Rab13-dependent trafficking of RhoA is required for directional migration and angiogenesis

Angiogenesis requires concomitant remodeling of cell junctions and migration, as exemplified by recent observations of extensive endothelial cell movement along growing blood vessels. We report that a protein complex that regulates cell junctions is required for VEGF-driven directional migration and for angiogenesis in vivo. The complex consists of RhoA and Syx, a RhoA guanine exchange factor cross-linked by the Crumbs polarity protein Mupp1 to angiomotin, a phosphatidylinositol-binding protein. The Syx-associated complex translocates to the leading edge of migrating cells by membrane trafficking that requires the tight junction recycling GTPase Rab13. In turn, Rab13 associates with Grb2, targeting Syx and RhoA to Tyr(1175)-phosphorylated VEGFR2 at the leading edge. Rab13 knockdown in zebrafish impeded sprouting of intersegmental vessels and diminished the directionality of their tip cells. These results indicate that endothelial cell mobility in sprouting vessels is facilitated by shuttling the same protein complex from disassembling junctions to the leading edges of cells.     

Multiple Roles of the SO42?/Cl?/OH? Exchanger Protein Slc26a2 in Chondrocyte Functions

Mutations in the SO₄²⁻/Cl⁻/OH⁻ exchanger Slc26a2 cause the disease diastrophic dysplasia (DTD), resulting in aberrant bone development and, therefore, skeletal deformities. DTD is commonly attributed to a lack of chondrocyte SO₄²⁻ uptake and proteoglycan sulfation. However, the skeletal phenotype of patients with DTD is typified by reduction in cartilage and osteoporosis of the long bones. Chondrocytes of patients with DTD are irregular in size and have a reduced capacity for proliferation and terminal differentiation. This raises the possibility of additional roles for Slc26a2 in chondrocyte function. Here, we examined the roles of Slc26a2 in chondrocyte biology using two distinct systems: mouse progenitor mesenchymal cells differentiated to chondrocytes and freshly isolated mouse articular chondrocytes differentiated into hypertrophic chondrocytes. Slc26a2 expression was manipulated acutely by delivery of Slc26a2 or shSlc26a2 with lentiviral vectors. We demonstrate that slc26a2 is essential for chondrocyte proliferation and differentiation and for proteoglycan synthesis. Slc26a2 also regulates the terminal stage of chondrocyte cell size expansion. These findings reveal multiple roles for Slc26a2 in chondrocyte biology and emphasize the importance of Slc26a2-mediated protein sulfation in cell signaling, which may account for the complex phenotype of DTD.     

Larval feeding status regulates the transcript levels of genes encoding PTTH and allatoregulatory peptides in silkworm Bombyx mori

In Bombyx mori, two dorsolateral neurosecretory cells (NSCs) in each of the two brain lobes have been identified as prothoracicotropic hormone (PTTH) producing cells. This neuropeptide in insects stimulates the prothoracic gland for the synthesis and release of ecdysone, responsible for the molting events. Allatotropin (AT) and allatostatin (AST) are allatoregulatory neuropeptides that regulate juvenile hormone biosynthesis. Here, by using RT-qPCR, we showed that in B. mori, nutritional stress modulates the mRNA expression of AT and AST-C (allatostain type C) in the central nervous system consisting of the brain lobes and all the associated ganglia. Using whole-mount in situ hybridization, we showed that the feeding status of Bombyx larvae also influences the expression of PTTH in the NSCs of the brain. Food deprivation significantly decreased the mRNA expression levels of PTTH in larvae at active or terminal growth period. Further, we showed that insulin modulates the expression level of PTTH. However, its action was dependent on the feeding status of the larvae. At feeding, the insulin decreased the PTTH expression level, while at food deprivation, the insulin increased the PTTH expression level. The data thus indicates that larval feeding status plays an important role in altering the mRNA expression levels of allatoregulatory peptide genes and PTTH.     

The Expression of Connexins and SOX2 Reflects the Plasticity of Glioma Stem-Like Cells

Glioblastoma (GBM) is the most malignant primary brain tumor, with an average survival rate of 15 months. GBM is highly refractory to therapy, and such unresponsiveness is due, primarily, but not exclusively, to the glioma stem-like cells (GSCs). This subpopulation express stem-like cell markers and is responsible for the heterogeneity of GBM, generating multiple differentiated cell phenotypes. However, how GBMs maintain the balance between stem and non-stem populations is still poorly understood. We investigated the GBM ability to interconvert between stem and non-stem states through the evaluation of the expression of specific stem cell markers as well as cell communication proteins. We evaluated the molecular and phenotypic characteristics of GSCs derived from differentiated GBM cell lines by comparing their stem-like cell properties and expression of connexins. We showed that non-GSCs as well as GSCs can undergo successive cycles of gain and loss of stem properties, demonstrating a bidirectional cellular plasticity model that is accompanied by changes on connexins expression. Our findings indicate that the interconversion between non-GSCs and GSCs can be modulated by extracellular factors culminating on differential expression of stem-like cell markers and cell-cell communication proteins. Ultimately, we observed that stem markers are mostly expressed on GBMs rather than on low-grade astrocytomas, suggesting that the presence of GSCs is a feature of high-grade gliomas. Together, our data demonstrate the utmost importance of the understanding of stem cell plasticity properties in a way to a step closer to new strategic approaches to potentially eliminate GSCs and, hopefully, prevent tumor recurrence.     

Pro Free Will Priming Enhances “Risk-Taking” Behavior in the Iowa Gambling Task,but Not in the Balloon Analogue Risk Task: Two Independent Priming Studies

Studies indicated that people behave less responsibly after exposure to information containing deterministic statements as compared to free will statements or neutral statements. Thus, deterministic primes should lead to enhanced risk-taking behavior. We tested this prediction in two studies with healthy participants. In experiment 1, we tested 144 students (24 men) in the laboratory using the Iowa Gambling Task. In experiment 2, we tested 274 participants (104 men) online using the Balloon Analogue Risk Task. In the Iowa Gambling Task, the free will priming condition resulted in more risky decisions than both the deterministic and neutral priming conditions. We observed no priming effects on risk-taking behavior in the Balloon Analogue Risk Task. To explain these unpredicted findings, we consider the somatic marker hypothesis, a gain frequency approach as well as attention to gains and / or inattention to losses. In addition, we highlight the necessity to consider both pro free will and deterministic priming conditions in future studies. Importantly, our and previous results indicate that the effects of pro free will and deterministic priming do not oppose each other on a frequently assumed continuum.     

Duration of strike-induced chemosensory searching in long-term captive rattlesnakes at national zoo,audubon zoo,and San Diego Zoo

Rattlesnakes typically strike and release adult rodent prey. Striking is followed by a sustained, high rate of tongue flicking that guides the snake to the envenomated, dead prey. Wild-caught rattlesnakes exhibited this chemosensory searching for about 2.5 h, and the present study demonstrated that long-term captive rattlesnakes (Crotalus atrox, C durissus, C horridus, C vegrandis, C unicolor) at three zoos did the same. Because these zoo-raised snakes had always been offered dead rodents and because the snakes had become accustomed to ingesting them without striking, the present snakes had rarely exercised their innate predatory repertoires. The duration of chemosensory searching in these snakes indicates that this important aspect of the predatory repertoire had not been degraded as a consequence of long-term captive husbandry.     

Insertion of inverted Ter sites into the terminus region of the Escherichia coli chromosome delays completion of DNA replication and disrupts the cell cycle

To investigate the co-ordination between DNA replication and cell division, we have disrupted the DNA replication cycle of Escherichia coli by inserting inverted Ter sites into the terminus region to delay completion of the chromosome. The inverted Ter sites (designated Inv Ter :: spc ^r) were initially inserted into the chromosome of a Δ tus strain to allow unrestrained chromosomal replication. We then introduced a functional tus gene by transforming the Inv Ter :: spc ^r strain with a plasmid carrying the tus gene under control of an arabinose-inducible promoter. In the presence of 0.2% arabinose, the cells formed long filaments, suggesting that activation of the inverted Ter sites by Tus arrested DNA replication and delayed the onset of cell division. Induction of sfiA , a gene in the SOS regulon, was observed following arrest of DNA replication; however, when a sfiB114 allele was introduced into Inv Ter :: spc ^r strain, long filaments were still formed, suggesting that the sfi -independent pathway also caused filamentation. Either recA :: cam ^r or lexA3 alleles suppressed filamentation when introduced in the Inv Ter strain. Interestingly, in both the recA :: cam ^r and lexA3 mutants, virtually all cells had a nucleoid, suggesting that cell division was proceeding even though DNA replication was not complete. These results suggest that DNA replication and cell division are uncoupled when recA is inactivated or when genes repressed by LexA cannot be induced.     

Branching design of the bronchial tree based on a diameter-flow relationship

Kitaoka, Hiroko, and Béla Suki. Branching designof the bronchial tree based on a diameter-flow relationship.J. Appl. Physiol. 82(3): 968-976, 1997.We propose a method for designing the bronchial tree where thebranching process is stochastic and the diameter(d) of a branch is determined by itsflow rate (Q). We use two principles: the continuumequation for flow division and a power-law relationship betweend and Q, given by Q ~ dⁿ,where n is the diameter exponent. The value ofn has been suggested to be ~3. Weassume that flow is divided iteratively with a random variable for theflow-division ratio, defined as the ratio of flow in the branch to thatin its parent branch. We show that the cumulative probabilitydistribution function of Q, P(>Q) is proportional to Q¹. Weanalyzed prior morphometric airway data (O. G. Raabe, H. C. Yeh, H. M. Schum, and R. F. Phalen, Report No.LF-53, 1976) and found that the cumulative probabilitydistribution function of diameters, P(>d), isproportional to dⁿ, which supportsthe validity of Q ~ dⁿ sinceP(>Q) ~ Q¹. This allowed us toassign diameters to the segments of the flow-branching pattern. Wemodeled the bronchial trees of four mammals and found that theirstatistical features were in good accordance with the morphometricdata. We conclude that our design method is appropriate for robustgeneration of bronchial tree models.

     

Dynamic properties of lung parenchyma: mechanical contributions of fiber network and interstitial cells

Yuan, Huichin, Edward P. Ingenito, and Béla Suki.Dynamic properties of lung parenchyma: mechanical contributions offiber network and interstitial cells. J. Appl.Physiol. 83(5): 1420-1431, 1997.We investigatedthe contributions of the connective tissue fiber network andinterstitial cells to parenchymal mechanics in a surfactant-freesystem. In eight strips of uniform dimension from guinea pig lung, weassessed the storage (G) and loss (G") moduli by usingpseudorandom length oscillations containing a specially designed set ofseven frequencies from 0.07 to 2.4 Hz at baseline, during methacholine(MCh) challenge, and after death of the interstitial cells.Measurements were made at mean forces of 0.5 and 1 g and strainamplitudes of 5, 10, and 15% and were repeated 12 h later in the same,but nonviable samples. The results were interpreted using a linearviscoelastic model incorporating both tissue damping (G) and stiffness(H). The G and G" increased linearly with the logarithmof frequency, and both G and H showed negative strain amplitude andpositive mean force dependence. After MCh challenge, the G andG" spectra were elevated uniformly, and G and H increased by<15%. Tissue stiffness, strain amplitude, and mean force dependencewere virtually identical in the viable and nonviable samples. The G andhence energy dissipation were ~10% smaller in the nonviable samplesdue to absence of actin-myosin cross-bridge cycling. We conclude thatthe connective tissue network may also dominate parenchymal mechanicsin the intact lung, which can be influenced by the tone or contractionof interstitial cells.