oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2015 ( 28 )

2014 ( 24 )

2013 ( 58 )

2012 ( 101 )

Custom range...

Search Results: 1 - 10 of 545 matches for " Gunna Christiansen "
All listed articles are free for downloading (OA Articles)
Page 1 /545
Display every page Item
The vaa locus of Mycoplasma hominis contains a divergent genetic islet encoding a putative membrane protein
Thomas Boesen, Jeppe Emmersen, Agata Baczynska, Svend Birkelund, Gunna Christiansen
BMC Microbiology , 2004, DOI: 10.1186/1471-2180-4-37
Abstract: Mapping of vaa on existing physical maps of five M. hominis isolates by pulsed field gel electrophoresis revealed that vaa is located in a genomic region containing the majority of other characterized membrane protein genes of M. hominis. Sequencing of an 11 kb region containing the vaa locus of M. hominis isolate 132 showed the presence of conserved housekeeping genes at the borders of the region, uvrA upstream and the hitABL operon downstream to vaa. Analysis of 20 M. hominis isolates revealed that the vaa upstream region was conserved whereas the downstream region was highly variable. In isolate 132 this region contained an open reading frame (ORF) encoding a putative 160 kDa membrane protein. Homologous ORFs were present in half of the isolates, whereas this ORF, termed vmp (variable membrane protein), was deleted from the locus in the remaining isolates. Compellingly, the conserved upstream region and variable downstream region of vaa correlates with the genetic structure of vaa itself which consists of a conserved 5' end and a variable 3' end containing a variable number of exchangeable sequence cassettes.Our data demonstrate that the vaa locus contains a divergent genetic islet, and indicate pronounced intraspecies recombination. The high variability level of the locus indicate that it is a chromosomal 'hot spot', presumably important for sustaining diversity and a high adaptation potential of M. hominis.The mycoplasmas are wall-less prokaryotes characterized by small genomes (580 – 2200 kb) and a low G+C content, generally below 30%. They are the smallest self-replicating organisms known with cell diameters normally in the range of 0.3–0.8 μm [1], and are observed as parasites of insects, plants, animals and humans with strict host specificities. As a consequence of the direct exposure of proteins located on the surface of the cytoplasmic membrane to the surrounding environment, antigenic variation of surface proteins is observed among mycoplasmas. The often
The expression, processing and localization of polymorphic membrane proteins in Chlamydia pneumoniae strain CWL029
Brian Vandahl, Anna Pedersen, Kris Gevaert, Arne Holm, Jo?l Vandekerckhove, Gunna Christiansen, Svend Birkelund
BMC Microbiology , 2002, DOI: 10.1186/1471-2180-2-36
Abstract: Ten Pmps were identified in elementary bodies (EBs). Eight of these were investigated with respect to time dependent expression and all were found to be up-regulated between 36 and 48 hours post infection. Antibodies against Pmp6, 8, 10, 11 and 21 reacted with chlamydiae when infected cells were formalin fixed. Pmp6, Pmp20 and Pmp21 were found in cleaved forms, and the cleavage sites of Pmp6 and Pmp21 were identified.The Pmps are heavily up-regulated at the time of conversion of RB to EB, and at least ten Pmps are present in EBs. Due to their reaction in formalin fixation it is likely that Pmp6, 8, 10, 11 and 21 are surface exposed. The identified cleavage sites of Pmp6 and Pmp21 are in agreement with the theory that the Pmps are autotransporters.Chlamydiae are pathogenic gram-negative bacteria of which C. pneumoniae causes upper and lower respiratory tract infections in humans [1]. Going through a developmental cycle the chlamydiae alternate between infective elementary bodies (EBs) and replicative reticulate bodies (RBs) [2]. The bacteria are obligate and intracellular, residing inside a specialized phagosome, named the chlamydial inclusion. The duration of the developmental cycle for C. pneumoniae cultivated in cell culture is about 72 hours [3].The C. pneumoniae CWL029 genome sequence revealed the presence of a gene family, the pmp family, consisting of 21 members [4] that were paralogous to the pmps found in C. trachomatis [5] and C. psittaci [6-9]. The C. psittaci Pmps have been analysed by two-dimensional electrophoresis in an earlier study [37]. The Pmps are two-domain proteins with similarity to autotransporter proteins [4,10,11]. They are characterized by a high frequency of the two sequences FxxN and GGAI in the N-terminal part (twelve and seven repeats on average, respectively) [4], and their C-terminal part shows the characteristics of a β-barrel [10]. The GGAI motif and the prediction of a C-terminal β-barrel suggest that the Pmps are autotransporters,
Immune response to Mycoplasma pneumoniae P1 and P116 in patients with atypical pneumonia analyzed by ELISA
Mette Drasbek, Pernille K Nielsen, Kenneth Persson, Svend Birkelund, Gunna Christiansen
BMC Microbiology , 2004, DOI: 10.1186/1471-2180-4-7
Abstract: A recombinant protein derived from the P116 protein and one from the P1 protein were used in two ELISA tests, rP116-ELISA and rP1-ELISA. Human serum samples from patients with atypical pneumonia were tested and compared to the results of the complement fixation test. There was a good agreement between the two tests but the rP1-ELISA showed the best discrimination between positive and negative samples.Two ELISA tests based on recombinant proteins have been analysed and compared to the complement fixation test results. The two ELISA tests were found suitable for use in serodiagnostics of M. pneumoniae infections. The use of specific antigens eliminates the risk of cross reaction to an immune response against other bacteria.Mycoplasma pneumoniae is a human pathogen that colonizes the mucosal surfaces of the respiratory tract [1]. The pathogen infects the upper and the lower respiratory tract and is the leading cause of atypical pneumonia in children and young adults [2]. M. pneumoniae infections are often seen as epidemics occurring at intervals of 4–7 years. The patients show flu-like symptoms but characteristically the infection is chronic in onset and recovery [3].The lacking cell wall distinguishes Mollicutes from other eubacteria and due to the lack of cell wall M. pneumoniae is resistant to penicillin. A specific and early diagnosis is therefore important in order to select the right treatment. The standard methods for diagnosis of M. pneumoniae are culturing, serology and PCR. Since M. pneumoniae can be difficult to isolate [4] most of the laboratory diagnoses are serology tests, such as complement fixation test (CF test) and different enzyme-linked immunoabsorbent assays (ELISA) [5]. PCR has also been used for the detection of M. pneumoniae [6-8]. The CF test has a limited value producing inconclusive results, because it also measures antibodies deriving from earlier infections [9], and the glycolipid antigen which is not M. pneumoniae specific cross reacts wit
Determination of PCR efficiency in chelex-100 purified clinical samples and comparison of real-time quantitative PCR and conventional PCR for detection of Chlamydia pneumoniae
Tina Mygind, Svend Birkelund, Niels H Birkeb?k, Lars ?stergaard, J?rgen Jensen, Gunna Christiansen
BMC Microbiology , 2002, DOI: 10.1186/1471-2180-2-17
Abstract: We compared the performance of a newly developed real-time PCR with a conventional PCR method for detection of C. pneumoniae. The PCR methods were tested on reference samples containing C. pneumoniae DNA and on 136 nasopharyngeal samples from patients with a chronic cough. We found the same detection limit for the two methods and that clinical performance was equal for the real-time PCR and for the conventional PCR method, although only three samples tested positive. To investigate whether the low prevalence of C. pneumoniae among patients with a chronic cough was caused by suboptimal PCR efficiency in the samples, PCR efficiency was determined based on the real-time PCR. Seventeen of twenty randomly selected clinical samples had a similar PCR efficiency to samples containing pure genomic C. pneumoniae DNA.These results indicate that the performance of real-time PCR is comparable to that of conventional PCR, but that needs to be confirmed further. Real-time PCR can be used to investigate the PCR efficiency which gives a rough estimate of how well the real-time PCR assay works in a specific sample type. Suboptimal PCR efficiency of PCR is not a likely explanation for the low positivity rate of C. pneumoniae in patients with a chronic cough.C. pneumoniae causes upper respiratory tract infections, and in some studies it accounts for 6–10% of community-acquired pneumonia [1]. Seroprevalence among adults is 40–70%, increasing with age, indicating that most people are exposed at least once and that reinfections are common [2]. C. pneumoniae is the microorganism that most commonly is associated with the inflammation seen in atherosclerosis [3].C. pneumoniae infection has been detected by serological methods but PCR is currently viewed as an advantageous alternative since it detects the presence of the DNA of the organism. This allows for an early and clinically relevant diagnosis in contrast to the detection of C. pneumoniae specific antibodies that develop late in the cou
Development of real-time PCR for detection of Mycoplasma hominis
Agata Baczynska, Helle F Svenstrup, Jens Fedder, Svend Birkelund, Gunna Christiansen
BMC Microbiology , 2004, DOI: 10.1186/1471-2180-4-35
Abstract: Real-time PCR was optimized to detect 10 copies of M. hominis PG21 genomic DNA. A fluorescence signal was measured for all 20 other M. hominis isolates, and melting curves analysis showed variations in the melting temperature in agreement with sequence variation in the region of the probes. There was no amplification of other mycoplasmal DNA and human DNA. Eighty-three patient cervical swab samples from infertile women were cultured for M. hominis in the BEa medium. Two of the samples (2.4%) were positive after 48 hours of incubation. The real-time PCR detected the same two samples positive, and the DNA concentrations in the clinical specimens were calculated to 37.000 copies/ml and 88.500 copies/ml, respectively.The results demonstrate that real-time PCR may prove to be a rapid alternative to the traditional cultivation method. Information on bacterial load in genital swabs can be obtained. The assay allowed detection of M. hominis in a closed system reducing the risk of contamination by amplicon carry-over.Mycoplasmas are the smallest living prokaryotes known, capable of self-replication. They belong to the class Mollicutes and are distinguished phenotypically from other bacteria by their minute size and lack of a cell wall. Genetically they differ by having a small genome size and low G+C content {1} [1]. Mycoplasmas have adapted to a wide variety of hosts and can colonize man, other animals and plants. The colonising organisms are host specific. In humans, mycoplasmas colonize mainly the upper respiratory tract and the genitourinary tract.The first human Mycoplasma isolated was Mycoplasma hominis [2]. It is a heterogeneous genital mycoplasma [3] found in at least two-thirds of women with bacterial vaginosis (BV), compared to 10% of healthy women [4,5]. M. hominis has also been isolated from the endometrium and fallopian tubes of 10% women with salpingitis. However, its role as a primary pathogen is doubtful since it co-exists with many other bacteria in BV [6].
Evaluation of five DNA extraction methods for purification of DNA from atherosclerotic tissue and estimation of prevalence of Chlamydia pneumoniae in tissue from a Danish population undergoing vascular repair
Tina Mygind, Lars ?stergaard, Svend Birkelund, Jes S Lindholt, Gunna Christiansen
BMC Microbiology , 2003, DOI: 10.1186/1471-2180-3-19
Abstract: The five different DNA extraction methods were tested on homogenate of atherosclerotic tissue spiked with C. pneumoniae DNA or EB, on pure C. pneumoniae DNA samples and on whole C. pneumoniae EB. Recovery of DNA was measured with a C. pneumoniae-specific quantitative real-time PCR. A DNA extraction method based on DNA-binding to spin columns with a silica-gel membrane (DNeasy Tissue kit) showed the highest recovery rate for the tissue samples and pure DNA samples. However, an automated extraction method based on magnetic glass particles (MagNA Pure) performed best on intact EB and atherosclerotic tissue spiked with EB. The DNeasy Tissue kit and MagNA Pure methods and the highly sensitive real-time PCR were subsequently used on 78 atherosclerotic tissue samples from Danish patients undergoing vascular repair. None of the samples were positive for C. pneumoniae DNA. The atherosclerotic samples were tested for inhibition by spiking with two different, known amounts of C. pneumoniae DNA and no samples showed inhibition.As a highly sensitive PCR method and an optimised DNA extraction method were used, non-detection in atherosclerotic tissue from the Danish population was probably not caused by use of inappropriate methods. However, more samples may need to be analysed per patient to be completely certain on this. Possible methodological and epidemiological reasons for non-detection of C. pneumoniae DNA in atherosclerotic tissue from the Danish population are discussed. Further testing of DNA extraction methods is needed as this study has shown considerable intra- and inter-method variation in DNA recovery.Chlamydia pneumoniae is an important cause of human respiratory tract diseases [1]. The organism has also been associated with atherosclerosis and thromboembolic events by use of seroepidemiology and direct detection of the organism in atherosclerotic plaques [2]. Although the presence of C. pneumoniae DNA has been observed in atherosclerotic lesions, the pathological o
Increased Levels of IgG Antibodies against Human HSP60 in Patients with Spondyloarthritis
Astrid Hjelholt, Thomas Carlsen, Bent Deleuran, Anne Grethe Jurik, Berit Schi?ttz-Christensen, Gunna Christiansen, Svend Birkelund
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056210
Abstract: Spondyloarthritis (SpA) comprises a heterogeneous group of inflammatory diseases, with strong association to human leukocyte antigen (HLA)-B27. A triggering bacterial infection has been considered as the cause of SpA, and bacterial heat shock protein (HSP) seems to be a strong T cell antigen. Since bacterial and human HSP60, also named HSPD1, are highly homologous, cross-reactivity has been suggested in disease initiation. In this study, levels of antibodies against bacterial and human HSP60 were analysed in SpA patients and healthy controls, and the association between such antibodies and disease severity in relation to HLA-B27 was evaluated. Serum samples from 82 patients and 50 controls were analysed by enzyme-linked immunosorbent assay (ELISA) for immunoglobulin (Ig)G1, IgG2, IgG3 and IgG4 antibodies against human HSP60 and HSP60 from Chlamydia trachomatis, Salmonella enteritidis and Campylobacter jejuni. Disease severity was assessed by the clinical scorings Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Metrology Index (BASMI). Levels of IgG1 and IgG3 antibodies against human HSP60, but not antibodies against bacterial HSP60, were elevated in the SpA group compared with the control group. Association between IgG3 antibodies against human HSP60 and BASMI was shown in HLA-B27+ patients. Only weak correlation between antibodies against bacterial and human HSP60 was seen, and there was no indication of cross-reaction. These results suggest that antibodies against human HSP60 is associated with SpA, however, the theory that antibodies against human HSP60 is a specific part of the aetiology, through cross-reaction to bacterial HSP60, cannot be supported by results from this study. We suggest that the association between elevated levels of antibodies against human HSP60 and disease may reflect a general activation of the immune system and an increased expression of human HSP60 in the synovium of patients with SpA.
Wildtype and A30P Mutant Alpha-Synuclein Form Different Fibril Structures
S?ren Bang Nielsen, Francesca Macchi, Samuele Raccosta, Annette Eva Langkilde, Lise Giehm, Anders Kyrsting, Anna Sigrid Pii Svane, Mauro Manno, Gunna Christiansen, Niels Christian Nielsen, Lene Oddershede, Bente Vestergaard, Daniel Erik Otzen
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067713
Abstract: Parkinson’s Disease (PD) is a neurodegenerative movement disorder affecting millions of people worldwide. One of the key players in the development of the disease is the protein α-synuclein (aSN), which aggregates in the brain of PD patients. The aSN mutant A30P has been reported to cause early-onset familial PD and shows different aggregation behavior compared to wt aSN. Here we use a multidisciplinary approach to compare the aggregation process of wt and A30P aSN. In agreement with previous studies, we observe an initial lag phase followed by a continuous structural development of fibrils until reaching an apparent monomer-aggregate equilibrium state and a plateau in Thioflavin T (ThT) fluorescence intensity. However, at later timepoints A30P shows greater propensity than αSN wt to form dense bundled fibril networks. Combining small angle x-ray scattering, x-ray fibre diffraction and linear dichroism, we demonstrate that while the microscopic structure of the individual fibril essentially remains constant throughout the experiment, the formation of dense A30P fibril networks occur through a continuous assembly pathway while the formation of less dense wt fibril networks with fewer contact points follows a continuous path during the elongation phase and a second rearrangement phase after reaching the ThT fluorescence plateau. Our work thus highlights that structural rearrangements proceed beyond the plateau in ThT-based monitoring of the fibrillation process, and the density and morphology of the resulting fibril networks is highly dependent on the aSN form studied.
Evolution of Skull and Mandible Shape in Cats (Carnivora: Felidae)
Per Christiansen
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002807
Abstract: The felid family consists of two major subgroups, the sabretoothed and the feline cats, to which all extant species belong, and are the most anatomically derived of all carnivores for predation on large prey with a precision killing bite. There has been much controversy and uncertainty about why the skulls and mandibles of sabretoothed and feline cats evolved to become so anatomically divergent, but previous models have focused on single characters and no unifying hypothesis of evolutionary shape changes has been formulated. Here I show that the shape of the skull and mandible in derived sabrecats occupy entirely different positions within overall morphospace from feline cats, and that the evolution of skull and mandible shape has followed very different paths in the two subgroups. When normalised for body-size differences, evolution of bite forces differ markedly in the two groups, and are much lower in derived sabrecats, and they show a significant relationship with size and cranial shape, whereas no such relationship is present in feline cats. Evolution of skull and mandible shape in modern cats has been governed by the need for uniform powerful biting irrespective of body size, whereas in sabrecats, shape evolution was governed by selective pressures for efficient predation with hypertrophied upper canines at high gape angles, and bite forces were secondary and became progressively weaker during sabrecat evolution. The current study emphasises combinations of new techniques for morphological shape analysis and biomechanical studies to formulate evolutionary hypotheses for difficult groups.
The Making of a Monster: Postnatal Ontogenetic Changes in Craniomandibular Shape in the Great Sabercat Smilodon
Per Christiansen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029699
Abstract: Derived sabercats had craniomandibular morphologies that in many respects were highly different from those of extant felids, and this has often been interpreted functionally as adaptations for predation at extreme gape angles with hypertrophied upper canines. It is unknown how much of this was a result of intraspecific postnatal ontogeny, since juveniles of sabercats are rare and no quantitative study has been made of craniomandibular ontogeny. Postnatal ontogenetic craniomandibular shape changes in two morphologically derived sabercats, Smilodon fatalis and S. populator, were analysed using geometric morphometrics and compared to three species of extant pantherines, the jaguar, tiger, and Sunda clouded leopard. Ontogenetic shape changes in Smilodon usually involved the same areas of the cranium and mandible as in extant pantherines, and large-scale modularization was similar, suggesting that such may have been the case for all felids, since it followed the same trends previously observed in other mammals. However, in other respects Smilodon differed from extant pantherines. Their crania underwent much greater and more localised ontogenetic shape changes than did the mandibles, whereas crania and mandibles of extant pantherines underwent smaller, fewer and less localised shape changes. Ontogenetic shape changes in the two species of Smilodon are largely similar, but differences are also present, notably those which may be tied to the presence of larger upper canines in S. populator. Several of the specialized cranial characters differentiating adult Smilodon from extant felids in a functional context, which are usually regarded as evolutionary adaptations for achieving high gape angles, are ontogenetic, and in several instances ontogeny appears to recapitulate phylogeny to some extent. No such ontogenetic evolutionary adaptive changes were found in the extant pantherines. Evolution in morphologically derived sabercats involved greater cranial ontogenetic changes than among extant felids, resulting in greatly modified adult craniomandibular morphologies.
Page 1 /545
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.