Seed dynamics of an endemic palm in a Northwestern Mexican tropical dry forest: implications for population spatial structure

Seed dynamics are an important part of the life history of plants and may have strong implications on abundance and spatial distribution of populations. In this study, we explored how seed dynamics (removal, predation, germination) interact with micro-environmental conditions to affect the spatial structure of populations of Brahea aculeata (Arecaceae) in a tropical dry forest. B. aculeata is distributed throughout arroyo basins and attains its highest densities near to arroyos/rivers. We hypothesized that: (i) seed removal, predation and germination vary across topographic positions resulting in greater palm abundances adjacent to arroyos and (ii) seed removers/predators respond to both a seed density-dependent effect and a microclimate effect. To test this, in six arroyos basins, seeds were sown across three topographic positions (stream, mid and top of basins) with two seed abundances (1 and 10), protected and non-protected from potential predators. Predation, removal and germination were then followed. After 107 days, 100 % of the exposed seeds were removed/predated and none germinated. For seed removal, we found differences among topographic positions and seed densities with higher removal (up to 80 %) and lower predation rates for grouped seeds. Germination was only observed for protected seeds with higher germination rates in single (17 % ± 9) than in grouped seeds (4 % ± 1). The highest germination and establishment rates were adjacent to the streams; areas which had the lowest light intensity (mean ± SE = 883 ± 160 lm/ft²) and temperatures (mean ± SE = 20.1 ± 0.6 °C), and highest humidity (mean ± SE = 50.8 ± 1.8 %), especially during the rainy season. Differential seedling establishment rates across the landscape due to spatial patterns of seed predation/removal as well as micro-environmental variables appear to have implications for shaping the spatial structure of B. aculeata population at Sierra de Álamos, Mexico.     

Biochemical and physiological changes produced by Azotobacter chroococcum (INIFAT5 strain) on pineapple in vitro-plantlets during acclimatization

This study highlights some of the effects of the application of Azotobacter chroococcum (INIFAT5 strain) on in vitro-pineapple plantlets during acclimatization. The bacteria were sprayed immediately after transplanting to the ex vitro environment; the plants were then sprayed every 4 week. Subsequently (4 months) the evaluated variables included plantlet fresh and dry weights, leaf and root lengths, and composition of minerals, amino-acids, carbohydrates and proteins. Photosynthesis indicators were also evaluated. Significant effects of the application of Azotobacter over pineapple plantlets during acclimatization were observed in the mineral, amino-acid, carbohydrate and protein levels, as well as, in the photosynthesis indicators. Contrastingly, plant growth parameters showed modest increases caused by the bacteria, although they were statistically significant. Looking into specific minerals, the following significant effects of Azotobacter should be highlighted: increased levels of nitrogen, phosphorous, potassium, magnesium, copper and zinc. Moreover, contents of all amino-acids recorded showed significant increases in their levels in sprayed plantlets. Carbohydrates were also increased in leaves of plantlets bio-fertilized with the bacteria, mainly sucrose and fructose. Chlorophyll b levels were also significantly increased by Azotobacter. The biofertilizer did not modify levels of calcium, iron or manganese.     

Neurocognitive Impairment in Patients Treated with Protease Inhibitor Monotherapy or Triple Drug Antiretroviral Therapy

Background

In patients who remain virologically suppressed in plasma with triple-drug ART a switch to protease inhibitor monotherapy maintains high rates of suppression; however it is unknown if protease inhibitor monotherapy is associated to a higher rate of neurocognitive impairment.

Methods

In this observational, cross-sectional study we included patients with plasma virological suppression (≥1 year) without concomitant major neurocognitive confounders, currently receiving for ≥1 year boosted lopinavir or darunavir as monotherapy or as triple ART. Neurocognitive impairment was defined as per the 2007 consensus of the American Association of Neurology. The association between neurocognitive impairment and protease inhibitor monotherapy, adjusted by significant confounders, was analysed.

Results

Of the 191 included patients - triple therapy: 96, 1–2 years of monotherapy: 40 and >2 years of monotherapy: 55 - proportions (95% CI) with neurocognitive impairment were: overall, 27.2% (20.9–33.6); triple therapy, 31.6% (22.1–41.0); short-term monotherapy, 25.0% (11.3–38.7); long-term monotherapy: 21.4% (10.5–32.3); p = 0.38. In all groups, neurocognitive impairment was mildly symptomatic or asymptomatic by self-report. There were not significant differences in Global Deficit Score by group. In the regression model confounding variables for neurocognitive impairment were years on ART, ethnicity, years of education, transmission category and the HOMA index. Adjusted by these variables the Odds Ratio (95% CI) for neurocognitive impairment of patients receiving short-term monotherapy was 0.85 (0.29–2.50) and for long-term monotherapy 0.40 (0.14–1.15).

Conclusions

Compared to triple drug antiretroviral therapy, monotherapy with lopinavir/ritonavir or darunavir/ritonavir in patients with adequate plasma suppression was not associated with a higher rate of asymptomatic neurocognitive impairment than triple drug ART.     

Differential Subplastidial Localization and Turnover of Enzymes Involved in Isoprenoid Biosynthesis in Chloroplasts

Plastidial isoprenoids are a diverse group of metabolites with roles in photosynthesis, growth regulation, and interaction with the environment. The methylerythritol 4-phosphate (MEP) pathway produces the metabolic precursors of all types of plastidial isoprenoids. Proteomics studies in Arabidopsis thaliana have shown that all the enzymes of the MEP pathway are localized in the plastid stroma. However, immunoblot analysis of chloroplast subfractions showed that the first two enzymes of the pathway, deoxyxylulose 5-phosphate synthase (DXS) and reductoisomerase (DXR), can also be found in non-stromal fractions. Both transient and stable expression of GFP-tagged DXS and DXR proteins confirmed the presence of the fusion proteins in distinct subplastidial compartments. In particular, DXR-GFP was found to accumulate in relatively large vesicles that could eventually be released from chloroplasts, presumably to be degraded by an autophagy-independent process. Together, we propose that protein-specific mechanisms control the localization and turnover of the first two enzymes of the MEP pathway in Arabidopsis chloroplasts.     

The Administration of Cadmium for 2, 3 and 4 Months Causes a Loss of Recognition Memory,Promotes Neuronal Hypotrophy and Apoptosis in the Hippocampus of Rats

Cadmium (Cd) is a toxic metal and classified as a carcinogen whose exposure could affect the function of the central nervous system. There are studies that suggest that Cd promotes neurodegeneration in different regions of the brain, particularly in the hippocampus. It is proposed that its mechanism of toxicity maybe by an oxidative stress pathway, which modifies neuronal morphology and causes the death of neurons and consequently affecting cognitive tasks. However, this mechanism is not yet clear. The aim of the present work was to study the effect of Cd administration on recognition memory for 2, 3 and 4 months, neuronal morphology and immunoreactivity for caspase-3 and 9 in rat hippocampi. The results show that the administration of Cd decreased recognition memory. Likewise, it caused the dendritic morphology of the CA1, CA3 and dentate gyrus regions of the hippocampus to decrease with respect to the time of administration of this heavy metal. In addition, we observed a reduction in the density of dendritic spines as well as an increase in the immunoreactivity of caspase-3 and 9 in the same hippocampal regions of the animals treated with Cd. These results suggest that Cd affects the structure and function of the neurons of the hippocampus, which contribute to the deterioration of recognition memory. Our results suggest that the exposure to Cd represents a critical health problem, which if not addressed quickly, could cause much more serious problems in the quality of life of the human population, as well as in the environment in which they develop.

     

A novel regulatory mechanism of MAP kinases activation and nuclear translocation mediated by PKA and the PTP-SL tyrosine phosphatase

Protein tyrosine phosphatase PTP-SL retains mitogen-activated protein (MAP) kinases in the cytoplasm in an inactive form by association through a kinase interaction motif (KIM) and tyrosine dephosphorylation. The related tyrosine phosphatases PTP-SL and STEP were phosphorylated by the cAMP-dependent protein kinase A (PKA). The PKA phosphorylation site on PTP-SL was identified as the Ser(231) residue, located within the KIM. Upon phosphorylation of Ser(231), PTP-SL binding and tyrosine dephosphorylation of the MAP kinases extracellular signal-regulated kinase (ERK)1/2 and p38alpha were impaired. Furthermore, treatment of COS-7 cells with PKA activators, or overexpression of the Calpha catalytic subunit of PKA, inhibited the cytoplasmic retention of ERK2 and p38alpha by wild-type PTP-SL, but not by a PTP-SL S231A mutant. These findings support the existence of a novel mechanism by which PKA may regulate the activation and translocation to the nucleus of MAP kinases.     

Herbivore effects on developmental instability and fecundity of holm oaks

Plants are able to compensate for loss of tissue due to herbivores at a variety of spatial and temporal scales, masking detrimental effects of herbivory on plant fitness at these scales. The stressing effect of herbivory could also produce instability in the development of plant modules, and measures of such instability may reflect the fitness consequences of herbivory if instability is related to components of plant fitness. We analyse the relationships between herbivory, developmental instability and production of female flowers and fruits of holm oak Quercus ilex trees by means of herbivore removal experiments. Removal of leaf herbivores reduced herbivory rates at the tree level, but had no effect on mean production of female flowers or mature fruits, whereas herbivory tended to enhance flower production and had no effect on fruit abortion at the shoot level. Differences in herbivory levels between shoots of the same branch did not affect the size and fluctuating asymmetry of intact leaves. These results indicate compensation for herbivory at the tree level and over-compensation at the shoot level in terms of allocation of resources to female flower production. Removal of insect herbivores produced an increase in the mean developmental instability of leaves at the tree level in the year following the insecticide treatment, and there was a direct relationship between herbivory rates in the current year and leaf fluctuating asymmetry the following year irrespective of herbivore removal treatment. Finally, the production of pistillate flowers and fruits by trees was inversely related to the mean fluctuating asymmetry of leaves growing the same year. Leaf fluctuating asymmetry was thus an estimator of the stressing effects of herbivory on adult trees, an effect that was delayed to the following year. As leaf fluctuating asymmetry was also related to tree fecundity, asymmetry levels provided a sensitive measure of plant performance under conditions of compensatory responses to herbivory.     

Phosphorylation-regulated cleavage of the tumor suppressor PTEN by caspase-3: implications for the control of protein stability and PTEN-protein interactions

PTEN phosphatase is one of the most commonly targeted tumor suppressors in human cancers and a key regulator of cell growth and apoptosis. We have found that PTEN is cleaved by caspase-3 at several target sites, located in unstructured regions within the C terminus of the molecule. Cleavage of PTEN was increased upon TNFalpha-cell treatment and was negatively regulated by phosphorylation of the C-terminal tail of PTEN by the protein kinase CK2. The proteolytic PTEN fragments displayed reduced protein stability, and their capability to interact with the PTEN interacting scaffolding protein S-SCAM/MAGI-2 was lost. Interestingly, S-SCAM/MAGI-2 was also cleaved by caspase-3. Our findings suggest the existence of a regulatory mechanism of protein stability and PTEN-protein interactions during apoptosis, executed by caspase-3 in a PTEN phosphorylation-regulated manner.     

Ginseng increases intestinal elimination of albendazole sulfoxide in the rat

Herbal products show potential drug interactions, some of them with adverse effects. The main aim of this work was to study the effect of Panax ginseng on the intestinal elimination of the benzimidazole derivative albendazole sulfoxide (ABZSO). An upper small intestine segment was isolated and perfused in situ with saline, while ABZSO solution (10 mg/kg i.v.) was administered intravenously. Blood samples and intestinal secretion were collected over 60 min and analysed by HPLC. The intestinal clearance of ABZSO was 0.106+/-0.010 ml/min. Systemic co-administration of ginseng (10 mg/kg i.v.) increased significantly (P<0.05) the clearance of ABZSO (0.132+/-0.005 ml/min). The increase in ABZSO elimination could be the result of the effect of ginseng on metabolic pathways. These results highlight the interactions between herbal products (sometimes dietary constituents) and drugs such as benzimidazoles, since ginseng modifies the luminal clearance of this anthelminthic drug and could potentially interfere with drugs that undergo the same intestinal processes.