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Search Results: 1 - 10 of 708 matches for " Corinne Geertsema "
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Analysis of the Tomato spotted wilt virus Ambisense S RNA-Encoded Hairpin Structure in Translation
Christina Geerts-Dimitriadou, Yun-Yueh Lu, Corinne Geertsema, Rob Goldbach, Richard Kormelink
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031013
Abstract: Background The intergenic region (IR) of ambisense RNA segments from animal- and plant-infecting (-)RNA viruses functions as a bidirectional transcription terminator. The IR sequence of the Tomato spotted wilt virus (TSWV) ambisense S RNA contains stretches that are highly rich in A-residues and U-residues and is predicted to fold into a stable hairpin structure. The presence of this hairpin structure sequence in the 3′ untranslated region (UTR) of TSWV mRNAs implies a possible role in translation. Methodology/Principal Findings To analyse the role of the predicted hairpin structure in translation, various Renilla luciferase constructs containing modified 3′ and/or 5′ UTR sequences of the TSWV S RNA encoded nucleocapsid (N) gene were analyzed for expression. While good luciferase expression levels were obtained from constructs containing the 5′ UTR and the 3′ UTR, luciferase expression was lost when the hairpin structure sequence was removed from the 3′ UTR. Constructs that only lacked the 5′ UTR, still rendered good expression levels. When in addition the entire 3′ UTR was exchanged for that of the S RNA encoded non-structural (NSs) gene transcript, containing the complementary hairpin folding sequence, the loss of luciferase expression could only be recovered by providing the 5′ UTR sequence of the NSs transcript. Luciferase activity remained unaltered when the hairpin structure sequence was swapped for the analogous one from Tomato yellow ring virus, another distinct tospovirus. The addition of N and NSs proteins further increased luciferase expression levels from hairpin structure containing constructs. Conclusions/Significance The results suggest a role for the predicted hairpin structure in translation in concert with the viral N and NSs proteins. The presence of stretches highly rich in A-residues does not rule out a concerted action with a poly(A)-tail-binding protein. A common transcription termination and translation strategy for plant- and animal-infecting ambisense RNA viruses is being discussed.
Optimal Costly Information Gathering in Public Service Provision  [PDF]
Paul Geertsema, Christoph Schumacher
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23060
Abstract: Imperfect information regarding the true needs of recipients is a common problem for governmental or not-for-profit service providers. This can lead to potentially dangerous under-provision or wasteful over-provision of services. We provide a method for optimally improving a service provider’s information regarding true client need through costly information gathering. Our contribution is to allow providers to endogenously and optimally choose the intensity of information gathering. Providers do so by specifying the level of correlation between observed and true recipient need, subject to an arbitrary cost function over the specified correlation. We derive the conditions that characterize the choice of optimal correlation for providers with quadratic utility. Using a realistic exponential correlation cost function, we show that there exists a critical value of true client need variance below which it is never optimal to engage in information gathering. Further, for true client variance above this critical level the optimal correlation will always exceed 0.5. Our findings have a wide range of policy implications in areas such as health care, social wellfare and even counter-terroism.
Effective Chikungunya Virus-like Particle Vaccine Produced in Insect Cells
Stefan W. Metz,Joy Gardner,Corinne Geertsema,Thuy T. Le,Lucas Goh,Just M. Vlak,Andreas Suhrbier,Gorben P. Pijlman
PLOS Neglected Tropical Diseases , 2013, DOI: 10.1371/journal.pntd.0002124
Abstract: The emerging arthritogenic, mosquito-borne chikungunya virus (CHIKV) causes severe disease in humans and represents a serious public health threat in countries where Aedes spp mosquitoes are present. This study describes for the first time the successful production of CHIKV virus-like particles (VLPs) in insect cells using recombinant baculoviruses. This well-established expression system is rapidly scalable to volumes required for epidemic responses and proved well suited for processing of CHIKV glycoproteins and production of enveloped VLPs. Herein we show that a single immunization with 1 μg of non-adjuvanted CHIKV VLPs induced high titer neutralizing antibody responses and provided complete protection against viraemia and joint inflammation upon challenge with the Réunion Island CHIKV strain in an adult wild-type mouse model of CHIKV disease. CHIKV VLPs produced in insect cells using recombinant baculoviruses thus represents as a new, safe, non-replicating and effective vaccine candidate against CHIKV infections.
Studies on African zygaenoid moths (Lepidoptera: Zygaenoidea): descriptions of final instar larvae of Psycharium pellucens, P. montanum and Psycharium sp. A, with notes on the larva of P. barnardi and Somabrachys (Somabrachyidae)
H. Geertsema
African Zoology , 2011,
Abstract: Generalized descriptions of the larvae of Somabrachyidae, with brief notes on their biology and habits, are presented. Illustrations in colour as well as a key for the identification of final instar larvae of Psycharium pellucens, P. montanum and Psycharium sp. A are given; comprehensive of these larvae, with some notes on the description of the larva of P. barnardi and of Somabrachys
Studies on African zygaenoid moths (Lepidoptera: Zygaenoidea): adult morphology of Psycharium montanum (Somabrachyidae)
H. Geertsema
African Zoology , 2011,
Abstract: The morphology of the adult male ofPsycharium montanum is described and illustrated to serve as a basis for subsequent taxonomic and systematic studies on African flannel moths and related taxa. P. montanum exhibits features showing closer affinity to Limacodidae than to Megalopygidae
Studies on African zygaenoid moths (Lepidoptera: Zygaenoidea): Parapsycharium n.gen. (Somabrachyidae) from the Western Cape Province, South Africa
H. Geertsema
African Zoology , 2011,
Abstract: A new genus,Parapsycharium n.gen. and its type species, P. paarlense, are described in Somabrachyidae. A key to the somabrachyid genera Somabrachys Kirby, Psycharium Herrich-Sch ffer and Parapsycharium n.gen. is given. The description of the new taxon includes the description of its final instar larva.
Identiteit en kwaliteit: Over het nut van een identiteitsbeschrijving van het maatschappelijk werk
Henk Geertsema
Journal of Social Intervention : Theory and Practice , 2008,
Abstract: Social work is a helping profession that is present in a variety of contexts. This raises the question whether one can speak of a common identity of the profession. The author has addressed this question in his Ph.D-thesis from the point of view that social work is to be seen as an action theory based profession. Starting from this premise he made a reconstruction of the identity by means of both an international historical comparative theoretical research and four case studies with regard to contemporary social work in the Netherlands. Beside making a proposal for an action based identity formulation, the author investigates the possibilities for using this formulation for the solution of some contemporary problems of social workers in the Netherlands. In the second part of the article, he discusses the outcomes in relation to theories of action and improvement thereof. He states that improvement of social work activities can only be realized through more knowledge of social work’s history, active discussion of problems and solutions with a diversity of involved actors and professional exchange in informal and formal Communities of Practice.
The Handbook of Community Practice
Henk Geertsema
Journal of Social Intervention : Theory and Practice , 2009,
Abstract:
Functional processing and secretion of Chikungunya virus E1 and E2 glycoproteins in insect cells
Stefan W Metz, Corinne Geertsema, Byron E Martina, Paulina Andrade, Jacco G Heldens, Monique M van Oers, Rob W Goldbach, Just M Vlak, Gorben P Pijlman
Virology Journal , 2011, DOI: 10.1186/1743-422x-8-353
Abstract: Expression in the presence of either tunicamycin or furin inhibitor showed that a substantial portion of recombinant intracellular E1 and precursor E3E2 was glycosylated, but that a smaller fraction of E3E2 was processed by furin into mature E3 and E2. Deletion of the C-terminal transmembrane domains of E1 and E2 enabled secretion of furin-cleaved, fully processed E1 and E2 subunits, which could then be efficiently purified from cell culture fluid via metal affinity chromatography. Confocal laser scanning microscopy on living baculovirus-infected Sf21 cells revealed that full-length E1 and E2 translocated to the plasma membrane, suggesting similar posttranslational processing of E1 and E2, as in a natural CHIKV infection. Baculovirus-directed expression of E1 displayed fusogenic activity as concluded from syncytia formation. CHIKV-E2 was able to induce neutralizing antibodies in rabbits.Chikungunya virus glycoproteins could be functionally expressed at high levels in insect cells and are properly glycosylated and cleaved by furin. The ability of purified, secreted CHIKV-E2 to induce neutralizing antibodies in rabbits underscores the potential use of E2 in a subunit vaccine to prevent CHIKV infections.Chikungunya virus (CHIKV) is an arthropod-borne (arbo)virus that causes epidemics in Africa, India and South-East Asia [1]. Recent outbreaks in Italy in 2007 [2] and autochthonous transmission events in France in 2010 [3] exemplify the threat of continued spread of CHIKV in the Western world, which correlates with the concurrent expanding distribution of its insect vector. CHIKV is maintained in a sylvatic transmission cycle of mosquitoes, rodents and primates, with Aedes aegyti as the primary vector. However, the responsible vector causing the severe CHIKV epidemic on the Reunion Islands in 2005/2006 was Ae. albopictus [4]. This vector switch made the virus endemic in more temperate regions and resulted in the first European cases (Italy, 2007) of transmission by local
West Nile Virus: High Transmission Rate in North-Western European Mosquitoes Indicates Its Epidemic Potential and Warrants Increased Surveillance
Jelke J. Fros?,Corinne Geertsema,Chantal B. Vogels?,Peter P. Roosjen?,Anna-Bella Failloux?,Just M. Vlak?,Constantianus J. Koenraadt?,Willem Takken?,Gorben P. Pijlman
PLOS Neglected Tropical Diseases , 2015, DOI: 10.1371/journal.pntd.0003956
Abstract: Background West Nile virus (WNV) is a highly pathogenic flavivirus transmitted by Culex spp. mosquitoes. In North America (NA), lineage 1 WNV caused the largest outbreak of neuroinvasive disease to date, while a novel pathogenic lineage 2 strain circulates in southern Europe. To estimate WNV lineage 2 epidemic potential it is paramount to know if mosquitoes from currently WNV-free areas can support further spread of this epidemic. Methodology/Principal Findings We assessed WNV vector competence of Culex pipiens mosquitoes originating from north-western Europe (NWE) in direct comparison with those from NA. We exposed mosquitoes to infectious blood meals of lineage 1 or 2 WNV and determined the infection and transmission rates. We explored reasons for vector competence differences by comparing intrathoracic injection versus blood meal infection, and we investigated the influence of temperature. We found that NWE mosquitoes are highly competent for both WNV lineages, with transmission rates up to 25%. Compared to NA mosquitoes, transmission rates for lineage 2 WNV were significantly elevated in NWE mosquitoes due to better virus dissemination from the midgut and a shorter extrinsic incubation time. WNV infection rates further increased with temperature increase. Conclusions/Significance Our study provides experimental evidence to indicate markedly different risk levels between both continents for lineage 2 WNV transmission and suggests a degree of genotype-genotype specificity in the interaction between virus and vector. Our experiments with varying temperatures explain the current localized WNV activity in southern Europe, yet imply further epidemic spread throughout NWE during periods with favourable climatic conditions. This emphasizes the need for intensified surveillance of virus activity in current WNV disease-free regions and warrants increased awareness in clinics throughout Europe.
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