association between the effects of household water supply and positive results for hepatitis A serology. This was estimated using a path of integration between two methods of sensitivity analysis, called Rosenbaum's method and Greenland's external adjustment. The association between household water supply and positive results for hepatitis A (outcome) serology was insensitive to confounding unless the odds ratio for the association between the confounder and the outcome was ⩾4. The integration of the two sensitivity analysis methods presented proved useful when assessing the effects of a potential unmeasured confounder.
Epidemiological evidence forMycobacterium aviumsubspeciesparatuberculosisas a cause of Crohn's disease
Authors: UZOIGWE J. C. , KHAITSA M. L. , GIBBS P. S. 
Published: April 2007

SUMMARYMycobacterium aviumsubspeciesparatuberculosisis the causative agent of Johne's disease, a chronic enteritis in ruminants including cattle, sheep, goats, and farmed deer. Recently, this bacterium has received an increasingly wide interest because of a rapidly growing body of scientific evidence which suggests that human infection with this microorganism may be causing some, and possibly all, cases of Crohn's disease. Recent studies have shown that a high percentage of people with Crohn's disease are infected withM. aviumsubsp.paratuberculosis; whether the association of this bacterium and Crohn's disease is causal or coincidental is not known. Crohn's disease is a gastrointestinal disease in humans with similar histopathological findings to those observed in the paucibacillary form of Johne's disease in cattle. The search for risk factors in Crohn's disease has been frustrating. However, epidemiologists have gathered enough information that points to an association betweenM. aviumsubsp.paratuberculosisand Crohn's disease. This paper reviews epidemiological models of disease causation, the major philosophical doctrines about causation, the established epidemiological criteria for causation, and the currently known epidemiological evidence ofM. aviumsubsp.paratuberculosisas a possible cause of Crohn's disease.
An outbreak ofEscherichia coliO157:H7 infection in southern Sweden associated with consumption of fermented sausage; aspects of sausage production that increase the risk of contamination
Authors: SARTZ L. , De JONG B. , HJERTQVIST M. , PLYM-FORSHELL L. , ALSTERLUND R. , LÖFDAHL S. , OSTERMAN B. , STÅHL A. , ERIKSSON E. , HANSSON H.-B. , KARPMAN D. 
Published: April 2007

SUMMARYA large outbreak of enterohaemorrhagicEscherichia coli(EHEC) infections occurred in southern Sweden during autumn 2002. A matched case-control study was performed and indicated an association between consumption of fermented sausage and EHEC infection (odds ratio 5·4,P<0·002). Pulsed-field gel electrophoresis analysis identified a strain ofE. coliO157:H7 in clinical faecal isolates, which was identical to a strain isolated from sausage samples obtained from households of infected individuals. A combination of microbiological and epidemiological results established a link between sausage consumption and the outbreak in 30 out of a total of 39 investigated cases. Contaminated beef was suspected to be the source of infection. Delayed start of fermentation, lack of heat-treatment and a short curing period in cold temperature were identified as the main factors enabling EHEC survival. EHEC can survive throughout the entire production process of fermented sausage if curing conditions are inadequate.
Necrotizing fasciitis in captive juvenileCrocodylus porosuscaused byStreptococcus agalactiae: an outbreak and review of the animal and human literature
Authors: BISHOP E. J. , SHILTON C. , BENEDICT S. , KONG F. , GILBERT G. L. , GAL D. , GODOY D. , SPRATT B. G. , CURRIE B. J. 
Published: April 2007

SUMMARYWe observed an outbreak of necrotizing fasciitis associated withStreptococcus agalactiaeinfection in a group of juvenile saltwater crocodiles (Crocodylus porosus). We undertook screening of crocodiles and the environment to clarify the source of the outbreak and evaluated the isolates cultured from post-mortem specimens with molecular methods to assess clonality and the presence of known group B streptococcal virulence determinants. The isolates were indistinguishable by pulsed-field gel electrophoresis. They were a typical serotype Ia strain with the Cα-like protein gene, epsilon (oralp1), the mobile genetic elements IS381ISSag1and ISSag2, and belonged to multi-locus sequence type (ST) 23. All of these characteristics suggest they were probably of human origin. We review the medical and veterinary literature relating toS. agalactiaenecrotizing fasciitis, epidemiology and virulence determinants.
Exploring the Galaxy using space probes
Authors: Bjørk R. 
Published: April 2007

AbstractThis paper investigates the possible use of space probes to explore the Milky Way, as a means both of finding life elsewhere in the Galaxy and as finding an answer to the Fermi paradox. Exploration of the Galaxy is simulated by first examining how long time it takes a given number of space probes to explore 40 000 stars in a box from −300 to 300 pc above the Galactic thin disc, as a function of Galactic radius. The Galaxy is then modelled to consist of ∼260 000 of these 40 000 stellar systems all located in a defined Galactic Habitable Zone and how long a time it takes to explore this zone is shown. The result is that with eight probes, each with eight subprobes, ∼4% of the Galaxy can be explored in 2.92×108 years. Increasing the number of probes to 200, still with eight subprobes each, reduces the exploration time to 1.52×107 years.
Possible evidence for panspermia: the labelled release experiment
Authors: Levin Gilbert V. 
Published: April 2007

Abstract30 years after the Viking Mission landed on Mars (20 July 1976) to search for life, despite the positive findings of the Labelled Release (LR) experiment, the issue remains unresolved. The controversial history, following the immediate dismissal of the LR’s evidence for microbial activity in the Martian soil, and the later claim to its having found living microorganisms are reviewed. The bearing of post-Viking-to-current data on the issue is discussed in the context of the scientific community’s growing interest in the long-dismissed possibility of microbial life on Mars. Objections raised over the years to the biological interpretation of the Mars LR, those currently maintained, and their rebuttals are reviewed. A case is presented that enough evidence now exists for an objective review by astrobiologists to resolve this key issue, a review, surprisingly, not yet held. The results could greatly influence NASA’s currently shifting plans for Mars exploration. A variation of the LR experiment to test for chiral specificity in the metabolism of substrates by the active agent found in the Martian soil, and thus having the capability of obtaining an unambiguous answer to the life question, is proposed. Confirmation of life on Mars by this experiment can also determine whether Martian and Earth life forms share a common heritage. Together with mounting evidence for the viable transfer of microorganisms between the two planets, this would be evidence for panspermia, and establish the presence of a common biosphere in which the two planets participate. Should Martian microorganisms show a different chiral specificity than that of Earth life then this would indicate separate origins of the two neighbouring life forms, thereby strongly implying that life occurs widely throughout the cosmos. Any one of these possible outcomes would be a paradigm-breaking event.
Added astroglia promote greater synapse density and higher activity in neuronal networks
Authors: Boehler Michael D. , Wheeler Bruce C. , Brewer Gregory J. 
Published: April 2007

AbstractAstroglia are known to potentiate individual synapses, but their contribution to networks is unclear. Here we examined the effect of adding either astroglia or media conditioned by astroglia on entire networks of rat hippocampal neurons cultured on microelectrode arrays. Added astroglia increased spontaneous spike rates nearly two-fold and glutamate-stimulated spiking by six-fold, with desensitization eliminated for bath addition of 25 μM glutamate. Astrocyte-conditioned medium partly mimicked the effects of added astroglia. Bursting behavior was largely unaffected by added astroglia except with added glutamate. Addition of the GABAA receptor antagonist bicuculline also increased spike rates but with more subtle differences between networks without or with added astroglia. This indicates that networks without added astroglia were inhibited greatly. In all conditions, the log–log distribution of spike rates fit well to linear distributions over three orders of magnitude. Networks with added astroglia shifted consistently toward higher spike rates. Immunostaining for GFAP revealed a linear increase with added astroglia, which also increased neuronal survival. The increased spike rates with added astroglia correlated with a 1.7-fold increase in immunoreactive synaptophysin puncta, and increases of six-fold for GABAAβ, two-fold for NMDA-R1 and two-fold for Glu-R1 puncta, with receptor clustering that indicated synaptic scaling. Together, these results indicate that added astroglia increase the density of synapses and receptors, and facilitate higher spike rates for many elements in the network. These effects are reproduced by glia-conditioned media, with the exception of glutamate-mediated transmission.