bluuebunny/crossref_metadata_2025_split huggingface dataset:
F-spondin and mindin: two structurally and functionally related genes expressed in the hippocampus that promote outgrowth of embryonic hippocampal neurons
Authors: Feinstein Yael , Borrell Víctor , Garcia Cristina , Burstyn-Cohen Tal , Tzarfaty Vered , Frumkin Ayala , Nose Akinao , Okamoto Hitoshi , Higashijima Shin-ichi , Soriano Eduardo , Klar Avihu 
Published: April 2021

Abstract
Extracellular matrix (ECM) proteins play an important role in early cortical development, specifically in the formation of neural connections and in controlling the cyto-architecture of the central nervous system. F-spondin and Mindin are a family of matrix-attached adhesion molecules that share structural similarities and overlapping domains of expression. Genes for both proteins contain a thrombospondin type I repeat(s) at the C terminus and an FS1-FS2 (spondin) domain. Both the vertebrate F-spondin and the zebrafish mindins are expressed on the embryonic floor plate. In the current study we have cloned the rat homologue of mindin and studied its expression and activity together with F-spondin in the developing rodent brain. The two genes are abundantly expressed in the developing hippocampus. In vitro studies indicate that both F-spondin and Mindin promote adhesion and outgrowth of hippocampal embryonic neurons. We have also demonstrated that the two proteins bind to a putative receptor(s) expressed on both hippocampal and sensory neurons.
Ventral midline cells are required for the local control of commissural axon guidance in the mouse spinal cord
Authors: Matise Michael P. , Lustig Marc , Sakurai Takeshi , Grumet Martin , Joyner Alexandra L. 
Published: April 2021

Abstract
Specialized cells at the midline of the central nervous system have been implicated in controlling axon projections in both invertebrates and vertebrates. To address the requirement for ventral midline cells in providing cues to commissural axons in mice, we have analyzed Gli2 mouse mutants, which lack specifically the floor plate and immediately adjacent interneurons. We show that a Dbx1 enhancer drives tau-lacZ expression in a subpopulation of commissural axons and, using a reporter line generated from this construct, as well as DiI tracing, we find that commissural axons projected to the ventral midline in Gli2−/− embryos. Netrin1 mRNA expression was detected in Gli2−/− embryos and, although much weaker than in wild-type embryos, was found in a dorsally decreasing gradient. This result demonstrates that while the floor plate can serve as a source of long-range cues for C-axons in vitro, it is not required in vivo for the guidance of commissural axons to the ventral midline in the mouse spinal cord. After reaching the ventral midline, most commissural axons remained clustered in Gli2−/− embryos, although some were able to extend longitudinally. Interestingly, some of the longitudinally projecting axons in Gli2−/− embryos extended caudally and others rostrally at the ventral midline, in contrast to normal embryos in which virtually all commissural axons turn rostrally after crossing the midline. This finding indicates a critical role for ventral midline cells in regulating the rostral polarity choice made by commissural axons after they cross the midline. In addition, we provide evidence that interactions between commissural axons and floor plate cells are required to modulate the localization of Nr-CAM and TAG-1 proteins on axons at the midline. Finally, we show that the floor plate is not required for the early trajectory of motoneurons or axons of the posterior commissure, whose projections are directed away from the ventral midline in both WT and Gli2−/− embryos, although they are less well organized in Gli2−/−mutants.
FGF signalling plays similar roles in development and regeneration of the skeleton in the brittle star Amphiura filiformis
Authors: Czarkwiani Anna , Dylus David V. , Carballo Luisana , Oliveri Paola 
Published: April 2021

ABSTRACT
Regeneration as an adult developmental process is in many aspects similar to embryonic development. Although many studies point out similarities and differences, no large-scale, direct and functional comparative analyses between development and regeneration of a specific cell type or structure in one animal exist. Here, we use the brittle star Amphiura filiformis to characterise the role of the FGF signalling pathway during skeletal development in embryos and arm regeneration. In both processes, we find ligands expressed in ectodermal cells that flank underlying skeletal mesenchymal cells, which express the receptors. Perturbation of FGF signalling showed inhibited skeleton formation in both embryogenesis and regeneration, without affecting other key developmental processes. Differential transcriptome analysis finds mostly differentiation genes rather than transcription factors to be downregulated in both contexts. Moreover, comparative gene analysis allowed us to discover brittle star-specific differentiation genes. In conclusion, our results show that the FGF pathway is crucial for skeletogenesis in the brittle star, as in other deuterostomes, and provide evidence for the re-deployment of a developmental gene regulatory module during regeneration.
A combination of Notch signaling, preferential adhesion and endocytosis induces a slow mode of cell intercalation in the Drosophila retina
Authors: Blackie Laura , Tozluoglu Melda , Trylinski Mateusz , Walther Rhian F. , Schweisguth François , Mao Yanlan , Pichaud Franck 
Published: April 2021

ABSTRACT
Movement of epithelial cells in a tissue occurs through neighbor exchange and drives tissue shape changes. It requires intercellular junction remodeling, a process typically powered by the contractile actomyosin cytoskeleton. This has been investigated mainly in homogeneous epithelia, where intercalation takes minutes. However, in some tissues, intercalation involves different cell types and can take hours. Whether slow and fast intercalation share the same mechanisms remains to be examined. To address this issue, we used the fly eye, where the cone cells exchange neighbors over ∼10 h to shape the lens. We uncovered three pathways regulating this slow mode of cell intercalation. First, we found a limited requirement for MyosinII. In this case, mathematical modeling predicts an adhesion-dominant intercalation mechanism. Genetic experiments support this prediction, revealing a role for adhesion through the Nephrin proteins Roughest and Hibris. Second, we found that cone cell intercalation is regulated by the Notch pathway. Third, we show that endocytosis is required for membrane removal and Notch activation. Taken together, our work indicates that adhesion, endocytosis and Notch can direct slow cell intercalation during tissue morphogenesis.
The trophoblast clock controls transport across placenta in mice
Authors: Demarez Cécile , De Assis Leonardo Vinicius Monteiro , Krohn Markus , Ramella Nahuel , Schwaninger Markus , Oster Henrik , Astiz Mariana 
Published: April 2021

ABSTRACT
In mammals, 24-h rhythms of physiology and behavior are organized by a body-wide network of clock genes and proteins. Despite the well-known function of the adult circadian system, the roles of maternal, fetal and placental clocks during pregnancy are poorly defined. In the mature mouse placenta, the labyrinth zone (LZ) is of fetal origin and key for selective nutrient and waste exchange. Recently, clock gene expression has been detected in LZ and other fetal tissues; however, there is no evidence of a placental function controlled by the LZ clock. Here, we demonstrate that specifically the trophoblast layer of the LZ harbors an already functional clock by late gestation, able to regulate in a circadian manner the expression and activity of the xenobiotic efflux pump, ATP-binding cassette sub-family B member 1 (ABCB1), likely gating the fetal exposure to drugs from the maternal circulation to certain times of the day. As more than 300 endogenous and exogenous compounds are substrates of ABCB1, our results might have implications in choosing the maternal treatment time when aiming either maximal/minimal drug availability to the fetus/mother.
Collective nuclear behavior shapes bilateral nuclear symmetry for subsequent left-right asymmetric morphogenesis in Drosophila
Authors: Shin Dongsun , Nakamura Mitsutoshi , Morishita Yoshitaka , Eiraku Mototsugu , Yamakawa Tomoko , Sasamura Takeshi , Akiyama Masakazu , Inaki Mikiko , Matsuno Kenji 
Published: April 2021

ABSTRACT
Proper organ development often requires nuclei to move to a specific position within the cell. To determine how nuclear positioning affects left-right (LR) development in the Drosophila anterior midgut (AMG), we developed a surface-modeling method to measure and describe nuclear behavior at stages 13-14, captured in three-dimensional time-lapse movies. We describe the distinctive positioning and a novel collective nuclear behavior by which nuclei align LR symmetrically along the anterior-posterior axis in the visceral muscles that overlie the midgut and are responsible for the LR-asymmetric development of this organ. Wnt4 signaling is crucial for the collective behavior and proper positioning of the nuclei, as are myosin II and the LINC complex, without which the nuclei fail to align LR symmetrically. The LR-symmetric positioning of the nuclei is important for the subsequent LR-asymmetric development of the AMG. We propose that the bilaterally symmetrical positioning of these nuclei may be mechanically coupled with subsequent LR-asymmetric morphogenesis.
Mutation of an Arabidopsis Golgi membrane protein ELMO1 reduces cell adhesion
Authors: Kohorn Bruce D. , Zorensky Frances D. H. , Dexter-Meldrum Jacob , Chabout Salem , Mouille Gregory , Kohorn Susan 
Published: April 2021

ABSTRACT
Plant growth, morphogenesis and development involve cellular adhesion, a process dependent on the composition and structure of the extracellular matrix or cell wall. Pectin in the cell wall is thought to play an essential role in adhesion, and its modification and cleavage are suggested to be highly regulated so as to change adhesive properties. To increase our understanding of plant cell adhesion, a population of ethyl methanesulfonate-mutagenized Arabidopsis were screened for hypocotyl adhesion defects using the pectin binding dye Ruthenium Red that penetrates defective but not wild-type (WT) hypocotyl cell walls. Genomic sequencing was used to identify a mutant allele of ELMO1 which encodes a 20 kDa Golgi membrane protein that has no predicted enzymatic domains. ELMO1 colocalizes with several Golgi markers and elmo1−/− plants can be rescued by an ELMO1-GFP fusion. elmo1−/− exhibits reduced mannose content relative to WT but no other cell wall changes and can be rescued to WT phenotype by mutants in ESMERALDA1, which also suppresses other adhesion mutants. elmo1 describes a previously unidentified role for the ELMO1 protein in plant cell adhesion.
Automated in vivo drug screen in zebrafish identifies synapse-stabilising drugs with relevance to spinal muscular atrophy
Authors: Oprişoreanu Ana-Maria , Smith Hannah L. , Krix Sophia , Chaytow Helena , Carragher Neil O. , Gillingwater Thomas H. , Becker Catherina G. , Becker Thomas 
Published: April 2021

ABSTRACT
Synapses are particularly vulnerable in many neurodegenerative diseases and often the first to degenerate, for example in the motor neuron disease spinal muscular atrophy (SMA). Compounds that can counteract synaptic destabilisation are rare. Here, we describe an automated screening paradigm in zebrafish for small-molecule compounds that stabilize the neuromuscular synapse in vivo. We make use of a mutant for the axonal C-type lectin chondrolectin (chodl), one of the main genes dysregulated in SMA. In chodl−/− mutants, neuromuscular synapses that are formed at the first synaptic site by growing axons are not fully mature, causing axons to stall, thereby impeding further axon growth beyond that synaptic site. This makes axon length a convenient read-out for synapse stability. We screened 982 small-molecule compounds in chodl chodl−/− mutants and found four that strongly rescued motor axon length. Aberrant presynaptic neuromuscular synapse morphology was also corrected. The most-effective compound, the adenosine uptake inhibitor drug dipyridamole, also rescued axon growth defects in the UBA1-dependent zebrafish model of SMA. Hence, we describe an automated screening pipeline that can detect compounds with relevance to SMA. This versatile platform can be used for drug and genetic screens, with wider relevance to synapse formation and stabilisation.
An ultrastructural and radioautographic study of the evolution of the interphase nucleus in plant meristematic cells (Allium porrum)
Authors: Lafontaine J. G. , Lord A. 
Published: April 2021

ABSTRACT
Radioautography under both light and electron microscopy was exploited to investigate the structural changes of the chromatin reticulum which characterizes the interphase nucleus of a number of plants. Allium porrum meristematic plant cells were used for this purpose. In this species, the telophase chromosomes uncoil into dense strands which, during the G\ period, gradually give rise to a coarse reticulum. There then follows an extensive unravelling of portions of these strands, and high-resolution radioautography reveals that labelling with tritiated thymidine predominantly occurs over zones of the nucleus consisting of diffuse fine fibrillar material. As the S-period progresses, a chromatin reticulum reappears throughout the nuclear cavity, the tortuous strands being approximately 0-25 /μm in diameter. Most of the radioautographic grains still remain over the light nucleoplasmic areas but a number of these are now located on the outermost portion of the dense chromatin profiles. By the end of the S-period, the chromatin strands are slightly thicker (ca. 0-3 μm) and form a looser reticulum. Labelling has decreased noticeably in nuclei of that period, the radioautographic grains being grouped into clusters resting over more or less spherical regions of the chromatin reticulum. Judging from their localization at the surface of the nucleolus or close to the nuclear envelope, these structures correspond to chromocentres. The additional interesting finding that such nuclear structures appear much less compactly organized strongly suggests that chromocentres undergo important conformational modifications during duplication of their DNA.
Some properties of ribosome crystals isolated from hypothermically treated chick embryos
Authors: Dondi P. G. , Barker D. C. 
Published: April 2021

ABSTRACT
Ribosome crystals observed in hypothermically treated chick embryos exist as large dense aggregates and, for this reason, could be purified from a post-nuclear supernatant by centrifugation through a high-density discontinuous sucrose gradient.
A ribosome crystal fraction isolated in this way was observed, by electron microscopy, to contain intact crystals, resembling those seen in sectioned whole cells, with only minor contamination from morphologically indistinct particles.
The ribonucleic acid (RNA) content of this fraction was found to be the same as ribosomal RNA from mature chickens. However, their resistance to mild RNase treatment, lack of transfer RNA and endogenous messenger RNA activity indicate that such ribosome crystals are not a specific type of polysome.
The intertetramer bonds (i.e. bonds between tetramers in a crystal array) are much more susceptible to mild protease treatment than to treatment with ribonuclease (RNase), indicating a dependence on protein-protein interactions for their formation.
The role of endoplasmic reticulum in the repair of amoeba nuclear envelopes damaged microsurgically
Authors: Flickinger C. J. 
Published: April 2021

ABSTRACTThe nuclear envelopes of amoebae were damaged microsurgically, and the fate of the lesions was studied with the electron microscope. Amoebae were placed on the surface of an agar-coated slide. Using a glass probe, the nucleus was pushed from an amoeba, damaged with a chopping motion of the probe, and reinserted into the amoeba. Cells were prepared for electron microscopy at intervals of between 10 min and 4 days after the manipulation. Nuclear envelopes studied between 10 min and 1 h after the injury displayed extensive damage, including numerous holes in the nuclear membranes. Beginning 15 min after the manipulation, pieces of rough endoplasmic reticulum intruded into the holes in the nuclear membranes. These pieces of rough endoplasmic reticulum subsequently appeared to become connected to the nuclear membranes at the margins of the holes. By 1 day following the injury, many cells had died, but the nuclear membranes were intact in those cells that survived. The elaborate fibrous lamina or honeycomb layer characteristic of the amoeba nuclear envelope was resistant to early changes after the manipulation. Patches of disorganization of the fibrous lamina were present 5 h to 1 day after injury, but the altered parts showed evidence of progress toward a return to normal configuration by 4 days after the injury. It is proposed that the rough endoplasmic reticulum participates in the repair of injury to the nuclear membranes. The similarity of this repair process to reconstitution of the nuclear envelope in telophase of mitosis is noted, and the relationship between the nuclear envelope and the rough endoplasmic reticulum is discussed.
Ultrastructural observations of cell wall regeneration around isolated tobacco protoplasts
Authors: Burgess J. , Fleming E. N. 
Published: April 2021

ABSTRACT
The process of cell wall regeneration around cultured protoplasts isolated from tobacco mesophyll has been examined by electron microscopy. The initially formed wall contains 2 components which stain with conventional heavy metal stains. The first consists of unbranched fibres, at first oriented at right angles to the plasmalemma surface. As wall growth proceeds the fibres lengthen and assume an orientation parallel to the plasmalemma. It seems probable that this component is cellulose. The second component of the wall is more amorphous and more densely stained. It is most frequently seen in situations where leaching of materials into the medium would be expected to be minimal. The endoplasmic reticulum and the plasmalemma are the only membrane systems which appear to contribute towards wall formation. No pattern of structure has been detected to explain the orientation or method of synthesis of the microfibrillar part of the wall.
Accumulation of gene products in the oocytes of the dragonfly Cordulia aenea l.: I. the nematosomes
Authors: Halkka Liisa , Halkka O. 
Published: April 2021

ABSTRACT
The chromosomes of the active previtellogenic oocytes of the dragonfly Cordulia aenea L. extrude into the cytoplasm a substance, which is subsequently found there in the form of granulofibrillar masses. These nuclear extrusions evolve ultrastructurally into two components, nematosomes and dense masses. The nematosomes are later found transitorily adjacent to the mitochondria and undergo transformations that are synchronized with changes in oocyte activity. It is suggested that the nematosomes are storage structures for long-lived informational RNA and that they may be widely distributed in various types of cells containing such RNA.
Nucleocytoplasmic transport and distribution of an amino acid, in situ
Authors: Frank M. , Horowitz S. B. 
Published: April 2021

ABSTRACT
Ultra-low temperature techniques (microdissection and autoradiography) were used to study the nucleocytoplasmic distribution and transport of α-aminoisobutyric acid (AIB) in an amino acid-accumulating cell.
In amphibian oocytes incubated in AIB, the nuclear concentration of this non-metabolizable amino acid exceeds the cytoplasmic concentration by 45 %, remaining constant both over time and with variation in substrate concentration. The kinetics of uptake suggest that this nucleo-cytoplasmic asymmetry arises from solubility differences between the 2 compartments, and that the nuclear envelope plays a negligible role in amino acid transport.
A solute exclusion model is offered to explain the nucleocytoplasmic asymmetry.
Cellular uptake of soluble and aggregated ferritin: Distinction between pinocytosis and phagocytosis
Authors: Petitpierre-Gabathuler M.-P. , Ryser H. J.-P. 
Published: April 2021

ABSTRACT
Cellular uptake of ferritin amounting to 0·5 μg/mg cell protein or more can be measured colorimetrically on the basis of ferritin-iron content. 131I-serum albumin, soluble ferritin and aggregated ferritin used in equimolar concentrations are taken up differently by Sarcoma S180 cells in culture. The net uptakes in 2 h at 37 °C are 0·065, 4·3 and 24·7 μg I mg cell protein or 0·93, 8·0 and 45·7 μmol, respectively. Albumin uptake is not inhibited by a 26-fold molar ferritin excess but is significantly inhibited by a 43-fold excess.
The transport mechanism of the ferritins differs from that of albumin in that it is significantly inhibitable by 2 × 10−1 M monoiodoacetate. Soluble ferritin contains small aggregates which are removed by filtration through Millipore membranes of 0·05, 01 and 0·22 μm. When the 0·1μm filtrate is re-examined, uptake is no longer inhibited by iodoacetate. Since it can be inferred from other work that albumin is taken up by pinocytosis and ferritin aggregates by phagocytosis, the difference in susceptibility to inhibition is proposed as a way to distinguish pinocytosis from phagocytosis.
Ferritin may form larger visible aggregates in culture medium. The transport mechanism of this aggregated ferritin differs from that of soluble unfiltered ferritin in that it causes concomitant enhancement of albumin uptake. Albumin transported by virtue of this effect becomes partially susceptible to iodoacetate. Thus, in addition to a distinction between pinocytosis and phagocytosis, our data single out 2 forms of albumin transport and 3 forms of ferritin transport.
Localization of lectins in legume cotyledons
Authors: Clarke A. E. , Knox R. B. , Jermyn M. A. 
Published: April 2021

ABSTRACT
High-resolurion techniques for the localization of lectins are described. Concanavalin A (Con A) and phytohaemagglutinin (PHA) are localized using a fluorescent method with (FITC)-labelled immunoglobulins which bind to the lectins in sections of jack and red kidney bean cotyledons. Specificity is defined by the use of specific sugar inhibitors. Both Con A and PHA are found in cytoplasmic sites.
Lectins with β-glycoside specificity are detected with red-coloured artificial carbohydrate antigens. The β-galactosyl and β-glucosyl antigens bind specifically to clusters of spherical bodies in the intercellular spaces, to cell wall sites, and to the periphery of the cytoplasm associated with the cell membrane.
Circus movement in dissociated embryonic cells of a teleost,Oryzias latipes
Authors: Fujinami Noboru , Kageyama Tetsuo 
Published: April 2021

ABSTRACTThe dissociated early embryonic cells of the fresh water fish, Oryzias latipes, protrude hyaline lobopodia, which tend to rotate around the cell circumference in a propagating wave. Cells from late blastula or gastrula continuously show this ‘circus movement’, while most cells up to early blastula are rounded. The linear velocity of the lobopodium was estimated by means of time-lapse cinemicrography. The velocity increases slightly as cell diameter increases.The effects of pH, temperature and osmotic pressure of the immersion media on the movement were also quantitatively investigated. Cells become rounded and do not form lobopodial blebs when immersed in media below pH 5. The velocity is reduced by decreasing temperature, but the movement continues even at 5 °C. Cells placed in hypertonic salt solutions become crenated and do not continuously demonstrate the circus movement.