Role of differential adhesion in cell cluster evolution: from vasculogenesis to cancer metastasis

Cell–cell and cell–matrix adhesions are fundamental to numerous physiological processes, including angiogenesis, tumourigenesis, metastatic spreading and wound healing. We use cellular potts model to computationally predict the organisation of cells within a 3D matrix. The energy potentials regulating cell–cell (J_CC) and cell–matrix (J_MC) adhesive interactions are systematically varied to represent different, biologically relevant adhesive conditions. Chemotactically induced cell migration is also addressed. Starting from a cluster of cells, variations in relative cell adhesion alone lead to different cellular patterns such as spreading of metastatic tumours and angiogenesis. The combination of low cell–cell adhesion (high J_CC) and high heterotypic adhesion (low J_MC) favours the fragmentation of the original cluster into multiple, smaller cell clusters (metastasis). Conversely, cellular systems exhibiting high-homotypic affinity (low J_CC) preserve their original configuration, avoiding fragmentation (organogenesis). For intermediate values of J_CC and J_MC (i.e. J_CC/J_MC ～ 1), tubular and corrugated structures form. Fully developed vascular trees are assembled only in systems in which contact-inhibited chemotaxis is activated upon cell contact. Also, the rate of secretion, diffusion and sequestration of chemotactic factors, cell deformability and motility do not significantly affect these trends. Further developments of this computational model will predict the efficacy of therapeutic interventions to modulate the diseased microenvironment by directly altering cell cohesion.     

Risk Ranking of Antimicrobials in the Aquatic Environment from Human Consumption: An Irish Case Study

A mechanistic model is presented for determination of antimicrobial presence in the environment, using antimicrobial characteristics and Irish-specific usage data. The model simulates release of antimicrobials into the aquatic environment by integrating the effects of antimicrobial use, metabolism, degradation, and dilution. Predicted environmental concentrations (PECs) were ranked in relation to their potential to select for resistant bacteria, toxicity (chronic and acute), and hazard quotient (HQ). The simulated mean PECs of penicillins (PEN), β-lactams (BET), tetracyclines (TET), macrolides (MAC), quinolone/fluoroquinolones (Q/F), and sulphonamides/trimethoprim (S/T) were 1.05, 0.19, 0.06, 0.07, 0.02, and 0.08 mg/m³, respectively. All antimicrobials, excluding Q/F, showed a low HQ (<1) indicating low toxicity. Q/F had a HQ of 1.51 indicating moderate toxicity. All antimicrobial groups expressed varying resistance formation potential with Q/F having the highest. Q/F also exhibited the lowest degradation rate. A sensitivity analysis indicated a possible role for considering metabolism during regulation of new antimicrobials as this can significantly influence PEC values. The observed results suggest that current antimicrobial use can lead to levels in the environment that may increase resistance formation. The results and limitations presented here accentuate the need for further investigation into antimicrobials in the environment and contribution to resistant strains.     

Synthesis and evaluation of N-substituted indole-3-carboxamide derivatives as inhibitors of lipid peroxidation and superoxide anion formation

The in vitro antioxidant effects of novel N-substituted indole-3-carboxamides (I3CDs) 1-10 on rat liver microsomal NADPH-dependent lipid peroxidation (LP) levels and their free radicals scavenging properties were determined by the inhibition of superoxide anion formation (SOD). Among the synthesized compounds, 4, 5, 8 and 9 significantly inhibited SOD with an inhibition range at 84–100% at 10^{? 3} M concentration. The presence of halo substituents both ortho- and para- positions of these compounds resulted 100% inhibition of SOD. Comparison the activity results of halogenated and non-halogenated derivatives suggested that the halogenated compounds are more active than the non-halogenated compounds. On the other hand, the introduction of a para fluoro benzyl in the 1-position of indole (compounds 7, 8) has more impact on the SOD inhibition when the benzamide ring was mono halogenated. However, none of other compounds had a significant inhibitory effects on the level of lipid peroxidation.     

Catabolic and anabolic periarticular bone changes in patients with rheumatoid arthritis: a computed tomography study on the role of age,disease duration and bone markers

Introduction

The aim of this study was to determine the factors, including markers of bone resorption and bone formation, which determine catabolic and anabolic periarticular bone changes in patients with rheumatoid arthritis (RA).

Methods

Forty RA patients received high-resolution peripheral quantitative computed tomography (HR-pQCT) analysis of the metacarpophalangeal joints II and III of the dominantly affected hand at two sequential time points (baseline, one year follow-up). Erosion counts and scores as well as osteophyte counts and scores were recorded. Simultaneously, serum markers of bone resorption (C-terminal telopeptide of type I collagen (CTX I), tartrate-resistant acid phosphatase 5b (TRAP5b)), bone formation (bone alkaline phosphatase (BAP), osteocalcin (OC)) and calcium homeostasis (parathyroid hormone (PTH), 25-hydroxyvitamin D3 (Vit D)) were assessed. Bone biomarkers were correlated to imaging data by partial correlation adjusting for various demographic and disease-specific parameters. Additionally, imaging data were analyzed by mixed linear model regression.

Results

Partial correlation analysis showed that TRAP5b levels correlate significantly with bone erosions, whereas BAP levels correlate with osteophytes at both time points. In the mixed linear model with erosions as the dependent variable, disease duration (P <0.001) was the key determinant for these catabolic bone changes. In contrast, BAP (P = 0.001) as well as age (P = 0.018), but not disease duration (P = 0.762), were the main determinants for the anabolic changes (osteophytes) of the periarticular bone in patients with RA.

Conclusions

This study shows that structural bone changes assessed with HR-pQCT are accompanied by alterations in systemic markers of bone resorption and bone formation. Besides, it can be shown that bone erosions in RA patients depend on disease duration, whereas osteophytes are associated with age as well as serum level of BAP. Therefore, these data not only suggest that different variables are involved in formation of bone erosions and osteophytes in RA patients, but also that periarticular bone changes correlate with alterations in systemic markers of bone metabolism, pointing out BAP as an important parameter.     

Endogenous electromagnetic fields in plant leaves: a new hypothesis for vascular pattern formation

Electromagnetic (EM) phenomena have long been implicated in biological development, but few detailed, practical mechanisms have been put forth to connect electromagnetism with morphogenetic processes. This work describes a new hypothesis for plant leaf veination, whereby an endogenous electric field forming as a result of a coherent Frohlich process, and corresponding to an EM resonant mode of the developing leaf structure, is capable of instigating leaf vascularisation. In order to test the feasibility of this hypothesis, a three-dimensional, EM finite-element model (FEM) of a leaf primordium was constructed to determine if suitable resonant modes were physically possible for geometric and physical parameters similar to those of developing leaf tissue. Using the FEM model, resonant EM modes with patterns of relevance to developing leaf vein modalities were detected. On account of the existence of shared geometric signatures in a leaf's vascular pattern and the electric field component of EM resonant modes supported by a developing leaf structure, further theoretical and experimental investigations are warranted. Significantly, this hypothesis is not limited to leaf vascular patterning, but may be applicable to a variety of morphogenetic phenomena in a number of living systems.     

Receptor‐dependent regulation of dendrite formation of noradrenaline and dopamine in non‐gabaergic cerebral cortical neurons

The present study characterized the receptor‐dependent regulation of dendrite formation of noradrenaline (NA) and dopamine (DA) in cultured neurons obtained from embryonic day 16 rat cerebral cortex. Morphological diversity of cortical dendrites was analyzed on various features: dendrite initiation, dendrite outgrowth, and dendrite branching. Using a combination of immunocytochemical markers of dendrites and GABAergic neurons, we focused on the dendrite morphology of non‐GABAergic neurons. Our results showed that (1) NA inhibited the dendrite branching, (2) β adrenergic receptor (β‐AR) agonist inhibited the dendrite initiation, while promoted the dendrite outgrowth, (3) β1‐AR and β2‐AR were present in all the cultured neurons, and both agonists inhibited the dendrite initiation, while only β1‐AR agonist induced the dendrite branching; (4) DA inhibited the dendrite outgrowth, (5) D1 receptor agonist inhibited the dendrite initiation, while promoted the dendrite branching. In conclusion, this study compared the effects of NA, DA and their receptors and showed that NA and DA regulate different features on the dendrite formation of non‐GABAergic cortical neurons, depending on the receptors. © 2012 Wiley Periodicals, Inc. Develop Neurobiol 73: 370–383, 2013     

SNX18 tubulates recycling endosomes for autophagosome biogenesis

The role of membrane remodeling and phosphoinositide-binding proteins in autophagy remains elusive. PX domain proteins bind phosphoinositides and participate in membrane remodeling and trafficking events and we therefore hypothesized that one or several PX domain proteins are involved in autophagy. Indeed, the PX-BAR protein SNX18 was identified as a positive regulator of autophagosome formation using an image-based siRNA screen. We show that SNX18 interacts with ATG16L1 and LC3, and functions downstream of ATG14 and the class III PtdIns3K complex in autophagosome formation. SNX18 facilitates recruitment of ATG16L1 to perinuclear recycling endosomes, and its overexpression leads to tubulation of ATG16L1- and LC3-positive membranes. We propose that SNX18 promotes LC3 lipidation and tubulation of recycling endosomes to provide membrane for phagophore expansion.     

Recycling endosomes contribute to autophagosome formation

Autophagosome formation is a complex cellular process, which requires major membrane rearrangements leading to the creation of a relatively large double-membrane vesicle that directs its contents to the lysosome for degradation. Although various membrane compartments have been identified as sources for autophagosomal membranes, the molecular mechanism underlying these membrane trafficking steps remains elusive. To address this question we performed a systematic analysis testing all known Tre-2/Bub2/Cdc16 (TBC) domain-containing proteins for their ability to inhibit autophagosome formation by disrupting a specific membrane trafficking step. TBC proteins are thought to act as inhibitors of Rab GTPases, which regulate membrane trafficking events. Up to 11 TBC proteins inhibit autophagy when overexpressed and one of these, TBC1D14, acts at an early stage during autophagosome formation and is involved in regulating recycling endosomal traffic. We found that the early acting autophagy proteins ATG9 and ULK1 localize to transferrin receptor (TFR)-positive recycling endosomes (RE), which are tubulated by excess TBC1D14 leading to an inhibition of autophagosome formation. Finally, transferrin (TF)-containing recycling endosomal membranes can be incorporated into newly forming autophagosomes, although it is likely that most of the autophagosome membrane is subsequently acquired from other sources.     

Induction of localized auxin response during spontaneous nodule development in Lotus japonicus

In leguminous plants, rhizobial infection of the epidermis triggers proliferation of cortical cells to form a nodule primordium. Recent studies have demonstrated that two classic phytohormones, cytokinin and auxin, have important functions in nodulation. The identification of these functions in Lotus japonicus was facilitated by use of the spontaneous nodule formation 2 (snf2) mutation of the putative cytokinin receptor LOTUS HISTIDINE KINASE 1 (LHK1). Analyses using snf2 demonstrated that constitutive activation of cytokinin signaling causes formation of spontaneous nodule-like structures in the absence of rhizobia and that auxin responses are induced in proliferating cortical cells during such spontaneous nodule development. Thus, cytokinin signaling positively regulates the auxin response. In the present study, we further investigated the induction of the auxin response using a gain-of-function mutation of Ca²⁺/calmodulin-dependent protein kinase (CCaMK) that causes spontaneous nodule formation. We demonstrate that CCaMK^T265D-mediated spontaneous nodule development is accompanied by a localized auxin response. Thus, a localized auxin response at the site of an incipient nodule primordium is essential for nodule organogenesis.     

Peculiar tooth renewal in a Jurassic ray-finned fish (Lepisosteiformes, †Scheenstia sp.)

Tooth replacement in vertebrates is extremely diverse, and its study in extinct taxa gives insights into the evolution of the different dental renewal modes. Based on μ-CT scans of a left lower jaw of the extinct fish †Scheenstia (Actinopterygii, Lepisosteiformes), we describe in detail a peculiar tooth replacement mode that is, as far as we could ascertain from the literature, unique among vertebrates. The formation of the replacement teeth comprises a 180° rotation of their acrodin cap that occurs intraosseously within bony crypts, and their setting up appears to be synchronous. We propose a model for the dental renewal process and identify complementary anatomical features visible in the tomography such as the junction between the different tooth-bearing bones (prearticular–coronoid and dentary), as well as cavities corresponding to intraosseous crypts, nervous and/or vascular canals. The location of the cavities and their subsequent identification (e.g. Meckel's cavity, mandibular sensory canal) help us to identify the function of pores visible on the bone surface and understand their relation to internal anatomical features. Finally, recognition of this tooth replacement mode raises the question of whether it is specific to †Scheenstia or related to a particular dentition type and thus potentially occurs in other lineages.