Academic literature on the topic 'Phages de type T4'
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Journal articles on the topic "Phages de type T4"
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Godon, Jean-Jacques, Ariane Bize, Hoang Ngo, Laurent Cauquil, Mathieu Almeida, Marie-Agnès Petit, and Olivier Zemb. "Bacterial Consumption of T4 Phages." Microorganisms 9, no. 9 (August 31, 2021): 1852. http://dx.doi.org/10.3390/microorganisms9091852.
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The bacterial consumption of viruses not been reported on as of yet even though bacteria feed on almost anything. Viruses are widely distributed but have no acknowledged active biocontrol. Viral biomass undoubtedly reintegrates trophic cycles; however, the mechanisms of this phase still remain unknown. 13C-labelled T4 phages monitor the increase of the density of the bacterial DNA concomitant with the decrease of plaque forming units. We used 12C T4 phages as a control. T4 phage disappearance in wastewater sludge was found to occur mainly through predation by Aeromonadacea. Phage consumption also favours significant in situ bacterial growth. Furthermore, an isolated strain of Aeromonas was observed to grow on T4 phages as sole the source of carbon, nitrogen, and phosphorus. Bacterial species are capable of consuming bacteriophages in situ, which is likely a widespread and underestimated type of biocontrol. This assay is anticipated as a starting point for harnessing the bacterial potential in limiting the diffusion of harmful viruses within environments such as in the gut or in water.
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Tétart, Françoise, Carine Desplats, Mzia Kutateladze, Caroline Monod, Hans-Wolfgang Ackermann, and H. M. Krisch. "Phylogeny of the Major Head and Tail Genes of the Wide-Ranging T4-Type Bacteriophages." Journal of Bacteriology 183, no. 1 (January 1, 2001): 358–66. http://dx.doi.org/10.1128/jb.183.1.358-366.2001.
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ABSTRACT We examined a number of bacteriophages with T4-type morphology that propagate in different genera of enterobacteria,Aeromonas, Burkholderia, andVibrio. Most of these phages had a prolate icosahedral head, a contractile tail, and a genome size that was similar to that of T4. A few of them had more elongated heads and larger genomes. All these phages are phylogenetically related, since they each had sequences homologous to the capsid gene (gene23), tail sheath gene (gene 18), and tail tube gene (gene 19) of T4. On the basis of the sequence comparison of their virion genes, the T4-type phages can be classified into three subgroups with increasing divergence from T4: the T-evens, pseudoT-evens, and schizoT-evens. In general, the phages that infect closely related host species have virion genes that are phylogenetically closer to each other than those of phages that infect distantly related hosts. However, some of the phages appear to be chimeras, indicating that, at least occasionally, some genetic shuffling has occurred between the different T4-type subgroups. The compilation of a number of gene 23 sequences reveals a pattern of conserved motifs separated by sequences that differ in the T4-type subgroups. Such variable patches in the gene 23sequences may determine the size of the virion head and consequently the viral genome length. This sequence analysis provides molecular evidence that phages related to T4 are widespread in the biosphere and diverged from a common ancestor in acquiring the ability to infect different host bacteria and to occupy new ecological niches.
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Chibani-Chennoufi, Sandra, Josette Sidoti, Anne Bruttin, Marie-Lise Dillmann, Elizabeth Kutter, Firdausi Qadri, Shafiqul Alam Sarker, and Harald Brüssow. "Isolation of Escherichia coli Bacteriophages from the Stool of Pediatric Diarrhea Patients in Bangladesh." Journal of Bacteriology 186, no. 24 (December 15, 2004): 8287–94. http://dx.doi.org/10.1128/jb.186.24.8287-8294.2004.
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ABSTRACT A 3-week coliphage survey was conducted in stool samples from 140 Bangladeshi children hospitalized with severe diarrhea. On the Escherichia coli indicator strain K803, all but one phage isolate had 170-kb genomes and the morphology of T4 phage. In spot tests, the individual T4-like phages infected up to 27 out of 40 diarrhea-associated E. coli, representing 22 O serotypes and various virulence factors; only five of them were not infected by any of these new phages. A combination of diagnostic PCR based on g32 (DNA binding) and g23 (major capsid protein) and Southern hybridization revealed that half were T-even phages sensu strictu, while the other half were pseudo-T-even or even more distantly related T4-like phages that failed to cross-hybridize with T4 or between each other. Nineteen percent of the acute stool samples yielded T4-like phages, and the prevalence was lower in convalescent stool samples. T4-like phages were also isolated from environmental and sewage water, but with low frequency and low titers. On the enteropathogenic E. coli strain O127:K63, 14% of the patients yielded phage, all of which were members of the phage family Siphoviridae with 50-kb genomes, showing the morphology of Jersey- and beta-4 like phages and narrow lytic patterns on E. coli O serotypes. Three siphovirus types could be differentiated by lack of cross-hybridization. Only a few stool samples were positive on both indicator strains. Phages with closely related restriction patterns and, in the case of T4-like phages, identical g23 gene sequences were isolated from different patients, suggesting epidemiological links between the patients.
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Hammerl, J. A., C. Jackel, J. Reetz, S. Beck, T. Alter, R. Lurz, C. Barretto, H. Brussow, and S. Hertwig. "Campylobacter jejuni Group III Phage CP81 Contains Many T4-Like Genes without Belonging to the T4-Type Phage Group: Implications for the Evolution of T4 Phages." Journal of Virology 85, no. 17 (June 22, 2011): 8597–605. http://dx.doi.org/10.1128/jvi.00395-11.
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Letarov, A., X. Manival, C. Desplats, and H. M. Krisch. "gpwac of the T4-Type Bacteriophages: Structure, Function, and Evolution of a Segmented Coiled-Coil Protein That Controls Viral Infectivity." Journal of Bacteriology 187, no. 3 (February 1, 2005): 1055–66. http://dx.doi.org/10.1128/jb.187.3.1055-1066.2005.
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ABSTRACT The wac gene product (gpwac) or fibritin of bacteriophage T4 forms the six fibers that radiate from the phage neck. During phage morphogenesis these whiskers bind the long tail fibers (LTFs) and facilitate their attachment to the phage baseplate. After the cell lysis, the gpwac fibers function as part of an environmental sensing device that retains the LTFs in a retracted configuration and thus prevents phage adsorption in unfavorable conditions. A comparative analysis of the sequences of 5 wac gene orthologs from various T4-type phages reveals that the ∼50-amino-acid N-terminal domain is the only highly conserved segment of the protein. This sequence conservation is probably a direct consequence of the domain's strong and specific interactions with the neck proteins. The sequence of the central fibrous region of gpwac is highly plastic, with only the heptad periodicity of the coiled-coil structure being conserved. In the various gpwac sequences, the small C-terminal domain essential for initiation of the folding of T4 gpwac is replaced by unrelated sequences of unknown origin. When a distant T4-type phage has a novel C-terminal gpwac sequence, the phage's gp36 sequence that is located at the knee joint of the LTF invariably has a novel domain in its C terminus as well. The covariance of these two sequences is compatible with genetic data suggesting that the C termini of gpwac and gp36 engage in a protein-protein interaction that controls phage infectivity. These results add to the limited evidence for domain swapping in the evolution of phage structural proteins.
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Wang, Jiaying, Yan D. Niu, Jinding Chen, Hany Anany, Hans-W. Ackermann, Roger P. Johnson, Collins N. Ateba, Kim Stanford, and Tim A. McAllister. "Feces of feedlot cattle contain a diversity of bacteriophages that lyse non-O157 Shiga toxin-producing Escherichia coli." Canadian Journal of Microbiology 61, no. 7 (July 2015): 467–75. http://dx.doi.org/10.1139/cjm-2015-0163.
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This study aimed to isolate and characterize bacteriophages that lyse non-O157 Shiga toxin-producing Escherichia coli (STEC) from cattle feces. Of 37 non-O157 STEC-infecting phages isolated, those targeting O26 (AXO26A, AYO26A, AYO26B), O103 (AXO103A, AYO103A), O111 (AXO111A, AYO111A), O121 (AXO121A, AXO121B), and O145 (AYO145A, AYO145B) were further characterized. Transmission electron microscopy showed that the 11 isolates belonged to 3 families and 6 genera: the families Myoviridae (types rV5, T4, ViI, O1), Siphoviridae (type T5), and Podoviridae (type T7). Genome size of the phages as determined by pulsed-field gel electrophoresis ranged from 38 to 177 kb. Excluding phages AXO26A, AYO103A, AYO145A, and AYO145B, all other phages were capable of lysing more than 1 clinically important strain from serogroups of O26, O91, O103, O111, O113, O121, and O128, but none exhibited infectivity across all serogroups. Moreover, phages AYO26A, AXO121A, and AXO121B were also able to lyse 4 common phage types of STEC O157:H7. Our findings show that a diversity of non-O157 STEC-infecting phages are harbored in bovine feces. Phages AYO26A, AYO26B, AXO103A, AXO111A, AYO111A, AXO121A, and AXO121B exhibited a broad host range against a number of serogroups of STEC and have potential for the biocontrol of STEC in the environment.
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Büttner, Carina R., Yingzhou Wu, Karen L. Maxwell, and Alan R. Davidson. "Baseplate assembly of phage Mu: Defining the conserved core components of contractile-tailed phages and related bacterial systems." Proceedings of the National Academy of Sciences 113, no. 36 (August 23, 2016): 10174–79. http://dx.doi.org/10.1073/pnas.1607966113.
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Contractile phage tails are powerful cell puncturing nanomachines that have been co-opted by bacteria for self-defense against both bacteria and eukaryotic cells. The tail of phage T4 has long served as the paradigm for understanding contractile tail-like systems despite its greater complexity compared with other contractile-tailed phages. Here, we present a detailed investigation of the assembly of a “simple” contractile-tailed phage baseplate, that of Escherichia coli phage Mu. By coexpressing various combinations of putative Mu baseplate proteins, we defined the required components of this baseplate and delineated its assembly pathway. We show that the Mu baseplate is constructed through the independent assembly of wedges that are organized around a central hub complex. The Mu wedges are comprised of only three protein subunits rather than the seven found in the equivalent structure in T4. Through extensive bioinformatic analyses, we found that homologs of the essential components of the Mu baseplate can be identified in the majority of contractile-tailed phages and prophages. No T4-like prophages were identified. The conserved simple baseplate components were also found in contractile tail-derived bacterial apparatuses, such as type VI secretion systems, Photorhabdus virulence cassettes, and R-type tailocins. Our work highlights the evolutionary connections and similarities in the biochemical behavior of phage Mu wedge components and the TssF and TssG proteins of the type VI secretion system. In addition, we demonstrate the importance of the Mu baseplate as a model system for understanding bacterial phage tail-derived systems.
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Salem, Mabruka, Maria I. Pajunen, Jin Woo Jun, and Mikael Skurnik. "T4-like Bacteriophages Isolated from Pig Stools Infect Yersinia pseudotuberculosis and Yersinia pestis Using LPS and OmpF as Receptors." Viruses 13, no. 2 (February 13, 2021): 296. http://dx.doi.org/10.3390/v13020296.
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The Yersinia bacteriophages fPS-2, fPS-65, and fPS-90, isolated from pig stools, have long contractile tails and elongated heads, and they belong to genus Tequatroviruses in the order Caudovirales. The phages exhibited relatively wide host ranges among Yersinia pseudotuberculosis and related species. One-step growth curve experiments revealed that the phages have latent periods of 50–80 min with burst sizes of 44–65 virions per infected cell. The phage genomes consist of circularly permuted dsDNA of 169,060, 167,058, and 167,132 bp in size, respectively, with a G + C content 35.3%. The number of predicted genes range from 267 to 271. The phage genomes are 84–92% identical to each other and ca 85% identical to phage T4. The phage receptors were identified by whole genome sequencing of spontaneous phage-resistant mutants. The phage-resistant strains had mutations in the ompF, galU, hldD, or hldE genes. OmpF is a porin, and the other genes encode lipopolysaccharide (LPS) biosynthetic enzymes. The ompF, galU, and hldE mutants were successfully complemented in trans with respective wild-type genes. The host recognition was assigned to long tail fiber tip protein Gp38, analogous to that of T-even phages such as Salmonella phage S16, specifically to the distal β-helices connecting loops.
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Rabinovitch, Avinoam, Hilla Hadas, Monica Einav, Zeev Melamed, and Arieh Zaritsky. "Model for Bacteriophage T4 Development inEscherichia coli." Journal of Bacteriology 181, no. 5 (March 1, 1999): 1677–83. http://dx.doi.org/10.1128/jb.181.5.1677-1683.1999.
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ABSTRACT Mathematical relations for the number of mature T4 bacteriophages, both inside and after lysis of an Escherichia coli cell, as a function of time after infection by a single phage were obtained, with the following five parameters: delay time until the first T4 is completed inside the bacterium (eclipse period, ν) and its standard deviation (ς), the rate at which the number of ripe T4 increases inside the bacterium during the rise period (α), and the time when the bacterium bursts (μ) and its standard deviation (β). Burst size [B = α(μ − ν)], the number of phages released from an infected bacterium, is thus a dependent parameter. A least-squares program was used to derive the values of the parameters for a variety of experimental results obtained with wild-type T4 inE. coli B/r under different growth conditions and manipulations (H. Hadas, M. Einav, I. Fishov, and A. Zaritsky, Microbiology 143:179–185, 1997). A “destruction parameter” (ζ) was added to take care of the adverse effect of chloroform on phage survival. The overall agreement between the model and the experiment is quite good. The dependence of the derived parameters on growth conditions can be used to predict phage development under other experimental manipulations.
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ABEDON, STEPHEN T. "Bacteriophage T4 resistance to lysis-inhibition collapse." Genetical Research 74, no. 1 (August 1999): 1–11. http://dx.doi.org/10.1017/s0016672399003833.
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Lysis inhibition is a mechanism of latent-period extension and burst-size increase that is induced by the T4 bacteriophage adsorption of T4-infected cells. Mutants of T4 genes imm, sp and 5 (specifically the ts1 mutant of 5) display some lysis inhibition. However, these mutants experience lysis-inhibition collapse, the lysis of lysis-inhibited cells, earlier than wild-type-infected cells (i.e. their collapse occurs prematurely). Lysis from without is a lysis induced by excessive T4 adsorption. Gp5 is an inducer of lysis from without while gpimm and gpsp effect resistance to lysis from without. This paper shows that interfering with the adsorption of phages to imm-, sp- or 5ts1-mutant-infected cells, in a variety of contexts, inhibits premature lysis-inhibition collapse. From these data it is inferred that wild-type T4-infected cells display resistance to lysis-inhibition collapse by a mechanism resembling resistance to lysis from without.
Dissertations / Theses on the topic "Phages de type T4"
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Trojet, Sabrina. "Etude de la reconnaissance phage-bactérie : analyse fonctionnelle de l'adhésine gp38 des phages de la superfamille de type T4." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1358/.
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Le spectre d'hôtes d'un phage est majoritairement déterminé par les adhésines phagiques. Leur reconnaissance spécifique des récepteurs situés à la surface bactérienne constitue la première étape de l'adsorption des phages. Dans la superfamille des phages de Type T4, de telles adhésines sont situées à l'extrémité des fibres caudales longues des phages. Parmi les phages du sous-groupe des T-pair, la forme prédominante des adhésines est une version codée, par exemple, par le gène 38 des phages T2 et T6. Cette adhésine gp38 est composée de quatre Segments HyperVariables (HVS) séparés par cinq Motifs Riches en Glycine très conservés (GRM). Cependant, les déterminants de l'adhésine impliqués dans sa spécificité et dans le maintien de sa structure sont encore mal connus. Le rôle des différents composants (HVS et GRM) de l'adhésine a été examiné par une analyse comparative de nombreuses adhésines gp38 de type T2/T6 présentant des différences dans la spécificité d'hôte. Une analyse génétique plus approfondie a été facilitée par la construction de phage T6 avec des mutations non-sens dans son gène 38. Ces mutants ont alors été utilisés pour créer des phages recombinants avec des adhésines gp38 chimériques. Les résultats obtenus nous ont permis de confirmer que l'adhésine de Type T2/T6 possède deux domaines structuraux : un module N-terminal d'attachement au reste de la fibre caudale et un module C-terminal de spécificité. De plus, une analyse par délétion du module C-terminal de spécificité a révélé que la plupart, si ce n'est pas tous, des HVS et GRM sont essentiel pour la fonction de l'adhésine du phage T6. Un mécanisme qui modifie la reconnaissance spécifique des adhésines, par échange de segments dans le module C-terminal de spécificité, a été décrit. L'identification et la caractérisation d'une adhésine de type gp38 a aussi été entreprise, pour les phages pseudo T-pair, RB42 et RB43. Dans ces phages, l'adhésine gp38 dispose d'un module N-terminal d'attachement similaire à celui de T6, mais son domaine C-terminal constitue un nouveau déterminant de la spécificité, non apparenté à celui des phages T-pair. Ceci suggère que le caractère modulaire des adhésines semble être une caractéristique commune et répandue parmi les phages de la superfamille de Type T4. Une telle conception offre sans doute un avantage évolutif significatif permettant de faciliter la création d'une diversité dans le spectre d'hôte des phages par échange modulaire. Cette analyse de l'adhésine gp38 apporte de nouveaux éléments sur l'interaction entre le phage et son hôte bactérien, qui pourraient être exploités pour améliorer la thérapie antibactérienne. Par exemple, notre étude sur l'effet d'antibiotique sur le cycle de vie des phages révèle que la présence d'une concentration sub-létale en antibiotique permet d'augmenter significativement la production de phages par la bactérie infectée. Bien que les phages puissent être utilisés seul en alternative à l'antibio-thérapie, l'utilisation de cet effet synergique entre phage et antibiotique dans un traitement pourrait s'avérer plus efficace. De plus, toute modification de l'adhésine améliorant le spectre d'hôte des phages permettrait d'accroître significativement l'efficacité du traitement par thérapie phagiqueThe host range of a phage is determined largely by the phage's adhesins. Their specific recognition of receptors on the bacterial surface is the first critical step in phage adsorption. In the T4 phage superfamily, such adhesins are located at the tip of the phage's long tail fibers. How the adhesin protein's structure determines this specificity is not, however, fully understood. The predominant form of adhesin among the closely related T-even phage subgroup of the T4 Superfamily is the version encoded by gene 38 in such phages T2 and T6. This adhesin is composed of a set of four HyperVariable Segments (HVS) that are separated by five highly conserved Glycine-Rich Motifs (GRM). The role played by these various gp38 sequences has been examined by a comparative analysis of a large series of T2/T6 type gp38 adhesins with different receptor specificities. A further genetic analysis of these adhesins was facilitated by the construction of nonsense mutations in T6 gp38. These mutants were used to create recombinant phages with chimeric adhesin recognition sequences. The T2/T6 type adhesin has a two-domain structure: an N-terminal tail fiber attachment module and a C-terminal specificity module. An extensive deletion analysis of the specificity module revealed that most, if not all, of the multiple HVS and GRM elements are essential for adhesin function. A mechanism that alters the adhesins recognition specificity by segmental swapping within this modular specificity determinant is proposed. The identification and characterization of a gp38-like adhesin in the more distantly related phages RB42 and RB43 was also undertaken. In these phages, the gp38 adhesin has an N-terminal tail fiber attachment module similar to that in T6 but its C-terminal specificity determinant is novel and unrelated to that of the T-even phages. This suggests that a modular design of the adhesin may be a general and widespread feature of among the T4 superfamily phages. Such a design presumably offers a significant evolutionary advantage by facilitating the creation of diversity in the phage's host range by modular swapping. This analysis of the gp38 adhesin provides new insights into the molecular interaction between a phage and its host bacteria, which could be exploited for improving antibacterial therapy. For example, our study of the effect antibiotics on phage life cycle revealed that the presence of a sub-lethal concentration of antibiotic significantly increases the production of phages by infected bacteria. Although the phages could be used alone as an alternative to antibiotic therapy, the use of this "Phage-Antibiotic Synergy" could make them more effective than if used alone. Obviously, in a Phage-Antibiotic Synergy therapy regime, the phages employed could have their therapeutic host range ameliorated by manipulation of their adhesin sequences. Such modifications in the treatment protocol might significantly increase the efficacy of phage therapy
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Kalinienė, Laura. "Investigation of genome sequence and gene expression regulation in T4 related bacteriophages." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100702_105235-60207.
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The complete genome sequence of bacteriophage VR7 has been determined. The genome sequence is 169,285 nt, with an overall G+C content of 40,3%, compared with 35.3 % of T4. VR7 encodes 293 putative protein-encoding open reading frames (ORFs) and tRNAMet. In total, 211 of the 293 VR7 open reading frames encode putative proteins that share 30% ‒ 97% amino acid sequence identity with those found in T4; 46 ORFs resemble genes from other T4-like phages, 9 show similarities to genes of non T4 type phages and 27 ORFs lack any database matches. Homologs to the T4 α-gt, β-gt, SegA, SegB, SegC, SegD, SegE, I-TevI, I-TevII, I-TevIII, gp42, Ac, NrdG, NrdD, Arn, IPI, IPII, IPIII, Mrh as well as the T4-specific tRNAs are all absent in VR7. The amino acid sequences of the three major structural proteins gp23, gp18 and gp19 of VR7 show 84.9%, 71.3% and 69.9% aa identity respectively with adequate proteins of T4.
In total, 43 PE, 43 PM and 44 PL have been identified in VR7. Moreover, phage VR7 encodes homologues of all transcription-associated proteins of T4.
The functional complementation experiments of VR7 MotA, sharing only 34% amino acid sequence identity with MotA of T4, have been performed. It has been demonstrated, that the presence of plasmid encoded VR7 MotA complements the T4motAΔ mutant for growth in E. coli, and activates middle-mode transcription during the growth of T4motA-.
Bacteriophages VR5, VR7 and VR20 have been characterized. It has been demonstrated that these phages... [to full text]Nustačius 169,285 b.p. bakteriofago VR7 genomo nukleotidų seką aptikta viena tRNRMET ir 293 hipotetiniai ASR. Du šimtai vienuolika šio fago genų koduoja baltymus, kurie yra 30% ‒ 97% homologiški atitinkamiems fago T4 baltymams. Keturiasdešimt šeši fago VR7 baltymai neturi analogų T4, bet yra homologiški įvairių kitų T4 giminingų fagų baltymams, 9 baltymai nėra artimi T4-giminingų fagų koduojamiems baltymams, o 27 bakteriofago VR7 ASR koduoja baltymus, kuriems homologų NCBI duomenų bazėje nėra. Fago VR7 genome nėra genų, koduojančių bakteriofago T4 : α ir β gliukoziltransferazes (α-gt , β-gt) , DNR endonukleazes SegA, SegB, SegC, SegD, DNR metilazę Dam, dCMP hidroksimetilazę gp42, atsparumą akriflavinui sąlygojantį baltymą Ac bei ląstelės šeimininkės σ32 fosforilinime dalyvaujančio mrh geno produkto. Nustatyta, kad GC sudaro 40,3% fago VR7 genominės DNR, kai tuo tarpu fago T4 - 35%. Taipogi nustatyta, kad VR7 gp18, gp19 ir gp23 yra tik 71.3% , 69.9% ir 84.9% homologiški atitinkamiems fago T4 baltymams. Tiriant bakteriofago VR7 transkripcijos reguliaciją buvo aptikti 43 ankstyvieji, 43 vidurinieji bei 44 vėlyvieji promotoriai. Šio fago genominėje DNR taip pat buvo identifikuoti visų fago T4 transkripcijos reguliacijoje dalyvaujančių baltymų homologai. Klonavus bakteriofago VR7 geną motA buvo atliktas funkcinės komplementacijos tyrimas fago T4motA- sistemoje in vivo. Nustatyta, kad plazmidėje koduojamas fago VR7 viduriniosios transkripcijos aktyvatorius MotA, kurio... [toliau žr. visą tekstą]
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Boutemy, Laurence S. "Analysis of the Interactions between the 5' to 3' Exonuclease and the Single-Stranded DNA-Binding Protein from Bacteriophage T4 and Related Phages." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1223979052.
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Thesis (Ph. D.)--University of Toledo, 2008.Typescript. "Submitted as partial fulfillment of the requirements for the Doctor of Philosophy in Chemistry." Includes bibliographical references (leaves 305-309).
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Desplats, Carine. "Caractérisation de la diversité génétique existant au sein du groupe des bactériophages de type T4." Toulouse 3, 2002. http://www.theses.fr/2002TOU30009.
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Nous nous intéressons à un groupe de virus procaryotes dont le membre le plus célèbre est le coliphage T4. Ces 160 bactériophages sont caractérisés par un large spectre d'hôte (entérobactéries, vibrionacées, pseudomonads, cyanobactéries) et une forte diversité génétique. Notre but est de comprendre pourquoi et comment les variations génétiques existants entre les génomes sont générées au cours de leur évolution. Nous avons défini des marqueurs phylogénétiques dont la présence chez ces virus atteste de l'existence de liens phylétiques entre eux et à permis d'identifier quatre sous-populations, de plus en plus éloignées du point de vue phylogénétique de T4 : les T-pairs, les pseudo T-pairs, les schizo T-pairs et les exo T-pairs. L'analyse du génome de certains isolats a été entreprise. Seuls les résultats du séquençage partielle (60%) du génome du pseudo T-pair RB49 seront présentés ici. 70% des séquences présentent un niveau d'identité protéique significatif avec des protéines de T4, et cela en dépit d'une forte divergence des séquences nucléotidiques. . . .
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Lucchini, Sacha. "Genetic diversity of Streptococcus thermophilus phages and development of phage-resistant starters for the dairy industry /." [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13335.
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Berni, Benjamin. "Un effecteur trans-règne du système de sécrétion de type 6 est requis pour la sécrétion d’une nouvelle toxine antibactérienne chez Pseudomonas aeruginosa." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0302.
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Pseudomonas aeruginosa a développé de nombreuses stratégies dans le but de désarmer l’hôte eucaryote et prendre l'avantage sur ce dernier. Le T6SS est un complexe dynamique, homologue à la queue contractile du bactériophage T4. Il fonctionne à la manière d’une arbalète en injectant une flèche chargée d’effecteurs dans la cellule cible. Nous avons découvert un nouvel effecteur du T6SS de P. aeruginosa, Tle3, et sa protéine d’immunité associée, Tli3. Tli3 permet de contrecarrer la toxicité périplasmique dépendante de Tle3 dans le but de se prémunir des attaques fratricides. La caractérisation du mécanisme de sécrétion de Tle3 nous a permis de mettre en évidence l’existence d’une protéine adaptatrice, Tla3. Tla3 permet l’adressage et l’interaction de Tle3 avec VgrG2b, conduisant ainsi à la sécrétion de l’effecteur par la machinerie H2-T6SS. Tla3 est différente des autres protéines adaptatrices caractérisées à ce jour, définissant de ce fait une nouvelle famille d’adaptateur. De manière intéressante, ces travaux nous ont amené à découvrir que VgrG2b, précédemment caractérisée comme un effecteur anti-eucaryote, possède de surplus une activité anti-procaryote. En effet, ce dernier est toxique envers Escherichia coli. De manière surprenante, Tli3 peut également contrecarrer la toxicité de VgrG2b. VgrG2b est donc un nouvel effecteur trans-règne permettant de cibler les communautés microbiennes et l’hôte eucaryote. VgrG2b représente donc une cible intéressante dans la lutte contre P. aeruginosa dans le contexte environnemental et dans le contexte infectieuxPseudomonas aeruginosa has evolved multiple strategies to disarm and take advantage of its host. Among this, the type VI secretion system (T6SS) is utilized to deliver effectors into eukaryotic host as well as target bacteria. It assembles into a contractile bacteriophage tail-like structure that functions like a crossbow, injecting an arrow loaded with effectors into the target cell. Here, we report the discovery of a novel pair of antibacterial effector and immunity of P. aeruginosa, Tle3 and Tli3. Tli3 neutralizes the toxicity of Tle3 in the periplasm to protect from fratricide intoxication. The characterization of the secretion mechanism of Tle3 indicates that it requires a cytoplasmic adaptor, Tla3, to be targeted and loaded onto the VgrG2b spike and thus delivered by the H2-T6SS machinery. Tla3 is different from the other adaptors discovered so far and defines a novel family among T6SS with a DUF2875. Interestingly, this led us to discover that VgrG2b that we previously characterized as an anti-eukaryotic effector possesses an antibacterial activity as well, as it is toxic towards Escherichia coli. Excitingly Tli3 can counteract VgrG2b toxicity. VgrG2b is thus a novel trans-kingdom effector targeting both bacteria and eukaryotes. VgrG2b represents an interesting target for fighting against P. aeruginosa in the environment and in the context of host infection
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Boulanger, Pascale. "Mise en évidence et caractérisation de canaux ioniques impliqués dans le transport de l'ADN du bactériophage T4 à travers la membrane cytoplasmique d'Escherichia coli." Paris 11, 1988. http://www.theses.fr/1988PA112135.
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Implication de canaux ioniques dans la pénétration de l'ADN de phage dans la membrane cytoplasmique d'E. Coli. Au cours du processus infectieux, l'ADN de phage traverse la membrane cytoplasmique bactérienne. Ce transport de l'ADN s'accompagne d'une augmentation transitoire de la perméabilité de la membrane aux ions et à certains solutés. Ceci a conduit des auteurs à postuler que le passage de l'ADN puisse se faire à travers des canaux. La première partie de cette revue est consacrée à la mise en évidence des canaux ioniques formés au cours de l'infection par le phage T4. Puis, nous présentons les caractéristiques ioniques et structurales de ces canaux. Dans une seconde partie, nous présentons les données de la littérature concernant les modifications de perméabilité membranaire induits par différents phages et montrons qu'elles sont compatibles avec le modèle de transfert de l'ADN à travers des canaux. Enfin, nous discutons l'origine possible de ces canauxUpon infection, the phage DNA is transported through the bacterial cytoplasmic membrane. This crossing is accompanied by a transient increase of the permeability of the cytoplasmic membrane toward ions and small solutes. This has led several authors to propose that the DNA would cross the cytoplasmic membrane through channels. In the first part of the review we present data we have obtained with phage T4 which strongly support this proposal. We then present the structural and ionic characteristics of these channels. In the second part, we summarize the data obtained by several authors concerning the permeability changes induced by different phages and show that these results are compatible with a mode) of phage DNA transfer through channels. Finally, we discuss the possible origin of these channels
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Cowley, Lauren A. "Use of genome sequencing to investigate the molecular basis of bacteriaphage interaction of the Escherichia coli O157 typing phages and the elucidation of the biological and public health significance of phage type." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23583.
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Background Shiga toxin producing Escherichia coli (STEC) O157 causes severe gastrointestinal disease and haemolytic uremic syndrome, and has a major impact on public health worldwide with regular outbreaks and sporadic infection. Phage typing, i.e. the susceptibility of STEC O157 strains to a bank of 16 bacteriophages, has been used in the UK to differentiate STEC O157 for the past 25 years and the phage type (PT) can be an epidemiological marker of strains associated with severe disease or associated with cases that occur from foreign travel. However, little is known about the molecular interactions between the typing phages (TP) and STEC O157. The aims of this thesis were to use whole genome sequencing to elucidate the genetic basis for phage typing of STEC O157 and through this understand genetic differences between strains relevant to disease severity and epidemiology. Results Sequencing the STEC O157 TPs revealed that they were clustered into 4 groups based on sequence similarity that corresponded with their infectivity. Long read sequencing revealed microevolutionary events occuring in STEC O157 genomes over a short time period (approximately 1 year), evidenced by the loss and gain of prophage regions and plasmids. An IncHI2 plasmid was found responsible for a change in Phage Type (PT) from PT8 to PT54 during two related outbreaks at the same restaurant. These changes resulted in a strain (PT54) that was fitter under certain growth conditions and associated with a much larger outbreak (140 as opposed to 4 cases). TraDIS (Transposon directed Insertion site sequencing) was used to identify 114 genes associated with phage sensitivity and 44 genes involved in phage resistance, emphasising the complex nature of identifying specific genetic markers of phage susceptibility or resistance. Further work is required to prove their phage-related functions but several are likely to encode novel phage receptors. Deletion of a Stx2a prophage from a PT21/28 strain led to a strain that typed as PT32, supporting the concept that the highly pathogenic PT21/28 lineage I strains emerged from Stx2c+ PT32 strains in the last two decades by acquisition of Stx2a-encoding prophages. Conclusions This body of work has highlighted the complexity of bacteriophage interaction and investigated the genetic basis for susceptibility and resistance in E. coli. The grouping of the TPs showed that resistance or susceptibility to all members of a typing group was likely to be caused by one mechanism. IncHI2 was identified as one of the markers for the PT54 phenotype. The Stx2a prophage region was associated with the switch from PT32 to PT21/28, although PT32 strains containing both Stx2a and Stx2c-encoding prophages have been isolated and can provide insights into phage variation underpinning the susceptibility to the relevant typing phages. The TraDIS results indicated that susceptibility or resistance was governed by multiple genetic factors and not controlled by a single gene. The significance of LPS for initial protection from phage adsorption was evident and a number of novel genes controlling phage susceptibility and resistance identified including the Sap operon and stringent starvation protein A respectively. While SNP-based typing provides an excellent indication of the evolution and relatedness of strains, phage typing can provide real insights into short term evolution of the bacteria as PTs can be altered by mobile elements such as prophages and plasmids. This study has shown that, although complex, genetic determinants for PT can be mined from the genome and allow us to understand the evolution of this zoonotic pathogen between host species and during outbreaks.
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Moreau, Charles. "Effets des éléments alliés et de la trempe, lors des traitements thermiques T4 et des vieillissements artificiels, sur la microstructure et les propriétés mécaniques des alliages aluminium-silicium de type 413 /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2004. http://theses.uqac.ca.
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Brunet, Yannick. "Caractérisation moléculaire du systeme de secrétion de type VI d'escherichia coli enteroagrégatif et de ses mécanismes de régulation." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4032.
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Résumé : La compréhension des contraintes qui régissent l'assemblage des machineries supramoléculaires – qu'elles soient solubles ou bien ancrées dans les membranes biologiques – est un enjeu scientifique majeur.Le système de de sécrétion type VI (T6SS) est un organelle bactérien récemment mis en évidence qui a pour particularité de posséder une origine évolutive commune avec le bactériophage T4. En raison de cette origine évolutive commune, certaines sous unités du T6SS et du bactériophage T4 présentent des structures comparables. Cependant, un grand nombre des sous unités du T6SS reste à caractériser. Parmi celles-ci, les protéines SciB et SciC sont retrouvées dans tous les systèmes de sécrétion de type VI suggérant que ces deux protéines participent à la formation du "core-complexe": le complexe minimal requis pour le fonctionnement du T6SSThe recently identified type VI secretion system has been demonstrated to be involved in most of these processes. The T6SS is a highly complex macromolecular machine that allows Gram-negative bacteria to deliver effector proteins to both prokaryotic and eukaryotic cells in a contact-dependent manner. The T6SS promotes therefore antibacterial competition, virulence towards eukaryotes or even both. The T6SS is composed of a minimal set of 13 subunits, which are currently believed to form the core apparatus. They assemble two distinct sub-complexes: one is a cytosolic contractile structure related to the tail of contractile bacteriophages, whereas the other spans the whole cell envelope. Therefore, the T6SS is generally depicted as an inverted phage tail anchored to the cell envelope through its membrane-associated complex. Contractile tails are currently thought to assemble from four structural elements: the baseplate, the internal tube, the contractile sheath and the tail terminator. The aim of my Ph.D. work was to further characterize the assembly and function of the T6SS phage tail-like complex in enteroaggregative E. coli. In this thesis document, I provide evidence that the internal tube assembles from Hcp hexamers stacked in a head-to-tail manner and that this internal cylinder is used as a template during sheath assembly. I also characterized a sub-complex of three proteins (TssEFG) that forms the baseplate of the T6SS and controls the polymerization of the tube and sheath. Finally, I recently showed that the T6SS functions like a nano-crossbow to kill target cells as the contraction of the T6SS results in prey cell death during interbacterial competition
Books on the topic "Phages de type T4"
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Russek, Peter. Volkswagen transporter: Type T4 - 2.0 litre petrol, 1.9 and 2.4 litre diesel from 1991. Marlow: Peter Russek Publications, 1992.
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Podhipleux, Nilobon. Adsorption of the wild type and a synthetic structural stability variant of bacteriophage T4 lysozyme. 1998.
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Wang, Jun. Surface tension kinetics of the wild type and four synthetic, structural stability mutants of bacteriophage T4 lysozyme at the air-water interface. 1995.
Find full textBook chapters on the topic "Phages de type T4"
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Kutter, Elizabeth, Ketevan Gachechiladze, Alexandr Poglazov, Elena Marusich, Mikhail Shneider, Pia Aronsson, Alberto Napuli, Darlene Porter, and Vadim Mesyanzhinov. "Evolution of T4-Related Phages." In Molecular Evolution of Viruses — Past and Present, 213–25. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4613-1407-3_18.
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Mosig, Gisela. "T4-LIKE PHAGES (MYOVIRIDAE)." In Encyclopedia of Virology, 1706–16. Elsevier, 1999. http://dx.doi.org/10.1006/rwvi.1999.0274.
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"T2, T4, and T6 Phages." In Encyclopedia of Genetics, Genomics, Proteomics and Informatics, 1924. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6754-9_16609.
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Gurnell, Mark, and V. Krishna Chatterjee. "Thyroid hormone resistance syndrome." In Oxford Textbook of Endocrinology and Diabetes, 571–81. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199235292.003.3282.
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Thyroid hormones (thyroxine T4 and triiodothyronine T3) regulate many cellular processes in virtually every type of tissue. The diverse effects of thyroid hormone include regulation of growth, control of basal metabolic rate, enhanced myocardial contractility, and functional differentiation of the central nervous system. The synthesis of thyroid hormones is controlled by hypothalamic thyrotrophin-releasing hormone (TRH) and pituitary thyroid-stimulating hormone (TSH), and in turn, T4 and T3 regulate TRH and TSH production as part of a negative feedback loop.
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Molnár, Ildikó. "Deiodinase Enzymes and Their Activities in Graves’ Hyperthyroidism." In Graves' Disease [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97007.
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The origin of hyperthyroidism in Graves’ disease was displayed demonstrating the complexity of the processes. The role of stimulating TSH receptor antibodies is the one factor for the production of increased thyroidal T3 and T4. The T3 and T4 formation in colloid-embedded thyroglobulin and the activities of thyroidal deiodinases [type 1 (DIO1) and type 2 (DIO2)] play a crucial role in that. The findings of different authors were summarized with respect to highlighting the role of tissue-specific deiodinase activities. Apart from the results of experimental studies, the clinical results were brought to the front. The role of tissue-specific type 2 deiodinase activity was demonstrated according to thyroid function, the presence of autoantibodies against thyroid peroxidase (TPO), thyroglobulin (Tg) and TSH receptor. Autoantibodies against human eye muscle membrane and cytosol antigens had influencing effects on tissue-specific DIO2 activities, and the antieye muscle antibody immunoglobulin isotypes were associated with eye muscle enlargements. Antithyroid drug (ATD) therapy demonstrated relevant effects on tissue-specific DIO2 activities, which were manifested in the alterations of thyroid hormone levels. An asymptomatically appearance of autoantibodies against peptides corresponding to amino acid sequence of DIO2 was detected associating with thyroid hormone and anti-TPO, anti-Tg and TSH receptor antibody levels during the therapy.
Conference papers on the topic "Phages de type T4"
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Mneimneh, Farah, Nesreen Ghaddar, Kamel Ghali, Charbel Moussalem, and Ibrahim Omeis. "A Comparative Study on the Effectiveness of Evaporative and Phase Change Material Cooling Vests for People With Paraplegia." In ASME 2021 Heat Transfer Summer Conference collocated with the ASME 2021 15th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/ht2021-60491.
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Abstract Personal cooling vests to alleviate thermal strain in persons with thoracic spinal cord injury (SCI), named paraplegia, were tested. Mainly, phase change material (PCM) cooling vests were the most frequent type applied at different exercises and ambient conditions. Published results of PCM cooling vests indicated its significant effect in reducing body core temperature for persons having more than 50% of their trunk skin as sensate. Nevertheless, preferences of persons with SCI obtained from subjective voting during experimental studies revealed that the use of PCM cooling vests caused additional burden weight on the body and sometimes restricted the movement. It is of interest to investigate the effect of an alternative personal evaporative cooling vest (ECV), characterized by light weight and practical use without hindering body movement of persons with SCI. In this study, it is aimed to compare the effect of ECV on the physiological and psychological responses of persons with SCI compared to that of PCM cooling vests under the same ambient conditions and metabolic rates. The research methodology included human subject experiments for persons with mid-thoracic (T4-T8) and low-thoracic (T9-T12) injury where the sensate skin of the trunk is at least 50% of its area. Thirteen participants were recruited to perform an arm-crank exercise at a constant load of 30 W for 30-min while using ECV inside a controlled climatic chamber of hot conditions (30°C, 4 0% RH). Measurements of body core and skin temperatures as well as thermal comfort and sensation, perceived exertion and skin wettedness were done. Furthermore, Multi-way ANOVA test was conducted to analyse the results of three tests: no vest (NV), with ECV, and with PCM. Findings of mid- and low-thoracic groups showed similar effectiveness of ECV compared to PCM cooling vest in reducing core temperature, yet the change in perceived exertion was better with the use of ECV due to its light weight.
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Strandberg, L., D. Lawrence, and T. Ny. "ISOLATION OF THE GENOMIC REGION CODING FOR TYPE-1 PLASMINOGEN ACTIVATOR INHIBITOR." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644439.
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The type-1 Plasminogen Activator Inhibitor (PAI-1) has recently been identified as a member of the Serine Protease Inhibitor family (SERPINS). This family of proteins contain many serine protease inhibitors but also functionally unrelated proteins like ovalbumin and anginotensinogen. PAI-1 inhibits both u-PA and t-PA and might therefore be an important regulator of the fibrinolytic system.In order to study the evolution of the Serpin family as well as PAI-1 gene expression we have isolated the genomic region carrying the PAI-1 gene. A cDNA sequence for PAI-1 was used as probe to screen a human genomic library. When 2 million independent phages were screened, 13 positive clones were isolated. Characterisation of these clones showed that they could be divided into 3 overlapping groups covering a genomic region of approximately 30 kb. The gene was localized and characterized by restriction enzyme analysis, southern blotting using cDNA and oligomer probes, and DNA sequencing.
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Ny, T., L. Hansson, and B. Åstedt. "ISOLATION OF cDNA FOR TYPE-2 PLASMINOGEN ACTIVATOR INHIBITOR." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642855.
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The placental type plasminogen activator inhibitor (PAI-2) has been purified from extracts of human placenta and from a histiocytic lymphoma cell line. It is mainly an uPA inhibitor but it also inhibits the two-chain form of tPA.In order to determine the factors regulating PAI-2 gene expression and thereby clarify the physiological role of PAI-2 we have undertaken the molecular cloning of PAI-2 cDNA. A λgt11 expression library prepared from placental mRNA, was screened, immunologically using a monoclonal antibody probe developed against PAI-2 purified from human placenta. When 1.7×105 recombinant phages were screened six positive clones were obtained. Hybridization experiments and comparison of restriction enzyme cleavege pattern revealed that the DNA inserts of the six clones were, related. To identify the clones as coding for PAI-2, a lysogen made from one of them was induced, and the proteins were separated by SDS-PAGE. In immuno-blotting wxperiments the recombinant fusion protein and purified PAI-2 were recognized by the monoclonal antibody and a monospecific polyclonal antibody against PAI-2, revealing an immunological similarity. The nucleotide sequence of the largest cDNA was determined. It was found to code for a protein with extensive sequence homology with members of the serine protease inhibitor family (serpins) Alignment of the active center region with other serpins indicates that PAI-2 is an arg-serpin, as expected for an inhibitor of plasminogen activators.
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Nomiyama, Taishi, Naoto Sato, Kou Yamamoto, Shigeki Matsubara, Makoto Nakashima, and Takao Sugimoto. "T4: A two-tap based user interface system using a touch-type device for motor-impaired company employees." In 2015 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-TW). IEEE, 2015. http://dx.doi.org/10.1109/icce-tw.2015.7216811.
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Lusher, J. M., L. M. Aledort, S. Sarnaik, and J. Mosley. "HIV STATUS, T CELL SUBSETS, BLOOD PRODUCT USE, AND HEMATOLOGIC ABNORMALITIES IN CONGENITAL COAGULATION DISORDERS (CCD)." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644681.
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Data are presented on 485 subjects with CCDtreated with blood products at entry into a cooperative study of blood product safety; 376 subjects had hemophilia A, 86 had hemophilia B,and 23 had von Willebrand*is disease (vWD) . Anti-HIV was detected in a total of 323 (66.7%)subjects. Of those treated with pooled product303/397 (76.4%) had anti-HIV; of these, 256/316 (81%) had hemo. A, 44/76 (57.9%) had hemo. B, and 3/5 (60%) had vWD. Of those treated withunpooled products 20/88 (22.7%) had anti-HIV;of these 17/60 (28.3%) had hemo. A; 0 of 10 hadhemo. B, and 3/18 (16.6%) had vWD.The percent of T4 cells in all groups studied were significantly lower in anti-HIV (+) as compared toanti-HIV (-) patients (26% vs 42%) (p=0.0001).T4/T8 ratios demonstrated significant differences in all groups treated (p=0.001) when comparing anti-HIV (+) with anti-HIV (-). However, F VIII concentrate recipients who are anti-HIV(-) have significantly lower T4/T8 when compared to controls (p=0.0001) and single pooled F VIII deficient recipient patients (p=0.0264). Mean platelet counts, WBC, ALC, and Hgb were all significantly lower in anti-HIV ( + ) subjects (p <.001,=.0002,=.002, and =.02) A significantly higher % of anti-HIV (+) subjects had abnormally low WBC, ALC and platelet counts (table). In summary, anti-HIV (+) and lower T4/T8ratios were related to type of blood product used, being seen significantly less frequently in patients receiving only unpooled product. Thrombopenia, leucopenia, and lymphopenia were seen more frequently in anti-HIV (+) patients. _
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GOMPERTS, E. D., and K. WEINBERG. "LOSS OF IMMUNE TO RECALL ANTIGENS IN THERE HIV+ HEMOPHILIC CHILDREN." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644140.
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Three children with severe inherited bleeding disorders have been followed for a number of years at this center. One child (DOB 3/71) initially presented with mild hemophilia A, (Factor VIII 6%). He subsequently developed an inhibitor to Factor VIII (maximum 45 B. U.) and seroconverted to HIV+ Status 12/83. In 12/86 he had virtually lost his antibody response to infused Factor VIII (previously withheld), with a maximum increase in inhibitor titre to1 B. U. on challenge. In addition, his antitetanus antibody titre was very low at 0.01 u/ml earlier in theyear. His absolute T4 cell number at this time was very low at 64 and did not respond to skin antigen testing to PPD, tetanus and Candida.The second patient (severe hemophilia A DOB 7/76) had seroconvertedto HIV+ Status in 9/78. This child has lost his a-HBs seropositive status with an absolute T4 count of 239. His current anti-tetanus titre is 0.01 u/ml.The third patient (von Willebrand disease, Type III, DOB 7/74) seroconverted to HIV+E status by 5/83. His T4 absolute numbers have fallen to 53. His anti-tetanus antibody titre has fallen to extremely low levels (0.01 u/ml), and this failed to respond to re-immunization with tetanus toxoid. These three patients indicate that previously immunized children may lose their immune status and their ability to respond to recall antigens. It is pertinent to note that lymphocytes from all 3 patients failed to respond mitogenically in vitro to tetanus antigen pari passu with the observed very low anti-tetanus antibody titres. These phenomena would indicate that these patients are probably susceptible to previously preventable infectious agents including poliovirus, measles, mumps, rubella, diphtheria, tetanus and hepatitis B virus.
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Narayana Rao, Korukonda Venkata Lakshmi, B. V. S. S. S. Prasad, Ch Kanna Babu, and Girish K. Degaonkar. "Numerical and Experimental Investigations on Liner Heat Transfer in an Aero Engine Combustion Chamber." In ASME 2017 Gas Turbine India Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gtindia2017-4776.
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The Gas turbine combustion chamber is the highest thermally loaded component where the temperature of the combustion gases is higher than the melting point of the liner that confines the gases. Combustor liner temperatures have to be evaluated at all the operating conditions in the operating envelope to ensure a satisfactory liner life and structural integrity. On experimental side the combustion chamber rig testing involves a lot of time and is very expensive, while the numerical computations and simulations has to be validated with the experimental results. This paper is mainly based on the work carried out in validating the liner temperatures of a straight flow annular combustion chamber for an aero engine application. Limited experiments have been carried out by measuring the liner wall temperatures using k-type thermocouples along the liner axial length. The experiments on the combustion chamber testing are carried out at the engine level testing. The liner temperature which is numerically computed by CHT investigations using CFX code is verified with the experimental data. This helped in better understanding the flow characterization around and along the liner wall. The main flow variables used are the mass flow rate, temperature and the pressure at the combustor inlet. Initially, the fuel air ratio is used accordingly to maintain the same T4/T3 ratio. The effect of liner temperature with T3 is studied. Since T4 is constant, the liner temperature is only dependent on T3 and follows a specific temperature distribution for the given combustor geometry. Hence this approach will be very useful in estimating the liner temperatures at any given T3 for a given combustor geometry. Further the liner temperature is also estimated at other fuel air ratios (different T4/T3 ratios) by using the verified CHT numerical computations and found that TL/T3 remains almost constant for any air fuel ratio that is encountered in the operating envelope of the aero engine.
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Preston, F. E., M. Greaves, B. Sampson, P. B. A. Kernoff, G. Savidge, and N. Bax. "HYPOTHYROIDISM AND ACQUIRED VON WILLEBRAND'S DISEASE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644115.
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A diagnosis of type IA von Willebrand's disease was made in three patients presenting with a mild bleeding tendency. Previously unrecognised hypothyroidism was also confirmed in two patients. In the third, hypothyroidism was diagnosed four years after initial presentation. In all three patients, thyroxine therapy was associated with correction of the haemostatic defect and resolution of the bleeding tendency.The association of von Willebrand's disease and hypothyrodism prompted us to examine the relationship between thyrotrophin (TSH), T3, T4 and components of the factor VIII complex in 12 patients with clinical and biochemical hypothyroidism. Factor IX was also studied. Mean VIII:C (measured by 2 stage assay) was 0.90 u/ul (range 0.55 - 1.14); mean vWF:Ag 0-83 u/ul (range 0.44 - 1.64); mean VIII:Rcof 0.75 (range 0.45 - 1.55); mean factor IX 0.72 (range 0.39 - 1.19). Multimeric analysis of vWF:Ag performed in samples from 8 patients was normal. VIII:Rcof levels were significantly lower than those of normal controls. A significant inverse correlation was obtained between TSH and factor IX and T4 and vWF:Ag. Although there is a definite inverse relationship between TSH and factor IX, this is not evident with respect to factor VIII and a different mechanism is probably responsible for the modest reduction of vWF:Ag and the occurrence of clinically-evident von Willebrand's disease which we have demonstrated in a small proportion of hypothyroid patients.
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Ali Ablat, Muhammad, and Ala Qattawi. "Finite Element Analysis of Origami-Based Sheet Metal Folding Process." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67324.
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There are challenges in the conventional sheet metal folding for mass production; those are summarized by high tooling and energy costs and lack of dimensional accuracy. High cost per product is due to the need of specific manufacturing tools and equipment like dies and molds that are shape dedicated to certain product range and specifications. Lack of high accuracy is resulted from involved forming process, machine structure and springback effects in workpiece. Origami-based Sheet Metal (OSM) folding fabrication process has been utilized to overcome these challenges. This novel approach is an extension of the origami technique to sheet metal folding process and it requires creating numerous features along the bend line, called Material Discontinuities (MD). MD are fabricated by removal of material completely or partially through thickness direction of sheet metal along the bend line using laser cutting process or progressive stamping. MD can also be created by stamping where no material removal is present, rather stamping creates deformed pattern along the bend line to guide the folding. MD controls the material deformation during bending and results in reduced bending force, minimal tooling and machinery requirements. Despite the promising potential of OSM, there is little understating of the effect of the selected MD shape and geometry on the final workpiece, specifically this is of interest when comparing the energy and cost allocations for OSM with a well-establish process for sheet metal such as stamping. In this work, the effect of several types of MD on sheet metal folding process is investigated using Finite Element Analysis (FEA). In particular, wiping die bending of aluminum sheet with different MD shapes and geometries along the bend line is compared to the traditional sheet bending of final part in terms of stress distribution along the bending line and required bending force. FE simulations are carried out using structural and thermo-mechanical FE solver Code_Aster. Aluminum 2036-T4 is chosen as sheet metal material. Constitutive model in the simulation is J2 flow theory plasticity with isotropic hardening. The FEA results are validated by comparing it to the available empirical models in terms of bending forces. This study finds that the OSM technique reduced the required bending force significantly, which has important significance in energy and cost reduction. It also ranked the MD in terms of the required force to bend the same sheet metal type and thickness for further future investigation. However, the MD leads to localized high stress regions along the bending line, which may affect load-bearing capability of the final part. In addition, it may lead to cracks or fractures of sheet metal part in the high stress region, especially if MD are densely arranged along the bend line.
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Vasilyev, A., V. Zakharov, V. Lyashenko, R. Medvedev, O. Chelebyan, and A. Maiorova. "Experience of Low-Emission Combustion of Aviation and Bio Fuels in Individual Flames After Front Mini-Modules of a Combustion Chamber." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75419.
Full textAbstract:
In the world economy more and more attention is paid to the environment protection. This has brought a requirement for reduction of harmful substances emission from the gas turbine engine combustors to the foreground scene. Several concepts of low-emission combustion of liquid fuels have been suggested to solve the problem of nitric oxide emission reduction. The authors consider combustion of lean homogenized (quick-mixed) fuel-air mixtures to be the most promising concept for a multi-mode combustion chamber. Based on the accumulated experience, the authors have formed some notion with respect to design peculiarities of low-emission combustors. Based on such general notions, an attempt has been made to create a model combustion chamber for decreasing harmful substances emission. A design for compact mixing modules has been worked out, as well as for a perforated flame tube. 3D computations have been carried out for the flow in the combustor compartment with 3 mini-modules, so to compare design and experimental data. In calculations the air entered the flame tube through a channel with a rectangular cross-section and, further, through swirlers of three burners (60% of air flow). Besides, the air came into the gap between the flame tube and casing through two side channels and, further, it got inside the flame tube through cooling system holes (40% of air flow). In parallel, tests have been carried out in similar combustor compartment, using standard fuels, measuring harmful substances emission at gas temperature (T4) up to 1700 K. Data obtained testifies to essential reduction of nitric oxides in the experimental combustor being considered. Emission index NOx does not exceed value of 1 g/kg f in all the conditions investigated. Fuel efficiency is ≥ 99% for all the measurement regimes, except one, where it is 98%. Additionally, tests have been conducted, using bio fuel obtained from plant raw material. Research results have revealed problems of changeover to such type of fuel mixtures. Comparing test data with 3D simulation results, it can be noted that there, where computed value of the fuel combustion efficiency coincides with the measured one, NOx value also coincides. However, the emission index value is higher there, where the fuel combustion efficiency value obtained in computation is higher, i.e. where there are zones with higher temperature. The experimental results obtained have confirmed possibility of organizing low-emission combustion, as well as possibility of achieving the nitric oxide emission index level equal to 1 g/kg f at the combustor inlet temperature of 682K. It is evident that more detailed design study is required for transfer of the experimental technology to the working compartment of the combustion chamber. The achieved level of harmful substances emission, after improvement and implementation of technology, may allow meeting the strictest ICAO requirements and reducing the airport fees significantly.