Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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A tracer-based method enables tracking of plasmodium falciparum malaria parasites during human skin infection
Winkel, Béatrice M.F. ; Korne, Clarize M. de; Oosterom, Matthias N. van; Staphorst, Diego ; Bunschoten, Anton ; Langenberg, Marijke C.C. ; Chevalley-Maurel, Séverine C. ; Janse, Chris J. ; Franke-Fayard, Blandine ; Leeuwen, Fijs W.B. van; Roestenberg, Meta - \ 2019
Theranostics 9 (2019)10. - ISSN 1838-7640 - p. 2768 - 2778.
Cell tracking - Malaria - Molecular Imaging - Skin - Sporozoites

Introduction: The skin stage of malaria is a vital and vulnerable migratory life stage of the parasite. It has been characterised in rodent models, but remains wholly uninvestigated for human malaria parasites. To enable in depth analysis of not genetically modified (non-GMO) Plasmodium falciparum (Pf) sporozoite behaviour in human skin, we devised a labelling technology (Cy5M2, targeting the sporozoite mitochondrion) that supports tracking of individual non-GMO sporozoites in human skin. Methods: Sporozoite labelling with Cy5M2 was performed in vitro as well as via the feed of infected Anopheles mosquitos. Labelling was validated using confocal microscopy and flow cytometry and the fitness of labelled sporozoites was determined by analysis of infectivity to human hepatocytes in vitro, and in vivo in a rodent infection model. Using confocal video microscopy and custom software, single-sporozoite tracking studies in human skin-explants were performed. Results: Both in vitro and in mosquito labelling strategies yielded brightly fluorescent sporozoites of three different Plasmodium species. Cy5M2 uptake colocalized with MitoTracker® green and could be blocked using the known Translocator protein (TSPO)-inhibitor PK11195. This method supported the visualization and subsequent quantitative analysis of the migration patterns of individual non-GMO Pf sporozoites in human skin and did not affect the fitness of sporozoites. Conclusions: The ability to label and image non-GMO Plasmodium sporozoites provides the basis for detailed studies on the human skin stage of malaria with potential for in vivo translation. As such, it is an important tool for development of vaccines based on attenuated sporozoites and their route of administration.

Combined effects of nanoplastics and copper on the freshwater alga Raphidocelis subcapitata
Bellingeri, A. ; Bergami, E. ; Grassi, G. ; Faleri, C. ; Redondo Hasselerharm, P.E. ; Koelmans, A.A. ; Corsi, I. - \ 2019
Aquatic Toxicology 210 (2019). - ISSN 0166-445X - p. 179 - 187.
Nanoplastics are recognized as able to interact with other pollutants including heavy metals, and with natural organic matter, with implications for the potential risks to biota. We investigated the interaction of carboxylated polystyrene nanoparticles (PS–COOH NPs) with copper (Cu) and algal exudates (EPS) and how such interaction could affect Cu toxicity towards the freshwater microalga Raphidocelis subcapitata. PS–COOH NPs behavior in the presence of Cu and EPS was determined by dynamic light scattering (DLS), while PS–COOH NPs surface interaction with Cu ions and EPS was investigated by fluorimetric analysis. ICP-MS was used to test Cu ion adsorption to PS–COOH NPs in the presence and absence of algae. The interaction between PS–COOH NPs and the algal cell wall was assessed by fluorescence microscopy. Short- and long-term toxicity tests were carried out in parallel to assess the impact of PS–COOH NPs on algal growth. Results showed altered nanoparticle surface charge and hydrodynamic diameter following algal EPS exposure, supporting the hypothesis of a protein corona formation. In contrast, no absorption of Cu ions was observed on PS–COOH NPs, either in the presence or absence of algae. No differences on algal growth inhibition were observed between exposure to Cu only, and to Cu in combination with PS–COOH NPs, in short-term as well as long-term tests. However, after 72 h of exposure, the adsorption of PS-COOH NPs to algal cell walls appeared to correspond to morphological alterations, revealing potential disturbances in the mitotic cycle. Our findings confirm the ability of PS–COOH NPs to interact with EPS as shown for other nanomaterials. Environmentally realistic exposure scenarios are thus needed for evaluating nanoplastic toxicity, as nanoparticles will not maintain their pristine nature once released into natural media. Prolonged exposure and use of different end-points such as cell morphological changes and EPS production seem more reliable for the investigation of nanoplastic/algal cell interactions which can drive food chain transfer of nanoplastics and ultimately toxicity.
Species-specific alterations in Anopheles mosquito olfactory responses caused by Plasmodium infection
Stanczyk, N.M. ; Brugman, V.A. ; Austin, V. ; Sanchez-Roman Teran, F. ; Gezan, S.A. ; Emery, M. ; Visser, T.M. ; Dessens, J.T. ; Stevens, W. ; Smallegange, R.C. ; Takken, W. ; Hurd, H. ; Caulfield, John ; Birkett, M. ; Pickett, J. ; Logan, J.G. - \ 2019
Scientific Reports 9 (2019)1. - ISSN 2045-2322

Mosquitoes infected with malaria parasites have demonstrated altered behaviour that may increase the probability of parasite transmission. Here, we examine the responses of the olfactory system in Plasmodium falciparum infected Anopheles gambiae, Plasmodium berghei infected Anopheles stephensi, and P. berghei infected An. gambiae. Infected and uninfected mosquitoes showed differential responses to compounds in human odour using electroantennography coupled with gas chromatography (GC-EAG), with 16 peaks triggering responses only in malaria-infected mosquitoes (at oocyst, sporozoite or both stages). A selection of key compounds were examined with EAG, and responses showed differences in the detection thresholds of infected and uninfected mosquitoes to compounds including lactic acid, tetradecanoic acid and benzothiazole, suggesting that the changes in sensitivity may be the reason for differential attraction and biting at the oocyst and sporozoite stages. Importantly, the different cross-species comparisons showed varying sensitivities to compounds, with P. falciparum infected An. gambiae differing from P. berghei infected An. stephensi, and P. berghei infected An. gambiae more similar to the P. berghei infected An. stephensi. These differences in sensitivity may reflect long-standing evolutionary relationships between specific Plasmodium and Anopheles species combinations. This highlights the importance of examining different species interactions in depth to fully understand the impact of malaria infection on mosquito olfactory behaviour.

Does artemether-lumefantrine administration affect mosquito olfactory behaviour and fitness?
Boer, Jetske G. de; Busula, Annette O. ; Berge, Jet Ten; Dijk, Tessa S. van; Takken, Willem - \ 2019
Malaria Journal 18 (2019). - ISSN 1475-2875
Antimalarial medication - Epidemiology - Gametocytes - Host-searching - Olfaction - Post-treatment transmission - Skin odour

BACKGROUND: Artemisinin-based combination therapy (ACT) is the recommended treatment against uncomplicated Plasmodium falciparum infections, and ACT is widely used. It has been shown that gametocytes may be present after ACT and transmission to mosquitoes is still possible. Artemether-lumefantrine (AL) is a broadly used artemisinin-based combination medicine. Here, it is tested whether AL influences behaviour and fitness of Anopheles mosquitoes, which are the main vectors of P. falciparum. RESULTS: Dual-choice olfactometer and screenhouse experiments showed that skin odour of healthy human individuals obtained before, during and after AL-administration was equally attractive to Anopheles coluzzii and Anopheles gambiae sensu stricto, apart from a small (but significant) increase in mosquito response to skin odour collected 3 weeks after AL-administration. Anopheles coluzzii females fed on parasite-free blood supplemented with AL or on control-blood had similar survival, time until oviposition and number of eggs produced. CONCLUSIONS: Based on the results, AL does not appear to influence malaria transmission through modification of vector mosquito olfactory behaviour or fitness. Extending these studies to Plasmodium-infected individuals and malaria mosquitoes with parasites are needed to further support this conclusion.

Spatio-temporal distribution of mosquitoes and risk of malaria infection in Rwanda
Hakizimana, Emmanuel ; Karema, Corine ; Munyakanage, Dunia ; Githure, John ; Mazarati, Jean Baptiste ; Tongren, Jon Eric ; Takken, Willem ; Binagwaho, Agnes ; Koenraadt, Constantianus J.M. - \ 2018
Acta Tropica 182 (2018). - ISSN 0001-706X - p. 149 - 157.
Abundance - Entomological inoculation rate - Rwanda - Sporozoite rate - Vector distribution
To date, the Republic of Rwanda has not systematically reported on distribution, diversity and malaria infectivity rate of mosquito species throughout the country. Therefore, we assessed the spatial and temporal variation of mosquitoes in the domestic environment, as well as the nocturnal biting behavior and infection patterns of the main malaria vectors in Rwanda. For this purpose, mosquitoes were collected monthly from 2010 to 2013 by human landing catches (HLC) and pyrethrum spray collections (PSC) in seven sentinel sites. Mosquitoes were identified using morphological characteristics and PCR. Plasmodium falciparum sporozoite infection rates were determined using ELISA. A total of 340,684 mosquitoes was collected by HLC and 73.8% were morphologically identified as culicines and 26.2% as anophelines. Of the latter, 94.3% were Anopheles gambiae s.l., 0.4% Anopheles funestus and 5.3% other Anopheles species. Of An. gambiae s.l., An. arabiensis and An. gambiae s.s. represented 84.4% and 15.6%, respectively. Of all An. gambiae s.l. collected indoor and outdoor, the proportion collected indoors was 51.3% in 2010 and 44.9% in 2013. A total of 17,022 mosquitoes was collected by PSC of which 20.5% were An. gambiae s.l. and 79.5% were culicines. For the seven sentinel sites, the mean indoor density for An. gambiae s.l. varied from 0.0 to 1.0 mosquitoes/house/night. P. falciparum infection rates in mosquitoes varied from 0.87 to 4.06%. The entomological inoculation rate (EIR) ranged from 1.0 to 329.8 with an annual average of 99.5 infective bites/person/year. This longitudinal study shows, for the first time, the abundance, species composition, and entomological inoculation rate of malaria mosquitoes collected throughout Rwanda.
Characterization of the Theileria parva sporozoite proteome
Nyagwange, James ; Tijhaar, Edwin ; Ternette, Nicola ; Mobegi, Fredrick ; Tretina, Kyle ; Silva, Joana C. ; Pelle, Roger ; Nene, Vishvanath - \ 2018
International Journal for Parasitology 48 (2018)3-4. - ISSN 0020-7519 - p. 265 - 273.
Antigens - East Coast fever - MudPIT - Proteomics - Sporozoites - Theileria
East Coast fever is a lymphoproliferative disease caused by the tick-borne protozoan parasite Theileria parva. The sporozoite stage of this parasite, harboured and released from the salivary glands of the tick Rhipicephalus appendiculatus during feeding, invades and establishes infection in bovine lymphocytes. Blocking this initial stage of invasion presents a promising vaccine strategy for control of East Coast fever and can in part be achieved by targeting the major sporozoite surface protein p67. To support research on the biology of T. parva and the identification of additional candidate vaccine antigens, we report on the sporozoite proteome as defined by LC-MS/MS analysis. In total, 4780 proteins were identified in an enriched preparation of sporozoites. Of these, 2007 were identified as T. parva proteins, representing close to 50% of the total predicted parasite proteome. The remaining 2773 proteins were derived from the tick vector. The identified sporozoite proteins include a set of known T. parva antigens targeted by antibodies and cytotoxic T cells from cattle that are immune to East Coast fever. We also identified proteins predicted to be orthologs of Plasmodium falciparum sporozoite surface molecules and invasion organelle proteins, and proteins that may contribute to the phenomenon of bovine lymphocyte transformation. Overall, these data establish a protein expression profile of T. parva sporozoites as an important starting point for further study of a parasitic species which has considerable agricultural impact.
Plasmodium falciparum parasites with histidine-rich protein 2 (pfhrp2) and pfhrp3 gene deletions in two endemic regions of Kenya
Beshir, Khalid B. ; Sepúlveda, Nuno ; Bharmal, Jameel ; Robinson, Ailie ; Mwanguzi, Julian ; Busula, Annette Obukosia ; Boer, Jetske Gudrun De; Sutherland, Colin ; Cunningham, Jane ; Hopkins, Heidi - \ 2017
Scientific Reports 7 (2017)1. - ISSN 2045-2322
017-4052
Deletions of the Plasmodium falciparum hrp2 and hrp3 genes can affect the performance of HRP2-based malaria rapid diagnostic tests (RDTs). Such deletions have been reported from South America, India and Eritrea. Whether these parasites are widespread in East Africa is unknown. A total of 274 samples from asymptomatic children in Mbita, western Kenya, and 61 genomic data from Kilifi, eastern Kenya, were available for analysis. PCR-confirmed samples were investigated for the presence of pfhrp2 and pfhrp3 genes. In samples with evidence of deletion, parasite presence was confirmed by amplifying three independent genes. We failed to amplify pfhrp2 from 25 of 131 (19.1%) PCR-confirmed samples. Of these, only 8 (10%) samples were microscopic positive and were classified as pfhrp2-deleted. Eight microscopically-confirmed pfhrp2-deleted samples with intact pfhrp3 locus were positive by HRP2-based RDT. In addition, one PCR-confirmed infection showed a deletion at the pfhrp3 locus. One genomic sample lacked pfhrp2 and one lacked pfhrp3. No sample harbored parasites lacking both genes. Parasites lacking pfhrp2 are present in Kenya, but may be detectable by HRP-based RDT at higher parasitaemia, possibly due to the presence of intact pfhrp3. These findings warrant further systematic study to establish prevalence and diagnostic significance.
Forest resource projection tools at the European level
Schelhaas, M. ; Nabuurs, G.J. ; Verkerk, P.J. ; Hengeveld, G.M. ; Packalen, Tuula ; Sallnäs, O. ; Pilli, Roberto ; Grassi, J. ; Forsell, Nicklas ; Frank, S. ; Gusti, Mykola ; Havlik, Petr - \ 2017
In: Forest inventory-based projection systems for wood and biomass availability / Barreiro, Susana, Schelhaas, Mart-Jan, McRoberts, Ronald E., Kändler, Gerald, Springer (Managing forest ecosystems ) - ISBN 9783319561998 - p. 49 - 68.
Many countries have developed their own systems for projecting forest resources and wood availability. Although studies using these tools are helpful for developing national policies, they do not provide a consistent assessment for larger regions such as the European Union or Europe as a whole. Individual national-scale studies differ considerably in timing, underlying methodology and scenarios, and reports are not issued for all countries in the region. However, a clear demand for consistent projections at European scale still remains. This chapter describes the resource simulators and forest sector models EFISCEN, EFDM, CBM-CFS3, and GLOBIOM/G4M that can all be applied to individual European countries, as well as to Europe as a whole.
Gametocytemia and Attractiveness of Plasmodium falciparum-Infected Kenyan Children to Anopheles gambiae Mosquitoes
Busula, Annette O. ; Bousema, Teun ; Mweresa, Collins K. ; Masiga, Daniel ; Logan, James G. ; Sauerwein, Robert W. ; Verhulst, Niels O. ; Takken, Willem ; Boer, Jetske G. de - \ 2017
The Journal of Infectious Diseases 216 (2017)3. - ISSN 0022-1899 - p. 291 - 295.
chemical ecology - host finding - malaria transmission - olfactory behavior - vector control
It has been suggested that Plasmodia manipulate their vertebrate hosts to enhance parasite transmission. Using a dual-choice olfactometer, we investigated the attraction of Anopheles gambiae to 50 Kenyan children (aged 5-12 years) who were naturally infected with Plasmodium falciparum or noninfected controls. Microscopic gametocyte carriers attracted almost 2 times more mosquitoes than children who were parasite free, harbored asexual stages, or had gametocytes at submicroscopic densities. By using highly sensitive stage-specific molecular methods to detect P. falciparum, we show that gametocytes-and not their noninfectious asexual progenitors-induce increased attractiveness of humans to mosquitoes. Our findings therefore support the parasite host manipulation hypothesis.
Microorganism-mediated behaviour of malaria mosquitoes
Busula, Annette O. - \ 2017
Wageningen University. Promotor(en): W. Takken, co-promotor(en): J. de Boer. - Wageningen : Wageningen University - ISBN 9789463431156 - 199
culicidae - anopheles gambiae - anopheles arabiensis - mosquito-borne diseases - disease vectors - animal behaviour - host-seeking behaviour - plasmodium falciparum - hosts - man - cows - hens - odours - culicidae - anopheles gambiae - anopheles arabiensis - ziekten overgebracht door muskieten - vectoren, ziekten - diergedrag - gedrag bij zoeken van een gastheer - plasmodium falciparum - gastheren (dieren, mensen, planten) - mens - koeien - hennen - geurstoffen

Host-seeking is an important component of mosquito vectorial capacity on which the success of the other behavioural determinants depends. Blood-seeking mosquitoes are mainly guided by chemical cues released by their blood hosts. This thesis describes results of a study that determined the effect of microorganisms – host skin bacteria as well as malaria parasites – on host-seeking behaviour of female Anopheles gambiae sensu stricto and An. arabiensis in Homabay county, western Kenya. Semi-field and field experiments were conducted to determine the response of mosquitoes with different host preference to synthetic and natural odour blends from three vertebrate hosts, a human, a cow and a chicken. Screen house experiments were conducted to test whether specific skin bacteria or a mix of skin bacterial volatiles from the three vertebrate hosts mediate mosquito response. A review chapter in this thesis discusses how malaria parasites can manipulate human hosts to enhance their own transmission, by making the hosts more attractive to mosquitoes. Another experiment, using a dual-choice olfactometer, determined whether infection with malaria parasites increases human attractiveness to malaria mosquitoes, and whether the attractiveness of infected humans is Plasmodium falciparum-stage specific. Here, the same children participated in the study during infection with malaria parasites and after treatment with antimalarial drugs, artemisinin lumefantrine. Cage assays were further used to test mechanisms of attractiveness of P. falciparum-infected individuals using body odours or skin bacterial volatiles collected from the children at the two time points. Overall results show that skin bacterial volatiles play an important role in guiding mosquitoes with different host preferences to their specific host. For An. gambiae s.s., high (microscopic) densities of P. falciparum gametocytes (and not parasite-free, submicroscopic gametocytes or asexual stages of Plasmodium parasites) results into higher attractiveness of hosts, and body odours play a role in attractiveness of P. falciparum-infected humans. The results may help to develop more effective health policies and enable targeted interventions towards the most attractive hosts, which could contribute to reductions in malaria transmission. Identification of general or common attractive volatiles produced by the natural hosts as well as those from the gametocyte carriers may contribute to the development of an improved synthetic odour blend that may be used for sampling of mosquitoes with different host preferences. The use of powerful attractive odorants may result in reductions of vector-borne diseases transmitted by mosquitoes.

Design of trials for interrupting the transmission of endemic pathogens
Silkey, Mariabeth ; Homan, Tobias ; Maire, Nicolas ; Hiscox, Alexandra ; Mukabana, Richard ; Takken, Willem ; Smith, Thomas A. - \ 2016
Trials 17 (2016)1. - ISSN 1745-6215
Cluster randomization - Elimination - Stepped wedge design - Transmission model - Vector control

Background: Many interventions against infectious diseases have geographically diffuse effects. This leads to contamination between arms in cluster-randomized trials (CRTs). Pathogen elimination is the goal of many intervention programs against infectious agents, but contamination means that standard CRT designs and analyses do not provide inferences about the potential of interventions to interrupt pathogen transmission at maximum scale-up. Methods: A generic model of disease transmission was used to simulate infections in stepped wedge cluster-randomized trials (SWCRTs) of a transmission-reducing intervention, where the intervention has spatially diffuse effects. Simulations of such trials were then used to examine the potential of such designs for providing generalizable causal inferences about the impact of such interventions, including measurements of the contamination effects. The simulations were applied to the geography of Rusinga Island, Lake Victoria, Kenya, the site of the SolarMal trial on the use of odor-baited mosquito traps to eliminate Plasmodium falciparum malaria. These were used to compare variants in the proposed SWCRT designs for the SolarMal trial. Results: Measures of contamination effects were found that could be assessed in the simulated trials. Inspired by analyses of trials of insecticide-treated nets against malaria when applied to the geography of the SolarMal trial, these measures were found to be robust to different variants of SWCRT design. Analyses of the likely extent of contamination effects supported the choice of cluster size for the trial. Conclusions: The SWCRT is an appropriate design for trials that assess the feasibility of local elimination of a pathogen. The effects of incomplete coverage can be estimated by analyzing the extent of contamination between arms in such trials, and the estimates also support inferences about causality. The SolarMal example illustrates how generic transmission models incorporating spatial smoothing can be used to simulate such trials for a power calculation and optimization of cluster size and randomization strategies. The approach is applicable to a range of infectious diseases transmitted via environmental reservoirs or via arthropod vectors.

Spatial patterns of plasmodium falciparum clinical incidence, asymptomatic parasite carriage and anopheles density in two villages in Mali
Sissoko, M.S. ; Hoogen, L.L. Van Den; Samake, Yacouba ; Takken, Willem - \ 2015
American Journal of Tropical Medicine and Hygiene 93 (2015)4. - ISSN 0002-9637 - p. 790 - 797.

Heterogeneity in malaria exposure is most readily recognized in areas with low-transmission patterns. By comparison, little research has been done on spatial patterns in malaria exposure in high-endemic settings. We determined the spatial clustering of clinical malaria incidence, asymptomatic parasite carriage, and Anopheles density in two villages in Mali exposed to low- and mesoendemic-malaria transmission. In the two study areas that were <1 km2 in size, we observed evidence for spatial clustering of Anopheles densities or malaria parasite carriage during the dry season. Anopheles density and malaria prevalence appeared associated in some of our detected hotspots. However, many households with high parasite prevalence or high Anopheles densities were located outside the identified hotspots. Our findings indicate that within small villages exposed to low- or mesoendemic-malaria transmission, spatial patterns in mosquito densities and parasite carriage are best detected in the dry season. Considering the high prevalence of parasite carriage outside detected hotspots, the suitability of the area for targeting control efforts to households or areas of more intense malaria transmission may be limited.

Detection of Single-Nucleotide Polymorphisms in Plasmodium falciparum by PCR Primer Extension and Lateral Flow Immunoassay
Moers, A.P.H.A. ; Hallett, R.L. ; Borrow, R. ; Schallig, H.D.F.H. ; Sutherland, C.J. ; Amerongen, A. van - \ 2015
Antimicrobial Agents and Chemotherapy 59 (2015)1. - ISSN 0066-4804 - p. 365 - 371.
real-time pcr - carbon nanoparticles - malaria - dna - chloroquine - assay - amplification - sensitivity - resistance - travelers
The resistance of Plasmodium falciparum to some antimalarial drugs is linked to single-nucleotide polymorphisms (SNPs). Currently, there are no methods for the identification of resistant parasites that are sufficiently simple, cheap, and fast enough to be performed at point-of-care, i.e., in local hospitals where drugs are prescribed. Primer extension methods (PEXT) were developed to identify 4 SNPs in P. falciparum positioned at amino acids 86, 184, and 1246 of the P. falciparum multidrug resistance 1 gene (pfmdr1) and amino acid 76 of the chloroquine resistance transporter gene (pfcrt). The PEXT products were visualized by a nucleic acid lateral flow immunoassay (NALFIA) with carbon nanoparticles as the detection labels. PCR-PEXT-NALFIAs showed good correlation to the reference methods, quantitative PCR (qPCR) or direct amplicon sequence analysis, in an initial open-label evaluation with 17 field samples. The tests were further evaluated in a blind study design in a set of 150 patient isolates. High specificities of 98 to 100% were found for all 4 PCR-PEXT genotyping assays. The sensitivities ranged from 75% to 100% when all PEXT-positive tests were considered. A number of samples with a low parasite density were successfully characterized by the reference methods but failed to generate a result in the PCR-PEXT-NALFIA, particularly those samples with microscopy-negative subpatent infections. This proof-of principle study validates the use of PCR-PEXT-NALFIA for the detection of resistance-associated mutations in P. falciparum, particularly for microscopy-positive infections. Although it requires a standard thermal cycler, the procedure is cheap and rapid and thus a potentially valuable tool for point-of-care detection in developing countries
Optical properties, ethylene production and softening in mango fruits
Eccher Zerbini, P.C. ; Vanoli, M. ; Rizzolo, A. ; Grassi, M. ; Meirelles de Azevedo Pementel, A. ; Spinelli, L. ; Torricelli, A. - \ 2015
Postharvest Biology and Technology 101 (2015). - ISSN 0925-5214 - p. 58 - 65.
resolved reflectance spectroscopy - mangifera-indica l. - near-infrared spectroscopy - beta-carotene accumulation - kensington pride mango - long supply chains - harvest maturity - tomato fruit - postharvest behavior - biological variation
Firmness decay, chlorophyll breakdown and carotenoid accumulation, controlled by ethylene, are major ripening events in mango fruit. Pigment content and tissue structure affect the optical properties of the mesocarp, which can be measured nondestructively in the intact fruit by time-resolved reflectance spectroscopy (TRS). This work is aimed at improving the maturity assessment in mango (Mangifera indica L. cv Haden) from Brazil, using TRS absorption in both the carotenoid and chlorophyll regions in order to develop a model for fruit ripening. Scattering and absorption in the 540–900 nm spectral range by TRS, ethylene production and respiration rate, and firmness, were measured in one day on each individual fruit of a sample covering the range of maturity. The fruit displayed a variability which was attributed to the different biological age. Absorption spectra showed two peaks at 540 and 670 nm, corresponding respectively to the tail of carotenoid absorption and to chlorophyll-a absorption. Carotenoids increased substantially only in fruit where chlorophyll had almost disappeared. The absorptions at 540 and 670 nm, which described the maturity state of each fruit relative to the range of each wavelength, were combined in one index of biological age (biological shift factor) for each fruit and used in logistic models of ethylene increase and firmness decay respectively. The model explained about 80% of the variability in ethylene production rate. A similar result was obtained for firmness when scattering was added in the model. The combination of absorption at 540 and 670 nm measured by TRS in the intact fruit can be used to classify mango fruit according to maturity and to predict the ripening of individual fruit.
Plants of the annonaceae traditionally used as antimalarials: a review
Frausin, G. ; Lima, R.B.S. ; Hidalgo, A.D. ; Maas, P.J.M. ; Pohlit, A.M. - \ 2014
Revista Brasileira de Fruticultura 36 (2014)1. - ISSN 0100-2945 - p. 315 - 337.
medicinal-plants - antiplasmodial activity - dopaminergic-neurons - active constituents - remedies - malaria - cytotoxicity - alkaloids - efficacy - coast
Species of the Annonaceae family are used all over the tropics in traditional medicine in tropical regions for the treatment of malaria and other illnesses. Phytochemical studies of this family have revealed chemical components which could offer new alternatives for the treatment and control of malaria. Searches in scientific reference sites (SciFinder Scholar, Scielo, PubMed, ScienceDirect and ISI Web of Science) and a bibliographic literature search for species of Annonaceae used traditionally to treat malaria and fever were carried out. This family contains 2,100 species in 123 genera. We encountered 113 articles reporting medicinal use of one or more species of this family including 63 species in 27 genera with uses as antimalarials and febrifuges. Even though the same species of Annonaceae are used by diverse ethnic groups, different plant parts are often chosen for applications, and diverse methods of preparation and treatment are used. The ethanol extracts of Polyalthia debilis and Xylopia aromatica proved to be quite active against Plasmodium falciparum in vitro (median inhibition concentration, IC50 <1.5 mu g/mL). Intraperitoneal injection of Annickia chlorantha aqueous extracts (cited as Enantia chlorantha) cleared chloroquine-resistant Plasmodium yoelii nigeriensis from the blood of mice in a dose-dependant manner. More phytochemical profiles of Annonaceous species are required; especially information on the more commonly distributed antimalarial compounds in this family.
A sourcebook of methods and procedures for monitoring and reporting anthropogenic greenhouse gas emissions and removals associated with deforestation, gains and losses of carbon stocks in forests remaining forests, and forestation
Achard, F. ; Boschetti, L. ; Brown, S. ; Brady, M. ; DeFries, R. ; Grassi, G. ; Herold, M. ; Mollicone, D. ; Mora, B. ; Pandey, D. ; Souza, C. - \ 2014
Wageningen : GOFC-GOLD (GOFC-GOLD Report COP20-1) - 255
A sourcebook of methods and procedures for monitoring and reporting anthropogenic greenhouse gas emissions and removals associated with deforestation, gains and losses of carbon stocks in forests remaining forests, and forestation
Single Mutation in Shine-Dalgarno-Like Sequence Present in the Amino Terminal of Lactate Dehydrogenase of Plasmodium Effects the Production of an Eukaryotic Protein Expressed in a Prokaryotic System
Cicek, M. ; Mutlu, O. ; Erdemir, A. ; Ozkan, E. ; Saricay, Y. ; Turgut-Balik, D. - \ 2013
Molecular Biotechnology 54 (2013)2. - ISSN 1073-6085 - p. 602 - 608.
human malaria parasite - escherichia-coli - messenger-rna - recombinant proteins - bacillus-subtilis - ribosomal-rna - q-beta - falciparum - genome - gene
One of the most important step in structure-based drug design studies is obtaining the protein in active form after cloning the target gene. In one of our previous study, it was determined that an internal Shine-Dalgarno-like sequence present just before the third methionine at N-terminus of wild type lactate dehydrogenase enzyme of Plasmodium falciparum prevent the translation of full length protein. Inspection of the same region in P. vivax LDH, which was overproduced as an active enzyme, indicated that the codon preference in the same region was slightly different than the codon preference of wild type PfLDH. In this study, 5'-GGAGGC-3' sequence of P. vivax that codes for two glycine residues just before the third methionine was exchanged to 5'-GGAGGA-3', by mimicking P. falciparum LDH, to prove the possible effects of having an internal SD-like sequence when expressing an eukaryotic protein in a prokaryotic system. Exchange was made by site-directed mutagenesis. Results indicated that having two glycine residues with an internal SD-like sequence (GGAGGA) just before the third methionine abolishes the enzyme activity due to the preference of the prokaryotic system used for the expression. This study emphasizes the awareness of use of a prokaryotic system to overproduce an eukaryotic protein.
What causes the differences between national estimates of carbon emissions from forest management and large-scale models?
Groen, T.A. ; Verkerk, P.J. ; Böttcher, H. ; Grassi, G. ; Cienciala, E. ; Black, K.G. ; Fortin, M.J. ; Koethke, M. ; Lethonen, A. ; Nabuurs, G.J. ; Petrova, L. ; Blujdea, V. - \ 2013
Environmental Science & Policy 33 (2013). - ISSN 1462-9011 - p. 222 - 232.
biomass equations - norway spruce - scots pine - finland - birch
Under the United Nations Framework Convention for Climate Change all Parties have to report on carbon emissions and removals from the forestry sector. Each Party can use its own approach and country specific data for this. Independently, large-scale models exist (e.g. EFISCEN and G4M as used in this study) that assess emissions and removals from this sector by applying a unified approach to each country, still often based on country specific data. Differences exist between the national reported values and the calculations from the large scale models. This study compares these models with national reporting efforts for 24 EU countries for the period 2000–2008, and identifies the most likely causes for differences. There are no directly identifiable single input parameters that could be targeted to fully close the gap between country and model estimates. We found that the method applied by the country (i.e. stock-difference or gain-loss) contributes significantly to differences for EFISCEN and was the best explaining variable for G4M, although for the latter it was not significant. Other variables (biomass expansion factors, harvest volumes and the way harvest losses are treated) were not found to provide a conclusive explanation for the differences between the model estimations and the country submissions in an over-al analysis. However, at the level of individual countries several different causes for differences were identified. This suggests that to really close the gap between country submissions and large scale models, close collaboration between modellers and country experts is needed, calling for openness and willingness to share relevant data and to compare GHG inventories with independent estimates. This would enable to improve the confidence both in historical GHG inventories and in the models which are needed to project the future forest sink for several policy issues.
Haptoglobin phenotype prevalence and cytokine profiles during plasmodium falciparum infection in Dogon and Fulani ethnic groups living in Mali
Perdijk, O. ; Arama, C. ; Giusti, P. ; Maiga, B. ; Troye-Blomberg, M. ; Dolo, A. ; Doumbo, O. ; Persson, J.O. ; Bostrom, S. - \ 2013
Malaria Journal 12 (2013). - ISSN 1475-2875
hemoglobin scavenger receptor - severe malaria - soluble cd163 - west-africa - children - susceptibility - polymorphism - association - genotypes - ahaptoglobinemia
Background The Fulani are known to have a lower parasitaemia and less clinical episodes of malaria as compared to the Dogon sympatric ethnic group, living in Mali. Higher circulating malaria-specific antibody titers and increased pro-inflammatory cytokine levels have been shown in Fulani individuals. Several studies have tried to link haptoglobin (Hp) phenotypes with susceptibility to malaria, but without consensus. This study investigated the role of Hp phenotypes and cytokine levels in Dogon and Fulani during asymptomatic Plasmodium falciparum infection. Methods Two different cohorts were combined in this study: a 2008 cohort with 77 children aged between two and ten years and a 2001 cohort, with 82 children and adults, aged between 11 and 68 years. Hp phenotypes in plasma were measured by Western Blot. Circulating levels of sCD163, IL-6, IL-10, IFN-¿ and TNF were measured by ELISA. Multiple regression analysis was performed to associate Hp phenotypes with cytokine profiles. In addition, in vitro stimulation of peripheral blood mononuclear cells (PBMCs) with Hp:Hb complexes was performed and cytokine release in corresponding supernatants were measured using cytometric bead array. Results The results revealed a higher Hp2-2 phenotype prevalence in the Fulani. The Hp2-2 phenotype was associated with a higher susceptibility to P. falciparum infection in Dogon, but not in Fulani. In concordance with previous studies, Fulani showed increased inflammatory mediators (IL-6, IFN-¿) and additionally also increased sCD163 levels compared to Dogon, irrespective of infection. Furthermore, infected individuals showed elevated sCD163 levels compared to uninfected individuals, in both Fulani and Dogon. Multiple regression analysis revealed that the Hp1-1 phenotype was associated with higher levels of TNF and IFN-¿, as compared to the Hp2-2 phenotype. In vitro stimulation of PBMCs with Hb:Hp1-1 complexes resulted in a pro-inflammatory cytokine profile, whilst stimulation with Hb:Hp2-2 complexes showed a more balanced profile. Conclusions Ethnicity might be an important confounder on the Hp phenotype-dependent susceptibility to malaria and future studies could consider taking this into account when designing new immunological studies. Although, the relatively small sample size used in this study warrens for precautions in the interpretation of the data and these findings should ideally be validated in a bigger cohort.
First sign of carbon sink saturation in European forest biomass
Nabuurs, G.J. ; Lindner, M. ; Verkerk, P.J. ; Gunia, K. ; Deda, P. ; Michalak, R. ; Grassi, G. - \ 2013
Nature Climate Change 3 (2013). - ISSN 1758-678X - p. 792 - 796.
old-growth forests
European forests are seen as a clear example of vegetation rebound in the Northern Hemisphere; recovering in area and growing stock since the 1950s, after centuries of stock decline and deforestation. These regrowing forests have shown to be a persistent carbon sink, projected to continue for decades, however, there are early signs of saturation. Forest policies and management strategies need revision if we want to sustain the sink.
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