bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extracellular matrix histone H1 binds to perlecan, is present in regenerating skeletal muscle and stimulates myoblast proliferation
Authors: Henriquez Juan Pablo , Casar Juan Carlos , Fuentealba Luis , Carey David J. , Brandan Enrique 
Published: April 2021

Heparan sulfate chains of proteoglycans bind to and regulate the function of a wide variety of ligands. In myoblasts, heparan sulfate proteoglycans modulate basic fibroblast growth factor activity and regulate skeletal muscle differentiation. The aim of this study was to identify endogenous extracellular ligands for muscle cell heparan sulfate proteoglycans.[35S]heparin ligand blot assays identified a 33/30 kDa doublet(p33/30) in detergent/high ionic strength extracts and heparin soluble fractions obtained from intact C2C12 myoblasts. p33/30 is localized on the plasma membrane or in the extracellular matrix where its level increases during muscle differentiation. Heparin-agarose-purified p33/30 was identified as histone H1. In vitro binding assays showed that histone H1 binds specifically to perlecan. Immunofluorescence microscopy showed that an extracellular pool of histone H1 colocalizes with perlecan in the extracellular matrix of myotube cultures and in regenerating skeletal muscle. Furthermore, histone H1 incorporated into the extracellular matrix strongly stimulated myoblast proliferation via a heparan-sulfate-dependent mechanism.These results indicate that histone H1 is present in the extracellular matrix of skeletal muscle cells, where it interacts specifically with perlecan and exerts a strong proliferative effect on myoblasts, suggesting a role for histone H1 during skeletal muscle regeneration.
Sperm plasma-membrane-associated glutathione S-transferases as gamete recognition molecules
Authors: Hemachand Tummala , Gopalakrishnan Bagavathi , Salunke Dinakar M. , Totey Satish M. , Shaha Chandrima 
Published: April 2021

Glutathione S-transferases (GSTs) are enzymes that detoxify electrophilic compounds. Earlier studies from our laboratory showed that anti-GST antibodies interfered with the fertilising ability of spermatozoa from Capra hircus (goat) in vitro, suggesting that GSTs are localised at the cell surface. In this study, we provide evidence for the presence of GSTs of 24 kDa on the sperm plasma membrane attached by non-covalent interactions. The GST activity associated with the spermatozoal plasma membrane was significantly higher than the activity present in the plasma membranes of brain cells,hepatocytes, spleenocytes and ventriculocytes. Analysis of GST isoforms demonstrates the presence of GST Pi and Mu on the sperm plasma membranes. Both isoforms were able to bind to solubilised as well as intact zona pellucida(ZP) through their N-terminal regions but failed to bind to ZP once the oocytes were fertilised. Solubilised goat ZP separates into three components,one of which, the ZP3-like component, bound to sperm GSTs. High concentrations of anti-GST antibodies or solubilised ZP led to aggregation of sperm GSTs,resulting in the release of acrosin. In contrast, inhibition of sperm GST binding to ZP, by saturation of binding sites for sperm GSTs on the solubilised ZP using peptides designed from the N-terminii of GST Pi or Mu or blocking of binding sites for ZP on sperm GSTs with antibodies raised against the N-terminal GST peptides, inhibited essential prefertilisation changes in sperm.These data therefore demonstrate the strategic location of catalytically active defensive enzymes on the sperm surface that also act as zona-binding proteins. Therefore, sperm-surface GSTs serve as bifunctional molecules in a transcriptionally inactive cell whose requirement for cellular defense and economy of molecules that it can carry is greater than that of any somatic cell type.
Resistance of keratinocytes to TGFβ-mediated growth restriction and apoptosis induction accelerates re-epithelialization in skin wounds
Authors: Amendt Christiane , Mann Amrit , Schirmacher Peter , Blessing Manfred 
Published: April 2021

The pleiotropic growth factor TGFβ plays an important role in regulating responses to skin injury. TGFβ targets many different cell types and is involved in all aspects of wound healing entailing inflammation,re-epithelialization, matrix formation and remodeling. To elucidate the role of TGFβ signal transduction in keratinocytes during cutaneous wound healing, we have used transgenic mice expressing a dominant negative type II TGFβ receptor exclusively in keratinocytes. We could demonstrate that this loss of TGFβ signaling in keratinocytes led to an accelerated re-epithelialization of full thickness excisional wounds accompanied by an increased proliferation in keratinocytes at the wound edge. Furthermore, we show that impaired TGFβ signaling in keratinocytes reduces apoptosis in re-epithelialized wounds of transgenic animals.A cDNA array identified the transcription factor early growth response factor 1 (Egr1) as a target gene for TGFβ in late phases of the wound healing process. As a member of the immediate-early gene family, Egr1 is upregulated shortly after injury and induces the expression of growth factor genes. We could demonstrate that Egr1 expression is also upregulated in skin wounds which have already undergone re-epithelialization. In conclusion, we attribute the enhanced re-epithelialization in our transgenics to the resistance of keratinocytes to TGFβ-mediated growth restriction and apoptosis induction. We also propose a new role for TGFβ induced Egr1 in late phase wound repair.
NCAM regulates cell motility
Authors: Prag Søren , Lepekhin Eugene A. , Kolkova Kateryna , Hartmann-Petersen Rasmus , Kawa Anna , Walmod Peter S. , Belman Vadym , Gallagher Helen C. , Berezin Vladimir , Bock Elisabeth , Pedersen Nina 
Published: April 2021

Cell migration is required during development of the nervous system. The regulatory mechanisms for this process, however, are poorly elucidated. We show here that expression of or exposure to the neural cell adhesion molecule (NCAM) strongly affected the motile behaviour of glioma cells independently of homophilic NCAM interactions.Expression of the transmembrane 140 kDa isoform of NCAM (NCAM-140) caused a significant reduction in cellular motility, probably through interference with factors regulating cellular attachment, as NCAM-140-expressing cells exhibited a decreased attachment to a fibronectin substratum compared with NCAM-negative cells. Ectopic expression of the cytoplasmic part of NCAM-140 also inhibited cell motility, presumably via the non-receptor tyrosine kinase p59fyn with which NCAM-140 interacts.Furthermore, we showed that the extracellular part of NCAM acted as a paracrine inhibitor of NCAM-negative cell locomotion through a heterophilic interaction with a cell-surface receptor. As we showed that the two N-terminal immunoglobulin modules of NCAM, which are known to bind to heparin, were responsible for this inhibition, we presume that this receptor is a heparan sulfate proteoglycan. A model for the inhibitory effect of NCAM is proposed, which involves competition between NCAM and extracellular components for the binding to membrane-associated heparan sulfate proteoglycan.
How nematode sperm crawl
Authors: Bottino Dean , Mogilner Alexander , Roberts Tom , Stewart Murray , Oster George 
Published: April 2021

Sperm of the nematode, Ascaris suum, crawl using lamellipodial protrusion, adhesion and retraction, a process analogous to the amoeboid motility of other eukaryotic cells. However, rather than employing an actin cytoskeleton to generate locomotion, nematode sperm use the major sperm protein (MSP). Moreover, nematode sperm lack detectable molecular motors or the battery of actin-binding proteins that characterize actin-based motility. The Ascaris system provides a simple ‘stripped down’ version of a crawling cell in which to examine the basic mechanism of cell locomotion independently of other cellular functions that involve the cytoskeleton. Here we present a mechanochemical analysis of crawling in Ascaris sperm. We construct a finite element model wherein (a) localized filament polymerization and bundling generate the force for lamellipodial extension and (b) energy stored in the gel formed from the filament bundles at the leading edge is subsequently used to produce the contraction that pulls the rear of the cell forward. The model reproduces the major features of crawling sperm and provides a framework in which amoeboid cell motility can be analyzed. Although the model refers primarily to the locomotion of nematode sperm, it has important implications for the mechanics of actin-based cell motility.Movies available on-line.
Activation of SGK1 by HGF, Rac1 and integrin-mediated cell adhesion in MDCK cells: PI-3K-dependent and -independent pathways
Authors: Shelly Candace , Herrera Roman 
Published: April 2021

The SGK1 protein belongs to the AGC gene family of kinases that are regulated by phosphorylation mediated by PDK1. SGK1 regulation is accomplished by several pathways including growth-factor and stress-mediated signaling. We have expanded the analysis of SGK1 regulation in epithelial cells. We used HA-tagged SGK1 to transiently transfect MDCK cells and study the regulation of SGK1 upon stimulation with HGF, cAMP or upon adhesion of the cells to immobilized fibronectin. In addition, we studied the regulation of SGK1 activity by small GTP-binding proteins of the Rho family.Treatment of MDCK cells with HGF leads to a time-dependent activation of SGK1 that is blocked by wortmanin. This activation requires the conserved phosphorylation site present in the activation loop of the kinase (T256 in SGK1) and the phosphorylation site present in a hydrophobic domain at its C-terminus (S422 in SGK1), which are targets for PDK1/PDK2-mediated regulation of SGK1. We tested whether SGK1 could be activated by cAMP as it contains a putative PKA site. We were unable to demonstrate a significant activation of HA-SGK1 by cAMP stimulation under conditions where we detect cAMP-mediated phosphorylation of the transcription factor CREB.Cotransfection of SGK1 with activated small GTP-binding proteins revealed that Rac1, but not Rho or Rap1, induces activation of SGK1. However, this activation was wortmanin insensitive and dominant-negative Rac1 did not inhibit the HGF-mediated activation of SGK1. Adhesion of MDCK cells to immobilized fibronectin also leads to activation of SGK1. However, it appears that the integrin-mediated activation of HA-SGK1 differs from AKT activation in the fact that AKT phosphorylation was blocked by wortmanin (or LY294002)whereas HA-SGK1 was not. The adhesion-dependent activation, however, requires the intact phosphorylation sites of SGK1. Co-transfection of HA-SGK1 with RacV12 results in increased activity in adherent cells compared with HA-SGK1 alone. Since RacN17 failed to inhibit adhesion dependent-activation of SGK1,it suggests that integrin activation is achieved by a parallel Rac-independent pathway.The activation of SGK1 by HGF and integrin provides a link between HGF-mediated protection of MDCK from de-attachment induced apoptosis(anoikis). We demonstrate that dephosphorylation of the transcription factor FKRHL1 induced by cell de-attachment is prevented by activated SGK1,suggesting that SGK1 regulates cell survival pathways.In summary, we demonstrate that SGK1 activation could be achieved through signaling pathways involved in the regulation of cell survival, cell-cell and cell-matrix interactions. SGK1 activation can be accomplished via HGF,PI-3K-dependent pathways and by integrin-mediated, PI-3K independent pathways. In addition, activation of SGK1 by the small GTP-binding protein Rac1 has been observed.
An ultrastructural study of the pancreatic acinar cell in mitosis, with special reference to changes in the golgi complex
Authors: Melmed R. N. , Benitez Carol J. , Holt J. 
Published: April 2021

ABSTRACT
Changes occurring in the rat pancreatic acinar cell during mitosis have been studied by electron microscopy. Special attention has been given to those occurring in the Golgi complex. There is an initial increase in the number of small vesicles between the rough-surfaced endoplasmic reticulum and the saccules of the Golgi apparatus. These persist throughout the mitotic cycle. The Golgi apparatus becomes considerably smaller in metaphase. In anaphase the normal stacked appearance of its saccules is lost. In telophase the Golgi complex is restored to its normal interphase appearance and the small vesicles may contribute both to the reformation of its saccules and to the cleft forming between the daughter cells. Condensing vacuoles and zymogen granules appear to form throughout mitosis, although they have a much greater heterogeneity of size than in the interphase cell. The possible significance of some of these changes is discussed.
Chromosome analysis of two related heteroploid mouse cell lines by quinacrine fluorescence
Authors: Allderdice P. W. , Miller O. J. , Miller D. A. , Warburton D. , Pearson P. L. , Klein G. , Harris H. 
Published: April 2021

ABSTRACT
The fluorescent banding patterns of quinacrine-stained metaphase chromosomes have been studied in 2 related mouse cell lines, A9 and a malignant derivative of A9, A9HT. In both cell lines virtually every chromosome has a distinctive banding pattern which permits its recognition. More than three quarters of the chromosomes have structural rearrangements, but the origin of nearly two thirds of the chromosomes could be determined by their banding patterns. The quinacrine fluorescence technique permits far more detailed characterization and comparison of heteroploid cell lines than any previous method. A9 and A9HT are karyologically quite similar, with many of the same marker chromosomes. There are, however, characteristic differences. A9HT, although it has a smaller average number of chromosomes per cell, appears to be more heterogeneous.
The spermatozoon of arthropoda: XVIII. the non-motile bifurcated sperm of psychodidae flies
Authors: Baccetti B. , Dallai R. , Burrini A. G. 
Published: April 2021

ABSTRACT
The spermatozoa of some species of Diptera belonging to the Psychodidae are described. In the 4 species examined, they appear needle-shaped, non-motile, anteriorly flattened, posteriorly bifid. Flagella, and any microtubule system, are lacking, and the only organelles encountered are an extremely elongated nucleus, a prominent acrosome, a well developed subacrosomal body, a slender, somewhat elongated mitochondrial derivative and a conspicuous multilayered membrane wall, produced by the superimposition of the plasma membrane and the acrosomal membrane. The mitochondrion is devoid of a crystalline axis, while the acrosome contains a longitudinal, cross-striated para-crystalline body. Centrioles are absent throughout the spermatid stage. Sperms and spermatids are organized in syncytia of 210 elements.
The role of the epidermal cells in moulding the surface pattern of the cuticle in Rhodnius (hemiptera)
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
The patterns of folding in the epicuticle of Rhodnius result from mechanical forces directed by the epidermal cells and not from the action of physical forces arising spontaneously in the secreted substance. This conclusion is supported by observations on the cuticular folds over the abdomen of the larva and adult; on the formation of the plaques and the tactile setae arising from them; and on the taenidial folds in the tracheae.
At the time of formation of the outer epicuticle the boundaries of the definitive epidermal cells are clearly defined by adhesion zones. The total surface area of the cuticle is thus the sum of contributions determined by the individual cells.
The area of outer epicuticle deposited is greater than that of the apical plane of the cell. The cell surface is thrown into folds over which the epicuticle is laid down. But before the inner layers are deposited the cuticle is moulded by mechanical forces controlled by the epidermal cells.
Microtubules and fibre bundles appear to play an active part, notably in the outgrowth of setae, and perhaps in the raising of the initial folds in the abdominal surface and in the tracheae. The taenidial folds in the tracheae arise mainly at the sites of the folds in the preceding instar.
Cellular movements or changes in shape lead to aggregation of epidermal cells to form the ‘stellate pattern’ of the larval abdomen and the transverse ‘ripple pattern’ of the adult.
Distension of intercellular and intracellular vacuoles controls the moulding of the definitive stars in the larval cuticle, the transverse ridges in the adult, the smoothing of the cuticle over the plaques, the raising of the plaques in dome-like form above the rest of the cuticle, the expansion of the setae and the shaping of the taenidial folds in the tracheae.
The basement membrane provides a resistant substrate for these mechanical forces.
Human chromosomes in 18 man-mouse somatic hybrid cell lines analysed by quinacrine fluorescence
Authors: Allderdice P. W. , Miller O. J. , Pearson P. L. , Klein G. , Harris H. 
Published: April 2021

ABSTRACT
Chromosome studies were done on 18 somatic hybrid cell lines produced by fusing cells of the mouse A 9 line with cells of the human Daudi lymphoblastoid line derived from a patient with Burkitt’s lymphoma. The human chromosomes were identified by their quinacrine fluorescent banding patterns. In one hybrid line the human chromosomes were identified also by the centromeric heterochromatin staining technique. Every human chromosome was identified in one or more of the hybrid lines. Some lines were homogeneous in terms of their human chromosome content, while others were quite heterogeneous. Detailed analysis of the A 9 chromosomes in one hybrid line showed very few changes in comparison with the chromosome constitution of the average A 9 cell.
Hherisomes, Hedgehog specialized recycling endosomes, are required for high level Hedgehog signaling and tissue growth
Authors: Pizette Sandrine , Matusek Tamás , Herpers Bram , Thérond Pascal P. , Rabouille Catherine 
Published: April 2021

ABSTRACT
In metazoans, tissue growth and patterning is partly controlled by the Hedgehog (Hh) morphogen. Using immuno-electron microscopy on Drosophila wing imaginal discs, we identified a cellular structure, the Hherisomes, which contain the majority of intracellular Hh. Hherisomes are recycling tubular endosomes, and their formation is specifically boosted by overexpression of Hh. Expression of Rab11, a small GTPase involved in recycling endosomes, boosts the size of Hherisomes and their Hh concentration. Conversely, increased expression of the transporter Dispatched, a regulator of Hh secretion, leads to their clearance. We show that increasing Hh density in Hherisomes through Rab11 overexpression enhances both the level of Hh signaling and disc pouch growth, whereas Dispatched overexpression decreases high-level Hh signaling and growth. We propose that, upon secretion, a pool of Hh triggers low-level signaling, whereas a second pool of Hh is endocytosed and recycled through Hherisomes to stimulate high-level signaling and disc pouch growth. Altogether, our data indicate that Hherisomes are required to sustain physiological Hh activity necessary for patterning and tissue growth in the wing disc.
Sex in the Salicaceæ and its Modification by Eriophyid Mites and other Influences
Authors: Heslop Harrison J. W. 
Published: April 2021

ABSTRACTThe species of the two genera Populus and Salix are ordinarily diœcious. In the whole of the British Salix species and hybrids examined a preponderance of female plants, slight in the diploid forms, but great in the polyploids, was discovered. In the diploids this excess, if significant, probably arises from the slower growth of pollen tubes carrying the male determining gametes. In the polyploids that influence is assisted (a) by the occurrence ofapomixis with thelytoky; (b) by pseudo-fertilisation with thelytoky; (c) by circumstances arising from peculiarities marking the chromosome complexes of polyploid diœcious plants. Hybrid Salices, when combinations of diploid species, invariably possess males. Other hybrids of which at least one parent is polyploid, are exclusively female as far as observation goes or, at best, produce but few males. These latter features may arise from circumstances detailed in (4), or there may be a deliberate and permanent switch-over of the heterogametic sex as in my Lycia-Nyssia crosses. Certain hybrids produce, in addition to plants of the normal male and female types, androgynous or monœcious forms. These are explained as arising through environmental influences temporarily switching the metabolism of a male plant over from its normal condition to that characteristic of the opposite sex. If that be the correct view the switch-over must occur, with a subsequent reversal, annually. In the Capreœ group intersexual florets occur. Such are induced by the attacks of parasites in the form of mites of the Eriophyid group, in particular of Epitriments salicobius. They act by effecting local changes in the metabolism of the plant. The phenomenon is thus one of parasitic castration. Many similar cases are known, for which, for the most part, fungi are responsible.
Genetical and Cytological Studies in Hybrid Roses
Authors: Blackburn Kathleen B. , Heslop Harrison J. W. 
Published: April 2021

ABSTRACT
Rosa Sabini and R. Wilsoni are reciprocal crosses between R. pimpinellifolia and some Tomentosa microgene. Rosa pimpinellifolia is a balanced tetraploid, both the egg cell and the generative nucleus possessing 14 chromosomes. The Tomentosa microgenes are unbalanced pentaploids, the microspores, when functional, carrying 7 chromosomes in their nuclei, and the egg cells 28. Reciprocal crosses between R. pimpinellifolia and tomentosa forms should not therefore agree in chromosome complements. With pimpinellifolia as seed parent the cross should have 14 + 7 (= 21) in its somatic nuclei, and with the same plant as pollen parent the number should be 28 + 14 (= 42). R. Wilsoni undoubtedly has R. pimpinellifolia as seed parent, yet its chromosome number is 42. It has, therefore, like Primula Kewensis, doubled its original complement. In doing so, again like that hybrid, it has attained fertility.
The Function of the Anal Gills of the Mosquito Larva
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACTIn a recent paper (Wigglesworth, 1932a) the theory was put forward that the chief function of the so-called rectal glands of terrestrial insects is the reabsorption of water from the excreta in the rectum, and it was suggested that many of the supposedly respiratory structures in aquatic insects, such as the anal gills of the mosquito larva (which may perhaps be looked upon as homologous with rectal glands that have prolapsed through the anus), might also be concerned in absorbing water, not from the excreta, but from the surrounding medium. It has been shown in another place (Wigglesworth, 1932b) that the properties of the anal gills are such that they must almost certainly absorb water, but in the present paper this hypothesis will be proved experimentally.
Rheotaxis in Planaria Alpina
Authors: Beauchamp R. S. A. 
Published: April 2021

ABSTRACT
Pl. alpina is normally active in the evening and quiescent during the day. Pl. alpina is shown to become positively rheotactic when developing sexually, but becomes negatively rheotactic on completing the sexual cycle. Starvation leads to de-dififerentiation and the loss of positive rheotaxy. Feeding produces a temporary positive rheotaxy and a temporary negative geotaxy. Continued feeding leads, if temperature conditions are suitable, to the re-development of those characters which produce positive rheotaxy in sexual individuals. The development and consequently the behaviour of PL alpina is controlled by temperature and the food supply. Considerable migrations up and down the stream are brought about by changes in the animal’s behaviour.