| 1. |
- Boman, Kurt, et al.
(författare)
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Remote-controlled robotic arm for real-time echocardiography : the diagnostic future for patients in rural areas?
- 2009
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Ingår i: Telemedicine journal and e-health. - : Mary Ann Liebert Inc. - 1530-5627 .- 1556-3669. ; 15:2, s. 142-147
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Tidskriftsartikel (refereegranskat)abstract
- There exists a great clinical need for improving specialist consultation and utilization of echocardiography in areas remote from hospital-based care. This paper presents the development and first technical assessment of a concept of cardiovascular consultation utilizing long distance, real-time echocardiography as a diagnostic tool in rural areas. The development of CARdiological consultation at a DISTance (CARDISTA) was achieved in three stages, comprising tests of different broadband infrastructures, videoconference systems, microphones, cameras, monitors, and loudspeakers. The CARDISTA concept includes a cardiologist and a sonographer, a robotic arm (Medirob), a portable ultrasound machine, and presently available information technology using an advanced broadband backbone. The three stages provided, with some remaining doubts, echocardiographic examination at a distance comparable to hospital-based examinations. A continuous broadband capacity of 20 megabits per second (Mbps) seemed to be a vital component of CARDISTA for achieving the highest-quality imaging. With this broadband capacity, it was possible to achieve a transmission delay below 200 ms. The technical tests of the CARDISTA concept revealed promising results in enabling long distance real-time echocardiography for specialist consultation. CARDISTA is now ready for clinical testing and evaluation in rural areas for patients with heart diseases, especially heart failure.
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| 2. |
- Bröms, Jeanette E, et al.
(författare)
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Diminished LcrV secretion attenuates Yersinia pseudotuberculosis virulence.
- 2007
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Ingår i: J Bacteriol. - 0021-9193.
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Tidskriftsartikel (refereegranskat)abstract
- Many Gram negative bacterial pathogenicity factors that function beyond the outer membrane are secreted via a contact-dependent type III secretion system. Two types of substrates are predestined for this mode of secretion; anti-host effectors that are translocated directly into target cells and the translocators required for targeting of the effectors across the host cell membrane. N-terminal secretion signals are important for recognition of the protein cargo by the type III secretion machinery. Even though such signals are known for several effectors, a consensus signal sequence is not obvious. One of the tranclocators, LcrV, has been attributed other functions in addition to its role in translocation. These functions include regulation, presumably via interaction with LcrG inside the bacteria and immunomodulation via interaction with TLR2. Here we wanted to address the significance of the specific targeting of LcrV to the exterior for its function in regulation, effector targeting and virulence. The results, highlighting key N-terminal amino acids important for LcrV secretion, allowed us to dissect the role of LcrV in regulation from that in effector targeting/virulence. While only low levels of exported LcrV were required for in vitro effector translocation as deduced by a cell infection assay, fully functional export of LcrV was found to be a prerequisite for its role in virulence in the systemic murine infection model.
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| 3. |
- Bröms, Jeanette E, et al.
(författare)
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Tetratricopeptide repeats are essential for PcrH chaperone function in Pseudomonas aeruginosa type III secretion.
- 2006
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Ingår i: FEMS Microbiol Lett. - 0378-1097. ; 256:1, s. 57-66
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Tidskriftsartikel (refereegranskat)abstract
- The type III secretion system (T3SS) is a specialized apparatus evolved by Gram-negative bacteria to deliver effector proteins into host cells, thus facilitating the establishment of an infection. Effector translocation across the target cell plasma membrane is believed to occur via pores formed by at least two secreted translocator proteins, the functions of which are dependent upon customized class II T3SS chaperones. Recently, three internal tetratricopeptide repeats (TPRs) were identified in this class of chaperones. Here, defined mutagenesis of the class II chaperone PcrH of Pseudomonas aeruginosa revealed these TPRs to be essential for chaperone activity towards the translocator proteins PopB and PopD and subsequently for the translocation of exoenzymes into host cells.
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| 4. |
- Edqvist, Petra J, et al.
(författare)
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Tetratricopeptide repeats in the type III secretion chaperone, LcrH : their role in substrate binding and secretion.
- 2006
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 59:1, s. 31-44
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Tidskriftsartikel (refereegranskat)abstract
- Non-flagellar type III secretion systems (T3SSs) transport proteins across the bacterial cell and into eukaryotic cells. Targeting of proteins into host cells requires a dedicated translocation apparatus. Efficient secretion of the translocator proteins that make up this apparatus depends on molecular chaperones. Chaperones of the translocators (also called class-II chaperones) are characterized by the possession of three tandem tetratricopeptide repeats (TPRs). We wished to dissect the relations between chaperone structure and function and to validate a structural model using site-directed mutagenesis. Drawing on a number of experimental approaches and focusing on LcrH, a class-II chaperone from the Yersinia Ysc-Yop T3SS, we examined the contributions of different residues, residue classes and regions of the protein to chaperone stability, chaperone-substrate binding, substrate stability and secretion and regulation of Yop protein synthesis. We confirmed the expected role of the conserved canonical residues from the TPRs to chaperone stability and function. Eleven mutations specifically abrogated YopB binding or secretion while three mutations led to a specific loss of YopD secretion. These are the first mutations described for any class-II chaperone that allow interactions with one translocator to be dissociated from interactions with the other. Strikingly, all mutations affecting the interaction with YopB mapped to residues with side chains projecting from the inner, concave surface of the modelled TPR structure, defining a YopB interaction site. Conversely, all mutations preventing YopD secretion affect residues that lie on the outer, convex surface of the triple-TPR cluster in our model, suggesting that this region of the molecule represents a distinct interaction site for YopD. Intriguingly, one of the LcrH double mutants, Y40A/F44A, was able to maintain stable substrates inside bacteria, but unable to secrete them, suggesting that these two residues might influence delivery of substrates to the secretion apparatus.
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| 5. |
- Francis, Matthew S, et al.
(författare)
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Regulation of type III secretion systems
- 2002
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Ingår i: Current Opinion in Microbiology. - 1369-5274 .- 1879-0364. ; 5:2, s. 166-172
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Tidskriftsartikel (refereegranskat)abstract
- Type III secretion systems are utilised by numerous Gram-negative bacteria to efficiently interact with a host. Appropriate expression of type III genes is achieved through the integration of several regulatory pathways that ultimately co-ordinate the activity of a central transcriptional activator usually belonging to the AraC family. The complex regulatory cascades allow this virulence strategy to be utilised by different bacteria even if they occupy diverse niches that define a unique set of environmental cues. Simulating the appropriate combination of signals in vitro to allow a meaningful interpretation of the type III assembly and secretion regulatory cascade remains a common goal for researchers. Pieces of the puzzle slowly emerge to provide insightful views into the complex regulatory networks that allow bacteria to assemble and utilise type III secretion to efficiently colonise a host.
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| 6. |
- Garbom, Sara, et al.
(författare)
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Identification of novel virulence-associated genes via genome analysis of hypothetical genes.
- 2004
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 72:3, s. 1333-1340
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Tidskriftsartikel (refereegranskat)abstract
- The sequencing of bacterial genomes has opened new perspectives for identification of targets for treatment of infectious diseases. We have identified a set of novel virulence-associated genes (vag genes) by comparing the genome sequences of six human pathogens that are known to cause persistent or chronic infections in humans: Yersinia pestis, Neisseria gonorrhoeae, Helicobacter pylori, Borrelia burgdorferi, Streptococcus pneumoniae, and Treponema pallidum. This comparison was limited to genes annotated as hypothetical in the T. pallidum genome project. Seventeen genes with unknown functions were found to be conserved among these pathogens. Insertional inactivation of 14 of these genes generated nine mutants that were attenuated for virulence in a mouse infection model. Out of these nine genes, five were found to be specifically associated with virulence in mice as demonstrated by infection with Yersinia pseudotuberculosis in-frame deletion mutants. In addition, these five vag genes were essential only in vivo, since all the mutants were able to grow in vitro. These genes are broadly conserved among bacteria. Therefore, we propose that the corresponding vag gene products may constitute novel targets for antimicrobial therapy and that some vag mutants could serve as carrier strains for live vaccines.
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| 7. |
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| 8. |
- Olsson, Jan, et al.
(författare)
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The YopD translocator of Yersinia pseudotuberculosis is a multifunctional protein comprised of discrete domains.
- 2004
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 186:13, s. 4110-4123
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Tidskriftsartikel (refereegranskat)abstract
- To establish an infection, Yersinia pseudotuberculosis utilizes a plasmid-encoded type III translocon to microinject several anti-host Yop effectors into the cytosol of target eukaryotic cells. YopD has been implicated in several key steps during Yop effector translocation, including maintenance of yop regulatory control and pore formation in the target cell membrane through which effectors traverse. These functions are mediated, in part, by an interaction with the cognate chaperone, LcrH. To gain insight into the complex molecular mechanisms of YopD function, we performed a systematic mutagenesis study to search for discrete functional domains. We highlighted amino acids beyond the first three N-terminal residues that are dispensable for YopD secretion and confirmed that an interaction between YopD and LcrH is essential for maintenance of yop regulatory control. In addition, discrete domains within YopD that are essential for both pore formation and translocation of Yop effectors were identified. Significantly, other domains were found to be important for effector microinjection but not for pore formation. Therefore, YopD is clearly essential for several discrete steps during efficient Yop effector translocation. Recognition of this modular YopD domain structure provides important insights into the function of YopD.
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