bluuebunny/crossref_metadata_2025_split huggingface dataset:
The binding of the mucoprotein from gastric mucus to cells in tissue culture and the inhibition of cell adhesion
Authors: Allen A. , Minnikin S.Megan 
Published: April 2021

ABSTRACT
The mucoprotein, which is responsible for the formation of gastric mucous gel in pig, has been shown to bind equally well to suspensions of baby hamster kidney cells, polyoma-virus-transformed baby hamster kidney cells and HeLa cells. The binding of the mucoprotein to the cells is dependent on Ca2+/Mg2+ ions and is 5-fold greater at 37 than 4 °C. Prolonged treatment of the cells with trypsin reduces their binding capacity for the mucoprotein to less than half. The rate of adhesion of single “S-labelled baby hamster kidney cells, polyoma-transformed baby hamster kidney cells and HeLa cells to the different monolayers has been studied and found to be about the same for all 3 types of cell. The same gastric mucoprotein which bound to the cells also inhibited the adhesion of the different types of single cells to the monolayers. Thus, about one μmol l.-1 of gastric mucoprotein reduced the adhesion of single BHK cells to BHK monolayers to one-seventh of that in the absence of mucoprotein. The binding of the mucoprotein to the cells is essentially irreversible, and also single cells preincubated with the mucoprotein do not adhere to the monolayers when no free mucoprotein is present. Both the binding of the mucoprotein to the cells and its inhibitory action on cell adhesion are abolished if high concentrations of calf serum are included in the medium. Red blood cells neither adhere to each other nor do they bind the mucoprotein. The interaction of the mucoprotein with the cells is specific in that bovine serum albumin, calf serum, glycogen and hyaluronic acid neither affected the adhesion between the cells nor in the case of bovine serum albumin bound significantly. Furthermore, measurements of binding show that only a fraction of the purified mucoprotein (6%) has the necessary primary and/or tertiary structure to combine with the receptor sites on the cell surface. The similarities between the adhesion of the cells to monolayers and the binding of the gastric mucoprotein to these cells is discussed in terms of the importance of cell surface mucoproteins in cell adhesion.
Fine structure of the haplosporidan Kernstab, a persistent, intranuclear mitotic apparatus
Authors: Perkins F. O. 
Published: April 2021

ABSTRACT
The fine structure of the haplosporidan mitotic apparatus is described from observations of plasmodial nuclei of Minchinia nelsoni, M. costalis, Minchinia sp., and Urosporidium crescens. The apparatus, which is the Kernstab of light-microscope studies, consists of a bundle of microtubules terminating in a spindle pole body (SPB) at each end of the bundle. A few microtubules extend from SPB to SPB, but most either extend from an SPB and terminate in the nucleoplasm or lie in the nucleoplasm, free of either SPB. The bundle lengthens during mitosis, increasing the SPB-to-SPB distance by a factor of 2 to 3 as compared to interphase nuclei. SPBs arc not in contact with the nuclear envelope, being found always in the nucleoplasm which is delimited by the nuclear envelope throughout mitosis. The mitotic apparatus is persistent through interphase, at least in a form which is not significantly different from that found in mitotic nuclei.
Cell locomotion within a contact-inhibited monolayer of chick embryonic liver parenchyma cells
Authors: Garrod D. R. , Steinberg M. S. 
Published: April 2021

ABSTRACT
Using time-lapse filming, the relative movement of cells (nuclei) within a contact-inhibited monolayer of chick embryonic liver parenchyma cells has been studied. Two techniques were employed to determine the amount of relative cell movement during a culture period of 6 h. Firstly, the number of neighbours lost or gained by each nucleus was counted. Secondly, the relative distance moved by each nucleus in relation to other nuclei in the monolayer was measured. (The numerical results obtained from these analyses and details of the methods used are given in the text.) A considerable amount of relative movement of nuclei within the monolayer was found during this short period of culture.
Although some gaps were occasionally seen between the cells in the monolayer, it was observed that cells were able both to ‘ruffle ‘and to translocate when no gap was detectable; i.e. the cells appeared able to move while entirely surrounded by other cells. Because of this, we suggest that the monolayering of these epithelioid cells on a surface may be due to restriction of overlapping between them rather than to inhibition of movement by mutual contact. We argue that the term ‘contact inhibition of overlapping’ relates to this behaviour better than the term ‘contact inhibition of movement’.
The erythroid cells of anaemic Xenopus laevis. II. Studies on nuclear non-histone proteins
Authors: Hilder V. A. , Thomas Nesta , Maclean N. 
Published: April 2021

ABSTRACT
The mass ratio of nuclear non-histone protein: DNA in the immature circulating erythroid cells of phenylhydrazine-induced anaemic Xenopus is approximately threefold higher than in mature erythrocytes. This is largely due to the presence of increased amounts of low and intermediate molecular weight proteins in the nuclei of the immature cells. There are a few qualitative differences in the components of this class of proteins between the mature and immature cells, the most notable of which is the presence of a protein of molecular weight approximately 115 000 in the former which is not detectable in the latter. These changes are discussed in relation to the changing synthetic capacities of the cells and to certain generalizations about the function of the nuclear non-histone proteins based on studies of other differentiating systems.
The light microscope as an optical diffractometer
Authors: Gall J. G. 
Published: April 2021

ABSTRACT
The analysis of electron micrographs by optical diffraction was introduced recently by Klug & Berger (1964). Their experiments were conducted with a special diffractometer designed for use with diffracting masks up to several inches in diameter. A method is described here for using a conventional light microscope as an optical diffractometer which can accept masks up to 5 mm in diameter. A-100 μ electron-microscope aperture is used as a pinhole source of illumination, and the micrograph to be studied is introduced above the objective. The diffraction pattern produced by the micrograph appears in the usual image plane of the microscope within the eyepiece.
Identification of glycogen in thin sections of amphibian embryos
Authors: Perry Margaret M. 
Published: April 2021

ABSTRACT
Embryonic amphibian cells when examined with the electron microscope were observed to contain an abundance of small particles, approximately 325 Å in diameter. The periodic acid/ Schiff reaction and enzymic digestion were employed to determine the nature of the particles, and from the results of these tests they were concluded to be glycogen. Treatment of thin sections with periodic acid/lead citrate solutions resulted in a marked increase in contrast of the glycogen particles compared with other cell structures, and in a clearly defined substructure of 40-Å grains appearing within the particles. This differential staining method enabled the particulate glycogen to be distinguished from ribosomes.
Further observations on the fine structure of Chrysochromulina chiton with special reference to the haptonema, ‘peculiar’ golgi structure and scale production
Authors: Manton Irene 
Published: April 2021

ABSTRACT
A more detailed study of ‘peculiar’ Golgi structure in this organism has been attempted than in any similar species, using modem fixation methods. Where comparisons are possible there is close resemblance to the related genus Prymnesium, to a degree sufficient to suggest that this particular type of Golgi system is likely to be a major phyletic indicator for the class Hapto-phyceae. Certain stages of scale production have been traced and some developmental aspects of the whole system are discussed, though full interpretation is deferred. Some additional features of haptonema structure are described for the sake of completeness in characterizing the particular strain of the species under investigation. These include information on the internal structure of the haptonema tip.
Fine structure of chicken thymic epithelial vesicles
Authors: Isler H. 
Published: April 2021

ABSTRACT
This paper describes the fine structure of epithelial vesicles as observed in the thymus of the chicken. Three types of vesicles are found. The largest is made up of a stratified columnar epithelium containing lymphoid cells. The lumen contains a fairly light material and cell debris. The lumen-bordering cells are columnar and their microvilli are sometimes developed to such an extent as to appear as a brush border. The wall of the vesicles contains lymphocytes and granular cells with dense granules 100–500 nm in diameter. Smaller vesicles are found which contain no lymphoid cells. They are made of a simple or stratified epithelium containing typical mucous cells, and columnar cells similar to the bordering cells of the large vesicles. The third type is an intracytoplasmic vesicle in epithelial reticular cells, which differs from usual vacuoles by the presence of microvilli and its often unusually large size. The morphology of the first 2 types of vesicles indicates a secretory capability, the function of which is unknown. Data from the literature suggest that the third type produces the factor(s) conferring cellular immunological competence.
Fine-Structural Studies of the Gametes and Embryo ofFucus VesiculosusL. (Phaeophyta): I. Fertilization and Pronuclear Fusion*
Authors: Brawley Susan H. , Wetherbee Richard , Quatrano Ralph S. 
Published: April 2021

ABSTRACTIn the marine brown alga, Fucus vesiculosus L., the sperm pronucleus is delimited by an envelope following penetration of the egg by the sperm. This envelope disintegrates as the pronucleus begins its migration through the cytoplasm of the egg. The highly condensed chromatin of the sperm pronucleus disperses slightly following disintegration of the envelope. Microtubules of unknown origin are associated with the sperm pronucleus during its migration. The flagellar microtubules remain in the peripheral cytoplasm but lose their tight 9 + 2 configuration. The sperm eyespot and mitochondria follow the pronucleus through the cytoplasm toward the egg pronucleus. The mitochondria of the sperm are distinguished from those of the egg by their longitudinally oriented cristae and by electron-opaque material in the intracristal space. The pronucleus of the egg becomes convoluted along the surface nearest to the advancing sperm pronucleus. Immediately prior to pronuclear fusion, many egg mitochondria aggregate in the vicinity of the sperm pronucleus. At this time, only the portion of the sperm pronucleus facing the egg pronucleus is surrounded by an envelope. The egg mitochondria disperse rapidly after pronuclear fusion. The sperm mitochondria and eyespot are still in the perinuclear region in 16-h-old embryos. At this time, the osmiophilia of the sperm eyespot has increased, and the sperm mitochondrial membranes are less distinct than in earlier stages. The fine-structural features of fertilization in Fucus are discussed in relation to the fertilization patterns in other cryptogams and marine invertebrates and to polar axis determination in the Fucaceae.
Electron Microscopy of Interphase Chromosomes In Situ: Binding of Permanganate to Chicken Erythrocytes
Authors: Davies H. G. 
Published: April 2021

ABSTRACT
From quantitative electron-microscope observations on the binding of permanganate to regions of erythrocytes and reticulocytes of known chemical composition, it is concluded that KMnO4, like phosphotungstic acid (PTA), binds preferentially to sites on proteins. Compared with PTA, KMnO4 binding exhibits less anomalous behaviour. The data support the hypothesis previously put forward that the 2 regions, or phases, in condensed chromatin differ in both molecular composition and concentration. The increase in binding to protein which occurs during nuclear haemolysis is interpreted in terms of protein–protein interaction in the chromatin of the intact cell.
Platelet Dense Bodies: A Quantitative Microprobe Analysis
Authors: Skaer R. J. , Peters Patricia D. , Emmines J. P. 
Published: April 2021

ABSTRACT
The electron microprobe shows that the dense bodies of human platelets have a mean P:Ca peak ratio of 1·2. After treatment with dry chloroform/methanol this falls to 0·89. These ratios vary slightly from patient to patient. The use of calcium and phosphorus standards enables these peak ratios to be converted to atomic ratios. The size of the phosphorus peak remaining after lipid extraction was given absolute terms with reference to the known quantities of adenine nucleotides and inorganic pyrophosphate in dense bodies. From the mean P:Ca atomic ratio of 1·76 the quantity of calcium in dense bodies was 0·6 mg/1011 platelets or 2·97 mg Ca/g dry weight of platelets. This is within the published range for total platelet calcium. If all the phosphorus extracted by lipid solvents were phospholipid there would be 5·65 mg/1011 platelets, and it would occupy most of the space inside dense bodies. The dense bodies of pig platelets contain both magnesium and calcium in a varying ratio to each other. These results are discussed in relation to control mechanisms that may influence aggregation.
Surface morphology and agglutination of lectin-treated human lymphocytes and lymphoblasts
Authors: Temmink J. H. M. , Collard J. G. , Roosien J. , Bosch J. F. Van Den 
Published: April 2021

ABSTRACT
Two human lymphoblasts (Raji and EB3) and normal human peripheral lymphocytes were exposed to different concentrations of Concanavalin A and wheat germ agglutinin. The lectininduced agglutination was determined and correlated with lectin-induced changes in the surface morphology of these cells as studied in a scanning electron microscope. Whenever the lectin induced high agglutinability in a cell type, it also invariably had a smoothing effect on the cell surface. In contrast, when cells did not agglutinate well with a certain lectin, their cell surface remained essentially rough (villous) after addition of the lectin. The correlation found between increased agglutinability and altered cell surface morphology upon treatment with certain lectins suggests that both phenomena result from one and the same process. Additional evidence for this postulate is presented.
Pollen ultrastructure in anther cultures of Datura innoxia: II. The generative-cell wall
Authors: Dunwell J. M. , Sunderland N. 
Published: April 2021

ABSTRACT
In young pollen grains of Datura innoxia, a wall of the usual hemispherical type separates the 2 gametophytic cells initially and, in the electron, microscope, appears as an electron-translucent matrix which is contiguous with the intine. Before detachment of the generative cell from the intine, the matrix decreases in thickness and in places is dispersed altogether leaving the plasmalemmae on either side of it in close apposition. A particularly prominent zone, triangular in profile, is left where the wall joins with the intine. After detachment of the cell, remnants of the matrix can be seen distributed irregularly around the cell and it is supposed that these are partly derived from material in the triangular zone as the cell is drawn away from the intine. The wall residues persist throughout the maturation phase of the pollen and are considered to be either callose resulting from incomplete digestion of the initial wall, or some other polysaccharide material which is unevenly laid down along the wall and concentrated at the junction with the intine.
In pollen induced into embryogenesis by anther culture, wall material is also distributed irregularly around the detached cell in a series of discrete zones, but these are more extensive than in vivo, closer together and in many instances highly dilated. The wall profiles thus have a beaded appearance, the ‘beads’ being connected together by short links of the 2 apposed plasmalemmae. The contents of the swollen zones have a similar electron density to that of the matrix in vivo but also show traces of a fibrillar component. It is postulated that this unusual swelling is a prelude to dispersal of the wall by disruption of the plasmalemmal links and to the establishment of cytoplasmic continuity between the 2 cells. The significance of such binucleate pollen grains in the formation of non-haploid embryos is discussed.
Scanning electron-microscopical and other observations of sperm fertilization reactions in Limulus polyphemus L. (Merostomata: xiphosura)
Authors: Brown George Gordon 
Published: April 2021

ABSTRACT
Sperm fertilization reactions of Limulus polyphemus were examined by scanning electron and/or light microscopy. The following were considered: sperm motility, attachment of sperm to egg, acrosome reaction, and penetration of the acrosomal filament. The spermatozoa after semination are non-motile and become active only in close proximity to a defined region surrounding the egg. Egg materials diffusing into this region induce sperm motility and stimulate large numbers of spermatozoa to move towards the egg surface. Each sperm initially attaches by the apical tip and undergoes the acrosome reaction which causes a more permanent secondary attachment by the adhesion of acrosomal contents to the egg surface. The acrosome reaction also initiates the penetration of the acrosomal filament through the egg envelope, an event occurring in 70–80% of the attached spermatozoa (about 106). Shortly after this penetration, a secondary reaction occurs which involves a spiralling of the flagellum and an incorporation into the sperm body of the flagellar fibrous components, which then become closely apposed to the sperm nucleus.
These sperm fertilization reactions were performed or initiated with 0·34 M CaCl2 in whole eggs, egg sections, excised egg envelopes and/or the outer basement lamina of the egg envelope. The Limulus fertilization system is very valuable since sperm reactions can be examined biochemically, which may lead to a better understanding of the chemical mechanisms involved in sperm-egg interactions in all animal species.
Mechanism of myofibril growth and proliferation in fish muscle
Authors: Patterson S. , Goldspink G. 
Published: April 2021

ABSTRACT
The mechanisms of myofibril growth proliferation were investigated in the red and white muscles of fish. In both types of muscle the ratio of lattice filament spacings between the Z disk and M line was found to be greater than that required for perfect transformation of a square into a hexagonal lattice. This mismatch was considered to result in the thin filaments being pulled obliquely instead of at right angles to the Z disk. The angle of pull of the thin filaments was measured in longitudinal sections. The splitting process was found to decrease the degree of pull. Splitting was also observed in transverse sections of the peripheral myofibrils. In both red and white fibres these myofibrils were found to commence splitting when they reached a size of approximately 1·2 μm diameter. Evidence from ultrastructural and autoradiographical studies suggested that growth of the myofibrils within the fibres is centrifugal. The outermost myofibrils appear to be the ones which are being built up and which split. The data indicated that in fish muscle a considerable number of filaments may be added to the daughter regions whilst splitting of the myofibril is still continuing.
Occurrence of intercellular bridges between follicle epithelial cells in the ovary of Apis mellifica queens
Authors: Ramamurty P. S. , Engels W. 
Published: April 2021

ABSTRACT
Hitherto unknown intercellular bridges or fusomes between the follicle epithelial cells investing the oocytes of Apis mellifica queens have been observed both with light and electron microscopy. Usually each follicle cell has 2–3 intercellular bridges. In surfacial paraffin sections, the intercellular bridges can be seen to connect a series of follicle cells which may be branching. The intercellular bridges lie close to the egg cortex and this position is relatively constant. The width of the fusomal ring canal varies in different develoμmental stages. In stages 3 and 4 of oogenesis, which are the main vitellogenic stages, the intercellular bridges measure 0·5 μm, while in stages 1 and 2 they have a diameter ranging from 1·5 to 3·5 μm. In these stages the intercellular bridges are provided with numerous transverse microfilaments which disappear later. The fusomal lips are thickened and consist of electron-dense material and an additional layer of less electron-dense material both inside and outside. Ribosomes flow across the bridge.
The intercellular bridges may serve to synchronize the differentiation and functional activity of the follicle epithelium during the course of oogenesis.
Studies on the de novo formation of centrioles: aster formation in the activated eggs of sea urchin
Authors: Miki-Noumura Taiko 
Published: April 2021

ABSTRACT
Aster formation was studied in sea-urchin eggs artificially activated by Loeb’s double method. The number of asters found in an activated egg ranged from 15–40. Observation by electron microscopy revealed the presence of a centriole in a high percentage of isolated asters, strongly suggesting that these centrioles are formed de novo in the activated eggs. Using negatively stained specimens, which were isolated with 5 % hexylene glycol solution containing buffer and EGTA, the whole aster could be examined by electron microscopy. A microtubular framework in the aster, extending radially from the astral centre was observed. The effect of mitotic inhibitors on aster formation was found to be similar to that on cell division.
Substrate retention of fractured retraction fibres during detachment of trypsin1zed BHK21 fibroblasts
Authors: Whur P. , Koppel H. , Urquhart C. M. , Williams D. C. 
Published: April 2021

ABSTRACT
When BHK21 fibroblasts adhering to glass were incubated in trypsin they became spherical within a few minutes. They did not, however, respond simultaneously; the most trypsin-resistant cells in an unsynchronized population were of greater length, had more processes projecting from the cell body, and were more spread out than the most trypsin sensitive cells. In no instance did trypsin detach cells from their substrate, even when the incubation period was prolonged to 5 h in trypsin concentrations almost sufficient to cause cell lysis. Scanning electron-microscope observations showed that initially flat cells rounded up in trypsin to reveal persistent adhesion sites joined to the cell body by retraction fibres. Such cells could be dislodged only by agitation; when this occurred parts of the cell remained attached to the substrate in the form of small spheres and fibres; these were remnants of the retraction fibres and adhesion sites. We propose that the adhesion sites are not susceptible to proteolytic degradation, presumably because of steric hindrance, and that this causes detachment to be dependent upon mechanical dislocation. We suggest that some of the descriptions of substrate-associated ‘cell exudates’ in the literature may refer to these cell remnants on the substrate which consist of membrane-bound fragments of cytoplasm rather than secreted products.
Constraints on the relative sizes of the cell populations in Hydra attenuata
Authors: Bode Hans R. , Flick Kristine M. , Bode Patricia M. 
Published: April 2021

ABSTRACT
The steady-state relative population sizes of the several cell populations in Hydra attenuata were examined. In contrast to the constant average population size ratios between groups of animals, these ratios vary within limits between individual animals within a group. By maintaining animals on different feeding regimes (number of shrimp larvae ingested per day), the steady-state population size ratios were altered. The kinds of changes that occurred in these ratios suggest where controls may be operating to maintain the steady-state population sizes.