Growth and biochemical profiling of artificially associated micropropagated oil palm plantlets with Herbaspirillum seropedicae

The challenges of various biotic and abiotic stresses can imperil the growth of micropropagated plantlets either direct or indirectly. Hence, in this study, a mutual relationship was established between diazotrophs and micropropagated plantlets to enhance plant growth and development. Artificial symbiosis was created for different inoculums of Herbaspirillum seropedicae (Z78), namely sonicated cells, broth culture, and pellet cells with micropropagated oil palm plantlets Elaeis guineensis Jacq. Results reveal significant differences on root volume, total protein content, and Brix value for Z78 broth culture treatment compared with plantlets treated with 25% N. High nitrogenase enzyme activities (6.7?×?10^?4?µmol?C₂H₄ g^?1?h^?1) and indole-3-acetic acid production (205.21?µmol (g?FW)^?1) were also detected on roots of plantlets treated with Z78 broth culture. These beneficial traits reviewed that the application of diazotrophs (Z78) in associative manner for micropropagated plantlets hold vast potential for promoting plant growth and plant’s healthiness.     

Lafora disease: from genotype to phenotype

The progressive myoclonic epilepsy of Lafora or Lafora disease (LD) is a neurodegenerative disorder characterized by recurrent seizures and cognitive deficits. With typical onset in the late childhood or early adolescence, the patients show progressive worsening of the disease symptoms, leading to death in about 10 years. It is an autosomal recessive disorder caused by the loss-of-function mutations in the EPM2A gene, coding for a protein phosphatase (laforin) or the NHLRC1 gene coding for an E3 ubiquitin ligase (malin). LD is characterized by the presence of abnormally branched water insoluble glycogen inclusions known as Lafora bodies in the neurons and other tissues, suggesting a role for laforin and malin in glycogen metabolic pathways. Mouse models of LD, developed by targeted disruption of the Epm2a or Nhlrc1 gene, recapitulated most of the symptoms and pathological features as seen in humans, and have offered insight into the pathomechanisms. Besides the formation of Lafora bodies in the neurons in the presymptomatic stage, the animal models have also demonstrated perturbations in the proteolytic pathways, such as ubiquitin-proteasome system and autophagy, and inflammatory response. This review attempts to provide a comprehensive coverage on the genetic defects leading to the LD in humans, on the functional properties of the laforin and malin proteins, and on how defects in any one of these two proteins result in a clinically similar phenotype. We also discuss the disease pathologies as revealed by the studies on the animal models and, finally, on the progress with therapeutic attempts albeit in the animal models.     

Engineered silver nanoparticles are sensed at the plasma membrane and dramatically modify the physiology of Arabidopsis thaliana plants

Silver nanoparticles (Ag NPs) are the world's most important nanomaterial and nanotoxicant. The aim of this study was to determine the early stages of interactions between Ag NPs and plant cells, and to investigate their physiological roles. We have shown that the addition of Ag NPs to cultivation medium, at levels above 300 mg L^?1, inhibited Arabidopsis thaliana root elongation and leaf expansion. This also resulted in decreased photosynthetic efficiency and the extreme accumulation of Ag in tissues. Acute application of Ag NPs induced a transient elevation of [Ca²⁺]_cyt and the accumulation of reactive oxygen species (ROS; partially generated by NADPH oxidase). Whole‐cell patch‐clamp measurements on root cell protoplasts demonstrated that Ag NPs slightly inhibited plasma membrane K⁺ efflux and Ca²⁺ influx currents, or caused membrane breakdown; however, in excised outside‐out patches, Ag NPs activated Gd³⁺‐sensitive Ca²⁺ influx channels with unitary conductance of approximately 56 pS. Bulk particles did not modify the plasma membrane currents. Tests with electron paramagnetic resonance spectroscopy showed that Ag NPs were not able to catalyse hydroxyl radical generation, but that they directly oxidized the major plant antioxidant, l ‐ascorbic acid. Overall, the data presented shed light on mechanisms of the impact of nanosilver on plant cells, and show that these include the induction of classical stress signalling reactions (mediated by [Ca²⁺]_cyt and ROS) and a specific effect on the plasma membrane conductance and the reduced ascorbate.     

Protein bioinformatics and mixtures of bivariate von Mises distributions for angular data

A fundamental problem in bioinformatics is to characterize the secondary structure of a protein, which has traditionally been carried out by examining a scatterplot (Ramachandran plot) of the conformational angles. We examine two natural bivariate von Mises distributions--referred to as Sine and Cosine models--which have five parameters and, for concentrated data, tend to a bivariate normal distribution. These are analyzed and their main properties derived. Conditions on the parameters are established which result in bimodal behavior for the joint density and the marginal distribution, and we note an interesting situation in which the joint density is bimodal but the marginal distributions are unimodal. We carry out comparisons of the two models, and it is seen that the Cosine model may be preferred. Mixture distributions of the Cosine model are fitted to two representative protein datasets using the expectation maximization algorithm, which results in an objective partition of the scatterplot into a number of components. Our results are consistent with empirical observations; new insights are discussed.     

Combined monte carlo and molecular dynamics simulation of fully hydrated dioleyl and palmitoyl-oleyl phosphatidylcholine lipid bilayers

We have applied a new equilibration procedure for the atomic level simulation of a hydrated lipid bilayer to hydrated bilayers of dioleyl-phosphatidylcholine (DOPC) and palmitoyl-oleyl phosphatidylcholine (POPC). The procedure consists of alternating molecular dynamics trajectory calculations in a constant surface tension and temperature ensemble with configurational bias Monte Carlo moves to different regions of the configuration space of the bilayer in a constant volume and temperature ensemble. The procedure is applied to bilayers of 128 molecules of POPC with 4628 water molecules, and 128 molecules of DOPC with 4825 water molecules. Progress toward equilibration is almost three times as fast in central processing unit (CPU) time compared with a purely molecular dynamics (MD) simulation. Equilibration is complete, as judged by the lack of energy drift in 200-ps runs of continuous MD. After the equilibrium state was reached, as determined by agreement between the simulation volume per lipid molecule with experiment, continuous MD was run in an ensemble in which the lateral area was restrained to fluctuate about a mean value and a pressure of 1 atm applied normal to the bilayer surface. Three separate continuous MD runs, 200 ps in duration each, separated by 10,000 CBMC steps, were carried out for each system. Properties of the systems were calculated and averaged over the three separate runs. Results of the simulations are presented and compared with experimental data and with other recent simulations of POPC and DOPC. Analysis of the hydration environment in the headgroups supports a mechanism by which unsaturation contributes to reduced transition temperatures. In this view, the relatively horizontal orientation of the unsaturated bond increases the area per lipid, resulting in increased water penetration between the headgroups. As a result the headgroup-headgroup interactions are attenuated and shielded, and this contributes to the lowered transition temperature.     

Serial Echocardiographic and Clinical Evaluation of Valvular Regurgitation Before,During, and After Treatment with Fenfluramine or Dexfenfluramine and Mazindol or Phentermine

RYAN, DONNA H., GEORGE A. BRAY, FRED HELMCKE, GARY SANDER, JULIA VOLAUFOVA, FRANK GREENWAY, PRAMILLA SUBRAMANIAM, AND D. LUKE GLANCY. Serial echocardiographic and clinical evaluation of valvular regurgitation before, during, and after treatment with fenfluramine or dexfenfluramine and mazindol or phentermine. Obes Res. Objective: The prevalence of cardiac valvular regurgitation demonstrated by echocardiography in patients who took appetite-suppressant medication for weight loss has been assessed at 5%-30%. We studied 86 patients who had echo-cardiograms before treatment with appetite suppressants to determine the incidence of new cases and to evaluate the clinical implication of the echocardiographic findings. Research Methods and Procedures: We studied 69 men [Mean± Standard Deviation (S) age 49±81] and 17 women (mean±S age 50±7) who had 233 echocardiograms before, during, and after a weight-loss program that used predominantly fenfluramine (or dexfenfluramine) with mazindol (or phentermine). Mean drug exposure was 17 months. Blinded echocardiographic readings were performed to identify and grade aortic regurgitation (AR) or mitral regurgitation (MR). Results: Seven of 86 patients (8%) had pre-existing regurgitation with five (6%) meeting our case definition. Thirteen (16. 5%) of initially normal patients developed valvular regurgitation and were new cases. Of the new cases, 12 were grade IAV AR and one was both grade II/III MR and IIDV AR. All 13 patients were asymptomatic, and only two aortic insufficiency murmurs could be auscultated. There was significantly greater risk for developing valvulopathy for those who took medications longer than 6 months (p = 0. 03), and no new cases were observed in patients exposed for less than 8 months. No increased risk associated with age, presence of hypertension, or exposure to fenfluramine-phentermine combination was demonstrated. Although there was a higher incidence of new regurgitation in women (31% vs. 13% for men), this was not statistically significant (p = 0. 093). Discussion: Some patients who had normal echocardiograms at baseline developed cardiac valvular regurgitation after exposure to fenfluramine or dexfenfluramine with mazindol or phentermine. The development of valvulopathy was significantly correlated with duration of exposure. The clinical implications of echocardiographically demonstrated regurgitation are uncertain, since there were only two audible murmurs and no other clinically relevant signs or symptoms among the patients.     

Improved photoluminescence stability and defect passivation in SbBr3 post-treated CsPbBr3 quantum dots under ambient conditions

Inorganic cesium lead halide perovskites have evoked wide popularity because of their excellent optoelectronic properties, high photoluminescence (PL) quantum yield (PLQY), and narrowband emission. Here, cesium lead bromide (CsPbBr₃) quantum dots (QDs) were synthesized via the ligand-assisted re-precipitation method. Post-synthesis treatment of CsPbBr₃ QDs using antimony tribromide improved the PL stability and optoelectronic properties of the QDs. In addition, the PLQY of the post-treated sample was enhanced to 91% via post-treatment, and the luminescence observed was maintained for 8 days. The post-synthesis treatment ensured defect passivation and improved the stability of CsPbBr₃ perovskite QDs. High-resolution transmission electron microscopy revealed the presence of more ordered, uniform-sized CsPbBr₃ QDs after post-synthesis treatment, and the uniformity of the sample improved as the day passed. The formation of a mixed crystal phase was observed from X-ray diffraction in both as-synthesized, as well as post-treated QDs samples with the possibility of a polycrystalline nature in the post-treated CsPbBr₃ QDs as per the selected area electron diffraction pattern. The X-ray photoelectron spectroscopy spectra confirmed the presence of antimony and the possibility of defect passivation in the post-treated samples. These QDs can act as potential candidates in various optoelectronic applications such as photodetectors and light-emitting diodes due to their high PLQY and longer lifetime.