Leaf-induced gibberellin signaling is essential for internode elongation, cambial activity, and fiber differentiation in tobacco stems

The gibberellins (GAs) are a group of endogenous compounds that promote the growth of most plant organs, including stem internodes. We show that in tobacco (Nicotiana tabacum) the presence of leaves is essential for the accumulation of bioactive GAs and their immediate precursors in the stem and consequently for normal stem elongation, cambial proliferation, and xylem fiber differentiation. These processes do not occur in the absence of maturing leaves but can be restored by application of C(19)-GAs, identifying the presence of leaves as a requirement for GA signaling in stems and revealing the fundamental role of GAs in secondary growth regulation. The use of reporter genes for GA activity and GA-directed DELLA protein degradation in Arabidopsis thaliana confirms the presence of a mobile signal from leaves to the stem that induces GA signaling.     

Methionine sulfoxides on PrPSc: a prion-specific covalent signature

Prion diseases are fatal neurodegenerative disorders believed to be transmitted by PrP (Sc), an aberrant form of the membrane protein PrP (C). In the absence of an established form-specific covalent difference, the infectious properties of PrP (Sc) were uniquely ascribed to the self-perpetuation properties of its aberrant fold. Previous sequencing of the PrP chain isolated from PrP(27-30) showed the oxidation of some methionine residues; however, at that time, these findings were ascribed to experimental limitations. Using the unique recognition properties of alphaPrP mAb IPC2, protein chemistry, and state of the art mass spectrometry, we now show that while a large fraction of the methionine residues in brain PrP (Sc) are present as methionine sulfoxides this modification could not be found on brain PrP (C) as well as on its recombinant models. In particular, the pattern of oxidation of M213 with respect to the glycosylation at N181 of PrP (Sc) differs both within and between species, adding another diversity factor to the structure of PrP (Sc) molecules. Our results pave the way for the production of prion-specific reagents in the form of antibodies against oxidized PrP chains which can serve in the development of both diagnostic and therapeutic strategies. In addition, we hypothesize that the accumulation of PrP (Sc) and thereafter the pathogenesis of prion disease may result from the poor degradation of oxidized aberrantly folded PrP.     

H-Ras Nanocluster Stability Regulates the Magnitude of MAPK Signal Output

H-Ras is a binary switch that is activated by multiple co-factors and triggers several key cellular pathways one of which is MAPK. The specificity and magnitude of downstream activation is achieved by the spatio-temporal organization of the active H-Ras in the plasma membrane. Upon activation, the GTP bound H-Ras binds to Galectin-1 (Gal-1) and becomes transiently immobilized in short-lived nanoclusters on the plasma membrane from which the signal is propagated to Raf. In the current study we show that stabilizing the H-Ras-Gal-1 interaction, using bimolecular fluorescence complementation (BiFC), leads to prolonged immobilization of H-Ras.GTP in the plasma membrane which was measured by fluorescence recovery after photobleaching (FRAP), and increased signal out-put to the MAPK module. EM measurements of Raf recruitment to the H-Ras.GTP nanoclusters demonstrated that the enhanced signaling observed in the BiFC stabilized H-Ras.GTP nanocluster was attributed to increased H-Ras immobilization rather than to an increase in Raf recruitment. Taken together these data demonstrate that the magnitude of the signal output from a GTP-bound H-Ras nanocluster is proportional to its stability.     

Processive Endoglucanase Active in Crystalline Cellulose Hydrolysis by the Brown Rot Basidiomycete Gloeophyllum trabeum

Brown rot basidiomycetes have long been thought to lack the processive cellulases that release soluble sugars from crystalline cellulose. On the other hand, these fungi remove all of the cellulose, both crystalline and amorphous, from wood when they degrade it. To resolve this discrepancy, we grew Gloeophyllum trabeum on microcrystalline cellulose (Avicel) and purified the major glycosylhydrolases it produced. The most abundant extracellular enzymes in these cultures were a 42-kDa endoglucanase (Cel5A), a 39-kDa xylanase (Xyn10A), and a 28-kDa endoglucanase (Cel12A). Cel5A had significant Avicelase activity—4.5 nmol glucose equivalents released/min/mg protein. It is a processive endoglucanase, because it hydrolyzed Avicel to cellobiose as the major product while introducing only a small proportion of reducing sugars into the remaining, insoluble substrate. Therefore, since G. trabeum is already known to produce a β-glucosidase, it is now clear that this brown rot fungus produces enzymes capable of yielding assimilable glucose from crystalline cellulose.     

Effect of Plasticizer on Release Kinetics of Diclofenac Sodium Pellets Coated with Eudragit RS 30 D

The present study was designed to investigate the effect of two plasticizers, i.e., triethyl citrate (TEC) and polyethylene glycol 6000 (PEG 6000) on the in vitro release kinetics of diclofenac sodium from sustained-release pellets. Ammonio methacrylate copolymer type B (Eudragit RS 30 D) is used as the release-retarding polymer. Both plasticizers were used at 10% and 15% (w/w) of Eudragit RS 30 D. Pellets were prepared by powder layering technology and coated with Eudragit RS 30 D by air suspension technique. Thermal properties of drug and drug-loaded beads were studied using differential scanning calorimeter (DSC). DSC thermogram represented the identity of raw materials and exhibited no interaction or complexation between the active and excipients used in the pelletization process. Dissolution study was performed by using USP apparatus 1. No significant difference was observed among the physical properties of the coated pellets of different batches. When dissolution was performed as pure drug, about 8.22% and 90% drug was dissolved at 2 h in 0.1 N HCl and at 30 min in buffer (pH 6.8), respectively. From all formulations, the release of drug in acid media was very negligible (maximum 1.8 ± 0.08% at 2 h) but in buffer only 12% and 30% drug was released at 10 h from coated pellets containing TEC and PEG 6000, respectively, indicating that Eudragit RS 30 D significantly retards the drug release rate and that drug release was varied according to the type and amount of plasticizers used. The amount of TEC in coating formulation significantly effected drug release (p < 0.001), but the effect of PEG 6000 was not significant. Formulations containing PEG 6000 released more drug (98.35 ± 2.35%) than TEC (68.01 ± 1.04%) after 24 h. Different kinetic models like zero order, first order, and Higuchi were used for fitting drug release pattern. Zero order model fitted best for diclofenac release in all formulations. Drug release mechanism was derived with Korsmeyer equation.     

New tryptophanase inhibitors: towards prevention of bacterial biofilm formation

Tryptophanase (tryptophan indole-lyase, Tnase, EC 4.1.99.1), a bacterial enzyme with no counterpart in eukaryotic cells, produces from L-tryptophan pyruvate, ammonia and indole. It was recently suggested that indole signaling plays an important role in the stable maintenance of multicopy plasmids. In addition, Tnase was shown to be capable of binding Rcd, a short RNA molecule involved in resolution of plasmid multimers. Binding of Rcd increases the affinity of Tnase for tryptophan, and it was proposed that indole is involved in bacteria multiplication and biofilm formation. Biofilm-associated bacteria may cause serious infections, and biofilm contamination of equipment and food, may result in expensive consequences. Thus, optimal and specific factors that interact with Tnase can be used as a tool to study the role of this multifunctional enzyme as well as antibacterial agents that may affect biofilm formation. Most known quasi-substrates inhibit Tnase at the mM range. In the present work, the mode of Tnase inhibition by the following compounds and the corresponding Ki values were: S-phenylbenzoquinone-L-tryptophan, uncompetitively, 101 microM; alpha-amino-2-(9,10-anthraquinone)-propanoic acid, noncompetitively, 174 microM; L-tryptophane-ethylester, competitively, 52 microM; N-acetyl-L-tryptophan, noncompetitively, 48 microM. S-phenylbenzoquinone-L-tryptophan and alpha-amino-2-(9,10-anthraquinone)-propanoic acid were newly synthesized.     

The gliding speed of migrating birds: slow and safe or fast and risky?

Aerodynamic theory postulates that gliding airspeed, a major flight performance component for soaring avian migrants, scales with bird size and wing morphology. We tested this prediction, and the role of gliding altitude and soaring conditions, using atmospheric simulations and radar tracks of 1346 birds from 12 species. Gliding airspeed did not scale with bird size and wing morphology, and unexpectedly converged to a narrow range. To explain this discrepancy, we propose that soaring‐gliding birds adjust their gliding airspeed according to the risk of grounding or switching to costly flapping flight. Introducing the Risk Aversion Flight Index (RAFI, the ratio of actual to theoretical risk‐averse gliding airspeed), we found that inter‐ and intraspecific variation in RAFI positively correlated with wing loading, and negatively correlated with convective thermal conditions and gliding altitude, respectively. We propose that risk‐sensitive behaviour modulates the evolution (morphology) and ecology (response to environmental conditions) of bird soaring flight.     

A novel herbal treatment reduces depressive-like behaviors and increases BDNF levels in the brain of stressed mice

Aims

Depression is a chronic, recurring and potentially life-threatening illness. Current treatments for depression are characterized by a low success rate and associated with a wide variety of side effects. The aim of the present study was to evaluate the behavioral and biological anti-depressant effects of a novel herbal treatment (NHT), as well as to assess its potential side effects, in comparison to treatment with the selective serotonin reuptake inhibitor escitalopram.

Main methods

Depressive-like behavior was evaluated using the forced swim test (FST) and the tail suspension test (TST). Sexual behavior was evaluated following treatment by measuring latency before first mount and number of total mounts. Brain derived neurotrophic factor (BDNF) levels were evaluated using enzyme-linked immunosorbent assay. Serotonin transporter (SERT) levels in the pre-frontal cortex (PFC) and hypothalamus were evaluated using high affinity binding assay.

Key findings

(1) The NHT reduced depressive-like behavior in the FST and TST; (2) BDNF levels in the PFC of mice treated both with the NHT and escitalopram were increased; (3) SERT levels in the hypothalamus were significantly higher in the NHT group, in comparison to escitalopram and the control groups, and significantly lower in the PFC of the NHT group in comparison to the escitalopram group; and (4) the NHT led to less sexual dysfunction, compared to treatment with escitalopram.

Significance

Our NHT has the potential of being highly efficacious in treating depression in humans, while causing minimal to no influence on sexual function.