Tiller hierarchy and defoliation frequency determine bud viability in the grass <Emphasis Type="Italic">Poa ligularis</Emphasis>

Bud viability after various defoliation frequency treatments was determined in the perennial bunchgrass Poa ligularis under arid field conditions from 2002 to 2005. Bud respiratory activity was examined on various stem base hierarchies using the tetrazolium test, as validated with the vital stain Evan’s blue. The hypothesis of this work was that the total and viable axillary bud numbers on stem bases of all study stem base hierarchies are reduced as defoliation frequency increases. Interpretation of the results differed when they were expressed as a percentage rather than on a number per stem base basis. The total number of axillary buds per stem base was similar in all defoliation frequencies. When the results were expressed on a percentage basis, the order on stem bases having metabolically active buds was daughter tillers > stem bases with green tillers > stem bases without green tillers in all defoliation frequencies. The reverse order was found when considering dead buds. How the results are expressed thus deserves our attention when reporting results on bud viability in perennial grasses. An increased defoliation frequency increased the percentage of dead and dormant buds after the third or fourth defoliation of P. ligularis during the 1st study year. These percentages of bud viability, however, increased after the first defoliation during the 2nd study year. Bud viability was affected not only by the cumulative effects of defoliation but also by climatic variables throughout the seasons. However, our results show that P. ligularis can be defoliated up to twice a year without affecting bud viability, and thus its potential capacity for regrowth after defoliation.     

Structure of vegetation patches in northwestern Patagonia, Argentina

Vegetation of arid and semiarid environments has in general a patchy distribution. Our objective was to (a) determine several qualitative and quantitative analytical characteristics of vegetation patches in an arid zone of Patagonia, Argentina, and (b) investigate relationships between them. Annual precipitation in this area was 200 mm during 1999–2005. Eight transects involving ten patches each were studied within a 15 × 15 km area. Mean (±1 SE) values (n = 80) in the vegetation patches were 315 ± 25 and 207 ± 16 cm for the greatest and lowest patch diameter, respectively; 23 ± 2 cm for mound height; 113 ± 12 cm for maximum vegetation height; and 170 ± 18 cm and 58 ± 2% for distance to the next vegetation patch and vegetation patch cover within a transect, respectively. Correlations between greatest and lowest diameters, mound height, maximum plant height and distance to the closest vegetation patch were all significant (P < 0.01; n = 80). In all vegetation patches, the greatest and lowest frequencies were found for the grass Stipa spp. (71.2%) and the shrub Grindelia chiloensis (Cornel.) Cabrera (12.5%). Stipa spp. and the shrub Atriplex lampa (Moq.) D. Dietr. showed the highest simultaneous frequency (50%). A reasonable association among species (>45%) was found for Stipa spp., Atriplex lampa and the shrubs Larrea divaricata Cav., Lycium chilense Miers ex Bertero and Junellia ligustrina (Lag.) Moldenke. Larrea divaricata and Atriplex lampa contributed more than 84% of the total patch standing crop (5,777 ± 435 g). Average patch size and specific diversity were 5.93 ± 0.33 m² and 1.31 ± 0.11, respectively. Aboveground standing crop of the two dominant shrubs decreased as plant species diversity increased (P < 0.05). Conservation of vegetation patches is crucial to prevent increased soil erosion and desertification in the study ecological system.     

Studies on the participation of epididymal sperm protein DE/CRISP-1 in egg activation.

Protein DE (32 kDa) associates with sperm during epididymal maturation and participates in sperm-egg fusion through its binding to complementary sites on the egg surface. In the present work we investigated the participation of DE in two mechanisms probably involved in egg activation: the ability of DE to trigger activation by its interaction with the binding sites on the egg surface (receptor model) and its ability to regulate intracellular calcium channels (sperm factor model). The incubation of eggs with DE did not promote activation parameters such as calcium oscillations or meiosis resumption. Secondly, microinjection of DE into eggs was ineffective in either eliciting calcium release or modifying oscillations induced by an activating sperm extract. Together, these results argue against the participation of DE in egg activation, restricting the activity of this protein and its egg binding sites to the sperm-egg fusion process.     

Cell Budding from Normal Appearing Epithelia: A Predictor of Colorectal Cancer Metastasis?

Background: Colorectal carcinogenesis is believed to be a multi-stage process that originates with a localized adenoma, which linearly progresses to an intra-mucosal carcinoma, to an invasive lesion, and finally to metastatic cancer. This progression model is supported by tissue culture and animal model studies, but it is difficult to reconcile with several well-established observations, principally among these are that up to 25% of early stage (Stage I/II), node-negative colorectal cancer (CRC) develop distant metastasis, and that circulating CRC cells are undetectable in peripheral blood samples of up to 50% of patients with confirmed metastasis, but more than 30% of patients with no detectable metastasis exhibit such cells. The mechanism responsible for this diverse behavior is unknown, and there are no effective means to identify patients with pending, or who are at high risk for, developing metastatic CRC.Novel findings: Our previous studies of human breast and prostate cancer have shown that cancer invasion arises from the convergence of a tissue injury, the innate immune response to that injury, and the presence of tumor stem cells within tumor capsules at the site of the injury. Focal degeneration of a capsule due to age or disease attracts lymphocyte infiltration that degrades the degenerating capsules resulting in the formation of a focal disruption in the capsule, which selectively favors proliferating or “budding” of the underlying tumor stem cells. Our recent studies suggest that lymphocyte infiltration also triggers metastasis by disrupting the intercellular junctions and surface adhesion molecules within the proliferating cell buds causing their dissociation. Then, lymphocytes and tumor cells are conjoined through membrane fusion to form tumor-lymphocyte chimeras (TLCs) that allows the tumor stem cell to avail itself of the lymphocyte''s natural ability to migrate and breach cell barriers in order to intravasate and to travel to distant organs. Our most recent studies of human CRC have detected nearly identical focal capsule disruptions, lymphocyte infiltration, budding cells, and the formation of TLCs. Our studies have further shown that age- and type-matched node-positive and -negative CRC have a significantly different morphological and immunohistochemical profile and that the majority of lymphatic ducts with disseminated cells are located within the mucosa adjacent to morphologically normal appearing epithelial structures that express a stem cell-related marker.New hypothesis: Based on these findings and the growth patterns of budding cells revealed by double immunohistochemistry, we further hypothesize that metastatic spread is an early event of carcinogenesis and that budding cells overlying focal capsule disruptions represent invasion- and metastasis-initiating cells that follow one of four pathways to progress: (1) to undergo extensive in situ proliferation leading to the formation of tumor nests that subsequently invade the submucosa, (2) to migrate with associated lymphocytes functioning as “seeds” to grow in new sites, (3) to migrate and intravasate into pre-existing vascular structures by forming TLCs, or (4) to intravasate into vascular structures that are generated by the budding cells themselves. We also propose that only node-positive cases harbor stem cells with the potential for multi-lineage differentiation and unique surface markers that permit intravasation.     

Intense photon emission induced by fracture of γ–irradiated Dy‐, Tm‐, Sm‐ and Mn‐doped CaSO4 single crystals

When an γ‐irradiated Dy‐, Tm‐, Sm‐ or Mn‐doped CaSO₄ crystal is impulsively deformed, two peaks appear in the ML intensity versus time curve, whereby the first ML peak is found in the deformation region and the second in the post‐deformation region of the crystals. In this study, intensities I_m1 and I_m2 corresponding to first and second ML peaks, respectively, increased linearly with an impact velocity v₀ of the piston used to deform the crystals, and times t_m1 and t_m2 corresponding to the first and second ML peaks, respectively, decreased with impact velocity. Total ML intensity initially increased with impact velocity and then reached a saturation value for higher values of impact velocity. ML intensity increased with increasing γ‐doses and size of crystals. Results showed that the electric field produced as a result of charging of newly‐created surfaces caused tunneling of electrons to the valence band of the hole‐trapping centres. The free holes generated moved in the valence band and their subsequent recombination with electron trapping centres released energy, thereby resulting in excitation of luminescent centres. Copyright © 2012 John Wiley & Sons, Ltd.     

Genetic and molecular characterization of pathogenic isolates of Pyricularia grisea from wheat (Triticum aestivum Lam.) and triticale (x Triticosecale Wittmack) in the state of Paraná, Brazil

Isolates of Pyricularia grisea from wheat (Triticum aestivum Lam.) and triticale (x Triticosecale Wittmack) spikes with blast symptoms were analyzed by classical (VCG) and molecular (RAPD) techniques. P. grisea mutants, unable to use sodium nitrate (nit) as nitrogen source, were obtained with potassium chlorate. For vegetative compatibility (VCG) tests, genetically complementary nit mutant pairs were inoculated in a medium with sodium nitrate as a single nitrogen source. P. grisea isolates were divided into two vegetative compatibility groups and two RAPD groups. Since vegetative compatible strains may mutually exchange genetic and cytoplasmatic material, the contribution of the parasexual cycle in the genetic variability of Brazilian P. grisea isolates is discussed.