Large Protrusions Research Articles

The Investigation of the Influence of Low-Temperature Plasma and Steam Sterilization on the Properties of Track Membranes Made of Polyethylene Terephthalate

The influence of modification by low-temperature atmospheric-pressure plasma and steam sterilization on the properties of track membranes based on polyethylene terephthalate is studied. It is found that the action of hot steam under pressure changes the topography of the surface of the membranes with the formation of artifacts in the form of large oval-shaped protrusions with a height of 300–400 nm and a density of up to 0.007 protrusions/μm2 on the surface, increases the surface roughness by 40% and the wetting angle by 9°–18° for the initial membranes and by 36.8°–39.6° for the membranes modified in plasma, and decreases their surface energy to the initial value of 33 mJ/m2. Despite the morphological and structural changes in the surface, sterilization by hot steam under pressure does not lead to any noticeable change in the surface charge and ζ potential of the track membranes. Hot steam under pressure does not promote further crystallization of the membrane, keeping the polymer with a crystalline phase of 40–42%. Thus, to preserve the properties acquired by the membrane after the plasma treatment, it is necessary to search for a different sterilization method (gamma radiation, ethylene oxide sterilization).

Frequency-modulation Kelvin probe force microscopy under tapping mode operation for surfaces with large protrusions

Kelvin probe force microscopy (KPFM) is a useful technique for simultaneously visualizing topography and contact potential difference (CPD). Although frequency-modulation (FM) KPFM has high spatial resolution and sensitivity, it is not readily applicable to measuring large protrusions owing to the instability of the feedback condition. Here we investigate the combined use of amplitude-modulation and FM for tip-sample distance control and electrostatic force detection, respectively. The proposed method enabled simultaneous acquisition of topography and CPD images of gold nanoparticles on a Nb-doped TiO2(100) surface. The effect of the tip shape and tilt angle on the CPD images is also discussed.

Thermocapillary stress and meniscus curvature effects on slip lengths in ridged microchannels

Pressure-driven flow in the presence of heat transfer through a microchannel patterned with parallel ridges is considered. The coupled effects of curvature and thermocapillary stress along the menisci are captured. Streamwise and transverse thermocapillary stresses along menisci cause the flow to be three-dimensional, but when the Reynolds number based on the transverse flow is small the streamwise and transverse flows decouple. In this limit, we solve the streamwise flow problem, i.e. that in the direction parallel to the ridges, using a suite of asymptotic limits and techniques – each previously shown to have wide ranges of validity thereby extending results by Hodes et al. (J. Fluid Mech., vol. 814, 2017, pp. 301–324) for a flat meniscus. First, we take the small-ridge-period limit, and then we account for the curvature of the menisci with two further complementary limits: (i) small meniscus curvature using boundary perturbation; (ii) arbitrary meniscus curvature but for small slip (or cavity) fractions using conformal mapping and the Poisson integral formula. Heating and cooling the liquid always degrade and enhance (apparent) slip, respectively, but their effect is greatest for large meniscus protrusions, with positive protrusion (into the liquid) being the most sensitive. For strong enough heating the solutions become complex, suggesting instability, with large positive protrusions transitioning first.

Organoids of Human Endometrium: A Powerful In Vitro Model for the Endometrium-Embryo Cross-Talk at the Implantation Site.

Embryo implantation has been defined as the “black box” of human reproduction. Most of the knowledge on mechanisms underlining this process derives from animal models, but they cannot always be translated to humans. Therefore, the development of an in vitro/ex vivo model recapitulating as closely and precisely as possible the fundamental functional features of the human endometrial tissue is very much desirable. Here, we have validated endometrial organoids as a suitable 3D-model to studying epithelial endometrial interface for embryo implantation. Transmission and scanning electron microscopy analyses showed that organoids preserve the glandular organization and cell ultrastructural characteristics. They also retain the responsiveness to hormonal treatment specific to the corresponding phase of the menstrual cycle, mimicking the in vivo glandular-like aspect and functions. Noteworthy, organoids mirroring the early secretive phase show the development of pinopodes, large cytoplasmic apical protrusions of the epithelial cells, traditionally considered as reliable key features of the implantation window. Moreover, organoids express glycodelin A (GdA), a cycle-dependent marker of the endometrial receptivity, with its quantitative and qualitative features accounting well for the profile detected in the endometrium in vivo. Accordingly, organoids deriving from the eutopic endometrium of women with endometriosis show a GdA glycosylation pattern significantly different from healthy organoids, confirming our prior data on endometrial tissues. The present results strongly support the idea that organoids may closely recapitulate the molecular and functional characteristics of their cells/tissue of origin.

Phylogenetic analysis of the subfamily Prodidominae (Arachnida: Araneae: Gnaphosidae)

AbstractProdidominae was recently re-established as a subfamily of Gnaphosidae, comprising 316 species placed in 33 genera. In this study, we conduct a cladistic analysis including 59 species of Prodidominae and 32 outgroup species. The matrix is composed of 291 morphological characters and the data are analysed under the parsimony criterion, using differing weighting regimes. Prodidominae is not recovered as monophyletic, because Anagrina did not arise within the subfamily. Cryptotoerithus, Molycria, Myandra, Nomindra, Wesmaldra and Wydundra arise to form a clade. Thus, we re-establish Molycriinae as a distinct subfamily in Gnaphosidae, sister to Prodidominae. We redefine the limits of Prodidominae to include the genera Austrodomus, Brasilomma, Caudalia, Chileomma, Chileuma, Chilongius, Eleleis, Indiani, Katumbea, Lygromma, Lygrommatoides, Moreno, Namundra, Neozimiris, Nopyllus, Paracymbiomma, Plutonodomus, Prodidomus, Purcelliana, Theuma, Theumella, Tivodrassus, Tricongius, Zimirina and Zimiris. Species of these genera share the presence of anterior lateral spinnerets with pyriform gland spigots associated with patches of long setae and the presence of a large protrusion between coxae IV with erect setae and unsclerotized margins. In addition, we propose three new synonymies: Oltacloea as a junior synonym of Tricongius, and Prodida as junior synonym of Prodidomus. Lygromma ybyguara is transferred to Tricongius.

Ice-phobic glass-substrate surfaces coated with polypeptides inspired by antifreeze protein

Abstract The development of ice-phobic glass-substrate surfaces for industrial applications, such as preventing the formation of ice on vehicle windshields, is important. We have previously developed a glass surface coated with a polypeptide whose amino acid sequence is identical to part of an antifreeze protein. For this polypeptide, we showed that the ice adhesion strength was reduced by the coexistence of smooth surface parts exposing hydrophobic amino-acid residues and protrusion surface parts exposing hydrophilic amino-acid residues. In this report, we improve the experimental methods and conduct experiments on the freezing of water disks in steel washers on polypeptide-coated and uncoated surfaces. Under constant cooling surface temperatures, the ice adhesion strength of the coated surfaces decreased by up to 67% when compared with that of uncoated surfaces. Atomic force microscopy observations of the polypeptide-coated glass revealed small and large protrusions on the surface, which were formed by the aggregation of polypeptide. These protrusions and the smooth surface are primarily responsible for the reduced ice adhesion strength. In addition, repeated freezing of the water disks on the surfaces revealed that the coated surfaces could maintain their characteristics for up to 100 repetitions. In addition, the transparency of the glass plate was not changed by the coating. Thus, this polypeptide coating technique should be suitable for improving deicing properties of windshields, traffic lights, and surveillance cameras.

Streptococcus pneumoniae Surface Adhesin PfbA Exhibits Host Specificity by Binding to Human Serum Albumin but Not Bovine, Rabbit and Porcine Serum Albumins.

PfbA (Plasmin(ogen) and Fibronectin Binding protein A) is an adhesin present on the surface of Streptococcus pneumoniae. Initial studies characterized PfbA as plasmin(ogen) and fibronectin binding protein and later it was found that it binds with many other proteins of the extracellular matrix such as fibrinogen, collagen and laminin. It also binds to blood protein human serum albumin (HSA). Interestingly, PfbA exhibits no binding with serum albumins of bovine (BSA), rabbit (RSA) and porcine (PSA) which are sequentially and structurally homologous to HSA. This suggests that PfbA is likely involved in host specificity. Therefore, to get more insights into this aspect, a detailed analysis, which includes the interaction of rPfbA with HSA/BSA/RSA/PSA at different pHs by bio-layer interferometry, comparison of sequences and surface electrostatic potential of HSA/BSA/RSA/PSA, lysine modification of HSA by succinylation and subsequent interaction analysis of succinylated HSA with rPfbA and the secondary structural content estimation by FT-IR spectroscopy was carried out. Since large protrusions are another important geometric feature of protein surfaces, the property was also analyzed for HSA/BSA/RSA/PSA. The results of the above studies clearly suggest that the rPfbA exhibits host specificity by selectively binding only to HSA and not with its homologous BSA/RSA/PSA. Since the three dimensional structures of these albumins are highly similar, it is likely that rPfbA utilizes the differences in the surface electrostatic charge in combination with surface protrusions of HSA/BSA/RSA/PSA for the selective molecular recognition process and this feature may be important in the pathogenesis of pneumococcal infection.

Relationship between mechanical properties and processing performance of agglomerated diamond abrasive compared with single diamond abrasive

Fixed abrasive is taking the place of loose abrasive owing to its high efficiency and little pollution. The self-conditioning ability of fixed abrasive pads (FAPs) plays a favorable role in the lapping process. In this paper, agglomerated diamond (AD) abrasives were prepared for the sapphire lapping process. Material removal rate (MRR), material removal rate variation (MRRV) and surface topography of sapphire wafers lapped by fixed AD abrasive pad were investigated. Abrasive wear and wear debris were characterized. The material removal mechanisms of AD abrasives were discussed. Comparison of mechanical properties between AD and SD in abrasive wear process was analyzed. Influence of mechanical properties of AD abrasives on processing performance was explained. Comparing with fixed single diamond (SD) abrasive pads, the higher MRR, the lower MRRV and surface roughness of sapphire wafer were obtained in the fixed AD abrasive lapping process. Stable large protrusion height and consecutive sharp edges of AD abrasives ensure the excellent lapping performance. The protrusion height of abrasives is positive correlated with the self-conditioning ability of FAPs. The stable protrusion height of AD abrasives is attribute to two points: one is the rough surface of an AD abrasive with multiple sharp cutting edges improves the bonding strength between the abrasives and the pad matrix; the other is the detached diamond particles due to the micro-fracture phenomenon of AD abrasives accelerates the abrasion of matrix.

Characterization of Zinc Carboxylates in an Oil Paint Test Panel

ABSTRACTZinc (carboxylate) soaps, formed by reactions between zinc oxide (ZnO) and fatty acids in a drying oil, are known to cause deterioration in the paint layers of modern and contemporary oil paintings. This study investigates zinc carboxylates that developed in an oil painting test panel designed to mimic the aging and degradation encountered in actual works of art. Following accelerated and natural aging, protrusions were noted on the surface of the test panel. A large protrusion with erupted gel features was extracted from the test panel, mounted in top view, and then cut to reveal the sample's cross section. The gel features, which resulted from the unreacted oil binder's separation from the paint matrix, facilitated zinc carboxylate formation. Using reflectance µ-FTIR and SEM-EDX analysis, the morphologies and spatial distributions of zinc carboxylates within the gel regions of the protrusion were studied. A concentration gradient of zinc within the gel material was observed in the cross-sectional view, indicating patterns of zinc carboxylate formation and migration.

'Crystal Macrosetae': Novel Scales and Bristles in Male Arctiine Moths (Lepidoptera: Erebidae: Arctiinae) Filled with Crystallizing Material.

Scales, exoskeletal features characteristic of the Lepidoptera, occur in enormous structural and functional diversity. They cover the wing membranes and other body parts and give butterflies and moths their often stunning appearance. Generally, the patterns made by scales are visual signals for intra- and interspecific communication. In males, scales and/or bristles also make up the androconial organs, which emit volatile signals during courtship. Here, a structurally and putative functionally novel type of scales and bristles is reported: ‘crystal macrosetae’. These lack trabeculae and windows, are made up by a very thin and flexible envelope only and contain crystallizing material. In ‘crystal scales’, there is a flat surface ornamentation of modified ridges, while ‘crystal bristles’ often show large protrusions. Crystal macrosetae usually cannot be reliably recognized without destruction. Apparently, they serve as containers for large amounts of material that is viscous in living moths, highly hygroscopic, crystallizes when specimens dry up, and can be visualized by scanning electron microscopy. Crystal macrosetae occur in males only, always associated with or making up androconial organs located on various parts of the body, and have numerous forms with diverse surface ornamentation across many species and genera. The newly identified structures and the discovery of crystallizing material in scales and bristles raise many questions and could shed new light on ontogenetic development of macrosetae, and on the biology and physiology as well as the evolution and systematics of Arctiinae. There is evidence that crystal macrosetae occur in other moths too.

A computational model for chemo-mechanical degradation of historical oil paintings due to metal soap formation

A large percentage of oil paintings in museum collections suffers from chemo-mechanical degradation phenomena that are primarily due to metal soap formation. Metal soaps result from the chemical reaction between metal ions present in the pigments and saturated fatty acids released by the oil paint. They appear as large protrusions that disfigure the surface texture, possibly triggering mechanical damage and flaking of the painting. Despite that these phenomena have been widely observed in situ, the interaction between chemical and mechanical degradation processes is far from being understood. This paper proposes a chemo-mechanical model to predict metal soap formation and the resulting chemo-mechanical damage in historical oil paintings. The chemical process is described by means of a diffusion-reaction model, whereby the spatial growth of the metal soap crystal takes place in a small reaction zone at the boundary of the crystal. Metal soap crystallization and growth, driven by the diffusion of saturated fatty acids and metal ions, result in a chemically-induced volumetric growth strain. This introduces stresses in the paint, ultimately promoting crack nucleation and propagation. The fracture process is simulated with a cohesive zone approach, using interface elements equipped with a traction-separation law. The mass flux-concentration relation at the interfaces is consistently specified as a function of the mechanical damage. A set of numerical simulations illustrates the capability of the model to predict metal soap crystallization and growth and the fracture induced in the paint. The study finally illustrates the influence of various chemical and mechanical parameters (i.e., the size of the metal soap nucleus, the mismatch in elastic stiffness parameters between the metal soap and paint materials, the fracture length scale of the paint material, the chemical growth strain and the reaction rate) on the chemo-mechanical degradation of the paint layer.

ICTV Virus Taxonomy Profile: Megabirnaviridae.

Megabirnaviridae is a family of non-enveloped spherical viruses with dsRNA genomes of two linear segments, each of 7.2-8.9 kbp, comprising 16.1 kbp in total. The genus Megabirnavirus includes the species Rosellinia necatrix megabirnavirus 1, the exemplar isolate of which infects the white root rot fungus (Rosellinia necatrix) to which it confers hypovirulence. Megabirnaviruses are characterized by their bisegmented genome with large 5'-untranslated regions (1.6 kb) upstream of both 5'-proximal coding strand ORFs, and large protrusions on the particle surface. This is a summary of the ICTV Report on the family Megabirnaviridae, which is available at ictv.global/report/megabirnaviridae.This Profile is dedicated to the memory of our valued colleague Professor Said A. Ghabrial.

The Impact of Coarse‐Grain Protrusion on Near‐Bed Hydrodynamics

In steep rivers, sediment is often transported over immobile cobbles and boulders. Previous studies of such conditions have observed that the entrainment rate of the mobile sediment strongly depends on the level of protrusion of the immobile grains. Here experiments are conducted in a laboratory flume in order to quantify how different levels of protrusion of large aggregates above a fixed fine‐sediment bed, modeled as a patch of hemispheres, modify the local hydrodynamics near the fine‐sediment bed. Five protrusion levels defined by P=k/R= {0%, 20%, 40%, 60%, 80%} were investigated, where k is the protrusion height and R the radius. For small protrusion (P=20%), enhanced shear stress and turbulence intensity on the fine‐sediment bed is observed as the mixing layer generated at the hemisphere top impacts the fine‐sediment bed. Moreover, sweep events generated near the top of the hemispheres reach the fine‐sediment bed. For large protrusions (P ≥ 60%), the mixing layer generated near the top of the hemispheres does not reach the fine grains with the consequence that the shear stress drops. The remaining turbulence near the fine‐sediment bed, although enhanced by the wakes generated by the hemispherical caps, is quasi‐isotropic. The transition between these two distinct near‐bed flow regimes is found to be around P=40%, corresponding to the protrusion levels observed by Grams and Wilcock, https://doi.org/10.1002/2013JF002925) above which the erosion of fine sediment ceases.

Mechanical properties and corrosion resistance of Ni-Co-SiC composite coatings by magnetic field-induced jet electrodeposition

Ni-Co alloys and Ni-Co-SiC composite coatings were manufactured by magnetic field-induced jet electrodeposition. The microstructure and nanoparticles distribution of the coatings were characterized by field emission scanning electron microscopy, energy dispersive X-ray spectrometry, and X-ray diffraction. The surface roughness, adhesion and corrosion resistance of the coatings were measured using a three-dimensional profilometer, a scratch tester, and an electrochemical workstation. The cellular protrusions on the composite coatings decreased with the addition of nano-SiC particles. However, a large number of small spherical structures grew into large cellular protrusions with an extremely high SiC concentration under traditional jet electrodeposition. The composite coatings under magnetic field-induced jet electrodeposition showed a uniform growth and no protrusions, the nano-SiC particles were also uniformly distributed. The Ni-Co-SiC composite coating exhibited a single-phase solid solution structure, and its adhesion increased to 33.2 N, which was 2.65 times that of the Ni-Co alloy coating. The corrosion current density of the composite coating was 4.768 μA cm−2, which was sufficient to protect sintered NdFeB magnets.

Boundary conditions of implicit affective influences on effort-related cardiovascular response

A large percentage of oil paintings in museum collections suffers from chemo-mechanical degradation phenomena that are primarily due to metal soap formation. Metal soaps result from the chemical reaction between metal ions present in the pigments and saturated fatty acids released by the oil paint. They appear as large protrusions that disfigure the surface texture, possibly triggering mechanical damage and flaking of the painting. Despite that these phenomena have been widely observed in situ, the interaction between chemical and mechanical degradation processes is far from being understood. This paper proposes a chemo-mechanical model to predict metal soap formation and the resulting chemo-mechanical damage in historical oil paintings. The chemical process is described by means of a diffusion-reaction model, whereby the spatial growth of the metal soap crystal takes place in a small reaction zone at the boundary of the crystal. Metal soap crystallization and growth, driven by the diffusion of saturated fatty acids and metal ions, result in a chemically-induced volumetric growth strain. This introduces stresses in the paint, ultimately promoting crack nucleation and propagation. The fracture process is simulated with a cohesive zone approach, using interface elements equipped with a traction-separation law. The mass flux-concentration relation at the interfaces is consistently specified as a function of the mechanical damage. A set of numerical simulations illustrates the capability of the model to predict metal soap crystallization and growth and the fracture induced in the paint. The study finally illustrates the influence of various chemical and mechanical parameters (i.e., the size of the metal soap nucleus, the mismatch in elastic stiffness parameters between the metal soap and paint materials, the fracture length scale of the paint material, the chemical growth strain and the reaction rate) on the chemo-mechanical degradation of the paint layer.

The family Ascothoracidae Grygier, 1987, a review with descriptions of new abyssal taxa parasitizing ophiuroids and remarks on the invalidity of the genus Parascothorax Wagin, 1964 (Crustacea: Thecostraca: Ascothoracida)

Two new ascothoracidan species in the family Ascothoracidae Grygier, 1987, Ascothorax rybakovi sp. nov. and Cardiosaccus pedri gen. et sp. nov., are described from the Kuril-Kamchatka Trench at abyssal depths of 5150–5700 m. They are among the deepest known ascothoracidans. They live as mesoparasites in permanent cysts within the bursae of the brittle stars Ophiacantha pacifica Lutken and Mortensen, 1899 and Amphiophiura pacifica Litvinova, 1971, respectively. This is the first study of new forms of Ascothoracidae in which SEM has been used in the descriptions, including the lattice organs and the early nauplius. Cardiosaccus differs from Ascothorax in displaying the following apomorphic traits: (i) absence of thoracopod 1; (ii) a smaller fifth antennular segment that is completely fused with the claw; (iii) absence of small setae at the base of this claw; and (iv) an extremely large ventral protrusion of the fourth abdominal segment. Material of Parascothorax synagogoides Wagin, 1964 from near the type locality, studied with SEM, could not be distinguished from Ascothorax by any reliable morphological criteria. Cyst structure and the manner of cyst formation cannot be used, because although cyst is the result of the parasites activity, this is a feature of the host, not something inherent to the parasite. Moreover, the inferred settlement of the larvae of P. synagogoides on the outer edge of the bursal slit is best regarded as plesiomorphic behavior, reflecting how the Ascothoracidae became bursal mesoparasites in the first place. We therefore regard Parascothorax as invalid and refer P. synagogoides to Ascothorax. Within the family Ascothoracidae as now constituted, Ascothorax is cosmopolitan and speciose and includes species that exclusively infect a single host species, whereas Cardiosaccus is monotypic and restricted to the northwest Pacific. Ascothorax rybakovi sp. nov. is the third species of this genus known to harbor hyperparasitic cryptoniscid isopods.

Abstract 1943: PARG inhibitors exhibit synthetic lethality with XRCC1 deficiency and a cellular mechanism of action that is distinct from PARP inhibition

Abstract Poly(ADP-ribose) glycohydrolase (PARG) hydrolyzes poly(ADP-ribose) (PAR) chains that are polymerized by PARP enzymes, completing the PAR cycle. Small molecule inhibitors of PARG result in a dose dependent increase in cellular PAR after DNA damage. Here we demonstrate that depletion of XRCC1, a scaffolding protein with an essential role in base-excision repair (BER), sensitizes cancer cells to PARG inhibition. XRCC1 deficient cells exhibit increased nuclear PAR foci in response to PARG inhibition even in the absence of DNA damaging agents. Inhibition of PARP1 with RNAi or small molecule inhibitors rescues cell growth inhibition and reduces the amount of cellular PAR accumulation in PARG inhibitor treated cells. This indicates that the cellular growth inhibition is dependent upon cellular PAR levels, demonstrating selectivity of the small molecule inhibitors for PARG. We hypothesized that inhibition of PAR hydrolysis could result in depletion of cellular NAD as this could prevent recycling of PAR to NAD. Consistent with this hypothesis, PARG inhibition enhanced NAD depletion after treatment of cells with the DNA damaging agent methyl methanesulfonate (MMS). Live cell imaging of XRCC1 depleted cells treated with a PARG inhibitor revealed that cells have large membrane protrusions, similar to the morphology of cells that have been treated with a NAMPT inhibitor, which results in depletion of cellular NAD. Furthermore, addition of the NAD precursor, nicotinamide mononucleotide (NMN) rescued proliferation of PARG inhibited cells. Taken together, these data support a hypothesis in which PARG inhibitors are cytotoxic to sensitive cancer cells via depletion of NAD, ultimately starving the cell of ATP. Thus, PARG inhibition is a novel strategy for exploiting synthetic lethality in cancer cells. The defects that sensitize cancer cells to PARG inhibition are distinct from those that sensitize to PARP inhibitors, namely defects in homology directed repair. Approximately 15% of breast cancer samples exhibit low or no XRCC1 by IHC. A subset (approximately 35%) of the XRCC1 low patient samples also have defects in BRCA1, suggesting that the majority of XRCC1 low tumors may not be responsive to PARP inhibitors. Small molecule PARG inhibitors are currently being evaluated for efficacy in XRCC1 low xenograft models. Citation Format: Leenus Martin, Tzuling Cheng, Dominic I. James, Habiba Begum, Kate M. Smith, Allan Jordan, Ian Waddell, Kedar Vaidya, Marcus Fischer, Bing Yao, Jason Drummond, Leah Cleary, Ruben Martinez, James Sutton, Nandini Ravindran, James Joseph, Eleni Venetsanakos, Michael Dillon, Jeffrey H. Hager, Lisa D. Belmont. PARG inhibitors exhibit synthetic lethality with XRCC1 deficiency and a cellular mechanism of action that is distinct from PARP inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1943.

RNAi screening of subtracted transcriptomes reveals tumor suppression by taurine-activated GABAA receptors involved in volume regulation.

To identify coding and non-coding suppressor genes of anchorage-independent proliferation by efficient loss-of-function screening, we have developed a method for enzymatic production of low complexity shRNA libraries from subtracted transcriptomes. We produced and screened two LEGO (Low-complexity by Enrichment for Genes shut Off) shRNA libraries that were enriched for shRNA vectors targeting coding and non-coding polyadenylated transcripts that were reduced in transformed Mouse Embryonic Fibroblasts (MEFs). The LEGO shRNA libraries included ~25 shRNA vectors per transcript which limited off-target artifacts. Our method identified 79 coding and non-coding suppressor transcripts. We found that taurine-responsive GABAA receptor subunits, including GABRA5 and GABRB3, were induced during the arrest of non-transformed anchor-deprived MEFs and prevented anchorless proliferation. We show that taurine activates chloride currents through GABAA receptors on MEFs, causing seclusion of cell volume in large membrane protrusions. Volume seclusion from cells by taurine correlated with reduced proliferation and, conversely, suppression of this pathway allowed anchorage-independent proliferation. In human cholangiocarcinomas, we found that several proteins involved in taurine signaling via GABAA receptors were repressed. Low GABRA5 expression typified hyperproliferative tumors, and loss of taurine signaling correlated with reduced patient survival, suggesting this tumor suppressive mechanism operates in vivo.

Multiple membrane extrusion sites drive megakaryocyte migration into bone marrow blood vessels.

Platelets, cells central to hemostasis and thrombosis, are formed from parent cell megakaryocytes. Whilst the process is highly efficient in vivo, our ability to generate them in vitro is still remarkably inefficient. We proposed that greater understanding of the process in vivo is needed and used an imaging approach, intravital correlative light-electron microscopy, to visualize platelet generation in bone marrow in the living mouse. In contrast to current understanding we found that most megakaryocytes enter the sinusoidal space as large protrusions rather than extruding fine proplatelet extensions. The mechanism for large protrusion migration also differed from that of proplatelet extension. In vitro, proplatelets extend by sliding of dense bundles of microtubules, whereas in vivo our data showed an absence of microtubule bundles in the large protrusion, but the presence of multiple fusion points between the internal membrane and the plasma membrane, at the leading edge of the protruding cell. Mass membrane fusion therefore drives megakaryocyte large protrusions into the sinusoid, significantly revising our understanding of the fundamental biology of platelet formation in vivo.

Turbulent channel flow over an anisotropic porous wall – drag increase and reduction

The effect of the variations of the permeability tensor on the close-to-the-wall behaviour of a turbulent channel flow bounded by porous walls is explored using a set of direct numerical simulations. It is found that the total drag can be either reduced or increased by more than 20 % by adjusting the permeability directional properties. Drag reduction is achieved for the case of materials with permeability in the vertical direction lower than the one in the wall-parallel planes. This configuration limits the wall-normal velocity at the interface while promoting an increase of the tangential slip velocity leading to an almost ‘one-component’ turbulence where the low- and high-speed streak coherence is strongly enhanced. On the other hand, strong drag increase is found when high wall-normal and low wall-parallel permeabilities are prescribed. In this condition, the enhancement of the wall-normal fluctuations due to the reduced wall-blocking effect triggers the onset of structures which are strongly correlated in the spanwise direction, a phenomenon observed by other authors in flows over isotropic porous layers or over ribletted walls with large protrusion heights. The use of anisotropic porous walls for drag reduction is particularly attractive since equal gains can be achieved at different Reynolds numbers by rescaling the magnitude of the permeability only.