Modelling sugar diffusion across plant leaf cuticles: the effect of free water on substrate availability to phyllosphere bacteria

We present a continuous model for the diffusion of sugars across intact plant leaf cuticles. It is based on the flow of sugars from a source, representing the leaf apoplast, to a sink, in the shape of a hemispherical drop of water on the outside of the cuticle. Flow is a function of the difference between sugar concentrations C_Source and C_Sink, permeability P of the cuticle, volume V_Sink of the water drop, as well as its contact angle α with the cuticle surface. Using a bacterial bioreporter for fructose, and a two‐compartment experimental set‐up consisting of isolated cuticles of walnut (Juglans regia) carrying water droplets while floating on solutions with increasing concentrations of fructose, we determined a value of 1 × 10^?6 m h^?1 for P. Using this value, we explored different scenarios for the leaching of sugars across plant leaf cuticles to reveal in quantitative terms how diffusion takes longer when V_Sink increases, P decreases or α increases. Bacterial growth was modelled as a function of changes in P, α and V_Sink and was consistent with observations or suggestions from the literature in relation to the availability of free water on leaves. These results are discussed in the light of bacteria as ecosystem engineers, i.e. with the ability to modify the plant leaf surface environment in favour of their own survival, e.g. by increasing cuticle leakage or leaf wetness. Our model represents a first step towards a more comprehensive model which will enhance our quantitative understanding of the factors that play a role in nutrient availability to bacterial colonizers of the phyllosphere, or plant leaf surface.     

Characterization of mature rat oligodendrocytes: a proteomic approach

Oligodendrocytes are glial cells responsible for the synthesis and maintenance of myelin in the central nervous system (CNS). Oligodendrocytes are vulnerable to damage occurring in a variety of neurological diseases. Understanding oligodendrocyte biology is crucial for the dissemination of de- and remyelination mechanisms. The goal of the present study is the construction of a protein database of mature rat oligodendrocytes. Post-mitotic oligodendrocytes were isolated from mature Wistar rats and subjected to immunocytochemistry. Proteins were extracted and analyzed by means of two-dimensional gel electrophoresis and two-dimensional liquid chromatography, both coupled to mass spectrometry. The combination of the gel-based and gel-free approach resulted in confident identification of a total of 200 proteins. A minority of proteins were identified in both proteomic strategies. The identified proteins represent a variety of functional groups, including novel oligodendrocyte proteins. The results of this study emphasize the power of the applied proteomic strategy to study known or to reveal new proteins and to investigate their regulation in oligodendrocytes in different disease models.     

Adenomatous polyposis coli-deficient zebrafish are susceptible to digestive tract neoplasia

Truncation of the tumour suppressor adenomatous polyposis coli (APC) constitutively activates the Wnt/beta-catenin signalling pathway. This event constitutes the primary transforming event in sporadic colorectal cancer in humans. Moreover, humans or mice carrying germline truncating mutations in APC develop large numbers of intestinal adenomas. Here, we report that zebrafish that are heterozygous for a truncating APC mutation spontaneously develop intestinal, hepatic and pancreatic neoplasias that are highly proliferative, accumulate beta-catenin and express Wnt target genes. Treatment with the chemical carcinogen 7,12-dimethylbenz[a]anthracene accelerates the induction of these lesions. These observations establish apc-mutant zebrafish as a bona fide model for the study of digestive tract cancer.     

CYTOGENETIC STUDIES IN THE GENUS TRIBOLIUM (POACEAE: ARUNDINEAE)

The genus Tribolium Desv. consists of nine species, i.e., T. utriculosum (Nees) Renv., T. ciliare (Stapf) Renv., T. echinatum (Thunb.) Desv., T. hispidum (Thunb.) Desv., T. acutiflorum (Nees) Renv., T. obliterum sensu Davidse, T. glomeratum sensu Davidse, T. uniolae (L.f.) Renv., and T. brachystachyum (Nees) Renv. The genus has a basic chromosome number of 6, and from diploid to hexaploid specimens have been examined. Precocious segregation of metaphase I bivalents were observed in four species. Multivalent formation results in unequal chromosome segregation during anaphase I, and several cells with an 11–13 chromosome distribution have been observed. The presence of univalents and anaphase I bridges in all T. brachystachyum specimens suggests a hybrid origin for the species. B-chromosomes were present in specimens from four species. The B-chromosomes are similar to the euchromosomes with the exception that they do not participate in meiosis. The B-chromosomes have a possible isochromosome origin. The cytogenetic evidence presented supports the combination of Plagiochloa and Lasiochloa into Tribolium and indicates that the genus is closely related to Urochlaena, whereas it is not closely related to Prionanthium.     

In vitro effects of 2‐methoxyestradiol‐bis‐sulphamate on the non‐tumorigenic MCF‐12A cell line

A priority in recent anti‐cancer drug development has been attaining better side‐effect profiles for potential compounds. To produce highly specific cancer therapies it is necessary to understand both the effects of the proposed compound on cancer and on normal cells comprising the rest of the human body. Thus in vitro evaluation of these compounds against non‐carcinogenic cell lines is of critical importance. One of the most recent developments in experimental anti‐cancer agents is 2‐methoxyestradiol‐bis‐sulphamate (2ME‐BM), a sulphamoylated derivative of 2‐methoxyestradiol. The aim of this study was to evaluate the in vitro effects of 2ME‐BM on cell proliferation, morphology and mechanisms of cell death in the non‐carcinogenic MCF‐12A breast epithelial cell line. The study revealed changes in proliferative capacity, morphology and cell death induction in response to 2ME‐BM exposure (24 h at 0.4 µM). Microscopy showed decreased cell density and cell death‐associated morphology (increased apoptotic characteristics), a slight increase in acidic intracellular vesicles and insignificant ultra‐structural aberrations. Mitotic indices revealed a G₂M‐phase cell cycle block. This was confirmed by flow cytometry, where an increased fraction of abnormal cells and a decrease in cyclin B1 levels were observed. These results evidently demonstrate that the non‐carcinogenic MCF‐12A cell line is less susceptible when compared to 2ME‐BM‐exposed cancer cell lines previously tested. Further in vitro research into the mechanism of this potentially useful compound is warranted. Copyright © 2010 John Wiley & Sons, Ltd.     

Impaired attribution of emotion to facial expressions in anxiety and major depression

Background

Recognition of others'' emotions is an important aspect of interpersonal communication. In major depression, a significant emotion recognition impairment has been reported. It remains unclear whether the ability to recognize emotion from facial expressions is also impaired in anxiety disorders. There is a need to review and integrate the published literature on emotional expression recognition in anxiety disorders and major depression.

Methodology/Principal Findings

A detailed literature search was used to identify studies on explicit emotion recognition in patients with anxiety disorders and major depression compared to healthy participants. Eighteen studies provided sufficient information to be included. The differences on emotion recognition impairment between patients and controls (Cohen''s d) with corresponding confidence intervals were computed for each study. Over all studies, adults with anxiety disorders had a significant impairment in emotion recognition (d = −0.35). In children with anxiety disorders no significant impairment of emotion recognition was found (d = −0.03). Major depression was associated with an even larger impairment in recognition of facial expressions of emotion (d = −0.58).

Conclusions/Significance

Results from the current analysis support the hypothesis that adults with anxiety disorders or major depression both have a deficit in recognizing facial expression of emotions, and that this deficit is more pronounced in major depression than in anxiety.     

Characterization of EVL-I as a protein kinase D substrate

EVL-I is a splice variant of EVL (Ena/VASP like protein), whose in vivo function and regulation are still poorly understood. We found that Protein Kinase D (PKD) interacts in vitro and in vivo with EVL-I and phosphorylates EVL-I in a 21 amino acid alternately-included insert in the EVH2 domain. Following knockdown of the capping protein CPβ and spreading on laminin, phosphorylated EVL-I can support filopodia formation and the phosphorylated EVL-I is localized at filopodial tips. Furthermore, we found that the lamellipodial localization of EVL-I is unaffected by phosphorylation, but that impairment of EVL-I phosphorylation is associated with ruffling of lamellipodia upon PDBu stimulation. Besides the lamellipodial and filopodial localization of phosphorylated EVL-I in fibroblasts, we determined that EVL-I is hyperphosphorylated and localized in the cell–cell contacts of certain breast cancer cells and mouse embryo keratinocytes. Taken together, our results show that phosphorylated EVL-I is present in lamellipodia, filopodia and cell–cell contacts and suggest the existence of signaling pathways that may affect EVL-I via phosphorylation of its EVH2 domain.     

Folding into a beta-hairpin can prevent amyloid fibril formation

The tetrapeptide KFFE is one of the shortest amyloid fibril-forming peptides described. Herein, we have investigated how the structural environment of this motif affects polymerization. Using a turn motif (YNGK) or a less rigid sequence (AAAK) to fuse two KFFE tetrapeptides, we show by several biophysical methods that the amyloidogenic properties are strongly dependent on the structural environment. The dodecapeptide KFFEAAAKKFFE forms abundant thick fibril bundles. Freshly dissolved KFFEAAAKKFFE is monomeric and shows mainly disordered secondary structure, as evidenced by circular dichroism, NMR spectroscopy, hydrogen/deuterium exchange measurements, and molecular modeling studies. In sharp contrast, the dodecapeptide KFFEYNGKKFFE does not form fibrils but folds into a stable beta-hairpin. This structure can oligomerize into a stable 12-mer and multiples thereof, as shown by size exclusion chromatography, sedimentation analysis, and electrospray mass spectrometry. These data indicate that the structural context in which a potential fibril forming sequence is present can prevent fibril formation by favoring self-limiting oligomerization over polymerization.