Electronic Microscope Unit

Laboratory, South Africa

Electronic Microscope Unit

Laboratory, South Africa
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Candresse T.,French National Institute for Agricultural Research | Candresse T.,University of Bordeaux 1 | Filloux D.,CIRAD - Agricultural Research for Development | Muhire B.,University of Cape Town | And 11 more authors.
PLoS ONE | Year: 2014

Comprehensive inventories of plant viral diversity are essential for effective quarantine and sanitation efforts. The safety of regulated plant material exchanges presently relies heavily on techniques such as PCR or nucleic acid hybridisation, which are only suited to the detection and characterisation of specific, well characterised pathogens. Here, we demonstrate the utility of sequence-independent next generation sequencing (NGS) of both virus-derived small interfering RNAs (siRNAs) and virion-associated nucleic acids (VANA) for the detailed identification and characterisation of viruses infecting two quarantined sugarcane plants. Both plants originated from Egypt and were known to be infected with Sugarcane streak Egypt Virus (SSEV; Genus Mastrevirus, Family Geminiviridae), but were revealed by the NGS approaches to also be infected by a second highly divergent mastrevirus, here named Sugarcane white streak Virus (SWSV). This novel virus had escaped detection by all routine quarantine detection assays and was found to also be present in sugarcane plants originating from Sudan. Complete SWSV genomes were cloned and sequenced from six plants and all were found to share >91% genome-wide identity. With the exception of two SWSV variants, which potentially express unusually large RepA proteins, the SWSV isolates display genome characteristics very typical to those of all other previously described mastreviruses. An analysis of virus-derived siRNAs for SWSV and SSEV showed them to be strongly influenced by secondary structures within both genomic single stranded DNA and mRNA transcripts. In addition, the distribution of siRNA size frequencies indicates that these mastreviruses are likely subject to both transcriptional and post-transcriptional gene silencing. Our study stresses the potential advantages of NGS-based virus metagenomic screening in a plant quarantine setting and indicates that such techniques could dramatically reduce the numbers of non-intercepted virus pathogens passing through plant quarantine stations. © 2014 Candresse et al.

Rollinson H.,Earth and Environmental science | Adetunji J.,Earth and Environmental science | Souch G.,Electronic Microscope Unit | Greenwood M.,University of Derby
Mercian Geologist | Year: 2012

We report the results of a pilot study, carried out at the University of Derby during 2010 on the nature of the inorganic particulate matter in the air in west Derby. We have found three chemically distinct groups of particles. 1 : Sulphates, including Ca-sulphates (Gypsum), Na-sulphates and mixed grains in which sulphate has nucleated on a silicate host, which reflect a combination of anthropogenic and natural processes; the sulphate may be derived from industrial areas around the Bristol Channel or more locally from the A38 road adjacent to the sampling site. 2: Phosphate-silicate compounds that may be derived from fertilisers or from the local crematorium. 3: A variety of silicates, including quartz and feldspar, of natural origin but not necessarily of local provenance, and also an unusual anthropogenic iron-rich silicate. We conclude from a study of the measured compositions, grain shape and grain size that they are not harmful to human health. © 2012 East Midlands Geological Society.

Compton S.G.,University of Leeds | Ball A.D.,Electronic Microscope Unit | Collinson M.E.,Royal Holloway, University of London | Hayes P.,Natural History Museum in London | And 2 more authors.
Biology Letters | Year: 2010

Fig wasps and fig trees are mutually dependent, with each of the 800 or so species of fig trees (Ficus, Moraceae) typically pollinated by a single species of fig wasp (Hymenoptera: Agaonidae). Molecular evidence suggests that the relationship existed over 65 Ma, during the Cretaceous. Here, we record the discovery of the oldest known fossil fig wasps, from England, dated at 34 Ma. They possess pollen pockets that contain fossil Ficus pollen. The length of their ovipositors indicates that their host trees had a dioecious breeding system. Confocal microscopy and scanning electron microscopy reveal that the fossil female fig wasps, and more recent species from Miocene Dominican amber, display the same suite of anatomical characters associated with fig entry and pollen-carrying as modern species. The pollen is also typical of modern Ficus. No innovations in the relationship are discernible for the last tens of millions of years. © 2010 The Royal Society.

Abd El-Sadek M.S.,Anna University | Kumar J.R.,Anna University | Babu S.M.,Anna University | El-Hamidy M.S.,Electronic Microscope Unit
Journal of Alloys and Compounds | Year: 2010

Multi-functional CdTe@Mn(OH)2 core-shell nanoparticles were synthesized in aqueous solution by a seed-mediated growth approach. Initially, CdTe nanocrystals were synthesized with bi-functional molecule mercaptoacetic acid as a stabilizer. The Mn2+ in the form of MnCl2 was added to CdTe nanocrystals in aqueous solution and slowly hydrolyzed to deposit a layer of hydroxide (Mn(OH)2) onto the luminescent CdTe nanocrystals as a core in the presence of stabilizer at pH ≈ 11.2. The effect of refluxing time and the concentration of Mn2+ on the optical properties of these samples were evaluated using UV-vis absorption and photoluminescence analysis. The emission peak of the (CdTe@Mn(OH)2) composite nanoparticles shifted to 640 nm from 605 nm (CdTe seed). The sizes of CdTe and CdTe@Mn(OH)2 composite nanoparticles averaged about 3.22 nm and 7.94 nm respectively. © 2010 Elsevier B.V. All rights reserved.

Robin L.,Design Science | Laws K.J.,Design Science | Xu W.,Design Science | Kurniawan G.,Design Science | And 3 more authors.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2010

The three-dimensional morphology of crystalline plates that form in as-cast Mg65+x (Cu0.667Y0.333)30 x Zn 5(x = 6, 12, 14, and 16) bulk metallic glass (BMG) composites was investigated by focused ion beam (FIB) tomography. The size, shape, and distribution of the plates were found to be dependent both on alloy composition and cooling rate of the melt, whereby rapid cooling and lower x values generated a lower volume fraction of plates due to a decreased propensity for crystallization. Using FIB tomography, it was demonstrated that these plates may nucleate at micron-sized cuboidal, spherical, and irregularly shaped particles that form first during the casting process. The plates subsequently grow in preferential directions during cooling of the alloy to below the glass transition temperature to ultimately generate a multivariant, interwoven crystalline structure throughout the amorphous matrix. This complex structure is argued to contribute to the improved toughness of the alloy by hindering the propagation of gross shear bands and promoting the formation of multiple shear bands. © The Minerals, Metals & Materials Society and ASM International 2009.

PubMed | Electronic Microscope Unit
Type: Journal Article | Journal: Planta | Year: 2014

Studies on the fine structural changes accompanying xylem differentiation in wheat coleoptile have indicated that the microtubules are concerned with the inception of a regular wall thickening pattern, and later with wall deposition at the thickening site. The endoplasmic reticulum is situated characteristically in continuous profiles between the thickenings. Radioautographic studies at the electron microscope level using labelled glucoses have shown that the endoplasmic reticulum, golgi bodies and the cytoplasm near the microtubules were often labelled during deposition into nearby thickenings of radioactive materials derived from the tritiated glucoses. Incorporation into the wall occurred mainly at the top of the thickenings. The plastids of the xylem cells were also often labelled, but only during the earlier stages of differentiation; when massive wall deposition was evident, such an incorporation was never observed. The fine structural and radioautographic results are briefly discussed in terms of the possible functions of the organelles in the plant cell.

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