Tributylbenzylammonium (TBBA+)-dependent fusicoccin (FC)-induced H+ extrusion in maize roots: relationship between the stimulating effects of TBBA+ on H+ extrusion and on Cl- efflux

The mechanism of the stimulating effect of lipophilic cations on H⁺ extrusion in maize root segments (Zea mays L.) has been investigated. The measurement of the uptake of [³H]tributylbenzylammonium ([³H]TBBA⁺), the most active lipophilic cation on H⁺ extrusion, indicated that although a relevant fraction of TBBA⁺ taken up by the tissue is adsorbed to cell surfaces, a fraction of the cation enters the cells. However no correlation was observed between the rate of TBBA⁺ uptake and that of H⁺ extrusion. On the other hand, the lipophilic cations active on H⁺ extrusion (TBBA⁺ and dibenzyldimethylammonium (DDA⁺)), in the presence of fusicoccin (FC), induced under the same conditions an efflux of Cl^-, while tetramethylammonium (TMA⁺), inactive on H⁺ extrusion, did not. The stimulation of Cl^- efflux by TBBA⁺ was independent of the anion present in the medium and was inhibited by Na-orthovanadate, an inhibitor of plasma membrane ATPase and of TBBA⁺-induced H⁺ extrusion. These results suggest that the stimulation of H⁺ extrusion by TBBA⁺ depends on its effect on Cl^- efflux rather than on its penetration into the cells.Abbreviations DDA⁺ dibenzyldimethylammonium - FC fusicoccin - 3-O-MG 3-O-methyl glucose - PD transmembrane electric potential difference - TBBA⁺ tributylbenzylammonium - TCF tissue concentration factor - TMA⁺ tetramethylammonium - TPB^- tetraphenylboron     

Saccharomyces cerevisiae Rif1 cooperates with MRX-Sae2 in promoting DNA-end resection

Diverse roles in DNA metabolism have been envisaged for budding yeast and mammalian Rif1. In particular, yeast Rif1 is involved in telomere homeostasis, while its mammalian counterpart participates in the cellular response to DNA double-strand breaks (DSBs). Here, we show that Saccharomyces cerevisiae Rif1 supports cell survival to DNA lesions in the absence of MRX or Sae2. Furthermore, it contributes to the nucleolytic processing (resection) of DSBs. This Rif1-dependent control of DSB resection becomes important for DSB repair by homologous recombination when resection activities are suboptimal.     

JAK2 V617F Genotype Is a Strong Determinant of Blast Transformation in Primary Myelofibrosis

Purpose

The influence of JAK2 V617F mutation on blast transformation (BT) and overall survival (OS) in primary myelofibrosis (PMF) is controversial. In a large cohort of patients we applied competing risks analysis for studying the influence of JAK2V617F mutation on BT in PMF.

Patients and Methods

In 462 PMF–fibrotic type patients (bone marrow [BM] fibrosis grade >0) we computed the incidence of BT and death in the framework of Cox regression analysis and of Fine and Gray competing risks analysis for BT.

Results

At the Cox regression analysis, having either a wild-type (wt) or a homozygous JAK2V617F genotype were factors for BT (HR, 1.98 and 2.04, respectively, with respect to the heterozygous genotype), but not for OS. At the competing risks regression analysis, the risk for BT in wt and homozygous V617F patients increased with respect to Cox analysis, giving a sHR of 2.17 and 2.12, respectively. Correcting the results for the variables that could have influence on BT, JAK2V617F wt and homozygous genotypes remained independently associated with BT. In a validation cohort of 133 independent cases with PMF-prefibrotic type (BM fibrosis grade  = 0), the BT predictive model including JAK2V617F genotype and older age retained high discriminant capacity (C statistics, 0.70; 95% CI, 0.47 to 0.92).

Conclusion

The accumulation of mutated alleles in the JAK2V617F clone or the selective acquisition of a proliferative advantage in the wt clone are two relevant routes to BT in PMF. The influence of these results on treatment decisions with anti-JAK2 agents should be tested.     

Plasma 24S-hydroxycholesterol levels in elderly subjects with late onset Alzheimer's disease or vascular dementia: a case-control study

Background  

In central nervous system cholesterol cannot be degraded but is secreted into circulation predominantly in the form of its polar metabolite 24(S)-hydroxycholesterol (24S-OH-Chol). Some studies suggested an association between 24S-OH-Chol metabolism and different neurological diseases including dementia. A possible decrease in 24S-OH-Chol plasma levels has been reported late onset Alzheimer's disease (LOAD) and vascular dementia (VD), but results of previous studies are partially contradictory.     

Further studies on oxygen loading in blood from anemic patients

Functional parameters of the whole blood oxygen loading from 66 anemic subjects, compared with those from 66 normal adult of both sexes display the following behaviour: a) Adult males and females differ for p50 values, which are higher in females because of their lower Hb level. This difference is already well known and appears to be statistically significant. b) The same difference is amplified in anemic subjects, where also pH lowering contributes to the right-shift of p50. c) The inverse relationship between p50 and DPG values differs if analysed at the actual pHs, at pH corrected at 7.4, or extrapolated from Bohr effect. In fact, the three relative plots do not parallel, and their most significant intersects drop around 0.8-0.9 value of DPG, and 26-27 torr of p50, i.e. within normal limits.     

Evaluation of Bt-toxin uptake by the non-target herbivore, Myzus persicae (Hemiptera: Aphididae), feeding on transgenic oilseed rape

As consequence of the concern about the biosafety of genetically modified plants, biological and ecological studies are considered crucial for environmental risk assessment. Laboratory experiments were carried out in order to evaluate the transfer of the Cry1Ac Bt-toxin from a transgenic Bt-oilseed rape to a non-target pest, Myzus persicae Sulzer. Cry1Ac protein levels in plants and aphids were determined using a double sandwich enzyme-linked immunosorbent assay. Phloem sap from (Bt+) and (Bt-) oilseed rape plants was collected from leaves using a standard method of extraction in an EDTA buffer. Bt-toxin was present in phloem sap, with a mean concentration of 2.7 +/- 1.46 ppb, corresponding to a 24-fold lower level than in oilseed rape leaves. Toxin was also detected in aphid samples, with a mean concentration in the positive samples of 2.0 +/- 0.8 ppb. The evidence that Bt-toxin remains in herbivores, in this case an aphid, could be useful to clarify functional aspects linked to possible consequences of Bt-crops on food chains involving herbivore-natural enemy trophic systems. Further studies are needed in order to improve the knowledge on the functional aspects linked to the transfer of the Cry1Ac Bt-toxin from GM-oilseed rape to aphids and their possible consequence.     

Variability in nitrogen fixation of common bean (Phaseolus vulgaris L.) intercropped with maize

Thirty one selected bean lines were evaluated in the field for ability to support N₂ fixation when intercropped with maize which received 0, 30 and 60 kg N ha^–1 as ammonium sulphate. The amount of fixed N₂ was estimated using the natural variation of ¹⁵N and wheat as the standard non-fixing crop. Nitrogen as low as 15 kg N ha^–1 at sowing suppressed nodule weight and activity (acetylene reduction activity) but not nodule number, suggesting that the main effect of mineral N was on nodule development and function. ¹⁵N data revealed a high potential of the bean genotypes to fix N₂, with the most promising ones averaging between 50–60% of seed N coming from fixation. Bean lines CNF-480, Puebla-152, Mexico-309, Negro Argel, CNF-178, Venezuela-350 and WBR22-3, WBR22-50 and WBR22-55 were ranked as good fixers.     

Expression and gene rearrangement of the T-cell receptor in human thymomas

Human thymomas are epithelial neoplasms frequently associated with an exuberant lymphoid component. This mixture of epithelial cells and lymphocytes closely mimicks the organization of normal thymic cortex. However, it is not known whether thymocytes in thymoma express the T-cell receptor (TCR) for the antigen. We have analyzed the molecular configuration of TCR genes and their phenotypic expression in eight thymomas. In all we detected polyclonal rearrangements of TCR genes and cytoplasmic expression of TCR molecules in most thymocytes, thus indicating that rearranged TCR genes in thymomas are functioning genes. In addition, these findings suggest that the epithelial component of thymomas, even if neoplastic, is still capable of directing thymocyte differentiation.