bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for the involvement of Plasmodium falciparum proteins in the formation of new permeability pathways in the erythrocyte membrane
Authors: Baumeister Stefan , Winterberg Markus , Duranton Christophe , Huber Stephan M. , Lang Florian , Kirk Kiaran , Lingelbach Klaus 
Published: March 2006

SummaryThe intraerythrocytic developmental stages of the malaria parasite Plasmodium falciparum are responsible for the clinical symptoms associated with malaria tropica. The non‐infected human erythrocyte is a terminally differentiated cell that is unable to synthesize proteins and lipids de novo, and it is incapable of importing a number of solutes that are essential for parasite proliferation. Approximately 12–15 h after invasion the parasitized cell undergoes a marked increase in its permeability to a variety of different solutes present in the extracellular milieu. The increase is due to the induction in the erythrocyte membrane of ‘new permeability pathways’ which have been characterized in some detail in terms of their transport and electrophysiological properties, but which are yet to be defined at a molecular level. Here we show that these pathways are resistant to trypsin but are abolished by treatment of intact infected erythrocytes with chymotrypsin. On resuspension of chymotrypsinized cells in chymotrypsin‐free medium the pathways progressively reappear, a process that can be inhibited by cytotoxic agents, and by brefeldin A which inhibits protein secretion. Our results provide evidence for the involvement of parasite encoded proteins in the generation of the pathways, either as components of the pathways themselves or as auxiliary factors.
Cloning, functional expression and characterization ofMesorhizobium lotiarylamineN‐acetyltransferases: rhizobial symbiosis supplies leguminous plants with the xenobiotic N‐acetylation pathway
Authors: Rodrigues‐Lima Fernando , Dairou Julien , Diaz Clara L. , Rubio Maria C. , Sim Edith , Spaink Herman P. , Dupret Jean‐Marie 
Published: March 2006

SummaryArylamineN‐acetyltransferases (NATs) are xenobiotic‐metabolizing enzymes involved in the detoxification of numerous aromatic chemicals. The NAT‐dependent N‐acetylation pathway has not previously been detected in plants. We demonstrate here the occurrence of the NAT‐dependent pathway in leguminous plants, due to symbiosis withMesorhizobium loti. We cloned two NAT enzymes fromM. lotiand showed that these two recombinant enzymes catalysed the N‐acetylation of several known NAT substrates, including aniline‐derived pesticide residues. We also demonstrate the existence of a functional NAT‐dependent acetylation pathway in the root nodules ofLotus japonicusinoculated withM. loti.M. lotiis the first non‐eukaryotic organism shown to express two catalytically active NAT isoforms. This work also provides the first evidence for acquisition of a xenobiotic detoxification pathway by a plant through symbiosis with a soil microbe.
Yeast ribosomal P0 protein has two separate binding sites for P1/P2 proteins
Authors: Krokowski Dawid , Boguszewska Aleksandra , Abramczyk Dariusz , Liljas Anders , Tchórzewski Marek , Grankowski Nikodem 
Published: March 2006

SummaryThe ribosome has a distinct lateral protuberance called the stalk; in eukaryotes it is formed by the acidic ribosomal P‐proteins which are organized as a pentameric entity described as P0‐(P1‐P2)2. Bilateral interactions between P0 and P1/P2 proteins have been studied extensively, however, the region on P0 responsible for the binding of P1/P2 proteins has not been precisely defined. Here we report a study which takes the current knowledge of the P0 – P1/P2 protein interaction beyond the recently published information. Using truncated forms of P0 protein and several in vitro and in vivo approaches, we have defined the region between positions 199 and 258 as the P0 protein fragment responsible for the binding of P1/P2 proteins in the yeast Saccharomyces cerevisiae. We show two short amino acid regions of P0 protein located at positions 199–230 and 231–258, to be responsible for independent binding of two dimers, P1A‐P2B and P1B‐P2A respectively. In addition, two elements, the sequence spanning amino acids 199–230 and the P1A‐P2B dimer were found to be essential for stalk formation, indicating that this process is dependent on a balance between the P1A‐P2B dimer and the P0 protein.
Four signalling domains in the hybrid histidine protein kinase RodK of Myxococcus xanthus are required for activity
Authors: Rasmussen Anders Aa. , Wegener‐Feldbrügge Sigrun , Porter Steven L. , Armitage Judith P. , Søgaard‐Andersen Lotte 
Published: March 2006

SummaryIn prokaryotes, the principal signal transduction systems operating at the level of protein phosphorylation are the two‐component systems. A number of hybrid histidine protein kinases in these systems contain several receiver domains, however, the function of these receiver domains is unknown. The RodK kinase in Myxococcus xanthus has an unconventional domain composition with a putative N‐terminal sensor domain followed by a histidine kinase domain and three receiver domains. RodK is essential for the spatial coupling of the two morphogenetic events underlying fruiting body formation in M. xanthus, aggregation of cells into nascent fruiting bodies and the subsequent sporulation of these cells. RodK kinase activity is indispensable for RodK activity. By systematically substituting the conserved, phosphorylatable aspartate residues in the three receiver domains, genetic evidence is provided that each receiver domain is important for RodK function and that each receiver domain has a distinct function, which depends on phosphorylation. Biochemical analyses provided indirect evidence for phosphotransfer from the RodK kinase domain to the third receiver domain. This is the first example of a hybrid histidine protein kinase in which four signalling domains have been shown to be required for full activity.
Regulation of protein phosphatase type 1 and cell cycle progression by PfLRR1, a novel leucine‐rich repeat protein of the human malaria parasite Plasmodium falciparum
Authors: Daher Wassim , Browaeys Edith , Pierrot Christine , Jouin Hélène , Dive Daniel , Meurice Edwige , Dissous Colette , Capron Monique , Tomavo Stanislas , Doerig Christian , Cailliau Katia , Khalife Jamal 
Published: March 2006

SummaryThe protein called ‘suppressor of the dis2 mutant (sds22+)’ is an essential regulator of cell division in fission and budding yeasts, where its deletion causes mitotic arrest. Its role in cell cycle control appears to be mediated through the activation of protein phosphatase type 1 (PP1) in Schizosaccharomyces pombe. We have identified the Plasmodium falciparum Sds22 orthologue, which we designated PfLRR1 as it belongs to the leucine‐rich repeat protein family. We showed by glutathione‐S‐transferase pull‐down assay that the PfLRR1 gene product interacts with PfPP1, that the PfLRR1–PfPP1 complex is present in parasite extracts and that PfLRR1 inhibits PfPP1 activity. Functional studies in Xenopus oocytes revealed that PfLRR1 interacted with endogenous PP1 and overcame the G2/M cell cycle checkpoint by promoting progression to germinal vesicle breakdown (GVBD). Confirmatory results showing the appearance of GVBD were observed when oocytes were treated with anti‐PP1 antibodies or okadaic acid. Taken together, these observations suggest that PfLRR1 can regulate the cell cycle by binding to PP1 and regulating its activity.
Two distinct regions of the large serine recombinase TnpX are required for DNA binding and biological function
Authors: Adams Vicki , Lucet Isabelle S. , Tynan Fleur E. , Chiarezza Martina , Howarth Pauline M. , Kim Jonathan , Rossjohn Jamie , Lyras Dena , Rood Julian I. 
Published: March 2006

SummaryThe large serine recombinase, TnpX, from the Clostridium perfringens integrative mobilizable element Tn4451, consists of three domains and has two known DNA binding regions. In this study random and site‐directed mutagenesis was used to identify other regions of TnpX that were required for biological activity. Genetic and biochemical analysis of these mutants led to the identification of important TnpX residues in the N‐terminal catalytic pocket. In addition, another region of TnpX (aa 243–261), which is conserved within large serine recombinases, was shown to be essential for both excision and insertion. Mutation of charged residues within this region led to a loss of biological activity and aberrant DNA binding. This phenotype was mediated by interaction with the distal DNA binding region (aa 598–707). In these mutants, removal of residues 598–707 resulted in loss of DNA binding, despite the presence of the primary DNA binding region (aa 533–583). Analysis of mutations within the aa 243–261 region indicated that different protein conformations were involved in the insertion and the excision reactions. In summary, we have shown that TnpX is a complex protein that has multiple intra‐ and intermolecular interaction sites, providing insight into the structural and functional complexity of this important enzyme family.
Theileria parva and the bovine CTL response: down but not out?
Authors: MCKEEVER D. J. 
Published: March 2006

SUMMARYTheileria parva is a tick‐borne intracellular protozoan of cattle, with obligate sequential differentiation stages in lymphocytes and erythrocytes. Immunity is mediated by cytotoxic T lymphocytes (CTL) that target and clear parasitized lymphocytes but allow persistence of infected erythrocytes, which are required for transmission to the tick. The life cycle of T. parva is haploid with the exception of a brief diploid stage in the tick vector during which sexual recombination occurs. There is evidence for antigenic diversity in field parasite populations, although broad immunity can be acquired following exposure to a limited number of strains. The CTL response in individual animals is tightly focused and its specificity is strongly influenced by major histocompatibility complex (MHC) phenotype. This review discusses the issue of how CTL immunity is likely to impact on parasite population structure in the light of available information on diversity of the parasite and its ability to recombine.
Adherence by Staphylococcus intermedius to canine corneocytes: a preliminary study comparing noninflamed and inflamed atopic canine skin
Authors: McEwan Neil A. , Mellor Dominic , Kalna Gabriel 
Published: March 2006

AbstractThe adherence by three strains of Staphylococcus intermedius to corneocytes collected from healthy dogs was compared to the adherence to corneocytes collected from the inflamed (erythematous) and noninflamed (normal appearing) skin of dogs suffering from atopic dermatitis. All three strains of S. intermedius adhered in greater numbers to corneocytes from both inflamed and noninflamed atopic skin than to corneocytes from healthy dogs. Adherence was greatest to corneocytes from inflamed atopic skin but one strain showed no statistical difference for adherence to inflamed and noninflamed atopic skin. These findings suggest that S. intermedius adheres extensively to both inflamed and noninflamed canine atopic skin. This may be important in the colonization of atopic skin by this microorganism. Strain variation in the ability of S. intermedius to adhere to canine atopic corneocytes is probable.
Mast cells and angiogenesis in canine melanomas: malignancy and clinicopathological factors
Authors: Mukaratirwa Sydney , Chikafa Lynne , Dliwayo Rachel , Moyo Ndumiso 
Published: March 2006

AbstractThe biological significance of mast cells and angiogenesis in canine melanomas is unclear. Eighty canine melanomas (56 malignant and 24 benign), investigated to determine the relationship between mast cell count (MCC), microvessel density (MVD) and clinicopathology, revealed significantly higher MCC and MVD counts in malignant melanomas. Evaluation of the prognostic significance of MCC and MVD in malignant melanomas showed a significant correlation between MCC and MVD both within and at the edges of the tumour. Multivariate analysis indicated that MCC and MVD were independent predictors of survival but the former was a significantly better prognostic marker. Greater numbers of mast cells and microvessels were found in malignant melanomas of poor prognosis. The findings demonstrate a prognostic significance of MCC and MVD in canine melanocytic tumours.
An evaluation of the clinical, cytological, infectious and histopathological features of feline acne
Authors: Jazic E. , Coyner K. S. , Loeffler D. G. , Lewis T. P. 
Published: March 2006

AbstractClinical, cytological, microbial and histopathological features of feline acne were investigated in 22 cats referred or volunteered to a veterinary dermatology practice in the south‐west region of the USA. For comparison, same parameters were evaluated in five unaffected pet cats. Additionally, all cats were evaluated by immunohistochemistry (IHC) for the presence of feline calicivirus (FCV) and feline herpes virus (FHV‐1) in acne lesions. The age of onset of acne in affected cats ranged from 6 months to 14 years with a median of 4 years. The most common dermatologic lesions were comedones (73%), alopecia (68%), crusts (55%), papules (45%) and erythema (41%). Pruritus was reported in 35% of the affected cats. Cytological evidence ofMalassezia pachydermatitiswas present on 4/22 (18%) of affected cats.Microsporum caniswas isolated from a single affected cat. Bacteria were isolated from 10 of the 22 (45%) affected cats; coagulase‐positive staphylococci and alpha‐haemolytic streptococci were most common. Histopathological features included lymphoplasmacytic periductal inflammation (86%), sebaceous gland duct dilatation (73%), follicular keratosis with plugging and dilatation (59%), epitrichial gland occlusion and dilatation (32%), folliculitis (27%), pyogranulomatous sebaceous adenitis (23%) and furunculosis (23%). In one affected cat from a household with five cats, simultaneously having feline acne, FCV antigen was detected in the biopsy of the chin by IHC. Chin tissue samples from all other affected cats, as well as the five healthy cats, were negative by IHC for FCV and FHV‐1 antigens.
Evaluation of IgG subclass responses against Dermatophagoides farinae allergens in healthy and atopic dogs
Authors: Hou Chia‐Chun , Day Michael J. , Nuttall Timothy J. , Hill Peter B. 
Published: March 2006

AbstractA semiquantitative chemiluminescent Western blot analysis system was developed and validated to evaluate antigen‐specific IgG subclass responses to electrophoretically separated proteins of Dermatophagoides farinae in healthy and atopic dogs.Both groups mounted similar D. farinae‐specific IgG1 and IgG4 responses to multiple antigens, but IgG2 and IgG3 responses were difficult to detect. The most commonly recognized bands in both groups were 18 and 98 kDa antigens for IgG1 and 18, 45, 66, 98, 130 and 180 kDa for IgG4. The number of bands recognized per dog did not differ significantly, but significantly more atopic dogs had an IgG1 response to a 180 kDa protein. The overall D. farinae‐specific IgG1 and IgG4 responses were slightly higher, but not significantly different, in the healthy group. The results suggest that some antigens produced by D. farinae can induce different subclass responses. However, as most of these responses are seen in both healthy and atopic dogs, they are likely to merely represent recognition of foreign proteins presented to the immune system, rather than involvement in the pathogenesis of atopic dermatitis. The role of the 180 kDa antigen warrants further study.
The evolution of the phenotypic covariance matrix: evidence for selection and drift inMelanoplus
Authors: ROFF D. A. , MOUSSEAU T. 
Published: March 2006

AbstractPhenotypic variation in trait means is a common observation for geographically separated populations. Such variation is typically retained under common garden conditions, indicating that there has been evolutionary change in the populations, as a result of selection and/or drift. Much less frequently studied is variation in the phenotypic covariance matrix (hereafter,Pmatrix), although this is an important component of evolutionary change. In this paper, we examine variation in the phenotypic means andPmatrices in two species of grasshopper,Melanoplus sanguinipesandM. devastator. Using thePmatrices estimated for 14 populations ofM. sanguinipesand three populations ofM. devastatorwe find that (1) significant differences between the sexes can be attributed to scaling effects; (2) there is no significant difference between the two species; (3) there are highly significant differences among populations that cannot be accounted for by scaling effects; (4) these differences are a consequence of statistically significant patterns of covariation with geographic and environmental factors, phenotypic variances and covariances increasing with increased temperature but decreasing with increased latitude and altitude. This covariation suggests that selection has been important in the evolution of thePmatrix in these populations Finally, we find a significant positive correlation between the average difference between matrices and the genetic distance between the populations, indicating that drift has caused some of the variation in thePmatrices.
Limits to adaptation in asexual populations
Authors: DE VISSER J. A. G. M. , ROZEN D. E. 
Published: March 2006

AbstractIn asexual populations, the rate of adaptation is basically limited by the frequency and properties of spontaneous beneficial mutations. Hence, knowledge of these mutational properties and how they are affected by particular evolutionary conditions is a precondition for understanding the process of adaptation. Here, we address how the rate of adaptation of asexual populations is limited by its population size and mutation rate, as well as by two factors affecting the fraction of mutations that confer a benefit, i.e. the initial adaptedness of the population and the variability of the environment. These factors both influence which mutations are likely to occur, as well as the probability that they will ultimately contribute to adaptation. We attempt to separate the consequences of these basic population features in terms of their effect on the rate of adaptation by using results from evolution experiments with microorganisms.
Effects of inbreeding and rate of inbreeding in Drosophila melanogaster– Hsp70 expression and fitness
Authors: PEDERSEN K. S. , KRISTENSEN T. N. , LOESCHCKE V. 
Published: March 2006

AbstractInduction of heat shock proteins (Hsp) is a well‐known mechanism through which cells cope with stressful conditions. Hsp are induced by a variety of extrinsic stressors. However, recently intrinsic stressors (aging and inbreeding) have been shown to affect expression of Hsp. Increased homozygosity due to inbreeding may disrupt cellular homeostasis by causing increased expression of recessive deleterious mutations and breakdown of epistatic interactions. We investigated the effect of inbreeding and the rate of inbreeding on the expression of Hsp70, larval heat resistance and fecundity. In Drosophila melanogaster we found that inbred lines (F ≈ 0.67) had significantly up‐regulated expression of Hsp70, and reduced heat resistance and fecundity as compared with outbred control lines. A significant negative correlation was observed between Hsp70 expression and resistance to an extreme heat stress in inbred lines. We interpreted this as an increased requirement for Hsp70 in the lines suffering most from inbreeding depression. Inbreeding depression for fecundity was reduced with a slower rate of inbreeding compared with a fast rate of inbreeding. Thus, the effectiveness of purging seems to be improved with a slower rate of inbreeding.
Rapid and convergent evolution of parental care in hydrobiid gastropods from New Zealand
Authors: HAASE M. 
Published: March 2006

AbstractAlthough parental care occurs in most phyla encompassing a wide array of forms, little is known about its evolution in invertebrates. Two types of egg capsules have been known among ovoviviparous New Zealand hydrobiid gastropods, elastic capsules and simple membranes. Based on a phylogenetic analysis using two mtDNA sequence fragments, I asked whether the second state was derived from the first or whether brooding had multiple origins. The evolution of ovoviviparity was also investigated in the context of habitat transition between brackish and freshwater. Maximum parsimony and Markov chain models of character state transformations in a maximum likelihood framework suggested that hydrobiids have invaded freshwater three times independently. Two of these invasions were followed by the evolution of ovoviviparity, probably in adaptation to changing water levels during periods of irregular precipitation. The syntopy of two congeneric species, one oviparous and the other one brooding, indicated that the transition between reproductive modes must have occurred rapidly.
Responses to selection on male‐phase duration in Chamerion angustifolium
Authors: ROUTLEY M. B. , HUSBAND B. C. 
Published: March 2006

AbstractProtandry (when male function precedes female) can enhance fitness by reducing selfing and increasing pollen export and outcrossed siring success. However, responses to selection on protandry may be constrained by genetic variation and correlations among floral traits. We examined these potential constraints in protandrous Chamerion angustifolium (Onagraceae) by estimating genetic variation in male‐phase duration and associated floral traits using a paternal half‐sib design and selection experiment. Narrow‐sense heritability of male‐phase duration was estimated as 0.23 (SE ± 0.04) and was positively correlated with floral display. The selection experiment shortened male‐phase duration 0.8 SD from the parental average of 17.0 h and lengthened it by 2.0 SD. Furthermore, fixed floral longevity caused a negative association between male‐ and female‐phase durations. These results suggest that selection on male‐phase duration is not limited by genetic variation. However, changes in male‐phase duration may influence pollinators through correlated changes in floral display and reduced opportunities for pollen receipt during female phase.
Sexual functionality of Leptopilina clavipes (Hymenoptera: Figitidae) after reversing Wolbachia‐induced parthenogenesis
Authors: PANNEBAKKER B. A. , SCHIDLO N. S. , BOSKAMP G. J. F. , DEKKER L. , VAN DOOREN T. J. M. , BEUKEBOOM L. W. , ZWAAN B. J. , BRAKEFIELD P. M. , VAN ALPHEN J. J. M. 
Published: March 2006

AbstractFemales infected with parthenogenesis‐inducing Wolbachia bacteria can be cured from their infection by antibiotic treatment, resulting in male production. In most cases, however, these males are either sexually not fully functional, or infected females have lost the ability to reproduce sexually. We studied the decay of sexual function in males and females of the parasitoid Leptopilina clavipes. In western Europe, infected and uninfected populations occur allopatrically, allowing for an investigation of both male and female sexual function. This was made by comparing females and males induced from different parthenogenetic populations with those from naturally occurring uninfected populations. Our results indicate that although males show a decay of sexual function, they are still able to fertilize uninfected females. Infected females, however, do not fertilize their eggs after mating with males from uninfected populations. The absence of genomic incompatibilities suggests that these effects are due to the difference in mode of reproduction.