| 1. |
|
|
| 2. |
|
|
| 3. |
- Foti, M., et al.
(författare)
-
P56Lck anchors CD4 to distinct microdomains on microvilli
- 2002
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 99:4, s. 2008-2013
-
Tidskriftsartikel (refereegranskat)abstract
- Cell-surface microvilli play a central role in adhesion, fusion, and signaling processes. Some adhesion and signaling receptors segregate on microvilli but the determinants of this localization remain mostly unknown. In this study, we considered CD4, a receptor involved in immune response and HIV infection, and p56Lck, a CD4-associated tyrosine kinase. Analysis of CD4 trafficking reveals that p56Lck binds tightly to CD4 independently of its activation state and inhibits CD4 internalization. Electron microscopy analysis established that p56Lck mediates CD4 association with microvilli whereas biochemical data indicate that p56Lck expression renders CD4 insoluble by the nonionic detergent Triton X-100. In addition, cytoskeleton-disrupting agent increased CD4 solubility, suggesting the involvement of cytoskeletal elements in CD4 anchoring to microvilli. This concept was supported further by the observation that the lateral mobility of CD4 within the plasma membrane was decreased in cells expressing p56Lck. Finally, isolation of detergent-resistant membranes revealed that the complex CD4-p56Lck is enriched within these domains as opposed to conditions in which CD4 does not interact with p56Lck. In conclusion, our results show that p56Lck targets CD4 to specialized lipid microdomains preferentially localized on microvilli. This localization, which prevents CD4 internalization, might facilitate CD4-mediated adhesion processes and could correspond to the signaling site of the receptor.
|
|
| 4. |
- Hedman, Johannes, et al.
(författare)
-
Evaluation of amylase testing as a tool for saliva screening of crime scene trace swabs
- 2011
-
Ingår i: FORENSIC SCIENCE INTERNATIONAL-GENETICS. - : ELSEVIER IRELAND LTD, ELSEVIER HOUSE, BROOKVALE PLAZA, EAST PARK SHANNON, CO, CLARE, 00000, IRELAND. - 1872-4973 .- 1878-0326. ; 5:3, s. 194-198
-
Tidskriftsartikel (refereegranskat)abstract
- Amylase testing has been used as a presumptive test for crime scene saliva for over three decades, mainly to locate saliva stains on surfaces. We have developed a saliva screening application for crime scene trace swabs, utilising an amylase sensitive paper (Phadebas (R) Forensic Press test). Positive results were obtained for all tested dried saliva stains (0.5-32 mu L) with high or intermediate amylase activity (840 and 290 kU/L). Results were typically obtained within 5 min, and all samples that produced DNA profiles were positive. However, salivary amylase activities, as well as DNA concentrations, vary significantly between individuals. We show that there is no correlation between amylase activity and amount of DNA in fresh saliva. Even so, a positive amylase result indicates presence of saliva, and thereby presence of DNA. Amylase testing may be useful for screening in investigations where the number of DNA analyses is limited due to cost, e. g., in volume crime.
|
|
| 5. |
- Hedman, Johannes, et al.
(författare)
-
Improved forensic DNA analysis through the use of alternative DNA polymerases and statistical modeling of DNA profiles
- 2009
-
Ingår i: BIOTECHNIQUES. - : Eaton Publishing. - 0736-6205 .- 1940-9818. ; 47:5, s. 951-958
-
Tidskriftsartikel (refereegranskat)abstract
- DNA evidence, linking perpetrators to crime scenes, is central to many legal proceedings. However, DNA samples from crime scenes often contain PCR-inhibitory substances, which may generate blank or incomplete DNA profiles. Extensive DNA purification can be required to rid the sample of these inhibitors, although these procedures increase the risk of DNA loss. Most forensic laboratories use commercial DNA amplification kits (e.g., AmpFlSTR SGM Plus) with the DNA polymerase AmpliTaq Gold as the gold standard. Here, we show that alternative DNA polymerase-buffer systems can improve the quality of forensic DNA analysis and efficiently circumvent PCR inhibition in crime scene samples, without additional sample preparation. DNA profiles from 20 of 32 totally or partially inhibited crime scene saliva samples were significantly improved using Bio-X-Act Short, ExTaq Hot Start, or PicoMaxx High Fidelity instead of AmpliTaq Gold. A statistical model for unbiased quality control of forensic DNA profiles was developed to quantify the results. Our study demonstrates the importance of adjusting the chemistry of the PCR to enhance forensic DNA analysis and diagnostic PCR, providing an alternative to laborious sample preparation protocols.
|
|
| 6. |
|
|
| 7. |
- Hedman, Johannes, et al.
(författare)
-
Pre-PCR processing in bioterrorism preparedness : improved diagnostic capabilities for laboratory response networks
- 2013
-
Ingår i: Biosecurity and bioterrorism. - : Mary Ann Liebert. - 1538-7135 .- 1557-850X. ; 11:S1, s. S87-S101
-
Tidskriftsartikel (refereegranskat)abstract
- Diagnostic DNA analysis using polymerase chain reaction (PCR) has become a valuable tool for rapid detection of biothreat agents. However, analysis is often challenging because of the limited size, quality, and purity of the biological target. Pre-PCR processing is an integrated concept in which the issues of analytical limit of detection and simplicity for automation are addressed in all steps leading up to PCR amplification—that is, sampling, sample treatment, and the chemical composition of PCR. The sampling method should maximize target uptake and minimize uptake of extraneous substances that could impair the analysis—so-called PCR inhibitors. In sample treatment, there is a trade-off between yield and purity, as extensive purification leads to DNA loss. A cornerstone of pre-PCR processing is to apply DNA polymerase-buffer systems that are tolerant to specific sample impurities, thereby lowering the need for expensive purification steps and maximizing DNA recovery. Improved awareness among Laboratory Response Networks (LRNs) regarding pre-PCR processing is important, as ineffective sample processing leads to increased cost and possibly false-negative or ambiguous results, hindering the decision-making process in a bioterrorism crisis. This article covers the nature and mechanisms of PCR-inhibitory substances relevant for agroterrorism and bioterrorism preparedness, methods for quality control of PCR reactions, and applications of pre-PCR processing to optimize and simplify the analysis of various biothreat agents. Knowledge about pre-PCR processing will improve diagnostic capabilities of LRNs involved in the response to bioterrorism incidents.
|
|
| 8. |
- Hedman, Johannes, et al.
(författare)
-
Synergy between DNA polymerases increases polymerase chain reaction inhibitor tolerance in forensic DNA analysis
- 2010
-
Ingår i: Analytical Biochemistry. - - : Elsevier Inc.. - 0003-2697 .- 1096-0309. ; 405, s. 192-200
-
Tidskriftsartikel (refereegranskat)abstract
- The success rate of diagnostic polymerase chain reaction (PCR) analysis is lowered by inhibitory substancespresent in the samples. Recently, we showed that tolerance to PCR inhibitors in crime scene salivastains can be improved by replacing the standard DNA polymerase AmpliTaq Gold with alternative DNApolymerase–buffer systems (Hedman et al., BioTechniques 47 (2009) 951–958). Here we show thatblending inhibitor-resistant DNA polymerase–buffer systems further increases the success rate of PCRfor various types of real crime scene samples showing inhibition. For 34 of 42 ‘‘inhibited” crime scenestains, the DNA profile quality was significantly improved using a DNA polymerase blend of ExTaq HotStart and PicoMaxx High Fidelity compared with AmpliTaq Gold. The significance of the results was confirmedby analysis of variance. The blend performed as well as, or better than, the alternative DNA polymerasesused separately for all tested sample types. When used separately, the performance of the DNApolymerases varied depending on the nature of the sample. The superiority of the blend is discussed interms of complementary effects and synergy between the DNA polymerase–buffer systems.
|
|
| 9. |
|
|
| 10. |
- Holm, Åsa, et al.
(författare)
-
Leishmania donovani lipophosphoglycan causes periphagosomal actin accumulation : correlation with impaired translocation of PKCα and defective phagosome maturation
- 2001
-
Ingår i: Cellular Microbiology. - : Hindawi Limited. - 1462-5814 .- 1462-5822. ; 3:7, s. 439-447
-
Tidskriftsartikel (refereegranskat)abstract
- Lipophosphoglycan (LPG) is the major surface glycoconjugate of Leishmania donovani promastigotes. The repeating disaccharide–phosphate units of LPG are crucial for promastigote survival inside macrophages and establishment of infection. LPG has a number of effects on the host cell, including inhibition of PKC activity, inhibition of nitric oxide production and altered expression of cytokines. LPG also inhibits phagosomal maturation, a process requiring depolymerization of periphagosomal F-actin. In the present study, we have characterized the dynamics of F-actin during the phagocytosis of L. donovani promastigotes in J774 macrophages. We observed that F-actin accumulated progressively around phagosomes containing wild-type L. donovani promastigotes during the first hour of phagocytosis. Using LPG-defective mutants and yeast particles coated with purified LPG, we obtained evidence that this effect could be attributed to the repeating units of LPG. LPG also disturbed cortical actin turnover during phagocytosis. The LPG-dependent accumulation of periphagosomal F-actin correlated with an impaired recruitment of the lysosomal marker LAMP1 and PKCα to the phagosome. Accumulation of periphagosomal F-actin during phagocytosis of L. donovani promastigotes may contribute to the inhibition of phagosomal maturation by physically preventing vesicular trafficking to and from the phagosome.
|
|
