bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactions between mesoderm cells and the extracellular matrix following gastrulation in the chick embryo
Authors: Brown A. J. , Sanders E. J. 
Published: April 2021

ABSTRACT
In the gastrulating chick embryo, the mesoderm cells arise from the epiblast layer by ingression through the linear accumulation of cells called the primitive streak. The mesoderm cells emerge from the streak with a fibroblastic morphology and proceed to move away from the mid-line of the embryo using, as a substratum, the basement membrane of the overlying epiblast and the extracellular matrix. We have investigated the roles of fibronectin and laminin as putative substrata for mesoderm cells using complementary in vivo and in vitro methods. We have microinjected agents into the tissue space adjacent to the primitive streak of living embryos and, after further incubation, we have examined the embryos for perturbation of the mesoderm tissue. These agents were: cell-binding regions from fibronectin (RGDS) and laminin (YIGSR), antibodies to these glycoproteins, and a Fab’ fragment of the antibody to fibronectin. We find that RGDS, antibody to fibronectin, and the Fab’ fragment cause a decrease in the number of mesoderm cells spread on the basement membrane, and a perturbation of cell shape suggesting locomotory impairment. No such influence was seen with YIGSR or antibodies to laminin.
These results were extended using in vitro methods in which mesoderm cells were cultured in fibronec tin-free medium on fibronectin or laminin in the presence of various agents. These agents were: RGDS; YIGSR; antibodies to fibronectin, fibronectin receptor, laminin and vitronectin; and a Fab’ fragment of the fibronectin antiserum. We find that cell attachment and spreading on fibronectin is impaired by RGDS, antiserum to fibronectin, the Fab’ fragment of fibronectin antiserum, and antiserum to fibronectin receptor. The results suggest that although the RGDS site in fibronectin is important, it is probably not the only fibronectin cell-binding site involved in mediating the bevaviour of the mesoderm cells. Cells growing on laminin were perturbed by YIGSR, RGDS and antibodies to laminin, suggesting that mesoderm cells are able to recognise at least two sites in the laminin molecule. We conclude that the in vivo dependence of mesoderm cells on fibronectin is confirmed, but that although these cells have the ability to recognise sites in laminin as mediators of attachment and spreading, the in vivo role of this molecule in mesoderm morphogenesis is not yet certain.
Enhanced assembly of basement membrane matrix by endodermal cells in response to fibronectin substrata
Authors: Austria Martin R. , Couchman John R. 
Published: April 2021

ABSTRACT
Basement membranes are complex extracellular matrices contributing to the regulation of growth, migration and differentiation of many cell types. However, little is known about the mechanisms regulating the deposition and assembly of basement membrane from its constituents. We have investigated the role of extracellular matrix molecules in the control of basement membrane matrix assembly by cultured endodermal (PFHR-9) cells. In the presence of fibronectin-depleted serum, substrata of fibronectin or laminin induced an increase in deposition of laminin, type IV collagen and proteoglycans by PFHR-9 cells, in comparison to cells adherent to type I collagen-coated, vitronectin-coated or uncoated substrata.
Direct effects of fibronectin or laminin on the degree of cell spreading or rate of proliferation were not responsible for enhanced matrix deposition. The effect did not result from a redirection of basement membrane components to the matrix, since there was no decrease in matrix constituents released to the culture supernatants. Furthermore, the synthesis and release of other molecules that are not basement membrane constituents was unaltered in response to different extracellular matrix substrata. Experiments with fibronectin fragments showed that a 105×10;lMr ‘cell’-binding domain (containing the cell attachment sequence Arg-Gly-Asp-Ser) was an important contributor to enhanced matrix deposition, while the N-terminal 29×103Mr heparin-binding domain also contributed to the effect, particularly with respect to heparan sulfate proteoglycan deposition. It seems that fibronectin has a dual role of action in promoting basement membrane matrix assembly, through direct cell surface interactions, and through the binding of fibronectin to other matrix components that may nucleate or stabilize the matrix assembly.
Intranuclear distribution of Epstein-Barr virus-encoded nuclear antigens EBNA-1, -2, -3 and -5
Authors: Jiang Wei-Qin , Wendel-Hansen Vidar , Lundkvist Åke , Ringertz Nils , Klein George , Rosén Anders 
Published: April 2021

ABSTRACT
Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs) express at least seven virally encoded proteins. Their functional role, and their relationships to each other and to normal nuclear constituents are virtually unknown. As the first step towards a topographical study, the intranuclear distribution of EBV-encoded nuclear antigens EBNA-1, -2, -3 and -5 (abbreviated El, E2 etc.) was examined in EBV-transformed LCLs by immunofluorescence and digital image analysis of fluorescence patterns. E1-E3 showed a finely granular distribution. The E2 patterns were virtually identical when comparing indirect staining using an E2-specific mouse monoclonal antibody with anticomplement immunofluorescence using a human antibody, rendered monospecific to E2 by absorption. The E1/E2 patterns showed 32% overlap and the E2/E3 10% overlap in the high overlap category (66.7-100%), while the E2/E2 comparison with two reagents showed 61 % overlap in this category. This suggests that E2 and E3 largely appear in different nuclear structures, whereas El appears to be randomly distributed with regard to E2. The E5 pattern was radically different from that of El, E2 and E3. The anti-E5 mouse monoclonal antibody detected 4-10 huge, globular, sharply circumscribed dots, located in dispersed chromatin areas, while the distribution of El, E2 and E3 showed no obvious relationship to chromatin distribution. The methods described here allow a more refined topographical analysis of the EBNA protein family, mostly in relation to each other, in relation to other nuclear proteins, and with respect to specialized functional domains in interphase chromatin. The topology of the EBNA proteins relative to other nuclear components may provide important clues about the role of growth transformation-associated proteins in cellular immortalization and viral latency.
Further observations on nucleolar tails in amphibian oocytes
Authors: León Pedro , Kezer James , Schabtach Eric 
Published: April 2021

ABSTRACT
Large oocytes from some amphibian species possess beaded or unbeaded intranuclear tails that penetrate the extrachromosomal nucleoli through a distinct pit in their surface and attach to the central core component Here we show, using light and electron microscopy, that tails anchor nucleoli to the nuclear envelope through intricate attachment structures. These structures are composed of interconnected spherical masses containing highly convoluted tubules and associated extratubular proteins, directly in contact with the inner nuclear membrane. Fibers emerging from the nuclear pores seemingly hold the attachment complex in place. Beads on the nucleolar tails are formed by the accumulation of proteins on the outer surface of smooth tubules. The function of these intranuclear tubules is unknown.
Comparative behavior of lysosomes and the pre-lysosome compartment (PLC) in in vivo cell fusion experiments
Authors: Deng Yuping , Griffiths Gareth , Storrie Brian 
Published: April 2021

ABSTRACT
Interspecies cell fusion was used to compare protein intermixing within the mannose 6-phosphate receptor (MPR)-enriched pre-lysosome compartment (PLC) and within the MPR-negative lysosomal compartment. Both compartments were positive for lysosomal glycoprotein (Igp) membrane markers but were morphologically distinct In most experiments, rat-mouse cell syncytia were formed by u.v.-inactivated Sindbis virus-mediated fusion. By immunogold electron microscopy of syncytia, extensive intermixing of species-specific lysosomal membrane proteins was observed in both lysosomes and PLC. At 3 h post cell fusion, multiple-label immunogold studies showed that 82% of the lysosome-like structures positive for the rat lysosomal membrane protein LIMP-I were also positive for the mouse lysosomal membrane protein mLAMP-1. By immunofluorescence, LIMP-I and mLAMP-1 co-localized with a t| of 30 min after cell fusion; although the Igp-positive organelle populations had evidently interchanged their proteins, the lysosomal structures remained small, punctate bodies distributed throughout the syncytoplasm as observed in single cells. In contrast, the initially separate units of the PLC congregated with a t| of 1 h to form large, pre-lysosome complexes associated with individual nuclear clusters. At the electron-microscope level, gold markers endocytized by the rat and mouse parent cells in a 1h uptake followed by a 16-20 h chase co-localized in these extended PLC complexes, as did the membrane markers mLAMP-1 and LIMP-I. The density of labeling for rat MPR in the extended PLCs was markedly decreased, consistent with membrane fusions and dilution of the antigen upon congregation of the PLC compartments from the donor cells. The extended PLC complex behaved as a late endocytic compartment, as shown by co-localization of the MPR and rhodamine-dextran following a 10 min dextran uptake and a 50 min chase. These differences in behavior between lysosomes and the PLC in rat-mouse cell syncytia suggest that the pathway(s) of protein intermixing with respect to the two organelles may be different.
Rapid epithelialisation of fetal wounds is associated with the early deposition of tenascin
Authors: Whitby David J. , Longaker Michael T. , Harrison Michael R. , Adzick N. Scott , Ferguson Mark W. J. 
Published: April 2021

ABSTRACT
Wound healing is a complex process involving the interaction of many cell types with the extracellular matrix (ECM). Fetal skin wound healing differs from that in the adult in that it occurs rapidly and without scar formation. The mechanisms underlying these differing processes may be related to the fetal environment, the stage of differentiation of the fetal cells or the ECM deposited in the wound. The spatial and temporal distribution of two components of the ECM, fibronectin and tenascin, were studied by immunostaining of cryosections from trunk wounds of fetal and adult sheep.
Epithelialisation was complete earlier in the fetal wound than in the adult. The distribution of fibronectin was similar in fetal and adult wounds but tenascin was present earlier in the fetal wound. Fibronectin has several roles in wound healing including acting as a substratum for cell migration and as a mediator of cell adhesion through cell surface integrins. The attachment of fibroblasts to fibronectin is inhibited by tenascin and during development the appearance of tenascin in the ECM of migratory pathways correlates with the initiation of cell migration. Similarly, the appearance of tenascin in healing wounds may initiate cell migration. Tenascin was present in these wounds prior to cell migration and the rapid epithelialisation of fetal wounds may be due to the early appearance of tenascin in the wound.
Distinct effects of cell-cell communication and corticosteroids on the synthesis and distribution of cytokeratins in cultured rat hepatocytes
Authors: Baffet Georges , Loyer Pascal , Glaise Denise , Corlu Anne , Etienne Pierre-Luc , Guguen-Guillouzo Christiane 
Published: April 2021

ABSTRACT
Cytokeratins CK 8 and CK 18 are the two keratins expressed in the liver. They are known to undergo extensive changes in expression with alteration of the hepatocyte phenotype in vitro. In this study, we have investigated the variation in levels of these two cytokeratins in hepatocytes selected from different situations in vivo. The amounts of corresponding transcripts were compared; cytokeratin 8 and 18 mRNAs were present at similar levels in hepatocytes freshly isolated from adult liver and, unexpectedly, from 17-day-old foetuses and newborn rats, whereas they were markedly higher in regenerating hepato-cytes isolated early after partial hepatectomy. In order to investigate whether the different factors that can promote hepatocyte differentiation also produce a similar set of cytoskeletal changes, we have analysed both the expression and the distribution of cytokeratins in hepatocytes under different culture conditions allowing modulation of differentiation. Establishment of cell-cell contacts and addition of glucocorticoids were used as two modulating factors. Coculturing hepatocytes with rat liver epithelial cells (RLEC), which favours active expression of liver-specific genes, resulted in a gradual decline of cytokeratin mRNAs, whereas pure hepatocyte cultures, which exhibit rapid phenotypic changes, expressed increasing levels of CK 8 and CK 18 transcripts. Furthermore, intracellular CK distribution was dramatically modified in parallel: the CK-positive material formed a fine network of fibrils uniformly distributed in the cytoplasm of hepatocytes in pure culture, whereas in cocultured cells CK immunofluorescence appeared principally located at the cellular periphery and it was regularly arranged in long fibrils just beneath the plasma membrane. In contrast, addition of corticosteroids that strongly induces serum albumin synthesis in both pure cultures and cocultures increased the expression of cytokeratin genes in the two systems in a dose-dependent manner, and did not markedly affect their cellular location. These results confirm that the expression level of CKs 8 and 18 varies with the state of differentiation of mature hepatocytes in vivo and in vitro. They demonstrate that both the expression level and cytoplasmic distribution are involved in the morphological changes associated with the differentiated hepatocyte phenotype. In addition, they suggest that cell-cell interactions and glucocorticoids act as distinct regulators of cytoskeletal architecture.
Mikboskofische bt.tckf. in den inneren bad nvn das leben dee gewächse, &C. (Microscopical Glance into the Intimate Structure and Life of Plants. In the form of Popular Lectures.)
Authors: Ross-Massler E. A. 
Published: April 2021

ABSTRACT
The whole is contained in four discourses. In the first the author compares the different modes in which natural history, or the idea contained in it, is comprehended by different classes of minds. To the one it is simply a chamber of mystery—to another a study—to a third a means of climbing to ease and renown—to a fourth a picture-book. To all, he says, it ought to be a “beautiful maternal home, to be a stranger in which should be regarded, in any one, as a loss and shame.” He touches upon the question whether natural history is a real or merely a humanistic science, and decides in favour of the latter, seeing that the homo is still a part of the kingdom of nature—a convenient, but surely a dangerous argument ! He lauds the value of the microscope in the natural sciences ; and then proceeds, in more immediate application to his subject, to show, that plants consist of cells., explaining what is meant by the latter. In the second discourse the theme is continued ; the peculiar forms of cells are described, and then the cell-contents : colouring matter, crystals, nucleus, starch, and the spiral filaments. The ensuing chapter discourses about the vessels and their modifications, and then adverts to the tissues formed immediately from the elementary organs, such as the cuticle with its stomata, hairs, setæ, and scales ; to the structure of the leaf and ligneous stem in the mono- and dicotyledonous plants. The fourth chapter embraces the distinction between animals and plants, with respect to individuality and their various vital actions ; the nutrition of plants and their importance with respect to the habitability of the earth ; and lastly, the alternating relation between animals and plants. The last discourse treats of the root, the changes of matter effected in the interior of plants, the ascent and descent of the nutritive sap, and finally, of the parts belonging to fructification, and of fructification itself.
On the Irritability of Ciliated Cells
Authors: Virchow Rud. 
Published: April 2021

ABSTRACT
Among the many extraordinary circumstances with which the phenomenon of ciliary motion is surrounded, it has not been the least, that we have scarcely been acquainted with a proper excitant of it. Whilst we were able to call the contractile substances into activity by mechanical, physical, and chemical agencies, the founders of the doctrine of ciliary motion, Purkinje and Valentin, could, as regards the cilia, find nothing but means to impede or destroy it. And the influence of mechanical agitation, the only means by which they had seen the failing vibration again become more vigorous, was doubted by Sharpey. Can it be said, therefore, that the ciliary substance is wholly and entirely different from the other contractile substances ?
On the Germination of the Spores of the Uredineæ
Authors: Tulasne M. L. B. 
Published: April 2021

ABSTRACT
The author had previously shown that the spores of the Uredineæ, like the pollen-grains of phanerogamous plants, had a variable number of pores, from which afterwards tubular filaments arose, apparently analogous to those which are the first result of the germination of the spore of a fungus.
Botanical Letters to A Friend
Authors: Unger Dr. F. , Paul Dr. B. 
Published: April 2021

ABSTRACT
Nothing distinguishes our age more than the tendency that exists on the part of those who cultivate Science to diffuse its truths as widely and extensively as possible. The age of conservation in science is. over, and the dream of those who would confine it to our universities, colleges, or royal societies, is for ever dispelled. Much as we are indebted for this condition of things to the practical sagacity of Englishmen, and can boast of a large popular scientific literature in our own language, we have yet to offer a large meed of praise to the professors of science in the German universities, for their attempts to teach beyond the limits of their college walls, and to gain an audience amongst the hitherto despised Philistines. To Humboldt, Liebig, Schleiden, Buff, Moleschott, Schacht, we are indebted for treatises tending to diffuse a knowledge of the highest truths of science, and to these we may now add the name of Unger. These Botanical Letters are an indication of the progress of botanical science. Let any one compare the manuals and introductions formerly put into the hands of students with this volume, and they will see how great has been the advancement in correct observation and generalization within the last few years. Instead of the mere dry details of the forms of the organs of plants, we are introduced to a knowledge of their intimate structure and the laws of their developement ; instead of an absurd comparison of plants and animals, and rude guesses at the functions of the former from a study of those of the latter, we have the physiology of the plant, established upon observations made upon its own structure alone. To all who have attended to the study of the physiology of plants it is known, that the use of the microscope, and that alone, has produced this change and tended to this advancement. The structure of organised bodies and their functions can no longer be studied without this instrument ; and it is only as it is skilfully used that we can expect to attain a true knowledge of the laws which govern the existence of organised beings.
Anatomisch-Histologische Untersuchungen Ueber Fische Und Reptilien
Authors: Leydig Dr. Franz 
Published: April 2021

ABSTRACT
We have more than once had occasion Quar. Jour, of Micros. Science,’ Nos. IV., V.) to refer to the labours of Dr. Leydig, who has done more than any one, of late years, towards extending our knowledge of histology to the lower Vertebrata and to the Invertebrata.
Der Baum. Studien Uber Bau Und Leben Der Hoheren Gewächse
Authors: Sohaoht Von Dr. H. 
Published: April 2021

ABSTRACT
We have already noticed Dr. Schacht’s previous works on the microscope as applied to botanical subjects, and his more important one upon the Plant-cell—and have again the pleasing task of directing our readers’ attention to another from his indefatigable pen—which, like the former, contains a vast amount of matter interesting especially to the microscopic observer.
Contributions to the knowledge of cutaneous diseases, Caused by parasitic growths
Authors: Gudden B. 
Published: April 2021

ABSTRACT
Bateman, following Willan, describes four species under the genus Pityriasis, two of which, P. capitis and P. rubra, varying according to their seat, consist merely in a morbidly increased formation of the epidermis ; P. nigra is unknown to the author, but P. versicolor, as was first noticed by Eichstadt in Froriep’s Notizen, 1846, depends upon a parasitic vegetable growth.
A flora and fauna within living animals
Authors: Leidy Joseph 
Published: April 2021

ABSTRACT
That there are animals which inhabit the bodies of other animals as their natural locality has long been known. Many of these are so obvious as to be popularly recognized under the name of “Worms.” It is, however, only since the extensive employment of the microscope in aiding vision, that any large addition has been made to those generally known. Not only is it found that each species of animal has its peculiar parasitic animal and plant, but every species of animal appears to have a Flora and a Fauna of its own. Formerly a country was necessary to supply the materials of a Fauna or Flora, but with the microscope in hand the stomach of an insect affords abundance of peculiar species of animals and plants for such a purpose. Dr. Leidy’s work is not an account of all the species of plants found in living animals, but an account of certain new genera and species of plants discovered by himself in the stomach and intestines of a few species of insects. In an introduction, Dr. Leidy refers to the plants and animals of the human body. These are treated of at length in the works of Dujardin,* Diesing,-†- and Robin.‡
On some new or little-known Diseases of Plants, caused by Fungi
Authors: Braun Alex , Caspary  , Bary Anton De 
Published: April 2021

ABSTRACT
In the introductory part of this brochure, Dr. A. Braun says that, “As the history of the civilization of the human race has its dark side in the development of many obstinate social evils which accompany the march of advancing civilization, so also has horticulture and agriculture, together with the bright, their dark side. There are certain diseases to which plants, in the state of cultivation show themselves to be more obnoxious than when they are in their natural localities, and subject to the original conditions requisite for their flourishing. That this dark side fully deserves the attention of the gardener and of the farmer, is obvious, from the incalculable evils that ensue upon the mysterious and unexpected appearance of one of these vegetable plagues. The more difficult it appears to investigate the causes of these diseases, and to discover means by which they may be arrested or prevented, so much the more are they worthy of profound study.”
On a “Black Fur on the Tongue.”
Authors: Coblenz Eulenberg 
Published: April 2021

ABSTRACT
The author relates that in the preceding year a child, two years old, was brought to him whose tongue was covered with a perfectly black coating. The organ, from the tip to the back, appeared as if it were smeared with ink ; and at first sight the supposition necessarily entertained was, that the child had licked some black object, or had swallowed a coloured liquid. Except a slight diarrhœa, the boy presented no other morbid symptoms. For his age, he. was well developed, and had never had any important illness. The author’s immediate treatment was confined to washing the tongue with vinegar and water.