Spelling suggestions: "subject:"plateletactivating factor"" "subject:"plateletactivation factor""
41 |
A study of the characterisation, procoagulant activity and Annexin V binding properties of platelet-derived microparticles.Connor, David Ewan, Clinical School - St Vincent's Hospital, Faculty of Medicine, UNSW January 2007 (has links)
Platelet-derived microparticles, released as a result of platelet activation, promote coagulation through the surface exposure of phosphatidylserine, acting as the catalytic site for the conversion of prothrombin to thrombin by the activated coagulation factors X and V. Although elevated numbers of circulating platelet-derived microparticles can be detected in a number of clinical disorders, the methods for the detection of these microparticles are far from standardised. In addition, recent reports have also speculated that not all microparticles may expose phosphatidylserine, demonstrating that the binding of Annexin V, a phosphatidylserine-specific binding protein, is not detectable on a population of microparticles. The initial stage of this thesis was to establish a flow cytometric method for the detection and enumeration of microparticles based on their capacity to bind Annexin V and to utilise this assay to investigate a number of the issues that have limited assay standardisation. The assay could be performed on either stimulated or unstimulated plasma or whole blood samples. Interestingly, plasma microparticle counts were significantly higher than whole blood microparticle counts. The effects of centrifugation alone could not be attributed as the sole source of this discrepancy. The antigenic characteristics of platelet-derived microparticles were also investigated, with platelet-derived microparticles demonstrated to express the platelet glycoproteins CD31, CD41a, CD42a and CD61. Platelet-derived microparticles also expressed CD42b, and this expression was significantly decreased when compared to their progenitor platelets. The expression of the platelet activation markers CD62p, CD63, CD40L and PAC-1 was dependent upon the sample milieu, suggesting that the centrifugation conditions required to generate platelet-poor plasma may lead to artefactual increases in the expression of platelet activation markers. An investigation of the role of the GpIIb/IIIa complex on the formation of platelet-derived microparticles was also performed. A monoclonal antibody to the GpIIb/IIIa complex (Abciximab) significantly inhibited in vitro collagen-stimulated platelet-derived microparticle formation. Interestingly, platelets obtained from two subjects with impaired GpIIb/IIIa activation, demonstrated normal microparticle formation following collagen stimulation, suggesting that the presence of GpIIb/IIIa complex, but not its activation, is required for collagen-induced microparticle formation. A novel mechanism for microparticle formation was also investigated, with platelet-derived microparticles demonstrated to form in response to the sclerosing agents sodium-tetradecyl sulphate and polidocanol. Interestingly, the removal of plasma proteins by the washing of platelets left platelets more susceptible to sclerosant-induced microparticle formation, suggesting that plasma proteins may protect platelets from microparticle formation. The procoagulant activity of platelet-derived microparticles was also investigated using a novel coagulation assay (XACT) specific for the procoagulant phospholipid. An evaluation of this assay demonstrated a significant correlation between Annexin V binding microparticle counts and procoagulant activity in both whole blood and plasma samples. There was more procoagulant activity in whole blood samples than in plasma samples, suggesting that the procoagulant phospholipid activity was also associated with erythrocytes or leukocytes. To further investigate this phenomenon, a whole blood flow cytometric assay was developed to assess Annexin V binding to erythrocytes, leukocytes, platelets and microparticles. This assay demonstrated that a large proportion of Annexin V binding (51.0%) was associated with erythrocytes. Interestingly, a proportion of the Annexin V binding erythrocytes (24.5%) and leukocytes (78.8%) were also associated with platelet CD61 antigen, suggesting that they also bound a platelet or platelet-derived microparticle. The effect of sample anticoagulant on microparticle procoagulant activity was investigated. Microparticle counts were most stable in EDTA anticoagulated samples, but were stable in sodium citrate for up to 15 minutes following sample collection. The procoagulant activity of microparticles was significantly inhibited by EDTA in collagen-stimulated platelet-rich plasma samples, when compared to sodium citrate anticoagulated samples. Although the initial method used to investigate microparticles was based upon their ability to bind Annexin V, it was consistently observed that a large proportion of events in the size region of a microparticle were Annexin V negative. An investigation was therefore commenced into the procoagulant activity of microparticles based on their capacity to bind Annexin V. The presence of Annexin V negative microparticles was confirmed by flow cytometry and the proportion of microparticles that bound Annexin V was dependent upon type of agonist used to stimulate microparticle formation. Varying the assay constituents (calcium concentration / Annexin V concentration / buffer type) did not alter the proportion of Annexin V binding microparticles. When compared to Annexin V positive microparticles, Annexin V negative microparticles expressed significantly higher levels of CD42b on their surface, but possessed significantly decreased expressions of CD62p, and CD63. A significant correlation between the percentage of Annexin V binding and XACT procoagulant activity was found (p=0.03). Furthermore, Annexin V binding inhibited greater than 98% of procoagulant phospholipid activity, suggesting that Annexin V binding was a true reflection of procoagulant activity. Microparticles could be sorted using either a flow cytometric or magnetic sorting strategy. By electron microscopy, Annexin V negative events isolated following magnetic sorting were vesicular structures and not small platelets or the remnants of activated platelets. In summary, this thesis has demonstrated the ability of the flow cytometer and XACT assays to detect microparticles and their procoagulant activity. It has also shown that the use of Annexin V to detect microparticles may warrant further investigation.
|
42 |
Engineering antibodies against complex platelet antigens using phage display technologyDe Leon, Ellen Jane, Biotechnology & Biomolecular Sciences, Faculty of Science, UNSW January 2007 (has links)
Platelets are small anucleate cell fragments found in blood whose physiological role is important in maintaining haemostasis. In vivo, platelet surface glycoproteins mediate the mechanistic roles of platelets, and polymorphic changes to these glycoproteins have been observed to have significant effects on the platelet cellular function and such changes may include over-expression, under-expression and antigenicity of the protein. Human platelet antigens (HPA) are a result of polymorphic differences in platelet surface glycoproteins which have been found to be variably expressed in the population. Foetal maternal alloimmune thrombocytopaenia (FMAIT) is a condition that is observed in the unborn foetus and neonates due to HPA incompatibility between the mother and the foetus. HPA incompatibility accounts for a majority of severe thrombocytopaenic cases in neonates, and delayed diagnosis and treatment of such a condition often lead to intracranial haemorrhage. The risk in neonates diagnosed with FMAIT becomes increasingly significant in cases where intra-uterine (during pregnancy) platelet transfusion is the only effective therapeutic option. There are currently no antenatal screening programs for this condition, and laboratory diagnosis of FMAIT relies on the detection of maternal alloantibodies and parental HPA typing. For these reasons a significant amount of research is currently being invested into the isolation of recombinant antibodies with specific reactivity against FMAIT-related platelet antigens. Stable and specific recombinant platelet antibodies have great potential as a diagnostic agent in antenatal screening and broad-scale HPA typing of blood donors for platelet transfusion. Further characterisation of the isolated antibody may lead to a possible therapeutic agent. Studies by previous researchers have shown that the traditional methods (ie. Mouse monoclonal and EBV transformation) of obtaining monoclonal antibodies against FMAIT-related antigens have proven unsuccessful. The continuing progress in the discipline of phage display has produced several novel antibodies against self and non-self antigens. A further advantage in the application of phage display technology for the isolation of novel antibodies is the easy transition from bacterial to mammalian expression for the characterisation of glycosylated antibodies. The main focus of this project was to create and isolate a recombinant human anti-HPA-3a antibody using phage display for its possible application as a therapeutic or diagnostic agent.
|
43 |
Genetic Ablation of the Platelet Activating Factor Receptor Does Not Impair Learning and Memory in Wild-Type Mice or Alter Amyloid Plaque Number in a Transgenic Model of Alzheimer’s DiseasePeshdary, Vian 25 January 2012 (has links)
We have recently established that aberrant alkylacylglycerophosphocholine metabolism results in the increased tissue concentration of platelet activating factors (PAFs) in the temporal cortex of Alzheimer Disease (AD) patients and in TgCRND8 mice over-expressing mutant human amyloid precursor protein. PAF lipids activate a G-protein coupled receptor (PAFR) reported to be expressed by microglia and subsets of neurons in rat. It is not known whether this same expression pattern is recapitulated in mice however, as the expression has only been inferred by use of pharmacological PAFR antagonists, many of which impact on both PAFR-dependent and PAFR-independent signalling pathways. PAFR plays a role in long term potentiation (LTP) induction in rats. PAFR has also been implicated in behavioural indices of spatial learning and memory in rats. Contradictory reports using mice provide ambiguity regarding the role of PAFR in LTP induction in mice. To assess whether PAFR is expressed in murine neurons, I localized PAFR mRNA in wild-type C57BL/6 mice using PAFR KO mice as a negative control. I further showed that the loss of PAFR did not impair learning and memory although this assessment must be considered preliminary as the behavioural test employed was not optimized to detect changes in learning and memory of C57BL/6 mice over time adequately.Finally, I showed that the loss of PAFR in TgCRND8 mouse model of AD had no impact upon Aβ plaque number. My observations suggest that PAFR is restricted to microglial-like cells in mouse hippocampus and as such, it may not play a role in learning and memory.
|
44 |
Genetic Ablation of the Platelet Activating Factor Receptor Does Not Impair Learning and Memory in Wild-Type Mice or Alter Amyloid Plaque Number in a Transgenic Model of Alzheimer’s DiseasePeshdary, Vian 25 January 2012 (has links)
We have recently established that aberrant alkylacylglycerophosphocholine metabolism results in the increased tissue concentration of platelet activating factors (PAFs) in the temporal cortex of Alzheimer Disease (AD) patients and in TgCRND8 mice over-expressing mutant human amyloid precursor protein. PAF lipids activate a G-protein coupled receptor (PAFR) reported to be expressed by microglia and subsets of neurons in rat. It is not known whether this same expression pattern is recapitulated in mice however, as the expression has only been inferred by use of pharmacological PAFR antagonists, many of which impact on both PAFR-dependent and PAFR-independent signalling pathways. PAFR plays a role in long term potentiation (LTP) induction in rats. PAFR has also been implicated in behavioural indices of spatial learning and memory in rats. Contradictory reports using mice provide ambiguity regarding the role of PAFR in LTP induction in mice. To assess whether PAFR is expressed in murine neurons, I localized PAFR mRNA in wild-type C57BL/6 mice using PAFR KO mice as a negative control. I further showed that the loss of PAFR did not impair learning and memory although this assessment must be considered preliminary as the behavioural test employed was not optimized to detect changes in learning and memory of C57BL/6 mice over time adequately.Finally, I showed that the loss of PAFR in TgCRND8 mouse model of AD had no impact upon Aβ plaque number. My observations suggest that PAFR is restricted to microglial-like cells in mouse hippocampus and as such, it may not play a role in learning and memory.
|
45 |
Hemodynamic effects of endothelin-1 and platelet-activating factor after nitric oxide synthase inhibition in the ratLee, Hing-lun., 李慶麟 January 1999 (has links)
published_or_final_version / Medical Sciences / Master / Master of Medical Sciences
|
46 |
Genetic Ablation of the Platelet Activating Factor Receptor Does Not Impair Learning and Memory in Wild-Type Mice or Alter Amyloid Plaque Number in a Transgenic Model of Alzheimer’s DiseasePeshdary, Vian 25 January 2012 (has links)
We have recently established that aberrant alkylacylglycerophosphocholine metabolism results in the increased tissue concentration of platelet activating factors (PAFs) in the temporal cortex of Alzheimer Disease (AD) patients and in TgCRND8 mice over-expressing mutant human amyloid precursor protein. PAF lipids activate a G-protein coupled receptor (PAFR) reported to be expressed by microglia and subsets of neurons in rat. It is not known whether this same expression pattern is recapitulated in mice however, as the expression has only been inferred by use of pharmacological PAFR antagonists, many of which impact on both PAFR-dependent and PAFR-independent signalling pathways. PAFR plays a role in long term potentiation (LTP) induction in rats. PAFR has also been implicated in behavioural indices of spatial learning and memory in rats. Contradictory reports using mice provide ambiguity regarding the role of PAFR in LTP induction in mice. To assess whether PAFR is expressed in murine neurons, I localized PAFR mRNA in wild-type C57BL/6 mice using PAFR KO mice as a negative control. I further showed that the loss of PAFR did not impair learning and memory although this assessment must be considered preliminary as the behavioural test employed was not optimized to detect changes in learning and memory of C57BL/6 mice over time adequately.Finally, I showed that the loss of PAFR in TgCRND8 mouse model of AD had no impact upon Aβ plaque number. My observations suggest that PAFR is restricted to microglial-like cells in mouse hippocampus and as such, it may not play a role in learning and memory.
|
47 |
Engineering antibodies against complex platelet antigens using phage display technologyDe Leon, Ellen Jane, Biotechnology & Biomolecular Sciences, Faculty of Science, UNSW January 2007 (has links)
Platelets are small anucleate cell fragments found in blood whose physiological role is important in maintaining haemostasis. In vivo, platelet surface glycoproteins mediate the mechanistic roles of platelets, and polymorphic changes to these glycoproteins have been observed to have significant effects on the platelet cellular function and such changes may include over-expression, under-expression and antigenicity of the protein. Human platelet antigens (HPA) are a result of polymorphic differences in platelet surface glycoproteins which have been found to be variably expressed in the population. Foetal maternal alloimmune thrombocytopaenia (FMAIT) is a condition that is observed in the unborn foetus and neonates due to HPA incompatibility between the mother and the foetus. HPA incompatibility accounts for a majority of severe thrombocytopaenic cases in neonates, and delayed diagnosis and treatment of such a condition often lead to intracranial haemorrhage. The risk in neonates diagnosed with FMAIT becomes increasingly significant in cases where intra-uterine (during pregnancy) platelet transfusion is the only effective therapeutic option. There are currently no antenatal screening programs for this condition, and laboratory diagnosis of FMAIT relies on the detection of maternal alloantibodies and parental HPA typing. For these reasons a significant amount of research is currently being invested into the isolation of recombinant antibodies with specific reactivity against FMAIT-related platelet antigens. Stable and specific recombinant platelet antibodies have great potential as a diagnostic agent in antenatal screening and broad-scale HPA typing of blood donors for platelet transfusion. Further characterisation of the isolated antibody may lead to a possible therapeutic agent. Studies by previous researchers have shown that the traditional methods (ie. Mouse monoclonal and EBV transformation) of obtaining monoclonal antibodies against FMAIT-related antigens have proven unsuccessful. The continuing progress in the discipline of phage display has produced several novel antibodies against self and non-self antigens. A further advantage in the application of phage display technology for the isolation of novel antibodies is the easy transition from bacterial to mammalian expression for the characterisation of glycosylated antibodies. The main focus of this project was to create and isolate a recombinant human anti-HPA-3a antibody using phage display for its possible application as a therapeutic or diagnostic agent.
|
48 |
A study of the characterisation, procoagulant activity and Annexin V binding properties of platelet-derived microparticles.Connor, David Ewan, Clinical School - St Vincent's Hospital, Faculty of Medicine, UNSW January 2007 (has links)
Platelet-derived microparticles, released as a result of platelet activation, promote coagulation through the surface exposure of phosphatidylserine, acting as the catalytic site for the conversion of prothrombin to thrombin by the activated coagulation factors X and V. Although elevated numbers of circulating platelet-derived microparticles can be detected in a number of clinical disorders, the methods for the detection of these microparticles are far from standardised. In addition, recent reports have also speculated that not all microparticles may expose phosphatidylserine, demonstrating that the binding of Annexin V, a phosphatidylserine-specific binding protein, is not detectable on a population of microparticles. The initial stage of this thesis was to establish a flow cytometric method for the detection and enumeration of microparticles based on their capacity to bind Annexin V and to utilise this assay to investigate a number of the issues that have limited assay standardisation. The assay could be performed on either stimulated or unstimulated plasma or whole blood samples. Interestingly, plasma microparticle counts were significantly higher than whole blood microparticle counts. The effects of centrifugation alone could not be attributed as the sole source of this discrepancy. The antigenic characteristics of platelet-derived microparticles were also investigated, with platelet-derived microparticles demonstrated to express the platelet glycoproteins CD31, CD41a, CD42a and CD61. Platelet-derived microparticles also expressed CD42b, and this expression was significantly decreased when compared to their progenitor platelets. The expression of the platelet activation markers CD62p, CD63, CD40L and PAC-1 was dependent upon the sample milieu, suggesting that the centrifugation conditions required to generate platelet-poor plasma may lead to artefactual increases in the expression of platelet activation markers. An investigation of the role of the GpIIb/IIIa complex on the formation of platelet-derived microparticles was also performed. A monoclonal antibody to the GpIIb/IIIa complex (Abciximab) significantly inhibited in vitro collagen-stimulated platelet-derived microparticle formation. Interestingly, platelets obtained from two subjects with impaired GpIIb/IIIa activation, demonstrated normal microparticle formation following collagen stimulation, suggesting that the presence of GpIIb/IIIa complex, but not its activation, is required for collagen-induced microparticle formation. A novel mechanism for microparticle formation was also investigated, with platelet-derived microparticles demonstrated to form in response to the sclerosing agents sodium-tetradecyl sulphate and polidocanol. Interestingly, the removal of plasma proteins by the washing of platelets left platelets more susceptible to sclerosant-induced microparticle formation, suggesting that plasma proteins may protect platelets from microparticle formation. The procoagulant activity of platelet-derived microparticles was also investigated using a novel coagulation assay (XACT) specific for the procoagulant phospholipid. An evaluation of this assay demonstrated a significant correlation between Annexin V binding microparticle counts and procoagulant activity in both whole blood and plasma samples. There was more procoagulant activity in whole blood samples than in plasma samples, suggesting that the procoagulant phospholipid activity was also associated with erythrocytes or leukocytes. To further investigate this phenomenon, a whole blood flow cytometric assay was developed to assess Annexin V binding to erythrocytes, leukocytes, platelets and microparticles. This assay demonstrated that a large proportion of Annexin V binding (51.0%) was associated with erythrocytes. Interestingly, a proportion of the Annexin V binding erythrocytes (24.5%) and leukocytes (78.8%) were also associated with platelet CD61 antigen, suggesting that they also bound a platelet or platelet-derived microparticle. The effect of sample anticoagulant on microparticle procoagulant activity was investigated. Microparticle counts were most stable in EDTA anticoagulated samples, but were stable in sodium citrate for up to 15 minutes following sample collection. The procoagulant activity of microparticles was significantly inhibited by EDTA in collagen-stimulated platelet-rich plasma samples, when compared to sodium citrate anticoagulated samples. Although the initial method used to investigate microparticles was based upon their ability to bind Annexin V, it was consistently observed that a large proportion of events in the size region of a microparticle were Annexin V negative. An investigation was therefore commenced into the procoagulant activity of microparticles based on their capacity to bind Annexin V. The presence of Annexin V negative microparticles was confirmed by flow cytometry and the proportion of microparticles that bound Annexin V was dependent upon type of agonist used to stimulate microparticle formation. Varying the assay constituents (calcium concentration / Annexin V concentration / buffer type) did not alter the proportion of Annexin V binding microparticles. When compared to Annexin V positive microparticles, Annexin V negative microparticles expressed significantly higher levels of CD42b on their surface, but possessed significantly decreased expressions of CD62p, and CD63. A significant correlation between the percentage of Annexin V binding and XACT procoagulant activity was found (p=0.03). Furthermore, Annexin V binding inhibited greater than 98% of procoagulant phospholipid activity, suggesting that Annexin V binding was a true reflection of procoagulant activity. Microparticles could be sorted using either a flow cytometric or magnetic sorting strategy. By electron microscopy, Annexin V negative events isolated following magnetic sorting were vesicular structures and not small platelets or the remnants of activated platelets. In summary, this thesis has demonstrated the ability of the flow cytometer and XACT assays to detect microparticles and their procoagulant activity. It has also shown that the use of Annexin V to detect microparticles may warrant further investigation.
|
49 |
Papel do fator de ativação de plaquetas na infecção de macrófagos por Leishmania infantum e identificação de uma Paf-acetilhidrolase no parasita.Ferreira, Vinicius Costa Souza January 2014 (has links)
Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2015-02-10T16:31:37Z
No. of bitstreams: 1
Vinicius Costa Souza Ferreira, Papel do fator... 2014.pdf: 10087481 bytes, checksum: 8c34a10bbc4c46304eaf9166412e6f0f (MD5) / Approved for entry into archive by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2015-02-10T16:31:51Z (GMT) No. of bitstreams: 1
Vinicius Costa Souza Ferreira, Papel do fator... 2014.pdf: 10087481 bytes, checksum: 8c34a10bbc4c46304eaf9166412e6f0f (MD5) / Approved for entry into archive by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2015-02-10T16:32:18Z (GMT) No. of bitstreams: 1
Vinicius Costa Souza Ferreira, Papel do fator... 2014.pdf: 10087481 bytes, checksum: 8c34a10bbc4c46304eaf9166412e6f0f (MD5) / Made available in DSpace on 2015-02-10T16:32:18Z (GMT). No. of bitstreams: 1
Vinicius Costa Souza Ferreira, Papel do fator... 2014.pdf: 10087481 bytes, checksum: 8c34a10bbc4c46304eaf9166412e6f0f (MD5)
Previous issue date: 2014 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, Brasil / A leishmaniose visceral é causada pelo parasita Leishmania infantum. A
infecção ocorre quando flebótomos infectados se alimentam na derme do
hospedeiro vertebrado, inoculando o parasita. A infecção produz uma resposta
com diversas moléculas inflamatórias, como os mediadores lipídicos. O fator de
ativação de plaquetas (PAF) é um potente mediador lipídico derivado de um
lisofosfolipídio. PAF participa da fisiologia normal da célula e possui um perfil
pró-inflamatório. A participação de mediadores lipídicos, como eicosanóides e
PAF, já foi identificada na imunopatogênese das leishmanioses. PAF gerado
pelo hospedeiro tem efeito leishmanicida e de controle da infecção por L.
amazonensis. PAF-acetilhidrolases (PAF-AH) são fosfolipases A2 que
hidrolisam PAF e foi demonstrado que PAF-AH podem ser um fator de
virulência devido a essa habilidade. O objetivo desse estudo foi avaliar o papel
do PAF e de uma PAF-AH na infecção de macrófagos por L. infantum. Foi
observado que PAF 1μM, quando adicionado durante e após a infecção, foi
capaz de diminuir 50% da infecção após 72 horas, bem como a viabilidade dos
parasitas dentro dos macrófagos num mecanismos independente do seu
receptor PAFR e da produção de óxido nítrico. PAF 10μM interrompeu o
crescimento de promastigotas de L. infantum em cultura axênica. Uma PAFAH,
com elevada identidade e semelhança com PLA2/PAF-AH de outros
tripanossomatídeos, foi identificada no genoma de L. infantum. A clonagem e
expressão recombinante produziu uma proteína de cerca de 69kDa, com
atividade PAF-AH. Frações celulares do parasita, enriquecidas com estruturas
de membrana também apresentaram atividade PAF-AH. Os resultados indicam
que PAF é capaz de diminuir a infecção de macrófagos por L. infantum e que o
parasita possui uma PAF-AH funcional possivelmente envolvida com sua
virulência. / Visceral leishmaniasis is caused by Leishmania infantum parasites. Infection
occurs when infected sandflies feed on vertebrate host skin delivering the
parasite which survive, multiply and spread on the parasitophorous vacuoles of
macrophages. The inflammatory response during the infection leads to the
production of diverse bioactive molecules, as lipid mediators. The platelet
activating factor (PAF) is a lipid mediator derived from a lysophospholipid. PAF
has a role in normal cellular physiology, acting as proinflamatory molecule. The
participation of some lipid mediators, as eicosanoids and PAF has been
identified in leishmaniasis. PAF produced by the host is able to kill the parasite
and control the infection by L. amazonensis. PAF-acetylhydrolases (PAF-AH)
are phospholipases A2 (PLA2) that hydrolyse PAF, and possibly involved in
pathogen virulence. The aim of this study was to evaluate the role of PAF on
macrophages infection by L. infantum and identify a PAF-AH expressed by the
parasite. PAF 1μM, added during and after the infection, was able to reduce
approximately 50% of infection, as well as, the viability of parasites inside
macrophages. Apparently this reduction occurs by an classical PAF receptor
and nitric oxide production independent mechanism. PAF 10μM inhibited L.
infantum promastigotes growing in axenic culture. A PAF-AH with high identity
to PLA2/PAF-AH of others trypanosomatids was identified in L. infantum
genome. The cloning and recombinant expression produced a 69kDa protein
with PAF-AH activity. Cellular fractions from parasites, with membrane
structures also presented PAF-AH activity. The results suggest that PAF is able
to decrease machophage infection by L. infantum witch has a functional PAFAH
possibly related to its virulence
|
50 |
Genetic Ablation of the Platelet Activating Factor Receptor Does Not Impair Learning and Memory in Wild-Type Mice or Alter Amyloid Plaque Number in a Transgenic Model of Alzheimer’s DiseasePeshdary, Vian January 2012 (has links)
We have recently established that aberrant alkylacylglycerophosphocholine metabolism results in the increased tissue concentration of platelet activating factors (PAFs) in the temporal cortex of Alzheimer Disease (AD) patients and in TgCRND8 mice over-expressing mutant human amyloid precursor protein. PAF lipids activate a G-protein coupled receptor (PAFR) reported to be expressed by microglia and subsets of neurons in rat. It is not known whether this same expression pattern is recapitulated in mice however, as the expression has only been inferred by use of pharmacological PAFR antagonists, many of which impact on both PAFR-dependent and PAFR-independent signalling pathways. PAFR plays a role in long term potentiation (LTP) induction in rats. PAFR has also been implicated in behavioural indices of spatial learning and memory in rats. Contradictory reports using mice provide ambiguity regarding the role of PAFR in LTP induction in mice. To assess whether PAFR is expressed in murine neurons, I localized PAFR mRNA in wild-type C57BL/6 mice using PAFR KO mice as a negative control. I further showed that the loss of PAFR did not impair learning and memory although this assessment must be considered preliminary as the behavioural test employed was not optimized to detect changes in learning and memory of C57BL/6 mice over time adequately.Finally, I showed that the loss of PAFR in TgCRND8 mouse model of AD had no impact upon Aβ plaque number. My observations suggest that PAFR is restricted to microglial-like cells in mouse hippocampus and as such, it may not play a role in learning and memory.
|
Page generated in 0.121 seconds