Structural modification of bacterial cellulose fibrils under ultrasonic irradiation.

Ιn the present study we investigated ultrasounds as a pretreatment process for bacterial cellulose (BC) aqueous suspensions. BC suspensions (0.1-1% wt) subjected to an ultrasonic treatment for different time intervals. Untreated BC presented an extensively entangled fibril network. When a sonication time of 1min was applied BC fibrils appeared less bundled and dropped in width from 110nm to 60nm. For a longer treatment (3-5min) the width of the fibrils increased again to 100nm attributed to an entanglement of their structure. The water holding capacity (WHC) and ζ-potnential of the suspensions was proportional to the sonication time. Their viscosity and stability were also affected; an increase could be seen at short treatments, while a decrease was obvious at longer ones. Concluding, a long ultrasonic irradiation led to similar BC characteristics as the untreated, but a short treatment may be a pre-handling method for improving BC properties.

First Report of Olive mild mosaic virus and Sowbane mosaic virus in Spinach in Greece.

Uncommon, viruslike symptoms (yellowing, line patterns, leaf deformation, and necrosis), were observed in spinach fields in the Marathon area, Greece in 2004. Seedlings from the same seed lot, grown in the greenhouse, also developed the same viruslike symptoms, indicating that the causal agent(s) of the disorder is seed-transmissible. Spinach seedlings of the same variety but a different lot and herbaceous indicators (Chenopodium quinoa, C. amaranticolor, Sonchus oleraceus, and Nicotiana benthamiana) were mechanically inoculated with infected material. Spinach developed yellowing or necrotic spots whereas indicators showed variety of symptoms including mosaic, vein banding, and necrotic lesions. Virus purifications, double-stranded RNA extractions, cloning, and sequencing (2,3) followed by a combination of molecular (reverse transcription [RT]-PCR and immunocapture RT-PCR) and serological (ELISA) techniques with antisera provided by Dr. Avgelis were performed as described (4), verifying the presence of two viruses in the diseased seedlings: Sowbane mosaic virus (SoMV), a sobemovirus, was present in spinach and indicators with mottling and leaf deformation, whereas Olive mild mosaic virus (OMMV), a necrovirus, was present in plants with necrotic spots. All RT-PCR products amplified with primers SoMV-F (5'-CAAATGGTCTTGGTCAGCAGTC)/SoMV-R (5'-GCATACGCTCGACGATCTG) and OMMV-F (5'-CAAACCCAGCCTGTGTTCGATG)/OMMV-R (5'-CATCAGTTTGGTAATCCATTGA) were sequenced and found to confirm the other results. The SoMV-spinach isolate polyprotein gene sequence (GenBank Accession No. DQ450973) has 95% sequence identity with the type isolate from C. quinoa (GenBank Accession No. GQ845002), whereas the OMMV-spinach isolate (GenBank Accession No. JQ288895) has 92% sequence identity with the OMMV type isolate from olive (GenBank Accession No. AY616760). SoMV has been found to naturally infect spinach in the Netherlands (1) and, to our knowledge, this is the first report on spinach in Greece. The presence of OMMV in spinach is, to our knowledge, the first report worldwide. Its natural host range is limited to olive, tulip, and now spinach. OMMV might be transmitted by Olpidium spp. and may, according to data of its close relatives, persist in the soil for several decades. Pollen- and seedborne viruses (PSVs) like sobemoviruses and necroviruses are of particular importance for a crop like spinach where crop increase takes place in small, seed production-designated areas. If a PSV spreads in such an area it has the potential to become a major problem for the industry, especially when it remains undetected. Infected seed can be shipped worldwide with PSVs, causing diseases and becoming endemic in areas where they were absent. For this reason and the fact that field losses can exceed 50%, rigorous monitoring for the presence of SoMV and OMMV in seed fields is essential to minimize the possibility of the viruses moving to new areas. References: (1) L. Bos and N. Huijberts. Eur. J. Plant Pathol. 102:707, 1996. (2) S. M. Girgis et al., Eur. J. Plant Pathol. 125:203, 2009, (3) I. E. Tzanetakis et al. J. Virol. Methods 124:73, 2005. (4) I. E. Tzanetakis et al. Virus Res. 121:199, 2006.

Physiological and ultrastructural changes in "green islands" on Avena sterilis leaves caused by (8R,16R)-(-)-pyrenophorin.

The biochemical and ultrastructural changes in "green islands" (GIs) on detached Avena sterilis leaves caused by the macrodiolide (8R,16R)-(-)-pyrenophorin in the dark were examined. In the absence of light, leaf segments retained their photosynthetic pigments for 96 h after treatment with (8R,16R)-(-)-pyrenophorin (70 muM), whereas in the untreated leaves complete senescence, loss of photosynthetic pigments and cell disorganization were observed 72 h after detachment. Proteolytic enzyme activity in treated tissues with pyrenophorin remained at low levels for 96 h after treatment and protein dissipation was lower in the treated than in the untreated. Although tissues in "GIs" seem macroscopically healthy, electron microscopy observations revealed structurally disorganized cells filled with granular, electron-dense material. Chloroplasts were severely damaged and contained a large number of plastoglobuli. Similar ultrastructural changes were also observed in A. sterilis tissues treated with the phytotoxin under illumination, indicating a mechanism operating both under illumination and in the dark.

Study on the mechanism of Bioelectric Recognition Assay: evidence for immobilized cell membrane interactions with viral fragments.

The Bioelectric Recognition Assay (BERA) is a whole-cell based biosensing system that detects the electric response of cultured cells, suspended in a gel matrix, to various ligands, which bind to the cell and/or affect its physiology. Previous studies have demonstrated the potential application of this method for rapid, inexpensive detection of viruses in a crude sample. However, the understanding, so far, of the fundamental processes that take place during cell-virus interactions within the probe has been rather limited. In the present study, we combined electrophysiological and fluorescence microscopical assays, so that we can prove that animal and plant cells immobilized in BERA sensors respond to different viruses primarily by changing their membrane potential. The response of immobilized cells against different viruses did not depend on the virus ability to penetrate the cell, but was modified after binding each virus to a virus-specific antibody or removal of its coat protein after treatment with a protease. Consequently, we were able to assay the presence of a virus in its complete form or fragments thereof. Combination of immunological recognition with the electrophysiological response of immobilized cells allows for a considerable increase of the specificity of the BERA biosensory assay. In addition, rather than simply detect the presence of a protein or genomic sequence, the method can help gain information on the bioactivity of a virus.

Scanning electron microscopic observations of the development of the chicken caecum.

The surface pattern of the caeca of the chicken was examined using the scanning electron microscope (SEM) in stages ranging from 11th day of foetal development to 60 days of post-natal life. During incubation the proximal region (basis) of the caecum presented a few irregular elevations, which were later regarded as villi and after hatching, gradually, became longer and wider. These structures were found to be similar to those of the small intestine. The middle (corpus) and distal (apex) regions of caecum presented ridges/folds with short and blunt villi that were even shorter in the apex. The ridges/folds were running longitudinally the inner surface of the corpus while those of the apex were not so well developed.

Polyphenol deposition in leaf hairs of Olea europaea (Oleaceae) and Quercus ilex (Fagaceae).

The subcellular localization (cytoplasm, vacuoles, cell walls) of polyphenol compounds during the development of the multicellular nonglandular leaf hairs of Olea europaea (scales) and Quercus ilex (stellates), was investigated. Hairs of all developmental stages were treated with specific inducers of polyphenol fluorescence, and the bright yellow-green fluorescence of individual hairs was monitored with epifluorescence microscopy. During the early ontogenetic stages, bright fluorescence was emitted from the cytoplasm of the cells composing the multicellular shield of the scales of O. europaea. Transmission electron micrographs of the same stages showed that these cells possessed poor vacuolation and thin cell walls. The nucleus of these cells may be protected against ultraviolet-B radiation damage. The progressive vacuolation that occurred during maturation was followed by a shifting of the bright green-yellow fluorescence from the perinuclear region and the cytoplasm to the cell walls. The same trends were observed during the development of the nonglandular stellate hairs of Quercus ilex, in which maturation was also accompanied by a considerable secondary thickening of the cell walls. Despite the differences in morphology, high concentrations of polyphenol compounds are initially located mainly in the cytoplasm of the developing nonglandular hairs, and their deposition on the cell walls takes place during the secondary cell wall thickening. These structural changes during the development of the leaf hairs make them a very effective barrier against abiotic (uv-B radiation) and probably biotic (pathogenic) stresses.