Involvement of lignin and hormones in the response of woody poplar taproots to mechanical stress

Mechanical stress is a widespread condition caused by numerous environmental factors that severely affect plant stability. In response to mechanical stress, plants have evolved complex response pathways able to detect mechanical perturbations and inducing a suite of modifications in order to improve anchorage. The response of woody roots to mechanical stresses has been studied mainly at the morphological and biomechanical level, whereas investigations on the factors triggering these important alterations are still at the initial stage. Populus has been widely used to study the response of stem to different mechanical stresses and, since it has the first forest tree genome to be decoded, represents a model woody plant for addressing questions on the mechanisms controlling adaptation of woody roots to changing environments. In this study, a morphological and physiological analysis was used to investigate factors controlling modifications in Populus nigra woody taproots subjected to mechanical stress. An experimental model analyzing spatial and temporal mechanical force distribution along the woody taproot axis enabled us to compare the events occurring in its above-, central- and below-bending sectors. Different morphogenetic responses and local variations of lignin and plant hormones content have been observed, and a relation with the distribution of the mechanical forces along the stressed woody taproots is hypothesized. We investigated the differences of the response to mechanical stress induction during the time; in this regard, we present data referring to the effect of mechanical stress on plant transition from its condition of winter dormancy to that of full vegetative activity.     

Oral Bisphosphonates and Risk of Atrial Fibrillation and Flutter in Women: A Self-Controlled Case-Series Safety Analysis

Background

A recent trial unexpectedly reported that atrial fibrillation, when defined as serious, occurred more often in participants randomized to an annual infusion of the relatively new parenteral bisphosphonate, zoledronic acid, than among those given placebo, but had limited power. Two subsequent population-based case-control studies of patients receiving a more established oral bisphosphonate, alendronic acid, reported conflicting results, possibly due to uncontrolled confounding factors.

Methodology/Principal Findings

We used the United Kingdom General Practice Research Database to assess the risk of atrial fibrillation and flutter in women exposed to the oral bisphosphonates, alendronic acid and risedronate sodium. The self-controlled case-series method was used to minimise the potential for confounding. The age-adjusted incidence rate ratio for atrial fibrillation or flutter in individuals during their exposure to these oral bisphosphonates (n = 2195) was 1.07 (95% CI 0.94–1.21). The age-adjusted incidence rate ratio for alendronic acid (n = 1489) and risedronate sodium (n = 649) exposed individuals were 1.09 (95% CI 0.93–1.26) and 0.99 (95% CI 0.78–1.26) respectively. In post-hoc analyses, an increased risk of incident atrial fibrillation or flutter was detected for patients during their first few months of alendronic acid therapy.

Conclusions/Significance

We found no robust evidence of an overall long-term increased risk of atrial fibrillation or flutter associated with continued exposure to the oral bisphosphonates, alendronic acid and risedronate sodium. A possible signal for an increase in risk during the first few months of therapy with alendronic acid needs to be re-assessed in additional studies.     

Trypanosoma cruzi: Biological characterization of a isolate from an endemic area and its susceptibility to conventional drugs

We describe some biological and molecular characteristics of a Trypanosoma cruzi isolate derived from a Triatomine captured in Nicaragua. PCR based typification showed that this isolate, named Nicaragua, belonged to the lineage Tc I. Nicaragua infected culture cells were treated with allopurinol, showing different behavior according to the cellular compartment, being cardiomyocyte primary cultures more resistant to this drug. The course of the infection in a mice experimental model and its susceptibility to benznidazole and allopurinol was analyzed. In benznidazole treatment, mice reverted the high lethal effect of parasites during the acute infection, however, a few parasites were detected in the heart of 88% of mice 1 year post-infection. Since T. cruzi is a heterogeneous species population it is important to study and characterize different parasites actually circulating in humans in endemic areas. In this work we show that T. cruzi Nicaragua isolate, is sensitive to early benznidazole treatment.     

Possibility of limiting the un-justified irradiation in 131I therapy of Graves' disease: A thyroid mass-reduction based method for the optimum activity calculation

ObjectiveIn Graves' disease therapy, the amount of ¹³¹I is usually decided following two different modalities: the administration of a fixed activity or of an activity individually calculated based on a fixed value of target absorbed dose. Although the effectiveness of each of these approaches is good (about 80% of patients cured), the ALARA principle must be applied avoiding the un-justified radioactivity to the patient himself, the people living/working near him and the environment. In this paper a new approach to the ¹³¹I therapy in Graves' disease, based on the optimum value of the final thyroid mass, is presented.Design97 Graves' disease patients (29 males) were randomly assigned into three groups (GR1, GR2, GR3). In two of them (GR1, GR3) the radioiodine administering activity was calculated based on two fixed thyroid absorbed dose values (100 Gy for GR1; 400 Gy for GR3), in GR2 it was calculated based on the desired final optimum thyroid mass value m_f = 0.24 m₀/U₀ResultsThe rate of cured patients are 48% (GR1), 97% (GR2) (z-test, p < 0.001) and 97% (GR3). The average activity administered to GR2 (393 ± 157 MBq) is lower than that administrered to GR3 patients (524 ± 201 MBq) (p = 0.007, two-tails unpaired t-test); the thyroid absorbed dose in GR2 (262 ± 78 Gy) is lower than in GR3 patients (407 ± 23 Gy) (p < 0.001, two-tails unpaired t-test).ConclusionOur results demonstrate that the thyroid-mass based approach optimizes the treatment avoiding an un-justified excess or a not-effective too low activity without time and resources consuming.     

Water relations in grassland and desert ecosystems exposed to elevated atmospheric CO2

Atmospheric CO₂ enrichment may stimulate plant growth directly through (1) enhanced photosynthesis or indirectly, through (2) reduced plant water consumption and hence slower soil moisture depletion, or the combination of both. Herein we describe gas exchange, plant biomass and species responses of five native or semi-native temperate and Mediterranean grasslands and three semi-arid systems to CO₂ enrichment, with an emphasis on water relations. Increasing CO₂ led to decreased leaf conductance for water vapor, improved plant water status, altered seasonal evapotranspiration dynamics, and in most cases, periodic increases in soil water content. The extent, timing and duration of these responses varied among ecosystems, species and years. Across the grasslands of the Kansas tallgrass prairie, Colorado shortgrass steppe and Swiss calcareous grassland, increases in aboveground biomass from CO₂ enrichment were relatively greater in dry years. In contrast, CO₂-induced aboveground biomass increases in the Texas C₃/C₄ grassland and the New Zealand pasture seemed little or only marginally influenced by yearly variation in soil water, while plant growth in the Mojave Desert was stimulated by CO₂ in a relatively wet year. Mediterranean grasslands sometimes failed to respond to CO₂-related increased late-season water, whereas semiarid Negev grassland assemblages profited. Vegetative and reproductive responses to CO₂ were highly varied among species and ecosystems, and did not generally follow any predictable pattern in regard to functional groups. Results suggest that the indirect effects of CO₂ on plant and soil water relations may contribute substantially to experimentally induced CO₂-effects, and also reflect local humidity conditions. For landscape scale predictions, this analysis calls for a clear distinction between biomass responses due to direct CO₂ effects on photosynthesis and those indirect CO₂ effects via soil moisture as documented here.     

Effects of anions and/or cell volume on the permeance of an apical water pathway induced by Hg in toad skin epithelium

Hg compounds block membrane transport units behaving as water channels. Here we show that Hg induces an apical water pathway in toad skins pretreated with 10^–3 M CH₃ClHg or HgCl₂, added to the outer bathing medium. Washing with SO₄-Ringer caused a several-fold increase in net water flow (J _w ) and osmotic permeability coefficient (P _f ) that was reversed by re-exposure to Cl- or NO₃-Ringer and mimicked by gluconate-Ringer. These P _f changes could be elicited repeatedly and were present if, and only if, anion replacements took place in the inner bathing solution. Such inner polarity was related to the anion permeability of the epidermal basolateral membrane: impermeant anions (SO₄, gluconate) increased P _f ; permeant anions (Cl, NO₃) did not change basal P _f but reversed the high P _f induced by impermeant anions. Hg induced the appearance of aggregates that persisted despite repeated washings of the skins during 4–5 h, and whether P _f was high (SO₄-Ringer) or low (Cl-Ringer) before skin fixation.The Hg-induced apical water pathway in toad skin appears to be a unique model for studying the interplay between cell volume, cell ionic composition and water permeability.We thank P. Brawand and P. Fruleux for technical assistance. This work has been supported by grants from the Swiss National Science Foundation (Nos. 31-30030.90 to A.G. and R.C.dS., and 32-34090.92 to P.M.)     

Immunohistochemical expression of HGF, c-MET and transcription factor STAT3 in colorectal tumors

By immunohistochemistry, we have investigated the expression of hepatocyte growth factor (HGF), HGF-R or c-met and the transcritor factor STAT3 in a series of 80 colorectal tumours (40 adenomas and 40 adenocarcinomas). The expression of HGF, c-met and STAT3 was revealed in 40/40 (100%) of adenomas and in 26/40 (65%) of adenocarcinomas; the remaining 14/40 (35%) carcinomas expressed c-met but failed to express HGF and STAT3. Positive immunoreaction score was defined through the number of stained cells: low (1-10%), moderate (11-50%) and high (>51%). In adenomas, the HGF immunoreaction was high in 33 (82.5%) and moderate in 7 (17.5%); the c-met staining was high in 3 (7.5%) and moderate in 37 (92.5%); and the STAT3 reactivity was high in 25 (62.5%) and moderate in 15(37.5%). In carcinomas, the HGF immunoreaction was moderate in 21 (80.7%) and low in 5 (19.2%); the c-met staining was high in 14 (35%), moderate in 25 (62.5) and low in 1 (2.5%); and the STAT3 reactivity was moderate in 17 (65.3%) and low in 9 (34.6%). In both type of lesions, HGF and c-met showed a membranous and cytoplasmic location. In adenomas, STAT3 was detected in cytoplasm and nucleus and in carcinomas it was limited to cytoplasm. While the HGF/c-met/STAT3 expression in adenomas was significantly different from carcinomas (c2 = 17, p < 0.0001), no correlation was found among HGF, c-met, or STAT3 immunostaining with histotype or degree of dysplasia in adenomas and the same for histotype, grading or staging in carcinomas. These features, suggesting a role of the HGF/c-met/STAT3 signal in colon tumorigenesis, indicate that a reduced expression of HGF and c-met is associated to progression of adenoma into carcinoma.