Axis elongation

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A context dependent combination of Wnt receptors controls axis elongation and leg development in a short germ insect

A context dependent combination of Wnt receptors controls axis elongation and leg development in a short germ insect

In conclusion, we have shown that a variety of tissue-specific outcomes are guided by a combinatorial code of three Wnt receptors and one Wnt co-receptor in Tribolium. We have identified the presegmental region in the Tribolium embryo as the necessary tissue for axis elongation at the Wnt receptor level and uncovered a network of signalling pathways within the PSR that controls this process. Our findings provide parallels to the involvement of FGF and Wnt signalling in vertebrate development (Dequéant and Pourquié, 2008). Both the FGF and Wnt signalling pathways are involved in axial patterning and serve as crucial regulators of animal embryogenesis. Future work will aim to identify the correct receptor-ligand combinations in the presegmental region and the appendages to disclose the complexity of the Wnt signalling pathway in short germ insects.

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Automated cell tracking identifies mechanically oriented cell divisions during Drosophila axis elongation

Automated cell tracking identifies mechanically oriented cell divisions during Drosophila axis elongation

segmentation errors (A) or corrected seeds and resulting segmented cells (B). Yellow arrowheads denote incorrect segmentation results in cells only partially within the field of view. (C) Percentage of correctly segmented cells when seeds were not edited (red) or when they were edited (blue). (D) Time necessary to correct the segmentation results by editing polygons (red) or seeds (blue). (C,D) 3629 cells were segmented in n=10 images from ten different embryos. (E) Ventral germband cells expressing Gap43:mCherry at different time points with respect to the onset of cell division during axis elongation, which occurred at 375 s. Anterior left, ventral midline across the centre (dashed line). (F-H) Segmentation of the images in E based on the seeds at t=0 s, directly copied over time (F), using optic flow to correct the position of the seeds (G), or using seed centering and optic flow (H). Arrowheads indicate cells whose areas were tracked in K. Examples are magnified on the right. White arrows track a cell that requires seed centering for proper segmentation. (I,J) Percentage of correctly segmented cells (I) and s.d. of the measured cell areas (J) when seeds are copied across time points (red), or transferred using optic flow (blue) or seed centering and optic flow (green). 1210 cells were segmented, tracked and measured in n=5 embryos, for a total of 6050 delineated cells. (K) Area of three cells indicated by arrowheads in F-H. Line and arrowhead colours correspond; continuous lines indicate the use of optical flow to propagate seeds in time, dashed lines show the results using seed copying. (C,D,I,J) Error bars, s.e.m. Scale bars: 20 μ m.

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Multi scale quantification of tissue behavior during amniote embryo axis elongation

Multi scale quantification of tissue behavior during amniote embryo axis elongation

Technological advances in microscopy have significantly improved our understanding of the morphogenetic events that control vertebrate axis formation, in particular by allowing observation of cellular behaviors over different stages of development. Pioneer studies using frog and fish embryos indicate that convergent extension is a central mechanism for the formation of the anterior part of the body axis of vertebrates (Shih and Keller, 1992a,b; Warga and Kimmel, 1990). During convergent extension, cells migrate and intercalate, which causes the narrowing of the tissues in one direction and their elongation in the perpendicular direction. This process is conserved in amniotes as it has been documented in chicken (Lawson and Schoenwolf, 2001) and mouse (Ybot-Gonzalez et al., 2007). In the second phase of elongation, which follows this first phase of large convergent extension movements, the axis extends without considerable change in its width. During this phase, the growth of the caudal region of the embryo is thought to be crucial to the elongation process. By deleting caudal structures and developing time-lapse imaging analysis to identify the regions controlling axis elongation in the avian embryo, we previously highlighted the crucial role of paraxial mesoderm in axis extension and provided evidence of the graded random motility of cells as a primary driver of elongation (Bénazéraf et al., 2010). Although this newly described collective behavior was demonstrated to be important in posterior tissue elongation, it does not explain how movements and growth are coordinated between different tissues in the posterior part of the elongating embryo.

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Axis elongation during Xenopus tail bud stage is regulated by GABA expressed in the anterior to mid neural tube

Axis elongation during Xenopus tail bud stage is regulated by GABA expressed in the anterior to mid neural tube

Strangely, we could not detect any effect on early embryos by the GABA treatment (Fig. 2 A,B; Supplementary Fig. S1) even though its inhibitors such as PTZ and PTX were active (Figs. 2-4; Supplementary Fig. S2), and GABA could rescue the effect by PTZ (Fig. 2). The reason why the GABA treatment had no activity in early embryogenesis might be because the speed of axis elon- gation in tail-bud embryos is already accelerated to a maximum velocity. In the case of convergent extension, some reports have suggested that elongation speed reaches a maximum. Both gain- and loss-of-function experiments for frizzled 7, which is considered to be a key regulator of convergent extension, lead to the same phenotypic effects such as inhibition of elongation in Xenopus (Djiane et al., 2000). Both loss- and gain-of Lrp6, which is a Wnt co-receptor, also inhibits convergent extension in Xenopus embryos and explants (Tahinci et al., 2007). Moreover, Dishevelled, which is a cytoplasmic phosphoprotein that acts directly downstream of frizzled receptors, is found to inhibit convergent extension in both gain- and loss-of-function studies (Wallingford et al., 2002). In zebrafish, the activity gradient of bone morphogenetic proteins (BMPs) regulates convergent extension during gastrulation, but the difference in embryo length and mesendoderm length is not detected in both ventralized chordino and dorsalized somitabun mutants (Myers et al., 2002). The same as for the case of conver- gent extension, the speed of axis elongation in the tail-bud may not be accelerated by any regulators. It is no wonder that intact speed cannot be increased because the elongation should be cooperative and followed with various other events and contributes to build a functional and well-organized stereostructure inside the embryo.

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Wnt5a and Wnt11 regulate mammalian anterior posterior axis elongation

Wnt5a and Wnt11 regulate mammalian anterior posterior axis elongation

In addition to reduced migration of NPCs, we propose that reduced A-P axis elongation is also caused by reduced paraxial mesoderm formation in the absence of Wnt5a and Wnt11 (Fig. 5). In the PS of the late gastrula embryo there is continuous EMT (Arnold and Robertson, 2009). Cells ingress and then delaminate from the epiblast ectoderm to form a loose mesenchyme that will later form the paraxial mesoderm. In this process, the ingressing cells turn off the Sox2 enhancer N1, whereas Tbx6 expression is upregulated (Takemoto et al., 2011). Once formed, the mesoderm is then separated from the neural ectoderm by a layer of FN-containing basement membrane. In Wnt5a −/− ; Wnt11 −/− embryos, reduced T expression and expanded Sox2 expression suggest that reduced paraxial mesoderm formation might also be caused by incomplete EMT. FN deposition requires dynamic cell rearrangements and the increase in cell adhesion that we observed in this region might thus be responsible for the lack of FN (Dzamba et al., 2009). The defective EMT therefore led secondarily to incomplete formation of the FN-containing basement membrane, reduced axial mesoderm migration causing a thinner notochord, and reduced paraxial mesoderm migration causing the formation of smaller and irregular somites. Therefore, in this study we have identified that Wnt5a and Wnt11 are required to control EMT in the late gastrula embryo.

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Ezh2 regulates anteroposterior axis specification and proximodistal axis elongation in the developing limb

Ezh2 regulates anteroposterior axis specification and proximodistal axis elongation in the developing limb

those of control littermates (Fig. 3A). These findings correlated with those from later stages as these mutants survived well into adulthood. Skeletal preparations and faxitron X-ray from the neonatal period through to adulthood clearly demonstrated that the mutants exhibited shortened proximodistal limb segments. The zeugopod (forearm) segment was most severely shortened, whereas the autopod (hand) was relatively preserved (Table 1). Although digit one was shortened, the first metacarpal was present (Fig. 3A). This disproportionate shortening resembles human mesomelia (Jones, 2006) as well as the phenotype of Hoxa11;Hoxd11 double mutants to some degree (Davis et al., 1995). Therefore, the skeletal phenotype derived from the deletion of Ezh2 using Prx1::Cre primarily resulted in shortened segment lengths, affecting the anteroposterior axis to a far lesser extent than that obtained using T::Cre.

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Wnt3alinks left right determination with segmentation and
anteroposterior axis elongation

Wnt3alinks left right determination with segmentation and anteroposterior axis elongation

The anteroposterior (AP) body axis is the first axis to be established during the formation of the mammalian body plan. The left-right (LR) axis is specified last, and is oriented orthogonally to the pre-existing AP and DV axes. The specification and coordination of all three vertebrate body axes is controlled by a small group of cells known as the Spemann- Mangold organizer (Niehrs, 2004). A transient structure, termed the node, is generally considered to be the murine equivalent of the Spemann-Mangold organizer; however, the node first forms at the anterior end of the primitive streak of the gastrulating embryo on embryonic day (E) 7.5, well after AP polarity has been established. The timing of node formation correlates well with LR axis specification, and with the beginning of somitogenesis and the development of the trunk. Somitogenesis generates the segmental structures of the trunk and is a major morphogenetic force driving the elongation of the AP axis. The node plays an important role in trunk development as node ablation results in the loss of LR and dorsoventral (DV) polarity, retarded somite formation and shortened trunks (Davidson et al., 1999). Thus, the node functions as a trunk organizer, coordinating axis determination with trunk elongation.

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Cell polarity and morphogenesis : functions and mechanisms of cell divisions in vertebrate gastrulation

Cell polarity and morphogenesis : functions and mechanisms of cell divisions in vertebrate gastrulation

Our results demonstrate the importance of non-canonical Wnt/PCP signaling in controlling cell division orientation and axis elongation in the early zebrafish embryo. Given that the PCP pathway has been shown to regulate spindle orientation during asymmetric cell division in C. elegans and Drosophila (Gho and Schweisguth, 1998; Schlesinger et al., 1999), our findings suggest that it plays an evolutionarily conserved role in vertebrates. Oriented cell division is a common feature of many vertebrate developmental processes, ranging from the generation of cell layers (Chalmers et al., 2003), to primitive streak extension (Wei and Mikawa, 2000) and neurogenesis (Das et al., 2003). An interesting and testable possibility is that these processes have a similar dependence on PCP signaling. Together with our existing knowledge of the various roles of PCP signaling, our results highlight the central nature of the PCP pathway in

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Whole population cell analysis of a landmark rich mammalian epithelium reveals multiple elongation mechanisms

Whole population cell analysis of a landmark rich mammalian epithelium reveals multiple elongation mechanisms

Tissue elongation is a fundamental component of developing and regenerating systems. Although localised proliferation is an important mechanism for tissue elongation, potentially important contributions of other elongation mechanisms, specifically cell shape change, orientated cell division and cell rearrangement, are rarely considered or quantified, particularly in mammalian systems. Their quantification, together with proliferation, provides a rigorous framework for the analysis of elongation. The mammalian palatal epithelium is a landmark-rich tissue, marked by regularly spaced ridges (rugae), making it an excellent model in which to analyse the contributions of cellular processes to directional tissue growth. We captured confocal stacks of entire fixed mouse palate epithelia throughout the mid- gestation growth period, labelled with membrane, nuclear and cell proliferation markers and segmented all cells (up to ~20,000 per palate), allowing the quantification of cell shape and proliferation. Using the rugae as landmarks, these measures revealed that the so- called growth zone is a region of proliferation that is intermittently elevated at ruga initiation. The distribution of oriented cell division suggests that it is not a driver of tissue elongation, whereas cell shape analysis revealed that both elongation of cells leaving the growth zone and apico-basal cell rearrangements do contribute significantly to directional growth. Quantitative comparison of elongation processes indicated that proliferation contributes most to elongation at the growth zone, but cell shape change and rearrangement contribute as much as 40% of total elongation. We have demonstrated the utility of an approach to analysing the cellular mechanisms underlying tissue elongation in mammalian tissues. It should be broadly applied to higher-resolution analysis of links between genotypes and malformation phenotypes.

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WORK OF RUPTURE AS AN INDICATOR TO ABRASION RESISTANCEPROPERTY OF SELECTED WOVEN FABRICS

WORK OF RUPTURE AS AN INDICATOR TO ABRASION RESISTANCEPROPERTY OF SELECTED WOVEN FABRICS

Work of rupture, sometimes called toughness, is the energy needed to break a fiber or fabric. It gives a measureof the ability of the material to withstand sudden shocks of given energy. The units for this are joules. As a result, when a mass (m), attached to a textile specimen, is dropped from a height (h), it acquires akinetic energy, equal to (mgh). Accordingly, if this energy is greater than the work of rupture, breakage will occur. On the contrary, if the energy is less, the specimen will withstand the shock. Thusthe work of rupture is the appropriate quantity to consider in such events as theopening of a parachute, a falling climber being stopped by a rope and all the occasionswhen sudden shocks are liable to cause breakage. It should be noted that the significant feature in the application of the work of rupture is that the shock contains a given amount of energy; the fact that it occurs rapidly is not directly relevant, though the rate of loading will affect the value of the work of rupture. In comparing materials to see which is least likely to break, it is important to consider the conditions under which breakage would occur and then to decide which quantity is the appropriate one to use. For instance, it is no use for a climbing rope to have a high tenacity if its work of rupture is low. In actual practice, more complicated tensile conditions may occur, for example a sudden shock may be applied to a specimen already carrying a steady load. It should also be remembered that breakage may occur as a result of the repeated applications of forces, not necessarily along the fiber axis.[4]–[6]

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The Dual Activity Responsible for the Elongation and Branching of β (1,3) Glucan in the Fungal Cell Wall

The Dual Activity Responsible for the Elongation and Branching of β (1,3) Glucan in the Fungal Cell Wall

Gas1p and Bgl2p are among the best-characterized glycosyltransferases (48). Our study data have allowed a better understanding of their role. The phenotypes of the single gas1Δ and double gas1Δ bgl2Δ mutants the we analyzed were in agreement with the observations by Plotnikova et al. (48) indicating that Gas1p and Bgl2p are func- tionally related. Bgl2p is one of the most abundant cell wall proteins and is able to introduce ␤ -(1,6)-linkages on ␤ -(1,3)-glucan (24). However, Bgl2p preferred shorter ␤ -(1,3)-oligomers, as there was a decrease in its activity upon an increase in the length of the oligomeric substrate (see Fig. S5 in the supplemental material). Initially, recom- binant Gas1p showed ␤ -(1,3)-elongase activity followed by the introduction of ␤ -(1,6)- linkages on the ␤ -(1,3)-glucan, suggesting that branching activity of Gas1p is depen- dent on the elongation of the ␤ -(1,3)-glucan chain that generates an appropriate substrate for branching. In support of this hypothesis, with ␤ -(1,3)-oligomers of greater chain length, there was a shorter incubation time before the appearance of branches. There was a significant increase in the branching when Gas1p and Bgl2p were incu- bated together with ␤ -(1,3)-oligomers, suggesting their cooperative branching activity. Bgl2p preferring shorter ␤ -(1,3)-oligomers and Gas1p elongating ␤ -(1,3)-oligomers prior to its ␤ -(1,6)-branching activity suggest the hypothesized mechanism of branching activity depicted in Fig. 8. Supporting our model, the branching signal seen in the LamA-digested AI fraction from the gas1Δ mutant could be destroyed completely upon FIG 8 Mechanism of S. cerevisiae cell wall ␤ -(1,3)-glucan branching—a model. Short linear ␤ -(1,3)- glucans are synthesized by a plasma membrane-bound glucan synthase complex using UDP-glucose as the substrate. The short linear glucans entering cell wall space undergo further elongation by Gas1p or are linked to another short ␤ -(1,3)-glucan by Bgl2p through a linear ␤ -(1,6)-linkage. Gas1p utilizes self-elongated glucan for branching, or it can elongate a Bgl2p-catalyzed product which contains a free carbon(C)-3 hydroxyl ( ⫺ OH) group(s) on the ␤ -(1,6)-linked glucose unit. In the following step, Gas1p further elongates and branches ␤ -(1,3)-glucan, resulting in the formation of a ramified ␤ -(1,3)-glucan.

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Development of an Internet Addressable Pneumatically Controlled Instrument for Applying Strain to Cells In-Vitro

Development of an Internet Addressable Pneumatically Controlled Instrument for Applying Strain to Cells In-Vitro

The pressure seen by the transducer is not necessarily the same pressure as that in the chamber. In Bigras paper “Nonlinear Observer for Pneumatic System With Non Negligible Connection Port Restriction”, he compares the pressure variation in the chambers and in the pipe. According to his research there is a large degree of pressure difference from the pressure in the chamber and pressure in the pipe pressure connected to the transducer. To accurately control the chamber pressure a relations between the sensor and the chamber must be developed. In the journal article, “In vitro strain-induced endothelial cell dysfunction determined by DNA synthesis” and earlier work performed by Flexcell International calibration curves where derived by placing dots 1mm apart across the diameter of the membranes. Calibrated pressure was applied to the membranes and the elongation was measures using optical measuring devices. Equation 12 through Equation 21 is the resulting calibration equations provided by Flexcell International.

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Effects of soil resistance to root penetration on leaf expansion in wheat

Effects of soil resistance to root penetration on leaf expansion in wheat

Baake and Buff (1986) avoid modelling cell division and expansion in the division zone by introducing an injection function, which adds new cells to a cell file at the base o f the elongation only zone. Lopez Säez et al. (1975) assume constancy of the number of cells in the division zone and the duration of the cell cycle and assume proliferating cells to be of constant length, regardless of their progression through the cell cycle. Arkebauer and Norman (1995a) propose a simple model in which the size of proliferating cells increases from 600 to 1200 pm. Cell division occurs by definition upon reaching the upper limit. The duration of the cell cycle (growth from 600 to 1200 pm 3) of dividing cells (and thereby indirectly also cell expansion rates) is determined by an empirical dependence of cell cycle duration on temperature. The number of proliferative cells in their model varies throughout leaf development, as function of daughter ratio (the proportion of cells that will remain proliferative (capable of dividing again) after each division) vs time. When this daughter ratio becomes 0, leaf expansion ceases after all cells have completed their expansion. Bertaud et. al. (1986) also modelled cell expansion during progression through the cell cycle. Their model allows for random variation in the length at which cells divide. According to this model cell division occurs at a random length between 2*Z^TUn(;c) and Lmm{x) , with Lmm(x) and Lmax(x) the minimal and maximal lengths observed in experiments with roots at location x. The length and number of cells in the division zone in this model are not input parameters; they are derived from cell division rules and empirically determined distributions of spatial velocity and cell length.

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FtsZ Dependent Elongation of a Coccoid Bacterium

FtsZ Dependent Elongation of a Coccoid Bacterium

reus cells are approximately spherical, and there are no previous reports of a sphere-to-rod transition in cocci. Putative mecha- nisms to generate elongated cells of S. aureus include expressing an actin-like cytoskeleton or inhibiting cell division or septal cell wall synthesis. However, expression of B. subtilis MreB (23) or Mbl (our unpublished observations) does not result in elongated S. au- reus cells. Similarly, mutations that reduce FtsZ function can pro- duce enlarged spherical cells (24, 25), showing that the peripheral PG synthesis that occurs in S. aureus does not support elongation (10). Serendipitously, while characterizing PC190723-resistant S. aureus mutant M5 (22), which carries a G-to-D substitution at the 193rd residue of FtsZ within helix 7, we noticed the presence of cells that were not spherical. In order to examine the shape alter- ations of this mutant in more detail, we labeled the COL wild-type and M5 mutant strains with fluorescently modified vancomycin (Van-FL, which labels the entire cell wall in S. aureus) and the DNA dye Hoechst 33342. Superresolution imaging of the labeled cells by structured illumination microscopy (SIM) confirmed the presence of cells with altered morphology, including curved elon- gated cells (Fig. 1a). Despite the substantial morphological changes, M5 mutant cells were able to grow reasonably well, albeit more slowly than parental strain COL grown in batch culture (47 versus 25 min, respectively, see Fig. S1 in the supplemental mate- rial).

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Innate immune activation of astrocytes impairs neurodevelopment via upregulation of follistatin-like 1 and interferon-induced transmembrane protein 3

Innate immune activation of astrocytes impairs neurodevelopment via upregulation of follistatin-like 1 and interferon-induced transmembrane protein 3

How does Fstl1 impair morphologic neuronal develop- ment? The role of Fstl1 is controversial because some find- ings suggest that Fstl1 functions as a pro-inflammation cytokine [24, 30–32], but others suggest a role as an anti-inflammatory cytokines [25, 33, 34]. Fstl1 protects cells from apoptosis in heat failure through Fstl1 receptor disco-interacting protein 2 (DIP2), which activates the Akt signaling pathway [35, 36]. Some reports suggest that Fstl1 works as a scavenger by sequestering bone morphogenetic protein (Bmp)-4, which results in blockage of BMP signal- ing during development [37 – 39]. The addition of both Fstl1 and ACM suppressed neurite outgrowth, but addition of Fstl1 alone did not. Co-treatment of Fstl1 with Bmp-4 unaffected to neurites elongation (Additional file 6: Figure S6). A possible explanation is that secreted Fstl1 from astrocytes may inhibit signals promoting neurite outgrowth BMP-independent manner. In DRG neurons, Fstl1 impairs neurite elongation through activation of Na/K-ATPase [40]. The similar mechanism might oper- ate in the hippocampal neurons. In this study, we could not address the role of Fstl1 in vivo because of tech- nical limitation; it is hard to manipulate gene expres- sion specifically in astrocytes of neonatal mice. Thus, further studies are needed to disclose the role of Fstl1 in polyI:C-induced neuronal impairment.

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Cyclic Rhamnosylated Elongation Factor P Establishes Antibiotic Resistance in Pseudomonas aeruginosa

Cyclic Rhamnosylated Elongation Factor P Establishes Antibiotic Resistance in Pseudomonas aeruginosa

The role of posttranslational modifications in determining the activities of translation factors is less extensively described in bac- teria than in eukaryotes. Phosphorylation has been shown to neg- atively regulate the activities of elongation factor Tu (EF-Tu) in Mycobacterium tuberculosis (11) and Bacillus subtilis (12) and of glutamyl-tRNA synthetase in E. coli (13, 14), thereby limiting pro- tein synthesis during specific phases of bacterial growth and differentiation. In E. coli and S. enterica EF-P, the (R)-␤-Lys mod- ification helps prevent poly-proline-induced translational stalling by increasing EF-P’s binding affinity for stalled ribosomes, thereby maintaining protein homeostasis and ensuring the proper stoichiometry of different components of the proteome (7, 15– 18). Eukaryotes have a conserved homolog of EF-P, known as eukaryotic initiation factor 5A (eIF5A), that also functions to al- leviate poly-proline pausing but is posttranslationally modified with hypusine (19, 20). While EF-P is universally conserved in bacteria, the pathway for its posttranslational modification is not, prompting a search for alternative modification pathways.

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Purification and characterization of elongation factor 2 (EF2) and cyclic AMP-independent protein kinases from soybean (Glycine max, L) cotyledons.

Purification and characterization of elongation factor 2 (EF2) and cyclic AMP-independent protein kinases from soybean (Glycine max, L) cotyledons.

the embryonic axis. At the time of germination, cotyledons possess an active protein synthetic machinery and assist in the synthesis of food to some extent and mobilize stored food material in an available form to the growing embryo. Growth and expansion of the cotyledons in size during germination are mainly due to cell enlargement and not cell division. During advanced stages of seed germination, metabolism in cotyledons consists primarily of catabolic events. As the seedling grows older and becomes independent, cotyledons wither and fall off from the parent plant. Thus cotyledons in early stages of seed germina­ tion possess both anabolic and catabolic activity, while catabolic processes become most predominant as they age. Therefore, cotyledons serve as a unique system to study biochemical changes during the pro­ cess of senescence or aging.

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Root hydrotropism is controlled via a cortex specific growth mechanism

Root hydrotropism is controlled via a cortex specific growth mechanism

a Relative elongation rate and b curvature of a hydrotropically bending root during the first 5 h after transfer to a split-agar plate with 400 mM sorbitol. Solid lines show the trajectories of points equally spaced at time zero. Representative data from four independent repeats shown. c Modelling the hydrotropism response: The transition between the meristem and elongation zone is marked by a drop in yield stress leading to a rise in elongation rate (centre); the large yield stress y 0 in the meristem inhibits cell expansion; cortical cells on the dry side of the root

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Rho GTPase controls Drosophila salivary gland lumen size through regulation of the actin cytoskeleton and Moesin

Rho GTPase controls Drosophila salivary gland lumen size through regulation of the actin cytoskeleton and Moesin

All measurements of lumen length, lumen width, apical domain elongation ratio, apical-basal axis length and number of nuclei were performed with LSM 510 Image Browser software (Carl Zeiss). Lumen length measurements were based on E-cad immunofluorescence staining of stage 13 embryos, from the proximal tip to the distal tip of gland lumens. Lumen width was measured in the middle of the proximal one third of the gland, approximately eight cells away from the proximal end of the gland (supplementary material Fig. S1). Apical domain elongation ratio of an individual gland cell was measured according to E-cad immunofluorescence staining of stage 12 embryos. Elongation ratio represents the ratio of a single measurement of the longest length of the apical domain oriented along the proximal-distal axis to a single measurement of the longest length of the apical domain along the dorsal- ventral axis (Pirraglia et al., 2010). Measurements of apical domain elongation ratio were performed with the eight most proximal cells in each gland. Apical-basal axis length was visualized using Neurotactin and DaPKC staining of stage 12 embryos, and was measured from the basal to the apical membrane of the four most proximal cells at the anterior side of each gland. The number of nuclei surrounding the lumen was counted based on orthogonal views of E-cad- and dCREB-A-stained stage 12 embryos, in the proximal one third of the gland, approximately eight cells away from the proximal end. Statistical analysis was conducted using Microsoft Excel (Microsoft, Redmond, WA, USA) and STATA software (Statacorp, TX, USA).

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Evaluation of Tensile Properties of SiC/SiC Composites with Miniaturized Specimens

Evaluation of Tensile Properties of SiC/SiC Composites with Miniaturized Specimens

Not all CMCs follow the Weibull theory, due to the presence of multiple fracture modes, even though the constituent materials are brittle ceramics. We identified significant width effect on tensile strength, tensile elastic modulus and PLS. They are closely dependent on the axial fiber volume fraction and differed in specimen widths. Data scatter tended to increase in shorter gauge widths. In general, these data are adequately normalized by simple model prediction using the fiber volume content for any size of the composites. However, strength reduction by the stitching effect needs to be avoided in shorter widths. In conclusion, specimen width is recommended to be 3.0–4.0 mm to include a couple of fiber bundles. In contrast, off-axis tensile strength is decreased in narrower gauge widths because of the size- related change of fracture mode from the mixed mode of in- plane shear to fiber detachment. Therefore specimen gauge width should be 6.0–10.0 mm or larger for off-axis tensile testing. Specimen thickness has a minor effect on tensile strength in the range of 1.0–3.0 mm. However, thinner specimens (<1:0 mm) tend to decrease tensile strength, resulting in difficult testing in normal operation. Porous composites such as chemical vapor infiltrated (CVI) SiC/SiC composites contain many submicron inter-laminar pores; for those we do not recommend using test specimens thinner than 1.0 mm. Specimen thickness of 1.5–2.0 mm is recommended to reduce the irradiation volume. No meaningful length effect, which was found in tensile strength in 30.0–50.0 mm- long specimens with 15.0–20.0 mm gauge length under the constant axial fiber volume fraction, is a great advantage to design the miniature specimen.

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