The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Wim Vyverman - One of the best experts on this subject based on the ideXlab platform.
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The pyrenoid ultrastructure in Oocystis lacustris.
Fottea, 2009Co-Authors: Maya P. Stoyneva, Elisabeth Ingolic, Georg Gärtner, Wim VyvermanAbstract:The fine structure of vegetative cells of Oocystis lacustris has been studied with special attention to the ultrastructure of the pyrenoid and its starch sheath. The TEM-investigation showed that the pyrenoid matrix is homogenous, not traversed by thylakoids and the surrounding starch sheath is continuous, horseshoe-shaped or fragmented in 2 starch plates. This starch sheath structure is regarded as a common feature within Oocystis and closely related genera Eremosphaera and Neglectella.
Maya P. Stoyneva - One of the best experts on this subject based on the ideXlab platform.
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The pyrenoid ultrastructure in Oocystis lacustris.
Fottea, 2009Co-Authors: Maya P. Stoyneva, Elisabeth Ingolic, Georg Gärtner, Wim VyvermanAbstract:The fine structure of vegetative cells of Oocystis lacustris has been studied with special attention to the ultrastructure of the pyrenoid and its starch sheath. The TEM-investigation showed that the pyrenoid matrix is homogenous, not traversed by thylakoids and the surrounding starch sheath is continuous, horseshoe-shaped or fragmented in 2 starch plates. This starch sheath structure is regarded as a common feature within Oocystis and closely related genera Eremosphaera and Neglectella.
Lucy J Robertson - One of the best experts on this subject based on the ideXlab platform.
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detection of cryptosporidium parvum oocysts in faeces comparison of conventional coproscopical methods and the polymerase chain reaction
Veterinary Parasitology, 1996Co-Authors: K A Webster, H V Smith, M Giles, L Dawson, Lucy J RobertsonAbstract:Abstract Conventional and coproscopical methods were compared with the polymerase chain reaction (PCR) for the detection of Cryptosporidium oocysts in bovine faeces. Oocysts were not detected in samples seeded with 10 000 oocysts following formol ether sedimentation and examination using auramine phenol (AP) or by immunofluorescent (IF) staining. When oocysts were concentrated using sucrose flotation the threshold of detection was 4000 oocysts per gram for both staining methods. Following salt flotation 4000 oocysts per gram could be reliably detected by AP staining but the detection limit was increased to 6000 oocysts per gram using IF staining. The recovery of oocysts was significantly less than expected for all techniques. A specific PCR coupled with immunomagnetic particle separation (IMS) of samples detected five oocysts per ml of diluted faeces, which corresponds to 80–90 oocysts per gram. Even allowing for the dilution of formed faecal samples, required for IMS, this represents an increase in sensitivity of several orders of magnitude over the conventional corpodiagnostic methods.
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application of dapi and immunofluorescence for enhanced identification of cryptosporidium spp oocysts in water samples
Water Research, 1994Co-Authors: A M Grimason, Zia Bukhari, H V Smith, A T Campbell, J F W Parker, Lucy J RobertsonAbstract:The usefulness of the nuclear fluorochrome 4′, 6-diamidino-2-phenylindole (DAPI) as an adjunct in the identification of Cryptosporidium spp oocysts by immunofluorescence has been studied. Because DAPI binds to the nuclei of sporozoites contained within oocysts it can be used to confirm the presence of sporulated oocysts by epifluorescence microscopy. This increased number of observable internal features enhances the ability to identify sporulated oocysts in water samples. This method should facilitate confirmation of putative Cryptosporidium spp oocysts detected in water and water-related samples, and reduce the likelihood of either false-positives or false-negative results occurring.
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novel methodology for the detection of cryptosporidium parvum a comparison of cooled charge couple devices ccd and flow cytometry
Water Science and Technology, 1993Co-Authors: A T Campbell, Lucy J Robertson, H V SmithAbstract:Flow cytometry and CCD were assessed for their usefialness in the detection of oocysts of Cryptosporidium . Oocysts were labelled with FITC-monoclonal antibody and with the nuclear stains 4’6-diamidino-2-phenyl indole (DAPI) and propidium iodide (PI) before analysis by flow cytometer and CCD. Although the flow cytometer tested was able to concentrate particles and place them on a slide for subsequent viewing, readily sorting oocysts from contaminating debris, confirmation by fluoresence microscopy was still essential, even when additional parameters such as the inclusion of DAPI is used. Initial observations from the use of CCD, however, suggested that screening samples for oocysts was a possibility. Three dimensional visualisation of individual oocysts can map precisiely both the detailed morphology and the exact size of oocysts, thereby making confirmation by fluoresence microscopy unneccesary.
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survival of cryptosporidium parvum oocysts under various environmental pressures
Applied and Environmental Microbiology, 1992Co-Authors: Lucy J Robertson, A T Campbell, H V SmithAbstract:The survival of various isolates of Cryptosporidium parvum oocysts under a range of environmental pressures including freezing, desiccation, and water treatment processes and in physical environments commonly associated with oocysts such as feces and various water types was monitored. Oocyst viability was assessed by in vitro excystation and by a viability assay based on the exclusion or inclusion of two fluorogenic vital dyes. Although desiccation was found to be lethal, a small proportion of oocysts were able to withstand exposure to temperatures as low as -22 degrees C. The water treatment processes investigated did not affect the survival of oocysts when pH was corrected. However, contact with lime, ferric sulfate, or alum had a significant impact on oocyst survival if the pH was not corrected. Oocysts demonstrated longevity in all water types investigated, including seawater, and when in contact with feces were considered to develop an enhanced impermeability to small molecules which might increase the robustness of the oocysts when exposed to environmental pressures.
Shulian Xie - One of the best experts on this subject based on the ideXlab platform.
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reticulocystis yunnanense gen et sp nov a new member of freshwater oocystaceae algae trebouxiophyceae chlorophyta
European Journal of Phycology, 2020Co-Authors: Xudong Liu, Qinghua Wang, Huan Zhu, Benwen Liu, Fabio Rindi, Guoxiang Liu, Shulian XieAbstract:Oocystis-like algae are diverse and found throughout the world. In this study, two new strains of algae with colonies resembling Oocystis were identified and successfully cultured in the laboratory...
J P Dubey - One of the best experts on this subject based on the ideXlab platform.
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survival and infectivity of toxoplasma gondii and cryptosporidium parvum oocysts bioaccumulated by dreissena polymorpha
Journal of Applied Microbiology, 2020Co-Authors: Elodie Geba, J P Dubey, Angélique Rousseau, Stéphanie La Carbona, Loïc Favennec, Sandie Escottebinet, Le A Guernic, Gilles Gargala, Isabelle Villena, Stephane BetoulleAbstract:AIMS The study was aimed to understand the depuration process of Cryptosporidium parvum and Toxoplasma gondii oocysts by zebra mussel (Dreissena polymorpha), to consider the use of the zebra mussel as a bioremediation tool. MATERIALS AND METHODS Two experiments were performed: (i) individual exposure of mussel to investigate oocyst transfers between bivalves and water and (ii) in vivo exposure to assess the ability of the zebra mussel to degrade oocysts. RESULTS (i) Our results highlighted a transfer of oocysts from the mussels to the water after 3 and 7 days of depuration; however, some oocysts were still bioaccumulated in mussel tissue. (ii) Between 7 days of exposure at 1000 or 10 000 oocysts/mussel/day and 7 days of depuration, the number of bioaccumulated oocysts did not vary but the number of infectious oocysts decreased. CONCLUSION Results show that D. polymorpha can release oocysts in water via (pseudo)faeces in depuration period. Oocysts remain bioaccumulated and infectious oocyst number decreases during the depuration period in zebra mussel tissues. Results suggest a degradation of bioaccumulated C. parvum and T. gondii oocysts. SIGNIFICANCE AND IMPACT OF THE STUDY This study highlighted the potential use of D. polymorpha as a bioremediation tool to mitigate of protozoan contamination in water resources.
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evaluation of propidium monoazide based qpcr to detect viable oocysts of toxoplasma gondii
Parasitology Research, 2019Co-Authors: J P Dubey, Aurélien Dumètre, Angélique Rousseau, Loïc Favennec, Sandie Escottebinet, Isabelle Villena, Dominique Aubert, Stéphanie La CarbonaAbstract:Information on the viability of Toxoplasma gondii oocysts is crucial to establish the public health significance of this environmental transmission stage that can contaminate water and foods. Interest for molecular-based methods to assess viability is growing and the aim of our study was to assess, for the first time, a propidium monoazide (PMA)-qPCR approach to determine the viability of T. gondii oocysts. Untreated and heat-killed (99 °C, 5 min) oocysts were incubated with PMA, a photoreactive DNA binding dye, and analyzed by confocal microscopy and flow cytometry to characterize oocysts' dye permeability. Different PMA concentrations (50 to 150 μM), incubation temperatures (22, 37, and 45 °C), amplicon length, selected targeted gene, and dyes (PMA, PMAxx™) were evaluated to define optimal conditions to discriminate specifically viable oocysts by PMA-qPCR. In theory, PMA binding to DNA would inhibit PCR amplification in dead but not in viable oocysts. Incubation at 22 °C with 100 μM PMA coupled to qPCR targeting a 123-bp sequence of the 529-bp repeat element allowed the distinction between viable and heated oocysts. However, the reduction of viability following heating of oocysts at high temperature was slight and, contrarily to reverse transcriptase-qPCR, the qPCR signal was not totally suppressed in heated suspensions. Therefore, PMA-qPCR is able to assess the impact of heating on T. gondii oocysts' viability but underestimates the efficacy of this treatment. The relevance of this technique to evaluate the efficacy of other inactivation processes and assess exposure of humans to this pathogen requires further investigations.
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simultaneous detection of the protozoan parasites toxoplasma cryptosporidium and giardia in food matrices and their persistence on basil leaves
Food Microbiology, 2016Co-Authors: Jeanne Hohweyer, J P Dubey, Aurélien Dumètre, Catherine Cazeaux, Emmanuelle Travaille, Emilie Languet, Dominique Aubert, Christine Terryn, Nadine Azas, Maryline HoussinAbstract:Toxoplasma gondii, Cryptosporidium spp. and Giardia intestinalis are emerging pathogen parasites in the food domain. However, without standardized methods for their detection in food matrices, parasitic foodborne outbreaks remain neglected. In this study, a new immunomagnetic separation assay (IMS Toxo) targeting the oocyst's wall of T. gondii was developed using a specific purified monoclonal antibody. Performance of this IMS Toxo coupled to microscopic and qPCR analyses was evaluated in terms of limit of detection (LOD) and recovery rate (RR) on: i) simple matrix (LOD = 5 oocysts; RR between 5 and 56%); ii) raspberries and basil (LOD = 33 oocysts/g; RR between 0.2 and 35%). Finally, to simultaneously extract the three protozoa from these food matrices, T. gondii oocysts were directly concentrated (without IMS Toxo) from the supernatant of the IMS of Cryptosporidium and Giardia (oo)cysts. This strategy associated to qPCR detection led to LOD <1 to 3 (oo)cysts/g and RR between 2 and 35%. This procedure was coupled to RT-qPCR analyses and showed that the three protozoa persisted on the leaves of basil and remained viable following storage at 4 °C for 8 days. These data strengthen the need to consider these protozoa in food safety.
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survival of toxoplasma gondii oocysts in eastern oysters crassostrea virginica
Journal of Parasitology, 2004Co-Authors: David S Lindsay, Marina V Collins, Sheila M Mitchell, Carly N Wetch, Alexa C Rosypal, George J Flick, Anne M Zajac, Alan Lindquist, J P DubeyAbstract:Toxoplasma gondiihas recently been recognized to be widely prevalent in the marine environment. It has previously been determined that Eastern oysters (Crassostrea virginica) can remove sporulated T. gondii oocysts from seawater and that oocysts retain their infectivity for mice. This study examined the long-term survival of T. gondii oocysts in oysters and examined how efficient oysters were at removing oocysts from seawater. Oysters in 76-L aquaria (15 oysters per aquarium) were exposed to 1 3 10 6 oocysts for 24 hr and examined at intervals up to 85 days postexposure (PE). Ninety percent (9 of 10) of these oysters were positive on day 1 PE using mouse bioassay. Tissue cysts were observed in 1 of 2 mice fed tissue from oysters exposed 21 days previously. Toxoplasma gondii antibodies were found in 2 of 3 mice fed oysters that had been exposed 85 days previously. In another study, groups of 10 oysters in 76-L aquaria were exposed to 1 3 10 5 ,5 3 104 ,o r 13 104 sporulated T. gondii oocysts for 24 hr and then processed for bioassay in mice. All oysters exposed to 1 3 10 5 oocysts were infected, and 60% of oysters exposed to 5 3 10 4 oocysts were positive when fed to mice. The studies with exposure to 1 3 104 oocysts were repeated twice, and 10 and 25% of oysters were positive when fed to mice. These studies indicate that T. gondii can survive for several months in oysters and that oysters can readily remove T. gondii oocysts from seawater. Infected filter feeders may serve as a source of T. gondii for marine mammals and possibly humans.
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sporulation and survival of toxoplasma gondii oocysts in seawater
Journal of Eukaryotic Microbiology, 2003Co-Authors: David S Lindsay, Marina V Collins, Sheila M Mitchell, Carly N Wetch, George J Flick, Alan Lindquist, Rebecca A Cole, J P DubeyAbstract:Abstract We have been collaborating since 1992 in studies on southern sea otters (Enhdyra lutris nereis) as part of a program to define factors, which may be responsible for limiting the growth of the southern sea otter population. We previously demonstrated Toxoplasma gondii in sea otters. We postulated that cat feces containing oocysts could be entering the marine environment through storm run-off or through municipal sewage since cat feces are often disposed down toilets by cat owners. The present study examined the sporulation of T. gondii oocysts in seawater and the survival of sporulated oocysts in seawater. Unsporulated oocysts were placed in 15 ppt artificial seawater, 32 ppt artificial seawater or 2% sulfuric acid (positive control) at 24 C in an incubator. Samples were examined daily for 3 days and development monitored by counting 100 oocysts from each sample. From 75 to 80% of the oocysts were sporulated by 3 days post-inoculation under all treatment conditions. Groups of 2 mice were fed 10,00...
