bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of myofibrillogenesis in cardiac lethal mutant axolotl hearts rescued by RNA derived from normal endoderm
Authors: Davis Lynn A. , Lemanski Larry F. 
Published: April 2021

ABSTRACT
A strain of axolotl, Ambystoma mexicanum, that carries the cardiac lethal or c gene presents an excellent model system in which to study inductive interactions during heart development. Embryos homozygous for gene c contain hearts that fail to beat and do not form sarcomeric myofibrils even though muscle proteins are present. Although they can survive for approximately three weeks, mutant embryos inevitably die due to lack of circulation. Embryonic axolotl hearts can be maintained easily in organ culture using only Holtfreter’s solution as a culture medium. Mutant hearts can be induced to differentiate in vitro into functional cardiac muscle containing sarcomeric myofibrils by coculturing the mutant heart tube with anterior endoderm from a normal embryo. The induction of muscle differentiation can also be mediated through organ culture of mutant heart tubes in medium ‘conditioned’ by normal anterior endoderm. Ribonuclease was shown to abolish the ability of endoderm-conditioned medium to induce cardiac muscle differentiation. The addition of RNA extracted from normal early embryonic anterior endoderm to organ cultures of mutant hearts stimulated the differentiation of these tissues into contractile cardiac muscle containing well- organized sarcomeric myofibrils, while RNA extracted from early embryonic liver or neural tube did not induce either muscular contraction or myofibrillogenesis. Thus, RNA from anterior endoderm of normal embryos induces myofibrillogenesis and the development of contractile activity in mutant hearts, thereby correcting the genetic defect.
Haemocytes secrete basement membrane components in embryonic locusts
Authors: Ball Eldon E. , Couet Heinz Gert de , Horn Peggy L. , Quinn Joan M. A. 
Published: April 2021

ABSTRACTSeveral monoclonal antibodies raised against a glycoprotein-enriched fraction of adult muscle membranes of Locusta migratoria selectively stain particles within haemocytes and basement membrane in developing locust embryos. Haemocytes containing immunoreactive particles are found associated with areas where basement membrane is being laid down. The underlying ectoderm does not show immunoreactivity. We conclude that haemocytes contribute to basement membrane formation in embryonic locusts.
Distribution of cytoplasmic and axonemal dyneins in rat tissues
Authors: Yoshida Toshimichi , Takanari Hideki , Izutsu Kosaku 
Published: April 2021

ABSTRACT
Microtubule-associated protein IC (MAP 1C) is now defined as brain cytoplasmic dynein. Recent studies have suggested that cytoplasmic dynein is a motor protein responsible for the intracellular microtubule-based motility in neuronal and non-neuronal cells. We have prepared an antibody against bovine brain MAP 1C and have examined the localizations of cytoplasmic dynein in rat tissues. Immunoblots of extracts from the tissues showed that the dynein was present in brain, testis, liver, kidney and lung. Immunohistochemical experiments have demonstrated that dynein is localized in Purkinje cells of cerebellum and axons of central and peripheral nervous systems. In non-neuronal tissues, the antibody staining was intense in many types of cells, such as hepatocytes, epithelia of renal convoluted tubules, secretory cells of adrenal medulla and spermatids. Glomeruli of kidney, bronchial epithelia and type II pneumocytes of lung, pancreatic islets and acini, adrenal cortex and Sertoli cells were moderately positive upon exposure to the cytoplasmic dynein antibody. On the other hand, the localization of axonemal dynein was examined using antibodies against flagellar dynein of sea urchin spermatozoa. Anti-axonemal dynein labeled cilia and flagella in rat tissues whereas anti-MAP 1C did not stain axonemes. We also tested for immunological crossreactivity between cytoplasmic and axonemal dyneins to probe for molecular similarities. Anti-axonemal dynein reacted with MAP 1C weakly. These results have confirmed that cytoplasmic dyneins are distributed widely among rat organs, not only in neuronal but also in non-neuronal tissues. There is no similarity in the localization of cytoplasmic and axonemal dyneins but there is some similarity in molecular antigenicity.
Recognition of collagen by fibroblasts through cell surface glycoproteins reactive with Phaseolus vulgaris agglutinin
Authors: Asaga Hiroaki , Yoshizato Katsutoshi 
Published: April 2021

ABSTRACT
The role of glycochains of cell surface glycoproteins in the cell to collagen interaction was examined by studying the effect of lectins on the fibroblast-mediated collagen gel contraction. Lectins of Phaseolus vulgaris agglutinin (PHA), concanavalin A (ConA), lentil seed agglutinin (LCA), pea agglutinin (PSA), Ricinus communis ag-glutinin-60 (RCA), and wheat germ agglutinin (WGA) dose-dependently inhibited gel contraction, while lectins of mushroom agglutinin (ABA), peanut agglutinin (PNA), pokeweed mitogen (PWM), and soybean agglutinin (SBA) did not. Of these lectins, PHA seemed to be worthy of further analysis, because PHA, but not other lectins, inhibited spreading of fibroblasts on collagen fibrils but not on plastic or gelatin, suggesting that cell-surface glycoproteins responsive to the lectin are involved in the specific binding of fibroblasts to native collagen fibrils. The inhibitory effect of PHA-E4, an isolectin of PHA, was more intense than that of PHA-L4, another isolectin of PHA. The collagen gel contraction was also inhibited by tunicamycin and monensin in a concentration-dependent and reversible manner. These results strongly suggest that PHA-E4-reactive glycoproteins of the fibroblast surface play an important role in cell to collagen binding during the gel contraction. Five membrane proteins including β1 subunits of the integrin family were obtained by affinity chromatography with PHA-E4.
The extended tubulin superfamily
Authors: McKean Paul G. , Vaughan Sue , Gull Keith 
Published: April 2021

Although most eukaryotic cells can express multiple isotypes of αβ-tubulin, the significance of this diversity has not always been apparent. Recent data indicate that particular αβ-tubulin isotypes, both genome encoded and those derived by post-translational modification, can directly influence microtubule structure and function — thus validating ideas originally proposed in the multitubulin hypothesis over 25 years ago.It has also become increasingly evident over the past year that some (but intriguingly not all) eukaryotes encode several other tubulin proteins, and to date five further members of the tubulin superfamily, γ, δ, ϵ, 𝛇 and η, have been identified. Although the role of γ-tubulin in the nucleation of microtubule assembly is now well established, far less is known about the functions of δ-, ϵ-, 𝛇- and η-tubulin. Recent work has expanded our knowledge of the functions and localisation of these newer members of the tubulin superfamily, and the emerging data suggesting a restricted evolutionary distribution of these `new' tubulin proteins, conforms to established knowledge of microtubule cell biology. On the basis of current evidence, we predict that δ-, ϵ-, 𝛇- and η-tubulin all have functions associated with the centriole or basal body of eukaryotic cells and organisms.
Growth factors but not gap junctions play a role in injury-induced Ca2+ waves in epithelial cells
Authors: Klepeis Veronica E. , Cornell-Bell Ann , Trinkaus-Randall Vickery 
Published: April 2021

This paper characterizes the early responses of epithelial cells to injury. Ca2+ is an important early messenger that transiently increases in the cytoplasm of cells in response to external stimuli. Its elevation leads to the regulation of signaling pathways responsible for the downstream events important for wound repair, such as cell migration and proliferation. Live cell imaging in combination with confocal laser scanning microscopy of fluo-3 AM loaded cells was performed. We found that mechanical injury in a confluent region of cells creates an elevation in Ca2+ that is immediately initiated at the wound edge and travels as a wave to neighboring cells, with [Ca2+]i returning to background levels within two minutes. Addition of epidermal growth factor (EGF), but not platelet-derived growth factor-BB, resulted in increased [Ca2+]i, and EGF specifically enhanced the amplitude and duration of the injury-induced Ca2+ wave. Propagation of the Ca2+ wave was dependent on intracellular Ca2+ stores, as was demonstrated using both thapsigargin and Ca2+ chelators (EGTA and BAPTA/AM). Injury-induced Ca2+ waves were not mediated via gap junctions, as the gap-junction inhibitors 1-heptanol and 18α-glycyrrhetinic acid did not alter wave propagation, nor did the cells recover in photobleaching experiments. Additional studies also demonstrated that the wave could propagate across an acellular region. The propagation of the injury-induced Ca2+ wave occurs via diffusion of an extracellular mediator, most probably via a nucleotide such as ATP or UTP, that is released upon cell damage.Movies available on-line
Cell-cell adhesion and signal transduction duringDictyosteliumdevelopment
Authors: Coates Juliet C. , Harwood Adrian J. 
Published: April 2021

The development of the non-metazoan eukaryote Dictyostelium discoideum displays many of the features of animal embryogenesis, including regulated cell-cell adhesion. During early development, two proteins, DdCAD-1 and csA, mediate cell-cell adhesion between amoebae as they form a loosely packed multicellular mass. The mechanism governing this process is similar to epithelial sheet sealing in animals. Although cell differentiation can occur in the absence of cell contact, regulated cell-cell adhesion is an important component of Dictyostelium morphogenesis, and a third adhesion molecule, gp150, is required for multicellular development past the aggregation stage.Cell-cell junctions that appear to be adherens junctions form during the late stages of Dictyostelium development. Although they are not essential to establish the basic multicellular body plan, these junctions are required to maintain the structural integrity of the fruiting body. The Dictyostelium β-catenin homologue Aardvark (Aar) is present in adherens junctions, which are lost in its absence. As in the case of its metazoan counterparts, Aar also has a function in cell signalling and regulates expression of the pre-spore gene psA.It is becoming clear that cell-cell adhesion is an integral part of Dictyostelium development. As in animals, cell adhesion molecules have a mechanical function and may also interact with the signal-transduction processes governing morphogenesis.
The factor affecting the spreading of chondrocytes upon inorganic substrate
Authors: Takeichi M. 
Published: April 2021

ABSTRACT
The effect of conditioned medium (CM) prepared from mass-cultures of chick embryonic cells was studied on the spreading behaviour of chondrocyte derived from sterna of 16-day-old chick embryos.
Freshly dissociated chondrocytes exhibited a quite rounded form, and this shape did not change when they were cultured with fresh medium (Eagle’s MEM + 6 % foetal calf serum) in vitro for several days. Non-dialysable material(s) in CM added into the fresh medium stimulated the formation of pseudopods of chondrocytes, without primarily affecting the synthesis of chondroitin sulphates. Such an activity of CM was not lost after boiling, but it was lost following treatment with proteases. The chondrocytes covered with newly deposited acsidmucopoly saccharides were insensitive to the effect of CM, but they became sensitive to form pseudopods after treatment of the cells with chondroitinase.
These results suggest that CM contains a macromolecular material(s) to enhance the motility or adhesiveness of chondrocytes.
A quantitative analysis of the effects of the intraneural injection of lysophosphatidyl choline
Authors: Gregson N. A. , Hall Susan M. 
Published: April 2021

ABSTRACT
Some quantitative aspects of the demyelinating lesion, and its progress, produced by the in vivo injection of lysophosphatidyl choline (LPC) into the myelinated peripheral nerves of adult mice have been investigated. The extent of the lesion has been shown to be highly localized to the injection site and dependent on the concentration of LPC. The length of the demyelinating zone appears to be determined within the first hour following the injection. The resulting demyelination occurs in units of whole internodes and over 40 % of the fibres involved show the loss of only one internode. The length of the demyelinated zone does not show any obvious dependency on axon diameter. Remyelination has started by day 14 and involves on average the replacement of each original internode by 2 new segments. There is a cellular proliferation in response to the injection, starting within the first week and achieving a maximum between 2–3 weeks. Of the extra cells 70—80 % are not axon-associated and of these 50% are supemumary Schwann cells. The use of 14C-oleate and 3H-stearyl LPC indicates that the injected LPC can be converted into lecithin, but also that the fatty acid moiety of LPC becomes distributed amongst the other lipid classes. Pretreatment of the nerve with small amounts of KCN blocks the metabolism of the injected LPC and renders all of the cells subject to lysis.
Ultrastructure of an unusual contractile vacuole in several chrysomonad phytoflagellates
Authors: Aaronson S. , Behrens U. 
Published: April 2021

ABSTRACT
The ultrastructure of the contractile vacuole of Ochromonas and Poterioochromonas species is described. It appears to be a permanent structure in the anterior end of the phytoflagellate, consisting of a central cavity with a unit-membrane lining from which flattened saccules protrude in all directions.
The contracted saccules are about 40 nm in diameter and are made up of a single trilammellar unit membrane about 9 nm thick and continuous with the central cavity membrane. In their contracted state the saccules contain transverse fibrils which may be involved in the contraction of the saccules ; these fibrils are no longer seen when the central cavity and the saccules swell. The saccules seem to merge and become continuous with the central cavity during the swelling of the contractile vacuole.
Nuclear sheets in the egg of a fern, Dryopteris filix-mas
Authors: Bell P. R. 
Published: April 2021

ABSTRACT
In the maturing egg of Dryopteris filix-mas the nucleus is shown to produce sheet-like extensions into the cytoplasm, resembling those described in certain somatic cells of animals. In these sheets the distance between the 2 inner membranes of the envelope is regularly of the order of 45-50 nm, and the nuclear material is organized into a monolayer of electron-opaque aggregates 35-40 nm in diameter, occasionally with a central space.
Much of the osmiophilic material of the aggregates is removed by pronase and trypsin, leaving granular osmiophilic material, but no fibrils. Ribonuclease and deoxyribonuclease produced little effect. Tritiated thymidine, fed for 6 h before fixation to maturing eggs, could not be shown to be incorporated into the aggregates, despite marked incorporation into plastids and mitochondria. In the absence of compelling evidence that the electron-opaque material is chromatin, it is proposed that the aggregates represent enzyme complexes concerned with membrane growth, believed to be active in the nuclear evaginations. These complexes are not considered to be confined to the sheet-like parts of evaginations, but to be brought into an aggregated form in the sheets as a result of compression, as suggested for the similar organization of chromatin in the nuclear sheets of animal cells.
Variation in eyespot ultrastructure in Chlamydomonas reinhardi (ac-31)
Authors: Gruber Helen E. , Rosario Benjamin 
Published: April 2021

ABSTRACT
Several morphological variations in eyespot complex fine structure were exhibited in some cells of the pale-green mutant strain ac-31 of Chlamydomonas reinhardi. The cells were grown in minimal medium supplemented with 0·2 % sodium acetate and were harvested by centrifugation and prepared for electron-microscopic examination.
Microtubules were seen near the flagella, confirming previous observations. Microtubules were also seen near the eyespot complex. Although a direct connexion between the microtubules of the flagellar and eyespot region was never observed, this does not exclude the possibility that it exists and thus provides a structural and functional connexion between the two organelles.
Occasionally irregular curved bodies intimately associated with the eyespot complex of some cells appeared to displace the chloroplast and cell membranes. These bodies often appeared to be nearly covered by a limiting membrane and were found near empty ‘cavities’ in the eyespot plate. Crystalline arrays of dense bodies were observed in some sections. The significance of these bodies is discussed in relation to the functional state of the carotenoid pigments making up the eyespot granules. An hypothesis for the formation of the rod-like structures is presented, based upon the observation of granules which had fused together to form a helix.
On the mechanism of the increased aggregation by neuraminidase of 16 c malignant rat dermal fibroblasts in vitro
Authors: Lloyd C. W. , Cook G. M. W. 
Published: April 2021

ABSTRACT
The aggregation of briefly trypsinized 16 C malignant rat dermal fibroblasts as measured by gyratory shaker/electronic particle counting technique is increased by neuraminidase. Enzyme treatment also exposes soybean and Ricinus communis agglutinin-binding sites as judged by cell agglutination. Desialysed bovine submaxillary mucin and desialysed, agalacto fetuin reversed the neuraminidase-stimulated increase in aggregation, whereas desialysed fetuin and ovalbumin did not. The effective glycoproteins also acted as acceptors in cellular sialyl- and galactosyl-transferase reactions, and these activities are detected in plasma membrane fractions.
The possibility that neuraminidase increases cellular aggregation by generating acceptor sites for interaction with cell surface glycosyltransferases, is discussed.
Cytokinesis in the heliozoan Actinophrys sol
Authors: Ockleford C. D. 
Published: April 2021

ABSTRACT
A study of cytokinesis in the heliozoan Actinophrys sol has been made using low-temperature treatments, antimitotic drugs, cytochalasin B, light microscopy and electron microscopy. It reveals that microtubular axopodia remain extended during cell division and play a major role in it.
Data indicate that when organisms are attached to the bases of culture dishes the normal locomotive mechanism of the presumptive daughter cells pulls them apart. However, when Actinophrys are floating freely in their culture medium, they are still able to undertake division. In this situation interactions between axopodia from opposite daughter cell bodies appear to facilitate the movement apart of the prospective daughter cells.
The present study and other published accounts indicate that a type of cytokinesis exists which is not explicable in terms of the ‘contractile ring’ or ‘fusing vesicle’ theories. To account for these observations a ‘barge pole’ model of division is suggested.
The localization of enzymes in fixed sections of soybean root nodules by electron microscopy
Authors: Marks I. , Sprent Janet I. 
Published: April 2021

ABSTRACT
Attempts were made to localize the following enzymes within bacteroids and host tissue: reduced-NAD oxidoreductase, succinate oxidoreductase, adenosinetriphosphate phosphorylase, diaminobenzidineoxidase, and xylylene diamine oxidase. Diaminobenzidine (DAB) staining was localized within the mitochondrial membranes and within the bacteroid cytomembrane and associated vesicles, whereas dehydrogenase enzymes within the bacteroids were for the greater part mesosomal. Peroxidative reduction of DAB and xylylene diamine within the bacteroid nuclear regions occurred in the presence of catalase, to which the cytomembrane appeared to be impermeable. A cyanide-insensitive oxidase localized within the bacteroid mesosomes and nuclear regions was not affected by the addition of catalase, aminotriazole or pyruvate. Ca2+-stimulated ATP-phosphorylase was localized within the bacteroid cytomembrane, whereas a Mg2+-stimulated ATP-phosphorylase was localized within the host cell plasma membrane.
Ultrastructural and biochemical observations on interphase nuclei isolated from chicken erythrocytes
Authors: Walmsley M. E. , Davies H. G. 
Published: April 2021

ABSTRACTAdult hen erythrocyte nuclei are isolated from cells or haemolysed in situ by acting on the plasma membrane with rotating knives or with non-ionic detergents. When the isolation medium contains magnesium 10ns (1 mM), sucrose (0·4 M) and Tris buffer (0· 01 M, pH 7· 5) called SMTOG (see text), the ultrastructure in thin sections through the condensed chromatin bodies, after staining with either uranyl-lead or phosphotungstic acid (PTA), is similar to that found in the intact cell. Hence it can be concluded that the 2 phases which comprise chromatin, the o- and the "-phase, survive nuclear isolation. These are so called because the structural units in chromatin are arranged at the surface of the nucleus into one or more layers and give rise to oddly (o) and evenly (e) numbered bands. The o-phase is also largely retained after extensive washing in 0 ·07 M NaCl as shown by electron microscopy and biochemical measurements; only 6% of the total nuclear protein is removed, a value small compared with the fractional amount of the chromatin protein calculated to lie in the o-phase, about 70%. After extensive washing in saline-EDTA there are structural changes in chromatin, but biochemical data show that the molecules in the o-phase are also largely retained; loss of protein amounts to between 5 and 11%.These data suggest that the o-phase is a structural component of the chromatin bodies. They support the hypothesis that condensed chromatin is formed by folding superunit threads. These units consist of a central thread-like element about 17 nm diameter which stains preferentially with uranyl-lead and forms the e-phase, with an outer cylindrical shell forming the o-phase of total diameter about 28 nm.The 5–10% proteins removed by salt washes are located exclusively in a particulate component, quite likely the chromatin. They have been examined by sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis. There are about 10 or more protein species, ranging in molecular weight from 21000 upwards. The groups of large granules previously found in the nuclear sap of intact erythrocytes are shown to be associated with an amorphous or finely fibrillar body. During nuclear isolation and subsequent washes, we observed the fate of this large granule complex as well as that of the nuclear envelope and the filled cavities in chromatin.